View
218
Download
0
Category
Tags:
Preview:
Citation preview
Group 896GPRS Radio Resource Management
Allocation of Radio Resources to packet-switched traffic in GPRS-like
networks
By group 896
Supervisors: Students:Hans Peter Schwefel Xin ZhouPatrick Eggers Jimena Llorente Martinez
Devendra PrasadFrançois DelawardeGwénaël CogetHaibo Wang
Group 896GPRS Radio Resource Management
Project Description:
•Analyze existing GPRS radio resource management strategies.
•Define scenarios and input parameters, for which an algorithm for the assignment of resources to packet-switch traffic will be developed.
•Evaluate/validate the algorithm in simplified simulation models.
Group 896GPRS Radio Resource Management
GPRS Introduction:
• Reuse the existing GSM infrastructure
• Introduce packet-switched routing functionality• Better data transfer rates (multislot capabilities)• Low cost and connectivity-oriented
• Migration Path to 3G Networks
Group 896GPRS Radio Resource Management
Comparison between GSM/GPRS
Group 896GPRS Radio Resource Management
GPRS architecture
Group 896GPRS Radio Resource Management
GPRS protocols stack
Um Gb GnMS
BSS
SGSN GGSN GiTE R
LLC
SNDCP GTP GTP
GSM RF
RLC
LLC Relay
BSSGP
MAC
L1
FrameRelay
L1
FrameRelay
BSSGP
L2
L1
IP
L2
L1
IP
UDP UDP
SNDCP
LLC
RLC
MAC
GSM RF
L2 L2
L1 L1
IP
PPP
PCMCIA/ IrDA
PPP
PCMCIA/ IrDA
IP
IP
TCP/UDP
TCP/UDP
Appli
Um Gb GnMS
BSS
SGSN GGSN GiTE R
LLC
SNDCP GTP GTP
GSM RF
RLC
LLC Relay
BSSGP
MAC
L1
FrameRelay
L1
FrameRelay
BSSGP
L2
L1
IP
L2
L1
IP
UDP UDP
SNDCP
LLC
RLC
MAC
GSM RF
L2 L2
L1 L1
IP
PPP
PCMCIA/ IrDA
PPP
PCMCIA/ IrDA
IP
IP
TCP/UDP
TCP/UDP
Appli
Group 896GPRS Radio Resource Management
GPRS Protocols:
GSM-RF layer: Reuse of GSM multiple access methods (TDMA/FDMA)
MAC layer: Multiplexing Scheduling Contention resolution (UL)
RLC layer: Segmentation/Re-assembly ARQ
Group 896GPRS Radio Resource Management
Radio Resource Management (RRM)
• Introduction-Functions
• GSM/GPRS establishment• GSM/GPRS call maintaining• GSM/GPRS release
-Dedicated/Shared channels
• Best Effort Strategy <-> Our Proposed RRM Strategy• Resource Allocation• Reassignment• Scheduling
Group 896GPRS Radio Resource Management
Best Effort : Access Control
Group 896GPRS Radio Resource Management
EXAMPLE: Resource Assignment Best Effort
Group 896GPRS Radio Resource Management
Best Effort: Round Robin Scheduling
Group 896GPRS Radio Resource Management
Proposed Strategy : Access Control
Group 896GPRS Radio Resource Management
Proposed Strategy: Resource Assignment
TS
G GTS1
gTBFincoG
gTBFincoavailable GTS
GTS
min
min
Group 896GPRS Radio Resource Management
Proposed Strategy: Scheduling
Example:
TBF G=3 30%TBF G=6 60%TBF G=1 10%
GTBFnutilizatio TS
GTS /
Group 896GPRS Radio Resource Management
Simulation Model- General AssumptionsOnly downlink traffic in 1 micro-cell, Transmission time step was set to 20ms(1 RLC block)
Cell Hand-over: NoPower Control: NoReuse Pattern: 1/3Cell Radius: 500m Frequency Hopping: Ideal Random Frequency Hopping
Mobility User Distribution: Uniform DistributedUser Moving: TU3 Mobility Tracking: No
Mobile Phone
Always in “active” stateCapable of using 1~4 Time Slot
Group 896GPRS Radio Resource Management
C/I --- BLER Assumption
We designed a network-level simulator which utilized the simulation result of a link-level simulator in reference[3].
TU3 Model Reuse pattern 1/3 Ideal Frequency Hopping Fast fading is considered Mean BLER
C/I
BLER
Mapping FunctionC/I
CS_x
BLER
Group 896GPRS Radio Resource Management
Radio Channel Model(1) Path Loss --- global mean power(2) Slow Fading --- local mean power(3) Fast Fading --- instantaneous power
(1) Path loss
(2) Slow fading
(3) Fast fading
Group 896GPRS Radio Resource Management
C/I Generation1. Mean C/I --- Path Loss and Reuse Pattern
Path Loss PDF(r)
pdf(r)=k*r, 15m<r<500m
Group 896GPRS Radio Resource Management
0: Investigated Cell
1~6: Co-channel Cell
D: Reuse Distance
R: Cell Radius
r: MS-BTS Distance12
3
4 5
60
D
R
r
Reuse Pattern C/I Calculation
Group 896GPRS Radio Resource Management
PDF(r) Mean C/I
Group 896GPRS Radio Resource Management
2. C/I per MS --- Shadowing Effect
Lognormal Distribution (mean C/I, STD)
C/I for Each Mobile
Group 896GPRS Radio Resource Management
Coding Scheme Selection
CIR 0~5 CS1CIR 6~9 CS2CIR 10~16 CS3CIR 16~30+ CS4
Throughput vs. C/I
Group 896GPRS Radio Resource Management
BLER Generation
Random Seed< BLER Block Correct
RandomSeed
Random Seed> BLER Block Erroneous
C/I
CS_x
BLER Generation
MappingTable
Group 896GPRS Radio Resource Management
Frequency Correlation Function
Group 896GPRS Radio Resource Management
Path Loss
Shadowing Effect
MS ID
Distance Generation
Mean C/I
C/I per MS
CS_x Selection
BLER Mapping
RandomSeed
Block CorrectOr Erroneous
pdf(r)
Group 896GPRS Radio Resource Management
Traffic ModelThe definition of a GPRS session in our model:
Packet 1 Packet 2 Packet 3
Packet Call1 Packet Call 2 Packet Call 3
Session1 Session2 Session3
Time[ s]
Time[ m]
Time[ h]
Session3
Group 896GPRS Radio Resource Management
Voice
Voice
Voice
Data
Data
Data
Traffics: Mixture of GSM Voice calls and GPRS Data sessions
Each session/call was randomly assigned to a Mobile Station(MS), where each MS only represent a propagation condition(C/I) corresponding to a certain distance from the BTS.
Group 896GPRS Radio Resource Management
VOICE
DATA
DATA
VOICE
Session size(# bits)
Traffic Generation Method
Group 896GPRS Radio Resource Management
1. 1 session assigned to 1MS corresponding to a certain radio condition
2. 1MS can have multiple sessions based on radio condition
3. All the sessions are in the BSS to be transmitted
4. No Handover
5. Based on one Cell Configuration
6. No uplink simulation
7. Higher layers(TCP/IP, LLC) is not considered
8. ARQ for uplink is not considered
Model Assumptions
Group 896GPRS Radio Resource Management
Parameters Stochastic Process
ParameterValues
GSM Arrival Time Exponential
Holding Time Exponential
GPRS Arrival Time Exponential
Session Size Geometrical P=0.5Object Size = 50 KbytesMean Session Size=100Kbytes
GSM
1/ 120secGSM
GPRS
Parameters List
Traffic Load = 5 ~ 29 ErlangGSM Voice: Traffic_Load*70%;GPRS Data: Traffic_Load*30%
Group 896GPRS Radio Resource Management
Mapping GPRS session to RLC blocks
Session size (bits)
GPRS SESSION
time
time
CS-x
RLC blocks
arrival time
Mapping to block
Because in simulation the transmission was working on RLC block level.
Group 896GPRS Radio Resource Management
Simulator Implementation
•General Structure – Object Oriented
•Time-Driven and Event-Motivated Simulation Process – main() and traffic_Model
•Propagation Concerned Object – MS and air_Interface
•Proposed RRM features VS “Best Effort”
•Proposed RRM Object – BSS, FIFO_Priority and resource_Pool
Group 896GPRS Radio Resource Management
General Structure – Object Oriented
Access ();TS assignment (); TBF assignment ();
Scheduler ();Resource Update ();
BSS
Traffic Generator ( );
Traffic Model
Transmission ( );
Air Interface
Update Propagation ( );
Mobile Station
Output ( );
Trace
Push ( );Pop ( );
FIFO Priority
Add GSM ();Add GPRS ();
Release GSM ();Release GPRS ();
Scheduled ();
Resource Pool
Group 896GPRS Radio Resource Management
Time-Driven and Event-Motivated Simulation Process
Traffic ModelT, Length, MS T, Length, MS T, Length, MSGSM events Chain
T, Length, MST, Length, MST, Length, MSGPRS events Chain
Simulation Process T<T_EndT_nex t_Frame<T_next_Event?
Transmission
Scheduling
Resource Update
Access
Timer Update
Yes No
Output Trace
Group 896GPRS Radio Resource Management
Propagation Concerned Object
– MS and airInterface
MS:Assign C/I, CS, BLER to each mobile station, the process was carried on during the initialization step.
Air Interface:Frame[TRX][TS];During each RLC block transmission, generate a Random “ 0” or “1” representing “correct” or “error” according to the BLER for the MS which occupy current TS/Block.
Group 896GPRS Radio Resource Management
Proposed RRM vs “Best Effort”
Best Effort Proposed RRM
Access Queuing FIFO Graded FIFO
When access queue full and new request come
Block the new request
Block the last one in queue and push new one into queue
Scheduling Round-Robin Graded Round-Robin
Resource AllocationWhen coming GPRS session has to share a TS with existing ones
Depending on how many TFI already in a TS
Depending on the sum of grades in a TS
Voice Pre-emption Yes Yes
Group 896GPRS Radio Resource Management
Proposed RRM Object - 1– BSS, FIFOPriority and resourcePool
Resource Pool: store a table for all the TRX-TS.
TS data structure
Session ID, GradeTS Type 1: GSM
Session ID, GradeSession ID, GradeSession ID, GradeTS Type 2: GPRS
Pool[TRX][TS]
TS0 TS1 TS2 TS3 TS4 TS5 TS6TRX0TRX1TRX2TRX3
Group 896GPRS Radio Resource Management
Proposed RRM Object – 2
FIFO_Priority:The GPRS access queue based on grade. Queue length = 7
Session ID, PriorityAccess Queue Session ID, Priority Session ID, Priority
Priority: High Low
Priority = C/I of each session according to its assigned Mobile Station
BSS will always select the first one(highest priority) in queue to assign resources.
For two sessions with the same C/I, the new one will be put after the old one(FIFO).
Group 896GPRS Radio Resource Management
Proposed RRM Object – 3BSS:Manage all the “active” sessions.
Session ID, GradeGSM Sessions Session ID, Grade Session ID, Grade
Session ID, GradeGPRS Sessions Session ID, Grade Session ID, Grade
Access Control (Voice Pre-emption) TS/TBF assignment Scheduling Correctly-received RLC blocks counting Release finished GSM/GPRS or drop GPRS with max retransmissions. TFI re-assignment: after every transmission time step, try to raise
the TFI numbers for each GPRS session to 4.
Group 896GPRS Radio Resource Management
Performance Evaluation
• Simulator validation
• Simulations parameters
• Simulations results
• Future work
Group 896GPRS Radio Resource Management
Simulator Validation
• RRM strategies: use of output functions and breakpoints to check the behaviour of access queue, choice of TRX/TS, scheduler, reassignment, pre-emption…
• Propagation /Transmission: comparison between the curve used to map C/I, BLER and throughput and the one obtained
• Traffic Model: comparison between input parameters and traffic generated (number of sessions per hour, call length, session size…)
Group 896GPRS Radio Resource Management
Simulations ParametersParameter Name VALUE
Simulated Duration 4 hours
Traffic Load (TL) from 5 to 29 "Erlangs"
Number of simulations (per TL) 15
TRXS 4 (32 TSs)
Number of signalling channels 4
Number of traffic channels 28
Maximum number of multiplexed sessions per TS
32
Number of Mobile Nodes 30
Multi-slot capacity of Mobile 4TSs
Mean GSM call duration 120s
Mean GPRS session size 100kB
Access queue size 7 sessions
Maximum number of block retransmission
25
Group 896GPRS Radio Resource Management
Simulations Results
• Throughput per Cell Vs. Traffic Load
• Throughput per Session Vs. Traffic Load
• Access Delay Vs. Traffic Load
• Blocking Rate GPRS Vs. Traffic Load
• Throughput per Session Vs. C/I
Group 896GPRS Radio Resource Management
Throughput per Cell
Group 896GPRS Radio Resource Management
Throughput per Session
Group 896GPRS Radio Resource Management
Throughput Per Session Vs. C/I
Group 896GPRS Radio Resource Management
Mean access delay
Group 896GPRS Radio Resource Management
Blocking Rate GPRS
Group 896GPRS Radio Resource Management
Future Work
• Consideration of QoS requirements (traffic model with different types of service)
• Consideration of Uplink
• Investigation of higher layers
Group 896GPRS Radio Resource Management
Thank You !
Group 896GPRS Radio Resource Management
BackUp: for Q&A
1) In traffic generator while calculating the mean GPRS holding time:We use average data speed: 25kbps.Which comes from some simulation output on different traffic load.
2)
Recommended