Transceiver Design for Nonconcurrent Two-Way MIMO AF Relaying with QoS Guarantees
TL;DR: A MIMO AF transceiver that maximizes weighted sum-rate (WSR) while guaranteeing the QoS constraints that are cast as per-stream rate required by two ncTWR users is designed.
Abstract: We consider a cellular system with amplify-and-forward (AF) nonconcurrent two-way relaying (ncTWR), where a base station serves a transmit-only user and a receive-only user. Most of the state-of-the-art transceiver designs for AF multiple-input multiple-output (MIMO) ncTWR optimize a system-wide objective function subject to the transmit power constraints. Transceiver designs that incorporate quality-of-service (QoS) constraints are not well investigated in ncTWR literature. In this paper, we design a MIMO AF transceiver that maximizes weighted sum-rate (WSR) while guaranteeing the QoS constraints that are cast as per-stream rate required by two ncTWR users. The WSR maximization is a nonconvex problem due to its nonconvex objective. We solve this problem by separately approximating the objective at low and high signal-to-noise ratios (SNRs), with each approximation cast as a geometric program. With extensive numerical evaluations, we first demonstrate the improved performance of the proposed transceiver over existing designs without QoS constraints. We later investigate the effect of QoS constraints on the system WSR.
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TL;DR: This work investigates a novel multiple-input multiple-output common transceiver design for conventional symmetric and recently proposed asymmetric two-way relaying and demonstrates that the sum-rate of the proposed design not only matches the best known designs in asymmetric and symmetric TWR literature, but also outperforms them for certain antenna configurations.
Abstract: We investigate a novel multiple-input multiple-output common transceiver design for conventional symmetric and recently proposed asymmetric two-way relaying (TWR). In conventional symmetric TWR, a user exchanges data with a base station. Both base station and user can cancel back-propagating interference (BI). In asymmetric TWR, the base station performs TWR with two different users—a transmit-only user and a receive-only user, which experiences BI. The existing asymmetric TWR transceiver designs constraints the number of relay antennas to cancel the BI. The proposed transceiver relaxes these antenna constraints and works seamlessly for both asymmetric and symmetric TWR. Furthermore, the design also enables TWR communication between multiple users and a base station. The proposed design is also shown to have lower complexity than the existing designs. For the proposed transceiver, we maximize its sum rate using geometric programming for different TWR scenarios. We demonstrate using exhaustive numerical simulations that the sum-rate of the proposed design not only matches the best known designs in asymmetric and symmetric TWR literature, but also outperforms them for certain antenna configurations.
3 citations
Cites background from "Transceiver Design for Nonconcurren..."
...The proposed transceiver, in contrast, works for Nr < 2Nu antennas and therefore has relaxed antenna constraints than the designs in [15], [16]....
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...ATWR transceivers in [15], [16], as mentioned before, require Nr ≥ 2Nu antennas to cancel RUE’s BI....
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...Transceiver designed in [15], [16] impose the condition that the number of relay antennas Nr ≥ 2Nu , where Nu is the number of user antennas....
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...3) We also show that the proposed design has significantly lower computational complexity than the designs in [15], [16]....
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...References [15], [16] assume that the RUE cannot overhear the TUE and designed transceivers to cancel the BI and optimize quality-of-service constrained sum-rate in [15] and sum-rate alone in [16]....
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TL;DR: The proposed precoder is designed such that it not only cancels the BI experienced by the RUE but also enables receive data decoding with high diversity, and has lower bit error rate than the existing state-of-the-art ncTWR designs.
Abstract: We design a precoder for non-concurrent two-way relaying (ncTWR) where a base station (BS) serves a transmit-only user equipment (TUE) in the uplink and a receive-only user equipment (RUE) in the downlink. The RUE experiences back-propagating interference (BI). The proposed precoder is designed such that it not only cancels the BI experienced by the RUE but more importantly, enables receive data decoding with high diversity. The high diversity precoder is designed by deriving the closed-form pairwise error probability (PEP) expressions, and by optimizing the precoder elements to minimize the PEP. We analytically show that with $N_{r}$ -antenna relay, $N_{b}$ -antenna BS, and $N_{u}$ -antenna TUE and RUE, both BS and RUE decode their respective data with a diversity order of $\min (N_{u}^{2},(N_{r}-N_{u})N_{b})$ at high receive signal-to-noise ratio. We also numerically show that the proposed design has lower bit error rate than the existing state-of-the-art ncTWR designs.
3 citations
TL;DR: Numerical results demonstrate that the proposed decoupled beamforming scheme outperforms the existing works in terms of the SR and the computational complexity with satisfactory convergence.
Abstract: This paper investigates decoupled beamforming techniques for the distributed multi-input multi-output (MIMO) two-way relay networks (TWRN) with imperfect channel state informations (CSIs). The objective of this paper is to maximize the weighted sum rate (SR) with semi-infinite relay power constraints. Since the objective problem is difficult to be solved directly, considering the high signal-to-residual-interference-plus-noise ratio (SRINR) and employing the Cauchy-Schwarz inequality and S-lemma, the problem can be approximately converted into a source beamforming decoupled one. In addition, with the optimal relay beamforming design and maximum ratio combining (MRC) at the receiver, the MIMO channels are decoupled into parallel single-input single-output (SISO) channels. By this way, the suboptimal relay beamforming matrix can be efficiently obtained with minimal relay power constraint. Specifically, the semi-infinite constraints can be reformulated into a linear matrix inequality (LMI), which can be efficiently solved by using an alternating optimization algorithm. Numerical results demonstrate that our proposed decoupled beamforming scheme outperforms the existing works in terms of the SR and the computational complexity with satisfactory convergence.
2 citations
TL;DR: This work proposes a convergent iterative method for joint channel estimation and symbol detection with CC proportional to the block length, and addresses the convergence proof.
Abstract: We investigate a partially blind channel estimation and symbol detection in an amplify-and-forward two way relay scheme. We derive generalized likelihood ratio test detectors for reciprocal and non-reciprocal channels, whose computational complexity (CC) grow exponentially with the block length. Therefore, we propose a convergent iterative method for joint channel estimation and symbol detection with CC proportional to the block length. We also address the convergence proof. We further propose the simple blind and partially-blind approaches based on least squares (LS) and weighted LS estimation, respectively, for operation at low SNRs and analyze their mean square errors (MSE). Our simulations reveal the effectiveness of the proposed method compared with its counterparts.
1 citations
Cites background from "Transceiver Design for Nonconcurren..."
...Many studies assume that perfect channel state information (CSI) is available at the receiver [8]–[10]....
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TL;DR: The results show us that the proposed beamforming method outperforms the conventional schemes and can also effectively reduce the computational complexity when it is compared to the cutting-set schemes and also to the nonrobust ones.
Abstract: A generalized base station-relay-user equipment (BS-Relay-UE) beamforming design is investigated for a cooperative multiple-input multiple-output (MIMO) multirelay networks with imperfect channel state information (CSI). In order to minimize the worst-case mean square error (MSE) which is subject to a semi-infinite (SI) relay power constraints, a generalized optimal beamforming structure for the relay amplifying matrix is effectively proposed, and then the SI relay power constraints are converted into linear matrix inequalities (LMIs) version. In such conversion, the objective problem recasts as a decoupled biconvex semidefinite programming (SDP) one which can be efficiently solved by the proposed alternating algorithm. The system performance has been verified in terms of worst-case MSE using a set of qualitative analyses. The results show us that the proposed beamforming method outperforms the conventional schemes and can also effectively reduce the computational complexity when it is compared to the cutting-set schemes and also to the nonrobust ones.
1 citations
References
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TL;DR: A potential cellular architecture that separates indoor and outdoor scenarios is proposed, and various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications are discussed.
Abstract: The fourth generation wireless communication systems have been deployed or are soon to be deployed in many countries. However, with an explosion of wireless mobile devices and services, there are still some challenges that cannot be accommodated even by 4G, such as the spectrum crisis and high energy consumption. Wireless system designers have been facing the continuously increasing demand for high data rates and mobility required by new wireless applications and therefore have started research on fifth generation wireless systems that are expected to be deployed beyond 2020. In this article, we propose a potential cellular architecture that separates indoor and outdoor scenarios, and discuss various promising technologies for 5G wireless communication systems, such as massive MIMO, energy-efficient communications, cognitive radio networks, and visible light communications. Future challenges facing these potential technologies are also discussed.
2,048 citations
"Transceiver Design for Nonconcurren..." refers background in this paper
...Further, mobile femtocells that combine the concepts of a relay and a femtocell [29], and are being investigated for next-generation systems, can also have a large number of relay antennas....
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TL;DR: An overview of important topics and applications in the context of relaying covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks and solutions to combat shadowing at high radio frequencies.
Abstract: In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and converge extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to the working group 4 of the wireless world research forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.
1,907 citations
Book•
01 Jan 2009
1,040 citations
"Transceiver Design for Nonconcurren..." refers methods in this paper
...For example, an user RUE could concurrently be chatting using VoIP and downloading a file using FTP—two services with different QoS requirements [24]....
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...The SRS are commonly used in current cellular systems for channel acquisition [24]....
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TL;DR: The problem of designing jointly optimum linear precoder and decoder for a MIMO channel possibly with delay-spread, using a weighted minimum mean-squared error criterion subject to a transmit power constraint is addressed.
Abstract: We address the problem of designing jointly optimum linear precoder and decoder for a MIMO channel possibly with delay-spread, using a weighted minimum mean-squared error (MMSE) criterion subject to a transmit power constraint. We show that the optimum linear precoder and decoder diagonalize the MIMO channel into eigen subchannels, for any set of error weights. Furthermore, we derive the optimum linear precoder and decoder as functions of the error weights and consider specialized designs based on specific choices of error weights. We show how to obtain: (1) the maximum information rate design; (2) QoS-based design (we show how to achieve any set of relative SNRs across the subchannels); and (3) the (unweighted) MMSE and equal-error design for fixed rate systems.
916 citations
"Transceiver Design for Nonconcurren..." refers methods in this paper
..., for single-hop MIMO systems in [36] and [37], as well as for conventional one-/twoway MIMO relaying systems in [23], [38], and [39]....
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TL;DR: This work presents a systematic method of distributed algorithms for power control that is geometric-programming-based and shows that in the high Signal-to- interference Ratios (SIR) regime, these nonlinear and apparently difficult, nonconvex optimization problems can be transformed into convex optimized problems in the form of geometric programming.
Abstract: In wireless cellular or ad hoc networks where Quality of Service (QoS) is interference-limited, a variety of power control problems can be formulated as nonlinear optimization with a system-wide objective, e.g., maximizing the total system throughput or the worst user throughput, subject to QoS constraints from individual users, e.g., on data rate, delay, and outage probability. We show that in the high Signal-to- interference Ratios (SIR) regime, these nonlinear and apparently difficult, nonconvex optimization problems can be transformed into convex optimization problems in the form of geometric programming; hence they can be very efficiently solved for global optimality even with a large number of users. In the medium to low SIR regime, some of these constrained nonlinear optimization of power control cannot be turned into tractable convex formulations, but a heuristic can be used to compute in most cases the optimal solution by solving a series of geometric programs through the approach of successive convex approximation. While efficient and robust algorithms have been extensively studied for centralized solutions of geometric programs, distributed algorithms have not been explored before. We present a systematic method of distributed algorithms for power control that is geometric-programming-based. These techniques for power control, together with their implications to admission control and pricing in wireless networks, are illustrated through several numerical examples.
906 citations
Additional excerpts
...The algorithm is provably convergent [35], and we later show that the proposed algorithm (nearly) achieves the global optimum....
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