In this letter, we derive another exact bit error rate (BER) for decode-and-forward (DF) relay systems over Rayleigh fading channels. At first, our focus is on fixed-DF (FDF) relay schemes in which the probability density function (PDF) is derived based on error-events at relay nodes. Some insight into how erroneous detection and transmission at relay nodes affect both the combined signal-to-noise ratio (SNR) and the averaged BER is obtained, and cooperative diversity is observed from the closed-form BER expression. In addition, the developed analytical method is extended to adaptive-DF (ADF) schemes and the exact BER expressions are derived. Simulation results are finally presented to validate the analysis.

This letter evaluates the performance of an uplink multicarrier-code division multiple access (MC-CDMA) system when the frequency offsets of all users are random variables and the frequency offset for the desired user is compensated. The analysis confirms that performance degradation due to frequency offset is negligible if the estimation error of normalized frequency offset for the desired user is less than 10-1.

In this paper, we show exact bit error rates (BERs) for orthogonal space-time block code (OSTBC) decoded-and-forward (DF) relaying networks over independent and non-identically distributed (INID) Rayleigh fading channels. We consider both non-adaptive DF (non-ADF) and adaptive DF (ADF) schemes for OSTBC relay networks with arbitrary multiple-input multiple-output (MIMO) relay antenna configurations. For each scheme, we derive the probability density functions (PDFs) of indirect link and combined links, respectively. Based on the derived PDFs, we express exact BERs and then, their accuracy is verified by the comparison with simulation results. It is confirmed that the transmit diversity gain of the relay node can be obtained when the relay is close to the source and then, the receive diversity gain of the relay node as well as ADF gain over non-ADF can be obtained when the relay is close to the destination.

In this paper, we propose an analytical approach for adaptive decode-and-forward (ADF) relaying schemes consisting of burst data transmission based on pilot symbol assisted-channel estimation (PSA-CE) methods over quasi-static Rayleigh fading channels. At first, we focus on the error-event at relay nodes in which the transmission mode switching is carried out burst by burst, whereas previous studies assumed the transmission mode switching symbol-by-symbol, thus showing lower error rate bound. Under consideration of burst transmission for ADF relay systems, we derive exact error rate expressions which better estimate the performance of actual systems. Then, the average bit and burst error rates are derived in approximated expressions for an arbitrary link signal-to-noise ratio (SNR) related with channel estimation errors. Their accuracy is confirmed by comparison with simulation results. Furthermore, ADF relay systems with PSA-CE schemes are confirmed to select correctly decoded relay nodes without additional signaling between relay nodes and the destination node and it is verified to achieve the performance at a cost of negligible SNR loss.

This letter presents a method for obtaining an exact average symbol error rate (ASER) of M-phase shift keying (M-PSK) transmission for the Nth best opportunistic amplify-and-forward (OAF) relay systems over Rayleigh fading channels. This approach begins with deriving the relay selection probability when a relay is selected as the Nth best one with respect to the received signal-to-noise ratio. We then derive the modified moment generating function (MGF) for the Nth best OAF relay systems by taking the given Nth best-relay selection probability into consideration. Based on the modified MGF, we derive the exact ASER which accurately explicates the Nth best OAF relay system characteristics. Simulation results confirm the exactness of the analysis results for M-PSK transmission with respect to the number of relays, the Nth best relay selection, and the relay position.

The authors present an accurate analysis for multicode code division multiple access (CDMA) systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. This letter verifies that the previous analysis has used the additional Gaussian approximation (AGA) for multipath interferences so that there is the performance mismatch between the previous analysis and simulations. Furthermore, it is confirmed that the proposed analysis, which does not use AGA, provides an analytical bound.

This letter presents an analytical method for 64-QAM CDMA systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. Numerical results obtained from the proposed analysis indicate that an MPIC is required in order to mitigate the effects of multipath interference and to effectively increase the system capacity.