In mobile communication systems, the channel state information (CSI) is severely affected by the noise effect of the receiver. The adaptive subcarrier grouping (ASG) for sample matrix inversion (SMI) based minimum mean square error (MMSE) adaptive array has been previously proposed. Although it can reduce the additive noise effect by increasing samples to derive the array weight for co-channel interference suppression, it needs to know the signal-to-noise ratio (SNR) in advance to set the threshold for subcarrier grouping. This paper newly proposes adaptive zero padding (AZP) in the time domain to improve the weight accuracy of the SMI matrix. This method does not need to estimate the SNR in advance, and even if the threshold is always constant, it can adaptively identify the position of zero-padding to eliminate the noise interference of the received signal. Simulation results reveal that the proposed method can achieve superior bit error rate (BER) performance under various Rician K factors.

This letter proposes a transmission scheme called spatial vector (SV), which is effective for Nakagami-m fading multiple-input multiple-output channels. First, the analytical error rate of SV is derived for Nakagami-m fading MIMO channels. Next, an example of SV called integer SV (ISV) is introduced. The error performance was evaluated over Nakagami-m fading from m = 1 to m = 50 and compared with spatial modulation (SM), enhanced SM, and quadrature SM. The results show that for m > 1, ISV outperforms the SM schemes and is robust to m variations.

This paper proposes an open-loop correlation reduction precoding scheme for overloaded multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. In overloaded MIMO-OFDM systems, frequency diversity through joint maximum likelihood (ML) decoding suppresses performance degradation owing to spatial signal multiplexing. However, on a line-of-sight (LOS) channel, a channel matrix may have a large correlation between coded symbols transmitted on separate subcarriers. The correlation reduces the frequency diversity gain and deteriorates the signal separation capability. Thus, in the proposed scheme, open-loop precoding is employed at the transmitter of an overloaded MIMO system in order to reduce the correlation between codewords transmitted on different signal streams. The proposed precoding scheme changes the amplitude as well as the phase of the coded symbols transmitted on different subcarriers. Numerical results obtained through computer simulation show that the proposed scheme improves the bit error rate performance on Rician channels. It is also shown that the proposed scheme greatly suppresses the performance degradation on an independent Rayleigh fading channel even though the amplitude of the coded symbols varies.

Some statistical characteristics, including the means and the cross-correlations, of frequency-selective Rician fading channels seen by orthogonal frequency division multiplexing (OFDM) subcarriers are derived in this paper. Based on a pairwise error probability analysis, the mean vector and the cross-correlation matrix are used to obtain an upper bound of the overall bit-error rate (BER) in a closed-form for coded OFDM signals with and without inter-carrier interference. In this paper, the overall BER is defined as the average BER of OFDM signals of all subcarriers obtained by considering their cross-correlations. Numerical examples are presented to compare the proposed upper bound of the overall BERs and the overall BERs obtained by simulations.

Performance analysis of a dual-hop semi-blind amplify-and-forward (AF) relay system in mixed Nakagami-m and Rician fading channels, is proposed. We derived the closed-form expression for the cumulative distribution function (CDF) of the equivalent end-to-end signal to noise ratio (SNR), based on which the exact outage probability and symbol error probability (SEP) are investigated. The theoretical analysis is validated by Monte Carlo simulation results.

In this paper, BER (Bit Error Rate) performance in 22 MIMO (Multiple-Input Multiple-Output) spatial multiplexing systems under Rician fading channels is evaluated. We examine BER performances employing inverse channel detection (ICD) under Rician fading channels, adding the phase of the direct path and Rician factor as a parameter. The results clearly indicate that the phase of the direct path and Rician factor have a great influence on BER performances employing ICD under Rician fading channels.

The average bit error rate performances of M-ary orthogonal code shift keying (CSK) in Rician fading environments are analyzed in this letter. CSK is a digital modulation scheme that uses a code set as M-ary signals. In CSK, one code is selected from a code set containing M codes according to the information data. A signal is modulated by using this code and the effect of fading can be reduced by applying interleaving to the elements of the codes. In the analysis, the bit error probability is derived in closed form expression by using the Chernoff bound. The analysis results show that the error probability decreases when the code length is increased and that an arbitrarily small error probability is achieved as the code length approaches infinity, provided that Eb/N0 exceeds 1.42 dB.

Multiple-Input Multiple-Output (MIMO) systems that realize high-speed data transmission with multiple antennas at both transmitter and receiver are drawing much attention. In line-of sight (LOS) environments, the performance of MIMO systems depends largely on the difference of the phase difference of direct paths from transmit antennas to each receive antenna. When the phase difference of direct paths are close to each other, the spatial division multiplexing (SDM) channels are not orthogonal to each other so signal detection becomes difficult. In this paper, we propose a MIMO system with relative phase difference time-shift modulation (RPDTM) in Rician fading environments. The proposed scheme transmits independent signals from each antenna at each time slot where the relative phase difference between signal constellations used by transmit antennas varies in a pre-determined pattern. This transmission virtually changes the phase difference of direct paths from transmit antennas to each receive antenna without lowering data rate and without knowledge of the channels. In addition, forward error correction coding (ECC) is applied to exploit the time slots where the receiver can detect the signals easily to improve the detection performance. If there are time slots where the receiver can separate the received signal, the receiver can decode the data by using the time slots and the correlation between data. From the results of computer simulation, we show that MIMO system with RPDTM can achieve the better bit error rate (BER) than the conventional MIMO system. We also show that the MIMO system with RPDTM is effective by about Rician factor K = 10 dB.

In this letter, we analyze symbol error probability (SEP) and diversity gain of orthogonal space-time block codes (OSTBCs) in spatially correlated Rician fading channel. We derive the moment generating function (MGF) of an effective signal-to-noise ratio (SNR) at the receiver and use it to derive the SEP for M-PSK modulation. We use this result to show that the diversity gain is achieved by the product of the rank of the transmit and receive correlation matrix, and the loss in array gain is quantified as a function of the spatial correlation and the line of sight (LOS) component.

This paper investigates a modifying orthogonality factor for synchronous DS-CDMA uplink in dispersive Rician multipath fading channels, which reflects upon the effects of specular path power as well as decaying channel characteristics. Using this investigation, the orthogonal factors in indoor environments are evaluated and compared with the various parameters such as decaying factor, line-of-sight component, and the number of multipaths.

Two rotational transformations are used to derive a new expression for the symbol error probability (SEP) of an M-ary phase shift keying (MPSK) with an I-Q unbalance over additive white Gaussian noise (AWGN) and Rician fading channels. We used the new expression to investigate the effect of the I-Q unbalance on the MPSK SEP performance. Our investigation confirms that this approach is a convenient way to evaluate the average SEP of an MPSK for various cases of the Rician factor.

The bit error rate (BER) degradations of fast frequency hopping multiple access (FFH-MA) systems due to the frequency and timing offsets are investigated over a Rician fading channel. It is shown that as the received average SNR increases, the BER is affected much larger by frequency and timing offsets. When the frequency offset or the timing offset exists alone, the BER of the FFH-MA system is degraded much more due to the timing offset than due to the frequency offset. The BER degradation due to both the frequency offset and the timing offset is larger than the sum of the degradations due to each offset.

In order to investigate the sensitivity of fast frequency hopping-multiple access (FFH-MA) systems due to the frequency offset under Rician fading, we evaluate the bit error rate (BER) performance of the FFH-MA system using noncoherent M-ary frequency shift keying (FSK) with the hard decision decoding and the majority logic decision. Numerical results show that for satisfying the BER performance of 10-5 at a given normalized frequency offset of 0.2, the additional signal to noise ratio (SNR) of about 4 dB is required with the 8-ary FSK signaling compared to the case of the perfect frequency synchronization. While the frequency offset increases at a given SNR, the BER is more severely degraded, and subsequently, the BER performance is saturated at the normalized frequency offset of 0.5 regardless of fading environments. For the SNRs of more than 15 dB, the threshold level of the receiver suffering from normalized frequency offsets of less than 0.4 should be larger than that of the perfectly frequency synchronized receiver.

When M-ary QAM (MQAM) signals experience the Rician fading channels, diversity schemes can minimize the effects of these fadings since deep fades seldom occur simultaneously during the same time intervals on two or more paths. The symbol error probability of MQAM systems using L-branch maximum ratio combining (MRC) diversity reception is derived theoretically over frequency-nonselective slow Rician fading channels with an additive white Gaussian noise (AWGN). This derived evaluation is expressed as the infinite series composed of hypergeometric and gamma functions. These performance evaluations allow designers to determine M-ary modulation methods for Rician fading environments.

In this paper, we have analyzed transmission time for WAP (Wireless Application Protocol) over Bluetooth using a multi-slot segmentation scheme. In order for SAR to improve the transfer capability, the transmission of messages have been simulated using a fragmentation scheme that begins with the total package and incremental fragmentation for each layer using the WTP (Wireless Transaction Protocol) to define the resultant packet size and the level of fragmentation for each proceeding layer. The data is divided into individual packets at the baseband level. This scheme decreases transmission time of L2CAP (Logical Link Control And Adaptation Protocol) baseband packets by sending packets that span multiple slots. From the results, we were able to obtain packet transmission time and optimal WTP packet size for WAP over Bluetooth in a Rician fading channel.

This paper investigates the asymptotic error rate behaviour for noncoherent OOK signalling scheme in the presence of Nakagami-m fading. A transcendental equation to compute the optimum threshold level is also derived. Comparison on trends in optimum threshold level and its corresponding ratio of the Mark and Space error probabilities between different channels are presented.

The transmission quality in mobile wireless communications is affected by not only the thermal noise but also the multipass fading which changes drastically an amplitude and a phase of received signal. The paper proposes the theoretical and approximate methods for deriving an average bit error rate in DS-CDMA systems under the Rician fading environment on the assumption of the frequency non-selective fading, as parameters of the number of simultaneous access stations, the maximum Doppler frequency and so on. It is confirmed from the coincidence of theoretical and approximate results with simulation ones that the proposed approach is applicable to a variety of system parameters.

This paper proposes a coherent detection scheme that can reduce the estimation errors of the carrier phase due to Gaussian noise in communication systems where pilot symbol assisted modulation is employed to compensate for Rician fading distortion. This paper introduces two functions in addition to conventional fading estimation methods using Wiener interpolation, etc. The first is the weighted average function for reducing the estimation errors of the fading distortion detected by pilot symbols. The second is the moving average function for estimating the phase errors that are residual after being compensated for by the estimated fading distortion. This paper evaluates the bit error rate (BER) performance for the proposed method in both Rician fading channel and additive white Gaussian noise (AWGN) channel by computer simulation. Simulation results verify that the BER performance of the proposed method is superior to that of a conventional method in both Rician fading channel and AWGN channel. Simulation results also confirm that the degradation of the BER performance of the proposed method is only 0.1 dB in AWGN channel and only 0.3 dB in Rician fading channel compared with the theoretical curves even if we reduce the number of computations by simplifying the calculation of interpolation coefficients optimized for Wiener interpolation.

Conventional approach for frequency estimation usually assume a single tone without data modulation. In many applications such an assumption, realized by using either a separate pilot beacon or synchronization preamble is not feasible. This paper deals with frequency estimation of phase-modulated carriers in the absence of timing information and known data pattern. We introduce new frequency estimators that are based on the generalized maximum likelihood principle. The communication channels under consideration include both additive white Gaussian noise (AWGN) channels and correlated Rician fading channels. For the latter class, we distinguish between the case when the fading (amplitude) process is tracked and that when it is not tracked.

The final closed-form expression of the bit error rate (BER) is presented for a DS-CDMA system using a maximal ratio combining (MRC) diversity in conjunction with simple channel coding over a Rician fading channel. The accuracy of the BER evaluated by this expression is verified through comparison with a semi-analytic simulation result. The effect of diversity order and channel coding on the bit error rate performance is also considered for typical multipath delay profiles with different Rician ratios.