HYBRID FIXED-DWELL-TIME SEARCH TECHNIQUES FOR RAPID ACQUISITION OF ULTRA-WIDEBAND SIGNALS

Spread spectrum systems, such as UltraWideband impulse radio or Wideband-CDMA, are often required to work in dense multipath situations due to the frequency selective nature of the channels involved. Recent studies have concluded that the process of acquiring these wideband signals can be expedited by the presence of multipath. An acquisition analysis is presented here using a generalized signal flow graph approach which allows for an arbitrary search pattern and a multiple detection scenario generated by the multipath. A linear, or consecutive, search of the uncertainty region is shown to yield longer average search times when compared with a more efficient nonconsecutive serial search, namely the so called bit reversal search. Consideration is also given to a hybrid parallel/serial search scheme, arising from the use of multiple correlators in the receiver. It is shown that the bit reversal search leads to a near optimal hybrid search technique.