Video Streaming Transmission Over Multi-channel Multi-path Wireless Mesh Networks

1. Video Streaming Transmission Over Multi-channelMulti-path Wireless Mesh Networks Authors: GuojunShui, ShuqunShen Speaker :吳靖緯 MA0G0101 2008. WiCOM '08. 4th International Conference on Wireless Communications, Networking and Mobile Computing On page(s): 1- 4, Oct. 2008 2012.02.17

2. Outline • Introduction • Multi-channel multi-path routing • Performance evaluations • Conclusion

3. Introduction • Transmitting real-time video streaming requires high bandwidth, low delay jitter, and low error-rate. • Achieving each of these requirements in a WMNs is challenging itself, considering the limited bandwidth, high delay jitter, and the high bit error-rates of wireless medium. • All these problems could be caused by both the nature of wireless medium and high route breakages.

4. Introduction • Single-channel protocols have a single common channel shared by all nodes. • Collisions always occur when two or more nodes transmit simultaneously. • Comparing with single-channel protocols, utilization of multichannel technology, which allows simultaneous transmissions on different channels, increasing average network throughput and decreasing the propagation delay.

5. Introduction • In this paper, we proposed Multi-channel Multi-path Routing DSR(MM-DSR) protocols that builds two disjoint paths. • Real-time video streaming can be divided into two sub-streams and each of the sub-stream is transmitted through one of these two paths to avoid congestion.

6. Multi-channel multi-path routing • When the source needs a route to the destination but no route information is found in cache, it floods the ROUTE REQUEST (RREQ) messages to the entire network. • The destination node then sends ROUTE REPLY (RREP) messages responding to the RREQ back to the source node. • The source node selects multiple routes based on given metrics.

7. Multi-channel multi-path routing • Route Discovery • The source node will flood the RREQ messages in order to find paths to the destination. • Each RREQ identifies the source and destination of the route discovery, which contains unique request identification (ID). • When another node receives this RREQ and is the destination of the route discovery, it returns an RREP to the source of the route discovery.

8. Multi-channel multi-path routing • It will check if this RREQ is duplicated or not by the ID. • If it is not the duplicate, it appends its ID and rebroadcasts the packet. • Otherwise, it will discard this duplicate RREQ.

9. Multi-channel multi-path routing • An example of a MM-DSR routing protocol is shown in Figure 1, where the source node will select the two best routes from the route cache for data transmission at bands P1 and P2. • In this protocol, all the nodes can listen to both frequency bands P1 and P2.

10. Multi-channel multi-path routing • Route Selection Method • In order to measure the performance of each route for the selection process, we define the following metrics: • Hop count • Delay of route • Number of joint nodes between two routes

11. Multi-channel multi-path routing • In the route selection process, the source node will try to find the two best routes based on the above metrics. • First, a route with the smallest hop count has the highest priority. • If two or more routes have the same hop count, then delay of route is used to select the route with the smaller joint nodes. • The next step is choosing the second best route amongst the remaining routes.

12. Multi-channel multi-path routing • Route Maintenance • In MM-DSR, when one node detects a broken link, it will send the ROUTE ERROR (RERR) message. • Once the source node receives the RRER message, it will remove every route entry in the route cache, which uses the broken link.

13. Performance evaluations • Multiple Description Coding • Multiple description coding (MDC) is a technique that generates multiple equally important descriptions. • In a multiple description (MD) coder known as multiple description motion compensation (MDMC) is employed. • With this coder, two descriptions are generated by sending even pictures as one description and odd pictures as the other. • When both descriptions are received, the decoder can reconstruct a picture.

14. Performance evaluations • Simulation Environment • Our simulation modeled a wireless mesh network of 10 static Mesh Routers placed in a rectangular field of 400×1500 m2. • Each node has a radio propagation range of 250 meters and channel capacity was 2Mb/s. • Each run executed for 300 seconds of simulation time.

15. Performance evaluations • Results and Analysis • In the simulations, we use the “Packet Success Delivery Percentage” metric to evaluate the performance. • Packet Success Delivery Percentage: It is the ratio between the number of packets received by the destination nodes to the number of packets sent by the source nodes.

16. Performance evaluations • Figure 2 shows the Packet Success Delivery Percentage comparison between two protocols in WMNs, and the sizes of packet was 300, 350, 400, 450, and 500 bytes respectively.

17. Performance evaluations • As shown in Figure 3, for a packet size of 500 bytes, the MM-DSR results, compared with SMR, verify the profound effect that the elimination of inter-path interference can have on the multiple-path routing performance.

18. Performance evaluations • Figure 4 shows the average peak signal-to-noise ratio (PSNR) quality of video signals at the destination node for 150 frames.

19. Performance evaluations • In these experiments, MDMC is used to generate the video packets. • The source node then transmits them to the destination node using MM-DSR and SMR protocols respectively. • Such a significant gain is mainly due to the fact that MM-DSR improves the link connectivity and eliminates interference under wireless conditions.