Tsung-Chin Shih 、 Tsung-Chin Shih 、 Shun-Ren Yang National Tsing Hua University, Hsinchu, Taiwan, R.O.C. IEEE IWCMC 2011 A Cooperative MAC Protocol in Multi-Channel Wireless Ad Hoc Networks

Outline Introduction Goal Background The proposed protocol Simulation Conclusion

Introduction Many multichannel MAC protocols are designed to support parallel data transmissions on different frequency channels Dedicate Control Channel Spilt Phase Common Hopping Parallel Rendezvous

Introduction Single transceiver constraint In a multi-channel multi-hop environment, a hop cannot receive data and simultaneously forward data Cooperative communication

Goal We propose a SSCH-based protocol Incorporates the notion of cooperative communication into multi-channel MAC protocols Allowing a single transceiver to achieve the enhanced network capacity and reduced packet delay

Background SSCH: Introduction SSCH is one of the Parallel Rendezvous protocols Slotted Seeded Channel Hopping (SSCH) A new channel hopping protocol Increases network capacity using multiple channels Overcomes limitations of dedicated control channel

Background SSCH: Slots and Seeds Divide time into slots 3 channels New Channel = (Old Channel + seed) mod (Number of Channels) seed is from 1 to (Number of Channels - 1) Seed = 2 Seed = 1 (1 + 2) mod 3 = 0 (0 + 1) mod 3 = 1 A B

Background SSCH: Syncing Seeds 3 channels Seed Follow A: Change next (channel, seed) to (2, 2) A B B wants to start a flow with A 2

Background SSCH: Partial Synchronization Syncing to multiple nodes A sends packets to B & C Each node has multiple seeds Each seed can be synced to a different node If the number of channels is 3, and a node has 2 seeds: 1 and (1 + 1) mod 3 = 2 (2 + 2) mod 3 = 1 (2 + 1) mod 3 = 0 (1+ 2) mod 3 = 0

Background Illustration of the SSCH Protocol

The proposed protocol All the nodes use IEEE a as they do in the experimental configuration in SSCH There are N available channels, all of equal bandwidth and no channel overlaps any other Each node is equipped with a single half-duplex transceiver

The proposed protocol Relay Selection Channel Assignment

The proposed protocol Relay Selection Channel Reservation Cooperative Ready-To-Send (C-RTS) Relay Contention Cooperative Clear-To-Send (C-CTS) Data Transmission

The proposed protocol Three Scenarios Case 1: A, B, and D are all on the same channel Case 2: A and D are on the same channel, but B is on a different one. Case 3: A and B are on the same channel, but D is on a different one New coordination handshake

The proposed protocol Channel Assignment Node D Seeds

Simulation

Grid Topology Our proposed protocol Naive protocol Line Topology Only A, B, C, D, and E are in the line topology Single-bottleneck Topology This topology is like a grid topology, but H and K disappear C creates a bottleneck of this path in our protocol

Simulation NONCOOP Non-cooperative multi-channel MAC protocol (SSCH) COOP Our proposed cooperative multi-channel MAC protocol Naive COOP Naive cooperative multi-channel MAC protocol

Simulation Grid Topology

Simulation Line Topology

Simulation Single-bottleneck Topology

Conclusion Our proposed protocol achieves a higher network capacity and lower packet delay The overhead of the proposed relay node selection approach is significantly small

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