An Adaptive Multichannel MAC protocol for Wireless Ad Hoc Networks

1
An Adaptive Multi-channel MAC protocol for
Wireless Ad Hoc Networks

• Advisor Wen-Tsuen Chen
• Student Ting-Kai Huang

2
Outline

• Introduction
• Related works
• Proposed method
• Simulation results
• Conclusion

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Introduction

• Motivations
• the bandwidth requirement of applications
  nowadays is much more than before.
• gttrying to improve the channel utilization
• The potential bandwidth of one channel in
  standard is limited and low
• 802.11b 1, 2, 5.5, and11(Mbit/s)
• 802.11a 6, 9, 12, 18, 24, 36, 48, and 54(Mbit/s)
• 802.11g 1, 2, 5.5, 6, 9, 11, 12, 18, 22, 24, 33,
  36, 48, and54(Mbit/s)
• F. Cali, Dynamic tuning of the IEEE 802.11
  protocol to achieve a theoretical throughput
  limit, IEEE Trans. Networking, Vol. 8, pp.
  785-799, Dec. 2000.

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Introduction

• The 802.11 standard provides multiple channels
  for use, but we use just only one channel at a
  time now.
• 802.11b 14 available channels, 3 non-overlap
  channels
• 802.11a 12 available channels( 8 channels for
  outdoor use , and 4 channel for indoor use)

Channel 1
Channel 2
B
A
C
D
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Introduction

• Design a MAC protocol to exploit multiple
  channels in wireless ad hoc networks.
• It is an effective way to increase the networks
  capacity.
• Multi-channel MAC protocols can be divided into
  two parts
• Channel assignment
• Medium access control

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Introduction

• Channel assignment
• Static
• The number of channels is limited
• gthow to assign channel to each host with less
  interference between neighbors?
• Mobility
• Inefficient channel utilization
• There are free channels but no hosts can use
  them.
• Channel deadlock problem
• dynamic

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Introduction
Inefficient channel utilization
A
1
4
E
3
2
B
1
D
C
8
Introduction
Channel deadlock problem
RTS2
A Ch 1
B Ch 2
RTS3
RTS1
C Ch 3
D Ch 4
RTS4
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Introduction

• Static
• Dynamic
• Hosts listen on the same channel when they dont
  have packets to send.
• A Host negotiates with its receiver to reserved a
  channel for data transmission and releases the
  channel when it finishes the transmission.

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Introduction

• Medium Access Control
• The Carrier Sense Multiple Access/Collision
  Avoidance (CSMA/CA) is not suitable for
  multi-channel wireless networks.
• New Multi-channel hidden terminal problem
• J. So Multi-channel MAC for ad hoc
  networks Handling multi-channel hidden terminal
  using a single transceiver, ACM Int. Symp.
  Mobile Ad Hoc Networking and Computing, pp.
  222-233, 2004.

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New multi-channel hidden terminal problem
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Related Works

• In order to overcome the new multi-channel hidden
  terminal problem,
• gtEach host is equipped with multiple
  transceivers( as much as the number of channels.)
• Nasipuri, A. Zhuang, and J. Das,
  S.R.A multichannel CSMA MAC protocol for
  multihop wireless networks, IEEE Conf. WCNC,
  vol.3, pp. 1402-1406, Sept. 1999.

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Related Works

• Take hardware costs and energy consumption into
  consideration
• gt divide the channels into two classes
• Control channel
• Data channels
• gtEach host is equipped with two transceivers,
  one for control channel and the other for data
  channels.
• S.-L. Wu, A new nulti-channel MAC protocol
  with on-demand channel assignment for multi-hop
  mobile ad hoc networks, Proc. Int. Sym. Parallel
  Architectures, Algorithms and Networks, pp.
  232-237, Dec. 2000.

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Related Works

• Each host is equipped with just one transceiver
• not only divide the channels into two classes but
  also spilt the time into fixed interval
• Channel Scheduling
• P. Bahl, R. Chandra, and J. Dunagan, "SSCH
  Slotted seeded channel hopping for capacity
  improvement in IEEE 802.11 ad hoc wireless
  networks," ACM Int. Conf. Mobile Computing and
  Networking, pp 216- 230, 2004.

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Related Works

• 802.11 power saving mode like
• Fixed interval size limits the channel
  utilization
• J. So, Multi-channel MAC for ad hoc networks
  Handling multi-channel hidden terminal using a
  single transceiver, ACM Int. Symp. Mobile Ad Hoc
  Networking and Computing, pp. 222-233, 2004.

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Proposed Method

• Hosts negotiate with each other to choose the
  channel for data transmission.
• Divide channels into the control channel and data
  channels
• Divide each time frame into negotiation interval
  and data transmission interval

beacon
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Proposed Method

• Channel Negotiation and data transmission
• Channel selection
• Channel status information
• Channel selection rules
• Dynamic Interval Adjustment
• If any host needs to negotiate with someone, it
  sends a request to borrow some negotiation time
  from its neighbors. When the host finishes its
  work, it gives the time back to its neighbors.

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Channel Negotiation and Data Exchange
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Channel status information

• This channel selection algorithm attempts to
  balance the channel load as much as possible, so
  that the bandwidth wastage caused by contention
  and backoff is reduced.
• Each host maintains one in-use channel and two
  channel list , Free channel list , and Busy
  channel list, to keep track of necessary
  information for channel selection.
• In-use channel the channel that the host will
  use for data transmission in this time frame
• Free channel list the channels that no other
  neighboring hosts are using.
• Busy channel list the channels that are selected
  by hosts neighbors.
• counter

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Channel selection
A
B
MRTS
MCTS
RRTS
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Dynamic Interval Adjustment

• Trying to optimize the size of negotiation
  interval that every host could negotiate once in
  a time frame.
• In order to prevent extreme condition that may
  cause the adjustment mechanism working poorly,
  there are preset minimum and maximum values for
  the negotiation interval size.
• If any host needs to negotiate with someone, it
  sends a request to borrow some negotiation time
  from its neighbors. When the host finishes its
  work, it gives the time back to its neighbors.

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Dynamic Interval Adjustment

• The increment or decrement of the negotiation
  interval is a multiple of level of fixed size.

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Dynamic Interval Adjustment

• Prerequisite a host tries to negotiation for the
  first time.
• Increase request is added in control messages.
• Increase rules
• A host cannot announce a negotiation request in
  the last time frame
• A host successfully makes the negotiation but
  senses that the continuous idle time of the
  negotiation interval in the current interval is
  not longer that a particular length.

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Dynamic Interval Adjustment

• Increase rule

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Dynamic Interval Adjustment

• Decrease rule
• A host finishes its data transmission and does
  not have any packet in the next time frame.
• New type message, SHRINK .

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Dynamic Interval Adjustment

• Decrease rule

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Dynamic Interval Adjustment

• Further improvements
• Making negotiation with multiple destinations in
  a time frame
• Extending the data transmission time to next time
  frame
• 
  
• Each hosts negotiates with one destination once
  in a time frame.

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Simulations

• Metric
• Aggregate throughput over all flows in the
  network
• total throughput of network
• Average packets delivery delay over all flows in
  the networks
• queuing, backoff, channel negotiation and
  transmission delay

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Simulations

• Simulation model
• All hosts are within each others transmission
  range.
• In each case, half of the hosts are source hosts
  and the rest are destination, for the simulated
  flows
• Each flow transmits Constant Bit Rate (CBR)
  traffic
• The parameters we vary are
• number of hosts in the networks,
• the networks load, and
• the negotiation interval size.

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Simulations
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Simulations

• Optimal negotiation interval size evaluation
• Network traffic load is a fraction of aggregate
  bit rate of available channels
• Example.
• 10 traffic load is 1130.13.3 (Mbps),
• and the number of hosts is 8,
• gt CBR of one sender is 3.3/40.825(Mbps).

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Simulations

• The size of negotiation interval is correlated
  with number of hosts and network traffic load

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Simulations

• D-MMAC
• Increasing rules
• Based on the number of pending packets that the
  host could not negotiate with their destination
  successfully
• Overhearing the packets on the air
• Receiving the negotiation packet in data
  transmission
• Receiving the marked packets
• Decreasing rule
• If a host announces all the packets to the
  destinations, it sets it negotiation interval
  size to be minimum.
• E.-S. An energy efficient MAC protocol for
  wireless LANs, Proc. IEEE INFOCOM, Vol.3, pp.
  1756-1764, June 2002.

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Simulations
Aggregate throughput in TA-MMAC, D-MMAC, and MMAC
(a)CBR is 400 Kbits/sec
(b)CBR is 600 Kbits/sec
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Simulations
Aggregate throughput in TA-MMAC, D-MMAC, and MMAC
(c)CBR is 800 Kbits/sec
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Simulations
Average latency in TA-MMAC, D-MMAC, and MMAC
(b)CBR is 600 Kbits/sec
(a)CBR is 400 Kbits/sec
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Simulations
Average latency in TA-MMAC, D-MMAC, and MMAC
(c)CBR is 800 Kbits/sec
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Conclusions

• A new MAC protocol that can exploit multiple
  channels effectively by only using one
  transceiver per host.
• Our protocol can adjust to different traffic load
  in order to maximize the channel utilization.

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Future works

• Synchronization
• Broadcast messages

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thank you !