Trade-off between power consumption and delay in wireless packetized systems

Abstract

In packetized wireless systems, coding allows reliable transmission of multiple packets colliding at a receiver. Thus data may not need to incur delays such as those due to back-off schemes in traditional ALOHA systems. However, there is a trade-off between delay and power consumption. Recent work in this area has considered the case where multiple users are aware of the states of other users' queues. We consider a time-slotted multiple user system with random packet arrivals. The size of the packets and probability of arrival together represent the burstiness of the system. The time slots are considered to be long enough that capacity can be achieved over a single slot in a sense we define. We consider the difference in average power consumption when average delay, in terms of slots, is minimized, with and without knowledge of other users' queues. We also consider the case where average power is minimized without regard for delay. We present and analyze a simple scheme with limited information sharing about queues' states. Our scheme uses a hybrid multiple access/broadcast type code for the case of low queue lengths and a multiple access scheme in the case of large queue lengths. We show how this scheme allows trade-offs between power consumption and delay.