Simulation Study On Concurrent MAC Protocols In Multi-Hop Wireless Networks

With the rapid development of the wireless Internet, it becomes more and moredifficult for using limited spectrum resources to meet the growing demand for dataservices. Increasing the opportunity for each link to concurrently transmit is one of theeffective means to solve the scarcity of spectrum resources in multi-hop wirelessnetworks such as Wireless Mesh Networks, Wireless Sensor Networks, and VehicularAd Hoc Networks.Because an atomic operation defined in IEEE802.11is intrinsically bi-directional,to achieve concurrent transmission in the case of no time alignment, the intendingconcurrent transmitting node must lie outside the interference range of both the firstsending and receiving nodes. Therefore, in order to improve the wireless network spacereuse, it is far from sufficient to make a reservation of the channel only in time domainthrough RTS and CTS. An Interference Tolerance Aware MAC protocol (ITAMA) isproposed to improve the existing RTS/CTS mechanism. ITAMA adds space reservationmechanism based on the original time reservation mechanisms, allowing nodes outsidethe interference range to achieve concurrent transmission. It is a common way for amulti-hop wireless network to improve the frequency reuse by enabling exposed node tosend data or hidden node to receive data. According to the characteristics of RTS/CTSmechanism, another MAC protocol based on expected signal detection (ESMA)utilizing the ideas of cross-layer design and interference elimination is proposed. ESMAdetects the expected ACK frames and CTS frames on the basis of the semantics incontrolling signals. With the expected signal detected, exposed nodes ignore physicalcarrier-sensing and RTS network allocation vector, thus achieving concurrenttransmission.In the thesis, the principle and realization of the two spatial reuse methods arethoroughly described. To analyze the performance in detail via simulations, thecorresponding MAC simulation blocks using NS2simulators is implemented. Resultsshow that both MAC protocols can effectively improve the spatial reuse.