| 1. |
- Anchora, Luca, et al.
(författare)
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Capacity Gains due to Orthogonal Spectrum Sharing in Multi-Operator LTE Cellular Networks
- 2012
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Ingår i: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS). - 9781467307604 - 9781467307611 ; , s. 286-290
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Konferensbidrag (refereegranskat)abstract
- Static spectrum allocation leads to resource wastage and inter-operator spectrum sharing is a possible way to improve spectrum efficiency. In this work, we assume that two cellular network operators agree upon sharing part of their spectrum, which can then be dynamically accessed by either of them in a mutually exclusive way. Our goal is to numerically assess the gain, in terms of cell capacity, due to such orthogonal spectrum sharing. Hence, we propose a centralized algorithm that performs coordinated scheduling, in order to numerically evaluate an upper bound on the achievable sum capacity. The algorithm is centralized and exploits complete information on both networks to perform the optimum allocation. The simulation results illustrate the impact of the multiuser diversity and the asymmetry in the traffic load among the networks on the overall achievable gain.
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| 2. |
- Anchora, Luca, et al.
(författare)
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Resource Allocation and Management in Multi-Operator Cellular Networks with Shared Physical Resources
- 2012
-
Ingår i: Proceedings of the Ninth International Symposium on Wireless Communication Systems (ISWCS). - : IEEE. - 9781467307604 - 9781467307611 ; , s. 296-300
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Konferensbidrag (refereegranskat)abstract
- In this paper, we focus on next-generation cellular networks and discuss physical resources sharing among the operators. This implies cooperative usage of the available radio frequencies and also infrastructure sharing. In particular, we analyze the spectrum sharing gain achievable at different time scales and the main factors impacting on it. Then, we move towards a wider idea of resource sharing and consider a joint spectrum and infrastructure sharing (full sharing). We describe a two-layer resource management architecture that enables operators to reduce costs while still guaranteeing a good service level. The main findings of our investigations are to quantify the effectiveness of resource sharing and open up new perspectives for the operators of next-generation networks.
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| 3. |
- Auer, Gunther, et al.
(författare)
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Pilot Aided Channel Estimation for OFDM : A Separated Approach for Smoothing and Interpolation
- 2005
-
Ingår i: Proceedings of the 40th IEEE International Conference on Commununications (ICC). - 0780389387 ; , s. 2173-2178
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Konferensbidrag (refereegranskat)abstract
- In this paper pilot aided channel estimation (PACE) for OFDM is addressed. For PACE equidistantly spaced pilot symbols allow to reconstruct the channel response by means of interpolation. The optimum minimum mean squared error (MMSE) estimator performs smoothing and interpolation jointly. To reduce the complexity of the optimum MMSE estimator, we propose to separate the smoothing and interpolation tasks. The separated smoothing and interpolation estimator (SINE) consistsof a MMSE based smoother which only operates at the received pilot symbols, and an interpolator which is independent of the channel statistics. We show that the separated approach gets close to the optimum MMSE, while the complexity is grossly reduced. However, at high SNR an error floor is observed, which is caused by edge effects, i.e. subcarriers near the beginning and end of the band suffer from an increased interpolation error.
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| 4. |
- Ayanoglu, Ender, et al.
(författare)
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Computational Complexity of Decoding Orthogonal Space-Time Block Codes
- 2010
-
Ingår i: Proceedings of the IEEE International Conference on Communications (ICC). - 9781424464029 ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- The computational complexity of optimum decoding for an orthogonal space-time block code is quantified. Four equivalent techniques of optimum decoding which have the same computational complexity are specified. Modifications to the basic formulation in special cases are calculated and illustrated by means of examples.
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| 5. |
- Ayanoglu, Ender, et al.
(författare)
-
Computational Complexity of Decoding Orthogonal Space-Time Block Codes
- 2011
-
Ingår i: IEEE Transactions on Communications. - : IEEE Press. - 0090-6778 .- 1558-0857. ; 59:4, s. 936-941
-
Tidskriftsartikel (refereegranskat)abstract
- The computational complexity of optimum decoding for an orthogonal space-time block code {cal G}_N satisfying {cal G}_N^H{cal G}_N=c(∑_{k=1}^Kos_ko^2)I_N where c is a positive integer is quantified. Four equivalent techniques of optimum decoding which have the same computational complexity are specified. Modifications to the basic formulation in special cases are calculated and illustrated by means of examples. This paper corrects and extends and unifies them with the results from the literature. In addition, a number of results from the literature are extended to the case c>1.
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| 6. |
- Fathi, Mohammad, et al.
(författare)
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Distributed allocation of subcarrier, power and bit-level in multicell orthogonal frequency-division multiple-access networks
- 2014
-
Ingår i: IET COMMUNICATIONS. - : Institution of Engineering and Technology (IET). - 1751-8628 .- 1751-8636. ; 8:6, s. 781-788
-
Tidskriftsartikel (refereegranskat)abstract
- The downlink of multicell orthogonal frequency-division multiple-access (OFDMA) networks is studied, and the adaptive allocation of spectrum, power and rate is addressed. The authors consider networks with adaptive frequency reuse and discrete-level rates. Initially, the joint allocation problem is formulated as a centralised non-linear mixed-integer program (MIP), which is computationally intractable to solve optimally for practical problem sizes. Then, the capability of the receivers is exploited to estimate the subcarrier channel gains and the joint allocation problem is accordingly decomposed into subproblems, each of which is solved by a different base station with linear complexity. In the proposed iterative algorithm, the base stations perform rate and receiver allocation per subcarrier, with concurrent iterations. A filtering method is introduced to further decrease the algorithm complexity. Furthermore, for benchmarking purposes, the authors transform the original non-linear MIP to a linear MIP and find the optimal solution by means of standard branch-and-cut solvers. The merit of the proposed algorithm is demonstrated with numerical comparisons of its performance against the solutions of the linear MIP and the iterative waterfilling algorithm.
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| 7. |
- Fathi, Mohammad, et al.
(författare)
-
Distributed Resource Optimization in Multicell OFDMA Networks
- 2012
-
Ingår i: Proceedings of the IEEE Wireless Communications and Networking Conference (WCNC). - : IEEE. - 9781467304368 ; , s. 1316-1320
-
Konferensbidrag (refereegranskat)abstract
- We consider the joint allocation of receiver, bit, and power to subcarriers in the downlink of multicell orthogonal frequency-division multiple-access (OFDMA) networks. Assuming that the cells share the entire bandwidth and that the rates are discrete, we formulate the joint allocation problem as a nonlinear mixed integer program (MIP), which however has exponential worst-case complexity. We capitalize on the capability of the receivers to measure the interference-plus-noise on every subcarrier and decompose the joint problem into a set of smaller-scale linear MIPs solved by individual base stations. Accordingly, we propose a distributed algorithm with linear complexity, in which the base stations participate in the problem solution in a round-robin manner. Simulation results demonstrate the effectiveness of the proposed algorithm in comparison with the iterative waterfilling algorithm and the successive optimal solution, by means of standard branch-and-cut solvers, of the individual MIPs.
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| 8. |
- Gabry, Frédéric, et al.
(författare)
-
Secure Broadcasting in Cooperative Cognitive Radio Networks
- 2012
-
Ingår i: 2012 Future Network and Mobile Summit, FutureNetw 2012. - : IIMC. - 9781905824304
-
Konferensbidrag (refereegranskat)abstract
- This paper explores the trade-off between cooperation and secrecy in cognitive radio networks. We consider a scenario consisting of a primary and a secondary system. In the simplest case, each system is represented by a pair of transmitter and receiver. We assume a secrecy constraint on the transmission in the sense that the message of the primary transmitter has to be concealed from the secondary user. Both situations where the secondary transmitter is aware and unaware of the primary message are investigated and compared. Furthermore, we extend our results to the scenario where the secondary system comprises multiple users. For each case we sketch the derivation of the rates that are achievable from an information theoretic perspective. We then investigate the findings by numerical simulations. Our main result is that, in spite of the secrecy constraint, cooperation is beneficial in terms of the achievable rates. The secondary transmitter has the two contradicting tasks of helping the primary system and transmitting its own message. Our results show that both tasks can be accomplished simultaneously, improving both systems' performance. In particular, the secondary system can achieve a significant rate without decreasing the primary rate below the benchmark rate achievable without the help of the secondary transmitter. In the case of multiple secondary users, the rate region reduces, which results in a lower individual rate. However, the linear increase in sumrate counterbalances this effect.
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| 9. |
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| 10. |
- Garcia, Gabriel, 1985, et al.
(författare)
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Fast in-Band Position-Aided Beam Selection in Millimeter-Wave MIMO
- 2019
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 7, s. 142325-142338
-
Tidskriftsartikel (refereegranskat)abstract
- Millimeter-wave (mm-wave) and massive multiple-input-multiple-output technologies appear as key enablers in future emerging wireless communication systems. Propagation in mm-wave communications is well described by geometric channel models, where a clear relation between communication and positioning arises. On one hand, initial access, a procedure that precedes high data rate transmission and consists of beam selection and alignment between two devices, can benefit from position information. On the other hand, accurate positioning relies on high-quality communication links with proper beam alignment. This work analyzes the interplay between communication and positioning, proposes a new in-band position-aided beam selection protocol considering scenarios with line-of-sight and reflected paths, and possible beam alignment errors. Simulation results show significant reductions in latency with respect to standard beam selection protocols.
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| 11. |
- Garcia, Gabriel, 1985, et al.
(författare)
-
Transmitter Beam Selection in Millimeter-Wave MIMO with In-Band Position-Aiding
- 2018
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 17:9, s. 6082-6092
-
Tidskriftsartikel (refereegranskat)abstract
- Emerging wireless communication systems will be characterized by a tight coupling between communication and positioning. This is particularly apparent in millimeter-wave (mm-wave) communications, where devices use a large number of antennas, and the propagation is well described by geometric channel models. For mm-wave communications, initial access, consisting in the beam selection and alignment of two devices, is challenging and time consuming in the absence of location information. Conversely, accurate positioning relies on high-quality communication links with proper beam alignment. This paper studies this interaction and proposes a new position-aided transmitter beam selection protocol, which considers the problem of joint communication and positioning in scenarios with direct line-of-sight and scattering. Simulation results show significant reductions in latency with respect to a standard protocol.
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| 12. |
- Jorswieck, Eduard A., et al.
(författare)
-
Resource Sharing in Wireless Networks : The SAPHYRE Approach
- 2010
-
Ingår i: Proceedings of the Future Network and Mobile Summit Conference. - 9781905824168 ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- Physical resource sharing between wireless operators and service providers is necessary in order to support efficient, competitive, and innovative wireless communication markets. By sharing resources, such as spectrum or infrastructure, which are usually exclusively allocated interference is created on the physical layer. Therefore, the economic gains, regulatory overhead, and engineering efforts need to be addressed by a consolidated cross-layer approach. This paper describes briefly the approach taken by the EU FP7 project SAPHYRE.
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| 13. |
- Jorswieck, Eduard A., et al.
(författare)
-
Spectrum Sharing Improves the Network Efficiency for Cellular Operators
- 2014
-
Ingår i: IEEE Communications Magazine. - : IEEE Communications Society. - 0163-6804 .- 1558-1896. ; 52:3, s. 129-136
-
Tidskriftsartikel (refereegranskat)abstract
- The article describes the potential gain by spectrum sharing between cellular operators in terms of network efficiency. The focus of the study is on a specific resource sharing scenario: spectrum sharing between two operators in cellular downlink transmission. If frequency bands are allocated dynamically and exclusively to one operator - a case called orthogonal spectrum sharing - significant gains in terms of achievable throughput (spectrum sharing gains between 50 percent and 100 percent) and user satisfaction are reported for asymmetric scenarios at link and system level as well as from two hardware demonstrators. Additionally, if frequency bands are allocated simultaneously to two operators - a case called non-orthogonal spectrum sharing - further gains are reported. In order to achieve these, different enablers from hardware technologies and base station capabilities are required. However, we argue that all requirements are fulfilled in 3GPP and newer mobile standards. Therefore, the results and conclusions of this overview article encourage to seriously consider the inter-operator spectrum sharing technologies.
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| 14. |
- Karipidis, Eleftherios, et al.
(författare)
-
Capacity Statistics for Short DSL Loops from Measured 30 MHz Channel Data
- 2005
-
Ingår i: Proceedings of the 6th IEEE International Workshop on Signal Processing Advances for Wireless Communications (SPAWC). - 0780388674 ; , s. 174-178
-
Konferensbidrag (refereegranskat)abstract
- In recent years, there is growing interest in hybrid fiber-copper access solutions, as in fiber to the basement (FTTB) and fiber to the curb/cabinet (FTTC), combined with advanced vectored transmission modalities. The twisted pair segment in these architectures is in the range of a few hundred meters, thus supporting transmission over up to 30 MHz. In this paper, we assess the capacity potential of these very short loops using full-binder channel measurements collected by France Telecom R&D. Key statistics are provided for both uncoordinated and vectored transmission, and the vectoring benefit is evaluated. The results provide useful bounds for developers and providers alike.
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| 15. |
- Karipidis, Eleftherios, et al.
(författare)
-
Convex Transmit Beamforming for Downlink Multicasting to Multiple Co-Channel Groups
- 2006
-
Ingår i: Proceedings of the 31st IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - 142440469X ; , s. 973-976
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of transmit beamforming to multiple cochannel multicast groups. Since the direct minimization of transmit power while guaranteeing a prescribed minimum signal to interference plus noise ratio (SINR) at each receiver is nonconvex and NP-hard, we present convex SDP relaxations of this problem and study when such relaxations are tight. Our results show that when the steering vectors for all receivers are of Vandermonde type (such as in the case of a uniform linear array and line-of-sight propagation), a globally optimum solution to the corresponding transmit beamforming problem can be obtained via an equivalent SDP reformulation. We also present various robust formulations for the problem of single-group multicasting, when the steering vectors are only approximately known. Simulation results are presented to illustrate the effectiveness of our SDP relaxations and reformulations.
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| 16. |
- Karipidis, Eleftherios, et al.
(författare)
-
Crosstalk Models for Short VDSL2 Lines from Measured 30MHz Data
- 2006
-
Ingår i: EURASIP Journal on Applied Signal Processing. ; , s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, there has been a growing interest in hybrid fiber-copper access solutions, as in fiber to the basement (FTTB) and fiber to the curb/cabinet (FTTC). The twisted pair segment in these architectures is in the range of a few hundred meters, thus supporting transmission over tens of MHz. This paper provides crosstalk models derived from measured data for quad cable, lengths between 75 and 590 meters, and frequencies up to 30MHz. The results indicate that the log-normal statistical model (with a simple parametric law for the frequency-dependent mean) fits well up to 30MHz for both FEXT and NEXT. This extends earlier log-normal statistical modeling and validation results for NEXT over bandwidths in the order of a few MHz. The fitted crosstalk power spectra are useful for modem design and simulation. Insertion loss, phase, and impulse response duration characteristics of the direct channels are also provided.
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| 17. |
- Karipidis, Eleftherios, 1978-, et al.
(författare)
-
Efficient Computation of the Pareto Boundary for the MISO Interference Channel with Perfect CSI
- 2010
-
Ingår i: Proceedings of the International Symposium on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt). - 9781424475230 ; , s. 573-577
-
Konferensbidrag (refereegranskat)abstract
- We consider the two-user multiple-input single-output (MISO) interference channel and the rate region which is achieved when the receivers treat the interference as additive Gaussian noise and the transmitters have perfect channel state information (CSI). We propose a computationally efficient method for calculating the Pareto boundary of the rate region. We show that the problem of finding an arbitrary Pareto-optimal rate pair, along with its enabling beamforming vector pair, can be cast as a sequence of second-order cone programming (SOCP) feasibility problems. The SOCP problems are convex and they are solved very efficiently using standard off-the-shelf (namely, interior-point) algorithms. The number of SOCP problems that must be solved, for the computation of a Pareto-optimal point, grows only logarithmically with the desired accuracy of the solution.
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| 18. |
- Karipidis, Eleftherios, et al.
(författare)
-
Experimental Evaluation of Capacity Statistics for Short VDSL Loops
- 2005
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 53:7, s. 1119-1122
-
Tidskriftsartikel (refereegranskat)abstract
- We assess the capacity potential of very short very-high data-rate digital subscriber line loops using full-binder channel measurements collected by France Telecom R&D. Key statistics are provided for both uncoordinated and vectored systems employing coordinated transmitters and coordinated receivers. The vectoring benefit is evaluated under the assumption of transmit precompensation for the elimination of self-far-end crosstalk, and echo cancellation of self-near-end crosstalk. The results provide useful bounds for developers and providers alike.
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| 19. |
- Karipidis, Eleftherios, et al.
(författare)
-
Far-Field Multicast Beamforming for Uniform Linear Antenna Arrays
- 2007
-
Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 55:10, s. 4916-4927
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of transmit beamforming to multiple cochannel multicast groups is considered for the important special case when the channel vectors are Vandermonde. This arises when a uniform linear antenna antenna (ULA) array is used at the transmitter under far-field line-of-sight propagation conditions, as provisioned in 802.16e and related wireless backhaul scenarios. Two design approaches are pursued: (i) minimizing the total transmitted power subject to providing at least a prescribed received signal-to-interference-plus-noise-ratio (SINR) to each intended receiver; and (ii) maximizing the minimum received SINR under a total transmit power budget. Whereas these problems have been recently shown to be NP-hard, in general, it is proven here that for Vandermonde channel vectors, it is possible to recast the optimization in terms of the autocorrelation sequences of the sought beam vectors, yielding an equivalent convex reformulation. This affords efficient optimal solution using modern interior point methods. The optimal beam vectors can then be recovered using spectral factorization. Robust extensions for the case of partial channel state information, where the direction of each receiver is known to lie in an interval, are also developed. Interestingly, these also admit convex reformulation. The various optimal designs are illustrated and contrasted in a suite of pertinent numerical experiments.
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| 20. |
- Karipidis, Eleftherios, et al.
(författare)
-
Joint QoS Multicast Power / Admission Control and Base Station Assignment : A Geometric Programming Approach
- 2008
-
Ingår i: Proceedings of the 5th IEEE Workshop on Sensor Array and Multi-Channel Signal Processing (SAM). - 9781424422401 ; , s. 155-159
-
Konferensbidrag (refereegranskat)abstract
- The joint power control and base station (BS) assignment problem is considered under Quality-of-Service (QoS) constraints. If a feasible solution exists, the problem can be efficiently solved using existing distributed algorithms. Infeasibility is often encountered in practice, however, which brings up the issue of optimal admission control. The joint problem is NP-hard, yet important for QoS provisioning and bandwidth-efficient operation of existing and emerging cellular and overlay/underlay networks. Recognizing this, there have been several attempts to develop reasonable heuristics for joint admission and power control. This contribution takes a more disciplined approach. The joint problem is first concisely formulated as a constrained optimization problem, whose objective combines the BS assignment, admission, and power control components. The formulation also allows for multicasting. A geometric programming approximation is then developed, which forms the core of a heuristic, yet well-motivated centralized algorithm that generates approximate solutions to the original NP-hard problem. Numerical results against an enumeration baseline illustrate the merits of the approach.
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| 21. |
- Karipidis, Eleftherios, et al.
(författare)
-
Max-Min Power Control in Wireless Networks With Successive Interference Cancelation
- 2015
-
Ingår i: IEEE Transactions on Wireless Communications. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1536-1276 .- 1558-2248. ; 14:11, s. 6269-6282
-
Tidskriftsartikel (refereegranskat)abstract
- We consider a wireless network comprising a number of cochannel (hence mutually interfering) links. We study the power control problem of maximizing the rate that all links can simultaneously support under a novel setup, where receivers have interference cancelation (IC) capabilities. The problem of allocating the transmitting power is intertwined with determining the links on which receivers can perform IC and the order of cancelations. We provide and prove the theoretical results of the problem complexity and structural properties. For the problem solution, we propose a mixed-integer linear programming framework that enables jointly determining the optimal power and the IC patterns using off-the-shelf algorithms. This allows for the accurate assessment of the potential of IC for power control. Extensive numerical results are presented for performance evaluation, demonstrating the benefit of deploying IC in power control.
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| 22. |
- Karipidis, Eleftherios, et al.
(författare)
-
Mixed-Integer Linear Programming Framework for Max-Min Power Control with Single-Stage Interference Cancellation
- 2011
-
Ingår i: Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). - : IEEE conference proceedings. - 9781457705373 ; , s. 3448-3451
-
Konferensbidrag (refereegranskat)abstract
- We consider a wireless network comprising a number of mutually-interfering links. We study the transmit power control problem that determines the egalitarian signal-to-interference-plus-noise ratio under a novel setup. Namely, we assume that the receivers have multiuser detection capability, which enables decoding and cancellation of the interference, when it is strong enough. Determining the interference terms that can be cancelled is a combinatorial problem, which is intertwined with the power control problem. We propose a mixed-integer linear programming framework that jointly solves these problems optimally, using off-the-shelf algorithms. We illustrate with a simulation result the merit of the novel approach against the conventional one that precludes interference cancellation.
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| 23. |
- Karipidis, Eleftherios, et al.
(författare)
-
Optimal Scheduling and QoS Power Control for Cognitive Underlay Networks
- 2009
-
Ingår i: Proceedings of the 3rd IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'09). - : IEEE. - 9781424451807 ; , s. 408-411
-
Konferensbidrag (refereegranskat)abstract
- We study the NP-hard problem of scheduling andpower control with quality-of-service (QoS) constraints. We consider a generic wireless network comprising K mutually interfering links and N < K orthogonal time or frequency slots. We formulate the joint resource allocation problem as a constrained optimization problem, specifically, as a mixed integer programming (MIP) problem. This enables us to solve the problem exactly, and relatively efficiently for the vast majority of instances, using off-the-shelf algorithms. We also apply our formulation to the paradigm of cognitive underlay networks.
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| 24. |
- Karipidis, Eleftherios, et al.
(författare)
-
Pareto-optimal Beamforming for the MISO Interference Channel with Partial CSI
- 2009
-
Ingår i: Proceedings of the 3rd IEEE International Workshop on Computational Advances in Multi-Sensor Adaptive Processing (CAMSAP'09). - 9781424451807 ; , s. 5-8
-
Konferensbidrag (refereegranskat)abstract
- We consider the problem of finding Pareto-optimal (PO) operating points for the multiple-input single-output (MISO) interference channel when the transmitters have statistical (covariance) channel knowledge. We devise a computationally efficient algorithm, based on semidefinite relaxation, to compute the PO rates and the enabling beamforming vectors. We illustrate the effectiveness of our algorithm by a numerical example.
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| 25. |
- Karipidis, Eleftherios, et al.
(författare)
-
Quality of Service and Max-Min Fair Transmit Beamforming to Multiple Cochannel Multicast Groups
- 2008
-
Ingår i: IEEE Transactions on Signal Processing. - 1053-587X .- 1941-0476. ; 56:3, s. 1268-1279
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of transmit beamforming to multiple cochannel multicast groups is considered, when the channel state is known at the transmitter and from two viewpoints: minimizing total transmission power while guaranteeing a prescribed minimum signal-to-interference-plus-noise ratio (SINR) at each receiver; and a "fair" approach maximizing the overall minimum SINR under a total power budget. The core problem is a multicast generalization of the multiuser downlink beamforming problem; the difference is that each transmitted stream is directed to multiple receivers, each with its own channel. Such generalization is relevant and timely, e.g., in the context of the emerging WiMAX and UMTS-LTE wireless networks. The joint problem also contains single-group multicast beamforming as a special case. The latter (and therefore also the former) is NP-hard. This motivates the pursuit of computationally efficient quasi-optimal solutions. It is shown that Lagrangian relaxation coupled with suitable randomization/cochannel multicast power control yield computationally efficient high-quality approximate solutions. For a significant fraction of problem instances, the solutions generated this way are exactly optimal. Extensive numerical results using both simulated and measured wireless channels are presented to corroborate our main findings.
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