Optimal energy-efficient pair-wise cooperative transmission scheme for wimax mesh networks

Recently, there has been a steady trend toward the development of subscriber stations (SSs) to enable the ubiquitous communications. In the mobile environment, the power consumption of an SS is an important performance indicator because its battery life is limited. Many existing power-saving schemes for the IEEE 802.16e Mobile WiMax system have been proposed, such as scheduling algorithms for the sleep intervals. However, this type of approaches may be unrealistic for heavy network traffic since the SSs almost always have data to transmit. In this paper, we propose a new power-saving scheme by introducing the pair-wise matching procedure between the SSs prior to uplink data transmission in the WiMax mesh mode. According to the quality-of-service (QoS) requirement, we can preset the desired packet error rate (PER) or signal-to-interference-plus-noise-ratio (SINR) at the receiver end. Given the network topology and the channel state information, the required transmitting power per coded bit at each SS can be calculated. Then we may establish a cost function associated with the required transmitting power per coded bit and thus the optimal matching can be achieved by our proposed minimum weight matching algorithm. The numerical results show the significant improvement of the transmitting power consumption using our proposed method over the conventional scheme when we consider three aspects such as channel effects, coding/modulation options and network topology.