Power control and time division: the CDMA versus TDMA question

For wireless networks, time division multiple access (TDMA) offers certain well-known advantages over methods such as spread spectrum code division (CDMA). Foremost among them is the guarantee that other users will not interfere during a node's dedicated time slots. For this desirable isolation, the cost is synchronization. Viewing arbitrary time intervals as potential TDMA time slots, we ask whether it is possible to obtain some of the benefit of time division without incurring the synchronization cost. In particular, we address the question of whether a TDMA-like state can be induced on asynchronous channels in such a way as to reduce interference and energy consumption. Through analysis and simulation we find conditions under which it is desirable to use time division. We then show how autonomous power management may be used as a mechanism to induce a form of time division. In this context a backlog-sensitive power management system is presented.