Privileged Treatment of UMTS Subscribers in GSM Networks

Different user segments have various requirements and expectations towards the performance of mobile networks. Subscribers having experienced the high quality of UMTS networks desire to maintain high speech quality and excellent data throughput also in areas of missing UMTS but existing GSM coverage. In GSM networks a privileged treatment of UMTS subscribers by means of proper resource allocation provides a substantial quality improvement with respect to standard GSM subscribers. This strategy allows network operators to reduce the performance gap between both network areas experienced by UMTS subscribers. A detailed study on the performance of circuit switched speech and packet data services has been performed based on system level simulations. The results show significant speech quality advantages for users with dual-RAT terminals compared to standard GSM users as well as notably higher data throughput rates.     

A profile-based strategy for managing user mobility in third-generation mobile systems

Several strategies have been proposed recently to improve the performance of the location management scheme in mobile systems, the influence of mobility on network performance must be reduced, mainly due to the huge number of mobile hosts in conjunction with the small cell size. In this article we present a profile-based strategy (PBS) to reduce location update signaling cost by increasing the intelligence of the location procedure. This strategy associates with each user a list of cells where she is likely to be at a given probability in each time interval. The implementation of this strategy has been subject to extensive evaluation. The results obtained confirm the effectiveness of PBS in significantly reducing the costs of both location updates and call delivery procedures when compared to IS-41 and other well-known strategies in the literature.     

Cell Identification Codes for Tracking Mobile Users

The minimization of the wireless cost of tracking mobile users is a crucial issue in wireless networks. Some of the previous strategies addressing this issue leave an open gap, by requiring the use of information that is not generally available to the user (for example, the distance traveled by the user). For this reason, both the implementation of some of these strategies and the performance comparison to existing strategies is not clear. In this work we propose to close this gap by the use of Cell Identification Codes (CIC) for tracking mobile users. Each cell periodically broadcasts a short message which identifies the cell and its orientation relatively to other cells in the network. This information is used by the users to efficiently update their location. We propose several cell identification encoding schemes, which are used to implement different tracking strategies, and analyze the amount of information required by each tracking strategy. One of our major results is that there is no need to transmit a code which is unique for each cell. For example, a 3 bits CIC is sufficient to implement a distance-based tracking strategy in a two-dimensional system. In addition, we propose a combination of timer and movement tracking strategy, based on either a one-bit or a two-bit CIC, depending on system topology and user mobility. An important property of our framework is that the overall performance cost, and hence its comparison to existing methods, is evaluated for each tracking strategy. The CIC-based strategies are shown to outperform the geographic-based method currently used in existing networks, and the timer-based method, over a wide range of parameters. Moreover, this superiority increases as the number of users per cell increases.     

Numbering and addressing in IBCN for mobile communications

Numbering and addressing issues arising in the integrated broadband communication network (IBCN) for the support of the Universal Mobile Telecommunication System (UMTS) and Personal Telecommunication Service (PTS) are discussed. Mobile communications services will allow a user to roam within a network. Thus, there will be a need to identify several types of objects (terminals, network points of attachment, users, customers premises networks or CPN, etc.). The mobility properties of these objects will necessitate dynamic bindings between their addresses and names. The situation is further complicated because the mobility may be embedded. A mobile user may employ a mobile terminal in a mobile CPN. Therefore, in UMTS and PTS there is a need for dynamic binding of various identifiers with location information data. The exclusive use of personal telecommunication numbers (PTNs) as dialing numbers (DNs) is proposed in IBCN for UMTS and PTS. That is, PTNs will be used (during dialing) for making calls to mobile terminals, mobile users, and fixed subscribers. When the personal communication service is not provided, the DN corresponds to the terminal number of the equipment (fixed or mobile) of the called subscriber     

Mobile users: To update or not to update?

Tracking strategies for mobile users in wireless networks are studied. In order to save the cost of using the wireless links mobile users should not update their location whenever they cross boundaries of adjacent cells. This paper focuses on three natural strategies in which the mobile users make the decisions when and where to update: the time-based strategy, the number of movements-based strategy, and the distance-based strategy. We consider both memoryless movement patterns and movements with Markovian memory along a topology of cells arranged as a ring. We analyze the performance of each one of the three strategies under such movements, and show the performance differences between the strategies.The work of this author was done when he was with IBM, T.J. Watson Research Center, Yorktown Heights, NY, USA.Part of the work of this author was done when he was visiting IBM, T.J. Watson Research Center, Yorktown Heights, NY, USA.     

Vertical Handover Over Intermediate Switching Framework: Assuring Service Quality for Mobile Users

Ensuring quality of service (QoS) for the mobile users during vertical handover between IEEE 802.11 wireless local area networks (WLAN) and data network provided by Ultramodern Telecommunication Systems (UMTS) is one of the key requirements for seamless mobility and transfer of existing connections from one network to another. QoS fulfillment is a complex problem and requires participation of both the mobile users as well as the connection networks. The QoS assurance criteria for existing connections can be affected by fluctuations of data rates when a user moves from the high speed WLAN network to the low speed UMTS network, even in the presence of another WLAN network in its vicinity. This can happen if the alternate WLAN network is highly loaded. Therefore handover from a high speed network to a low speed network should be avoided, whenever possible. This paper proposes a QoS based handover procedure that prioritizes the existing connection over the new connections so that rate fluctuations due to handover can be avoided if there exist another WLAN network in the range of the mobile user. Whenever the possibility of handover is detected, a pre-handover bandwidth reservation technique is used to reserve bandwidth at the alternate WLAN networks to avoid QoS degradation. The proposed scheme is implemented in Qualnet network simulator and the performance is analyzed and compared with traditional handover techniques.     

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.     

Functional models of UMTS and integration into future networks

The universal mobile telecommunication system (UMTS) will implement terminal mobility and a form of personal mobility limited to UMTS. The most essential procedures to provide this are related to user registration, location management, handover and security. These mobility procedures are specified using specific functional models. In these models, the required functions are identified and the distribution of the functions in the network is anticipated. In a next step, the specific models are mapped onto a generic functional model. This generic model can be considered as the integration and unification of the specific models. Its structure reflects two important implementation aspects. First, the integration of UMTS into future networks for fixed telecommunications is anticipated. Secondly, the application of the intelligent network architecture for the implementation of the UMTS mobility procedures and service provision is assumed     

Flexible Universal Networks—A New Approach to Telecommunication Services?

GPRS, WLAN integration, Mobile Number Portability and UMTS are some of the new technologies which are foreseen to carry many new service applications. In the near future, it is expected that mobile networks will go beyond connecting people and will connect an increasing number of machines, appliances, consumer devices, sensors and actuators. Also, users will connect through personal area networks and the importance of user profiles and service profiles will grow. Given the current strictness of network design, those services will further increase the complexity of today's networks. The reason is established design principles, which require new, dedicated network elements for new service applications. In addition, the applications contain their own subscriber data, usually stored locally in the application's database (distributed across the network), managed from their own management systems and with their own interfaces to Subscriber Care and Accounting Systems. In current designs, databases like home location register, AAA-Servers, MMS, Number Portability and others keep a significant amount of identical data that have to be kept consistent across all applications. For Network Operators, the effort to plan, to administrate and to introduce new services in those networks increases dramatically. This paper presents a concept to simplify current and future telecommunication networks. The concept contains a number of measures that complement each other but can be implemented independently one from another. In addition, a Telco project is presented (Evolute) where some of the ideas presented in the paper have been implemented.     

Enhanced distance-based location management of mobile communication systems using a cell coordinates approach

In managing the locations of mobile users in mobile communication systems, the distance-based strategy has been proven to have better performance than other dynamic strategies, but is difficult to implement. A simple approach is introduced to implement the distance-based strategy by using the cell coordinates in calculating the physical distance traveled. This approach has the advantages of being independent of the size, shape, and distribution of cells, as well as catering for the direction of movement in addition to the speed of each mobile terminal. An enhanced distance-based location management strategy is proposed to dynamically adjust the size and shape of location area for each individual mobile terminal according to the current speed and direction of movement. It can reduce the location management signaling traffic of the distance-based strategy by half when mobile terminals have predictable directions of movement. Three types of location updating schemes are discussed, namely, Circular Location Area, Optimal Location Area, and Elliptic Location Area. Paging schemes using searching techniques such as expanding distance search based on the last reported location and based on the predicted location, and expanding direction search are also explored to further reduce paging signal traffic by partitioning location areas into paging areas.     

Analysis and Comparison of Location Strategies for Reducing Registration Cost in PCS Networks

In mobile environments, a personal communication service (PCS) network must keep track of the location of each mobile user in order to correctly deliver calls. A basic scheme used in the standard IS-41 and GSM protocols is to always update the location of a mobile user whenever the mobile user moves to a new location. The problem with this approach is that the cost of location update operations is very high especially when the mobile user moves frequently. In recent years, various location management strategies for reducing the location update cost have been proposed. However, the performance issue of these proposed algorithms remains to be investigated. In this paper, we develop two Markov chains to analyze and compare the performance of two promising location update strategies, i.e., the two location algorithm (TLA) and the forwarding and resetting algorithm (FRA). By utilizing the Markov chain, we are able to quickly answer what-if questions regarding the performance of PCS networks under various workload conditions and also identify conditions under which one strategy can perform better than the others. Using the cost due to location update and search operations between two successive calls to a mobile user as a performance measure, we show that when the mobile user exhibits a high degree of locality and the mobile user's call-to-mobility ratio (CMR) is low, TLA can significantly outperform both FRA and IS-41. On the other hand, when CMR is high, FRA is the winner. Furthermore, unlike TLA which may perform worse than IS-41 at high CMR values, FRA at identified optimal conditions can always perform at least as good as IS-41, suggesting that FRA over TLA should be used as a generic scheme in reducing the location cost in the PCS network to cover all possible per-user CMR values.     

X‐Region: A framework for location privacy preservation in mobile peer‐to‐peer networks

While enjoying various LBS (location‐based services), users also face the threats of location privacy disclosure. This is because even if the communications between users and LBS providers can be encrypted and anonymized, the sensitive information inside LBS queries may disclose the exact location or even the identity of a user. The existing research on location privacy preservation in mobile peer‐to‐peer (P2P) networks assumed that users trust each other and directly share location information with each other. Nonetheless, this assumption is not practical for most of the mobile P2P scenarios, for example, an adversary can pretend to be a normal user and collect the locations of other users. Aiming at this issue, this paper presents x‐region as a solution to preserve the location privacy in a mobile P2P environment where no trust relationships are assumed amongst mobile users. The main idea is to allow users to share a blurred region known as x‐region instead of their exact locations so that one cannot distinguish any user from others inside the region. We propose a theoretical metric for measuring the anonymity property of x‐region, together with three algorithms for generating an x‐region, namely, benchmark algorithm, weighted expanding algorithm, and aggressive weighted expanding algorithm. These algorithms achieve the anonymity and QoS requirements with different strategies. Our experiments verify the performance of the algorithms against three key metrics. Copyright © 2013 John Wiley & Sons, Ltd.     

密集网络中基于拓扑信息的用户调度与干扰管理

随着未来移动通信网络的密集化,如何利用少量的信道信息有效管理小区间干扰成为一个重要而又棘手的问题。本文面向密集多小区多用户单天线和多天线网络,研究利用拓扑信息协调小区间干扰的传输策略。为了解决不同小区多用户调度间的冲突,把用户调度与干扰管理收发机设计进行统一建模,基于统一模型引入潜在冲突图,并利用潜在冲突图进行拓扑干扰管理,提出了占用系统资源最少的传输策略。仿真结果表明,与先进行用户调度再协调小区间干扰的方法相比,所提出的方法在用户平均数据率和边缘用户数据率方面都能够获得显著的性能增益。      

Intelligent paging strategies for third generation mobiletelecommunication systems

Location management procedures, in conjunction with the millions of users expected to subscribe to third generation mobile telecommunication systems, will generate a huge signaling load. In this paper, we propose a method which aims at the reduction of signaling overhead on the radio link produced by the paging procedure. The key idea is the application of a multiple step paging strategy which operates as follows: at the instance of a call terminating to a mobile user who roams within a certain location area, paging is initially performed in a portion of the location area (the paging area) that the so-called “paging related information” indicates. On no paging response, the mobile user is paged in the complementary portion of the location area-this phase can be completed in more than one (paging) step. Various “paging related information” elements (e.g. recent interaction information, high mobility flag, etc.) can be used and several “intelligent” paging strategies can be defined. Representative paging strategies are analyzed in terms of network performance and quality of service (paging signaling, paging delay, processing power requirements), via a simulation tool which models a realistic city area environment     

Locating strategies for personal communication networks, a noveltracking strategy

The partition of location areas is designed to minimize the total costs of finding users' location and tracking their movement in personal communication networks (PCNs). A new scheme to partition and track mobile users and its implementation based on cellular architecture are proposed. According to the tracking strategy, the mobile station (MS) transmits only update messages at specific reporting cells, while the search for a mobile user is done at the vicinity of the cell to which the user has just reported. We use the cost analysis model to demonstrate the feasibility of updating and searching costs to reduce the amount of resources when using wireless channels. Simulations are performed to compare the performance of three schemes: always update, always search, and our new scheme     

Agent-Based Forwarding Strategies for Reducing Location Management Cost in Mobile Networks

An important issue in location management for dealing with user mobility in wireless networks is to reduce the cost associated with location updates and searches. The former operation occurs when a mobile user moves to a new location registration area and the network is being informed of the mobile user's current location; the latter operation occurs when there is a call for the mobile user and the network must deliver the call to the mobile user. In this paper, we propose and analyze a class of new agent-based forwarding schemes with the objective to reduce the location management cost in mobile wireless networks. We develop analytical models to compare the performance of the proposed schemes with existing location management schemes to demonstrate their feasibility and also to reveal conditions under which our proposed schemes are superior to existing ones. Our proposed schemes are particularly suitable for mobile networks with switches which can cover a large number of location registration areas.     

Information-Theory Based Optimal Location Management Schemes for Integrated Multi-System Wireless Networks

In a multisystem environment where a mobile node can utilize multiple interfaces and simultaneously connect to multiple providers, new opportunities exist for efficient location management strategies spanning heterogeneous cellular wireless networks. In this paper, an integrated framework is developed for location management in such a multi-system, fourth generation (4 G) wireless networks. This information-theoretic framework allows each individual sub-system to operate fairly independently, and does not require the knowledge of individual sub-network topologies. An efficient location management in such a loosely coupled network is designed by having a mobile node view its movement as a vector-valued sequence, and then transmit this sequence in an entropy coded form to the network. We demonstrate how an intelligent, integrated paging strategy must consider the joint residence probability distribution of a mobile node in multiple sub-networks. We prove that the determination of an optimal paging sequence is NP-complete, and also propose an efficient greedy heuristic to compute the paging sequence, both without and with bounds on the paging delay. Three different location tracking strategies are proposed and evaluated; they differ in their degrees of centralized control and provide tradeoff between the location update and paging costs. Simulation experiments demonstrate that our proposed schemes can result in more than 50% savings in both update and paging costs, in comparison with the basic movement-based, multi-system location management strategy.     

An efficient approach for DVB-H handover in DVB-H/UMTS hybrid networks

Handover in Digital Video Broadcasting for Handhelds （DVB-H） aims to provide continuous mobile broadcasting services when a user is traveling through cell boundaries. A good handover control can improve the power efficiency and gain much better reception quality. This letter provides a novel approach for DVB-H handover based on DVB-H/Universal Mobile Telecommunications System （UMTS） hybrid network, which moves the main handover function from the terminals to the networks, so that it reduces the operation complexity of the terminals and increases the power saving. When the terminal can not receive the DVB-H signal in the transmission shadow areas or because of some other reasons, the UMTS networks may offer the same service to users to make the service continuous. As the UMTS networks have the topology of the DVB-H networks, by communicating with the terminals, the UMTS networks can help the terminals to predict the handover, and avoid unnecessary handover.     

HLR Replication Protocols for Global Mobility Management in PCS Networks

The new trend for PCS networks is to provide mobile users with large-scalemobile capability across many service areas. In this scenario, global databasemanagement for PCS networks has become an increasingly important researchissue.In this paper, we examined two replicated database strategies,single-replica (SR) and multiple-replica (MR), for large-scalemobility of per-user data management in personal communicationnetworks. The SR strategy uses a single replica approach of HLR.The MR strategy replicates the per-user data of HLR in manyregions. The two strategies are based a partial replicationscheme, and a primary copy method is used to maintain replicas'consistency. Our numerical results show that the MR strategyoutperforms the SR strategy in most situations; however, it may beworse when the probability of a mobile user visiting a foreignregion is high and the query rates from other foreign regions arelow. Additionally, the number of replicas should be compact in theMR strategy in order to achieve a reasonable query response time.Therefore, we propose an adaptive multiple replication protocol tochoose a suitable replication strategy and to decide the optimizednumber of replicas.