Showing papers on "Mobile telephony published in 1993"

Overview of the GSM system and protocol architecture

Abstract: The global system for mobile telecommunications (GSM), which provides terminal mobility, with personal mobility provided through the insertion of a subscriber identity module (SIM) into the GSM network, is discussed. Cellular mobile communications, the cellular network infrastructure, and the specification of network databases and standards are described. The GSMs, numbering plan, radio channel structure, mobility management, call routing and signaling, protocol layering architecture, signaling transport protocols, and paging messaging systems are also described. >

The PARCTAB mobile computing system

Abstract: The PARCTAB is a personal digital assistant (PDA) that communicates via infrared (IR) datapackets to a network of IR transceivers. The infrared network is designed for in-building use, where each room becomes a communication cell. In contrast to the approach used by other PDAs, most PARCTAB applications run on remote hosts and therefore depend on reliable communication through the IR network. The infrastructure provides reliability as well as uninterrupted service when a PARCTAB moves from cell to cell. The PARCTAB and a supporting infrastructure has been operational since March 1993 at the Computer Science Lab at Xerox PARC. The system currently comprises thirty cells and twenty-five PARCTABs and will expand in the near future. There are three types of software components in the PARCTAB system: gateways, agents, and applications. Gateways implement a datagram service for sending and receiving packets using IR signals. Each tab is represented by an agent. An agent tracks the location of its tab and provides location independent reliable remote procedure calls. The protocols enforce security, preventing, for example, an unauthorized application from taking control of a tab. >

Mobile communication satellite payload

Abstract: A communications satellite payload provides for efficient communications between user devices, such as hand held cellular telephones, and terrestrial gateways that may be connected to world-wide public telephone and telegraph (PTTs) networks. The satellite payload simultaneously supports a plurality of independent antenna beams, for example 12 or 16 beams, on both the uplink and downlink for user devices employing full duplex communications. The satellite payload furthermore supports an identical number of full duplex channels between a terrestrial gateway and the satellite. The communications satellite payload is carried by one satellite of a plurality of such satellites in a low earth orbit (LEO) constellation to provide worldwide communications. Downlink beam forming occurs prior to final amplification of transmitted signals, thereby reducing losses within the beam forming equipment. A multi-element phased array of receiving antennas and a multi-element phased array of transmitting antennas is also disclosed, wherein each element of each phased array is utilized for each individual one of a plurality of received or transmitted beams.

Performance of CDMA mobile communication systems using antenna arrays

Abstract: The use antenna arrays in cellular code division multiple access mobile communications is studied. Techniques to localize each mobile within the cell and to generate tracking adaptive receive (and transmit) beams are addressed. The authors show that such enhancement of the CDMA system results in increased system capacity and improved robustness to power control errors. Preliminary simulation results are presented for capacity and robustness improvements for typical scenarios. >

Wireless private branch exchange system for use with mobile communication devices

Abstract: A wireless PBX system having at least one predetermined coverage area, and having a predefined group of mobile communication devices associated with each predetermined coverage area is provided. Each of the mobile communication devices belonging to a predefined group includes a first telephone number by which the mobile communication device may be reached via a wireless network, and a second, short extension number, identifying the mobile communication device as belonging to a particular group. Mobile communication devices within one of the at least one predefined groups may reach other mobile communication devices within their group or within another group by dialing the second extension number of the desired recipient mobile communication device, and may reach other communication devices not associated with any group by dialing an appropriate telephone number. In accordance with the present invention, a charging register records data about calls made by each mobile communication device and enables charging of calls at various levels depending on whether a call was placed between two mobile communication devices within a particular group, whether a call was placed between two mobile communication devices in two different groups, and whether a call was placed between a mobile communication device of a particular group to a communication device not belonging to any group.

Handling mobile clients: a case for indirect interaction

Abstract: Networking protocols are being modified to handle mobility of hosts. This paper argues that there is a need to make mobility explicit at every level of the OSI model - even above the network level through user or application level. Further, it is proposed that the mobile host and the first hop (wireless link) of communication be handled differently than the rest of the network. Hence, in networks with mobile hosts, we propose a radical approach of indirect interaction between clients and servers. >

Dual mode cellular modem

Abstract: A mobile phone includes a modem, hereinafter referred to as a cellular radio modem. This cellular radio modem supports two modes of operation--an analog mode, where the cellular radio modem provides an analog signal for transmission; and a digital mode, where the cellular radio modem provides a digital bit stream for transmission. During operation, i.e., the existence of a data connection to a far-end modem, the cellular radio modem is alerted by the cellular network to switch to the appropriate mode--analog or digital. The cellular radio modem then switches and continues transmission in the new mode. In this embodiment, the far-end modem is part of a modem-pool located within the Mobile Telecommunications Switching Office of the cellular network. The far-end modem automatically detects this switch by the cellular radio modem and itself switches to the appropriate mode. This allows a mobile data user to transparently move between the analog mode and the digital mode without disconnecting a preexisting data connection.

Methods for polling mobile users in a multiple cell wireless network

Abstract: A method for communicating information bidirectionally between a wired network (1) and a wireless network. The wireless network is of the type that includes header stations (12) each having a communication cell (2) associated therewith and one or more mobile communication units (10) disposed within the communication cell. The method includes a first step of, during a first portion of a wireless communication cycle, transmitting information over an uplink wireless communication channel from one or more of the mobile communication units to the header station. A second step of the method, accomplished during a second portion of the wireless communication cycle, transmits information over a downlink wireless communication channel from the header station to one or more of the mobile communication units. The information transmitted downlink includes frames of data received by the header station from the wired network. The first portion may be accomplished in part or in total by a CSMA protocol where the mobile units contend for access to the uplink communication channel. In one embodiment the header station initiates the first portion by transmitting to the header stations information for scheduling the sequence of the uplink transmissions.

Mobile communication congestion control system

Abstract: A mobile communication system contains a mobile switching center connected to a plurality of base stations constituting a radio service zone and a plurality of mobile stations. The mobile switching center monitors the usage of a traffic channel for each radio service zone and has a usage threshold value for each radio service zone, and informs those to the mobile station via the base station. The busy mobile station compares the traffic channel usage information and the usage threshold value information and the radio zone communicated. When the traffic channel usage is greater than the usage threshold value, the mobile station selects a hand-over radio zone destination based on the received signal strength and quality, and the traffic channel usage information and the usage threshold value information of the adjacent zone, and then transmits a hand-over request designating the hand-over radio zone destination to the mobile switching center.

Method and apparatus for assigning radio channels in mobile communications systems

Abstract: There is provided a method and an apparatus for assigning a radio channel between base and mobile stations in a mobile communication system, which provide advantages of first available and reuse partitioning systems and do not cause as great a proportional increase in a processing amount as an ARP system. A radio zone is divided into a number of regions having the same area which is equal to channel number N, usable in an entire system by concentric circles centering on a base station 12. Channels 1 to N s are allotted to the respective regions. Upon the issuance of a channel assignment request, a channel corresponding to the region where the mobile station is located or its neighboring channels is assigned preferentially.

User interface issues in mobile computing

Abstract: The age of mobile computing with small portable computers is upon us. However, systems researchers continue to focus on transferring their workstation environments to these machines rather than studying what tasks more typical users wish to perform. Furthermore, we argue that even in the unlikely event that these tasks are the same as those performed by researchers on their workstations, desktop environments and applications may still be inappropriate for the wide range of mobile devices that will be marketed. To explore this area, we have built a mobile computing device along with a user interface system that attempts to address some of these issues. >

Optical fiber feeder for microcellular mobile communication systems (H-O15)

Abstract: The authors investigate the feasibility of using an optical fiber feeder for microcellular mobile communication systems. The optical feeder enables compact and low-cost base stations, easy radio channel control, and flexible mobile communication systems. Basic transmission characteristics were investigated through optical transmission experiments. Using these results, it is estimated that the optical feeder can transmit 880 telephone channels for digital TDM systems and 2000 channels for analog FDM systems through 20 km of optical fiber. Furthermore, two kinds of novel techniques that enlarge dynamic range of the optical feeder are reported. >

A frame structure using consecutive slot assignments for mobile communications

Abstract: An improved frame structure for use in mobile communications systems utilizing slotted protocols is provided. According to the present invention, consecutive slots in a frame are assigned to each mobile unit so that the mobile unit transmits to a base station during the first slot and receives a transmission from the base station during the second slot. This frame structure, permits the mobile unit to monitor various frequencies for a longer and more continuous period of time. It is important for the mobile unit to have enough time to monitor frequencies while it is not transmitting or receiving so that base station handoff and interference avoidance handoff techniques can be performed by the mobile communications system. Furthermore, according to the frame structure provided by the present invention, the mobile units can be designed with a standard frequency synthesizer. The improved frame structure also allows channel distortion to be minimized by providing adaptive equalization with transmit precompensation and/or antenna diversity in the base stations.

Mobile telephone terminal and method of preventing unlawful use thereof

Abstract: A first ID code ESN (electronic serial number) for apparatus identification and a second ID code MIN (mobile identification number) such as a telephone number are stored beforehand in a non-volatile memory of a mobile telephone terminal. The mobile telephone terminal transmits these ID codes to a network at the time of communication, and whether or not this set of first and second ID codes has been registered is discriminated on the network side. Communication is allowed if the ID codes have been registered. In order to prevent unlawful use of the mobile telephone terminal in mobile communication, (1) the first ID code is encrypted on the side of a writing device and then inputted to the mobile telephone terminal when the first ID code is written in the non-volatile memory of the mobile telephone terminal, (2) the mobile telephone terminal writes the encrypted first ID code in the non-volatile memory as is, and (3) the encrypted first ID code is decoded at the time of communication and transmitted to the network along with the second ID code.

Mobile communications systems and interconnections strategies for use between different networks and different tariffs of such systems

Abstract: A flexible and equitable PCN/PSTN interconnection strategy between a communications network having mobile subscribers, such as a PCN network, and a PSTN whereby to form a communication system in which multiple tariffs can be applied, the tariff applied being determined by the actual location of the mobile subscriber involved in a call. The PSTN (2, 6, 9, 10) is not given total access to the PCN (1, 5, 8, 11) location registers, rather a PSTN to PCN call is via a PCN gateway (5) which does have access to the location registers. The gateway (5) accepts zonal calls with which are associated one tariff (zonal interconnect 4) but for, for example, local or interzonal calls, it provides drop back messages to the PSTN to arrange for appropriate rerouting to other gateways (1, 8) of the PCN which have different tariffs associated therewith (local interconnect 3, interzonal interconnect 7).

Method and apparatus for supporting mobile communications in mobile communications networks

Abstract: Distributed call setup and rerouting are realized in a mobile-communications network. A connection tree is set up within the network, e.g., upon a mobile user accessing a base station. The connection tree comprises communication routes from a fixed point in the network, the root of the tree, to each base station within a vicinity of the base station accessed by the mobile user. When the mobile user moves from one cell to another within the connection tree, the call is rerouted to another route within the connection tree.

Call processing using logical channel assignments

Abstract: A communications network includes satellites, which serve as switching nodes and move in orbits about the earth. The network additionally includes stationary switching offices. Mobile communication units communicate with the network through the satellites using TDMA data packets and network control messages. The switching offices couple to PSTNs. Each mobile unit is managed by a nearby switching office that assigns a logical channel identification (LCID) value to the unit. The unit and network use the LCID value to identify the unit in network communications so that network resources are conserved. The network insures that LCID values assigned to opposing parties in a call are included in all TDMA data packets transported to the opposing parties. Satellites and switching offices use these LCID values as logical channel assignments which do not change throughout the duration of the call, in spite of movement by satellites.

Introduction to Satellite Communications

Abstract: We begin our study of satellite communications by examining some of the special features that satellite systems have to offer in comparison with optical fibres and other communication media. The opportunity to provide efficient mobile communications via satellite is seen as likely to have a major influence on the design of future satellite systems.

Enhancing the performance of mobile communications systems

Abstract: This paper describes and quantitatively evaluates a new cell design method and new radio link control procedures that increase the capacity of micro-macrocell systems The cell design method is based on a technique of predicting the location of mobile subscribers in the base station area The first part of this paper outlines prediction strategies and their precision The second part describes a new cell selection method intended for use with a micro-macrocell overlay cell layout and shows that this method reduces the base station processing load This paper also considers channel assignment algorithms and handover algorithms for microcell systems Specific examples of these approaches are shown for the second-generation Japanese personal digital cellular system

Computer-aided design and evaluation of mobile radio local area networks in RTI/IVHS environments

Abstract: An approach to designing and evaluating protocols for a class of mobile radio networks is presented. Characteristics of these mobile radio LANs are described, derived from the background of road transport informatics/intelligent vehicle highway system (RTI/IVHS) applications. Performance measures defined as suitable for the requirements of multipoint intervehicle communication are based on the concept of the zone of relevance, an area around a vehicle where communication to relevant neighbors is required. The simulation environment MONET3 has been designed to evaluate these measures. Protocol design in MONET3 requires an exact model of propagation characteristics and a realistic model of road traffic. A measurement-based 60-GHz channel model developed for intervehicle communication is presented. MONET3 is interconnected to a dedicated traffic simulator, the Autobahn Simulator, originally designed for traffic engineering in RTI systems. A case study using the simulator is presented as an example. >

Model for location updating and handover rate estimation in mobile telecommunications

Abstract: A model for estimating car and pedestrian crossing rates at the border of an area is developed. Validation results based on real measurements display the excellent accuracy the model provides. The model is then adjusted to estimate location updating and handover rates in cellular mobile networks.

Traffic performance analysis for cellular communication systems with mixed platform types and queued hand-offs

Abstract: Cellular communication systems that support a mixture of platform types and queuing of hand-off calls are considered. In pure loss systems, if there are no channels available at the target gateway, the hand-off attempt fails and the call is forced to terminate. In delay systems, however, hand-off calls can be held in queue while the supporting mobile is within a transition region where acceptable performance can be provided by at least two different gateways (base stations). When only a finite number of hand-off calls can be queued, mixed delay/loss configurations arise. An analytical tractable model is developed to predict communications traffic performance in such systems. A suitable state characterization is identified which allows the problem to be formulated within the framework of multi-dimensional birth-death processes. The authors extend this approach and demonstrate how delay and combined delay/loss systems can be considered within the analytical framework that is being developed.

Positioning systems utilizing mobile telephone system for correction signals

Abstract: A positioning system where receiving stations such as multipurpose mobile communications devices (25) can thereby calculate their position; the system further including base stations (28) adapted to receive position information from the receiving stations (25) over a communications path (22) of a mobile telephone system. The system allows the receiving stations to receive a correction signal (13) from a correction station (14) over the communications path (22) on a special signalling layer (24) whereby the receiving stations can calculate a corrected position. The system can be used in conjunction with many forms of mobile telephone system.

Performance analysis of a dynamic channel allocation technique for terrestrial and satellite mobile cellular networks

Abstract: The paper deals with an efficient dynamic channel allocation (DCA) technique suitable for applications in both terrestrial and satellite cellular networks. A cost function is defined to allow an optimum selection of the channel to be allocated on demand. The performance of the novel DCA technique in terms of blocking probability has been derived by simulations. The obtained results are compared with those achieved by a fixed channel allocation (FCA) technique to show a better behaviour. >

Mobile communications in the 21st century

Abstract: If a scientist in 1892 had been sufficiently foolish to predict the development of communications in the 20th century, we can be certain that his prophesies would have been substantially incorrect. He perhaps would have forecasted correctly that the telephone would be nearly ubiquitous, but it is doubtful that he would have concluded that digital communications, with its roots in telegraphy, would be used to convey the human voice. Marconi had not conducted his famous radio communication experiments, but Hertz had demonstrated radio waves. It was therefore predictable, given some unforeseen and clever means of production and detection of radio waves, that these waves could be transmitted around the world. Satellite communications would have seemed unthinkable in an age before the South Pole was discovered, the first car appeared, or the first flight was made.

An analysis of multi-receiver, non-adaptive, slotted Aloha with capture for wireless communications in factories

Abstract: An architecture for incorporating mobile data users into an existing MAP/TOP (Manufacturing Automation Protocol/Technical and Office Protocol) system is presented. The scheme attaches a small number of radio base stations to the TOP network through which the mobiles may access the system by executing a capture-based, multi-receiver extension of the traditional nonadaptive slotted Aloha protocol. A two-component capture model motivated by the factory channel is developed, and the multireceiver system's throughput performance is analyzed under two transmission models: base location independent and spatially correlated. It is seen that there is significant throughput degradation when base coverage areas overlap, indicating that this overlap should be minimized during system design. >

Mobile communication system and mobile communication terminal equipment used for the same

Abstract: PURPOSE: To directly perform communication between the mobile communication terminal equipment and the other mobile communication terminal equipment without recognizing the telephone number of the communicating party. CONSTITUTION: A mobile communication terminal equipment 11 (13) out of the service area of a radio base station 21 adds and transmits an identification symbol showing a special communication class (repetition). Based on the identification symbol, a mobile communication terminal equipment 12 inside the range of enabling communication from the mobile communication terminal equipment 13 and inside the service area performs communication to the radio base station 21 or the mobile communication terminal equipment 11 based on the contents (repetition) of the identification symbol. When the identification symbol shows the request of repetition, the mobile communication terminal equipment 12 can repeat speaking even while the mobile communication terminal equipment 13 is out of the service area and when the identification symbol shows multiaddress communication, simultaneous speaking due to a lot of mobile object communication equipments 11, 12 and 13 is enabled while the other mobile object communication equipment exists inside the range to reach radio waves. COPYRIGHT: (C)1995,JPO

Evolution of mobile communications in the u.s. and europe : regulation, technology, and markets

Abstract: A rich source of information for all actively involved parties, this book analyzes and evaluates developments in nonmilitary, private, and public land mobile communications systems. It comprehensively describes all issues involved in the complex process of shaping the future of mobile communications.

Mobile communication method for controlling origination or termination of a call in a desired network

Abstract: In a mobile communication network, a mobile unit location register ML and a subscriber location register SL are provided. In the mobile unit location register the mobile location of a mobile unit MT is registered, whereas in the subscriber location register a mobile unit MT selected by each subscriber SB as a terminal for call terminating use is registered. Upon receiving a terminating call for a subscriber, a switching center SW reads out, from the subscriber location register SL, an identifying number TID of the mobile unit registered by the subscriber SB as a terminal for call terminating use and uses the mobile unit identifying number TID to read out the mobile location of the mobile unit MT from the mobile unit location register ML, thereafter sending the terminating call to the registered mobile unit of the read-out mobile location.