Dynamic DS-CDMA Aided by Successive Interference Cancellation for Massive Grant-Free Multiple-Access

Abstract

<p>We introduce a dynamic DS-CDMA (DyDS-CDMA) scheme for supporting massive grant-free multiple-Access (mGFMA), where each base-station (BS) or access point (AP) with limited degrees of freedom is expected to control a massive number of devices of ultra densely deployed. We assume that devices become active to transmit data on the basis of time-slots, and during a time-slot, each of devices activates independently and following a common activation probability. A low-complexity detector based on minimum mean-square error and successive interference cancellation, referred to as the MMSE-SICD, is proposed for signal detection in DyDS-CDMA systems. Assuming ideal active device identification and ideal channel estimation of active device, in this paper, we focus on the potential performance achievable by the DyDS-CDMA systems employing the MMSESICD. Our studies reveal that the DyDS-CDMA aided by the MMSE-SICD is high-efficiency for operation in mGFMA environments. Near single-user performance is achievable, when the average number of active devices per time-slot reaches two times of the system's degrees-of-freedom, and hence, the number of active devices of a time-slot may be much higher than two timing the system's degrees-of-freedom.</p>