An Accurate Computational Algorithm for Call Admission Control in Small Cell Networks

Small cell networks (SCNs) are the recent evolution of the cellular mobile networks. Based on the small-cell concept, SCNs aim to increase the data capacity and the subscriber's population. Call admission control (CAC) is used in SCNs to prevent the system congestion and the service degradation for in-progress calls by restricting the access to the network. In the literature, almost all the existing works on CAC in cellular mobile networks with guard channels and repeated blocked calls propose a multi-server retrial queue model, which it is generally represented by a two-dimensional continuous time Markov chain (CTMC). For which, no analytical solution is available and only numerical approximation can be studied. In this paper, we propose a novel efficient analytical approach based on a semi-recursive algorithm for the numerical computation of the CTMC steady state probabilities resulted from a finite population CAC retrial queuing model. We represent using the retrial queue model a CAC scheme with multiple guard channels that consider repeated attempts of fresh blocked calls and impatience handover calls. In our model, the small-cells population is considered finite. In addition, we develop the principal stationary performance indices. The numerical results show that the proposed algorithm is substantially more accurate and achieves efficient computation. Also, demonstrates that the consideration of cells with small size can achieve better performances in term of the call blocking probability.