Paging strategy optimization in personal communication systems

Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network. The total cost of updating and paging can be minimized by optimally dividing the cellular area into location registration (LR) areas. In current systems broadcast paging messages are sent within the LR area to alert the MS of an incoming call. In this paper we propose a selective paging strategy which uses the MS mobility and call patterns to minimize the cost of locating an MS within an LR area subject to a constraint on the delay in locating the MS. This revised version was published online in July 2006 with corrections to the Cover Date.     

One-dimensional location area design

Location management cost in a wireless network is expressed in this work as the sum of signaling cost due to paging and signaling cost due to registration. We introduce and compare a heuristic method and an asymptotic method for selecting a disjoint partition of a one-dimensional service area to minimize location management costs. In special cases for which the best design is known, the asymptotic design rule outperforms the heuristic rule, including cases for which the number of location areas is small. With offered load λ, per-event paging cost P, per-event registration cost R, and fixed traffic patterns, optimal location area edges depend on √λP/R and location management costs are proportional to √λPR     

An intra-LA location update strategy for reducing paging cost

The blanket paging strategy in current mobile networks may waste a lot of wireless bandwidth. While keeping the standard location area (LA) based location update (LU) strategy unchanged, we propose an intra-LA LU scheme to reduce the paging cost. While a mobile terminal (MT) is residing in an LA with a cell called anchor cell, where the MT usually stays for a significant period, an intra-LA LU is performed whenever the MT changes its location between the anchor cell and the rest of cells in the LA. For an incoming call, either the anchor cell or the rest of cells in the LA is paged to locate the MT. Thus the paging cost is greatly reduced, especially when the called MT is located in its anchor cell.     

Location update optimization in personal communication systems

Mobility tracking is concerned with finding a mobile subscriber (MS) within the area serviced by the wireless network. The two basic operations for tracking an MS, location updating and paging, constitute additional load on the wireless network. The total cost of updating and paging can be minimized by optimally dividing the service area into location registration (LR) areas. There are various factors affecting this cost, including the mobility and call patterns of the individual MS, the shape, size and orientation of the LR area, and the method of searching for the MS within the LR area. Based on various mobility patterns of users and network architecture, the design of the LR area is formulated as a combinatorial optimization problem. The objective is to minimize the location update cost subject to a constraint on the size of the LR area. This revised version was published online in July 2006 with corrections to the Cover Date.     

A simple analytical framework for location management in personalcommunication systems

Efficient mobility management for portable stations (PS's)-handoff, channel assignment and locating-will play an important role in future personal communication systems (PCS's). Among these tasks, location management plays a critical role for wide-area roaming. The key elements of locating are location registration/updating and paging. Due to the smaller cell size in PCS, the high boundary crossing rate of PS will result in more frequent location area (LA) updating. This, in turn, will result in more interrogations with location registers, which will generate a higher volume of access and signaling traffic (SS7 traffic). One solution to this problem is to increase the size of LA, which, unfortunately, also increases paging traffic. Efficient paging algorithms may generate relatively less paging traffic such that larger LA's may become plausible. Depending on the call-arrival rate to the cell, boundary crossing rate, optimum size of LA, and paging technique used, the overall cost could vary substantially. The paging techniques considered in this paper are simultaneous paging and sequential paging. The two schemes are studied in detail in order to understand the problems associated with location management in the PCS environment. In the authors' opinion, this paper provides, for the first time, a simple yet powerful analytical framework which can be used to analyze “intelligent” paging schemes as well as simultaneous and sequential paging     

Non-Blocking Pipeline Paging with Known Location Probabilities for Wireless Systems

Paging schemes for wireless systems have been well studied in the literature. However, most schemes are considered on per user basis. In these schemes, when an incoming call arrives at a mobile terminal (MT), a paging request (PR) is put in a queue. PRs are served in an FIFO manner. When a PR is served, a search process is carried out to find the corresponding MT in a location area (LA). Most schemes study how to achieve a better performance in terms of cost with/without delay constraints per PR, and totally ignore other PRs in the queue until the MT is found or all the cells in the LA have been paged. In this paper, we propose a non-blocking pipeline probability paging scheme, which assumes known knowledge on location probabilities of individual MTs, under a paging delay constraint, where the location probability of an MT in a cell is the probability that the MT is in the cell. The proposed scheme is independent of the number of PRs in the queue and the arrival rate of PRs. Our study shows that the proposed scheme outperforms both the sequential probability paging scheme with known knowledge on location probabilities of individual MTs and the blanket paging scheme in terms of discovery rate and the total delay. Finally, we study several optimization problems with quality of service constraint for the pipeline probability paging scheme.     

A crossing-tier location update/paging scheme in hierarchical cellular networks

Location update/paging strategies have been widely studied in the traditional single-tier cellular networks. We propose and evaluate a novel crossing-tier location update/paging scheme that can be used in a hierarchical macrocell/microcell cellular network. Location update is proceeded only in the macrocell tier, where a location area (LA) is made up by larger macrocells. A mobile user will stay in such a LA for longer time. Therefore, the cost on location update can be reduced due to the decreased frequency of location update. To reduce the paging delay, the paged mobile user will be searched in the macrocell tier only when the paging load is not high. Otherwise, it will be searched in the microcell tier, where a sequential searching method is applied. The operation for the scheme is simple, as the macrocell/microcell cellular network has the advantage because a mobile user can receive a signal from both a microcell and the overlaid macrocell. Analytical models have been built for cost and delay evaluation. Numerical results show that, at relatively low cost, the crossing-tier scheme also achieves low paging delay.     

Mobile user location update and paging under delay constraints

Wireless personal communication networks (PCNs) consist of a fixed wireline network and a large number of mobile terminals. These terminals are free to travel within the PCN coverage area without service interruption. Each terminal periodically reports its location to the network by a process calledlocation update. When a call for a specific terminal arrives, the network will determine the exact location of the destination terminal by a process calledterminal paging. This paper introduces a mobile user location management mechanism that incorporates a distance based location update scheme and a selective paging mechanism that satisfies predefined delay requirements. An analytical model is developed which captures the mobility and call arrival pattern of a terminal. Given the respective costs for location update and terminal paging, the average total location update and terminal paging cost is determined. An iterative algorithm is then used to determine the optimal location update threshold distance that results in the minimum cost. Analytical results are also obtained to demonstrate the relative cost incurred by the proposed mechanism under various delay requirements.     

Markov mobility model and registration area optimization in cellular networks

In cellular communication systems, in order for a network to keep track of inactive mobile stations (MSs), each inactive MS has to update its location from time to time, called location registration. To lighten the task of tracking inactive MSs, the network divides its cells into groups, called location areas (LAs) and tracks inactive MSs at the LA level: an inactive MS sends a registration message to the network to update its location only when it travels to a new LA. Obviously, the performance of a location area design depends on network traffic and the mobility of MSs. In the paper, we propose a general Markov mobility model for MSs in cellular networks, provide a procedure to automatically estimate the system parameters according to the network traffic, derive the performance of LA design, and provide a clustering algorithm to optimize LA designs. A numerical example is provided to show the effectiveness of the proposed procedures. Copyright © 2009 John Wiley & Sons, Ltd.     

A Combination of Optimal Partitioning and Location Prediction to Assist Paging in Mobile Cellular Networks

The correlated both in space and time user mobility behavior can aid significantly in the localization of a moving terminal in the network coverage area. However, there is always some uncertainty in mobile user position and a network-wide search cannot be done. Therefore, a predictive paging scheme must always be combined with a location update strategy and a compatible algorithm to conduct the search. In this paper, we introduce a new strategy that combines an optimal partitioning of the location area (LA) with a model to predict user movements, based on the additional information of the cell where the last interaction between the network and the terminal took place. We study the performance of the strategy under delay bounds and different mobility and call arrival characteristics. It is found that the new scheme further minimizes signaling costs and enhances previous sequential paging algorithms.     

A cost effective distributed location management strategy for wireless networks

The mobility feature of mobile stations (MSs) imposes a large burden on network traffic control as a result of location management. Design issues of location management include MS registration (updating) and call setup (paging). Previous approaches introduced several network topologies for updating and paging procedures, but most of them focused on a single problem: either updating optimization or paging optimization. In this paper, we design and integrate two mechanisms, distributed temporary location caches (TLCs) and distributed home location registers (HLRs), to reduce database access delay and to decrease network signaling traffic in both updating and paging for low power, low tier micro cellular systems. By using TLCs, our approach can improve the performance of updating and paging in comparison with previous approaches. Experimental results based on our analytic model show that our location management procedures have lower HLR access rate, lower registration cost, and lower call setup cost than other approaches.     

On optimum timer value of area and timer-based locationregistration scheme

In typical mobile communication systems, mobile station (MS) location information is updated when the MS crosses the location area boundary or the registration timer is expired. When a call attempt occurs, sequential paging rather than blanket paging is used to reduce the paging cost. We propose a new location update scheme in which to increase the paging accuracy, timer-based location update is performed within a location area. In this work, the optimum timer value of the area and timer-based location registration scheme with intelligent paging is derived. In case of a fixed location area, the optimum registration timer value depends on the speed and call arrival rate of the MS. If the speed or call arrival rate of the MS is high, location registration based on timer value should be performed frequently. Otherwise, location registration based on the crossing of location area is sufficient     

A novel location management scheme for cellular overlay networks

In Beyond Third Generation (B3G) wireless communications, multiple overlays of wireless access networks may cooperate to allow a user access to novel services, the future demands of which will significantly increase the load on location management systems within the networks. In this paper, we introduce the reader to our novel proposals for providing efficient Mobile Terminal (MT) Location Discovery and Paging across an inter-worked network consisting a Digital Video Broadcast (DVB) network and Universal Mobile Telecommunication System (UMTS) network. We further present numerical and simulation analyzes of our scheme. The numerical and simulation results allow broadcast and cellular network operators to configure their inter-worked system to reduce location management and paging costs whilst controlling average latency. Our results demonstrate that our UMTS LA plus DVB paging schemes offer promise for efficient MT discovery in an inter-network environment that includes uni-directional broadcast network such as DVB; under realistic scenarios we achieve a minimum 4 times reduction in paging cost across the inter-network compared with independent paging systems. Furthermore, we briefly introduce further aspects of research that must be addressed in order to fully evaluate our proposals.     

Paging and Registration in Cellular Networks: Jointly Optimal Policies and an Iterative Algorithm

This paper explores optimization of paging and registration policies in cellular networks. Motion is modeled as a discrete-time Markov process, and minimization of the discounted, infinite-horizon average cost is addressed. The structure of jointly optimal paging and registration policies is investigated through the use of dynamic programming for partially observed Markov processes. It is shown that there exist policies with a certain simple form that are jointly optimal. An iterative algorithm for policies with the simple form is proposed and investigated. The algorithm alternates between paging policy optimization, and registration policy optimization. It finds a pair of individually optimal policies. Majorization theory and Riesz's rearrangement inequality are used to show that jointly optimal paging and registration policies are given for symmetric or Gaussian random walk models by the nearest-location-first paging policy and distance threshold registration policies.     

Dynamic multi-step paging scheme in PMIPv6-based wireless networks

In Proxy Mobile IP (PMIPv6) networks, proxy-registrations are performed even for idle MNs, resulting in unnecessary signaling traffic. Although there have been many IP paging techniques aimed at reducing the unnecessary location update, they focus only on Mobile IP (MIP) since they had been developed before PMIPv6 was proposed. Thus, adopting existing IP paging support is not sufficient to support mobility in PMIPv6 networks. For more efficient support, we propose a dynamic multi-step paging scheme that pages an MN in multiple incremental steps instead of flooding paging messages to a whole paging area to significantly reduce the signaling traffic caused by the proxy location updates in the PMIPv6 networks. In addition, to improve the paging delay performance that may be deteriorated by the multi-step paging, the proposed scheme configures paging area dynamically to raise the efficiency of locating MNs. The size of a paging area is designed to be determined based on the speed of an MN. We also develop a thorough analytical model for evaluating the performance of the proposed scheme compared with a static paging scheme in terms of the signaling cost and the paging delay. Thorough analysis and simulation demonstrate that in the PMIPv6 network, our paging scheme can significantly reduce the signaling cost for IP paging, achieving a shorter paging delay, compared to that of a paging scheme with a fixed paging area.     

GSM网小区寻呼丢弃优化方法

小区寻呼丢弃数量不仅是衡量网络性能的重要指标之一,同时与用户感受密切相关。GSM网寻呼丢弃量与网络寻呼策略、LA（位置区）寻呼容量、寻呼组设置、业务分担参数设置等因素息息相关。主要针对造成寻呼丢弃的多种原因分析,并结合实际优化案例说明通过LA分裂、对MFRMS（寻呼信道复帧数）参数及T3314参数调整均能够有效改善小区寻呼拥塞从而降低寻呼丢弃数量,对全网寻呼成功率的提高也有一定效果。     

Design of location areas with QoS considerations in a cellular network

In this paper, we present a location area (LA) planning model which explicitly has more QoS-conscious constraints than any other models. In order to specify an acceptable level of QoS, paging delay time (PDT) and paging blocking rate (PBR) are introduced. The paging process is described by the M/M/c/K queuing system and queuing analysis is carried out to obtain PDT and PBR. Also, in the proposed model, the time-varying call arrival rates are used to define the paging load on each cell, which helps to reflect the pattern of incoming calls more precisely and subsequently to improve the QoS level. To evaluate the proposed model, some examples are solved along with the average rate model and the peak rate model. The results show that the proposed model has the capability to maintain the acceptable level of QoS with the reasonable location management cost, compared to other models. Also, the sensitivity analysis is performed to see the effect of PDT and PBR in the formulation and it turns out that both PBR and PDT are important elements of the QoS measure and influential to the location management cost.     

P-MIP: Paging Extensions for Mobile IP

As the number of Mobile IP users grows, so will the signalling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signalling overhead and optimize the mobility management performance. Currently, Mobile IP supports registration but not paging. In this paper, we argue that Mobile IP should be extended to support paging to improve the scalability of the protocol to handle large populations of mobile devices. To address this, we introduce P-MIP, a set of simple paging extensions for Mobile IP, and discuss the construction of paging areas, movement detection, registration, paging and data handling. We present analysis and simulation results for Mobile IP with and without paging extensions, and show that P-MIP can scale well supporting large numbers of mobile devices with reduced signalling under a wide variety of system conditions.     

Distributed paging and registration in wireless networks

The success of current and future wireless networks depends on their ability to provide connections to mobile terminals anywhere and at any time. It is therefore of crucial importance that wireless networks are able to quickly and efficiently locate mobile users at the time of an incoming call, which is achieved in current networks through a combination of paging and registration. In this article we present novel distributed paging and registration procedures that are naturally suited to future distributed wireless network architectures. In addition, the distributed nature of these strategies allows us to effectively balance the paging and registration traffic and the required signal processing throughout the network and alleviate any potential overloads of individual base stations.     

IP Paging Service for Mobile Hosts

In wireless networks, mobile hosts must update the network with their current location in order to get packets delivered. Paging facilitates efficient power management at the mobile host by allowing the host to update the network less frequently at the cost of providing the network with only approximate location information. The network determines the exact location of a mobile host through paging before delivering packets destined to the mobile host. In this paper, we propose the concept of paging as an IP service. IP paging enables a common infrastructure and protocol to support the different wireless interfaces such as CDMA, GPRS, wireless LAN, avoiding the duplication of several application layer paging implementations and the inter-operability issues that exist today. We present the design, implementation, and detailed qualitative and quantitative evaluation, using measurements and simulation, of three IP-based paging protocols for mobile hosts.