Mobile User Tracking Research Articles

Low-Complexity Mobile User Tracking in Quantized mmWave MIMO Systems

Low-Complexity Mobile User Tracking in Quantized mmWave MIMO Systems

UAV-Assisted Communications in SAGIN-ISAC: Mobile User Tracking and Robust Beamforming

UAV-Assisted Communications in SAGIN-ISAC: Mobile User Tracking and Robust Beamforming

Photonic Delay Processing With Centralized Etalon Cascade for Radio Beamsteering in Simplified 2 × 5 Phased-Array Radio Heads

The adoption of beam-centric radio communication schemes calls for efficient methods of beamforming with multi-element antennas. We present a delay generation method that employs a shared and centralized cascade of Gires-Tournois etalons for element-by-element radio frequency beamsteering at remote radio heads, thus adding no complexity at the antenna site. We experimentally demonstrate beamsteering of up to 32° in combination with a 2 × 5 phased-array antenna operated at a radio carrier frequency of 3.5 GHz and transmitting 64-ary quadrature amplitude modulated, orthogonal frequency division modulated radio signals. The radio transmission performance over mobile optical fronthaul and free-space radio propagation is evaluated through offline error vector magnitude estimation and real-time transmission of high-definition video traffic. We further show carrier phase switching at 2 kHz using direct emission frequency modulation of the involved optical light sources, proving the proposed concept to support the fast tracking of mobile users.

A takeover time-driven adaptive evolutionary algorithm for mobile user tracking in pre-5G cellular networks

Cellular networks are one of today’s most popular means of communication. This fact has made the mobile phone industry subject to a huge scientific and economic competition, where the quality of service is key. Such a quality is measured on the basis of reliability, speed and accuracy when delivering a service to a user no matter his location or behaviour are. This fact has placed the users’ tracking process among the most difficult and determining issues in cellular network design. In this paper, we present an adaptive bi-phased evolutionary algorithm based on the takeover time to solve this problem. The proposal is thoroughly assessed by tackling twenty-five real-world instances of different sizes. Twenty-eight of the state-of-the-art techniques devised to address the users’ mobility problem have been taken as the comparison basis, and several statistical tests have been also conducted. Experiments have demonstrated that our solver outperforms most of the top-ranked algorithms.

High-Dimensional Probabilistic Fingerprinting in Wireless Sensor Networks Based on a Multivariate Gaussian Mixture Model.

The extensive deployment of wireless infrastructure provides a low-cost way to track mobile users in indoor environment. This paper demonstrates a prototype model of an accurate and reliable room location awareness system in a real public environment in which three typical problems arise. Firstly, a massive number of access points (APs) can be sensed leading to a high-dimensional classification problem. Secondly, heterogeneous devices record different received signal strength (RSS) levels because of the variations in chip-set and antenna attenuation. Thirdly, APs are not necessarily visible in every scanning cycle leading to missing data issue. This paper presents a probabilistic Wi-Fi fingerprinting method in a hidden Markov model (HMM) framework for mobile user tracking. To account for spatial correlation of the signal strengths from multiple APs, a Multivariate Gaussian Mixture Model (MVGMM) was fitted to model the probability distribution of RSS measurements in each cell. Furthermore, the unseen property of invisible AP was investigated in this research, and demonstrated the efficiency as a beneficial information to differentiate between cells. The proposed system is able to achieve comparable localisation performance. Filed test results achieve a reliable 97% localisation room level accuracy of multiple mobile users in a real university campus Wi-Fi network.

Mobile user tracking system with ZigBee

In the paper an implementation of mobile nodes tracking system based on ZigBee and Wi-Fi wireless networks is presented. On the base of known algorithmic as well as circuit solutions a simple yet universal system, applied in prototype application dedicated for person's localization in museum premises has been developed. Since system utilizes entirely wireless communication, it can be applied in any closed objects. The system has been preliminarily verified in real in-situ environment.

Entropy-based location management in long-term evolution cellular systems

The recently emerging location-based services in long-term evolution (LTE) systems require the accurate and efficient tracking of mobile users. An optimal information-theoretic framework is developed for tracking area update (TAU) for next-generation LTE cellular systems. Shannon's entropy is used to characterise the location uncertainty of the mobile users. Based on this entropy-based tracking framework, two practical location management schemes, Bayesian-based TAU and entropy-coding based TAU, are proposed. The proposed schemes capture the users' mobility patterns online and perform profile-based paging to optimise the TAU cost. Of the two proposed schemes, the Bayesian-based TAU operates as an independently identically distributed process and improves the paging cost with less storage and computational overhead, whereas the entropy-coding-based TAU using the Lempel'Ziv strategy asymptotically minimises both the update and paging costs with higher storage and computational overheads than the Bayesian-based one. There is some trade-off between the update/paging costs and storage/computational overheads in the two proposed schemes. The simulation results demonstrate that both proposed schemes outperform the existing comparable schemes for LTE systems in all of the performance metrics.

Efficient security policy enforcement for the mobile environment

In the last decade, mobile communication has enjoyed unprecedented growth all over the world. The recent advances in mobile communication technologies including Global Positioning System (GPS) and Radio Frequency Identification (RFID) have propelled the growth of a number of mobile services. Typically, these require maintaining the mobile objects’ location and profile information and efficiently serving access requests on the past, present and future status of the moving objects. This creates inherent security and privacy challenges. One solution to this is to specify security policies to ensure controlled access. However, this significantly degrades system performance. To alleviate this, Atluri and Guo have proposed an unified index structure, S TPR-tree, to organize both the moving objects and authorizations specified over them. A significant limitation of this approach is that it is unable to store past location information of objects and is therefore not capable of supporting security policies based on tracking of mobile users. In this paper, we propose a new unified index structure, called the S PPF -tree, which maintains past, present and future positions of the moving objects along with authorizations by employing partial persistent storage. Besides demonstrating how the S PPF -tree can be constructed and maintained, we provide algorithms to process queries where either the subject or the object or both are mobile. We provide a comprehensive experimental evaluation to establish the scalability and performance of our approach.

Movement-Based Location Management for General Cell Residence Times in Wireless Networks

Location management of mobile users is of primary importance in personal communication networks (PCNs), and it is mainly aimed to facilitate the delivery of incoming calls to destination users and to make a more efficient use of network resources. In practical PCNs, the location management algorithms need to keep track of mobile users in a dynamic manner, and it is a design concern to minimize the generated signaling traffic. In this paper, we present the cost analysis for the dynamic movement-based location update scheme. Our model is based on renewal theory arguments, and it is general enough to include a variety of probability distributions for modeling cell residence times (CRTs) in hyperexponentially distributed location area residence times and exponentially distributed intercall times. We compare the location update cost for the dynamic and static schemes. We present numerical results regarding the exponential and circular CRT distributions and discuss the optimal threshold distance for location update that minimizes the cost of the dynamic movement-based scheme.

Mobility management in heterogeneous wireless networks

In heterogeneous wireless networks, mobile users are able to move from their home networks to different foreign networks while maintaining access capability to their subscribed services, which refers to global mobility. One of the key challenges in global mobility management is intersystem location management, which consists of keeping track of mobile users who roam into foreign networks. This paper presents an overview of mobility management in heterogeneous wireless networks and introduces a scheme which improves location management efficiency in terms of total signaling costs and intersystem paging delay. More specifically, cost reduction reaches about 50% when comparing the proposed architecture with conventional architectures.

A pointer forwarding based local anchoring (POFLA) scheme for wireless networks

For a Personal Communication System (PCS) network to effectively deliver services to the mobile users, it must have an efficient way to keep track of mobile users. Location management fulfills this task through location registration and call delivery procedures. To reduce the signaling traffic, many schemes such as local anchoring, pointer forwarding, and two-level pointer forwarding schemes have been proposed in the past few years. In this paper, we present a novel location management scheme, pointer forwarding based local anchoring scheme, that intends to mitigate the signaling traffic while keeping the tracking delay in check. In this scheme, one visitor location register (VLR) traversed by a user is selected as the mobility agent (MA) for the user at a time, which forms another level of management in order to make some registration traffic localized. The idea is as follows: instead of always carrying out location update to the home location register (HLR), which would become the bottleneck otherwise, many location updates are accomplished by the mobility agent. Moreover, pointers can be set up between VLRs under the coverage of the same MA. When the distance between the MA and the current VLR exceeds a certain threshold, the current VLR will become the new MA, which also updates the HLR (where a user's location information is the identification of the reported MA). The numerical results show that this scheme can significantly reduce the network signaling traffic load without increasing much of the call setup delay.

무선망에서 개선된 ZMHB 알고리즘의 성능 평가

핸드오프는 무선 셀룰러 환경에서 사용자의 이동성(Mobility)을 유지해줄 수 있는 가장 중요한 기술중의 하나이다. 핸드오프 기술은 사용자가 이동할 주변 셀에 대한 대역폭 예약과 관련이 있다. 또한, 대역폭 예약은 사용자가 이동한 새로운 영역에서 이전 영역에서와 같은 레벨의 데이터나 서비스를 받기 위해서 핸드오프 이전에 실시되어야 한다. 이러한 무선 셀룰러 환경에서 효과적으로 대역폭을 사용하기 위하여 사용자의 이동성을 예측하는 기술은 핸드오프 호의 실패율(Dropping Probability)과 핸드오프 지연(Latency)을 줄이는 효과적인 방법이다. 최근에 제시된 ZMHB 알고리즘은 기존의 알고리즘과는 달리 셀 내부의 이동 경로를 저장한 히스토리를 이용하여 사용자가 이동할 셀을 예측하였다. 그러나, 모든 사용자에 대하여 80～85% 정도의 예측 정확도만을 보인다. 본 논문에서는 ZMHB 알고리즘에서 사용하는 존(Zone)을 세분화하여 이동 패턴을 저장하고, 이를 예측에 이용하는 Detailed-ZMHB 예측 알고리즘을 제안하고 성능 평가 결과를 보인다. Handoff is one of the most important features for the user's mobility in a wireless cellular communication system. It is related to resource reservation at nearby cells. Resource reservation to the new connection point should occur prior to handoff to enable the user to receive the data or services at the new location, at the same level of service as at the previous location. For the efficient resource reservation, mobility prediction has been reported as an effective means to decrease the call dropping probability and to shorten the handoff latency in a wireless cellular environment. A recently proposed algorithm, ZMHB, makes use of the history of the user's positions within the current cell to predict the next cell. But, the prediction of the ZMHB algorithm is found to be 80∼85% accurate for regular and random movements. In this paper, we propose a new improved ZMHB mobility prediction algorithm, which is called Detailed-ZMHB that uses detailed-zone-based tracking of mo-bile users to predict user movements. The effectiveness of the proposed algorithm is then demonstrated through a simulation.

Simulation and analysis of Awerbuch–Peleg and GSM schemes for location tracking of mobile users

AbstractMobile users are increasingly demanding full access to networked communications while they are on the move. Several studies have shown that the overhead incurred by the network to keep track of the current location of mobile users is considerably high. The methods currently used for location tracking incur heavy unnecessary costs by requiring that users update locations in their home networks after each move regardless of the distance at which the move occurs, and that all search attempts for a mobile user are first routed to that user's home network. The Awerbuch–Peleg scheme presents a formal model for location tracking which attempts to minimize the cost of local operations—both move and find operations—through the construction of a regional hierarchy. In this paper we present a performance evaluation of the Awerbuch–Peleg scheme. We also compare its performance to that of the GSM‐based location tracking scheme. It is found that the Awerbuch–Peleg scheme in general results in higher costs than the GSM scheme. The reason for this is found to be some unexpected properties of the read and write sets which are key components of the Awerbuch–Peleg scheme. Copyright © 2001 John Wiley & Sons, Ltd.

A contention-free mobility management scheme based on probabilistic paging

In forthcoming personal communication systems (PCSs), small cells are deployed to achieve high spectral efficiency. This has significant impacts on location tracking of mobile users. The increase in location update (LU) load leads to more contention on the reverse control channel. Thus, many algorithms are designed to distribute the LU load to a larger number of cells. This avoids the inefficiency of random accessing due to high offered load. In an alternative approach (Wong 1995), a contention-free LU algorithm is proposed. Two or more mobile units are permitted to register with a base station simultaneously without contention. A probabilistic paging mechanism called Bloom filtering is used to select cells to be paged. Since there is no contention in LU, inefficiencies due to random accessing are bypassed. In this paper, we present another contention-free LU algorithm. It is hybrid in the sense that LUs are temporally or geographically triggered. The use of hybrid LU alleviates inefficiencies inherent to temporal triggered LU in Wong. Three selective paging schemes are considered in this paper. Tradeoff between paging delay and paging bandwidth is addressed. The performance of this algorithm is compared to Wong and other conventional strategies. Numerical results show that the new algorithm compares favorably with previous proposed strategies.

LATS: a load-adaptive threshold scheme for tracking mobile users

Mobile user tracking is a major issue. We propose a novel approach for user tracking, in which the tracking activity is adapted to both user and system activity. The basic idea is to make the user-location update-rate dependent not only on the user activity (such as the call profile and mobility pattern). Rather, it is also made dependent on the signaling load, which reflects the actual cost of the update operation. Thus, at low-signaling load locations, the users are to transmit location update messages more frequently. To carry out this approach, we propose a load-adaptive threshold scheme (LATS): the network determines for each cell a registration threshold level (which depends on the cell load) and announces it, as a broadcast message, to the users. The user computes its own registration priority and then transmits a registration message only if its priority exceeds the announced threshold level. Thus, whenever the local load on the cell is low, the registration activity increases, while in loaded cells the registration activity decreases. Our analysis shows that the LATS reduces the paging cost, in comparison with other dynamic methods, without increasing the wireless cost of registration. Moreover, if higher user density is coupled with less mobility (e.g., consider vehicles), then the LATS strategy offers further performance improvement. The load-adaptive strategy can be used in addition to any other dynamic tracking strategy. Furthermore, the computational complexity imposed on the user is identical to that required by an equivalent load-insensitive scheme.

Competitive Algorithms for Distributed Data Management

We deal with the competitive analysis of algorithms for managing data in a distributed environment. We deal with the file allocation problem, where copies of a file may be be stored in the local storage of some subsets of processors. Copies may be replicated and discarded over time so as to optimize communication costs, but multiple copies must be kept consistent and at least one copy must be stored somewhere in the network at all times. We deal with competitive algorithms for minimizing communication costs, over arbitrary sequences of reads and writes, and arbitrary network topologies. We define the constrained file allocation problem to be the solution of many individual file allocation problems simultaneously, subject to the constraints of local memory size. We give competitive algorithms for this problem on the uniform network topology. We then introduce distributed competitive algorithms for on-line data tracking (a generalization of mobile user tracking) to transform our competitive data management algorithms into distributed algorithms themselves.

Online tracking of mobile users

This paper deals with the problem of maintaining a distributed directory server, that enables us to keep track of mobile users in a distributed network. The paper introduces the graph-theoretic concept of regional matching , and demonstrates how finding a regional matching with certain parameters enables efficient tracking. The communication overhead of our tracking mechanism is within a polylogarithmic factor of the lower bound.

Lower bounds on the competitive ratio for mobile user tracking and distributed job scheduling

We prove a lower bound of Ω(log n/log log n) on the competitive ratio of any (deterministic or randomized) distributed algorithm for solving the mobile user problem introduced by Awerbuch and Peleg (1989, 1990), on certain networks of n processors. Our lower bound holds for various networks, including the hypercube, any network with sufficiently large girth, and any highly expanding graph. A similar Ω(log n/log log n) lower bound is proved for the competitive ratio of the maximum job delay of any distributed algorithm for solving the distributed scheduling problem of Awerbuch, (1992) on any of these networks. The proofs combine combinatorial techniques with tools from linear algebra and harmonic analysis and apply, in particular, a generalization of the vertex isoperimetric problem on the hypercube, which may be of independent interest.

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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Concurrent online tracking of mobile users

This paper deals with the problem of maintaining distributed directory server, that enables us to keep track of mobile users in a distributed network in the presence of concurrent requests. The paper uses the graph-theoretic concept of regional matching for implementing efficient tracking mechanisms. The communication overhead of our tracking mechanism is within a polylogarithmic factor of the lower bound.