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  • 151.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Characterization of outage performance for cognitive relay networks with mixed fading2014In: Forty-Eight Asilomar Conference on Signal, Systems and Computers: November 2-5 2014, IEEE conference proceedings, 2014, p. 84-84Conference paper (Refereed)
    Abstract [en]

    We consider a dual-hop underlay cognitive radio network with a single transceiver pair, which utilizes an amplify-and-forwardrelay to establish end-to-end communication. The secondary nodes, i.e., the transmitter and the relay, obey transmit power constraints which guarantee that the instantaneous peak interference at the primary receiver will not exceed a certain threshold. Each of the secondary communication links contains a line-of-sight component whereas the external links, to the primary receiver, are subject to Rayleigh fading. For this system model, we analyze the outage probability and demonstrate the accuracy of the obtained mathematical expressions via numerical simulations.

  • 152.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Closed-form capacity formula for multi-antenna cognitive radio networks with asymmetric fading2014In: 2014 IEEE International Conference on Communications, ICC 2014, IEEE Computer Society, 2014, p. 2141-2146Conference paper (Refereed)
    Abstract [en]

    A cognitive radio network with a multiple-input single-output secondary link and a multi-antenna primary receiver is considered. The secondary transmitter steers its transmission into the direction of its intended destination in order to maximize the received signal-to-noise ratio. Under this beam-forming strategy, the power allocation is optimized to achieve the ergodic capacity under the constraint that the long-term interference, caused at the primary receiver, will not exceed a predefined threshold. Assuming line-of-sight communication (Rician fading) for the secondary link and Rayleigh fading for the secondary-to-primary link channel, we derive the exact closed-form expression for the ergodic capacity. Numerical results corroborate theoretical findings and illustrate the manifold impact of the system parameters into its performance.

  • 153.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Univ S Australia, Inst Telecommun Res, Mawson Lakes 5095, Australia.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Closed-Form Capacity Result for Interference-Limited Environments With Mixed Fading2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 6, p. 2374-2387Article in journal (Refereed)
    Abstract [en]

    We study a multinode network, where a multiantenna transmitter T-x communicates with its desired receiver R-x, whereas a cluster P (sic) {P-x,P- n, n = 1,..., N} of unintended nodes is disturbed by the T-x-R-x (TR) communication. To prevent severe performance degradation, we impose a constraint on the total interference that is inflicted at the nodes of P. The TR link contains a line-of-sight component, whereas the propagation environment for each T-x-P-x, n link is shadowed. The T-x node is preprocessing the information sequence by means of a precoding matrix that is optimized to achieve the ergodic capacity under a constraint on the maximum admissible ergodic interference power, arriving on P. In this paper, we show that the optimum precoding strategy involves the transmission of a single stream over the precoding direction, i.e., the eigenvector of the precoding matrix, which corresponds to beamforming along the instantaneous direction of the TR-link channel. The solution of the remaining power allocation problem yields the optimal precoding matrix. For this setup, we provide an efficient stochastic characterization of the network, which allows us to obtain an analytical expression for the TR-link ergodic capacity; this problem has been previously open, even for the case of a single-antenna node T-x and a single-element set P. We complement the analysis by deriving the TR-link signal-to-noise ratio and the average bit error rate, which are associated with our transmission scheme. Numerical results corroborate the theoretical analysis and reveal an interplay between the network parameters and their impact on the TR-link performance.

  • 154.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Schrammar, Nicolas
    KTH, School of Electrical Engineering (EES), Communication Theory.
    K. Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    On Performance Trade-Offs in Cognitive Networks2010In: 2010 IEEE International Conference on Wireless Information Technology and Systems (ICWITS), IEEE , 2010, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In this paper we employ the recently proposed deterministic framework (Avestimehr et al.) to model and analyze cognitive networks. Despite its simplicity, this model captures fundamental aspects of networks and allows explicit calculation of the capacity of multicast relay networks. The performance results we obtain and the conclusions that we draw in the deterministic field can provide useful insights that can be applied on the analysis of Gaussian networks.

  • 155.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Beamforming and Orthogonal Space-Time Coding in Cognitive Networks with Partial CSI2013In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 61, no 3, p. 961-972Article in journal (Refereed)
    Abstract [en]

    We consider a pair of secondary users that coexist, in a cognitive network, with multiple primary user pairs. The secondary link is supplied with partial network side information (NSI), which comprises message side information and partial channel side information (CSI), available in different levels at both the transmitter and the receiver of the cognitive link. The cognitive transceiver design has to obey predefined quality-of-service (QoS) criteria, that need to be maintained at the primary receivers, and at the same time properly handle the incoming interference from each primary transmitter in order to establish reliable communication. In this framework, we investigate the design and performance of the combined beamforming and orthogonal space-time block coding (BOSTBC) strategy, whose merits are well-documented, as a candidate transmission scheme for the secondary link. We study both aspects, QoS and interference, of the composite problem and characterize how they affect the beamformer design and the cognitive link performance, in the presence of partial NSI. Further, we propose a CSI quality-dependent model for the QoS criteria which yields an interesting trade-off between the cognitive link design and the primary QoS. Numerical results illustrate the system performance in this framework.

  • 156.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On combined beamforming and OSTBC over the cognitive radio S-channel with partial CSI2012In: Proceedings of the 2012 7th International ICST Conference on Cognitive Radio Oriented Wireless Networks and Communications, CROWNCOM 2012, IEEE , 2012, p. 30-35Conference paper (Refereed)
    Abstract [en]

    A pair of secondary (cognitive, unlicensed) users is communicating in the presence of multiple primary (licensed) user pairs. The cognitive transceiver is implementing beamforming and orthogonal space-time block coding in the presence of external interference, induced by the primary system transmission, that has to be properly handled. Moreover, the cognitive link nodes, both the transmitter and the receiver, are supplied with different levels of network side information (NSI), i.e. primary messages and partial channel side information (CSI). We investigate how this side information can be taken into account in the cognitive system design and how interference affects the behaviour of the beamforming solution. Through numerical simulations, we illustrate the impact of partial CSI on system performance and discuss its implications on the feasibility of cognitive systems.

  • 157.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On combined beamforming and OSTBC over the cognitive radio Z-channel with partial CSI2012In: Communications (ICC), 2012 IEEE International Conference on, IEEE , 2012, p. 2380-2384Conference paper (Refereed)
    Abstract [en]

    We consider a pair of secondary nodes (SU) coupled, in Z-topology, with multiple pairs of primary nodes (PU). The secondary (cognitive) transmitter is combining beamforming with orthogonal space-time block coding (BOSTBC) and operates under Quality-of-Service (QoS) constraints that must be guaranteed for the primary receivers (PURx). The cognitive link is designed assuming imperfect channel state information (CSI) for all links, available at the SU transmitter (SUTx). Under this premise we characterize the optimal design in terms of CSI quality and interference and evaluate their impact on the performance of BOSTBC transmission in underlay cognitive networks.

  • 158.
    Stathakis, Efthymios
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Low Complexity Adaptive Antenna Selection for Cognitive Radio MIMO Broadcast Channels2012In: 2012 IEEE Global Communications Conference (Globecom), New York: IEEE , 2012, p. 3844-3849Conference paper (Refereed)
    Abstract [en]

    A multi-antenna cognitive radio network, with a single pair of primary users and a secondary broadcast channel, is considered. Under perfect channel state information (CSI), the rate-optimal strategy for the primary link is waterfilling, resulting in possibly unused dimensions. The secondary base station, supplied with perfect and global CSI, employs block diagonalization for interference-free message precoding and opportunistic interference alignment to avoid disturbing primary communication. In the absence of sufficient resources to serve all secondary users, a low complexity adaptive antenna selection strategy is proposed. This scheme constructs, in each time-slot, the set of active antennas by opportunistically reusing information and resources from the preceding selection round. Numerical results indicate a complexity reduction at a small rate-loss penalty, in comparison with existing selection methods.

  • 159. Subramanian, Ramanan
    et al.
    Land, Ingmar
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Asymptotic Throughput and Throughput-Delay Scaling in Wireless Networks: The Impact of Error Propagation2014In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 13, no 4, p. 1974-1987Article in journal (Refereed)
    Abstract [en]

    This paper analyzes the impact of error propagation on the achievable throughput and throughput-delay tradeoff in wireless networks. It addresses the particular class of multihop routing schemes for parallel unicast that achieve a throughput scaling of Theta(n(-1/2))per node in a network of n nodes. It is shown that in the finite-block-length case, necessitated by finite decoding memory at the nodes, the guaranteed per-node throughput in the network cannot scale better than o(n(-r)) per node for any r > 0. This bound on the guaranteed per-node throughput is tighter than the O(1/n) bound shown previously. Instead of focusing on the probability of error for each link, which is intractable, an approach of bounding mutual information is employed to show tight results on the achievable throughput and throughput-delay tradeoffs. It is shown that for multihop transmission protocols, error propagation leads to significant changes in the tradeoff between the throughput T (n) and the delay D(n), compared to previous results. The best known scaling behavior is only D(n) = Theta(n (log n) T (n)) under maximum throughput scaling, where the block length required scales as Omega(log n). When decoding memory at nodes is constrained to be O(log log n), the achievable tradeoff worsens to D(n) = Theta(n (log n)(2) T (n))

  • 160.
    Subramanian, Ramanan
    et al.
    University of South Australia.
    Land, Ingmar
    University of South Australia.
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    The influence of error propagation on the capacity of wireless networks2010In: 48th Annual Allerton Conference on Communication, Control, and Computing, 2010, p. 1488-1495Conference paper (Refereed)
    Abstract [en]

    In this paper, it is shown that the achievable throughput capacity of wireless networks suffers from a fundamental limitation under finite node resource constraints. It is shown that this reduction results from a fundamental lower bound on the error performance of the wireless-channel model. In particular, the problem is addressed for the classic parallel-unicast problem introduced by Gupta-Kumar (2000). Under an AWGN channel-model assumption and for a pathloss exponent of α > 2, it is shown that the best available scheme for this setup achieves a throughput-capacity scaling of only Θ(n-1/2(log n)-1) per node. This is significant since an upper bound on asymptotic throughput capacity, scaling as Θ(n-1/2), was earlier shown to have been achieved by a scheme introduced by Franceschetti et. al. in 2006. The gap between achievability and the upper bound did not figure in past work on this problem, mainly due to transmission models that implicitly assume wireless nodes to have unlimited storage and encoding/decoding capabilities. Under the assumption of finite node memory, it is shown that such transmission models are unjustified in a strict information-theoretic sense. The new reduction in capacity scaling occurs from a necessity to modify the schemes used for showing achievability, in order to ensure that the failure probability is arbitrarily small. The analysis presented in this paper employs well-known sphere-packing bounds on the error probability of any block code in terms of the channel-error exponent. The result shows that for wireless networks with resource-constrained nodes, (a) the tightness of the best-known upper bound on capacity scaling still needs to be investigated, and (b) perhaps a better scheme that achieves higher capacity-scaling can be devised, but it is still an open problem.

  • 161.
    Subramanian, Ramanan
    et al.
    University of South Australia.
    Land, Ingmar
    University of South Australia.
    Vellambi, Badri N.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Error propagation and the achievable throughput-delay trade-off in wireless networks2011In: IEEE Information Theory Workshop, 2011, p. 583-587Conference paper (Refereed)
    Abstract [en]

    New results on the achievable trade-off between the per-node throughput T(n) and the average delay D(n) in a static wireless network of n nodes are presented for physical link models. For links modeled by channels with additive white Gaussian noise with power-law attenuation, a trade-off of only D(n) = Θ(n (log n) T(n)) is guaranteed for T(n) = Θ(n-1/2). This follows from showing that there is significant information loss in the network due to error propagation, unless the length of the channel code employed is sufficiently high. Constraining the block length to be bounded yields worse trade-offs: only Θ(n (log n)2 T(n)) is guaranteed for optimal throughput, provided there is rich fading diversity.

  • 162.
    Sugimoto, Hiroki
    et al.
    OKI Techno Center, Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Cheah, Kok Leong
    National University of Singapore.
    Sun, Sumei
    National University of Singapore.
    Matsumoto, Yoshihiro
    OKI Techno Center, Singapore.
    Oyama, Takashi
    OKI Techno Center, Singapore.
    Receiving device and channel estimator for use in a CDMA communication system1998Patent (Other (popular science, discussion, etc.))
  • 163.
    Sun, Sumei
    et al.
    National University of Singapore.
    Sugimoto, Hiroki
    OKI Techno Center, Singapore.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    A multipath searcher with the hybrid CDMA interference canceller2000In: IEEE Vehicular Technology Conference , 2000, p. 931-935Conference paper (Refereed)
  • 164. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    A reactive tabu search heuristic for multiuser detection in CDMA2002In: IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, 2002, p. 472-472Conference paper (Other academic)
  • 165.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Asymptotically optimal nonlinear MMSE multiuser detection based on multivariate Gaussian approximation2006In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 54, no 8, p. 1427-1438Article in journal (Refereed)
    Abstract [en]

    In this paper, a class of nonlinear minimum mean-squared error multiuser detectors is derived based on a multivariate Gaussian approximation of the multiple-access interference for large systems. This approach leads to expressions identical to those describing the probabilistic data association (PDA) detector, thus providing an alternative analytical justification for this structure. A simplification to the PDA detector based on approximating the covariance matrix of the multivariate Gaussian distribution is suggested, resulting in a soft interference-cancellation scheme. Corresponding multiuser soft-input, soft-output detectors delivering extrinsic log-likelihood ratios are derived for application in iterative multiuser decoders. Finally, a large-system performance analysis is conducted for the simplified PDA, showing that the bit-error rate (BER) performance of this detector can be accurately predicted and related to the replica method analysis for the optimal detector. Methods from statistical neurodynamics are shown to provide a closely related alternative large-system prediction. Numerical results demonstrate that for large systems, the BER is accurately predicted by the analysis and found to be close to optimal performance.

  • 166.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Belief propagation for coded multiuser detection2006In: 2006 IEEE International Symposium on Information Theory, Vols 1-6, Proceedings, 2006, p. 1919-1923Conference paper (Refereed)
    Abstract [en]

    In this paper a simplified parallel belief propagation (BP) algorithm is suggested as a suboptimal soft-input soft-output multiuser detector in an iterative multiuser decoding scheme. The iterative decoding scheme itself is based on applying an outer BP algorithm for message passing between the BP multiuser detector and the single-user decoders. The performance of the iterative decoding process is investigated based on parallel scheduling of the outer BP algorithm. In addition, we analyze the large system BER performance of the corresponding multiuser decoding algorithms. By making Gaussian assumptions on the output of the single-user decoders and the BP multiuser detector, we derive expressions which describe approximately the BER performance of the algorithms. Finally, numerical examples are presented, demonstrating the accuracy of this approximation

  • 167. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Convex-constrained maximum-likelihood detection in CDMA2000In: IEEE International Symposium on Information Theory, 2000, p. 387-387Conference paper (Refereed)
  • 168. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Linear interference cancellation in CDMA based on block iterations2000In: IEEE Vehicular Technology Conference, 2000, p. 740-744Conference paper (Refereed)
  • 169. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Linear interference cancellation in CDMA based on iterative techniques for linear equation systems2000In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 48, no 12, p. 2099-2108Article in journal (Refereed)
  • 170.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Multiuser detection based on reduced complexity probabilistic data association2004In: 2004 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, PROCEEDINGS, 2004, p. 532-532Conference paper (Refereed)
    Abstract [en]

    We consider a multiuser detector based on modelling the multiple-access interference (MAI) as a vector of Gaussian random variables. This approach leads to the probabilistic data association (PDA) multiuser detector, which outputs good approximations to marginal posterior-mode optimal decisions. A simplification to the PDA detector is suggested, leading to a soft interference cancellation scheme. In the large system limit, the bit error rate performance of this detector can be accurately predicted, and shown to be identical to the optimal detector.

  • 171.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Multiuser detection in CDMA - A comparison of relaxations, exact, and heuristic search methods2004In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 3, no 5, p. 1802-1809Article in journal (Refereed)
    Abstract [en]

    In this paper, we compare several optimization methods for solving the optimal multiuser detection problem exactly or approximately. The purpose of using these algorithms is to provide complexity constraint alternatives to solving this nondeterministic polynomial-time (NP)-hard problem. An approximate solution is found either by relaxation or by heuristic search methods, while the branch and bound algorithm is used to provide an exact solution. Simulations show that these approaches can have bit-error rate (BER) performance which is indistinguishable from the maximum likelihood performance. A tabu search method is shown to be an effective (in terms of BER performance) and efficient (in terms of computational complexity) heuristic when compared to other heuristics like local search and iterative local search algorithms. When the number of users increases, the tabu search method is more effective and efficient than the semidefinite relaxation approach.

  • 172.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Power allocation for iterative multiuser decoding based on large system analysis2006In: 2006 4th International Symposium on Turbo Codes&Related Topics: 6th International ITG-Conference on Source and Channel Coding (TURBOCODING), 2006Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider a power allocation problem for iterative multiuser decoding in a coded code-division multiple access (CDMA) system. Subject to given bit error rate performance targets for all users, the power allocation problem is formulated based on previously proposed large system analysis results for iterative multiuser decoding. The resulting power allocation problem is in general nonconvex and cannot be solved efficiently. However, under certain assumptions the problem can be reformulated into a quasiconvex optimization problem, which in turn can be solved efficiently by a sequence of convex feasibility problems. The approach is applied to a complexity reduced belief propagation multiuser detector as well as to popular interference cancellation based detectors. Numerical results are presented to demonstrate the performance of the proposed power allocation algorithm in finite-size systems. It is found that the belief propagation detector is more power and complexity efficient than the interference cancellation based detectors.

  • 173. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Sphere-constrained maximum-likelihood detection in CDMA2000In: IEEE Vehicular Technology Conference, 2000, p. 517-521Conference paper (Refereed)
  • 174. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    The application of semidefinite programming for detection in CDMA2001In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 19, no 8, p. 1442-1449Article in journal (Refereed)
  • 175.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    The serial and parallel belief propagation algorithms2005In: 2005 IEEE International Symposium on Information Theory (ISIT), Vols 1 and 2, 2005, p. 729-733Conference paper (Refereed)
    Abstract [en]

    It has been shown that the stable fixed points of belief propagation (BP) algorithms correspond to extrema of the Bethe free energy. In this paper, we describe the dual problem for the minimization of the Bethe free energy and solve it using simple nonlinear block Gauss-Seidel and Jacobi algorithms. The use of the nonlinear block Gauss-Seidel algorithm corresponds to serial scheduling for the BP algorithm. In addition, it is shown that applying the nonlinear block Jacobi algorithm on the dual of the Bethe free energy corresponds to the parallel BP algorithm.

  • 176.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Aulin, Tor M.
    Chalmers University of Technology.
    The application of semidefinite programming for detection in CDMA2001In: IEEE International Symposium on Information Theory, 2001, p. 9-9Conference paper (Refereed)
  • 177.
    Tan, Peng Hui
    et al.
    National University of SingaporeCenter .
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Box-constrained maximum-likelihood detection in CDMA2000In: International Zurich Seminar on Broadband Communications, 2000, p. 55-62Conference paper (Refereed)
  • 178. Tan, Peng Hui
    et al.
    Rasmussen, Lars Kildehöj
    National University of Singapore.
    Lim, Teng Joon
    National University of Singapore.
    Constrained maximum-likelihood detection in CDMA2001In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 49, no 1, p. 142-153Article in journal (Refereed)
  • 179.
    Tan, Peng Hui
    et al.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Luo, Jiu
    University of Colorado at Boulder, USA.
    Iterative multiuser decoding based on probabilistic data association2003In: IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, 2003, p. 301-301Conference paper (Other academic)
  • 180.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    Chalmers University of Technology.
    Wiberg, P.-A.
    Halmstad University.
    Deadline dependent coding - a framework for wireless real-time communication2000In: Real-Time Computing Systems and Applications, 2000. Proceedings. Seventh International Conference on, Cheju Island, 12 Dec 2000-14 Dec 2000, 2000, p. 135-142Conference paper (Refereed)
    Abstract [en]

    A framework for real-time communication over a wireless channel is proposed. The concept of deadline dependent coding (DDC), previously suggested by the authors, is further developed using soft decision decoding of block codes to maximize the probability of delivering information before a given deadline. The strategy of DDC is to combine different coding and decoding methods with automatic repeat request (ARQ) in order to fulfil the application requirements. These requirements are formulated as two quality of service (QoS) parameters: deadline (tDL) and probability of correct delivery before the deadline (Pd), leading to a probabilistic view of real-time communication. An application can negotiate these QoS parameters with the DDC protocol, thus creating a flexible and dependable scheme.

  • 181.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Wiberg, Per A.
    Halmstad University.
    Concatenated hybrid ARQ - A flexible scheme for wireless real-time communication2002In: Proceedings Eighth IEEE Real-Time and Embedded Technology and Applications Symposium, 2002, p. 35-44Conference paper (Other academic)
    Abstract [en]

    The concept of deadline dependent coding (DDC) has previously been suggested by the authors for maximizing the probability of delivering the required information before a given deadline in a wireless communication system.. In this paper, these principles are further developed using concatenated codes with iterative decoding, providing a new level of flexibility and robustness for DDC protocols. The strategy of DDC is to combine different coding and decoding methods with automatic repeat request (ARQ) techniques in order to fulfill the application requirements within a wireless realtime communication system. These requirements are formulated as two quality of service (QoS) parameters: deadline (tDL) and probability of correct delivery before the deadline (Pd), leading to a probabilistic view of realtime communication. An application can negotiate these QoS parameters with the DDC protocol, thus creating a flexible and fault-tolerant scheme.

  • 182.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Aulin, Tor M.
    Chalmers University of Technology.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Wiberg, Per A.
    Halmstad University.
    Packet combining and doping in concatenated hybrid ARQ schemes using iterative decoding2003In: WCNC 2003: IEEE Wireless Communications And Networking Conference Record, Vols 1-3, 2003, p. 849-854Conference paper (Refereed)
    Abstract [en]

    We consider serially concatenated block codes in a hybrid ARQ scheme using iterative decoding. The extrinsic information generated in the iterative decoding process is saved and used when a retransmission is decoded. Two different strategies are examined; one using the extrinsic information only in the. very first iteration, whereas the other uses it in all subsequent iterations until another retransmission arrives. The latter can be seen as turbo or concatenated code combining whereas the former, where the extrinsic information is used only once may be seen as code doping, providing an alternative perspective. The strategy of saving the extrinsic information is also compared to traditional type-III, equal gain diversity combining. Using the extrinsic information from previous retransmissions is shown to improve performance not only in terms of bit error rate but also in terms of throughput and convergence speed and requires only negligible additional decoder complexity. The performance of this strategy is however not as good as simple equal gain combining.-As a consequence, the investigated schemes are not competitive alternatives, however, the code doping procedure can be used in conjunction with traditional diversity combining schemes, improving further on convergence speed.

  • 183.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Analytical approach for maximizing the average code rate of incremental redundancy schemes2005In: 2005 Asia-Pacific Conference on Communications (APCC), Vols 1& 2, 2005, p. 481-485Conference paper (Refereed)
    Abstract [en]

    An analytical design procedure for maximizing the average code rate of incremental redundancy retransmission schemes is presented. Union bounds are used as the tool to select good puncturing patterns and to obtain bounds on frame error rate for the punctured codes. This, in turn, is used for determining the optimal packet size of each retransmission, so that the average code rate is maximized.

  • 184.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Incremental redundancy deadline dependent coding for efficient wireless real-time communications2005In: 10th IEEE Conference on Emerging Technologies and Factory Automation, 2005, p. 417-424Conference paper (Refereed)
    Abstract [en]

    The concept of deadline dependent coding (DDC) has been demonstrated as a promising design approach for efficient and reliable real-time communications over wireless channels. The main idea behind the concept of DDC is to make all components of the communication protocol deadline dependent, tailoring the channel code and the retransmission protocol to the specific real-time constraints. The DDC framework allows critical reliability and timing constraints to be readily evaluated as a function of available system resources. Concatenated coding and iterative decoding within retransmission protocols enables additional flexibility and new adaptive design options. Here, we introduce an incremental redundancy retransmission scheme in conjunction with concatenated coding and show that this further improves the DDC scheme.

  • 185.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Brännström, Fredrik
    Chalmers University of Technology.
    Puncturing Strategies for Incremental Redundancy Schemes Using Rate Compatible Systematic Serially Concatenated Codes2006In: 4th International Symposium on Turbo Codes & Related Topics, 2006Conference paper (Refereed)
    Abstract [en]

    A rate compatible puncturing strategy intended for incremental redundancy retransmission schemes is derived. In particular, systematic serially concatenated codes with two or more component codes are considered, although the method is applicable to any type of concatenated code. Extrinsic information transfer charts are used to select a puncturing strategy such that the signal-to-noise ratio required to reach a target bit error rate is minimized.

  • 186.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Grant, Alex J.
    University of South Australia.
    Wiberg, Per A.
    Halmstad University.
    Optimal incremental-redundancy strategy for type-II hybrid ARQ2003In: 2003 IEEE International Symposium On Information Theory - Proceedings, 2003, p. 448-448Conference paper (Other academic)
    Abstract [en]

    Given a type-II hybrid ARQ scheme, we propose a general solution to find the optimal partitioning of n - k parity bits over at most M transmissions. The solution is in terms of maximizing the average code rate for a given puncturing pattern.

  • 187.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Grant, Alex J.
    University of South Australia.
    Wiberg, Per-Arne
    Halmstad University.
    Optimal type-II concatenated hybrid ARQ using single parity check codes2003In: Proc. International Symposium on Turbo Codes & Related Topics, 2003, p. 587-590Conference paper (Refereed)
    Abstract [en]

    We consider an incremental redundancy (IR) type-II hybrid ARQ scheme based on multidimensional single parity check (SPC) product codes. Random interleaving is applied between dimensions, resulting in equivalent systematic, parallel or serially concatenated SPC codes. This enables larger interleavers and a larger range of overall code rates. The puncturing pattern used for IR transmissions of the concatenated SPC codes is chosen specifically to reduce decoder complexity for the hybrid ARQ scheme, activating only those constituent decoders for which parity bits have been received. Given the proposed puncturing pattern and a maximum number of allowable transmissions, an approach for determining the optimal number of parity bits per IR transmission in terms of maximizing the overall code rate, is suggested. With this strategy, each data frame is accepted following the transmission of a minimum number of parity bits.

  • 188.
    Uhlemann, Elisabeth
    et al.
    Halmstad University.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Wiberg, Per-Arne
    Halmstad University.
    Wireless Real-Time Communication Using Deadline Dependent Coding: (Chapter 15)2006In: ARTES - A network for Real-Time research and graduate Education in Sweden 1997-2006: MRTC report (197/2006), Uppsala: Department of Information Technology, Uppsala university , 2006, p. 239-256Chapter in book (Other (popular science, discussion, etc.))
  • 189. Vehkapera, M.
    et al.
    Riihonen, T.
    Girnyk, Maksym
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Björnson, E.
    Debbah, M.
    Kildehøj Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wichman, R.
    Asymptotic analysis of asymmetric MIMO links: EVM limits for joint decoding of PSK and QAM2015In: 2015 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2015, Vol. 2015, p. 1869-1873Conference paper (Refereed)
    Abstract [en]

    Hardware non-idealities in wireless transmitter electronics cause distortion that is not captured by conventional linear channel models; in fact, error-vector magnitude (EVM) measurements in conformance testing conceptually reduce their collective effect to an additive noise component at each subcarrier. Motivated by the EVM, the present paper considers a 'binoisy' multiple-input multiple-output (MIMO) channel model where the additional non-idealities manifest themselves as an additive distortion noise term at the transmit side. Through this extended MIMO relation, the effects of hardware impairments on the achievable rates of different digital modulation schemes are studied via large system analysis. The numerical results illustrate how tolerable EVM levels depend non-trivially on various factors, including the signal-to-noise ratio, modulation order and the level of asymmetry in antenna array configurations.

  • 190. Vehkapera, Mikko
    et al.
    Riihonen, Taneli
    Girnyk, Maksym A.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bjornson, Emil
    Debbah, Merouane
    Kildehøj, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Wichman, Risto
    Asymptotic Analysis of SU-MIMO Channels With Transmitter Noise and Mismatched Joint Decoding2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 3, p. 749-765Article in journal (Refereed)
    Abstract [en]

    Hardware impairments in radio-frequency components of a wireless system cause unavoidable distortions to transmission that are not captured by the conventional linear channel model. In this paper, a "binoisy" single-user multiple-input multiple-output (SU-MIMO) relation is considered where the additional distortions are modeled via an additive noise term at the transmit side. Through this extended SU-MIMO channel model, the effects of transceiver hardware impairments on the achievable rate of multi-antenna point-to-point systems are studied. Channel input distributions encompassing practical discrete modulation schemes, such as, QAM and PSK, as well as Gaussian signaling are covered. In addition, the impact of mismatched detection and decoding when the receiver has insufficient information about the non-idealities is investigated. The numerical results show that for realistic system parameters, the effects of transmit-side noise and mismatched decoding become significant only at high modulation orders.

  • 191.
    Vehkaperä, Mikko
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Girnyk, Maksym
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Riihonen, Taneli
    Aalto University, Department of Signal Processing and Acoustics.
    Wichman, Risto
    Aalto University, Department of Signal Processing and Acoustics.
    Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On Achievable Rate Regions at Large-System Limit in Full-Duplex Wireless Local Access2013In: International Black Sea Conference on Communications and Networking, 2013Conference paper (Refereed)
    Abstract [en]

    High capacity requirements in wireless systems can be met, at the network level, by using dense small cell deployments and, at the link level, by improving spectral efficiency via spectrum reuse. In this context, we consider a small-area radio system, e.g. a pico- or femtocell, where a full-duplex access point serves simultaneously two half-duplex devices, one in downlink and one in uplink direction. All transceivers are equipped with multiple antennas exploited for spatial multiplexing. Instead of limiting the study to the total sum rate, we analyze the complete achievable rate regions of the two directions. We also take into account the effects of mismatched decoding at the receivers due to imperfect knowledge of the transceiver impairments. The analysis is conducted in the large-system limit using the replica method from statistical physics, which allows to encompass arbitrary channel input distributions. The analytical results characterize the effect of self-interference at the access point and inter-device interference on the achievable rate regions. Numerical examples for particular signaling schemes are also given.

  • 192.
    Vehkaperä, Mikko
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kabashima, Yoshiyuki
    Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Aurell, Erik
    KTH, School of Computer Science and Communication (CSC), Computational Biology, CB. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Analysis of Sparse Representations Using Bi-Orthogonal Dictionaries2012In: Information Theory Workshop (ITW), 2012 IEEE, IEEE , 2012, p. 647-651Conference paper (Refereed)
    Abstract [en]

    The sparse representation problem of recovering an N dimensional sparse vector x from M < N linear observations y = Dx given dictionary D is considered. The standard approach is to let the elements of the dictionary be independent and identically distributed (IID) zero-mean Gaussian and minimize the l1-norm of x under the constraint y = Dx. In this paper, the performance of l1-reconstruction is analyzed, when the dictionary is bi-orthogonal D = [O1 O2], where O1, O 2 are independent and drawn uniformly according to the Haar measure on the group of orthogonal M × M matrices. By an application of the replica method, we obtain the critical conditions under which perfect l 1-recovery is possible with bi-orthogonal dictionaries.

  • 193.
    Wang, Chao
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Performance analysis of coded secondary relaying in overlay cognitive radio networks2012In: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, p. 294-299Conference paper (Refereed)
    Abstract [en]

    We study the error and diversity-multiplexing tradeoff (DMT) performance of a (secondary) multi-user relay network, where a class of finite field network codes are applied in the relays to efficiently provide spatial diversity. To eliminate spectral efficiency loss induced by half-duplex limitation we adopt the cognitive radio overlay spectrum sharing concept and consider aligning the relays' operation with that of a primary system. To compensate the interference introduced by the secondary relaying, the secondary destination also transmits the primary signals to boost the signal power of the primary system. We also consider exploiting Automatic Repeat Request (ARQ) feedback signals from the secondary destination to minimize the energy consumption of the secondary system. In addition, by allowing multiple secondary sources to transmit non-orthogonally, the performance can be further enhanced.

  • 194.
    Wei, Lei
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    A near ideal noise whitening filter for an asynchronous time-varying CDMA system1996In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 44, no 10, p. 1355-1361Article in journal (Refereed)
  • 195.
    Wei, Lei
    et al.
    University of South Australia.
    Rasmussen, Lars Kildehöj
    University of South Australia.
    Wyrwas, Richard
    University of South Australia.
    Near optimum tree-search detection schemes for bit-synchronous multiuser CDMA systems over Gaussian and two-path Rayleigh-fading channels1997In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 45, no 6, p. 691-700Article in journal (Refereed)
  • 196.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Universal algorithm for compressive sampling2015In: 2015 23rd European Signal Processing Conference, EUSIPCO 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 689-693Conference paper (Refereed)
    Abstract [en]

    In a standard compressive sampling (CS) setup, we develop a universal algorithm where multiple CS reconstruction algorithms participate and their outputs are fused to achieve a better reconstruction performance. The new method is called universal algorithm for CS (UACS) that is iterative in nature and has a restricted isometry property (RIP) based theoretical convergence guarantee. It is shown that if one participating algorithm in the design has a converging recurrence inequality relation then the UACS also holds a converging recurrence inequality relation over iterations. An example of the UACS is presented and studied through simulations for demonstrating its flexibility and performance improvement.

  • 197. Zaki, Ahmed
    et al.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Generalized fusion algorithm for compressive sampling reconstruction and RIP-based analysis2017In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 139, p. 36-48Article in journal (Refereed)
    Abstract [en]

    We design a Generalized Fusion Algorithm for Compressive Sampling (gFACS) reconstruction. In the gFACS algorithm, several individual compressive sampling (CS) reconstruction algorithms participate to achieve a better performance than the individual algorithms. The gFACS algorithm is iterative in nature and its convergence is proved under certain conditions using Restricted Isometry Property (RIP) based theoretical analysis. The theoretical analysis allows for the participation of any off-the-shelf or new CS reconstruction algorithm with simple modifications, and still guarantees convergence. We show modifications of some well-known CS reconstruction algorithms for their seamless use in the gFACS algorithm. Simulation results show that the proposed gFACS algorithm indeed provides better performance than the participating individual algorithms.

  • 198.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Mitra, Partha P.
    Cold Spring Harbor Lab, 1 Bungtown Rd, New York, NY USA..
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Chatterjee, Saikat
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Estimate exchange over network is good for distributed hard thresholding pursuit2019In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 156, p. 1-11Article in journal (Refereed)
    Abstract [en]

    We investigate an existing distributed algorithm for learning sparse signals or data over networks. The algorithm is iterative and exchanges intermediate estimates of a sparse signal over a network. This learning strategy using exchange of intermediate estimates over the network requires a limited communication overhead for information transmission. Our objective in this article is to show that the strategy is good for learning in spite of limited communication. In pursuit of this objective, we first provide a restricted isometry property (RIP)-based theoretical analysis on convergence of the iterative algorithm. Then, using simulations, we show that the algorithm provides competitive performance in learning sparse signals vis-a-vis an existing alternate distributed algorithm. The alternate distributed algorithm exchanges more information including observations and system parameters.

  • 199.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Venkitaraman, Arun
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehöj
    Distributed Greedy Sparse Learning over Doubly Stochastic Networks2017In: 2017 25TH EUROPEAN SIGNAL PROCESSING CONFERENCE (EUSIPCO), IEEE , 2017, p. 361-364Conference paper (Refereed)
    Abstract [en]

    In this paper, we develop a greedy algorithm for sparse learning over a doubly stochastic network. In the proposed algorithm, nodes of the network perform sparse learning by exchanging their individual intermediate variables. The algorithm is iterative in nature. We provide a restricted isometry property (RIP)-based theoretical guarantee both on the performance of the algorithm and the number of iterations required for convergence. Using simulations, we show that the proposed algorithm provides good performance.

  • 200.
    Zaki, Ahmed
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Combining interference alignment and Alamouti codes for the 3-user MIMO interference channel2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), New York: IEEE , 2013, p. 3563-3567Conference paper (Refereed)
    Abstract [en]

    The interference channel (IC) is the basic underlying channel model for many practical multi-terminal communication scenarios. Here, we consider a modified three-user IC with dual-antenna transmitters and receivers where we allow one receiver to have a finite-rate unidirectional link to another receiver. This kind of receiver-to-receiver link may exist in cellular networks with base-station backhaul. For this scenario we propose a scheme that combines the interference-cancellation capability of Alamouti codes with the subspace-overlapping property of interference alignment to achieve a sum-rate of three symbols/channel use. The scheme does also simultaneously provide a diversity gain of two for every symbol which significantly improves the bit-error rate performance compared to zero-forcing techniques.

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