Adaptive Modulation with Adaptive Pilot Symbol Assisted Estimation and Prediction of Rapidly Fading Channels

Adaptive modulation requires channel state information (CSI) at both transmitter and re- ceiver. In practice, CSI can be acquired at the re- ceiver by inserting pilot symbols in the transmitted signal. Inthispaper,weflrstanalyzetheefiectchan- nel estimation and prediction errors have on bit er- ror rate (BER). Based on this analysis, we develop adaptive pilot symbol assisted modulation (PSAM) schemesthataccountforbothchannelestimationand predictionerrorstomeetthetargetBER.Whilepilot symbols facilitate channel acquisition, they consume part of transmitted power and bandwidth, which in turnreducesspectrale-ciency. Withimperfect(and thus partial) CSI available at the transmitter and receiver, two questions arise naturally: how often should pilot symbols be transmitted? and how much power should be allocated to pilot symbols? We ad- dress these two questions by optimizing pilot param- eters to maximize spectral e-ciency.