Design and Analysis of Prerake Ultrawideband Impulse Radio (PR-UWB-IR) With Turbo Outer Codes
The performance of a precoded ultrawideband impulse radio (UWB-IR) system using prerake as the inner code and superorthogonal turbo code (SOTC) or repetition code (RC) as outer codes is investigated in this paper. Prerake UWB-IR transmits information bits with time-reversed channel information. Due to the low transmission power of the UWB-IR, the sequence is repeated through outer coding. The prerake technique demands that the channel information be available to the transmitter. The tradeoff between the feedback channel information and several system performance metrics such as the length of the outer code and bit error rate (BER) is studied. It is shown that there exists a minimum feedback quantity required to achieve a target system performance in different communication scenarios. The optimal quantity of feedback channel knowledge and intersymbol interference (ISI) are investigated and verified by computer simulation.