Base station

About: Base station is a research topic. Over the lifetime, 85883 publications have been published within this topic receiving 1019303 citations. The topic is also known as: Mobile phone base stations & BS.

Multi-rate wireless communications system

Abstract: A flexible multi-rate communications system (100) is disclosed. It supports a plurality of distributed user terminals (104-106) in full-duplex simultaneous communications with a central base station (102), where each user terminal is provided on demand with one of multiple bit rates at a negotiated quality of service (QOS). In one embodiment of this system (100), each user is assigned a variable bit rate, a variable processing gain, a variable transmit power, and a unique fixed rate spreading code. This results in a constant bandwidth signal received at a relative power level corresponding to the negotiated QOS. The above embodiment can be implemented in Frequency Division Duplexing and Time Division Duplexing configurations. This system (100) can be used in wireless local loop, mobile cellular, and wireless multimedia access systems.

On the Spectral Efficiency of Full-Duplex Small Cell Wireless Systems

Abstract: We investigate the spectral efficiency of full-duplex small cell wireless systems, in which a full-duplex capable base station (BS) is designed to send/receive data to/from multiple halfduplex users on the same system resources. The major hurdle for designing such systems is due to the self-interference at the BS and co-channel interference among users. Hence, we consider a joint beamformer design to maximize the spectral efficiency subject to certain power constraints. The design problem is first formulated as a rank-constrained optimization one, and the rank relaxation method is then applied. However the relaxed problem is still nonconvex, and thus optimal solutions are hard to find. Herein, we propose two provably convergent algorithms to obtain suboptimal solutions. Based on the concept of the difference of convex functions programming, we approximate the design problem by a determinant maximization program in each iteration of the first algorithm. The second method is built upon the sequential parametric convex approximation method, which allows us to transform the relaxed problem into a semidefinite program in each iteration. Extensive numerical experiments under small cell setups illustrate that the full-duplex system with the proposed algorithms can achieve a large gain over the half-duplex one.

Spatial cloaking for anonymous location-based services in mobile peer-to-peer environments

Abstract: This paper tackles a privacy breach in current location-based services (LBS) where mobile users have to report their exact location information to an LBS provider in order to obtain their desired services. For example, a user who wants to issue a query asking about her nearest gas station has to report her exact location to an LBS provider. However, many recent research efforts have indicated that revealing private location information to potentially untrusted LBS providers may lead to major privacy breaches. To preserve user location privacy, spatial cloaking is the most commonly used privacy-enhancing technique in LBS. The basic idea of the spatial cloaking technique is to blur a user's exact location into a cloaked area that satisfies the user specified privacy requirements. Unfortunately, existing spatial cloaking algorithms designed for LBS rely on fixed communication infrastructure, e.g., base stations, and centralized/distributed servers. Thus, these algorithms cannot be applied to a mobile peer-to-peer (P2P) environment where mobile users can only communicate with other peers through P2P multi-hop routing without any support of fixed communication infrastructure or servers. In this paper, we propose a spatial cloaking algorithm for mobile P2P environments. As mobile P2P environments have many unique limitations, e.g., user mobility, limited transmission range, multi-hop communication, scarce communication resources, and network partitions, we propose three key features to enhance our algorithm: (1) An information sharing scheme enables mobile users to share their gathered peer location information to reduce communication overhead; (2) A historical location scheme allows mobile users to utilize stale peer location information to overcome the network partition problem; and (3) A cloaked area adjustment scheme guarantees that our spatial cloaking algorithm is free from a "center-of-cloaked-area" privacy attack. Experimental results show that our P2P spatial cloaking algorithm is scalable while guaranteeing the user's location privacy protection.

Method and apparatus for performing mobile assisted hard handoff between communication systems

Abstract: A method and apparatus for performing inter-system hard handoff between communication systems (S1, S2) or inter-frequency hard handoff within a CDMA communication system is disclosed. The purpose of this invention is to reduce the probability of dropped calls during intersystem hard handoff. In the event that a hard handoff attempt is unsuccessful, the mobile station (18) will return to the original system (S1) with information which the communication system of the present invention uses to assist in the performance of future handoff attempts. Alternatively, with no handoff attempt made, the mobile station (18) monitors the destination system (S2), then returns to the original system (S1) with information used to assist in subsequent handoff attempts. The information returned from monitoring a CDMA system consists of results of a search for one or more pilots given at offsets in a specific list provided to the mobile station (18) by the base station (B1-B5) or a set of offsets based upon a predetermined search algorithm.

Wireless location routing applications and architecture therefor

Abstract: A system for wirelessly locating mobile station/units (MS) and using resulting location determinations for providing a product or service is disclosed. The system is useful for routing an MS user to a plurality of desired locations, alerting an MS user to a nearby desired product or service based on satisfaction of user criteria, and providing enhanced security and 911 response. In one embodiment, the system responds to MS location requests via, e.g., Internet communication between a distributed network of location processing sites. A plurality of locating technologies including those based on: (1) TDOA; (2) pattern recognition; (3) timing advance; (5) GPS and network assisted GPS, (6) angle of arrival, (7) super resolution enhancements, and (8) supplemental information from low cost base stations can be activated, in various combinations, by system embodiments. MS location difficulties resulting from poor location accuracy/reliability and/or poor coverage are alleviated via such technologies in combination with automatically adapting and calibrating system performance according to environmental and geographical changes so that the system becomes progressively more comprehensive and accurate. Further, the system can be modularly configured for use in location signaling environments ranging from urban, dense urban, suburban, rural, mountain to low traffic or isolated roadways. Accordingly, the system is useful for 911 emergency calls, tracking, routing, people and animal location including applications for confinement to and exclusion from certain areas.