Performance Impact of LoS and NLoS Transmissions in Dense Cellular Networks

In this paper, we introduce a sophisticated path loss model incorporating both lin-of-sight (LoS) and non-line-of-sight (NLoS) transmissions to study their impact on the performance of dense small cell networks (SCNs). Analytical results are obtained for the coverage probability and the area spectral efficiency (ASE), assuming both a general path loss model and a special case with a linear LoS probability function. The performance impact of LoS and NLoS transmissions in dense small cell networks (SCNs) in terms of the coverage probability and the ASE is significant, both quantitatively and qualitatively, compared with previous work that does not differentiate LoS and NLoS transmissions. Our analysis demonstrates that the network coverage probability first increases with the increase of the BS density, and then decreases as the SCN becomes denser. This decrease makes the ASE suffer from a slow growth or even a decrease too. The ASE will grow almost linearly again as the BS density goes ultra dense. For practical regime of the small cell density, the performance results derived from our analysis are distinctively different from previous results, and show that the BS density matters.