Spectral Efficiency of Full-Duplex Multi-user System: Beamforming Design, User Grouping, and Time Allocation

et al. 2019

IEEE Trans. Commun.

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This paper investigates the coexistence of non-orthogonal multiple access (NOMA) and full-duplex (FD) to improve both spectral efficiency (SE) and user fairness. In such a scenario, NOMA based on the successive interference cancellation technique is simultaneously applied to both uplink (UL) and downlink (DL) transmissions in an FD system. We consider the problem of jointly optimizing user association (UA) and power control to maximize the overall SE, subject to user-specific quality-ofservice and total transmit power constraints. To be spectrally-efficient, we introduce the tensor model to optimize UL users' decoding order and DL users' clustering, which results in a mixed-integer nonconvex problem. For practically appealing applications, we first relax the binary variables and then propose two low-complexity designs. In the first design, the continuous relaxation problem is solved using the inner convex approximation framework. Next, we additionally introduce the penalty method to further accelerate the performance of the former design. For a benchmark, we develop an optimal solution based on brute-force search (BFS) over all possible cases of UAs. It is demonstrated in numerical results that the proposed algorithms outperform the conventional FD-based schemes and its half-duplex counterpart, as well as yield data rates close to those obtained by BFS-based algorithm. Index TermsFull-duplex radios, non-convex programming, non-orthogonal multiple access, self-interference, spectral efficiency, successive interference cancellation, user clustering.

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

IEEE Trans. Commun.

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“…To conduct a performance assessment, we examine the proposed algorithms (Algorithms 1, 2, and 3) and other three schemes: 1) An FD scheme with user grouping and fractional time (FD-UGFT) [20];…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Moreover, the FD system should achieve at least the same performance as HD counterpart even in unexpected conditions. In contrast with [15]- [20], this paper considers a small cell FD system, which is enabled with an HA antenna mode selection and two-phase transmission. In particular, the transmission time block is split into two phases, and for each phase, two HAs of the antennas at the FD-enabled BS can be independently selected for UL and DL transmissions.…”

mentioning

confidence: 99%

“…Secondly, HA antenna selection supports the BS in finding better channel conditions and enabling the hybrid transmission. Moreover, by a joint design of the HA antenna mode selection and the two-phase transmission, we can achieve a better system performance, with the harmful effects of residual SI and CCI significantly reduced when compared with a typical FD cellular network [17]- [20].…”

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confidence: 99%

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Joint Antenna Array Mode Selection and User Assignment for Full-Duplex MU-MISO Systems

IEEE Trans. Wireless Commun.

et al. 2019

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This paper considers a full-duplex (FD) multiuser multiple-input single-output system where a base station simultaneously serves both uplink (UL) and downlink (DL) users on the same time-frequency resource. The crucial barriers in implementing FD systems reside in the residual self-interference and cochannel interference. To accelerate the use of FD radio in future wireless networks, we aim at managing the network interference more effectively by jointly designing the selection of half-array antenna modes (in the transmit or receive mode) at the BS with time phases and user assignments. The first problem of interest is to maximize the overall sum rate subject to quality-of-service requirements, which is formulated as a highly non-concave utility function followed by non-convex constraints. To address the design problem, we propose an iterative low-complexity algorithm by developing new inner approximations, and its convergence to a stationary point is guaranteed. To provide more insights into the solution of the proposed design, a general max-min rate optimization is further considered to maximize the minimum per-user rate while satisfying a given ratio between UL and DL rates. Furthermore, a robust algorithm is devised to verify that the proposed scheme works well under channel uncertainty. Simulation results demonstrate that the proposed algorithms exhibit fast convergence and substantially outperform existing schemes. Index TermsFull-duplex radios, multiuser transmission, non-convex programming, robust design, self-interference, spectral efficiency, transmit beamforming, user assignment.Part of this work was presented at the IEEE Globecom 2017, Singapore [1]. I. INTRODUCTIONThe rapid growth of the demand for high data rate in the next-generation communication systems requires innovative technologies that make the maximal use of radio spectrum. Even though advanced techniques such as multiple-input multiple-output (MIMO) antennas have been implemented to improve network throughput [2], half-duplex (HD) systems, where uplink (UL) and downlink (DL) communications are carried out orthogonally in time domain or in frequency domain, may not be able to provide sufficient improvements in the spectral efficiency (SE). Full-duplex (FD) communications, which allow for simultaneous UL and DL transmissions in the same time-frequency resource, theoretically double the SE when compared to HD. As a result, FD communications have been recognized as a promising technology for the forthcoming 5G wireless networks [3]- [6].Although the potential gains of FD can be easily foreseen, its major drawback is self-interference (SI) from the transmit (Tx) to receive (Rx) antennas at an FD wireless transceiver (e.g., a base station (BS)), which is typically much stronger than the signal of interest. Recently, there have been many efforts to develop analog and digital SI cancellation techniques to bring the SI power at the noise level when the Tx power is relatively low [7]-[11]. Such results have spurred research at the system level, cons...

“…Since then, applying FD radio to a base station (BS) in small cell-based systems or to an access point in WiFi, in which the transmit power is relatively low, has been widely considered. FD for multiple-input multiple-output (MIMO) in single-cell systems has been investigated to achieve a higher spectral efficiency [9]- [11], and an extension to multi-cell scenarios has also been considered in [12]- [14]. Another downside of FD radio in a typical cellular network is that co-channel interference (CCI) caused by the UL transmission of UL users severely impairs the DL reception of DL users.…”

Section: Introductionmentioning

confidence: 99%

A New Design Paradigm for Secure Full-Duplex Multiuser Systems

IEEE J. Select. Areas Commun.

et al. 2018

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We consider a full-duplex (FD) multiuser system where an FD base station (BS) is designed to simultaneously serve both downlink (DL) and uplink (UL) users in the presence of half-duplex eavesdroppers (Eves). The problem is to maximize the minimum (max-min) secrecy rate (SR) among all legitimate users, where the information signals at the FD-BS are accompanied with artificial noise to debilitate the Eves' channels. To enhance the max-min SR, a major part of the power budget should be allocated to serve the users with poor channel qualities, such as those far from the FD-BS, undermining the SR for other users, and thus compromising the SR per-user. In addition, the main obstacle in designing an FD system is due to the selfinterference (SI) and co-channel interference (CCI) among users. We therefore propose an alternative solution, where the FD-BS uses a fraction of the time block to serve near DL users and far UL users, and the remaining fractional time to serve other users. The proposed scheme mitigates the harmful effects of SI, CCI and multiuser interference, and provides system robustness. The SR optimization problem has a highly nonconcave and nonsmooth objective, subject to nonconvex constraints. For the case of perfect channel state information (CSI), we develop a low-complexity path-following algorithm, which involves only a simple convex program of moderate dimension at each iteration. We show that our path-following algorithm guarantees convergence at least to a local optimum. Then, we extend the path-following algorithm to the cases of partially known Eves' CSI, where only statistics of CSI for the Eves are known, and worst-case scenario in which Eves can employ a more advanced linear decoder. The merit of our proposed approach is further demonstrated by extensive numerical results.