Showing papers by "NTT DoCoMo published in 1996"

Mobile communication system using efficient service area expansion scheme

Abstract: A service area expansion scheme for a mobile communication system, capable of efficiently connecting thinly populated areas (satellite zones) to a mobile communication network so as to expand the service area of the mobile communication system economically. In expanding the service area, remote base stations are set at thinly populated areas, while a remote mobile local switching station for connecting the remote base stations to the mobile communication network is provided. The remote base stations and the remote mobile local switching station are selectively connected through the public network by using the respective channel connection units for providing connections with the public network. The remote base stations and the remote mobile local switching station can be replaced by satellite base stations and a satellite mobile local switching station for connecting the satellite base stations to the mobile communication network. The satellite base stations and the satellite mobile local switching station are selectively connected through the satellite by using the respective satellite connection units for providing connections with the satellite.

Method and apparatus for call admission control in CDMA mobile communication system

Abstract: A call admission control scheme for a CDMA mobile communication system which can satisfy a given connection quality (blocking probability) while guaranteeing a predetermined communication quality. At each base station, a blocking probability and an outage probability of communication quality at each base station are calculated to adjust a maximum number of simultaneously connectable users at each base station according to the calculated results, and a call admission control is carried out according to the adjusted maximum number of simultaneously connectable users. A maximum number of simultaneously connectable users or an interference threshold can be determined from a first relationship between an offered traffic and a maximum number of simultaneously connectable users or an interference threshold for guaranteeing the prescribed communication quality and a second relationship between an offered traffic and a maximum number of simultaneously connectable users or an interference threshold for satisfying the prescribed blocking probability, and used for the call admission control.

Mobile radio communication system

Abstract: A radio base station calls a mobile station in its area through a downstream control channel or a communication channel to designate a channel the electric field level of which is to be measured. The mobile station measures the electric field level of the designated channel by using the electric field level measuring function of its own and reports the measured results to the base station through an upstream control channel or the communication channel. Therefore, a second mobile radio communication system can be constructed in the same area by utilizing a small-zone mobile radio communication system already existing in the area as a first mobile radio communication system.

Variable rate transmitting method, and transmitter and receiver using it

Abstract: A variable rate transmitting method in which the data transmission rate can be changed freely. The transmitting side supplies a transmission data sequence to an error detection encoding circuit (105) and a frame memory (103). The frame memory (103) holds variable-length data which are transmitted in frames. The error detection encoding circuit (105) calculates error detecting codes (for example, CRC codes for every frame of the transmission data). A multiplexing circuit (104) adds the calculated error detecting codes to the frame immediately before the transmission data, namely, at the head of the frame, and successively outputs data sequences one frame by one frame. On the receiving side, the error detecting codes of the data in the transmitted frame are calculated in the same way as that on the transmitting side and the calculated error detecting codes are compared with the error detecting codes at the head of the frame. The position where both error detecting codes coincide with each other is determined to be the last bit of the data in the frame. Therefore, variable-length data can be transmitted without informing the receiving side of the data length of each frame. This is equivalent to the case where the transmission rate can be freely changed.

System and method for short-cell multiplex atm transmission

Abstract: Short-cell multiplex for transmitting short data (basically, data of 48 bytes, but data of 48 bytes are also transmittable) generally shorter than the payload of a standard ATM cell through an ATM network. A standard ATM cell generating device (1) converts various forms of input information into short cells, efficiently transfers the short cells to a standard ATM cell in view of the length of the information into consideration, and outputs the standard ATM cell to a B-ISDN network (7). A standard ATM cell disintegrating device (2) disintegrates the standard ATM cell generated by the device (1) and inputted through the network (7) into short cells, converts the short cells into the original various forms of input information, and outputs the information through transmission lines. The short-cell ATM multiplex causes less delay, enhances the efficiency of transmission lines, and has a high compatibility with the standard ATM system.

Acquisition method and system of spreading code

Abstract: In a mobile communication system using spread spectrum, performing respective multiplications of an I and Q channel signals by a spreading code replica, integration over one spreading code period, and square-law detection of the integrated signals to remove data modulation components and residual carrier frequency components. The square-law detected signals are added to obtain signal power over one spreading code period while updating the clock phase of a digital control clock generator. The information of power is stored in a memory in an acquisition mode controller, and the clock phase of the digital control clock generator 30 is fixed at the spreading code replica phase at which a maximum correlation detection power over one spreading code period is obtained. Subsequently, a confirmation mode is started for confirming the spreading code acquisition phase. By thus providing the confirmation mode of the spreading code acquisition, the acquisition can be established in a short time with a low error acquisition probability, thereby enabling a tracking mode to be started soon.

ATM transmission method having silence compression controlling function and system transmitter and receiver using the method

Abstract: An ATM transmission system which transmits voice data in an asynchronous transfer mode (ATM), in which a silent section of a call is detected and the silent section is not physically sent as an ATM cell through a transmission line, realizing compression of the silent section on the transmission line. The sending side detects the silent section, generates voice/silence information, and generates a silence starting cell and a silence ending cell. The receiving side generates silent sections at regular time intervals upon receiving the silence starting cell and returns to its normal voice cell receiving state upon receiving the silence ending cell. Since the silent sections are not transmitted, the number of occupied bands is reduced on the transmission line and the efficiency of the transmission line can be improved.

System for transmission between base station and exchange of mobile communication using fixed-length cell

Abstract: A system for transmission between a base station and a mobile exchange of mobile communication of an ATM transmission system. The delay time due to the generation/sending of a cell is minimized and the quality of information which required for real time transfer is secured. Letting the transfer period of a kind of call a be T, kinds of calls b, c the transfer periods of which are twice and four times the period T are transferred at periods which are twice and four times the period T. A transfer frame (201) constituted of cell slots (201-1, 201-2 and 201-3) for transferring kind-of-call cells is provided in a transfer frame assembling/disassembling circuit (104) of a radio base station. Therefore a cell is transferred without delay by scheduling the transmission so that the cells may be sent to a transmission line (113) with a period T.

Method for synchronizing spreading code and device for synchronizing spreading code

Abstract: I- and Q-channel signals are multiplied by spreading replica codes (24) and the products are integrated only for one spreading code period (25). Modulated data components and vestigial carrier frequency components are eliminated by subjecting the integrated signals (26) to amplitude square-law detection. The signal power of the sum of the signals (27) subjected to the amplitude square-law detection is found over one spreading code period (updating the clock phase of a digital control clock generator (30)) and each power information is stored in a memory circuit in an initial synchronous mode control circuit (29). The clock phase of the generator (30) is fixed with the phase of the spreading replica code at the maximum correlation detected power for one spreading code period. Thereafter, a spreading-code synchronized phase confirming mode is started. Since the spreading code synchronization confirming mode is provided in such a way, initial synchronization is established with a low synchronization error probability and a tracking mode is started in a short time.

Mobile communications system and communications network

Abstract: A mobile communications system including a plurality of communications networks, each of which has one location register (a home location register or gate location register) and one or more visitor registers. Each of the visitor registers is located in each one of visiting areas for storing information about a communication terminal. The location register stores the number of the visitor register of the visiting area in which the communication terminal is present, and the information about the communication terminal. When the communication terminal moves between the communications networks, the information about the communication terminal is transferred between the location registers. When the communication terminal moves between the visiting areas in the same communications network, the information about the communication terminal is provided from the location register to the visitor register. When the communication terminal moves within the same visiting area, the information about the communication terminal can be obtained from the visitor register. This makes it possible to reduce the traffic on the common control line between the communications networks and in the communications network.

High-speed radiocommunication system

Abstract: A centralized control means controls the flow of all signals. A calling means transmits a call signal in response to a call instruction signal transmitted from the centralized control means. An information receiving means receives the call signal and transmits a response signal. A response receiving means transmits a response confirming signal when the means receives the response signal. Upon receiving the response confirming signal, the centralized control means transmits an information/control signal to an information distributing means. The information distributing means distributes the information/control signal to a plurality of information transmitting means. The information transmitting means simultaneously radios the information signals to information receiving means.

Method and device for multi-cell transmission

Abstract: A multicellular transmission apparatus in a mobile communication network, capable of preventing delay involved in reassembling short packets into fixed length packets (ATM cells), degradation of communication signals due to the delay, and reduction of the transmission efficiency involved in assembling the short packets into the fixed length packets. When low speed information transmitted from a telephone set (610) is converted into short packets by a communication data assemblers/disassemblers (402) in a mobile gateway switching center, followed by multiplexing of the short packets into the fixed length packets by fixed length packet assemblers/disassemblers (404), the short packets sent from a plurality of telephone sets are grouped for each destination node (a particular radio base station, for example) in the network, and are multiplexed into the fixed length packets belonging to the group bound for the destination of the short packets. This obviates the disassembling/reassembling of the fixed length packets at intermediate switching centers, thereby implementing an effective ATM switching system.

Cdma mobile communication method, system, and mobile station equipment

Abstract: A CDMA mobile communication system which creates the time during which peripheral base stations using different radio frequencies and executes the hand-off between base stations using different radio frequencies without momentary interruption. A mobile station (504) of the CDMA mobile communication system suspends the error correcting and decoding processing of received signals, outputs user data which are not subjected to the error correcting and decoding processing, and, during this suspending time, monitors the receiving levels of the peripheral base stations by switching the receiving frequency to the radio frequencies of the base stations. The base station (502) now in contact and the next base station (503) transmit only the user data during the hand-off period from the base station (502) to the next base station (503) using different frequencies and do not transmit transmission signals during the transmitting period of an error correcting and encoding check bit. The mobile station (504) receives and demodulates signals transmitted from the base station (502) and, during the transmitting period of the error correcting and encoding check bit, receives and demodulates signals transmitted from the next base station (503) by switching the frequency of its receiver to that of the next base station (503).

Cell selection method in cdma mobile communication system, its base station equipment and mobile station equipment

Abstract: PROBLEM TO BE SOLVED: To reduce the interference power and to prevent deterioration in the system capacity by discriminating cells through a transmission attenuation of a pilot channel. SOLUTION: A mobile station uses a pilot channel reception level measurement section 36 to measure a reception level of a pilot channel sent from a base station and receives information relating to transmission power of the pilot channel sent from the base station and a transmission attenuation calculation section 37 calculates a transmission attenuation of the pilot channel based on the information relating to the transmission power of the pilot channel and the reception level of the pilot channel. Then an inzone cell discrimination section 38 discriminates in-zone cells based on the attenuation.

Transmitter receiver for mobile communication system with frequency division duplex (FDD) and time division duplex (TDD)

Abstract: A transmitter receiver implementing both frequency division duplex (FDD) and time division duplex (TDD) in one device in a CDMA mobile communication system. In the FDD mode, data in an interleave memory (3A) in an interleaver (3) is read at a predetermined read rate V R = V N , where V N is a normal rate. In the TDD mode, a transmitting carrier frequency is set identical to a receiving carrier frequency, and the read rate V R of the interleave memory (3A) and the write rate V W of the deinterleave memory (11A) are set at V R = V W > 2V N . The transfer rate V T from column to column of the memories are set identical in the FDD mode and the TDD mode. This makes it possible to create a vacant duration while transferring from column to column, and to perform reception or transmission during the vacant duration. The remaining operation of the TDD mode is the same as the operation of the FDD mode.

Mobile communication system with a plurality of speech coding schemes

Abstract: Mobile communication is performed using an optimum voice coding system meeting the voice coding system provided by a radio zone and the voice coding capacity of a mobile station. Therefore, a control station which recognizes the state of handling of the voice coding system of a radio zone managed by the control station is made to store the selecting condition of a communication channel designated based on the use abilities of the voice coding system of a mobile station requested to establish a call set by an exchange and a mobile station to be connected when the communication channel between the mobile station and exchange is set up. In addition, by transmitting the selecting condition designated by the exchange as the information required to set up channel by another control station, the stored selecting condition is sent to each other when another radio zone extending across the control station is selected, or when the mobile station moves into another radio zone in which a voice coding system having the highest priority is usable, and consequently communication using a voice coding system of high priority is possible upon switching the channel during communication. Therefore, switching of communication channels using the optimum voice coding system can be made smoothly.

Multiplex transmitter for micro-frame

Abstract: A multiplex transmitter for loading micro-frames smaller than a standard ATM cell on the standard ATM cell in a multiplexing state. Input micro-frames are sequentially introduced to a distributing circuit (504) through an interface (503). The circuit (504) distributes the micro-frames by using input distribution information. The distribution information follows service conditions set for each connection or each micro-frame. A buffer is selected for a fetching circuit (506) in accordance with prefixed buffer selecting logic. A cell discarding and monitoring circuit (508) discards such micro-frames that exceed allowable cell discarding time of t2-1 to t2-m. A multiplex processing circuit (507) delivers a cell or vacant cell to a cell output circuit (511) in accordance with the cell output timing of the circuit (511).

Mobile communication system and communication network

Abstract: A mobile communication system in which each of communication networks is provided with one location register (home location register or gateway location register) and one or more service area registers. The service area registers are provided in the service areas respectively and store the communication terminal information of communication terminals existing in the service areas. The location register stores the numbers of the service area registers of the service areas in which communication terminals exist and the communication terminal information of the communication terminals. When a communication terminal moves from one communication network into another, the communication terminal information is transmitted from the location register of the one communication network to the location register of the another communication network. When a communication terminal moves from one service area into another service area in the same network, the communication terminal information is given to the service area register from the location register. When a communication terminal moves into a service area, the communication terminal information is transmitted from the service area register to the communication terminal. Therefore, the traffic of common control lines between and in communication networks can be reduced.

Subscriber number storing device and mobile station using the same

Abstract: A mobile station in which a plurality of subscriber numbers can be set from an external storing device (1) storing these subscriber numbers (K1 - Kn). The external storing device (1) is inserted into a reader (2) of the mobile station. The mobile station reads the plurality of subscriber numbers stored in the external storing device, and stores them in an internal storage (3), and then registers the subscriber numbers stored in the internal storage on a network. This makes it possible for a user to select a desired subscriber number in accordance with his needs, thereby improving the convenience of the user.

Variable rate transmission method and transmitter using the same

Abstract: of EP1357689A variable rate transmission method that can vary the transmission rate of data. A transmitting side supplies a transmitted data sequence to an error detecting encoder (105) and a frame memory (103). The frame memory (103) stores data of a variable length to be transmitted in one frame. The error detecting encoder (105) calculates an error detecting code (such as CRC code) for each frame of the transmitted data. A multiplexer (104) adds the calculated error detecting code ahead of the transmitted data to place it at the initial position of the frame, and sequentially outputs the data sequence frame by frame. A receiving side calculates an error detecting code of the data in each transmitted frame in the same manner as the transmitting side, and compares the calculated error detecting code with the error detecting code at the initial position of the frame. The end bit of the frame data is decided as a position at which the two error detecting codes coincide. This makes it possible to transmit variable length data without informing the receiving side of the data length in each frame. This is equivalent that the transmission rate can be varied freely.A variable rate transmission method that can vary the transmission rate of data. A transmitting side supplies a transmitted data sequence to an error detecting encoder (105) and a frame memory (103). The frame memory (103) stores data of a variable length to be transmitted in one frame. The error detecting encoder (105) calculates an error detecting code (such as CRC code) for each frame of the transmitted data. A multiplexer (104) adds the calculated error detecting code ahead of the transmitted data to place it at the initial position of the frame, and sequentially outputs the data sequence frame by frame. A receiving side calculates an error detecting code of the data in each transmitted frame in the same manner as the transmitting side, and compares the calculated error detecting code with the error detecting code at the initial position of the frame. The end bit of the frame data is decided as a position at which the two error detecting codes coincide. This makes it possible to transmit variable length data without informing the receiving side of the data length in each frame. This is equivalent that the transmission rate can be varied freely.