VoIP-Kapazität im Relay erweiterten IEEE System

Transcription

1 VoIP-Kapazität im Relay erweiterten IEEE System 21. ComNets-Workshop Mobil- und Telekommunikation Dipl.-Ing. Karsten Klagges ComNets Research Group RWTH Aachen University 16. März 2012 Karsten Klagges ComNets, RWTH Aachen University ComNets 1

2 Outline Relay stations in IEEE Motivation Resource Management Model Simulator and Models Simulator Architecture VoIP model Performance Evaluation Simulation Scenario Results Conclusion Karsten Klagges ComNets, RWTH Aachen University ComNets 2

3 Benefits Coverage of heavily shadowed areas Serving low performing MSs at the edge of the cell Trunking gain on back-haul link SDM operation of relay stations capacity gain Potential Challenges Increased packet delay over single-hop system Load balancing among relay stations Resource partitioning UL/DL Karsten Klagges ComNets, RWTH Aachen University ComNets 3

4 Single-hop TDD Frame Superframe: 20 ms Frame 1 Frame 2 Frame 3 Frame 4 Frame: 5 ms DL access zone UL access zone BS SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 RX SF 7 RX SF 8 RX Figure: Single-hop Frame Structure 20 ms periodic superframe Partition of frame in downlink (DL)- and uplink (UL) access zone Subdivision into sub-frames (SF) base station (BS) performs radio resource management and signals at the beginning of a frame (not shown) Karsten Klagges ComNets, RWTH Aachen University ComNets 4

5 Multi-hop TDD Frame Superframe: 20 ms Frame 1 Frame 2 Frame 3 Frame 4 BS DL access zone SF 1 SF 2 SF 3 Frame: 5 ms DL relay zone SF 4 SF 5 UL access zone SF 6 RX SF 7 RX UL relay zone SF 8 RX RS SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 RX RX RX RX RX Figure: Relay Enhanced Frame Partition of frame in DL- and UL access and relay zone RS communicates with BS in relay zone RS performs radio resource management in relay cell Karsten Klagges ComNets, RWTH Aachen University ComNets 5

6 Relay stations in IEEE Motivation Resource Management Model Simulator and Models Simulator Architecture VoIP model Performance Evaluation Simulation Scenario Results Conclusion Karsten Klagges ComNets, RWTH Aachen University ComNets 6

7 Simulator Core Simulation Model Database Configuration PyConfig Tree Node #1 Load generator Network (IP) Node #2 Load generator Network (IP) Statistic Tools DLL DLL Event Scheduler PHY PHY Random Number Generator Event Logging Radio Interference Simulation Engine (RISE) Figure: Simulator Architecture Simulator core provides Nodes contain protocol stack Communication between nodes via RISE Karsten Klagges ComNets, RWTH Aachen University ComNets 7

8 VoIP traffic model a = 0.01 b = 0.99 talking pause d = 0.99 c = 0.01 Figure: Brady VoIP model Codec RTP AMR 12.2 (12.2 kb/s) Encoder frame length 20 ms Voice frame size 320 bit Silence indicator inter arrival time 160 ms Silence indicator frame size 120 bit State update interval 20 ms Voice activity factor 50 % Mean talk spurt length 2 s Karsten Klagges ComNets, RWTH Aachen University ComNets 8

9 WiMAC MAC Layer Radio Resource Control and Management Service flow and Connection Management Convergence Sublayer Data Plane Convergence Classifier Buffer Interference Management BW Request ARQ CRC Error Model MAC / Physical Layer SFH DL MAP UL MAP DL Scheduler Frame Multiplexer UL Scheduler Figure: WiMAC MAC/PHY Layer Karsten Klagges ComNets, RWTH Aachen University ComNets 9

10 WiMAC MAC Layer of Relay Station Radio Resource Control and Management Service flow and Connection Management Data Plane Buffer Interference Management BW Request ARQ CRC Error Model MAC / Physical Layer SFH DL MAP UL MAP DL Scheduler Frame Multiplexer UL Scheduler Figure: WiMAC MAC/PHY Layer Karsten Klagges ComNets, RWTH Aachen University ComNets 10

11 Relay stations in IEEE Motivation Resource Management Model Simulator and Models Simulator Architecture VoIP model Performance Evaluation Simulation Scenario Results Conclusion Karsten Klagges ComNets, RWTH Aachen University ComNets 11

12 Simulation Scenario BS RS 3 sectors/cells each site 7 sites 500 m inter-site distance 3 relay stations per cell up to 75 mobile stations (MSs) per cell combined LOS/NLOS urban macro pathloss model LOS pathloss model for BS RS link Figure: Simulation scenario Karsten Klagges ComNets, RWTH Aachen University ComNets 12

13 System parameters 5 MHz bandwidth DL/UL resource ratio 5:18 with RSs DL/UL resource ratio 12:11 without RSs Frequency reuse 1 station BS RS MS power 43 dbm 24 dbm 24 dbm Karsten Klagges ComNets, RWTH Aachen University ComNets 13

14 Cell throughput DL cell throughput UL cell throughput DL cell throughput [bit/s] Number of UTs Hop mode: multi Hop mode: single RSs do not affect the cell capacity UL cell throughput [bit/s] Number of UTs Hop mode: multi Hop mode: single Karsten Klagges ComNets, RWTH Aachen University ComNets 14

15 Packet Delay DL packet delay with 30 MSs 1 UL packet delay with 30 MSs P (X < x) P (X < x) DL packet delay [s] Hop mode: multi Hop mode: single DL packet delay is not critical UL packet delay [s] UL packet delay shows significant decrease with RSs Hop mode: multi Hop mode: single Karsten Klagges ComNets, RWTH Aachen University ComNets 15

16 Channel estimation error Channel estimation error at MSs 1 Channel estimation error at BSs P (X < x) P (X < x) Hop mode: multi Hop mode: single Channel estimation error [db] Channel estimation error is unaffected by RSs 0.2 Hop mode: multi Hop mode: single Channel estimation error [db] Karsten Klagges ComNets, RWTH Aachen University ComNets 16

17 Number of transmissions Number of DL transmissions for successful delivery 1.55 Number of UL transmissions for successful delivery 1.8 Mean DL ARQ transmissions (BS) Number of UTs Hop mode: multi Hop mode: single RSs reduce the amount of retransmissions Mean UL ARQ transmissions (UT) Number of UTs Hop mode: multi Hop mode: single Karsten Klagges ComNets, RWTH Aachen University ComNets 17

18 User Data SINR distribution 1 User data SINR at MSs 1 User data SINR at BSs P (X < x) P (X < x) DL user data SINR [db] Hop mode: multi Hop mode: single Hop mode: multi Hop mode: single UL user data SINR [db] (at BS) RS provide a significant gain in user data SINR for UL and DL Karsten Klagges ComNets, RWTH Aachen University ComNets 18

19 Conclusion Benefits of relay stations Relays improve channel knowledge for UL transmissions Relays provide same DL quality of service with less resources Even low-powered relay stations improve system performance Open issues Packet delay must be limited by packet prioritization Load balancing among RSs is not possible Karsten Klagges ComNets, RWTH Aachen University ComNets 19

20 Thank you Karsten Klagges ComNets, RWTH Aachen University ComNets 20