Vicente Casares-Giner

On movement-based mobility tracking strategy-an enhanced version

An enhanced version of the movement-based location update with selective paging strategy proposed by Akyildiz, Ho and Lin (see IEEE/ACM Trans. Networking, vol.4, p.629-38, 1996) is presented. Although the terminal paging cost is slightly increased, a significant reduction in the location update cost is achieved. The net effect is, for low call-to-mobility ratio, a saving of around 10%-15% in the total cost (location+paging) per call arrival is achieved. Our proposal can be easily implemented in real cellular systems.

Global versus distance-based local mobility tracking strategies: a unified approach

We have considered fixed location areas for personal communication systems with hysteresis effect in the location update process. Our scheme can be seen as a hybrid between the global (static) and the distance-based local (dynamic), location update strategies, and clearly improves the performance when compared with previous proposals. Selective paging with delay constraint has also been considered. It can be implemented in standard cellular systems.

Comments on "Call Blocking Probability and Bandwidth Utilization of OFDM Subcarrier Allocation in Next-generation Wireless Networks"

We claim that the Markovian model proposed by J.-C. Chen and W.-S.E. Chen (2006) is not suitable for the intended physical system. A more adequate model is proposed, which additionally offers important advantages that are discussed in this letter.

Analysis of priority channel assignment schemes in mobile cellular communication systems: a spectral theory approach

A queueing system with two arrival streams is considered in this paper. A number of schemes assigning different priorities to each of the two arrival streams have been modeled. One of the streams (stream 1) is considered to require a higher priority to access the server than the other (stream 2). On the other hand, stream 1 has stringent constraints with regard to the waiting time, and thus it is treated according to a loss model whereas stream 2 is handled following a delay model. The analysis of the system is carried out by applying the generating function method combined with spectral expansion tools. This approach offers better numerical efficiency and stability over a wider range of system loads than the widely used matrix-geometric approach. The model is applied to a mobile cellular communications system where the call setup requests form the stream 2 and handover requests form the stream 1.

Mobility models for mobility management

The main goals of todays wireless mobile telecommunication systems are to provide both, mobility and ubiquity to mobile terminals (MTs) with a required quality of service. By ubiquity we understand the ability of a MT to be connected to the network anytime, anywhere, regardless of the access channels characteristics. In this chapter we deal with mobility aspects. We provide some basic background on mobility models that are being used in performance evaluation of relevant mobility management procedures, such as handover and location update. For handover, and consequently for channel holding time, we revisit the characterization of the cell residence time. Then, based on those previous results, models for the location area residence time are built. Cell residence time can be seen as a micro-mobility parameter while the latter can be considered as a macro-mobility parameter; and both have a significant impact on the handover and location update algorithms.

Analytical-numerical study of the handoff area sojourn time

In cellular systems, there is usually an overlap cell coverage area (area covered by two or more base stations) which has valuable practical applications: soft handoff is an important feature of CDMA systems, and in hard handoff, the overlap area allows the queuing of handover requests as a handover prioritization scheme. While an extensive research effort has been done to model the terminal residence time in a cell and the channel holding time, the sojourn time in the overlap area is a topic that still requires further study. We propose a model of the sojourn time in the overlap area, along with a novel numerical method to derive its probability distribution. The obtained results show that the common assumption of exponential distribution for this time is not suitable, whereas it can be satisfactorily fitted by the hyper Erlang distribution.

Performance analysis of access class barring for handling massive M2M traffic in LTE-A networks

The number of devices that communicate through the cellular system is expected to rise significantly over the coming years. But cellular systems, such as LTE-A, were designed to handle human-to-human traffic. Hence, they are not suitable for managing massive machine-to-machine communications. Therefore, additional congestion control methods must be developed and evaluated. Up to date, access class barring (ACB) and extended access barring (EAB) methods are the preferred solutions for reducing congestion in the access channels of the evolved NodeB. These methods are based on restricting the access of certain classes of UEs, so the system capacity is not exceeded. Due to the high complexity of the LTE-A system, evaluating its performance is not straightforward. Specifically, a large number of variables, coexistent mechanisms, and test scenarios make it difficult to identify the network parameters that enhance performance. In this paper, we analyze the ACB method in highly congested environments. For this, we evaluate the effect of ACB parameters (barring rates and barring times) by means of several key performance indicators (KPI) such as delay, energy consumption (preamble transmission attempts required) and success probability. We observed that ACB is appropriate for handling sporadic congestion intervals in LTE-A networks.

Effect of the handoff area sojourn time distribution on the performance of cellular networks

In cellular systems there is usually an overlap cell coverage area (area covered by two or more base stations) which has valuable practical applications. Particularly, it permits the queuing of handover requests as a handover prioritization scheme. The modeling of the sojourn time in the overlap area is a topic which is not sufficiently explored, and even less is the effect it may have on the performance of prioritized channel assignment schemes based on handover queuing. In this paper we develop an analytical model for a cellular system with channel reservation for handovers and handoff queuing. In our model, the common assumption of exponentially distributed maximum queuing time is removed and a general distribution is allowed. The model is used to quantify the influence that the coefficient of variation of the overlap area sojourn time has on system performance. We also propose an approximate model that is more versatile and numerically more efficient than the exact model.

Integration of Dispatch and Interconnect Traffic in a Land Mobile Trunking System. Waiting Time Distributions

The performance evaluation of integrated dispatch and interconnect traffic schemes are important in land mobile trunking system. Two such schemes have been analyzed by different methods. We present an unified approach to analyze various new schemes for integrating dispatch and interconnect traffic. Waiting time distribution under the First-In-First-Out (FIFO) discipline for dispatch calls, and lost probability for interconnect calls are obtained. Performance tradeoff between dispatch and interconnect traffic are displayed.

Generalized truncated methods for an efficient solution of retrial systems.

We are concerned with the analytic solution of multiserver retrial queues including the impatience phenomenon. As there are not closed-form solutions to these systems, approximate methods are required. We propose two different generalized truncated methods to effectively solve this type of systems. The methods proposed are based on the homogenization of the state space beyond a given number of users in the retrial orbit. We compare the proposed methods with the most well-known methods appeared in the literature in a wide range of scenarios. We conclude that the proposed methods generally outperform previous proposals in terms of accuracy for the most common performance parameters used in retrial systems with a moderated growth in the computational cost.