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الرحيم* * الرحمن الله بسمA preamble-based approach for

Providing QOS support in Wireless Sensor Network

Presented by: Diala Alwedyan

What does Preamble mean ??

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Preamble

Is a sequence of bits occupy the channel, and specify a specific priority which related to importance of data which wants to send.

It’s used for 1- Medium reservation signal.2- Notify others nodes that there is a competitive node.

2 minutes

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Wireless Sensor Network.TDMA protocol.Low Power Listening protocol.XMAC protocol.BMAC protocol.Back off Preamble based MAC protocol.Quality Of Service.Performance evaluation.

4 minutes

A Preamble-based approach for providing QoS support in wireless sensor network

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The range of applications for WSNs increases so does the demand for flexible and adaptive communication protocols.

Many solution are based on TDMA protocols since they provide good performance in static topology and predefined traffic patterns.

3 minutes

Wireless Sensor Network

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Time Division Multiple Access

•In TDMA, different users are allocated different time slots in the signal. Depending on the picture we can see that the two users are using the whole bandwidth, but at different time intervals.•It allows nodes to share the same frequency channel by dividing time into frames and each frame is divided into slots, each mobile have a transmitter.• every node wants to transmit should switch it's transceiver to transmit mode.

3 minutes

Base station

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TDMA

TDMA scheme divides the time into smaller slots, and sensor nodes communicate within their own slots in a contention-free manner.

 TDMA guarantees fairness among nodes as each node is assigned a unique slot in each frame, and increases the overall throughput in highly loaded networks.

4 minutes

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TDMA Problem

Problem : TDMA come with high complexity, and suffer

from the resource constrained nature of sensor nodes.

3 minutes

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Low Power Listening protocol

Low power listen protocol use preamble transmission to ensure that the destination is listening to the channel.

The purpose of low power listening is to: 1- minimizing energy efficiency. 2- maximizing throughput, In an

asynchronous low power listening scheme.

3 minutes

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SENDER

Low power listening protocol

RECEIVER

Long preamble Send Data

Target Address

Receiver Wakes up

Receive Data

Listen for additional Data

XMAC protocol

SENDER

RECEIVERTime

Time

Short preamble

ack

ack

Receive early ack

Send Data

Receive Data

Listen for additional Data

Time save

Disadvantage of long preamble:increases the overhearingAnd it causes overhead and cost.

5 minutes

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XMAC protocol in WSN

The advantage of X-MAC protocol over LPL is that the destination node can respond immediately instead of listening to the whole preamble.

The source node stops the preamble transmission and starts its data transmission after receiving the early acknowledgment from the destination node.

The X-MAC protocol is designed for asynchronous low power WSNs.

It uses short preambles to achieve a better performance than Low Power Listening (LPL) based protocols.

Why ?

4 minutes

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BMAC protocol

sleep

Wake up

Send long preamble

3 minutes

3 minutes

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BMAC Protocol

sleep

Wake up

Send long preamble

 note: duty cycle period is the time it takes for a signal to complete an on-and-off cycle. 5 minutes

disadvantage

•BMAC based on preamble which has duration longer than the duty cycle in order to assure that the neighbor node is able to detect the transmission.

•The destination node receives the preamble after wake up and remains awake to receive the data packet.

•This approach increase of energy efficiency, since nodes that are not interesting in this transmission can switch off there transceivers.• The nodes using BMAC perform an unsynchronized sleep and wake-up schedule.•BMAC is an efficient protocol, when traffic condition increases, B-MAC loses efficiency because nodes remain awake for a longer time waiting for the entire packet transmission.

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Back off Preamble MAC protocol

The paper follows a new approach which based on the transmission of preambles, the preambles used to specify the priority and solve contention resolution.

The quality of service is supported the back off preamble protocol.

3 minutes

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Back off Preamble-MAC Protocol in WSN

The BPS-MAC protocol divides the time during the medium access into time slots.

The preamble reserves signal, to inform other nodes that there is a competition for the medium access.

Each node switch it’s transceiver to transmit mode, in case it wants to transmit it’s preamble.

 

4 minutes

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Back off Preamble Protocol Cases

Case 1: if three nodes transmit sequence preambles with different length, the node which sends the longest preamble will access to the medium, and competing nodes will switch their transceivers to receive mode.

Case 2: if two nodes sense the channel and it’s an idle, then each node will start transmit it’s preamble, in the same interval and with the same preamble length, then collision occur.

4 minutes

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Back off Preamble

The example shows a scenario in which three nodes compete for the medium access.

After the transmission the preamble, the transceiver switches automatically back to receive mode.

S T 21 3 R T

S

S

1 2

T

T

21 3 R

1 2 R

T

B S

21 3

B BS B

R B

R T Data

S S B B

S B B B

5 minutes

Case1:

S

S

S

S

S

S

Time

A

B

C

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A

B

C

S T 21 3

T 21 3

T 1 2

R

R

R

T

T

T

B S

21 3

21 3

S B B B S B B B

R

R T Data

Data

S

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Case 2:

SS

SS S

SSS

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BPS-MAC protocol

Back off preamble based on MAC protocol is used to solve contention on radio channel, by providing priority to medium access.

 MAC protocol uses back off preamble to satisfy reliability in high node density, and high event driven data traffic.

Back off preamble is useful in WSN, because Back off preamble doesn't need a large memory, and it takes a low computational power.

3 minutes

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Back off Preamble

Node A

Assume node A wants to sends data to D, and node B wants to sends data to node C.

S

S

1 3 4T

T

2

1 2 R B

R

R

R

T Data

S S B B B B S T 1 2 R TData

Data

Data

3 minutes

SS

SSNode B

Node C

Node D

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The large number of slots is 3

Can the packet access the medium?

Sequence counter: number of already transmitted Preambles, and access counter: num of slots during an idle medium.

S: the maximum number of preamble sequences.

Collision free need node ID to mapped with medium access priority.

P: is next preamble is used for medium access prioritization.

7 minutes

Collision free access can be guaranteed if each device assignedUnique preamble sequence.

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A set of mechanisms that ensure a high quality of performance in application.

Providing QOS in an application means that:

1. Reliable delivery of data.2. Reduce data loss.3. fairness.4. Reduce delay.

Quality of Service

3 minutes

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QOS in WSN

The two approaches: IntServ and DefServ, cannot achieve quality of service in the wireless sensor networks.

WHY ??

1. These protocols need high requirements, such as: energy efficiency, limited memory and end-to-end bandwidth these make QOS a challenge task in WSN.

2. Unpredictable nature of the wireless links, unstable topology (due to node failure or link failure).

3 minutes

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Quality of service strategies

1. Topology aware.2. Network aware.3. Traffic aware.4. Buffer aware.5. Combined aware.

2 minutes

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1 .QOS Topology aware in WSN

The wireless sensor network contains backbone nodes(few power full nodes, little energy constrains) and non backbone nodes(limited energy).

Both use the same radio channel, but the backbone node has an important role in the WSN, so QoS mechanism gave for these node the highest priority, to enhance the performance of the WSN.

How quality of service solve

the problem of topology?

3 minutes

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2. QOS Network aware in WSN

• The self organization coordinate system in wireless sensor network made the topology more attractive monitoring tasks since nodes can be randomly placed in areas which are hardly accessible (radioactive contamination). And it is hard to reprogramming or shutdown of nodes in the WSN.

• The paper explain the need of replace the current nodes to new nodes, this way will make low performance because these nodes will use the same channel.

4 minutes

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3. QOS Traffic Aware in WSN

In a large WSN which contains a large number of nodes, the traffic streams have different priorities for a user.

Traffic-aware within MAC protocol can provide different quality of service for the different streams.

C

L

H

F

R A

B

W

M

DS

G

EI

K

N

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4. QOS Buffer aware in WSN

Allow the node, which has a large number of packets, to have a high priority, to assure that no packet will lose when the node has a full buffer. So MAC protocol will guarantee reliable delivery.

Any question

!!

3 minutes

Node R

Node T

Node D

Minimize delay and buffer utilization.

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5. QOS combined strategy in WSN

In this strategy, two of the above strategies can combined with each other, to improve the performance on a target scenario.

For example: combined the traffic-aware and buffer-aware strategy, such a combination represent a trade-off between delay of high priority packets and packet loss of packets due to buffer overflows.

3 minutes

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Performance evaluation

1- Single hop simulation

2- Multi hop simulation

The OPNET Modeler used to simulate the performance of the protocol.

2 minutes

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Single hop simulation of WSN

The paper simulate 2 types of traffic: event driven traffic/burst traffic with high priority(ex. Stress measurements), and periodic traffic with low priority(ex. Temperature measurements).

sink

Sensor nodes

-The ‘BPS-MAC protocol’ use 3 back off preamble sequences.-Each sequence has a maximum length of 4 slots.- ’Traffic’ Static QoS strategy has: 1- fixed preamble length for high priority traffic, equal to 4 slots. 2- fixed preamble length for low priority traffic, equal to 2 slots.- ‘WQL’ (weighted Quadrilateral Localization)  dynamic QoS strategy interested in buffer size as:Time slot=1, if the buffer size less than 25%.Time slot=2, if the buffer size between 25% and 50%.Time slot=3, if the buffer size between 50% and 75%.Time slot=4, if the buffer size greater than 75%.  

source

4 minutes

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Simulation in single hop

Low priority

4 minutesFigure 1 Figure 2

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Multi Hop Simulation Of WSN Imagine Each Node Is A Sensor In Backrest

Sink is  interface between the sensors and the internet.The nodes in a WSN measure various parameters or make detections, and report the information to the Sink.

Each circle shows a Mutli-hop nodes which sends a packet.

2 minutes

sink

source

1st hop2nd hop

3rd hop

Double hop

Triple hop

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Multi Hop Environment(simulated Application Scenario)

- A multi hop network is enable connectivity between all nodes in the plane.- In every 8 meters there are a powerful sensor node used to connect the sensors with sink.

In this example High node density is up to 60 nodes.

4 minutes

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Multi Hop Environment(Simulated Application Scenario)

The airplane contains six seats in each row. In each seat there is sensor in backrest.

This sensor can infer the sink about any information, whether the person is put the seatbelt, or the plate is secure, or if the seat is busy or not. This information is reported periodically to a sink in the front of the plane.

3 minutes

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Multi Hop Environment

A high node density (which introduced to be up to 60 nodes), will have huge impact on WSN performance and will increase the interference, so data traffic in the network will occur. Multi hop environment need to Zigbee functionality.

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Scenario A

Figure 3 Figure 43 minutes

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ZigBee

A high node density (which introduced to be up to 60 nodes), will have huge impact on WSN performance, and will increase the interference, so data traffic in the network will occur. Multi hop environment need to Zigbee functionality.

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Scenario B

4 minutesFigure 5 Figure 6

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Scenario C

4 minutesFigure 7 Figure 8

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Conclusion

The new approach of Back off preamble-MAC protocol enables a node to send short back off preamble with a priority, to resolve contention on radio channel.

The proposed approach minimize delay(’Traffic’ Static QoS strategy) and buffer utilization because the QoS strategies weighted Quadrilateral Localization takes into account the buffer fill state.

2 minutes

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QUESTIONS ??

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Thank you.

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Reference papers

http://www.intechopen.com/download/get/type/pdfs/id/38789 http://www.ejse.org/Archives/Fulltext/2009/Special/2009SP4.pdf https://www.google.jo/?gws_rd=cr&ei=M2OsUqWzFoHeswbSsYCQAw#q=calculate+medium+access+prioritization+ppt

http://protocols.netlab.uky.edu/~calvert/classes/571/lectureslides/WiFi.pdf http://www.intechopen.com/download/get/type/pdfs/id/38789 http://www.slideshare.net/AkshayPaswan/localization-scheme-for-underwater-wsn http://www.ym3a.com/vb/showthread.php?t=76583 http://technet.microsoft.com/en-us/library/cc757120(v=ws.10).aspx http://www.satsig.net/vsat-equipment/tdma-explanation.htm http://www.aoua.com/vb/showthread.php?t=215356 http://wirelesssensornet.blogspot.com/2008_06_01_archive.html http://www.speedguide.net/faq_in_q.php?qid=300 http://www.google.com/patents/US8537906 https://www.youtube.com/watch?v=QJ9exBjLhe8 http://www.networkset.net/2012/07/13/%D8%AA%D9%82%D9%86%D9%8A%D8%A9-%D8%A7%D9%84%D9%80-zigbee/

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Linux.Wireless.mac.html http://www.intechopen.com/books/wireless-sensor-networks-technology-and-applications

/wireless-sensor-networks-to-improve-road-monitoring http://en.wikipedia.org/wiki/Scheduling_(computing)