Coherent versus Non-Coherent Quantum-Assisted Solutions in Wireless Systems

Each mobile phone transmits its own uplink information to the base station, which results in their superposition. Therefore, the base station has to determine which symbol each of the users has transmitted with (coherent), or without (non-coherent) the knowledge of the channels' estimates. In both scenarios, an optimization problem has to be addressed. Conventional, low-complexity solutions experience degraded performance when the number of receive antenna elements at the base station is lower than the number of mobile terminals. The optimal, full-search-based equivalent multi-level symbol detector offers the best bit error ratio performance, but at a potentially excessive complexity. Quantum search algorithms may be invoked for achieving near-optimal performance at low complexity.