Dynamic Base Station Research Articles

LCMV Beamforming for a Novel Wireless Local Positioning System: Nonstationarity and Cyclostationarity Analysis

This paper investigates the implementation of a novel wireless local positioning system (WLPS). WLPS main components are: (a) a dynamic base station (DBS) and (b) a transponder, both mounted on mobiles. The DBS periodically transmits ID request signals. As soon as the transponder detects the ID request signal, it sends its ID (a signal with a limited duration) back to the DBS. Hence, the DBS receives noncontinuous signals periodically transmitted by the transponder. The noncontinuous nature of the WLPS leads to nonstationary received signals at the DBS receiver, while the periodic signal structure leads to the fact that the DBS received signal is also cyclostationary. This work discusses the implementation of linear constrained minimum variance (LCMV) beamforming at the DBS receiver. We demonstrate that the nonstationarity of the received signal causes the sample covariance to be an inaccurate estimate of the true signal covariance. The errors in this covariance estimate limit the applicability of LCMV beamforming. A modified covariance matrix estimator, which exploits the cyclostationarity property of WLPS system is introduced to solve the nonstationarity problem. The cyclostationarity property is discussed in detail theoretically and via simulations. It is shown that the modified covariance matrix estimator significantly improves the DBS performance. The proposed technique can be applied to periodic-sense signaling structures such as the WLPS, RFID, and reactive sensor networks.

A Novel Wireless Local Positioning System via a Merger of DS-CDMA and Beamforming: Probability-of-Detection Performance Analysis Under Array Perturbations

This paper investigates the probability-of-detection (POD) performance of a novel wireless local positioning system (WLPS) realized via direct sequence code division multiple access (DS-CDMA) and beamforming techniques. The proposed WLPS has unique signaling schemes that discriminate it from the traditional wireless systems and allows the WLPS to have many civilian and military applications. The WLPS consists of two main parts: 1) the detecting unit, a base station carried by a mobile unit defined as dynamic base station (DBS), and 2) the being detected unit, a transponder (TRX) that is mounted on the targets, each assigned a unique identification code. Each DBS should be capable of detecting and locating all available TRXs in its coverage area. As a result, the main complexity of this system is focused at the DBS receiver. In this paper, we introduce WLPS structure, and both theoretically and numerically compute, and compare the POD performance of the DBS receiver realized by a merger of DS-CDMA and antenna arrays. We also analyze and simulate the performance of this system under perturbations in the DBS antenna array vector. The simulations are particularly performed for vehicular collision avoidance applications

Joint packet scheduling and dynamic base station assignment for CDMA data networks

AbstractIn current code division multiple access (CDMA) based wireless systems, a base station (BS) schedules packets independently of its neighbours, which may lead to resource wastage and the degradation of the system's performance. In wireless networks, in order to achieve an efficient packet scheduling, there are two conflicting performance metrics that have to be optimized: throughput and fairness. Their maximization is a key goal, particularly in next‐generation wireless networks. This paper proposes joint packet scheduling and BS assignment schemes for a cluster of interdependent neighbouring BSs in CDMA‐based wireless networks, in order to enhance the system performance through dynamic load balancing. The proposed schemes are based on sector subdivision in terms of average required resource per mobile station and utility function approach. The fairness is achieved by minimizing the variance of the delay for the remaining head‐of‐queue packets. Inter‐cell and intra‐cell interferences from scheduled packets are also minimized in order to increase the system capacity and performance. The simulation results show that our proposed schemes perform better than existing schemes available in the open literature. Copyright © 2007 John Wiley & Sons, Ltd.

Positioning of Base Stations in Wireless Sensor Networks

Wireless sensor networks (WSN) have attracted much attention in recent years due to their potential use in many applications such as border protection and combat field surveillance. Given the criticality of such applications, maintaining a dependable operation of the network is a fundamental objective. However, the resource-constrained nature of sensor nodes and the ad hoc formation of the network, often coupled with an unattended deployment, pose non-conventional challenges and motivate the need for special techniques for dependable design and management of WSN. In this article, we highlight the potential of careful positioning of the base station (BS), which acts as a sink node for the collected data, as a viable means for increasing the dependability of WSN. We categorize published work on optimal positioning of BS in WSN. Referring to such work as static positioning, we further introduce dynamic schemes that reposition the BS during the network operation. We show that dynamic BS positioning can be very effective in optimizing the network functional and non-functional performance objectives and in coping with dynamic changes in the environment and available network resources

SCO link sharing in Bluetooth voice access networks

In this paper we consider the potential for SCO link sharing in Bluetooth-based telephony base stations. A design referred to as the Bluetooth distributed voice access protocol (DVAP) is introduced. In DVAP, Bluetooth mobiles collect connectivity information which is provided to the base station infrastructure. Mobile node migration is then used to reduce blocking when a Bluetooth base station is carrying a full load of active SCO links. A simple heuristic referred to as dynamic base station selection is used for making the base station assignment. Simulation results are presented which show that DVAP has better voice call blocking performance than existing Bluetooth base station collaboration designs (in: IEEE Workshop on Wireless Local Networks, Tampa, Florida, November 2001). It is also shown that intelligent base station selection can support much higher levels of traffic loading at a given voice call blocking rate compared to an arbitrary base station assignment.

Analysis of a class of distributed asynchronous power control algorithms for cellular wireless systems

In cellular wireless communication systems, uplink power control is needed to provide each mobile user with an acceptable signal to interference ratio (SIR) while simultaneously minimizing transmit power levels. We consider a class of distributed asynchronous power control algorithms based on the schemes used in IS-95 inner loop power control. Each user's received SIR is measured (using possibly outdated information) and compared to a threshold, and a single control bit is then sent to the user, indicating whether its power level should be increased or decreased. The SIR measurements and power updates do not require synchronization. We show that under certain conditions, this class of algorithms is stable and converges to a region around the optimal power assignment. We characterize this region and show that it can be made as small as desired by choosing the algorithm parameters appropriately. For an appropriate choice of algorithm parameters, we show that convergence occurs in a finite number of iterations and derive an upper bound. To illustrate our general results, we apply them to systems with fixed base station assignment, dynamic base station assignment, and macrodiversity. Finally, we give an example to illustrate the algorithm's robustness to errors in the power control commands.

Dynamic Base Station Selection for Personal Communication Systems with Distributed Control Schemes

Distributed control schemes allow base stations in personal communication systems to be placed at locations corresponding to high expected traffic. This flexible base station placement creates significant overlapping coverage areas that can be utilized to improve system performance [1]. A new technique for dynamic base station selection in systems with overlapping cells is considered and its effect on traffic performance is characterized. The technique realizes robust performance for personal communication systems in fluctuating and heavily tapered traffic. A mathematical analysis based on a state transition model is used to evaluate performance of a system that employs the proposed technique. The results indicate that improved blocking probability and carried traffic performance are obtainable. Computer simulations were undertaken confirm the analytical results.