Showing papers on "Cellular network published in 1992"

Method and apparatus for controlling transmission power in a CDMA cellular mobile telephone system

Abstract: A power control system for a cellular mobile telephone system in which system users communicate information signals between one another via at least one cell-site using code division multiple access spread spectrum communication signals. The power control system controls transmission signal power for each cellular mobile telephone in the cellular mobile telephone system wherein each cellular mobile telephone has an antenna (70), a transmitter (84), and a receiver (72, 74) and each cell-site also has an antenna (52), a transmitter (62), and a receiver (54, 56). Cell-site transmitted signal power is measured as received at the mobile unit. Transmitted power at the mobile unit is adjusted by transmit power control units (76, 80) in an opposite manner with respect to increases and decreases in received signal power. A power control feedback scheme may also be utilized. At the cell-site communicating with the mobile unit, the mobile unit transmitted power is measured by the received power measurement unit (60) at the cell-site. A command signal is generated at the cell-site and transmitted to the mobile unit for further adjusting mobile unit transmitter power corresponding to deviations in the cell-site received signal power. The feedback scheme is used to further adjust the mobile unit transmitter power so that mobile unit transmitted signals arrive at the cell-site at a desired power level.

Transmitter power control system

Abstract: A power control system for a cellular mobile telephone system in which system users communicate information signals between one another via at least one cell-site (12, 14) using code division multiple access spread spectrum communication signals. The power control system controls transmission signal power for each cellular mobile telephone (16, 18) in the cellular mobile telephone system wherein each cellular mobile telephone has an antenna (70), transmitter (84) and receiver (72, 74) and each cell-site also has an antenna (52), transmitter (62) and receiver (54, 56). The signal power of cell-site (12, 14) transmitted signals is measured as received at the mobile unit (16, 18). Transmitter power is adjusted at the mobile unit (16, 18) in an opposite manner with respect to increases and decreases in received signal power. A power control feedback scheme may also be utilized. At the cell-site (12, 14) in communication with the mobile unit (16, 18), the signal power of mobile unit (16, 18) transmitted signals is measured as received at the cell-site (12, 14). A command signal is generated at the cell-site (12, 14) and transmitted to the mobile unit (16, 18) for further adjusting mobile unit transmitter power corresponding to deviations in the cell-site (12, 14) received signal power. The feedback scheme is used to further adjust the mobile unit (16, 18) transmitter power so that mobile unit (16, 18) transmitted signals arrive at the cell-site (12, 14) at a desired power level.

A measurement-based prioritization scheme for handovers in mobile cellular networks

Abstract: A method of improving the quality of service in mobile cellular systems based on prioritization of handover requests is presented. The objective is to improve perceived quality of cellular service by minimizing both the probability of forced termination of ongoing calls due to handover failures and the degradation in spectrum utilization. A model based on a multiple-priority nonpreemptive queuing discipline is developed. New calls are blocked if all channels are occupied. Handover requests are queued such that as soon as a channel is available, it is offered to the mobile subscriber with the measurement results closest to the minimum acceptable power level for communication. Service rate is given by channel occupancy time distribution and is assumed to be exponential. The performance of a cellular system employing the proposed handover policy is evaluated analytically and by simulation, and results are compared to those obtained when the cellular system employs nonprioritized call handling and first-in/first-out queuing discipline. This provides lower probability of forced termination and less call blocking, less reduction in traffic, and less delay. >

The use of SS7 and GSM to support high density personal communications

Abstract: The authors present an organized method for quantifying the Signaling System 7 (SS7) traffic load associated with terminal mobility when the pan-European standard GSM is used for personal communication networks (PCNs). They use CCIR parameters for an extremely dense, outdoor center-city pedestrian environment to illustrate the possible heavy signaling load. Using the example parameters, the additional SS7 network burden is 4-11 times greater for cellular than for ISDN and 3-4 times greater for PCN than for cellular, depending on the visitor location register placement. The numerical results are very sensitive to assumptions on user mobility, cell size, and location area size. This highlights the need for careful investigation of these parameters in specific applications. >

Microcell system in digital cellular

Abstract: A cellular telephone system is described of the type wherein a plurality of contiguous cells, each having a different assigned set of transmission frequency channels, are arranged with handoff controller (98) for maintaining continuous communication with mobile telephones moving from cell to cell. The system allows multiple access by including device (251) for assigning at least one of the frequencies in the assigned set of frequencies to more than one mobile telephone. Three embodiments of the multiple access systems are disclosed. In one embodiment, frequency division multiple access is used (Fig. 4). In a second embodiment, time division multiple access is used (Fig. 4). In a third embodiment, code division multiple access is used (Fig. 10).

Multiple access telephone extension systems and methods.

Abstract: A method and system for conducting multiple access simultaneous telephone communications in full duplex either over the power lines of a building or using RF transmission. It employs a combination of multiple access techniques selected from among the following: time division, code division, and frequency division. The following features result: a) security coding to prevent unauthorized access and eavesdropping, b) multiple simultaneous conversations through identical and closely coupled transmission media, c) non-interference to other communications systems and users, and d) processing gain for operating in noisy environments.

Urban/suburban out-of-sight propagation modeling

Abstract: A model for the calculation of the path loss characteristics of a direct sequence (DS) spread spectrum signal which occurs when a mobile user is out-of-sight of the base station due to building blockage is presented. The environments studied are common throughout the world. Results for the experiments in which a base station antenna was set at heights of 6.6 m or 3.3 m, while the mobile antenna was fixed at a height of 1.5 m are presented. The goal of the experiments was to demonstrate the use of broadband DS spread spectrum code-division multiple-access (CDMA) as an efficient means of communication. >

Forward-link-power control in CDMA cellular systems

Abstract: The forward-link (base to mobile) power-control problem in code division multiple access (CDMA) cellular systems is studied. For a better understanding of the problem, a simple analytical model is developed for the neighboring-cell interference experienced by users as a function of distance from their home base station. Using this model, the recently proposed nth-power-of-distance power-control laws are investigated, especially with regard to the possibility of creation of a service hole. The investigation leads to the shape of the optimum radial distance dependent power-control law that will provide uniform service to all the users. >

Tracking mobile users in wireless networks

Abstract: A method and apparatus for efficiently tracking the location of a mobile station in a cellular network, especially in cellular networks having nonuniform traffic distribution. A mobile station reports to a base station only upon entering selected reporting cells. When communication with a mobile station is desired, the station is searched for in the vicinity of the last reporting cell in which the station appeared. The vicinity of a reporting cell is defined as the set of all intersecting cells reachable from the reporting cell without passing through another reporting cell.

The Universal Mobile Telecommunication System

Abstract: The concepts, requirements, and technologies of Europe's third generation mobile communication system-the Universal Mobile Telecommunications System (UMTS)-are discussed. The cellular architecture, radio resource, adaptive resource allocation and handover enabling techniques for realizing an effective UMTS access network are described. The modulation schemes, multiple access methods, and duplexing methods used in the third generation mobile system's flexible radio interface are also described. The architecture, mobility support, and protocol development of the UMTS fixed network are outlined. >

Implications of mobile cellular CDMA

Abstract: The results of four extensive field tests of code division multiple access (CDMA) cellular technology performed between November 1991 and September 1992 are presented. These tests include: validation system field tests conducted in San Diego, California, operating over five cell sites, comprising a total of eight sectors, and involving up to 70 mobile units, plus simulated other user and other base station interference; tests in Munster, Germany, the configuration of which consisted of two cell sites and two mobiles plus 20 simulated other users operating in the 1700-MHz band; tests in Geneva, Switzerland, the same as in Munster, but operated in the 800-900-MHz band, with cells located at GSM base station sites; and a field test conducted in Washington, DC, operating on two-sectored cell sites involving seven mobile units, plus simulated other user and other base station interference. >

Issues in wireless mobile computing

Abstract: The trend toward possible computers with interfaces to wireless network technologies is examined The question of needed research and specification of hardware is discussed, the major challenges, such as services for the mobile user, mobile internetworking and adjusting to new technologies are described, and a listing of outstanding questions which must be resolved is presented >

Intelligent network concepts in mobile communications

Abstract: A mobile cellular network architecture that is based on intelligent network concepts is presented. Subscriber service mobility and call management attributes of the network, including location information retrieval and updating, authentication, call routing, handover, charging, and operations and maintenance, are discussed. >

A comparison of CDMA and TDMA systems

Abstract: Two candidates for high-capacity cellular systems are simulated and analyzed, one code-division multiple access (CDMA) and one time-division multiple access (TDMA) system Simulations of the CDMA example indicate a high sensitivity to variations in certain system parameters The TDMA example is a GSM system using random frequency hopping and operating without frequency planning The simulations show that the TDMA system has at least the same capacity as the CDMA candidate Soft capacity, efficient use of voice activity, and diversity are features available in both systems >

Slot allocation strategies for TDMA protocols in multihop packet radio networks

Abstract: The authors derive an upper bound of the minimum time division multiple access (TDMA) frame length of any collision-free node assignment protocol in a packet radio network in which a node has multiple reception capacity. They also derive the optimum TDMA frame length for any fully connected network with large reception capacity. When the total number of nodes in the network is unknown, a heuristics to generate a TDMA protocol with frame length within some upper bound is presented for any network with large reception capacity. >

Power control based admission policies in cellular radio networks

Abstract: The problem of limiting the cochannel interference between transmitter-receiver pairs in a cellular network to acceptable levels, while accommodating as many transmissions as possible, is addressed. The controllable network parameters, are the transmission powers of the base stations, and possibly of mobiles too, in the cells. Efficient adaptive control of the powers guarantees quality of service above a certain threshold at all times, given the continuously changing traffic of communication requests in the network. The quality criterion used in this study is the carrier-to-interference ratio (C/I) at the receiver. >

Code time division multiple access: an indoor cellular system

Abstract: A wideband communications system for indoor cellular applications is proposed that is based on an accessing scheme called code time division multiple access (CTDMA) It combines some of the most important advantages of code-division multiple access (CDMA) and time-division multiple access (TDMA): a constant-envelope transmitted signal, a perfect separation of the users in one cell and a cluster size of one Simulation results of such a system offering an information data rate of 144 kb/s, applying frequency division duplex and occupying a total bandwidth of 2*20 MHz are presented >

An analysis of CDMA with imperfect power control

Abstract: The performance of code-division multiple access (CDMA) mobile communications systems operating with imperfect power control is examined. Exact upper and lower bounds are used to analyze the performance of a CDMA system in which the power in the multiple access interference has a log-normal distribution. The multiple access capability of a system with ideal power control is compared to the multiple access capability of a system with imperfect power control. >

Optical phase coding for code-division multiple access networks

Abstract: An all-optical code-division multiple access (CDMA) network is presented which uses optical phase information to encode and decode transmitted data from a low-coherence source, using simple, compact, reconfigurable optical delay networks. The use of a master encoding network to provide a reference for the system is demonstrated experimentally, and examples of phase codes ensuring minimum interference between users are given. >

The Pan-European Digital Cellular Mobile Radio System - known as GSM: 1st

Abstract: A flat still camera wherein a hollow section of the housing is reciprocable relative to the main section to thereby actuate the shutter and/or the film transporting mechanism. When the hollow section is moved to an extended position in which it exposes the lens and the view finder, the two sections define a slot into which a careless user is likely to introduce a finger, an eyelash or an eyelid while holding the camera in front of his eye and while moving the two sections with respect to each other. The rear end of the slot is closed by a portion of a door which is pivotably mounted on the main section and can be opened to afford access to the film chamber. Alternatively, the slot can be overlapped by a panel which is rigid with the main section or with the hollow section of the housing.

Performance issues and algorithms for dynamic channel assignment

Abstract: Performance issues and algorithms for dynamic channel assignment (DCA) in a time division multiple access (TDMA) portable radio system are considered. With DCA, a radio port can use any carrier frequency in any available time-slot to set up a radio link with a portable. The portable selects a radio port prior to channel assignment for initial access or link transfer. Port and portable together determine the proper combination of time-slot and carrier frequency. Once established, a radio link remains unchanged until a call is completed or a link transfer occurs. Some limitations of DCA, such as difficulty in providing beacon signals, blind slots, frequency switching speed requirements, assignment delay and failures, and synchronization requirements, diminish its perceived advantages. Since uplink and downlink radio channels experience different interferences, asymmetric performance can occur. An algorithm that improves the balance of two-way performance is proposed. However, performance trade-offs inherent in DCA limitations still need to be addressed. >

Frequency hopping CDMA for future cellular radio

Abstract: A code-division multiple access (CDMA) system based on slow frequency hopping (FH) is proposed. The hopping sequences are selected such that all users of each cell are using mutually orthogonal codes, and intercell correlation of hopping sequences is minimal. FEC and interleaving are used to mitigate the remaining interference. It is shown that with proper selection of system parameters, FH-CDMA enjoys the advantages so far claimed by DS-CDMA, i.e. FH-CDMA capacity benefits from interference averaging and can take advantage of the duty cycle associated with voice activity. It also yields a sectorization capability and one-cell frequency reuse pattern. Moreover, due to the orthogonal operation, the interference from cell co-users is eliminated. Since this is the major source of interference in nonorthogonal systems like DS-CDMA, FH-CDMA yields higher capacity capabilities (35 times AMPS). Other advantages of FH-CDMA with its implementation as a cellular system are discussed. >

An integrated voice and data radio access system

Abstract: A method for a digital mobile radio communication system to incorporate data transmission into full-duplex digital voice transmission channels is presented In this method a voice terminal sends a short packet to a base station prior to sending a voice signal When the base station receives the short packet or detects a collision between the short packet and data packet, it inhibits data transmission Finding a pause period of voice signal transmission, the base station broadcasts a message to enable the data transmission The results of computer simulation with voice data from real telephone conversations show that through the present system the almost maximum performance of the slotted ALOHA system is reached Applying the proposed method to a 12-channel, 32-kb/s voice coding TDMA system, one can get a data transmission channel with average capacity of 270 kb/s on the voice communication system >

Slotted ALOHA land-mobile radio networks with site diversity

Abstract: An analytical method for investigating slotted ALOHA land-mobile networks is presented. The probability of successful reception and throughput is assessed for a single base station, taking account of contending transmissions and receiver noise. Receiver capture is assumed to occur if the received signal power exceeds the joint interference power by a certain margin, called the receiver threshold. Rayleigh fading and UHF groundwave propagation are considered. Results are extended for a cellular network considering the interference from packet transmissions in other (co-channel) cells. It is seen that in packetswitched cellular nets, frequency re-use distances may be substantially smaller than in circuitswitched (CW) telephony networks, where each cell has to be safeguarded continuously from cochannel interference. Moreover, a technique to assess the throughput of ALOHA networks with multiple, geographically-separated base stations is presented and numerical results are given for uniform Poisson-distributed packet transmissions in the service area.

An overview of variable rate speech coding for cellular networks

Abstract: Variable rate speech coding is a critical system component for achieving very high capacity in future generation multiple access systems for cellular networks. A significant capacity gain comes from exploitation of the large fraction of the time during which a speaker is idle in a two-way conversation. Additional capacity gain can also be achieved by exploiting the time-varying entropy of active speech. While CDMA and packet-based multiple access systems, e.g. PRMA, are naturally suited for variable rate coding. TDMA can also be designed to benefit from voice activity patterns. >

Spatial topology and dynamics in CDMA cellular radio

Abstract: The architecture and dynamics of a code-vision multiaccess (CDMA) cellular radio network are discussed. The network's layout, power control equation, cell coverage, signal quality, cell radio design, and heterogeneous cell clustering are described. It is shown that the CDMA system is adaptive to the channel and to the traffic load and offers flexibility in the network design and operation. >

On the capacity of spread-spectrum CDMA for mobile radio

Abstract: The relative capacities of a basic frequency division multiple access (FDMA) and code-division multiple access (CDMA) system are examined. It is shown that in the absence of capacity enhancing features, such as voice activity detection and cell sectorization, the capacity of each system is comparable. The authors assess the sensitivity of the CDMA system to typical propagation conditions, power control errors, and realistic antenna patterns, and show that the capacity of a CDMA system may be significantly reduced under nonideal conditions. >

Combined orthogonal/convolutional coding for a digital cellular CDMA system

Abstract: A family of orthogonal/convolutional codes for mobile CDMA communications is discussed. Their design and implementational aspects are discussed. The R/sub 0/ parameter of this family of codes is analyzed and presented in a uniform format. It is shown that it is desirable to use a code with a higher mobile CDMA communications. Simulation results are given. In particular, the authors simulated a 2/6/64 orthogonal/convolutional code which has an advantage in E/sub b//N/sub 0/ of more than 1.2 dB over previously investigated coding schemes. >

Reconfiguration of a cellular communications network

Abstract: A method and apparatus for performing reconfiguration of a cellular network is provided. Cell parameters of affected radio network controlling units in the network are copied to a database, and the copied parameters are stored (11). A set of proposed changes to the stored parameters are prepared and the consistency of the prepared set of proposed changes is verified (12, 13). Any necessary alterations to the set of proposed changes responsive to the verification are made and the verified set of proposed changes are copied to the affected radio network controlling units (14, 15). The verified set of proposed changes are then introduced into the network (20-26). Additionally, at all times, an up-to-date image of all the cell parameters in all the radio network controlling units in the network is maintained in a system parameter database.