Optimal QoS-Constrained Resource Allocation in Downlink and Uplink Multicarrier Systems

When formulated as constrained optimizations of various kinds, resource allocation (RA) in wireless communication systems involves practically not only continuous variables such as transmit power, but also discrete variables such as modulation formats and coding rates. Multicarrier systems with frequency division multiple access (FDMA), e.g., OFDMA, require exclusive usage of their subcarriers (or subchannels) by a single user during a certain time unit, and therefore render the assignment of subcarriers a combinatorial problem which is a crucial part of RA. In this paper, we formulate the quality of service (QoS) constrained RA problems in multicarrier systems as optimizations over a finite set of available modes of operations (MOP) and employ integer programming techniques to solve them. Specifically, optimal algorithms are developed based on the branch and bound (BAB) and the branch and price (BAP) methods for three types of RA problems: the downlink transmit power minimization, the uplink sum transmit power minimization, and the downlink transmit power constrained energy minimization. Besides justifying the optimality of these algorithms, simulation results also provide performance comparisons on ARQ and HARQ protocols which serve as an application example of the algorithms proposed, i.e., providing comparison benchmark for different system, protocol, or suboptimal algorithm design.