A collision resolution paradigm for random access channel control in multi-access wireless networks

The random access channel (RACH) incurs a collision if more than one user make signaling requests over the same time slot, spreading code, or antenna element, in TDMA, CDMA, or SDMA wireless networks, respectively. We propose a hexanary-feedback collision resolution paradigm (HFCRP), capable of leveraging access efficiency of the RACH for all above wireless networks. HFCRP performs incremental contention resolution, managing a small subset of users at a time via a two-phase process. In the first phase, a group of users is probabilistically admitted, with a negligible probability of the group size greater than five. In the second phase, all users in the group are efficiently resolved. The two-phase process is augmented with hexanary feedback control facilitated by an envelope-PDF-based multi-user estimator (MR) implemented at the physical layer. Significantly, the MR measures the exact number of transmitting users (zero to five) in a contention slot by matching the envelope PDFs histograms of received signals to a library of pre-constructed PDFs. These six outcomes comprise the hexanary feedback being broadcast to users during the real-time operation of the two-phase process. Analytic and simulation results delineate that, performing in conjunction with the MR, HFCRP achieves high performance with respect to maximum stable throughput, saturated throughput, access delay, and blocking probability.