... groups: Amplify -and- Forward (AF) [3, 4, 8, 10–13],Compress -and- Forward (CF) [5, 20], and Decode -and- For- ward (DF) [1–3, 6, 7, 9, 15]. In the AF schemes, relays amplify (and maybe transform [4]) the ... IEEE Standard for local and metropolitan area networks—part 16: air interface for fixed and mobile broadband wireless access systems. Amendment 2:physical and medium access control layers for combined ... robustness ofthe scheme and the channel estimator). It can be observedthat the estimator is robust and accurate even for a highlyfrequency-selective channel. 5.3. LDPC and Channel Estimation. Recently,...