PERFORMANCE COMPARISON OF VARIOUS MAC

PROTOCOLS WITH CTMAC PROTOCOL

GROUP MEMBERSMadhur Sehgal (375)

Shobhit Rathour (417) Kiran Rekhi (418)

PROJECT MENTOR

Ms. Shivangi Borasia

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DECLARATION

I hereby declare that the project report entitled

“PERFORMANCE COMPARISON OF VARIOUS MAC PROTOCOLS WITH

CTMAC PROTOCOL”

is the bonafide record of the project carried out at

MUKESH PATEL SCHOOL OF TECHNOLOGY MANAGEMENT AND

ENGENEERING

in partial fulfillment of the requirements for the award of degree

Bachelor of Technology in Computer Science

of NMIMS University, Mumbai during the academic year 2011-12.

I further declare that the project report is not submitted to any other university in fulfillments

of the requirements for the award of any degree.

Madhur Sehgal 375

Shobhit Rathour 417

Kiran Rekhi 418

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Shri Vile Parle Kelavani Mandal’s

NMIMS (Deemed-to-be University)

Mukesh Patel School of Technology Management & EngineeringJVPD Scheme, Bhaktivedanta swami Marg,

Vile Parle (w), Mumbai- 400 056.

Certificate

Department of Computer Engineering

This is to certify that following students

Name of the students   Roll No.

Madhur Sehgal 375

Shobhit Rathour 417

Kiran Rekhi 418

have submitted their final year trimester end report entitled

PERFORMANCE COMPARISON OF VARIOUS MAC PROTOCOLS WITH

CTMAC PROTOCOL

as a part of their curriculum for the Fourth year, B.Tech, Trimester – X, during the academic year 2011-2012

Group Mentor: HOD:

Ms. Shivangi Borasia Dr. Sudeep Thepade

Sign: ________________________ Sign: ________________________

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ACKNOWLEDGEMENT

We would like to express our heartiest thanks to Ms. Shivangi Borasia, for providing us this great opportunity, feedback and support throughout the trimester that helped us completing our first part of the project. We would also like to express our sincere thanks to Professor Sudeep Thepade, Head, Computer Department, for his cooperation and helping us in earning this learning opportunity. We would also like to give our special thanks to Dr. D.J. Shah, Dean, for all the support and the facilities he made available for us.Furthermore, we acknowledge the support and feedback of our colleagues and friends.

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INDEX

Sr. No. Topic Page No.

1. Introduction 7

2. Problem Statement 8

3. Literature Survey

3.1 Wireless Network3.2 MANET3.3 MAC3.4 MAC Protocols3.5 ns-2

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99101116

4. Work done so far 17

5. Conclusion and Future Scope 18

6. References 19

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FIGURE INDEX

Fig. No. Figure Name Page No.

1 Simplified Aloha Scheme 11

2 Collision in Pure Aloha 11

3 Slotted Aloha 12

4 Collision in Slotted Aloha 12

5 CSMA/CD 13

6 CSMA/CA 14

7 CTMAC 15

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1. IntroductionThe medium access control (MAC) is a sub layer of the OSI link layer. It has to organize and handle how different stations may access a shared medium (the wire). It is well known that the problems related to resource-sharing mostly involve strong formal models. Indeed, the issues related to resource-sharing are fairness, good-put improvement, scalability and algorithms complexity. Medium Access Control (MAC) protocol is used extensively in providing network access for a collection of end users. As the network access part plays a vital role in a network, it is important to design an efficient yet reliable MAC protocol for a LAN. Many MAC protocols used in LANs are based on random access schemes. Due to the random nature of the protocol operation and the bursty nature of the traffic, it has been considered difficult to analyze a medium access protocol with all protocol details under a realistic traffic condition. Performance analyses of medium access protocols usually rely on simplifications of protocol details as well as arrival traffic models. Hence, the scope of the results of such performance analyses is somewhat limited. One of the goals of this thesis is to propose a new analytical approach for the performance analysis of a MAC protocol. The approach should not only retain all protocol details of the protocol operation, but also allow the use of a more general and realistic arrival process. The use of the approach will lead to more accurate performance results of the protocol. Besides, the recent growth in research, development and deployment of multimedia multi-service networks has prompted a need for a MAC protocol that can cope with the growing bandwidth demands as well as feature service differentiation to support transmission of real- time multimedia traffic with a certain quality of service (QoS).In this report, we are presenting, simulating and analyzing a set of well known MAC protocols. The protocols we are studying are Pure Aloha and Slotted Aloha. Aloha is one of the first protocols to have been proposed as a solution to Multiple Access Control.

2. Problem Statement

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During this project, we are going to get familiar with one of the most popular network simulators named ns 2 and implement and evaluate the performance of different MAC layer protocols by this tool.Evaluation of the performance of various MAC protocols considering certain parameters which will lead us to a final conclusion about the best performing protocol. A variety of workload and scenarios, as characterized by throughput, response time, delay, resource utilization, packet lost ratio and degradation mode etc of the ad hoc network will be simulated. The main advantage of simulation is that it allows us to systematically experiment with a wide variety of workloads and statistical parameters. But the results observed must not be considered on real world situations.

3. Literature Survey

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3.1 Wireless NetworkA wireless network is a decentralized wireless network. The network is ad hoc because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity.

3.2 Mobile Adhoc NetworkA mobile ad hoc network (MANET), sometimes called a mobile mesh network, is a self-configuring network of mobile devices connected by wireless links. Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router. The primary challenge in building a MANET is equipping each device to continuously maintain the information required to properly route traffic. Such networks may operate by themselves or may be connected to the larger Internet.MANETs are a kind of wireless ad hoc networks that usually has a routable networking environment on top of a Link Layer ad hoc network. They are also a type of mesh network, but many mesh networks are not mobile or not wireless.The growth of laptops and 802.11/Wi-Fi wireless networking have made MANETs a popular research topic since the mid- to late 1990s. Many academic projects evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced

by the routing protocol, and other measures.

3.3 Medium Access ControlThe Medium Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a sub-layer of the Data Link Layer specified in the seven-layer OSI model (layer 2). It provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multipoint network, typically a local area network (LAN) or metropolitan area network (MAN). The hardware that implements the MAC is referred to as a Medium Access Controller.The MAC sub-layer acts as an interface between the Logical Link Control (LLC) sub-layer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multipoint network. This channel may provide unicast , multicast or broadcast communication service.

3.4 MAC Protocols

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The various protocols that we will be using are as follows: Pure Aloha

The basic concept of ALOHA is very simple. When a node has a packet to transmit, it transmits the packet right away. A simple strategy like this may lead to scenarios where multiple nodes try to send at the same time, which might cause several collisions. As a result, several packets get corrupted. If the presence of a collision is detected by the sender, it retransmits after some random wait time.

Fig. 1: Simplified Aloha Scheme

Fig. 2: Collision in Pure Aloha

Slotted Aloha

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Slotted Aloha is an improvement of Pure Aloha. In Slotted ALOHA, the stations only transmit at the start of a slotted time which is equal to the transmission time. A new or retransmitted frame can be successfully transmitted if there are no other frames scheduled for transmission in transmission time.

Fig. 3: Slotted Aloha

Fig. 4: Collision in Slotted Aloha

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CSMA/CDIt is further realized that in wired LANs, in addition to sensing the broadcast channel before a transmission, a station can also detect if the data frame transmission suffers a collision during the transmission, this is sometimes called “listen while transmit”. With this feature, instead of blindly transmitting the entire data frame even though it has collided with others, a station can detect a collision and quickly abort the collided transmission so that the duration of a collision can be reduced. The protocol that implemented this feature is called the Carrier Sense Multiple Access with Collision Detection (CSMA/CD).The operation of the CSMA/CD protocols is the same as that of the CSMA protocols, except that in the case of a collision, all data frame transmissions involved in a collision will be aborted immediately after the collision is detected. The retransmissions of the unsuccessful transmissions are scheduled at some time later in the future.

Fig. 5: CSMA/CD

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CSMA/CACSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is a protocol for carrier transmission in 802.11 networks. Unlike CSMA/CD (Carrier Sense Multiple Access/Collision Detect) which deals with transmissions after a collision has occurred, CSMA/CA acts to prevent collisions before they happen. In CSMA/CA, as soon as a node receives a packet that is to be sent, it checks to be sure the channel is clear (no other node is transmitting at the time). If the channel is clear, then the packet is sent. If the channel is not clear, the node waits for a randomly chosen period of time, and then checks again to see if the channel is clear. This period of time is called the back off factor, and is counted down by a back off counter. If the channel is clear when the back off counter reaches zero, the node transmits the packet. If the channel is not clear when the back off counter reaches zero, the back off factor is set again, and the process is repeated.

Fig. 6: CSMA/CA

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CTMACIn wireless ad hoc network, throughput at the media access (MAC) layer can be increased by allowing as much as concurrent transmissions among neighboring nodes. A high-throughput MAC protocol, called Concurrent Transmission MAC (CTMAC), which supports concurrent transmission while allowing the network to have a simple design with a single channel, single transceiver, and single transmission power architecture helps to achieve the desired objective. CTMAC inserts additional control gap between the transmission of control packets (RTS/CTS) and data packets (DATA/ACK), which allows a series of RTS/CTS exchanges to take place between the nodes in the vicinity of the transmitting, or receiving node to schedule possible multiple, concurrent data transmissions. To safeguard the concurrent data transmission, collision avoidance information is included in the control packets and used by the neighboring nodes to determine whether they should begin their transmissions. The CTMAC protocol is just a concept and is yet to be implemented in the real world. The results show that it is but inevitable to be used in

the future.

Fig. 7:CTMAC Protocol

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3.5 NS-2Ns-2 is a widely used tool to simulate the behavior of wired and wireless networks. NS2 is developed as a collaborative environment. Ns provides substantial support for simulation of TCP, routing, and multicast protocols over wired and wireless (local and satellite) networks. It is distributed as open source software. A large number of institutes and researchers use maintain and develop NS2. NS2 versions are available for Linux, Solaris, windows and MAC os.NS2 is built using object oriented language c++ and otcl. NS2 interprets the simulation script written in otcl. The user writes his simulation as an otcl script. Results are obtained by NS2. It has to be processed further by other tools like network animator (NAM), Perl, awk script etc.

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4. WORK DONE SO FARStudied about network simulator ns-2 and its basic operations. Studied and selected two protocols for our project.Studied the IEEE paper “Performance Evaluation of Ad Hoc Routing Protocols Using NS2 Simulation” thoroughly.Studied the IEEE Paper “A High-Throughput MAC Protocol for Wireless Ad Hoc Networks” thoroughly.Studied about MANET and TCL concepts. Implementation of pure aloha and slotted aloha using different parameters.

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5. CONCLUSION AND FUTURE WORKWe have studied the basics of network simulator and implementation using tcl language. We carried out comparisons of different contention based MAC protocols on different parameters. The simulation tool shows that the efficiency of Pure Aloha and Slotted Aloha are approximately equal to the corresponding theoretical values.In next trimester we will continue evaluating other MAC protocols and draw a conclusion based on their performance calculated using different parameters. At last we would be able to conclude based on the comparisons which protocol stands the highest priority when tested under different scenarios.

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6. REFERENCESSamyak Shah, Amit Khandre, Mahesh Shirole and Girish Bhole ‘Performance Evaluation of Ad Hoc Routing Protocols Using NS2 Simulation’.B.Uma, V.R.Sarma Dhulipala ‘MAC Vs Routing Protocols in Mobile Adhoc Network’‘Performance Analysis and Enhancement of MAC Protocols’ By Chuan Heng Foh‘A High-Throughput MAC Protocol for Wireless Ad Hoc Networks’ By Wanrong Yu, Jiannong Cao, Xingming Zhou, Xiaodong Wang, Keith C. C. Chan, Alvin T. S. Chan, and H. V. Leong,

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