  This paper proposes an iterative detection and decoding (IDD) scheme and an
approach to improve the selection of access points (APs) in uplink cell-free
massive multiple-antenna systems. A cost-effective scheme for selection of APs
based on local log-likelihood ratios (LLRs) is developed that provides
sufficient statistics to the central processing unit and selects which APs
should be considered for each user. {Numerical results show that the proposed
IDD scheme works very well and the proposed LLRs-based approach to select APs
outperforms the existing techniques in terms of bit error rate and spectral
efficiency while requiring a comparable fronthaul load.
