Asynchronous Cell-Free Wireless Networks

Abstract

This paper introduces intentional symbol-level asynchronicity as an interference-management mechanism for the uplink of cell-free networks. Rather than treating timing offsets as impairments, user-specific delays are deliberately assigned to reduce multiuser interference and improve spectral efficiency. A scalable receiver architecture is devised with synchronous channel-estimation pilots, asynchronous data transmission, bounded matched-filter sampling, and windowed combining. The delay assignment is formulated by means of a conflict metric that measures the severity of multiuser interference and is solved through a low-complexity greedy algorithm. As a benchmark, an exact method is also formulated for small and moderate network sizes using mixed-integer linear programming. Numerical results with both rectangular and root-raised-cosine pulses confirm that considerable performance improvements are feasible relative to synchronous transmissions, even with small delay codebooks and short observation windows.