Abstract: A code sequence generator having a register for holding n-bit code, and a calculation circuit for performing matrix calculation on the content of the register, and sequentially generating a code sequence by feeding back the calculation results to the register. The matrix which is set in the calculation circuit is changed by selectively reading a matrix from a memory circuit that stores precalculated matrices. This makes it possible to set a desired register state in a short time even if the desired code sequence is very long, and to generate any code sequences without changing the rate of a clock signal.

Abstract: A spread spectrum communication receiver which can obviate a highly accurate, highly stable VCO used in a local signal oscillator.

Abstract: An up-link channel assignment scheme for cellular mobile communications systems employing multibeam antennas with beam selection, in which a channel that is selected from among all variable channels in the same frequency band may be assigned to each of the antenna beams in a base station for communications. Channel selection for a base station takes place independently of that for other cells, such that the process is autonomous. Channel selection is based upon an estimate of the signal-to-interference power ration ("SIR") in which a channel having the smallest SIR estimate that is larger than or equal to a given threshold value is chosen. Alternatively, a channel having the largest SIR estimate is selected.

Abstract: A transmission power control method of a mobile station in a CDMA (Code Division Multiple Access) system which primarily controls transmission power of the mobile station by using a closed loop control which enables high accuracy power control. When the received power at the base station of a signal from the mobile station suddenly increases owing to the state of buildings surrounding the mobile station, the transmission power of the mobile station must be quickly reduced to prevent the interference to other mobile stations. The mobile station measures an average value of the received power per transmission power control period of a desired signal from the base station, and detects the difference .DELTA.RSSI between the current average value and that of one of the previous transmission power control periods. If .DELTA.RSSI exceeds a reference power difference .DELTA.P.sub.th, transmission power P.sub.T corresponding to .DELTA.

Abstract: A CDMA communications method capable of multiplex transmission of data over a wide range from a low rate to high rate such as image data without a considerable increase in a circuit scale. A fundamental transmission rate is determined, for example, at 32 kbps, a rate higher than 8 kbps conventionally used. The data whose transmission rate is equal to the fundamental transmission rate is transmitted in frames including no vacant portion. Data whose transmission rate is lower than the fundamental transmission rate (16 kbps, for example) is transmitted in frames including vacant portions. The vacant portions are not transmitted. This makes it possible to receive data through other channels during a time period associated with the vacant portions. Data of a higher transmission rate, 128 kbps, for example, can be multiplexed and transmitted through four channels using different spreading codes.

Abstract: Mobile stations randomly set delay amounts for each message to be sent, on the basis of the timing of a symbol received from a base station, and delay transmission signals for time intervals corresponding to the delay amounts. The base station 11 despreads signals received from the mobile stations to extract basic symbol timing for each mobile station and, at the thus extracted timing, takes each despread output into the corresponding demodulator for demodulation.

Abstract: A base station and a mobile station in a mobile communication system capable of reducing interference among mobile stations and increasing a subscriber capacity of the system. The base station has a unit for measuring a measurement value for at least one of a receiving level and an interference ratio level of the mobile station transmission signals, and a unit for producing a mobile station transmission power control data specifying a mobile station transmission power required in adjusting the measurement value to a target level according to a number of base stations simultaneously in communication with the mobile station.

Abstract: A switching center 30 comprises a memory part M2, a memory part M3, and a memory part M4. The memory part M2 stores a terminating terminal number corresponding to and registered by each subscriber. The memory part M3 stores idle/busy information corresponding to each terminal. The memory part M4 stores idle/busy information corresponding to each subscriber. When a subscriber 11.sub.1 makes a call at a terminal 12.sub.2, the switching center 30 determines whether the idle/busy information for the subscriber 11.sub.1 stored in the memory part M4 is idle or busy. When the idle/memory information represents idle, the switching center 30 refers to the idle/busy information for the terminal 12.sub.2 stored in the memory part M3. When this idle/busy information represents idle, the switching center 30 reads out the terminal number of a terminating terminal of a terminating subscriber stored in the terminating terminal memory part M2 and performs an outgoing call connection process.

Abstract: In a mobile communication system which uses a code division multiple access (CDMA) scheme for communications between a base station and a plurality of mobile stations, the base station has a transmitting device in which a plurality of information sequences S1 through Sn are respectively spread by multipliers 11 through 1n with a common spreading code from a spreading code generator circuit 10, the spread codes are provided to transmitting timing control circuits 21 through 2n and then added by an adder 30 to perform transmitting timing offset multiplexing and then the spread signals are transmitted to the mobile stations at different transmitting timing. The mobile stations each have a receiving device which receives that one of the transmitted signals which was transmitted at timing predetermined for the mobile station and despreads the received signal with the same spreading code as that used in the transmitting device, thereby reconstructing the original information sequence concerned.

Abstract: A transmission power control method for a CDMA system including the steps of calculating an actual SIR (Signal-to-Interference Ratio) of a desired signal; deciding whether the actual SIR is greater than a predetermined reference SIR which satisfies a predetermined conununication quality; forming a transmission power control bit on the basis of a result of deciding; inserting the transmission power control bit periodically into a forward frame, which steps are performed at the base station, and steps of calculating tentative reverse transmission power in accordance with the transmission power control bit in the forward frame; deciding reverse transmission power such that the reverse transmission power is made equal to the tentative reverse transmission power when the tentative reverse transmission power is less than a predetermined maximum transmission power, but otherwise made equal to the predetermined maximum transmission power; and transmitting a signal from the mobile station to the base station at the re

Abstract: A method of communicating a speech signal over a communication medium which utilizes VOX (Voice Operated Transmitter) control, and a speech signal transmitting unit and a speech signal receiving unit used in said method. The speech signal includes at least one speech-active duration in which actual speech exists and one silent duration in which no actual speech exists. At a transmitting side, the speech signal is analyzed for each of successive frames thereof to determine whether each frame is in the speech-active duration, and is coded for each of successive frames thereof to produce a series of successive coded data of the speech signal. Then, in response to the detection of a speech starting frame of the speech-active duration, the coded data of the speech starting frame is switched to a preamble, and the preamble and the successive coded data subsequent to the speech starting frame are transmitted in the form of a series of successive frames.

Abstract: In a radio receiver for receiving a radio signal, a counter (32) counts an eventual intermediate frequency of an amplified signal based on a reference signal as a count datum. A frequency controller (27) controls a reference frequency of the reference signal according to the count datum. A reference oscillator (25) is controlled by the frequency controller to produce the reference signal. Receiving a radio signal by double superheterodyne, the radio receiver gives the eventual intermediate frequency to the amplified signal. In the amplified signal, the frequency controller suppresses an eventual frequency drift which results from frequency drifts of a first local oscillation and a second local oscillation. The radio receiver may be a single superheterodyne receiver.

Abstract: Pluralities of estimated desired and interference signal sequence candidates corresponding to the states of transition of desired and interference signals estimated to receive are sequentially generated in a state estimation part 40, from which they are provided to a desired signal estimation part 10 and an interference signal estimation part 20. These estimation parts 10 and 20 generate estimated desired and interference signals from the sequence candidates in accordance with conversion parameters from a channel parameter estimation part 50. A signal of their sum is subtracted in an error estimation part 30 from a received signal to yield an estimation error signal .epsilon.. The state estimation part 40 estimates estimated desired and interference signal sequences for the generated sequence candidates.

Abstract: A radio communication system operates between two radio terminals, and/or between a radio terminal and a fixed terminal through a network. In the present disclosure, the switching of codec-release mode and codec mode in the network is controlled by using a specific control line which is installed in addition to a speech line. Thus, when a radio terminal communicates with another radio terminal through a network, no codec is used in the network, and so, speech distortion and signal delay are not deteriorated due to signal conversion by using a codec.

Abstract: A frequency diversity communication system is provided whereby the number of hopping channels is reduced and a more continuous communication achieved as a mobile station travels from cell to cell by the combination of chips of symbols from the mobile sources. The transmitter divides each symbol of an input symbol sequence into a number K of chips, which are modulated with mutually different carrier frequencies. The receiver demodulates the signal sent by the transmitter by local frequencies corresponding respectively to the K different carrier frequencies. According to this invention, the carrier phase is coherent for each frequency of the received wave. Moreover, because the carrier phase is coherent, the outputs for each frequency of the received wave can be combined with the use of a training signal. The receiver also performs an estimation of the maximum likelihood of the transmitted symbol to eliminate the need for decoding.

Abstract: A base station of a CDMA communication system includes a transmission de-correlator for eliminating interferences between communication channels of a downlink. The transmission de-correlator has a memory storing a set of data representative of the products of transmission information bits for the respective channels, and the sums of the products of the spread code data sequences for the respective channels, and the elements of an inverse matrix with respect to a predetermined matrix of a cross-correlation between the spread code data sequences for the respective channels. The sums correspond to additions of the products along a direction of columns or to additions of the products along a direction of rows of the inverse matrix. A counting device is operative for causing the memory to sequentially output the data therefrom. An adder serves to calculate a sum of the data outputted from the memory.

Abstract: Radio zones 2a through 2d are each assigned radio frequency channels of the number corresponding to the zone traffic, one frequency f1 of the radio frequency channel is assigned in common to all radio zones, and radio channels of the same frequency are assigned spectrum spreading codes different for each zone. A mobile station is provided with two correlators 14 and 15. If the received signal level lowers when the mobile station stays in the radio zone 2a and is in conversation over the channel of a frequency f2, the mobile station once switches the communication to a channel of the common frequency f1 and continues the communication using one of the correlators, while at the same time the mobile station scans spectrum spreading codes for control channels of the respective radio zones by the other correlator for measuring the received signal levels of the control channels and determines a destination radio zone which provides the maximum received signal level.

Abstract: In order to change a subscriber alert mode of a radio pager from an audible alert mode to an inaudible alert mode, a normally open function switch is depressed while the radio pager operates in the audible alert mode. The function switch is subsequently depressed. Following this, a timer is set to count up to a predetermined time period. A pager display exhibits a silent time duration for which the pager will operate in the inaudible alert mode if the timer counts up the predetermined time period. Subsequently, another timer is set to count up to a predetermined time period if the function switch is released. Thereafter, if the second timer counts up the second predetermined time period and if the function switch remains released, the radio pager is set to operate in the inaudible alert mode for the set silent time duration.

Abstract: A received signal of a control channel of each cell is despread by each spreading code in a correlation detector. The received level of the despread output in a window, including its peak, is measured in a level measuring part and an interference signal level outside the window is also measured. In a control part the difference or ratio between the measured received level and the interference signal level is obtained as a comparison signal for each spreading code, and the comparison signal is compared in terms of magnitude to thereby determine the visited cell of a mobile station.

Abstract: A dielectric plate 21 can be mounted on a housing 11 in such a manner that it is slidably retracted into the housing. A strip antenna element of an electrical length approximately equal to a quarter wavelength is formed on one side of the dielectric plate along one marginal edge thereof, and an antenna element 23 composed of a straight conductor portion 23a and a coil 23b connected at one end thereto is formed on the dielectric plate 21 just above the strip antenna element 22. The electrical length of the antenna element 23 is also equal to a quarter wavelength. A parallel twin-lead type feeder of a length nearly equal to the quarter wavelength is also formed on the dielectric plate 21 in parallel to the strip antenna element 22. The feeder 26 is connected at one end to inner ends of the antenna elements 22 and 23 and at the other end to a feeder 27 via contact pieces 29a and 29b. The feeder 27 is connected directly to a radio circuit 12 in the housing 11.