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  • 1. Bao, J.
    et al.
    Ma, Z.
    Karagiannidis, G. K.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Zhu, Z.
    Joint Multiuser Detection of Multidimensional Constellations over Fading Channels2017In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 65, no 1, p. 161-172, article id 7723894Article in journal (Refereed)
    Abstract [en]

    We investigate the error performance of multidimensional constellations in the multiple access and broadcast channels. More specifically, we provide closed-form expressions for the pairwise error probability (PEP) of the joint maximum likelihood detection, for multiuser signaling in the presence of additive white Gaussian noise and Rayleigh fading. Arbitrary numbers of users and multidimensional signal sets are assumed, while the provided formula for the PEP is a function of the dimension-wise distances of the multidimensional constellation. Furthermore, a useful upper bound on the average symbol error probability is also obtained through the union bound. The analysis is applied to the sparse code multiple access systems. The analytical results are validated successfully through simulations, and show their importance in the multidimensional constellation design.

  • 2. Bao, J.
    et al.
    Ma, Z.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tsiftsis, T. A.
    Zhu, Z.
    Performance analysis of uplink sparse code multiple access with iterative multiuser receiver2017In: 2017 IEEE International Conference on Communications, ICC 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7996537Conference paper (Refereed)
    Abstract [en]

    This paper investigates the asymptotic performance of bit-interleaved coded modulation (BICM) with iterative multiuser detection and decoding in uplink sparse code multiple access (SCMA) systems. The extrinsic information transfer (EXIT) characteristics analysis of the joint multiuser detector for SCMA is provided, and shows that the average detection reliability for multiple users converges to the single-user case, if ideal feedback from the decoder is available to the detector. We develop a tight analytical bound on the convolutionally encoded bit-error rate (BER) for independent Rayleigh fadings, based on the single-user bound with arbitrary multidimensional constellations. Moreover, we analyze the achievable coding and diversity gains of the SCMA-BICM system with iterative receiver. Simulations are carried out to verify the effectiveness of the analysis.

  • 3. Bao, Jinchen
    et al.
    Ma, Zheng
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Zhu, Zhongliang
    Error Performance of Sparse Code Multiple Access Networks with Joint ML Detection2016In: 2016 IEEE 83RD VEHICULAR TECHNOLOGY CONFERENCE (VTC SPRING), IEEE, 2016Conference paper (Refereed)
    Abstract [en]

    This paper investigates error performance of sparse code multiple access (SCMA) networks with multiple access channels (MAC) and broadcast channels (BC). We give the closedform expression for the pairwise error probability (PEP) of joint maximum likelihood (ML) detection for multiuser signals over additive white Gaussian noise (AWGN) and Rayleigh fading channels with an arbitrary number of users and multidimensional codebooks. An upper bound for the average symbol error rate (SER) is calculated. The bound is tight in both AWGN channel and Rayleigh fading channels for high SNR regions. The analytical bounds are compared with simulations, and the results confirm the effectiveness of the analysis for both AWGN and Rayleigh fading channels.

  • 4. Cao, CongZhe
    et al.
    ZeSong, Fei
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    GaiShi, Huang
    ChengWen, Xing
    JingMing, Kuang
    An extended packetization-aware mapping algorithm for scalable video coding in finite-length fountain codes2013In: Science China Information Sciences, ISSN 1674-733X, Vol. 56, no 4, p. 042311-Article in journal (Refereed)
    Abstract [en]

    We propose an extended packetization-aware mapping algorithm based on fountain codes to enhance video stream performance which is vulnerable to packet losses. By properly utilizing the proposed algorithm in finite-length cases, the edges connecting to a source symbol are scattered over multiple encoding packets so that the decoding probabilities are increased. Furthermore, an improved degree distribution is designed to obtain better decoding probabilities. Numerical results, it is confirmed that the proposed algorithm in finite-length cases can augment decoding probabilities and the improved degree distribution can increase peak signal-to-noise ratio (PSNR) of scalable video coding (SVC) in a hostile communication environment.

  • 5.
    Cui, Yaping
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.;Chongqing Univ Posts & Telecommun, Sch Commun & Informat Engn, Chongqing 400065, Peoples R China..
    Fang, Xuming
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Fang, Yuguang
    Univ Florida, Dept Elect & Comp Engn, Gainesville, FL 32611 USA..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Optimal Nonuniform Steady mmWave Beamforming for High-Speed Railway2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 5, p. 4350-4358Article in journal (Refereed)
    Abstract [en]

    Using higher frequency bands (e.g., millimeter waves) to provide higher data rate is an effective way to eliminate performance bottleneck for future wireless networks, particularly for cellular networks based high-speed railway (HSR) wireless communication systems. However, higher frequency bands suffer from significant path loss and narrow-beam coverage, which pose serious challenges in cellular networks, especially under the HSR scenario. Meanwhile, as one of the key performance indexes of ultrareliable and low-latency communications in 5G systems, network reliability should be guaranteed to provide steady reliable data transmission along the railway, especially when safety-critical railway signaling information is delivered. In this paper, we propose a novel beamforming scheme, namely, optimal nonuniform steady mmWave beamforming, to guarantee the network reliability under an interleaved redundant coverage architecture for future HSR wireless systems. Moreover, we develop a bisection-based beam boundary determination (BBBD) method to determine the service area of each predefined RF beam. Finally, we demonstrate that the proposed optimal nonuniform steady mmWave beamforming can provide steady reliable data transmissions along the railway, and the network reliability requirements can be guaranteed when the proposed BBBD method is used. We expect that our optimal nonuniform steady mmWave beamforming provides a promising solution for future HSR wireless systems.

  • 6.
    Dai, Bin
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.;Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210018, Peoples R China..
    Ma, Zheng
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Tang, Xiaohu
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Fan, Pingzhi
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China..
    Secure Communication Over Finite State Multiple-Access Wiretap Channel With Delayed Feedback2018In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 36, no 4, p. 723-736Article in journal (Refereed)
    Abstract [en]

    Recently, it has been shown that the time-varying multiple-access channel (MAC) with perfect channel state information (CSI) at the receiver and delayed feedback CSI at the transmitters can be modeled as the finite state MAC (FS-MAC) with delayed state feedback, where the time variation of the channel is characterized by the statistics of the underlying state process. To study the fundamental limit of the secure transmission over multi-user wireless communication systems, we re-visit the FS-MAC with delayed state feedback by considering an external eavesdropper, which we call the finite state multipleaccess wiretap channel (FS-MAC-WT) with delayed feedback. The main contribution of this paper is to show that taking full advantage of the delayed channel output feedback helps to increase the secrecy rate region of the FS-MAC-WT with delayed state feedback. Moreover, by a degraded Gaussian fading example, we show the effects of feedback delay and channel memory on the secrecy sum rate of the FS-MAC-WT with delayed feedback.

  • 7. DengSheng, Lin
    et al.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    ShaoQian, Li
    Packet combining based on cross-packet coding2013In: Science China Information Sciences, ISSN 1674-733X, Vol. 56, no 2, p. 022302-Article in journal (Refereed)
    Abstract [en]

    We propose a packet combining scheme of using cross-packet coding. With the coding scheme, one redundant packet can be used to ensure the error-correction of multiple source packets. Thus, the proposed scheme can increase the code rate. Moreover, the proposed coding scheme has also advantages of decoding complexity, reducing undetectable errors (by the proposed low-complexity decoder) and flexibility (applicable to channels with and without feedback). Theoretical analysis under the proposed low-complexity decoding algorithm is given to maximize the code rate by optimizing the number of source packets. Finally, we give numerical results to demonstrate the advantages of the proposed scheme in terms of code rates compared to the traditional packet combining without coding or ARQ (automatic repeat-request) techniques.

  • 8.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Division for Communication Systems, Linköping University.
    Xiao, Ming
    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.
    Optimal Symbol-by-Symbol Costa Precoding for a Relay-Aided Downlink Channel2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 8, p. 2274-2284Article in journal (Refereed)
    Abstract [en]

    In this article, we consider practical approaches to Costa precoding (also known as dirty paper coding). Specifically, we propose a symbol-by-symbol scheme for cancellation of interference known at the transmitter in a relay-aided downlink channel. For finite-alphabet signaling and interference, we derive the optimal (in terms of maximum mutual information) modulator under a given power constraint. A sub-optimal modulator is also proposed by formulating an optimization problem that maximizes the minimum distance of the signal constellation, and this non-convex optimization problem is approximately solved by semi-definite relaxation. For the case of binary signaling with binary interference, we obtain a closed-form solution for the sub-optimal modulator, which only suffers little performance degradation compared to the optimal modulator in the region of interest. For more general signal constellations and more general interference distributions, we propose an optimized Tomlinson-Harashima precoder (THP), which uniformly outperforms conventional THP with heuristic parameters. Bit-level simulation shows that the optimal and sub-optimal modulators can achieve significant gains over the THP benchmark as well as over non-Costa reference schemes, especially when the power of the interference is larger than the power of the noise.

  • 9.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. MIT, Cambridge, USA.
    Medard, Muriel
    Xiao, Ming
    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), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Scalable Capacity Bounding Models for Wireless Networks2016In: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 62, no 1, p. 208-229Article in journal (Refereed)
    Abstract [en]

    The framework of network equivalence theory developed by Koetter et al. introduces a notion of channel emulation to construct noiseless networks as upper (respectively, lower) bounding models, which can be used to calculate the outer (respectively, inner) bounds for the capacity region of the original noisy network. Based on the network equivalence framework, this paper presents scalable upper and lower bounding models for wireless networks with potentially many nodes. A channel decoupling method is proposed to decompose wireless networks into decoupled multiple-access channels and broadcast channels. The upper bounding model, consisting of only point-to-point bit pipes, is constructed by first extending the one-shot upper bounding models developed by Calmon et al. and then integrating them with network equivalence tools. The lower bounding model, consisting of both point-to-point and point-to-points bit pipes, is constructed based on a two-step update of the lower bounding models to incorporate the broadcast nature of wireless transmission. The main advantages of the proposed methods are their simplicity and the fact that they can be extended easily to large networks with a complexity that grows linearly with the number of nodes. It is demonstrated that the resulting upper and lower bounds can approach the capacity in some setups.

  • 10.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    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.
    Lower bounding models for wireless networks2013In: Proceedings of IEEE International Symposium on Information Theory, 2013, IEEE conference proceedings, 2013, p. 1456-1460Conference paper (Refereed)
    Abstract [en]

    Motivated by the framework of network equivalencetheory [1], [2], we present capacity lower bounding models forwireless networks by construction of noiseless networks whichcan be used to calculate an inner bound for the correspondingwireless network. We first extend the “one-shot” lower boundingmodel [6] to many-user scenarios, and then propose a two-stepupdate of the one-shot models to incorporate the broadcast natureof wireless transmission. The main advantage of the proposedlower bounding method is its simplicity and the fact that it can beeasily extended to larger networks. We demonstrate by examplesthat the resulting lower bounds can even approach the capacityin some setups.

  • 11.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Research Lab of Electronics, MIT.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    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.
    Scalable capacity bounding models for wireless networksManuscript (preprint) (Other academic)
    Abstract [en]

    Based on the framework of network equivalence theory developed by Koetter et al., this paper presents scalable capacity upper and lower bounding models for wireless networks by construction of noiseless networks that can be used to calculate outer and inner bounds, respectively, for the original networks. A channel decoupling method is proposed to decompose wireless networks into point-to-point channels, and (potentially) coupled multiple-access channels (MACs) and broadcast channels (BCs). The upper bounding model, consisting of only point-to-point bit-pipes, is constructed by firstly extending the "one-shot" bounding models developed by Calmon et al. and then integrating them with network equivalence tools. The lower bounding model, consisting of both point-to-point and point-to-points bit-pipes, is constructed based on a two-step update of the one-shot models to incorporate the broadcast nature of wireless transmission. The main advantages of the proposed methods are their simplicity and the fact that they can be extended easily to large networks with a complexity that grows linearly with the number of nodes. It is demonstrated that the gap between the resulting upper and lower bounds is usually not large, and they can approach the capacity in some setups.

  • 12.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Research Lab of Electronics, Massachusetts Institute of Technology.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    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.
    Scalable upper bounding models for wireless networks2014In: Proceedings of IEEE International Symposium on Information Theory, IEEE conference proceedings, 2014, p. 241-245Conference paper (Refereed)
    Abstract [en]

    The framework of network equivalence theory developed by Koetter et al. introduces a notion of channel emulation to construct noiseless networks as upper/lower bounding models for the original noisy network. This paper presents scalable upper bounding models for wireless networks, by firstly extending the ``one-shot'' bounding models developed by Calmon et al. and then integrating them with network equivalence tools. A channel decoupling method is proposed to decompose wireless networks into decoupled multiple-access channels (MACs) and broadcast channels (BCs). The main advantages of the proposed method is its simplicity and the fact that it can be extended easily to large networks with a complexity that grows linearly with the number of nodes. It is demonstrated that the resulting upper bounds can approach the capacity in some setups.

  • 13.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Capacity Bounds for Backhaul-Supported Wireless Multicast Relay Networks with Cross-Links2011In: IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), 2011, NEW YORK: IEEE conference proceedings, 2011, p. 1-5Conference paper (Refereed)
    Abstract [en]

    We investigate the capacity bounds for a wireless multicast relay network where two sources simultaneously multicast to two destinations through Gaussian channels with the help of a full-duplex relay node. All the individual channel gains are assumed to be time-invariant and known to every nodes in the network. The transmissions from two sources and from the relay use the same channel resource (i.e. co-channel transmission) and the two source nodes are connected with an orthogonal error-free backhaul. This multicast relay network is generic in the sense that it can be extended to more general networks by tuning the channel gains within the range [0, ∞). By extending the proof of the converse developed by Cover and El Gamal for the Gaussian relay channel, we characterize the cut-set bound for this multicast relay network. We also present a lower bound by using decoding-and-forward relaying combined with network beam-forming.

  • 14.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Capacity bounds for relay-aided wireless multiple multicast with backhaul2010In: 2010 International Conference on Wireless Communications and Signal Processing, WCSP 2010, NEW YORK: IEEE conference proceedings, 2010, p. 1-5Conference paper (Refereed)
    Abstract [en]

    We investigate the capacity bounds for relay-aided two-source two-destination wireless networks with backhaul support between source nodes. Each source multicasts its own message to all destinations with the help of an intermediate relay node, which is full-duplex and shared by both sources. We are aiming to characterize the capacity region of this model given discrete memoryless Gaussian channels. We establish three capacity upper bounds by relaxing the cut-set bound, and by extending two capacity bounds originally derived for MIMO relay channels. We also present one lower bound by using decoding-and-forward relaying combined with network beam-forming.

  • 15.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul2011In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, no 9, p. 2502-2514Article in journal (Refereed)
    Abstract [en]

    We investigate cooperative network coding strategies for relay-aided two-source two-destination wireless networks with a backhaul connection between the source nodes. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding schemes, namely, finite field and linear network coding, and lattice coding. To further exploit the backhaul connection, we also propose network coding based beamforming. We measure the performance in term of achievable rates over Gaussian channels, and observe significant gains over benchmark schemes. We derive the achievable rate regions for these schemes and find the cut-set bound for our system. We also show that the cut-set bound can be achieved by network coding based beamforming when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.

  • 16.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Cooperative strategies for relay-aided multi-cell wireless networks with backhaul2010In: 2010 IEEE Information Theory Workshop, ITW 2010 - Proceedings, NEW YORK: IEEE conference proceedings, 2010, p. 1-5Conference paper (Refereed)
    Abstract [en]

    We investigate cooperative strategies for relay-aided multi-source multi-destination wireless networks with backhaul support. Each source multicasts information to all destinations using a shared relay. We study cooperative strategies based on different network coding (NC) schemes, namely, finite field NC (FNC), linear NC (LNC), and lattice coding. To further exploit the backhaul connection, we also propose NC-based beam-forming (NBF). We measure the performance in term of achievable rates over Gaussian channels and observe significant gains over a benchmark scheme. The benefit of using backhaul is also clearly demonstrated in most of scenarios.

  • 17.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Wireless multicast relay networks with limited-rate source-conferencing2013In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 31, no 8, p. 1390-1401Article in journal (Refereed)
    Abstract [en]

    We investigate capacity bounds for a wireless multicast relay network where two sources simultaneously multicast to two destinations with the help of a full-duplex relay node. The two sources and the relay use the same channel resources (i.e. co-channel transmission). We assume Gaussian channels with time-invariant channel gains which are known by all nodes. The two source nodes are connected by orthogonal limited-rate error-free conferencing links. By extending the proof of the converse for the Gaussian relay channel and introducing two lemmas on conditional (co-)variance, we present two genie-aided outer bounds of the capacity region for this multicast relay network. We extend noisy network coding to use source cooperation with the help of the theory of network equivalence. We also propose a new coding scheme, partial-decode-and- forward based linear network coding, which is essentially a hybrid scheme utilizing rate-splitting and messages conferencing at the source nodes, partial decoding and linear network coding at the relay, and joint decoding at each destination. A low-complexity alternative scheme, analog network coding based on amplify-and-forward relaying, is also investigated and shown to benefit greatly from the help of the conferencing links and can even outperform noisy network coding when the coherent combining gain is dominant.

  • 18.
    Du, Jinfeng
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Shamai (Shitz), Shlomo
    Technion - Israel Institute of Technology.
    Short-Message Noisy Network Coding with Partial Source Cooperation2012In: Information Theory Workshop (ITW), 2012 IEEE, IEEE conference proceedings, 2012, p. 144-147Conference paper (Refereed)
    Abstract [en]

    Noisy network coding (NNC) has been shown to outperform standard compress-and-forward (CF) in networks with multiple relays and/or multiple destinations. Recently, short-message noisy network coding (SNNC) has been proved to achieve the same rate region as NNC for independent sources but with significantly reduced encoding delay and decoding complexity. In this paper, we show that when partial cooperation between source nodes is possible, by performing rate-splitting, message exchange, and superposition coding with proper power allocation at the source nodes, SNNC can achieve a strictly larger rate region than NNC. The gain comes from coherent combining at all the receiving nodes.

  • 19.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Flowing with the water: On optimal monitoring of water distribution networks by mobile sensors2016Conference paper (Refereed)
  • 20.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Lifetime Maximization for Sensor Networks with Wireless Energy Transfer2016In: 2016 IEEE International Conference on Communications, ICC 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 20-25, article id 7510602Conference paper (Refereed)
    Abstract [en]

    In Wireless Sensor Networks (WSNs), to supply energy to the sensor nodes, wireless energy transfer (WET) is a promising technique. One of the most efficient procedures to transfer energy to the sensor nodes consists in using a sharp wireless energy beam from the base station to each node at a time. A natural fundamental question is what is the lifetime ensured by WET and how to maximize the network lifetime by scheduling the transmissions of the energy beams. In this paper, such a question is addressed by posing a new lifetime maximization problem for WET enabled WSNs. The binary nature of the energy transmission process introduces a binary constraint in the optimization problem, which makes challenging the investigation of the fundamental properties of WET and the computation of the optimal solution. The sufficient condition for which the WET makes WSNs immortal is established as function of the WET parameters. When such a condition is not met, a solution algorithm to the maximum lifetime problem is proposed. The numerical results show that the lifetime achieved by the proposed algorithm increases by about 50% compared to the case without WET, for a WSN with a small to medium size number of nodes. This suggests that it is desirable to schedule WET to prolong lifetime of WSNs having small or medium network sizes.

  • 21.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Poster: On the Immortality of Wireless Sensor Networks by Wireless Energy Transfer - A Node Deployment Perspective2017In: Proceedings of International Conference on Embedded Wireless Systems and Networks, 2017Conference paper (Refereed)
    Abstract [en]

    The lifetime of wireless sensor networks (WSNs) can be substantially extended by transferring energy wirelessly to the sensor nodes. In this poster, a wireless energy transfer (WET) enabled WSN is presented, where a base station transfers energy wirelessly to the sensor nodes that are deployed in several regions of interest, to supply them with energy to sense and to upload data. The WSN lifetime can be extended by deploying redundant sensor nodes, which allows the implementation of duty-cycling mechanisms to reduce nodes' energy consumption. In this context, a problem on sensor node deployment naturally arises, where one needs to determine how many sensor nodes to deploy in each region such that the total number of nodes is minimized, and the WSN is immortal. The problem is formulated as an integer optimization, whose solution is challenging due to the binary decision variables and a non-linear constraint. A greedy-based algorithm is proposed to achieve the optimal solution of such deployment problem. It is argued  that such scheme can be used in monitoring systems in smart cities, such as smart buildings and water lines.

  • 22.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Gkatzikis, Lazaros
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Xiag, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Energy Efficient Sensor Activation for Water Distribution Networks Based on Compressive Sensing2015In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 33, no 12, p. 2997-3010Article in journal (Refereed)
    Abstract [en]

    The recent development of low cost wireless sensors enables novel internet-of-things (IoT) applications, such as the monitoring of water distribution networks. In such scenarios, the lifetime of the wireless sensor network (WSN) is a major concern, given that sensor node replacement is generally inconvenient and costly. In this paper, a compressive sensing-based scheduling scheme is proposed that conserves energy by activating only a small subset of sensor nodes in each timeslot to sense and transmit. Compressive sensing introduces a cardinality constraint that makes the scheduling optimization problem particularly challenging. Taking advantage of the network topology imposed by the IoT water monitoring scenario, the scheduling problem is decomposed into simpler subproblems, and a dynamic-programming-based solution method is proposed. Based on the proposed method, a solution algorithm is derived, whose complexity and energy-wise performance are investigated. The complexity of the proposed algorithm is characterized and its performance is evaluated numerically via an IoT emulator of water distribution networks. The analytical and numerical results show that the proposed algorithm outperforms state-of-the-art approaches in terms of energy consumption, network lifetime, and robustness to sensor node failures. It is argued that the derived solution approach is general and it can be potentially applied to more IoT scenarios such as WSN scheduling in smart cities and intelligent transport systems.

  • 23.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Gkatzikis, Lazaros
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Energy efficient monitoring of water distribution networks via compressive sensing2015In: 2015 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2015, Vol. 2015, p. 6681-6686Conference paper (Refereed)
    Abstract [en]

    The recent development of low cost wireless sensors enables water monitoring through dense wireless sensor networks (WSN). Sensor nodes are battery powered devices, and hence their limited energy resources have to be optimally managed. The latest advancements in compressive sensing (CS) provide ample promise to increase WSNs lifetime by limiting the amount of measurements that have to be collected. Additional energy savings can be achieved through CS-based scheduling schemes that activate only a limited number of sensors to sense and transmit their measurements, whereas the rest are turned off. The ultimate objective is to maximize network lifetime without sacrificing network connectivity and monitoring performance. This problem can be approximated by an energy balancing approach that consists of multiple simpler subproblems, each of which corresponds to a specific time period. Then, the sensors that should be activated within a given period can be optimally derived through dynamic programming. The complexity of the proposed CS-based scheduling scheme is characterized and numerical evaluation reveals that it achieves comparable monitoring performance by activating only a fraction of the sensors.

  • 24.
    Du, Rong
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Gkatzikis, Lazaros
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    On Maximizing Sensor Network Lifetime by Energy Balancing2018In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 5, no 3Article in journal (Refereed)
    Abstract [en]

    Many physical systems, such as water/electricity distribution networks, are monitored by battery-powered wireless-sensor networks (WSNs). Since battery replacement of sensor nodes is generally difficult, long-term monitoring can be only achieved if the operation of the WSN nodes contributes to long WSN lifetime. Two prominent techniques to long WSN lifetime are 1) optimal sensor activation and 2) efficient data gathering and forwarding based on compressive sensing. These techniques are feasible only if the activated sensor nodes establish a connected communication network (connectivity constraint), and satisfy a compressive sensing decoding constraint (cardinality constraint). These two constraints make the problem of maximizing network lifetime via sensor node activation and compressive sensing NP-hard. To overcome this difficulty, an alternative approach that iteratively solves energy balancing problems is proposed. However, understanding whether maximizing network lifetime and energy balancing problems are aligned objectives is a fundamental open issue. The analysis reveals that the two optimization problems give different solutions, but the difference between the lifetime achieved by the energy balancing approach and the maximum lifetime is small when the initial energy at sensor nodes is significantly larger than the energy consumed for a single transmission. The lifetime achieved by energy balancing is asymptotically optimal, and that the achievable network lifetime is at least 50% of the optimum. Analysis and numerical simulations quantify the efficiency of the proposed energy balancing approach.

  • 25. Fei, Zesong
    et al.
    Cao, Congzhe
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hussain, Iqbal
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Kuang, Jingming
    Improved Luby transform codes in low overhead regions for binary erasure channels2014In: Transaction on Emerging Telecommunications Technologies, ISSN 2161-3915Article in journal (Refereed)
    Abstract [en]

    We study improved degree distribution for Luby transform (LT) codes, which exhibits improved bit error rates particularly in low overhead regions. We construct the degree distribution by modifying robust soliton distribution. The performance of our proposed LT codes is evaluated and compared with the conventional LT codes via And-Or tree analysis. Then we propose a transmission scheme based on our proposed degree distribution to improve the frame error rate in full recovery regions. Furthermore, the improved degree distribution is applied to distributed multi-source relay networks and unequal error protection. It is shown that our schemes achieve better performance and reduced complexity especially in low overhead regions, compared with conventional schemes.

  • 26. Fei, Zesong
    et al.
    Yuan, Jinhong
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Bai, Baoming
    Zhang, Shengli
    Lin, Dengsheng
    RECENT DEVELOPMENT OF ERROR CONTROL CODES FOR FUTURE COMMUNICATION AND STORAGE SYSTEMS2017In: China Communications, ISSN 1673-5447, Vol. 14, no 8, p. III-VArticle in journal (Other academic)
  • 27.
    Gao, Yulan
    et al.
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Yue
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Wu, Mingming
    Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Shao, Jinliang
    Univ Elect Sci & Technol China, Sch Math Sci, Chengdu 611731, Sichuan, Peoples R China..
    Game Theory-Based Anti-Jamming Strategies for Frequency Hopping Wireless Communications2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 8, p. 5314-5326Article in journal (Refereed)
    Abstract [en]

    In frequency hopping (FH) wireless communications, finding an effective transmission strategy to properly mitigate jamming has been recently considered as a critical issue, due to the inherent broadcast nature of wireless communications. Recently, game theory has been proposed as a powerful tool for dealing with the jamming problem, which can be considered as a player (jammer) playing against a user (transmitter). Different from existing results, in this paper, a bimatrix game framework is developed for modeling the interaction process between the transmitter and the jammer, and the sufficient and necessary conditions for Nash equilibrium (NE) strategy of the game are obtained under the linear constraints. Furthermore, the relationship between the NE solution and the global optimal solution of the corresponding quadratic programming is presented. In addition, a special analysis case is developed based on the continuous game framework in which each player has a continuum of strategies. Finally, we show that the performance can be improved based on our game theoretic framework, which is verified by numerical investigations.

  • 28.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Exact optimized-cost repair in multi-hop distributed storage networks2014In: 2014 IEEE International Conference on Communications, ICC, IEEE Computer Society, 2014, p. 4120-4124Conference paper (Refereed)
    Abstract [en]

    The problem of exact repair of a failed node in multi-hop networked distributed storage systems is considered. Contrary to the most of the current studies which model the repair process by the direct links from surviving nodes to the new node, the repair is modeled by considering the multi-hop network structure, and taking into account that there might not exist direct links from all the surviving nodes to the new node. In the repair problem of these systems, surviving nodes may cooperate to transmit the repair traffic to the new node. In this setting, we define the total number of packets transmitted between nodes as repair-cost. A lower bound of the repair-cost can thus be found by cut-set bound analysis. In this paper, we show that the lower bound of the repair-cost is achievable for the exact repair of MDS codes in tandem and grid networks, thus resulting in the minimum-cost exact MDS codes. Further, two suboptimal (achievable) bounds for the large scale grid networks are proposed.

  • 29.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Repair for distributed storage systems with erasure channels2013In: Communications (ICC), 2013 IEEE International Conference on, IEEE conference proceedings, 2013, p. 4058-4062Conference paper (Refereed)
    Abstract [en]

    We study the repair problem of distributed storage systems in erasure networks where the packets transmitted from surviving nodes to the new node might be lost. The fundamental storage-bandwidth tradeoff is calculated by multicasting analysis in erasure networks. The optimal tradeoff bound can be asymptotically achieved when the number of transmission (packets) goes to infinity. For a limited number of transmission, we study the probability of successful regenerating. Then, we investigate two approaches of increasing the probability of successful regenerating, namely, by connecting more surviving nodes or by increasing the storage space of nodes. Using more nodes may pose larger delay and in certain situation it might not be possible to connect to more nodes too. We show that in addition to reducing repair bandwidth, increasing storage space can also increase reliability for repair.

  • 30.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. 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.
    Decentralized minimum-cost repair for distributed storage systems2013In: Communications (ICC), 2013 IEEE International Conference on, IEEE conference proceedings, 2013, p. 1910-1914Conference paper (Refereed)
    Abstract [en]

    There have been emerging lots of applications for distributed storage systems e.g., those in wireless sensor networks or cloud storage. Since storage nodes in wireless sensor networks have limited battery, it is valuable to find a repair scheme with optimal transmission costs (e.g., energy). The optimal-cost repair has been recently investigated in a centralized way. However a centralized control mechanism may not be available or is very expensive. For the scenarios, it is interesting to study optimal-cost repair in a decentralized setup. We formulate the optimal-cost repair as convex optimization problems for the network with convex transmission costs. Then we use primal and dual decomposition approaches to decouple the problem into subproblems to be solved locally. Thus, each surviving node, collaborating with other nodes, can minimize its transmission cost such that the global cost is minimized. We further study the optimality and convergence of the algorithms. Finally, we discuss the code construction and determine the field size for finding feasible network codes in our approaches.

  • 31.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Li, Jun
    KTH, School of Electrical Engineering (EES).
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control.
    Lin, Z.
    Repair for distributed storage systems with packet erasure channels and dedicated nodes for repair2016In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, no 4, p. 1367-1383, article id 7422022Article in journal (Refereed)
    Abstract [en]

    We study the repair problem in distributed storage systems where storage nodes are connected through packet erasure channels and some nodes are dedicated to repair [termed as dedicated-for-repair (DR) storage nodes]. We first investigate the minimum required repair-bandwidth in an asymptotic setup, in which the stored file is assumed to have an infinite size. The result shows that the asymptotic repair-bandwidth over packet erasure channels with a fixed erasure probability has a closed-form relation to the repair-bandwidth in lossless networks. Next, we show the benefits of DR storage nodes in reducing the repair bandwidth, and then we derive the necessary minimal storage space of DR storage nodes. Finally, we study the repair in a nonasymptotic setup, where the stored file size is finite. We study the minimum practical-repair-bandwidth, i.e., the repair-bandwidth for achieving a given probability of successful repair. A combinatorial optimization problem is formulated to provide the optimal practical-repair-bandwidth for a given packet erasure probability. We show the gain of our proposed approaches in reducing the repair-bandwidth.

  • 32.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Salimi, Somayeh
    KTH, School of Electrical Engineering (EES), Communication Networks.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Secure Partial Repair in Wireless Caching Networks with Broadcast Channels2015In: 2015 IEEE Conference on Communications and NetworkSecurity, CNS 2015, 2015, p. 353-360, article id 7346846Conference paper (Refereed)
    Abstract [en]

    We study security in partial repair in wireless caching networks where parts of the stored packets in the caching nodes are susceptible to be erased. Let us denote a caching node that has lost parts of its stored packets as a sick caching node and a caching node that has not lost any packet as a healthy caching node. In partial repair, a set of caching nodes ( among sick and healthy caching nodes) broadcast information to other sick caching nodes to recover the erased packets. The broadcast information from a caching node is assumed to be received without any error by all other caching nodes. All the sick caching nodes then are able to recover their erased packets, while using the broadcast information and the non-erased packets in their storage as side information. In this setting, if an eavesdropper overhears the broadcast channels, it might obtain some information about the stored file. We thus study secure partial repair in the senses of information-theoretically strong and weak security. In both senses, we investigate the secrecy caching capacity, namely, the maximum amount of information which can be stored in the caching network such that there is no leakage of information during a partial repair process. We then deduce the strong and weak secrecy caching capacities, and also derive the sufficient finite field sizes for achieving the capacities. Finally, we propose optimal secure codes for exact partial repair, in which the recovered packets are exactly the same as erased packets.

  • 33.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Optimal-cost repair in multi-hop distributed storage systems2011In: IEEE International Symposium on Information Theory - Proceedings, IEEE , 2011, p. 1437-1441Conference paper (Refereed)
    Abstract [en]

    In distributed storage systems reliability is achieved through redundant storage nodes distributed in the network. Then a data collector can recover source information even if some nodes fail. To maintain reliability, an autonomous and efficient protocol should be used to reconstruct the failed node. Therepairprocess causes traffic in the network. Recent results in e.g., [1], [2] found the optimal traffic-storage tradeoff, and proposed regenerating codes to achieve the optimality. We investigate the link costs and the impact of network topologies during therepairprocess. We formulate the minimum costrepairproblem in joint and decoupled methods. We investigate the required field size for the joint method. For the decoupled method, we show that the optimization problem is linear for the linear cost. We further show that the cooperation of surviving nodes could efficiently exploit the network topology and reduce therepaircost. The numerical results in tandem, star and grid networks show the benefits of our methods in term of the repair cost.

  • 34.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Partial Repair for Wireless Caching Networks With Broadcast Channels2015In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 4, no 2, p. 145-148, article id 6987261Article in journal (Refereed)
    Abstract [en]

    We investigate the repair problem for wireless caching networks when parts of stored packets in cashing nodes are lost. We first develop theoretical lower bounds on the number of necessary transmission packets over error-free broadcast channels for repair. Then we discuss the impact of the distribution of the lost packets among caching nodes. Finally, we study the construction of repair codes and propose the optimal exact repair for some special scenarios.

  • 35.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Two-Layer Coding in Distributed Storage Systems With Partial Node Failure/Repair2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 4, p. 726-729Article in journal (Refereed)
    Abstract [en]

    We a distributed storage system where parts of the stored packets in storage nodes are subject to being lost. In a process, termed as the partial repair, the lost packets in a faulty node are recovered by the transmitted packets from other storage nodes and the available packets in the faulty node. To improve reliability of the stored data, and reduce the transmission costs, we propose a scheme that implements two-layer coding for storing files in the system. We study the minimum possible partial-repair bandwidth, and the codes that achieve the optimal bound.

  • 36.
    Gerami, Majid
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Shum, K. W.
    Lin, D.
    Optimal-cost repair in multi-hop distributed storage systems with network coding2016In: Transactions on Emerging Telecommunications Technologies, ISSN 2161-5748, Vol. 27, no 11, p. 1539-1549Article in journal (Refereed)
    Abstract [en]

    We study the transmission cost of repair in a distributed storage system, where storage nodes are connected together through an arbitrary network topology, and there is a cost in the use of the network link. Contrary to the classical model, where there exists a link between a pair of storage node, in our repair model there might not exist a link between some pairs of storage nodes or it might be expensive to use. For that, we propose surviving nodes cooperation in repair, meaning that the surviving nodes as the intermediate nodes combine their received packets with their own stored packets and then transmit coded packets towards the new node. We show that surviving node cooperation can reduce the repair-cost, the sum of the costs for transmitting repairing data between the surviving nodes and the new node. For the system that allows surviving node cooperation, we find the minimum-cost codes in repair by firstly deriving a lower bound of the repair-cost through an optimization problem and then proposing achievable codes. We show the gain of the proposed codes in reducing the repair-cost in some scenarios.

  • 37.
    Girnyk, Maksym
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kildehöj Rasmussen, Lars
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative communication in multi-source line networks2012In: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, p. 2379-2383Conference paper (Refereed)
    Abstract [en]

    Cooperative communication is shown to be an efficient method of combating fading in wireless networks. By "sharing" their antennas cooperating single-antenna nodes create a virtual multi-antenna system and therefore, benefit from spatial diversity. Network coding being a particular cooperative communication technique provides substantial gains in data rate, especially in networks with many sink nodes. By allowing intermediate nodes of a network to mix the incoming data streams, one can achieve the multicast capacity. Recently, Xiao and Skoglund showed that binary network coding (BNC) is not optimal for multi-user multi-relay networks in terms of diversity and proposed diversity network coding (DNC) scheme that outperforms BNC approach. Following this approach we examine potential diversity gains of using the DNC scheme for multi-source line networks. We show that the DNC technique outperforms both conventional time-orthogonal transmission and the BNC scheme. Further, the problem of optimal scheduling of the transmission is explored. We formulate the optimization problem and propose efficient solutions. Numerical results are presented to support theoretical findings.

  • 38.
    Girnyk, Maksym
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Power Allocation for Multi-Hop Decode-and-Forward Cognitive Radio Networks with Line Topology2012In: 2012 Swedish Communication Technologies Workshop, Swe-CTW 2012, Lund, 2012, p. 7-12Conference paper (Refereed)
    Abstract [en]

    In the present paper we study the power allocation for multi-hop underlay cognitive radio networks (CRNs) with line topology. That is, we consider a scenario, where a CRN operates in parallel to the primary network provided that the interference created to the primary network is limited by an acceptable threshold. The CNR is assumed to be a multi-hop relay network and hence before reaching the destination information from the source node may pass several hops from node to node. At each hop, the information is decoded and forwarded to the following node. It is further assumed that transmissions can be overheard by neighboring nodes, thereby creating interference. The power at each node can be optimally adjusted so that the end-to-end throughput of the CRN is maximized, while the constraint on interference towards the primary network is satisfied. In this paper, we show that for line CRNs the optimal power allocation is achieved when capacities of all intermediate links are equal and the interference constraint of the most disturbed primary user is fulfilled with equality. To simplify the computation of the optimal power allocation we derive two approximate solutions as well as several distributed power allocation schemes. The numerical results illustrate the interplay between the proposed solutions and the optimal power allocation.

  • 39.
    Girnyk, Maksym
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehöj
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Optimal Power Allocation in Multi-Hop Cognitive Radio Networks2011In: 2011 IEEE 22nd International Symposium On Personal Indoor And Mobile Radio Communications (PIMRC), New York: IEEE conference proceedings, 2011, p. 472-476Conference paper (Refereed)
    Abstract [en]

    Optimal power allocation in a multi-hop cognitive radio network is investigated. Information transmitted from the source passes through several wireless relay nodes before reaching the destination. At each hop, the received signal is decoded, re-encoded and retransmitted to the following node. Transmissions at every hop are overheard by nearby nodes and therefore cause interference. We study optimal power allocation strategies that maximize the end-to-end throughput of the network under the constraint of strictly limited interference to external users. We show that for networks that can be modeled as a line topology the optimal solution is achieved when the capacities of every intermediate link are equal and the interference power constraint is satisfied with equality. High-and low-SNR approximations that simplify the problem of finding the optimal power allocation are presented as well. The numerical results show good performance compared to schemes with equal power allocation.

  • 40.
    Huang, Jin
    et al.
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    State of the art on road traffic sensing and learning based on mobile user network log data2018In: Neurocomputing, ISSN 0925-2312, E-ISSN 1872-8286, Vol. 278, p. 110-118Article in journal (Refereed)
    Abstract [en]

    With the improvement of the storage and big data processing technology, mobile operators are able to extract and store a large amount of mobile network generated user behavior data, in order to develop various intelligent applications. One interesting application based on these data is traffic sensing, which uses techniques of learning human mobility patterns from updated location information in network interaction log data. Mobile networks, under which a huge amount of frequently updated location information of mobile users are tracked, can provide complete coverage to estimate traffic condition on roads and highways. This paper studies potential challenges and opportunities in intelligent traffic sensing from the data science point of view with mobile network generated data. Firstly, we classify the data resources available in the commercial radio network according to different taxonomy criteria. Then we outline the broken-down problems that fit in the framework of traffic sensing based on mobile user network log data. We study the existing data processing and learning algorithms on extracting traffic condition information from a large amount of mobile network log data. Finally we make suggestion on potential future work for traffic sensing on data from mobile networks. We believe the techniques and insights provided here will inspire the research community in data science to develop the machine learning models of traffic sensing on the widely collected mobile user behavior data.

  • 41.
    Huang, Yongming
    et al.
    Southeast Univ, Sch Informat Sci & Engn, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Zhang, Jianjun
    Southeast Univ, Sch Informat Sci & Engn, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES).
    Constant Envelope Hybrid Precoding for Directional Millimeter-Wave Communications2018In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 36, no 4, p. 845-859Article in journal (Refereed)
    Abstract [en]

    Millimeter wave (mmwave) communication has attracted increasing attention owing to its abundant spectrum resource. The short wavelength at mmwave frequencies facilitates placing a large number of antennas in a small space, and the mmwave channels are likely to be sparse in the directions. These two new features promise enhanced security by directional precoding. To explore this potential, we investigate the design of directional hybrid digital and analog precoding for the multiuser mmwave communication system with multiple eavesdroppers. Particularly, we consider two cost-efficient sub-connected hybrid architectures, i.e., multi-subarray architecture and switched phased- array architecture, and optimize the hybrid precoding under per-antenna constant envelope (CE) constraints. The goal of our design is to guarantee the receive quality of the legitimate users while minimizing the power leaked to the eavesdroppers, so as to realize a directional transmission for a general mmwave channel. The resulting problems are very challenging due to the nonlinear CE constraints and binary integer constraint from antenna selection. To address them, we leverage exact penalty function methods to find efficient solutions to the CE hybrid directional precoding. Our analysis shows that the proposed algorithm is able to converge to a stationary point under some mild conditions. Simulation results are finally provided to confirm the effectiveness of the proposed schemes and their superiority over the existing schemes under both single-path and multi-path mmwave channels.

  • 42.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Land, I.
    Chan, T.H.
    Xiao, Ming
    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.
    A new design framework for LT codes over noisy channels2014In: 2014 IEEE International Symposium on Information Theory (ISIT), IEEE , 2014, p. 2162-2166Conference paper (Refereed)
    Abstract [en]

    Luby transform (LT) codes are a class of rateless codes that automatically adapt their rate to the quality of the communication channel. In the original LT codes, fixed check-node degree distributions are used to combine variable nodes uniformly at random to extend the code graph and produce code bits. Here we propose a different approach: we design a sequence of rate-compatible degree distributions, and develop an algorithm that produces code bits in a manner such that the resulting degree distributions follow the designed sequence. Using this new design framework, we develop low-complexity LT codes suitable for time-varying noisy channels. Performance and complexity of the proposed LT codes are measured in terms of bit error rate and average number of edges per information and coded bit, respectively. Numerical examples illustrate the resulting trade-off between performance and complexity of the designed LT codes.

  • 43.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    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.
    Design of LT Codes with Equal and Unequal Erasure Protection over Binary Erasure Channels2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 2, p. 261-264Article in journal (Refereed)
    Abstract [en]

    The erasure floor performance of Luby Transform (LT) codes is mainly determined by the minimum variable-node degree. Thus we propose a modified encoding scheme that maximizes the minimum variable-node degree for transmission over binary erasure channels. The proposed scheme leads to an almost-regular variable-node degree distribution. The encoding process is generalized to accommodate arbitrary variable-node degree distributions for additional improved performance. The asymptotic performance is investigated using density evolution and compared with a conventional LT code. The scheme is further extended to enable a higher level of unequal erasure protection.

  • 44.
    Hussain, Iqbal
    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.
    Design of Spatially-Coupled Rateless Codes2012In: 2012 IEEE 23rd International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC), IEEE , 2012, p. 1913-1918Conference paper (Refereed)
    Abstract [en]

    We investigate the design and performance of spatially-coupled rateless codes. A modified encoding process is introduced for spatially-coupled Luby Transform (SCLT) codes which leads to an almost regular variable-node degree distribution at the encoding graph. The proposed SCLT codes outperform its counterparts significantly over binary erasure channels, particularly in the erasure floor region. To further improve the erasure floor performance, the approach of spatial coupling is then extended to Raptor codes by concatenating a high-rate pre-coder to the SCLT codes. It is shown that the spatial coupling improves the convergence threshold of Raptor codes. Different ensembles of spatially-coupled Raptor codes are constructed depending on whether pre-coders and/or LT codes are spatially-coupled. The performance of different ensembles of spatially-coupled Raptor codes is then evaluated and compared based on density evolution, leading to an improved spatially-coupled Raptor code in terms of convergence threshold and lower complexity.

  • 45.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Buffer-Based Distributed LT Codes2014In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, no 11, p. 3725-3739Article in journal (Refereed)
    Abstract [en]

    We focus on the design of distributed Luby transform (DLT) codes for erasure networks with multiple sources and multiple relays, communicating to a single destination. The erasure-floor performance of DLT codes improves with the maximum degree of the relay-degree distribution. However, for conventional DLT codes, the maximum degree is upper-bounded by the number of sources. An additional constraint is that the sources are required to have the same information block length. We introduce a D-bit buffer for each source-relay link, which allows the relay to select multiple encoded bits from the same source for the relay-encoding process; thus, the number of sources no longer limits the maximum degree at the relay. Furthermore, the introduction of buffers facilitates the use of different information block sizes across sources. Based on density evolution we develop an asymptotic analytical framework for optimization of the relay-degree distribution. We further integrate techniques for unequal erasure protection into the optimization framework. The proposed codes are considered for both lossless and lossy source-relay links. Numerical examples show that there is no loss in erasure rate performance for transmission over lossy source-relay links as compared to lossless links. Additional delays, however, may occur. The design framework and our contributions are demonstrated by a number of illustrative examples, showing the improvements obtained by the proposed buffer-based DLT codes.

  • 46.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rateless Codes for the Multiway Relay Channel2014In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 3, no 5, p. 457-460Article in journal (Refereed)
    Abstract [en]

    We consider distributed Luby transform (DLT) codes for efficient packet transmission in a multi-way relay network, where the links are modeled as erasure channels. Density evolution is applied for asymptotic performance analysis, and subsequently used in a linear-programming design framework for optimizing the degree distribution at the relay in terms of overhead. Moreover a buffer is introduced at the relay to enable efficient downlink transmission even if packets are lost during uplink transmission. Performance losses in terms of delay and/or erasure rates caused by link erasures during uplink transmission are thus alleviated. The proposed DLT codes provide significant improvements in overhead and decoded erasure rates. Numerical results for finite-length codes follow closely the asymptotic analysis. Our results demonstrate that the proposed buffer-based DLT codes outperform its counterparts for lossy uplink transmission.

  • 47.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Reduced-complexity decoding of LT codes over noisy channels2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), IEEE Communications Society, 2013, p. 3856-3860Conference paper (Refereed)
    Abstract [en]

    We propose an adaptive decoding scheme for Luby Transform (LT) codes over noisy channels which exhibits lower complexity as compared to the conventional LT decoder. The corresponding modified degree distributions have been derived for the low-complexity LT decoder. The complexity and performance comparison demonstrate that the decoding complexity can be reduced with negligible degradation in bit error rate performance.

  • 48.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Regularized Variable-Node LT Codes with Improved Erasure Floor Performance2013Conference paper (Refereed)
    Abstract [en]

    We consider the use of extrinsic information transfercharts for the design of Luby Transform (LT) codes over thebinary erasure channel (BEC). In particular, we formulate anoptimization problem to determine asymptotically good check-node degree distributions in terms of decoder overhead. Wefurther propose a modified encoding scheme that maximizes theminimum variable-node degree, thus optimizing the erasure-floorperformance at the expense of decoder overhead, and resultingin a regularized variable-node degree distribution. The two ap-proaches are combined to jointly improve decoder overhead anddecoder erasure floor by incorporating the proposed encodingstrategy into the convex optimization problem. The performanceof the proposed schemes is investigated for transmission over theBEC through density evolution and numerical simulations. Theoptimized codes compare favorably to conventional LT codes,and are further extended to enable improved performance forunequal erasure protection.

  • 49.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Rasmussen, Lars K.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Unequal error protection of LT codes over noisy channels2012In: 2012 Swedish Communication Technologies Workshop, Swe-CTW 2012, IEEE , 2012, p. 19-24Conference paper (Refereed)
    Abstract [en]

    We propose a new unequal error protection (UEP) scheme for Luby Transform (LT) codes over additive white Gaussian noise (AWGN) channels. In contrast to the state-of-the-art UEP scheme for LT codes where the effective code rates are exploited for UEP, we characterize the variable-node degree distribution to achieve UEP for LT codes. For performance analysis, we compare the lower bounds on bit error rate for our proposed scheme and a conventional UEP-based LT codes over AWGN channels for various parameters. Moreover, it is demonstrated through numerical examples that our proposed UEP scheme has better performance than the conventional UEP-based LT codes over a wide range of code rates and channel conditions.

  • 50.
    Hussain, Iqbal
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehoj
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of South Australia, Australia.
    Erasure Floor Analysis of Distributed LT Codes2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 8, p. 2788-2796Article in journal (Refereed)
    Abstract [en]

    We investigate the erasure floor performance of distributed Luby transform (DLT) codes for transmission within a multi-source, single-relay, and single-destination erasure-link network. In general, Luby transform (LT) codes exhibit a high erasure floor due to poor minimum-distance properties, which can be improved by maximizing the minimum variable-node degree. The same behavior is observed for DLT codes, and therefore a new combining scheme at the relay is proposed to maximize the minimum variable-node degree in the decoding graph. Furthermore, the encoding process at the sources and the combining scheme at the relay are coordinated to improve the transmission overhead. To characterize the asymptotic performance of the proposed DLT codes, we derive closed-form density-evolution expressions, considering both lossless and lossy source-relay channels, respectively. To support the asymptotic analysis, we evaluate the performance of the proposed DLT codes by numerical examples and demonstrate that the numerical results correspond closely to the analysis. Significant improvements in both the erasure floor and transmission overhead are obtained for the proposed DLT codes, as compared to conventional DLT codes.

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