This paper evaluates the performance of MANET for enhancing the QoS using cross layer architecture by combining Network layer and MAC layer protocols with Transport layer congestion control mechanisms operating in a mobile adhoc network. MAC layer used to maintain routing table, Network layer used to monitoring to packet datarate, These two layers helps to optimize the performance in MANET. So, combine the mechanisms of these layers to improve the QoS drastically. We examine the effects of different MAC protocols with AODV and DSR of routing algorithms with Slow start and Arithmetic Increase and Multiplicative Decrease (AIMD) mechanism of TCP. MAC protocols uses distributed coordination function (DCF) and enhanced distributed coordination function (EDCF). Specifically, we access the impact of multiple wireless hops and node mobility on the throughput performance of TCP on each MAC protocol with two routing algorithms. Similarly Results shows in all instances, the QoS parameters improvement in throughput, bandwidth-delay product, delivery ratio, and packet loss is reduced drastically to 25-30% in EDCF with AODV algorithm in network layer and AIMD mechanism in transport layer. But if DSR algorithm is used in the network layer instead of AODV it affects the QoS parameters. So we enhancing the performance to combining cross layer architecture between proactive and reactive Protocols, So we have taken OLSR proactive routing protocol used to Optimize the QoS in MANET. The proposed OLSR routing protocol performs better than AODV and DSR during high mobility and high network load. So it can be said that, OLSR performs better than AODV and DSR at all conditions; expect very low loads when the performances are very similar.
Keywords- Mobile adhoc networks, (MAC), (TCP), Slow start, AIMD, OLSR,AODV,DSR DCF.
1. INTRODUCTION
IEEE 802.11e Contention-Based Channel Access (EDCF) Performance Evaluation], IEEE 802.11e Medium Access Control (MAC) is an emerging supplement to the IEEE 802.11 Wireless Local Area Network (WLAN) standard to support Quality-of-Service (QoS). The 802.11e MAC is based on both centrally-controlled and contention-based channel accesses.
In this paper, we evaluate the contention-based channel access mechanism, called enhanced distributed coordination function (EDCF), in comparison with the 802.11 legacy MAC. The EDCF provides differentiated channel access to frames with different priorities. We also consider an optional feature of the EDCF, called contention-free burst (CFB), which allows multiple MAC frame transmissions during a single transmission opportunity (TXOP). Through our simulation study, we conclude that the EDCF can provide differentiated channel access for different traffic types. Furthermore, the CFB is found to enhance the EDCF performance by increasing the overall system throughput and achieving more acceptable streaming quality in terms of frame losses and delays. We introduced the contention-based channel access scheme for QoS support, called the EDCF, of the emerging 802.11e MAC. Based on the simulation, we compared the legacy 802.11 DCF and the 802.11e EDCF to show that the EDCF can provide differentiated channel access among different priority traffic. We also evaluated an optional feature called CFB. We would like to remark on two important aspects: first, it should be noted that in this work, we did not attempt to optimize the network performance via the fine- tuning of the EDCF parameters. One should be able to optimize the EDCF channel access by adapting the EDCF parameters including the TXOP limit during the run-time depending on the network load and supported applications. Second, for acceptable QoS provisioning, there should be an admission control process in place along with the properly-chosen EDCF parameters. Simulation Analysis of QoS parameters by combining MAC and TCP in MANETS], the performance evaluation of interaction between Transport and the MAC layer protocols operating in a mobile adhoc network. In Adhoc networks, certain QoS parameters like error rate, delay and packet loss are increased and certain parameters like throughput and delivery ratio are decreased in Transport layer is due to MAC problems and disconnection is also possible due to mobility or power failure. So, combine the mechanisms of these two layers to improve the QoS drastically so that people can design the network based on their requirements. We examine the effects of two different MAC protocols- IEEE 802.11and IEEE802.11e with Slow start and Arithmetic Increase and Multiplicative Decrease (AIMD) mechanism of TCP.IEEE802.11uses distributed coordination function (DCF) where IEEE802.11e uses enhanced distributed coordination function (EDCF). Specifically, The interaction between transport layer and the MAC protocol has a significant impact on the achievable throughput, Packet Delivery Ratio, Bandwidth Delay Product and packet loss in ad hoc networks.
ARCHITECTURAL DESIGN
Application Layer
(This layer generate multimedia packets and assign
priority )
Transport layer
(Implement Slow start & AIMD mechanism)
Network layer
(Implement OLSR Protocol)
MAC layer
(Implement EDCF&DCF algorithm)
Figure. 1 Layered structure
2. PROBLEM DESCRIPTION
The introduction of real-time audio, video and data services into wireless networks presents a number of technical obstacles to overcome. Traditional internet QoS protocols like RSVP cannot be easily migrated to the wireless environment due to the error-prone nature of wireless links and the high mobility of mobile devices. This is specially true for Mobile Ad Hoc Networks (MANETs) where every node moves arbitrarily causing the multi-hop network topology to change randomly and at unpredictable times. QoS framework is extended to be suitable for MANETs. In order to prove its correctness and efficiency the system is implemented and simulated using the ns-2 network simulator.
3. Existing System
OSI architecture allows each layer to be extracted independently, which simplifies the implementation of the architecture. However, the strictly layered architecture might not be the best model, because oftentimes it is not possible to optimize the network performance according to different situations without interaction among the different layers. Thus a cross-layer design is the solution for enhancing QoS in various wireless networks such as sensor networks, cellular networks and ad hoc networks. A cross-layer design is used to adjust the transmission rate in transport layer and provide channel information to the MAC layer from the physical layer; resource allocation is determined in the MAC layer according to multi-path routing information from the network layer. Our previous work was the interaction between transport layer mechanisms and MAC protocols and discussed the performance improvement between AIMD, Slow start with IEEE 802.11e and AIMD, Slow start with IEEE 802.11. Disadvantages of existing system, It is not possible to optimize the network performance according to different situations without interaction among the different layers, Disconnection problem (Network layer not able to detect the path to deliver the packets, There is no guarantee in the Qos In MANET, Increased error rate,delay,packet loss, Decreased throughput and delivery ratio.
4. Proposed System
The proposed works evaluates the performance evaluation by combining Network layer and MAC layer protocols with Transport layer congestion control mechanisms operating in a mobile adhoc network. In Adhoc networks, certain QoS parameters like error rate, delay and packet loss are increased and certain parameters like throughput and delivery ratio are decreased in Transport layer is due to MAC problems and disconnection is also possible due to mobility because the network layer is not able to detect the path to deliver the packets. So, combine the mechanisms of these three layers to improve the QoS drastically. We examine the effects of two different MAC protocols- IEEE 802.11and IEEE802.11e with OLSR routing protocol with Slow start and Arithmetic Increase and Multiplicative Decrease (AIMD) mechanism of TCP.IEEE802.11uses distributed coordination function (DCF) where IEEE802.11e uses enhanced distributed coordination function (EDCF). Specifically, we access the impact of multiple wireless hops and node mobility on the throughput performance of TCP on each MAC protocol with two routing algorithms. Additionally the other QoS parameters of delay, Bandwidth delay product, delivery ratio and packet loss is also investigated. advantages of proposed system, Optimized State Of Routing, Enhancement in the quality of service, Decreased error rate, delay, packet loss, Increased throughput and delivery ratio.
OLSR (Optimized Link State Routing)
The Optimized Link State Routing Protocol (OLSR) is an IP routing protocol optimized for mobile ad-hoc networks, which can also be used on other wireless ad-hoc networks. OLSR is a proactive link-state routing protocol, which uses Hello and Topology Control (TC) messages to discover and then disseminate link state information throughout the mobile ad-hoc network. Individual nodes use this topology information to compute next hop destinations for all nodes in the network using shortest hop forwarding paths. Benefits: Being a proactive protocol, routes to all destinations within the network are known and maintained before use. Having the routes available within the standard routing table can be useful for some systems and network applications as there is no route discovery delay associated with finding a new route. Advantages: OLSR is also a flat routing protocol, it does not need central administrative system to handle its routing process,.
SLOW-START
Slow-start is part of the congestion control strategy used by TCP, the data transmission protocol used by many Internet applications. Slow-start is used in conjunction with other algorithms to avoid sending more data than the network is capable of transmitting, that is, to avoid causing network congestion.
Fast recovery
There is a variation to the slow-start algorithm known as fast recovery, which uses fast retransmit followed by congestion avoidance. In the fast recovery algorithm, during congestion avoidance mode, when packets are not received, the congestion window size is reduced to the slow-start threshold, rather than the smaller initial value.
Additive Increase and Multiplicative Decrease (AIMD)
The additive increase/multiplicative-decrease (AIMD) algorithm is a feedback control algorithm used in TCP Congestion Avoidance. AIMD combines linear growth of the congestion window with an exponential reduction when a congestion takes place. The approach taken is to increase the transmission rate (window size), probing for usable bandwidth, until loss occurs. The policy of additive increase may, for instance, increase the congestion window by 1 MSS (Maximum segment size) every RTT (Round Trip Time) until a loss is detected. When loss is detected, the policy is changed to be one of multiplicative decrease, which may, for instance, cut the congestion window in half after loss.
5. IMPLEMENTATION
The OLSR protocol proposed in this project is compared with the AODV and DSR protocol. . NS2 is a open source method and program to implemented(eg. Linux,). It is a discrete event time simulator. With, a single entity can simulate several network nodes in the system.
Network Simulator (NS2) is used to simulate these protocols. Network Simulator (NS2) network layer is the place where those routing protocols are invoked to function. Second and the more important reason is related to our proposed protocol, working on the top of well known protocol such as OLSR protocol.
NS2 protocol has many routing Protocols. (e.g.: DSR, AODV). We implement an proactive routing protocol called OLSR (OPTIMIZED LINK STATE ROUTING PROTOCOL) by inserting the network layer and then recompiled the Network Simulator (NS2) .
SIMULATION PARAMETERS
Parameters
Values
Routing Protocol
OLSR
MAC
802.11
Transmission Rate
1 Mbps
Simulation Time
100 secondsk
Mobility
RWP
No. of nodes
20
Node speed
2 m/s
Pause time
0, 30s
Traffic
CBR
Network Area
1500 m X 1500m
SIMULATION RESULTS
ROUTE DISCOVERY
THROUGHPUT
Bandwidth_Delay
Packet _Delivery_Rate
Packet Loss Rate
CONCLUSION
The proposed OLSR routing protocol performs better than AODV and DSR during high mobility and high network load. OLSR always maintains a routing table, most often it can provide some routes quickly. So the average delay is reduced significantly. Packet delivery ratio is improved as it maintains the QoS information and looks for a path satisfying the QoS requirements of the applicants. Moreover it sends smaller number of control packet to handle route discovery and route failure. As a result, the control overhead is reduced. The trade-off is that each node requires more memory to store the neighbor information and comparatively larger routing table. The nodes also need more processing power to manipulate the neighborhood information and calculate the routes based on QoS information. So it can be said that, OLSR performs better than AODV and DSR at all conditions; expect very low loads when the performances are very similar. So, MAC layer information can be used to construct the neighbor table which will allow enhancing the performance in terms of delay and packet delivery as well as minimizing the control overhead . The results show that the interaction between transport layer with the Network and MAC protocols has a significant impact on the achievable throughput, Packet Delivery Ratio, Bandwidth Delay Product and packet loss in adhoc networks. these three layers know the status of other layers and collectively improve the QoS performance in Adhoc networks. The OLSR protocol enhances the quality of service.
