New metric for analyzing multi-step paging schemes in mobile networks

This paper considers several optimization problems of sequential paging with aggregation mechanism which has been shown to reduce significantly the paging cost of a wireless communication system. An important problem is to find the optimal aggregation factor subject to a constraint on the average paging delay. Another problem is, given a cost function that depends on both paging cost and paging delay, how to find the optimal aggregation factor to minimize that cost function. We have formulated and shown that these can be solved nicely due to the monotonicity and convexity of the average paging cost function and paging delay function. We demonstrate that the optimization problems of the aggregate factor and subnet clustering are not separable. This leads to joint optimization problems of aggregation factor and clustering that are investigated in this paper. The paper presents different algorithms to solve these joint optimization problems using the monotonicity in the aggregation factor and the number of clusters of the average paging cost and delay with the unconstrained optimal clustering and the structures of the constrained optimal clustering.

We consider the problem of minimizing paging cost, subject to delay constraint, in Personal Communication Services Network (PSCN) and present two intelligent paging strategies for third generation systems. They are termed as sequential intelligent paging (SIP) and parallel-o-sequential intelligent paging (PSIP). Unlike the conventional blanket paging where all cells in a location area are polled at a time, in SIP (PSIP) one cell (a group of cells) is polled at a time. The proposed schemes lead to a decrease in paging signaling load at the cost of some extra processing power. When better discovery rate per cycle is expected irrespective of the incoming traffic PSIP is always preferred to other paging schemes primarily because of its less amount of polling delay. If the incoming traffic rate is low, SIP performs better than PSIP in terms of paging cost per cycle. However, the polling costs per cycle and the discovery rates for both the schemes become equal as number of paging requests per cycle increases. An improvement in respect of paging cost per cycle and discovery rate over conventional paging is shown with the help of simulation results.

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.

A cost-effective approach to selective IP paging scheme using explicit multicast

Location management deals with how to track mobile users within the cellular network. It consists of two basic operations: location update and paging. The total location management cost is the sum of the location update cost and the paging cost. Location areas and reporting centers are two popular location management schemes. The motivation for the study is the observation that the location update cost difference between the reporting centers scheme and the location areas scheme is small whereas the paging cost in the reporting centers scheme is larger than that in the location areas scheme. The paper compares the performance of the location areas scheme and the reporting centers scheme under aggregate movement behavior mobility models by simulations. Simulation results show that the location areas scheme performs about the same as the reporting centers scheme in two extreme cases, that is, when a few cells or almost all cells are selected as the reporting cells. However, the location areas scheme outperforms the reporting centers scheme at the 100% confidence level with all call-to-mobility ratios when the reporting cells divide the whole service area into several regions.

In a high-capacity cellular network with limited spectral resources, it is desirable to minimize the radio bandwidth costs associated with paging when locating mobile users. Sequential paging, in which cells in the coverage area are partitioned into groups and paged in a non-increasing order of user location probabilities, permits a reduction in the average radio costs of paging at the expense of greater delay in locating the users. We present a polynomial time algorithm for minimizing paging cost under the average delay constraint, a problem that has previously been considered intractable. We show the conditions under which cluster paging, a simple heuristic technique proposed for use with dynamic location update schemes, is optimal. We also present analytical results on the average delay and paging cost obtained with sequential paging, including tight bounds.

When the cells in a location area are paged sequentially based on the specific information such as last registered area or mobile speed, paging load may be nonuniformly distributed among the cells. This nonuniform paging traffic causes additional paging delay due to the increase of waiting time in the cell with high paging load. In this paper, we introduce a new paging strategy in which the paging sequence in a location area is optimized based on both the location probability of a mobile terminal and paging load distribution among the cells. From numerical results, we show that the paging cost of our proposed scheme is very close to the optimal one. In addition, we observe the effects of the paging load distribution and the location probability distribution on the paging cost.

In this paper, we propose two information-theoretic techniques for efficiently trading off the location update and paging costs associated with mobility management in wireless cellular networks. Previous approaches always attempt to accurately convey a mobile's movement sequence and hence cannot reduce the signaling cost below the entropy bound. Our proposed techniques, however, exploit the rate distortion theory to arbitrarily reduce the update cost at the expense of an increase in the corresponding paging overhead. To this end, we describe two location tracking algorithms based on spatial quantization and temporal quantization, which first quantize the movement sequence into a smaller set of codewords and then report a compressed representation of the codeword sequence. Although the spatial quantization algorithm clusters individual cells into registration areas, the more powerful temporal quantization algorithm groups sets of consecutive movement patterns. The quantizers themselves are adaptive and periodically reconfigure to accommodate changes in the mobile's movement pattern. Simulation study with synthetic and real movement traces for both single-system and multisystem cellular networks demonstrate that the proposed algorithms can reduce the mobile's update frequency to 3-4 updates/day with reasonable paging cost, low computational complexity, storage overhead, and codebook updates.

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.

In sequential paging (SP) schemes, the paging process is considered on a per user basis. When an incoming call reaches a mobile terminal (MT), the associated location area is divided into several paging areas (PAs) and PAs are paged one by one until the MT is found. Even though SP algorithms can reduce the paging cost compared to blanket paging (BP), they introduce extra and unnecessary delay, and are not efficient. We present a pipeline paging (PP) scheme in which multiple paging requests (PRs) can be served in a pipeline manner for different paging areas. We study the proposed scheme via extensive simulations in terms of discovery rate, total delay, and cost under different traffic loads. Our study shows that the PP scheme outperforms both the BP and SP schemes in terms of discover rate and total delay, while maintaining a cost similar to that of the SP scheme. The study also shows that when the paging delay constraint D is as large as 6, the PP scheme achieves almost 171% of the BP's discovery rate and 58% of the BP's cost, whereas the SP's discovery rate is far less than that of the BP scheme.

In wireless mobile networks including vehicular networks, interference on communication links can repeatedly destroy routing paths due to mobility of nodes or sources of interference such as mobile jammers. This results in continual data loss and service interruption. To ensure long-lasting stable data delivery in the presence of interference in mobile environments, we present a resilient routing scheme that avoids high-risk nodes.

We study the performance of the two wireless TCP schemes-the split-connection and the snoop TCP under four rerouting schemes (full rerouting, partial rerouting, cell forwarding and virtual tree rerouting). The wireless TCP schemes are compared based on the source throughput, average round-trip delay and cumulative source disruption time. We analyse the performance of the wireless TCP schemes and their interaction with the rerouting schemes.

Caching frequently accessed data objects at the local buffer of a mobile user (MU) has been found to be very effective in improving information availability in mobile wireless environments. Several mechanisms have been proposed in the literature to address the challenging problem of cache consistency in cellular wireless networks. However, these mechanisms are limited to single cell systems. In this paper, we develop a novel Dynamic Scalable Asynchronous Cache Consistency Scheme (DSACCS) that can adaptively maintain mobile data objects globally or locally depending on the minimum consistency maintenance cost in multi-cell systems. The cost function is derived by taking into account each data object's update frequency, MUs' access pattern and roaming frequency, number of cells and number of MUs in the system. Extensive simulation studies demonstrate that DSACCS outperforms three existing cache strategies extended to multi-cell environments. The three cache consistency strategies are homogeneous invalidation reports (IRs), inhomogeneous IR without roaming check, and inhomogeneous IR with roaming check. Finally, an improvisation of DSACCS, called DSACCS-G, is proposed for grouping cells in order to facilitate effective cache consistency maintenance in multi-cell systems.

An increasing number of mobile users (MUs) share common interests in general information, such as traffic information, weather forecast, and domestic/international news. However, the centralized infrastructure-based system has not been designed for efficiently disseminating the information of common interest (IoCI) to numerous requesters. Thanks to the rapid development of mobile devices equipped with large storage and multiple communication modes, opportunistic communication between a pair of MUs can be readily realized. With the aid of opportunistic networks formed by MUs, we can improve the connectivity of cellular networks in the rural areas, we can offload the tele-traffic from the overloaded cellular networks, and we can efficiently disseminate the IoCI in the densely populated areas. We commence with a detailed survey on the cross-disciplinary research area of social network analysis aided telecommunication networking. We continue by focusing our attention on the family of integrated cellular and large-scale opportunistic networks, whose performance is dominated by the inter-contact duration as well as the contact duration between any pairs of MUs. A continuous-time-pure-birth Markov chain is invoked for analyzing the relevant performance. We demonstrate that the delivery ratio of the IoCI before it expires becomes higher than 90% with the aid of opportunistic networks consisting of 20 MUs. Moreover, our experiments based on the InfoCom 2006 mobility trace show that the opportunistic networks are capable of offloading 58% of the tele-traffic from the cellular networks. Thereafter, we propose a hybrid information dissemination scheme for the integrated cellular and small-scale opportunistic networks, which is comprised of two main stages: 1) the base station-aided single-hop multicast (BSSHM) stage and 2) the cooperative multicast aided spontaneous dissemination stage. In contrast to their large-scale counterparts, in small-scale opportunistic networks, the information dissemination is mainly affected by the mobility of the MUs, by the wireless channel attenuation and by the resource scheduling, where a discrete-time-pure-birth Markov chain is utilized for characterizing the relevant performance. We demonstrate that our hybrid information dissemination scheme outperforms the traditional BSSHM in terms of various delay metrics, despite consuming less energy.

The advancements in semiconductor technologies had a significant impact on the evolution of the mobile networks and the devices. With the advent of smartphones, it is now possible for telephony and VAS to be rendered by platforms which are not a part of the mobile network itself but powered by ‘Over the Top’ players like Whatsapp. The mobile network as it stands today, plays the role of delivering the fat pipe to the mobile users required for these applications. The network itself is lesser involved in delivering VAS to its users. Never the less, we still need a network to serve its mobile users. Is it feasible for a mobile device to communicate with another mobile device bypassing the mobile network for all services and agnostic to the distance between the devices? Staying within the framework of 5G, ‘Device to Device’ communication may be possible but only when the devices are in proximity with each other. It is imperative that we need to explore the feasibility to develop a solution where the devices can communicate and roam in absence of a layer 7 network and remain agnostic to the distance between the devices. If that is possible, we may find a way to replace the existing layer 7 mobile network with just a layer 1 access. The outcome is obvious: ‘A Network-less Network’. The prosaic signalling procedures related to a mobile network, specifically addressing, mobility and location management can be directly actuated by the mobile devices. In this chapter we investigate the viability and practicality of developing and implementing such a network solution.