Reducing Delay Time Using Rts Computer Science

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Ad hoc network or without infrastructure- Ad hoc network is temporary based network which does not rely on the infrastructure that is it is a decentralized kind of network. There are two problems associated with the Ad hoc network- one is Hidden node problem and other one Exposed node problem. And there are number of techniques to remove hidden node problem like RTS/CTS handshake, MACA, MACAW, MACA-BI etc. But in this paper I am going to elaborate on how to avoid delay time occur when during (RTS/CTS handshake) i.e. when CTS receiving node goes to waiting state. To reduce delay time I am integrating both the mechanism- RTS/CTS and RTR and to improve performance of the network. With RTS/CTS and RTR integration, if communication between the sender and receiver occur before expiration of CTS timer provided to other nodes within in its range, need not to wait for expiration of CTS timer they can communicate as soon as sender and receiver communication completed. And also analysis the throughput comparison of RTS/CTS and integration of RTS/CTS and RTR.

Today the technologies used in various fields are at peak. And wireless network is playing important role in our day today life. According to use wireless network is subdivided into two types-

1.1 Wireless network -

1.1.1 Infrastructure based- In which network rely on the pre-existing infrastructure like access points.

LAN- In this group of devices are connected together within a building.

MAN- This is a larger network as compared to the LAN , it will be for whole town or city

WAN- it consists of several LANS, it is confined to country and continent

1.1.2 Ad-hoc network or without fixed infrastructure- Ad-hoc network is temporary based network which does not rely on the infrastructure that is it is decentralized kind of network.

Fig 1.1- Ad hoc network

Single hop peer to peer- Every terminal has capability of communicating with every other user terminal. That all the devices are connected to each other.

Fig 1.2 - Single hop peer to peer

Multi-ad-hoc network-In this each terminal is aware of the neighboring terminal in its range. In this if any node wants to send data, it first passes to its neighbor node then it goes to other so data passes from one hop to another.

Fig 1.3 - Multi-ad-hoc network1.1.3 Characteristics of Ad-hoc network

Scalability-In single peer to peer network, expansion is always limited to the coverage. There is no simple way to scale up the network coverage. But in multi ad-hoc network number of terminal increase the coverage.

Flexibility-operation of infrastructure network requires deployment of network infrastructure that is very time consuming and expensive. On the other side ad-hoc network can be set up instantly and hence it is more expensive.

1Controllability-In infrastructures are implemented by using aces points and base points but in ad-hoc network implementation of these features requires more complicated structure demanding the change in the terminal.

Routing complexity-In infrastructure and peer to peer network there is no routing complexity but in multi ad-hoc network there is need of routing algorithm that directs data from one terminal to another.

Coverage- In peer to peer network maximum coverage is the distance between the terminals but in infrastructure devices communicate through access points and base stations

Reliability-In infrastructure communication depend upon the aces point or base station, if any point get failed ,network results in failure. But this problem does not exist in peer to peer ad-hoc network.

Store and forward delay- in peer to peer, information is transmitted once there is no storage and delay. But in case of infrastructure, transmission of data is twice, once from source to AP/BS and then from AP/BS to destination. In multi ad-hoc there are several sores and forwarding of data.

1.1.4 Problems associated with ad-hoc networks-

Hidden node problem- Hidden node: A sends to B; C sends to B -> Collision at B

Fig 1.4 -Hidden node problem2

Exposed node problem-Node A sends RTS to B, and node D sends RTS to the C. as a result c sends CTS to D. And b hears that CTS and B don't send CTS to A.

Fig 1.5 - Exposed node problem

As we know in general scenario, to communicate between the nodes, we use RTS/CTS mechanism -

RTS- It stands for Request to send, any node that want to send data or want to communicate with the other node, send RTS to that node.

CTS- It stands for clear to send, when a node received that RTS from other node. It corresponds to that node by sending CTS i.e. clear to send data.

RTR- It stands for ready to receive. This message is broadcasted when node get free from the communication i.e. it is free to communicate with the other nodes.

Ack- It stands for acknowledgement, it is sent when data get received by the receiving node to provide confirmation to the sending node.

1.1.5 Routing - Routing is the act of moving information from a source to a destination in an internetwork. During this process, at least one intermediate node within the internetwork is encountered.

Fig 1.6- Different routing protocols

1.1.5.1 Pro-active protocols or table driven - This type of protocols maintains fresh lists of destinations and their routes by periodically distributing routing tables throughout the network. The main disadvantages of such algorithms are:

Respective amount of data for maintenance.

Slow reaction on restructuring and failures

1.1.5.2 Reactive or on demand routing- This type of protocols finds a route on demand by flooding the network with Route Request packets. The main disadvantages of such algorithms are:

High latency time in route finding.

Excessive flooding can lead to network clogging.

1.1.5.3 Flow oriented routing- This type of protocols finds a route on demand by following present flows. One option is to unicast consecutively when forwarding data while promoting a new link. The main disadvantages of such algorithms are:

Takes long time when exploring new routes without a prior knowledge.

May refer to entitative existing traffic to compensate for missing knowledge on routes.

1.1.5.4 Hybrid routing (Reactive and pro-active)- This type of protocols combines the advantages of proactive and of reactive routing. The routing is initially established with some proactively prospected routes and then serves the demand from additionally activated nodes through reactive flooding. The choice for one or the other method requires predetermination for typical cases. The main disadvantages of such algorithms are:

Advantage depends on number of Mathavan nodes activated.

Reaction to traffic demand depends on gradient of traffic volume.

1.1.5.5 Dynamic routing protocols are classified depending on what the routers tell each other and how they use the information to form their routing tables-

1.1.5.6 Distance Vector Protocols- By using the distance vector protocols, each router over the internetwork send the neighboring routers, the information about destination that it knows how to reach. Moreover to say the routers sends two pieces of information first, the router tells how far it thinks the destination is and secondly, it tells in what direction (vector) to use to get to the destination. When the router receives the information from the others, it could then develop a table of destination addresses, distances and associated neighboring routers, and from this table then select the shortest route to the destination. Using a distance vector protocol, the router simply forwards the packet to the neighboring host (or destination) with the available shortest path in the routing table and assumes that the receiving router will know how to forward the packet beyond that point. The best example for this is the routing information protocol (RIP).

1.1.5.7 Link state protocol- In link state protocols, a router doesn't provide the information about the destination instead it provides the information about the topology of the network. This usually consist of the network segments and links that are attached to that particular router along with the state of the link i.e., whether the link is in active state or the inactive state. This information is flooded throughout the network and then every router in the network then builds its own picture of the current state of all the links in the network

As my thesis work is on the Hidden node problem, so there are number of mechanism were used to remove this problem-

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1.1.6 Techniques-

RTS/CTS MECHANISM-As we know in general scenario when two nodes send data to the same node at same .then collision occurs at that node as shown above in figure. This is known as hidden node problem so to remove this RTS/CTS mechanism is used in which any node that wants to send data or want to communicate with the other node, send RTS to that node and when a node received that RTS from other node. It corresponds to that node by sending CTS i.e. clear to send data. This CTS is broadcasted to all the nodes, the node that receive that CTS goes to waiting for approx time that is stated in CTS timer. Hence no other node communicates in that period of the time. Hence hidden node problem get removed.

Fig 1.7 RTS/CTS mechanismCARRIER SENSE MULTIPLE ACCESS (CSMA)

In Carrier Sense Multiple Access:

1. If the channel is idle then transmit.

2. If the channel for communication is free then it is going to transmit without any precaution that there might be collision.

3. If the channel is busy, wait for a random time.

4. Waiting time is calculated using Truncated Binary

5. Exponential Backoff (BEB) algorithm.

MACA-Multiple access collision avoidance, in this we include RTS/CTS/DATA. In these RTS/CTS mechanism is used in which any node that wants to send data or want to communicate with the other node, send RTS to that node and when a node received that RTS from other node. It corresponds to that node by sending CTS i.e. clear to send data. Both RTS and CTS contain approx timer for which data can be sent or for time for which other nodes should wait.

MACAW- As collision still occurs in MACA so MACAW was introduced in which we include RTS/CTS/DATA/ACK. New factor included is ACK which stands for acknowledgement. It is sent when data get received by the receiving node to provide confirmation to the sending nodes

MACA-BI- In this, there is no RTS is sending .It is receiver initiated MAC protocol. This reduces the number of control packets.

Comparison between MACA and MACA-BI- For the burst traffic, MACA-BI will be performance will be no better than MACA.

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Fig 1.8- Comparison between MACA and MACA-BI

PAMAS- It stands for Power aware multi-access protocol with signaling. In this nodes get themselves shut down, if they are overhearing the transmission that are directed towards them

If node has no packet to send .It will shut down itself, if it's neighboring node is transmitting.

And if node has packet to send but its neighboring node is transmitting then it will also shut down itself.

DBTMA- This mechanism is also used to solve hidden node problem, in this busy tone is broadcasted to other nodes both by sending and receiving nodes.

Fig 1.9- DBTMAThe other methods that can be employed to remove hidden node problem are:

1) Increase transmitting power

2) Use Omni-directional antennas.

3) Remove obstacles.

4) Move the node.

5) Use protocol enhancement software.

6) Use antenna diversity.

7) Wireless Central Coordinated Protocol

5With the entire mechanism Hidden node problem can be removed. But my main objective is to avoid the collision due to Hidden node problem in ad-hoc network and secure the data with the use of RTR along with RTS/CTS.And we are avoiding the Delay time during data communication when node are on waiting State.

Motivation- There are two problem associated with wireless adhoc network.

Hidden node problem- Hidden node: A sends to B; C sends to B -> Collision at B. In this when node A sends data to the node B unaware of the node C that C is also sending data to the node B. And as a result collision takes place at the node B .This problem is termed as Hidden node problem.

Fig 1.10 - Collision due to hidden node problem

Exposed node problem-Node A sends RTS to B, and node D sends RTS to the C. as a result c sends CTS to D. And b hears that CTS and B does not send CTS to A.

Fig 1.11 - Exposed node problem

To avoid these two problems number of mechanism are used which I have described above.And one of mechanism is RTS/CTS handshaking .These problem Associated with the adhoc network are the motivation of my thesis.

Contribution- Main contribution of work will be to make data secure from collision with the help of RTS/CTS handshake and RTR i.e to prevent hidden node problem and other one will be to reduce delay time that occurs when nodes goes to waiting state during RTS/CTS handshake if the communication occurs before the timer.

Organisation- The rest of this thesis is organized as follows.

Chapter 2 contains a brief introduction of Problem associated with ad hoc network and mechanism to remove Hidden node problem and exposed node problem. a.. The chapter also contains a brief introduction to functioning of RTS/CTS, MACA,MACAW etc. This also contains the Review of Literature .

Chapter 3 contains the Present work The first part of the chapter outlines the and formulation of the problem, the Objective of thesis and the methodology to be used .

Chapter 4 contains Results and Discussion

Chapter 5 discusses Conclusion and Future Scope of the thesis i.e. Reducing delay time by using RTS/CTS along with RTR. And also Contains the conclusion of the future directions of research in this area of work.

Chapter 6 contains the various References which are used in the literature review and various research papers that are used in this thesis.

Appendix is given in the seventh Chapter. Appendix contains the different Abbreviations and the Glossary of terms used in the Dissertation

CHAPTER 2LITERATURE REVIEW

Mainly there are two problems associated with wireless adhoc network. One is Hidden node problem and other one is Exposed node problem. And there are number of techniques to avoid this problem. In my thesis, I considered hidden node problem. There are number of techniques to solve hidden node problem.

Handshaking technique- This includes RTS/CTS technique. As we know in general scenario when two nodes send data to the same node at same then collision occurs at that node as shown above in figure1.10. This is known as hidden node problem so to remove this RTS/CTS mechanism is used in which any node that wants to send data or want to communicate with the other node, send RTS to that node and when a node received that RTS from other node. it corresponds to that node by sending CTS i.e. clear to send data. This CTS is broadcasted to all the nodes, the node that receive that CTS goes to waiting for approx time that is stated in CTS timer. Hence no other node communicates in that period of the time. Hence hidden node problem get removed.

C. Wu, V. Li in 1988 "Receiver-initiated busy-tone multiple access in packet radio networks Busy Tone Multiple Access (BTMA) is a protocol that is based on the RTS/CTS mechanism. In BTMA, a base station broadcasts a signal to the other terminals to eliminate the effect of hidden nodes when one station uses a channel. In fact, with this message, the base station reserves the channel for the sender until the end of transmission by broadcasting busy tone.

Z.J. Haas, J. Deng, F. R. Hall in 1988 , "Dual busy tone multiple access DBTMA - performance results," In this mechanism, Haas et al., proposed two narrow bandwidth tones known as sender's Busy Tone (BTs) and Busy Tone which generates via receiver (BTr) which uses a single shared channel. The first one is generated by a transmitter terminal after sending RTS, and it provides protection for an RTS packet. This means that there are two busy tones are generated one for sender and other for receiver. When destination node receive RTS it sends BTr for the protection of data .All nodes sensing any busy tones are not allowed to send RTS requests. RTS and BTr solves the Hidden node problem.

P. Karn in 1990 provides "MACA new channel access method for packet," Multiple access collision avoidance, in this we include RTS/CTS/DATA. In these RTS/CTS mechanism is used in which any node that wants to send data or want to communicate with the other node, send RTS to that node and when a node received that RTS from other node. It corresponds to that node by sending CTS i.e. clear to send data. Both RTS and CTS contain approx timer for which data can be sent or for time for which other nodes should wait.

Vaduvur Bharghavan in 1994 provides MACAW (A media access protocol for wireless LAN) . It uses RTS/CTS/DS/DATA/ACK. For avoiding an unnecessary deferral situation, a DS packet is generated by Node as an announcement for a successful connection to other Nodes.

C.-K. Toh, V. Vassiliou G. Guichal, C.-H. Shih in 2000, "March: a medium access control protocol for multihop wireless ad hoc networks," The multiple access with reduced handshake (MARCH) protocol utilizes the broadcast characteristics of an omnidirectional antenna to reduce the number of control messages required to transmit a data packet in multihop ad hoc networks. In MARCH, the RTS-CTS handshake is used only by the first hop of a route to forward data packets while for the rest it utilizes a new CTS-only handshake. Since fewer control packets are transmitted, the probability of packet collision is reduced and therefore the channel throughput is increased. Simulation results demonstrate that MARCH outperforms MAC protocols that employ only the RTS-CTS handshake.

6Aruna jayasurya, Sylvie perrea, Arek dadej, in 2004 Steven Gordan institute of telecommunication and research .university of South Australia "Hidden vs. Exposed Terminal Problem in Ad hoc Networks" .In this paper hidden node and exposed node problems are discussed and "Analytical and simulation showed that exposed problem dominates in ad-hoc network as compared to the hidden node. And also relative throughput performance of ad-hoc network is compared with RTS/CTS and without RTS/CTS. Analytical and Simulation showed that performance get degraded with the use of RTS and CTS.

Ashikar rehman and Pawel Gburzynski in 2006 Department of Computing Science University of Alberta Edmonton, Alberta, Canada, T6G 2E8 "Hidden problems in hidden node problem". In this paper few problems introduced by the RTS/CTS mechanism of collision avoidance and focus on the virtual jamming problem, which allows a malicious node to effectively jam a large fragment of a wireless network at a minimum expense of power. We propose a solution to this problem and provide experimental data illustrating the impact of virtual jamming and the effectiveness of our proposed solution

AO HAN and Weije Lu in 2009 Department of Electronics and Information Engineering Huazhong University of Science and Technology (HUST)" An Improvement of MACA in Alleviating Hidden Terminal Problem in Ad-hoc Networks" It is well known that unfairness is a classic problem in back off algorithm such as BEB, which always leads to node "starve to death" phenomenon. Unfairness is also a common issue in MAC protocol design. MACA-RPOLL proposed in this paper not only has larger channel utilization than MACA but also settles the unfairness problem commendably. In general, using the receiver-polling mechanism it is alleviated that hidden terminals' effect on the performance of the channel. The performance comparison between MACA and MACA-RPOLL is based on a rough analytical model. Finally it is validated that MACA-RPOLL has better performance that MACA in some scenarios.

A.A. Abdullah, Lin Cai, F. Gebali in Sep. 2010 "Enhanced busy-tone-assisted MAC protocol for wireless ad hoc networks," In Enhanced Busy Tone Multiple Access (EBTMA) , BTMA and MACA are combined to get better performance in terms of throughput, packet delivery ratio, and average delay. In fact, two channels are used in this mechanism. The first one is used for transmitting RTS/CTS/DATA/ACK packets, while the second one is used for transferring the busy tone signals. Furthermore, it uses a back-off counter similar to that used in MACA. The simulation results show that EBTMA has 0.4 Mbps better throughput rate compared to BTMA. Although this mechanism gains better throughput, combining BTMA and MACA imposes a cost in hardware.

Viral V. Kapadia, Sudarshan N. Patel and Rutvij H. Jhaveri in 2011 explained the comparative study of Hidden node problem and solution using different techniques. and protocols. Techniques include RTS/CTS, CSMA, MACA, MACAW, Increase transmitting power from the nodes, using Omni directional antennas, removing nodes etc. so conclusion derived by them was that Hidden node problem can be solved by many means but each solution is for particular scenario. Using different techniques like Increase Transmitting Power From the Nodes, Use Omni-directional antennas, Remove obstacles, Move the nodes, Use protocol enhancement software, Use antenna diversity, Wireless Central Coordinated Protocol etcetera would increase the performance of ad-hoc networks a lot.

Mostefa Fatima Zohra,Mekkakia maaza Zoulikha.Khelifa in 2011 explained "Techniques of detection of the hidden node in wireless ad-hoc network" In this paper two techniques Passive detection and active detection are discussed to detect Hidden node terminal .In the wireless ad hoc networks, every node is assured by an individual battery which the consumption for the communication and the calculation of data must be optimized to avoid the problem of energy consumption. In the wireless ad hoc network, MAC protocol synchronizes the access of nodes to the channel. The access to the medium collides with two classic problems in wireless, hidden node problem and exposed node problem. But in this paper we consider hidden node problem. The active detection and the passive detection allow resolving the problem of the hidden node. In the passive detection a mechanism RTS / CTS is used. The paper treats the power consumption provoke by RTS/CTS mechanism to detect hidden node for every node to have a better knowledge of the topology of the network and preserving its energy consumption. Simulation results showed that two active detection to produce a high consumption in bandwidth., passive detection give not all hidden nodes in the network but active detection indicates all hidden nodes.

L.Boroumand, R.H Khokhar,L.A. Bakhtiar and M.Pourvahab in April 2012' explained "A Review of techniques to solve Hidden node problem in wireless network " In this paper all the existing mechanism to solve Hidden node problem are characterize into three categories Handshaking, Busy tone multiple access and routing management mechanism. In this weaknesses and strengths are also discussed.

CHAPTER 3PRESENT WORK

3.1 Objective- The objective of this dissertation is to avoid delay time occurs during RTS/CTS handshake in Hidden node problem. As we know to avoid hidden node problem, we use RTS/CTS mechanism. For removing Delay time and to improve throughput of the network I am integrating concept of RTS/CTS with RTR.

3.2 Methodology- In ad-hoc network, nodes communicate by sending data from one node to another especially in multi-hop ad-hoc network. But there are two problems associated with communication.

Hidden node problem-- Hidden node: A sends to B; C sends to B -> Collision at B

Fig 3.1 -Hidden node problem

Exposed node Problem- Node A sends RTS to B, and node D sends RTS to the C. as a result c sends CTS to D. And b hears that CTS and B don't send CTS to A.

To remove hidden node problem, RTS/CTS mechanism is used in which node that wants to communicate with other node send RTS (Request to send) to that node and RTS receiving send CTS (clear to send) to RTS sending node and all the nodes which are in its range .These CTS receiving nodes goes to waiting state for a time that is provided in CTS control packet i.e. CTS timer. And I have taken assumption that if the communication between the sender and receiver node occurs before CTS timer expires, then the nodes which receive CTS timer i.e. which were in the range of receiver node still has to wait till CTS timer expires even if the communication between the sender and receiver has completed .so these CTS receiving node has to wait. So a kind of delay is developed in the network. To remove this I am integrating RTR with RTS/CTS.

3.3 Formulation of Hypothesis- In this paper I am introducing concept of RTR with RTS/CTS .As we know nodes communicate to each other by sending RTS/CTS control packet. Let us consider Node A wants to communicate with Node B. Node A sends RTS to Node B and Node B reply with CTS which is broadcasted to all the nodes within its range i.e. Node C.Node C after receiving CTS donot interfere in the communication between A and B Nodes. As I have taken assumption that if communication ends before the expected time sent by CTS then the node (Node B) which was previously communicating will send RTR signal to all other nodes which are in its range and other nodes will start sending data to RTR sending node.

Fig 3.2- Showing integration of RTS/CTS and RTR

When RTR is broadcasted to other nodes, these nodes will communicate or send data according to two techniques-

3.3.1 According to distance preference - when CTS is broadcasted to other nodes, these nodes goes to the waiting state , so if communication done before the approximate timer of the CTS . Then the receiving node send RTR to other nodes to reduce delay time . This RTR is broadcasted to all the nodes and nodes will communicate or send according to distance preference .This means that node which is at shorter distance will send data to that Node so a kind of Queue is developed and all nodes will communicate according to this queue. That having smallest distance will be at the top of queue will be added at top position. And that topmost node will communicate first or send data first.

3.3.2 According to data size preference- when CTS is broadcasted to other nodes, these nodes goes to the waiting state , so if communication done before the approximate timer of the CTS . Then the receiving node send RTR to other nodes to reduce delay time . This RTR is broadcasted to all the nodes and nodes will communicate or send according to data size preference .This means that node which has smaller data size will send data to that Node so a kind of Queue is developed and all nodes will communicate according to this queue. That having smallest data size will be at the top of queue will be added at top position. And that topmost node will communicate first or send data first. So we can this queue is according to our operating system concept i.e. SJF( shortest job first). Node which smallest in data size will execute first.

Shortest job first-Fig-3.3 SJF3.4 Sources of Data

Information will be gathered from the previous research work done on these topics; the code or the Anti-Collision algorithm will be studied & scrutinized to make it perform efficiently for the different methods as well.

3.5 Research Design The research design is a pattern or an outline of a research projects working. The research design for this particular research follows the descriptive design.

Algorithm and Flow chart are as following:3.6 Algorithm:

Step 1: START

Step 2: Sender -> RTS

Step 3: Reciever -> CTS + Time by receiver

Step 4: If (Communication ends before time) then:

Step 5: Receiver -> RTR

Step 6: Waiting Queue <- nodes with CTS(distance preference and data size preference)

Step 7: Send data

Step 8: Else: Timer++

Step 9: END

3.7 Flowchart

Yes

Send RTR

START

DATA SENDING

Sender send node RTS

Receiver node Replay back with CTS and timer to all nodes in its range

IF communication ends before CTS timer between sender and receiverNODES in WAITING QUEUE.Retransmit

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END

Fig 3.5-FlowchartCHAPTER 4RESULT AND DISCUSSION4.1MATLAB DESCRIPTION-

NS-2 is an open source system that is developed using C++ and Tool Control Language TCL. Researchers can freely add new components to the system to server their own purposes. The latest version of NS-2 is version 2.34. Within this version, most of the standard protocols supported. You can find protocol from media access layer protocols such as CSMA/CD up to application protocols as FTP and HTTP. For routing protocols, there are unicast and multicast routing protocols for wire network and DSR, DSDV, AODV for wireless ad-hoc networks. Most of these protocols were developed by researchers and adopted into standard version of NS-2.

In order to experiment security features for network, we need to add security functions into NS-2. Of course for specific experiments there are specific requirements. The purpose of this project is only to illustrate a way to add security functions into NS-2

Our approach is to build a new protocol at network layer - IP layer. We also define new packet format to represent new protocols. The new protocol is represented by a class derived from built-in class in NS-2. Within new derived class we will add encryption and decryption for data field in the data packet. We will also implement message digest generation function to ensure the secure and integrity of data packet during transmission in data aggregation. We consider our data as plain text. The cryptography algorithm is One way hash chain and outlier detection method.

The programming language is C++.

Environment development requirements:

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Article name: Reducing Delay Time Using Rts Computer Science essay, research paper, dissertation