1. Video Streaming Transmission Over Multi-channel Multi-path Wireless Mesh Networks 2012.02.17 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 Authors: Guojun Shui, Shuqun Shen

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

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. 3

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. 4

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. 5

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. 6

7. Multi-channel multi-path routing A.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. 7

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. 8

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. 9

10. Multi-channel multi-path routing B.Route Selection Method In order to measure the performance of each route for the selection process, we define the following metrics: (1)Hop count (2)Delay of route (3)Number of joint nodes between two routes 10

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. 11

12. Multi-channel multi-path routing C.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. 12

13. Performance evaluations A.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. 13

14. Performance evaluations B.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. 14

15. Performance evaluations C.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. 15

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. 16

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. 17

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. 18

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. 19

20. Conclusion Thus, in this paper we have considered using multiple channel approaches to improve the overall performance of the multiple hop communication for networks. Compared with SMR, MM-DSR protocol can indeed reduce the probability of losing both routes simultaneously. MM-DSR can eliminate the interference between multiple routes, which result in considerably improving the throughput. 20