Rolando Carrasco - Academia.edu (original) (raw)
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Papers by Rolando Carrasco
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
As fading due to multipath propagation is an important issue in wireless systems, diversity techn... more As fading due to multipath propagation is an important issue in wireless systems, diversity techniques are employed in order to reduce the multipath fading effect. Cooperative communication represents a new class of diversity schemes in which multiple nodes equipped with a single antenna cooperate to generate a virtual multiple-antenna transmission system and thus offer the benefits of spatial diversity. This paper investigates the performance of the well known decode-and-forward cooperative technique on the flat fading indoor channel and also on the pedestrian and vehicular frequency-selective fading channels with decision feedback equalisation, which model the physical layer of UMTS networks in different environments. The performance is evaluated in terms of bit error rate as a function of signal-to-noise ratio with simulation results showing that decode-and-forward relaying provides a remarkable performance improvement over direct transmission.
2009 1st International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology, 2009
ABSTRACT In this paper we present a coded cooperation scheme using nonbinary LDPC codes and show ... more ABSTRACT In this paper we present a coded cooperation scheme using nonbinary LDPC codes and show how it can be used in a multi-user environment to achieve full transmit diversity. It is well known that non-binary LDPC codes over GF(q) outperform binary LDPC codes, but at a cost of increased decoding complexity. To ensure that this scheme can be practically implemented, we demonstrate how the Belief Propagation (BP) algorithm can be simplified, with a complexity dependent only on the row weight of the parity check matrix and independent of the finite field size. We show that this decoding algorithm has only a small degradation in performance compared with BP decoding on quasi-static fading channels and present the performance of a coded cooperation scheme using non-binary LDPC codes defined in GF(4) and GF(16).
A list decoder can outperform the conventional unique decoder by giving a list of transmitted mes... more A list decoder can outperform the conventional unique decoder by giving a list of transmitted message candidates and can be applied to Reed-Solomon (RS) codes and algebraic-geometric (AG) codes. This paper presents the first efficient list decoder which is developed from the framework of the GuruswamiSudan (GS) algorithm for AG codes. Fast implementation methods for the algorithm’s key processes – interpolation and factorisation are also proposed. By applying this list decoder to the best performing AG codes, Hermitian codes, simulation results show that Hermitian codes defined over GF(64) can outperform similar code rate RS codes defined over GF(256) on the AWGN and Rayleigh fading channels, achieving up to a 4.05 dB coding gain using the same interpolation multiplicity.
IEE Proceedings - Communications, 2005
Algebraic geometry is a branch of mathematics with many applications such as statistics, computer... more Algebraic geometry is a branch of mathematics with many applications such as statistics, computer science and economics. It can also be applied to coding theory to construct nonbinary block codes from curves with impressive parameters e.g. large code lengths, high code rates and large minimum distances. The design and construction of algebraic-geometric codes is described, and the performance evaluated over the additive white gaussian noise (AWGN) and Rayleigh fading channels and make comparisons with similar Reed-Solomon codes. Simulation results show that algebraic-geometric codes constructed from hermitian curves (hermitian codes) outperform Reed-Solomon codes of similar code rate and defined over the same finite field and show that hermitian codes would be suitable for a mobile radio environment.
IEEE Transactions on Vehicular Technology, 2011
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
In this paper, we derive stability conditions for low-density-parity-check (LDPC) codes with Gray... more In this paper, we derive stability conditions for low-density-parity-check (LDPC) codes with Gray mapped M-ary phase-shift keying (M-PSK) and M-ary quadrate-amplitude-modulation (M-QAM) constellations. The stability of the LDPC decoder with higher order modulation schemes is examined on both additive-white-Gaussian-noise (AWGN) and block Rayleigh fading channels and threshold stability conditions under iterative decoding are obtained using density evolution techniques. It is shown that both on block Rayleigh fading channel when the ideal channel state information (CSI) of the fading process is known, and on AWGN channel, the stability condition of the underlying code is bounded by the Bhattacharya noise parameter. We show that the derived stability condition is both sufficient and necessary condition for iterative belief propagation decoding assuming cycle free massage passing between variable and check nodes. The evolution of stability condition is assessed as the modulation order ...
John Wiley & Sons, Ltd eBooks, Dec 11, 2008
The filter-based turbo equalization scheme has been proposed in several papers to avoid the prohi... more The filter-based turbo equalization scheme has been proposed in several papers to avoid the prohibitive complexity imposed by the trellis-based turbo equalization. In the existing literature,the filter-based approach has been solely implemented by a linear MMSE filter, the coeffi cients of which are updated to minimize the mean-square error for every output symbol of the equalizer. A new turbo equalization algorithm is introduced in this paper. It has a lower computational complexity compared to most of the existing MMSE filter-based turbo equalization schemes. The complexity reduction is accomplished by deriving log-likelihood ratios (LLRs) directly from the output of an interference canceler, thus avoiding the MMSE filtering and its inherent matrix inversion for each symbol estimate. Numerical results show that the proposed scheme enables ISI-free transmission for some frequency selective channels.
International Journal of Computers Communications & Control, 2014
International Journal of Computers Communications & Control, 2014
IEE Proceedings - Communications, 2006
Electronics Letters, 2011
ABSTRACT Cooperative communication looks very promising as a next-generation wireless network arc... more ABSTRACT Cooperative communication looks very promising as a next-generation wireless network architecture. Li Chen, Rolando Carrasco and Ian Wassell tell us why and how they are working to improve system performance
Electronics Letters, 2001
An efficient code holding technique for a Wide-band Code Division Multiple Access (WCDMA) Interne... more An efficient code holding technique for a Wide-band Code Division Multiple Access (WCDMA) Internet Protocol (IP) access network is proposed, which reduces the number of codes required and allows BandWidth to be supplied On Demand (BWOD). Performance is evaluated in terms of end-to-end delays for different multimedia applications. Introduction: In Third Generation (3G) systems it is anticipated that wireless, wired and satellite communications will all be integrated as one system, in which multimedia data will be transferred[1]. In IMT-2000, or Universal Mobile Telecommunications System (UMTS) mobile users will access the fixed networks for different traffic types, WCDMA is the most promising proposed air interface[2]. Within UMTS there are separate circuit and packet switched channels; in this paper an entirely packet switched system is proposed, in which all services are treated in the same way. This paper addresses the needs of different data types in terms of end-to-end delay and the amount of traffic transmitted, which have been modelled and simulated in OPNET TM simulation environment. Similar issues have previously been studied in an ATM access network using a service adaptable virtual connection tree algorithm in [3, 4]. There are 512 downlink-scrambling codes [2], so this paper proposes a way of allowing many users to share those codes. System Model and Simulation: The simulation model is constructed using two user-defined nodes, the Base Station (BS) and the Mobile Station (MS). The radio link's characteristics between the BS and MS are modified by one or more of the fourteen customised design stages of the radio transceiver. The state machine for a MS is shown in Fig. 1, the MS is initialised and has an IPv4 address assigned to it, the Wait state is then enterred. The transmission and receive processes are modelled dynamically and can occur simultaneoulsy from the Wait state (parallel processes).
3rd European Conference on Speech Communication and Technology (Eurospeech 1993)
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
As fading due to multipath propagation is an important issue in wireless systems, diversity techn... more As fading due to multipath propagation is an important issue in wireless systems, diversity techniques are employed in order to reduce the multipath fading effect. Cooperative communication represents a new class of diversity schemes in which multiple nodes equipped with a single antenna cooperate to generate a virtual multiple-antenna transmission system and thus offer the benefits of spatial diversity. This paper investigates the performance of the well known decode-and-forward cooperative technique on the flat fading indoor channel and also on the pedestrian and vehicular frequency-selective fading channels with decision feedback equalisation, which model the physical layer of UMTS networks in different environments. The performance is evaluated in terms of bit error rate as a function of signal-to-noise ratio with simulation results showing that decode-and-forward relaying provides a remarkable performance improvement over direct transmission.
2009 1st International Conference on Wireless Communication, Vehicular Technology, Information Theory and Aerospace & Electronic Systems Technology, 2009
ABSTRACT In this paper we present a coded cooperation scheme using nonbinary LDPC codes and show ... more ABSTRACT In this paper we present a coded cooperation scheme using nonbinary LDPC codes and show how it can be used in a multi-user environment to achieve full transmit diversity. It is well known that non-binary LDPC codes over GF(q) outperform binary LDPC codes, but at a cost of increased decoding complexity. To ensure that this scheme can be practically implemented, we demonstrate how the Belief Propagation (BP) algorithm can be simplified, with a complexity dependent only on the row weight of the parity check matrix and independent of the finite field size. We show that this decoding algorithm has only a small degradation in performance compared with BP decoding on quasi-static fading channels and present the performance of a coded cooperation scheme using non-binary LDPC codes defined in GF(4) and GF(16).
A list decoder can outperform the conventional unique decoder by giving a list of transmitted mes... more A list decoder can outperform the conventional unique decoder by giving a list of transmitted message candidates and can be applied to Reed-Solomon (RS) codes and algebraic-geometric (AG) codes. This paper presents the first efficient list decoder which is developed from the framework of the GuruswamiSudan (GS) algorithm for AG codes. Fast implementation methods for the algorithm’s key processes – interpolation and factorisation are also proposed. By applying this list decoder to the best performing AG codes, Hermitian codes, simulation results show that Hermitian codes defined over GF(64) can outperform similar code rate RS codes defined over GF(256) on the AWGN and Rayleigh fading channels, achieving up to a 4.05 dB coding gain using the same interpolation multiplicity.
IEE Proceedings - Communications, 2005
Algebraic geometry is a branch of mathematics with many applications such as statistics, computer... more Algebraic geometry is a branch of mathematics with many applications such as statistics, computer science and economics. It can also be applied to coding theory to construct nonbinary block codes from curves with impressive parameters e.g. large code lengths, high code rates and large minimum distances. The design and construction of algebraic-geometric codes is described, and the performance evaluated over the additive white gaussian noise (AWGN) and Rayleigh fading channels and make comparisons with similar Reed-Solomon codes. Simulation results show that algebraic-geometric codes constructed from hermitian curves (hermitian codes) outperform Reed-Solomon codes of similar code rate and defined over the same finite field and show that hermitian codes would be suitable for a mobile radio environment.
IEEE Transactions on Vehicular Technology, 2011
2010 7th International Symposium on Communication Systems, Networks & Digital Signal Processing (CSNDSP 2010), 2010
In this paper, we derive stability conditions for low-density-parity-check (LDPC) codes with Gray... more In this paper, we derive stability conditions for low-density-parity-check (LDPC) codes with Gray mapped M-ary phase-shift keying (M-PSK) and M-ary quadrate-amplitude-modulation (M-QAM) constellations. The stability of the LDPC decoder with higher order modulation schemes is examined on both additive-white-Gaussian-noise (AWGN) and block Rayleigh fading channels and threshold stability conditions under iterative decoding are obtained using density evolution techniques. It is shown that both on block Rayleigh fading channel when the ideal channel state information (CSI) of the fading process is known, and on AWGN channel, the stability condition of the underlying code is bounded by the Bhattacharya noise parameter. We show that the derived stability condition is both sufficient and necessary condition for iterative belief propagation decoding assuming cycle free massage passing between variable and check nodes. The evolution of stability condition is assessed as the modulation order ...
John Wiley & Sons, Ltd eBooks, Dec 11, 2008
The filter-based turbo equalization scheme has been proposed in several papers to avoid the prohi... more The filter-based turbo equalization scheme has been proposed in several papers to avoid the prohibitive complexity imposed by the trellis-based turbo equalization. In the existing literature,the filter-based approach has been solely implemented by a linear MMSE filter, the coeffi cients of which are updated to minimize the mean-square error for every output symbol of the equalizer. A new turbo equalization algorithm is introduced in this paper. It has a lower computational complexity compared to most of the existing MMSE filter-based turbo equalization schemes. The complexity reduction is accomplished by deriving log-likelihood ratios (LLRs) directly from the output of an interference canceler, thus avoiding the MMSE filtering and its inherent matrix inversion for each symbol estimate. Numerical results show that the proposed scheme enables ISI-free transmission for some frequency selective channels.
International Journal of Computers Communications & Control, 2014
International Journal of Computers Communications & Control, 2014
IEE Proceedings - Communications, 2006
Electronics Letters, 2011
ABSTRACT Cooperative communication looks very promising as a next-generation wireless network arc... more ABSTRACT Cooperative communication looks very promising as a next-generation wireless network architecture. Li Chen, Rolando Carrasco and Ian Wassell tell us why and how they are working to improve system performance
Electronics Letters, 2001
An efficient code holding technique for a Wide-band Code Division Multiple Access (WCDMA) Interne... more An efficient code holding technique for a Wide-band Code Division Multiple Access (WCDMA) Internet Protocol (IP) access network is proposed, which reduces the number of codes required and allows BandWidth to be supplied On Demand (BWOD). Performance is evaluated in terms of end-to-end delays for different multimedia applications. Introduction: In Third Generation (3G) systems it is anticipated that wireless, wired and satellite communications will all be integrated as one system, in which multimedia data will be transferred[1]. In IMT-2000, or Universal Mobile Telecommunications System (UMTS) mobile users will access the fixed networks for different traffic types, WCDMA is the most promising proposed air interface[2]. Within UMTS there are separate circuit and packet switched channels; in this paper an entirely packet switched system is proposed, in which all services are treated in the same way. This paper addresses the needs of different data types in terms of end-to-end delay and the amount of traffic transmitted, which have been modelled and simulated in OPNET TM simulation environment. Similar issues have previously been studied in an ATM access network using a service adaptable virtual connection tree algorithm in [3, 4]. There are 512 downlink-scrambling codes [2], so this paper proposes a way of allowing many users to share those codes. System Model and Simulation: The simulation model is constructed using two user-defined nodes, the Base Station (BS) and the Mobile Station (MS). The radio link's characteristics between the BS and MS are modified by one or more of the fourteen customised design stages of the radio transceiver. The state machine for a MS is shown in Fig. 1, the MS is initialised and has an IPv4 address assigned to it, the Wait state is then enterred. The transmission and receive processes are modelled dynamically and can occur simultaneoulsy from the Wait state (parallel processes).
3rd European Conference on Speech Communication and Technology (Eurospeech 1993)