Concurrent search of mobile users in cellular networks

In this paper, we propose to concurrently search for a number of mobile users in a wireless cellular network based on the probabilistic information about the locations of mobile users. The concurrent search approach guarantees that all k mobile users will be located within k time slots. It is shown that even in the worst case when mobile users appear equally in all the cells of the network, the concurrent search approach is able to reduce the average paging cost by 25%. More importantly, this is achieved without an increase in the worst case paging delay or in the worst case paging cost. Depending on the total number of mobile users to be located, total number of cells in the network, and the probabilistic information about the locations of mobile users, the reduction of the average paging cost due to the usage of the concurrent search approach ranges from 25% to 88%. The case in which perfect probabilistic information is unavailable is also studied.     

Analytical expressions for blocking and dropping probabilities for mobile streaming users in wireless cellular networks

We consider a wireless cellular network serving streaming traffic. We study in this context the effect of the users mobility on their quality of service (QoS). If the arrival of a new user violates the capacity constraint, then his call is blocked. If the user is first admitted but the capacity constraint is violated later when he attempts to move, then his call is dropped. The blocking and dropping probabilities are the main QoS indicators in this model called forced termination (FT). We introduce an alternative model, called transitions backtrack (TB), where a user backtracks when his motion violates the capacity constraint. In this model, a relevant QoS indicator is the number of times the user backtracks called number of motion blocking per call. We propose some explicit expressions for the above QoS indicators as functions of the mean user speed. These expressions are validated by simulations. In particular we observe that the dropping probability in the FT model is well approximated by the number of motion blocking per call in the TB model which is expressed analytically.     

Tracking mobile users in wireless communications networks

Tracking strategies for mobile wireless networks are studied. A cellular architecture in which base stations that are interconnected by a wired network communicate with mobile units via wireless links is assumed. The cost of utilizing the wireless links for the actual tracking of mobile users is considered. A tracking strategy in which a subset of all base stations is selected and designed as reporting centers is proposed. Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported. It is shown that, for an arbitrary topology of the cellular network (represented by the mobility graph), finding an optimal set of reporting centers is an NP-complete problem. Optimal and near-optimal solutions for important special cases of the mobility graph are presented     

Location management strategies for cellular mobile networks

Location management in mobile communication systems is concerned with those network functions necessary to allow the users to be reached wherever they are in the network coverage area. The basic operations for that purpose-paging and location updating-are resource-consuming since both involve signalling over the radio link between the mobile stations and base stations. Future cellular mobile communication networks (wireless personal communication networks (PCN)) will have to support a large number of users, so a significant amount of radio signalling can be expected. This paper describes the conventional location management strategy (the one used in modern cellular systems like the Global System for Mobile communications (GSM)) and reviews, describes and comments on some alternative location management proposals for future high-density PCN environments that aim to reduce this expected high (radio) signalling load     

Adaptive methods for location management in mobile cellular networks

Future mobile cellular networks will include complex algorithms and procedures that make them able to react optimally to the fluctuating conditions (propagation, traffic, services, ...). Among these mechanisms, location management is an important one as it deals with an essential function of the mobile cellular networks: locate each subscriber to provide him/her with the subscribed services. In this paper, we present the location management methods that are currently implemented in cellular networks and the adaptive methods that have been proposed for future mobile cellular networks. These methods are evaluated for different scenarios and their performance are compared by means of simulations.     

Probabilistic location update for advanced cellular mobile networks

We propose a probabilistic location update (PLU) scheme for advanced cellular mobile networks. The performance of PLU is analyzed and compared with those of two extreme location update schemes. As a result, we demonstrate a merit of PLU, that is, simple implementation with an acceptable performance level     

Planning effective cellular mobile radio networks

This paper deals with the automatic selection and configuration of base station sites for mobile cellular networks. An optimization framework based on simulated annealing is used for site selection and for base-station configuration. Realistic path-loss estimates incorporating terrain data are used. The configuration of each base station involves selecting antenna type, power control, azimuth, and tilt. Results are presented for several design scenarios with between 250 and 750 candidate sites and show that the optimization framework can generate network designs with desired characteristics such as high area coverage and high traffic capacity. The work shows that cellular network design problems are tractable for realistic problem instances     

Towards intelligent geographic load balancing for mobile cellular networks

We investigate a novel geographic load-balancing scheme for cellular networks that intelligently changes cellular coverage according to the geographic traffic distribution in real time. A cooperative negotiation approach for the real-time control of cellular network coverage is described. The performance of the whole cellular network is improved by contracting and shaping the antenna radiation pattern around a traffic "hot spot" and expanding adjacent cells coverage to fill in the coverage loss. By the use of real time cooperative negotiations between base stations and associated antennas, a near optimal local coverage agreement is reached in the context of the whole cellular network. Results showing the advantage of this technique are presented. Global optimization using constrained real-coded genetic algorithms (RCGA) provides a benchmark. Convergence using penalty functions to manage the constraints was first investigated but gave poor results. A transformation of the problem space is used to remove the constraints, and a criterion that is necessary for successful transformations is explained.     

Dynamic resource allocation in mobile heterogeneous cellular networks

User mobility is a challenging issue in macro and femto cellular networks for the fifth-generation and newer mobile communications due to the time-varying interference and topology experienced. In this paper, we consider an OFDMA-based two-tier network with one macro cell and several femto cells, wherein each macro user and/or femto user can leave or enter its serving cell frequently, referred to as user mobility. A resource allocation problem with different rate requirements of mobile users is then formulated. Assuming well knowledge of the user locations and the channel state information, we propose a dynamic algorithm with static and dynamic parts for a better trade-of between computational complexity and system throughput. The static algorithm, named interference weighted cluster algorithm in this paper, is based on the graph theory to cluster the femtocells by minimizing the interference between clusters, while the dynamic algorithm is to deal with the user mobility by sharing the resource blocks under the constraints of rate requirements. Numerical results are demonstrated to show the effectiveness of the proposed dynamic resource allocation algorithm in terms of capacity, computational time, and outage probability.

     

Handover and channel assignment in mobile cellular networks

A taxonomy of channel assignment strategies is provided, and the complexity in each cellular component is discussed. Various handover scenarios and the roles of the base station and the mobile switching center are considered. Prioritization schemes are discussed, and the required intelligence distribution among the network components is defined     

Optimal base stations location and configuration for cellular mobile networks

In this paper, we study the problem of base stations location and configuration. Antenna configuration includes number of antennas installed at the base station, the azimuth of each base station, the tilt, height, and transmitted power for each antenna for cellular mobile networks. Towards this end, a mathematical model is formulated using integer programming (IP).The objective of the model is to minimize the cost of the network. The model guarantees that each demand point is covered. A demand point represents a cluster of uniformly distributed multiple users. In addition, the signal-to-interference-plus-noise ratio at each demand point is set at a given threshold value. A none-line-of-site situation is considered while calculating the path loss using COST-231-Walfisch-Ikegami propagation model. To illustrate the capability of the formulated IP model, we use a discretized map of some area with demand points. The IP model is solved using a commercial software, LINGO 12. Possible future research directions are stated in the conclusion.

     

Modeling of customer retrial phenomenon in cellular mobile networks

In the planning of modern cellular mobile communication systems, the impact of customer behavior has to be carefully taken into account. Two models dealing with the call retrial phenomenon are presented. The first model considers a base station with a finite customer population and repeated attempts. A Markov chain modeling is proposed, and an efficient recursive solution of the state probabilities is presented. The second model focuses on the use of the guard channel concept to prioritize the handover traffic. Again, the retrial phenomenon plays an important role. The influence of the repeated attempt effect on the quality of service experienced by the mobile customers is discussed by means of numerical results     

Active tracking: Locating mobile users in personal communication service networks

The problem of tracking mobile users in Personal Communication Service (PCS) networks is discussed. We propose a novel approach for reducing the wireless cost of tracking users. The basic idea is to use nonutilized system resources for initiating queries about the location of mobile users, in addition to the process of user registration. Queries are applied at each cell, independently of the other cells, whenever the load on the local control channel drops below a predefined threshold. Our study focuses on two issues: (1) proposing the initiated queries approach and an algorithm for its application, and (2) studying and quantifying the value of location information and evaluating the parameters affecting it. Our analysis shows that the expected benefit due to location knowledge in a Markovian motion model depends, among other things, on the determinant of the transition matrix and on the variability of the location distribution function. The active tracking approach, as opposed to other dynamic strategies, does not require any modification of user equipment. The importance of this property is in its practicality: An implementation of a new registration strategy in current systems would require a modification of the users equipment. Moreover, the proposed method can be easily implemented in addition to any known tracking strategy, to reduce further the tracking cost. The performance of the active tracking method is evaluated under two registration strategies: The geographicbased strategy, currently used in cellular networks, and the profilebased strategy, suggested elsewhere. Under both strategies, it significantly reduces the tracking cost.     

A memetic algorithm for assigning cells to switches in cellular mobile networks

Assigning cells to switches in cellular mobile networks is an NP-hard problem which, for real size mobile networks, could not be solved using exact methods. In this context, heuristic approaches like memetic algorithms can be used. This paper proposes a memetic algorithm (MA) to solve this problem. The implementation of this algorithms has been subject to extensive tests. The results obtained confirm the efficiency and the effectiveness of MA to provide good solutions for moderate- and large-sized cellular mobile networks, in comparison with tabu search and Merchant and Sengupta's heuristics. This heuristic can be used to solve NP-hard problems, like designing and planning, in the next-generation mobile networks.     

Performance comparison of different spread-spectrum signalingschemes for cellular mobile radio networks

Different spread-spectrum signaling schemes in a cellular mobile radio network are compared in terms of throughput and packet error probability. Bounds on the bit and packet error probabilities are derived for data modulation schemes with binary phase shift keying with noncoherent demodulation. Reed-Solomon coding is employed for error-correction purposes. In all cases, the effect of varying interference power (according to some inverse power of distance) of the desired signal, of the interfering signals, and of Rayleigh nonselective channel fading is accurately taken into account. The throughput in the mobile-to-base transmission mode is evaluated for the above data modulation, demodulation, and forward-error-control coding schemes. The comparison shows that, under the varying interference power model, the frequency-hopped scheme performs best among all schemes with the same bandwidth. Power control mechanisms are required to improve the performance of direct-sequence systems     

Estimation of performance measures for product form cellular mobile communications networks

Telecommunication Systems - This paper investigates cellular mobile communications networks. The purpose of the paper is twofold. First, it is shown that the restrictive assumption of reversible...     

Performance of FH-MFSK cellular mobile radio in the presence of nonsynchronous users

Monte Carlo simulation of an FH-MFSK spread-spectrum cellular mobile radio system in the presence of nonsynchronous users is presented. Impairments such as short-term and shadow fading are introduced. Performance curves showing the number of simultaneous users the system can accept are given. Both clustering and no-clustering strategies are considered.     

State-dependent control of call arrivals in layered cellular mobile networks

Layered cellular mobile networks have been widely proposed as a way of accommodating traffic growth in mobile communications. There is a need, however, to give some form of priority to handover attempts over fresh call attempts to ensure that handovers are fast and reliable. A class of call control policies with state-dependent control of fresh call arrivals is considered for this purpose. A modified version of the Value Iteration Algorithm is used to solve a Markov decision model for the optimal call control policy. The network blocking performance under optimal state-dependent control is compared with the performance under a much simpler channel reservation policy for a model of a cellular sub-network. The channel reservation policy is shown to perform nearly as well as the optimal policy at lower loads, where fresh call blocking is less than 5%, indicating that it is both an effective and an efficient method for ensuring good handover performance.     

Iterative approximation analysis of guard-channel-based strategies in mobile cellular networks

A new mathematical method to analyse the performance of guard-channel-based strategies is proposed. The analysis is based on the iterative calculation of the average effective channel holding time. The method presented provides higher accuracy than alternative solutions previously reported in the literature     

Energy-efficient and delay-aware mobile cloud offloading over cellular networks

Telecommunication Systems - The latest mobile applications, such as GPS, games, virus scanning, and face detection and recognition, are compute-intensive applications consuming a lot of energy when...