Telex Ngatched - Academia.edu (original) (raw)
Papers by Telex Ngatched
IEEE Access, 2018
In this paper, a hybrid satellite-terrestrial relay network (HSTRN) interconnecting a satellite a... more In this paper, a hybrid satellite-terrestrial relay network (HSTRN) interconnecting a satellite and multiple terrestrial nodes is considered, where communication is achieved by the satellite transmitting information to a destination through multiple relays at the appearance of an eavesdropper attempting to intercept the transmissions from both the satellite and relays. We present the single-relay selection and multi-relay selection as well as round-robin scheduling schemes to investigate the physical-layer security of this considered HSTRN by adopting the decode-and-forward relay strategy. Specifically, in a single-relay selection scheme, a relay is chosen as the ''best'' relay which has the maximum instantaneous capacity of relay-destination channel out of the decoding relay set, which is composed of all the relays capable to decode the received signals from the satellite successfully. By contrast, in a multi-relay selection scheme, all relays of the decoding relay set are invoked simultaneously to aid the satellite communicating with the destination. Moreover, suppose that only the main channels' state information is known while the wiretap channels' state information is unavailable due to the passive eavesdropper, we analyze the secrecy performance in accordance with secrecy outage probability of the HSTRN by driving out the closed-form expressions for the single-relay selection and baseline round-robin scheduling schemes, as well as by computer simulations for multi-relay selection scheme. Numerical results show that the two relay selection schemes generally outperform the round-robin scheduling baseline scheme in the light of improving the secrecy performance of HSTRN even when the legitimate links are inferior to the wiretap links. INDEX TERMS Hybrid satellite-terrestrial relay network, physical-layer security, secrecy outage probability, relay selection.
2010 IEEE International Conference on Communications, 2010
ABSTRACT
2015 IEEE 14th Canadian Workshop on Information Theory (CWIT), 2015
2015 IEEE International Conference on Communication Workshop (ICCW), 2015
2015 IEEE 14th Canadian Workshop on Information Theory (CWIT), 2015
IEEE Communications Letters, 2015
Wiley Encyclopedia of Electrical and Electronics Engineering, 1999
ABSTRACT This article reviews the visible light communications (VLC), a technology in which the v... more ABSTRACT This article reviews the visible light communications (VLC), a technology in which the visible spectrum is modulated to transmit data. It presents the VLC communication system: the transmitter, the channel, and the receiver. The single and multichannel transceivers are presented. The channel for a system that uses a single light-emitting diodes (LED) and the matrix representing the multicolor channel are discussed. Various modulation schemes, basic techniques used to implement a VLC system, and different causes of dimming are discussed. In addition, standardization of the VLC technology, applications, as well as challenges for VLC practical implementation and commercialization are reviewed.
2014 IEEE International Conference on Communications (ICC), 2014
2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013
2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
This paper presents a low-complexity iterative joint detection and decoding algorithm for finite ... more This paper presents a low-complexity iterative joint detection and decoding algorithm for finite geometry-low density parity check (FG-LDPC) coded multiple-input multiple-output (MIMO) systems, in which the MIMO channel detector and the FG-LDPC decoder iteratively exchange soft information. The key to the simplicity of the algorithm is the use of a bit flipping-based decoder for FG-LDPC code. An important issue addressed
IEEE Communications Letters, 2015
2014 IEEE Global Communications Conference, 2014
Optics Express, 2015
A novel joint symbol timing and carrier frequency offset (CFO) estimation algorithm is proposed f... more A novel joint symbol timing and carrier frequency offset (CFO) estimation algorithm is proposed for reduced-guard-interval coherent optical orthogonal frequency-division multiplexing (RGI-CO-OFDM) systems. The proposed algorithm is based on a constant amplitude zero autocorrelation (CAZAC) sequence weighted by a pseudo-random noise (PN) sequence. The symbol timing is accomplished by using only one training symbol of two identical halves, with the weighting applied to the second half. The special structure of the training symbol is also utilized in estimating the CFO. The performance of the proposed algorithm is demonstrated by means of numerical simulations in a 115.8-Gb/s 16-QAM RGI-CO-OFDM system.
IEEE Communications Letters, 2015
In this paper, a cognitive radio (CR) network composed of K secondary users who cooperatively sen... more In this paper, a cognitive radio (CR) network composed of K secondary users who cooperatively sense a channel using the k-out-of-K fusion rule to determine the presence of the primary user is studied. The sensing-throughput tradeoff problem is investigated in a realistic environment where both the sensing channels and reporting channels are characterized by fading channels. It is observed that taking into consideration the probability of reporting error in the CR network increases the sensing time and reduces the maximum average throughput of the secondary users. To mitigate the effect of the probability of reporting error, a transmit diversity based cooperative spectrum sensing method using randomized space-time block coding (RSTBC) is proposed. Simulations results show that the spatial diversity gain induced by RSTBC significantly decreases the sensing time and improves the throughput of the secondary users.
International Journal of Autonomous and Adaptive Communications Systems, 2013
ABSTRACT
IEEE Transactions on Signal Processing, 2000
In this paper we study the system level performance of cognitive radio (CR) networks under averag... more In this paper we study the system level performance of cognitive radio (CR) networks under average received interference power constraints. Under the assumption of uniform node placements and a simple power control scheme, we derive the closed-form expression for the cumulative distribution function (CDF) of the maximum allowable transmit power of the target CR transmitter. We further study two CR network scenarios: a CR based central access network and a CR assisted virtual multiple-input multiple-output (MIMO) network. The average uplink capacities of both networks are derived and analyzed, with an emphasis on understanding the effect of the numbers of primary users and CR users on the capacity. Numerical and simulation results demonstrate that the CR based central access network is more suitable for less-populated rural areas where a lower density of primary receivers is expected, while the CR assisted virtual MIMO network performs better in urban environments with a dense population of mobile CR users.
IEEE Transactions on Communications, 2000
This paper presents a hybrid decoding algorithm for low-density parity-check (LDPC) codes based o... more This paper presents a hybrid decoding algorithm for low-density parity-check (LDPC) codes based on the interior point method with barrier function for linear programming (LP) decoding introduced by Wadayama [16]. First, an efficient implementation of Wadayama's algorithm is presented. The main idea behind the modification is to approximate the barrier function for the fundamental polytope defining the code so that it contains only one linear constraint for each of the parity-check constraints. A two-stage hybrid decoding which combines the interior point decoding and a low-complexity decoding algorithm for LDPC codes is then proposed. Simulation results show that the approximations introduced in the proposed algorithms do not result in any performance degradation, while considerably reducing the decoding complexity and latency. Index Terms-Belief propagation (BP) algorithm, convex optimization, low-density parity-check (LDPC) codes, finite geometries, interior point algorithm, weighted bit-flipping (WBF) algorithm.
IEEE Transactions on Communications, 2000
In this letter, an improved bit-flipping decoding algorithm for high-rate finite-geometry low-den... more In this letter, an improved bit-flipping decoding algorithm for high-rate finite-geometry low-density parity-check (FG-LDPC) codes is proposed. Both improvement in performance and reduction in decoding delay are observed by flipping multiple bits in each iteration. Our studies show that the proposed algorithm achieves an appealing tradeoff between performance and complexity for FG-LDPC codes.
IEEE Access, 2018
In this paper, a hybrid satellite-terrestrial relay network (HSTRN) interconnecting a satellite a... more In this paper, a hybrid satellite-terrestrial relay network (HSTRN) interconnecting a satellite and multiple terrestrial nodes is considered, where communication is achieved by the satellite transmitting information to a destination through multiple relays at the appearance of an eavesdropper attempting to intercept the transmissions from both the satellite and relays. We present the single-relay selection and multi-relay selection as well as round-robin scheduling schemes to investigate the physical-layer security of this considered HSTRN by adopting the decode-and-forward relay strategy. Specifically, in a single-relay selection scheme, a relay is chosen as the ''best'' relay which has the maximum instantaneous capacity of relay-destination channel out of the decoding relay set, which is composed of all the relays capable to decode the received signals from the satellite successfully. By contrast, in a multi-relay selection scheme, all relays of the decoding relay set are invoked simultaneously to aid the satellite communicating with the destination. Moreover, suppose that only the main channels' state information is known while the wiretap channels' state information is unavailable due to the passive eavesdropper, we analyze the secrecy performance in accordance with secrecy outage probability of the HSTRN by driving out the closed-form expressions for the single-relay selection and baseline round-robin scheduling schemes, as well as by computer simulations for multi-relay selection scheme. Numerical results show that the two relay selection schemes generally outperform the round-robin scheduling baseline scheme in the light of improving the secrecy performance of HSTRN even when the legitimate links are inferior to the wiretap links. INDEX TERMS Hybrid satellite-terrestrial relay network, physical-layer security, secrecy outage probability, relay selection.
2010 IEEE International Conference on Communications, 2010
ABSTRACT
2015 IEEE 14th Canadian Workshop on Information Theory (CWIT), 2015
2015 IEEE International Conference on Communication Workshop (ICCW), 2015
2015 IEEE 14th Canadian Workshop on Information Theory (CWIT), 2015
IEEE Communications Letters, 2015
Wiley Encyclopedia of Electrical and Electronics Engineering, 1999
ABSTRACT This article reviews the visible light communications (VLC), a technology in which the v... more ABSTRACT This article reviews the visible light communications (VLC), a technology in which the visible spectrum is modulated to transmit data. It presents the VLC communication system: the transmitter, the channel, and the receiver. The single and multichannel transceivers are presented. The channel for a system that uses a single light-emitting diodes (LED) and the matrix representing the multicolor channel are discussed. Various modulation schemes, basic techniques used to implement a VLC system, and different causes of dimming are discussed. In addition, standardization of the VLC technology, applications, as well as challenges for VLC practical implementation and commercialization are reviewed.
2014 IEEE International Conference on Communications (ICC), 2014
2013 IEEE Wireless Communications and Networking Conference (WCNC), 2013
2009 IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, 2009
This paper presents a low-complexity iterative joint detection and decoding algorithm for finite ... more This paper presents a low-complexity iterative joint detection and decoding algorithm for finite geometry-low density parity check (FG-LDPC) coded multiple-input multiple-output (MIMO) systems, in which the MIMO channel detector and the FG-LDPC decoder iteratively exchange soft information. The key to the simplicity of the algorithm is the use of a bit flipping-based decoder for FG-LDPC code. An important issue addressed
IEEE Communications Letters, 2015
2014 IEEE Global Communications Conference, 2014
Optics Express, 2015
A novel joint symbol timing and carrier frequency offset (CFO) estimation algorithm is proposed f... more A novel joint symbol timing and carrier frequency offset (CFO) estimation algorithm is proposed for reduced-guard-interval coherent optical orthogonal frequency-division multiplexing (RGI-CO-OFDM) systems. The proposed algorithm is based on a constant amplitude zero autocorrelation (CAZAC) sequence weighted by a pseudo-random noise (PN) sequence. The symbol timing is accomplished by using only one training symbol of two identical halves, with the weighting applied to the second half. The special structure of the training symbol is also utilized in estimating the CFO. The performance of the proposed algorithm is demonstrated by means of numerical simulations in a 115.8-Gb/s 16-QAM RGI-CO-OFDM system.
IEEE Communications Letters, 2015
In this paper, a cognitive radio (CR) network composed of K secondary users who cooperatively sen... more In this paper, a cognitive radio (CR) network composed of K secondary users who cooperatively sense a channel using the k-out-of-K fusion rule to determine the presence of the primary user is studied. The sensing-throughput tradeoff problem is investigated in a realistic environment where both the sensing channels and reporting channels are characterized by fading channels. It is observed that taking into consideration the probability of reporting error in the CR network increases the sensing time and reduces the maximum average throughput of the secondary users. To mitigate the effect of the probability of reporting error, a transmit diversity based cooperative spectrum sensing method using randomized space-time block coding (RSTBC) is proposed. Simulations results show that the spatial diversity gain induced by RSTBC significantly decreases the sensing time and improves the throughput of the secondary users.
International Journal of Autonomous and Adaptive Communications Systems, 2013
ABSTRACT
IEEE Transactions on Signal Processing, 2000
In this paper we study the system level performance of cognitive radio (CR) networks under averag... more In this paper we study the system level performance of cognitive radio (CR) networks under average received interference power constraints. Under the assumption of uniform node placements and a simple power control scheme, we derive the closed-form expression for the cumulative distribution function (CDF) of the maximum allowable transmit power of the target CR transmitter. We further study two CR network scenarios: a CR based central access network and a CR assisted virtual multiple-input multiple-output (MIMO) network. The average uplink capacities of both networks are derived and analyzed, with an emphasis on understanding the effect of the numbers of primary users and CR users on the capacity. Numerical and simulation results demonstrate that the CR based central access network is more suitable for less-populated rural areas where a lower density of primary receivers is expected, while the CR assisted virtual MIMO network performs better in urban environments with a dense population of mobile CR users.
IEEE Transactions on Communications, 2000
This paper presents a hybrid decoding algorithm for low-density parity-check (LDPC) codes based o... more This paper presents a hybrid decoding algorithm for low-density parity-check (LDPC) codes based on the interior point method with barrier function for linear programming (LP) decoding introduced by Wadayama [16]. First, an efficient implementation of Wadayama's algorithm is presented. The main idea behind the modification is to approximate the barrier function for the fundamental polytope defining the code so that it contains only one linear constraint for each of the parity-check constraints. A two-stage hybrid decoding which combines the interior point decoding and a low-complexity decoding algorithm for LDPC codes is then proposed. Simulation results show that the approximations introduced in the proposed algorithms do not result in any performance degradation, while considerably reducing the decoding complexity and latency. Index Terms-Belief propagation (BP) algorithm, convex optimization, low-density parity-check (LDPC) codes, finite geometries, interior point algorithm, weighted bit-flipping (WBF) algorithm.
IEEE Transactions on Communications, 2000
In this letter, an improved bit-flipping decoding algorithm for high-rate finite-geometry low-den... more In this letter, an improved bit-flipping decoding algorithm for high-rate finite-geometry low-density parity-check (FG-LDPC) codes is proposed. Both improvement in performance and reduction in decoding delay are observed by flipping multiple bits in each iteration. Our studies show that the proposed algorithm achieves an appealing tradeoff between performance and complexity for FG-LDPC codes.