Precoder Design for Signal Superposition in MIMO-NOMA Multicell Networks

Abstract

Abstract-The throughput of users with poor channel conditions, such as those at a cell edge, is a bottleneck in wireless systems. A major part of the power budget must be allocated to serve these users in guaranteeing their quality-of-service (QoS) requirement, hampering QoS for other users and thus compromising the system reliability. In nonorthogonal multiple access (NOMA), the message intended for a user with a poor channel condition is decoded by itself and by another user with a better channel condition. The message intended for the latter is then successively decoded by itself after canceling the interference of the former. The overall information throughput is thus improved by this particular successive decoding and interference cancellation. This paper aims to design linear precoders/beamformers for signal superposition at the base stations of NOMA multi-input multi-output multi-cellular systems to maximize the overall sum throughput subject to the users' QoS requirements, which are imposed independently on the users' channel condition. This design problem is formulated as the maximization of a highly nonlinear and nonsmooth function subject to nonconvex constraints, which is very computationally challenging. Path-following algorithms for its solution, which invoke only a simple convex problem of moderate dimension at each iteration are developed. Generating a sequence of improved points, these algorithms converge at least to a local optimum. Extensive numerical simulations are then provided to demonstrate their merit.Index Terms-Multi-user interference system, multiinput multi-output (MIMO), nonorthogonal multiple access (NOMA), nonconvex optimization, quality-of-service (QoS), successive interference cancellation (SIC), signal superposition.

Joint Power Control and User Association for NOMA-Based Full-Duplex Systems

“…In these works, a joint power and user clustering (i.e., users with distinct channel conditions are grouped to perform NOMA jointly) has not been reported yet. Although the works in [31] and [32] proposed a two-zone pairing that randomly pairs two UEs from different zones, the use of random user pairing scheme may cause significant performance loss, compared to the optimal one. The authors in [9] studied a multi-zone based clustering, where the BS randomly selects one UE from each zone to form a cluster, leading to a suboptimal solution.…”

“…Remark 2: As pointed out in [32], a larger cluster size with more distinct channel conditions among DL users is more desirable. This is because a large size of a DL cluster with very different channel gains plays a vital role in NOMA systems.…”

“…can successfully decode the U d 2j 's message by SIC [28], [32]. Toward this end, we consider the following modified problem of (9)…”

Uplink Nonorthogonal Multiple Access Technologies Toward 5G: A Survey

“…Furthermore, NOMA can be jointly designed with cooperative multiple point (CoMP) [9,109,110] or multipleantenna technology [41,[111][112][113]. Also, there have been some initial studies about employing NOMA in wireless power transfer network to increase the access opportunities [114][115][116].…”

Reconsidering Design of Multi-Antenna NOMA Systems With Limited Feedback

“…It was noted in [9] that all existing works on multi-antenna NOMA systems can be classified into two categories: 1) there is a cluster of multiple users supported by each channel spatial dimension (or by a beamforming (BF) vector) in average that perform NOMA independently with the other clusters [9][10][11][12][13][14][15], and 2) there is only one user supported by each channel spatial dimension in average 1 [16,17]. For the first category, [2] proposed a BF-based NOMA scheme, where a user clustering and power allocation algorithm was proposed to reduce the inter-cluster and intra-cluster interference.…”