Application of renewal theory to call handover counting and dynamic location management in cellular mobile networks

Handovers in a cellular system provide mobility and freedom to connect to any desired cell at any instance. It is necessary to manage handovers better, to cater to the services that a user desires. In any given cell, the newly originating connections and the incoming handover connections both have been mostly treated as exponential arrivals from a queueing model perspective. However, such models provide no flexibility to match real-world mobility scenarios, other than the one rate parameter. In contrast, in this paper, we propose matrix exponential modeling of handover arrivals to provide the potential to much more accurately characterize arrivals and prioritize resource allocation for handovers, especially handovers for emergency or public safety needs. With the use of a ‘B’ matrix for representing a handover arrival, we have a rich set of dimensions to model system handover behavior. We can study multiple parameters and the interactions between system events along with the user mobility, which would trigger a handoff in any given scenario. Here we show the fundamental modeling approach and demonstrate usefulness of the model while investigating impacts and sensitivities of certain key parameters.

Handover performance prioritization for public safety and emergency networks

Traditionally, system-level performance evaluation of mobile wireless communication networks has been addressed by only considering resource insufficiency, whereas the effect of an unreliable wireless channel has largely been ignored because of the complexity that its inclusion entails. To fill this void, a general analytical model for the system-level performance evaluation of mobile wireless networks taking into account both resource insufficiency and link unreliability is proposed in this paper. The effect of link unreliability is captured through the appropriate probabilistic characterization of the ldquounencumbered call-interruption time.rdquo Additionally, useful functional relationships between the call-interruption processes of the proposed analytical model and some system-level parameters that can easily be obtained from statistics collected at base stations (BSs) are derived. For the sake of generality, the involved time variables (i.e., cell dwell time, unencumbered call-interruption time, and channel holding time) are considered generally distributed. Then, general and easily computable mathematical expressions for many useful performance metrics under more realistic considerations are obtained. The analytical model proposed here is able to provide new and important insights into the dependence of system performance on link unreliability. Such understanding of this teletraffic engineering issue is vital for planning, designing, dimensioning, and optimizing mobile cellular networks for present and future wireless communication systems beyond the third generation.

System-Level Analysis of Mobile Cellular Networks Considering Link Unreliability

-In this paper, a teletraffic model to analyze wireless mobile cellular networks with hyper-Erlang distributed cell dwell time is developed. We demonstrate that the residual cell dwell time is also hyper-Erlang distributed with a greater number of stages. More important, it is shown that the phases on each stage of the hyper-Erlang distributed cell dwell and residual cell dwell times have the same mean permanence time. This fact allows us to make our teletraffic model computationally tractable by keeping track in a single state variable all the calls (new and handed off) in a phase (of any stage) with both the same mean permanence time and order within the stages. For this feature, it is also shown that the, so called, global cell dwell time (for new and handoff calls) can be represented by a Coxian model. This Coxian model can be the mixture of Coxian probability distributions. The teletraffic model proposed in this paper represents a step toward the development of a general, analytical, and computationally tractable modelling tool for the performance evaluation of mobile wireless communication networks under more realistic considerations.

Teletraffic Model for the Performance Evaluation of Cellular Networks with Hyper-Erlang Distributed Cell Dwell Time

In this paper, under the assumption that the unencumbered service time is exponentially distributed, a novel algebraic set of general equations that examines the relationships between cell dwell time (CDT) and residual cell dwell time as well as between cell dwell time and channel holding time (CHT) are derived. This work includes relevant new analytical results and insights into the dependence of CHT characteristics on the CDT distribution. For instance, it is found that when CDT is Coxian or hyper-exponentially distributed, CHT is also Coxian or hyper-exponentially distributed, respectively.

On the Functional Relationship between Channel Holding Time and Cell Dwell Time in Mobile Cellular Networks

Phase-type models of channel holding times in cellular communications systems

In this paper, we derive the distribution of the channel-holding time when both cell-residence and call-holding times are phase-type distributed. Furthermore, the distribution of the number of handovers, the conditional channel-holding time distributions, and the channel-holding time when cell residence times are correlated are derived. All distributions are of phase type, making them very general and flexible. The channel-holding times are of importance in performance evaluation and simulation of cellular mobile communication systems.

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T. K. Christensen

Papers

Phase-type models of channel holding times in cellular communications systems

Phase-type models of channel-holding times in cellular communication systems