Outage Analysis of Offloading in Heterogeneous Networks: Composite Fading Channels

Small cells deployment is one of the most significant long-term strategic policies of the mobile network operators. In heterogeneous networks (HetNets), small cells serve as offloading spots in the radio access network to offload macro users (MUs) and their associated traffic from congested macrocells. In this paper, we perform analytical analysis and investigate how the radio channel propagation impairments such as multipath fading, shadowing, and small cell base station density affect MUs' offloading to small cells network (SCN). In particular, we exploit composite fading channels in our evaluation when an MU is offloaded to SCN with varying small cell base station density in the stochastic geometry HetNets framework. We derive the expressions for service outage probability (equivalently service coverage probability) of the MU in macro cell network and SCN under two different composite fading scenarios, viz., Nakagami-Lognormal channel fading and time-shared (combined) shadowed/unshadowed channel fading. We propose efficient approximations for the probability density functions of the channel fading (power) for the aforementioned composite fading distributions that do not have closed-form expressions employing Gauss-Hermite integration and finite exponential series, respectively. Finally, the service outage probability performance of MU with and without offloading services is analyzed under various system parameters and channel fading conditions.