General-rank transmit beamforming for multi-group multicasting networks using OSTBC

Law, Ka Lung; Wen, Xin; Pesavento, Marius

doi:10.1109/spawc.2013.6612095

Cited by 14 publications

(24 citation statements)

References 17 publications

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“…The well known randomization technique is then used to find a rank-1 approximation of the optimal general-rank matrices, that will satisfy all the constraints, whilst ensuring that (5b) is tight [15]. It should be noted that a general rank covariance matrix may be as well implemented via space-time-block coding schemes such as [17].…”

Section: Sdr For Minimum Rate Maximizationmentioning

confidence: 99%

Beamforming optimization with hybrid association in C-RANs under a limited backhaul

Zamani

Shojaee

Taghizadeh

et al. 2017

2017 International Symposium on Wireless Communication Systems (ISWCS)

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Abstract-With the densification of heterogeneous networks in terms of both users and base stations (BS) being identified as an integral part of future communication systems, the problem of association needs to be reconsidered since conventional schemes which are simply based on the received signal strength lead to small cells being idle. Coordinated multipoint (CoMP) techniques show great potential in improving the network performance, however, the gain of such cooperative solutions is bottlenecked by the backhaul. We present an approach for determining the beamforming in the downlink (DL) for all users, while making use of a hybrid association strategy that depends on both power and distance. Moreover, we make use of CoMP transmission as a tool for interference management and performance improvement, this can be especially beneficial for cell edge users suffering from high interference which is common in heterogeneous networks. An optimization problem is formulated that provides flexibility in declaring individual transmit power and backhaul constraints per BS and maximizes the weighted minimum user rate in order to promote fairness. As the optimization problem is nonconvex we employ semi-definite-relaxation to obtain a sub-optimal solution. Using simulations we evaluate the performance of the proposed strategy and the gain achieved in comparison to conventional schemes. A suggestion is made for the optimal cooperation level based on multiple performance criteria.

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Section: Sdr For Minimum Rate Maximizationmentioning

confidence: 99%

Beamforming optimization with hybrid association in C-RANs under a limited backhaul

Zamani

Shojaee

Taghizadeh

et al. 2017

2017 International Symposium on Wireless Communication Systems (ISWCS)

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“…Let denote an optimal solution of the relaxed optimization problem of (35) in which constraint (35c) is omitted. Then we can perform the phase rotation on according to (36) where the diagonal matrix is given by (37) Since satisfies all the constraints in (35), including constraint (35c), it is a feasible solution to the unrelaxed problem (35). As the total transmitted power associated with is the same as that associated with the optimal solution , we conclude that is an optimal solution to the original problem (35).…”

Section: A Phase Rotation Invariance Propertymentioning

confidence: 99%

“…In other words, relaxing the real-valued requirements expressed in constraints (35c) in the beamforming problem (35) results in an equivalent problem. An optimal solution for the original problem can always be computed from the solution of the relaxed problem by applying the phase rotation proposed in (36). Therefore, we can, without loss of generality, omit constraint (35c) when solving (35).…”

Section: A Phase Rotation Invariance Propertymentioning

confidence: 99%

“…A similar approach of rank-two beamforming is proposed for single-group multicasting using a relay network in [35]. The concept of rank-two beamforming has later been extended in [36] and [37] to solve the multi-group multicast beamforming problem in which beamforming is used to simultaneously deliver independent data services to users in predefined subscriber groups.…”

Section: Introductionmentioning

confidence: 99%

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General Rank Multiuser Downlink Beamforming With Shaping Constraints Using Real-Valued OSTBC

Law

Wen

et al. 2015

IEEE Trans. Signal Process.

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Abstract-In this paper we consider optimal multiuser downlink beamforming in the presence of a massive number of arbitrary quadratic shaping constraints. We combine beamforming with full-rate high dimensional real-valued orthogonal space time block coding (OSTBC) to increase the number of beamforming weight vectors and associated degrees of freedom in the beamformer design. The original multi-constraint beamforming problem is converted into a convex optimization problem using semidefinite relaxation (SDR) which can be solved efficiently. In contrast to conventional (rank-one) beamforming approaches in which an optimal beamforming solution can be obtained only when the SDR solution (after rank reduction) exhibits the rank-one property, in our approach optimality is guaranteed when a rank of eight is not exceeded. We show that our approach can incorporate up to 79 additional shaping constraints for which an optimal beamforming solution is guaranteed as compared to a maximum of two additional constraints that bound the conventional rank-one downlink beamforming designs. Simulation results demonstrate the flexibility of our proposed beamformer design.Index Terms-Downlink beamforming, shaping constraints, semidefinite relaxation (SDR), orthogonal space time block coding (OSTBC). I. INTRODUCTIONWith the massive growth of the number of wireless communication users and the increasing demands for high-rate services, the spectral resource is becoming more and more scarce. Research on spectrally efficient transmission schemes for current and next generation cellular networks that are capable of mitigating effects of multiuser and co-channel interference is attracting considerable interest [1]. As a spectrally efficient multi-antenna technique [2], downlink beamforming has been extensively studied in the past few years [3]- [8]. With the aid of channel state information (CSI) at the transmitter, downlink beamforming is employed at the base station of cellular networks to serve multiple co-channel users simultaneously using spatially selective transmission.As a pioneering work in downlink beamforming, the authors in [3] consider the problem of minimizing the total transmitted power subject to quality of service (QoS) constraints in the form of minimum signal to interference plus noise ratio (SINR) requirements at each user. A particular form of uplink-downlink duality theory is established in [3] and under this framework the downlink beamforming problem is solved

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“…Outer approximation techniques replace the QCQPs by convex semidefinite programs (SDPs) which can be solved efficiently [12]- [19]. In the latter approach, the weight vector is replaced by a positive semidefinite Hermitian matrix.…”

Section: Introductionmentioning

confidence: 99%

Rank-Two Beamforming and Power Allocation in Multicasting Relay Networks

Schad

Law

Pesavento

2015

IEEE Trans. Signal Process.

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Abstract-In this paper, we propose a novel single-group multicasting relay beamforming scheme. We assume a source that transmits common messages via multiple amplify-and-forward relays to multiple destinations. To increase the number of degrees of freedom in the beamforming design, the relays process two received signals jointly and transmit the Alamouti space-time block code over two different beams. Furthermore, in contrast to the existing relay multicasting scheme of the literature, we take into account the direct links from the source to the destinations. We aim to maximize the lowest received quality-of-service by choosing the proper relay weights and the ideal distribution of the power resources in the network. To solve the corresponding optimization problem, we propose an iterative algorithm which solves sequences of convex approximations of the original nonconvex optimization problem. Simulation results demonstrate significant performance improvements of the proposed methods as compared with the existing relay multicasting scheme of the literature and an algorithm based on the popular semidefinite relaxation technique.

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General-rank transmit beamforming for multi-group multicasting networks using OSTBC

Cited by 14 publications

References 17 publications

Beamforming optimization with hybrid association in C-RANs under a limited backhaul

Beamforming optimization with hybrid association in C-RANs under a limited backhaul

General Rank Multiuser Downlink Beamforming With Shaping Constraints Using Real-Valued OSTBC

Rank-Two Beamforming and Power Allocation in Multicasting Relay Networks

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