A Cooperative Multi-Channel MAC A Cooperative Multi-Channel MAC Protocol for Protocol for Wireless NetworksWireless Networks

IEEE Globecom 2010

Devu Manikantan Shila, Tricha Anjali and Yu ChengDept. of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, USA

OutlineOutline

IntroductionGoalsThe Proposed MAC ProtocolSimulation Conclusion

IntroductionIntroduction

How to provide robust communication over fading channels is a crucial challenge in wireless networks ◦cooperative communications achieve spatial

diversity and thereby reduce the negative effects of fading on wireless channels

IntroductionIntroduction

Deploying cooperative relays in large-scale wireless networks lead to :◦An elevated level of interference

Degraded throughput Higher packet losses

Multiple channel ◦mitigate the wireless interference

GoalsGoals

Designing a protocol ◦Integrate the capabilities of both cooperative

communications and multiple channels into wireless networks

The Proposed MAC ProtocolThe Proposed MAC Protocol

CoopMC MAC protocol◦There are C channels in the network ◦Each node (source, destination and relay) is

equipped with two half-duplex interface◦Cooperative link

Direct path Relay path

◦Assume that each source node is aware of the best helper nodes

The Proposed MAC ProtocolThe Proposed MAC Protocol

Data Structures in CoopMC design◦Each node maintains

Neighbor-table (Ntable) Find a best helper node to assist the communication

Good Channel State Information Minimum interfering neighbors

Channel-table (CTable) Counter that indicates the number of neighbors that have planned to

utilize the channel

The Proposed MAC ProtocolThe Proposed MAC Protocol

Based on the existing Multichannel MAC protocol (MMAC)◦Control phase

Pre-defined channel◦Data phase

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦If the channel is busy

Sender should wait until the channel is idle plus a DIFS time period

Sender Destination

Relay

1. Carry sense

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦If the channel is idle for a DIFS time period and has

completed the required backoff process

2. send CTU(CTable)

Sender Destination

Relay

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦A helper node cannot cooperate

Channel is busy due to other transmissions Helper node has already agreed to serve another

transmission

3. send CTU-R(CTable)

Sender Destination

Relay

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦Destination selects two channels based on the

CTables at sender, relay and itself

4. send CTU-ACK(1,2)

Sender Destination

Relay

1

2

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦Destination selects two channels based on the

CTables at sender, relay and itself

4. send CTU-ACK(1,2)

Sender Destination

Relay

1

2

1

1

2

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase

5. send CTU-RES(1)

Sender Destination

Relay

1

2

The Proposed MAC ProtocolThe Proposed MAC Protocol

Channel negotiation during the Control Phase◦If the CTUR-RES packet is not heard, the sender

and destination switch to direct transmission mode in the DATA Phase

5. send CTU-RES(1)

Sender Destination

Relay

1

2

6. send CTUR-RES(1,2)

ExampleExample

Control phase

ExampleExample

Data phase

Sender Destination

Relay

1

21

Channel 2

Simulation Simulation

NS-2 simulator◦A grid of 40 wireless nodes located in

1000x1000(m)◦Bit rate of channel is 2Mbps◦Transmission range of each node is 250m◦Randomly select the source and destination pairs◦Traffic flow adopted UDP/CBR

Simulation Simulation

Assume that sufficient number of relay nodes are present in the network

Packet size is 1000 bytes.The beacon interval is set to 150ms and control

phase duration as 32ms

Simulation Simulation

Aggregate Throughput vs. Packet Arrival Rate

Simulation Simulation

Sensitivity of models to wireless errors

Simulation Simulation

Impact of Channels on Throughput

ConclusionConclusion

The auther proposed a cooperative multi-channel (CoopMC) MAC protocol ◦Allocates each cooperative transmission,

dynamically, onto a different channel. The simulation results ◦Greatly reduce the interference in cooperative

wireless network◦Provide an enhanced performance

Thanks for your attention