Designing of Simulation Model forPerformance Testing on

3G Radio Link Control Protocol

MallikaMallika UnhawiwawatUnhawiwawatCentre for Network Research

Department of Computer EngineeringFaculty of Engineering

Prince of Songkla University

`Outline

• Radio Link Control (RLC) Protocol in 3G Systems

• Design of RLC Simulation Model• Simulation Description• Simulation Processes• Conclusion and Future work

`Radio Link Control Protocol

`Radio Link Control Protocol

Functions in RLC– Segmentation and reassembly– Transfer of user data (RLC Service Data

Units (SDUs)– Service Data Unit (SDU) discard– Protocol error detection and recovery– Padding

`Radio Link Control Protocol

Functions in RLC– Error correction– In-sequence delivery of upper layer PDUs– Duplicate detection– Ciphering

`Radio Link Control Protocol

Operations in Transmitting sidePolling MechanismSDU Discard Mechanism

Operation in Receiving sideStatus Report Transmission Mechanism

`Polling Mechanism

Polling Mechanism triggersPoll_Timer: started when a polling is submitted to the

lower layerPoll_Periodic_Timer: started when a RLC session is

createdPoll_Prohibit_Timer: prohibit transmission of polls

within a certain periodicLast_PDU_In_Buffer: when the last AMD PDU is

scheduled, poll is set

`Polling Mechanism

Polling Mechanism triggersLast_PDU_In_Retransmission_Buffer

Window_Based_Polling

Every_Poll_PDU_PDU

Every_Poll_SDU_SDU

`SDU Discard Mechanism

Avoid buffer overflow in RLC layerReduce the maximum transmission delay

• Triggers:1. Timer-based discard with explicit signaling 2. SDU discard after MAX_DAT number of

retransmissions

`Design of RLC Simulation Model

Transport

Network

Data link

Physical

TCP/UDP

IP

RLC

MAC

Physical

RRC

OSI UMTSTransport

Network

Data link

Physical

TCP/UDP

IP

RLCMAC

Physical

RRC

OSI UMTS

Fig Fig 11:: UMTS Simulation model compares with OSI model

`Design of RLC Simulation Model

• Transparent Mode (TM)

Fig 3: Model of two transparent mode peer entities

Transmission Buffer

Segmentation

Reassambly

Reception Buffer

Transmitting side Receiving side

`Design of RLC Simulation Model

• Unacknowledged Mode (UM)

Fig 4: Model of two unacknowledged mode peer entities

Transmission Buffer

Segmentation &Concatenation/Padding

Reassambly

Remove RLC header

Add RLC header Reception Buffer

Transmitting side Receiving side

`Design of RLC Simulation Model

• Acknowledged Mode (AM)

Fig 5: Model of two acknowledged mode peer entities

Segmentation&Concatenation

Add RLC header Retransmission Buffer

Transmission Buffer

Setup header Demultiplex

Multiplex

Reception Buffer

Remove RLC header &extract information

Reassembly

Control UnitTransmitting side Receiving side

`Design of RLC Simulation Model

• UML models for RLC of all operation modes

RLC

recv()RLC()sendUp()sendDown()getSpeed()getQueueLength()getTotalQueueLength()getTotalSpeed()command()exists()

RLCFrameType

RLCHeaderExtension

hdr_rlcseqno_ : intlength_ : intpoll_ : booloriglength_ : int

rlctype()seqno()length()headerext()poll()origtype()origlength()

1

1

+rlctype_1

1

11

+headerext_

11

Fig 6: UML diagram of RLC class

`Design of RLC Simulation Model

RLCMode

RLCFlowDiscardTimer

RLCFlowDiscardTimer()expire()

RLCFlowPollTimer

RLCFlowPollTimer()expire()

RLCFlowPollProhibitTimer

RLCFlowPollProhibitTimer()expire()

RLCFlowPollPeriodicTimer

RLCFlowPollPeriodicTimer()expire()

RLCPollMode

RLCDataFlowseqno_ : intpoll_ : boolackno_ : intdelay_ : doublepdusize_ : intttitime_ : doublespeed_ : intpolltime_ : doublepollperiodictime_ : doublepollprohibittime_ : doublelastpollpdu_ : int

RLCDataFlow()recv()sendUp()sendDown()send_poll()discardPdu()generateAckListSufi()produce_new_data_pdu()compare_data_pdu()delete_up_to_in_packet_buf()delete_up_to_r_pdu_buf()delete_up_to_in_seg_buf()delete_all_r_sdu_buf()setSpeed()getQueueLength()debug()handleAmPacket()handleStatusPacket()handlePollRequest()

0..1

1

#rlcDataFlow_

0..11

#rlcDataFlow_

0..1

1

#rlcDataFlow_

0..11

#rlcDataFlow_

1

1

#mode_

1

1

#discardtimer_

1 1

#polltimer_

1

1#pollprohibittimer_

1

1

#pollperiodictimer_

1

1

#pollmode_

0..1

1

0..11

0..1

10..1

1

1

11

1

1 1

1

1

1

1

1

1

Fig 7: UML diagram of RLCDataFlow class

4. `Simulation Description

• The simulation will be implemented with Network Simulation version 2.

• The upper layers in the transmitting side of RLC generate ftp and voice data traffic and send to RLC layer.

• In case of ftp traffic, RLC operates in AM mode, the data flow and functions would be done as shown in Fig 5.

• Voice traffic has higher priority than ftp data traffic.

`Simulation Description

Parameters ValueSDU traffic model Voice and FTP

PDU size 40 bytes

TTI 20 ms

Service rate 384 kbps (or 24 PDUs per TTI)

SDU Discard function Timer based discard

Round Trip Delay 200 ms

RLC window size 4096 PDUs

`Simulation Processes

UE UTRAN

voiceTCP/UDP

IP

RLC

MAC

Physical

RLC

MAC

Physical

384 kbps, 100 ms

Fig 8: Simulation Protocol Stack

`Simulation Processes

UE UTRAN

voice ftpTCP/UDP

IP

RLC

MAC

Physical

RLC

MAC

Physical

384 kbps, 100 ms

Fig 8: Simulation Protocol Stack

`Simulation Processes

TCP/UDP

IP

RLC

MAC

Physical

RLC

MAC

Physical

384 kbps, 100 ms

UE UTRAN

ftp • delay time, throughput and error checking are considered.

• changing some parameters and restarting all simulation process again

Fig 8: Simulation Protocol Stack

`Conclusion and Future works

• We present the overview and designed of RLC simulation model for performance testing and show in UML diagrams.

• The simulation model will be completely implemented in NS2 and used to analyze the RLC performance.

Comment and QuestionsComment and Questions

Thank you Thank you