Capacity gain of physical layer caching in backhaul-limited dense wireless networks

Dense wireless network is a promising solution to meet the huge capacity demand in 5G wireless systems. However, there are two fundamental implementation issues, namely the interference issue and the backhaul cost issue. To simultaneously resolve these two issues, we propose a novel network architecture called the backhaul limited cached dense wireless network (C-DWN), where a physical layer (PHY) caching scheme is employed at the BSs but only a small fraction of the BSs have payload backhauls. There are two fundamental benefits of PHY caching, namely the cache-induced MIMO cooperation gain and the cacheassisted Multihopping gain. We show that the total network capacity of the backhaul limited C-DWN scales linear with the total number of BSs. Moreover, we analyze the per BS throughput of two order-optimal achievable schemes for a regular C-DWN. Finally, we study the impact of various system parameters on the PHY caching gain and provide fundamental design insight for the backhaul limited C-DWN. Our results show that the backhaul limited C-DWN is a cost-effective solution for future high-speed wireless content delivery networks.