The Pre-Rake technique for the downlink transmission in TDD-based CDMA wireless systems has been shown to provide greater capacity and a simpler receiver design at the mobile receiver. Nevertheless this technique is very affected by fast changing channels, since it relies on uplink channel measurements for the downlink transmission. In this paper a semi-analytical approach to the performance, i...

Differential space-time modulation (DSTM) schemes were recently proposed to fully exploit the receive and transmit antenna diversities without the need for channel state information. DSTM is attractive in fast flat fading channels since accurate channel estimation is difficult to achieve. In this paper, we propose a new modulation scheme to improve the performance of DS-CDMA systems in fast tim...

This paper presents an architecture of Multiband Impulse Radio UWB (MB-IR-UWB) system based on Prolate Spheroidal Wave Function (PSWF) by binary time hopping pulse position modulation (TH-PPM) over multipath fading channel. In order to combat multipath fading, Rake receiver using maximal ratio combining (MRC) is applied to this system, which can successfully capture the unique multipath-rich pr...

The study was focused on the machined surface quality of titanium alloy under different milling conditions, including milling speed, tool rake angle and cooling method. The surface quality was investigated in terms of residual stress and surface roughness. The results show that the compressive residual stresses are generated on the machined surface under all milling conditions. The compressive ...

In this paper we propose an enhanced maximal ratio combining (MRC) scheme for RAKE receivers in mobile CDMA terminals. It is based on the original MRC scheme derived by Brennan, where the RAKE finger noise powers are used in the combining weights. This enhanced scheme performs nearly as well as Brennan's original MRC scheme, but unlike Brennan’s method, it does not require the estimation of the...

In wideband wireless communication systems the RAKE receiver is commonly used to collect the resolvable multipath energy and counter the effects of fading through diversity. However, in channels with large delay and energy spread, its high complexity still remains a major issue. This motivates the study and application of computationally efficient finger placement algorithms that significantly ...

Implementable rake receivers have less correlators than there are propagation paths in the channel. In the case of slowly time-variant channels the rake receiver is able to adapt to the channel by selecting the paths with the maximum momentary power [Gue92a, Gue92b]. In practice, it is not possible to select the best paths for every modulation interval. The bit error probability of rake receive...

Despite its simplicity, the stochastic gradient method used by the majority of adaptive algorithms, e.g. the LMS algorithm, has a slow convergence speed, thus limiting its use in mobile applications operating in a time-varying channel. A blind adaptive step size algorithm has been proposed in [3] in order to enhance the convergence speed of a stochastic gradient based adaptive algorithm in an A...

Abstract The uplink performance of a direct-sequence code division multiple access (DS-CDMA) packet cellular system is limited by multi-access interference (MAI) from the other users. On one hand, adaptive antenna array (AAA) is a promising technique to increase the link capacity by suppressing the MAI of mobile radio communications systems. On the other hand, transmit power control (TPC) is an...