A Reliability-oriented Transmission Service in Wireless Sensor Networks Yunhuai Liu, Yanmin Zhu and Lionel Ni Computer Science and Engineering Hong Kong University of Science and Technology {yunhuai, zhuym, Speaker: Peixin Wang

Motivation Related Work and challenges Existing routing techniques and their drawbacks In-middle Recovery and Proliferation Routing design Analysis of Proliferation Routing Performance Evaluation Conclusion

Motivation Reliable transmission service is in dire need for many applications in wireless sensor networks (WSNs). However,Most existing routing protocols seriously suffer from low end-to-end success rates in real deployments which may lead to great loss.

Related Work and challenges Two categories: Packet-loss avoidance,Packet-loss recovery Packet-loss avoidance: select more productive forwarding nodes （ no guarantee of the service quality ） or by multi-path transmissions （ no recovery mechanisms ） Packet-loss recovery: recover the packet loss when it happens. Existing recovery can be classified as end-to-end recovery (big latency and large energy cost)and per-hop recovery(no guaranteed service quality).

Related Work and challenges The first challenge is the long transmission paths in large-scale WSNs. The second challenge is the self-congestion phenomena due to the radio interference and collisions. The third challenge is the bad link propagation problem due to the unreliable links.

Existing routing techniques and their drawbacks Flooding-like routing (Impact of network density and environment) Packet-loss avoidance approaches by multi-path in essential share a common idea of restricted flooding in a particular region. They have a similar behavior in the context of the one dimensional network. Drawbacks :the radio interference and packet congestions with the increasing nodes

Existing routing techniques and their drawbacks (Impact of routing metrics) MCFN-like routing: a representative of hop-count based routing algorithms using single path to transmit GPSR-like routing: also employs single data path. But geographic information is used instead of the hop count. Drawbacks: Experimental results (not shown in the paper) show that MCFN-like routing presents poor success rate no matter how many intermediate nodes are deployed.

In-middle Recovery and Proliferation Routing design The basic idea of In-middle Recovery is that packet-loss is detected and recovered in a several-hop manner rather than per-hop or end-to-end.(fill the gap between the traditional per-hop recovery and end-to-end recovery mechanisms) Advantages : 1.Packet-loss due to congestions will not be further degraded by the per-hop recovery. 2.A level of end-to-end transmission service quality can be guaranteed when transmissions are monitored and recovered in a larger scale than per-hop. 3.In-middle recovery is able to offer a great potential of compatibility and flexibility.

In-middle Recovery and Proliferation Routing design The core idea of proliferation routing is randomized dispersity of packet copies combined with a reproduction procedure. Three components: Capability-based path finder to find more productive data paths for seeds; Seed splitter to disperse the seeds over the network so that congestions and radio interferences can be reduced; Seed reproduction to compensate packet-loss during transmissions.

In-middle Recovery and Proliferation Routing design Capability-based path finder The idea is that every node maintains a capability value that reflects the estimated transmission success rate from the node to the sink by a single path. Beacon messages are exchanged between neighboring nodes to calculate the link quality. This process repeats and propagates until every node obtains its capability.

In-middle Recovery and Proliferation Routing design Multiple seeds with seeds splitter The major difference: the trails of seeds are designed to be disjoint The travel of a seed has two phases: the randomized dispersity phase and the deterministic phase. The advantages : 1.congestions and radio interferences can be mitigated 2. high dynamic wireless links are alleviated 3. hot-spot problem can be avoided

In-middle Recovery and Proliferation Routing design Seed reproduction Besides the original data source, intermediate forwarding nodes are also allowed to reproduce seeds.

In-middle Recovery and Proliferation Routing design

Analysis of Proliferation Routing Three key parameters: reproduction coefficient,, random walk steps w, seed lifetime r.

Reproduction coefficient

Random walk steps w

Seed lifetime r

Performance Evaluation Experimental results :set the control parameters =3, w=4 and r=8 as suggested in the last section, no reproduction due to the space limitation

Simulation results

Conclusion This paper proposed a novel in-middle recovery mechanism by designing and implementing proliferation routing scheme. Carefully designed system parameters grant designers more freedom to provide a guaranteed level of end-to-end transmission service quality Analysis and experiment results show that the success rate can be maintained to up 80% with a moderate communication overhead.