# A Joint Strategy for Fair and Efficient Energy Usage in WLANs in the Presence of Capture Effect
## 2 Related Works  
[PERSON] et al. [5] conducted an experimental study using PDA to analyze the power consumption in both PSM and CAM. Authors found that background traffic significantly deteriorates the performance of PSM. From the experiments they observed that PDA network interface changes from PSM to CAM as the traffic rate exceeds a certain limit. [PERSON] et al. [7] proposed a power saving strategy based on balancing the energy and delay metrics. Their proposed strategy suggests that AP should restrict the number of nodes in wakeup mode during the beacon interval to achieve better performance. However, their proposed strategy is not useful for CAM as there is no sleep mode in CAM. [PERSON] et al. [4] proposed analytic models to measure the energy consumption in a WLAN carrying TCP traffic. Authors also proposed the opportunistic power save mode (OPSM), according to which only one station downloads a file from an AP at any instant whereas all other stations wait for random durations of time to conserve energy [8]. [PERSON] et al. [9] proposed a transmission power control mechanism for the energy efficient operation of PCF. Their proposed mechanism, however, is not suitable for the DCF-based medium access control (MAC) protocol. [PERSON] et al. [10] conducted experiments on 802.11n testbed and found that PSM is largely ineffective for short inter-packet arrival times. The range of offered loads and traffic patterns used for the experiment show that the opportunity for the interfaces to go into sleep mode decreases. In [11] authors conducted extensive experiments and observed that PSM suffers significant increase in the energy consumption due to CAM traffic. Authors proposed network assisted power management (NAPman) energy-aware fair scheduler that aims to enhance energy efficiency in PSM clients without causing unfairness to the CAM clients. All the above literature reviewed either identify the shortcomings of the power saving mechanism of IEEE 802.11 or propose solution for the energy efficient operation of WLAN. However, these solutions are based on MAC and do not take the PHY characteristics into account. Unlike the above studies, some recent research works have explored the use of PHY capture effect to improve the throughput of WLAN. For example, in [6], authors performed experiments and showed that there exists capture effect on wireless interfaces. Moreover in [12; 13; 14], authors proposed models for the performance analysis of IEEE 802.11 WLAN in the presence of capture effect. Most fairness studies concerning energy issues in battery operated networks try to prolong the network lifetime and balance energy consumption. Fair energy consumption is mostly studied in ad hoc wireless local area network taking into account the routing protocols [15] or in sensor networks taking into account cross-layer design between MAC and network layer [16; 17; 18; 19]. The same amount of energy consumption amongst nodes is considered as the fairest case in these studies [20]. In [21], authors conducted a measurement study on device-to-device communication and found the unfair energy consumption between the two nodes, one of them being master and the other being slave. The authors further proposed the concept of fair role switching to maintain fairness among the nodes. In [22; 23] authors proposed adaptive transmission power control for senders in a wireless body area network (WBAN) based upon the received signal strength (RSSI) value that it receives from the base station. The authors in this work, however, ignored the unfairness in energy consumption among the group of WBAN nodes having higher RSSI compared to the group of WBAN nodes having lower RSSI. In [24], authors proposed a mechanism called a differentiated-received-power transmit power control (DRP-TPC) according to which a wireless node configures its transmission power based upon path-loss and distance from the access point. DRP-TPC increases the effect of capture at the receiver when simultaneous transmission are received at the receiver.