manali pamas review[1]

8/13/2019 Manali PAMAS Review[1]

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INDEX

Objective Ad-hoc networksThe MACA protocolThe PAMAS protocol

Powering off radiosEffect of powering off on delay & throughput

Power conserving behavior of PAMASTheoremsEnhancements to PAMASConclusion

disadvantages


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OBJECTIVE

A new multi-access protocol for ad-hoc radionetworksPAMAS = MACA protocol + signalling channel

Conserves battery power at nodes by intelligentlypowering off nodes that are not activelytransmitting/receiving pkts. Delay & Throughput characteristics of PAMAS


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AD-HOC NETWORKS

Multi-hop wireless networks where all nodes cooperativelymaintain network connectivity.

Transmission from one node to another is potentiallyoverheard by all neighbors of the transmitting node, thusall these nodes consume power even though packettransmission was not directed at them!


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Hidden terminal problem


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MACA Protocol

Whenever a node wishes to transmit a packet to aneighbor, it first transmits a RTS message.The receiver responds with a CTS message.

Upon receiving the CTS message, the sender beginstransmitting the packet.


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The PAMAS protocol

Salient Features:-PAMAS conserves battery power by selectively powering offnodes that are not actively transmitting or receivingpackets.

MACA protocol + separate signalling channelRTS/CTS signalling channelPacket transmission- data channel signalling channel when and for how long nodes can powerthemselves off.


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1

5

3

24

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Powering Off Radios - 1

If a node has no packets to transmit, it should power itselfoff if a neighbor node begins transmitting.

If at least one of the neighboring nodes is transmitting andanother is receiving, the node ought to power off because itcannot transmit or receive a packet. (even if transmit queueis non empty)

Each node makes the decision to power off independently.Neighbor transmitting hear over data channel.Neighbor receiving hear busy tone by receiver.


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Powering Off Radios - 2

For how long is a node powered off ? Probing.

What happens if a neighbor wishes to transmit a pkt

to a node that has powered off itself ?Powered off - RTS unanswered -> BEB. Powered on No response to RTS as neighbor transmitting.

Packet delays do not increase as a result of powering

off nodes. period of time node is powered off it can neither receive/transmitpkts.


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Power conserving behavior of PAMAS- 1

Simulations:Random Network Topology Line topology Fully connected network topology

Densely connected networks -> most power savingsIf 1 node transmits most of its neighbors can power off.

Sparse networks -> least power savings.fewer nodes can power off because more simultaneous

transmissions are possible.


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Assumptions:Network size 10 to 20 nodes Traffic arrived at each node Poisson process Transmit Queue FIFO buffer (size= 2n, n- #nodes)

Packet size 512BRTS/CTS 32B each Busy Tone 64B Bandwidth 12.8 Kbps (to keep simulations small)

Units of energy consumed:-Idle (powered on but not hearing transmissions) - 0 Transmitting - 1Receiving 0.5


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Energy expended per packet :

Energy expended on using power conservation:

Power Savings:


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Power saved in complete/fully connected networks with10 or 20 nodes.

Lambda function ofload (pkts/sec/node)

Observations:-

1. Power consumptionreduced by 50% at highloads & even more atlow loads.

2. Power saved at lowloads higher fornetwork with morenodes.

Best Case performanceof PAMAS


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Power saved in line networks with 10 or 20 nodes.

Observations:-

1. Power saving is20 at light loadsto less than 10at heavy loads.


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Power saved in random networks with 10 nodes.

Observations:-

1. Power saved as afunction of edgeprobability.

2. Power savingincreases as networkconnectivity increases.

3. Sparse NetworkLight loads: 20 - 30High loads: 10

4. Dense Network

Light loads: 60 - 70High loads: 30 - 40


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Power saved in random networks with 20 nodes.


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Theorems - 1

In a Line Topology with uniform traffic the amountfor energy saving due to PAMAS for large n, under

light load conditions is 20%.heavy load conditions, is bounded by 15% without controloverhead and by 12.5% with control overhead.

If the average number of neighbors of a transmittingnode is d then the approximate amount of powersavings (under light load conditions) is given by


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Theorems - 2

The average power savings (under heavy loadconditions) in random graphs with an edgeprobability p is,

where is the average value of the number ofsimultaneous transmitters in a random graph withan edge probability of p.


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Theorems - 3

Power Saving for mobile Ad-Hoc networks: Network topology changes constantly.Under light load conditions , as n - > , the power

savings is bounded by 75%.

Under heavy load conditions , the power savings is bounded by about 30% to 40% for n ranging from 10to 20.


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Enhancements to PAMAS

Receiver transmits ACK when packet received correctly MACAW

Sender does not receive ACK, sends RTS with same pkt no., receiver replies with ACK instead of CTS .

Allow node to transmit multiple packets if it has acquired channel increasedelay, reduce time in channel access.

RTS/CTS/Busy tone - total length of transmission .

Power off data interface when signalling interface is trying to acquire channel.

Support for Broadcast .


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Support for Broadcasting

RTS/CTS meaningless Tx hears noise.Tx sends RTS_B

Only if no neighbor is transmitting/scheduled to transmit.

Node receiving another transmission- busy tone.

Others do not respond.Broadcast message no response in 1 RTT + processing delay.

Problem: Broadcast may collide with another transmission at some receiver.

- NACK_B- Power saving by using unique id. For RTS_B.


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Conclusion

PAMAS has good power conserving behavior.10% - sparsely connected network.

70% - fully connected network.

Power saving does not affect the delay or throughput of basic protocol.

Similar power awareness can be used in other multi access protocols. (eg:FAMA, MACA, MACAW, MACA/PR)

Power-aware routing protocols needed PAMAS has no idea about the entire pkt transmission path.

high power-consuming route, the savings by PAMAS might be sacrificed.


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manali pamas review[1]

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