Wireless Ad Hoc and Sensor Networks

Distributed Power Control and Rate Adaptation 297of the wireless nodes is extended. Additionally, the network capacityis maximized in terms of high-aggregate throughput. In conclusion, thepower control MAC protocol offers a superior performance in terms ofconvergence and maximizes the network capacity compared to 802.11standards. Results justify theoretical conclusions.The increased throughput is because of the increased channel utilizationand not because of higher spatial reuse, because the pulse train toovercome the hidden-terminal problem is sent at the maximum power.Consequently, the spatial reuse factor is not significantly altered. To furtherincrease the throughput and spatial reuse factor, the transmissionpower has to be changed dynamically for all frames. This amounts toadaptive selection of the first RTS-CTS exchange, as well as power usedfor the train of pulses. Therefore, potential future work may involveadaptive selection of transmitter powers for the train of pulses to mitigatethe hidden-terminal problem, while increasing the spatial reuse in thepresence of fading channels.Next, energy-efficient rate adaptation protocols are introduced thatadaptively select the rate based on channel state and queue utilization.Additionally, the algorithms minimize energy consumption. The selectionof the rate is performed online by taking into account the congestion,required throughput, and buffer occupancy. The heuristic scheme minimizesbuffer overflows by altering back-off intervals based on congestionlevel. Alternatively, the solution based on the dynamic programmingapproach is able to precisely control incoming flow, thus preventing anypacket losses due to buffer overflows. Moreover, by precisely controllingthe congestion level, a 96% higher throughput and 131% higher energyefficiencyis achieved over the RBAR protocol. Simulations confirm thatthe data can be transmitted faster with fewer dropped packets whileconsuming less energy. Thus, the network lifetime is extended and QoSimproved.Finally, in this chapter, the implementation of a novel DAPC algorithmfor wireless communication systems was discussed. Now, withhardware implementation, the algorithm can be put to test in the realworldwireless channel. A test platform for evaluating wireless MACprotocols was developed with a vision for future expansion and development.Satisfactory performance from the DAPC was observed fromthe experimental results. The protocol was shown to provide suitablepower adjustment to maintain desired SNR even under extreme channelconditions.Future work will involve testing the protocol for larger networks withmore paired connections. Moreover, more complex DAPC MAC protocolcan be tested for cellular network, RFID reader network, and wireless adhocor sensor networks.