Harnessing Channel Collisions for Efficient Massive Access in 5G Networks: A Step Forward to Practical Implementation

The forthcoming fifth generation of cellular networks (5G) is envisioned to support massive machine type communication (MTC) where a vast number of MTC devices utilize the wireless spectrum to create what is called Internet-of-Things. The vision calls for a paradigm shift in the design and operation of wireless access schemes to enable efficient and reliable massive connectivity with many channel collisions occurring when (uncoordinated) multiple MTC devices concurrently access a shared wireless channel. Motivated by recent results in information theory, this paper proposes a promising approach to the massive access problem by combining the concept of network densification (i.e., ultra-dense deployment of base stations) with physical-layer network coding and pulse-shaped (filtered) OFDM as the most promising air-interface for 5G. The basic idea is to exploit channel collisions at nearby base stations to reliably decode linear equations of transmitted messages. The linear equations are then forwarded through the backbone to a macro base station that solves a system of linear equations to reconstruct the original messages.