Cooperative MS-grouping schemes based on three cost metrics for improving battery lifetime and energy efficiency

In this paper, we propose a mobile grouping procedure to cooperate, and propose three different cost metrics for grouping: the remaining battery energy, WLAN physical (PHY) data-rate, and the number of MSs in the expected cooperation group. Moreover, we propose three cooperative MS-grouping schemes based on the above three metrics in order to extend the battery lifetime of MSs with both WLAN and Bluetooth interfaces and to increase energy efficiency. When the data rate is low, the proposed cooperative MS-grouping scheme based on the number of MSs in the expected cooperative group can maximize the average battery lifetime and energy efficiency. However, when the data rate is high, the proposed cooperative MS-grouping scheme based on the available PHY data-rate in WLAN channel outperforms the other two cost metrics based schemes. Furthermore, we obtain a threshold which determines whether the MS should cooperate or not. The threshold is the number of cooperative MSs in the WLAN access point (AP) coverage. If the number of cooperative MSs in the WLAN AP coverage is larger than the threshold, the cooperative grouping schemes become more energy-efficient. Otherwise, the non-cooperation mode is more energy-efficient. Moreover, these cooperation schemes are more energy-efficient in low mobility regime.