HSUPA TechnologyContents

11 Architecture of the HSUPA

32 Basic Principle of the HSUPA

32.1 Physical Channels Introduced to the HSUPA

32.1.1 Introduction to the E-DPDCH (E-DCH Dedicated Physical Data Channel)

42.1.2 Introduction to E-DPCCH Channel (E-DCH Dedicated Physical Control Channel)

52.1.3 Introduction to the E-AGCH Channel (E-DCH Absolute Grant Channel)

62.1.4 Introduction to E-RGCH (E-DCH Relative Grant Channel)

72.1.5 Introduction to E-HICH (E-DCH HARQ Acknowledge Indication Channel)

72.2 Basic Principles of the HSUPA

133 Basic Functions of the HSUPA

133.1 HSUPA Common Carrier with R99

133.2 HSUPA Dedicated Carrier

143.3 HSUPA cell indicator in idle mode

143.4 HSUPA UE Category Support

143.5 HSUPA 2ms TTI

153.6 HSUPA HARQ

153.7 PS Interactive/Background Service over HSUPA

163.8 PS Streaming Service over HSUPA

163.9 RAB Combination for CS over DCH and PS over HSUPA

174 HSUPA Mobility Management

174.1 E-DCH Serving Cell Change

194.2 Switching between E-DCH and DCH

235 Key Calculations and Algorithms in Node B

235.1 Introduction to HARQ

255.2 HSUPA E-AGCH CLPC

275.3 HSUPA E-RGCH/HICH CLPC

1 Architecture of the HSUPA

HSUPA is the enhanced uplink technology of the WCDMA. In system architecture, the HSUPA differs from the R99/R4 in which it adds two new MAC entities. That is, it introduces MAC-e to the Node B and MAC-es to the SRNC. Figure 1-1 shows the architecture of the HSUPA protocol.

Figure 1-1 Architecture of the HSUPA protocol

From the architecture of Figure 1-1, you can find that the HSUPA differs from the R99/R4 in which the MAC-e and MAC-es have been introduced to the Node B and SRNC respectively. The MAC-e entity of the Node B is mainly responsible for HARQ retransmission, scheduling, and demultiplexing of MAC-e; the MAC-es entity of the SRNC is mainly responsible for re-ordering and the macro diversity combination.

2 Basic Principle of the HSUPA

2.1 Physical Channels Introduced to the HSUPA

To realize the functions and attributes of HSUPA, 3GPP R6 introduces five new physical channels to the physical layer: In the uplink, it adds a dedicated data channel E-DPDCH (up to 4 E-DPDCHs for each UE) and a dedicated control channel E-DPCCH for the UEs especially; in the downlink, it adds the common physical channels E-HICH, E-AGCH, and E-RGCH.

The E-DPDCH is an uplink physical channel for carrying the E-DCH data especially;

The E-DPCCH is an uplink control channel for carrying the E-DCH control information especially;

The E-AGCH is a downlink common physical channel for carrying the E-DCH absolute grant data;

The E-RGCH is a downlink physical channel for carrying the E-DCH relative grant data especially;

The E-HICH is a downlink physical channel for carrying the E-DCH HARQ acknowledgement indications;

2.1.1 Introduction to the E-DPDCH (E-DCH Dedicated Physical Data Channel)

E-DPDCH is used to carry uplink data and its spreading factor ranges from 2 to 256. The spread factor is in reverse proportion to the carried traffic volume. The modulation mode of E-DPDCH is BPSK. Similar to HSDPA, the channel also introduces 2ms TTI while reserving 10ms TTI. Figure 2-1 shows the structure of the E-DPDCH channel.

Figure 2-1 Structure of the E-DPDCH

When the spreading factor is 2 or 4, the E-DPDCH supports multi-code transmission. When adopting multi-code transmission, the E-DPDCH supports the maximum configuration of 2SF2 + 2SF4. Table 2-1 Timeslot format of E-DPDCH channel

2.1.2 Introduction to E-DPCCH Channel (E-DCH Dedicated Physical Control Channel)

Figure 2-2 shows the structure of the E-DPCCH channel. The E-DPCCH channel is used to carry the control information of the E-DCH.

E-TFCI: the transmission format combination indicator of the E-DCH channel (7bit)

RSN: HARQ retransmission sequence number (2bit)

Happy Bit: scheduling feedback bit from the UE (1bit)

Figure 2-2 Structure of E-DPCCH channel

The E-DPCCH adopts the spreading factor of 256 invariably. The modulation mode is BPSK. Similar to the E-DPDCH, the E-DPCCH supports 2ms TTI and reserves 10ms TTI.

2.1.3 Introduction to the E-AGCH Channel (E-DCH Absolute Grant Channel)

E-AGCH is a downlink common physical channel for carrying E-DCH absolute grant information. The channel only exists in the serving cells of E-DCH. Figure 2-3 shows the structure of the E-AGCH channel.

Figure 2-3 Structure of E-AGCH

E-AGCH adopts a spreading factor of 256 invariably and the modulation mode of BPSK. The absolute grant information consists of a grant value (5 bits) and process activation indicator (1 bit). The process activation indication bit is used to indicate whether the absolute grant targets at a specific HARQ process or all HARQ processes.

2.1.4 Introduction to E-RGCH (E-DCH Relative Grant Channel)

E-RGCH is a downlink physical channel for carrying E-DCH relative grant information. Figure 2-4 shows the frame structure of the E-RGCH.

Figure 2-4 Structure of E-RGCH channel

E-RGCH adopts a spreading factor of 128 and the modulation of QPSK invariably. The E-RGCH channel sends an absolute grant for every 3, 12, or 15 consecutive timeslots and sends 40 three-state-value sequences for every slot. The channels are divided into two types: E-RGCH in the serving cell and E-RGCH in the non-serving cell. E-RGCH in the serving cell can carry instructions (UP, HOLD, and DOWN) of increasing, keeping, and decreasing the power of a UE. E-RGCH in the non-serving cell is used to carry cell payload indication information and instructions of keeping and decreasing the power of a UE. The UE can receive relative grant information from serving cells and non-serving cells and combine the received grant information.

The setting of TTI decides the mode in which the E-RGCH relative grant information is sent.

When TTI is 2 ms, the relative grant information from the serving cell is sent once every 2 ms.

When TTI is 10 ms, the relative grant information from the serving cell must be sent within 12 timeslots, that is, the relative grant instruction is sent once every 8 ms.

The relative grant information from the non-serving cell must be sent within 15 timeslots, that is, the relative grant instruction is sent once every 10 ms.

2.1.5 Introduction to E-HICH (E-DCH HARQ Acknowledge Indication Channel)

E-HICH channel is a downlink physical channel carrying HARQ confirmation indication (ACK and NACK). An HARQ confirmation indication is carried over 3 or 12 consecutive timeslots corresponding to TTI of 2ms or 10ms respectively.. In RLS containing serving cells, the HARQ confirmation indication value is 1 (ACK) or -1 (NACK); in RLS with non-service E-DCH, the HARQ acknowledge indication value is 1 (ACK) or 0 (NACK).

E-HICH adopts the spreading factor of 128 and the modulation of QPSK invariably and has the same structure as the E-RGCH. If an E-RGCH channel and an E-HICH channel target at the same UE, they share the same spreading factor of 128. They are distinguished from each other through different signature sequences.

2.2 Basic Principles of the HSUPA

During the working process of HSUPA, UE first sends scheduling messages to the Node B over the E-DPDCH channel. The parameters PeriodSIG, PeriodSING are configured to UE for sending period of scheduling messages. The scheduling message includes 4-bit-long high priority logic channel ID, 9-bit-long UE buffer occupancy status (including 5-bit-long Total E-DCH Buffer Status, namely TEBS, and 4-bit-long Highest priority Logical channel Buffer Status, namely HLBS), 5-bits-long UE power status, and the scheduling request of the Happy bit carried over the E-DPCCH for requesting the Node B to distribute resources. The parameter HappyBitDelCond is configured to UE for reporting delay of the Happy bit.

The serving Node B decides the scheduling grant according to the QoS information and scheduling request information of the UE. The scheduling grant has the following attributes:

The scheduling grant is limited to the selection of E-DCH TFC and is not used in the selection of DCH TFC;

The scheduling grant controls the maximum E-DPDCH/DPCCH power ratio of the activating process. In case of non-activating process, the power ratio is 0 and the UE is prohibited to send data;

All grants are certain and the scheduling grant can be sent at the interval of TTI or lower frequency.

The scheduling grant sent by the Node B can be divided into two categories: absolute grant and relative grant. The former is the absolute limitation on the maximum resources available to the UE; the later increases or reduces the value of the previous grant. The absolute grant is sent by the serving cell of the serving E-DCH and is effective to a UE, a group of UEs, or all UEs. The relative grant (updating) is sent by the serving Node B or non-serving Node B as the supplement of the absolute grant. The scheduling mechanism controlled by the Node B can swiftly control the Raise over Thermal (RoT).

The UE can select Retransmission Sequence Number (RSN), HARQ RV version, and the power difference between E-DPDCH and E-DPCCH according to the scheduling information (consisting of absolute grant and relative grant) and the ACK/NACK sent previously and then send data.

From the perspective of the overall UTRAN protocol, the basic working principles of the HSUPA technology are shown in Figure 2-5.

Figure 2-5 Basic principles of HSUPA

Figure 2-5 shows the connection between the UE that uses the E-DCH and is in the soft handover (SHO) status and the URTAN, as well as the protocols related to the HSUPA at both the UE and network side.

E-DCH active set: the cell set carried by the E-DCH between the Node B and the UE. E-DCH active set can be a sub-set of the DCH active set.

E-DCH serving cell: the cell where the UE receives the absolute grants. The UE has only one E-DCH serving cell.

E-DCH serving RLS: a group of RLs containing the E-DCH serving cell. It is generally the cell set of the E-DCH active set under the Node B of the E-DCH serving cell.

Non-serving E-DCH RLS: the E-DCH cell set of all non-serving E-DCH RLS under the Node B which no E-DCH serving cell.

The HSUPA is characterized by the scheduling under control of the Node B. The following describes the scheduling process:

A UE has an E-DCH serving cell. The Node B of the E-DCH serving cell is responsible for E-DCH scheduling. The E-DCH serving cell sends scheduling command (namely absolute grant) over the downlink E-AGCH channel to the UE. The absolute grant specifies the absolute value of the maximum resources available to a UE. The absolute grant includes E-RNTI and maximum transmit power of the UE.

The E-DCH serving cell and non-E-DCH serving cell send relative grant over the downlink E-RGCH channel to the UE. The relative grant is used to adjust the absolute grant. The values of the relative grant include UP, HOLD, and DOWN. Only serving E-DCH RLS can send UP; while non-serving E-DCH RLS can only send HOLD or DOWN. When the uplink payload is too large, the non-serving E-DCH RLS sends DOWN.

Upon receiving the grant information, the UE makes a choice in respect of the E-TFC, sends data (including resent data) over the E-DPDCH, sends the E-TFC information over E-DPCCH, and sends HARQ RV (RSN) and the Happy bit. The Happy bit is used to inform Node B whether the UE are satisfied with the allocated resources and grants or not, that is, whether higher grant is needed.

The Node B performs combination for the E-DCH data received by different cells of the Node B and submits it to the Mac-e for processing. Each UE has a Mac-e in Node B. The Mac-e demultiplexes Mac-e PDU into MAC-es PDU and sends it to the RNC. The Mac-e also sends the E-DCH scheduling information and HARQ response ACK/NACK.

Each UE has a Mac-es entity in the SRNC. The Mac-es entity performs macro diversity combination for MAC-es PDUs from different Node Bs, reorders and divides them into Mac-d PDU, and then sends them to the Mac-d.HSUPA also supports non-scheduling transmission which means UE can transmit at any time without the scheduling information. The non-scheduling transmission just likes the DPCH and is usually used to carry the service which is delay sensitive, such as signaling, conversational service, streaming service. Each service can be configured non-scheduling transmission or scheduling transmission by the parameter EdchTrGrantType.3 Basic Functions of the HSUPA

3.1 HSUPA Common Carrier with R99

Carrier frequency sharing between the HSUPA and R99 means that the cell can provide uplink R99 service and HSUPA service simultaneously and can allocate common resources reasonably between the R99 and the HSUPA. These common resources include transmit power and downlink channels of E-AGCH, E-RGCH and E-HICH, transport bandwidth of the Iub interface, and uplink interference of the cell.

The HSUPA is generally used with the HSDPA. If you use the RAN and have purchased the license of the HSUPA basic function package, you can enable the HSUPA function in a cell supporting the HSDPA. By configuring the parameter HspaSptMeth in OMCR, you can enable a cell to support both R99 and HSUPA services simultaneously. The perfect RRM algorithm can guarantee reasonable allocation of cell common resources between these two types of services.

3.2 HSUPA Dedicated Carrier

The HSUPA is generally used with the HSDPA together. You can adopt the same carrier frequency for the R99 and HSUPA to realize R99 and HSUPA services simultaneously or use different carrier frequency for them to support HSUPA/HSDPA service only.

When the operator has more frequency resources than what are needed by the R99 service, it can adopt different frequencies for HSUPA/HSDPA service. Since the frequency utilization efficiency of the E-DCH is higher than that of the DCH, the operator can obtain higher uplink peak rate and cell throughput, improve the QoS of the service, and reduce the cost of high speed data service.

To realize the traditional CS service and low-speed PS service carried on the DCH, it is also need a frequency to carry R99 service. RAN provides access of different frequencies for the users according to the service type.

If you use the RAN and have purchased the license of the HSUPA basic function package, you can enable the HSUPA function for a cell. By configuring the parameter HspaSptMeth in OMCR, you can enable a cell to support HSUPA/HSDPA only. The cell does not support the R99 service separately but supports concurrent provisioning of the CS services and the PS services

3.3 HSUPA cell indicator in idle mode

The indicator of a HSUPA cell can be broadcasted through the system message SIB5 or SIB5bis. When searching cells, the terminal can figure out whether a cell supports the HSUPA service according to the indicator and then selects a desired cell accordingly. For example, a user holding the HSUPA data card can search the carrier frequency supporting the HSUPA service within a sector. The terminal decides the policy of selecting a cell according to the capability of cells.

3.4 HSUPA UE Category Support

RAN supports all HSUPA terminal category levels of the 3GPP protocol. The category levels reflect the extent to which a terminal supports the HSUPA service. RNC configures the Maximum Set of E-DPDCHs (NBAP IE) to Node B according to the minimum SF between the SF supported by UE category and the SF required by the MBR in RAB ASSIGNMENT REQUEST.

Figure 3-1 Requirements of 3GPP on HSUPA UE categories3.5 HSUPA 2ms TTIRAN supports the HSUPA with the TTI of 2ms. Each cell can be configured supporting 2ms TTI or not by the parameter Tti2msSuptInd. Each service can be configured 2ms TTI or 10ms TTI by the parameter ETTI.When adopting 2ms short frame, the HSUPA can reduce the transmission time delay. As a result, the air interface can transmit data at a time delay smaller than that of 10ms frame, and the frame alignment time during the data framing of the transmitter also decreases. The use of 2ms frame can reduce the Round Trip Time (RTT) of HARQ process under the control of the Node B and decrease the scheduling response time. In contrast to 10ms frame, 2ms frame can more effectively utilize the resources and obtain larger system capacity.

The 2ms TTI HSUPA adopts the scheduling interval of 2ms. The Node B specifies the value of Rate Grant (RG) according to the payload of the current cell and sends it to the user. With the increase of cell load, the 2ms TTI HSUPA, in contrast to the 10ms TTI HSUPA, can improve the performance generated from the cell throughput. Obviously, the smaller the TTI, the larger the performance will be.

3.6 HSUPA HARQ

The HSUPA adopts a fast HARQ which allows the Node B to fast retransmit data wrongly received. The fast HARQ is implemented in the MAC-e layer, which is terminated at the Node B. In the traditional R99, the data packets are retransmitted by the Radial Link Controller (RLC) under the control of the RNC. In the acknowledgement mode, the RLC retransmits the RLC signaling and data from the Iub interface with the time delay of more than 100ms. The retransmission time delay of HARQ(the retransmission time delay of 10ms TTI is 40ms; the retransmission time delay of 2ms TTI is 16ms) is much shorter than the retransmission time delay in the RLC layer, greatly reducing the time delay jittering of TCP/IP service and services sensitive to response time.

3.7 PS Interactive/Background Service over HSUPA

HSUPA services are carried over the enhanced dedicated channel E-DCH. Adopting the BPSK modulation and HARQ, the E-DCH channel provides higher bit rate and enables multiple users to share the load of uplink cells, which make it suitable to carry interactive and background services with the high bursting feature. The peak rate of the channel can effectively improve the QoS.

RAN supports the maximum uplink bit rate of 5.76Mbps. But the actual maximum bit rate available to users depends on the capability level of the terminal, the maximum bit rate (MBR) subscribed in the core network (CN), payload of the system, and the radio environment at the time of access.

3.8 PS Streaming Service over HSUPA

RAN supports carrying PS streaming services over E-DCH channel.

The PS streaming service requires guaranteed transmission bit rate and smaller time delay. According to the RAB parameters assigned by the CN, the RNC sends the GBR configured for the PS streaming service to the Node B, instructs the service to use the non-scheduling grants, so as to guarantee that the PS streaming service enjoys the priority in the scheduling by the Node B and meets the requirement of GBR. The mapping of scheduling priority is related to the QoS mapping of the RRM. 3.9 RAB Combination for CS over DCH and PS over HSUPA

RAN supports concurrent provisioning of the CS services and the PS I/B/S services carried over the HSUPA. The CS services include:

CS AMR voice conversation services

CS data conversation services, such as video telephony service

CS data streaming service, such as FAX service

CS WAMR voice conversation services

The current provisioning of one CS service and up to three PS services is supported.

When the CS services and the PS services carried over HSUPA channel are provided concurrently, the actual maximum bit rate of the uplink PS services depends on the capability level of the terminal, the MBR subscribed in the core network (CN), payload of the system, and the radio environment at the time of access.

4 HSUPA Mobility Management

RAN supports seamless handover of a UE inside the coverage of the HSUPA, between the coverage of HSUPA and R5/R99, and between the coverage of HSUPA and 2G. The cell attribute (HspaSptMeth) of the HSUPA coverage can be set to Support HSUPA, HSDPA and DCH, or Support HSUPA and HSDPA; the cell attribute (HspaSptMeth) of the HSDPA coverage can be set to Support HSDPA and DCH, Support HSDPA only, Support HSUPA, HSDPA and DCH, or Support HSUPA and HSDPA; the cell attribute (HspaSptMeth) of R99 can be set to Not Support HSUPA and HSDPA.For improving the compatibility of HSUPA over Iur, RAN supplies two more parameters RNCFEATSWITCH2, RNCFEATSWITCH4 which can be configured based neighbor RNC. The RNCFEATSWITCH2 is used to configure the neighbor RNC support HSUPA or not. If the neighbor RNC doesnt support HSUPA, RNC will transfer EDCH to DCH before do the Iur signaling flow. The RNCFEATSWITCH4 is configured to use DSCR or not when doing hard handover SRNS relocation for HS-DSCH configuration.

Similar to DCH, E-DCH is a dedicated uplink channel that supports SHO. Most mobility algorithms of the E-DCH are the same as those of the DCH. The only difference between them lies in the fact that the E-DCH supports E-DCH serving cell variation and switching from the E-DCH to the DCH caused by the mobility.

The following takes the intra-RNC E-DCH handover as an example to describe the flow. The inter-RNC E-DCH handover is similar to the intra-RNC E-DCH handover.

4.1 E-DCH Serving Cell Change

Similar to the HSDPA, the HSUPA also has a serving cell change flow. The difference lies in the fact that the E-DCH is an uplink link that supports SHO. The bearer of the E-DCH serving cell is the same as that of the E-DCH non-serving cell. When the E-DCH serving cell varies within the active set, the Iub/Iur interface does not need to set up a new E-DCH bearer.

The following figure shows the E-DCH serving cell change flow.

Figure 4-1 E-DCH intra-frequency cell change flow

Before the E-DCH serving cell changes, the UE has maintained connections with multiple cells:

1. The UE measures the quality of the intra-frequency cells in the neighboring cell list according to the measurement control mechanism of the RNC, judges the occurrence of intra-frequency events, and sends the measurement report to the RNC.

2. The RNC decides to change the E-DCH serving cell according to the events reported by the UE and availability of the radio resources.

3. The RNC sends the NBAP message Radio Link Reconfiguration Prepare to the serving Node B and reconfigures it as the non-serving E-DCH RL.

4. The RNC sends the NBAP message Radio Link Reconfiguration Prepare to the destination Node B and reconfigures it as the serving E-DCH RL.

5. The serving Node B returns the Radio Link Reconfiguration Ready message to the RNC.

6. The destination Node B returns the Radio Link Reconfiguration Ready message to the RNC.

7. The RNC sends the Radio Link Reconfiguration Commit message with the time of changing the E-DCH serving RL to the serving Node B.

8. The RNC sends the Radio Link Reconfiguration Commit message with the time of changing the E-DCH serving RL to the destination Node B.

9. The RNC sends the RRC message Physical Channel Reconfiguration to the UE and instructs it to change the E-DCH serving cell.

10. The UE switches to the new E-DCH serving RL at the time specified by the RNC and sends the RRC message Physical Channel Reconfiguration Complete to the RNC.

4.2 Switching between E-DCH and DCH

The switching between E-DCH and DCH includes intra-cell switching and inter-cell switching.

The following figure shows the flow of intra-cell switching between E-DCH and DCH. For example, the UE supports handover from the cell supporting the E-DCH to an inter-frequency neighboring cell not supporting E-DCH. In this case, it is necessary to enable the compression mode. Because the UE does not support concurrent processing of the E-DCH and compression mode, it is necessary to perform intra-cell fallback from E-DCH channel to DCH channel.

Figure 4-2 Intra-cell fallback from E-DCH to DCH

1. The RNC sends the NBAP message Radio Link Reconfiguration Prepare to the Node B to reconfigure the E-DCH channel as a DCH channel.

2. The Node B returns the Radio Link Reconfiguration Ready message to the RNC.

3. The RNC sends the Radio Link Reconfiguration Commit message with the time of channel switching to the Node B.

4. The RNC sends the RRC message Transport Channel Reconfiguration to the UE to reconfigure the E-DCH channel as a DCH channel.

5. The UE switch the E-DCH channel to the DCH channel at the time specified by the RNC and sends the RRC message Transport Channel Reconfiguration Complete to the RNC.The following figure shows the flow of inter-cell switching between E-DCH and DCH. The following takes the hard handover from a cell supporting E-DCH to an intra-frequency neighboring cell not supporting E-DCH as an example and describes a scenario of fallback from inter-cell E-DCH to DCH.

Figure 4-3 Inter-cell fallback from E-DCH to DCH1. The RNC sends the NBAP message Radio Link Setup Request to the target Node B to set up a radio link of the DCH channel.

2. The destination Node B returns the Radio Link Setup Response message to the RNC.

3. The RNC sends the RRC message Transport Channel Reconfiguration to the UE to reconfigure the E-DCH channel as a DCH channel.

4. The UE sends the RRC message Transport Channel Reconfiguration Complete to the RNC to swithch the E-DCH channel to a DCH channel.

5. The RNC sends the NBAP message Radio Link Deletion Request to the source NdoeB to delete the bearer of the original E-DCH.

6. The source Node B returns the Radio Link Deletion Response message to the RNC.

5 Key Calculations and Algorithms in Node B

5.1 Introduction to HARQ

The HARQ integrates the Forward Error Correction (FEC) and Automatic Repeat Request (ARQ). HARQ adjusts the bit rate of a channel according to the condition of the link and integrates the FEC with retransmission. HARQ allows the receiver to save the received data when decoding fails and requests the transmitter to retransmit data. The receiver combines the retransmitted data with the previously-received data. The HARQ technology can improve the system performance, effectively adjust the bit rate of valid code elements, and compensate the code errors brought about by the link adaptation. Introduced to the HSUPA by the 3GPP, HARQ can effectively reduce the transmission time delay and improve the retransmission efficiency.

A basic principle of the quick HARQ of the HSUPA is to add a HARQ entity to the Node B. In case of receiving failure, the Node B requests the UE to retransmit the uplink packets. In the uplink, the HARQ adopts N channels SAW protocol (NSAW), which is similar to the protocols used by the HSDPA. Additionally, the Node B can also use different methods to combine the retransmission tasks of a packet and reduce the reception Ec/No of each transmission requirement. The HARQ function of the HSUPA is mainly applied in the MAC-e and physical layer of the Node B. Through the HARQ, the Node B can effectively improve the data transmission speed and reduce the time delay.

In the HSUPA, 10ms TTI corresponds to 4 HARQ processes; and 2ms TTI corresponds to 8 HARQ processes.

The HARQ technology has two implementation modes: If the retransmitted data is the same as the data transmitted initially, this mode is referred to as Chase Combine (CC) or soft combining; if the retransmitted data is different from the data transmitted initially, this mode is referred to as Incremental Redundancy (IR).The later mode is better than the former in performance and requires larger memory in the terminal. The default memory of a terminal is designed according to the MBR and soft combining mode supported by the terminal. When the terminal works at the MBR, it can only use the soft combining. When working at lower transmission rate, the terminal supports both of the two modes. The IR mode needs a more complex memort of the UE. The 3GPP does not impose limitations on the specific mode. The CC mode can be viewed as a special form of the IR mode. The parameter HarqRvConfig is used to specify which HARQ mode should be used.

The system adopting the quick HARQ may have a higher Block Error Rate (BLER) in the first transmission. This is because the time delay of the packets with retransmission reception errors drops obviously in comparison with the RLC retransmission. Higher BLER target can reduce the transmission power requirement on the UE when it transmits data at a certain bit rate. If two cells have the same payload, the application of the quick HARQ can improve the capacity of the cell. When the data rate is invariable, reducing the energy of each bit helps to improving the coverage. Certainly, improving the BLER target excessively is costly because the time delay at the peak rate does not occur frequently when the RLC retransmission is not started, but data is retransmitted in large quantity, the user can feel the average time delay. Because more and more packets need to be retransmitted, the valid throughput of invariable bit rate also drops with the increase of the BLER.

In the SHO process, the HSUPA HARQ introduces a complex process that is unavailable in the HSDPA HARQ. In CDMA system, the SHO gain comes from the correct reception of packets at a Node B while another Node B is unable of decoding. Therefore, one Node B sends an ACK and another Node B sends a NACK. On this occasion, the network has received the packet, and the UE shall no longer send the same packet. Accordingly, in the Node B with reception failure, the HARQ process can recover from the incorrect reception. The RNC must ensure the sequence of packet transmission and combine the packets received at different Node Bs selectively.

Figure 5-1 SHO of HSUPA HARQ

5.2 HSUPA E-AGCH CLPC

E-AGCH closed-loop power control which can make a closed-loop according to the feedback of DPCCH and CQI will apply the service channel power control on the control channels. When the channel quality information obtained by DPCCH or CQI forms the power control command, this command will not only be transmitted to service channel but also to the corresponding control channel in order to implement the consistent association of service channel and corresponding control channel and ensure the reliable transfer of control information. The power control can be used to resist the modification of radio environment.

The advantages of E-AGCH closed-loop power control are shown as below:

To effectively reduce the network interference for the channel without power control to increase system capacity;

To effectively use DL transmit power, reduce interference and improve HSUPA performance..

From the protocol description, E-AGCH power control is controlled by NodeB. ZTE adopts two methods in the following:

Fixed power control. Concomitant CQI/HS-SCCH power control.

If the concomitant CQI/HS-SCCH power control method is used for E-AGCH, RNC will change the power-offset value during the soft hand-over because E-AGCH has no soft hand-over combination. HS-SCCH can control the channel quality due to the outer-power control. Therefore the concomitant CQI/HS-SCCH power control for E-AGCH can provide better performance.

The first method is directly controlled by HSUPA scheduler to adjust E-AGCH power value. For the second method, HSDPA will report the latest scheduled HS-SCCH power to HSUPA. The last E-AGCH power is derived from the sum of HS-SCCH power and the fixed power offset of HS-SCCH relative to E-AGCH.

The power control method selection is configured by OAM.

Fixed power control arithmetic:The fixed power control arithmetic is to use higher fixed transmit power to be sufficient for each HSUPA user (The fixed power transmission must be satisfied with the performance when UE is located in the cell margin). The power configuration is easier for this method. However, it will possibly waste Node B power resources to create the unnecessary interference in the cell.

Concomitant CQI/HS-SCCH power control arithmetic:E-AGCH is HSUPA control channel which is transmitted to UE by Node B. Based on an overall consideration of E-AGCH, the power control strategy is described in the following.

According to the description of 3GPP protocol, one UE can be HSUPA user and HSDPA user simultaneously because the same serving cell exists between HSUPA and HSDPA. E-AGCH which belongs to HSUPA serving cell can use CQI and HS-SCCH of HSDPA information to implement E-AGCH power control and can adjust E-AGCH transmit power according to CQI information reported by UE and HS-SCCH power control.

CQI is the HS-SCCH channel quality indicator and will not be affected by the handover state and service type. Due to the feedback of HS-SCCH demodulation in Node B, the influence of the receiver performance and the speed of different UE can be shielded by the outer power control arithmetic to control the channel quality.

Because of the same demodulation requirement between E-AGCH and HS-SCCH, the concomitant HS-SCCH power control for E-AGCH power based on the blinding of E-AGCH and HS-SCCH transmit power can effectively use HS-SCCH outer power control to dynamically adjust E-AGCH transmit power with the channel quality. This method can save E-AGCH power loss and reduce the unnecessary interference to other downlink channels. 5.3 HSUPA E-RGCH/HICH CLPC

E-RGCH/HICH closed-loop power control which can make a closed-loop according to the feedback of DPCCH and CQI will apply the service channel power control on the control channels. When the channel quality information obtained by DPCCH or CQI forms the power control command, this command will not only be transmitted to service channel but also to the corresponding control channel in order to implement the consistent association of service channel and corresponding control channel and ensure the reliable transfer of control information. The power control can be used to resist the modification of radio environment.

The advantages of E-RGCH/HICH closed-loop power control are shown as below:

To effectively reduce the network interference for the channel without power control to increase system capacity;

To effectively use DL transmit power, reduce interference and improve HSUPA performance..

From the protocol description, E-RGCH/HICH power control is controlled by NodeB. ZTE adopts two methods in the following:

Fixed power control. Concomitant DPCCH outer power control.

The method of concomitant DPCCH outer power control will achieve better performance because E-RGCH/HICH has soft handover combination to ensure the performance without power-offset change.

For the method 1, E-RGCH/HICH power value is directly controlled by HSUPA scheduler. For the method 2, the association between E-RGCH/HICH and DPCCH channel power is directly implemented by hardware.

The power control method selection is configured by OAM.

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DRNC

Iur/Iub FP

SRNC

FP

MAC-d

MAC-es

MAC-e

Scheduler

Iur/Iub FP

NodeBs

UE

MAC-e/

MAC-es

MAC-d

DTCHs

MAC-e

FP

NodeBd

E-DPDCH

E-DPCCH

serving cell

E-AGCH

(Absolute Grants,

"E-RNTI" -> UE)

E-HICH (ACK/NACKs)

E-RGCH (relative grants)

(ChCode, signature -> UE)

MRC

MRC

1 TNL bearer per MAC-d flow