In this paper, the exact bit error rate (BER) expressions are derived for dual-hop (DH) decoded-and-forward (DF) relaying networks with orthogonal space-time block code (OSTBC) transmissions over Rayleigh fading channels. We consider both fixed-DF (FDF) and adaptive-DF (ADF) schemes and then, for each of them, the BER expressions are derived by including not only the case of indirect link but also the case of combining indirect and direct links. Simulation results are also presented to verify the accuracy by comparing with numerical results and to provide an insight to the diversity order relationship between FDF and ADF schemes.

This paper investigates the effects of asynchronous multiple access interference (MAI) on the performance of orthogonal frequency-division multiple access (OFDMA) uplink systems in frequency-selective Rayleigh fading environments. We first analyze the MAI and its statistical characteristics using the Gaussian approximation. Then the analytical expression for the uncoded average symbol error probability (SEP) is obtained with various modulation schemes. Comparison with simulation results shows a tight agreement of the proposed analysis over a wide range of asynchronous timing errors and for various numbers of asynchronous users. Numerical examples show that when asynchronous timing errors reside within the guard interval, a performance of uncoded SEP- 10-3 can be feasible even in high dispersive environments. Furthermore, the effect of the Gaussian approximation is examined, and the performance comparison between interleaved- and block-type subcarrier allocation schemes is provided.

The author presents new analytical approach of the bit error rate (BER) performance for multicode code division multiple access (CDMA) systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. Numerical results obtained from the proposed analytical approach indicate that the performance mismatch between the previous analysis and simulations is generated by the additional Gaussian approximation (AGA) for multipath interferences. Furthermore, it is confirmed that the proposed analysis not using AGA presents an analytical bound.

This letter presents an analysis of asynchronous multicarrier code-division multiple-access (MC-CDMA) systems with a guard period (GP) in the form of a cyclic prefix over frequency-selective multipath fading channels, which results in closed-form bit-error rate performance. Furthermore, it confirms that the frequency diversity of MC-CDMA systems is identical to the path diversity. The analytical approach proposed here is extended to the case without a GP. The derived analytical results show that a GP is required for MC-CDMA systems in order to mitigate not only the effect of intersymbol interference and intercarrier interference, but also the desired signal power degradation.

The authors present an analysis of the effect of timing offset on channel estimation for comb-type pilot-aided orthogonal frequency division multiplexing (OFDM) systems. Residual timing offset does not negatively affect the channel estimation of the pilot subcarrier, but does corrupt the channel information obtained via interpolation. This paper provides the mean square error (MSE) channel estimation performance when a linear interpolation technique is used in a comb-type pilot-aided OFDM system. Analysis shows that the performance degradation of the channel estimator due to imperfect frame synchronization is dependent on the frequency correlation of the channels and the amount of timing offset

In this paper, we evaluate the performance of 1/spl times/ evolution data and voice (1/spl times/EV/DV) systems with multiple antennas at both the transmitter and the receiver. The multicode interference (MCI) in 1/spl times/EV/DV systems is hard to compensate in multipath fading channels. Especially, the effect of MCI is more severe when using multiple antennas. We can improve the receiver performance by using multipath interference cancellation (MPIC) scheme. Simulation results show that 1/spl times/EV/DV systems with the multiple antennas and the MPIC scheme can achieve higher data rate than single antenna system in the frequency selective fading channel.

This paper contains our proposal for a new decoding algorithm for an iterative decoded V-BLAST system. The proposed algorithm is based on maximum a posteriori (MAP) decision criterion. In a V-BLAST system concatenated with channel coding, the extrinsic information from the soft output channel decoder can be utilized as a priori probability, making it possible to apply MAP decision criteria to the V-BLAST decoding process. The MAP decision criterion is applied to the V-BLAST ordering and slicing procedure, resulting in a considerable gain in bit error performance. As the iteration rate increases, the proposed system exhibits performance similar to that of systems with ideal sliced.

In this paper, asynchronous multicarrier-code division multiple access (MC-CDMA) systems with a carrier-frequency offset for the uplink is analyzed over multi-path fading channels. Moreover, SINR degradations caused by a carrier-frequency offset are evaluated. Derived and simulation results show that the performance of asynchronous MC-CDMA systems is sensitive to both the correlation among sub-carriers and the carrier-frequency offset. Furthermore, it is verified that a guard period is required for MC-CDMA systems in order to mitigate inter-symbol interference (ISI).

This paper proposes a novel detection scheme using a radial basis function (RBF) network in a multi-input multi-output (MIMO) environment. In order to evaluate the performance of the proposed MIMO-RBF receiver, simulations are performed over the rich-scattering fading channel. Simulation results confirm that the proposed scheme shows the similar bit-error rate (BER) performance of a maximum likelihood detection (MLD) and outperforms Vertical-Bell Laboratories Layered Space-Time using minimum-mean-square-error nulling (VBLAST-MMSE) as well as VBLAST using zero-forcing nulling (VBLAST-ZF). Moreover, we investigate the effect on the performance of the number of RBF center with two modulation formats (i.e. BPSK and QPSK) and different number of transmit and receive antennas. The performance of the proposed detector is verified with respect to an initialization-rate of RBF centers.

This paper studies the channel estimation schemes of a time division duplexing (TDD) code division multiple access (CDMA) system with a parallel interference canceller (PIC) in multipath fading channels. Furthermore, the effective interpolation method which maintains the flexibility of Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) TDD mode is proposed. By Monte Carlo simulations, it is verified that the proposed interpolation method can be used in order to obtain the proper performance of a multistage PIC and in order to reduce the required Eb/No for a given bit error rate.(BER).

We propose a new suboptimal detector that uses orthogonal polynomial approximation to determine the stage weighting factors at each interference cancellation (IC) stage. The performance of the new detector using the proposed scheme is compared with that of other sub-optimal detectors in the near-far and additive white Gaussian noise (AWGN) environments. Simulation results show that the average convergence rate of the proposed method for obtaining the optimum solution through estimation of the minimum (and maximum) eigenvalue of the code correlation matrix is faster than for other sub-optimal detectors based on IC. In addition, the method described here is also able to obtain better BER performance, with the same number of stages, than conventional parallel interference cancellation in the above environments.

The authors propose a multiuser detector with channel estimation capability using a radial basis function (RBF) network in a synchronous multicarrier-code division multiple access (MC-CDMA) system. The authors propose to connect an RBF network to the frequency domain to effectively utilize the frequency diversity. Simulations were performed over frequency-selective and multi-path fading channels. These simulations confirmed that the proposed receiver can be used both for the channel estimation and as a multi-user receiver, thus permitting an increase in the number of active users.

The performance of an MC-CDMA system with carrier frequency offsets in correlated multipath fading is mathematically analyzed. The bit error rate is obtained from such analysis for the uplink Rayleigh fading channel. The derived results show that the performance of the MC-CDMA system is sensitive to the frequency offset, and the correlation of the subcarriers. That is, the performance degradation of the MC-CDMA system is caused by both carrier frequency offset and correlation among subcarriers. From the derived results, however, the performance degradation due to correlation among subcarriers is more severe than effect of frequency offset.

A multi-user detector with an ability of channel estimation using a radial basis function (RBF) network is proposed in a multicarrier-code division multiple access (MC-CDMA) system. In the proposed scheme, the RBF network is connected to the frequency domain to effectively utilize the frequency diversity. Simulations were performed over the frequency selective and multipath fading channel. From these simulations, the proposed receiver is verified to be used for both the channel estimation and the multi-user receiver that permits more active users.