1 wcdma ran protocols and procedures chapter 5 rlc and mac protocols

1

WCDMA RAN Protocols and Procedures

Chapter 5RLC and MAC Protocols

2

Objectives of Chapter 5, RLC and MAC Protocols

After this chapter the participants will be able to:

1. Explain the RLC functions.

2. List the different modes of RLC (transparent, unacknowledged and acknowledged mode) and explain the structure of the Protocol Data Unit (PDU) involved in these cases.

3. Explain the MAC functions.

4. Explain the MAC architecture, its entities and their usage for the mapping of transport channels.

5. List the contents of the MAC Protocol Data Unit (PDU).

6. Explain the Transport Format selection and the relation between Combinations (TFC) and Sets (TFCS).

7. Explain Channel Type Switching.

8. Explain the structure and mapping of physical channels.

3

INTRODUCTION

4

Uu interface protocol architecture (figure 5-1) (1)

L3/RRC

cont

rol

cont

rol

cont

rol

cont

rol

LogicalChannels

TransportChannels

PHY

L2/MAC

L1

RLC L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLC

RLC

UuS boundary

BMC L2/BMC

RRC

Control

PDCPPDCP L2/PDCP

PhysicalChannels

5

• The control interfaces between the RRC and all the lower layer protocols are used by the

RRC layer :

* configure characteristics of the lower layer protocol entities, including parameters for

the physical, transport and logical channels.

* to command the lower layers to report measurement results and errors to the RRC.

Uu interface protocol architecture (figure 5-1) (2)

6

RADIO LINK CONTROL (RLC) PROTOCOL

-- INTRODUCTION--

7

INTRODUCTION

• The RLC work in transparent, unacknowledged and acknowledged mode.

• in the control plane, the service provided by the RLC layer is called Signalling Radio

Bearer (SRB).

• In the user plane, the service provided by the RLC layer is called a Radio Bearer (RB)

8

Protocol Data Unit (PDU) and Service Data Unit (SDU) (1)(figure 5-2)

SDU : Service Data Unit

PDU : Protocol Data Unit

PCI: Protocol Control Information

Processing done for the SDUs at layer N can be e.g.:-Add overhead (e.g. sequence number, ch type info)-Segmentation, etc.

PDCP PDCP PDU

RLC

RLC SDURLC SDURLC PCIRLC PCI

RLC PDU

MACMAC SDUMAC SDU

PDCP PDU

RLC SDURLC SDU

RLC PDU

MAC SDUMAC SDU

Uu interface

RLC PCIRLC PCI payloadpayload RLC PCIRLC PCI payloadpayload

9

• the Radio Link Control (RLC) layer receives a PDCP PDU.

• In the RLC layer, the data will be known as an RLC SDU

• After the header is added, the data is called an RLC PDU

• In the Medium Access Layer (MAC) this is now a MAC SDU.

• The MAC layer may add a MAC header and send MAC PDUs to the physical layer.

Protocol Data Unit (PDU) and Service Data Unit (SDU) (2)

10


-- RLC FUNCTIONS --

11

RLC Protocol Entity (1)

RLC Services– L2 connection establishment and release– Transparent data transfer– Unacknowledged data transfer– Acknowledged data transfer

RLC Functions– Segmentation and re-assembly– Concatenation– Padding– Transfer of user data in transparent,

unacknowledged and acknowledged mode.– Error correction (ARQ) – In-sequence delivery– Duplicate detection– Flow control– Sequence number check– Ciphering

L3

cont

rol

cont

rol

cont

rol

cont

rol

LogicalChannels

TransportChannels

PHY

L2/MAC

L1

RLC L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLC

RLC

UuS boundary

BMC L2/BMC

RRC

Control

PDCPPDCP L2/PDCP

12


1. Segmentation and reassembly

• Performs segmentation/reassembly of variable length higher layer PDUs into/from

smaller RLC Payload Units (PUs).

2. Concatenation

• If the contents of an RLC SDU do not fill an integral number of RLC PDUs, the first

segment of the next RLC SDU may be put into the RLC PDU in concatenation with the

last segment of the previous RLC SDU

3. Padding

• When concatenation is not applicable and the remaining data to be transmitted does

not fill an entire RLC SDU of given size, the remainder of the data field is filled with

padding bits.

4. Transfer of user data

• RLC supports acknowledged, unacknowledged and transparent data transfer.

Transfer of user data is controlled by QoS setting.

13


14


15


-- RLC MODES --

17

RLC Layer Architecture (figure 5-3)

Tx

Tx

Tx Tx/Rx

Rx

Rx

Rx

Rx

TxTx/Rx

TM UM AM

• In Transparent and Unacknowledged Mode the RLC entities are unidirectional

• In Acknowledged Mode, it is bi-directional

18

RLC Transparent Mode PDU(figure 5-4)

Data

The RLC TM PDU introduces no overhead Protocol functions may still be applied e.g. segmentation

TM is used for voice and circuit switched data where delay should be as low as possible. It is also used for the SRB for BCCH and PCCH.

19

RLC Transparent Mode Entities(figure 5-5)

Transmitting TM- RLC entity Transmission

buffer

Segmentation

TM-SAP

CCCH/DCCH/DTCH/SHCCH – UE BCCH/PCCH/DCCH/DTCH – UTRAN

Receiving TM- RLC entity

Reception buffer

Reassembly

TM-SAP

Radio Interface (Uu)

CCCH/DCCH/DTCH/SHCCH – UTRAN BCCH/PCCH/DCCH/DTCH – UE

UE/UTRAN UTRAN/UE

20

RLC Unacknowledged Mode PDU (figure 5-6)

Oct1

E Length Indicator

Data

PAD Oct N

E Length Indicator (Optional)

.

.

.

E Sequence Number

(Optional)

.

.

.(Optional)

Sequence number.E: Extension bit. Indicates whether next octet will be a length

indicator and E bit.Data shall be a multiple of 8 bits.If the transmitted data does not fill an entire PDU the remainder of

the data field is filled with padding bits.

Cip

her

ing

Un

it

• no retransmission protocol is used and data delivery is not guaranteed. Received erroneous data is

either marked or discarded depending on the configuration.

21

RLC Fields (table 5-1)

length indicators

• Length Indicators are also used to define whether Padding is included in the UMD PDU.

• It may be 7 bits (if the largest PDU size is ≤ 125 octets) or 15 bits long (otherwise).

• some length indicator sequences are predefined

22

Predefined length indicators. (table 5-2) Length: 7 bits

Bit Description0000000 The previous RLC PDU was exactly filled with the last segment of an RLC SDU

and there is no "Length Indicator" that indicates the end of the RLC SDU in theprevious RLC PDU.

1111100 UMD PDU: The first data octet in this RLC PDU is the first octet of an RLCSDU. AMD PDU: Reserved (PDUs with this coding will be discarded by thisversion of the protocol).

1111101 Reserved (PDUs with this coding will be discarded by this version of theprotocol).

1111110 AMD PDU: The rest of the RLC PDU includes a piggybacked STATUS PDU.UMD PDU: Reserved (PDUs with this coding will be discarded by this versionof the protocol).

1111111 The rest of the RLC PDU is padding. The padding length can be zero.

23

RLC Unacknowledged Mode Entities (figure 5-7)

Transmitting UM RLC entity

Transmission buffer

UM -SAP

Receiving UM RLC enti ty

Reception buffer

UM -SAP

Radio Interface (Uu)

Segmentation & Concatenation

Ciphering

Add RLC header

Reassembly

Deciphering

Remove RLC header

DCCH/DTCH – UE CCCH/SHCCH/DCCH/DTCH/CTCH – UTRAN

DCCH/DTCH – UTRAN CCCH/SHCCH/DCCH/DTCH/CTCH – UE

UE/UTRAN UTRAN/UE Segmentation & Concatenation

Padding Ciphering Sequence number

check Transfer of user data

• Example for UM RLC: The cell broadcast service is an example of a user service that

could utilise UM as well as the RRC Connection Setup/Reject message sent on

CCCH/FACH.

24

RLC Acknowledged Mode PDU (figure 5-8)

Sequence NumberSequence Number

D/C

ELength Indicator

Data

PAD or a piggybacked STATUS PDU

Oct1Oct2

OctN

P HEELength Indicator

.

.

.

(Optional)Oct3

(Optional)

D/C: Data/Control PDU indicator bit P: Poll bit. To be used to request for

a Status PDU. HE: Header Extension bits. Indicates if the

next octet will be data or a length indicatorand E bit.

E: Extension bit. Indicates whether next octet will be a length indicator and E bit.

Cip

he

rin

g U

nit

• Example for AM RLC:

* for packet-type services such as Internet

browsing and email (DTCH).

* also used for signalling, when it is

important that the signalling is received

correctly but delay is not the most

important.

25

RLC fields (table 5-3 and 5-4)

D/C field

Length: 1bit.

The D/C field indicates the type of an AM PDU. It can be either data or control PDU.

Bit Description0 Control PDU1 Data PDU

NOTE: There are some predefined sequence numbers

26

RLC Fields continued (table 5-5 and 5-6)

27

RLC fields continued (table 5-7)

• The Status PDU : is used for retransmission. The receiver transmits status reports to the

sender in order to inform the sender about which AMD PDUs have been received and not

received.

28

RLC PDU Formats- Status PDU (figure 5-9)

D/C: Data/control PDU indicator. SUFI: Super Field. This field can be either a list, bitmap, relative bitmap,

Acknowledgment field etc. Which type of field it is is indicated within the SUFI.

Octet 1

Octet 2

Octet N

D/C PDU type SUFI 1

SUFI1

SUFIK

29

Super Fields (SUFI)

Acknowledgement: Gives the SN up to which all PDUs are received correctly

List: Lists the SNs of the PDUs which were not received correctlyBitmap: Indicates the erroneous PDUs in a bitmapRelative List: Optimised method of listing erroneous PDUs

Move Receive Window: Moves the receiving window when SDU discard is performed

No More Data: Indicates the end of a Status ReportWindow Size: This field is for flow control purposes

30

RLC Acknowledged Mode PDU (figure 5-10)

Transmission buffer

Retransmission buffer &

management

MUX

Set fields in PDU Header (e.g. set poll bits) & piggybacked STATUS PDU

RLC Control Unit

Received

acknow

ledgements

Acknowledgements

DCCH/ DTCH*

AM-SAP

DCCH/ DTCH**

DCCH/ DTCH**

AM RLC entity

Demux/Routing

DCCH/ DTCH*

DCCH/DTCH**

DCCH/ DTCH**

Reception buffer & Retransmission

management

Receiving side

Segmentation/Concatenation

Ciphering (only for AMD PDU)

Add RLC header

Reassembly

Deciphering

Remove RLC header & Extract Piggybacked information

Piggybacked status Optional

Transmitting side

UE/UTRAN

31

MEDIUM ACCESS CONTROL (MAC) PROTOCOL

---INTRODUCTION---

32

• The MAC layer offers services to upper layers in the form of :

* data transfer on logical channels

* reallocation of radio resources

* MAC parameters :

reconfiguration of MAC functions such as change of identity of UE, change of

transport format (combination) sets, change of transport channel type.

* reporting of measurements:

such as traffic volume and quality indication

33


---MAC FUNCTIONS---

34

MAC Protocol Entity (1)L3

cont

rol

cont

rol

cont

rol

cont

rol

LogicalChannels

TransportChannels

PHY

L2/MAC

L1

RLC L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLC

RLC

UuS boundary

BMC L2/BMC

RRC

Control

PDCPPDCP L2/PDCP

MAC Services– Data Transfer

– Reallocation of resources

– Measurement reporting

MAC Functions– Mapping between logical channels and transport channels

– Selection of appropriate Transport Format for each Transport Channel depending on the instantaneous source rate

– UE identification on common transport channels

– Multiplexing of logical channels (common and dedicated)

– Traffic volume measurement

– Transport Channel Type switching

– Ciphering for transparent mode RLC

35

MAC Functions– Mapping between logical channels and transport channels

– Selection of appropriate Transport Format for each Transport Channel depending on the instantaneous source rate

– Priority handling between data flows of one UE

achieved by selecting “high bit rate” and “low bit rate” Transport Formats

for different data flows.

– UE identification on common transport channels

the identification of the UE (Cell Radio Network Temporary Identity (C-

RNTI) or UTRAN Radio Network Temporary Identity (U-RNTI)) is included in

the MAC header.

MAC Protocol Entity (2)

36

– Multiplexing of logical channels (common and dedicated)

– Traffic volume measurement

* Measure on the amount of data in the RLC transmission buffer

* MAC compares the amount of data corresponding to a transport channel with

the threshold set by RRC. If the amount of data is too high or too low, MAC

sends a measurement report on traffic volume status to RRC.

* use these reports for triggering reconfiguration of Radio Bearers and/or

Transport Channels.

– Transport Channel Type switching

– Ciphering for transparent mode RLC

MAC Protocol Entity (3)

37


---ARCHITECTURE---

38

Logical Channels

Provided by L2/MAC sublayer to higher layersDefined by which type of information is transported

Control Channels– Broadcast Control Channel (BCCH, DL)– Paging Control Channel (PCCH, DL)– Common Control Channel (CCCH, DL & UL)– Dedicated Control Channel (DCCH, DL & UL)

Traffic Channels– Dedicated Traffic Channel (DTCH, DL & UL)– Common Traffic Channel (CTCH, DL)

39

Transport ChannelsServices provided by the physical layer (layer 1) to the MAC

layerDefined by “how and with what characteristics” the data is

transported

Common Transport Channels– Broadcast Channel (BCH) (DL)

– Paging Channel (PCH) (DL)

– Random Access Channel (RACH) (UL)

– Forward Access Channel (FACH) (DL)

– Downlink Shared Channel (DSCH) (DL)

– Common Packet Channel (CPCH) (UL)

Dedicated Transport Channels– Dedicated Channel (DCH) (UL & DL)

Same channel used by several usersNo UE identification provided by L1, in-band signaling of UE identity

For exclusive use of one userUE inherently identified by the physical channel

40

MAC architecture (figure 5-11)

FACH RACH

DCCH DTCHDTCH

DSCH

MAC Control

Iur or local

MAC Control

DCH DCH

MAC-dServing RNCper UE

USCHTDD only

MAC-c/shControlling RNC, per cell

CPCHFDD only

CCCH CTCHBCCH SHCCH TDD only

PCCH

FACHPCH USCHTDD only

DSCH

BCCH MAC Control

MAC-b

BCH

TransparentRBS, per cell

41


---MAC PDU AND FLOW---

42

PDU in MAC

• The MAC PDU : consists of an optional MAC header and a MAC Service Data Unit (MAC

SDU).

• Transport Block: Each RLC PDU (e.g. TMD, UMD or AMD) is mapped onto one and only one

Transport Block.

• Transport Block Set(TBS): In the UE for the uplink, all MAC PDUs delivered to the physical

layer within one Time Transmission Interval (TTI) are defined as Transport Block Set (TBS).

It consists of one or several Transport Blocks, each containing one MAC PDU.

43

MAC DATA PDU (figure 5-12)

MAC SDUC/TUE-Id

MAC header MAC SDU

TCTF UE-Idtype

Ciphering Unit

RLC PDU

Target Channel Type Field (TCTF) identifies the type of logical channel (CCCH, BCCH, CTCH, DTCH/DCCH) on RACH/FACH.

UE-Id provides an identifier of the UE on common transport channels.UE-Id type is needed to ensure correct coding of the UE-Id field.C/T identifies the logical channel number (in case of MAC multiplexing of

several DTCH and DCCH).

44

Target Channel Type Field (TCTF) (table 5-1 and 5-2)

TCTF Designation

00 BCCH

01000000 CCCH

01000001-01111111

Reserved(PDUs with this coding will be discarded

by this version of the protocol)

10000000 CTCH

10000001-10111111

Reserved(PDUs with this coding will be discarded

by this version of the protocol)

11 DCCH or DTCHover FACH

TCTF Designation

00 CCCH

01 DCCH or DTCHover RACH

10-11 Reserved(PDUs with this coding will be discarded by this version of the protocol)

Provides identification of the logical channel class on FACH or RACH

45

C/T Field (table 5-3)

C/T field

Designation

0000 Logical channel 1


... ...


1111 Reserved(PDUs with this coding will be

discarded by this version of the protocol)

Provides identification of the logical channel instance when multiple channels are carried on the same transport channel.

46

UE Id Field (table 5-4)

UE Id type Length of UE Id field

U-RNTI 32 bits

C-RNTI 16 bits

Provides an identifier of the UE on common transport channels.

47

UE-Id Type Field (table 5-5)

UE-Id Type field 2 bits

UE-Id Type

00 U-RNTI

01 C-RNTI

10

Reserved(PDUs with this coding will be discarded by this version of the protocol)

11

Reserved(PDUs with this coding will be discarded by this version of the protocol)

Needed to ensure correct coding of the UE-Id field

48

WCDMA RAN side MAC architecture / MAC-d details (1)

DCCH

UE

DTCH DTCH

DCH DCH

MAC-d to MAC-c/sh

MAC-Control

C/T MUX

DL scheduling/ priority handling

Ciphering

Transport Channel Type Switching

Flow Control MAC–c/sh /

MAC-d

C/T MUX / Priority setting

Deciphering

49

WCDMA RAN side MAC architecture / MAC-d details (2)

• Transport Channel Type Switching : If requested by RRC, MAC switches the mapping

of one designated logical channel between common and dedicated transport channels.

• C/T MUX : a C/T field is added indicating the logical channel instance where the data

originates. This is always needed for common transport channels, such as the FACH, but

for dedicated it is only needed when several logical channels are multiplexed into C/T

MUX.

• Priority setting function : is responsible for priority setting on data received from

DCCH/DTCH.

• flow control functionflow control function : exists between MAC-c/sh and MAC-d to limit buffering in the

MAC-c/sh entity.

• Ciphering/deciphering : in MAC-d is only performed for transparent mode data.

50

WCDMA RAN side MAC architecture / MAC-c/sh details (1)

CTCH

FACH

MAC-c/sh to MAC –d

RACH

MAC – Control

CPCH (FDD only )

CCCH

FACH

BCCH SHCCH (TDD only)

PCCH

PCH

TFC selection

DSCH USCH TDD only

Flow Control MAC-c/sh / MAC -d

TCTF MUX / UE Id MUX

USCH TDD only

DSCH

DL: code allocation

Scheduling / Priority Handling/ Demux

TFC selection

51

WCDMA RAN side MAC architecture / MAC-c/sh details (2)

• UE id MUX: After receiving the data from MAC-d, the MAC-c/sh entity first adds the UE

identification type, which is the actual UE identification (CRNTI or U-RNTI).

• the scheduling/priority handling functionthe scheduling/priority handling function : is to decide the exact timing when the PDU is

passed to layer 1 via the FACH transport channel with an indication of what transport

format used.

• The Transport Format Combination (TFC) selection : is done in the downlink for FACH,

PCH and DSCH.

• DL code allocation : is only used to indicate the code if DSCH is used.

52

CTCH

FACH

MAC-c/sh

RACH

MAC-ControlCCCH

FACH

BCCHPCCH

PCH

TFC selection

Flow ControlMAC-c/sh/MAC-d

TCTF MUX / UE Id MUX

Scheduling / Priority Handling/ Demux

DCCH DTCH DTCH

DCH DCH

MAC-d

DL scheduling/priority handling

Ciphering

Transport Channel Type Switching

C/T MUXPrioritysetting

Deciphering

C/T MUX

MAC Model/WCDMA RAN side (figure 5-13 and figure 5-14 connected)

53


---TRANSPORT FORMAT---

54

• The Transport Format (TF) and Transport Format Set (TFS) : describes the data

transfer format offered by L1 to MAC (and vice versa) and is configured by RRC for a

specific transport channel. Each transport channel is configured with one or more Transport

Formats (TF). This is referred to as the Transport Format Set (TFS)

* The maximum number of TFs per transport channel is 32 (numbered 0-31).

* Each TF corresponds to a certain number of equal size transport blocks, i.e. Transport

Block Set (TBS), which may be transmitted on the transport channel within the same

interval.

* The length of the interval is defined by the Transmission Time Interval (TTI), which is a

fixed periodicity of transport blocks and can have a length of 10, 20, 40 and 80 ms.

55

Transport Format Set (TFS) (figure 5-15)

TF1

TF2

TF3

Only the dynamic attributes differ between the TFs within the TFS

Increasing bit rate

TFS

56

Transport format (figure 5-16)

Describes instantaneous characteristics of a transport channel and the data transfer format offered by L1.

Semi-static part– Transmission Time Interval (TTI)

– Channel-coding scheme

– Reconfiguration by RRC is needed.

Dynamic part– Number of transport blocks per TTI

– Number of bits per transport block

TTI

Transport Block

Transport Block

Transport Block

Transport Block

Transport Block

Transport Block

L bits

N

57

Transport Channel Coding (figure 5-17)

Add CRC

Channel coding

Interleaving

Transport Channel

Coded Transport Channel

CRC (Cyclic Redundancy Check)– Calculated for and added to each transport block– CRC length : 0/8/12/16/24 bits

FEC (Forward Error Correction)– Convolution coding (R=1/2, R=1/3)– Turbo coding (R=1/3)

Channel Interleaving– Block interleaving over one TTI

58

TTI (typically 20 ms)

Rate = R Rate = R/4 Rate = R/2

Examples of transport channel structures, simple variable rate speech and packet data (figure 5-18)

Simple variable-rate speech TTI = 20 ms Convolutional coding One transport block per TTI (one speech frame)

Variable-length transport blocks

TTI

One ”packet” One ”packet”

One ”packet”

One ”packet”

One ”packet”

One ”packet”

Packet data Turbo coding

Fixed-length transport blocks Variable number of transport block per TTI

59

Characterization of Transport Format

60

A connection typically consists of multiple transport channelsin each direction

One set of transport formats per transport channel Transport Format Combination (TFC):

– The instantaneous combination of transport formats for all transport channels to (from) one UE

– Signaled over L1 as Transport Format Combination Indicator (TFCI)

UTRAN

UE

DL TrCh #1 DL TrCh #M UL TrCh #1 UL TrCh #N

Multiple transport channels (figure 5-19)

61

Transport Format Set (TFC) (figure 5-20) A combination of currently valid Transport Formats at a given point of time containing one Transport Format for each transport channel.

TF1

TF2

TF3

TF1

TF2

TF3

TF1

TF2

TF3

Transport channel 1

Transport channel 2

Transport channel 3

TFC1

62

Transport Format Set (TFCS) (figure 5-21)

TF1

TF2

TF3

TF1

TF2

TF3

TF1

TF2

TF3

Transport channel 1

Transport channel 2

Transport channel 3

TFC1

TFC2

TFC3

TFC4

TFCS

TFCS is the set of TFCs that has been configured (by RRC)MAC selects a TFC out of the TFCSCurrent TFC is indicated by the Transport Format Combination Indicator

(TFCI) in each physical frame every 10 ms

63

Summary of Data Exchange through transport channels Transport block: the basic unit exchanged between L1 and MAC

Transport block set: a set of transport blocks which are exchanged between L1 and MAC at the same time instance on the same TrCH

The Transmission Time Interval (TTI) and the error protection scheme to apply are semi-static parameters for the TrCH while the number of transport blocks and their size are dynamic ones

Transport format: a defined format offered by L1 for the delivery of a Transport Block Set during a TTI

Transport format set: a set of Transport Formats associated to a Transport Channel

Transport Format Combination: a combination of transport formats submitted simultaneously to L1, containing one Transport Format for each transport channel.

Transport Format Combination Set: a set of transport format combinations

The Transport Format Combination Indicator (TFCI): on L1 indicates the currently valid TFC.

64


---CHANNEL SWITCHING---

65

• The purpose of Channel Switching : is to optimize the use of the radio

resources, by dynamically changing the resources allocated to the best-effort users. When

there are plenty of resources available, the best-effort user receives high bit rates but when

the system is heavily loaded and there are not many resources left,

66

Channel Switching

1. CELL_FACH to CELL_DCH: Bufferbased

2. CELL_DCH to CELL_FACH: Throughput

3. Upswitch: Bandwidth

4. Downswitch: DL Code Power Based

5. Downswitch: Handover Based

6. Downswitch: CELL_FACH to Idle due to inactivity

7. Multi-RAB Upswitch: Bufferbased

8. Multi-RAB Downswitch: Throughput based

Channel Switching

1. CELL_FACH to CELL_DCH: Bufferbased

2. CELL_DCH to CELL_FACH: Throughput

3. Upswitch: Bandwidth

4. Downswitch: DL Code Power Based

5. Downswitch: Handover Based

6. Downswitch: CELL_FACH to Idle due to inactivity

7. Multi-RAB Upswitch: Bufferbased

8. Multi-RAB Downswitch: Throughput based

Copyright © Ericsson Education. All rights reserved

Cell_DCH 64/384

Cell_DCH 64/64

Cell_FACH

Cell_DCH 64/128

Idle Mode

6. No activity6. No

activity

1. Common to Dedicated

based on buffer size

1. Common to Dedicated

based on buffer size

Soft CongestionSoft

Congestion

5. SHO can initiate a

switch if it fails to add

a RL

5. SHO can initiate a

switch if it fails to add

a RL

4. Coverage triggered downswitch4. Coverage

triggered downswitch3. Upswitch

based on bandwidth

3. Upswitch based on

bandwidth

2. Dedicated to common based on throughput

Cell_DCHSpeech + PS 64/64Cell_DCH

Speech + PS 64/64

Cell_DCHSpeech + PS 0/0Cell_DCH

Speech + PS 0/0

7. UL or DL buffer

size above a threshold

7. UL or DL buffer

size above a threshold

8. UL & DL throughput =

0 for a certain time

67

1. Switch from Cell_FACH to Cell_DCH state

• based on the buffer load.

• Downlink buffer load measurements in the S-RNC , uplink buffer load

measurement by the UE in the MAC layer.

• in the Idle State or Cell_FACH the UE will read the System Information and

configure its measurements.

• For the DCH state, measurements are configured by a “Measurement

Control” message.

• In the UL case the UE sends a “Measurement Report” to the RNC when the

buffer size is reached. In the DL case, the RNC handles the switch internally.

68

2. switch from Cell_DCH to Cell_FACH

• Throughput based

• triggers the MAC layer to report to RRC and send a “Measurement Report” to the

RNC for low throughput in UE.

• If both the throughput in the UL and the DL is below the set values, a switch from

Cell_DCH to Cell_FACH will be performed via Radio Bearer Reconfiguration

procedure.

3. Up Switch between the Radio Bearers for the Cell_DCH state

• based on bandwidth need.

• The supported bit rates are 64/64, 64/128 and 64/384 kbps.

• When the throughput becomes close to the maximum user bandwidth (64 or 128

kbps) the procedure is triggered.

• In the UL case, the UE sends a “Measurement Report” and in the DL case it is

handled in the RNC internally.

69

4. Down Switch between the Radio Bearers for the Cell_DCH state

• performed due to coverage, i.e. due to DL power.

• In this case the congestion control triggers it based on measurements via NBAP

(from RBS to RNC).

5. Other channel switching type is not indicated here !!!!

70

Channel switching (UL) (figure 5-22)

Release dedicated channel

Random-AccessRequest

Random-Access Channel

Packet Packet Packet

Dedicated Channel

TTime-out

Switch to common

Switch todedicated

Random-AccessRequest

User 1 User 2

71

MAC SDUC/T

MAC header MAC SDU

Ciphering Unit

RLC PDU

No MAC header is needed for the DTCH.

Multiplexing of logical channels (DCCHs used for SRBs, C/T MUX)

Mapped on DCH transport channels

Channel Switching from dedicated to common (DCCH and DTCH) before switching (figure 5-24)

Channel switching

MAC-d

DTCH

TFC Selection

DCH DCH

Physical layer L1

Ciphering

C/T MUX

DCCHs

MAC SDU

MAC SDU

Ciphering Unit

RLC PDU

DCCHs DTCH

72

Channel Switching from dedicated to common (DCCH and DTCH) after switching (figure 5-25)

MAC SDUC/TUE-Id

MAC header MAC SDU

TCTF UE-Idtype

Ciphering Unit

RLC PDU

Switching is transparent for the logical channels

DTCH and DCCH mapped to RACH/FACH

MAC header fields to distinguish logical channels and UEs

DCCH DTCH

Channel switching

C/T MUXUE ID

TCTF MUX

CCCH CTCH BCCH

RACHFACH

MAC-d

MAC-c

Physical layer, L1

73

CIPHERING

74

• The protection of the user data and some of the signaling information is done by both

integrity protection, executed by RRC layer and ciphering, performed either in RLC or in

the MAC layer according to the following rules:

* If a radio bearer is using a non-transparent RLC mode (AM or UM), ciphering is

performed in the RLC sub layer.

* If a radio bearer is using the transparent RLC mode, ciphering is performed in the

MAC sub layer (MAC-d entity).

>> If ciphering is used it is between S-RNC and UE <<

75

SRNC

f8CK

COUNT-CBEARER

DIRECTION

LENGTH

f8CK

COUNT-CBEARER

DIRECTION

LENGTH

PLAIN TEXT BLOCK

CIPHERTEXTBLOCK

PLAIN TEXTBLOCK

SRNC/ /

SenderUE or SRNC

ReceiverSRNC or UE

Ciphering of user and signaling data transmitted over the radio access link (figure 5-26) (1)

KEYSTREAM KEYSTREAM

76

• Procedure for ciphering:

* The input parameters to the algorithm : the ciphering key, CK, a time-dependent input,

COUNT-C, the bearer identity, BEARER, the direction of transmission, DIRECTION,

and the length of the key stream required, LENGTH.

* Based on these input parameters the algorithm generates the output keystream block,

KEYSTREAM, that is used to encrypt the input plaintext block, PLAINTEXT, to

produce the output ciphertext block, CIPHERTEXT.

Ciphering of user and signaling data transmitted over the radio access link (figure 5-26) (2)

77

Input Parameters to the Cipher Algorithm (1)

• COUNT-C : ciphering sequence number

• CK, Ciphering Key: The CK is established during the Authentication procedure

using cipher key derivation function f3 available in the USIM and in the HLR/AUC

• BEARER : There is one BEARER parameter per radio bearer associated with the same

user . The radiobearer identifier is input to avoid that for different keystream an identical

set of input parameter value is used.

• DIRECTION : The value of the DIRECTION is 0 for UL messages and 1 for DL.

78

Input Parameters to the Cipher Algorithm(2)

• LENGTH : The parameter determines the length of the required keystream block .

• Ciphering key selection: There is one CK for CS radio bearer, CKCS, connections

and one CK for PS radio bearer, CKPS, connections.

79

PHYSICAL CHANNELS

80

Physical channels

The final Layer 1 bit stream to be carried over the air– Multiple multiplexed coded transport channels (CCTrCH)

– Layer 1 control information Pilot bits Transmit Power Control (TPC) commands and other

Feedback Information (FBI) Transport Format Combination Indicator (TFCI)

Mapped to combination of – Carrier frequency

– Code (channelization/scrambling code pair)– Relative phase (UL only): On either the I branch or the Q branch of a QPSK

signal (uplink only).

81

Physical-layer overview (figure 5-27)

Channel coding

Transport channels

Multiplexing

Mapping to physical channels

Spreading Spreading

Physical channels

Physical-layerprocedures

and measurements

Channel coding

5 MHz

Modulation Modulation

3.84 Mcps

Transport-channelprocessing

82

RRC Connection Establishment (figure 5-28)

WCDMA RANWCDMA RAN

”RRC Connection Request” CCCH/RACH

”RRC Connection Setup” CCCH/FACH

”RRC Connection Setup Complete” DCCH/DCH

Idle Mode

WCDMA RANConnected

Mode

83

Physical Random Access Channel (figure 5-29)

I

Q

Random Access Message (10, 20, 40, or 80 bits per slot)

RACH Message Control Slot (0.666 mSec)

Pilot (8 bits)

RACH Message Data Slot (0.666 mSec)

TFCI (2 bits)

1 Frame = 15 slots = 10 mSec

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

84

RACH carrying RRC Connection request (figure 5-30)

384Rate 1/2 CC

300Rate Matching

1st Interleaving

Transparent Mode => no RLC header

20

RACH Message part 30ksps SF 128

PILOT TFCI

166

CRC 16

184

2 bit MAC header

168

MAC layer

8 tail bits

192

166

166 8.4 Kbps => 166 bits in 20msec

2nd Interleaving

20Slot segmentation

I branch Q8 2Control part

85

Secondary Common Control Physical Channel (figure 5-31)

Carries the Forward Access Channel (FACH) and Paging Channel (PCH)

Spreading Factor = 256 to 41 Slot = 0.666 mSec = 2560 chips = 20 * 2k data bits; k = [0..6]


20 to 1256 bits0, 2, or 8 bits

DataTFCI or DTX Pilot

0, 8, or 16 bits

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

86

FACH carrying RRC Connection setup (figure 5-32)

376

1st Interleaving

160 160

CRC 16

184 184

752Rate 1/2 CC

Unacknowledged Mode (UM) => 8 bit RLC

8 bit MAC

152 152

1080

2nd Interleaving

MAC layer

168 168

8 tail bits

152 152 Max rate 3040 bps => 10msec = 304 bits = 2X152

S-CCPCH 60ksps => SF = 64

8 8 L1 (8 bit TFCI)72 72Slot segmentation

Rate Matching

87

Uplink DPDCH/DPCCH (figure 5-33)

Coded Data, 10 x 2k bits, k=0…6 (10 to 640 bits)

Dedicated Physical Data Channel (DPDCH) Slot (0.666 mSec)

Pilot FBI TPC

Dedicated Physical Control Channel (DPCCH) Slot (0.666 mSec)


I

QTFCI

DPCCH: 15 kb/sec data rate, 10 total bits per DPCCH slot

PILOT: Fixed patterns (3, 4, 5, 6, 7, or 8 bits per DPCCH slot)

TFCI: Transmit Format Combination Indicator (0, 2, 3, or 4 bits)

FBI: Feedback Information (0, 1, or 2 bits)

TPC: Transmit Power Control bits (1 or 2 bits); power adjustment in steps of 1, 2, or 3 dB

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

88

Uplink Signaling Radio Bearer on DPDCH/DPCCH (figure 5-34)

PILOT TFCI TPC

DPDCH 60ksps => SF = 64 I branch

Q6 2 2DPCCH 15ksps

600 Rate Matching

40 40

2nd Interleaving

Slot segmentation

172

516Rate 1/3 CC

1st Interleaving

CRC 16

164

1488 tail bits

MAC Layer4 bit MAC

136136 8 bit RLC

144

RRC UM RRC AM or NAS DT normal or high priority

128128

144

16 bit RLC

4 bit MAC

136 bits in 10 msec => 13.6 kbps

128bits in 10 msec => 12.8 kbps

89

Downlink DPDCH/DPCCH (figure 5-35)

1 Slot = 0.666 mSec = 2560 chips = 10 x 2k bits, k = [0...7]

SF = 512/2k = [512, 256, 128, 64, 32, 16, 8, 4]

The DPDCH carries user traffic, layer 2 overhead bits, and layer 3 signaling data.The DPCCH carries layer 1 control bits: Pilot, TPC, and TFCI

Downlink Closed-Loop Power Control steps of 1 dB dB

The DPDCH carries user traffic, layer 2 overhead bits, and layer 3 signaling data.The DPCCH carries layer 1 control bits: Pilot, TPC, and TFCI

Downlink Closed-Loop Power Control steps of 1 dB dB

Data 2TFCIData 1 TPC


DPDCH

Pilot

DPDCH DPCCH DPCCH

1 2 3 4 5 6 7 8 9 10 11 12 13 140

90

Downlink Signaling Radio Bearer on DPDCH/DPCCH (figure 5-36)

172

516Rate 1/3 CC

1st Interleaving

CRC 16

164

1488 tail bits

MAC Layer4 bit MAC

136136 8 bit RLC

144

128128

144

16 bit RLC

4 bit MAC

510 Rate Matching

2nd Interleaving

DPDCH/DPCCH = 30ksps => SF = 128

4 2 422 TPC & 4 PILOT


128bits in 10 msec => 12.8 kbps

RRC UM RRC AM or NAS DT normal or high priority

34 34Slot segmentation

91

Uplink Speech RAB mapping (figure 5-37)

1st Interleaving

IBranch Q

140 140 140 140

2nd speech block152 167 68

600 bits (600 symbols) 600 bits (600 symbols)

600 600

40 40

#2 110

40 40

#1 110 152 167 68

129 129 129 129

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Convolutional coding

8 tail bits

Radio frame equalization

136

144CRC 12

93

1/3 1/3 1/2

304

81

103 6020 msec of each subflow

103 60

334 136

152 167 68152 167 68

303+1 333+1 136

81

152 167 68

DPDCH 60kbps => SF=64

2nd interleaving 600

40 40

140Rate match 360

QPILOT TFCI TPC 6 2 2DPCCH 15kbps

152 167 68



40 40

140Rate match 360

Frame segmentation

RRC UM RRC AM or NAS DT normal priority

Rate matching

92

Uplink Speech RAB mapping (during SID frame) (figure 5-38)

• After every eight frames the UE sends a Silence Descriptor (SID) frame, which is used

during the discontinuous speech periods.

93

Downlink Speech RAB mapping (figure 5-39)

119 119 119 119


600 600

600 600

#2 110#1 110 152 167 68

476

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

136

RRC UM

8 bit RLC

RRC AM or NAS DT normal priority

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136


119


119

1st interleaving

144

DPDCH 60ksps => SF=128 DPDCH 60kbps => SF=128

2 TPC 4 Pilot 2 TPC 4 Pilot

Convolutional coding

8 tail bits

CRC 12

93

303 (1/3) 333 (1/3) 136 (1/2)

81

103 60

103 60

81

Rate matching

20 msec of each subflow

34 34 34 34 40 40 40 40

316294 172

294 316 172147 147 158 158 86 86

147 158 86 147 158 86

94

Uplink CS 64 RAB mapping (figure 5-40)

IBranch Q

157 157 157 157

2nd speech block152


600 600

40 40

#2 110

40 40

129 129 129 129

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC


128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136



160 160

1572243




160 160

1572243

Rate matching

12 Trellis termination bits

1st Interleaving

Turbo Coding 3936

1974 1974

2243 2243

640 640

640 640

64 kbps = 1280 in 20 msec =>2X640 bit Transport Blocks

144CRC 16

152 #2 110

95

Downlink CS 64 RAB mapping (figure 5-41)

137 137 137 137

2nd speech block

548

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136


140 140

137


140 140

137

1st interleaving

144

DPDCH 120ksps => SF=32 DPDCH 120ksps => SF=32

1963 1963

Rate matching

12 Trellis termination bitsTurbo Coding 3936

640 640

640 640 CRC 16

39263926

1963 1963

4 / 8 / 8 TPC/TFCI/PILOT

600600

64 kbps = 1280 in 20 msec =>2X640 bit Transport Blocks


96

Uplink Streaming 57.6 kbps RAB mapping (figure 5-42)

IBranch Q

182 182 182 182



600 600

40 40

#2 110

40 40

#1 110 152 167 68

129 129 129 129

8 tail bits

CRC 16

164148

516 Rate 1/3 CC1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136



160 160

1822218




160 160

1822218

Rate matching


1st Interleaving 7116

Turbo Coding 7104

2218

Up to 4X576 TBs in 40 msec => max data rate = 57.6 kbps

1 2 3 4

16 16 16 16576 576 576 576144

CRC 16


2218 2218 2218

1779 1779 1779 1779

97

Downlink Streaming 57.6 kbps RAB mapping (figure 5-43)

159 159 159 159

2nd speech block

636

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136


140 140

159


140 140

159

1st interleaving

144

DPDCH 120ksps => SF=32 DPDCH 120kbss => SF=32

1941

Rate matching


77647764

1941 1941

Up to 4X576 TBs in 40 msec => max data rate = 57.6 kbps

1 2 3 4

16 16 16 16576 576 576 576 CRC 16

600600



1941 1941 1941

98

Uplink PS DATA CELL_FACH (DCCH on RACH) (figure 5-44)

RRC AM, NAS DT normal or low priority

16 CRC 16

184

168

MAC layer

8 tail bits

Rate 1/2 Convolutional Coding 384

1st Interleaving

24 bit MAC

136

RRC UM

136 8 bit RLC

144144

128

128 16 bit RLC

24 bit MAC

2nd Interleaving

Rate Matching 300

20

RACH message part 30ksps => SF = 128

PILOT TFCI

20

8 2

Slot segmentation

IBranch Q



99

Uplink PS DATA CELL_FACH (DTCH on RACH) (figure 5-45)

Frame segmentation 384

2nd Interleaving

Rate Matching 300

20

RACH message 30ksps => SF = 128

PILOT TFCI

20

16 CRC 16

376

360MAC layer

8 tail bits


1st Interleaving

AM => 16 bit RLC

320

336 24 bit MAC

320

Max user plane 320 bits in 20 msec => 16 kbps

8 2

Frame segmentation 384

2nd Interleaving

Rate Matching 300

20

RACH message 30ksps => SF = 128

PILOT TFCI

20

8 2

100

Downlink PS DATA CELL_FACH (DCCH on FACH) (figure 5-46)

376

1st Interleaving

CRC 16

184 184


Rate Matching 1080

2nd Interleaving

S-CCPCH = 60ksps => SF = 64

8

72 72

8

168 168

8 tail bits

MAC layer24 bit MAC

136

RRC UM

8 bit RLC


128

128

144

16 bit RLC

24 bit MAC

40 msec

136

144

Slot segmentation



TFCI bits

101

Downlink PS DATA CELL_FACH (DTCH on FACH) (figure 5-47)

Rate Matching 1080

2nd Interleaving

S-CCPCH = 60ksps => SF = 64

8

72 72

8

Slot segmentation

376

1st interleaving

CRC 16

1128Turbo Coding

360

12 trellis termination bits

320

336

320 AM => 16 bit RLC header

24 bit MAC header

Max user plane = 320 bits in 10msec => 32 kbps

TFCI bits

102

Uplink PS 64 RAB mapping (figure 5-48)

IBranch Q

154 154 154 154



600 600

40 40

#2 110

40 40

#1 110 152 167 68

129 129 129 129

8 tail bits

CRC 16

164148

516 Rate 1/3 CC1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136



160 160

1542246




160 160

1542246

Rate matching


Up to 4X320 TBs in 20 msec => max data rate = 64 kbps

144


Turbo Coding 4224

2118 2118

2246 2246

1 2 3 4320 320 320 32016 16 16 16

16 16 16 16336 336 336 336

16 bit RLC

CRC 16


103

Downlink PS 64 RAB mapping (figure 5-49)

134 134 134 134

2nd speech block

536

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec136


160 160

134


160 160

134

144

DPDCH 120ksps => SF=32 DPDCH 120kbss => SF=32

1966 1966

Frame segmentation1st interleaving

1966 1966

Rate matching


39323932


1 2 3 4320 320 320 32016 16 16 16

16 16 16 16336 336 336 336

16 bit RLC

CRC 16

600600



104


132 132 132 132

2nd speech block

528

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec

Frame segmentation

136


288 288

132


288 288

132

1st interleaving

144

DPDCH 240ksps => SF=16 DPDCH 240ksps => SF=16

4188 4188

Rate matching


83768376

4188 4188


16 bit RLC

CRC 16

600600



320 320 320 32016 16 16 16 320 320 320 32016 16 16 16

16 16 16 16 16 16 16 16

105


95 95 95 95

Next 3 blocks

380

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

MAC Layer4 bit MAC

1368 bit RLC

128128144

16 bit RLC

4 bit MAC

40 msec136

144

12 Trellis termination

bits

9025

95


608 608

DPDCH 480ksps => SF=8

9025

Turbo Coding 12672

16 16 16 16 16 16 16 16 16 16 16 16

320 320 320 32016 16 16 16 320 320 320 32016 16 16 16 320 320 320 32016 16 16 16


Rate matching

1st interleaving

8 TCI 8 TPC 18 Pilot

600600600


106

IBranch

Q

125 125 125 125

129 129 129 129

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

4 bit MAC

1368 bit RLC

128

128

144

16 bit RLC

4 bit MAC

40 msec

8 tail bits

136

144CRC 12

93

1/3 1/3 1/2

304

81

103 60


103 60

334 136

148 158 88148 158 88

303+1 333+1 136

81

148 158 88



160 160

125

PILOT TFCI TPC 6 2 2DPCCH 15kbps

148 158 88



160 160

125


Uplink MultiRAB, Speech RAB + PS 64/64 RAB mapping (figure 5-52)


Turbo Coding 4224

2118 2118

1881 1881

1 2 3 4

320 320 320 320

336 336 336 336

16 bit RLC

CRC 16

18811881

107

109 109 109 109

436

8 tail bits

CRC 16

164

148

516 Rate 1/3 CC

1st interleaving

4 bit MAC

136

RRC UM

8 bit RLC


128

128

144

16 bit RLC

4 bit MAC

40 msec

136


109

144

DPDCH 120 ksps => SF=32

4 TPC 8 Pilot 8 TFCI

CC

8 tail bits

CRC 12

93

303 (1/3) 333 (1/3) 136 (1/2)

81

103 60

103 60

81


160 160

RM 276RM 258 RM 154

1st Int. 258 1st Int. 276 1st Int. 154

129 129 138 138 77 77

129 138 77

Downlink MultiRAB, Speech RAB + PS 64/64 RAB mapping (figure 5-53)

1647 1647


RM 3294

1st Int. 3294


1 2 3 4

320 320 320 320

336 336 336 336

16 bit RLC

CRC 16

1647

1 wcdma ran protocols and procedures chapter 5 rlc and mac protocols

Documents

rlc entities

rlc modes

rlc work

rlc protocol entity

rlc tm pdu

transfer of user data

previous rlc sdu

rlc layer architecture