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• 101.
Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
ABB Corp Res, S-72226 Vasteras, Sweden.. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Univ Elect Sci & Technol China, Dept Aeronaut & Astronaut, Chengdu 611731, Sichuan, Peoples R China.. Univ Elect Sci & Technol China, Natl Key Lab Sci & Technol Commun, Chengdu 611731, Sichuan, Peoples R China..
Clone Detection Based on Physical Layer Reputation for Proximity Service2019Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 7, s. 3948-3957Artikel i tidskrift (Refereegranskat)

Proximity-based service (ProSe) provides direct communications among smart sensor nodes in proximity which aims at reserving resource consumption and alleviating the load in base stations, which is a promising solution for smart sensor systems that possess limited computing and energy resources. During the ProSe direct communications, most of the prior art security methods are usually provided by the ProSe function and are based on complex cryptography. However, despite the computing complexity, it is difficult for cryptographic methods to detect clone attack which is a common kind of attack in sensor systems. Clone nodes feature different physical positions but claim colliding IDs with captured nodes. Thus, clone nodes can be detected by spatial differences, in particular, by the surveillance of physical layer channel state information (CSI). However, CSI is not absolute static due to the random noise in wireless propagation environment. Accordingly, the detection accuracy varies with the stability of CSI. To address this challenge, we take the first attempt to introduce physical layer reputation and then elaborate the physical layer reputation based clone detection protocol to detect clone attack in multiple scenarios. The proposed protocol significantly improves the detection rate and false alarm rate and it is validated both by simulations and realizations.

• 102. Phutathum, A.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
A study of distributed storage systems with network coding in wireless networks2014Ingår i: 2014 IEEE International Conference on Communication Systems, IEEE ICCS 2014, 2014, s. 293-297Konferensbidrag (Refereegranskat)

Increasing multimedia applications on the networks e.g., video and voice over the Internet, have attracted lots of interest to the distributed storage systems. Recently, lots of research has been performed on applying network coding to distributed storage systems. Although there are intensive theoretical studies in this field, very few practical simulations have been reported. We simulate distributed storage systems using network coding. In particular, we first use random linear network in reconstructing a file and in the repair process. We observe that probability of successful repair and successful downloading approaches to one for a large finite field size. In addition, we apply a lower complexity code and measure their probability of successful downloading, probability of successful repair, repair time and processing time. Our numerical results show for random linear codes, connecting to more storage nodes can substantially reduce the required finite field size. This leads to lower coding complexity.

• 103.
KTH. Northwestern Polytechnical University, China.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Energy-Efficient Cooperative Network Coding With Joint Relay Scheduling and Power Allocation2016Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 64, nr 11, s. 4506-4519Artikel i tidskrift (Refereegranskat)

The energy efficiency (EE) of a multi-user multi-relay system with the maximum diversity network coding (MDNC) is studied. We explicitly find the connection among the outage probability, energy consumption, and EE, and formulate the maximizing EE problem under the outage probability constraint. Relay scheduling (RS) and power allocation (PA) are applied to schedule the relay states (transmitting, sleeping, and so on) and optimize the transmitting power under the practical channel and power consumption models. Since the optimization problem is NP hard, to reduce computational complexity, the outage probability is first tightly approximated to a log-convex form. Furthermore, the EE is converted into a subtractive form based on the fractional programming. Then, a convex mixed-integer nonlinear problem is eventually obtained. With a generalized outer approximation algorithm, RS and PA are solved in an iterative manner. The Pareto-optimal curves between the EE and the target outage probability show the EE gains from PA and RS. Moreover, by comparing with the no network coding (NoNC) scenario, we conclude that with the same number of relays, MDNC can lead to EE gains. However, if RS is implemented, NoNC can outperform MDNC in terms of the EE when more relays are needed in the MDNC scheme.

• 104.
Nanjing Univ Aeronaut & Astronaut, Minist Ind & Informat Technol, Key Lab Dynam Cognit Syst Electromagnet Spectrum, Nanjing 210016, Peoples R China.;Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Peoples R China..
KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Jinan Univ, Sch Elect & Informat Engn, Zhuhai 519070, Peoples R China.. Northwestern Polytech Univ, Sch Elect & Informat, Xian 710072, Shaanxi, Peoples R China.. Inst Telecomunicacoes, P-3810193 Aveiro, Portugal..
Energy Efficient Two-Tier Network-Coded Relaying Systems Considering Processing Energy Costs2019Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 68, nr 1, s. 999-1003Artikel i tidskrift (Refereegranskat)

In this paper, a two-tier network coding (TNC) scheme is proposed for the multi-user multi-relay transmission scenarios. Specifically, TNC is conducted at each individual relay, where two groups of source messages are combined into one network codeword that is forwarded to dual destinations. Finally, two groups of source messages are jointly recovered from different network codewords at the destinations. Both analytical and simulation results demonstrate that the proposed scheme outperforms the current state of art in terms of the energy efficiency (EE). In addition, the impacts of multiple parameters, including the number of users, SNR and relay locations on the average EE have been demonstrated, which provide valuable insights for the system designs of future wireless networks.

• 105.
KTH.
KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap. KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
Efficient Coded Cooperative Networks With Energy Harvesting and Transferring2017Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 16, nr 10, s. 6335-6349Artikel i tidskrift (Refereegranskat)

In this paper, a multi-user multi-relay network with integrated energy harvesting and transferring (IEHT) strategy is studied. In our system, a simultaneous two-level cooperation, i.e., information-and energy-level cooperation is conducted for uplink data transmissions (from the users to a destination). Specifically, network coding is employed at the relays to facilitate the information-level cooperation; meanwhile, ET is adopted to share the harvested energy among the users for the energy-level cooperation. For generality purposes, the Nakagami-m fading channels that are independent but not necessarily identically distributed (i.n.i.d.)are considered. The problem of energy efficiency maximization under constraints of the energy causality and a predefined outage probability threshold is formulated and shown to be non-convex. By exploiting fractional and geometric programming, a convex form-based iterative algorithm is developed to solve the problem efficiently. Close-to-optimal power allocation and energy cooperation policies across consecutive transmissions are found. Moreover, the effects of relay locations, wireless energy transmission efficiency, battery capacity as well as the existence of direct links are investigated. The performance comparison with the current state of solutions demonstrates that the proposed policies can manage the harvested energy more efficiently.

• 106.
KTH, Skolan för elektro- och systemteknik (EES). School of Electronics and Information, Northwestern Polytechnical University, China.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. Department of Electrical Engineering, Technological Educational Institute of Central Greece, Greece and School of Engineering, Nazarbayev University, Kazakhstan. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES). School of Electronics and Information, Northwestern Polytechnical University, China.
On the Energy Efficiency in Multi-user Multi-relayCoded Network2016Konferensbidrag (Refereegranskat)

In this paper, the energy efficiency (EE) of a cooperative diversity system with maximum diversity network coding (MDNC) is studied. In the considered system, channel state information (CSI) is only available at the receivers for all the channels. We formulate the problem of maximizing the EEunder the constraint on the outage probability. The problem is NP-hard due to the non-convexity of the outage probability function and the nonlinear fractional structure of the introducedEE. To solve the optimization problem efficiently, first, the outage probability function is tightly approximated as a log-convex form in the high signal-to-noise ratio (SNR) region. Further, based on the fractional programming, we transform the introduced EEinto a subtractive-form, which is proved to be a convex form. The tradeoff between outage probability and EE is given. The results show that our power allocation (PA) policy can substantially increase the EE. We show that EE can be increased if more relays forward the messages. Additionally, we also investigate the effect of the relay locations on the EE and demonstrate that the increase in the transmission distance in the first hop causes the loss of the EE. The loss can be reduced by our PA policy.

• 107. Rezaei, Fatemeh
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Delay and Stability Analysis of Caching in Heterogeneous Cellular Networks2016Ingår i: 2016 23RD INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT), IEEE, 2016Konferensbidrag (Refereegranskat)

In this paper, we propose a general delay and stability performance analysis in Heterogeneous Cellular Caching Networks (HCCNs), based on queuing theory. We introduce new performance metrics in HCCNs and propose an optimization problem which minimizes the average experienced delay for users by ensuring the stability of the network. In addition, from the design perspective, we address the problem of finding the minimum cache size for the small cell base stations (SBSs) for having a tolerable average delay and also a stable network. Finally, the analytic expressions derived in this paper are validated through real trace-driven experiments on traffic of YouTube video requests.

• 108.
Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China.;Xidian Univ, State Key Lab Integrated Serv Networks, Xian, Shaanxi, Peoples R China..
Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu 610031, Sichuan, Peoples R China.;Southeast Univ, Natl Mobile Commun Res Lab, Nanjing, Jiangsu, Peoples R China.. Univ Manchester, Sch Elect & Elect Engn, Manchester, Lancs, England.. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. KTH, Skolan för elektroteknik och datavetenskap (EECS), Intelligenta system, Teknisk informationsvetenskap. Carleton Univ, Dept Syst & Comp Engn, Ottawa, ON, Canada..
Optimal Power Allocations for 5G Non-Orthogonal Multiple Access with Half/Full Duplex Relaying2019Ingår i: ICC 2019 - 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), IEEE , 2019Konferensbidrag (Refereegranskat)

Recently, power allocation has attracted more and more attention in order to optimize the performance of nonorthogonal multiple access (NOMA) systems. Different from existing works, the power allocation problems are investigated for cooperative NOMA systems with dedicated amplify-and-forward half-duplex relay (NOMA-HDR) and full-duplex relay (NOMA-FDR). From the fairness standpoint, the power allocation problems are formulated to maximize the minimum achievable user rate in the considered systems. The problems for both NOMA-HDR and NOMA-FDR systems with two-user and M-user are addressed. The closed-form power allocation policy of two-user NOMA-HDR system is obtained. Also, the optimal numerical power allocation policies for two-user NOMA-FDR and M-user NOMA-HDR systems are obtained. In addition, the problem for M-user NOMA-FDR systems is solved in noise-limited environment. Simulation results show that the proposed NOMA-HDR or NOMA-FDR scheme with power adaption clearly outperforms the NOMA-HDR or NOMA-FDR scheme with fixed power allocation. Besides, when the residual self-interference channel gain is small, the performance of NOMA-FDR system is better than the NOMA-HDR system.

• 109. Song, K.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Performance analysis of relay-aided heterogeneous networks with interference cancellation2015Ingår i: 2015 IEEE International Conference on Communication Workshop, ICCW 2015, IEEE conference proceedings, 2015, s. 985-990Konferensbidrag (Refereegranskat)

We investigate the downlink performance of relay-aided heterogeneous networks (HetNet). An interference cancellation scheme employed at macro base stations is first proposed based on the cancellation of cross-tier interference from the macro base station to small cell users. Then, we derive the expressions of the probability density function (PDF) and cumulative distribution function (CDF) of the received SINRs of both macro and small cell users, and provide the closed-form average bit error rate (BER) and outage probability of the system. Through the derivation and simulation, we show the overall performance improvement of HetNet with interference cancellation in mathematical expression. The numerical results closely follow our analysis.

• 110. Song, K.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Performance analysis of antenna selection in two-way decode-and-forward relay networks2014Konferensbidrag (Refereegranskat)

This paper investigates the performance of a two-way decode-and-forward (DF) multi-antenna relay network. A joint antenna selection scheme for all nodes is first proposed based on the maximizing the worse received signal to noise ratio (SNR) of two end users. Then, we derive the probability density function (PDF) and cumulative distribution function (CDF) of the received SNRs of both users. We also achieve the closed-form expressions of average bit error rate (BER) and outage probability of the relay system. Furthermore, we reveal the asymptotic behavior of our system when transmitting SNR or the number of antennas is large. Our analysis shows that the proposed DF antenna selection scheme achieves full diversity. The numerical results finally verify the accuracy of our analysis.

• 111. Song, K.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Performance Analysis of Antenna Selection in Two-Way Relay Networks2015Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 63, nr 10, s. 2520-2532, artikel-id 7064785Artikel i tidskrift (Refereegranskat)

We investigate the performance of multi-antenna two-way relay networks, where both amplify-and-forward (AF) and decode-and-forward (DF) relaying strategies are considered. First an antenna selection scheme among all nodes is proposed based on maximizing the worse received signal-to-noise ratio (SNR) of two end users. Then, we derive the probability density function (PDF) and cumulative distribution function (CDF) of the received SNRs of both users. We also obtain the closed-form expressions of average bit error rates (BER) and the outage probability of our system. Furthermore, we study the asymptotic behavior of our system when transmitting SNR or the number of antennas is large. The results show that the proposed antenna selection scheme achieves full diversity, and the simulation results closely match to our theoretical analysis. To further improve the spectrum efficiency of the system, a hybrid selection antenna scheme is proposed. Finally, the numerical results show that our scheme outperforms the state of art.

• 112. Song, Kang
KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
Performance Analysis of Heterogeneous Networks With Interference Cancellation2017Ingår i: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 66, nr 8, s. 6969-6981Artikel i tidskrift (Refereegranskat)

The performance of heterogeneous networks (HetNets) is investigated with both direct and relay-aided transmission strategies in a macrocell. We first propose an interference cancelation scheme at the macro base station on the basis of canceling cross-tier interferences from the macro base station to small-cell users. Then, expressions of the probability density function (PDF) and cumulative distribution function (CDF) of all receivers in both macro and small cells are derived, and the closed-form overall outage probability, average bit error rate (BER), and spectral efficiency of the network are obtained. Based on the derivations, we propose two adaptive relay-aided transmission schemes with instantaneous and statistical channel state information (CSI) to further improve the spectral efficiency. We show that the SNR boost at the small-cell mobile station comes from the cancelation of the cross-layer interference by the macro base station. Therefore, the performance of the small cell is improved greatly with interference cancelation, while the overall performance of the HetNet is also ameliorated. The numerical results finally show the validity of our analysis.

• 113.
Zhejiang Univ, State Key Lab Ind Control Technol, Hangzhou 310027, Zhejiang, Peoples R China..
Shanghai Huawei Technol Corp Campus, Shanghai 200040, Peoples R China.. Wuhan Univ, Sch Cyber Sci & Engn, Wuhan 430072, Hubei, Peoples R China.;Nanjing Univ, State Key Lab Novel Software Technol, Nanjing 210023, Jiangsu, Peoples R China.. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre. Zhejiang Univ, State Key Lab Ind Control Technol, Hangzhou 310027, Zhejiang, Peoples R China..
Sparsest Random Sampling for Cluster-Based Compressive Data Gathering in Wireless Sensor Networks2018Ingår i: IEEE Access, E-ISSN 2169-3536, Vol. 6, s. 36383-36394Artikel i tidskrift (Refereegranskat)

Compressive data gathering (CDG) has been recognized as a promising technique to collect sensory data in wireless sensor networks (WSNs) with reduced energy cost and better traffic load balancing. Besides, clustering is often integrated into CDG to further facilitate the network performance. However, existing cluster-based CDG methods generally require a large number of sensor nodes to participate in each compressive sensing (CS) measurement gathering and rarely consider possible node failures due to power depletion or malicious attacks, leading to insufficient energy efficiency and poor system robustness. In this paper, we propose a sparsest random sampling scheme for cluster-based CDG (SRS-CCDG) in WSNs to achieve energy efficient and robust data collection. Specifically, sensor nodes are organized into clusters. In each round of data gathering, a random subset of sensor nodes sense the monitored field and transmit their measurements to the corresponding cluster heads (CHs). Then, each CH transmits the data gathered within its cluster to the sink. In SRS-CCDG, each sensor reading is regarded as one CS measurement, and both intra-cluster and inter-cluster data transmissions can be realized by two methods, i.e., relaying or direct transmission. Furthermore, we propose analytical models that study the relationship between the size of clusters and the energy cost when using different intra-cluster and inter-cluster transmission schemes, aimed at finding the optimal size of clusters and transmission schemes that could lead to minimum energy cost. Then, we present a centralized clustering algorithm based on the theoretical analysis. Finally, we investigate the robustness of signal recovery performance of SRS-CCDG when node failures happen. Extensive simulations demonstrate that SRS-CCDG can significantly reduce the energy cost and improve the system robustness to node failures.

• 114.
Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu, Sichuan, Peoples R China..
Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu, Sichuan, Peoples R China.. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Southwest Jiaotong Univ, Key Lab Informat Coding & Transmiss, Chengdu, Sichuan, Peoples R China..
Performance Analysis for MmWave MIMO-SCMA systems Using Lens Antenna Array2019Ingår i: 2019 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS WORKSHOPS (ICC WORKSHOPS), IEEE , 2019Konferensbidrag (Refereegranskat)

The recent concept of beamspace multiple input multiple output (MEMO) can significantly reduce the number of required radio frequency (RE) chains in millimeter wave (mmWave) massive MEMO systems without obvious performance loss. However, the number of supported users cannot be larger than the number of RF chains in hybrid MEMO architectures. To break this fundamental limit, we introduce the concept of sparse code multiple access (SCMA) with beamspace MEMO, then a useful upper bound on the average symbol error probability is obtained through the union bound. The bound is tight in beamspace nunWave MEMO-SCMA systems for high SNR regions. The analytical result is compared with simulations, and the results confirm the effectiveness of the analysis for mmWave MEMO-SCMA channels.

• 115. Wang, C.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Message from the HWNQoE 2015 workshop chairs2015Ingår i: Proceedings - 15th IEEE International Conference on Computer and Information Technology, CIT 2015, 14th IEEE International Conference on Ubiquitous Computing and Communications, IUCC 2015, 13th IEEE International Conference on Dependable, Autonomic and Secure Computing, DASC 2015 and 13th IEEE International Conference on Pervasive Intelligence and Computing, PICom 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, artikel-id 7362998Konferensbidrag (Refereegranskat)
• 116. Wang, C.
KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap.
Message from the HWNQoE-2017 Workshop Chairs2018Ingår i: Proceedings - 2017 IEEE International Conference on Internet of Things, IEEE Green Computing and Communications, IEEE Cyber, Physical and Social Computing, IEEE Smart Data, iThings-GreenCom-CPSCom-SmartData 2017Volume 2018-January, 30 January 2018, Page lxviiiJoint 10th IEEE International Conference on Internet of Things, iThings 2017, 13th IEEE International Conference on Green Computing and Communications, GreenCom 2017, 10th IEEE International Conference on Cyber, Physical and Social Computing, CPSCom 2017 and the 3rd IEEE International Conference on Smart Data, Smart Data 2017; Exeter; United Kingdom; 21 June 2017 through 23 June 2017; Category numberE6190; Code 134517, Institute of Electrical and Electronics Engineers (IEEE), 2018, Vol. 2018-JanuaryKonferensbidrag (Övrigt vetenskapligt)
• 117.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Performance analysis of coded secondary relaying in overlay cognitive radio networks2012Ingår i: 2012 IEEE Wireless Communications and Networking Conference, WCNC, IEEE Communications Society, 2012, s. 294-299Konferensbidrag (Refereegranskat)

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

• 118.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
Diversity-Multiplexing Tradeoff Analysis of Coded Multi-User Relay Networks2011Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 59, nr 7, s. 1995-2005Artikel i tidskrift (Refereegranskat)

We study the impact of multiple access strategies on the diversity-multiplexing tradeoff (DMT) performance in wireless multi-user relay networks. The networks contain multiple independent sources, multiple half-duplex decode-and-forward (DF) relays, and one common destination. Instead of separately retransmitting each source message, the relays employ a class of spectrally efficient finite field network codes to assist the sources. It is shown that fully orthogonal or fully non-orthogonal transmission among sources/relays does not necessarily provide optimized DMT performance. We propose a novel transmission protocol that divides the sources and relays into individual clusters. The nodes within one cluster transmit non-orthogonally while the transmissions of different clusters span orthogonal channels. We provide the method to calculate the achievable DMT for each clustering strategy. The network DMT performance can thus be optimized by properly clustering the multiple sources and relays.

• 119.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
Diversity-multiplexing tradeoff analysis of multi-source multi-relay coded networks2010Ingår i: 2010 International Symposium on Information Theory and its Applications (ISITA), 2010, s. 422-427Konferensbidrag (Refereegranskat)

We study the impact of efficient network coding and multiple access techniques in a two-source two-relay one-destination wireless network through the diversity-multiplexing tradeoff (DMT) analysis. We compare the standard relaying protocol without network coding and the protocols using either a binary network coding (BNC) or an appropriately designed non-binary finite-field network coding (FFNC) at the relays. It is shown that the use of the non-binary FFNC strictly outperforms the other two protocols in terms of DMT. In addition, we propose a new transmission strategy based on the non-binary FFNC design and the non-orthogonal multiple access technique to further improve the DMT performance. Our results highlight the advantages of applying appropriate network coding in multi-source multi-relay networks.

• 120.
KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Efficient multiple access protocols for coded multi-source multi-relay networks2011Ingår i: 2011 IEEE International Conference on Communications (ICC), IEEE conference proceedings, 2011, s. 1-6Konferensbidrag (Refereegranskat)

We study the impact of multiple access protocols on the diversity-multiplexing tradeoff (DMT) performance in wireless multi-user relay networks. In the networks K half-duplex decode-and-forward (DF) relays employ a class of finite field network codes to assist in the communication between M independent sources and a common destination. The sources and relays are divided into individual clusters. The nodes within one cluster transmit non-orthogonally while the transmissions of different clusters span orthogonal channels. We provide the method to calculate the achievable DMT for each clustering strategy. The network DMT performance can thus be optimized by properly clustering the sources and the relays.

• 121.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Strong Secrecy for Interference Channels from Channel Resolvability2015Ingår i: 2015 49th Asilomar Conference on Signals, Systems and Computers, IEEE Computer Society, 2015, s. 559-563, artikel-id 7421191Konferensbidrag (Refereegranskat)

The achievable rate region is studied for interference channels with confidential messages under strong secrecy constraints. The problem is investigated based on the framework of the channel resolvability theory. The information-spectrum method introduced by Han and Verdu is first generalized to an arbitrary interference channel to obtain a direct channel resolvability result. The derived resolvability results are then shown to be the achievable strong secrecy rates for the stationary and memoryless interference channel. Our results provide further evidence that channel resolvability can be a powerful and general framework for strong secrecy analysis in multiuser networks.

• 122.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Strong secrecy for interference channels: Achievable rate region and degrees of freedomManuskript (preprint) (Övrigt vetenskapligt)

The achievable rate region and degrees of freedom are studied for interference channels with confidential messages under strong secrecy constraints. The problem is studied based on the framework of Han and Verd$\acute{\textrm{u}}$'s channel resolvability theory. It is shown that if the random binning rate for securing a confidential message is slightly above the resolution of its corresponding wiretapped channel, strong secrecy can be guaranteed. At first, the information-spectrum method introduced by Han and Verd$\acute{\textrm{u}}$ is generalized to an arbitrary interference channel to obtain a direct channel resolvability result. After specifying the channel transition probability, the derived resolvability results are shown to be the achievable strong secrecy rates for the stationary and memoryless interference channel. As an application, the secure degrees of freedom (SDOF) for the $K$-user Gaussian interference channel with confidential messages are investigated under strong secrecy constraints. It is shown that the optimal SDOF of the considered network is $\frac{K-1}{2K-1}$ for each user, which equals to its counterpart with weak secrecy constraints. The optimal SDOF scheme is achieved by combining the resolvability-based secrecy coding and artificial noise alignment on the real line. A suboptimal ergodic secure alignment is also proposed for the time-varying interference channels to achieve a sum SDOF of $\frac{K-3}{2K-2}$ for each user. Following the footsteps of Hayashi and of Bloch and Laneman, our results provide further evidence that channel resolvability can be a powerful and general framework for strong secrecy analysis in multiuser networks.

• 123.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. Ericsson Res, S-16483 Stockholm, Sweden..
Princeton Univ, Dept Elect Engn, Princeton, NJ 08544 USA.;Tech Univ Berlin, Informat Theory & Applicat Chair, D-10587 Berlin, Germany.. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. KTH, Skolan för elektroteknik och datavetenskap (EECS), Teknisk informationsvetenskap. Royal Inst Technol, Dept Informat Sci & Engn, S-10044 Stockholm, Sweden.. Princeton Univ, Dept Elect Engn, Princeton, NJ 08544 USA..
Strong Secrecy for Interference Channels Based on Channel Resolvability2018Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 64, nr 7, s. 5110-5130Artikel i tidskrift (Refereegranskat)

Interference channels with confidential messages are studied under strong secrecy constraints, based on the framework of channel resolvability theory. It is shown that if the random binning rate for securing a confidential message is above the resolution of its corresponding wiretapped channel, strong secrecy can be guaranteed. The information-spectrum method introduced by Han and Verdu is generalized to an arbitrary interference channel to obtain a direct channel resolvability result as a first step. For stationary and memoryless channels with discrete output alphabets, the results show that the achievable rates under weak and strong secrecy constraints are the same. This result is then generalized to channels with continuous output alphabets by deriving a reverse direction of Pinsker's inequality to bound the secrecy measure from above by a function of the variational distance of relevant distributions. As an application, Gaussian interference channels are studied in which the agreement between the best known weak and strong secrecy rate regions also appear. Following the footsteps of Csiszar, Hayashi and of Bloch and Laneman, these results provide further evidence that channel resolvability is a powerful and general framework for strong secrecy analysis in multiuser networks.

• 124.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Secrecy degrees of freedom of the 2 interference channel with delayed CSIT2014Ingår i: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 3, nr 4, s. 341-344, artikel-id 6784143Artikel i tidskrift (Refereegranskat)

We consider the two-hop interference channel with confidential messages (ICC), where each transmitter sends one confidential message to its intended destination through two trusted relays. We study the secrecy degrees of freedom (SDoF) of the considered 2 ?2 ?2 ICC with delayed channel state information at transmitters (CSIT). We settle the optimal SDoF of the considered network to be (1/2, 1/2). Thus, the considered network has a strictly larger sum SDoF than a two-user one-hop ICC with even full CSIT. Moreover, we study the SDoF of the network with limited Shannon feedback, that only one relay can obtain the delayed CSIT and output feedback from the destinations. The optimal SDoF is also shown to be (1/2, 1/2), revealing that only limited feedback can also bring SDoF gain. Our proposed achievable schemes in both cases are integrated forms of the retrospective interference alignment and artificial noise transmission.

• 125.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
Secrecy degrees of freedom of the two-user MISO broadcast channel with mixed CSIT2015Ingår i: 2015 IEEE Information Theory Workshop, ITW 2015, IEEE conference proceedings, 2015Konferensbidrag (Refereegranskat)

The secrecy degrees of freedom (SDOF) of the multiple-input single-output (MISO) broadcast channel with confidential messages (BCC) is studied. The network consists of a two-antenna transmitter and two single-antenna receivers, each demanding a confidential message from the transmitter. The problem is investigated with mixed channel state information at transmitter (CSIT), which is a combination of perfect delayed CSIT and inaccurate current CSIT. When the variance of the estimation error for the current CSIT scales with O(P-α), with α ∈ [0, 1], it is shown that the optimal sum SDOF of the considered BCC is 1+α. Furthermore, the optimal SDOF region of the considered MISO BCC is shown to be a polygon scaling with α. The proposed scheme is based on an artificial noise alignment that can combine the benefits of both types of delayed and current CSIT. These results can be seen as an extension of results of Yang et al. and Gou-Jafar to multiuser networks with secrecy constraints.

• 126.
KTH.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Secrecy degrees of freedom of wireless X networks using artificial noise alignment2015Ingår i: IEEE International Symposium on Information Theory - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2015, s. 616-620Konferensbidrag (Refereegranskat)

The problem of transmitting confidential messages in the M × K wireless X network is considered, in which each transmitter intends to send one confidential message to every receiver. In particular, the secrecy degrees of freedom (SDOF) of the considered network are studied by an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission. At first, an SDOF upper bound is derived for the M × K X network with confidential messages (XNCM) to be equation. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when either K = 2 or M = 2 for the considered XNCM with time/frequency varying channels. For K, M ≥ 3, it is shown that an SDOF of equation can be achieved, even when an external eavesdropper appears. The key idea of the proposed scheme is to inject artificial noise into the network, which can be aligned in the interference space at receivers for confidentiality. The proposed method provides a linear approach for secure interference alignment.

• 127.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
Secure Degrees of Freedom of Wireless X Networks Using Artificial Noise Alignment2015Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, nr 7, s. 2632-2646Artikel i tidskrift (Refereegranskat)

The problem of transmitting confidential messages in M x K wireless X networks is considered in which each transmitter intends to send one confidential message to every receiver. In particular, the secure degrees of freedom (SDOF) of the considered network are studied based on an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission. At first, an SDOF upper bound is derived for the M x K X network with confidential messages (XNCM) to be K(M-1)/K+M-2. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when K = 2 for the considered XNCM with time-/frequency-varying channels. For K >= 3, it is shown that SDOF of K(M-1)K+M-1 can be achieved, even when an external eavesdropper is present. The key idea of the proposed scheme is to inject artificial noise into the network, which can be aligned in the interference space at receivers for confidentiality. Moreover, for the network with no channel state information at transmitters, a blind ANA scheme is proposed to achieve SDOF of K(M-1)K+M-1 for K, M >= 2, with reconfigurable antennas at receivers. The proposedmethod provides a linear approach to secrecy coding and interference alignment.

• 128.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
On the degrees of freedom of two-hop MISO broadcast networks with mixed CSIT2013Ingår i: 2013 IEEE Global Communications Conference (GLOBECOM), IEEE , 2013, s. 1909-1914Konferensbidrag (Refereegranskat)

We consider a downlink two-hop MISO broadcast network with a 2-antenna source communicating to 2 single-antenna destinations, via 2 single-antenna relays. We investigate spectrally efficient transmission and the associated achievable sum degrees of freedom (DoF) with mixed channel state information at the transmitter (CSIT), which consists of perfect delayed CSIT and imperfect instantaneous CSIT. When the variance of the estimation error of the instantaneous CSIT lies on level of O(P-α) for the transmission power P and some α [0, 1], we show that the sum DoF 4-2α over 3-2α [4 over 3, 2] can be achieved by a novel interference alignment (IA) scheme. The result shows that rather than exploiting only delayed or imperfect instantaneous CSIT, the transmission design taking advantages of both can achieve higher sum DoF.

• 129.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Degrees of freedom of multi-hop MIMO broadcast networks with delayed CSIT2013Ingår i: IEEE Wireless Communications Letters, ISSN 2162-2337, Vol. 2, nr 2, s. 207-210Artikel i tidskrift (Refereegranskat)

We study the sum degrees of freedom (DoF) of a class of multi-layer relay-aided MIMO broadcast networks with delayed channel state information at transmitters (CSIT). In the assumed network a K-antenna source intends to communicate to K single-antenna destinations, with the help of N-2 layers of K full-duplex single-antenna relays. We assume identical and independent fading channels on every hop. Two practical delayed CSIT feedback scenarios are studied. If the source can obtain the CSI feedback signals from all layers, we prove the optimal sum DoF of the network to be K 1+12+...+1K. If the CSI feedback is only within each hop, we show that when K=2 the optimal sum DoF is 4 3, and when K≥ 3 the sum DoF 32 is achieved asymptotically.

• 130.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
A two-phase maximum-likelihood sequence estimation for receivers with partial CSI2013Ingår i: 9th International Conference on Information, Communications and Signal Processing, ICICS 2013, IEEE Computer Society, 2013, s. 6782818-Konferensbidrag (Refereegranskat)

The optimality of the conventional maximum-likelihood sequence estimation (MLSE), also known as the Viterbi Algorithm (VA), relies on the assumption that the receiver has perfect knowledge of the channel coefficients or channel state information (CSI). However, in practical situations that fail the assumption, the MLSE method becomes suboptimal and then exhaustive checking is the only way to obtain the ML sequence. At this background, considering directly the ML criterion for partial CSI, we propose a two-phase low-complexity MLSE algorithm, in which the first phase performs the conventional MLSE algorithm in order to retain necessary information for the backward VA performed in the second phase. Simulations show that when the training sequence is moderately long in comparison with the entire data block such as 1/3 of the block, the proposed two-phase MLSE can approach the performance of the optimal exhaustive checking. In a normal case, where the training sequence consumes only 0.14 of the bandwidth, our proposed method still outperforms evidently the conventional MLSE.

• 131.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Joint data and channel estimation using semi-blind MLSE algorithms2013Ingår i: 2013 IEEE 14th Workshop on Signal Processing Advances in Wireless Communications, SPAWC, IEEE , 2013, s. 400-404Konferensbidrag (Refereegranskat)

Operation-intensive exhaustive checking is the unique optimal method for performing joint maximum-likelihood (JML) data and channel estimation. Thus, several suboptimal methods incorporating conventional maximum-likelihood sequence estimation (MLSE) or its extensions have been proposed in order to reduce complexity. However, most of them suffer from either long convergence delay or unsatisfactory performance. Therefore, based on a two-phase MLSE algorithm designed for partially coherent receivers, we propose a novel low-complexity and low-latency batch algorithm for JML process. The proposed algorithm first searches for several of the best candidate training sequences using priority-first search, and then applies the training sequences to the two-phase MLSEs to obtain the maximum-likelihood data sequence. Simulation results show that when the candidate training sequence length is adequate, the proposed algorithm can achieve the performance of optimal exhaustive checking.

• 132. Wu, L.
KTH, Skolan för elektro- och systemteknik (EES), Teknisk informationsvetenskap.
Sparse Signal Aloha: A Compressive Sensing-Based Method for Uncoordinated Multiple Access2017Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, nr 6, s. 1301-1304, artikel-id 7849200Artikel i tidskrift (Refereegranskat)

We investigate the problem of sparse signal medium access control in the wireless sensor networks. The proposed sparse signal Aloha (SSA) transmits sampled compressive data to the fusion center using Aloha random access protocol. In order to maximize the overall data transmission rate in the presence of packet collision, redundant data are randomly subsampled at individual sensor nodes according to an optimal subsampling rate before transmission. Data loss due to random subsampling and collision in the wireless channel are compensated using compressive sensing recovery method at the fusion center. Simulation results verify the theoretical analysis and show the significant improvement of SSA compared with existing CS-based random access method.

• 133.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Cross-layer design of rateless random network codes for delay optimization2010Ingår i: 2010 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, 2010Konferensbidrag (Refereegranskat)

We study joint network-coding and channel-coding design to optimize delay performance. In our systems, network codes (network layer) are on top of channel codes (physical layer). Network codes run in a rateless random method, i.e., source and intermediate nodes randomly produce and transmit codewords until transmission succeeds. Thus, the rateless network codes have block-erasure-correction capability. The physical layer codewords are disturbed by channel noise. For the constraint of finite transmission time (finite block length), transmission errors are inevitable in the physical layer. We show that the physical-layer erasure probability is affected by both layers. Then, there is an interaction between network codes and channel codes, concerning the delay measure of the networks. We model the delay of each generation as the independent, identically distributed random variables. We show tradeoffs between the network layer and the physical layer on the length of network codewords, and on the transmission time of physical-layer codewords. To measure delay performance, we use expected delay and network-layer decoding error probability of a given delay, which are measures for networks without and with strict maximum-delay constraints, respectively. We show how to evaluate these measures for the coded networks with erasure channels. Then, we formulate problems to optimize the delay performance, and solutions are suggested.

• 134.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Serially concatenated continuous phase modulation with ring convolutional codes2004Ingår i: 2004 IEEE INTERNATIONAL SYMPOSIUM ON INFORMATION THEORY, PROCEEDINGS, NEW YORK: IEEE , 2004, s. 513-513Konferensbidrag (Refereegranskat)

Serially concatenated continuous phase modulation (SCCPM) systems with ring convolutional codes (CC) are investigated. Both EXIT chart and union bound techniques are used to compare with the simulation results and are used as analysis tools. The latter is for the first time generalized to a non-binary interleaver for a serially concatenated system, where both the order and position of the permuted non-zero symbols have to be considered.

• 135.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Chalmers University of Technology.
Irregular repeat continuous phase modulation2005Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 9, nr 8, s. 723-725Artikel i tidskrift (Refereegranskat)
• 136.
Chalmers University of Technology.
Chalmers University of Technology.
On analysis and design of low density generator matrix codes for continuous phase modulation2007Ingår i: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 6, nr 9, s. 3440-3449Artikel i tidskrift (Refereegranskat)

We investigate the analysis and design of low density generator matrix (LDGM) codes for continuous phase modulation (CPM). The system uses LDGM codes as an outer code for CPM. For additive white Gaussian noise channels, we derive the union bound to analyze the error floor performance. Design principles for lowering error floors are suggested from this analysis. We propose a design approach of jointly considering the LDGM code degree and the CPM modulation index. Then we consider the rate-adaptive system for slowly fading channels. By changing the rate of the LDGM codes, the information rate of the CPM signals is adapted according to channel variations. We use a low-rate LDGM code as the mother code. Higher rates are achieved by puncturing the output of these codes. To exploit the rate-flexible property of punctured LDGM codes, a rate function is proposed to calculate the rate of each transmitted block. Thus, we can have a quasi-continuous information rate. Numerical results show that this approach can improve the energy efficiency from a discrete-rate adaptation. Using the rate-daptive approach, up to 11 dB transmitted energy gain can be achieved from the non-adaptive scheme in the low bit-error-rate region (smaller than 10(-3)) for minimum shift keying (MSK).

• 137. Xiao, Ming
On the Bit Error Probability of Noisy Channel Networks With Intermediate Node Encoding2008Ingår i: IEEE Transactions on Information Theory, ISSN 0018-9448, E-ISSN 1557-9654, Vol. 54, nr 11, s. 5188-5198Artikel i tidskrift (Refereegranskat)

We investigate the calculation approach of the sink bit error probability (BEP) for a network with intermediate node encoding. The network consists, of statistically independent noisy channels. The main contributions are, for binary network codes, an error marking algorithm is given to collect the error weight (the number of erroneous bits). Thus, we can calculate the exact sink BEP from the channel BEPs. Then we generalize the approach to nonbinary codes. The coding scheme works on the Galois field 2(m), where m is a positive integer. To reduce computational complexity, a subgraph decomposition approach is proposed. In general, it can significantly reduce computational complexity, and the numerical result is also exact. For approximate results, we discuss the approach of only considering error events in a single channel. The results well approximate the exact results in low BEP regions with much lower complexity.

• 138.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori. KTH, Skolan för elektro- och systemteknik (EES), Centra, ACCESS Linnaeus Centre.
Chalmers University of Technology.
Optimal Decoding and Performance analysis of a Noisy Channel Network with Network Coding2009Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 57, nr 5, s. 1402-1412Artikel i tidskrift (Refereegranskat)

We investigate sink decoding approaches and performance analysis for a network with intermediate node encoding (coded network). The network consists of statistically independent noisy channels. The sink bit error probability (BEP) is the performance measure. First, we investigate soft-decision decoding without statistical information on the upstream channels (the channels not directly connected to the sink). Numerical results show that the decoder cannot significantly improve the performance from a hard-decision decoder. We develop union bounds for analysis. The bounds show the asymptotic (regarding SNR: signal-to-noise ratio) performance of the decoder. Using statistical information about the upstream channels, we can find the error patterns of final hop channels (channels directly connected to sinks).With the error patterns, maximum-likelihood (ML) decoding can be performed, and a significant improvement in the BEP is obtained. To evaluate the union bound for the ML decoder, we use an equivalent point procedure. It is reduced to the least-squares problem with a linear constraint in the medium-to-high SNR region. With deterministic knowledge of the errors in the upstream channels, a genie-aided decoder can further improve the performance. We give the union bound for the genie decoder, which is straightforward to evaluate. By analyzing these decoders, we find that knowledge about the upstream channels is essential for good sink decoding.

• 139.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Serially concatenated continuous phase modulation with low density generator matrix codes2005Ingår i: 2005 IEEE 6th Workshop on Signal Processing Advances in Wireless Communications, NEW YORK: IEEE , 2005, s. 76-80Konferensbidrag (Refereegranskat)

We propose a new scheme of serially concatenated continuous phase modulation (SCCPM) by using nonsysternatic low, density. generator matrix (LDGM) codes as the outer code. We use the EXIT chart/function to optimize the LDGM codes. We also show the EXIT function for CPM when the SNR (Signal-to-Noise-Ratio) is fixed. A property of the LDGM code degree is investigated. The union bound is used to analyze the error floor. Numerical results show that this scheme converges earlier (lower SNR) than previous considered SCCPM schemes for iterative decoding.

• 140.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Chalmers University of Technology.
Serially concatenated continuous phase modulation with symbol interleavers: Performance, properties and design principles2006Ingår i: European transactions on telecommunications, ISSN 1124-318X, E-ISSN 2161-3915, Vol. 17, nr 4, s. 439-449Artikel i tidskrift (Refereegranskat)
• 141.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
A physical layer aspect of network coding with statistically independent noisy channels2006Ingår i: 2006 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, VOLS 1-12, 2006, Vol. 9, s. 3996-4001Konferensbidrag (Refereegranskat)

We investigate the physical layer bit error probability (BEP) of a network using network coding (coded network). The network consists of statistically independent noisy channels. Thus, transmitted bits are subject to the noise disturbance. An error marking algorithm is given to calculate the error weight (the number of erroneous bits) in the sinks. Then we can calculate the sink BEP of a coded network from the channel BEPs. We formulate the minimizing BEP problem. We show that coding schemes with the same flow may have different sink BEPs. Two approaches are suggested to reduce the complexity.

• 142.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Design of low density generator matrix codes for continuous phase modulation2005Ingår i: GLOBECOM '05: IEEE Global Telecommunications Conference, Vols 1-6 - DISCOVERY PAST AND FUTURE, 2005, s. 1245-1249Konferensbidrag (Refereegranskat)

We investigate the low density generator matrix (LDGM) codes for continuous phase modulation (CPM). The nonsystematic version of LDGM codes is used in the scheme. The overall system has linear encoding complexity due to the low complexity of the LDGM codes. A property of the check node degree of the LDGM code is shown. We use the EXIT chart/function to optimize the LDGM codes. The EXIT function of CPM with a fixed SNR (Signal-to-Noise-Ratio) is shown. We derive the union bound to analyze the error floor performance. Design approaches for lowering error floors are suggested from the analysis process. Numerical results show that this scheme converges earlier (lower SNR) than best found serially concatenated CPM (SCCPM) for iterative decoding while maintaining comparable error floors.

• 143. Xiao, Ming
Energy-efficient network coding for the noisy channel network2006Ingår i: 2006 IEEE International Symposium on Information Theory, Vols 1-6, Proceedings, NEW YORK: IEEE , 2006, s. 778-782Konferensbidrag (Övrigt vetenskapligt)

We investigate energy-efficient network coding with a bit error probability (BEP) constraint. The network consists of statistically independent binary noisy channels. An error marking algorithm is used to calculate the number of erroneous bits in the sinks. Then we can accurately calculate the BEP in the sinks from the channel BEPs. For a given coding scheme, we formulate the optimal energy allocation problem. We show that the problem is convex for BPSK modulation. Then, we check the problem of the joint optimal network coding and energy allocation. A procedure is formulated to solve the problem. A pruning rule is suggested to reduce the search effort. Numerical results show the energy saving from the equal energy allocation and non-optimal coding.

• 144. Xiao, Ming
Maximum-likelihood decoding and performance analysis of a noisy channel network with network coding2007Ingår i: 2007 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS, 2007, s. 6103-6110Konferensbidrag (Refereegranskat)

We investigate sink decoding methods and performance analysis approaches for a network with intermediate node encoding (coded network). The network consists of statistically independent noisy channels. The sink bit error probability (BEP) is the performance measure. We first discuss soft-decision decoding without statistical information on the upstream channels (the channels not directly connected to the sink). The example shows that the decoder cannot significantly improve the BEP from the hard-decision decoder. We develop the union bound to analyze the decoding approach. The bound can show the asymptotic (regarding SNR: signal-to-noise ratio) performance. Using statistical information of the upstream channels, we then show the method of maximum-likelihood (ML) decoding. With the decoder, a significant improvement in the BEP is obtained. To evaluate the union bound for the ML decoder, we use an equivalent signal point procedure. It can be reduced to a leastsquares problem with linear constraints for medium-to-high SNR.

• 145.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
On performance bounds for serially concatenated codes with the general inner code and interleaver2005Ingår i: Proceedings of the IEEE ITSOC Information Theory Workshop 2005 on Coding and Complexity, NEW YORK: IEEE , 2005, s. 258-262Konferensbidrag (Refereegranskat)

We investigate the union bound for symbol interleaved serially concatenated codes (SCC) with non-uniform error properties. We calculate the distance spectrum of the SCC using the input difference symbol sequence spectrum (DSSS) of the inner code. Then we modify the trellis search algorithm for general codes to calculate the DSSS. We also show the mapping approach between difference symbols with the different alphabet size. For the symbol interleaver, we use the multinomial coefficient to calculate the probability of the permuted sequence. Numerical results for symbol interleaved serially concatenated continuous phase modulation (SCCPM) show that the bound is tight in the medium to high signal-to-noise ratio (SNR) region.

• 146.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
On the error probability of a noisy channel network using network coding2006Ingår i: 2006 IEEE WIRELESS COMMUNICATIONS AND NETWORKING CONFERENCE (WCNC 2006), VOLS 1-4, Las Vegas, NV, 2006, Vol. 1, s. 19-24Konferensbidrag (Refereegranskat)

We investigate the bit error probability (BEP) of a network using network coding (coded network). The network consists of independent binary noisy channels. An error marking algorithm is used to calculate the error weight (the number of erroneous bits) in the sinks. Hence, we can calculate the sink BEP of a coded network from the channel BEPs. Then we formulate the minimizing BEP problem. We show that coding schemes with the same flows may have different BEPs. Two approaches are given to reduce the complexity for the problem.

• 147.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Rate-adaptive CPM with punctured LDGM codes in slow-fading channels2006Ingår i: 2006 IEEE International Symposium on Information Theory, Proceedings, NEW YORK: IEEE , 2006, s. 1324-1328Konferensbidrag (Refereegranskat)

We investigate rate-adaptive continuous phase modulation (CPM) with punctured low-density generator matrix (LDGM) codes. We give an adaptive principal component analysis (PCA) CPM receiver for slow-fading channels. With the merit of. the PCA receiver, the new receiver avoids the eigenvalue decomposition in every symbol interval, and uses a fixed filter-bank. By changing the rate of the LDGM codes, the information rate of CPM signals is adapted to the channel state information (CSI). We use a low rate LDGM code as the mother code, and higher rates are achieved by puncturing the output of the LDGM codes. To exploit the rate-flexible property of punctured LDGM codes, a rate function is proposed to calculate the rate of each transmitted block. Thus, we can have a quasi-continuous information rate. Numerical results for MSK show that up to 11dB transmitted energy gain can be achieved in the low bit-error-rate region (smaller than 10(-3)), compared to the nonadaptive systems.

• 148.
Telecommunication Theory, Department of Computer Engineering, Chalmers University of Technology.
Telecommunication Theory, Department of Computer Engineering, Chalmers University of Technology.
Serially concatenated continuous phase modulation with convolutional codes over rings2006Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 54, nr 8, s. 1387-1396Artikel i tidskrift (Refereegranskat)

In this paper, we investigate serially concatenated continuous phase modulation (SCCPM) with convolutional codes (CC) over rings. The transmitted signals are disturbed by additive white Gaussian noise. The properties for systems with both infinite and finite block lengths are investigated. For an infinite-length system, we check the convergence threshold using the extrinsic information transfer chart. For a finite-length system, we use union-bound techniques to estimate the error floors. In the union-bound analysis, we consider both the order and the position of nonzero permuted symbols. A simple method for determining a CPM error event through the sum of the input symbol sequence is shown. Thus, we can determine if the output symbol sequence of an error event in the ring CC can form an error event in CPM. Two properties concerning the interleaver gain (IG) are investigated. A recursive search algorithm for the maximal IG is shown. Compared with previous SCCPM with a binary CC, the proposed system shows an improvement concerning the convergence threshold or error floors.

• 149.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Serially concatenated continuous phase modulation with low density generator matrix codes: Property, optimization and performance analysis2005Ingår i: Proceedings of the IEEE ITSOC Information Theory Workshop 2005 on Coding and Complexity, NEW YORK: IEEE , 2005, s. 253-257Konferensbidrag (Refereegranskat)

We propose a new scheme of serially concatenated continuous phase modulation (SCCPM) by using nonsystematic low density generator matrix (LDGM) codes as the outer code. A property of the LDGM code degree is investigated. We use the EXIT chart/function to optimize the LDGM codes. The EXIT function of CPM with a fixed SNR (Signal-to-Noise-Ratio) is shown. We derive the union bound to analyze the error floor performance. Design principles are proposed from the analysis process. Numerical results show that this scheme converges earlier (lower SNR) than previous SCCPM for iterative decoding.

• 150.
KTH, Skolan för elektro- och systemteknik (EES), Kommunikationsteori.
Serially concatenated continuous phase modulation with symbol interleavers: Performance, properties and design principles2004Ingår i: GLOBECOM '04: IEEE GLOBAL TELECOMMUNICATIONS CONFERENCE, 2004, s. 179-183Konferensbidrag (Refereegranskat)

Serially concatenated continuous phase modulation (SCCPM) systems with symbol interleavers are investigated. The transmitted signals are disturbed by additive white Gaussian noise (AWGN). Iterative detection with extrinsic information is used at the receiver side. Compared to bit interleaved SCCPM systems, this scheme shows a substantial improvement in convergence threshold at the price of a higher error floor. In addition to showing this property, we also investigate the underlying reason by error event analysis. In order to estimate bit error rate performance, we generalize traditional union bounds for a bit interleaver to the non-binary interleaver. For the latter, both the order and the position of permuted non-zero symbols have to be considered. From the analysis, some principal properties are presented. Finally some design principles are proposed. The paper concentrates on SCCPM, but the proposed analysis methods and conclusions can be widely used in many other systems such as serially concatenated trellis coded modulation etcetera.

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