Showing papers on "Cellular network published in 2001"

Mobility increases the capacity of ad-hoc wireless networks

Abstract: The capacity of ad-hoc wireless networks is constrained by the mutual interference of concurrent transmissions between nodes. We study a model of an ad-hoc network where n nodes communicate in random source-destination pairs. These nodes are assumed to be mobile. We examine the per-session throughput for applications with loose delay constraints, such that the topology changes over the time-scale of packet delivery. Under this assumption, the per-user throughput can increase dramatically when the nodes are mobile rather than fixed. This improvement can be achieved by exploiting node mobility as a type of multiuser diversity.

A rate-adaptive MAC protocol for multi-Hop wireless networks

Abstract: Wireless local area networks (W-LANs) have become increasingly popular due to the recent availability of affordable devices that are capable of communicating at high data rates. These high rates are possible, in part, through new modulation schemes that are optimized for the channel conditions bringing about a dramatic increase in bandwidth efficiency. Since the choice of which modulation scheme to use depends on the current state of the transmission channel, newer wireless devices often support multiple modulation schemes, and hence multiple datarates, with mechanisms to switch between them Users are given the option to either select an operational datarate manually or to let the device automatically choose the appropriate modulation scheme (data rate) to match the prevailing conditions. Automatic rate selection protocols have been studied for cellular networks but there have been relatively few proposals for W-LANs. In this paper we present a rate adaptive MAC protocol called the Receiver-Based AutoRate (RBAR) protocol. The novelty of RBAR is that its rate adaptation mechanism is in the receiver instead of in the sender. This is in contrast to existing schemes in devices like the WaveLAN II [15]. We show that RBAR is better because it results in a more efficient channel quality estimation which is then reflected in a higher overall throughput Our protocol is based on the RTS/CTS mechanism and consequently it can be incorporated into many medium access control protocols including the widely popular IEEE 802.11 protocol. Simulation results of an implementation of RBAR inside IEEE 802.11 show that RBAR performs consistently well.

Providing robust and ubiquitous security support for mobile ad-hoc networks

Abstract: Providing security support for mobile ad-hoc networks is challenging for several reasons: (a) wireless networks are susceptible to attacks ranging from passive eavesdropping to active interfering, occasional break-ins by adversaries may be inevitable in a large time window; (b) mobile users demand "anywhere, anytime" services; (c) a scalable solution is needed for a large-scale mobile network. In this paper, we describe a solution that supports ubiquitous security services for mobile hosts, scales to network size, and is robust against break-ins. In our design, we distribute the certification authority functions through a threshold secret sharing mechanism, in which each entity holds a secret share and multiple entities in a local neighborhood jointly provide complete services. We employ localized certification schemes to enable ubiquitous services. We also update the secret shares to further enhance robustness against break-ins. Both simulations and implementation confirm the effectiveness of our design.

An analysis of the optimum node density for ad hoc mobile networks

Abstract: An ad hoc mobile network is a collection of nodes, each of which communicates over wireless channels and is capable of movement. Wireless nodes have the unique capability of transmission at different power levels. As the transmission power is varied, a tradeoff exists between the number of hops from source to destination and the overall bandwidth available to individual nodes. Because both battery life and channel bandwidth are limited resources in mobile networks, it is important to ascertain the effects different transmission powers have on the overall performance of the network. This paper explores the nature of this transmission power tradeoff in mobile networks to determine the optimum node density for delivering the maximum number of data packets. It is shown that there does not exist a global optimum density, but rather that, to achieve this maximum, the node density should increase as the rate of node movement increases.

System and method for providing geographic-based advertising

Abstract: A geographic-based communications service system has a mobile unit for transmitting/receiving information, and access points connected to a network. The access points are arranged in known geographic locations and transmit and receive information from the mobile unit. When one of the access points detects the presence of the mobile unit, it sends a signal to the network indicating the location of the mobile unit and the information requested by the mobile unit. Based on the signal received from the access point, the network communicates with information providers connected to the network and provides data to the mobile unit through the access point corresponding to the location of the mobile unit.

Distributed power control in ad-hoc wireless networks

Abstract: Mobile ad-hoc networking involves peer-to-peer communication in a network with a dynamically changing topology. Achieving energy efficient communication in such a network is more challenging than in cellular networks since there is no centralized arbiter such as a base station that can administer power management. We propose and evaluate a power control loop, similar to those commonly found in cellular CDMA networks, for ad-hoc wireless networks. We use a comprehensive simulation infrastructure consisting of group mobility, group communication and terrain blockage models. A major focus of research in ad-hoc wireless networking is to reduce energy consumption because the wireless devices are envisioned to have small batteries and be incapable of energy scavenging. We show that this power control loop reduces energy consumption per transmitted byte by 10-20%. Furthermore, we show that it increases overall throughput by 15%.

Multi-sensor fusion

Abstract: Systems and methods are disclosed for establishing a mobile network in which each mobile unit, such as a car, becomes a node able to receive and transmit a wide variety of information, including for example, traffic conditions, vehicle mechanical/electrical status, interactive game playing information, streaming audio and video, email, and voice mail. In one aspect, multi-sensor fusion technology is used to determine the best value of a monitored variable, for example, the real time locations of each mobile unit, that may be communicated to others via the network. In addition, a new method of traffic control using real time traffic positioning and density data is disclosed. Further, methods and systems for enhancing driver safety are disclosed. In another aspect, the system may use a unique secure dynamic link allocation system to improve the information transfer from one node (mobile unit) to another and to other networks, such as the Internet.

System and method for the transfer of digital data to a mobile device

Abstract: A mobile device is capable of accessing electronic shop server web sites which contain digital products for sale and hotspot network locations where these digital products may be downloaded to the mobile device without incurring cellular phone charges or public switched telephone network charges. The mobile device has a short range transceiver for low power radio frequency over the short distance and a network transceiver for cellular telephone signals. The hotspot network locations contain a hotspot device for transmitting the digital products to the mobile devices via the low power radio frequency signal. The mobile device has the capability of detecting the presence of the low power radio frequency signal when it is in range of the signal. Using this system, method and computer program a user of a mobile device may download large amounts digital data without incurring telephone or cellular phone charges.

Ad hoc peer-to-peer mobile radio access system interfaced to the pstn and cellular networks

Abstract: An ad-hoc, peer-to-peer radio access system for cellular communications systems using time division duplex as a way of maximizing the bits/hz/km2 for cellular systems. The network architecture of the ad-hoc system allows the radio access to be integrated with the fixed components of a conventional cellular system, PSTN or ISP. The objective is to make the system of the invention transparent to the features and services provided by the external network. The advantages of such a system to a cellular operator are that significantly less infrastructure is required, and that the RF spectrum is more efficiently utilized resulting in much lower building and operating costs. The system architecture is comprised of remote terminals, routers, gateways, and at least one gateway controller that interfaces the ad-hoc system to a cellular network system. The ad-hoc system of the invention allows for both voice and data transmissions and receptions.

On the relaying capability of next-generation GSM cellular networks

Abstract: The latest developments and experimentation in mobile ad hoc networks show that MANETs will be an alternative candidate in many private and public multimedia networks. Current interest in MANET systems has grown considerably because they can rapidly and economically extend the boundaries of any terrestrial network; integrating MANET and GSM offers a great number of benefits (e.g., increasing capacity, improving coverage) at the cost of increasing the complexity of the mobile terminal and its battery consumption. The objective of this article is to address new concepts in the GSM system, dealing with both standardized features as well as theoretically and technologically feasible improvements, which contribute to evolutionary changes in general. Dynamic evolution of GSM presents a platform for Universal Mobile Telecommunication System introduction and major trends in GSM development are addressed, in particular progress towards a generic platform to accommodate relaying capability in GSM cellular networks. A GSM simulation tool has been constructed for quantifying the integrated system characteristics.

Wireless LAN access network architecture for mobile operators

Abstract: The evolution of IP-based office applications has created a strong demand for public wireless broadband access technology offering capacity far beyond current cellular systems. Wireless LAN access technology provides a perfect broadband complement for the operators' existing GSM and GPRS services in an indoor environment. Most commercial public wireless LAN solutions have only modest authentication and roaming capability compared to traditional cellular networks. This article describes a new wireless LAN system architecture that combines the WLAN radio access technology with mobile operators' SIM-based subscriber management functions and roaming infrastructure. In the defined system the WLAN access is authenticated and charged using GSM SIM. This solution supports roaming between cellular and WLAN access networks and is the first step toward an all-IP network architecture. The proto-type has been implemented and publicly verified in a real mobile operator network.

Mobile network estimation

Abstract: Mobile systems must adapt their behavior to changing network conditions. To do this, they must accurately estimate available network capacity. Producing quality estimates is challenging because network observations are noisy, particularly in mobile, ad hoc networks. Current systems depend on simple, exponentially-weighted moving average (EWMA) filters. These filters are either able to detect true changes quickly or to mask observed noise and transients, but cannot do both. In this paper, we present four filters designed to react quickly to persistent changes while tolerating transient noise. Such filters are agile when possible, but stable when necessary, adapting their behavior to prevailing conditions. These filters are evaluated in a variety of networking situations, including persistent and transient change, congestion, and topology changes. We find that one filter, based on techniques from statistical process control provides performance superior to the other three. Compared to two EWMA filters, one agile and the other stable, it is able to offer the agility of the former in four of five scenarios and the stability of the latter in three of four scenarios.

Localized voice mail system

Abstract: The present invention relates to a system and method for using a localized voice mail system that allows voice mail messages on a cellular telephone network to be stored on a remote server or other computer. These messages can be stored on a server of the cellular network or of the cellular telephone service subscriber. The method further entails downloading copies of the stored messages into another computer or a cellular telephone's memory. In this embodiment, a cellular telephone can retrieve voice mail messages even when the cellular telephone is roaming or cannot pick up a carrier signal. In another embodiment, a method is described for organizing voice mail messages stored in a cellular telephone's memory into convenient groups, directories or folders formatted to be compatible with the computer and cellular telephone.

On-demand QoS routing in multihop mobile networks

Abstract: The emergence of nomadic applications have generated a lot of interest in next generation wireless network infrastructures which provide differentiated service classes. So it is important to study how the quality of service (QoS) should be guaranteed. To accomplish this, we develop an admission control scheme which can guarantee bandwidth for real-time applications in multihop mobile networks. In our scheme, a host need not discover and maintain any information of the network resources status on the routes to another host until a connection request is generated for the communication between the two hosts, unless the former host is offering its services as an intermediate forwarding station to maintain connectivity between two other hosts. This bandwidth guarantee feature is important for a mobile network to interconnect wired networks with QoS support. Our connection admission control scheme can also work in a standalone mobile ad hoc network for real-time applications. This control scheme contains end-to-end bandwidth calculation and bandwidth allocation. Under such a scheme, the source is informed of the bandwidth and QoS available to any destination in the mobile network. This knowledge enables the establishment of QoS connections within the mobile network and the efficient support of real time applications. In the case of an ATM interconnection, the bandwidth information can be used to carry out intelligent handoff between ATM gateways and/or to extend the ATM virtual circuit service to the mobile network with possible renegotiation of QoS parameters at the gateway. We examine via simulation the system performance in various QoS traffic flows and mobility environments. The "on-demand" feature enhances the performance in the mobile environment because the source can keep more connectivity with enough bandwidth to a receiver in the path-finding duration.

Instant message proxy for circuit switched mobile environment

Abstract: An instant message (IM) proxy (24) according to the present invention is capable of maintaining the availability status of a mobile subscriber (12) even when the mobile subscriber is roaming or temporarily out of a mobile network coverage area, and even after the IM proxy unsuccessfully attempts to send an instant message (42) to the mobile subscriber. Messages will continue to be re-sent to the mobile subscriber (12) in the near-real time manner characteristic of a typical instant message system until IM parameters programmed into a retry counter (38) and/or the timer (40) located at the proxy (24) are exceeded and the IM proxy drops the message. In addition, the IM proxy (24) of the present invention is capable of bundling instant messages intended for the mobile subscriber (12) to minimize mobile system overhead connection costs while at the same time minimizing IM system latency.

A system for ensuring encrypted communication after handover

Abstract: A fraudulent intruder can eavesdrop on a call by removing information about an encryption algorithm when a multimode mobile station sends an unpro-tected initial signaling message containing this information over the radio interface to the mobile telecommunications system. The attempt can be pre-vented in a universal mobile telecommunications system (UMTS) comprising at least two radio access networks providing mobile stations with access to at least one core network, a multimode mobile station, and at least one core network. During connection setup with a first radio access network, the mul-timode mobile station sends an unprotected initial signaling message that includes information about those encryption algorithms that the multimode mobile station supports when it communicates in a second radio access network. The first radio access network saves some or all the information of it. Then it composes and sends an integrity-protected message that includes information about the encryption algorithms supported by the multimode mobile station in the second radio access network.

Shared channel structure, ARQ systems and methods

Abstract: A forward link design is provided employing CDMA (code division multiple access) technologies in which time division multiplexing is employed between data and control information on the forward link to service multiple users per slot Another forward link design employing CDMA (code division multiple access) technologies is provided in which code division multiplexing between data and control information is employed on the forward link to service multiple users per slot, which is preferably backwards compatible with legacy standards such as IS2000A A reverse link design is also provided

Fast handovers and context transfers in mobile networks

Abstract: We describe recent work enabling fast handovers and context transfer between access routers offering Internet connectivity for mobile (often wireless) nodes. We present our framework for engineering general context transfer solutions, and a protocol which uses the framework to provide a simple yet general mechanism for carrying out context transfers during handovers. Since our mechanism operates at the network level, we expect that it will be the most expedient way to provide for seamless handovers between heterogeneous networks. We report our results which show that fast handovers with context transfer at the network layer can support uninterrupted voice over IP (VoIP). Thus, our context transfer framework will catalyze the arrival of a unified wireless telecommunications network, with voice and data connectivity anytime, anywhere. Towards that end, we describe how our results and context transfer framework relate to other work within the IETF.

Convergence of telephone signaling, voice and data over a packet-switched network

Abstract: Cellular communications apparatus (70) includes a plurality of cellular network switches (28, 54), each switch adapted to transmit and receive signaling messages and media data, and a plurality of gateways (74, 78). At least one gateway is associated with each of the plurality of network switches. The gateway is coupled to receive the signaling messages and media data transmitted by the associated switch and to convey the messages and data together over a common, packet-switched communication link (76) to another of the gateways associated with another one of the network switches.

Arranging data ciphering in a wireless telecommunication system

Abstract: Arranging data ciphering in a telecommunication system comprising at least one wireless terminal, a wireless local area network and a public land mobile network. At least one first ciphering key according to the mobile network is calculated in the mobile network and in the terminal for a terminal identifier using a specific secret key for the identifier. Data transmission between the mobile network and the terminal is carried out through the wireless local area network. A second ciphering key is calculated in the terminal and in the mobile network using said at least one first ciphering key. The second ciphering key is sent from the mobile network to the wireless local area network. The data between the terminal and the network is ciphered using said second ciphering key.

Efficient location of mobile radiotelephones using cellular and GPS information

Abstract: The invention specifies various methods for the provision or calculation of a reference location for GPS-equipped mobile communications devices, specifically, GPS-equipped cellular phones. This is accomplished by providing certain GPS-related information over the cellular network, and by calculating reference locations based on various criteria, aided by actual position fixes provided by the built-in GPS receiver.

LEAP: A FIPA Platform for Handheld and Mobile Devices

Abstract: The ever-increasing importance of the market of portable devices is promoting the migration of technologies originally developed for the fixed network to the mobile network. This paper describes the general aim and the current results of a European-scale project intended to provide the enabling technology for deploying multi-agent systems across fixed and mobile networks. The LEAP project achieves its goal realising a FIPA platform that can be deployed seamlessly on any Java-enabled device with sufficient resources and with a wired or wireless connection. Such a platform is implemented as a new kernel for JADE to ease the migration of legacy agents to the mobile network and it exploits a modular design to scale its functionality with the capabilities of the device.

Communications using adaptive multi-rate codecs

Abstract: A communications network (10) includes a data network (24) that is coupled to a wireless access network (19) and other devices. The wireless access network (19) enables access by mobile stations (16, 17) of the data network (24). Each mobile station (16, 17), and optionally, one or more of other devices coupled to the data network (24), contains an adaptive multi-rate codec (coder/decoder) that can be set to operate at a plurality of rates. Based on the selected one of the plurality of rates, the mobile station (16 or 17) or other device sets a quality-of-service (QoS) indicator value in a packet carrying data, such as real-time data, over the wireless access network (19) and/or data network (24). By varying QoS requirements using the QoS indicator value for different codec rates, bandwidth requirements are varied so that more efficient usage of the data network is provided.

Wireless mobile communications at the start of the 21st century

Abstract: At the start of the 21st century, the wireless mobile markets are witnessing unprecedented growth fueled by an information explosion and a technology revolution. In the radio frequency arena, the trend is to move from narrowband to wideband with a family of standards tailored to a variety of application needs. Many enabling technologies including wideband code-division multiple access, software-defined radio, intelligent antennas, and digital processing devices are greatly improving the spectral efficiency of third-generation systems. In the mobile network area, the trend is to move from traditional circuit-switched systems to packet-switched programmable networks that integrate both voice and packet services, and eventually evolve toward an all-IP network. Furthermore, accompanied by wireless mobile location technology, wireless mobile Internet is expected to revolutionize the services that can be provided to consumers in the right place and at the right time. Wireless mobile communications may not only complement the well established wireline network; it may also become a serious competitor in years to come. We review the history of the wireless mobile communications, examine the current progress in standards and technologies, and discuss possible trends for wireless mobile solutions.

Terrestrial digital multimedia/television broadcasting system

Abstract: A system for transmitting information as frames in digital format between users on a network using a single frequency and TDMA and/or CDMA communications. Broadcasting, multicasting and unicasting are provided, and communications may be part of a downlink and/or an uplink signaling scheme that allows user-user and user-central station communication. A synchronization segment or pre-amble for a frame may include identification of the source and/or the intended recipient. Walsh, Haar, Rademacher coding of selected frame components, among others, can be incorporated. Reed Solomon encoding, signal interleaving and intra-leaving, trellis encoding and turbo encoding are used for error detection and correction. The system provides two-way communication with the Internet and/or with a cellular network and/or for smaller networks of users.

Wireless chat automatic status tracking

Abstract: A technique and apparatus to provide status tracking of presence and/or location of a mobile, wireless device to a requesting entity even outside of a particular wireless system. This allows wireless service providers the ability to monitor and log changes in the status of mobile stations within and/or outside their networks. Embodiments are disclosed wherein presence and/or location information is provided to entities outside of a particular servicing wireless network using the mechanisms of call processing components of a mobile network (e.g., call setup procedures), and using standard mechanisms currently available to any appropriately conforming Mobile Switching Center (MSC) element. In one disclosed embodiment, a wireless chat tracking system is implemented which utilizes a change in mobile registration status to automatically notify a chat group system outside the wireless network of current status information activity regarding a relevant device, e.g., registration activity or inactivity timeout. In the wireless chat automatic status tracking system, a registration notification (REGNOT) message is either explicitly forwarded or copied to an external IP based application (e.g., to a mobile chat group system). The change in mobile registration is communicated via a suitable signaling link (e.g., SS7, TCP/IP, etc.) between a Home Location Register (HLR) and the chat group system. Therefore, instead of a conventionally closed system using SS7 messages, REGNOT messages are pushed out over TCP/IP connections to external applications (e.g., chat servers) to automatically notify the external system of the location of a particular user.

A data fusion architecture for enhanced position estimation in wireless networks

Abstract: The problem of position determination of a mobile user in a wireless network has been studied extensively-particularly in the context of military operations and emergency 911 service in cellular networks. The Global Positioning System (GPS) and network-based angle of arrival (AOA), time difference of arrival (TDOA), and time of arrival (TOA) techniques offer solutions to the position estimation problem. However, each method has limitations that prevent its adoption as a universal solution. Data fusion is a collection of methods and techniques for merging disparate types of information. We present a data fusion model for the enhanced accuracy of position estimates within wireless networks. We illustrate our model with several examples and conclude with recommendations for future research directions.

A strategy to manage cache consistency in a disconnected distributed environment

Abstract: Modern distributed systems involving large number of nonstationary clients (mobile hosts, MH) connected via unreliable low-bandwidth communication channels are very prone to frequent disconnections. This disconnection may occur because of different reasons: The clients may voluntarily switch off (to save battery power), or a client may be involuntarily disconnected due to its own movement in a mobile network (hand-off, wireless link failures, etc.). A mobile computing environment is characterized by slow wireless links and relatively underprivileged hosts with limited battery powers. Still, when data at the server changes, the client hosts must be made aware of this fact in order for them to invalidate their cache, otherwise the host would continue to answer queries with the cached values returning incorrect data. The nature of the physical medium coupled with the fact that disconnections from the network are very frequent in mobile computing environments demand a cache invalidation strategy with minimum possible overheads. In this paper, we present a new cache maintenance scheme, called AS. The objective of the proposed scheme is to minimize the overhead for the MHs to validate their cache upon reconnection, to allow stateless servers, and to minimize the bandwidth requirement. The general approach is (1) to use asynchronous invalidation messages and (2) to buffer invalidation messages from servers at the MH's Home Location Cache (HLC) while the MH is disconnected from the network and redeliver these invalidation messages to the MH when it gets reconnected to the network. Use of asynchronous invalidation messages minimizes access latency, buffering of invalidation messages minimizes the overhead of validating MH's cache after each disconnection and use of HLC off-loads the overhead of maintaining state of MH's cache from the servers. The MH can be disconnected from the server either voluntarily or involuntarily. We capture the effects of both by using a single parameter: The percentage of time a mobile host is disconnected from the network. We demonstrate the efficacy of our scheme through simulation and performance modeling. In particular, we show that the average data access latency and the number of uplink requests by a MH decrease by using the proposed strategy at the cost of using buffer space at the HLC. We provide analytical comparison between our proposed scheme and the existing scheme for cache management in a mobile environment. Extensive experimental results are provided to compare the schemes in terms of performance metrics like latency, number of uplink requests, etc., under both a high and a low rate of change of data at servers for various values of the parameters. A mathematical model for the scheme is developed which matches closely with the simulation results.

Using a system for prediction of musical preferences for the distribution of musical content over cellular networks

Abstract: A system and a methond for predicting the musical taste and/or preferences of the user and its integration into services provided by a wireless network provider Although the present application is directed toward implementations with wireless providers, the present invention can also be implemented on a regular, i.e., wireless, network. The core of the present invention is a system capable of predicting whether a given user, i.e., customer, likes or does not like a specific song from a pre-analyzed catalog Once such a prediction has been performed, those items that are predicted to be liked best by the user may be forwarded to the mobile device of the user on the cellular (or other wireless) network. The system maintains a database containing properiety information about the songs in the catalog and, most important, a description (profile) of the musical taste of each of its customers, identified by their cellular telephone number

Access system for a cellular network

Abstract: The present invention relates to a method and system for providing access to a cellular network (8), wherein a terminal device (1) is connected to an access de-vice (2) according to access specifications of a broadband access network (12) which is not specifically designed to be used as a part of cellular network (8). The terminal device (1) indicates to the access device (2) that it wishes to be connected to the cellular network (8), and a session or call and a radio bearer is setup between the terminal device (1) and the cellular network (8). To achieve this, a service node (5) provided in the cellular network (8) requests a suitable access bearer from the access network (12) and the access device (2) sets up a corresponding access channel towards the terminal device (1). The terminal device (1) then associates the access channel to the correct radio bearer by using a corresponding identification. Thereby, service functions of the cellular network, e.g. UMTS services, can be distributed via any access network and existing broadband or high-speed access networks can be implemented in new cellular network structures. A huge capacity enhancement can thus be offered to the network operators of the cellular network without any standardization effort or license fee and at very small investment and maintenance costs.