Adaptive Channel Estimation in Wireless Communications - Adaptive Signal Processing in Wireless Communications - page 34

2
Adaptive Channel
Estimation
in Wireless
Communications

2.1 Introduction ............................................................ 35
2.2 Wireless Channel Models...................................... 36
Time-Variant (Doubly Selective) Channels •
Time-Invariant Channels
2.3 Channel Estimation................................................ 43
Training-Based Channel Estimation • Blind
Channel Estimation • Semiblind Approaches •
Superimposed Training-Based Approaches
2.4 Adaptive Channel Estimation .............................. 55
Block-Adaptive Channel Estimation Using
CE-BEM • Adaptive Channel Estimation via
Subblock Tracking • Symbol-Adaptive Joint
Channel Estimation and Data Detection
2.5 Simulation Examples.............................................. 60
Example 1 • Example 2
2.6 Conclusions.............................................................. 66
Acknowledgment ............................................................... 67
References ........................................................................... 67

Jitendra K. Tugnait
Auburn University

2.1 Introduction

Propagation of signals through wireless channels (indoors or outdoors) results in the
transmitted signal arriving at the receiver through multiple paths. These paths arise due
to reflection, refraction, or diffraction in the channel. Multipath propagation results
in a received signal that is a superposition of several delayed and scaled copies of the
transmitted signal giving rise to frequency-selective fading. Frequency-selective fading
(defined as changes in the received signal level in time) is caused by destructive interfer-
ence among multiple propagation paths. The environment around the transmitter and
the receiver can change over time, particularly in a mobile setting, leading to variations