1. Multichannel Medium Access Control (MMAC) Eng.Ahmed Ali El-Kosairy eng.aelkosairy@gmail.com

2. Multichannel Medium Access Control (MMAC) Need to know MAC : IEEE- 802.11It only utilizes one channel at presentThe primary reason is that hosts with a single half-duplex transceiver can only transmit or listen to one channel at a time. 3. MAC -Con has 2 modes DCF (Distributed Coordination Function)PCF (Point Coordination Function) For centrally coordinated infrastructure-based networks 4. MAC-Con DCF (Distributed Coordination Function) for ad hoc networksbased on CSMA with Collision Avoidance (CSMA/CA) protocol which: combination of the CSMA and MACA schemes. 5. MMAC MMAC is an adaptation to the DCF to use multiple channels.How does it work : Similar to the Dynamic Power-Saving Mechanism (DPSM) scheme 6. Dynamic Power-Saving Mechanism (DPSM) Time is divided into beacon intervals All nodes wake up at the beginning of a beacon interval for a fixed duration of time (ATIM window) Exchange ATIM (Ad-hoc Traffic Indication Message) during ATIM window 7. DPSM-Con Nodes that receive ATIM message stay up during for the whole beacon interval Nodes that do not receive ATIM message may go into doze mode after ATIM window 8. How does it work (MMAC) Divide time into beacon intervals At the beginning of each beacon interval, all nodes must listen to a predefined common channel for a fixed duration of time (ATIM window) Nodes negotiate channels using ATIM messages Nodes switch to selected channels after ATIM window for the rest of the beacon interval Use PCL 9. Preferred Channel List (PCL) Each node maintains PCLRecords usage of channels inside the transmission rangeHigh preference (HIGH) Medium preference (MID) Already selected for the current beacon interval No other vicinity node has selected this channelLow preference (LOW) This channel has been chosen by vicinity nodesCount number of nodes that selected this channel to break ties 10. Channel Negotiation Common ChannelSelected ChannelABeaconBCDTime ATIM Window Beacon IntervalKey Ideas 11. Channel Negotiation In ATIM window, sender transmits ATIM to the receiverSender includes its PCL in the ATIM packetReceiver selects a channel based on senders PCL and its own PCL Order of preference: HIGH > MID > LOW 12. Channel Negotiation-con Tie breaker: Receivers PCL has higher priority Receiver sends ATIM-ACK to sender including the selected channel Sender sends ATIM-RES to notify its neighbors of the selected channel 13. Channel Negotiation Common ChannelABSelected ChannelATIMATIM RES(1) BeaconATIMACK(1)CDTime ATIM Window Beacon IntervalKey Ideas 14. Channel Negotiation Common ChannelABCDSelected ChannelATIMATIM RES(1) BeaconATIMACK(1) ATIMACK(2)ATIMATIMRES(2)TimeATIM Window Beacon IntervalKey Ideas 15. Channel Negotiation Common ChannelABCDATIMATIM RES(1)Selected ChannelRTSDATAChannel 1 BeaconChannel 1 CTSATIMACK(1) ATIMACK(2)ACKCTSACKChannel 2Channel 2 ATIMATIMRES(2)RTSDATATimeATIM Window Beacon IntervalKey Ideas 16. Advantages of MAC The performance of MMAC is better than that of IEEE 802.11 and Dynamic Channel Assignment (DCA) in terms of throughput. It can be easily integrated with IEEE 802.11 Power-Saving Mechanism (PSM) mode while using a simple hardware. 17. Aggregate Throughput (Kbps)Performance Test 25002500MMAC2000DCA1500 1000 500MMAC2000 1500DCA1000802.111 10 100 1000 Packet arrival rate per flow (packets/sec)30 nodes5001802.11 10 100 1000 Packet arrival rate per flow (packets/sec)64 nodesMMAC shows higher throughput than DCA and 802.11 18. Disadvantages of MACIt has a longer packet delay than DCA. More over, it is not suitable for multi hop ad hoc networks as it assumes that the nodes are synchronized. 19. Looking forA better scheme for clock synchronization 20. Dynamic Channel Assignment with Power Control (DCA-PC) 21. DCA-PC DCA-PC is an extension of their DCA protocol that did not consider the issue of power control. It combines concepts of power control and multiple-channel medium access in the context of MANETs. 22. How Does It work The hosts are assigned channels dynamically Every node is equipped with two half-duplex transceivers, and the bandwidth is divided into Control channel ,which: operate to exchange control pktMultiple data channels Exchanging data and acknowledgments (with power control). 23. How Does It work-2 When a host needs a channel to talk to another, it engages in an RTSCTSRES exchangewhere RES is a special reservation packet indicating the appropriate data channel to be used. 24. How Does It work-3 very node keeps a table of power levels to be: These power levels are calculated based on: used when communicating with any other node. the RTSCTS exchanges on the control channelBecause: every node is always listening to the control channel.it can even dynamically update the power values based on the other control exchanges happening around it 25. Advantages of DCA-PC DCA-PC has been shown to achieve higher throughput than DCA. DCA-PC is a novel attempt at solving dynamic channel assignment and power control issues in an integrated fashion.