SWITCHED PILOT AVERAGING FOR A SUBCHANNEL DEMODULATOR
Original Publication Date: 1997-Mar-01
Included in the Prior Art Database: 2002-May-14
An algorithm is described which improves mits reference symbols (called "pilots") at known the sensitivity of a pilot-based multiple sub-channel times in a fixed frame format. The receiver demod- modulation system while simultaneously main- ulates these symbols and uses them for gain/phase taining full carrier tracking bandwidth of the references in the process of decoding the transmit- demodulator. ted data symbols. Given a transmitted pilot P, a transmitted symbol S, a received (interpolated) BODY pilot Prx, and a received data symbol Srx the decoder computes normalized data symbol S' A pilot-based linear modulation system trans- according to: S' = PIprx * Srx = estimate of transmitted data symbol S (1) A problem with a system like this is direct cou- The problem described above is shown pictori- pling of noise on the pilot symbols to the normal- ally below in Figure 1. The problem with the coher- ized data symbols. This reduces the optimality of ent demodulator is that noise vector Np is coupled the decode process and can reduce the sensitivity of onto transmitted symbol S and increases the per- the system by 2dB or more. ceived noise on the received data symbol Srx beyond the channel noise Ns.