Abstract. Time division duplex (TDD) multi carrier-code division multiple access (MC-CDMA) system... more Abstract. Time division duplex (TDD) multi carrier-code division multiple access (MC-CDMA) systems have recently been proposed as potential candidates for next generation (4G) technology. In order to mitigate multiple access interference, in this paper we investigate ...
Page 1. This article has been accepted for publication in a future issue of this journal, but has... more Page 1. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. XX, NO. XX, MONTH 200X 1 ...
The 5th International Symposium on Wireless Personal Multimedia Communications, 2002
ABSTRACT We investigate the evolution of the trellis path through the state diagram of a turbo co... more ABSTRACT We investigate the evolution of the trellis path through the state diagram of a turbo code versus the number of iterations ni. Simulations show that the BER and the number of states with probability above a given threshold have the same convergence behavior versus ni. As a consequence we propose a new criterion to stop the iterative decoding process. A new algorithm to avoid the channel parameters estimation is proposed too. The joint combination of the proposed algorithms perform the same as the optimum solution with reduced computational complexity.
The 5th International Symposium on Wireless Personal Multimedia Communications, 2002
ABSTRACT Standard scheduling algorithms to optimize the resource allocation in a time division du... more ABSTRACT Standard scheduling algorithms to optimize the resource allocation in a time division duplex (TDD) consider only the traffic situation and the priority of different services. However it is necessary to take into account the time varying nature of wireless channels and the power control (PC) algorithms used to counteract interference limited systems like CDMA. PC can be open loop power control (OLPC) or closed loop power control (CLPC), the latter one is preferable especially in presence of a real time traffic and fast fading channels. Here, we propose new scheduling algorithm which allocate up-link (UL) and down-link (DL) slots in order to use efficiently CLPC, while the resource unit (code and slot) are selected taking into account quality of services requirements (e.g. delay) and the corresponding channel state.
2010 IEEE International Conference on Communications Workshops, 2010
ABSTRACT This paper presents a low-complexity/low-latency algorithm for estimating and tracking t... more ABSTRACT This paper presents a low-complexity/low-latency algorithm for estimating and tracking time-varying fading channels in Orthogonal Frequency Division Multiplexing (OFDM) systems. More specifically, it is described a decision directed (DD) channel estimation (CE) method, consisting of two main steps: 1) Data detection of the current received OFDM symbol is performed by using the channel coefficients estimated in correspondence to the previous OFDM symbol; 2) The channel corresponding to the current OFDM symbol is estimated by using a subset of the newly detected data symbols. The data subset, used to perform successive refinement on the channel estimation, is found by choosing the OFDM subcarriers with the highest expected signal-to-noise ratio (SNR). Such a subcarrier selection strategy aims to obtain robustness against the introduction of incorrect data symbols in the channel estimation process. The extension of the presented technique to multiple receive antennas is also discussed. The proposed estimation method is potentially useful for IEEE 802.11p compliant vehicular communication systems, whose basic modulation parameters are herein used for computer simulation of the information error rate.
ABSTRACT In this paper, space-time bit-interleaved coded OFDM (orthogonal frequency division mult... more ABSTRACT In this paper, space-time bit-interleaved coded OFDM (orthogonal frequency division multiplexing) modulated systems are studied. Using multiple antennas at transmitter and receiver side, spatial diversity can be exploited with ordinary channel codes followed by an interleaver. Moreover, the combined use with OFDM modulation enable effective frequency selectivity exploitation in multipath channels. High spectral efficiency can be achieved using high modulation orders and increasing the number of transmitting antennas. Asymptotical performances are analyzed using pairwise error prob- ability evaluation. It is shown as transmission parameters and radio channel characteristics impact on achievable diversity order and coding gain. Different channel codes are taken into account. Convolutional codes with several constraint lengths are simulated and results are compared with those of turbo coded solution. The iterative receiver complexity grows at the increase of modulation order, subcarriers and number of antennas. Simplified detection criteri- ons can be used for signals separation at receiver side. Turbo coded system allows for iterative approaches with reduced complexity when some turbo decoding iterations are performed between successive detection steps.
Orthogonal frequency division multiplexing (OFDM) carrying Offset QAM (OQAM) symbols is analyzed ... more Orthogonal frequency division multiplexing (OFDM) carrying Offset QAM (OQAM) symbols is analyzed for wireless transmissions over frequency and time selective channels. Performance limits are evaluated assuming a maximum likelihood receiver that is able to exploit the diversity branches offered by the channel. Simplified equalization making use of the zero forcing criterion is proposed and discussed, pointing out the role played
ABSTRACT The pairwise error probability (PEP) for multiple- input multiple-output (MIMO) radio in... more ABSTRACT The pairwise error probability (PEP) for multiple- input multiple-output (MIMO) radio interfaces is investigated by means of a novel formulation based on compound matrices. The proposed approach is suitable for any MIMO system having average upper-bounded PEP written as [det( I + gamma A )]-zeta, where A is a Hermitian matrix, zeta an integer number, and gamma the signal-to-noise ratio (SNR); that bound frequently results in MIMO single- and multicarrier transmissions. It is shown that the minimization of the bounded PEP should consider the whole set of nonzero compound matrices of A . In particular, the SNR of interest marks the compound matrix that mainly drives the system performance. Both diversity advantage and coding gain are given as continuous functions of the variable gamma, hence, their asymptotic behaviors are taken as important case of studies. The interaction effects between channel code and propagation environment are also discussed. It is shown how the eigenvectors and eigenvalues of the autocorrelation channel matrix may be considered for code design. It is also proved the maximization of the code rank is not always a necessary requirement for performance improvement being its optimal value fixed by the channel structure and SNR of interest. Finally, the analysis is applied to space-time trellis-coded transmissions over spatially correlated slow Rayleigh-fading channels.
Abstract. Time division duplex (TDD) multi carrier-code division multiple access (MC-CDMA) system... more Abstract. Time division duplex (TDD) multi carrier-code division multiple access (MC-CDMA) systems have recently been proposed as potential candidates for next generation (4G) technology. In order to mitigate multiple access interference, in this paper we investigate ...
Page 1. This article has been accepted for publication in a future issue of this journal, but has... more Page 1. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. XX, NO. XX, MONTH 200X 1 ...
The 5th International Symposium on Wireless Personal Multimedia Communications, 2002
ABSTRACT We investigate the evolution of the trellis path through the state diagram of a turbo co... more ABSTRACT We investigate the evolution of the trellis path through the state diagram of a turbo code versus the number of iterations ni. Simulations show that the BER and the number of states with probability above a given threshold have the same convergence behavior versus ni. As a consequence we propose a new criterion to stop the iterative decoding process. A new algorithm to avoid the channel parameters estimation is proposed too. The joint combination of the proposed algorithms perform the same as the optimum solution with reduced computational complexity.
The 5th International Symposium on Wireless Personal Multimedia Communications, 2002
ABSTRACT Standard scheduling algorithms to optimize the resource allocation in a time division du... more ABSTRACT Standard scheduling algorithms to optimize the resource allocation in a time division duplex (TDD) consider only the traffic situation and the priority of different services. However it is necessary to take into account the time varying nature of wireless channels and the power control (PC) algorithms used to counteract interference limited systems like CDMA. PC can be open loop power control (OLPC) or closed loop power control (CLPC), the latter one is preferable especially in presence of a real time traffic and fast fading channels. Here, we propose new scheduling algorithm which allocate up-link (UL) and down-link (DL) slots in order to use efficiently CLPC, while the resource unit (code and slot) are selected taking into account quality of services requirements (e.g. delay) and the corresponding channel state.
2010 IEEE International Conference on Communications Workshops, 2010
ABSTRACT This paper presents a low-complexity/low-latency algorithm for estimating and tracking t... more ABSTRACT This paper presents a low-complexity/low-latency algorithm for estimating and tracking time-varying fading channels in Orthogonal Frequency Division Multiplexing (OFDM) systems. More specifically, it is described a decision directed (DD) channel estimation (CE) method, consisting of two main steps: 1) Data detection of the current received OFDM symbol is performed by using the channel coefficients estimated in correspondence to the previous OFDM symbol; 2) The channel corresponding to the current OFDM symbol is estimated by using a subset of the newly detected data symbols. The data subset, used to perform successive refinement on the channel estimation, is found by choosing the OFDM subcarriers with the highest expected signal-to-noise ratio (SNR). Such a subcarrier selection strategy aims to obtain robustness against the introduction of incorrect data symbols in the channel estimation process. The extension of the presented technique to multiple receive antennas is also discussed. The proposed estimation method is potentially useful for IEEE 802.11p compliant vehicular communication systems, whose basic modulation parameters are herein used for computer simulation of the information error rate.
ABSTRACT In this paper, space-time bit-interleaved coded OFDM (orthogonal frequency division mult... more ABSTRACT In this paper, space-time bit-interleaved coded OFDM (orthogonal frequency division multiplexing) modulated systems are studied. Using multiple antennas at transmitter and receiver side, spatial diversity can be exploited with ordinary channel codes followed by an interleaver. Moreover, the combined use with OFDM modulation enable effective frequency selectivity exploitation in multipath channels. High spectral efficiency can be achieved using high modulation orders and increasing the number of transmitting antennas. Asymptotical performances are analyzed using pairwise error prob- ability evaluation. It is shown as transmission parameters and radio channel characteristics impact on achievable diversity order and coding gain. Different channel codes are taken into account. Convolutional codes with several constraint lengths are simulated and results are compared with those of turbo coded solution. The iterative receiver complexity grows at the increase of modulation order, subcarriers and number of antennas. Simplified detection criteri- ons can be used for signals separation at receiver side. Turbo coded system allows for iterative approaches with reduced complexity when some turbo decoding iterations are performed between successive detection steps.
Orthogonal frequency division multiplexing (OFDM) carrying Offset QAM (OQAM) symbols is analyzed ... more Orthogonal frequency division multiplexing (OFDM) carrying Offset QAM (OQAM) symbols is analyzed for wireless transmissions over frequency and time selective channels. Performance limits are evaluated assuming a maximum likelihood receiver that is able to exploit the diversity branches offered by the channel. Simplified equalization making use of the zero forcing criterion is proposed and discussed, pointing out the role played
ABSTRACT The pairwise error probability (PEP) for multiple- input multiple-output (MIMO) radio in... more ABSTRACT The pairwise error probability (PEP) for multiple- input multiple-output (MIMO) radio interfaces is investigated by means of a novel formulation based on compound matrices. The proposed approach is suitable for any MIMO system having average upper-bounded PEP written as [det( I + gamma A )]-zeta, where A is a Hermitian matrix, zeta an integer number, and gamma the signal-to-noise ratio (SNR); that bound frequently results in MIMO single- and multicarrier transmissions. It is shown that the minimization of the bounded PEP should consider the whole set of nonzero compound matrices of A . In particular, the SNR of interest marks the compound matrix that mainly drives the system performance. Both diversity advantage and coding gain are given as continuous functions of the variable gamma, hence, their asymptotic behaviors are taken as important case of studies. The interaction effects between channel code and propagation environment are also discussed. It is shown how the eigenvectors and eigenvalues of the autocorrelation channel matrix may be considered for code design. It is also proved the maximization of the code rank is not always a necessary requirement for performance improvement being its optimal value fixed by the channel structure and SNR of interest. Finally, the analysis is applied to space-time trellis-coded transmissions over spatially correlated slow Rayleigh-fading channels.
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