Showing papers on "Mobile telephony published in 1991"

On the capacity of a cellular CDMA system

Abstract: It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

Spread spectrum for mobile communications

Abstract: The characteristics of spread spectrum that make it advantageous for mobile communications are described. The parameters that determine both the performance and the total capacity are introduced, and an analysis which yields (approximately) the number of users that can simultaneously communicate, while maintaining a specified level of performance, is presented. Spread spectrum overlay, wherein a code-division multiple-access (CDMA) network shares a frequency band with narrow-band users, is analyzed, and it is seen that excision of the narrowband signals from the CDMA receivers before despreading can improve both performance and capacity. >

Integrated mobile robot control

Abstract: This paper describes the structure, implementation, and operation of a real-time mobile robot controller which integrates capabilities such as: position estimation, path specification and tracking, human interfaces, fast communication, and multiple client support. The benefits of such high-level capabilities in a low-level controller was shown by its implementation for the Navlab autonomous vehicle. In addition, performance results from positioning and tracking systems are reported and analyzed.

Method for regulating power in a digital mobile telephony system

Abstract: The present invention relates to a method of regulating or adjusting the transmission power when transmitting signals between a mobile station and a base station in a digital mobile telephony system. The output power is regulated with the intention of constantly maintaining the transmission power at an optimum level, by which is meant that the transmission power is as low as possible such as to prevent unnecessary disturbance of neighbouring channels transmitting information on the same frequency, but sufficiently high for the transmitted information to be interpreted in the receiver. The measurement values of signal strength and signal-transmission quality are collected, the mean values of the signal strength and transmission quality are calculated on the basis of the collected measurement values. kith the aid of the calculated mean values, there is calculated an anticipated value of signal strength and transmission quality *(*Z_QQ) at the next time-point, provided that the transmission power is maintained unchanged in relation to the transmission power at the present or instant time-point. Finally, the transmission power at the next time-point is regulated on the basis of these anticipated values. The transmission power is increased when the anticipated transmission quality is poorer than the desired quality and is increased when the anticipated quality is higher than the highest permitted quality or when the anticipated signal strength is greater than the maximum permitted value. The transmission power is otherwise maintained unchanged.

Radio base station for mobile communication

Abstract: PURPOSE:To solve problems such as the difficulty of land obtaining and undesivable influence to be extended upon the scenery of a city in respect to a radio base station for mobile communication such as an automobile telephone. CONSTITUTION:The radio station is provided with a strut 30 for supporting a street lamp, an antenna 20 mounted on the strut 30, a connection terminal to a cable transmission line 40 connected to a telephone exchange network, transmitting/receiving parts 12, 13 connected between the connection terminal and the antenna 20, a power supply part 15 for receiving AC power from a feeder 32 shaved with the street lamp and supplying operation power to the transmitting/receiving parts 12, 13, and a body part 10 fixed to the inside of the strut 30.

Route guidance system for provding a mobile station with optimum route data in response to a guidance request together with base station data indicative of an identification of a base station

Abstract: A mobile telecommunications system includes a plurality of base stations each being communicatable with a mobile station by radio. A telecommunications network accommodates the plurality of base stations for switching communications to the plurality of base stations. A system center is connected to the telecommunications network for selecting an optimum route on the basis of instantaneous traffic conditions. Any of the base stations sends to the mobile station base station data representative of the base station. When the mobile station sends a guidance request for requesting route guidance data, the telecommunications network reports the guidance request to the system center. The system center selects, in response to the guidance request, an optimum route matching instantaneous traffic conditions and transmits optimum route data representative of the optimum route to the mobile station over the telecommunications network.

Mobile telephony system intended for indoor and outdoor subscriber use

Abstract: A mobile telephony system includes an internal part-system, which is installed in a building and an external part-system. The internal part-system has internal base stations which are connected to a mobile switching center, to which external base stations are also connected. The mobile telephony system is assigned a frequency band which comprises a plurality of channels. The external part-system is divided into cells and has fixed channel assignment with a few channels to each external base stations. The internal part-system is adaptive and the internal base stations have access to all channels of the system. In order to determine whether a mobile station belongs to the internal or to the external part-system, an internal identification word is transmitted from the internal base stations and an external identification word is transmitted from the external base stations. When the signal strength of the internal identification word exceeds a threshold value, the mobile station transmits an internal identification word to the internal base stations. If the signal strength falls beneath this threshold value, the mobile station identifies itself to the external part-system.

Handover criterion for macro and microcellular systems

Abstract: In order to realize fast handover in both microcells and macrocells, the relationship between averaging, the received signal level comparison method, and handover detection delay was analyzed. The analytical results were verified by handover simulations performed using experimental propagation data. As the criterion for accurate and stable handover in both the macrocell and the microcell, a combined handover decision is suggested which consists of long-term averaging with a small hysteresis margin and short-term averaging with a large hysteresis margin. >

Distributed control methods for management of migrating data stations in a wireless communications network

Abstract: In a wireless communications network having a plurality of header stations (12) in bidirectional wireless communication with one or more mobile communication units (10), a method of managing ownership of the mobile units. In accordance with the method the following steps are executed. A first step receives, with a mobile communication unit located at a position (44) that is served by two or more of the header stations, a transmission from each of the header stations. The received transmissions are received over the wireless communications network and each uniquely identify the transmitting header station. The method further includes a step of selecting, with the mobile communication unit, one of the header stations as a header station to manage future wireless communications for the mobile communications unit. A further step is performed if the selected header station is not a header station that is presently managing wireless communications for the mobile communications unit. This further step transmits a message over the wireless network from the mobile communications unit to the selected header station requesting that the mobile communications unit be assigned to the selected header station.

Location registration system in mobile communication

Abstract: In a mobile communication system in which the service area is covered with a plurality of location registration areas each having a plurality of cells each relating to a specific base station, each location registration area has a plurality of groups so that the cells belonging to any group overlaps partly with the cells of other groups, but do not completely coincide with cells of other groups, and each mobile station belongs to one of said groups When a mobile station moves beyond the border of location registration areas, the location updating for the mobile station is carried out at the cell in which the mobile station stays In that case, as the mobile stations are classified into a plurality of groups, the traffic in each cell for location updating is dispersed to many cells, and the maximum traffic density for location updating per cell is reduced So, the number of control channels in the system for location updating may be reduced

Multiple-mode cellular telephone control device

Abstract: A mobile communication apparatus such as a cellular telephone for automotive use is provided with selectable modes for accessing stored telephone numbers either by speed-dial codes (i.e., memory storage location) or alphabetic names associated with each telephone number. A user interface is employed having an alpha mode for displaying (20) and entering (21-32) alphabetic names corresponding to telephone numbers. The alpha mode (22) includes a jump function and a scrolling function for browsing stored alphabetic names. A normal mode (23) is provided for storing telephone numbers at desired storage locations. A speed-dial mode (21) is also provided for instant dialling of the most frequently called numbers.

Mobile telephony system

Abstract: A mobile telephony system intended for use by outdoor subscribers, for instance in cars, while affording, at the same time, high traffic capacity and relatively disturbance-free speech transmission to subscribers located within a building, for instance an office building. Signal transmission between mobile stations (MS, MSI) and base stations (BS1, BSI) is effected with radio waves in a first part-system (7), for instance intended for telephony traffic via car telephones, and with light, at least in the area nearest the mobile stations (MSI), in a second part-system (6) intended, for instance, for an office building. Signal transmission with light can also be effected in areas that contain electronic apparatus which is sensitive to radio disturbances, for instance in hospitals and/or in areas in which strong radio disturbances capable of preventing mobile telephony transmission with radio waves occur. Certain mobile stations may be capable of being switched between signal transmission with radio waves and signal transmission with light, which enables these stations to be used in both part-systems (7, 6).

Security Aspects of Mobile Communications

Abstract: Security requirements and services of a mobile communication system differ, due to the radio communication between the user and the base station, extensively from those of a fixed network. There is no physical link in the form of a (fixed) telephone line between the user and the local exchange, which could serve to “identify” the user for routing and charging purposes. His identity has to be verified over an air interface. Authentication by means of cryptographic procedures is thus required to stop impostors from taking on the identity of somebody else and “transferring” calls and charges. Eavesdropping on the radio path and intercepting a conversation or data or tracing the whereabouts of a user by listening to signalling data are other serious threats. This paper discusses the countermeasures designed into one of the most advanced radio networks, the Global System for Mobile Communications, as well as some security aspects of the network management related to these measures. Some of the differences between this system and the planned Digital European Cordless Telephone system are highlighted.

A multi-DSP implementation of a broad-band adaptive beamformer for use in a hands-free mobile radio telephone

Abstract: An implementation of a broadband adaptive array on a multiprocessor digital signal processing system for use in a hands free mobile radio telephone is described. This implementation of a five-microphone adaptive Griffiths-Jim array can handle FIR filters with up to 128 taps behind each microphone at a sampling rate of 8 kHz. The filter structure makes it possible to combine an adaptive array with a noise canceler. The near-field problem has been solved by using focusing, a speech-controlled adaptive algorithm, and a short hourglass. Preliminary measurements indicate a considerable potential for this technique in hands-free mobile telephony. The array gives a 20-30 dB suppression of a broadband jammer covering 300-1100 Hz, even with three reflecting walls surrounding the microphone. >

Maintaining stable virtual circuit data connections with spare protocol handler

Abstract: This invention relates to apparatus and methods for providing cellular mobile telecommunication service in accordance with the requirements of the Global Systems for Mobile Communications (GSM) standard. A modular switching system is provided which performs the functions of the mobile switching center plus those of a home location register, authentication center, visitor location register, and equipment identity register. The latter functions are advantageously spread among the modules of the switching system, thus avoiding the getting started cost of expensive dedicated data bases. A wireless global switching module advantageously switches mobile communications control messages among the modules of the system and between the modules and the base station systems, and terminates signaling links between the mobile switching center and the base station systems. Arrangements are provided for maintaining stable virtual circuit connections in this module even in the presence of protocol handler failures. The state of each virtual circuit is kept in a protocol handler (PH) controlling the circuit and, whenever a stable state is reached, notifying an adjacent PH; if the controlling PH fails, the adjacent PH takes over control of that virtual circuit for immediate purposes, and a spare PH serves any new requests that would normally be served by the failed PH. The spare PH transmits messages, originally destined to the failed PH, to the adjacent PH for those virtual circuits already in use at the time of the failure and being served by the adjacent PH.

Graph theoretical considerations of channel offset systems in a cellular mobile system

Abstract: The problem of assigning channels in a channel-offset-type of cellular mobile radio communication system is formulated as a problem of assigning channels to the vertices of a network. It is shown that the assignment problem in a network is a generalized graph coloring problem. When the interchannel interference function is a rational number, the optimal channel offset scheme is obtained. and upper and lower bounds of the minimum total bandwidth in a channel-offset scheme are derived. These factors give basic and useful knowledge for designing a channel-offset system of a cellular mobile system, and they are useful not only for a fixed channel assignment but also for a dynamic channel assignment and rearrangement. >

Implementation of a real-time mobile channel simulator using a DSP chip

Abstract: The problem of implementing a real-time channel simulator that can be used to test mobile communications equipment in the laboratory is considered. The objective of the design is to replicate the statistical characteristics of the multipath fading environment on a single-chip, fixed-point 16-b digital signal processor (DSP). The simulator design permits the user to select the simulation parameters, including vehicular speed, carrier frequency, ratio between the line-of-sight component and the multipath component, and the variance of average power. The design is based on variable-sampling-rate DSP techniques, and offers a novel solution to suppress the aliasing terms at intermediate stages where access to analog filters is cumbersome and costly. >

Numbering and addressing in IBCN for mobile communications

Abstract: Numbering and addressing issues arising in the integrated broadband communication network (IBCN) for the support of the Universal Mobile Telecommunication System (UMTS) and Personal Telecommunication Service (PTS) are discussed. Mobile communications services will allow a user to roam within a network. Thus, there will be a need to identify several types of objects (terminals, network points of attachment, users, customers premises networks or CPN, etc.). The mobility properties of these objects will necessitate dynamic bindings between their addresses and names. The situation is further complicated because the mobility may be embedded. A mobile user may employ a mobile terminal in a mobile CPN. Therefore, in UMTS and PTS there is a need for dynamic binding of various identifiers with location information data. The exclusive use of personal telecommunication numbers (PTNs) as dialing numbers (DNs) is proposed in IBCN for UMTS and PTS. That is, PTNs will be used (during dialing) for making calls to mobile terminals, mobile users, and fixed subscribers. When the personal communication service is not provided, the DN corresponds to the terminal number of the equipment (fixed or mobile) of the called subscriber. >

Mobile trunked radio system design and simulation

Abstract: The fundamentals of trunked land mobile radio systems are examined. Many novel resource allocation methods have been examined to meet the unique needs of this service. These assignment algorithms are based on radio unit registration, user group talk zone requirements, and the channel availability. Computer simulation has been used to support this resource allocation method design. In particular, a discrete-event model of a wide area dynamic site assignment based trunked radio system is described. Simulation results are presented for an example comparing the performance of a particular trunking system using the forced vs. dynamic critical assignment method. The example system is to support 7777 radio users across 25 base sites. >

Adjustable transmission power for mobile communications with omnidirectional and directional antennas in a one- and multi-hop environment

Abstract: A model for analyzing the performance of a multihop S-ALOHA packet radio network is presented. Analytic results from this model show that adjustable transmission power improves the network performance substantially. A vehicle, before transmitting to another one, adjusts its transmission power such that the other vehicle is just reached. This minimizes the area covered by a transmission and reduces the possible distance to potential receivers of other ongoing transmissions, resulting in a higher throughput and a reduced backlog time. It is shown that adjusting the transmission power is very promising in terms of network performance in a hidden-station environment and therefore shows promise for RTI (road traffic informatics) communication networks, especially if the probability of selecting a receiving vehicle is a function of distance. >

Globalstar: Linking The World Via Mobile Connections

Abstract: 1.0 Summary GLOBALSTAR enhances worldwide mobile services using a constellation of low earth orbiting satellites. The key feature of this system is its ability to offer low-cost, high quality and flexible services not currently available in areas not economical to serve terrestrially. It utilizes existing public and/or private network facilities to extend mobile users' global connectivity. GLOBALSTAR subscribers will be able to communicate wherever and whenever they happen to be. Furthermore, such operation is deemed to be both profitable and low risk.

An evaluation of direct sequence CDMA for future mobile communication networks

Abstract: The performance and some of the implementation aspects of a practical mobile radio communications network employing direct-sequence code-division multiple access (DS-CDMA) are examined. The use of spread-spectrum techniques results in a wideband system, thus permitting the potential exploitation of multipath signal energy and permitting a means of reducing interference arising from other users of the spectrum. An analytical performance model is developed in order to assess the spectral efficiency of a DS-CDMA communications network. The computer model permits the performance evaluation of various path diversity schemes alongside numerous digital-modulation and error-correction coding techniques while operating in a mobile radio channel. In order to substantiate the results presented, novel power control and handoff protocols are also proposed in light of the assumptions made. >

A new radio access protocol and network architecture for mobile packet data

Abstract: A novel mobile data technology designed to support low-cost, hand-portable wireless data terminals is reviewed. The end-to-end service, the radio protocol, and the fixed network architecture are described. The radio protocol incorporates specific features to simplify hardware design, and the fixed network architecture provides for economical rollout. The UK implementation of the network is described, and a novel communications service is introduced, based on a mobile packet data network but effectively delivering two-way message paging to the user. >

Site diversity in land-mobile cellular telephony network with discontinuous voice transmission

Abstract: Cellular radio channels suffer from signal outages due to multipath fading and shadowing. Analytical expressions are given for the probability that the instantaneous C/I-ratio drops below a required protection ratio. A radio signal from a mobile subscriber exhibits outages at different base station sites with relatively low correlation. The quality of communication over a mobile telephone circuit can be improved by appropriately combining voice segments received at various base stations. The probability of dropping a voice segment for an end-to-end «up-link» circuit (mobile-to-PSTN) in an interference-limited cellular network with discontinuous voice transmission and macro diversity is evaluated mathematically. Asymptotic expressions of the signal outage probability for high average C/I-ratios are presented in closed form.

Link control in terrestrial/satellite mobile communication systems

Abstract: Algorithms and signalling requirements of procedures for link selection and handover are discussed, both for terrestrial and satellite land mobile communications. For terrestrial cellular systems the methods are well known in principle, it is argued that similar procedures could also be employed in satellite multi-beam systems. Choice of terrestrial or satellite links in integrated dual mode systems is considered in some detail.

Network aspects for the third generation mobiles-RACE project 1043

Abstract: The RACE (Research and Development in Advanced Communications Technologies in Europe) 1043 mobile telecommunication project studies a third-generation mobile telecommunication system called the Universal Mobile Telecommunication System (UMTS). A brief description is given of the fundamental requirements to be met by UMTS and some results in the fixed network area achieved during the first three years of the project are highlighted. An important characteristic of UMTS is the universal aspect, which means availability anywhere, both indoors and outdoors. It is explained that an essential subject in UMTS is the integration with networks for fixed telecommunications. New network concepts are also needed to reduce the signaling load within the network. Two of these new concepts, separation of call and connection control and distributed databases, are discussed. >

2.6 Ghz Band Multipath Characteristics for Urban Microcellular Telecommunication Systems

Abstract: L O Summary Measurement of multipath delay profile characteristics in the 2.6 GWz band has been carried out within a 2 x 1.5 km area in metropolitan Tokyo to investigate the feasibility of a high speed digital micro-cellular portable radio system. The measurement system has time resolution of 40 ns. In this paper we present the spatial variations of the power delay profile and the delay-Doppler spectra, and we show the cumulative distribution of the delay spread and the error rate caused by multipath in the micro-cellular propagation environment.

A multi-carrier amplifier for future mobile communications systems

Abstract: The goal of dynamic channel allocation has eluded cellular system designers and operators alike since the concept of cellular mobile communications first became a reality. The idea of virtually instantaneous frequency re-planning of selected parts (or even all) of a cellular network has obvious attractions and alone would justify the considerable efforts being invested by a number of organisations towards this goal. The achievement of this flexibility would either require the use of remotely tunable combiners or of a broadband, highly linear power amplifier. The former option is unlikely ever to achieve the total flexibility promised by the use of a linear amplifier and hence this latter field has been the subject of considerable recent interest. >