MAC Protocol in Wireless Mobile AdHoc Networks

1
MAC Protocol in Wireless Mobile Ad-Hoc Networks

• Tiantong You

2
Contents

• Introduction to CSMA/CA (IEEE 802.11 b)
• CSMA/CP
• Performance evaluation
• Conclusion
• References

3
IEEE 802.11 MAC

• Distributed Coordination Function (DCF)
• DIFS, PIFS, SIFS
• Random SDN
• Virtual Sense Mechanism (hidden terminal, exposed
  terminal)
• Point Coordination Function (PCF)

(a)
g
g
d
d
e
h
A
A
B
C
B
C
f
f
(b)
(c)
4
S CSMA
S-CSMA could solve the hidden terminal problem,
but at the same time, it will make the exposed
terminal problem more serious.
d
c
b
a
5
CSMA/CP (1)

• Two channel (0.20.8)
• Data channel
• Control channel
• Variable transmission range in data channel
• Sending of data packets is not based on CSMA
  again but on the negotiated schedule that was
  made through control channel
• Goal of CSMA/CP is to solve the exposed terminal
  problem and hidden terminal problem.

f
e
g
h
p
b
o
a
c
d
n
j
m
i
k
l
6
CSMA/CP (2)

• Sending control packets in Control channel
• Fixed transmission range in control channel
• BROADEN (binary-countdown/RTS/OTS/agree-to-send
  (ATS) /disagree-to-send (DTS)/ ensure-to-send
  (ETS) / neaten-to-send (NTS)
• Three tables (MT table, Receiving duty table,
  Sending duty table)
• Other control packets include ACK or NACK

ETS
NTS
OTS
RTS
a
b
c
ATS or DTS
7
Binary countdown
Time slot
A
b
b
A
c
d
c
d
Node A (10)1010 Node b (10)0101 Node c
(01)1101 Node d (00)1111 Note q- quit s-
send
The solid and dash circles represent the control
packet transmit range and sensing range (or
binary competition signal transmit range) of node
A .
(A)
(B)
8
Time Format
Competition period
Competition period
Competition period
Time
Binary countdown period
control packet
Time
Binary countdown slots
Sync-beacon slot
Media sensing slot
9
Synchronization

• Other Methods
• GPS
• Access point
• Mobile Point Coordinator (MPC)

a
b
c
SB
a
SB
SB
b
SB
c
10
Simulation

• Mobility model ( S, P)
• Traffic model (MR, PR, BL)
• Next time -1/? log(x)

11
Table (1)
12
Table (2)
13
Performance Evaluation (1)
It can be seen that the collision rate of CSMA/CA
rises sharply with the increase of ?, until the
maximum value (around 35) is reached.
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Performance Evaluation (2)
There are two main reasons for CSMA/CP to achieve
higher throughput (1) CSMA/CP has no collisions
so it can achieve higher throughput (2) CSMA/CP
supports variable-radius transmissions while
CSMA/CA is assumed to transmit with fixed radius
in the simulation.
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Conclusion

• In this paper, we proposed a new MAC protocol,
  BROADEN which is the first protocol reported in
  the literature that can achieve 100
  collision-free media access in both the control
  channel and the data channel in multihop ad hoc
  networks.
• Moreover, it solves the hidden, exposed, and
  moving terminal problems at the same time without
  relying on busy tone or any additional
  transceiver.
• BROADEN can also easily prioritize packets of
  different classes or elapsed time, effectively
  supporting differentiated service in multihop ad
  hoc networks.

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References

• T. You, C.-H. Yeh, and H. Hassanein, A new class
  of collision-prevention MAC protocols for ad hoc
  wireless networks, IEEE Int'l Conf.
  Communications (IEEE ICC'03), May 2003, to
  appear.
• IEEE Standard for Wireless LAN LAN Medium Access
  Control (MAC) and Physical Layer (PHY)
  Specifications, IEEE Standard 802.11, 1997
• T.You, H.S.Hassanein and H.T.Mouftah,
  Infrastructure-Based MAC for Wireless Ad Hoc
  Networks, IEEE LCN Workshop on Wireless Local
  Networks, Nov. 2002.
• T. You, C.-H. Yeh, and H. Hassanein, CSMA/IC A
  New Class of Collision-free MAC Protocols for Ad
  Hoc Wireless Networks, Proc. IEEE Int'l Symp
  Computer Communications (IEEE ISCC'03), June/July
  2003, to appear.

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Thank You