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The operation of a decision-directed RAKE receiver is described that has the advantage of not requiring any bandwidth overhead for training bits. The performance is illustrated using bit error rate (BER) graphs and burst error length cumulative distribution functions (CDF's) obtained from Monte Carlo simulations. The receiver simulated operates over a fast-fading (100-Hz Doppler) mobile channel at a bit rate of 4.8 kbit/s using a 900-MHz carrier. It is shown that the receiver is not greatly affected by error propagation. However, the incurred lag on the channel impulse response estimate is the major limitation mechanism, and the resulting irreducible BER is quantified for various numbers of taps in our receiver design. The RAKE receiver performance is examined and compared using maximal-ratio, equal-gain, and differential phase combining techniques.

A performance analysis of techniques used for identifying the angles of arrival of plane waves on a narrowband array of sensors shows that the multiple signal classification (MUSIC) fails when the sources are highly correlated. Algorithms such as spatial smoothing (SS) and forward-backward spatial smoothing (FBSS) help to solve this problem. The bearings and separation of sources control the performance of SS. FBSS provides better results for the same smoothing depending upon the relative signal phases. Simulation results confirm the superiority of SS and FBSS over MUSIC.

The paper investigates adaptive equalization of time-dispersive mobile ratio fading channels and develops a robust high performance Bayesian decision feedback equalizer (DFE). The characteristics and implementation aspects of this Bayesian DFE are analyzed, and its performance is compared with those of the conventional symbol or fractional spaced DFE and the maximum likelihood sequence estimator (MLSE). In terms of computational complexity, the adaptive Bayesian DFE is slightly more complex than the conventional DFE but is much simpler than the adaptive MLSE. In terms of error rate in symbol detection, the adaptive Bayesian DFE outperforms the conventional DFE dramatically. Moreover, for severely fading multipath channels, the adaptive MLSE exhibits significant degradation from the theoretical optimal performance and becomes inferior to the adaptive Bayesian DFE.

The paper investigates the application of a radial basis function network to digital communications channel equalization. It is shown that the radial basis function network has an identical structure to the optimal Bayesian symbol-decision equalizer solution and, therefore, can be employed to implement the Bayesian equalizer. The training of a radial basis function network to realize the Bayesian equalization solution can be achieved efficiently using a simple and robust supervised clustering algorithm. During data transmission a decision-directed version of the clustering algorithm enables the radial basis function network to track a slowly time-varying environment. Moreover, the clustering scheme provides an automatic compensation for nonlinear channel and equipment distortion. This represents a radically new approach to the adaptive equalizer design. Computer simulations are included to illustrate the analytical results.

Multicarrier code division multiple access (MCCDMA) is a spread-spectrum technique which allows simple implementation of multiuser detection techniques. Combining this with differential phase shift keying (DPSK) allows a low complexity receiver design which achieves the channel estimation implicitly. If only downlink communication is considered, performing the DPSK at a subcarrier level allows significant performance gains and employing a joint phase estimation approach for all users signals allows the implementation of an effective equal gain combining receiver. Theoretical predictions and simulations of the performance in additive white Gaussian noise are demonstrated. Comparison with similar systems is shown through simulations in a fast fading typical mobile channel. Index Terms--Differential detection, mobile communication, multicarrier CDMA, multiple access, noncoherent detection.

In this paper, we seek to characterize the performance of spatial modulation (SM) and spatial multiplexing (SMX) with an experimental testbed. Two National Instruments (NI) PXIe devices are used for the system testing: one for the transmitter and one for the receiver. The digital signal processing (DSP) that formats the information data in preparation for transmission is described, along with the DSP that recovers the information data. In addition, the hardware limitations of the system are also analyzed. The average bit-error ratio (ABER) of the system is validated through both theoretical analysis and simulation results for SM and SMX under the line-of-sight (LoS) channel conditions. [ABSTRACT FROM PUBLISHER]