Resource Allocation for Power Minimization in the Downlink of THP-based Spatial Multiplexing MIMO-OFDMA Systems

In this work, we deal with resource allocation in the downlink of spatial multiplexing MIMO-OFDMA systems. In particular, we concentrate on the problem of jointly optimizing the transmit and receive processing matrices, the channel assignment and the power allocation with the objective of minimizing the total power consumption while satisfying different quality-of-service requirements. A layered architecture is used in which users are first partitioned in different groups on the basis of their channel quality and then channel assignment and transceiver design are sequentially addressed starting from the group of users with most adverse channel conditions. The multi-user interference among users belonging to different groups is removed at the base station using a Tomlinson-Harashima pre-coder operating at user level. Numerical results are used to highlight the effectiveness of the proposed solution and to make comparisons with existing alternatives.Comment: 12 pages, 6 figures, IEEE Trans. Veh. Techno

Multicast Scheduling and Resource Allocation Algorithms for OFDMA-Based Systems: A Survey

Multicasting is emerging as an enabling technology for multimedia transmissions over wireless networks to support several groups of users with flexible quality of service (QoS)requirements. Although multicast has huge potential to push the limits of next generation communication systems; it is however one of the most challenging issues currently being addressed. In this survey, we explain multicast group formation and various forms of group rate determination approaches. We also provide a systematic review of recent channel-aware multicast scheduling and resource allocation (MSRA) techniques proposed for downlink multicast services in OFDMA based systems. We study these enabling algorithms, evaluate their core characteristics, limitations and classify them using multidimensional matrix. We cohesively review the algorithms in terms of their throughput maximization, fairness considerations, performance complexities, multi-antenna support, optimality and simplifying assumptions. We discuss existing standards employing multicasting and further highlight some potential research opportunities in multicast systems

Precoder design for multi-antenna transmission in MU-MIMO with QoS requirements

Abstract. A multiple-input multiple-output (MIMO) interference broadcast channel (IBC) channel is considered. There are several base stations (BSs) transmitting useful information to their own users and unwanted interference to its neighboring BS users. Our main interest is to maximize the system throughput by designing transmit precoders with weighted sum rate maximization (WSRM) objective for a multi-user (MU)-MIMO transmission. In addition, we include the quality of service (QoS) requirement in terms of guaranteed minimum rate for the users in the system. Unfortunately, the problem considered is nonconvex and known to be non-deterministic polynomial (NP) hard. Therefore, to determine the transmit precoders, we first propose a centralized precoder design by considering two closely related approaches, namely, direct signal-to-interference-plus-noise-ratio (SINR) relaxation via sequential parametric convex approximation (SPCA), and mean squared error (MSE) reformulation. In both approaches, we adopt successive convex approximation (SCA) technique to solve the nonconvex optimization problem by solving a sequence of convex subproblems. Due to the huge signaling requirements in the centralized design, we propose two different distributed precoder designs, wherein each BS determines only the relevant set of transmit precoders by exchanging minimal information among the coordinating BSs. Initially, we consider designing precoders in a decentralized manner by using alternating directions method of multipliers (ADMM), wherein each BS relaxes inter-cell interference as an optimization variable by including it in the objective. Then, we also propose a distributed precoder design by solving the Karush-Kuhn-Tucker (KKT) expressions corresponding to the centralized problems. Numerical simulations are provided to compare different system configurations with QoS constraints for both centralized and distributed algorithms