Personal Communication Services Research Articles

An Approach for Location Area Planning in a Personal Communication Services Network (PCSN)

This paper deals with an approach for planning location areas (LAs) in a personal communication services network (PCSN) to be overlaid on an existing wired network. Given the average speed of mobile terminals, the number of mobile switching centers (MSCs), their locations, call handling capacity of each MSC, handoff cost between adjacent cells and call arrival rate, an important consideration in a PCSN is to identify the cells in every LA to be connected to the corresponding MSC in a cost effective manner. In this work, while planning a location area, we present a two-step approach, namely optimization of total system recurring cost (subproblem I) and optimization of hybrid cost (subproblem II). The planning first determines the optimum number of cells in an LA from subproblem I. Then, it finds out the exact LAs by assigning cells to the switches, while optimizing the hybrid cost which comprises the handoff cost and the cable cost, in subproblem II. This divide-and-conquer strategy provides a practical way for designing LAs. As our approach toward LA planning takes into accounts both cost and network planning factors, this unique combination will be of great interest to PCSN designers. It develops an optimum network planning method for a wide range of call-to-mobility ratios that minimizes the total system recurring cost while still ensuring a good system performance. Our study shows that acceptable results are achievable with a reasonable computational effort, which supports the engineered planning of a PCSN.

A general distribution formula of the count of mobiles crossing location areas between two data traffic arrivals

Location management is a challenging part in mobile communication. Studying the situation that the count of mobiles crossing location areas between two data traffic arrivals is significant to evaluate the costs and performances of various location management strategies, when 4G mobile communication faces vast data traffic. In this paper, we propose a new model for mobile terminal movement in personal communications services networks. Based on this model with Markov arrival process for data traffic arrival process to mobile terminal, general distribution time the mobile terminal resides in LA<sub><i>o</i></sub>, another general distribution time the mobile terminal resides in LA<sub><i>n</i></sub>, by using density evolution method, we present a general distribution formula of the count of mobiles crossing location areas between two successive data traffic arrivals.

이동망에서 결함 허용 위치 관리를 위한 포인터 포워밍 방법

One of the main challenges in personal communication services(PCS ) Is to locate many mobile terminals that nay move from place to place frequently. This kind of system operation is called location management. This task entails sophisticated signaling traffic and database queries. Several strategies have been proposed to improve the efficiency of location management. These strategies use location register databases to store the current locations of mobile terminals, and are vulnerable to failure of the location register databases. In this paper, we propose a fault-tolerant pointer forwarding scheme with distributed home location register in order to tolerate the failure of location registers. The performance of the proposed scheme is evaluated analytically by simulation, and Is compared with Biaz`s bypass forwarding strategy and two-path forwarding strategy.

Empowering next-generation wireless personal communication networks

Next-generation wireless systems should provide to the user access to a broad range of services in a transparent way, independent of user location by making the technology invisible and embedded in the natural surroundings. Reaching this goal requires efficient cooperation between heterogeneous networking technologies and different protocols. Wireless personal networks are an integral part of such an emerging heterogeneous infrastructure. It is highly desirable, and in fact required due to economical constraints, to incorporate the present wireless systems in building the new paradigm. The key protocol glue between systems is the use of IP. Based on this scenario, we describe an architecture suited for the present and future personal mobile communications networks and services.

Design and analysis of location management for 3g cellular networks

Location management is a key issue in personal communication service networks to guarantee the mobile terminals to continuously receive services when moving from one place to another. We study two location management schemes, a dynamic movement-based scheme (DYNAMIC-3G) and a static scheme (STATIC-3G), for 3G cellular networks where home location registers, gateway location registers (GLRs), and visitor location registers form a three-level hierarchical mobility database structure. For both schemes, the cost functions are formulated analytically. We prove that there is an optimal movement threshold that minimizes the total cost function of DYNAMIC-3G and propose a binary search algorithm to find the optimal threshold. Furthermore, we present performance evaluation and comparison of the proposed schemes with the previous schemes in 2G cellular networks where the GLR is not present. Our studies validate the optimality of the DYNAMIC-3G scheme and show that the proposed schemes outperform the previous schemes, especially when the remote-local-cost ratio is high. The comparison results between DYNAMIC-3G and STATIC-3G indicate that DYNAMIC-3G should be adopted when the mobility rate is low, and STATIC-3G should be adopted otherwise. Furthermore, DYNAMIC-3G tends to perform better than STATIC-3G when the paging cost is high or the number of cells in a location area is large.

Two-level, multistate Markov model for satellite propagation channels

A new model to provide more states of the Markov model while limiting the size of the Markov transition matrix is proposed to save processing time and reduce memory requirements in predicting the fading statistics and error probability of land mobile satellite systems (LMSS) and satellite personal communication services (S-PCS). Propagation fading is treated as slow fading (or shadowing) and fast fading (or multipath fading). Both of these levels can be separated into several propagation states. Two Markov state transition matrices are introduced to simulate the variation in the strength of the received signal caused by shadowing and multipath fading. Fading statistics and error probability in typical mobile user environments are accurately predicted. The advantage of this new model over the traditional single Markov state transition model is that it can generate more accurate simulation results and help to predict performance. This simple and efficient model extends the application of the Markov process method to propagation channel modelling for LMSS and S-PCS.

Backoff strategies for demand re-registration in PCS database failure recovery

Mobility Databases, Home Location Register (HLR) and Visitor Location Register (VLR), are utilized to support mobility management for Mobile Stations (MSs) in Personal Communications Services (PCS) networks. If the location database fail, the subscribers' services will be seriously degraded due to the loss or corruption of location information. Previous work proposed demand re-registration with a p-persistent backoff strategy and a checkpoint method that demonstrates better performance than the periodic re-registration policy. In demand re-registration, after a VLR fails, it broadcasts a re-registration request to all MSs. Backoff strategies are needed since collisions may occur if all MSs try to re-register after receiving the request. Choosing a good backoff strategy for demand re-registration has several benefits that are our goals in this paper. A better strategy will save the re-registration traffic in terms of signaling cost. Moreover, a better strategy will allow an MS to re-register earlier to reduce the probability that a call termination with expensive paging operations happens earlier than location information recovery. In this paper, we propose and study seven backoff strategies for demand re-registration: one optimal p-persistent strategy, three dynamic p-persistent strategies, and three non-persistent strategies. Among these proposed strategies, the optimal p-persistent strategy is optimal in the sense of optimality among all the p-persistent strategies; the three dynamic p-persistent strategies improve p-persistent strategies by allowing the p-value to change with time; the three non-persistent strategies include a binary exponential backoff strategy, an exponential backoff strategy, and a non-exponential non-persistent backoff strategy; our studies show that they can be approximately equivalent to special dynamic p-persistent strategies. Our studies also show that one of the dynamic p-persistent backoff strategies is the best strategy among all the seven proposed strategies and our results indicate that with better backoff strategies, the performance of demand re-registration can be dramatically improved.

A compact normal walk model for PCS networks

Model-based movement patterns play a crucial role in evaluating the performance of mobility-dependent Personal Communication Service (PCS) strategies. This study proposes a new normal walk model to represent more closely the daily movement patterns of a mobile station (MS) in PCS networks than a conventional random walk model. The proposed walk model uses a drift angle θ to determine the direction in which an MS leaves a hexagonal cell in the next one step. The angle θ is assumed to approach the normal distribution with the parameters: μ = 0° and σ is on the interval [5°; 90°], based on the concept that most trips follow the shortest path, to make the movement patterns more realistic. A compact classification that types cells with side indices is further developed to partition an n-layer cluster of PCS networks into 12 mirror regions; consequently, the number of states can be reduced significantly, and the computational complexity is also reduced in the probability derivation. Two metrics are formulated in experiments to measure the expected and average numbers of steps taken by an MS to move out of an n-layer cluster. Experimental results confirm that for σ = 10°, 30°, 60°, and 90°, the discrepancies between the analytical computations and the simulated values are all within ±0.46%, and most are even within ±0.35%. Moreover, when σ is set to 71°, a normal walk can almost represent, and even replace, a conventional random walk, since the discrepancies between them are all within ±0.71%.

Effect of personal mobility management in mobile communication networks

Personal mobility (PM) is one of the key issues in realizing a personal communications service (PCS) in emerging third-generation mobile communication networks such as IMT-2000. It can be realized through the universal personal telecommunication (UPT) service. Two PM management schemes are proposed to manage PM information related to UPT users for incoming call (incall) registration/deregistration, incall registration reset by a mobile terminal (MT) owner, and incall delivery to UPT users in mobile communication networks based on the location information managed by the user's home network. The relative cost, i.e., the ratio of cost per unit time for supporting both terminal mobility (TM) and PM management to that of TM management, is derived, and the effect of PM management is analyzed from the aspects of update or query cost, signaling delivery cost, and processing cost. These results can be utilized in the implementation of PM management in IMT-2000.

Resource management in LEO satellite networks

To provide truly global coverage needed by increased Personal Communication Services (PCS), a new generation of mobile satellite networks has been proposed. These low Earth orbit (LEO) mobile satellite networks handle multimedia traffic and can be used for non-real-time as well as real-time service to remote areas. Due to the many handoffs, resource management and connection admission control are important tasks for fair bandwidth sharing and QoS guarantees. Because the total link capacity has to be divided among several carriers and given the limited buffer capacity of the ATM switch, resource management is vital. It ensures the ability of the network to provide users with their negotiated QoS while protecting the network and the end-systems from congestion. We introduced a simple connection admission control (CAC) priority policy based on the delay and cell loss requirements for the investigated types of traffic. We took into account the handoff status of the satellite beams involved. Thus, we propose an onboard buffer architecture with separated buffers for new calls and intra-satellite handoff calls. The priority scheme applied is as follows: highest priority is given to CBR, followed by rt-VBR, nrtVBR and ABR.

Narrow passband high-temperature superconducting filters of highly compact sizes for personal communication service applications

A novel highly compact high-temperature superconducting filter based on spiral lumped elements was demonstrated for personal communication system applications. The filter consists of eight-pole microstrip resonators enclosed in a substrate 0.5 /spl times/ 5 /spl times/ 32 mm. The filter was designed to have a bandwidth of 17 MHz and a center frequency of 1760 MHz. A low insertion loss of 0.4 dB in the passband with an out-of-band rejection loss of about -70 dB was observed at 65 K. Measured characteristics of the filter showed good agreement with simulated responses.

Optimal location management for two-tier PCS networks

One of the most important issues in Personal Communication Service (PCS) networks is location management, which keeps track of the Mobile Terminals (MTs) moving from place to place. In this paper, we analytically derive cost functions of location updates and paging for a dynamic movement-based location management scheme for PCS networks with two-tier mobility databases. We prove analytically that there is a unique optimal movement threshold that minimizes the total cost of Home Location Register location updates, Visitor Location Register location updates, and paging, per call arrival. An effective algorithm is proposed to find the optimal movement threshold. Furthermore, we propose a hybrid location management scheme, in which when the call-to-mobility ratio is larger than a threshold, the optimal dynamic movement-based scheme is adopted. Otherwise, the static location update is adopted. The Newton approximation method is adopted to find this threshold. Our study shows that the proposed hybrid scheme outperforms both the dynamic movement-based scheme and the static location update scheme.

Optimal fractional movement-based scheme for PCS location management

In this letter, we propose a fractional movement-based location update scheme for personal communication service networks. Similar to the well-known fractional guard channel scheme for channel assignments, in our proposed scheme, the movement threshold is a real number with a fraction instead of an integer. We prove analytically that there is a unique optimal fractional movement threshold that minimizes the total cost of location updates and paging per call arrival.

Q-Win --- A New Admission and Handoff Management Scheme for Multimedia LEO Satellite Networks

Low Earth Orbit (LEO) satellite networks are deployed as an enhancement to terrestrial wireless networks in order to provide broadband services to users regardless of their location. In addition to global coverage, these satellite systems support communications with hand-held devices and offer low cost-per-minute access cost, making them promising platform for Personal Communication Services (PCS). LEO satellites are expected to support multimedia traffic and to provide their users with the negotiated Quality of Service (QoS). However, the limited bandwidth of the satellite channel, satellite rotation around the Earth and mobility of end-users makes QoS provisioning and mobility management a challenging task. One important mobility problem is the intra-satellite handoff management. The main contribution of this work is to propose Q-Win, a novel call admission and handoff management scheme for LEO satellite networks. A key ingredient in our scheme is a companion predictive bandwidth allocation strategy that exploits the topology of the network and contributes to maintaining high bandwidth utilization. Our bandwidth allocation scheme is specifically tailored to meet the QoS needs of multimedia connections. The performance of Q-Win is compared to that of two recent schemes proposed in the literature. Simulation results show that our scheme offers low call dropping probability, providing for reliable handoff of on-going calls, good call blocking probability for new call requests, while maintaining bandwidth utilization high.

Polarization-adjustable omnidirectional dipole array

The paper presents a unique omnidirectional three-element dipole array that can be adjusted to provide vertical, horizontal, or circular polarization for a variety of wireless applications. The 2:1 voltage standing wave ratio bandwidth of the antenna over all configurations is greater than 10%, but performance data is presented for the personal communication services (PCS) band (1850-1990 MHz).

A method for expressing mobile propagation loss characteristics in a street microcell system

Data from the received signal-level in the personal handy-phone system commercial communication service are used to evaluate a method for expressing mobile propagation loss characteristics. The standard deviation of the difference between the measured signal level and the signal level given by empirical equations is calculated on the basis of a macrocell mode (loss versus direct distance from base station) and a street microcell mode (classified as base-station road and crossed road). The results show that the expression of street microcell mode is better than that of the macrocell mode.

Dynamic location strategy for hot mobile subscribers in personal communications

It is possible to continually receive large numbers of calls in their movements for hot mobile subscribers who are the valued clients in Personal Communications Services (PCS). This paper introduces an efficient location strategy for those hot subscribers in PCS with hierarchical database architecture. The proposed strategy can dynamically adjust the positions of bypass pointers according to the mobility and calling pattern of each user. When a callee moves out of his/her current registration area (RA), our strategy is to calculate a new appropriate position for the caching databases. Then we may adjust the caching databases to the appropriate positions instead of just deleting them, as what is done in Eager-Caching strategy. Simulation results are provided to demonstrate the cost effectiveness of the proposed strategy for hot subscribers under various parameters in comparison with the Basic and Eager-Caching strategies.

무선 이동망을 위한 적응적 분산 동적 위치 관리 알고리즘의 설계 및 평가

미래의 PCS(Personal Communication Service) 네트워크 설계에서 하나의 중요한 문제는 위치 정보의 효율적인 관리이다. 이 논문에서, 우리는 n 위치 정보 데이터베이스들 중에 k개에 이동 단말의 위치를 저장하는 적응적 분산 동적 위치 관리 알고리즘을 제안한다. 제안하는 알고리즘은 무선 이동망 내의 위치 정보 데이터베이스들의 공간 지역성과 원격 이동 단말들로부터 로컬 이동 단말의 위치 질의 선호도에 따라 사본인자, k를 적응적으로 선택한다. 제안하는 알고리즘의 성능을 분석적 모델과 시뮬레이션을 통하여 평가한다. 성능 평가 결과, 호 이동율에 관계없이 제안한 알고리즘의 성능이 Krishnamurthi의 알고리즘에 비해 성능이 우수함을 알 수 있었다. An important issue in the design of future Personal Communication Service (PCS) networks is the efficient management of location information. In this paper, we propose an adaptive distributed dynamic location management algorithm that stores the position of the mobile terminal in k of the n location information databases (LIDs). The proposed algorithm chooses adaptively k. replication factor according to both the space locality of LIDs in wireless mobile networks and the location query popularity to local mobile terminal from remote mobile terminals. The performance of proposed algorithm is evaluated by both an analytical model and a simulation. Based on the results of performance evaluation, we know that the performance of the proposed algorithm is better than that of Krishnamurthi's algorithm regardless of call-mobility ratio.

Distributed call admission control for a heterogeneous PCS network

Personal communication service (PCS) networks offer mobile users multimedia applications with different quality-of-service (QoS) and bandwidth requirements. This paper proposes a distributed call admission algorithm to provide QoS guarantees for multimedia traffic carried in a heterogeneous PCS network, where the parameters (e.g., number of channels, new and hand-off call arrival rates) of cells can be varied. The algorithm is based on the moveable boundary scheme that dynamically adjusts the number of channels for different types of traffic. With the moveable boundary scheme, the bandwidth can be utilized efficiently while satisfying the QoS requirements for different types of traffic. In addition, by taking the effect of hand-off traffic into account, we develop an analytical model for the network using the proposed algorithm. Using our model, the impact of hot-spot traffic caused by hand-offs can be effectively analyzed. The analytical model is validated by simulation.

Electromagnetic Modeling of a Spherical Phantom Head by a Dyadic Green's Function Approach

The accurate modeling of electromagnetic (EM) effects is now an increasingly important design requirement for the advancement of PCS (personal communication services). Also, possible adverse effects of EM fields, especially on the brain and the nervous system, are of increasing concern, particularly with reference to mobile transceivers held close to the head. The spherical head model, while not accurate, provides easy and reasonably effective means for the estimation of the "worst case SAR (specific absorption rate)" either through modeling or experimentation. The purpose of this work is to analyze a model based on a solution of DGF (dyadic Green's function) in spherical coordinates that will describe the field distributions inside a biological head. Numerical results from analytical expressions are computed for the problem of the spherical head model (multilayered homogeneous lossy dielectric spherical model) in close proximity to a dipole antenna and then compared with the results from the same model using the finite-difference time-domain, EMU-FDTD electromagnetic simulator. The medium is assumed to be homogeneous, isotropic, linear, nondispersive, and stationary. A critical evaluation of the method is discussed. The results presented here show that this method correlates well with other techniques.