Abstract: The station selects a communication frequency of the station among the hopping frequencies, and then, receives, as reception frames, the frames, which are transmitted from the access points through the selected communication frequency. The station extracts the control frames from the reception frames, and monitors the extracted control frames during a monitoring time interval. After that, the station determines the selected access point, on the basis of the results of the monitoring. And also, the station synchronizes itself with the selected access point on the basis of information included in the extracted control frames, together with the dwell time assigned for the selected access point.

Abstract: When an access-desired data base is set up in a private network, a public network, a contract provider for connecting the public network and the private network concerned, the private network in which the data base is set up, and a user terminal having an IP capsule encryption function for accessing the public network are used. The user terminal 10 connects to the contract provider 300 through the public network 200 at a visiting place, and achieves an IP address from the contract provider. The contract provider 300 accesses the private network 100 on the basis of the terminal request concerned, and the private network 100 authenticates an access of the terminal 10 concerned. The terminal 10 encrypts the communications, and carry out IP encapsulated communications through the public network 200 and the contract provider 300.

Abstract: An automatic equalizer has a sampling-clock producing arrangement which is for, before selecting a sample timing, producing a sampling clock at the rate of L times of that after selecting, and after selecting the sample timing, producing a tap-coefficient selection signal according to the sample timing, and a sampling clock at the rate of 1/L times of that before selecting, according to the sample timing. In the sampling-clock producing arrangement, demodulation components are obtained in absolute values of impulse-response signals with respect to L sample timings, respectively. A selecting arrangement selects the sample timing by the use of the demodulation components. The impulse-response signals are produced in response to a sampled received-signal obtained by sampling a received signal with the sampling clock.

Abstract: An automatic equalizer comprises a transmission symbol sequence generation circuit 101, a parallel received signal estimation circuit 102, subtracters 103-1 through 103-6, absolute value squaring arithmetic circuits 104-1 through 104-6, adders 105-1 through 105-4, and a discriminator 106. Maximum likelihood estimation can be performed with simple operations by means of using added error signals given by adding square error signals obtained from estimated error signals for an N number of delayed received signals delayed by a time instant corresponding to 0 through (N−1) symbols, to select the transmission symbol sequence having the smallest error.

Abstract: In each cell of a plurality of cells of a mobile communication network assigned with a predetermined number of radio channels, a base station allocates to a call one of the radio channels according to autonomous channel reuse partitioning as a communication channel on transmitting messages to and from a mobile unit which is currently present alive in the cell under consideration. For use as the communication channel, the radio channel should preferably have a base and a mobile carrier to interference ratio which is equal to or greater than a first allocation threshold level determined by a sum of a power control margin for base and mobile transmission powers and a second allocation threshold level determined to be sufficient for transmission of the messages. If such a radio channel is not available, another of the radio channels is used as the communication channel that has the base and the mobile carrier to interference ratios both equal to or greater than the second allocation threshold level.

Abstract: A message routing system for use in a mobile packet communication system where communication between mobile terminals is conducted by evaluating headers of data messages. The source and destination of each data message is determined by evaluating the inherent address and position address of each data message without each header containing any association data relating the inherent address and the position address. By facilitating such a message routing process, the amount of communications between mobile terminals is reduced.

Abstract: A mobile packet communication system has a plurality of mobile terminals movable between a plurality of auxiliary networks. Each of the mobile terminals has an inherent address processing layer for adding a packet header based on the inherent address thereof to transmission data from a higher layer, and a positional address processing layer for adding a packet header based on the positional address thereof to the transmission data to which the packet header based on the inherent address has been added by the inherent address processing layer. The packet headers contain no header information representing an association between the inherent address and the positional address. The mobile packet communication system facilitates a control process for maintaining data relative to an association between addresses and reduces an amount of communications required by such a control process.

Abstract: A channel assignment method wherein, when cover areas of base stations in a mobile radio communication system of the cellular system hierarchically overlap each other, communication channels are used commonly by the hierarchies to achieve effective utilization of frequencies by dynamic channel assignment. When a request for communication occurs, communication channels to which different selection orders between different hierarchies are applied are checked in terms of the channel quality based on the selection order, and a channel which exceeds a certain quality at first is assigned to the request for communication, but when a channel with which a required quality is obtained cannot be found in one of the hierarchies, selection of a channel is performed for another hierarchy by similar operations.

Abstract: In packet communication, when applying end-to-end control protocol such as the fourth layer protocol of Open Systems Interconnection (OSI), a large delay existing in only a portion within the network gives rise to an extreme drop in throughput. The present invention is intended to avoid this problem without altering the fourth layer protocol. This network is structured such that a sending terminal and a receiving terminal are connected by a plurality of routers, and a portion of the routers have large propagation delay. Each router is constructed from a virtual terminal controller that, from the time connection is established until disconnection of the communication circuit, operates identically to the opposing terminal upon receiving a signal from the terminal to which it is connected; a memory circuit that stores data upon reception of the data; and a data link controller that raises throughput of a circuit having large delay.

Abstract: Disclosed is a hardware arrangement for equalizing waveform distortion caused by multipath fading in a digital radio communications system, which hardware arrangement uses a recursive least-squares algorithm into which a forgetting factor is introduced. An incoming signal (PSK signal for example) is applied to an automatic gain controller which generates a first signal whose value varies with a signal-to-noise ratio of the incoming signal. A forgetting factor controller is coupled to the automatic gain controller to receive the first signal and generates the forgetting factor the value of which varies with the value of the first signal. An adaptive equalizer receives the incoming signal and the forgetting factor. The adaptive equalizer equalizes the waveform distortion using the forgetting factor according to the recursive least-squares algorithm.

Abstract: A coherent PSK demodulator includes a frequency multiplier for multiplying the frequency of an incoming M-ary PSK signal by a factor M to extract a carrier component of the PSK signal. An adaptive line enhancer is connected to the frequency multiplier for emphasizing the line spectrum of the extracted carrier component. A frequency divider is connected to the output of the enhancer to divide its frequency by a factor M and applies its output to a product demodulator as a local carrier for demodulating the incoming M-ary PSK signal. In a preferred embodiment, a synchronizer is connected between the output of the adaptive line enhancer and the frequency divider. Alternatively, a closed-loop phase error canceller is connected to the output of the product demodulator.

Abstract: In a synchronization circuit for use in demodulating an input signal carrying a transmission data signal at a symbol rate, a sampling circuit samples the input signal at a predetermined sample rate which may be different from the symbol rate, to produce a sequence of sampled signals. The sampled signal sequence is interpolated by the use of an interpolator into first and second partial interpolated signals which have different phases from each other. The first and second partial interpolated signals are processed by a processing circuit to produce timing errors between the first partial interpolated signals and the sampled signal sequence. The processing circuit controls the phases of the first and second partial interpolated signals with reference to the timing errors so that the both partial interpolated signals are derived at predetermined points of the sampled signal sequence.