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WCDMA Radio Interface Physical Layer

ISSUE 1.0

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HUAWEI TECHNOLOGIES CO., LTD. Page 1All rights reserved

The physical layer offers data transport services

to higher layers.

The access to these services is through the use

of transport channels via the MAC sub-layer.

The physical layer is expected to perform the

following functions in order to provide the data

transport service, for example Modulation and

spreading/demodulation and despreading, Inner -

loop power control etc.

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References� TS 25.104 UTRA (BS) FDD Radio Transmission and

Reception

� TS 25.201 Physical layer-general description

� TS 25.211 Physical channels and mapping of

transport channels onto physical channels (FDD)

� TS 25.212 Multiplexing and channel coding (FDD)

� TS 25.213 Spreading and modulation (FDD)

� TS 25.214 Physical layer procedures (FDD)

� TS 25.308 UTRA High Speed Downlink Packet Access(HSDPA); Overall description; Stage 2

� TR 25.877 High Speed Downlink Packet Acces (HSDPA) -Iub/Iur Protocol Aspects

� TR 25.858 Physical layer aspects of UTRA High Speed Downlink Packet Access

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� Upon completion of this course, you will be able to:

�Outline radio interface protocol Architecture

�Describe key technology of UMTS physical layer

�Describe UMTS physical layer procedures

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Chapter 1 Physical Layer OverviewChapter 1 Physical Layer Overview

Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology

Chapter 3 Physical Layer Processing ProcedureChapter 3 Physical Layer Processing Procedure

Chapter 4 Physical Layer ProceduresChapter 4 Physical Layer Procedures

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UTRAN Protocol Structure

RNS

RNC

RNS

RNC

Core Network

NodeB NodeB NodeB NodeB

Iu Iu

Iur

Iub IubIub Iub

UTRAN:UMTS Terrestrial Radio Access Network.

The UTRAN consists of a set of Radio Network Subsystems connected to the Core Network through the Iu interface.

A RNS consists of a Radio Network Controller and one or more NodeBs. A NodeB is connected to the RNC through the Iub interface.

Inside the UTRAN, the RNCs of the RNS can be interconnected together through the Iur. Iu(s) and Iur are logical interfaces. Iur can be conveyed over direct physical connection between RNCs or virtual networks using any suitable transport network.

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Radio Interface Protocol Structure

L3control

control

control

control

Logical Channels

Transport Channels

C-plane signaling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLCRLC

Duplication avoidance

UuS boundary

BMC L2/BMC

control

PDCPPDCP L2/PDCP

DCNtGC

Radio Bearers

RRC

The radio interface (Uu) is layered into three protocol layers:

�the physical layer (L1)

�the data link layer (L2)

�the network layer (L3).

The layer 1 supports all functions required for the transmission of bit streams on the physical medium. It is also in charge of measurements function consisting in indicating to higher layers, for example, Frame Error Rate (FER), Signal to Interference Ratio (SIR), interference power, transmit power, … It is basically composed of a “layer 1 management” entity, a “transport channel” entity, and a “physical channel” entity.

The layer 2 protocol is responsible for providing functions such as mapping, ciphering, retransmission and segmentation. It is made of four sublayers: MAC(Medium Access Control), RLC (Radio Link Control), PDCP (Packet Data Convergence Protocol) and BMC (Broadcast/Multicast Control).

The layer 3 is split into 2 parts: the access stratum and the non access stratum. The access stratum part is made of “RRC (Radio Resource Control)” entity and “duplication avoidance” entity. The non access stratum part is made of CC, MMparts.

Not shown on the figure are connections between RRC and all the other protocol layers (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer control services.

The protocol layers are located in the UE and the peer entities are in the node B or the RNC.

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Many functions are managed by the RRC layer. Here is the list of the most important:

�Establishment, re-establishment, maintenance and release of an RRC connection between the UE and UTRAN: it includes an optional cell re-selection, an admission control, and a layer 2 signaling link establishment. When a RNC is in charge of a specific connection towards a UE, it acts as the Serving RNC.

�Establishment, reconfiguration and release of Radio Bearers: a number of Radio Bearers can be established for a UE at the same time. These bearers are configured depending on the requested QoS. The RNC is also in charge of ensuring that the requested QoS can be met.

�Assignment, reconfiguration and release of radio resources for the RRC connection: it handles the assignment of radio resources (e.g. codes, shared channels). RRC communicates with the UE to indicate new resources allocation when handovers are managed.

�Paging/Notification: it broadcasts paging information from network to UEs.

�Broadcasting of information provided by the non-access stratum (Core Network) or access Stratum. This corresponds to “system information” regularly repeated.

�UE measurement reporting and control of the reporting: RRC indicates what to measure, when and how to report.

�Outer loop power control: controls setting of the target values.

�Control of ciphering: provides procedures for setting of ciphering.

The RRC layer is defined in the 25.331 specification from 3GPP.

The RLC’s main function is the transfer of data from either the user or the control plane over the Radio interface. Two different transfer modes are used: transparent and non-transparent. In non-transparent mode, 2 sub-modes are used: acknowledged or unacknowledged.

RLC provides services to upper layers:

�data transfer (transparent, acknowledged and unacknowledged modes),

�QoS setting: the retransmission protocol (for AM only) shall be configurable by layer 3 to provide different QoS,

�notification of unrecoverable errors: RLC notifies the upper layers of errors that cannot be resolved by RLC.

The RLC functions are:

�mapping between higher layer PDUs and logical channels,

�ciphering: prevents unauthorized acquisition of data; performed in RLC layer for non-transparent RLC mode,

�segmentation/reassembly: this function performs segmentation/reassembly of variable-length higher layer PDUs into/from smaller RLC Payload Units. The RLC size is adjustable to the actual set of transport formats (decided when service is established). Concatenation and padding may also be used,

�error correction: done by retransmission (acknowledged data transfer mode only),

�flow control: allows the RLC receiver to control the rate at which the peer RLC transmitting entity may send information.

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MAC services include:

�Data transfer: service providing unacknowledged transfer of MAC SDUs between peer MAC entities.

�Reallocation of radio resources and MAC parameters: reconfiguration of MAC functions such as change of identity of UE. Requested by the RRC layer.

�Reporting of measurements: local measurements such as traffic volume and quality indication are reported to the RRC layer.

The functions accomplished by the MAC sublayer are listed above. Here’s a quick explanation for some of them:

�Priority handling between the data flows of one UE: since UMTS is multimedia, a user may activate several services at the same time, having possibly different profiles (priority, QoS parameters...). Priority handling consists in setting the right transport format for a high bit rate service and for a low bit rate service.

�Priority handling between UEs: use for efficient spectrum resources utilization for bursty transfers on common and shared channels.

�Ciphering: to prevent unauthorized acquisition of data. Performed in the MAC layer for transparent RLC mode.

�Access Service Class (ACS) selection for RACH transmission: the RACH resources are divided between different ACSs in order to provide different priorities on a random access procedure.

PDCP

UMTS supports several network layer protocols providing protocol transparency for the users of the service.

Using these protocols (and new ones) shall be possible without any changes to UTRAN protocols. In order to perform this requirement, the PDCP layer has been introduced. Then, functions related to transfer of packets from higher layers shall be carried out in a transparent way by the UTRAN network entities.

PDCP shall also be responsible for implementing different kinds of optimization methods. The currently known methods are standardized IETF (Internet Engineering Task Force) header compression algorithms.

Algorithm types and their parameters are negotiated by RRC and indicated to PDCP.

Header compression and decompression are specific for each network layer protocol type.

In order to know which compression method is used, an identifier (PID: Packet Identifier) is inserted. Compression algorithms exist for TCP/IP, RTP/UDP/IP, …

Another function of PDCP is to provide numbering of PDUs. This is done if lossless SRNS relocation is required.

To accomplish this function, each PDCP-SDUs (UL and DL) is buffered and numbered. Numbering is done after header compression. SDUs are kept until information of successful transmission of PDCP-PDU has been received from RLC. PDCP sequence number ranges from 0 to 65,535.

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BMC (broadcast/multicast control protocol)

The main function of BMC protocol are:

Storage of cell broadcast message. the BMC in RNC stores the cell broadcast message received over the CBC-RNC interface for scheduled transmission.

Traffic volume monitoring and radio resource request for CBS. On the UTRAN side, the BMC calculates the required transmission rate for the cell broadcast service based on the messages received over the CBC-RNC interface, and requests appropriate .CTCH/FACH resources from from RRC

Scheduling of BMC message. The BMC receives scheduling information together with each cell broadcast message over the CBC-RNC interface. Based on this scheduling information, on the UTRAN side the BMC generates schedule message and schedules BMC message sequences accordingly. On the UE side ,the BMC evaluates the schedule messages and indicates scheduling parameters to RRC, which are used by RRC to configure the lower layers for CBS discontinuous reception.

Transmission of BMC message to UE. The function transmits the BMC messages according to the schedule

Delivery of cell broadcast messages to the upper layer. This UE function delivers the received non-corrupted cell broadcast messages to the upper layer

The layer 1 (physical layer) is used to transmit information under the form of electrical signals corresponding to bits, between the network and the mobile user. This information can be voice, circuit or packet data, and network signaling.

The UMTS layer 1 offers data transport services to higher layers. The access to these services is through the use of transport channels via the MAC sublayer.

These services are provided by radio links which are established by signaling procedures. These links are managed by the layer 1 management entity. One radio link is made of one or several transport channels, and one physical channel.

The UMTS layer 1 is divided into two sublayers: the transport and the physical sublayers. All the processing (channel coding, interleaving, etc.) is done by the transport sublayer in order to provide different services and their associated QoS. The physical sublayer is responsible for the modulation, which corresponds to the association of bits (coming from the transport sublayer) to electrical signals that can be carried over the air interface. The spreading operation is also done by the physical sublayer. These sublayers are well described in chapters 6 and 7.

These two parts of layer 1 are controlled by the layer 1 management (L1M) entity. It is made of several units located in each equipment, which exchange information through the use of control channels.

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Spreading Technology� Spreading consists of 2 steps�

� Channelization operation, which transforms data symbols into chips. Thus increasing the bandwidth of the signal, The number of chips per data symbol is called the Spreading Factor�SF�.The operation is done by multiplying with OVSF code.

� Scrambling operation is applied to the spreading signal .

Data bit

OVSF code

Scrambling code

Chips after spreading

Spreading is applied to the physical channels. It consists of two operations. The first is the channelization operation, which transforms every data symbol into a number of chips, thus increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor (SF). The second operation is the scrambling operation, where a scrambling code is applied to the spread signal.

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Channelization Code

� OVSF code is used as channelization code

� The channelization codes are uniquely described as Cch,SF,k, where SF is the

spreading factor of the code and k is the code number, 0 ≤ k ≤ SF-1.

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

The channelization codes are Orthogonal Variable Spreading Factor (OVSF) codes. They are used to preserve orthogonality between different physical channels. They also increase the clock rate to 3.84 Mcps. The OVSF codes are defined using a code tree.

In the code tree, the channelization codes are individually described by Cch,SF,k, where SF is the Spreading Factor of the code and k the code number, 0 ≤ k ≤ SF-1.

A channelization sequence modulates one user’s bit. Because the chip rate is constant, the different lengths of codes enable to have different user data rates. Low SFs are reserved for high rate services while high SFs are for low rate services.

The length of an OVSF code is an even number of chips and the number of codes (for one SF) is equal to the number of chips and to the SF value.

The generated codes within the same layer constitute a set of orthogonal codes. Furthermore, any two codes of different layers are orthogonal except when one of the two codes is a mother code of the other. For example C4,3 is not orthogonal with C1,0 and C2,1, but is orthogonal with C2,0.

Each Sector of each Base Station transmits W-CDMA Downlink Traffic Channels with up to 512 code channels.

Code tree repacking may be used to optimize the number of available codes in downlink.

Exercise: Find code Cch,8,3 and code Cch,16,15

OVSF shortage

Scrambling enables neighboring cells to use the same channelization codes. This allows the system to use a maximum of 512 OVSF codes in each cell. Notice that the use of an OVSF code forbids the use of the other codes in its branch. This reduces considerably the number of available codes especially for high rate services. This may lead to an OVSF shortage. In such a case, secondary scrambling codes may be allocated to the cells and enable the reuse of the same OVSF in the same cell.

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Scrambling Code

� Scrambling code: GOLD sequence.

� Scrambling code period: 10ms ,or 38400 chips.

� The code used for scrambling of the uplink DPCCH/DPDCH may be of

either long or short type, There are 224 long and 224 short uplink

scrambling codes. Uplink scrambling codes are assigned by higher

layers.

� For downlink physical channels, a total of 218-1 = 262,143 scrambling

codes can be generated. scrambling codes k = 0, 1, …, 8191 are used.

Uplink scrambling code

All the physical channels in the uplink are scrambled. In uplink, the scrambling code can be described as either long or short, depending on the way it was constructed. The scrambling code is always applied to one 10 ms frame. Different scrambling codes will be allocated to different mobiles.

In UMTS, Gold codes were chosen for their very low peak cross-correlation.

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Scrambling codes for downlink physical channels

Set 0

Set 1

…

Set 511

Primary scrambling code 0

……

Secondary scrambling code 1

Secondary scrambling code 15

Primary scrambling code

511�16

……

Secondary scrambling code 511�16�15

8192 scrambling codes

512 sets

Primary Scrambling Code

……

A primary scrambling code and 15 secondary scrambling codes are included in a set.

Downlink link scrambling code

The scrambling codes used in downlink are constructed like the long uplink scrambling codes. They are created with two 18-cell shift registers.

218-1 = 262,143 different scrambling codes can be formed using this method. However, not all of them are used. The downlink scrambling codes are divided into 512 sets, of one primary scrambling code and 15 secondary scrambling codes each.

The primary scrambling codes are scrambling codes n=16*i where i=0…511. The 15 secondary scrambling codes associated to one primary scrambling code are n=16*i + k, where k=1…15. For now 8192 scrambling codes have been defined.

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Primary Scrambling Code Group

Primary scrambling codes for downlink physical channels

Group 0

…


……


8*63

……


63*8�7512 primary

scrambling codes

……

Group 1

Group 63



64 primary scrambling code groups

Each group consists of 8 primary scrambling codes

There is a total of 512 primary codes. They are further divided into 64 primary scrambling code groups of 8 primary scrambling codes each. Each cell is allocated one and only one primary scrambling code. The group of the primary scrambling code is found by the mobiles of the cell using the SCH, while the specific primary scrambling code used is given by the CPICH. The primary CCPCH and the primary CPICH channels are always scrambled with the primary scrambling code of the cell, while other channels can be scrambled by either the primary or the secondary scrambling code.

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Chapter 2 Physical Layer Key TechnologyChapter 2 Physical Layer Key Technology



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Section 1 Physical ChannelSection 1 Physical Channel Structure and FunctionsStructure and Functions

Section 2 Channel MappingSection 2 Channel Mapping

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WCDMA radio interface has three kinds of channels

� In terms of protocol layer, the WCDMA radio interface has three channels: Physical channel, transport channel and logical channel.

� Logical channel: Carrying user services directly. According to the types of the carried services, it is divided into two types: Control channel and service channel.

� Transport channel: It is the interface of radio interface layer 2 and physical layer, and is the service provided for MAC layer by thephysical layer. According to whether the information transported is dedicated information for a user or common information for all users, it is divided into dedicated channel and common channel.

� Physical channel: It is the ultimate embodiment of all kinds of information when they are transmitted on radio interfaces. Each kind of channel which uses dedicated carrier frequency, code (spreading code and scramble) and carrier phase (I or Q) can be regarded as a dedicated channel.

In UMTS, there are 3 types of channels:

�Logical channels: each logical channel type is defined by <what type of information > is transferred.

�Transport channels: each transport channel is described by <how > and with <what characteristics > data is transmitted over the radio interface.

�Physical channels: provide the real transmission resource, being in charge of theassociation between bits and physical symbols (electrical signals). It corresponds, in UMTS, to a frequency , a specific set of codes and phase.

As a conclusion:

Physical Channel = information container

Transport Channel = characteristics of transmission

Logical Channel = specification of the information global content

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Control channel

Traffic channelDedicated traffic channel (DTCH)

Common traffic channel (CTCH)

Broadcast control channel (BCCH)

Paging control channel (PCCH)

Dedicate control channel (DCCH)

Common control channel (CCCH)

Logical Channel

As in GSM, UMTS uses the concept of logical channels.

A logical channel is characterized by the type of information that is transferred.

For example, some channels are used to transfer dedicated information, some for transfer of general control information, etc..

As in GSM, logical channels can be divided into two groups: control channels for control plane information and traffic channel for user plane information.

The traffic channels are:

�Dedicated Traffic CHannel (DTCH): a point-to-point bi-directional channel, that transmits dedicated user information between a UE and the network. That information can be speech, circuit switched data or packet switched data. The payload bits on this channel come from a higher layer application (the AMR codec for example). Control bits can be added by the RLC (protocol information) in case of a non transparent transfer. The MAC sublayer will also add a header to the RLC PDU.

�Common Traffic CHannel (CTCH): a point-to-multipoint downlink channel for transfer of dedicated user information for all or a group of specified UEs. This channel is used to broadcast BMC messages. These messages can either be cell broadcast data from higher layers or schedule messages for support of Discontinuous Reception (DRX) of cell broadcast data at the UE. Cell broadcast messages are services offered by the operator, like indication of weather, traffic, location or rate information.

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The control channels are:

Broadcast Control CHannel (BCCH): a downlink channel that broadcasts all system information types (except type 14 that is only used in TDD). For example, system information type 3 gives the cell identity. UEs decode system information on the BCH except when in Cell_DCH mode. In that case, they can decode system information type 10 on the FACH and other important signaling is sent on a DCCH.

Paging Control CHannel (PCCH): a downlink channel that transfers paging information. It is used to reach a UE (or several UEs) in idle mode or in connected mode (Cell_PCH or URA_PCH state). The paging type 1 message is sent on the PCCH. When a UE receives a page on the PCCH in connected mode, it shall enter Cell_FACH state and make a cell update procedure.

Dedicated Control CHannel (DCCH): a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used for dedicated signaling after a RRC connection has been done. For example, it is used for inter-frequency handover procedure, for dedicated paging, for the active set update procedure and for the control and report of measurements.

Common Control CHannel (CCCH): a bi-directional channel for transmitting control information between network and UEs. It is used to send messages related to RRC connection, cell update and URA update. This channel is a bit like the DCCH, but will be used when the UE has not yet been identified by the network (or by the new cell). For example, it is used to send the RRC connection request message, which is the first message sent by the UE to get into connected mode. The network will respond on the same channel, and will send him its temporary identities (cell and UTRAN identities). After these initial messages, the DCCH will be used.

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Dedicated Channel (DCH)

-DCH is an uplink or downlink channel

Broadcast channel (BCH)

Forward access channel (FACH)

Paging channel (PCH)

Random access channel (RACH)

High-speed downlink shared channel (HS-DSCH)

Common transport channel

Dedicated transport channel

Transport Channel

In order to carry logical channels, several transport channels are defined. They are:

�Broadcast CHannel (BCH): a downlink channel used for broadcast of system information into the entire cell.

�Paging CHannel (PCH): a downlink channel used for broadcast of control information into the entire cell, such as paging.

�Random Access CHannel (RACH): a contention based uplink channel used for initial access or for transmission of relatively small amounts of data (non real-time dedicated control or traffic data).

�Forward Access CHannel (FACH): a common downlink channel used for dedicated signaling (answer to a RACH typically), or for transmission of relatively small amounts of data.

�Dedicated CHannel (DCH): a channel dedicated to one UE used in uplink ordownlink.

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Physical Channel

� A physical channel is defined by a specific carrier frequency, code (scrambling code, spreading code) and relative phase.

� In UMTS system, the different code (scrambling code or spreadingcode) can distinguish the channels.

� Most channels consist of radio frames and time slots, and each radio frame consists of 15 time slots.

� Two types of physical channel:UL and DL

Physical Channel

Frequency, Code, Phase

Now we will begin to discuss the physical channel. Physical channel is the most important and complex channel, and a physical channel is defined by a specific carrier frequency, code and relative phase. In CDMA system, the different code (scrambling code or spreading code) can distinguish the channel. Most channels consist of radio frames and time slots, and each radio frame consists of 15 time slots. There are two types of physical channel: UL and DL. Let’s look at the uplink physical channel first.

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Downlink Physical Channel� Downlink Dedicated Physical Channel

�(Downlink DPCH)

� Downlink Common Physical Channel�Primary Common Control Physical Channel (PCCPCH)�Secondary Common Control Physical Channel (SCCPCH)�Synchronization Channel (SCH)�Paging Indicator Channel (PICH)�Acquisition Indicator Channel (AICH)�Common Pilot Channel (CPICH)�High-Speed Packet Downlink Shared Channel (HS-PDSCH)�High-Speed Shared Control Channel (HS-SCCH)

Downlink Physical Channel

The different physical channels are:

�Synchronization CHannel (SCH): used for cell search procedure. There is the primary and the secondary SCHs. Downlink.

�Primary Common Control Physical CHannel (PCCPCH): used to carry BCH ,that issystem information

�Secondary Common Control Physical CHannel (SCCPCH): used to carry FACH ,that is common DL data

�Primary Common Pilot CHannels (P-CPICH): used for coherent detection of common channels. They indicate the phase reference. Downlink.

�Dedicated Physical Data CHannel (DPDCH): used to carry dedicated data coming from layer 2 and above (coming from DCH). Uplink and Downlink.

�Dedicated Physical Control CHannel (DPCCH): used to carry dedicated control information generated in layer 1 (such as pilot, TPC and TFCI bits). Uplink and Downlink.

�Page Indicator CHannel (PICH): carries indication to inform the UE that paging information is available on the S-CCPCH. Downlink.

�Acquisition Indicator CHannel (AICH): it is used to inform a UE that the network has received its access request. Downlink.

�High Speed Packet Downlink Shared CHannel (HS-PDSCH): it is used to carry subscribers BE service data (mapping on HSDPA) coming from layer 2. Downlink.

�High Speed Shared Control Channel (HS-SCCH): it is used to carry control message to HS-PDSCH such as modulation scheme, UE ID etc. Downlink.

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Uplink Physical Channel

� Uplink Dedicated Physical Channel�Uplink Dedicated Physical Data Channel (Uplink DPDCH)

�Uplink Dedicated Physical Control Channel (Uplink DPCCH)

�High-Speed Dedicated Physical Channel (HS-DPCCH)

� Uplink Common Physical Channel

�Physical Random Access Channel (PRACH)

Uplink Physical Channel

The different physical channels are:

�Dedicated Physical Data CHannel (DPDCH): used to carry dedicated data coming from layer 2 and above (coming from DCH). Uplink and Downlink.

�Dedicated Physical Control CHannel (DPCCH): used to carry dedicated control information generated in layer 1 (such as pilot, TPC and TFCI bits). Uplink and Downlink.

�Physical Random Access CHannel (PRACH): used to carry random access information when a UE wants to access the network. Uplink.

�High Speed Dedicated Physical Control CHannel (HS-DPCCH): it is used to carry feedback message to HS-PDSCH such CQI,ACK/NACK. Uplink.

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Function of physical channel

Node B UE

P-CCPCH-Primary Common Control Physical ChannelP-CCPCH-Primary Common Control Physical Channel

SCH- Synchronisation Channel

P-CPICH-Primary Common Pilot Channel

SCH- Synchronisation Channel

P-CPICH-Primary Common Pilot Channel

Cell broadcast channels

DPDCH-Dedicated Physical Data ChannelDPDCH-Dedicated Physical Data Channel

DPCCH-Dedicated Physical Control ChannelDPCCH-Dedicated Physical Control Channel

Dedicated channels

Paging channels

PICH-Paging Indicator ChannelPICH-Paging Indicator Channel

S-CCPCH-Secondary Common Control Physical ChannelS-CCPCH-Secondary Common Control Physical Channel

PRACH-Physical Random Access ChannelPRACH-Physical Random Access Channel

AICH-Acquisition Indicator ChannelAICH-Acquisition Indicator Channel

Random access channels

HS-DPCCH-High Speed Dedicated Physical Control ChannelHS-DPCCH-High Speed Dedicated Physical Control Channel

HS-SCCH-High Speed Share Control Channel HS-SCCH-High Speed Share Control Channel

HS-PDSCH-High Speed Physical Downlink Share ChannelHS-PDSCH-High Speed Physical Downlink Share Channel

High speed downlink share channels

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Primary Synchronization Channel (P-SCH)� Used for cell search� Two sub channels: P-SCH and S-SCH. � SCH is transmitted at the first 256 chips

of every time slot.� PSC is transmitted repeatedly in each

time slot.

� SSC specifies the scrambling code groups of the cell.

� SSC is chosen from a set of 16 different codes of length 256, there are altogether 64 primary scrambling code groups.

Primary SCH

Secondary SCH

Slot #0 Slot #1 Slot #14

acsi,0

pac pac pac

acsi,1 acs

i,14

256 chips2560 chips

One 10 ms SCH radio frame

When a UE is turned on, the first thing it does is to scan the UMTS spectrum and find a UMTS cell. After that, it has to find the primary scrambling code used by that cell in order to be able to decode the BCCH (for system information). This is done with the help of the Synchronization Channel.

The SCH is a pure downlink physical channel broadcasted over the entire cell. It is transmitted unscrambled during the first 256 chips of each time slot, in time multiplex with the P-CCPCH. It is the only channel that is not spread over the entire radio frame. The SCH provides the primary scrambling code group (one out of 64 groups), as well as the radio frame and time slot synchronization.

The SCH consists of two sub-channels, the primary and secondary SCH. These sub-channels are sent in parallel using code division during the first 256 chips of each time slot.

The P-SCH, which is repeated at the beginning of each time slot. The same code is used by all the cells and enables the mobiles to detect the existence of the UMTS cell and to synchronize itself on the time slot boundaries. This is normally done with a single matched filter or any similar device. The slot timing of the cell is obtained by detecting peaks in the matched filter output.

This is the first step of the cell search procedure. The second step is done using the secondary synchronization channel.

Each cell of a node B has its own SCH timing, so that there is no overlapping.

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slot numberScramblingCode Group #0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16Group 1 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10Group 2 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12Group 3 1 2 3 1 8 6 5 2 5 8 4 4 6 3 7Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2

…Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10

Secondary Synchronization Channel (S-SCH)

�……..

2560 chips

acp

Slot # ?

P-SCH acp

Slot #?

16 6S-SCH

acp

Slot #?

11 Group 2Slot 7, 8, 9256 chips

The S-SCH also consists of a code, the Secondary Synchronization Code (SSC) that indicates which of the 64 scrambling code groups the cell’s downlink scrambling code belongs to. 16 different SSCs are defined. Each SSC is a 256 chip long sequence.

There is one specific SSC transmitted in each time slot, giving us a sequence of 15 SSCs. There is a total of 64 different sequences of 15 SSCs, corresponding to the 64 primary scrambling code groups. These 64 sequences are constructed so that one sequence is different from any other one, and different from any rotated version of any sequence. The UE correlates the received signal with the 16 SSCs and identifies the maximum correlation value.

The S-SCH provides the information required to find the frame boundaries and the downlink scrambling code group (one out of 64 groups). The scrambling code (one out of 8) can be determined afterwards by decoding the P-CPICH. The mobile will then be able to decode the BCH.

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Common Pilot Channel(CPICH)� Common Pilot Channel (CPICH)

� Carries pre-defined sequence.

� Fixed rate 30Kbps� SF=256

� Primary CPICH� Uses the fixed channel code -- Cch,256,0� Scrambled by the primary scrambling code� Only one CPICH per cell� Broadcast over the entire cell� The P-CPICH is a phase reference for SCH, Primary CCPCH, AICH, PICH.

By default, it is also a phase reference for downlink DPCH. Pre-defined symbol sequence

Slot #0 Slot #1 Slot # i Slot #14

Tslot = 2560 chips , 20 bits

1 radio frame: Tr = 10 ms

The Common Pilot Channel (CPICH) is a pure physical control channel broadcasted over the entire cell. It is not linked to any transport channel. It consists of a sequence of known bits that are transmitted in parallel with the primary and secondary CCPCH.

The CPICH is used by the mobile to determine which of the 8 possible primary scrambling codes is used by the cell, and to provide the phase reference for common channels.

Finding the primary scrambling code is done during the cell search procedure through a symbol-by- symbol correlation with all the codes within the code group. After the primary scrambling code has been identified, the UE can decode system information on the P-CCPCH.

There are two types of common pilot channels, the primary and secondary CPICH. The use of the S-CPICH is optional.

The P-CPICH is the phase reference for the SCH, P-CCPCH, AICH and PICH. It is broadcasted over the entire cell. The channelization code used to spread the P-CPICH is always Cch,256,0 (all ones). Thus, the P-CPICH is a fixed rate channel. Also, it is always scrambled with the primary scrambling code of the cell.

If it is used, the S-CPICH provides the phase reference for the secondary CCPCH and the downlink DPCH. It is transmitted over the entire cell or only over a part of the cell. It is spread by an arbitrary channelization code of SF=256, and scrambled with the primary or with a secondary scrambling code.

28


Primary Common Control Physical Channel (PCCPCH)� Fixed rate, fixed OVSF code�30kbps�Cch,256,1�� Carry BCH transport channel� The PCCPCH is not transmitted during the first 256 chips of each time slot.� Only data part� STTD transmit diversity may be used

PCCPCH Data18 bits

Slot #0

1 radio frame: T f = 10 ms

Slot #1 Slot #i

256 chips

Slot #14

T slot = 2560 chips,20 bits

SCH

The Primary Common Control Physical Channel (P-CCPCH) is a fixed rate (SF=256) downlink physical channel used to carry the BCH transport channel. It is broadcasted continuously over the entire cell like the P-CPICH.

The figure above shows the frame structure of the P-CCPCH. The frame structure is special because it does not contain any layer 1 control bits. The P-CCPCH only has one fix predefined transport format combination, and the only bits transmitted are data bits from the BCH transport channel. It is important to note that the P-CCPCH is not transmitted during the first 256 chips of the slot. In fact, another physical channel (SCH) is transmitted during that period of time. Thus, the SCH and the P-CCPCH are time multiplexed on every time slot.

Channelization code Cch,256,1 is always used to spread the P-CCPCH. Also, it is always scrambled by the primary scrambling code of the cell.

29


Paging Indicator Channel (PICH)� PICH is a fixed-rate (SF=256) physical channel used to carry the Paging Indicators (PI).� Frame structure of PICH: one frame of length 10ms consists of 300 bits of which 288 bits

are used to carry paging indicators and the remaining 12 bits are not defined.� N paging indicators {PI0, …, PIN-1} in each PICH frame, N=18, 36, 72, or 144. � If a paging indicator in a certain frame is set to 1, it indicates that UEs associated with

this paging indicator should read the corresponding frame of the associated S-CCPCH.

One radio frame (10 ms)

b1b0

288 bits for paging indication 12 bits (undefined)

b287 b288 b299

The Page Indicator Channel (PICH) is a fixed rate (30kbps, SF=256) physical channel used by the NodeB to inform a UE (or a group of UEs) that a paging information will soon be transmitted on the PCH. Thus, the mobile only decodes the S-CCPCH when it is informed to do so by the PICH. This enables to do other processing and to save the mobiles’ battery.

The PICH carries Paging Indicators (PI), which are user specific and calculated by higher layers. It is always associated with the S-CCPCH to which the PCH is mapped.

The frame structure of the PICH is illustrated above. It is 10 ms long, and always contains 300 bits (SF=256). 288 of these bits are used to carry paging indicators, while the remaining 12 are not formally part of the PICH and shall not be transmitted. That part of the frame (last 12 bits) is reserved for possible future use.

In order not to waste radio resources, several PIs are multiplexed in time on the PICH. Depending on the configuration of the cell, 18, 36, 72 or 144 paging indicators can be multiplexed on one PICH radio frame. Thus, the number of bits reserved for each PI depends of the number of PIs per radio frame. For example, if there is 72 PIs in one radio frame, there will be 4 (288/72) consecutive bits for each PI. These bits are all identical. If the PI in a certain frame is “1”, it is an indication that the UE associated with that PI should read the corresponding frame of the S-CCPCH.

30


Secondary Common Control Physical Channel (SCCPCH)� Carry FACH and PCH. � Two kinds of SCCPCH: with or without TFCI. UTRAN decides if a TFCI should be transmitted, UE must support TFCI.

� Possible rates are the same as that of downlink DPCH

� SF =256 - 4. � FACH and PCH can be mapped to the same or separate SCCPCHs. If mapped to the same S-CCPCH, they can be mapped to the same frame.

DataN bits

Slot #0 Slot #1 Slot #i Slot #14

1 radio frame: T f = 10 ms

T slot = 2560 chips,

DataPilot

N bitsPilotN bitsTFCITFCI

20*2 kbits (k=0..6)

The Secondary Common Control Physical Channel (S-CCPCH) is used to carry the FACH and PCH transport channels. Unlike the P-CCPCH, it is not broadcasted continuously. It is only transmitted when there is a PCH or FACH information to transmit. At the mobile side, the mobile only decodes the S-CCPCH when it expects a useful message on the PCH or FACH.

A UE will expect a message on the PCH after indication from the PICH (page indicator channel), and it will expect a message on the FACH after it has transmitted something on the RACH.

The FACH and the PCH can be mapped on the same or on separate S-CCPCHs. If they are mapped on the same S-CCPCH, TFCI bits have to be sent to support multiple transport formats

The figure above shows the frame structure of the S-CCPCH. There are 18 different slot formats determining the exact number of data, pilot and TFCI bits. The data bits correspond to the PCH and/or FACH bits coming from the transport sublayer. Pilot bit are typically used when beam forming techniques are used.

The SF ranges from 4 to 256. The channelization code is assigned by the RRC layer as is the scrambling code, and they are fixed during the communication. They are sent on the BCCH so that every UE can decode the channel.

As said before, FACH can be used to carry user data. The difference with the dedicated channel is that it cannot use fast power control, nor softhandover. The advantage is that it is a fast access channel.

31


Physical Random Access Channel (PRACH)� The random-access transmission data consists of two parts:

� One or several preambles�each preamble is of length 4096chips and consists of 256 repetitions of a signature whose length is 16 chips�16 available signatures totally

� 10 or 20ms message part�Which signature is available and the length of message part are determined by

higher layer

Message partPreamble

4096 chips10 ms (one radio frame)

Preamble Preamble

Message partPreamble

4096 chips 20 ms (two radio frames)

Preamble Preamble

The Physical Random Access Channel (PRACH) is used by the UE to access the network and to carry small data packets. It carries the RACH transport channel. The PRACH is an open loop power control channel, with contention resolution mechanisms (ALOHA approach) to enable a random access from several users.

The PRACH is composed of two different parts: the preamble part and the message part that carries the RACH message. The preamble is an identifier which consists of 256 repetitions of a 16 chip long signature (total of 4096 chips). There are 16 possible signatures which correspond to the 16 OVSF codes of SF=16. Basically, the UE randomly selects one of the 16 possible preambles and transmits it at increasing power until it gets a response from the network (on the AICH). That preamble is scrambled before being sent. That is a sign that the power level is high enough and that the UE is authorized to transmit, which it will do after acknowledgment from the network. If the UE doesn’t get a response from the network, it has to select a new signature to transmit. The message part is 10 or 20 ms long (split into 15 or 30 time slots) and is made of the RACH data and the layer 1 control information.

32


PRACH Access Timeslot Structure

#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14

5120 chips

radio frame: 10 ms radio frame: 10 ms

Access slot #0 Random Access Transmission

Access slot #1

Access slot #7

Access slot #14

Random Access Transmission

Random Access Transmission

Random Access TransmissionAccess slot #8

The PRACH transmission is based on the access frame structure. The access frame is access of 15 access slots and lasts 20 ms (2 radio frames).

To avoid too many collisions and to limit interference, a UE must wait at least 3 or 4 access slots between two consecutive preambles.

The PRACH resources (access slots and preamble signatures) can be divided between different Access Service Classes (ASC) in order to provide different priorities of RACH usage. The ASC number ranges from 0 (highest priority) to 7 (lowest priority).

33


PRACH Message Structure

PilotN bits

Slot # 0 Slot # 1 Slot # i Slot # 14

Message part radio frame TRACH = 10 ms

Tslot = 2560 chips, 10*2

Pilot

TFCIN bitsTFCI

DataN data bitsData

Control

kbits (k=0..3)

The data and control bits of the message part are processed in parallel. The SF of the data part can be 32, 64, 128 or 256 while the SF of the control part is always 256. The control part consists of 8 pilot bits for channel estimation and 2 TFCI bits to indicate the transport format of the RACH (transport channel), for a total of 10 bits per slot.

The OVSF codes to use (one for RACH data and one for control) depend on the signature that was used fo the preamble (for signatures s=0 to s=15: OVSFcontrol= Cch,256,m, where m=16s + 15; OVSFdata= Cch,SF,m, where m=SF*s/16.

34


Acquisition Indicator Channel (AICH)� Frame structure of AICH�two frames, 20 ms �consists of a repeated

sequence of 15 consecutive AS, each of length 40 symbols(5120 chips). Each time slot consists of two parts�an Acquisition-Indicator(AI) and a part of duration 1024chips with no transmission.

� Acquisition-Indicator AI have 16 kinds of Signature.

� CPICH is the phase reference of AICH.

AS #14 AS #0 AS #1 AS #i AS #14 AS #0

a1 a2a0 a31 a32a30 a33 a38 a39

AI part Unused part

20 ms

The Acquisition Indicator Channel (AICH) is a common downlink channel used to control the uplink random accesses. It carries the Acquisition Indicators (AI), each corresponding to a signature on the PRACH (uplink). When the node B receives the random access from a mobile, it sends back the signature of the mobile to grant its access. If the node B receives multiple signatures, it can sent all these signatures back by adding the together. At reception, the UE can apply its signature to check if the node B sent an acknowledgement (taking advantage of the orthogonality of the signatures).

The AICH consists of a burst of data transmitted regularly every access slot frame. One access slot frame is formed of 15 access slots, and lasts 2 radio frames (20 ms). Each access slot consists of two parts, an acquisition indicator part of 32 real-valued symbols and a long part during which nothing is transmitted to avoid overlapping due to propagation delays.

s (with values 0, +1 and -1, corresponding to the answer from the network to a specific user) and the 32 chip long sequence <bs,j> is given by a predefined table. There are 16 sequences <bs,j>, each corresponding to one PRACH signatures. A maximum of 16 AIs can be sent in each access slot. The user can multiply the received multi-level signal by the signature it used to know if its access was granted.

The SF used is always 256 and the OVSF code used by the cell is indicated in system information type 5.

35


Uplink Dedicated Physical Channel (DPDCH&DPCCH)

� DPDCH and DPCCH are I/Q code multiplexed within each radio frame

� DPDCH carries data generated at Layer 2 and higher layer

� DPCCH carries control information generated at Layer 1

� Each frame is 10ms and consists of 15 time slots, each time slotconsists of 2560 chips

� The spreading factor of DPDCH is from 4 to 256

� The spreading factor of DPDCH and DPCCH can be different in the same Layer 1 connection

� Each DPCCH time slot consists of Pilot, TFCI�FBI�TPC

Now look at the feature of uplink dedicated physical channel.

Pilot is used to help demodulate

TFCI: transport format combination indicator

FBI:used for the FBTD. (feedback TX diversity)

TPC: used to transport power control command.

Dedicated channels are established between one UE and the network to carry user dedicated data and control.

There are two kinds of uplink dedicated physical channels, the Dedicated Physical Data Channel (DPDCH) and the Dedicated Physical Control Channel (DPCCH). The DPDCH is used to carry the DCH transport channel. The DPCCH is used to carry the physical sublayer control bits.

There can be up to 6 uplink DPDCHs, but only one DPCCH is associated to these DPDCHs on each radio link. More than one DPDCH is used for data rates above 960 ksps (maximum capacity of one DPDCH). Thus, the maximum channel bit rate for one UE is 960 * 6 = 5.76 Msps in uplink, which can correspond to a user bit rate of 2.048 Mbps.

36


Frame Structure of Uplink DPDCH/DPCCH

PilotNpilot bits

TPCNTPCbits

DataNdatabits


Tslot = 2560 chips, 10*2k bits (k=0..6)

1 radio frame: T = 10 msf

DPDCH

DPCCHFBI

NFBI bitsTFCI

NTFCI bits

One the figure above, we can see the DPDCH and DPCCH time slot constitution. The parameter k determines the number of symbols per slot. It is related to the spreading factor (SF) of the DPDCH by this simple equation: SF=256/2k. The DPDCH SF ranges from 4 to 256. The SF for the uplink DPCCH is always 256, which gives us 10 bits per slot. The exact number of pilot, TFCI, TPC and FBI bits is configured by higher layers. This configuration is chosen from 12 possible slot formats. It is important to note that symbols are transmitted during all slots for the DPDCH

The different slot formats of the DPDCH and the DPCCH are given in TS 25.211.

The SF of the DPDCH is determined by higher layers.

37


Downlink Dedicated Physical Channel (DPDCH+DPCCH)

� DCH consists of dedicated data and control information.

� Control information includes�Pilot�TPC�TFCI(optional).

� The spreading factor of DCH can be from 512 to 4,and can be changed during connection

� DPDCH and DPCCH is time multiplexed.

Downlink physical channels are used to carry user specific information like speech, data or signaling, as well as layer 1 control bits. Like it was mentioned before, the payload from the DPDCH and the control bits from the DPCCH are time multiplexed on every time slot. The figure above shows how these two channels are multiplexed. There is only one DPCCH in downlink.

38


Frame Structure of Downlink DPCH

One radio frame, Tf = 10 ms


Tslot = 2560 chips, 10*2 kbits (k=0..7)

Data2Ndata2 bits

DPDCH

TFCINTFCI bits

PilotNpilot bits

Data1Ndata1 bits

DPDCH DPCCH DPCCH

TPCNTPC bits

We have known that the uplink DPDCH and DPCCH are I/Q code multiplexed. But the downlink DPDCH and DPCCH is time multiplexed. This is main difference. The chips of one slot is also 2560. Because the SF of downlink DPCH can be 512, so the k can be 7.

Downlink physical channels are used to carry user specific information like speech, data or signaling, as well as layer 1 control bits. Like it was mentioned before, the payload from the DPDCH and the control bits from the DPCCH are time multiplexed on every time slot. The figure above shows how these two channels are multiplexed. There is only one DPCCH in downlink.

Basically, there are two types of downlink DPCH. They are distinguished by the use or non use of the TFCI field. TFCI bits are not used for fixed rate services or when the TFC doesn’t change.

The parameter k in the figure above determines the total number of bits per time slot. It is related to the SF, which ranges from 4 to 512.

39


High-Speed Physical Downlink Shared Channel (HS-PDSCH)

� Bear service data and layer2 overhead bits mapped from the transport channel

� SF=16, can be configured several channels to increase data service

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, M*10*2k bits (k=4)

DataNData 1bits

1 subframe: Tf = 2 ms

HS-PDSCH is a downlink physical channel that carries user data and layer2 overhead bits mapped from the transport channel: HS-DSCH.

The user data and layer2 overhead bits from HS-DSCH is mapped onto one or several HS- PDSCH and transferred in 2 ms subframe using one or several channelization code with fixed SF=16

40


High-Speed Shared Control Channel (HS-SCCH)

� Carries physical layer signalling to a single UE ,such as modulation scheme (1 bit) ,channelization code set (7 bit), transport Block size (6bit),HARQ process number (3bit), redundancy version (3bit), new data indicator (1bit), Ue identity (16bit)

� HS-SCCH is a fixed rate (60 kbps, SF=128) downlink physical channelused to carry downlink signalling related to HS-DSCH transmission

Slot #0 Slot#1 Slot #2

T slot= 2560 chips, 40 bits

DataNData 1bits

1 subframe: Tf = 2 ms

HS-SCCH uses a SF=128 and has q time structure based on a sub-frame of length 2 ms,i.e. the same length as the HS-DSCH TTI. The timing of HS-SCCH starts two slot prior to the start of the HS-PDSCH subframe.

The following information is carried on the HS-SCCH (7 items)

1.Modulation scheme(1bit) QPSK or 16QAM

2.Channelization Code Set (7bits)

3.Transport Size ( 6bits)

4.HARQ process number (3bits)

5.Redundancy version (3bits)

6.New Data Indicator (1bit)

7.UE identity (16 bits)

In each 2 ms interval corresponding to one HS-DSCH TTI , one HS-SCCH carries physical-layer signalling to a single UE. As there should be a possibility for HS-DSCH transmission to multiple users in parallel (code multiplex), multiplex HS-SCCH may be needed in a cell. The specification allows for up to four HS-SCCHs as seen from a UE point of view .i.e. UE must be able to decode four HS-SCCH.

41


High-Speed Dedicated Physical Control Channel (HS-DPCCH )

� HS-DPCCH carries information to acknowledge downlink transport blocks and feedback information to the system for scheduling and link adaptation of transport block

�CQI and ACK/NACK

� Physical Channel ,Uplink, SF=256,power control

S u b f r a m e # 0 S u b f r a m e # i S u b f r a m e # 4

H A R Q - A C K C Q I

O n e r a d i o f r a m e T f = 1 0 m s

O n e H S -D P C C H s u b f r a m e ( 2 m s )

2 × T s lo t = 5 1 2 0 c h i p sT s lo t = 2 5 6 0 c h i p s

The uplink HS-DSCH related physical layer signalling consists of:

1.Acknowledgements for HARQ

2.Channel Quality Indicator (CQI)

As the HS-SCCH uses SF=256, there are a total of 30 channel bits per 2 ms sub frame (3 time slot). The HS-DPCCH information is divided in such a way that the HARQ acknowledgement is transmitted in the first slot of the subframe while the channel quality indication is transmitted in the rest slot.

42


Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology

Section 1 Physical Channel Structure and FunctionsSection 1 Physical Channel Structure and Functions

Section 2 Channel MappingSection 2 Channel Mapping

43


Mapping Between ChannelsLogical channels Transport channels Physical channels

BCCH BCH P-CCPCH

FACH S-CCPCH

PCCH PCH S-CCPCH

CCCH RACH PRACH

FACH S-CCPCH

CTCH FACH S-CCPCH

DCCH, DTCH DCH DPDCH

HS-DSCH HS-PDSCH

RACH, FACH PRACH, S-CCPCH

This page indicates how the mapping can be done between logical, transport and physical channels. Not all physical channels are represented because not all physical channels correspond to a transport channel.

The mapping between logical channels and transport channels is done by the MAC sublayer.

Different connections can be made between logical and transport channels:

� BCCH is connected to BCH and may also be connected to FACH;

� DTCH can be connected to either RACH and FACH, to RACH and DSCH, to DCH and DSCH, to a DCHor a CPCH;

� CTCH is connected to FACH;

� DCCH can be connected to either RACH and FACH, to RACH and DSCH, to DCH and DSCH, to a DCHor a CPCH;

� PCCH is connected to PCH;

� CCCH is connected to RACH and FACH.

These connections depend on the type of information on the logical channels.

44






45



Section 1 Coding and Multiplexing TechnologySection 1 Coding and Multiplexing Technology

Section 2 Spreading TechnologySection 2 Spreading Technology

Section 3 Modulation TechnologySection 3 Modulation Technology

46


CRC of TB

� Error detection is provided on transport blocks through a CyclicRedundancy Check (CRC)

� CRC size is informed by higher layer signal

�0�8�12�16�24(optional)

� If no TB are input, no CRC bits should be attached. If TB are input with TB SIZE=0,CRC bits shall be also added ,but all CRC are zero

Error detection is provided on transport blocks through a Cyclic Redundancy Check (CRC). The size of the CRC is 24, 16, 12, 8 or 0 bits and it is signalled from higher layers what CRC size that should be used for each TrCH.

47


TB Concatenation and Code Block Segmentation

� All transport blocks in a TTI are serially concatenated .

� The maximum size of the code blocks depends on whether convolutional coding or turbo coding is used for the TrCH .

� Convolutional code: if TBS SIZE>504,segmented to multiple code block of the same size.

� Turbo code:if TBS SIZE>5114, segmented to multiple code block of the same size.

� No coding:no segmentation

� If codes cannot be segmented evenly, fill in “0” bits at the beginning of the first code block.

� If the code block length of Turbo code<40, fill in “0” bits at the beginning to keep the code length constantly as 40

All transport blocks in a TTI are serially concatenated. If the number of bits in a TTI is larger than Z, the maximum size of a code block in question, then code block segmentation is performed after the concatenation of the transport blocks. The maximum size of the code blocks depends on whether convolutional coding or turbo coding is used for the TrCH.

convolutional coding: Z = 504;

turbo coding: Z = 5114.

48


Channel coding

� The following channel coding schemes can be applied to TrCHs:

�Convolutional coding, coding rates 1/3 and 1/2 are defined

�Turbo coding, The coding rate of Turbo coder is 1/3

�No coding

� Usage of coding

�BCH, PCH and RACH——1/2 Convolutional coding

�DCH and FACH——1/2 or 1/3 Convolutional coding ,1/3 Turbo coding, no coding

The following channel coding schemes can be applied to TrCHs:

- convolutional coding;

- turbo coding.

Usage of coding scheme and coding rate for the different types of TrCH is shown in above slide

49


Rate Matching

� Rate matching means that bits on a transport channel are repeated or punctured.

� The number of bits on a transport channel can vary between different transmission time intervals(TTI). In the downlink the transmission is interrupted if the number of bits is lower than maximum. When the number of bits between different transmission time intervals in uplink is changed, bits are repeated or punctured to ensure that the total bit rate after TrCH multiplexing is identical to the total channel bit rate of the allocated dedicated physical channels.

Rate matching means that bits on a transport channel are repeated or punctured. The objective of rate matching is to Balance the multiplexing of Eb/I0 of each TrcH mapped to the same CCTrCH, to Match channel(uplink) and to Avoid multi-code transmission. Rate matching has two types:dynamic matching and static matching. downlink, there is no repeating, only puncturing

50


Interleaving

� Function: reduce the influence of fast fading.

� Two kinds of interleaving: 1st interleaving and 2nd interleaving

�The length of 1st interleaving is TTI of TrCH, 1st interleaving is a inter-frame interleaving

�The length of 2nd interleaving is a physical frame, 2nd interleaving is a intra-frame interleaving.

51


Radio Frame Segmentation

� When the transmission time interval (TTI) is longer than 10 ms, the input bit sequence is segmented and mapped onto consecutive Firadio frames.

� Following radio frame size equalisation in the UL the input bit sequence length is guaranteed to be an integer multiple of Fi.

� Following rate matching in the DL the input bit sequence length is guaranteed to be an integer multiple of Fi.

� Fi: Number of radio frames in the transmission time interval of TrCHi.

52


Multiplexing of TrCH

� Every 10 ms, one radio frame from each TrCH is delivered to the TrCH multiplexing. These radio frames are serially multiplexed into a coded composite transport channel (CCTrCH)

� The format of CCTrCH is indicated by TFCI

� TrCH can have different TTI before multiplexing

� 2 types of CCTrCH:Common and dedicated

�Common CCTrCH should be multiplexed by common TrCH;

�Dedicated CCTrCH should be multiplexed by dedicated TrCH

� There is only one CCTrCH in uplink and one or several CCTrCH in downlink for one user

53


Insertion of Discontinuous Transmission (DTX) Indication Bits

� In the downlink, DTX is used to fill up the radio frame with bits.

� DTX indication bits only indicate when the transmission should be turned off, they are not transmitted.

� 1st insertion of DTX indication bits

�This step of inserting DTX indication bits is used only if the positions of the TrCHs in the radio frame are fixed

� 2nd insertion of DTX indication bits

�The DTX indication bits inserted in this step shall be placed atthe end of the radio frame.

54


Physical Channel Segmentation and Mapping

� When multiple physical channels are used, one CCTrCH radio framecan be divided into multiple physical frames –multicode transmission

� Each physical channel of multicode transmission must have the same SF

� DPCCH and DPDCH of uplink physical channel is code multiplexed.

� DPCCH and DPDCH of downlink physical channel is time multiplexed

� Uplink physical channel must be fully filled except when compressed mode is used

� In downlink, the PhCHs do not need to be completely filled with bits that are transmitted over the air. Values correspond to DTX indicators, which are mapped to the DPCCH/DPDCH fields but are not transmitted over the air.

55


10�20� 40 or 80ms

data

data

data

TrCH-i

dataCRC dataCRC dataCRC

dataCRCdataCRC dataCRCd a t aCBL CBL CBL

0�8�16 or 24bits

Size Z�512�Ktail � Conventional code

5120�Ktail �Turbo code

CedBL CedBL CedBLCoded data Channel CodingRate matched data

Rate matched data DTXor

orData before 1st interleavingData after 1st interleaved

Radio frame Radio frame Radio frame

Number of Rado frame�1�2�4 or 8

TrCH-1 TrCH-2 TrCH-ICCTrCHTrCH-1 TrCH-2 TrCH-I DTXCCTrCH

Ph-1 Ph-2 Ph-P

10ms

10msPh-1 Ph-2 Ph-P

TPC TFCI pilot

SpreadingScrambling

SpreadingScrambling

SpreadingScrambling

TrCH-i+1

data1 data2 TPC TFCI pilotdata1 data2 TPC TFCI pilotdata1 data2

Transport channel multiplexing structure for downlinkTransport channel multiplexing structure for downlink

56


Example of Coding and Multiplexing

The number of TrChs 3

Transport block size 81, 103, and 60 bitsCRC 12 bits (attached only to TrCh#1)

Coding CC, coding rate = 1/3 for TrCh#1, 2 coding rate = 1/2 for TrCh#3

TTI 20 ms

Transport block size 148 bits

Transport block set size 148 bits

CRC 16 bitsCoding CC, coding rate = 1/3

TTI 40 ms

Parameters for 12.2kb/s AMR speech

Parameters for 3.4kb/s control channel

57


Example of Coding and MultiplexingTrC h#1Transport b lock

CRC a ttachm en t

CRC

Tail b it a ttachm en t

C onvo lu tion al cod ing R =1/3 , 1 /2

R ate m atch in g

81

81

303

Tail893

303+N RM 11 st in te rleav in g

1 2

R ad io frame segm enta tio n

#1 a

To TrC h M ultip lex ing

303 +N RM 1

N RF1 = (30 3 +N RM 1)/2

N RF2 = (33 3+ N RM 2)/2

N RF3 = (13 6+ N RM 3)/2

# 1b

TrC h#2103

103

333

Tail8103

333 +N RM 2

# 2a

TrC h#360

60

136

Ta il860

136 +N RM 3

# 3a

136 +N RM3

# 3b

333 +N RM 2

#2bN RF1 N RF1 N RF2 N RF2 N RF3 N RF3

58


Example of Coding and Multiplexing(3.4kbps)T r a n s p o r t b l o c k

C R C a t t a c h m e n t

C R C

C o n v o l u t i o n a l c o d i n g R = 1 / 3

R a t e m a t c h i n g

1 4 8

1 4 8

5 1 6 * B

T a i l8 * B

( 5 1 6 + N R M ) * B

1 s t i n t e r l e a v i n g

1 6 b i t s

R a d i o f r a m e s e g m e n t a t i o n

# 1[ ( 1 2 9 + N R M ) * B + N D I ] /

4

T o T r C h M u l t i p l e x i n g

( 5 1 6 + N R M ) * B + N D I

# 2 # 4

T a i l b i t a t t a c h m e n t

1 6 4 * B

# 3

T r B k c o n c a t i n a t i o n B T r B k s ( B = 0 , 1 )

1 6 4 * B

( 5 1 6 + N R M ) * B + N D I

I n s e r t i o n o f D T X i n d i c a t i o n *

[ ( 1 2 9 + N R M ) * B + N D I ] /4

[ ( 1 2 9 + N R M ) * B + N D I ] /4

[ ( 1 2 9 + N R M ) * B + N D I ] /4

* I n s e r t i o n o f D T X i n d i c a t i o n i s u s e d o n l y i f t h e p o s i t i o n o f t h e T r C H s i n t h e r a d i o f r a m e i s f i x e d .

59


Example of Coding and Multiplexing

12.2 kbps data 3.4 kbps data

TrCHmultiplexing

30 ksps DPCH

2nd interleaving

Physical channelmapping

#1#1a #1c

1 2 15

CFN=4Nslot

Pilot symbol TPC

1 2 15

CFN=4N+1slot

1 2 15

CFN=4N+2slot

1 2 15

CFN=4N+3slot

#1b #2#2a #2c#2b #3#1a #1c#1b #4#2a #2c#2b

#1a #2a #1b #2b #1c #2c #1a #2a #1b #2b #1c #2c #1 #2 #3 #4

510 510 510 510

12.2 kbps data

60



Section 1 Coding and Multiplexing TechnologySection 1 Coding and Multiplexing Technology



61


Uplink DPCCH/DPDCH Spreading� The DPCCH is always spread by code cc = Cch,256,0� When only 1 DPDCH exists,(Cd,1 = Cch,SF,k ) k=SF/4� The code used for scrambling of the uplink DPCCH/DPDCH may be of either long

or short type

IΣ

j

c d , 1 β d

S lo n g , n o r S s h o r t , n

I + j Q

D P D C H 1

Q

c d , 3 β d

D P D C H 3

c d , 5 β d

D P D C H 5

c d , 2 β d

D P D C H 2

c d , 4 β d

D P D C H 4

c d , 6 β d

D P D C H 6

c c β c

D P C C H

ΣUp to 6 DPDCH for one user

The figure above illustrates the principle of the uplink spreading of DPDCH and DPCCH. Firsteach channel is spread by an OVSF code. As it was mentioned before, channelization codes are only used to spread the information in uplink

The channelization code used for DPCCH is always Cch,256,0 (all ones). If only one DPDCH is used, it is spread by code Cch,SF,k , where k is linked to SF by k=SF/4. When more than one DPDCH is used, they will all have a SF equal to 4. DPDCHn is spread by code cd,n = Cch,4,k , where k=1 for n ∈ {1,2} , k=3 for n ∈ {3,4} , and k=2 for n ∈ {5,6}. Thus, the same channelization code can be used by two different DPDCHs in uplink. After channelization, the chip rate is equal to 3.84 Mcps.

After channelization, the spread signals are weighted by a gain factor (βc for DPCCH and βd for all DPDCHs). These gain factors are quantized into 4 bits, giving values between 0 and 1. There is at least one of the values βc and βd that is equal to 1. These gain factors may vary for each TFC, and are either signaled or computed.

Then, the streams of chips are summed up giving a multilevel signal. After this addition, the real-valued chips on the I and Q branches are summed up and treated like a complex-valued stream of chips. This stream is scrambled by a complex-valued scrambling code. For DPDCH and DPCCH, a unique scrambling code of 38,400 chips (corresponding to one radio frame) is used. That code can be either of long or short type.

Finally, the complex chips are I and Q multiplexed and sent over the air interface. The result of all this is a BPSK modulation, which gives us 1 bit per symbol. We will study that part in the next section.

There can be up to 6 uplink DPDCHs, but only one DPCCH is associated to these DPDCHs on each radio link. More than one DPDCH is used for data rates above 960 ksps (maximum capacity of one DPDCH). Thus, the maximum channel bit rate for one UE is 960 * 6 = 5.76 Mbps in uplink, which can correspond to a user bit rate of 2.048 Mbps.

62


Uplink PRACH Spreading

� Message part is shown in the following figure�the value of gain factors is the same with DPDCH/DPCCH

jβccc

cd βd

Sr-msg,n

I+jQ

PRACH messagecontrol part

PRACH messagedata part

Q

I

This is the PRACH spreading figure. the value of gain factors is the same with DPDCH/DPCCH

The preamble signature s, 0 ≤ s ≤ 15, points to one of the 16 nodes in the code-tree that corresponds to channelization codes of length 16. The sub-tree below the specified node is used for spreading of the message part. The control part is spread with the channelization code cc of spreading factor 256 in the lowest branch of the sub-tree, i.e. cc = Cch,256,m where m = 16�s + 15. The data part uses any of the channelization codes from spreading factor 32 to 256 in the upper-most branch of the sub-tree. To be exact, the data part is spread by channelization code cd = Cch,SF,m and SF is the spreading factor used for the data part and m = SF�s/16.

The scrambling code used for the PRACH message part is 10 ms long, and there are 8192 different PRACH scrambling codes defined.

63


Downlink Spreading

� Downlink physical channel except SCH is first serial-to-parallel converted , spread by the spreading code, and then scrambled by a complex-valued scrambling code.

� The beginning chip of the scrambling code is aligned with the frame boundary of P-CCPCH.

� Each channel have different gain factor

I

Data of physical channel except SCH

S→→→→P

Cch,SF,m

j

Sdl,n

Q

I+jQ S

Each pair of two consecutive real-valued symbols is first serial-to-parallel converted and mapped to an I and Q branch. The mapping is such that even and odd numbered symbols are mapped to the I and Q branch respectively.

The I and Q branches are then both spread to the chip rate by the same real-valued channelization code Cch,SF,m. The channelization code sequence shall be aligned in time with the symbol boundary. The sequences of real-valued chips on the I and Q branch are then treated as a single complex-valued sequence of chips.

64


Downlink Spreading

Different physical channel come from point S

ΣΣΣΣ

G1

G2

GP

GS

S-SCH

P-SCH ΣΣΣΣ

Each complex-valued spread channel, corresponding to point S in the Figure, is separately weighted by a weight factor Gi. The complex -valued P-SCH and S-SCH, are separately weighted by weight factors Gp and Gs. All downlink physical channels are then combined using complex addition.

65



Section 1 Coding and Multiplexing Technology Section 1 Coding and Multiplexing Technology



66


Uplink Modulation� The chip rate is 3.84Mbps� In the uplink, the complex-valued chip sequence generated by the

spreading process is QPSK modulated

S

Im{S}

Re{S}

cos(ωt)

Complex-valued sequence after spreading

-sin(ωt)

Split real & imag parts

Pulse shaping

Pulse shaping

The complex-valued sequence S after spreading is split into real part and imaginary part. Then the real part is multiplied by cos(wt) after pulse shaping. The imaginary part is multiplied by –sin(wt) after shaping.

67


Downlink Modulation� The chip rate is 3.84Mbps� In the downlink, the complex-valued chip sequence generated by the

spreading process is QPSK modulated

S

Im{S}

Re{S}

cos(ωt)

Complex-valued sequence after spreading

-sin(ωt)

Split real & imag parts

Pulse shaping

Pulse shaping

The complex-valued sequence S after spreading is split into real part and imaginary part. Then the real part is multiplied by cos(wt) after pulse shaping. The imaginary part is multiplied by –sin(wt) after shaping.

68






69


Synchronization Procedure—Cell Search

Frame synchronization and code-group identification

Scrambling-code identification

UE uses SSC to find frame synchronization and identify the code group of the cell found in the first step

UE determines the primary scrambling code through correlation over the CPICH with all codes within the identified group, and then detects the P-CCPCH and reads BCH information�

Slot synchronizationUE uses PSC to acquire slot synchronization to a cell

The purpose of the Cell Search Procedure is to give the UE the possibility of finding a cell and of determining the downlink scrambling code and frame synchronization of that cell. This is typically performed in 3 steps:

�PSCH (Slot synchronization): The UE uses the SCH’s primary synchronization code to acquire slot synchronization to a cell. The primary synchronization code is used by the UE to detect the existence of a cell and to synchronize the mobile on the TS boundaries.This is typically done with a single filter (or any similar device) matched to the primary synchronization code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output.

�SSCH (Frame synchronization and code-group identification): The secondary synchronization codes provide the information required to find the frame boundaries and the group number. Each group number corresponds to a unique set of 8 primary scrambling codes. The frame boundary and the group number are provided indirectly by selecting a suite of 15 secondary codes. 16 secondary codes have been defined C1, C2, ….C16. 64 possible suites have been defined, each suite corresponds to one of the 64 groups. Each suite of secondary codes is composed of 15 secondary codes (chosen in the set of 16), each of which will be transmitted in one time slot. When the received codes matches one of the possible suites, the UE has both determined the frame boundary and the group number.

�CPICH (Scrambling-code identification): 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 the 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.

70


Synchronization Procedure— Channel Timing Relationship

AICH accessslo ts

SecondarySCH

PrimarySCH

ττττS-CCPCH,k

10 ms

ττττ PICH

#0 #1 #2 #3 #14#13#12#11#10#9#8#7#6#5#4

P -CCPCH, (SFN modulo 2) = 0 P -CCPCH, (SFN modulo 2) = 1

CPICH

k:th S -CCPCH

PICH for k:th S -CCPCH

n:th DPCHττττ DPCH,n

This page shows the transmission timing of the various downlink channels. The 256 chips gap in the beginning of each of the PCCPCH slots is to accommodate the transmission of the SCH. The SCH is always transmitted from the base station and is transmitted at the same timing reference as the CPICH. The SCCPCH is only transmitted when there is data available. Therefore ,it has its own transmission timing. The timing offset is a multiple of 256 chips. The PICH has a fixed time offset time offset with respect to the SCCPCH to be able to tell UE that there is paging coming on the PCH mapped onto the SCCPCH

71


Random access procedure START

Choose a RACH sub channel fromavailable ones

Get available signatures

Set Preamble Retrans Max

Set Preamble _Initial _Power

Send a preamble

Check the corresponding AI

Increase message part power by p-m based on preamble power

Set physical status to be RACHmessage transmitted Set physical status to be Nack

on AICH received

Choose a access slot again

Counter> 0 & Preamble power-maximum allowed power<6 dB

Choose a signature and increase preamble transmit power

Set physical status to be Nackon AICH received

Get negative AI

No AI

Report the physical status to MAC

END

Get positive AI

The counter of preamble retransmit Subtract-1, Commanded preamble power

increased by Power Ramp Step

N

Y

Send the corresponding message part

72


Random Access Procedure—RACH� Physical random access procedure

�1. Derive the available uplink access slots, in the next full access slot set, for the set of available RACH sub-channels within the given ASC. Randomly select one access slot among the ones previously determined. If there is no access slot available in the selected set, randomly select one uplink access slot corresponding to the set of available RACH sub-channels within the given ASC from the next access slot set. The random function shall be suchthat each of the allowed selections is chosen with equal probability�

�2. Randomly select a signature from the set of available signatureswithin the given ASC. �

�3. Set the Preamble Retransmission Counter to Preamble_ Retrans_ Max

73


Random Access Procedure—RACH

� 4. Set the parameter Commanded Preamble Power to Preamble_Initial_Power

� 5. Transmit a preamble using the selected uplink access slot, signature, and preamble transmission power.

� 6. If no positive or negative acquisition indicator (AI ≠ +1 nor –1) corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot:

− A: Select the next available access slot in the set of available RACH sub-channels within the given ASC;

− B: select a signature;

− C: Increase the Commanded Preamble Power;

− D: Decrease the Preamble Retransmission Counter by one. If the Preamble Retransmission Counter > 0 then repeat from step 6. Otherwise exit the physical random access procedure.

74


Random Access Procedure—RACH

�7. If a negative acquisition indicator corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot, exit the physical random accessprocedure Signature

�8. If a positive acquisition indicator corresponding to the selected signature is detected , Transmit the random access message threeor four uplink access slots after the uplink access slot of the last transmitted preamble

�9. exit the physical random access procedure

75


Transmit diversity ModeApplication of Tx diversity modes on downlink physical channelApplication of Tx diversity modes on downlink physical channel

––applied–AICH

––applied–HS-SCCH

–appliedapplied–HS-PDSCH

––applied–PICHappliedappliedapplied–DPCH

––applied–S-CCPCH

–––appliedSCH

––applied–P-CCPCH

Mode 2Mode 1STTDTSTDClosed loop modeOpen loop modePhysical channel type

Transmitter-antenna diversity can be used to generate multipath diversity in places where it would not otherwise exist. Multipath diversity is a useful phenomenon, especially if it can be controlled. It can protect the UE against fading and shadowing. TX diversity is designed for downlink usage. Transmitter

diversity needs two antennas, which would be an expensive solution for the UEs.

The UTRA specifications divide the transmitter diversity modes into two categories: (1) open-loop mode and (2) closed-loop mode. In the open-loop mode no feedback information from the UE to the Node B is available. Thus the UTRAN has to determine by itself the appropriate parameters for the TX diversity. In the closed-loop mode the UE sends feedback information up to the Node B in order to optimize the transmissions from the diversity antennas.

.

76

Thus it is quite natural that the open-loop mode is used for the common channels, as they typically do not provide an uplink return channel for the feedback information. Even if there was a feedback channel, the Node B cannot really optimize its common channel transmissions according to measurements made by one particular UE. Common channels are common for everyone; what is good for one UE may be bad for another. The closed-loop mode is used for dedicated physical channels, as they have an existing uplink channel for feedback information. Note that shared channels can also employ closed loop power control, as they are allocated for only one user at a time, and they also have a return channel in the uplink.There are two specified methods to achieve the transmission diversity in the open-loop mode and two methods in closed-loop mode

77


Transmit Diversity-STTD

� Space time block coding based transmit antenna diversity(STTD�� 4 consecutive bits b0, b1, b2, b3 using STTD coding

b0 b1 b2 b3

b0 b1 b2 b3

-b2 b3 b0 -b1

Antenna 1

Antenna 2Channel bits

STTD encoded channel bitsfor antenna 1 and antenna 2.

The TX diversity methods in the open-loop mode are

(1) space time-block coding-based transmit-antenna diversity (STTD)

(2) time-switched transmit diversity (TSTD).

In STTD the data to be transmitted is divided between two transmission antennas at the base station site and transmitted simultaneously. The

channel-coded data is processed in blocks of four bits. The bits are time reversed and complex conjugated, as shown in above slide. The STTD method, in fact, provides two brands of diversity. The physical separation of the antennas provides the space diversity, and the time difference derived from the bit-reversing process provides the time diversity.

These features together make the decoding process in the receiver more reliable. In addition to data signals, pilot signals are also transmitted via both

antennas. The normal pilot is sent via the first antenna and the diversity pilot via the second antenna. The symbol sequence for the second pilot is given in

The two pilot sequences are orthogonal, which enables the receiving UE to extract the phase information for both antennas.

The STTD encoding is optional in the UTRAN, but its support is mandatory for the UE’s receiver.

78


Transmit Diversity-TSTD

Time switching transmit diversity (TSTD) is used only on SCH chaTime switching transmit diversity (TSTD) is used only on SCH channel.nnel.

Antenna 1

Antenna 2

ac si,0

acp

acsi,1

acp

acsi,14

acp

Slot #0 Slot #1 Slot #14

acsi,2

acp

Slot #2

(Tx OFF) (Tx OFF)(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)(Tx OFF)(Tx OFF)

Time-switched transmit diversity (TSTD) can be applied to the SCH. Just as with STTD, the support of TSTD is optional in the UTRAN, but mandatory in the UE. The principle of TSTD is to transmit the synchronization channels via the two base station antennas in turn. In even-numbered time slots the SCHs are transmitted via antenna 1, and in odd-numbered slots via antenna 2. This is depicted in above Figure. Note that SCH channels only use the first 256 chips of each time slot (i.e., one-tenth of each slot).

79


Closed –Loop Mode

The closed-loop-mode transmit diversity can only be applied to the downlink channel if there is an associated uplink channel. Thus this mode canonly be used with dedicated channels The chief operating principle of the closed loop mode is that the UE can control the transmit diversity in the base station by sending adjustment commands in FBI bits on the uplink DPCCH. This is depicted in next slide .The UE uses the base station’s common pilot channels to estimate the channels separately. Based on this estimation, it generates the adjustment information and sends it to the UTRAN to maximize the UE’s received

power.

There are actually two modes in the closed-loop method. In mode 1 only the phase can be adjusted; in mode 2 the amplitude is adjustable as well as the phase. Each uplink time slot has one FBI bit for closed-loop-diversity control. In mode 1 each bit forms a separate adjustment command, but in mode 2 four bits are needed to compose a command

80


Transmit Diversity�Closed Loop Mode� Closed loop mode transmit diversity

� Used in DPCH and PDSCH�

� Channel coding, interleaving and spreading are done as in non-diversity mode. The spread complex valued signal is fed to both TX antenna branches, and weighted with antenna specific weight factors w1 and w2.

� The weight factors are determined by the UE, and signalled to the UTRAN access point (=cell transceiver) using the D-bits of the FBI field of uplink DPCCH.

� The calculation of weight factor is the key point of closed loop Tx diversity.there are two modes with different calculation methods of weight factor�

− 1�mode 1 uses phase adjustment�the dedicated pilot symbols of two antennas are different(orthogonal)

− 2�mode 2 uses phase/amplitude adjustment� the dedicated pilot symbols of two antennas are the same.

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