61105273 GBSS BSC6000 Feature Description

BSC6000 Feature Description

Date 2009-12-03

HUAWEI TECHNOLOGIES CO., LTD.


V2.3 (2009-12-03) Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd of 57

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Contents

1 Coverage Enhancement........................................................................................................... 4

2 Wide Coverage ......................................................................................................................... 5

3 Voice Capacity Improvement ................................................................................................. 6

4 Frequency Efficiency Improvement .................................................................................... 10

5 Network Synchronization..................................................................................................... 10

6 Energy Saving......................................................................................................................... 10

7 Abis Transmission Saving.................................................................................................... 10

8 Networking Framework........................................................................................................ 10

9 System Reliability.................................................................................................................. 10

10 Speed Coverage .................................................................................................................... 10

11 2G/3G Seamless Coverage .................................................................................................. 10

12 BTS Satellite Transmission................................................................................................. 10

13 Satellite Transmission......................................................................................................... 10

14 Enhanced Voice Service ...................................................................................................... 10

15 Cell Broadcast....................................................................................................................... 10

16 CS General Enhancement ................................................................................................... 10

17 AMR Package ....................................................................................................................... 10

18 PS QoS................................................................................................................................... 10

19 Cell Reselection of PS Domain .......................................................................................... 10

20 GPRS/EGPRS Service.......................................................................................................... 10

21 EGPRS Service Enhancement............................................................................................. 10

22 High Speed Data Service .................................................................................................... 10

23 VIP Service Support ............................................................................................................ 10

24 Gb IP...................................................................................................................................... 10



1 Coverage Enhancement

1.1 Transmit Diversity Function Description:

The transmit diversity function of the BTS uses two TRXs in the DTRU to transmit the co-carrier signals of some correlation. The two independent multi-path signals are then in the downlink. Then, the two independent multi-path signals are treated by the equalizer of the MS. The diversity gain is obtained, and the quality of the received signal is improved. At last, the downlink coverage effect is improved.

When the transmit diversity is used, the DRFU works in the single-carrier mode. You need to enable this function through the dada configuration.

Benefits:

l The receiving gain of the MS is increased. l The coverage effect of the downlink is improved. l The network construction cost is reduced.

1.2 4-Way Receiver Diversity Function Description:

The feature 4-way receiver diversity increases the receiver sensitivity of the DRFU by up to 3~5 dB, making it possible to achieve ubiquitous coverage with fewer sites in plain.

Benefits:

The 4-way receiver diversity can be used together with the Transmit Diversity to increase the coverage of the BTS, and to reduce the number of BTSs.



2 Wide Coverage

2.1 Extended Cell Function Description:

This function can break the limit of the 35 km and realize the wide coverage. This provides the good technical support for the operator the provide coverage in special area.

In GSM specifications, the timing advance (TA) of cell has a restriction of 8 bit at the radio interface, which leads to the situation that the cell coverage radius should be within 35 km.

In regions such as vast land, with scattered subscribers, with low traffic, and the infrastructure facilities such as transmission and power supply are hard to be constructed or unavailable. The radius of cell shall be over 35 km.

The extended cell breaks the restriction of radius within 35 km. Supported by BTS hardware, it can cover a range with radius of up to 120 km.

Operators can use this technology to fast construct their GSM networks with fewer stations and at lower cost, and to attract the mobile subscribers in special regions to improve revenue.

When the cell coverage radius exceeds 35 km, signal delay exceeds the duration corresponding with the maximum value 8bit specified in GSM specifications.

If an MS reaches the ordinary coverage edge, it transmits at the maximum TA allowed by system. If the MS continues to move outwards, the system is no longer able to implement adaptive adjustment on TA value due to the TA has reached its maximum. Part of signaling transmitted by MS reaches the BTS receiver at next time timeslot.

It is this principle that extended cell uses to realize the cell extension. That is, two continuous timeslots are assigned for each MS call, and the receiving window of BTS receiver is also extended to the width of two timeslots. Thus, the cell coverage radius is extended to over 35 km. To enable the MSs in extended range to initiate call at any time, BCCH, CCCH and SDCCH shall always be assigned with two timeslots.

Benefits:

With this function, the operator can expand its network coverage in special area, for example, in the vast plain or in the sea, thus increasing the operation efficiency.



3 Voice Capacity Improvement

3.1 Concentric Cell Function Description:

The concentric cell can distribute the traffic flexibly and improve the multiplexing rate of the frequency. Thus, the quality of network and the coverage range are improved.

The CONCENTRIC CELL technology divides an ordinary cell into two service layers: Overlaid subcell and underlaid subcell.

For the MS in the underlaid subcell, try to distribute the less reuse frequency, such as BCCH frequency. For the MS in the Overlaid subcell, try to distribute the more reuse frequency, such as frequency except BCCH.

The frequency inside the Overlaid subcell adopts more reuse frequency mode, which can improve system capacity effectively. As shown in figure, the MSs in the overlaid subcell are far from the interference. Therefore, even though the overlaid adopts the more frequency reuse, the voice quality still can be ensured. The underlaid adopts the loose reuse frequency, thus, the voice quality can also be ensured.

Figure 3-1 Aggressive frequency reuse of concentric cell

Cell A Cell BUnderLaid subcell

InterferenceSignal

OverLaid subcell

Improve system capacity:



The concentric cell divides the cell coverage into overlaid subcell and underlaid subcell. The overlaid subcell and underlaid subcell can adopt different multiplexing modes. For the overlaid subcell cell, it adopts more reuse frequency mode such as 1x3 due to its small coverage. For the underlaid subcell cell, it adopts less reuse frequency mode such as 4x3

Improve coverage

Increase the power of the power amplifier for the BCCH TRX, the coverage range of the cell can be widened. The TRXs of the cell may output different powers. Thus, the coverage range of the TRXs also differs. The actual coverage range of the cell is determined by the minimum coverage of the TRXs.

The concentric cell can make the TRXs with wider coverage range as the underlaid subcell to solve the coverage problem in the remote area. It makes the TRXs with smaller coverage range as the overlaid subcell to solve the capacity problem in the near area. Finally, the coverage range of the cell is widened.

The main function of concentric cell is implemented through the two modules: radio resource management module and handover decision module.

Channel assignment technology of concentric cell

Different channel assignment strategies are adopted for different situations, including:

– Immediate assignment

There is no reference receiving level, receiving quality and TA for immediate assignment. In order to guarantee the service quality, the SDCCH of underlaid subcell is assigned preferentially. Only when there is no signaling channel available in the underlaid subcell, will the signaling channel in the overlaid subcell be assigned. .

– Assignment

The channel assignment strategy of concentric cell is used to assign channels. The overlaid subcell channel will be assigned as far as possible when the subscriber is in the overlaid subcell coverage. The underlaid subcell channel will be assigned when no overlaid subcell channel is available. Similarly, the underlaid subcell channel will be assigned as far as possible when the subscriber is in the underlaid subcell coverage. The overlaid subcell channel will be assigned when no underlaid subcell channel is available. Select the suitable service layer to serve the subscriber.

Concentric cell Handover algorithm

The concentric cell handover algorithm is an extension of the Huawei handover algorithm. It enables the BSC to intelligently distribute the traffic and thus use the frequency resources more reasonably.

It is developed based on the current Huawei handover algorithm. It incorporates the concentric cell handover judgment function into the current Huawei handover algorithm.

When the MS moves across the edge of the overlaid Subcell and underlaid Subcell, the concentric cell handover is initiated. Thus, the MS can receive the service in a proper service layer. If the target layer is congested, the handover is not initiated.

For the inter-cell handover, if the target cell is concentric cell, the system also uses the concentric cell handover algorithm to choose a proper layer to provide service.

Benefits:

The operator can use the more reuse frequency to expand the system capacity.



The operator can also extend the coverage range by using different service layers to bear different traffic.

3.2 Enhanced Dual-Band Network Function Description:

The enhanced dual-band network function enhances the resource sharing capability of the channels in the overlaid and underlaid subcells based on the multi-band networking.

Two physically independent cells (two co-site cells with different coverage radiuses) on different bands are configured with BCCHs and SDCCHs so that the cells form a cell group logically, mapping with the overlaid subcell and the underlaid subcell respectively. For the two cells in the group, the traffic channel resources are shared and the cell load is balanced through the enhanced dual-band network algorithm. The overlaid and underlaid subcells can obtain the information, such as level, channel, and load about each other, so the KPIs (for example, handover success rate and assignment success rate) can be kept at proper values when the channels in the overlaid and underlaid subcells are shared.

Benefits:

Multi-band networking can be implemented and the telecom operators are provided with the band expansion capabilities. In addition to the proper KPIs, the system capacity is enhanced through the sharing of the resources in the overlaid and underlaid subcells.

3.3 Flex MAIO Function Description:

In a site with large capacity, inter-frequency or intra-frequency interference may easily occur among channels because of the limited frequency resources and the aggressive frequency reuse. For example, when the MA has some neighbor frequencies, inter-frequency interference may occur among the channels if the channels that carry the same number of the timeslot on different TRXs use neighbor MAIOs and the channels are seized.

If the Flex MAIO function is performed so that an MAIO is assigned to a certain channel under activation, the MAIO value is dynamically adjusted based on the interference on the current channel. The MAIO value is assigned to the channel so that the interference for the call is minimized from the perspective of the entire network.

The Huawei BSS equipment records the interference conditions in each timeslot and updates the timeslot interference record upon channel activation or channel release.

Benefits:

When the frequencies are limited, the cells in the BTS can optimally use the frequencies. Thus the inter-frequency and intra-frequency interference among channels in the GSM telecommunications system is minimized and the aggressive reuse of frequency resources in the BTS is realized. Therefore, the system capacity is enhanced.

Dependency:



The function can be used only after the frequency hopping function is enabled. It can be regarded as an optimization to the frequency hopping function.

3.4 ICC(Interference Counteract Combine) Function Description:

Inference Counteract Combine is a new receiver algorithm for the transceiver which drastically improves the uplink radio quality and speech quality.

The prerequisite for ICC is that two antennas are used to receive two diversity signals, and then the ICC will compare to the training sequence to find out the characteristics of the interference signals, and remove the invalid signals from the desired signals.

Benefits:

ICC not only can decrease the interference impacting on uplink signals but increase the network capacity where networks are uplink limited and improve speech quality since interference is reduced, as well as ICC can increase data throughput due to fewer retransmissions and the possibility to use higher coding schemes.



4 Frequency Efficiency Improvement

4.1 Frequency Hopping (RF hopping, baseband hopping) Function Description:

The frequency hopping (FH) can avoid the attenuation caused by multi-path transmission and same frequency interference, and improve the average C/I of the interference restriction system (especially in cities), thus greatly improving the quality of session, strengthening the capability of high-density multiplexing and increasing the system capacity. Adopting FH can improve the transmission quality of the slowly moving MS. Besides, FH can also improve the security of communication.

FH means that the carrier containing meaningful information hops under the control of a sequence. This sequence is called frequency-hopping sequence (HSN). FH mode can be divided into frame FH and timeslot FH by the concept of time-domain and can be divided into and into RF FH and base band FH by carrier realization mode.

Huawei BSS realizes the baseband FH and RF FH at the timeslot level, and the baseband FH and RF FH at the frame level.

RF FH:

Both Tx and Rx join the FH. In a cell, the number of FH frequencies engaged in the FH can be larger than the number of TRXs.

The RF FH is implemented through real-time switchover between two frequency synthesizers. There are two advantages for this implementation:

Lower the speed requirements on the frequency synthesizer.

When there is no FH, two frequency synthesizers work in the active/standby mode, thus enhancing the system reliability.

Huawei BTS adopts dynamic loop bandwidth and Ping-Pong handover to solve the conflict between fast FH and signal quality. It can realize the unrestricted FH in the bandwidth of the supported frequency band. All FH indexes satisfy the requirements specified in the GSM protocols.

Baseband FH:

Each transmitter works on a fixed frequency. Tx is not involved in FH. The transmitting FH is realized by switching the baseband signal. Rx is involved in FH. Therefore, the number of FH



frequencies in a cell cannot be larger than number of the TRXs of the cell. When a TRX is faulty, the system starts the baseband FH TRX cooperation to ensure the conversation quality in the cell.

Huawei BTS adopts the technology of FH_BUS, which implements FH on the basis of timeslot exchange. Each transmitter is tuned to a fixed frequency, and has a fixed ID. The coder of transmitter encodes the downlink signal to convert the data to burst format. It calculates the channel (that is, TRX) to be modulated for the burst according to FH algorithm, and adds the attached information related to power control to generate a special data packet. The coder transmits the data packet periodically (sub-timeslot). Modulator checks the TRX ID of the data packet from each sub-timeslot. If the TRX ID is different from the local TRX, it will receive that from the next sub-timeslot. If the TRX IDs are the same, it will accept the data packet, and delay for a timeslot and then transmitted to the air interface. Baseband FH has a very high requirement on the real-time identification of the ID of TRX. Huawei base band FH technology realizes fast and reliable TRX ID identification on the basis of the ASIC.

Benefits:

The FH can greatly improve the quality and security of the call. It can also improve the networking capacity of the BTSs using Aggressive Frequency Reuse Pattern (AFR), and improves the system capacity.

4.2 Antenna Frequency Hopping Function Description:

For the realized frequency hopping (FH) function of the Huawei BSS, the RF FH and baseband FH cannot realize the FH of the BCCH TRX, and the FH of the BCCH TRX cannot realize the FH of timeslot 0 on the BCCH TRX. In the GSM cells, however, timeslot 0 on the BCCH TRX is important for the MS in idle mode to search for the network and for the MS in dedicated mode to measure the neighbor cells. If the MS is in an unfavorable position or the antenna of the BCCH TRX is damaged, the MS cannot receive the broadcast control messages from the BCCH TRX properly. The antenna FH function enables the data of all the timeslots on the BCCH TRX to be transmitted on the antenna of all the TRXs in the cell in turn. Thus the space diversity is increased and the quality of the BCCH TRX data received by the MS is improved. Therefore, the network performance is enhanced.

Benefits:

The receive performance of the MS is improved, and the space diversity is realized. Therefore, the network performance is enhanced.

Dependency:

The function needs to be supported by the BTS.

4.3 BCCH Dense Frequency Multiplexing Function Description:

The function allows the operator to densely multiplex frequencies on BCCH carriers. In networks with limited frequency resources, this function can reduce the frequencies occupied by the BCCH carriers, and provide more frequencies for the traffic channels. This function



can increase system capacity and reduce investment in sites, without changing the original hardware.

Every cell is configured with a BCCH carrier. Timeslot 0 of the carrier is mapped to the broadcast channel (BCH) or the common control channel (CCCH). The synchronization message, system message, paging message, and assignment message are carried in the timeslot to all subscribers of the cell continuously. These messages directly relate to cell residence, cell reselection, call initiation, and paging response. Therefore, the BCCH becomes the most important channel in the GSM telecommunication.

Generally, the 4*3 mode is adopted for the BCCH frequency planning. This can ensure that the C/I ratio of the shared/adjacent frequencies on the BCCH carrier is very high. The BCCH occupies 12 frequencies. In a network with a higher frequency multiplexing level and limited frequency resources, if 3*3 multiplexing is implemented for the frequencies of the BCCH, the interference on the TCH on the BCCH carrier increases and the performance drops to an intolerable level.

The BCCH dense frequency multiplexing function divides a cell into two different logical layers: The TCH layer on the BCCH carrier and the frequency hopping layer. The frequency hopping layer serves the whole system, covers the whole network, and provides coverage for calls at the edge of a cell. To guarantee the performance of call access, the TCH layer on the BCCH carrier must modify the coverage of its absorbed traffic. The interference in places near the BTS is smaller than the interference at the peripheral area and edge of a cell. Therefore, the TCH layer on the BCCH carrier provides the coverage for calls near the BTS only.

In the initial access and channel allocation triggered by handover (in case of non-BCCH dense frequency multiplexing), the system first allocates traffic channels among non-BCCH carriers to ensure the subscriber access performance. When a call on a non-BCCH carrier in a cell is initiated, if the subscriber is near the BTS, it means that the BCCH dense frequency multiplexing only has smaller impact on the call. The system hands over the call to the BCCH carrier and reserves the channels on non-BCCH carriers to ensure the access performance of other calls.

Benefits:

l Reduces the frequencies occupied by the BCCH and improves frequency spectrum utilization rate.

l Increases the available frequencies of traffic channels and frequencies in frequency hopping, increases the system capacity without changing the original hardware, and reduces the investment in new sites and cells.

l The TCH layer on the BCCH carrier is only used by the subscribers in a cell near the BTS. Because the interference on the uplink decreases, the subscribers can obtain better voice quality if this function is enabled.

l Reduces the chance of random access failure and enhances the access performance.

4.4 Support for E-GSM and R-GSM Frequency Band Function Description:

E-GSM (including P-GSM900 and extended GSM900) is the extension of P-GSM900. The serving frequency of E-GSM is as follow:

Uplink: 880 MHz –915 MHz



Downlink: 925 MHz–960 MHz

The frequency No.: 0–124, and 975–1023.

R-GSM is the extension of E-GSM. The serving frequency of R-GSM is as follows:

Uplink: 876 MHz–915 MHz:

Downlink: 921 MHz–960 MHz

The frequency No.: 0–124, and 955–1023.

The E-GSM 900, R-GSM 900 and the P-GSM belong to the same frequency band while their frequencies are not adjacent. Thus the extended frequency band of E-GSM and R-GSM are introduced.

The E-GSM extended frequency band refers to the E-GSM frequency band other than the P-GSM frequency band.

The R-GSM extended frequency band refers to the E-GSM frequency band other than the R-GSM frequency band.

For the cells configured with E-GSM extended frequency band or R-GSM extended frequency band, the system takes the frequency band support capability of MSs and the channel into consideration to adopt different channel assignment strategies.

For immediate assignment, the system assigns channel for the MS according to the frequency support capability of BCCH. When assign the channel, the system obtains the classmark of MS and then obtains the frequency support capability of MS according to the classmark.

Among all the channels that support the MS, the system prefers to assign the channel other than the intersecting channels. For example, if a MS supports E-GSM and the current channel has P-GSM frequency band and E-GSM extended frequency band, the channel of E-GSM extended frequency band is assigned. The P-GSM channel is reserved for the MSs that have weak frequency band support capability.

Benefits:

The service can be borne by the extended frequency band, which extends the frequency range.

4.5 IBCA Availability: GBSS8.1

Function Overview

IBCA stands for interference based channel allocation. In IBCA, when a call accesses the network, the interference of the new call to the established calls and the interference of the established calls to the new call are calculated. Based on the calculation, the network allocates a channel with the minimum interference to the new call. This approach minimizes the overall interference in the network, improves the efficiency of the frequency usage, and increases the network capacity while maintaining the voice quality in the whole network.

Benefits:

IBCA provides these benefits:

l Increasing the frequency usage by 30%–40% and increasing the network capacity while maintaining the network quality



l Reducing the overall interference and improving the network quality. l Improving the voice quality.

Function Description:

In GSM, the loose frequency reuse makes better network quality, higher network KPI, and excellent voice quality, but reduced network capacity, which is a disadvantage comparing to the tight frequency reuse. The tight frequency reuse scheme increases the network capacity. However, the probability of the TRXs using the same frequency or adjacent frequencies increases. This results in more co-channel interference or adjacent channel interference, which can further leads to decreased network quality.

Based on the timeslot synchronization on the air interface, the IBCA function takes into account the interference strength of all idle channels and allocates the channel with the minimum interference to the network preferentially. IBCA performs the following:

l Calculates the interference of the established calls to the new call. IBCA must be used along with the frequency hopping. The idle channels with different MAIO values transmit signals over the air interface with different frequencies, and the interference they experience from the established calls may vary. The IBCA function calculates the interference to each idle channel when different MAIO values are applied.

l Calculates the interference to the established calls caused by the new call. If the established calls can interfere with the new call, once the call accesses the network, the new call also interferes with the established calls. The IBCA evaluates the carrier-to-interference ratio of the new call to the established calls.

Taking into account the preceding two types of interference, allocate a channel with minimum interference to the network and the MAIO value to the call for access request. The IBCA function consists of the intra-BSC IBCA and inter-BSC IBCA. In other words, the IBCA-enabled cell can belong to either one BSC or to multiple BSCs.

The implementation of the IBCA improves the frequency usage, and further increases the network capacity. In addition, the interference between the established calls and the new call is also considered when allocating a channel to the new call. Thus, the IBCA helps to improve the call quality.

Dependency:

Impacts on the BSC hardware

l To implement the IBCA, two service processing boards should be added to the BSC for data processing.

l The Inter-BSC IBCA requires IP connection between the two BSCs. If Abis over IP or A over IP, connect the IP interface boards of the two BSCs with Ethernet cables directly. If the Abis or A interface is not based on IP, add two pairs of IP interface boards and then connect the two BSCs through the IP interface boards.



5 Network Synchronization

5.1 Soft-Synchronized Network Function Description:

Most of the current GSM networks are non-synchronous networks, that is, all BTSs are not synchronized, and every BTS adopts different frame number, timeslot number, and TA offset. There are two network synchronization modes: hardware synchronization and software synchronization. In the hardware synchronization mode, every BTS is equipped with a GPS device. Through the synchronization by satellite transmission, network-wide synchronization is realized. But this mode necessitates extra cost. In the software synchronization mode, Um interface software is used to realize BSC-wide synchronization. The software adjusts the frame number, timeslot, and offset of the BTSs to synchronize all BTSs under the BSC.

In a non-synchronous network, it is impossible to estimate the interference on the adjacent channels. The interference can be alleviated through loose frequency multiplexing and frequency hopping.

In a synchronous network, the system can estimate the interference of shared/adjacent channels in any inter-cell overlapping area, and avoid collision of inter-cell shared/adjacent channels through the dynamic frequency and channel allocation algorithm. This greatly improves the frequency resource utilization rate and the network capacity.

The synchronous network helps the ICC to achieve the optimum performance. When the useful signals are synchronized with the interference signals in time, the interference signals keep unchanged during the burst. The interference feature calculated according to the training sequence can effectively counteract the interference during the burst. At the moment, the ICC performance is the best.

Benefits:

l Synchronizes all BTSs under a BSC through software without the need of extra expensive hardware device. The necessary hardware devices include a GPS device for every BTS. The satellite is used to realize synchronization.

l Synchronizes the BTSs, and realizes the IBCA function. The simulation result shows that: The IBCA technology applied in the synchronous network can improve the network capacity by 20–50%.

l Synchronizes the BTSs and greatly improves the performance of ICC and SAIC. According to the simulation result, the ICC technology applied in the synchronous network can improve the network performance by 5.5 dB in contrast to the performance



of the asynchronous network. The SAIC technology in the asynchronous network can improve the network capacity by 40%.

l Improves the KPIs, including mean opinion score (MOS) of the voice service, paging success rate, handover success rate, call drop rate, and traffic volume.



6 Energy Saving

6.1 Discontinuous Transmission (DTX) Downlink Function Description:

Downlink Discontinuous transmission (DTX) can reduce the transmit power of BTS. This can reduce the co-channel disturbance in the radio interface and the sensitivity of the GSM voice signal to the error in the radio interface.

DTX includes Voice Activity Detection (VAD) and Silence Descriptor (SID). In addition, to ensure the continuity of the service, the system automatically generates the comfortable noise.

Voice Activity Detection (VAD): When TRAU detects through VAD that the data received from MSC contains no voice information, it clears the voice flag bit in the TRAU frame. After recognizing the flag bit, BTS disconnects the downlink till the flag bit is set.

When TRAU receives the uplink frame, it also discriminate the SID flag. If the SID flag is set, it means the MS is in the transmission intermittent period.

Silence Descriptor (SID): the noise coding flow is the same as the voice signal coding flow. The SID frame also experiences the channel coding, interleaving, ciphering and modulation and then it is turned into the field containing the noise messages and sent out in eight continuous burst, just as the voice frame does.

Comfortable noise: When receive the uplink frames, the TRAU judges the SID flag. When the SID is set, it means the MS is in the intermittent period. To make the listener feel that the GSM provides continuous service for it, the TRAU inserts comfortable noise in the uplink link.

TRAU uses DTX to reduce the transmit power of BTS and MS. This further reduces the co-channel interference of radio interface and extends the standby time of MS. At the same time, the receiving MS generates the comfortable noise to make the user feel that the communications is continuous when the receiving MS detects it is in the DTX mode.

Configuring the uplink discontinuous transmission (DTX) and downlink DTX separately: The uplink DTX and downlink DTX can be configured separately. That is, you can enable the uplink DTX and downlink DTX simultaneously or separately. The flexible configuration helps maintain the balance between the intra-network interference and the speech quality.



Benefits:

This function reduces the power consumption of the BTS, reduces the interference within the system, and reduces the inter-modulation within the BTS. Viewed from the whole network, the co-channel interference is reduced. Thus, the network capacity is improved.

6.2 Discontinuous Transmission (DTX) Uplink Function Description:

Uplink discontinuous transmission (DTX) can reduce the transmit power of MS. This can reduce the co-channel disturbance in the radio interface and the sensitivity of the GSM voice signal to the error in the radio interface.

DTX includes Voice Activity Detection (VAD) and Silence Descriptor (SID). In addition, to ensure the continuity of the service, the system automatically generates the comfortable noise.

Voice Activity Detection (VAD): When TRAU detects through VAD that the data received from MSC contains no voice information, it clears the voice flag bit in the TRAU frame. After recognizing the flag bit, BTS disconnects the downlink till the flag bit is set.

When TRAU receives the uplink frame, it also discriminate the SID flag. If the SID flag is set, it means the MS is in the transmission intermittent period.

Silence Descriptor (SID): the noise coding flow is the same as the voice signal coding flow. The SID frame also experiences the channel coding, interleaving, ciphering and modulation and then it is turned into the field containing the noise messages and sent out in eight continuous burst, just as the voice frame does.

Comfortable noise: When receive the uplink frames, the TRAU judges the SID flag. When the SID is set, it means the MS is in the intermittent period. To make the listener feels that the GSM provides continuous service for it, the TRAU inserts comfortable noise in the uplink link.

TRAU uses DTX to reduce the transmit power of BTS and MS. This further reduces the co-channel interference of radio interface and extends the standby time of MS. At the same time, the receiving MS generates the comfortable noise to make the user feel that the communications is continuous when the receiving MS detects it is in the DTX mode.

Configuring the uplink discontinuous transmission (DTX) and downlink DTX separately: The uplink DTX and downlink DTX can be configured separately. That is, you can enable the uplink DTX and downlink DTX simultaneously or separately. The flexible configuration helps maintain the balance between the intra-network interference and the speech quality.

Benefits:

This function reduces the power consumption of the MS, reduces the interference within the system, and reduces the inter-modulation within the BTS. Viewed from the whole network, the co-channel interference is reduced. Thus, the network capacity is improved.

6.3 TRX Power Amplifier Intelligent Shutdown Function Description:



Not all the cells on the existing network are busy all the time. When some cells are idle, some TRXs are sufficient to meet the current traffic requirements. In this case, you can enable the system to shut down idle TRXs to reduce the power consumption of the BTS and the operation expenditure of telecom operators.

The intelligent shutdown of TRXs can be enabled at a specific period. After this function is enabled, idle TRXs are shut down to save energy according to the prediction of traffic load and traffic volume. Alternatively, switch on the TRXs that are shut down to enable these TRXs to be available for use anytime. Before shutting down a TRX, the BSC will initiate an intra-cell handover to hand over the calls on the TRX to other TRXs. When there is no call on the TRX, the BSC orders the BTS to shut down the TRX. If some calls on the TRX cannot be handed over, the BSC stops ordering the BTS to shut down the TRX.

Generally, channel allocation measures are used together with this function. During channel allocation, channels are allocated to some centralized TRXs. The channels of the main BCCH TRX are preferentially assigned so that the channel utilization of the non-main BCCH TRX is decreased and the overall power consumption of the BTS is reduced. Besides, the BTS allocates channels based on the priorities of TRXs. Channels are preferentially assigned to TRXs with high priorities. In this way, the BSC centralizes busy channels into a few TRXs so that idle TRXs can be shut down as many as possible.

Benefits:

The power consumption of TRXs in the BTS must be taken into account. This function can reduce the overall power consumption of the BTS without affecting services. In this way, the electricity expenditure of telecom operators is greatly reduced and meanwhile the battery life is improved.



7 Abis Transmission Saving

7.1 Flex Abis Function Description:

The traditional BSC assigns the transmission resources on the Abis interface in a fixed way so that one timeslot on the Abis interface maps with one timeslot on the air interface. Thus the timeslots on the Abis interface and those on the air interface cannot be shared. In actual situation, for different BTSs and cells as well as the packet service and the circuit service, the resources on the air interface are not always seized. When a BTS is busy and another BTS is idle, or when the packet service is busy and the circuit service is idle, the resource usage is enhanced if the Abis resources can be shared among different BTSs, cells, or services. If the function is used in a multi-cell and high-configuration site, a multiply cascaded BTS, or a cell configured with the EDGE service, the resources can be utilized in a more effective manner.

Huawei Flex Abis supports the Abis timeslot resources shared by the PS service and the CS service. A special algorithm is designed to balance the Abis resources between the PS service and the CS service. In Flex Abis solution, a certain number of Abis resources are allocated to the PS service to ensure the QoS for some PS service users.

In PS domain, the transmission resources on the Abis interface are allocated based on 16 kbit/s sub-timeslot. A main timeslot is allocated to the PDCH, and then additional timeslots are allocated in steps of 16 kbit/s based on the required coding rate on the Um interface. In Huawei algorithm, transmission resources are allocated based on the 16 kbit/s timeslot, which greatly improves the bandwidth utilization.

In CS service, the timeslot transmission on the Abis interface uses the resource pool mode. Abis resources are allocated to TRXs only when the TRXs are busy. This can improve the utilization of Abis resources. Except for synchronous timeslot (TS0), RSL timeslot (radio signaling link), and OML timeslot (operation and maintenance link), all the other Abis resources are included in the Abis Pool.

For Huawei BSS, the assignment of half-rate channels on the Abis interface can be triggered based on the load of the Abis resources. The minimum Abis resource for allocation is 8 kbit/s. When the resource utilization on the Um interface does not reach the congestion threshold but the transmission resource utilization has reached the congestion threshold, 8 kbit/s half-rate channels on the Abis interface are assigned to improve the utilization of Abis resources.

Benefits:



The function can realize the sharing of the Abis resources among BTSs, cells, or services. Thus the reusability of the resources can be enhanced. The operating costs of the telecom operators can be reduced if the transmission resources are limited, for example, satellite transmission.

7.2 Abis Congestion Triggered HR Allocation Function Overview

When the Abis interface congestion occurs, the calls are handed over from TCHF to TCHH.

Benefits

This function helps to save the Abis transmission resources and reduce the network construction cost. When the Abis interface congestion occurs, the speech quality is degraded to guarantee the system capacity.


In heavy traffic hours, if the Abis transmission resources are not sufficient, the Abis transmission may be congested earlier than the air interface. The TCHF-to-TCHH conversion based on the air interface load and the mechanism of preferentially allocating TCHH cannot guarantee the system capacity. Based on the congestion status on the Abis interface, the Abis congestion triggered HR allocation function performs dynamic TCHF-TCHH conversion, preferentially allocates TCHH, and carries out queuing and pre-emption to ease the Abis interface congestion and to increase the system capacity.

Dynamic TCHF-TCHH conversion: When the Abis interface congestion occurs, the qualified calls, such as calls originated by non-VIP subscribers, calls with high speech quality, or calls with allowed path loss, are handed over from TCHF to TCHH. This eases the congestion on the Abis interface and improves the system capacity. When the Abis interface congestion is rectified, the qualified calls in the cell are handed over from TCHH to TCHF to improve the speech quality of the calls.

Preferentially allocating the TCHH: When the A interface congestion occurs, the TCHHs are preferentially allocated to the newly accessed calls to slow down the congestion.



8 Networking Framework

8.1 Multi-Cell Function Function Description:

Under special circumstance, one BTS is required to support more than three cells. Huawei GSM BSS can support up to twelve cells.

Huawei BTS3900, BTS3900A, support six cells in one cabinet, and support twelve cells in two cabinets.

Under the 900/1800M dual band networking, the operator can use this function to provide twelve 900M and 1800M cells with one BTS, thus saving the investment.

Benefits:

Within this function, one BTS can provide twelve cells, thus saving the investment for the operator.



9 System Reliability

9.1 MSC Pool Function Description:

MSC Pool function indicates that a maximum of 32 MSCs form a resource pool to provide network services for the mobile subscribers under one group of BSCs. Through the MSC Pool function, one BSC can be connected with multiple MSCs, and evenly distribute its traffic load to all the MSCs in the resource pool based on the network resource indicator (NRI) and the load sharing principle. The chart below shows the typical network topology for the MSC Pool function.

Figure 9-1 Typical network topology for the MSC Pool function

BSCArea 1

BSCArea 2

MSC 2

MSC 1

MSC 5

MSC 4 MSC 7

Pool Area 2

MSC 8

Pool Area 3

BSCArea 5

BSCArea 6

BSCArea 3

BSCArea 4

BSCArea 7

BSCArea 8

MSC 3 MSC 6

Pool Area 1

As shown in Figure 9-1, MCS 1, MCS 2, and MCS 3 form an MSC pool (Pool Area 1). All the calls or data in the tour BSC service areas (BSC Area 1, BSC Area 2, BSC Area 5, and BSC Area 6) are routed to the MSC pool for further processing.

The following describes three routing modes:



l Routing by NRI

The NRI is carried in the TMSI of an MS. It is assigned to the MS by the MSC. When the MS needs to use network services, it sends its TMSI to the network. Upon receipt of the TMSI, the BSC resolves the NRI from the TMSI and then routes the services of the MS to the MSC based on the MSC signaling point corresponding to the NRI in the configuration data.

l Routing by network load

In the BSC configuration data, every MSC in the MSC pool is configured with a static load factor, which indicates the load sharing percentage of services shared on each MSC. The BSC routes services to MSCs based on the load factors in a loading sharing principle.

l Routing by IMSI

When the IMSI carried in the network-initiated paging message is consistent with the IMSI carried in the MS-initiated paging message, the BSC routes the services of the MS to the MSC that returns a paging response.

Benefits:

The MSCs in the MSC pool bears traffic load evenly and share resources.

The MSC Pool function can:

l Improve the network capacity and save the cost of telecom operators l Achieve disaster-recovery backup and improve network reliability because the addition

or deletion of an MSC does not affect normal services. l Automatically balance the traffic load on an MSC and reduce the operation and

maintenance cost of telecom operators l The MSC pool is logically seen as one MSC. It can reduce inter-MSC handovers and

improve network performance.

9.2 SGSN Pool Function Description:

The Gb Flex is also referred to as the SGSN pool. The SGSN pool refers to the pool that consists of SGSNs. The BSC connects to every SGSN in the pool. The SGSNs in the pool realize resource sharing and load sharing. Consequently, traffic is evenly distributed among the SGSNs; intra-office handover is reduced; disaster tolerance capability is enhanced.

The pool area refers to the service area of one or multiple RAN nodes. In the area, an MS can roam without changing the service node of the CN. One or multiple CNs provides service concurrently. Pool area overlapping is allowed.

For newly-registered subscribers, the BSC determines the CN node based on the load balancing algorithm, and routes the NAS message to the corresponding NSE.

For registered subscribers, the BSC finds the CN node according to the NRI in TLLI (the relation between the NRI and the CN node is configured in the BSC), and routes the NAS message to the corresponding NSE. If the CN node cannot be found according to the NRI, the BSC selects a CN node based on the load balancing algorithm, and routes the NAS message to the corresponding NSE.

Benefits:



l Realizes even distribution of traffic among the SGSNs in the pool. l Reduces inter-office handover and enhance disaster tolerance. l Reduces service interruption during SGSN capacity expansion, and improves working

efficiency.



10 Speed Coverage

10.1 Fast Move Handover Function Description:

In a fast-moving train, it takes a short time for an MS to move across a cell. Therefore, a handover must be performed quickly. To reduce the failure rate of handovers, a handover must be quickly initiated when required. If the handover fails (for example, the interference occurs to the radio interface suddenly), a second handover must be quickly initiated.

Fast PBGT handover algorithm enables the better cell handover in a short period of time. Compared with the existing PBGT handover algorithm, the fast PBGT handover algorithm has the following improvement:

l Handing over an MS to a proper target cell by predicting the moving direction of the MS.

l Accelerating the handover decision to improve the handover speed.

Benefits:

This function can improve the success rate of handovers in fast-moving environment.



11 2G/3G Seamless Coverage

11.1 GSM/WCDMA service based handover Function Description:

With the application of the WCDMA system, the networking with both the GSM system and the WCDMA system is widely used. The QoS on the two radio access systems is different. The problem of using different radio access system resources for different services needs to be solved immediately. According to the service hierarchy principle, different services are handed over to different systems. For example, the voice services are preferentially handed over to the GSM system, and the data services are retained in the WCDMA system.

In the assignment procedure, the MSC sends the service handover information to the BSC through the ASSIGNMENT REQUEST message. If the service handover information indicates that the call is handled in the UTRAN preferentially, the directed retry procedure can be initiated to hand over the call to the WCDMA system.

The HANDOVER REQUEST message received by the BSC may also carry the service handover information. The BSC uses this information for subsequent handover decision.

Benefits:

This function improves the QoS by preferentially selecting the GSM system or the WCDMA system based on the user services.

11.2 2G/3G Cell Reselection Based on MS State Summary

This function is designed to optimize the 2G/3G cell reselection (3G network includes the WCDMA and TD-SCDMA). It enables the dual-mode MS to take different reselection strategies in idle state or in packet transfer state and to access a 2G network or 3G network by condition.

Benefits

This function helps operators to flexibly determine the 2G or 3G network to be selected when the MS is in idle state or in packet transfer state according to the network planning requirements.

Description



In the construction phase of the 3G network, operators need to select a proper network planning strategy to ensure that the MS accesses a 2G or 3G network by condition. The decision is made taking into account the coverage of 3G network and the MS compatibility with the 3G network. The 2G/3G Cell Reselection Based on MS State function provides operators with different cell reselection strategies based on different MS states.

For example, in the early construction phase of the 3G network, operators expect that the 3G network can load off some traffic of the 2G network. However, the communications in packet transfer state may be interrupted after cell reselection due to incomplete coverage of the 3G network or incompatibility between the MS and 3G network. As a result, the KPIs may be affected. With this function, operators allow the MS in idle state to search for neighbor 3G cells by setting the parameter Qsearch_I to a specific value. Similarly, operators can prohibit the MS in packet transfer state to search for neighbor 3G cells by setting the parameter Qsearch_P to a specific value. In this way, operators can flexibly select 2G network or 3G network according to the MS state.

With the GBFD-6201 Network-Controlled Cell Reselection (NC2) function, the BSC controls the inter-RAT cell reselection, allowing the MS in packet transfer state to select a neighbor 3G cell. With this function, however, the MS in packet transfer state is prohibited to select a neighbor 3G cell. Therefore, these two functions are mutually exclusive. This problem can be solved depending on which function operators prefer.



12 BTS Satellite Transmission

12.1 Satellite Transmission over Abis Interface Function Description:

The satellite transmission enables the operator to provide services on the mountainous area, far-flung area, isolated island and other areas that the conventional transmission cannot reach.

Satellite communication is the development and the special form of microwave communication. It is a supplement and backup of the conventional communication means.

Satellite communication features wide coverage, fine mobility, and flexible link calling. It is little affected by the landform. Meanwhile, it has the problems such as delay, jitter, and bit error, which makes the Abis interface of ordinary GSM equipment not support satellite transmission.

Because the link lease is very expensive and the quality is particularly sensitive to environment, the solution of Abis interface transmission by using satellite transmission should be positioned for the emergency communication and for the special areas where the ordinary transmission means is dissatisfactory.

The star networking mode is usually adopted for the satellite transmission.

Under the satellite Transmission over Abis interface, the voice quality can reach the normal voice quality. However, because the satellite transmission has transmission delay, the voice has some delay too under the satellite transmission.

BSC supports satellite transmission on Abis interface between BSC and BTS, the maximum delay allowed on G-Abis interface is 800 ms.

Benefits:

The operator can use this function to deploy BTSs and provide service in the area where the conventional means is hard to reach.



13 Satellite Transmission

13.1 Satellite Transmission over A Interface Function Description:

With this function, the operator can deploy network in the area where the conventional transmission cannot reach.

The operator can deploy the BSS in the isolated island or a small area. The Abis interface adopts the terrestrial transmission or satellite transmission. Then the A interface adopts the satellite transmission to connect the BSS to the CN.

Huawei also provide the A interface monitoring function. It can monitor the circuit usage of the A interface. Thus, the operator can adjust the bandwidth of the circuit in the A interface to save the cost.

The satellite transmission can also be used to provide service for emergency communications or hot spots.

Benefits:

The operator can use this function to deploy the BSS system and provide service for the area that the conventional transmission is hard to reach.

13.2 Satellite Transmission over Ater Interface Function Description:

With this function, the operator can deploy network in the area where the conventional transmission cannot reach.

With this function, the TRUA unit can be placed in the CN side. Thus, the circuit of the A interface can use 4:1 compression, which can greatly reduce the required bandwidth of the A interface circuit.

Huawei also provide the A interface monitoring function. It can monitor the circuit usage of the A interface. Thus, the operator can adjust the bandwidth of the circuit in the A interface to save the cost.

Benefits:

The operator can use 4:1 compression to save the cost for A interface circuit.

The operator can deploy the BSS network for the emergency communications or in the area where the conventional transmission cannot reach.



13.3 Satellite Transmission over Gb Interface Function Description:

PCU supports satellite transmission on Gb interface between PCU and SGSN, the maximum delay allowed on Gb interface is 800 ms.

Dependency:

Integrated PCU have Gb interface, so this function is needed.



14 Enhanced Voice Service

14.1 Enhanced Full Rate


Enhanced Full Rate (EFR) can provide better voice quality.

EFR adopts the Algebraic code excitation linear prediction (ACELP) algorithm.

Transcoder & Rate Adaptation Unit (TRAU) converts the voice signal received from MSC into frames in the format of 20 ms/frame. A frame of voice data contains 160 PCM sampling points, totally 1280 bit. The output parameters after encoding are 244 bit, making up the 320 bit TRAU frame together with the synchronous header and control parameter.

Decoding is a reverse process of coding. After TRAU receives the TRAU frames sent from the BSC, it restores them into speech data by applying decoding algorithm before sending them to MSC.

Forced EFR Function enabled in BSC: Provided that the EFR function can help improve the speech quality and both the MS and the BSC support the EFR function, the EFR function can be forcedly enabled on the BSC side if EFR is unavailable because the MSC does not support it. In this case, EFR should be shielded on the MSC side to avoid assignment failure or handover failure. This function is mainly applied in the areas with poor speech quality.

Benefits:

With this function, the operator can provide better voice quality without affecting the network capacity.



15 Cell Broadcast

15.1 Short Message Service Cell Broadcast (TS23) Function Description:

The Short Message Service Cell Broadcast (SMSCB) is a teleservice (TS23) that can periodically broadcast messages to all the MSs in a specified area. The MSs can receive the broadcast messages continuously or discontinuously according to the system configuration. The typical application of this function is to provide the weather information and traffic information.

SMSCB allows broadcasting the short message to all MSs in certain areas. These areas may be one or several cells, or even the entire PLMN. The short messages from Cell Broadcast Centre (CBC) are managed and dispatched by the CDB of the BSC. And then BSC forwards the messages to BTS. Then, BTS broadcasts the messages to all the MSs in a scheduled interval.

The cell broadcast database (CDB) receives and stores the short messages from CBC. It dispatches and transmits the short messages, and responds to the query of CBC.

The cell broadcast function supports the MSs to use the DRX mode to receive the cell broadcast messages. The BSC needs to send the scheduling messages to support the DRX mode. MS can read concerned short messages in less time by reading the scheduling messages, thus minimizing power consumption.

The cell broadcast supports the flow control for the BTS.

The transmit sequence of the short messages in each cell is dispatched by CDB but are actually transmitted by BTS. Each TRX of BTS maintains one message buffer and sends the short broadcast messages periodically to MSs through the specified channel. When the BTS cannot send the messages out in time, it will report this asynchronous state to BSC in the form of load indication message.

By controlling the flow of the broadcast messages, CDB can balance the cell broadcast system to maximally satisfy the requirement of sending the broadcast messages.

Benefits:

With this function, the operators can promote the value-added services such as weather forecast, stock information, and traffic information to increase the revenues.



16 CS General Enhancement

16.1 Acoustic Echo Cancellation(AEC) Function Description:

Because of the manufacture structure of the MS, the sound wave from the speaker is reflected to the earpiece. And the MS sends the received voice signal back to the receiving party. The quality of the call between the calling party and the receiving party is affected. This kind of echo is called the acoustic echo. For the speaker and the earpiece of the MS is too close to each other, the MS produces much acoustic echo in the communication system.

The AEC (acoustic echo cancellation) module of the TC (transcoder) processes the current voice signal of the speaker of the MS besides MSC or the fixed-line phone. The TC keeps the main characters of the current voice signal. After a delay, the TC compares the main characters of the voice signal with that of the current voice signal from terminal. If codes of similar characters exist, the codes are nonlinearly treated. Therefore, the voice signal reflected to the earpiece is counteracted. And the acoustic echo is cancelled.

Benefits:

Cancel the acoustic echo which is produced because of the manufacture structure of the terminal. The voice quality is improved.

16.2 TFO Function Description:

In a traditional mobile network system which does not adopt the TFO, the voice signals are coded at the calling MS, and then transmitted to the initiatory TRAU for decoding through the radio interface. The decoded PCM dada stream is then transmitted to the terminal TRAU for coding through the 64 kbit/s transmission links, and then transmitted to the receiving MS for decoding through radio interface. The voice signals go through two times of coding and decoding operations. This process is called repeat coding and decoding operations.

The TFO is to solve the problem of voice signal loss in repeat coding and decoding operations in the traditional MS-MS calling process. When the calling MS and the receiving MS use the same voice coding scheme, the codec at the initiatory Radio Leg A and the terminal Radio Leg B are disabled. And voice signal are transparently transmitted between the calling MS and the receiving MS. In this case, the voice signal is coded at the calling MS for one time, and decoded at the receiving MS for one time. Repeat coding and decoding operations do not exist.

Support for the TFO function of AMR: GBSS8.1 supports the TFO function of AMR to improve the transmission quality of AMR.

Benefits:



The conversation quality is improved effectively for the repeat coding and decoding operations during a call from one MS to another MS is cancelled.

Dependency:

The path between the initiatory TRAU and the terminal TRAU must be transparent.

Both the TRAUs must support the TFO.

16.3 Voice Quality Index (VQI) Function Overview

The voice quality index (VQI) function provides a direct method to measure the voice quality of the radio network. The measurement of the uplink VQI values and downlink VQI values quantifies the voice quality of the network. The quantification provides the reference for future network optimization.

Benefits

l VQI quantifies the voice quality in the network and provides the reference for future network optimization, which facilitates the improvement of the network quality.

l VQI efficiently measures the voice quality in the network, facilitates the quick voice problem locating, and thus effectively reduces the operators’ O&M cost.


VQI establishes the mapping between the radio network performance and voice quality. The VQI value, which helps learn the voice quality, is calculated based on the radio quality parameters of the uplink voice and downlink voice. The VQI value calculation for the voice quality applies the MOS analysis method. MOS is used to assess the quality of the middle- and low-rate voice coding. The MOS value ranges from 1 to 5.

Based on the five-level MOS analysis method, Huawei further divides the voice quality level into 11 VQIs. The VQI value of the voice quality is obtained through the analysis of the BER, FER, LFE, and CODE of the uplink voice and downlink voice. The quantified voice quality facilitates the voice problem locating and network optimization.

16.4 Enhanced Measurement Report(EMR) Function Description:

The EMR is a new type of downlink measurement report introduced in R99. The EMR is reported to the network from an MS. In comparison with the MR, some measurement items such as BER and FER, are added to the EMR. Thus enhanced measurement can be provided for the serving cell and the performance of the power control and handover algorithm can be enhanced. Using the EMR, the MS can report the measurement results of more neighbor cells in a measurement report. A common MR can report the measurement results of a maximum of 6 GSM neighbor cells, but an EMR can report the measurement results of up to 15 neighbor cells. Thus the overall performance of the GSM system is enhanced. The EMR supports the measurement of the WCDMA/TD_SCDMA neighbor cells. Thus the interoperability between the GSM system and the WCDMA/TD_SCDMA system can be realized so that the requirement for service continuity is met.

Benefits:



The enhanced measurement can improve the monitoring capability on the speech quality, enhance the performance of the power control and handover algorithm, and serve as the basis for the interoperability between the GSM system and the WCDMA system and the TD-SCDMA system.

16.5 BTS power lift for handover Function Description:

When the level decreases quickly, handover is triggered. In this case, the power control algorithm may not adjust the power of an MS and a BTS in time, thus the MS cannot receive handover commands from the BTS. Thus call drops occur.

This function can quickly adjust the transmit power of the BTS to the maximum before the BTS sends a handover command to the MS; thus avoiding call drops caused by the fast decrease in the level.

Benefits:

This function has the following Benefits:

l Reducing the number of call drops caused by handover l Increasing the success rate of handover l Improving the quality of the received signals l Increasing the revenue of operators

16.6 Dynamic HR/FR Adaptation Function Description:

During call establishment, the network assigns a half-rate or a full-rate channel to the call based on the usage of the cell resources. For a long-duration call, the usage of the cell resource may change: During the call establishment phase, if the TCH seizure ratio is high, a half-rate channel is assigned to the call. After the call lasts for a period, many calls are released and the TCH seizure ratio decreases. In this case, TCHs in the cell are sufficient and a full-rate channel can be assigned to the call to improve voice quality. If the TCH seizure ratio is low during the call establishment phase, a full-rate TCH may be assigned to the call. After the call lasts for a period, many calls access the cell and the TCH seizure ratio increases. In this case, the available TCHs in the cell are insufficient.

If the dynamic adjustment between full-rate and half-rate channels is enabled, the half-rate/full-rate channels of established calls can be adjusted based on the usage of cell resources. When the TCHs in a cell are sufficient, full-rate channels are preferably assigned to new calls and calls with poor communication quality can be handed over from half-rate channels to full-rate channels, thus improving communication quality. When the TCHs in a cell are insufficient, half-rate channels are preferably assigned to new calls and calls with good communication quality may be handed over from full-rate channels to half-rate channels, thus expanding the cell capacity.

Benefits:

When the traffic volume in a cell is low, calls are handed over from half-rate channels to full-rate channels to improve the communication quality. When the TCHs in a cell are



insufficient, calls are handed over from full-rate channels to half-rate channels to expand the cell capacity.



17 AMR Package

17.1 AMR FR Function Description:

In an environment of some interference, better voice service quality can be provided if the system uses the AMR FR.

In the same environment, the voice service quality provided when the system uses the AMR FR is equal to or better than that when the system use the EFR.

The AMR is an integration of multiple voice coding and decoding rates. Different coding and decoding rates lead to different rates of voice code streams. The AMR enables the BTS and MS to select an appropriate coding and decoding algorithm, and to adjust the coding rate according to specific radio environment. Therefore, the voice service quality of the whole radio communication system is improved.

In an environment of much interference, better quality of voice service can be provided when the system uses the AMR FR than that when the system uses the EFR or FR. And the AMR FR is more robust, with better ability of anti-interface, and is more adaptive to the aggressive frequency reuse.

If the voice channel coding rate is higher, the more information of voice features is provided in the coded code stream, and the voice is more realistic, but the less redundancy information is in the code stream, and the anti-interference ability of code stream is poorer. In a hard communication environment, error code may occur and voice frames may be lost, and then voice maybe discontinued. If the voice channel coding rate is lower, the more redundancy information is in the coded code stream and the anti-interference ability and error correction ability of code stream is stronger. Then, the voice is more continued.

The AMR FR provides a code rates selection, as shown below.



Table 17-1 Code rates selection

Channel Coding Rate

12.2 kbit/s

10.2 kbit/s

7.95 kbit/s

7.40 kbit/s

6.70 kbit/s

5.90 kbit/s

5.15 kbit/s

TCH/AFS

4.75 kbit/s

Benefits:

l Increase the bearable system capacity l Enhance the anti-interference ability. l Adapt to the aggressive frequency reuse. l Improve the network index in an increasing complex radio environment when combining

with the frequency hopping technology. l Provide a better quality of voice service.

17.2 AMR HR Function Description:

In an environment of some interference, better voice service quality can be provided if the system use the AMR HR.

In the same environment, the voice service quality provided when the system uses the AMR HR is equal to or better than that when the system uses the HR.

To use the AMR HR function, you must enable the HR function in the system.

For better voice quality can be provide when the system use the AMR in an environment of some interference, the AMR HR can be used extensively to enhance the system capacity. When much interference exists and the voice service quality is worse, the system automatically switches to the AMR FR in real-time. And the service quality and system capacity are balanced in real-time. The system can provide good voice service quality to subscribers when the system capacity is extended.

The AMR HR provides a selection for coding rates, as shown below.



Channel Coding Rate

7.95 kbit/s

7.40 kbit/s

6.70 kbit/s

5.90 kbit/s

5.15 kbit/s

TCH/AHS

4.75 kbit/s

Benefits:

l Increase the bearable system capacity l Enhance the anti-interference ability. l Adapt the aggressive frequency reuse. l Improve the network index in an increasing complex radio environment when combining

with the frequency hopping technology. l Provide a better quality of voice service.

17.3 AMR Power Control Function Description:

This function provides different power control modes for different AMR modes.

Better anti-interference ability, larger network capacity, and better voice quality can be provided.

The AMR voice codec can select one of the coding rates according to the radio channel quality, to achieve an optimized combination of voice coding rate and channel coding rate. The AMR voice codec can provide the best voice quality under the current radio environment and can meet the communication requirement in all kinds of radio environment.

More redundancy information in the coded AMR code stream provides stronger anti-interference and error correction ability. And the voice continuity is improved.

The system automatically decides whether to adopt the AMR. If the system uses the AMR, the power controls strategy for the AMR calling is different from that for the None-AMR calling. Therefore, the network interference is reduced, the BTS transmission power is saved, and the standby time of MS is longer.

Benefits:

l The transmission power is reduced; l The MS has a longer standby time. l The network interference is reduced. l The frequency usage is increased. l The network service quality is better.



17.4 AMR FR/HR Dynamic Adjustment Function Description:

Through the dynamical switching of AMR HR and AMR FR, the cell capacity and the voice service quality are balanced. To use the AMR HR/FR dynamic switching function, you must enable the HR and AMR HR function first.

When the BSS completes the initial voice coding after setting up a call, the BSS calculates the RQI (radio quality index) according to the uplink signal quality measured by the BTS. According to the uplink quality, the code sets activated by the BSC, and the corresponding threshold, the system decides the coding and decoding manner of the uplink. And then, the BSS dynamically adjusts the voice coding rate of the uplink, and asks the MS to use the selected voice coding rate of uplink. According to the RQI and network capacity parameters, the BSS decides whether to enable the HR/FR channel switching in the cell, in order to balance the voice service quality and the cell capacity.

The dynamic HR/FR switching in different radio environments and different capacity configurations helps to balance the voice service quality and the cell capacity.

Benefits:

Less maintenance work is required. For the system can do automatically adjustment according to the environment.

Network capacity is increased, and the voice service quality is not degraded.

The income can be raised and operation cost can be cut for the operators.

17.5 AMR Wireless Link Timer Function Description:

The wireless link timer is used to detect the quality of a wireless link. When the timer expires due to poor wireless link quality, the system deactivates the wireless channel, and interrupts the conversation. The timer can improve channel utilization efficiency, and prevent channels with poor quality from occupying wireless channel resources.

This function provides a special wireless link timer for AMR calls. AMR calls enjoy higher robustness than common calls. When a common call fails due to poor link quality, the AMR voice service can maintain good conversation quality. If the wireless link timer of the AMR call and that of a common call adopt the same settings, the chance of AMR call drop increases and the conversation quality deteriorates. By adopting a maximum value for the AMR wireless link timer, you can make the AMR call endure the worst environment and reduce the call drop rate.

You can configure the wireless link timers for the AMR HR and the AMR FR separately.

Benefits:

You can prolong the conversation of AMR voice service, reduce the call drop rate, and improve the benefits of the operator by setting the wireless link timer of AMR voice service and that of non-AMR voice service separately, because the AMR voice service has strong anti-interference capability.



17.6 AMR Coding Rate Threshold Adaptive Adjustment Function Overview

Through the settings of the target speech quality and the real-time speech quality monitoring, adjust the coding rate adjustment threshold so that the AMR speech can select the appropriate coding rate and the speech quality can approach the target speech quality.

Benefits

The appropriate coding rate can be selected for the AMR speech to guarantee the performance of the AMR speech service.

Function Description

The AMR speech rate set consists of multiple coding rates. Based on the measurement of the receive level, receive quality, and carrier-to-interference ratio, the BTS and MS adjust the AMR call control parameters by using the algorithm to select a speech source coding rate that suits the existing radio environment. The appropriate selection helps obtain an optimal combination of the channel quality and speech coding rate, and improve the speech quality to the greatest extent in the existing radio environment.

Generally, the AMR speech coding rate adjustment threshold is set to a fixed value based on the network planning engineers’ assessment of the radio channel quality. If the radio channel quality changes or the network planning engineers’ assessment of the radio channel quality is inaccurate, the AMR speech will fail to select the appropriate coding rate. The AMR speech quality is then affected.

The adaptive adjustment of AMR rate threshold function adjusts the coding rate adjustment threshold based on the settings of the target speech quality and the real-time speech quality monitoring, so that the appropriate coding rate can be selected for the AMR speech to guarantee the performance of the AMR speech service.



18 PS QoS

18.1 Streaming QoS(GBR) Function Description:

Providing Streaming QoS (GBR) to support streaming and PoC service Streaming Media and PoC Service.

This function improves the radio resource allocation policy of the system:

1) For the MS supporting GBR, the resources are allocated according to the bandwidth negotiated by the network and the MS.

2) For the MS that does not support GBR, the resources are allocated in the BEST EFFORT mode.

It works with the SGSN and the MS to establish, modify and delete the PFC, and provides the function for querying specific MSPFC. (This function requires that both the MS and the SGSN support the PFM/PFC procedure, and the license at the PCU side is required).

According to the radio environment of the air interface, the air interface resources are dynamically allocated to the MS to ensure that the bandwidth is not less than the GBR. When the air interface resources are insufficient, the system notifies the SGSN.

If the BSC/PCU cannot offer sufficient transmission resources for the streaming user with high priority, the transmission resources of the streaming user with low priority will be preempted. If the transmission resources of other streaming users cannot be preempted, the streaming user waits in the queue for the release of transmission resources. If the wait time expires, the access of the streaming user fails because of insufficient resources. This function enhancement ensures that the streaming users with high priority use the transmission resources preferentially. This can reduce access failures due to insufficient resources and improve the experience of the streaming users with high priority.

18.2 QoS ARP&THP Function Description:

If the PFM(Packet Flow Management) procedure is activated, the PCU can obtain the PFC(Packet Flow Context) correctly. When the user service type is interactive, the PCU handles the service requests issued by the MS according to the priority (1, 2, or 3) defined in the ARP(Allocation/Retention Priority) if the ARP field exists. If the THP(Traffic handle Priority) conditions are met at the same time, values are assigned to the blocks on the assigned channels based on the ARP and the THP.

If the THP field does not exist but the service type is interactive and the ARP is valid, the PCU handles the service requests issued by the MS according to the priority defined in the ARP. The value of the ARP can be 1, 2, or 3.



For other cases different from the previous two cases, the PCU handles the service requests issued by the MS according to the best effort process.

Benefits:

Through the function, the operator can configure the QoS data in the HLR for every subscriber according to the subscriber’s requirements on upload/download speed. As a result, the subscriber with higher requirements on data service can occupy more bandwidth and enjoy higher download speed and better quality of service. The function is applicable to the GPRS and EGPRS data subscribers.

The function possesses the following advantages:

l High-end subscribers can enjoy higher download speed, while low-end subscribers are subject to speed restriction.

l The operator can set more flexible charging policies. l The network resources can be put into full play.

18.3 PS Active Queue Management Function Overview

When the PS Active Queue Management function is enabled, the real-time status of the network is monitored. Once the network is congested, the system drops the data packets proactively and TCP sending end adjusts the sending rate to maintain the buffer queue at a certain length to ease the congestion.

Benefits

l The PS Active Queue Management function is applicable to scenarios where congestion may occur because of bandwidth limitation. This function helps maintain high utilization of the bandwidth, shorten the delay of the packet service, and enhance the fairness of the bandwidth sharing among the data flows.

l The PS Active Queue Management function improves the packet service performance. For example, when large files are involved in the packet service of the MS subscriber, such as FTP downloading and Email sending, this function shortens the service delay and thus improves the user experience.


In GSM, the packet service uses TCP/IP in most cases. When multiple connections co-exist, the strong connection in a system may result in long transmission time over the weak connection in the system. For example, there may be an FTP downloading task, which is followed by an HTTP request. In such a case, most of the original link resources may be occupied by the FTP task, and thus the system takes an excessively long time to process the HTTP request.

The PS Active Queue Management function provides active queue management and real-time monitoring of the buffer queue to monitor the network congestion. Once the network is congested, the system drops the data packets proactively and adjusts the sending rate at the TCP sending end to maintain the buffer queue at a certain length to ease the congestion. Compared to the reactive queue management (a technique which drops the overflowed packets only when the queue is full), the PS Active Queue Management function eases the



network congestion caused by the TCP data flow, and thus improves the service throughput and shortens the service delay.

The PS Active Queue Management function performs queue management for only interactive services, background services, and services that do not support the QoS. The queue management is not performed for real-time services, such as conversational services and streaming services.



19 Cell Reselection of PS Domain

19.1 Intra BSC Network Assisted Cell Change (NACC) Function Description:

Network Assisted Cell Change (NACC) means that the network notifies the MS about the neighboring cell information in advance to fast the cell reselection speed. Thus, the time of data transmission interruption due to cell reselection is reduced.

NACC is a function introduced in the Release 4 protocols. It supports the MS:

l To notify the network side when the MS decides to implement cell reselection l To delay the cell reselection to let the network side to send the neighboring cell

information message

NACC does not control the MS to implement the cell reselection while it can assist the MS to implement the cell reselection. It fasts the cell reselection.

Support for resource reservation in the target cell: When the network receives the cell reselection decision of the MS, it reserves the required radio resources in the target cell to ensure that the MS can obtain sufficient resources for service recovery after reselection.

Support for NACC between BSCs or between BSC and RNC: This application enhancement can reduce the delay of cell reselection between BSCs or between the BSC and the RNC. It requires the BSC to support the RIM procedure to obtain the system information of the external cell. During cell reselection, if the BSC has the system information of the external cell, it sends the system information to the MS. Otherwise, the BSC initiates the RIM procedure to request the system information and save the system information for future use.

Benefits:

The time of data transmission interruption due to cell reselection is reduced, thus improving the user satisfaction. The system transmission bandwidth is reduced because the system information is obtained in the original cell as possible as it can be.



20 GPRS/EGPRS Service

20.1 GPRS Function Description:

Huawei GPRS system is evolved from the GSM system by adding GPRS Support Node (GSN) and Packet Control Unit (PCU) and upgrading the software.

GPRS provides data service for the moving subscribers. The Huawei PCU is external. It connects to BSC through Pb interface.

GPRS uses open structure, and can implement smooth upgrade. The standard interfaces ensure the compatibility of the equipment.

GPRS supports QoS and dynamic allocation of radio resources. At the same time, the flexible networking and configuration can save large amount of investment cost for the operators.

M900/M1800 GPRS provides rich packet services, such as,

l Mobile Internet access l E-commerce, including e-bank, e-currency l Group management l remote control/test l Service reservation system, such as, hotel, theater, flight reservation l Services base on group-call, such as, stock information broadcasting l The BSS GPRS mainly has the following three functions: l Radio link management l Radio resource management l Providing route for the packet data

The GPRS radio link management function includes setting up, maintaining and releasing the radio link.

The radio resource management function includes coding/decoding, configuring, multiplexing the radio packet channel, switchover between the circuit traffic channel and the packet traffic channel, controlling the access of the MSs to solve the channel contention, assigning channel for MSs according to the requested QoS.

The GPRS system also provides routing function to transmit the packet data to the SGSN and receives the downlink data from SGSN as well.

Huawei GPRS supports the following functions:

l Sending packet system information l A/B/C three GPRS terminal modes l Radio Link Control (RLC) acknowledged mode and non-acknowledged mode



l CS1/CS2/CS3/CS4 four coding schemes l NC0 Network control mode l Network operating mode I, Network operating mode II, and Network operating mode III l QoS, assignment, paging, flow control l Dynamic conversion between TCH and PDCH l Packet access

20.2 CS-3/CS-4 Function Description:

Support CS-3 and CS-4 coding scheme without the need of hardware upgrade.

Benefits:

l Adopts CS3/CS4, and improves the GPRS service rate. l Improves the packet service performance for areas where the EGPRS is not supported. l Improves the satisfaction of subscribers.

20.3 EGPRS Function Description:

The Enhanced Data Rate for GSM Evolution (EDGE) is the evolution of the GSM. It greatly improves the data rate of the GSM. EDGE includes a set of enhancement standards for the GSM interface. It enables the GSM network to bear the 3G services.

EDGE includes EGPRS and ECSD. The EGPRS is an enhancement of the current GPRS system. It improves the rate of the data channel.

EGPRS improves the transmission capability of the single timeslot through adding the 8PSK modulation on the Um interface. It bundles multiple timeslot to improve the transmission capability of a single user.

Huawei EGPRS has the following features:

MCS1–MCS9

Huawei support all nine code schemes for EGPRS, in both uplink and downlink directions. See below for details.

Table 20-1 Code schemes for EGPRS

Scheme

Code rate (Note 2)

Header Code rate

Modulation

RLC blocks per Radio Block

Raw Data within one Radio Block (Note 1)

Family

BCS

Tail payload

HCS

Data rate per PDCH kb/s

MCS-9 1.0 0.36 2 2x592 A 2x 2x6 59.2



Scheme

Code rate (Note 2)

Header Code rate

Modulation

RLC blocks per Radio Block

Raw Data within one Radio Block (Note 1)

Family

BCS

Tail payload

HCS

Data rate per PDCH kb/s

MCS-8 0.92 (0.98)

0.36 2 2x544 A 54.4

MCS-7 0.76 (0.81)

0.36 2 2x448 B

12

44.8

MCS-6 0.49 (0.52)

1/3 1 592 48+544

A 29.6 27.2

MCS-5 0.37 (0.40)

1/3

8PSK

1 448 B 22.4

MCS-4 1.0 0.53 1 352 C 17.6

MCS-3 0.85 (0.96)

0.53 1 296 48+248 and 296

A 14.8 13.6

MCS-2 0.66 (0.75)

0.53 1 224 B 11.2

MCS-1 0.53 (0.60)

0.53

GMSK

1 176 C

12

6

8

8.8

NOTE: the italic captions indicate the padding.

Incremental redundancy and link adaptation

EGPRS adopts two link quality control methods: Link Adaptation (LA) and Incremental Redundancy (IR).

The incremental redundancy uses software bit combination to increase the data rate.

It initially uses a coding with very less error protection. When information is received incorrectly, additional coding is transmitted and then soft combined in the receiver with the previously received information. Soft-combining increases the probability of decoding the information. This procedure will be repeated until the information is successfully decoded.

Huawei support incremental redundancy both for downlink and uplink directions.

EGPRS code scheme dynamic adjustment

This is a link adaptation mode similar to standard GPRS. The system can dynamically adjust the EGPRS code scheme basing on BEP report from the mobile and BLER information, in order to achieve the best transmission result.

Dynamical additional sub-timeslot

The dynamic additional sub-timeslot technology can well solve the transmission of the CS-3 and CS-4 on the G-Abis interface.

The dynamic additional sub-timeslot technology is to assign a static 16 kbit/s sub-timeslot and a dynamic 16 kbit/s sub-timeslot on the G-Abis interface for each PDCH using CS-3 or CS-4.



EGPRS BSS can support the MCS3–MCS9 without upgrading the hardware of BTS, BSC, and PCU. At the same time, the multiplexing of the G-Abis interface is maximally improved. Thus, the investment on the G-Abis interface transmission equipment is saved.

The assignment strategies of 16 kbit/s sub-timeslot are shown below:

Table 20-2 Number of 16 kbit/s timeslot on the Abis interface

Coding scheme Assigned 16 kbit/s timeslot on Abis interface

MCS1–MCS 2 1

MCS3–MCS 6 2

MCS7 3

MCS8–MCS 9 4

In PS domain, the transmission resources on the Abis interface are allocated based on 16 kbit/s sub-timeslot. A main timeslot is allocated to the PDCH, and then additional timeslots are allocated in steps of 16 kbit/s based on the required coding rate on the Um interface. Huawei adopts 16 kbit/s as the unit so that bandwidth usage is greatly improved and bandwidth is saved as much as possible.

The EGPRS capable MS and GPRS capable MS can be multiplexed onto the same EDGE PDCH. The EGPRS MS uses the MCS coding scheme, and the GPRS MS uses the CS coding scheme.

Benefits:

The operator can use the current frequency spectrum to provide high-speed packet service, thus increasing the revenue.



21 EGPRS Service Enhancement

21.1 Packet Channel Dispatching Function Description:

If the EGPRS/GPRS services are activated, the function supports multiple packet channel priority levels so that the operators can implement diversified strategies for the operation of data services.

The following table lists the types of the GPRS/EGPRS channels:

SN Type of Preferred Channel

Definition Remarks

1 GPRS channel For the GPRS service only

2 Common EGPRS channel

For the GPRS and EGPRS services The EGPRS and GPRS services have the same priority. You can use the switch to control whether the EGPRS downlink and the GPRS uplink can multiplex the PDCH simultaneously.

3 EGPRS preferred channel

The channel is preferentially used by the EGPRS service. When the channel is completely idle, the GPRS service can use it. If the EGPRS service, however, needs to seize the channel, the GPRS service should release the channel. (The EGPRS and GPRS services cannot multiplex the EGPRS preferred channel.)

The EGPRS service has a higher priority than the GPRS service. The throughput of data services can be increased.

4 EGPRS dedicated channel

For the EGPRS service only Timeslot-level dedicated channels are supported. The EGPRS user rate is guaranteed. The EGPRS dedicated channel is especially suitable for the important applications such as service presentation hall, Olympic stadiums, and high-end office buildings.

The EGPRS dedicated channels can be configured into static channels only. The other three preferred channels can be configured into static channels or dynamic channels.

The BSC6000 allows the GPRS and the EGPRS to use different channel dispatching policies.



When the system allocates PDCHs:

For the GPRS services, the precedence order of channel assignment is as follows: GPRS channel > EGPRS normal channel > EGPRS priority channel.

For the EGPRS services, the precedence order of channel assignment is as follows: EGPRS special channel > EGPRS priority channel > EGPRS normal channel.

It is prohibited that the GPRS end users use uplink channels and the EGPRS end users use the downlink channels.

The co-timeslot of the EGPRS and the GPRS can occur on only common EGPRS channels. The system can prevent the EGPRS downlink and the GPRS uplink from multiplexing the same PDCH by setting "whether the system allows the EGPRS downlink and the GPRS uplink to multiplex the same channel". If you want to eliminate the possibility of EDGE/GPRS co-timeslot, do not configure EGPRS normal channels.

Benefits:

By adding service channel types, the function can satisfy the operator’s requirements for defining various policies to increase operation revenues.

The lower multiplexing rate of EGPRS services and GPRS services helps improve the EGPRS service rate so that overall network performance is improved and customer experience is enhanced.

21.2 Load Sharing Function Description:

The BSC6000 supports load sharing. If the loads over channels are imbalanced because of the establishment or release of the TBF, the MSs that are carried on the channels with heavy load can be migrated to the channels with light load. In this way, load sharing is realized and the single-user rate increases.

When an MS accesses, the system can adjust the load distribution between TRXs according to the distributed loads on these TRXs.

When an MS releases channels, the system can adjust the load distribution between TRXs according to the distributed loads on these TRXs. For example, an MS performs data transmission for a long time. During the data transmission, if radio resources are released by other MSs, the network determines whether the TRX used by the MSs that release radio resources is idle. If the TRX is idle, the MS performing long-time data transmission is reassigned the channels on the idle TRX. Thus, the throughput of the MS is increased.

In addition, when radio resources are released, the load of the GPRS channels is also taken into consideration. If the load decreases, some GPRS calls are transferred from EGPRS channels to GPRS channels. Therefore, the channel usage is improved and the impact on EGPRS services is reduced.

Benefits:

This function improves the channel usage and the service rate.



22 High Speed Data Service

22.1 EDA(Extended Dynamic Allocation) Function Description:

With the widespread application of PS domain, the customer becomes concerned about the bandwidth of the uplink. For the GPRS and EGPRS services, the bandwidth of the downlink is generally wider than that of the uplink. However, there are exceptions. For example, an Email of larger size is transmitted through GPRS/EGPRS. In this situation, the requirement for the bandwidth of the uplink is high. The EDA function can enable an MS to be assigned with four timeslots on the uplink so that the high requirement for the bandwidth of the uplink can be met.

The function is based on the uplink dynamic allocation. The BSC assigns multiple uplink timeslots for the MS. The MS listens to all the assigned PDCHs. When the MS hears the USF that is assigned to it on the assigned PDCH, the MS can use the uplink block corresponding to this PDCH and the uplink block corresponding to the PDCH that is assigned with a greater timeslot number. If the MS can transmit uplink blocks, it need not listen to the following assigned channels. Therefore, the MS can use more uplink channels than those in the case of uplink dynamic allocation.

The uplink extended dynamic allocation needs the support from the MS. The MS will indicate whether it supports GPRS uplink extended dynamic allocation and EGPRS uplink extended dynamic allocation through the message containing the information about radio access capability.

Benefits:

l Helps to improve the uplink rate. l Realizes the transmission of large data traffic on the uplink. l Improves the subscriber’s satisfaction.

22.2 DTM Function Overview

The dual transfer mode (DTM) function allows simultaneous transfer of CS service and PS service. That is, a subscriber can send photos and browse websites while having a call. The 3G network provides concurrent CS service and PS service. With the DTM function, a GSM network can provide its subscribers with services similar as that provided in a 3G network. In addition, in areas with insufficient 3G coverage, subscribers can access the services that are similar to 3G services through the 2G network by using the DTM function.

Benefits



l The DTM function supports simultaneous processing of the CS service and PS service. The PS service can be used without interrupting the CS service.

l DTM allows the implementation of concurrent CS service and PS service in a 2G network. The concurrent CS service and PS service is originally available only in a 3G network.

l The DTM function is the foundation for the concurrent CS service and PS service. For example, the Class11 DTM function and HMC DTM function are both based on the DTM function.

With the development of time, the new point of profit growth shifts to the data service. The concurrent CS service and PS service becomes the new requirement. Without the DTM function, only the class A mobile phone with complex hardware supports the concurrent CS service and PS service. Due to the complexity of the class A mobile phone, few manufacturers provide such mobile phones. With the DTM function, the class B mobile phone can support the concurrent CS service and PS service, which lays the foundation for wide application of data services. With the interaction between the CS service and PS service and the multimedia services provided by the operators, the call duration prolongs and a large amount of data traffic is generated. This can bring the operators considerable revenue increase.


DTM is a 3GPP-defined standard function. DTM implements the simplified class A mobile phone operation, that is, the concurrent CS service and PS service. In DTM mode, the CS resource (TCH) and PS resource (PDCH) are allocated to the mobile phone simultaneously. According to the multislot capability of the mobile phone, different number of channels can be allocated to the MS in the uplink and downlink to meet the requirement for different bandwidth. DTM supports MS multislot class 5 and all higher classes. According to the MS multislot capability, a maximum of two channels can be allocated to the MS in the uplink or downlink with one channel for CS service and the other for PS service.

The DTM function must be enabled along with the A interface collaboration paging function. In such a case, the mobile phone is able to accept the paging request of the CS domain from the A interface while engaging in the PS service. When DTM is enabled in a cell, the BSC that serves the cell supports the A interface collaboration paging function.

For an MS supporting DTM, when the MS initiates a location update request in CS mode, the CS channel (FACCH or SDCCH) can be used for the location update and no separate PDCH is required. This saves the PS channel resources.

In DTM mode, the MS can establish a PS connection only after a CS connection is established. If an MS engaged in the PS service needs to switch to DTM mode, the TBF must be released first; after that, the MS switches to CS mode and establishes a TBF connection; at this time, the MS can work in DTM mode. The following figure illustrates the state transition in DTM mode.



22.3 14.4Kbps Circuit Switched Data Function Overview

The GBSS equipment supports the transfer of PS services on individual speech channels and on the 14.4 Kbps CS circuits.

Benefits

Compared with common CS-based PS services, this function provides PS services with higher bandwidth.

Function Description

Huawei GBSS equipment supports various bearer services defined in the protocols. The BSS provides lower-layer connections and transparently transmits the service data to the upper layer instead of processing these services. Huawei BSS supports the transfer of the PS services on individual speech channels and on the 14.4 Kbps circuits.



23 VIP Service Support

23.1 Enhanced Multi Level Precedence and Preemption(EMLPP)


Enhanced Multi-Level Precedence and Pre-emption (eMLPP) allows a user to initiate calls with different priorities. The network side takes different channel assignment strategies for the users according to the priorities. If the network is congested, the cal with higher priority is served preferably.

The eMLPP function needs the support of MS to ensure that the user can initiate calls with different priorities under different situation. The normal conversation of the users with higher priority is ensured by preemption, queue, directed retry, and forced handover.

Preemption: MSC determines whether the preemption is allowed. MSC sends the assignment request or handover request to the BSC to notify it whether the preemption is allowed. If the preemption is allowed and the BSC enables the eMLPP function, BSC hands over the call with the lowest priority to its neighboring cell through forced handover. The release resources are assigned to the call with higher priority. If the eMLPP function of BSC is disabled, BSC directly releases the resource of the users with lower priority to ensure the call of the users with higher priority.

Directed retry: BSC determines whether the directed retry is allowed. When the cell has no idle traffic channel and the cell allows directed retry, the call is handed over from SDCCH to the TCH of the neighboring cell.

Queue: MSC determines whether the queue is allowed. MSC sends the assignment request or handover request message to the BSC to notify it whether queue is allowed.

When the cell has no idle traffic channel and the MSC allows queue, BSC places the TCH request into the queue, when there are idle TCHs, the TCH is assigned to the waiting call in the queue.

The eMLPP function can improve the network capacity and improves the satisfaction of the user in busy hour. It is a supplementary of the load sharing solution.

Benefits:

This function can provide different classes of services for the users with different priorities. It improves the QoS for the high end users and improves the satisfaction of the users.

Dependency:

This function needs the support of CN, HLR, and MS.



24 Gb IP

24.1 Gb over IP Function Description:

The Gb over IP function enables the operators to create IP transmission between the PCU and the SGSN and to increase transmission modes. Thus the operators can fully utilize the characteristics of IP transmission and save the transmission cost.

The function can simultaneously support two end-to-end communication modes between the PCU and the SGSN: frame relay (FR) and IP network. The NS module chooses different uplink and downlink handling processes based on transmission modes. The FR uplink and downlink handling process is performed according to the existing implementation mode. For the network transmission mode, the uplink and downlink handling process of the IP network is used.

With the growth of the packet data services, the requirement for the Gb bandwidth increases. The function enables the IP header to be compressed and the data over the Gb interface to share the transmission bandwidth. Thus the transmission efficiency is enhanced and the transmission cost is reduced. After the characteristics of the function are used, the Gb interface maintenance commands of the system become simple, the maintenance process is simplified, and the fault location and troubleshooting methods are diversified.

Benefits:

l Reduces the cost of network investment. l Adopts IP transmission to simplify the network maintenance, and reduce operation cost

and maintenance expense. l Adopts IP transmission to increase the bandwidth over the Gb interface. As a result, the

Gb interface no longer restricts the subscriber’s bit rate. l Facilitates the provisioning of the SGSN pool function.

61105273 GBSS BSC6000 Feature Description

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Transcript of 61105273 GBSS BSC6000 Feature Description