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LA-MAC: A Load Adaptive MAC Protocol for MANETs. IEEE Global Telecommunications Conference(GLOBECOM )2009. Presented by Qiang YE Smart Grid Subgroup Meeting. Outline. Introduction LA-MAC Overview CSMA Mode TDMA Mode Hybrid Mode LA-MAC Implementation Performance Evaluation Conclusion. - PowerPoint PPT Presentation
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
IEEE Global Telecommunications Conference(GLOBECOM )2009.
Presented by Qiang YE Smart Grid Subgroup Meeting
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Outline
IntroductionLA-MAC OverviewCSMA ModeTDMA ModeHybrid ModeLA-MAC
ImplementationPerformance EvaluationConclusion
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Introduction
CSMA and TDMA are two mainstream MAC protocols currently used in
Mobile Ad hoc Networks.CSMA: a contention-based MAC protocol
firstly appeared in IEEE 802.11 Wireless LAN DCF functionality to
coordinate the channel access among usersAdvantages: Indepentdent
of network topology and sychrony informationGood performance under
low contentionDisadvantages:Degraded performance under high
contention
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
TDMA A slot-based MAC protocolAdvantages:Collision freeGood performance under high contention levelDisadvantages:Global synchrony informationInefficiency under low contention level
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
According to the pros and cons of both algorithms, A hybird MAC
is motivated to perform better tradeoff between these two. See
Fig.1
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
The key contributions of this paper:
Strengthen the advantages of both CSMA and TDMA
Make a good cross-layer implementation on the real MANET
testbed.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Outline
IntroductionLA-MAC OverviewCSMA ModeTDMA ModeHybrid ModeLA-MAC
ImplementationPerformance EvaluationConclusion
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC Overview
CSMA Mode: LA-MAC simply employs a random backoff mechanism similar
to IEEE 802.11 MAC protocol. Before transmitting, it waits for a
random back-off, then senses the channel, if idle, it tranmits
immediately, otherwise wait and back-off again. when the receiver
receives the data, it sends ACK to indicate whether it receives
successfully or not
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
TDMA Mode each node collects its one-hop neighbor information utilizing a periodic Ping-like broadcast mechanism.
Then each node exchanges its one-hop neighbor list with its one-hop neighbors to get the two hop neighborhood information.
Then, Dynamic Time Slot Assignment (DTSA) can be executed.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Hybrid Modea node can be in two states: Low Contention (LC) and High Contention (HC)In LC, all nodes can transmit in CSMA mode.A node can stay in HC state for a predefined period THC HC LC if it does not receive notification among this period. LC HC if the node misses Nth ACKs In HC, the two hop neighbors of the slot owner is not allowed to transmit. Only the owner and its one hop neighbor can compete for the slot access.(more like TDMA)
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Outline
IntroductionLA-MAC OverviewCSMA ModeTDMA ModeHybrid ModeLA-MAC
ImplementationPerformance EvaluationConclusion
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC Implementation
It presents the implementation of LA-MAC on Universal Software
Radio Peripheral (USRP) software defined nodes.See figure 2. MANET
nodes built on USRP and GNU Radio, GNU Radio runs on the host and
USRP is connected to the host via a USB connection. While USRP
functions as the RF frontend and the baseband processing unit, the
PHY and DATA LINK layers are implemented in GNU Radio.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Fig.2 The system architecture of a MANET testbed node.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Carrier sensingGNU Radio offers a basic Python-based implementation of CSMA to which we refer as GR-CSMA. It has some problems of carrier sensing .Inband signaling provides a potential solution to this problem (but the USB delay still unavoidable). See Fig. 3
LA-MAC can also offload the carrier sensing function to the FPGA
chipset on the USRP node to solve this problem. (a random back-off
is introduced to avoid collisions among simultaneous
transmissions)
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Collision Avoidance Collisions are mainly due to hidden terminal problem. RTS/CTS is not used on the host due to the timing issue, so the hybrid mode mentioned before can deal with this problem.
Clock synchronization LA-MAC requires a node to maintain clock synchronization with other nodes in its contention area. The timestamp field in the meta-data is used for synchronization.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Outline
IntroductionLA-MAC OverviewCSMA ModeTDMA ModeHybrid ModeLA-MAC
ImplementationPerformance EvaluationConclusion
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Performance Evaluation
The paper presents the experimental studies to compare the
performance of LA-MAC protocol against GR-CSMA and TDMA.Two
scenarios are considered in the paper:One hop scenario: 16 nodes
are distributed within a one-hop distance of one another.Two hop
scenario (With hidden terminals) see fig.4
Fig.4 Topology of Two hop scenario
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
In the simulation, both the transmission latency(RTT time) and
the maximum achievable data throughput(MADT) are analyzed between
above three MACs:Transmission latency:LA-MAC is forced to be in
CSMA mode(LA-CSMA). The RTT time in LA-CSMA is lower than GR-CSMA
due to the following reasons:FPGA carrier sensingRandom back-off
mechanismMADT:In the one-hop scenario, Fig.5. shows the throughput
versus the contention level of the network. LA-CSMA(independent of
contention level) out performs GR-CSMA due to the above to reasons
to avoid collisions
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
In the two- hop scenario, see Fig.6, LA-MAC achieves a
reasonable trade-off between TDMA and CSMA
Fig.5 The throughput comparison of the one-hop experiment.
Fig.6 The throughput comparison in the two-hop experiment.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Outline
IntroductionLA-MAC OverviewCSMA ModeTDMA ModeHybrid ModeLA-MAC
ImplementationPerformance EvaluationConclusion
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
Conclusion
In this paper, we present Load-Adaptive MAC (LA-MAC) protocol for
MANETs capable of switching modes of operation. While LA-MAC
operates in CSMA mode for light traffic loads, it switches to TDMA
mode of operation for heavy traffic loads and increased contention
conditions. We implement and host LA-MAC in a MANET testbed formed
by a collection of USRP nodes. Our implementation approach uses GNU
Radio and inband signaling technology.Our experimental results show
that LA-MAC achieves a better performance measured in terms of
throughput than CSMA and TDMA over either one-hop or two-hop MANET
topologies.
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
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LA-MAC: A Load Adaptive MAC Protocol for MANETs
LA-MAC: A Load Adaptive MAC Protocol for MANETs
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