Feedback Allocation for OFDMA Systems With Slow Frequency-Domain Scheduling

Abstract

We study the problem of allocating limited feedback resources across multiple\nusers in an orthogonal-frequency-division-multiple-access downlink system with\nslow frequency-domain scheduling. Many flavors of slow frequency-domain\nscheduling (e.g., persistent scheduling, semi-persistent scheduling), that\nadapt user-sub-band assignments on a slower time-scale, are being considered in\nstandards such as 3GPP Long-Term Evolution. In this paper, we develop a\nfeedback allocation algorithm that operates in conjunction with any arbitrary\nslow frequency-domain scheduler with the goal of improving the throughput of\nthe system. Given a user-sub-band assignment chosen by the scheduler, the\nfeedback allocation algorithm involves solving a weighted sum-rate maximization\nat each (slow) scheduling instant. We first develop an optimal\ndynamic-programming-based algorithm to solve the feedback allocation problem\nwith pseudo-polynomial complexity in the number of users and in the total\nfeedback bit budget. We then propose two approximation algorithms with\ncomplexity further reduced, for scenarios where the problem exhibits additional\nstructure.\n