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  • 101.
    Demay, Gregory
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Source Coding for Erasure Channels2011Studentarbete övrigt, 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The main goal of this thesis is to bound the rate-distortion performance of the aforementioned sparse-graph codes for lossy compression of a BES. As our main contributions, we first derive lower bounds on the rate-distortion performance of LDGM codes for the BES, which are valid for any LDGM code of a given rate and generator node degree distribution and any encoding function. Our approach follows that of Kudekar and Urbanke, where lower bounds were derived for the BSS case. They introduced two methods for deriving lower bounds, namely the counting method and the test channel method. Based on numerical results they observed that the two methods lead to the same bound. We generalize these two methods for the BES and prove that indeed both methods lead to identical rate-distortion bounds for the BES and hence, also for the BSS. Secondly, based on the technique introduced by Martinian and Wainwright, we upper bound the rate-distortion performance of the check regular Poisson LDGM (CRP LDGM) ensemble and the compound LDGM-LDPC ensemble for the BES.We also show that there exist compound LDGM-LDPC codes, with degrees independent of the blocklength, which can achieve any given point on the Shannon rate-distortion curve of the BES.

  • 102.
    Demay, Gregory
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehöj
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimality of LDGM-LDPC compound codes for lossy compression of binary erasure source2010Ingår i: 2010 20th International Symposium on Information Theory and Its Applications, ISITA 2010 and the 2010 20th International Symposium on Spread Spectrum Techniques and Applications, ISSSTA 2010, 2010, s. 589-594Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider the Binary Erasure Source (BES) introduced by Martinian and Yedidia. Based on the technique introduced by Martinian and Wainwright, we upper bound the rate-distortion performance of the check regular Poisson LDGM ensemble and the compound LDGM-LDPC ensemble for the BES. We also show that there exist compound LDGM-LDPC codes, with degrees independent of the block-length, which can achieve any given point on the Shannon rate-distortion curve of the BES.

  • 103.
    Demay, Gregory
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rathi, Vishwambhar
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rasmussen, Lars Kildehöj
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Rate distortion bounds for binary erasure source using sparse graph codes2010Ingår i: Data Compression Conference, DCC 2010, 2010, s. 49-58Konferensbidrag (Refereegranskat)
    Abstract [en]

    We consider lower bounds on the rate-distortion performance for the binary erasure source (BES) introduced by Martinian and Yedidia, using sparse graph codes for compression. Our approach follows that of Kudekar and Urbanke, where lower bounds on the rate distortion performance of low-density generator matrix (LDGM) codes for the binary symmetric source (BSS) are derived. They introduced two methods for deriving lower bounds, namely the counting method and the test channel method. Based on numerical results they observed that the two methods lead to the same bound. We generalize these two methods for the BES and prove that indeed both methods lead to identical rate-distortion bounds for the BES and hence, also for the BSS.

  • 104. DengSheng, Lin
    et al.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    ShaoQian, Li
    Packet combining based on cross-packet coding2013Ingår i: Science China Information Sciences, ISSN 1674-733X, Vol. 56, nr 2, s. 022302-Artikel i tidskrift (Refereegranskat)
    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.

  • 105.
    Deniaux, Tiphanie
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Investigate more robust featuresfor Speech Recognition usingDeep Learning2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The new electronic devices and their constant progress brought up the chal-lenge of improving the speech recognitions systems. Indeed, people tend touse more and more hands-free devices that are inclined to be used in noisyenvironments. The evolution of Machine Learning techniques has been very ef-ficient for the last decade and speech recognition system using those techniquesappeared. The main challenge of Automatic Speech Recognition systems nowa-days is the improvement of the robustness to noise and reverberations. DeepLearning methods were used to either improve the speech representations ordefining better distributions probabilities. The problem we face is the drop inthe performance of ASR systems when inputs are noisy. The general approachis to define novel speech features that are more robust using Deep Neural Net-works. To do so we got through different implementations as the incorporationof autooencoders in the MFCC block diagram or the deep denoising autoen-coders with different pre-training methods. The final solution is a system thatbuild more robust features from noisy MFCC. Our input is the demonstrationthat a denoising system using q quantized DDAEs defined by the clustering ofthe training data using K-means is more efficient than one denoising systemapplied to the whole data. The performance gained using such a system is of 2to 3% in terms of phone error rate and might be improved using more trainingdata and better tuned NN parameters.

  • 106. Ding, Zhiguo
    et al.
    Krikidis, Ioannis
    Rong, Beiyu
    Thompson, John S.
    Wang, Chao
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Yang, Sheng
    On Combating The Half-Duplex Constraint In Modern Cooperative Networks: Protocols And Techniques2012Ingår i: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 19, nr 6, s. 20-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A key issue that characterizes cooperative wireless networks is the half-duplex constraint (HDC), which refers to the inability of current modems to receive and transmit data in the same frequency at the same time. This hardware limitation results in inefficient use of system resources (bandwidth loss) as it requires dedicated bandwidth allocation for relay transmissions. Methods to overcome the HDC have been studied intensively in the literature of cooperative networks in recent years, and several approaches have been proposed. In this article we highlight four different techniques which combat the HDC by using existing technology. The first approach is non-orthogonal protocols, which allow the source to be active during relay transmissions. The second approach is the overlap of several relaying transmissions in order to mimic an ideal full-duplex operation. The third solution is the two-way relay channel where two sources exchange data via the assistance of a shared relay. Finally, the fourth approach incorporates cooperation on the "network" level and uses the cognitive radio concept to enable relay transmissions during silent periods of source terminals. These techniques summarize some of the most significant HDC solutions that cover both the physical and network layers.

  • 107.
    Do, Hieu
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Fundamental Aspects of Cooperative Interference Management2013Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Today and future wireless networks are facing one of their greatest limiting factors:interference. This is due to the unprecedented increase in the number of connecteddevices. Therefore, in order to meet the ever increasing demand for data rate andquality of services, more advanced techniques than what we have today are requiredto deal with interference. This thesis takes a step towards interference managementin multiuser wireless systems by means of relaying and cooperation. We study fourfundamental building blocks in network information theory, propose new codingschemes, and derive limits on the capacity regions.

    The first problem we consider is the one-sided interference channel with bidirectional and rate-limited receiver cooperation. We propose a coding scheme that tailors two versions of superposition coding with classical relaying protocols. Theproposed scheme unifies and recovers previous results for the unidirectional coop-eration, yet in simpler forms. Analytical and numerical results confirm the benefitsof cooperation and illuminate the ideas behind the coding strategy.

    The second problem generalizes the first one by allowing the existence of bothcrossover links in the channel. We propose a coding scheme for this channel byextending noisy network coding to encompass rate-splitting at the encoders. Theachievable rate region is shown to be the same as a region achieved by explicitbinning. As a corollary, we prove that noisy network coding achieves the capacityregion of the Gaussian channel within 1 bit, under strong interference. Our resultis among the first to show constant-gap optimality of noisy network coding for amultiple-unicast problem, and to demonstrate equivalence in terms of achievablerates of two different coding approaches for a noisy interference network.

    We follow up by introducing a dedicated relay into the interference channelwhich simultaneously helps both receivers. For this third problem, the interferencechannel with a relay, we propose new coding schemes based on layered codes for long- and short-message quantize-forward techniques. The short-message schemesshow improvements in the achievable rates compared to other known coding tech-niques, especially when the channel is asymmetric, while relaxing the excessive delayissue of the long-message scheme. The analysis also reveals the trade-off betweenachievable rates, encoding and decoding delays, and complexity.

    In the fourth problem, we propose a new model for cooperative communication,the interfering relay channels, which consists of two neighboring relay channelsinducing interference to each other. Each relay, by utilizing a finite-capacity andnoise-free link to its own receiver, helps the receiver decode the desired message.We characterize the exact and approximate capacity region and sum-capacity forvarious classes of channels. The established results generalize and unify severalknown results for the relay and interference channels.The methods and results shown in this thesis aim at providing insight intopotential techniques for cooperative interference management in real-world systems.

  • 108.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Chung, Sae-Young
    Korea Advanced Institute of Science and Technology (KAIST), School of EECS.
    Linear Beamforming and Superposition Coding with Common Information for the Gaussian MIMO Broadcast Channel2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 8, s. 2484-2494Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Gaussian multiple-input multiple-output broadcast channel (MIMO GBC) is considered. Throughout the paper it is assumed that 1) input signals are Gaussian and 2) perfect channel state information is available at the transmitter and at the receivers. By considering each data stream as a single user, the uplink-downlink signal-to-interference-plus-noise (SINR) duality is generalized to the MIMO case with general cross-talk matrix. The duality is subsequently applied to finding the solution for the SINR-balancing problem. The result serves as a tool for characterizing achievable rate regions of different coding strategies. Next, we investigate a superposition coding scheme proposed by Cover-van der Meulen-Hajek and Pursley (nicknamed CMHP [1]), where there is a common message to both users. We consider a MIMO broadcast channel with two users, each user has two antennas and the transmitter has four antennas. Assuming one common stream is sent by CMHP coding and successive decoding, a lower bound to the CMHP rate region is found. Behaviors of the CMHP rate region and sumrate are analyzed. We find the sumrate gaps between DPC, CMHP, and MMSE at high SNR for general 2-user multiple-input single-output (MISO) Gaussian broadcast channel. The result suggests when CMHP is beneficial for sumrate.

  • 109.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    A new inner bound for the interference relay channel2012Ingår i: 2012 46th Annual Conference on Information Sciences and Systems, CISS 2012, IEEE , 2012, s. 6310756-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes a new coding scheme for the discrete memoryless interference channel with a dedicated relay. The scheme is built upon rate-splitting encoding, layered noisy network coding, and joint decoding. The result is extended to two Gaussian channels. For the Gaussian channel whose relay is connected to the destinations via orthogonal links we indirectly show that the proposed scheme achieves a bounded gap to the capacity region under certain channel conditions. For the Gaussian channel wherein the relay receives and transmits in the same spectral resource with the transmitters the numerical results show that the proposed scheme achieves higher sum rate than other compress-forward-based schemes. This work, together with our previous work [1], shows that noisy network coding can be extended by the well-known rate-splitting technique of the interference channel to achieve a bounded gap to the capacity region of some multi-unicast networks.

  • 110.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    An Achievable Rate Region for the Gaussian Z-interference Channel with Conferencing2009Ingår i: 2009 47TH ANNUAL ALLERTON CONFERENCE ON COMMUNICATION, CONTROL, AND COMPUTING, VOLS 1 AND 2, NEW YORK: IEEE , 2009, s. 75-81Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an achievable rate region for a 2-user Gaussian Z-interference channel with a noiseless and bidirectional digital communication link between the receivers. The region is achieved by utilizing the rate-splitting encoding technique, and the decode-and-forward and compress-and-forward strategies. In the very strong interference regime, the capacity region is achieved. In the weak interference regime, the asymptotic sum rate is characterized and shown to be possibly unbounded, which is in contrast to a recent result by Yu and Zhou for a similar scenario, however, with a unidirectional communication link between the receivers.

  • 111.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Capacity bounds for the Z channel2011Ingår i: IEEE Information Theory Workshop (ITW), 2011, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a new achievable rate region for the discrete memoryless Z channel (DM-ZC) using Marton coding with rate splitting. The region is shown to include previously known achievable rate regions. Secondly we study a class of degraded Z channels, the bijective degraded Z channel (BDZC). An outer bound for the BDZC is proved, which is shown to meet the inner bound for the deterministic settings. For the Gaussian Z channel with weak crossover link, we show that if Gaussian inputs are optimal then a coding scheme based on Marton coding without rate splitting achieves to within half a bit per real dimension from the boundary of the capacity region.

  • 112.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Coding for the Z Channel With a Digital Relay Link2010Ingår i: 2010 IEEE Information Theory Workshop, ITW 2010 - Proceedings, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers a discrete memoryless four-node network where two nodes want to send three independent messages to the other two nodes. The two receiving nodes are allowed to cooperate by means of a unidirectional noiseless link with finite capacity. A coding scheme is proposed which combines rate splitting, block Markov multi-level superposition coding with binning and joint decoding. The general achievable rates are then specialized to degraded channel and Gaussian channel, where it is shown that the sum capacity for the Gaussian channel is achieved under certain conditions. Results in this paper recover and unify previously known results for the discrete memoryless Z channel without cooperation, and results for the Gaussian Z-interference channel with a digital relay link.

  • 113.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Layered quantize-forward for the two-way relay channel2012Ingår i: Information Theory Proceedings (ISIT), 2012 IEEE International Symposium on, IEEE , 2012, s. 423-427Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes two new coding schemes for the discretememoryless two-way relay channel. The main target is to show thebenefits of compress-forward without Wyner-Ziv binning and oflayered relaying in networks wherein a relay is to help multipledestinations, that may have unequal channel quality and/or haveaccess to different side information. Numerical results for aGaussian channel show that the new coding schemes outperformvariants of compress-forward relaying and offer a good trade-offbetween achievable rates and complexity and decoding delay. The ideacan also be applied to other relay networks.

  • 114.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Noisy network coding approach to the interference channel with receiver cooperation2011Ingår i: 49th Annual Allerton Conference on Communication, Control, and Computing, 2011., 2011, s. 839-846Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work proposes a new coding scheme for thediscrete memoryless two-user interference channel whose receivers can cooperate to decode their desired messages. Thecoding scheme is built upon Han-Kobayashi rate splitting andsuperposition coding at the transmitters, noisy network coding,and non-unique joint decoding at the receivers. As a case studythe general achievable region leads to an inner bound for theGaussian interference channel whose receivers cooperate throughrate-limited orthogonal channels. It is shown that this innerbound is equivalent to the one-round quantize-bin-and-forwardinner bound established by Wang and Tse, thereby showing thatnoisy network coding achieves within 1 bit/s/Hz to the capacityregion when the interference is strong, and achieves within 1 bit/s/Hz to the capacity region of the Gaussian compound multipleaccess channel with conferencing decoders regardless of channelparameters.

  • 115.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    The Gaussian Z-interference channel with rate-constrained conferencing decoders2010Ingår i: 2010 IEEE International Conference on Communications, 2010, s. 5502610-Konferensbidrag (Refereegranskat)
    Abstract [en]

    We derive achievable rate regions for a 2-user Gaussian Z-interference channel with conferencing decoders. We identify different cases where the rate-limitedness of the conference link from the interference-free receiver to the interfered receiver affects the conferencing strategy as well as the achievable rate region. Furthermore, an outer bound to the capacity region based on cut-set and genie-aided bounds is presented.

  • 116.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Vu, Mai
    Tufts University.
    Capacity Region of a Class of Interfering Relay Channels2013Ingår i: 2013 IEEE Information Theory Workshop (ITW), IEEE , 2013, s. 6691350-Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies a new model for cooperative communication, the interfering relay channels. We show that thehash-forward scheme introduced by Kim for the primitive relay channel is capacity achieving for a class of semideterministic interfering relay channels. The obtained capacity result generalizes and unifies earlier capacity results for a class of primitive relay channels and a class of deterministic interference channels.

  • 117.
    Do, Hieu
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Vu, Mai
    Dept. of Electrical and Computer Engineering, Tufts University.
    Gaussian Interfering Relay Channels2013Ingår i: 2013 Asilomar Conference on Signals, Systems and Computers, IEEE Computer Society, 2013, s. 1968-1972Konferensbidrag (Refereegranskat)
    Abstract [en]

    We extend the primitive relay channel (PRC) in-troduced by Cover and Kim to a more general scenario wheretwo Gaussian PRC’s cause interference to each other. We show that extended hash-and-forward relaying with proper power allocation can achieve bounded gaps to the capacity region of the Gaussian channel in different regimes of channel parameters.

  • 118.
    Do, Hieu T.
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Ericsson Research, Sweden.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Layered Coding for the Interference Channel With a Relay2014Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 60, nr 10, s. 6154-6180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper studies and derives new results for the interference channel with a relay (ICR). Three inner bounds for the discrete memoryless ICR are proposed, based on three coding strategies that employ layered code at the relay. The first scheme is inspired by layered noisy network coding, proposed by Lim et al. for the two-way relay channel, the second and the third schemes rely on simpler encoding and decoding processes, dubbed layered quantize-forward. Performance of the proposed schemes is investigated for two classes of channels with Gaussian noise: the interference channel with in-band relay reception/out-of-band relay transmission and the interference with in-band relay reception/in-band relay transmission. For the former class of channels, it is shown that the first proposed scheme achieves the same inner bound as the generalized hash-forward scheme with incremental binning. In addition, the inner bound is within 0.5 bit of the capacity region under certain conditions on the channel parameters. For the latter class of channels, new upper bounds on sum-rate are established by extending known upper bounds for symmetric channels. The first inner bound is shown to be within 0.5 bit of the capacity region if the relay's power exceeds a certain threshold, which depends on channel parameters. Numerical examples show that the proposed schemes can achieve significantly higher sum-rates when compared with other compress-forward schemes. Analysis also reveals a tradeoff between achievable rates, coding delay, and complexity of the proposed schemes. Results in this paper provide a better understanding of coding for the ICR, in particular, they show that layered coding is a beneficial element in multiuser networks with relays.

  • 119.
    Do, Tan Tai
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Fundamental Limits in Wireless Wideband Networking2015Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The rapid growth of the wireless communication industry recently does not only bring opportunities but also challenges on developing radio technologies and solutions that can support high data rate as well as reliable and efficient communications. Two fundamental factors that limit the transmission rate are the available transmit energy and the available bandwidth. In this thesis, we investigate fundamental limits on energy and bandwidth efficiencies in wireless wideband networking. The framework and results can be used for performance assessment, design, and development of practical cellular networks.

    First, we study the energy efficiency of a bidirectional broadcast channel in the wideband regime, i.e., where the bandwidth tends to infinity and the spectral efficiency is disregarded. In particular, we consider a transmit strategy for a Gaussian MIMO bidirectional broadcast channel that maximizes the energy efficiency, i.e., minimizes the energy required to reliably transmit one information bit. A closed-form solution of the optimal transmit covariance matrix is derived, which shows that using a single beam transmit strategy is optimal. Additionally, an extension to a multi-pair Gaussian MIMO bidirectional broadcast channel is studied, in which we propose a simple transmit strategy motivated from the optimal transmit strategy for the single user-pair setup. We show that serving a selected user-pair with full power is optimal in the sense of maximizing the achievable energy efficiency. Discussions on the optimality of the proposed transmit scheme for the multi-pair setup are also provided.

    Next, we study the bandwidth efficiency of another wireless wideband network, in which the available bandwidth is large but still finite. Accordingly, we consider the bandwidth efficiency limit of an uplink wideband CDMA channel. Various realistic assumptions such as asynchronous transmission, inter-symbol interference, continuous-time waveform transmitted signal, etc. are incorporated into the problem formulation. In order to tackle the problems that arise with those assumptions, we derive an equivalent discrete-time channel model based on sufficient statistics for optimal decoding of the transmitted messages with perfect channel knowledge. The capacity regions are then characterized using the equivalent channel model. In addition, an extension to a system with imperfect channel state information and mismatched filtering at the receiver is considered. Achievable rate regions are characterized considering two different assumptions on decoding strategy, i.e., the optimal decoding based on the actual statistics of channel estimation errors and the sub-optimal approach treating the estimation errors as additive worst-case noise. Moreover, we also present a low-complexity receiver for the uplink wideband CDMA channel, which is based on a decision feedback equalizer structure.

  • 120.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Kim, Su Min
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Peters, Gunnar
    Waveform domain framework for capacity analysis of uplink WCDMA systems2015Ingår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, artikel-id 253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the capacity limit of an uplink WCDMA system considering a continuous-time waveform signal. Various realistic assumptions are incorporated into the problem, which make the study valuable for performance assessment of real cellular networks to identify potentials for performance improvements in practical receiver designs. An equivalent discrete-time channel model is derived based on sufficient statistics for optimal decoding of the transmitted messages. The capacity regions are then characterized using the equivalent channel considering both finite constellation and Gaussian distributed input signals. The capacity with sampling at the receiver is also provided to exemplify the performance loss due to a typical post-processing at the receiver. Moreover, we analyze the asymptotic capacity when the signal-to-noise ratio goes to infinity. The conditions to simultaneously achieve the individual capacities are derived, which reveal the impacts of signature waveform space, channel frequency selectivity and signal constellation on the system performance.

  • 121.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Kim, Sumin
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Peters, G.
    Capacity analysis of uplink WCDMA systems with imperfect channel state information2015Ingår i: IEEE Vehicular Technology Conference, IEEE , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers the capacity limit of an uplink wideband CDMA (WCDMA) system assuming imperfect channel state information at the receiver (CSIR). In order to make the studied results useful for the performance assessment of real cellular networks, various realistic assumptions are included in the problem. A discrete-time channel model is derived based on the mismatched filtering at the receiver. Capacity inner bounds are then characterized based on the discrete-time channel model considering different assumptions on decoding strategy. Numerical results are also provided to show the effect of imperfect CSIR on the capacity.

  • 122.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Kim, Su Min
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Peters, Gunnar
    Uplink Waveform Channel With Imperfect Channel State Information and Finite Constellation Input2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 2, s. 1107-1119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper investigates the capacity limit of an uplink waveform channel assuming imperfect channel state information at the receiver (CSIR). Various realistic assumptions are incorporated into the problem, which make the study valuable for performance assessment of real cellular networks to identify potentials for performance improvements in practical receiver designs. We assume that the continuous-time received signal is first discretized by mismatched filtering based on the imperfect CSIR. The resulting discrete-time signals are then decoded considering two different decoding strategies, i.e., an optimal decoding strategy based on specific statistics of channel estimation errors and a sub-optimal decoding strategy treating the estimation error signal as additive Gaussian noise. Motivated by the proposed decoding strategies, we study the performance of the decision feedback equalizer for finite constellation inputs, in which inter-stream interferences are treated either using their true statistics or as Gaussian noise. Numerical results are provided to exemplify the benefit of exploiting the knowledge on the statistics of the channel estimation errors and inter-stream interferences. Simulations also assess the effect of the CSI imperfectness on the achievable rate, which reveal that finite constellation inputs are less sensitive to the estimation accuracy than Gaussian input, especially in the high SNR regime.

  • 123.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Kim, Sumin
    KTH, Skolan för elektro- och systemteknik (EES), Signalbehandling.
    Peters, G.
    Capacity analysis of continuous-time time-variant asynchronous uplink wideband CDMA system2014Ingår i: IEEE Vehicular Technology Conference, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper considers the capacity limit of an uplink wideband CDMA system. In order to make the studied results useful for the performance assessment of real cellular networks, various realistic assumptions are included in the problem. An equivalent discrete-time channel model is derived based on sufcient statistic for optimal decoding of transmit messages. The capacity regions are then characterized considering nite constellation and Gaussian input assumptions. For further insight, an analysis on the asymptotic capacity is considered, in which the conditions to simultaneously achieve the individual capacities are derived.

  • 124.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Oechtering, Tobias J.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Optimal Transmission for the MIMO Bidirectional Broadcast Channel in the Wideband Regime2013Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, nr 20, s. 5103-5116Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper considers a transmit strategy for an AWGN MIMO bidirectional broadcast channel in the wideband regime. In order to characterize the boundaries of the wideband capacity and energy per bit regions, the transmit strategy at the relay is designed to maximize the weighted wideband rate sum. A closed form of the optimal transmit covariance matrix is derived, which shows that a single beam transmit strategy is optimal. The transmit strategies for some special cases are also analyzed. The fairness versus energy efficiency tradeoff is then discussed. In addition, an extension to multipair MIMO bidirectional broadcast channel is studied in which we show that serving a certain pair with full power is optimal in the sense of maximizing the achievable weighted wideband rate sum. Finally, a discussion on the conjecture of the minimum energy per bit for multi-pair systems is provided.

  • 125.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Achievable energy per bit for the multi-pair MIMO bidirectional broadcast channel2012Ingår i: European Wireless, 2012. EW. 18th European Wireless Conference, 2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a transmit strategy for the AWGN multi-pair MIMO bidirectional broadcast channels in the wideband regime. An achievable wideband rate region and an achievable energy per bit region are provided. The transmit covariance matrix at the relay has been designed in order to maximize the wideband weighted rate sum. A closed form of the optimal matrix is derived, which shows that a single beam transmit strategy is optimal. In addition, an energy efficiency versus fairness analysis is considered. Lastly, some discussions on the minimum energy per bit are given.

  • 126.
    Do, Tan Tai
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Oechtering, Tobias
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal transmission for the MIMO bidirectional broadcast channel in the wideband regime2011Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC, 2011, s. 356-360Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents an optimal transmit strategy for multiple antennas bidirectional broadcast channels in the wideband regime. The transmit covariance matrix at the relay has been designed in order to maximize the wideband weighted sum rate. A closed form of the optimal matrix is derived, which shows that a single beam transmit strategy is optimal. The transmit strategies for some special cases, the wideband capacity region, and the minimum energy per bit versus fairness issues are also discussed.

  • 127.
    Dombrowski, Christian
    et al.
    RWTH Aachen University.
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    EchoRing: A Low-Latency, Reliable Token-passing MAC Protocol for Wireless Industrial Networks2015Ingår i: European Wireless 2015; 21th European Wireless Conference; Proceedings of, IEEE conference proceedings, 2015, s. 1-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    Spurred by recent industrial trends, such as factoryautomation or phase synchronization in the smart grid, thereis a significant interest for wireless industrial networks lately.In contrast to traditional applications, the focus is on carryingout communication at very short latencies together with highreliabilities. Meeting such extreme requirements with wirelessnetworks is challenging. A potential candidate for such a networkis a token-passing protocol, as it allows to bound latencies.However, it lacks mechanisms to cope with the dynamics ofwireless channels. In this paper, we present EchoRing, a novelwireless token-passing protocol. Cooperative communication andan improved fault tolerance allow this decentralized protocol tosupport industrial applications over wireless networks. Based onexperimental results, we demonstrate the suitability of EchoRingto support demands of industrial applications. EchoRing outper-forms other schemes by several orders of magnitude in terms ofreliability for latencies of and below10ms.

  • 128.
    Dombrowski, Christian
    et al.
    RWTH Aachen University.
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    EchoRing- Meeting Hard Real-time Constraints by Decentralized Wireless Networks2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Given the rising demand for wireless solutions in the area of machine-to-machine communication, we present the novel EchoRing protocol. It is designed to serve the communication needs of industrial applications, while being optimized for the wireless channel specifically. Directly taking known principles of tethered communication to the wireless domain is likely to yield degraded performance results. Additional techniques have to be added to make known principles be able to master the challenges of wireless channel dynamics. On the other hand, the majority of currently existing wireless communication standards are developed to allow mobility on the last hop of a transmission path that originates in the Internet or a local home network. Hence, the focus is on supporting the best-effort paradigm of the data streams. However, in industrial environments this best-effort paradigm gets replaced by the need to steadily achieve very high reliabilities at very short deadlines.

    In this demonstration, we will show how industrial applications can be interconnected wirelessly despite the drawbacks of the wireless channel. The experimental setup allows to compare different medium access control protocols under varying conditions.

     

  • 129. Dombrowski, Christian
    et al.
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Reducing Outage Probability over Wireless Channels Under Hard Real-Time Constraints2011Konferensbidrag (Refereegranskat)
  • 130. Dombrowski, Christian
    et al.
    Junges, Sebastian
    Katoen, Joost Pieter
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Model-Checking Assisted Protocol Design for Ultra-Reliable Low-Latency Wireless Networks2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recently, the wireless networking community is getting more and more interested in novel protocol designs for safety-critical applications. These new applications come with unprecedented latency and reliability constraints which poses many open challenges. A particularly important one relates to the question how to develop such systems. Traditionally, development of wireless systems has mainly relied on simulations to identify viable architectures. However, in this case the drawbacks of simulations – in particular increasing run-times – rule out its application. Instead, in this paper we propose to use probabilistic model checking, a formal model-based verification technique, to evaluate different system variants during the design phase. Apart from allowing evaluations and therefore design iterations with much smaller periods, probabilistic model checking provides bounds on the reliability of the considered design choices. We demonstrate these salient features with respect to the novel EchoRing protocol, which is a token-based system designed for safety-critical industrial applications. Several mechanisms for dealing with a token loss are modeled and evaluated through probabilistic model checking, showing its potential as suitable evaluation tool for such novel wireless protocols. In particular, we show by probabilistic model checking that wireless tokenpassing systems can benefit tremendously from the considered fault-tolerant methods. The obtained performance guarantees for the different mechanisms even provide reasonable bounds for experimental results obtained from a real-world implementation.

  • 131. Dombrowski, Christian
    et al.
    Petreska, Neda
    Görtzen, Simon
    Schmeink, Anke
    Gross, James
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Energy-efficient multi-hop transmission for machine-to-machine communications2013Ingår i: 2013 11th International Symposium and Workshops on Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, WiOpt 2013, 2013, s. 341-348Konferensbidrag (Refereegranskat)
    Abstract [en]

    Emerging machine-to-machine communication scenarios are envisioned to deal with more stringent quality-of-service demands. This relates mainly to outage and latency requirements, which are for example for safety-critical messages quite different than for traditional applications. On the other hand, it is widely accepted that machine-to-machine communication systems need to be energy-efficient because of the widespread use of battery-powered devices, but also due to their huge deployment numbers. In this paper, we address these issues with respect to multi-hop transmissions. Specifically, we deal with minimizing the consumed energy of transmitting a packet with end-to-end outage and latency requirements. We account for the cases in which the system can utilize solely average channel state information, or in addition obtain and profit from instantaneous channel state information. The developed solution is based on convex optimization. It is shown numerically that despite accounting for the energy consumption of acquiring instantaneous channel state information, especially as the outage and latency requirements become tough, it is by up to 100 times more energy efficient to convey a packet with instantaneous than with average channel state information.

  • 132. Doroslovački, M. I.
    et al.
    Larsson, Erik G.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. George Washington University, United States .
    Nonuniform linear antenna arrays minimising Cramér-Rao bounds for joint estimation of single source range and direction of arrival2005Ingår i: IEE Proceedings-Radar Sonar and Navigation, Institution of Electrical Engineers (IEE), 2005, nr 4, s. 225-231Konferensbidrag (Refereegranskat)
    Abstract [en]

    Different antenna placements in nonuniform linear arrays for the joint estimation of the range and direction-of-arrival (DOA) of one source are considered. It is shown that the Cramér-Rao bound (CRB) for the range and DOA estimates can be expressed as a function of the angles at which the source sees the antennas. This new formulation of the CRB easily reveals the geometrical properties that the array should have in order to minimise the CRB. Based on the new representation of the CRB, a result found in the literature (which was concerned with the special case of a number of antennas that is divisible by four) is generalised to include the case of an arbitrary number of antennas. Furthermore, it is shown that symmetric arrays are close to uniformly optimal for different DOAs when the range is much larger than the aperture of the arrays.

  • 133.
    Du, Jinfeng
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Cooperative Strategies in Multi-Terminal Wireless Relay Networks2012Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Smart phones and tablet computers have greatly boosted the demand for services via wireless access points, keeping constant pressure on the network providers to deliver vast amounts of data over the wireless infrastructure. To enlarge coverage and enhance throughput, relaying has been adopted in the new generation of wireless communication systems, such as in the Long-Term Evolution Advanced standard,  and will continue to play an important role in the next generation wireless infrastructure. Depending on functionality, relaying can be characterizing into three main categories: amplify-and-forward (AF), compression-and-forward (CF), and decode-and-forward (DF).  In this thesis, we investigate different cooperative strategies in wireless networks when relaying is in use.

    We first investigate  the capacity outer and inner bounds for a wireless multicast relay network where two sources, connected by error-free backhaul, multicast to two destinations with the help of a full-duplex relay node.  For high-rate backhaul scenarios, we find the exact cut-set bound of the capacity region by extending the proof of the converse for the Gaussian relay channel. For low-rate backhaul scenarios, we present two genie-aided outer bounds by extending the previous proof and introducing two lemmas on conditional (co-)variance. Our inner bounds are derived from various cooperative strategies by combining DF/CF/AF relaying with network coding schemes. We also extend the noisy network coding scheme and the short-message noisy network coding approach to correlated sources. For low-rate backhaul, we propose a new coding scheme, partial-decode-and-forward based linear network coding. We derive the achievable rate regions  for these schemes and measure the performance in term of achievable rates over Gaussian channels. By numerical investigation we observe significant gains over benchmark schemes and demonstrate that the gap between upper and lower bounds is in general not large. We also show that for high-rate backhaul, the cut-set bound can be achieved  when the signal-to-noise ratios lie in the sphere defined by the source-relay and relay-destination channel gains.

    For wireless networks with independent noise, we propose a simple framework to get capacity outer and inner bounds based on the ``one-shot'' bounding models. We first extend the models for two-user broadcast channels to many-user scenarios and then establish the gap between upper and lower bounding models. For networks with coupled links, we propose  a channel decoupling method which can decompose the network into overlapping multiple-access channels and broadcast channels.  We then apply the one-shot models and create an upper bounding network with only  bit-pipe connections. When developing the lower bounding network, we propose a  two-step update of these models for each coupled broadcast and multiple-access channels. We demonstrate by some examples that the resulting upper bound is in general very good and the gap between the upper and lower bounds is usually not large.

    For relay-aided downlink scenarios, we propose a cooperation scheme by cancelling interference at the transmitter. It is indeed a symbol-by-symbol approach to one-dimension dirty paper coding (DPC). 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.  Bit-level simulation shows that the optimal and sub-optimal modulators can achieve significant gains over the Tomlinson-Harashima precoder (THP) benchmark and over non-DPC reference schemes, especially when the power of the interference is larger than the power of the noise.

  • 134.
    Du, Jinfeng
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Modulation for interference avoidance on the AWGN channel2006Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Theoretic results have shown that the capacity of a channel does not decrease if the receiver observes the transmitted signal in the presence of interference, provided that the transmitter knows this interference non-causally. That is, if the transmitter has non-causal access to the interference, by using proper precoding this interference could be “avoided” (as if it were not present) under the same transmit power constraint. It indicates that lossless (in the sense of capacity) precoding is theoretically possible at any signal-to-noise-ratio (SNR). This is of special interest in digital watermarking, transmission for ISI channels as well as for MIMO broadcast channels. Recent research has elegantly demonstrated the (near) achievability of this “existence-type” result, while the complexity is notable. An interesting question is what one can do when very little extra complexity is permitted. This thesis treats such special cases of this problem in order to shed some light on this question. In the AWGN channel with additive interference, an optimum modulator is designed under the constraint of a binary signaling alphabet with binary interference.Tomlinson-Harashima precoding (THP), which is originally proposed for ISI channels, is improved by picking up optimized parameters and then taken as a benchmark. Simulation results show that the Optimum Modulator always outperforms the THP with optimized parameters. The difference in performance, in terms of mutual information between channel input and output as well as coded bit error rate with Turbo codes, is significant in many scenarios.

  • 135.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Larsson, Erik G.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Costa precoding in one dimension2006Ingår i: 2006 IEEE International Conference on Acoustics, Speech, and Signal Processing, IEEE conference proceedings, 2006, s. 717-720Konferensbidrag (Refereegranskat)
    Abstract [en]

    We design an optimum modulator for the Costa (dirty-paper) precoding problem under the constraint of a binary signaling alphabet, and assuming the interference symbols belong to a binary constellation. We evaluate the performance of our technique in terms of the mutual information between the channel input and output, and compare it to that of Tomlinson-Harashima precoding (THP) with optimized parameters. We show that our optimal modulator is always better than THP. In many relevant scenarios, the performance difference is significant.

  • 136.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    Division for Communication Systems, Linköping University.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Optimal Symbol-by-Symbol Costa Precoding for a Relay-Aided Downlink Channel2011Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, nr 8, s. 2274-2284Artikel i tidskrift (Refereegranskat)
    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.

  • 137.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. MIT, Cambridge, USA.
    Medard, Muriel
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Scalable Capacity Bounding Models for Wireless Networks2016Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 62, nr 1, s. 208-229Artikel i tidskrift (Refereegranskat)
    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.

  • 138.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Lower bounding models for wireless networks2013Ingår i: Proceedings of IEEE International Symposium on Information Theory, 2013, IEEE conference proceedings, 2013, s. 1456-1460Konferensbidrag (Refereegranskat)
    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.

  • 139.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Research Lab of Electronics, MIT.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Scalable capacity bounding models for wireless networksManuskript (preprint) (Övrigt vetenskapligt)
    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.

  • 140.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Research Lab of Electronics, Massachusetts Institute of Technology.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Scalable upper bounding models for wireless networks2014Ingår i: Proceedings of IEEE International Symposium on Information Theory, IEEE conference proceedings, 2014, s. 241-245Konferensbidrag (Refereegranskat)
    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.

  • 141.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Signell, Svante
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Novel Preamble-Based Channel Estimation for OFDM/OQAM Systems2009Ingår i: 2009 IEEE International Conference On Communications , Vols 1-8, IEEE conference proceedings, 2009, s. 4135-4140Konferensbidrag (Refereegranskat)
    Abstract [en]

    OFDM/OQAM has been considered as an attractive alternative to classic OFDM with cyclic prefix (CP) over doubly dispersive channels. By utilising well designed pulse shapes and removing CP, OFDM/OQAM has the advantage of reduced out-of-band energy and a theoretically higher spectral efficiency. However, channel estimation over doubly dispersive channels has been a big problem for OFDM/OQAM due to the non-orthogonality between the real and imaginary parts of its modulated signals. Therefore conventional channel estimation (CE) methods used for OFDM cannot be directly applied to OFDM/OQAM. Recently a preamble-based CE method - interference approximation method (IAM) - has been proposed to ease this task. By treating the intrinsic interference from neighbour symbols as known information, two heuristic preamble sequences have been constructed based on tentative observations, which turn out to be suboptimal. In this paper, we present a general theoretical framework for LAM preamble design and apply it to identify the optimal LAM preamble sequence which results in a higher gain. Numerical results have verified the effectiveness of the theoretical framework and a gain of 2.4 dB against CP-OFDM has been demonstrated with the new preamble in various doubly dispersive channels with a QPSK modulation.

  • 142.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. Research Lab of Electronics, MIT.
    Sweeting, Naomi
    MIT.
    Adams, David C.
    MIT.
    Médard, Muriel
    MIT.
    Network reduction for coded multiple-hop networks2015Ingår i: 2015 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2015, s. 4518-4523Konferensbidrag (Refereegranskat)
    Abstract [en]

    Data transmission over multiple-hop networks is impaired by random deleterious events, and characterizing the probability of error for the end-to-end transmission is challenging as the size of networks grows. Adams et al. showed that, when re-encoding at intermediate nodes is enabled, coded transmission over tandem/parallel links can be reduced to a single equivalent link with a specified probability function. Although iterative application of the tandem/parallel reduction techniques in alternation can simplify the task, they are generally not sufficient to reduce an arbitrary network to a single link. In this paper, we propose upper- and lower- bounding processes to bound the end-to-end probability distribution of a network by combining the parallel/tandem link reduction with the structure of flows over the network. We evaluate the performance of the proposed bounding methods at the 99% success rate of end-to-end data transmission over randomly generated acyclic networks. The numerical results demonstrate that our bounding approaches enable us to characterize a network by a single probability function to a very good precision.

  • 143.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Capacity Bounds for Backhaul-Supported Wireless Multicast Relay Networks with Cross-Links2011Ingår i: IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), 2011, NEW YORK: IEEE conference proceedings, 2011, s. 1-5Konferensbidrag (Refereegranskat)
    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.

  • 144.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Capacity bounds for relay-aided wireless multiple multicast with backhaul2010Ingår i: 2010 International Conference on Wireless Communications and Signal Processing, WCSP 2010, NEW YORK: IEEE conference proceedings, 2010, s. 1-5Konferensbidrag (Refereegranskat)
    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.

  • 145.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Cooperative Network Coding Strategies for Wireless Relay Networks with Backhaul2011Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, nr 9, s. 2502-2514Artikel i tidskrift (Refereegranskat)
    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.

  • 146.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Cooperative strategies for relay-aided multi-cell wireless networks with backhaul2010Ingår i: 2010 IEEE Information Theory Workshop, ITW 2010 - Proceedings, NEW YORK: IEEE conference proceedings, 2010, s. 1-5Konferensbidrag (Refereegranskat)
    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.

  • 147.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Médard, Muriel
    Department of Electrical Engineering and Computer Science, MIT.
    Wireless multicast relay networks with limited-rate source-conferencing2013Ingår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 31, nr 8, s. 1390-1401Artikel i tidskrift (Refereegranskat)
    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.

  • 148.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Shamai (Shitz), Shlomo
    Technion - Israel Institute of Technology.
    Short-Message Noisy Network Coding with Partial Source Cooperation2012Ingår i: Information Theory Workshop (ITW), 2012 IEEE, IEEE conference proceedings, 2012, s. 144-147Konferensbidrag (Refereegranskat)
    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.

  • 149.
    Du, Jinfeng
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
    Xiao, Pei
    University of Surrey Guildford, UK.
    Wu, Jinsong
    Bell Laboratories, Alcatel-Lucent, Shanghai, China.
    Chen, Qingchun
    Southwest Jiaotong University, Chengdu, China.
    Design of isotropic orthogonal transform algorithm-based multicarrier systems with blind channel estimation2012Ingår i: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 6, nr 16, s. 2695-2704Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Orthogonal frequency division multiplexing (OFDM) technique has gained increasing popularity in both wired andwireless communication systems. However, in the conventional OFDM systems the insertion of a cyclic prefix (CP) and the transmission of periodic training sequences for purpose of channel estimation decrease the system’s spectral efficiency. As an alternative to OFDM, isotropic orthogonal transform algorithm (IOTA)-based multicarrier system adopts a proper pulse shaping with good time and frequency localisation properties to avoid interference and maintain orthogonality in real field among sub-carriers without the use of CP. In this study, the authors propose linearly precoded IOTA-based multicarrier systems to achieve blind channel estimation by utilising the structure of auto-correlation and cross-correlation matrices introduced by precoding. The results show that the proposed IOTA-based multicarrier systems achieve better power and spectral efficiency compared with the conventional OFDM systems.

  • 150.
    Du, Rong
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Fischione, Carlo
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Xiao, Ming
    KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
    Flowing with the water: On optimal monitoring of water distribution networks by mobile sensors2016Konferensbidrag (Refereegranskat)
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