1. A Dynamic Reservation Protocol for Multi-Priority Multi-Rate Data Services on GSM Networks

2. 2 Introduction uOn GSM networks most research works are based on integrating voice and data services together in one physical channel uTwo major differences uvoice traffic is subject to real time constraint but can tolerate some level of packet loss, while data services require error-free transmission but can tolerate some delay uvoice traffic is generally symmetrical while data traffic is asymmetrical uIntegrating data traffic onto TDMA channels designed for voice traffic may lead to poor channel utilization

3. 3 Advantages uData terminals can access uplink channel without contention achieving very high channel utilization efficiency and improving the service performance under heavy traffic load uIt can adapt to traffic variations by dynamically changing the transmission cycle lengths uIt can accommodate different service priorities and different latency constraints of multimedia traffic uIt can accommodate CBR, VBR and ABR services uTypical applications: wireless E-mail, web browsing, telemedicine, voice messaging, telemetry

4. 4 Frame Structure of GSM Traffic Channel uTraffic channels in GSM networks are TDMA slots that can support both data and voice traffic uEach TDMA slot can accommodate 48 bits user data u8 slots are grouped into a frame u26 frames are grouped into a multiframe uDuplex channels are assigned in GSM uThis assignment however is very inefficient for asymmetric data traffic (browsing WWW pages, Road Traffic Information)

5. 5 Virtual Circuit Connection uConnection setup request signal uService type uPerformance requirements (priority, latency constraint) uSetup confirm signal uThe assigned carrier pair for the data terminal to use uA virtual circuit number uThe position of the slot for the terminal to make transmission reservations

6. 6 Type of control Signals uCycle_Start signal uRequest signal uMake a reservation in the current cycle uChange the service priority uMaintain the virtual circuit uTerminate the virtual circuit connection uSchedule signals

7. 7 Signals for the Virtual Circuit Connection Cycle_Start downlink uplink Cycle_Start Schedules Requests multiframe 1multiframe L............. Data...

8. 8 Control Signals uAll control signals are 48-bit long (1 slot) uCycle_Start signal Group ID, Starting position of the Schedule signal, Network status information uRequest signal Virtual Circuit Number, Service Priority Change, Number of Requested Slots, Link Control (acknowledgment of received data) uSchedule signals Virtual Circuit Number, Number of assigned slots, Starting position for both uplink and downlink

9. 9 Multi-priority uAssign different access rights to different priority classes uLet a two-class case with priority of class 1>priority of class 2 uDivide class 2 terminals into n equal groups uIn each transmission cycle all class 1 terminals and one class 2 group are allowed to make reservation

10. 10 Assignment Algorithm uLet N 1 the number of class 1 terminals, N 2 the number of class 2 terminals uReservation slots in each cycle N 1 +(N 2 /n) uTransmission slots in the uplink m 0 =208L - N 1 - (N 2 /n) (208=26*8 is the number of slots in one multiframe) uLet r i the number of requested slots from terminal i and R=[r 1,r 2,…,r N ] a vector with at most N 1 +(N 2 /n) elements uLet α i the actual number of slots assigned to terminal i and A=[α 1,α 2,…,α Ν ]

11. 11 Assignment Algorithm uIf the total number of requested slots is no larger than m 0 A=R u Otherwise 1) Initialize A to 0 and total number of remaining slots m to m 0 2) Find the smallest r i denoted as r min and update α i =α i +min(r min, r i, m). Decrement r i and m accordingly 3) Repeat step 2 until m=0 uTransmission order: class 1 terminals transmit first following by class 2 terminals. Among those belonging to same class terminals with shorter messages transmit first

12. 12 Performance Evaluation uNumber of logged terminals N uEach terminal generates messages according to a Poisson process with rate λ=0.33 per second uThe message length is geometrically distributed with a mean X=192 bytes uMessage delay: time until the next transmission cycle, request, schedule, transmission

13. 13 Message Delay Versus Number of Terminals λ=1/3 Χ=192 delay 1000, terminals 140, channel utilization 0.875

14. 14 Message Delay Versus Number of Terminals λ=1/6 Χ=192 delay 1000, terminals 250, channel utilization 0.8

15. 15 Message Delay Versus Number of Terminals λ=1/3 Χ=384

16. 16 Comparison of Message Delay Between the First and Second Class Terminals λ=1/3 Χ=192 N 1 =N 2 =N/2

17. 17 Average Message Delay for Single-Class and Two- Class Priority λ=1/3 Χ=192