Low-Complexity Power-Efficient Schedulers for LTE Uplink with Delay-Sensitive Traffic

This paper investigates power-efficient scheduling for the uplink of Long-Term Evolution (LTE) systems. The aim is to minimize the total transmit power while satisfying particular delay requirements. The scheduling process is formulated as a dynamic programming problem. We show that the global optimal solution requires knowledge of future arrival rates and future channel gains for all users. Alternatively, we propose two low-complexity heuristic schedulers. The first heuristic scheduler controls the maximum allowable transmit power (MATP) for each user based on the queue length. In particular, if the queue length of a user is relatively small, the scheduler reduces the user's transmission rate and the MATP to minimize the total transmit power. On the other hand, when the queue length is large, the scheduler increases both the transmission rate and the MATP to satisfy the delay requirements. The second heuristic scheduler controls the minimum acceptable bit-per-Watt ratio (BPWR) for each user. Users can only transmit if their BPWRs are greater than an acceptable level, which allows only high power-efficient transmission. The minimum acceptable BPWR is adaptively changed based on the queue length of each user. The performance of the heuristic schedulers is evaluated and compared with the optimal solution and other existing schedulers.