Multi-Path Multimedia Transmission in Ad-hoc Networks Related Work Marcin Michalak

2 Agenda ad-hoc networks multi-path –routing –content experimental results references summary

3 Environment ad-hoc networks – no infrastructure, multihop, multi-path, mobile, wireless users want good quality real need for QoS – network may get congested not much to rely on…

4 Important parameters delay (~ no. hops) jitter available bandwidth stability of path packet error rate congestion ad-hoc: all variable

5 Multi-Path independent paths - independent loss probability “it has been observed that for multi-path transmission the end-to-end application sees a virtual average path which exhibits a smaller variability in quality than any of the individual paths”  more is better  how to do it?:  routing issue – getting multiple paths  content issue – dividing content

6 Multipath Routing Current algorithms already provide information about multiple routes, but only use one at a time Transmission: –redundant: data + error correction –non-redundant: all paths transmit data some promising work on Internet, using relays load balancing (but interference) still a very open issue

7 Path Selection correlation factor: no. of links connecting 2 paths paths should be unrelated, to avoid interference (sharing same link): a) two node-disjoint, unrelated paths b) node-disjoint, 7-related c) link-disjoint node-

8 Path Selection (2) shared-channel model the larger c.f., the larger delay – interference Path should be: node-disjoint short have small correlation factor

9 Experimental Results 50 nodes 1500m x 500m field 900s simulation time TX range 250m speed 5-10 m/s CBR: 512B / 250ms pause time s delay including queue and propagation improvement limited under pause time 300s

10 SMR – Split Multipath Routing Sung-Ju Lee (HP) and Mario Gerla (UCLA) on-demand discovery using request/reply cycles goal: build maximally disjoint paths 2 routes: shortest delay + max disjoint (shortest hop) source routing per-packet allocation

11 SMR - Simulation SMR-1: route recovery when any of the routes is invalidated SMR-2: only when both are invalidated comparison to DSR – single path

12 SMR – Packet Delivery Rate GloMoSim 50 mobile hosts (1000 m) 2 area prop. range 250m channel 2Mbps run 300 sec speed 0-10 m/s SMR-2 SMR-1 DSR simulation ends on 300 s....

13 SMR – End-to-End Delay 300 s seems to be a limit? DSR uses longer paths SMR-1 SMR-2 DSR

14 Coding possibilities Single Description Reference Picture Selection (RPS) – from H263+ Multiple Description (MD) layered coding (+ARQ) – good for mcast Video Redundancy Coding

15 Multiple Description Coding (MDC) Code video into a number of descriptions, each of roughly equal importance Properties : –receiving either bitstream gives good quality –receiving both bitstreams gives highest quality MD Coder (from HP slides – John Apostolopoulos) Original Video Decoder 1 Decoder 2 Decoder 3 Stream 2 Stream 1 Good Quality Video Highest Quality Video Good Quality Video

16 Results (Panwar...) MD coding works well for low-error links Layered Coding + ARQ is better for high-error links, but increases delay packet loss rate(3%,3%)(10%,10%)(5%,10%) RPS Layer Coding + ARQ MDMC VRC Average PSNR of Decoded Images (dB)

17 References “Split Multipath Routing with Maximally Disjoint Paths in Ad hoc Networks”, Sung-Ju Lee & Mario Gerla “Real-Time Voice Communication over the Internet Using Packet Path Diversity”, Liang, Steinbach, Bernd Girod, Stanford University “On-Demand Multipath Routing for Mobile Ad Hoc Networks”, Kui Wu and Janelle Harms, University of Alberta “Video Transport over Ad-hoc Networks Using Multiple Paths”, S.Lin, Y.Wang, S.Mao and S.Panwar

18 Summary multi-path transmission seems to be a good solution – better quality, lower average delay not only for multimedia several video coding techniques many issues still open

19 Questions? –is this all as good as presented? ?