Abstract: In the case where two wireless communication systems are located close to each other and possibly interfere with each other, it is detected if broad band interference takes place, and, when broad band interference takes place, the use of frequencies is limited within such a frequency range in which the wireless communication systems are little affected by the interference. An interference detection system for detecting interference between one system and another system in a wireless communication making use of frequency division multiplexing is described.

Abstract: In a communication channel set up method, the utilization state of a prescribed frequency in the first frequency band that causes interferences to the first communication system when the communication channel of a particular frequency in the second frequency band is used at the second communication system is detected, and if the prescribed frequency in the first frequency band is currently used, the communication channel other than that of the particular frequency is allocated to the second communication system.

Abstract: A mobile station receives a signal based on a TDD method by receiving a signal based on a FDD method to acquire information of the signal based on the TDD method in a mobile communication system. For instance, the mobile station receives a signal based on a CDMA-FDD method. Then, the mobile station acquires information (e.g. information relating to a code, a frequency and a timing) of a signal based on a CDMA-TDD method from the signal based on the CDMA-FDD method. Then, the mobile station receives the signal based on the CDMA-TDD method on the basis of the acquired information.

Abstract: A method of frequency utilization in mobile communication which is capable of realizing efficient frequency utilization in the case where widths of the uplink communication frequency bandwidth and the downlink communication frequency bandwidth are different in mobile communication is disclosed.

Abstract: A channel assigning method and a communication apparatus for executing appropriate channel assignment in a mobile communication system when both a channel for a service area based on a FDD method and a channel for a service area based on a TDD method can be assigned are provided. For example, if both a channel for a service area based on a CDMA-FDD method and channels for service areas based on a CDMA-TDD method can be assigned to a request for channel assignment, and a handover frequency of the mobile station related to the request is high, the channel for the service area based on the CDMA-FDD method is assigned.

Abstract: A CDMA communications system that can shorten a delay time until the establishment of traffic, and prevent excessive transmission power. Although transmission request signals RQ1, RQ2, RQ3, . . . sent from mobile stations through a common channel undergo only open loop power transmission control, and hence have large fluctuations in their received levels, their interference amount to message signals can be kept low because their received power is averagely about 1/a of that of the message signals MSG1, MSG2, MSG3, . . . The message signals are sent from the mobile stations in accordance with the power transmission control bits contained in a forward link signal ACK sent from the base station, followed by closed loop power transmission control. This enables the received level fluctuations at the base station to be kept low.

Abstract: A CDMA communications system that can shorten a delay time until the establishment of traffic, and prevent excessive transmission power. Although transmission request signals RQ1, RQ2, RQ3, . . . sent from mobile stations through a common channel undergo only open loop power transmission control, and hence have large fluctuations in their received levels, their interference amount to message signals can be kept low because their received power is averagely about 1/a of that of the message signals MSG1, MSG2, MSG3, . . . The message signals are sent from the mobile stations in accordance with the power transmission control bits contained in a forward link signal ACK sent from the base station, followed by closed loop power transmission control. This enables the received level fluctuations at the base station to be kept low.

Abstract: A mobile station position estimation scheme for a cellular mobile communication system which is capable of estimating a position of a mobile station in a simple manner even in the general cellular mobile communication systems in which base stations are not synchronized. According to this mobile station position estimation scheme, a first signal sequence and a second signal sequence which are uniquely predetermined for the mobile station are exchanged between the mobile station and the base station, and then a position of the mobile station is estimated at one station among the base station and the mobile station, by obtaining a phase difference between the first signal sequence and the second signal sequence and calculating an estimated distance between the base station and the mobile station according to the phase difference.

Abstract: In CDMA mobile communication of the packet switching mode which is one-way, the packet is transmitted to divide to a frame unit. In this time, the first, the second and the third transmission timing which are obtained to divide to three pieces the predetermined frame are set up for increasing the transmission efficiency by realizing the retransmission of the frame unit, as the transmission timing of a backward control signal in a backward channel,. Base station 100 transmits a forward signal (a forward control signal and an user data signal) by using code A (a forward channel) at any frame. When the forward signal is received at this frame by mobile station 70, mobile station 70 transmits a receiving acknowledgment signal (a backward control signal) of the forward signal by using code A' at the first transmission timing of the next frame.

Abstract: In an error control device, an error correction decoding portion 33 selects a bit position which has low reliability from the received signal by means of a predetermined bit number, generates error patterns by assuming that the errors exist at the bit position, and carries out modified Chase decoding for the received signals on the basis of each error pattern in modified Chase decoding portion 332. Modified Chase decoding portion 332 calculates the reliability of each error pattern by using the reliability of each bit in the received signal.

Abstract: A DS-CDMA transmission method capable of improving the accuracy of channel estimation using pilot symbols by eliminating cross-correlation between pilot symbols inserted into code channels in CDMA multiplexing carrying out fast signal transmission. In each frame assembler, the pilot symbols, which are used for channel estimation for coherent detection, are inserted into coded information data on code channels at fixed intervals, and then the data is modulated by the modulator. The modulated data symbols in each code channel from the modulator are spread by the spreading modulator, the pilot symbols are spread using a spreading code, whereas the information symbols are spread using different spreading codes assigned to respective code channels. The spread signals of the code channels are summed up by the adder to be transmitted.

Abstract: A transmitted signal is enciphered or concealed to thereby prevent interference, even when data indicative of the receiver terminal is made public because of the use of a common access channel. In the transmitter, in a random-number bit adder 6, a random-number .alpha. (digital signal) generated by a random-number generator 5 is inserted into a transmitting data signal DA generated by a transmitting data generator 1, and the resultant is outputted as a signal (DA, .alpha.). An encipherment processor 2 enciphers the signal (DA, .alpha.) and outputs it as a signal (DA, .alpha.)'. In the receiver, this signal (DA, .alpha.)' is deciphered into (DA, .alpha.), and the random-bits .varies. are removed from (DA, .alpha.) to restore the signal DA.

Abstract: In a CDMA mobile communication system, for realizing a multiple-access, a common reverse channel 10 is divided into an access channel 10A and a message channel 10B. When data (packet) to be transmitted occurs in any mobile station 1-4, mobile station having data to be transmitted transmits a transmission request signal including information, such as packet size or the like, by using the access channel 10A. In contrast, base station 30 transmits a transmission permission signal, which designates a transmission timing of data and a spreading code to be used as transmitting, on the basis of the state of utilization of message channel 10B and the state of occurrence of data. Mobile stations 1-4 transmits data in accordance with the spreading code and the transmission timing which are designated from base station 30.

Abstract: When data is transferred by using a plurality of time slots, the transferring period is shortened by adopting priority to assign the required number of slots. The base station BS which accepted packet P1 generates a "BUSY" signal and an echo at the final portion of the first time slot TS which begins at time t4. The base station BS, recognizing that there is a packet following the packet P1, generates a "RESERVED" signal at the final portion of the time slot TS which begins at time t5. The mobile station MS-A learns that the first time slot is assigned by recognizing the "BUSY" signal and the echo, and that the second time slot is also assigned by recognizing the "RESERVED" signal. Therefore, the first and second time slots are used successively for fast transferring.

Abstract: An ARQ data transmission scheme in which the overhead due to the ARQ control data is reduced to resolve the problem of the throughput deterioration. The error correction code for the original data is used for each re-transmission block or sub-block, and the block or sub-block corresponding to each re-transmission block or sub-block is found by carrying out the error correction operation with respect to each block or sub-block to be re-transmitted which is stored in the memory, so that there is no need to include the block or sub-block number for identifying each block or sub-block in the re-transmission frame, and consequently the ratio of the ARQ control data with respect to the transmission data can be made relatively smaller and the throughput can be improved.

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: 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: 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.