Showing papers on "Cellular network 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. >

Method and apparatus for planning a cellular radio network by creating a model on a digital map adding properties and optimizing parameters, based on statistical simulation results

Abstract: A method and a system for planning a cellular radio network. The method includes creation of a model representing the cellular radio network and its radio environment on a digital map. The method further includes adding system properties affecting the traffic control process of the cellular radio network to the model representing the cellular radio network and its radio environment for route specific operational simulation of the cellular radio network. The simulation preferably utilizes subscriber mobility models and immobile and/or mobile individual subscribers generated on the digital map. The simulation events are stored separately for each street, location, network element and/or cause. The optimization of the parameters of the cellular network is performed on the basis of the stored information. Simulation of an operating cellular network on the basis of statistical data obtained from the network allows an adaptive control of the system parameters.

Advantages of CDMA and spread spectrum techniques over FDMA and TDMA in cellular mobile radio applications

Abstract: A unified theoretical method for the calculation of the radio capacity of multiple-access schemes such as FDMA (frequency-division multiple access), TDMA (time-division multiple access), CDMA (code-division multiple access) and SSMA (spread-spectrum multiple access) in noncellular and cellular mobile radio systems is presented for AWGN (additive white Gaussian noise) channels. The theoretical equivalence of all the considered multiple-access schemes is found. In a fading multipath environment, which is typical for mobile radio applications, there are significant differences between these multiple-access schemes. These differences are discussed in an illustrative manner revealing several advantages of CDMA and SSMA over FDMA and TDMA. Novel transmission and reception schemes called coherent multiple transmission and coherent multiple reception are briefly presented. >

Distributed code assignments for CDMA packet radio networks

Abstract: Code-division multi-access (CDMA) techniques allow many users to transmit simultaneously in the same band without substantial interference by using approximately orthogonal (low cross-correlation) spread-spectrum waveforms. Two-phase algorithms have been devised to assign and reassign spread-spectrum codes to transmitters, to receivers and to pairs of stations in a large dynamic packet radio network in polynomial times. The purpose of the code assignments is to spatially reuse spreading codes to reduce the possibility of packet collisions and to react dynamically to topological changes. These two-phase algorithms minimize the time complexity in the first phase and minimize the number of control packets needed to be exchanged in the second phase. Therefore, they can start the network operation in a short time, then switch to the second phase with the goal of adapting to topological changes. A pairwise code-assignment scheme is proposed to assign codes to edges. Simulations based on well-controlled topologies (sparse topologies) show that the scheme requires much fewer codes than transmitter-based code assignment, while maintaining similar throughput performance. >

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. >

Tracking mobile users in wireless communications networks

Abstract: Tracking strategies for mobile wireless networks are studied. A cellular architecture in which base stations that are interconnected by a wired network communicate with mobile units via wireless links is assumed. The cost of utilizing the wireless links for the actual tracking of mobile users is considered. A tracking strategy in which a subset of all base stations is selected and designed as reporting centers is proposed. Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported. It is shown that, for an arbitrary topology of the cellular network (represented by the mobility graph), finding an optimal set of reporting centers is an NP-complete problem. Optimal and near-optimal solutions for important special cases of the mobility graph are presented. >

Communications resource assignment in a wireless telecommunications system

Abstract: Fast resource assignments, especially needed in microcellular network architectures having many fast moving subscribers and high traffic volume, is provided through the use of a priority based resource assignment apparatus and procedure. Part of the communications resources in a cellular network, for example, one carrier frequency and/or one time slot, or particular code division multiple access sequences are dedicated to the execution of the assignment procedure. Available communications resources are auctioned to cellular subscribers contending for resources based upon a level of priority assigned to each contending subscriber. The priority level may be based on such things as the quality of service to which a customer subscribes or the particular needs of a subscriber at the time the subscriber is contending for resources, for example, the subscriber's request for resources may be prompted by a need to make a handoff. The procedure involves an auction period when a determination is made regarding which of a group of contending subscribers has the highest priority level. The procedure then enters a resource assignment period where an available communications resource is actually assigned to the subscriber having the highest priority level. The auction and assignment periods are then repeated for the remaining contending subscribers until there are no longer any contending subscribers or there are no longer any available resources. Fast resource assignment could be used to increase system capacity and efficiency of spectrum utilization through the ability to perform speech activity resource sharing.

Cellular communications test system

Abstract: A testing system (28) for wireless communication networks, particularly cellular networks, having a test set (30, 36) located in a cell site which communicates through the cell's base station to a responder (32, 38) at the mobile telephone switching office (MTSO, 34). The test set (30, 36), which includes a measurement module (48), controller (44), modem (46), and cellular phone (50), initiates the call to the responder (32, 38), and directs the responder to transmit and receive certain test signals which are then measured by the measurement module. The test set (30, 36), which may be fixed or mobile, provides essentially continuous monitoring of voice channels within a given cell, and can send an alarm in near real-time to the network control center when a faulty voice channel is detected.

Tracking mobile users in wireless communications networks

Abstract: Tracking strategies for mobile wireless networks are studied, assuming a cellular architecture where base stations interconnected by a wired network communicate with mobile units via wireless links The cost of utilizing the wireless links for the actual tracking of mobile users is investigated A tracking strategy in which a subset of all base stations is selected and designated as reporting centers is proposed Mobile users transmit update messages only upon entering cells of reporting centers, while every search for a mobile user is restricted to the vicinity of the reporting center to which the user last reported It is shown that for an arbitrary topology of the cellular network (represented by the interference graph), finding an optimal set of reporting centers is an NP-complete problem Optimal and near-optimal solutions for important special cases of the interference graph are given >

Integrated personal/cellular communications system architecture

Abstract: An integrated PCN/DNC system architecture has a switching center (22), coupled to a public switched telephone (PSTN), which selectively transfers signals between the PSTN and a digital cellular network (DCN) or a personal communications network (PCN) which is allocated a portion of the cellular communications band by a local cellular operator. Each PCN subnetwork (20) of the PCN includes several microcells (18) arranged in a multi-dimensional grid, and the allocated cellular channels are divided into sets assigned to columns of the grid. The allocated portion of the cellular spectrum is reused within each PCN subnetwork (20) by assigning the same set to more than one of the columns so that different communications signals can be transferred over the same cellular channels.

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.

Tdma for mobile access in a cdma system

Abstract: A method and system for increasing the capacity of radiotelephone communication systems by eliminating interference to communication traffic caused by random access burst from unconnected mobile station are disclosed. Access slots are provided in CDMA signals by interrupting other communication traffic of mobile stations using the same frequency at periodic intervals. This allows mobile access bursts to be received at a base station without interfering with other traffic.

Power control for random access call set-up in a mobile telephone system

Abstract: The present invention includes a system and method for minimizing interference between two radio stations, e.g., a mobile radio telephone and a fixed base station, at the initiation of a radio communication. A mobile station initiates a random access at the lowest power level and increases the transmission power level until the base station detects the access signal. Once detected, the power level of the message is maintained at the detected level so that the signal interference is avoided. The present invention also provides a mechanism for synchronizing random access communications between mobile stations and the base station despite variation in distances between the mobile and base stations.

CDMA cellular engineering issues

Abstract: The frequency reuse efficiency for the proposed code division multiple access (CDMA) cellular system is analytically derived, and it is shown that the cell capacity of a fully loaded multiple cell system is about 75% of what would be available for a single cell system. In addition, an engineering issue in transitioning from analog advanced mobile phone system (AMPS) to CDMA system is discussed. Calculating excessive interference power due to a CDMA channel, it is shown that when a CDMA channel is introduced in a cell, there should be at least one ring of buffer cells, in which the analog channels falling into the CDMA band are not reused. >

Method and apparatus for controlling signal quality in a cdma cellular telecommunications system.

Abstract: A system and a method for controlling the radio signal quality between a plurality of mobile stations (MS) and a plurality of base stations (BS) connected to a mobile switching center (MSC) of a code division multiple access (CDMA) cellular telecommunications system is described. According to the invention, each base station (BS) is adapted to measure the quality of each active CDMA communication link and to report for each active CDMA radio communication to the mobile switching center (MSC) the corresponding measured communication signal quality. The mobile switching center (MSC) is adapted to perform an averaging process on said reported quality measure values, in order to calculate a recommended quality measure threshold value. The base stations (BS) are adapted to receive said recommended threshold value for use in an uplink closed loop power control algorithm for the mobile stations (MS).

Mobile cellular radio systems

Abstract: A frequency hopped cellular mobile radio system, comprising a plurality of base stations each affording a cellular region, or cell, within which communication is facilitated with a plurality of mobile units, each of which mobile units is free to move from cell to cell, the system having in combination the following features; a synchronization system which serves to bring all mobile units within a cell into synchronization, as observed from the base station of that cell, whereby orthogonal frequency hopping between mobile units of the cell is facilitated, frequency hopping between mobile units in different cells being non-orthogonal; an affiliation strategy which tends to constrain each mobile unit to maintain communication with a base station selected in dependence upon received signal strength; mobile unit transmission power control in dependence upon received signal/noise ratio at a base station, whereby transmitted mobile power tends towards the minimum necessary for acceptable communication; a frequency hopping strategy, wherein the number of bits per hop is limited to a few bits per hop, the actual number of hops being chosen having regard to performance and overall framing delay constraints; Nyquist filtering of signals effective to constrain interference between hops both in the time domain and in the frequency domain, hopped dwells being arranged to extend in time beyond a nominal bit transmission period (before and after the period) so as to overlap; differential phase shift keying (DPSK) modulation combined with randomized quadrature phase shift keyed (QPSK) modulation to de-correlate interference between cells; and, a system of error control coding.

Integrated services on wireless multiple access networks

Abstract: The performance requirements of the multimedia services which are likely to be supported by future wireless systems are discussed. The effects of these requirements on the choice and the design of the radio multiple access technique are pointed out. The bandwidth management system that is needed by each of the two main access techniques, namely, time division multiple access (TDMA) and code division multiple access (CDMA), in order to efficiently multiplex these services onto the available bandwidth is discussed. >

Method and arrangement for processing short messages in a cellular network

Abstract: A method and arrangement for processing short messages in a mobile services switching centre (GMSC) of a cellular radio network. The method comprises the following steps: an A-subscriber (AMS) sends a short message provided with the routing address of a B-subscriber (BMS); the routing address contained in the short message is checked in the mobile services switching centre (GMSC); and when the routing address is that of the B-subscriber (BMS), the mobile services switching centre (GMSC) requests the routing information of the B-subscriber (BMS) from the home location register (HLR); if the B-subscriber can be reached, the home location register (HLR) sends the routing information to the requesting mobile services switching centre (GMSC); and the mobile services switching centre (GMSC) routes the short message to the B-subscriber (BMS) on the basis of the routing information received.

Design and performance analysis of the algorithms for channel allocation in cellular networks

Abstract: The authors consider the problem of dynamic channel allocation in cellular networks. Each cell can use any channel, subject to the interference constraints. Channel allocation algorithms are executed by the network switch in a centralized way. The authors show how to design and use objective functions aimed at proper channel allocation and improvement of network performance. As a figure of merit of network performance, they consider the blocking probability in the network as a whole, and the maximum blocking probability in any particular cell of the network ("hot-spot" in the network). They designed three specific channel allocation policies, based on three different objective functions. Compared with two other benchmark policies, the approach shows significant improvement. Performance analysis of various channel allocation policies is virtually impossible without simulations, which are prohibitively time-consuming in the case of small blocking probabilities. The authors propose an original approximate method based on a short simulation and an analytic approximation. The method exhibits good accuracy and significant improvement in efficiency. >

Off-load cellular system for off-loading cellular service from a main cellular system to increase cellular service capacity

Abstract: An off-load cellular system controls cellular service between a main cellular system and the off-load cellular system and provides off-load cellular service to a mobile telephone. The off-load cellular system includes a receiver circuit, monitoring and receiving an origination message broadcast from the mobile telephone located in the off-load cellular system, and a system controller, for receiving the origination message output from the receiver circuit, and for outputting a connect signal indicating whether the off-load cellular service is to be provided to the mobile telephone responsive to the origination message. In addition, the off-load cellular system includes a connection controller for receiving the connect signal output from the system controller, for transmitting to the mobile telephone a voice connect message indicating a frequency to obtain the off-load cellular service responsive to the connect signal, and for connecting the mobile telephone with a calling party, providing the off-load cellular service to the mobile telephone.

CDMA with interference cancellation: A technique for high capacity wireless systems

Abstract: An enhanced version of DS-code division multiple access (CDMA), called CDMA-IC, is proposed, which dramatically improves capacity. In this system, known information about the interference is utilized to improve the carrier-to-interference ratio of weaker signals. The basic idea is to detect signals in a nonincreasing signal strength order, and, during that process, to subtract the already detected signals. With the proposed scheme, a capacity of up to 40 times advanced mobile phone system (AMPS) is estimated. The necessary signal processing is explained, and results from simulations are shown. >

Multiple access options for cellular based personal communications

Abstract: The possible evolution of time division multiple access (TDMA) by, e.g., introducing frequency hopping and/or adaptive channel allocation, is described. The possibilities of direct sequence (DS) code division multiple access (CDMA) are considered. The different multiple access methods are examined. In particular, the concept of hierarchical cell structures is emphasized. The capacity depends on both the cell capacity and the ability to support hierarchical cell structures.

Method of position determination for a mobile through global-positioning-system satellites

Abstract: Each of a plurality of base stations F in the cell 9 of a ground mobile communication system or in a mobile network control center E which controls the base stations F, is used as a fixed reference station. Errors in the positions determined by CPS reference station E, F are transmitted from the reference station to the mobile stations via the control channels of the communication system, and are used to correct the positions of the mobile stations B obtained by CPS. If a satellite is temporarily blocked (eg by a building) the position is extrapolated on the basis of compass or gyroscope measurements and wheel speed movements.

Diversity and automatic link transfer for a TDMA wireless access link

Abstract: The paper describes diversity and automatic link transfer techniques which have been proposed for low-power digital wireless access to telephone networks using a TDMA architecture. Experimental results which quantify and demonstrate the performance of those techniques are presented. An experimental prototype radio link consistent with Bellcore's Technical and Framework advisories on wireless access was used to obtain the performance results. The present work is targeted towards understanding the implications to local exchange networks of wireless technology alternatives that could provide access to those networks. >

Mobile radio systems

Abstract: An asynchronous transmission mode (ATM) system adapted for use with mobile terminals, the system comprising a mobile network interface unit connected to a network, a plurality of base stations connected to the network, and at least one mobile terminal arranged to communicate with the base stations over a radio link, the network being arranged to connect the mobile network interface unit and the base stations, said connections being defined by a virtual path identifier, a unique virtual channel identifier being allocated at set up of a call or connection by the mobile network interface unit, for identifying a call or connection associated with a mobile terminal being handled within an area controlled by the mobile network interface unit, the virtual channel identifier being placed in a virtual channel identifier field of ATM cell carrying user data associated with the call or connection.

Structural properties of a low Earth orbit satellite constellation - the Walker delta network

Abstract: The Walker (1984) delta satellite constellation appears to be practical to serve as a low Earth orbit satellite network to provide world-wide networking. The structural properties of the Walker delta network, including diameter, mean message traversal, traffic density, and network saturation conditions are investigated and presented. Three different traffic patterns are used in this study. It has been found that for a fixed number of satellites, the Walker delta network can provide minimum mean message traversal, minimum traffic density and maximum traffic injection rate provided that the number of orbital planes is equal to the number of satellites in each orbital plane. Regarding the injection of messages from ground stations to the satellite network, the network with a smaller size can accept more messages than a network with a larger size before the network saturates. Furthermore, an adaptive routing algorithm, which always routes the message to its destination through one of several available minimal paths, is also presented. >

MSAT and cellular hybrid networking

Abstract: Westinghouse Electric Corporation is developing both the Communications Ground Segment and the Series 1000 Mobile Phone for American Mobile Satellite Corporation's (AMSC's) Mobile Satellite (MSAT) system. The success of the voice services portion of this system depends, to some extent, upon the interoperability of the cellular network and the satellite communication circuit switched communication channels. This paper will describe the set of user-selectable cellular interoperable modes (cellular first/satellite second, etc.) provided by the Mobile Phone and described how they are implemented with the ground segment. Topics including roaming registration and cellular-to-satellite 'seamless' call handoff will be discussed, along with the relevant Interim Standard IS-41 Revision B Cellular Radiotelecommunications Intersystem Operations and IOS-553 Mobile Station - Land Station Compatibility Specification.

Digital cellular network/system with mobile stations communicating with base stations using frequency-hopping and having enhanced effect of interference diversity

Abstract: A digital TDMA/FDMA (Time Division Multiple Access/Frequency division Multiple Access) cellular network system, suitable for a microcellular network and to maximize the advantage to be gained from interference diversity, including base stations forming radio cells, each having a determined static frequency of a channel of the cell and including a first transceiver continuously transmitting control data of the system concerning the cell at the control channel frequency, at least in one predetermined time slot of a TDMA frame. The TDMA frame of the first transceiver includes traffic channels at least in a part of the other time slots. Each base station further includes at least one second transceiver for the traffic channels. The system further includes mobile stations connected to the base stations via a radio path. The traffic channels of the second transceiver units use frequency-hopping, at least in a part of the radio cells, in such a way that, on those traffic channels aligned with the predetermined time slots of the control data of the cell in the first transceiver, substantially all frequencies of the available frequency band, except the control data transmission frequency determined for the cell, belong to the hopping sequence. On those traffic channels which are in the other time slots, substantially all frequencies of the available frequency band belong to the hopping sequence.

The intelligent network signaling and switching costs of an alternate location strategy using memory

Abstract: In future high density microcellular personal communications systems (PCS), it is expected that most of the signaling traffic will come from registrations. An alternate location strategy has been proposed to reduce the signaling traffic on the radio link by increasing the responsibilities placed upon the fixed network. A fixed network performance comparison to the classic location strategy being implemented in evolving digital cellular and cordless standards is presented. The key measures are SS7 traffic and switching complexity. An example based on the Groupe Speciale Mobile (GSM) system illustrates the results.

Reverse channel performance improvements in CDMA cellular communication systems employing adaptive antennas

Abstract: The authors examine the performance enhancements that can be achieved by employing adaptive antennas in code division multiple access (CDMA) cellular radio systems. The goal is to determine what improvements are possible using narrowbeam antenna techniques, assuming that adaptive algorithms and the associated hardware to implement these systems can be realized. Simulations and analytical results are presented which demonstrate that adaptive antennas at the base station can dramatically improve the reverse channel performance of multi-cell radio systems, and new analytical techniques for characterizing mobile radio systems which employ frequency reuse are described. The authors also discuss the effects of using adaptive antennas at the portable unit. >