Multipath Resistant Coherent Timing-Error-Detector for DS-CDMA applications

A new coherent timing error detector (TED) for timing/code tracking loops used inside RAKE receivers in CDMA systems is presented. In contrast to the conventional TED it is well suited for the case of multipath propagation channels. In order to accomplish this task a compensation term is introduced inside the tracking loop directly behind the conventional TED. This compensation term is calculated using the knowledge on the relative delays of all paths and their respective channel coefficients. A compensation scheme like the one described here becomes necessary whenever closely spaced paths have to be tracked. This fact makes this algorithm a favorable candidate for indoor scenarios where individual paths can be spaced even more closely than one chip. The performance of the presented scheme is assessed by means of simulation

Optimal Training for Time-Selective Wireless Fading Channels Using Cutoff Rate

<p/> <p>We consider the optimal allocation of resources&#8212;power and bandwidth&#8212;between training and data transmissions for single-user time-selective Rayleigh flat-fading channels under the cutoff rate criterion. The transmitter exploits statistical channel state information (CSI) in the form of the channel Doppler spectrum to embed pilot symbols into the transmission stream. At the receiver, instantaneous, though imperfect, CSI is acquired through minimum mean-square estimation of the channel based on some set of pilot observations. We compute the ergodic cutoff rate for this scenario. Assuming estimator-based interleaving and <inline-formula><graphic file="1687-6180-2006-047245-i1.gif"/></inline-formula>-PSK inputs, we study two special cases in-depth. First, we derive the optimal resource allocation for the Gauss-Markov correlation model. Next, we validate and refine these insights by studying resource allocation for the Jakes model.</p