21 Radio Resource Management

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1

Radio Resource

Allocationfor

Global System for MobileCommunications



2

Reference (1/2)

[1] ETSI/TC, “Digital cellular

telecommunications system (Phase 2+); GSMPublic Land Mobile Network (PLMN) access

reference configuration”, GSM Tech. Spec.GSM 04.02 Version 5.0.0, ETSI May1996.

[2] Eberspacher, J. and Vogel, H.-J. GSM

Switching, Services and Protocols, JohnWiley & Sons Ltd, England, 1999.



3

Reference (2/2)

[3] Milosh, I., Moshe, Z., Paul, F. and Maxim, G.

Performance Between Circuit AllocationSchemes for Half- and Full-Rate Connections

in GSM. IEEE Trans. on Vehicular

Technology , 47(3):790-797, August 1998.

[4] Lin, Y.-B., “Performance Modeling for Mobile

Telephone Networks,” IEEE Trans. on

Vehicular Technology , vol. 47, pp. 790-797,

August 1998.



4

Outlines

Introduction

Improving GSM Call Completion by CallReestablishment

Channel Assignment for GSM Half-Rate andFull-Rate Traffic

Channel Allocation for GPRS

Conclusions & Future Works

Publication Lists

今天要報告的主題共分為四大部份:

先對 GSM系統做簡單的介紹

接下來報告我對 GSM Radio Resource Allocation所做的兩大研究 “Improving

GSM Call Completion by Call Reestablishment” , “Channel Assignment forGSM Half-rate and Full-rate Traffic”.

最後我針對 Future Work: Channel Allocation for GPRS Packet Data加以闡述.

在這三個 Topic中

Improving以及 Channel Assignment是針對 Circuit Mode的 Traffic加以分析.

Channel Allocation是針對 Packet Mode的 Traffic做研究.

而 Channel Assignment以及 Channel Allocation可用類似的Modeling

Technique.



5

Introduction (1/4)

Global System for Mobile Communication

(GSM) is a standard adopted by cellularsystems widely developed in Europe and

Asia.

GSM combines TDMA and FDMA

technologies for radio channel allocation.

• A frequency carrier is divided into eight time slotsper frame, which are used to support speech anddata transmission.

Global System for Mobile Communication (GSM)系統是亞洲地區以及歐洲地區廣範被使用的 PCS系統.

它在 Air Interface所採用的技術是 TDMA (Time Division Multiple Access)以

及 FDMA (Frequency Division Multiple Access).在每個 Frequency Carrier上再依時間軸切分為 Frame.每個 Frame具八個Time Slot.

每個Time Slot即為一 Channel.

也就是在一個 Frequency Carrier上可以容納 8個使用者.



6

Introduction (2/4)

MS: Mobile StationBTS: Base Transceiver Station

BSC: Base Station ControllerBSS: Base Station SubsystemMSC: Mobile Switching Center

PSTN: Public Switched Telephone NetworkHLR: Home Location Register

VLR: Visitor Location RegisterAUC: Authentication CenterOMC: Operation and Maintenance Center

BTS

BTSBTS

BTS

BTS

BTS

BSC

BSC

MS

MSAbis interface

Um interface

MSC

Base Station Subsystems

A interface

HLR VLR AUC

PSTN

OMC

Operating Subsystem

Network Switching

Subsystem

GSM Architecture

MS可經由 Radio Interface與 BTS連結.

BSC負責控至數個 BTS.

MSC為一 Switch負責將通話 Route PSTN.

HLR,VLR,為資料庫用來存放MS的位置.

AUC負責產生以及存放 Security-related的資料,例如用來任證與加密的 Key.

OMC負則監控目前網路的正常運作.



7

Introduction (3/4)

GSM Communication Setup

• An MS initiates a communication session bymaking an access request to a BSC if the MS is inthe cell. If no free channel, the call is blocked.

GSM Handoff Operation

• If the MS moves to another cell duringconversation, the radio link to the old BSS isdisconnected, and a radio link to a new BSS isrequired. If the new BSS has no idle channels, the

call is forced to terminate.

一個Mobile Station可經由

Communication Setup的程序來接續上 GSM網路.

它的運作方式是

(i) 由MS經由 Radio Interface向 BSC發出Access Request.

(ii) 若目前沒有 Idle的 Channel則此通Call會被Block 掉

若在通話中,因Mobile Station移動的關係移出了原先通話的 Cell.則會啟動Handoff Operation.

它的運作方式是

(I) MS先中斷與舊BSS間的無線電聯結.

(ii)再與新的BSS建立無線電聯結,若新的 BSS沒有IDLE的Channel供此

Handoff Call使用,則這通電話便被強迫斷話.



8

Introduction (4/4)

The services offered by the GSM system arelimited to voice and low-speed data.

GSM Spec. phase 2+ is defined for better QoSand network quality perception, e.g.,• Advanced Speech Services

• General Packet Radio Service

Compared with the voice circuit-switchedservices, new services generate new type oftraffic.

Our objective is to allocate the radio channelsto both new and traditional service users in anefficient way.



9

Research 1:

Improving GSM CallCompletionby Call Reestablishment



10

Call Interruption (1/2)

Call Interruption Phenomenon:• A radio link may be temporarily disconnected due

to obstacle shielding.

GSM call reestablishment service:• If a communication channel is interrupted, the

network still reserves the trunk and/or the channelfor the interrupted call, and an interruption timer istriggered.

• If the timer expires or the remote party hangs upthe phone before the interruption period is over,

the interrupted call is actually forced to terminate.



11

Call Interruption (2/2)

GSM call reestablishment service:• Otherwise, the interrupted call is resumed by the

call reestablishment mechanism. This serviceincreases end user satisfaction and networkquality perception.

In this research, we investigated three callRe-EStablishment (RES) mechanisms for thisservice.• Re-EStablishment 1 (RES 1)

• Re-EStablishment 2 (RES 2)

• Re-EStablishment 3 (RES 3)



12

Re-EStablishment 1 (RES 1)

A call interruption timer is implemented in theBSC.

The BSC reserves the radio resource for theinterrupted call before the call interruption timerexpires.

The link between the MSC and the other callparty is reserved before the call interruptiontimer expires.

The interrupted call cannot be re-established if

the MS moves to another BSS during theinterruption period.



13

RES 1 Message Flow: Intra-BSS Call Re-establishment

MS BSS0 MSC

Call is interrupted in this period

Timer starts

Timer stops1. call re-establishment request

Call is re-established at BSS0

2. call re-establishment request

acknowledgement



14

RES 1 Message Flow: RadioResource Release

MS BSS0 MSC


Timer starts

Timer expires1. radio interface failure

2. clear command message3. clear complete message



15

Re-EStablishment 2 (RES 2) [1][2]

A call interruption timer is implemented in theMSC.

The BSC releases the radio resource for theinterrupted call when the interruption occurs.

The link in the MSC to the other call party isreserved before the call interruption timerexpires.

The interrupted call cannot be re-establishedif the MS moves to another BSS during the

interruption period.



16

RES 2 Message Flow: Intra-BSS CallRe-establishment

MS BSS0 MSC


Timer starts

Timer stops

1. Clear Request [radio interface failure]



acknowledgement

2. Clear Command

3. Clear Complete


5. Cipher Mode Command

6. Cipher Mode Complete

7. Assignment Request

8. Assignment Complete



17

Re-EStablishment 3 (RES 3)

A call interruption timer for the interrupted callis implemented in the BSC.

The BSC reserves the radio resource for theinterrupted call before the call interruptiontimer expires.

The link in the MSC to other call party isreserved before the call interruption timerexpires.

The interrupted call may be re-established if

the MS moves to another BSS after theinterruption period.



18

RES 3 Message Flow: Intra-BSS CallRe-establishment

MS BSS0 MSC


Timer starts

Timer stops1. call re-establishment request



acknowledgement



19

RES 3 Message Flow: Inter-BSS CallRe-establishment

MS BSS0 MSC

The call is interrupted in

this period, and the MS

moves to

BSS1

BSS1

1. call reestablishment request

5. Cipher Mode Command

2. call reestablishment

request3. clear command message

The call is re-established on the

link at BSS1

Timer stops

Timer starts

4. clear complete message

6. Cipher Mode Complete

7. Assignment Request

8. Assignment Complete

9. call reestablishment

request acknowledgement10. call reestablishment request acknowledgement



20

RES 3 Message Flow: RadioResource Release

MS BSS0 MSC


Timer starts

Timer expires1. radio interface failure

2. clear command message3. clear complete message



21

Performance Evaluation: Output

Measure

Analytical Models (for RESs1, and 3) andSimulation Models (for RESs 1, 2, and 3)

were built to investigate the performance forRES mechanisms.

P nc : the probability that the call is notcompleted due to• new call blocking

• force termination due to handover

• force termination due to call interruption



22

Performance Evaluation: InputParameters

λo: new call arrival rate to a cell

1/ µx: the mean of conversation period 1/ µy: the mean of interruption period

1/ µz: the mean of the time period between when the

interruption begins and when the first of the following

two events occurs (i) the interruption timer expires and

(ii) the remote party hangs up the phone

α: the probability that at the end of a conversation period,

the radio channel is interrupted

1/ η: the expected cell residence time



23

Timing Chart

tc

x1 y1 x2 y2 x3

τ m tm,1

call arrival call completion

enter cell 0 move to cell 1 leave cell 1

tm,0

x j y j xk

x j

tm,i

tc,i

… …

…enter cell i leave cell i

time

z1 z2 z j

*

*



24

CASE (I)

tk

x1 y1 x2 y2 x3

τ m

call arrival

enter cell 0 enter cell 1

tm,0

xk yk

time

z1 z2 zk

xk+1

The MS moves to cell 1 during theconversation period.



25

CASE (II)

x1 y1 x2 y2 x3

τ m

call arrival


tm,0

xk+1 yk+1…z1 z2 zk+1

the call can be resumed

tD,k

The call is re-established at cell 0 after theMS leaves the shielding area.



26

CASE (III)

tD,k

x1 y1 x2 y2 x3

τ m

call arrival


tm,0

yk xk+1

z1 z2

yk+1

zk+1zk

The interruption period ends before theinterruption timer expires, and the remote

party does not hang up the phone



27

CASE (IV)

tc'

x1 y1 x2 y2 x3

τ m

call arrival


tm,0

xk+1 yk+1

time

z1 z2 zk+1

the call cannot be resumed

tD,k

The user hangs up the phone beforethe interruption period is over.



28

CASE (V)

call arrival

tD,k

x1 y1 x2 y2 x3

τ m


tm,0

yk xk+1

time

z1 z2

yk+1

zk+1zk

The interruption period ends after the

interruption timer expires or after the

remote party hangs up the phone.



29

Analytic Model for RES 1

Pb: the probability that all channels are busy when a call (either anew call or a handoff call) arrives.

Let Ph,1

(Ph,2

) be the probability that a connected new (handoff) callat the cell will hand off to the next cell.

Let Pi,1 (Pi,2) be the probability that a connected new (handoff) call atthe cell will be disconnected due to interruption.

( )( )y x y x

y

hh occurs RESin I CASE PPµ αβµ µ η µ η

η η

−++

+=== ]1)(Pr[2,1,

( )

( )( ) ( )( ) y x y x

x

y x y x

y x

ii occurs RESinV or III CASE occurs RESin IV CASE PP

µ αβµ µ η µ η

η αµ

µ αβµ µ η µ η

µ β αµ

−+++−++

−

=

+==

1

]1)()(Pr[]1)(Pr[2,1,



30

Analytic Model for RES 1: Derivationfor Pb (1/2)

The net trafficρ is derived as follows

The blocking probability Pb is expressed as

Pb is obtained by assigning a initial λ h and the IterativeAlgorithm

][][

][)1(][)1(

2,1,

2,1,

cihihcinio

chihcnio

t E Pt E P

t E Pt E P

λ λ

λ λ ρ

++

−+−=

∑=

=c

i

i

c

b

i

cP

0

)! / (

)! / (

ρ

ρ



31

Analytic Model for RES 1: Derivationfor Pb (2/2)

tcn: the channel occupation time of a new call thatis either complete in a cell or handed off to the

next cell.

tch: the channel occupation time of a handoff call.

tcin: the channel occupation time of a new call

which is either forced to terminate due to an

interruption at cell 0 or is handed off to the nextcell during the interruption period.

tcih: the channel occupation time of a handoff callwhich is disconnected due to the interruption.



32

Analytic Model for RES 1: Derivationfor Pnc

Consider an observation period, the Pnc isderived as follows.

For a homogeneous cell structure (thehandoff rate entering the cell is equal to thehandoff rate leaving the cell), we obtain

λh =λo(1-Pb)Ph,1+λh (1-Pb)Ph,2

2,1,

2,1,

)1()1(

)1()1(

ib

o

h

ibb

o

h

b

hiboibhbob

nc

PPPPPP

t o

t PPt PP

t o

t Pt PP

−+−++=

∆

∆−+∆−+

∆

∆+∆=

λ

λ

λ

λ

λ

λ λ

λ

λ λ



33

Results: the Effects ofμz

µ z (unit: µx)(α = 0.2; η = 0.7 µx; µy = 10 µx;λo = 2 µx)



34

Results: the Effects of λo

λo (unit: µx)(α=0.2; η= 0.7µx; µy=10 µx; µz=1.0 µx)



35

Results: the Effects of η

(λo = 2 µx ; α = 0.2; µy = 10 µx; µz=1.0 µx)η (unit: µx)



36

Results: the Effects ofμy

µy (unit: µx)(λo = 2 µx ; η = 0.7 µx; α = 0.2; µz=1.0 µx)



37

Summary of Research 1

Improving GSM Call Completion by Call Re-Establishment

Call re-establishment significantly reduces

the call incompletion probability for the

interrupted calls.

In most cases, both RES 1 and RES 2 have

the same performance, and RES 3 maysignificantly outperform RES 1 and RES 2,

especially for small call arrival rate λo andlarger mobility rate η .



38

Research 2:Channel Assignment for GSMHalf-Rate and Full-Rate Traffic



39

GSM Half-Rate and Full-Rate Traffic

GSM supports full-rate calls and half-rate calls.

A full-rate call uses one time slot in every frame,

while a half-rate call uses one time slot in everytwo frames.

By introducing the half-rate call, the capacity ofGSM increases.

Mixing full- and half-rate calls in a frequencycarrier results in eight full-rate calls, 16 half-ratecalls, or any feasible combinations.

Once an MS initiates a full-rate (half-rate) callrequest, the MS will operate in full-rate (half-rate)mode until the call is terminated.



40

An Example for Full- and Half-RateTraffic

Frame 1

Time Slot Number

0 1 2 3 4 5 6 7

H 1 F 2 H 2 F 3F 1

Time slot 0 in frame 2

is vacant

Frame 2

Time slot 3 is used by

Half #2 and 3

Half #4 uses time slot 6

in frame 2

F 2 H 3 F 3 H 4F 1

empty time slot

F x the time slot is occupied by full-rate call x

H y the time slot is occupied by half-rate call y



41

Channel Assignment Schemes [3]

Random: All full-rate and half-rate calls are

assigned to any free time slots without anycontrol.

Best-Fit: Each incoming full-rate call is

allocated an empty full time slot. A half-rate call

is always assigned a partially occupied time

slot that has already contained a half-rate call.If no such time slot exists, then an empty full

time slot is assigned to the half-rate call. Note

that when a half-rate call departs, it is possible

that more than one partially time slots exist.



42

Channel Assignment Schemes (Cont.)

Repacking: This scheme is similar to the best-fit scheme except that when a full-rate call

arrives to a cell, the scheme repacks the half-rate calls if two partially occupied time slots

exist. Repacking is achieved by intracellhandoff technology.

Fair-Repacking: This scheme is a variation of

the repacking scheme. The only difference

between repacking and fair-repacking is that in

fair-repacking, if only one half time slot is left ina cell, the next incoming half-rate call will be

blocked.



43

Performance Evaluation: OutputMeasures

The simulation models (for the four schemes), and the analytic

model (for repacking) are proposed.

Pf,f (Pf,h): the force-termination probability for the full-rate (half-rate)

call

Pb,f (Pb,h): the new call blocking probability for a full-rate (half-rate)

call

Pnc,f (Pnc,h): the probability that a full-rate (half-rate) call is not

completed (i.e., either blocked or forced to terminate)

Pnc = (λfPnc,f+λhPnc,h)/(λf+λh): the probability that a full-rate or

half-rate call is not completed



44


λf (λh): the new full-rate (half-rate) callarrival rate to a cell

1/ μf (1/ μh): the expected full-rate (half-rate)

call holding time

ηf (ηh): the full-rate (half-rate) MS mobility

rate

c: total number of time slots in a cell



45

Analytic Model for Repacking :TimingDiagram

t mi,0 t mi,1 t mi,j-1 t mi,j

τ mi,0 t ci,j

t ci,j-1

t ci type i call arrival type i call completion

time



46

Analytical Model for Repacking:Derivation forλh,i,ρi, and Pnc,i

From [4],λh,i,ρi, and pnc,i (for i = f or h) can

be expressed as

)]()1(1[

)](1[)1(*

,

*

,

,

imii f i

iimiiib

ih f p

f p

µ µ

λ µ η λ

−−

−−=

−−−

−=)]()1(1[

)](1[1

*

,

*

imii f i

imii

i

ii

f p

f

µ µ

µ η

µ

λ ρ

i f

imii f i

imiiibibinc p

f p f p p p ,*

,

*

,,,

)]()1(1[)](1[)1(

−− −−+=µ µ µ η



47

Analytic Model for Repacking: Derivationfor Pb,i (1/2)

A stochastic process with state n=(nh,nf) is used toderive the new call blocking probability pb,i (i=f or h).

The state space S of the processS={(nh,nf)|nh+2nf≦2c, 0≦nh≦2c, and 0≦nf≦c}

According to Zachary and Kelly, the stationary

probability of n is

where G is

)!

)(!

()( 1

h

n

h

f

n

f

nnGn p

h f

ρ ρ −=

])!

)(!

[(∑∈=sn h

n

h

f

n

f

nnG

h f

ρ ρ



48

Analytic Model for Repacking: Derivationfor Pb,i (2/2)

Pb,f is , where

E1 = {(nh,nf)|nh+2nf=2c or nh+2nf=2c-1,

0≦nh≦2c, 0≦nf≦c}

Pb,h is , where

E2 = {(nh,nf)|nh+2nf=2c, 0≦nh≦2c, 0≦nf≦c}

∑∈

=1

, )( E n

f b n p p

∑∈

=2

, )( E n

hb n p p



49

The Iterative Algorithm

Step 1. Select initial values for λh,h andλh,f.

Step 2. Compute pb,f

and pb,h

.

Step 3. λh,f,old←λh,f andλh,h,old←λh,h.

Step 4. Computeλh,f andλh,h.

Step 5. Ifλh,f andλh,h converges then go toStep 6, otherwise, go to Step 2.

Step 6. Compute pnc,f, pnc,h.



50

Results: Effects of the Proportionofλf

λf/(λf+λh)(a)ηf=ηh=2μf

λf/(λ

f+λ

h)(b)ηf=ηh=0.1μf

(c=7,λf+λh=4μf ,μh=μf)



51

Results: Effects of Incoming CallTraffic

λf (unit:μf)

(a)λ

f

(unit:μf

)

(b)

(c=7,ηf=ηh=2μf ,μh=μf ,λh=λf)



52

Results: Effects of MS Mobilityηf

andηh

λf (unit:μf)(a)

λf (unit:μf)(b)

(c=7,ηf=2μf ,μh=μf ,λh=λf)



53

Results: Effects of MS Mobilityηf

andηh (Cont.)

λf (unit:μf)

(a)

λf (unit:μf)

(b)

(c=7,ηh=2μf ,μh=μf ,λh=λf)



54

Results: Effects of c

λf (unit:μf)

(c=21,ηf=ηh=0.1μf ,μh=μf ,λh=λf)



55


The repacking scheme can significantlyimprove the p

ncperformance over the other

three schemes (about 20% improvements)

pnc increases when the proportion of full-rate

call traffic increases.

Changingηf (ηh) has significant effect on

pnc,f (pnc,h), and only insignificant effect onpnc,h (pnc,f) in the repacking scheme.



56

Research 3:Channel Allocation for GPRS



57

Channel Allocation for GPRS

Based on the GSM radio architecture, GPRSshares the radio resources with GSM voice

users to provide users data connections withvariable data rates and high bandwidthefficiency.

In GPRS service, allocation of physical channelsis flexible (i.e., multiple channels can beallocated to a user).

In this research, we will propose four algorithms

for the GPRS users and GSM voice users.



58

GPRS Architecture

: Signalling and Data Transfer Interface

: Signalling Interface

MSExternal Data

Network

Other GPRS Network

MSC/VLR HLR

SGSN GGSN

GGSNSGSN

BSS

MS: Mobile Station

BSS: Base Station SubsystemMSC: Mobile Switching Center

HLR: Home Location Register

VLR: Vistor Location Register

SGSN: Serving GPRS

Support Node

GGSN: Gateway GPRS

Support Node

在GPRS架構中

MS, BSS, VLR以及 HLR均作了一些修改.

例如: HLR新增存放 GPRS User資訊的功能.

另外新增了SGSN與 GGSN兩種 GSN

SGSN負責將 Packet Data Route至MS端.

GGSN做為GPRS與其它Data Network 連結的Gateway.

GPRS網路中用 GPRS Tunnel Protocol (GTP)來

Tunnel User Data以及 signaling message.



59

GPRS Uplink Packet Transfer

MS Network

Data Block Transmission on PDTCH

Step 2.

Step 3. Resource Request on PDTCH

Step 4. Packet Resource Re-assignment on PDCCH

Step 5. Packet Resource Re-assignment Ack on PDCCH


Step 7. Last Data Block Transmission on PDTCH

Step 8. Final Block Ack/Nack


Access and Assignment (PCCCH/PDCCH)Step 1.

Data Block Transmission on PDTCHStep 6.

此張圖介紹了 GPRS Uplink Packet Transfer的Message Flow.

At Step 4, the amount of PDCHs for the request will be recorded in the QoS

Profile of the user at SGSN.

注意:在 Step 1與 Step 4中有兩種 Allocate Radio Resource給MS的方式.

一為 fixed resource allocation另一為 dynamic resource allocation.這亦是我們要研究的點.



60

Four Resource AllocationAlgorithms

Fixed Resource Allocation (FRA)

Dynamic Resource Allocation (DRA)

Fixed Resource Allocation with Queuecapability (FRAQ)

Dynamic Resource Allocation with Queue

capability (DRAQ)



61

Assumptions for Allocation Algorithms

A GPRS data request specifies K channels fortransmission.

The packets are transmitted at rate μp if singlechannel is assigned to a GPRS request.Consequently, if k channels are assigned to aGPRS data request, then this packet requestwill be delivered with rate kμp .

There are L free channels at a cell when aGPRS data request or a GSM voice call request

arrives.



62

Fixed Resource Allocation (FRA)

FRA: For a data request of K channels, theBS assigns K channels to the GPRS packet

request if K<=L. Otherwise, the GPRS packetrequest is rejected.



63

Dynamic Resource Allocation (DRA)

DRA: For a data request of K channels, DRAallocates at most K channels to the request. If

L>=K then K channels are allocated to therequest. If 0<L<K then L channels areallocated to the request. If L=0 then therequest is rejected.



64

Fixed Resource Allocation withQueue capability (FRAQ) (1/2)

FRAQ handles GPRS data requests in thesame way as FRA. For GSM voice call

requests, FRAQ provides a queue to hold GSMvoice call requests when all channels are busy.

These queued GSM requests are served

immediately when idle channels are available.



65

Fixed Resource Allocation withQueue capability (FRAQ) (2/2)

FRAQ may selectively queue new calls only,the handoff calls only, or both new and handoff

calls, and the corresponding mechanisms areFRAQ_N (for new call only), FRAQ_H (for

handoff calls only), and FRAQ_NH (for both

new calls and handoff calls)



66

Dynamic Resource Allocation withQueue capability (DRAQ)

DRAQ assigns channels to a GPRS data

request in the same way as DRA and assignschannels to GSM voice call requests in the

same way as FRAQ.

There are three DRAQ variations: DRAQ_N

(for new calls only), DRAQ_H (for handoff

calls only), and DRAQ_NH (for both new callsand handoff calls).



67

Performance Evaluation: OutputMeasures

The simulation models (for the eight schemes) andanalytic models (for FRA, DRA, FRAQ) are proposed.

In the models, we consider the mobility of voice usersbut ignore the effect of mobility on GPRS packettransmission.

Pbp (Pbv): the blocking probability for the GPRS packet(the new call blocking probability for the GSM voice call)

Pncv: the probability that a GSM voice call is notcompleted (either blocked or forced to terminate).

cp: the average number of channels for a served packet

Wavg: the average waiting time for the accepted voicecall requests



68


ηv: the GSM voice user mobility rate

λp

(λv): the GPRS packet arrival rate to a

cell (the new GSM voice call arrival rate to acell)

1/ μp (1/ μv): the expected GPRS packettransmission time if one channel is used toserve the packet (the expected GSM voicecall holding time)

C: the number of channels in a cell

Q: the maximum number of voice callrequests buffered in the queue.



69

Analytic Model for DRA (1/3)

DRA is modeled by a (K+1)-state Markov process.

State (nv, npK, npK-1, npK-2, …, np1) denotes that a cell

is occupied by nv voice users, npk GPRS packets(each allocated K channels), …, and np1 GPRSpackets (each allocated 1 channel).

For the illustration purpose, we consider K=3. Thus, astate is represented by (i,j,k,l), where i=nv, j=np3,k=np2, l=np1.

State space

}0,2 / 0,3 / 0

,0,230|),,,{(

C land C k C j

C iC lk jilk jiS DRA

≤≤≤≤≤≤

≤≤≤+++≤=



70

Analytic Model for DRA (2/3)

Letπi,j,k,l be the steady probability for state

(i,j,k,l).πi,j,k,l

=0 if state (i,j,k,l) not in SDRA

.

Let E1 be the set of the states where no free

channel is available

1),,,(

,,, =∑∈ DRASlk ji

lk jiπ

}0,2 / 0,3 / 0

,0,230|),,,{(1

C land C k C j

C iC lk jilk ji E

≤≤≤≤≤≤

≤≤=+++≤=



71

State Transition Diagram for DRA

i, j, k, l

i-1, j, k, l

v

i, j-1, k, l i, j, k-1, l

i, j, k, l-1

i+1, j, k, l

i, j+1, k, l i, j, k+1, l

i, j, k, l+1 (i+1) М v

3( j+1) µ p 2(k+1) µ p

δ+ Λv

i М v

3jµ p 2kµ p δ3 λ p δ2 λ p

lµ p

δ1 λ p

δ+

3 λ p δ+

2 λ p

δ+

1 λ p

(l+1) µ p



72

Analytic Model for DRA: Derivationfor Pbp, Pbv, Pfv,

and Pncv

The packet requests and voice calls (either

handoff call or new call) are blocked whenthere is no free channel. Thus,

The Pncv can be obtained from the voice call

traffic model as we used in half-rate research.

∑∈

===1),,,(

,,,

E lk ji

lk ji f bb vv pPPP π

fvvm fvv

vmvbv

bvncv p f p

f p

p p

−−

−−

+= )]()1(1[

)](1[)1(

*

*

µ µ

µ η



73

Results: Comparing for the EightResource Allocation Algorithms

(DRAQ_NH;λp=5μv;λv=μv;μp=100μv;

ηv=0.2μv; C=7; Q=7)



74

Results: Effects of the Variances ofPacket Transmission Times

(DRAQ_NH;λp=5μv;λv=5μv;μp=100μv;ηv=0.2μv; C=7; Q=7)



75

Results: Effects of the Variances ofPacket Inter Arrival Times

(DRAQ_NH;λp=5μv;λv=5μv;μp=100μv;

ηv=0.2μv; C=7; Q=7)



76

Results: Effects of the Variances ofGSM Voice User Cell Residence Times

(DRAQ_NH;λp=5μv;λv=5μv;μp=100μv;

ηv=0.2μv; C=7; Q=7)



77

Results: The Average Number ofChannels for a Served Packet in

DRAQ_NH (C=7; Q=7)



78

Results: The Average Waiting Timefor the Accepted Voice Call Requests

in DRAQ_NH

(λv=μv;μp=100μv;ηv=0.2μv; C=7; Q=7)



79


Dynamic allocation effectively increases the

GPRS packet acceptance rate, and thequeuing mechanism significantly reduces the

voice call incompletion probability.

If too many channels are allocated to a

packet transmission, both packet and voice

call droppings will increase.



80

Conclusions and Contributions

Our study provided guidelines radio resource

allocation for the different type of trafficgenerated by GSM new services.

• Interrupted Call Traffic

• Half-Rate Voice Call Traffic

• GPRS Packet Data Traffic

We proposed channel allocation schemes,analytic models, and simulation models.



81

Future Work

OVSF Code Channel Assignment for IMT-

2000.

Channel Allocation for Opportunity DrivenMultiple Access (ODMA)



82

Publication Lists

Journal Papers

1. Lin, Phone and Lin, Yi-Bing, Channel Allocation for GPRS Packet Data. Accepted and to appear in IEEE Trans. on Vehicular Technology, 2001.

2. Pang, Ai-Chun, Lin, Phone and Lin, Yi-Bing, Modeling Mis-routing Calls Due to User Mobility in Wireless VoIP. Accepted and toappear in IEEE Communications Letter , 2000.

3. Lin, Yi-Bing, Lin, Phone and Chuang, Yu-Min, Modeling CDPD Channel Holding Times. Accepted and to appear in IEICE Trans. onCommunications , E83-B(9):2051-2055, (Sep. 2000).

4. Lin, Phone and Lin, Yi-Bing, Channel Assignment For GSM Half-Rate and Full-Rate Traffic. Computer Communications, 23 (2000):476-482.

5. Lin, Phone, Lin, Yi-Bing and Jeng, J.-Y., Improving GSM Call Completion by Call Re-Establishment. IEEE Journal on Selected Areas inCommunications , 17(7): 1305-1317 (July 1999).

6. Lin, Yi-Bing and Lin, Phone, Performance Modeling of Location Tracking Systems. ACM Mobile Computing and Communications Review , 2(3):24-27 (July-Aug 1998).

Conference Papers

1. Cheng, Ray-Gung and Lin, Phone, OVSF Code Channel Assignment for IMT-2000. IEEE VTC2000 Tokyo, Pages 2188-2192.

2. Chuang, Yu-Ming, Lin, Phone and Lin, Yi-Bing, Modeling CDPD Channel Holding Times. 1999 National Computer Symposium (2),Pages B-11-B-14.

3. Chen, S.-C. S., Yang, C.-S. and Lin, Phone, Software Radio. 5th Mobile Computing Workshop, 74-80 (March 1999).

4. Chen, S.-C. S., Lin, Phone and Lin, Yi-Bing, IMT-2000. 4th Mobile Computing Workshop, 66-72 (March 1998).

5. Lin, Phone and Tsai, W.-N., A Simulation Study of Multiple-Location Scheme for PCS Mobility Management. 3rd Workshop on MobileComputing, 37-45 (March 1997).

Submitted Papers

1. Lin, Phone and Lin, Yi-Bing, Implementation and Performance Evaluation for Mobility Management of a Wireless PBX Network. IEEE Journal on Selected Areas in Communications (in revision).

Pending Patents

1. Chen, S.-C. S., Lin, Phone, and Lin, Yi-Bing, A Call Re-establishment Mechanism “RES” for GSM Call Completion (with ITRI/CCL,submitted to R.O.C., USA, and Europe Patent Offices).

2. Cheng, R.-G., Lin, Phone, and Lin, Yi-Bing, Opportunity Driven Multiple Access (with ITRI/CCL, to be submitted to R.O.C. and USAPatent Offices).

21 Radio Resource Management

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