MARCH : A Medium Access Control Protocol
For Multihop Wireless Ad Hoc Networks
2007. 5. 23성 백 동
< 출처 - IEEE 2000 > <Sensor Network Seminar 2007 >
Agenda
Abstract Introduction Related work
Sender-Initiated MAC Protocols Receiver-Initiated MAC Protocols
The MARCH Procotol The Overhearing Mechanism MARCH Illustration
Perframance Evaluation End-to-End Throughput End-to-End Delay
Conclusion
2
Abstract
MARCH utilizes the broadcast characteristics of an omnidirectional
antenna to reduce the number of control message RTS-CTS handshake is used only by the first hop of a route
collision is reduced and channel throughput is increased
3
Introduction
A multihop wireless ad hoc network consists of mobile hosts(MHs) equipped with radio devices to cooperatively form a communication network MHs
may not be within transmission range of each other Can build a connection through other MHs
Need to MAC protocol Use a common radio channel to communicate with one another CSMA
Simple hidden terminal problem
Degrades performance
4
Introduction
Other protocols Developed various MAC protocol with an additional control handshake
before data transmission sender-initiated protocols receiver-initiated protocols
less control overhead is required Outperform sender-initiated protocol but vulnerable
MARCH(Multiple Access with ReduCed Handshake) combines the advantages of both sender- and receiver-initiated
protocols reduces the number of handshakes Outperform sernder-initiated protocol
5
Related work
Sender-Initiated MAC Protocols MACA(Multiple Access Collision Avoidance)
Use a request-response dialogue to solve the HTM problem Request-to-send(RTS) and Clear-to-send(CTS)
MACAW Improvement of MACA Use more handshakes to handle problems associated with control
packet collision FAMA(Floor Acquisition Multiple Access)
Improve MACA Adds carrier sensing capability in order to reduce the possibility of
collision Performance is quite limited when the traffic load is high
high probability of control packet collision A lot of reTX and lowering the channel throughput
6
Related work
Receiver-Initiated MAC Protocols reduce the number of control packets MACA-BI(MACA By Invitation)
Based on the prediction predict the packet arrival time at its neighboring MHs
send ready-to-receive (RTR) packets RIMA(Receiver Initiated Multiple Access)
Improved MACA-BI Employs a new packet arrival prediction method
Assumes that all MHs have the same packet arrival rate. When an MH receives a data packet, it assumes that its neighboring MH
also receives a data packet. It then sends an RTR packet to invite the neighboring MH to transmit.
Reduce control overhead if the data packet arrival at a sender can be correctly predicted by its
receiver
7
The MARCH Protocol
reduced the amount of control overhead. Operates without resorting to any traffic prediction
Exploits the broadcast characteristic of omnidirectional antennas to reduce the number of required handshakes
Approach An MH has knowledge of data packet arrival at its neighboring
MHs from the over heard CTS packet. It can then initiate an invitation for the data to be relayed
8
The MARCH Protocol
The Overhearing Mechanism The overheard CTS1 packet can be used to convey the information
of a data packet arrival at MHB to MHC Figure shows the new handshake process through the route RTS-CTS handshake reduced to a single CTS(CTS-only)
handshake after the first hop Reduction in the control overhead is a function of the route length Ad hoc route of L hops
The number of handshakes needed to send a data packet from the source to destination
2L in MACA , L in MACA-BI, and (L+1) in MARCH If L is large, MARCH will have very similar number of handshakes as in
MACA_BI
9
The MARCH Protocol
10
The RTS-CTS handshake in MACAThe proposed handshake mechanism in MARCH protocol
The MARCH Protocol
MARCH Illustration Include information in an CTS/RTS packet
The MAC address of the sender and the receiver The route identification number(RTID)
Assume each MH keeps sensing the channel and will not transmit until the
channel is free
11
The MARCH Protocol
Two routes - can be established through an appropriate routing protocol Route 1 consists of MHA , MHB , MHC, MHD
Route 2 includes MHY , MHC, and MHZ
MHZ will overhear the CTS2 packet To avoid MHZ misinterpreting it and initiating an unnecessary CTS-
only handshake
The MAC Layer has access to tables that maintain information on the routes the node participates Consult to understand if it should respond to a control msg to
certain route
MARCH does not participate in routing, nor makes any decisions about the data packets exchanged in the network layer
12
Two overlapping routes in an ad hoc mobile network
The MARCH Protocol
13
X
A
B C
Z
D
Y
RTS1
CTS1
CTS1
CTS2
CTS2
Overhear CTS2To avoid MHZ misinterpreting, the RTID method
Include Timer TW
Route 1
Route 2
Performance Evaluation
Test environment Simulations using the OPNET tool Compared the performance( throughput , overhead and delay)
of MARCH with MACA Neighboring MHs are separated by 10 m Each MH is within the tx range of its upstream and downstream
MH2 The channel is considered to be error free and its capacity is
1Mbps Data size = 2048 bits Control packet size = 128 bits Generate data packets according to a Poissaon process with an
arrival rate varying from 10 pkt/sec to 350 pkt/sec The TX-RX/RX-TX turn-around time of a radio transceiver is 25
usec and the length of a time slot is 1 usec
14
Network topology
Performance Evaluation
15
1
Route 1
Route 2
2 3
8
9
45
7
6
10m
Performance Evaluation
End-to-End Throughput Under high traffic load, MARCH achieves about 66% improvement
when compared to MACA The reduced handshake mechanism
MH2 must content with MH1 and MH3 for the channel It is difficult for MH2 to forward data packet to MH3
RTS packets transmitted by MH2 may collide at MH3, with other packets coming from MH7 , MH4, or MH8
In MARCH Transmissions between MH2 and MH3
The CTS packets from MH3 may only collide with RTS packets from MH1
16
End-to-End Throughput Performance
Performance Evaluation
The control overhead associated with each protocol in MACA
when the traffic load is greater than 50 pkt/sec, control packet collisions result in a lot of reTX
an increase in control overhead in MARCH
has a lower probability of control packet collision Its control overhead is much less than MACA at all traffic loads
17Route Control Overhead
Performance Evaluation
End-to-end Delay Under light traffic load, the delay in MARCH is higher than MACA
The reduced handshake mechanism introduces an extra delay close to the packet inter-arrival time at each intermediate MH
As the traffic load increases beyond 50 pkt/sec the delay in MACA grows significantly when compared to MARCH
since control packet collisions cause a lot of queuing delay at MH2 and MH7
Packet queueing due to collisions does not happen in MARCH until the traffic load is above 100 pkt/sec
18End-to-End Delay
Conclusion
MARCH improves throughput, delay, and control overhead performance by
reducing the number of handshakes Exploits the fact that control messages are overheard by
neighbors More deterministic and does not resort to network prediction
The concepts can be applied to other multi-channel MAC protocols to further improve their communication performance
19
Top Related