Users In Cellular Networks Research Articles

Reservation policies for revenue maximization from secondary spectrum access in cellular networks

We consider the problem of providing opportunistic spectrum access to secondary users in wireless cellular networks. From the standpoint of spectrum license holders, achieving benefits of secondary access entails balancing the revenue from such access and its impact on the service of primary users. While dynamic optimization is a natural framework to pursue such a balance, spatial constraints due to interference and uncertain demand characteristics render exact solutions difficult. In this paper, we study guiding principles for spectrum license holders to accommodate secondary users via reservation-based admission policies. Using notions of dynamic optimization, we first develop the concept of average implied cost for establishing a connection in an isolated locality. The formula of the cost provides an explicit characterization of the value of spectrum access. We then generalize this concept to arbitrary topologies of interference relations and show that the generalization is justified under an analogue of the reduced load approximation judiciously adapted from the wireline to the wireless setting. An explicit characterization of this quantity demonstrates the localized nature of the relationship between overall network revenue and reservation parameters. Based on this relationship, we develop an online algorithm for computing optimal reservation parameters at the cells based on localized message passing. The results in the paper are verified through a numerical study.

Analytical expressions for blocking and dropping probabilities for mobile streaming users in wireless cellular networks

We consider a wireless cellular network serving streaming traffic. We study in this context the effect of the users mobility on their quality of service (QoS). If the arrival of a new user violates the capacity constraint, then his call is blocked. If the user is first admitted but the capacity constraint is violated later when he attempts to move, then his call is dropped. The blocking and dropping probabilities are the main QoS indicators in this model called forced termination (FT). We introduce an alternative model, called transitions backtrack (TB), where a user backtracks when his motion violates the capacity constraint. In this model, a relevant QoS indicator is the number of times the user backtracks called number of motion blocking per call. We propose some explicit expressions for the above QoS indicators as functions of the mean user speed. These expressions are validated by simulations. In particular we observe that the dropping probability in the FT model is well approximated by the number of motion blocking per call in the TB model which is expressed analytically.

Evaluation of Delay of Voice End User in Cellular Mobile Networks with 2D Traffic System

Evaluation of Delay of Voice End User in Cellular Mobile Networks with 2D Traffic System

Searching for Multiple Mobile Users

The problem of searching for mobile users in cellular networks is addressed in this study. Previous studies addressing this issue have focused on the problem of searching for a single user. As it is shown in this study, the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard. When the potential locations of different users overlap, the derivation of an optimal concurrent search for many independent users from a set of optimal single user searches is NP-hard, In reality, a cellular network has to serve many competing search requests sharing a limited bandwidth. Since the problem of maximizing the expected rate of successful searches under delay and bandwidth constraints is NP-hard, this study proposes a heuristic algorithm, that is optimal for most probable cases, and its worst case running time complexity is O(n(log n + C log C)), where n is the number of mobile users that must be found, and C is the number of their potential locations.The approximation ratio of the proposed search algorithm is less than 2. That is, the expected number of searches is always less than twice the number of searches expected from an optimal search algorithm. Even under the worst case condition, the proposed method can potentially increase the expected rate of successful searches by 100 percent in comparison to the existing search strategy currently used by cellular networks. Moreover, the proposed search strategy outperforms a greedy search strategy that considers only the users' location probabilities and ignores their deadline constraints. Under certain conditions, the expected rate of successful searches generated by the proposed method is twice the equivalent rate generated by the greedy search strategy. In addition, the proposed search strategy outperforms a heuristic algorithm that searches around the user last known location.

Interworking of WLAN-UMTS networks: an IMS-based platform for session mobility

In this article a framework for interworking between a WLAN and the UMTS is presented. The uniqueness of this architecture is that the IP multimedia subsystem proposed by the 3GPP has been used as an arbitrator for network coupling and real-time session management. Apart from the advantage of a cellular network user being able to enjoy higher levels of bandwidth over a WLAN, IMS also provides a common platform for unified session control, as well as higher levels of terminal and service mobility over a heterogeneous networking environment. The article concludes by presenting the potential of this model for service continuity during and after vertical handoff with simulation results for validation.

DIP-MIP: Distributed individual paging extension for mobile IP in IP-based cellular networks

The mobility-enabling protocol Mobile IP supports location registration but not paging. However, current cellular networks use registration as well as paging procedures to minimize signaling cost. Accordingly, an extension to Mobile IP using distributed individual paging, the so-called DIP-MIP, is proposed. In DIP-MIP, each mobile host derives its own paging area size by optimizing a signaling cost function based on its individual mobility pattern. The cost function itself may use either of two mobility models – fluid flow and random walk – and the performance of DIP-MIP is analyzed for both. The impact of various parameters on the DIP-MIP signaling cost is studied as well. The performance of DIP-MIP is shown to be superior to that of Mobile IP (MIP) in reducing signaling load, managing mobility and supporting a large number of mobile users in IP-based cellular networks.

Construction of an optimal multicast tree for group communication in a cellular network using genetic algorithm

The recent advances in wireless technology has enabled users of Mobile cellular networks in different parts of the world not only to communicate with each other but also to participate in real time applications, viz., video conferencing, multiparty games, online auctions, access to distributed databases, etc., on the fly. All these applications require a Multicast Tree (MT) to be constructed among the group users with the source being the root of the MT. Traditional methods used in a wired network to construct a MT take into account only the distance or delay between the nodes. These methods when extended to mobile networks fail because of the inherent dynamism in a mobile network. To overcome this problem and to give an optimized solution to this problem, a novel Genetic Algorithm (GA) based approach to construct an Optimal Multicast Tree (OMT) with four constraints viz., probability of delay over a path, queuing delay at a node, residual bandwidth of a link, and the speed of the user is proposed in this paper. Further, for a network of N nodes and E edges, with k independent constraints, it has been derived that the time complexity and space complexity for GA based algorithm are O ( N 2) and O ( N), respectively, whereas the time complexity and space complexity for the non-GA based multi constrained algorithm are O ( N 2 k ) and O ( N 2). These results show that the GA based algorithm is insensitive to the number of constraints and it constructs OMT faster than the traditional algorithms.

An Integrated AP for Seamless Interworking of Existing WMAN and WLAN Standards

Broadband Fixed Wireless Access (BFWA) systems represent a potential technological foundation for the Fourth Generation of Wireless Mobile Communication Systems (4G) as they can replace wired broadband and, with sufficient widespreading deployment, can significantly cut into the usage of cellular networks in many areas. In this context, the seamless interworking of Wireless Metropolitan Area Network (WMAN) and Wireless Local Area Network (WLAN) technologies is an efficient solution to provide the indoor extension of BFWA systems coverage, which would largely contribute to their success and penetration in the market. In this paper, we introduce a novel Access Point (AP), called WMAN/WLAN AP (WWAP), which essentially integrates in a compact device a WMAN Subscriber Station (SS) and a WLAN AP in order to extend the WMAN coverage in-house and to guarantee the end-to-end Quality of Service (QoS). Besides the technical features, the market trends and the usage scenarios where the WWAP might be a cost-effective and a very efficient solution are outlined. Finally, simulation results are carried out in order to demonstrate the effectiveness of the proposed AP.

Concurrent Search of Mobile Users in Cellular Networks

In this paper, we propose to concurrently search for a number of mobile users in a wireless cellular network based on the probabilistic information about the locations of mobile users. The concurrent search approach guarantees that all k mobile users will be located within k time slots. It is shown that even in the worst case when mobile users appear equally in all the cells of the network, the concurrent search approach is able to reduce the average paging cost by 25%. More importantly, this is achieved without an increase in the worst case paging delay or in the worst case paging cost. Depending on the total number of mobile users to be located, total number of cells in the network, and the probabilistic information about the locations of mobile users, the reduction of the average paging cost due to the usage of the concurrent search approach ranges from 25% to 88%. The case in which perfect probabilistic information is unavailable is also studied.

Concurrently searching for mobile users in cellular networks

In today's systems, upon arrival of calls to mobile users, the system attempts to locate the users sequentially (one by one) through a paging operation. In this letter, we propose to concurrently search for a number of mobile users in a mobile network, significantly reducing the cost of locating mobile users. The reduction in the paging costs due to such a concurrent search can be quite substantial, depending on the knowledge of the probabilities of the users' locations, the number of cells in the network, and the number of mobiles to be located. Additionally, we propose a low-complexity heuristic that reduces the average paging cost by 25%, in the case of no knowledge of probabilities of the mobiles' locations. With such knowledge, further reduction in the average paging costs of up to 90% can be achieved.