Design of a Power Control MAC Protocol for Mobile Ad Hoc Networks

Abstract

Power conservation is a major issue in Mobile Ad Hoc networks, as most of the nodes are battery powered. Power control is not related to any particular layer, since we can apply power conservation methods in all layers. But most of the power control mechanisms are working in MAC layer.

Here we designed a Power Control MAC protocol for MANET. Our first aim was to control the overall power consumption and the second was improve the throughput of the network. Thus our protocol includes two phases; in the first phase we reduce the power consumption and in the second phase we improve the aggregate throughput of the network. Our work is based on the IEEE 802.11 MAC protocol. We added an additional field to the RTS and CTS control packets
(PRTS in RTS packet to indicate the power used to send RTS packet and PData in the CTS packet to indicate the power with which sender can send DATA packet) for the design purpose. For reducing the power consumption we used the following method: We send the RTS packet with maximum or default power. The receiver after receiving the RTS packet calculate the data transmission power PData using
the received power Pr , RTS transmission power PRTS and the receiving threshold Rth. After calculating the PData that power is assigned to the PData field of the CTS frame and then the CTS frame will send with the same power PData. Then
after receiving the CTS frame the sender will send the DATA frame using the power PData and the receiver will send the ACK packet with the same power. In the second phase we have to improve the throughput of the network. For that purpose
we made some modifications in the virtual carrier sensing mechanism. We used a NAVR with NAV to make the VCS scheme suitable for our protocol. It make more nodes to send packets at a time and thus improves the spatial reusability.
The improvement in spatial reusability increases the aggregate throughput of the network.