Daji Qiao Sunghyun Choi Amjad Soomro Kang G. Shin Energy-efficient PCF operation of IEEE 802.11a WLANs via transmit power control. 39-54 2003 42 Computer Networks 1 http://dx.doi.org/10.1016/S1389-1286(02)00440-1 db/journals/cn/cn42.html#QiaoCSS03