TABLE OF CONTENTS While the ML techniques discussed in the previous section can yield good ranging accuracies, they may not be very practical due to the a-priori knowledge requirements and/or implementation complexities. In this section, various low-complexity ranging algorithms specifically introduced for UWB systems are reviewed.
The reason that the peak selection discussed above may not yield an accurate range estimate is the possible existence of other MPCs prior to the strongest one. One way to improve the performance of the peak detector is to consider the largest correlation peaks prior to making a decision for a range estimate. Three algorithms based on this principle are (1) single search, (2) search and subtract, and (3) search, subtract, and readjust [227].
The single search algorithm first calculates the absolute values of the MF outputs as given in (5.22). Then, strongest correlation peaks are calculated, which correspond to strongest MPCs. Let the time indices corresponding to these MPCs be represented by 
1 , 2 , , , where i represents the time index for the ith strongest component. Then, the TOA of the received signal is estimated as [227]
where T smp denotes the sampling period of the receiver.
For resolvable channels, the single search algorithm discussed above may successfully lock onto the correct correlation peaks. However, for non-resolvable channels, estimation of individual MPCs and...
