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Wideband Code Division Multiple Access (W–CDMA) Definition and Overview

Definition Wideband code division multiple access (W–CDMA) is a CDMA channel that is four times wider than the current channels that are typically used in 2G networks in North America.

Overview In January 1998, European Telecommunications Standards Institute (ETSI) decided to choose the W–CDMA technology to be the multiple access techniques for the third-generation mobile telephone system. For a mobile communication system, a key parameter is the system capacity. A number of methods to increase system capacity in a W–CDMA network are discussed. This tutorial presents results from different antenna pattern parameters and sectorization techniques for optimizing the maximum number of active subscribers.

Cell Site Loading

Given the limit on spectrum resources, efficient optimization techniques are needed for realizing cost-efficient ways to maximize the capacity in a W–CDMA network. The capacity is essentially interference limited by the overall interference level in the coverage area of each site. A computer simulation for investigating the system capacity was performed that modeled the radio channel in an urban environment. The simulator included many of the CDMA characteristics such as power control and different parameter setting in the hand over algorithm. Given this simulation, antenna characteristics such as sector orientation, number of sectors per site, horizontal beamwidth, and front-to-back ratio were studied. Also studied was the influence of the radio environment, giving rise to different orthogonality factors.

The signal-to-interference ratio typically limits the probability of having service in a dense cell site. As we can see from Figure 1, the roll off of service probability for voice traffic is quite quick—from 160 to 180 users per cell site in a typical three-sector configuration compared to about 90 users for omni site configurations. The error bars in the following figures annotate plus or minus one standard deviation about the mean value obtained from the numerical simulations. The numerically obtained results using a set of network statistics for a typical urban setting are shown in Figure 1.

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Figure 1. Cell Site Loading in a Three-Sector Network Configuration

Three-Sector Cell Site Configurations With the given set of simulation conditions, the practical number of users per W–CDMA channel is between 170 and 175. Depending on the antenna characteristics, the number of actual users that can talk on a given sector face will change. The typical shape for cell site footprints is a hexagonal shape. For such a shape, the typical number of sectors per cell is one, three, or six. When using three or six sectors, there are two standard orientations. These orientations and shapes are demonstrated for three sector cell site configurations in Figure 2 and Figure 3.

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Figure 2. Typical Three-Sector Cell Site Configuration

Figure 3. Typical Three-Sector Cell Site Configuration Rotated by 30 Degrees

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Using these two different types of three-sector cell site configurations, the optimum horizontal half power beamwidth is predicted. The results for the configuration depicted in Figure 2 are presented in Figure 4, and the results for the configuration depicted in Figure 3 are presented in Figure 5.

Figure 4. Capacity Predictions for a Typical Three-Sector Cell Site Configuration

Figure 5. Capacity Predictions for a Typical Three-Sector Cell Site Configuration Rotated by 30 Degrees

The results presented above show that the optimal beamwidth for the configurations demonstrated in Figure 2 and Figure 3 is 65 and 80 degrees respectively.

Capacity Limitations Due To Orthogonality and Antenna Performance The capacity of the W–CDMA network is also limited to the amount of self-induced interference by the mobiles using the same sector face. This self-induced interference is the disruption of the orthogonality of the codes by the multipath in the wireless network. Although the fingers in the rake receiver will provide some additional diversity in a high multipath environment, the multipath is detrimental to the orthogonality of the W–CDMA channel. For the previous results, an orthogonality factor of 0.4 is used. A study of maximum orthogonality and no orthogonality in relation to antenna beamwidth can be seen in Figure 8 and Figure 9.

Figure 8. Capacity Predictions for a Typical Three-Sector Cell Site Configuration

Rotated by 30 Degrees with a Maximum Level of Orthogonality

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Figure 9. Capacity Predictions for a Typical Three-Sector Cell Site Configuration

Rotated by 30 Degrees with No Measurable Amount of Orthogonality

Here, the optimal beamwidth of the antenna is quite invariant to the level of orthogonality in the network. Over the complete range of orthogonality, the optimal beamwidth varies from 75 to 80 degrees.

The previous two figures show that the orthogonality of the W–CDMA channel significantly impacts the network capacity. Another contributor to the degradation of the W–CDMA channel is the radiation from the antennas in the backward direction. All of the results presented previously are for antennas with a front-to-side ratio of 30 dB. If the radiation from the base station antenna is increased in the backward direction in the form of a single back lobe, the degradation of the capacity can be studied. The results of this numerical study are shown in Figure 10. The different lines are for the back-lobe beamwidths 60, 30, and 10 degrees.

Figure 10. Capacity Predictions for a Typical Three-Sector Cell Site Configuration

Rotated by 30 Degrees for Different Back-Lobe Beamwidths

The results in Figure 10 show that as the total energy in the backward directed lobe is increased by either increasing the beamwidth of the back lobe or by decreasing its front-to-back ratio, the capacity of the W–CDMA network diminishes. In general, the capacity of the W–CDMA network can be made optimized by choosing antennas that have the proper beamwidth for the given environment and cell site configuration.

Co-location, Isolations Spurious emissions are emissions, which are caused by unwanted transmitter effects such as harmonics emission, parasitic emission, intermodulation products and frequency conversion products, but exclude out of band emissions. This is measured at the base station RF output port.

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Spectrum Emission Mask, 3GPP TS 25.104 Fig. 6.2

Spurious emissions limits for protection of the BS receiver The table above corresponds to -80 dBm / 3.84MHz spurious emission requirements from UMTS DL to UMTS UL.

EXAMPLE

Spurious emission DL to UL - 80 dBm See above

Max sensitivity degradation

- 121 dBm

BS reference sensitivity

Min required isolation 41 dB

UMTS FDD isolation requirement due to spurious emissions Note: Check with your vendor, they will quote a lower figure

The receiver blocking characteristics is a measure of the receiver ability to receive a wanted signal at its assigned channel frequency in the presence of an unwanted interferer on frequencies other than those of the adjacent channels.

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EXAMPLE

Max Node B power 43 dBm = 20W Blocking level - 40 dBm 3GPP 25104 7.5.1 Min required isolation 83 dB

UMTS FDD - FDD isolation requirement due to receiver blocking

Note: Check with your vendor, they will quote a lower figure The transmit intermodulation performance is a measure of the capability of the transmitter to inhibit the generation of signals in its non linear elements caused by presence of the wanted signal and an interfering signal reaching the transmitter via the antenna. The transmit intermodulation level shall not exceed the out of band emission or the spurious emission requirements. Summary: Co-location and isolation related issues

� Co-location issues; base station receivers; spurious emission and blocking

� Co-existence issues; mobile phone receivers; spurious emission and blocking

� Intermodulation issues

� All wireless systems need to be considered

� Vendor equipment specification far better that 3GPP specifications Solution considerations

� Equipment specifications

� Horisontal antenna separation

� Vertical antenna separation

� Additional filtering

� Antenna beamwidth

� Antenna bearing

� Frequency coordination with other carriers

� Smart designs for common antenna systems

Cell search procedure During the cell search, the UE searches for a cell and determines the downlink

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scrambling code and frame synchronisation of that cell. The cell search is typically carried out in three steps: Step 1: Slot synchronisation During the first step of the cell search procedure the UE uses the SCH's primary synchronisation code to acquire slot synchronisation to a cell. This is typically done with a single matched filter (or any similar device) matched to the primary synchronisation code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output. Step 2: Frame synchronisation and code-group identification During the second step of the cell search procedure, the UE uses the SCH's secondary synchronisation code to find frame synchronisation and identify the code group of the cell found in the first step. This is done by correlating the received signal with all possible secondary synchronisation code sequences, and identifying the maximum correlation value. Since the cyclic shifts of the sequences are unique the code group as well as the frame synchronisation is determined. Step 3: Scrambling-code identification During the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified through symbol-by-symbol correlation over the CPICH with all codes within the code group identified in the second step. After the primary scrambling code has been identified, the Primary CCPCH can be detected and the system- and cell specific BCH information can be read. If the UE has received information about which scrambling codes to search for, steps 2 and 3 above can be simplified

Structure of synchronization channel

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The Synchronisation Channel (SCH) is a downlink signal used for cell search. The SCH consists of two sub channels, the Primary and Secondary SCH. The 10 ms radio frames of the Primary and Secondary SCH are divided into 15 slots, each of length 2560 chips. Picture above illustrates the structure of the SCH radio frame. The Primary SCH consists of a modulated code of length 256 chips, the primary synchronization code (PSC) is transmitted once every slot. The PSC is the same for every cell in the system. The Secondary SCH consists of repeatedly transmitting a length 15 sequence of modulated codes of length 256 chips, the Secondary Synchronisation Codes (SSC), transmitted in parallel with the Primary SCH. The SSC is denoted cs

i,k in figure 20, where i = 0, 1, …, 63 is the number of the scrambling code group, and k = 0, 1, …, 14 is the slot number. Each SSC is chosen from a set of 16 different codes of length 256. This sequence on the Secondary SCH indicates which of the code groups the cell's downlink scrambling code belongs to. Summary of the process:

Channel Synchronisation acquired Note

Primary SCH

Chip, Slot, Symbol Synchronisation

256 chips The same in all cells

Secondary SCH

Frame Synchronisation,Code Group (one of 64)

15-code sequence of secondary synchronisation codes. There are 16 secondary synchronisation codes. There are 64 S-SCH sequences corresponding to the 64 scrambling code groups 256 chips, different for different cells and slot intervals

Common Pilot CH

Scrambling code (one of 8)

To find the primary scrambling code from common pilot CH

PCCPCH *) Super Frame Synchronisation, BCCH info

Fixed 30 kbps channel 27 kbps rate spreading factor 256

SCCPCH **) Carries FACH and PCH channels Variable bit rate

*) Primary Common Control Physical Channel **) Secondary Common Control Physical Channel

Call Setup

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Basic Mobile Originating Call Diagram

3G Frequencies According to "WARC-92 frequencies for IMT-2000" resolution: "The bands 1885-2025 MHz and 2110-2200 MHz are intended for use, on a worldwide basis, by administrations wishing to implement International Mobile Telecommunications-2000 (IMT-2000). Such use does not preclude the use of these bands by other services to which they are

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allocated." Here is the summary of UMTS frequencies: 1920-1980 and 2110-2170 MHz Frequency Division Duplex (FDD, W-CDMA) Paired uplink and downlink, channel spacing is 5 MHz and raster is 200 kHz. An Operator needs 3 - 4 channels (2x15 MHz or 2x20 MHz) to be able to build a high-speed, high-capacity network. 1900-1920 and 2010-2025 MHz Time Division Duplex (TDD, TD/CDMA) Unpaired, channel spacing is 5 MHz and raster is 200 kHz. Tx and Rx are not separated in frequency. 1980-2010 and 2170-2200 MHz Satellite uplink and downlink. Carrier frequencies are designated by a UTRA Absolute Radio Frequency Channel Number (UARFCN). The general formula relating frequency to UARFN is: UARFCN = 5 * (frequency in MHz)

WARC-92 IMT-2000 Frequencies

WRC-2000 in Istanbul • Identified the bands 1710 - 1885 and 2500 - 2690 MHz for IMT-2000

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• Identified those parts of the band 806 - 960 MHz which are allocated to the mobile service on a primary basis • Admitted that High Altitude Platform Stations (HAPS) may use the WARC-92 frequency bands for terrestrial IMT-2000 on restrictive conditions • Decided that the frequency bands 1525 - 1544, 1545 - 1559, 1610 - 1626.5, 1626.5 - 1645.5, 1646.5 - 1660.5 and 2483.5 - 2500 MHz may be used for the satellite component of IMT-2000, as well as the bands 2500 - 2520 MHz and 2670- 2690 MHz, depending on market developments • Decided that "the bands, or portions of the bands, 1710 - 1885 MHz and 2500 - 2690 MHz, are identified for use by administrations wishing to implement International Mobile Telecommunications-2000 (IMT-2000). This identification does not preclude the use of these bands by any application of the services to which they are allocated and does not establish priority in the Radio Regulations".

WRC-2000 IMT-2000 Frequencies

From the TS 25.101 Specification:

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UTRA FDD frequency bands

TX-RX frequency separation

UARFCN definition

UARFCN definition (Band II additional channels)

UTRA Absolute Radio Frequency Channel Number

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Main UMTS Codes Here us a summary of the main UMTS FDD codes:

Synchronisation Codes

Channelisation Codes

Scrambling Codes, UL

ScramblingCodes, DL

Type

Gold Codes

Primary Synchronization Codes (PSC) and

Secondary Synchronization Codes

(SSC)

Orthogonal Variable Spreading

Factor (OVSF) codes

sometimes called

Walsh Codes

Complex-Valued Gold Code

Segments (long) or Complex-Valued S(2)

Codes (short)

Pseudo Noise (PN) codes

Complex-Valued Gold

Code Segments

Pseudo Noise

(PN) codes

Length 256 chips 4-512 chips 38400 chips / 256 chips 38400 chips

Duration 66.67 µs 1.04 µs - 133.34 µs 10 ms / 66.67 µs 10 ms

Number of codes

1 primary code / 16 secondary codes

= spreading factor4 ... 256 UL, 4 ... 512 DL

16,777,216

512 primary / 15 secondary

for each primary code

Spreading No, does not change bandwidth

Yes, increases bandwidth

No, does not change

bandwidth

No, does not change

bandwidth

Usage

To enable terminals to locate and

synchronise to the cells' main control

channels

UL: to separate physical data and control data from

same terminal DL: to separate connection to

different terminals in a same cell

Separation of terminal

Separation of sectors

UMTS Time Slots UMTS has several different time slot configuration depending on the used channel. Here is an example of DPCH (Dedicated Physical Channel) downlink and uplink time slot allocation. TCP stands for Transmit Power Control, Feedback Information (FBI) is used for closed loop transmission diversity. Transport Format Combination Indicator (TFCI) contains

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the information relating to data rates. Pilot bits are always the same and are used for channel synchronisation.

DPCH Time Slot Structure

Channel Coding Channel coding and multiplexing example for DTCH and DCCH:

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Channel coding example for the UL 64 kbps channel

UMTS Handover There are following categories of handover (also referred to as handoff): • Hard Handover Hard handover means that all the old radio links in the UE are removed before the new radio links are established. Hard handover can be seamless or non-seamless. Seamless hard handover means that the handover is not perceptible to the user. In practice a handover that requires a change of the carrier frequency (inter-frequency handover) is always performed as hard handover. • Soft Handover Soft handover means that the radio links are added and removed in a way that the UE always keeps at least one radio link to the UTRAN. Soft handover is performed by means of macro diversity, which refers to the condition that several radio links are active at the

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same time. Normally soft handover can be used when cells operated on the same frequency are changed. • Softer handover Softer handover is a special case of soft handover where the radio links that are added and removed belong to the same Node B (i.e. the site of co-located base stations from which several sector-cells are served. In softer handover, macro diversity with maximum ratio combining can be performed in the Node B, whereas generally in soft handover on the downlink, macro diversity with selection combining is applied.

Generally we can distinguish between intra-cell handover and inter-cell handover. For UMTS the following types of handover are specified:

• Handover 3G -3G (i.e. between UMTS and other 3G systems) • FDD soft/softer handover • FDD inter-frequency hard handover • FDD/TDD handover (change of cell) • TDD/FDD handover (change of cell) • TDD/TDD handover • Handover 3G - 2G (e.g. handover to GSM) • Handover 2G - 3G (e.g. handover from GSM) The most obvious cause for performing a handover is that due to its movement a user can be served in another cell more efficiently (like less power emission, less interference). It may however also be performed for other reasons such as system load control.

• Active Set is defined as the set of Node-Bs the UE is simultaneously connected to (i.e., the UTRA cells currently assigning a downlink DPCH to the UE constitute the active set). • Cells, which are not included in the active set, but are included in the CELL_INFO_LIST belong to the Monitored Set. • Cells detected by the UE, which are neither in the CELL_INFO_LIST nor in the active set belong to the Detected Set. Reporting of measurements of the detected set is only applicable to intra-frequency measurements made by UEs in CELL_DCH state. The different types of air interface measurements are: • Intra-frequency measurements: measurements on downlink physical channels at the same frequency as the active set. A measurement object corresponds to one cell. • Inter-frequency measurements: measurements on downlink physical channels at frequencies that differ from the frequency of the active set. A measurement object corresponds to one cell. • Inter-RAT measurements: measurements on downlink physical channels belonging to another radio access technology than UTRAN, e.g. GSM. A measurement object corresponds to one cell. • Traffic volume measurements: measurements on uplink traffic volume. A measurement object corresponds to one cell.

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• Quality measurements: Measurements of downlink quality parameters, e.g. downlink transport block error rate. A measurement object corresponds to one transport channel in case of BLER. A measurement object corresponds to one timeslot in case of SIR (TDD only). • UE-internal measurements: Measurements of UE transmission power and UE received signal level. • UE positioning measurements: Measurements of UE position. The UE supports a number of measurements running in parallel. The UE also supports that each measurement is controlled and reported independently

Random Access The Random Access Channel (RACH) is an uplink transport channel. The RACH is always received from the entire cell. The RACH is characterized by a collision risk and by being transmitted using open loop power control.

RACH access slot numbers and their spacing

RACH preamble is of length 4096 chips and consists of 256 repetitions of a signature of length 16 chips. There are a maximum of 16 available signatures. All 16 preamble signature codes available in every cells. The 10 ms RACH message part radio frame is split into 15 slots, each of length Tslot = 2560 chips. Each slot consists of two parts, a data part to which the RACH transport channel is mapped and a control part that carries Layer 1 control information. The data

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and control parts are transmitted in parallel. A 10 ms message part consists of one message part radio frame, while a 20 ms message part consists of two consecutive 10 ms message part radio frames. The data part consists of 10*2k bits, where k=0,1,2,3. This corresponds to a spreading factor of 256, 128, 64, and 32 respectively for the message data part.

Structure of the random-access message part radio frame

The Acquisition Indicator Channel (AICH) is a fixed rate (SF=256) physical channel used to carry Acquisition Indicators (AI). Acquisition Indicator AIs corresponds to signature s on the PRACH.

Structure of Acquisition Indicator Channel

The Access Preamble Acquisition Indicator channel (AP-AICH) is a fixed rate (SF=256) physical channel used to carry AP acquisition indicators (API) of CPCH. AP acquisition indicator APIs corresponds to AP signature s transmitted by UE. The Collision Detection Channel Assignment Indicator channel (CD/CA-ICH) is a fixed rate (SF=256) physical channel used to carry CD Indicator (CDI) only if the CA is

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not active, or CD Indicator/CA Indicator (CDI/CAI) at the same time if the CA is active. The structure of CD/CA-ICH is shown in figure 25. CD/CA-ICH and AP-AICH may use the same or different channelisation codes. The CD/CA-ICH has a part of duration of 4096chips where the CDI/CAI is transmitted, followed by a part of duration 1024chips with no transmission that is not formally part of the CD/CA-ICH. The part of the slot with no transmission is reserved for possible use by CSICH or possible future use by other physical channels. Uplink Common Packet channel (CPCH) is an extension to the RACH channel for packet-based user data. PCPCH Access Example:

PCPCH (similar to RACH) and AICH transmission as seen by the UE

DPCCH PCPCH AP-AICH CD/CA-ICH AP CD/CA

Dedicated Physical Control Channel Physical Common Packet Channel Access Preamble Acquisition Indicator Channel Collision Detection/Channel Assignment Indicator Channel Access Preamble Collision Detection/Channel Assignment

Indicators are means of fast low-level signalling entities which are transmitted without using information blocks sent over transport channels. The meaning of indicators is specific to the type of indicator. The indicators defined in the current version of the specifications are: • Acquisition Indicator (AI) • Access Preamble Indicator (API)

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• Channel Assignment Indicator (CAI) • Collision Detection Indicator (CDI) • Page Indicator (PI) • Status Indicator (SI) Indicators may be either boolean (two-valued) or three-valued. Their mapping to indicator channels is channel specific. Indicators are transmitted on those physical channels that are indicator channels (ICH).

UTRAN Protocol Model The general protocol model for UTRAN Interfaces is shown below. The structure is based on the principle that the layers and planes are logically independent of each other. Therefore, as and when required, the standardisation body can easily alter protocol stacks and planes to fit future requirements.

General Protocol Model for UTRAN Interfaces Horizontal Layers The Protocol Structure consists of two main layers, Radio Network Layer, and Transport Network Layer. All UTRAN related issues are visible only in the Radio Network Layer, and the Transport Network Layer represents standard transport technology that is selected to be used for UTRAN, but without any UTRAN specific requirements.

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Vertical Planes The Control Plane Includes the Application Protocol, i.e. RANAP, RNSAP or NBAP, and the Signalling Bearer for transporting the Application Protocol messages. Among other things, the Application Protocol is used for setting up bearers for (i.e. Radio Access Bearer or Radio Link) in the Radio Network Layer. The User Plane Includes the Data Stream(s) and the Data Bearer(s) for the Data Stream(s). The Data Stream(s) is/are characterised by one or more frame protocols specified for that interface. The Transport Network Control Plane does not include any Radio Network Layer information, and is completely in the Transport Layer. It includes the ALCAP protocol(s) that is/are needed to set up the transport bearers (Data Bearer) for the User Plane. It also includes the appropriate Signalling Bearer(s) needed for the ALCAP protocol(s). The Transport Network Control Plane is a plane that acts between the Control Plane and the User Plane. The introduction of Transport Network Control Plane is performed in a way that the Application Protocol in the Radio Network Control Plane is kept completely independent of the technology selected for Data Bearer in the User Plane. Indeed, the decision to actually use an ALCAP protocol is completely kept within the Transport Network Layer. Iur Interface Protocol Structure

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Iur layers

Further Reading:

Iur specification numbers

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Protocol layering specification numbers

Channel Multiplexing Structure This is a short overview how data stream is modified during processing in layer 2 and 1 in downlink direction. Uplink coding is done in a similar way. Ciphering happens in RCL or MAC-d part of the layer 2. f8 algorithm gets five inputs to generate a keystream block that is ciphered by binary addition to a data stream. Channel coding separates different down link connection to users within a cell. In the uplink direction Channel coding is used for separation of physical data and control channels. Half-rate and 1/3-rate convolutional coding is used for low data rates, turbo coding is used for higher bit rates. Channel coding includes the spreading. Rate matching is dynamic frame-by-frame operation and done either by puncturing or by repetition of the data stream. Interleaving is done in two stages. It is first done by inter-frame and then by intra-frame.

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Transport channel multiplexing structure for downlink

Synchronisation Different UTRAN synchronisation required in a 3G network: • Network synchronisation • Node synchronisation • Transport channel synchronisation • Radio interface cynchronisation • Time alignment handling

Synchronisation Issues Model Network Synchronisation relates to the distribution of synchronisation references to the UTRAN Nodes and the stability of the clocks in the UTRAN (and performance requirements on UTRAN internal interfaces). The distribution of an accurate frequency reference to the network elements in the UTRAN is related to several aspects. One main issue is the possibility to provide a synchronisation reference with a frequency accuracy better than 0.05 ppm at the Node B in order to properly generate signals on the radio interface. Node Synchronisation relates to the estimation and compensation of timing differences among UTRAN nodes. FDD and TDD modes have different requirements on the

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accuracy of the timing difference estimation and on the necessity to compensate for these differences. Positioning / Localisation functions may also set requirements on Node Synchronisation. The Transport Channel Synchronisation mechanism defines synchronisation of the frame transport between RNC and Node B, considering radio interface timing. The Radio Interface Synchronisation relates to the timing of the radio frame transmission (either in downlink [FDD] or in both directions [TDD]). FDD and TDD have different mechanisms to determine the exact timing of the radio frame transmission and also different requirements on the accuracy of this timing. In FDD Radio Interface Synchronisation is necessary to assure that the UE receives radio frames synchronously from different cells, in order to minimise UE buffers. The Time Alignment Handling procedure over Iu relates to the control of DL transmission timing in the CN nodes in order to minimise the buffer delay in SRNC. This procedure is controlled by SRNC.

UTRA Channels UTRA FDD radio interface has logical channels, which are mapped to transport channels, which are again mapped to physical channels. Logical to Transport channel conversion happens in Medium Access Control (MAC) layer, which is a lower sublayer in Data Link Layer (Layer 2). Logical Channels: Broadcast Control Channel (BCCH), Downlink (DL) Paging Control Channel (PCCH), DL Dedicated Control Channel (DCCH), UL/DL Common Control Channel (CCCH), UL/DL Dedicated Traffic Channel (DTCH), UL/DL Common Traffic Channel (CTCH), Unidirectional (one to many) Transport Channels: Dedicated Transport Channel (DCH), UL/DL, mapped to DCCH and DTCH Broadcast Channel (BCH), DL, mapped to BCCH Forward Access Channel (FACH), DL, mapped to BCCH, CCCH, CTCH, DCCH and DTCH Paging Channel (PCH), DL, mapped to PCCH Random Access Channel (RACH), UL, mapped to CCCH, DCCH and DTCH Uplink Common Packet Channel (CPCH), UL, mapped to DCCH and DTCH Downlink Shared Channel (DSCH), DL, mapped to DCCH and DTCH Physical Channels: Primary Common Control Physical Channel (PCCPCH), mapped to BCH

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Secondary Common Control Physical Channel (SCCPCH), mapped to FACH, PCH Physical Random Access Channel (PRACH), mapped to RACH Dedicated Physical Data Channel (DPDCH), mapped to DCH Dedicated Physical Control Channel (DPCCH), mapped to DCH Physical Downlink Shared Channel (PDSCH), mapped to DSCH Physical Common Packet Channel (PCPCH), mapped to CPCH Synchronisation Channel (SCH) Common Pilot Channel (CPICH) Acquisition Indicator Channel (AICH) Paging Indication Channel (PICH) CPCH Status Indication Channel (CSICH) Collision Detection/Channel Assignment Indication Channel (CD/CA-ICH)

UTRA Channels

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UMTS Location Based Services UMTS networks will support location service features, to allow new and innovative location based services to be developed. It will be possible to identify and report in a standard format (e.g. geographical co-ordinates) the current location of the user's terminal and to make the information available to the user, ME, network operator, service provider, value added service providers and for PLMN internal operations. The location is provided to identify the likely location of specific MEs. This is meant to be used for charging, location-based services, lawful interception, emergency calls, etc., as well as the positioning services. Location Information consists of: • Geographic Location • Velocity (the combination of speed and heading ) • Quality of Service information (horizontal & vertical accuracy and response time) 3GPP specification also describes location based service reliability, priority, security, privacy and other related aspects.

Location-independent Most existing cellular services, stock prices, sports reports

PLMN or country Services that are restricted to one country or one PLMN

Regional (up to 200km) Weather reports, localized weather warnings, traffic information (pre-trip)

District (up to 20km) Local news, traffic reports

Up to 1 km Vehicle asset management, targeted congestion avoidance advice

500m to 1km Rural and suburban emergency services, manpower planning, information services (where are?)

100m (67%) 300m (95%)

U.S. FCC mandate (99-245) for wireless emergency calls using network based positioning methods

75m-125m Urban SOS, localized advertising, home zone pricing, network maintenance, network demand monitoring, asset tracking, information services (where is the nearest?)

50m (67%) 150m (95%)

U.S. FCC mandate (99-245) for wireless emergency calls using handset based positioning methods

10m-50m Asset Location, route guidance, navigation

Example of location services The table below lists the attributes of specific location based services as determined by the GSM Alliance Services Working Group. It is possible for the network operator or service provider to define additional, non-standardised service types.

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Location based services categories Standardized Service Types

Public Safety Services Emergency Services Emergency Alert Services

Location Sensitive Charging

Tracking Services Person Tracking Fleet Management Asset Management

Traffic Monitoring Traffic Congestion Reporting

Enhanced Call Routing Roadside Assistance Routing to Nearest Commercial Enterprise

Location Based Information Service Navigation City Sightseeing Localized Advertising Mobile Yellow Pages

Service Provider Specific Services

Standardized Service Types UE locations is reported periodically. The periodic reporting function is generally applicable for asset management services and exists as several variants, each applicable to different value added services:

Location reporting only within predetermined period

e.g. commercial asset tracking and, subject to provision of privacy, manpower planning.

Periodic location reporting within specified period and reporting triggered by a specific event

e.g. high value asset security, stolen vehicle monitoring, home zone charging.

Periodic location reporting triggered by a specific event

e.g. 24hr depot management, transit passenger information systems

A LCS Client is a logical functional entity that makes a request to the PLMN LCS server for the location information of one or more than one target UEs. A LCS server consists of a number of location service components and bearers needed to serve the LCS clients. The LCS server shall provide a platform which will enable the support of location based services in parallel to other telecommunication services such as speech, data, messaging, other teleservices, user applications and supplementary services. Using the Location Service Request, an LCS client communicates with the LCS server to request the location information for one or more target UEs within a specified set of quality of service parameters. As shown in below, a location service may be specified as immediate or deferred.

Request Type Response Time Number of Responses Immediate Immediate Single Deferred Delayed (event driven) One or More

Location Service Requests

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The LCS Server will provide, on request, the current or most recent Location Information (if available) of the Target UE or, if positioning fails, an error indication plus optional reason for the failure.

For emergency services (where required by local regulatory requirements), the geographic location may be provided to an emergency services LCS Client either without any request from the client at certain points in an emergency services call (e.g. following receipt of the emergency call request, when the call is answered, when the call is released) or following an explicit request from the client. The former type of provision is referred to as a “push” while the latter is known as a “pull”.

Type of Access Information Items

Push

Current Geographic Location (if available) MSISDN IMSI IMEI NA-ESRK NA-ESRD State of emergency call: – unanswered, answered, released

Pull Geographic location, either: - Current location - Initial location at start of emergency call

Location information that may be provided

The specification Release '99 specifies the following LCS positioning methods:

• Cell coverage based positioning method • Observed Time Difference Of Arrival (OTDOA) method with network configurable idle periods • Network assisted GPS methods

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OTDOA Location Method

UMTS RRC States Picture below shows the RRC states in UTRA RRC Connected Mode, including transitions between UTRA RRC connected mode and GSM connected mode for CS domain services, and between UTRA RRC connected mode and GSM/GPRS packet modes for PS domain services. It also shows the transitions between Idle Mode and UTRA RRC Connected Mode and furthermore the transitions within UTRA RRC connected mode.

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RRC States and State Transitions including GSM

CELL_DCH state is characterised by: • A dedicated physical channel is allocated to the UE in uplink and downlink. • The UE is known on cell level according to its current active set. • Dedicated transport channels, downlink and uplink (TDD) shared transport channels, and a combination of these transport channels can be used by the UE. CELL_FACH state is characterised by: • No dedicated physical channel is allocated to the UE. • The UE continuously monitors a FACH in the downlink. • The UE is assigned a default common or shared transport channel in the uplink (e.g. RACH) that it can use anytime according to the access procedure for that transport channel. • The position of the UE is known by UTRAN on cell level according to the cell where the UE last made a cell update. • In TDD mode, one or several USCH or DSCH transport channels may have been established. CELL_PCH state is characterised by: • No dedicated physical channel is allocated to the UE. • The UE selects a PCH with the algorithm, and uses DRX for monitoring the selected PCH via an associated PICH. • No uplink activity is possible. • The position of the UE is known by UTRAN on cell level according to the cell where the UE last made a cell update in CELL_FACH state.

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URA_PCH State is characterised by: • No dedicated channel is allocated to the UE. • The UE selects a PCH with the algorithm, and uses DRX for monitoring the selected PCH via an associated PICH. • No uplink activity is possible. • The location of the UE is known on UTRAN Registration area level according to the URA assigned to the UE during the last URA update in CELL_FACH state. Call reselection procedures:

States and procedures in the cell reselection process in connected mode When a cell reselection is triggered, the UE evaluates the cell reselection criteria based on radio measurements, and if a better cell is found that cell is selected, procedure Cell reselection. If the change of cell implies a change of radio access technology, the RRC connection is released, and the UE enters idle mode of the other RAT. If no suitable cell is found in the cell reselection procedure, the UE eventually enters idle mode. When an Initial cell reselection is triggered, the UE shall use the Initial cell reselection procedure to find a suitable cell. One example where this procedure is triggered is at

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radio link failure, where the UE may trigger an initial cell reselection in order to request re-establishment of the RRC connection. If the UE is unable to find a suitable cell, the UE eventually enters idle mode.

Paging The Paging Channel (PCH) is a downlink transport channel. The PCH is always transmitted over the entire cell. The transmission of the PCH is associated with the transmission of physical-layer generated Paging Indicators, to support efficient sleep-mode procedures. Paging Channel selection System information block type 5 (SIB 5) defines common channels to be employed in Idle mode. In a cell, a single or several PCHs may be established. Each Secondary Common Control Physical Channel (SCCPCH) indicated to the UE in system information may carry up to one PCH. Thus, for each defined PCH there is one uniquely associated PICH also indicated. In case that more than a single PCH and associated PICH are defined in SIB 5, the UE shall perform a selection according to the following rule: • The UE shall select a SCCPCH from the ones listed in SIB 5 based on IMSI as follows: "Index of selected SCCPCH" = IMSI mod K, where K is equal to the number of listed SCCPCHs which carry a PCH (i.e. SCCPCHs carrying FACH only shall not be counted). These SCCPCHs shall be indexed in the order of their occurrence in SIB 5 from 0 to K-1. "Index of selected SCCPCH" identifies the selected SCCPCH with the PCH and the uniquely associated PICH to be used by the UE. If the UE has no IMSI, for instance when making an emergency call without USIM, the UE shall use as default number IMSI = 0. The UE may use Discontinuous Reception (DRX) in idle mode in order to reduce power consumption. When DRX is used the UE needs only to monitor one Page Indicator, PI, in one Paging Occasion per DRX cycle. The Paging Indicator Channel (PICH) is a fixed rate (SF=256) physical channel used to carry the paging indicators. The PICH is always associated with an S-CCPCH to which a PCH transport channel is mapped. Picture below illustrates the frame structure of the

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PICH. One PICH radio frame of length 10 ms consists of 300 bits. Of these, 288 bits are used to carry paging indicators. The remaining 12 bits are not formally part of the PICH and shall not be transmitted (DTX). The part of the frame with no transmission is reserved for possible future use.

Structure of Paging Indicator Channel (PICH) Two Paging Procedures: Paging procedure is used to transmit paging information to selected UEs in idle mode, CELL_PCH or URA_PCH state using the paging control channel (PCCH). Upper layers in the network may request paging, to e.g. establish a signalling connection. UTRAN may initiate paging for UEs in CELL_PCH or URA_PCH state to trigger a cell update procedure. In addition, UTRAN may initiate paging for UEs in idle mode, CELL_PCH and URA_PCH state to trigger reading of updated system information. UTRAN initiates the paging procedure by transmitting a PAGING TYPE 1 message on an appropriate paging occasion on the PCCH. UE dedicated paging procedure is used to transmit dedicated paging information to one UE in connected mode in CELL_DCH or CELL_FACH state. Upper layers in the network may request initiation of paging. For a UE in CELL_DCH or CELL_FACH state, UTRAN initiates the procedure by transmitting a PAGING TYPE 2 message on the DCCH using AM RLC. Two Paging Message Types: PAGING TYPE 1 message is used to send information on the paging channel. One or several UEs, in idle or connected mode, can be paged in one message, which also can contain other information PAGING TYPE 2 message is used to page an UE in connected mode (CELL_DCH or CELL_FACH state), when using the DCCH for CN originated paging. PICH / S-CCPCH timing relation

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Picture below illustrates the timing between a PICH frame and its associated single S-CCPCH frame, i.e. the S-CCPCH frame that carries the paging information related to the paging indicators in the PICH frame. A paging indicator set in a PICH frame means that the paging message is transmitted on the PCH in the S-CCPCH frame starting tPICH chips after the transmitted PICH frame.

Timing relation between PICH frame and associated S-CCPCH frame

tPICH = 7680 chips (3 slots) Paging Block Periodicity (PBP): Period of the occurrence of Paging Blocks. (For FDD, PBP = 1). Paging occasion: (FDD) The SFN of the PICH frame where the UE monitors its paging indicator (i.e. the SFN of the PCCPCH frame in which the PICH frame begins).

WCDMA Link Budget Link budget planning is part of the network planning process, which helps to dimension the required coverage, capacity and quality of service requirement in the network. UMTS WCDMA macro cell coverage is uplink limited, because mobiles power level is limited to (voice terminal 125mW). Downlink direction limits the available capacity of the cell, as BTS transmission power (typically 20-40W) has to be divided to all users. In a network environment both coverage and capacity are interlinked by interference. So by improving one side of the equation would decrease the other side. System is loosely balanced by design. The object of the link budget design is to calculate maximum cell size under given criteria:

• Type of service (data type and speed) • Type of environment (terrain, building penetration) • Behavior and type of mobile (speed, max power level) • System configuration (BTS antennas, BTS power, cable losses, handover gain) • Required coverage probability • Financial and economical factors (use of more expensive and better quality equipment or not the cheapest installation method)

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and to match all of those to the required system coverage, capacity and quality needs with each area and service. In an urban area, capacity will be the limiting factor, so inner city cells will be dimensioned by required Erlangs/km² for voice and data. Even using 25dB as inbuilding penetration loss into the building core area, link budget would typically allow about 300m cell range, which is a way too much for a capacity purposes. In a rural area uplink power budget will determine the maximum cell range, when typically cells are less congested. A typical cell range in rural areas will be several kilometers depending on a terrain. Below is an example of how WCDMA voice call link budget can be done. Some of the values can be debated, including the propagation model, but it gives an idea of the calculation methods.

UMTS link budget

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WCDMA Spreading TDD WCDMA uses spreading factors 4 - 512 to spread the base band data over ~5MHz band. Spreading factor in dBs indicates the process gain. Spreading factor 128 = 21 dB process gain). Interference margin is calculated from that: Interference Margin = Process Gain - (Required SNR + System Losses)

• Required Signal to Noise Ration is typically about 5 dB • System losses are defined as losses in receiver path. System losses are typically 4 - 6 dBs

Overview of Spreading Process

Compressed Mode During inter-frequency handover the UE’s must be given time to make the necessary measurements on the different WCDMA carrier frequency. 1 to 7 slots per frame can be allocated for the UE to perform this intra frequency (hard handover). These slots can either be in the middle of the single frame or spread over two frames. This compressed mode operation can be achieved in three different methods:

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• Decreasing the spreading factor by 2:1. This will increase the data rate so bits will get sent twice as fast. • Puncturing bits. This will remove various bits from the original data and hence reduce the amount of information that needs to be transmitted. • The higher layer scheduling could also be changed to use less timeslots for user traffic. From the 3GPP TS 25.212: In compressed frames, Transmission Gap Length slots from Nfirst to Nlast are not used for transmission of data. As illustrated below, the instantaneous transmit power is increased in the compressed frame in order to keep the quality (BER, FER, etc.) unaffected by the reduced processing gain. The amount of power increase depends on the transmission time reduction method. What frames are compressed, are decided by the network. When in compressed mode, compressed frames can occur periodically, or requested on demand. The rate and type of compressed frames is variable and depends on the environment and the measurement requirements.

The frame structure for uplink compressed frames is illustrated below.

There are two different types of frame structures defined for downlink compressed frames. Type A maximises the transmission gap length and type B is optimised for power

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control. The frame structure type A or B is set by higher layers independent from the downlink slot format type A or B.

• With frame structure of type A, the pilot field of the last slot in the transmission gap is transmitted. Transmission is turned off during the rest of the transmission gap (below).

• With frame structure of type B, the TPC field of the first slot in the transmission gap and the pilot field of the last slot in the transmission gap is transmitted. Transmission is turned off during the rest of the transmission gap (below).

UMTS Power Control Open loop power control is the ability of the UE transmitter to sets its output power to a specific value. It is used for setting initial uplink and downlink transmission powers when a UE is accessing the network. The open loop power control tolerance is ± 9 dB (normal conditions) or ± 12 dB (extreme conditions) Inner loop power control (also called fast closed loop power control) in the uplink is the ability of the UE transmitter to adjust its output power in accordance with one or more Transmit Power Control (TPC) commands received in the downlink, in order to keep the received uplink Signal-to-Interference Ratio (SIR) at a given SIR target. The UE transmitter is capable of changing the output power with a step size of 1, 2 and 3 dB, in the slot immediately after the TPC_cmd can be derived. Inner loop power control frequency is 1500Hz. The serving cells estimate SIR of the received uplink DPCH, generate TPC commands (TPC_cmd) and transmit the commands once per slot according to the following rule: if SIRest > SIRtarget then the TPC command to transmit is "0", while if SIRest < SIRtarget then the TPC command to transmit is "1". Upon reception of one or more TPC commands in a slot, the UE derives a single TPC command for each slot, combining multiple TPC commands if more than one is received in a slot. Two algorithms are supported by the UE for deriving a TPC_cmd. Which of these two algorithms is used, is determined by a UE-specific higher-layer parameter, "PowerControlAlgorithm".

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Algorithm 1: • The power control step is the change in the UE transmitter output power in response to a single TPC command Algorithm 2: • If all five estimated TPC command are "down" the transmit power is reduced by 1 dB • If all five estimated TPC command are "up" the transmit power is increased by 1 dB • Otherwise the transmit power is not changed

Transmitter power control range

The transmit power of the downlink channels is determined by the network. The power control step size can take four values: 0.5, 1, 1.5 or 2 dB. It is mandatory for UTRAN to support step size of 1 dB, while support of other step sizes is optional. The UE generates TPC commands to control the network transmit power and send them in the TPC field of the uplink DPCCH. Upon receiving the TPC commands UTRAN adjusts its downlink DPCCH/DPDCH power accordingly. Outer loop power control is used to maintain the quality of communication at the level of bearer service quality requirement, while using as low power as possible. The uplink outer loop power control is responsible for setting a target SIR in the Node B for each individual uplink inner loop power control. This target SIR is updated for each UE according to the estimated uplink quality (BLock Error Ration, Bit Error Ratio) for each Radio Resource Control connection. The downlink outer loop power control is the ability of the UE receiver to converge to required link quality (BLER) set by the network (RNC) in downlink. Power control of the downlink common channels are determined by the network. In general the ratio of the transmit power between different downlink channels is not specified in 3GPP specifications and may change with time, even dynamically. Additional special situations of power control are Power control in compressed mode and Downlink power during handover.