MAC Protocol For Ad Hoc Networks Research Articles

Neighbor initiated approach for avoiding deaf and hidden node problems in directional MAC protocol for ad-hoc networks

In this paper we propose a MAC called "Neighbor Initiated Approach for avoiding Deaf and Hidden node problems in directional MAC protocol for Ad Hoc networks", which takes advantage of the multi beam smart antennas. Through the antenna, a node can simultaneously transmit/receive a packet to/from all the directions around it. Thus the antenna switches itself in transmission and reception mode. In our scheme all transmission and reception will be directional. We discussed the hidden and deaf node problems with directional MAC and proposed the scheme to overcome those shortcomings. Our scheme has been inspired by the IEEE 802.11, which includes a new scheme to inform its neighbors who was deaf due to other communication. Moreover, the simultaneous transmission of the RTS/CTS through it's all beams prevent the hidden node problem. In our scheme the idle nodes stay in reception mode for sensing the channel through its M non overlapping beams, as a substitute of omnidirectional antenna. It prevents the hidden node problem due to asymmetry in gain. We have simulated our scheme by OPNET 16.0, and compared our results with CDR MAC, DMAC and IEEE 802.11 protocols. Our results show that NIADH performs better than that of the existing protocols in majority of the scenarios.

Reservation MAC protocols for Ad-Hoc Networks

Multimedia and real-time applications require bandwidth guarantees, which may be achieved by resource reservation. Several researches were done to propose efficient reservation MAC protocols for ad-hoc networks. In these schemes, channel is segmented into super-frames composed of fixed number of slots. They allocate slots to each traffic source, and make sure that neighbor nodes record the reservation in order to ensure consistency of reservations between neighbor nodes. However, resource reservation in ad-hoc networks remain a very challenging task due to the instability of radio channels, node mobility and lack of coordination between mobile nodes. Proposed reservation MAC protocols like CATA, FPRP, R-CSMA and SRMA/PA have limitations and are suitable only for particular situations. In this paper, we propose a comparative analysis of the most representative reservation MAC protocols. We identify the major issues unresolved by reservation MAC protocols. A performance evaluation and comparative analysis with the IEEE 802.11e are achieved through the NS-2 simulator.

Connection-oriented multi-channel MAC protocol for ad-hoc networks

This work proposes an on-demand connection-oriented multi-channel MAC protocol for ad-hoc networks. The major features of the proposed protocol are as follows: (a) each mobile node is equipped with only two network interfaces; (b) MAC layer broadcast primitive is supported; and (c) no time synchronization is required. Compared with other multi-channel MAC protocols, the proposed protocol reduces the cost of channel negotiation by considering the property that a connection typically generates multiple packets for transmitting. The NS-2 is used to evaluate the performance of the proposed protocol. Simulation results indicate that the proposed protocol can reduce the cost of channel negotiation and increase the network throughput.

Reverse-Engineering MAC: A Non-Cooperative Game Model

This paper reverse-engineers backoff-based random-access MAC protocols in ad-hoc networks. We show that the contention resolution algorithm in such protocols is implicitly participating in a non-cooperative game. Each link attempts to maximize a selfish local utility function, whose exact shape is reverse-engineered from the protocol description, through a stochastic subgradient method in which the link updates its persistence probability based on its transmission success or failure. We prove that existence of a Nash equilibrium is guaranteed in general. Then we establish the minimum amount of backoff aggressiveness needed, as a function of density of active users, for uniqueness of Nash equilibrium and convergence of the best response strategy. Convergence properties and connection with the best response strategy are also proved for variants of the stochastic-subgradient-based dynamics of the game. Together with known results in reverse-engineering TCP and BGP, this paper further advances the recent efforts in reverse-engineering layers 2-4 protocols. In contrast to the TCP reverse-engineering results in earlier literature, MAC reverse-engineering highlights the non-cooperative nature of random access.

Performance Analysis of a Flexible MAC Protocol for Real-Time Services in Vehicular Ad-Hoc Networks

Several MAC protocols for ad-hoc networks have been proposed in the literature for topologies with a large number of nodes. In particular, the MAC protocols based on 802.11 cannot guarantee the delays needed by real-time traffic, as they are mainly based on the CSMA/CA random access scheme, which inserts significant random inter-frame delay components, strongly dependent on network load. Other MAC protocols assign dynamically a dedicated channel to each connected node. In this way, it is possible to guarantee a strictly controlled delay for real-time traffic at the expense of a greater bandwidth waste. The goal of this paper is to evaluate the performance of a MAC protocol of this latter family. Our analysis is focused on scenarios with fast moving users, while in the literature most of the proposed MACs, also for mobile ad-hoc networks, are studied in the case of stationary users. Our study shows that the system performance strongly depends on the users’ speed and provides an accurate analysis of the performance degradation registered as speed grows.