Showing papers on "Base station published in 1982"

A new frequency channel assignment algorithm in high capacity mobile communication systems

Abstract: A new algorithm for frequency channel assignment in mobile radio communication is proposed. The algorithm uses flexible fixed channel assignment which enables the calls having all their nominal channels busy to borrow channels from the neighboring cells provided that co-channel interference will not result. The borrowed channel cannot be used in three interfering cells; therefore reassignment strategy is used when a call is terminated on a nominal channel to switch a call in progress in a borrowed channel to that nominal one and set free the borrowed channel in the three interfering cells. Thus the traffic carried on borrowed channels is minimized. Also different call switching strategies are proposed to give priority to some channels to be used by the nominal cells and other channels to be borrowed by neighboring cells. These strategies considerably reduce the blocking probability. A simulation study of the algorithm was carried out on 49 hexagonal zones having uniform traffic density. Also a combined telephone and dispatch traffic was included in the simulation study. The results showed that the new algorithm is better than the other channel assignment schemes. This can be applied in high capacity mobile communications systems to utilize the spectrum efficiently.

Cochannel Interference in High-Capacity Mobile Radio Systems

Abstract: The probability of cochannel interference is evaluated for a mobile radio system operating in Rayleigh fading and log-normal shadowing environment. All cochannel cells surrounding the base station are taken into consideration in this evaluation. The results obtained are used to calculate the reuse distance and the cluster size (number of cells in a group). The blocking probability, the number of channels in each cell, the protection ratio, and the standard deviation are taken as parameters in this evaluation. The results show that shadowing has a severe effect on the interference level and on the channel reuse distance ratio.

Radio mobile communication system wherein probability of loss of calls is reduced without a surplus of base station equipment

Abstract: In a mobile radio communication system, a control station supplies a traffic adjusting signal to a particular one of base stations, channels allotted to which are used up to a predetermined number in communication therethrough between the control station and mobile stations in the service area thereof provided that some of the channels allotted to an adjacent base station are idle. The signal narrows the service area of the particular base station as by reducing the base station output power. Alternatively, the signal varies a communicable distance of each mobile station in the service area of the particular base station. For example, the signal makes the particular base station raise the mobile station output power to make some of the mobile stations carry out the communication through the adjacent base station. As a further alternative, the signal varies both the service area and the communicable distance. For example, the signal makes the particular base station raise the reference level used in communication therethrough. Instead, a lower reference level is developed in each mobile station for use in communication through the adjacent base station.

Accessing of transmission channels of a communication system

Abstract: In a communications system with a plurality of subscriber stations independent of each other, where each subscriber station can access a joint duplex transmission channel according to a multiple access method, the probability of simultaneous attempts to get access becomes very image, and thereby the probability of signal destruction is particularly increased. In order to avoid a blockage of the service channel each subscriber station occupies the duplex transmission channel with a short access signal for initiating a transmission starting from the subscriber station. The subscriber station characterized by the position in time and/or the information contents of the short access signal is thereupon invited by the central base station to emit an access signal to join practical access to the communication exchange.

Secure mobile radio telephony

Abstract: An arrangement for generating an encryption key for use in encrypting communications between a mobile radio telephone unit and a base station is disclosed which can be readily changeable in real time. Each mobile unit is equipped with a machine-readable nonbroadcast code and the base station can access a translation table correlating the nonbroadcast code with the public directory number of the mobile unit. Upon changing frequencies, as for example, when a mobile unit moves from one geographical cell area to another, the current and previous frequencies or channel numbers are left to select sets of digit positions in the nonbroadcast code. The contents of these digit positions are then convolved and inserted into a modified version of the nonbroadcast code generated by convolving the original code with a shifted replica thereof. The key so generated may be used to encrypt communications for the use of any known encrypting circuitry.

Data muting method and apparatus for radio communications systems

Abstract: Apparatus that mutes data signals communicated between a central station (100) and mobile (120) and portable radios (122) in a dispatch radio system. The centraL station (100) includes a base station (110) having an RF transmitter and RF receiver, a dispatcher console (102), a general communications controller (GCC), (104), a digital communications computer (108) and a display terminal (106). The dispatcher console provides for voice communications. The GCC (104) provides for data communications. The GCC (104) and mobile (120) and portable radios (122) include data muting apparatus embodying the present invention. The data muting apparatus includes a noise detector (210, 602) for detecting the presence of a carrier signal and muting circuitry (220, 606) for muting the receiver output for a predetermined time interval when a carrier signal has been detected. During the predetermined time interval, other circuitry (620) may detect a synchronization word in a received data signal and mute the receiver output until still other circuitry (626) detects the last bit of a following information work and unmutes the receiver output.

Malfunction detection system for a mobile radio telephone system

Abstract: A malfunction detection system sends a test calling signal to the mobile base station receiver and receives a response signal from the mobile station transmitter. A controller in the malfunction detection system monitors the access channel for proper operation and transmits an alarm signal to the mobile station controller when a problem is detected.

Digital mobile telephone system using TD/FDMA scheme

Abstract: Multiple access is an indispensable technique for efficient radio spectrum utilization in mobile radio systems, because a large number of subscribers can be connected only when they require radio channels. Frequency division multiple access (FDMA) scheme using single channel per carrier (SCPC) has been widely used. However, the SCPC-FDMA scheme has some problems, such as difficulty in setting up a large number of base station transceivers and in realizing a low-cost highly stabilized local oscillator. A time and frequency division multiple access (TD/FDMA) scheme, which is a combination scheme of TDMA and FDMA, is proposed as one of the possible solutions for these problems. After explaining the background of the proposal, some of the restrictions of the TD/FDMA scheme resulting from the land mobile radio channel characteristics are described. Basic concept of the digital mobile radio telephone system using TD/ FDMA scheme is then presented. An example of the possible system design is finally shown.

Communication control system

Abstract: A communication control system includes a plurality of base stations for making communication with a plurality of cars and a central base station The central base station conducts centralized supervisory of each base station The car travel while transmitting data signals indicating that car number codes have not been provided thereto The base station transmits a car number code provided by the central base station to each car when the base station receives the data signals The car receives and stores the car number code The base station calls the cars through the provided car number codes when the base station communicates with the cars

Data transmission for maritime and land mobiles using stored channel simulation

Abstract: Channel simulators with synthetically generated complex multiplicative and additive Gaussian distortions are widely used for investigating non-frequency-selective fading channels. An alternative is to record the channel distortions (i.e. amplitude and phase variations) by probing the real channel and to use these stored signals to control the simulator in the lab. This stored channel method (SCM) has been applied to the following mobile radio channels • satellite to ship • SAR emergency buoy to satellite • base station to land mobile for low data rates A collection of tapes has been obtained for these channels under various conditions. They were used to compare several data transmission schemes at different data rates and various S/N-ratios, but with the same replayed fading fluctuations. The SCM was used to evaluate low rate data transmissions (< 10 Kbit/sec) with various modulation schemes such as CBPSK, digital FM, and DPSK/FM. Bit error rate results are presented. The experience with the SCM, its advantages and limitations are being discussed.

Teletraffic Analysis for Multicell Mobile Radio Telephone Systems

Abstract: New teletraffic formulas are derived for the congestion in multicell mobile radio telephone systems. Fixed, dynamic, and hybrid channel asignment are considered and "tromboning," where mobileto-mobile calls go via a base station, is taken into account. The formulas agree with previously published sumulation results.

Radio communication system

Abstract: PURPOSE:To recover accidents such as lowering of service in a short time to improve the reliability of the system, by using a service channel as a control channel in the land mobile radiotelephony system. CONSTITUTION:If a control channel P1 cannot be used by disturbing waves or the like in a radio zone Z2, the use of the channel P1 is stopped to use a channel S6 out of service channels S4-S6 as a new control channel in the zone Z2. In this case, in a radio base station B2, transmission and receiving frequencies for the channel P1 of transmitter and receivers 1 and 2 for the control channel are switched to those for the channel S6 by a switch 3, and connections of lines 14 and 15 to transmitter and receivers 12 and 13 for the service channel S6 are disconnected. Consequently, frequencies of transmitter and receivers for the channel P1 are switched to those for the channel S6 in base stations B1 and B3.

Controlling system of mobile communication

Abstract: PURPOSE:To attain the control of connection at the radio zone boundary, by dividing mobile stations into plural groups, and measuring the reception level of a control channel of other base stations other than the time slot assigned to the mobile station itself. CONSTITUTION:The mobile stations are grouped into m-group, and the control channel number is assumed as n (f1-fn), then the mobile station in a base station #1 selects the channel f1 being the maximum reception level. When the mobile station is the group 1, a synchronizing signal L and a modulation signal P1 transmitted from the base station are demodulated, and when the signal P1 is an incoming call to the mobile station of itself, responsed to the base station for connection control. In other case, the reception channel is switched to the other control channel, the reception level is measured and when there is any control channel higher than the reception level at the channel f1, it is regarded as the radio zone, and is similarly operated at the control channel having a high reception level.

Control system for mobile radio communication

Abstract: PURPOSE:To increase the efficiency of communication, by the centralized control of a central station for the selection of control channel and switching at failure used among a plurality of base stations and a number of mobile stations within a radio communication area. CONSTITUTION:The base station which makes communication and control with a number of mobile stations 6 with in a communication area is provided with a communication transceiver 2, control channel transceiver 3, and interference detecting receiver 4, and connection with the mobile station 6 is made with radio and the connection to the central station 5 is made via lines 10-14. When an interference detecting receiver 4 at normal operation detects the interference more than the threshold value at the existing control channel, it is informed to the central station and the central station designates other channels to change the channel for a control channel transceiver 3 and the interference detecting receiver 4. Each mobile station starts the scanning for predetermined channel through the increase in the S/N of the control channel in use and fixes it to the channels more than the threshold value. Thus, the communication efficiency for a number of mobile stations can be kept and increased.

Mobile radio communication system

Abstract: PURPOSE:To attain the communication of the whole mobile stations in the same service area simultaneously, by detecting the receiving input electric field of a control channel controlling signal being always sent to a base station, and controlling a transmitter output level for the control channel inversely proportional to said field so as to be increased and decreased at a random period. CONSTITUTION:The communication between a mobile station 1 and a fixed station 5 is executed through a base station 2. The waiting mobile station 1 receives a control signal from the base station 2. the receiving part of the mobile station 1 consists of a high frequency amplifier part 12, mixer 13, intermediate frequency amplifier 14, demodulator 15, low frequency amplifier 16 and a speaker 17, and a transmitting part consists of a power amplifier 24, exciter 23, multiplier 22, modulator 21, and a microphone 20. A communication controlling circuit 25 receives signal a control channel, and when the receiving intensity of the base station 2 is increased, the output of the amplifier 14 is increased. An automatic power controller 26 reduces the excitation power of the exciter 23 to reduce the output of the amplifier 24. In the service area, the field intensity originated from each mobile station and reached to the base station is unrelated to the position of each mobile station.

Mobile communication controlling system

Abstract: PURPOSE:To attain the constitution of an economical base system, by providing a channel in the unit of radio zones as to a transmission system of a mobile station. CONSTITUTION:A control signal transmitted from a control station to each base station includes a synchronizing signal representing a time slot informing the channel information from each base station. In each station, when this synchronizing signal is detected at a synchronizing signal detector 13, the location of a prescribed time slot is recognized by a counter 14 started at the same time as the start of the detector 13 by starting a bit counter 14. Thus, a signal output gate 15 is opened, the control signal from a signal output terminal 16 to a transmitter is outputted and a control signal for making the transmitter to the transmitting state is outputted from a signal output terminal 17. When the transmission of a signal is finished, the counter 14 is started until the next transmission timing and the saie operation is repeated. Thus, the service performance is improved, the load of a controller is decreased and the constitution of the economical base station system is attained.

Mobile radio communication system

Abstract: PURPOSE:To avoid the generation of interference and crosstalk of electromagnetic waves, even with the transmission in the same frequency from a plurality of base stations, by alternately transmitting a free line signal representing the vacancy of a line and a selecting signal CONSTITUTION:When a mobile station 1 is within a service area of a base stations 2-3, a control station 3 sequentially changes over a switching device 6 with a controller 4 and transmits electromagnetic waves fA modulating a callout signal alternately from each base station Electromagnetic waves fM of the mobile station 1 is received at base stations 2-3 and 2-2, is compared at a n SN ratio controller 5 at a station 3, information is given to the controller 4 and switching is made so that electromagnetic waves from a base station with the good SN ratio and at being in the propressing direction of the mobile station 1 with priority When the base station 2 is called out in the electromagnetci waves in frequency fM from the mobile station 1, the base station 2 compares the received waves at the controller 5 of the station 3 and the electromagnetic waves in the frequency fA are transmitted from the base station with good SN ratio

Basic study on portable radio telephone system design

Abstract: A commercial service for an 800 MHz band fully automatic land mobile telephone system was initiated in Japan in 1979, and the number of subscribers is now over ten thousand. As the use of in-car mobile telephones become more wide spread, the demand for portable telephones will necessarily appear in the near future. Portable telephones can be introduced early and economically, if the service areas are outdoors and common mobile system base station equipment is utilized. In this paper, propagation characteristics for outdoor service portable telephones are first discussed. Diversity improvements of signal to noise ratio are shown for various combining methods, to compensate for portable telephone excess propagation loss. Using these results, portable telephone service quality is discussed when it is used with common mobile telephone system base station equipment. A new diversity antenna is proposed for base station diversity reception.

Spread-Spectrum Mobile Radio with Variable-Bit-Rate Speech Transmission

Abstract: We describe a digital mobile radio system in which users experiencing poor transmission reduce the number of bits per second used for speech coding from 32000 to 28000. They do so in a manner that greatly reduces the binary error rate. The reduced error rate more than compensates for increased quantization noise. We predict two statistics of user satisfaction in a mobile radio service area: POW, the percentage of users experiencing poor or worse transmission, and GOB, the percentage good or better. In a typical environment the maximum number of users that can operate within a 20 MHz band with POW ≤ 5 percent is 137, compared to 91 users when everyone transmits 32 kbits/s. The modulation technique is FH-FSK (frequency hopped, frequency shift keying) and the digital code is embedded ADPCM (adaptive differential pulse code modulation), in the mobile radio service area, signal strength depends on distance from mobile unit to a central base station. There is slow (shadow) fading due to terrain and building variations and rapid (Rayleigh) fading due to multipath propagation. To predict user satisfaction we have combined three different analyses: 1) a theory of FH-FSK, 2) a theory of the signal-to-noise ratio statistics in mobile radio service areas, and 3) a model, based on computer simulations and subjective testing data, of the dependence of subjective speech quality on ADPCM transmission rate and binary error rate.

Charging system for mobile communication system

Abstract: PURPOSE:To reduce charging signals from a control station, by measuring the time from the call start to the coming of the charging signal from the public corporation to detect a message billing index in the control station and by transmitting this message billing index information to a mobile station to generate a charging pulse in the mobile station. CONSTITUTION:Subscriber's telephone sets TEL1-TELn and a charging control part KTC which generates a charging signal for every start and lapse of a call unit time corresponding to the call distance are connected to an exchange EX2 of a telephone station LP in the public corporation side connected to a public corporation telephone line LP. A channel is connected to a public telephone set TELP in the side of a mobile station TS through one of base stations ZN1-ZNn by a trunk TRK of a control station MS. At this time, a charging signal such as a charging pulse is sent to the line LP from the control part KCT and is received by the trunk TRK, and a charging signal fa is sent to the mobile station TS through an exchange EX1, and the time till the next charging signal is measured to discriminate a message billing index, and message billing index information signal fb is transmitted, and a charging pulse is generated in the mobile station TS.

Position detection system

Abstract: PURPOSE:To detect the movement position of a portable radio equipment automatically by a command signal from a base station. CONSTITUTION:In the service area Sa of a base station (a), radio stations b1-bn for position detection having serice areas Sb1-Sbn are arranged. The service areas Sb1-Sbn cover all the service area Sa of the base station (a). The base station (a) sends a command signal. On judging that the command signal is addressed to a portable radio station Cn, the station Cn lowers its transmission output below rated one and sets its transmission frequency to one for position detection to send a pilot signal for position detection at the transmission frequency. The radio station bm having received the signal transfers the details of it to the base station (a). The base station (a) discriminates the number of the radio station bm to detect the position of the portable radio station Cn. The portable radio station Cn has communication with the base station (a) with large output during call service.

Large capacity information transmission system using car telephone system

Abstract: PURPOSE:To enable information offer service, by transmitting the information from a radio base station with the request from a car station in a spectrum diffusing communication system, and discriminating if it is for the station itself or not with an identification signal in the signal. CONSTITUTION:An identification number indicating a car station 2 and a transmission request signal are transmitted to a radio base station 4 through a radio link 3 by using one of radio channels from the car station 2 in a redio zone 1. The radio base station 4 is connected to a road traffic information data base station 7 via an exclusive line 5 and a radio line controlling station 6. The road traffic information is transmitted in a spectrum diffusing communication system, by reusing the band corresponding almost to the entire radio channels assigned for the transmission from the base to the car stations. The car station 2 receives a spectrum diffusing communication signal in common to discriminate if it is for the station itself from the identification number in the demodulated output.

Radio repeating device

Abstract: PURPOSE:To prevent the generation of beat disturbance at a base station and the deterioration of an S/N ratio by controlling the actuation start time of a repeating station and by inhibiting the actuation start, i.e., the transmission to the base station of an unnecessary repeating station. CONSTITUTION:Receivers Rx1 and Rx1' receive signals from a mobile station, and receivers Rx2 and Rx2' receive signals from an adjacent repeater. Circuits N and N' have operation characteristics that a relay B is operated slow when the intensity of an electric field is small or fast when large. When the mobile station Z sends a signal for communication with a base station, it is received by repeating stations X and Y at the same time, but both the stations X and Y normally have a difference in incoming electric field. When the incoming electric field of the station X is greater than that of the station Y, a transmitter Tx is actuated to perform transmission. At the station Y, on the other hand, the incoming electric field SSI is small, the operation of a relay B' is delayed, and a relay D' is operated by a signal from the adjacent station to the base station while a transmitter is not driven.

Mobile radio communication system

Abstract: PURPOSE:To enable commnication between mobile stations with an arbitrary encryption circuit, by selecting the encryption circuit corresponding to a mobile station number and providing a function connected to a transmission and reception circuit at a base station. CONSTITUTION:Mobile stations A1, A2... have individual encryption circuits 13a, 13b.... The mobile station transmits a control signal to a base station B prior to communication. The base station B recognizes the mobile station number from a received signal, selects the encryption circuit corresponding to the encryption circuit of the mobile station of the number out of an encryption circuit group 20 and connects it to a transmission/reception circuit 17. To call a specific mobile station from the base station, the encryption circuit corresponding to that of the mobile station is selected in advance for callout.

Mobile radio communication system

Abstract: PURPOSE:To enable communication with high quality, even for a mutual communication with a control station, by performing the detection of an opposing mobile station which performing radio communication in time division, in order from the base station which makes signal reception at first. CONSTITUTION:A control station A performs setting of connection/disconnection control and transmission/communication path for transmitter/receiver of base stations B1, B2 and also has the centralized control function of the base stations B1, B2. The stations B1, B2 are operated with semi-duplex communication, the base station B1 makes communication with a mobile station in a zone Z1, and the base station B2 makes communication with a mobile station in a zone Z2. On the other hand, mobile stations M1, M2 consist of an antenna 9, transmission reception switch 10, transceivers 11, 14, transponder 12, and incoming call information device 13 and the like. When the transponder 12 has a function to transmit response signal automatically, when the callout signal of the base station coincides the station number itself.

Data transmission system of terminal station

Abstract: PURPOSE:To reduce the possibility of the occurrrence of interference at a base station greatly by transmitting modification data with a time slot provided separately from one assigned to a transmitting station according to a polling signal, when registered data is to be modified. CONSTITUTION:In addition to a transmitter-receiver TRX for communication with a base station, a terminal station is provided with a receiver RX, which receives a radio wave from a sign post emitting a radio wave modulated by a code corresponding to an area, for every area. The output of this receiver is sent to a discrimination part DS, where an area code is discriminated to supply a transmission control part TC with an output which corresponds to whether a fare meter PM is in operation or not together with the output of the discrimination part DS. Once a polling signal from the base station is received by the transmitter-receiver TRX and a modulator- demodulator MDM, a control part TC, when having data to be registered to the base station, modulates and demodulates the data and transmits the resulting data from the transmitter-receiver TRX together with the number of the transmitting- station by using a time slot assigned to a group that the transmitting station has.

Simple on-line communication system

Abstract: PURPOSE:To improve economy by connecting radio base stations, which correspond to radio equipments mounted on moving bodies, to a central dispatching center by a couple of bare-wire channels, and providing a line-loss compensating amplifier, whose direction is variable, to a halfway point of the bare-wire channels being is service. CONSTITUTION:When a radio wave is transmitted from a train in the service area of some radio base station, e.g. 2', the receiver of the transmitter-receiver 4 of the base station 2' performs squlch operation to close an audio signal switch 7. Then, the received audio signal passes through a two-wire bare conductor 3 and after line loss is compensated by an amplifier 8, it is inputted to a control board 1 to flow the audio signal in a speaker. For answering from an operator, on the other hand, the individual number of the base station 2' is dialed on the control board 1 and a speech is made with a transmission pressed. While the transmission button is pressed, a direction changeover switch 10 is changed over to change the direction of the amplifier 8 from the control board 1 over to a radio base station.

Mobile communication exchange system

Abstract: PURPOSE:To avoid useless space and economy for mobile communication without encryption, by providing a encryption device with makes communication as encryption in a radio line commonly and inserting a communication line suitably as required. CONSTITUTION:Between a mobile body M' and a mobile system exchanger MCE', connection is made via a transceiver TRX1 of a base station. When an exchanger MCE' receives a signal representing the mobile body number succeeding to a call- out signal from a mobile body M', this is given to an encryption request identifying circuit PRD contained in a mobile body exchanging controller CONT1. The circuit PRD discriminates the mobile body number if the subscriber requires encryption, and if so, the information is tentatively stored in a storage circuit MEM. Next, in the mobile body M', call processing is made in the path of telephone set TE1 T1 of selector switch S transceiver TRX2 and it is made in the path of base station TRX1 trunk TRK-A for radio line, and trunk TRK-B for exchange network telephone exchanger network, at the exchanger side.

Automatic equalization for simulcasting

Abstract: The simultaneous transmission of the same audio from several conventional FM base stations over a wide area has been known to provide operational advantages and performance improvement in many cases. The technique has seen limited application, however, due to the requirement of stable microwave audio links to each of the base stations. A system that circumvents this requirement is described. Automatic equalization periodically compensates for changes in amplitude response and phase delay, allowing operation over conventional private lines leased from the telephone company. The system uses these same facilities to synchronize continuous tone-coded subaudible squelch (CTCSS). The simulcast electronics interfaces to the dispatch system through a microcomputer that also controls the signalling subsystems, providing the dispatcher with the ideally simple "push-to-talk" operation.

Mobile telephone controlling system

Abstract: PURPOSE:To enable incoming service during call, by transmitting control information required for the exchange connection during the call from a mobile telephone set side through a control line, and performing specified control operation through the reception and discrimination of the control information at exchanger side. CONSTITUTION:When a hook switch 205 of a handset 201 is depressed at a calling state, a control section 202 measures the on-hook time, and if it is a prescribed time or more, the processing for end of call is made. If within the prescribed time, it is discriminated as hooking and a hooking signal with a signal form (given for redundancy as error correction code) suitable for radio lines is transmitted to a base station via a radio section 203 and a mobile station antenna 204. When the radio line controlling station receives a hooking signal, relay to the exchange station is made with a control line. The exchanger receives and discriminates the control information to start the specified control operation.