Achievable Rate Region for Iterative MultiUser Detection via Lowcost Gaussian Approximation We establish a multiuser extrinsic information transfer (EXIT) chart area theorem for the interleavedivision multipleaccess (IDMA) scheme, a special form of superposition coding, in multiple access channels (MACs). A lowcost multiuser detection (MUD) based on the Gaussian approximation (GA) is assumed. The evolution of meansquare errors (MSE) of the GAbased MUD during iterative processing is studied. We show that the Kdimensional tuples formed by the MSEs of K users constitute a conservative vector field. The achievable rate is a potential function of this conservative field, so it is the integral along any path in the field with value of the integral solely determined by the two path terminals. Optimized codes can be found given the integration paths in the MSE fields by matching EXIT type functions. The above findings imply that i) lowcost GAbased MUD can provide near capacity performance; ii) the sumrate capacity (region) can be achieved independently of the integration path in the MSE fields; and iii) the integration path can be an extra degree of freedom for code design.

Performance Evaluation of IDMABased Random Access Considering User Detection and Channel Estimation This paper evaluates the performance of interleave division multiple access (IDMA)based random access in order to support massive machinetype communications (mMTC) in the fifth generation mobile communication system taking into account actual user detection and channel estimation using a preamble attached to the packet. To suppress the packet loss due to contention and achieve multipacket reception, accurate user detection and channel estimation, which are used in the successive interference canceller (SIC)process in IDMA, are essential. Multiple preamble sequences, each of which has a onetoone relationship with the interleaver pattern prepared in the system, are generated by applying a cyclic time shift and orthogonal masking operations to ZadoffChu (ZC) sequences. Based on the threshold decision on the correlation between the received signal and each preamble sequence, user detection and channel estimation are performed. Computer simulation results show the impact of the preamble overhead, miss detection and false alarm in the user detection, channel estimation error, and the case when multiple users simultaneously select the same interleaver on the achievable performance of IDMAbased random access.