Nec Corporation

Nippon Electric Co., Ltd.

Toshinori Hotta

Yuji Goto

Osamu Yamamoto

Yukio Takimoto

Yasuhito Isoe

Tomoyuki Ooi

Yuuhei Ishi

Yasunori Yoshizawa

In a earth station having a particular address and comprising a terminal and a transmitting section for transmitting a transmission data signal including an address signal representative of the particular address towards a satellite through a single communication channel, a receiving section receives a reception data signal comprising the transmission data signal which is sent from the satellite through the single communication channel. By detecting the particular address, a decision circuit decide whether or not the receiving section correctly receives the reception data signal within a predetermined time interval after the transmitting section starts transmission of the transmission data signal. When the receiving section does not correctly receive the reception data signal, the transmitting section stops the transmission of the transmission data signal and an alarm signal is supplied to the terminal. Alternatively, the transmission data signal may include another address signal representative of another address of another earth station.

Earth station capable of carrying out communication without a control

In an earth station having a particular address and comprising a terminal and a transmitting section for transmitting a transmission data signal including an address signal representative of the particular address towards a satellite through a single communication channel, a receiving section receives a reception data signal comprising the transmission data signal which is sent from the satellite through the single communication channel. By detecting the particular address, a decision circuit decides whether or not the receiving section correctly receives the reception data signal within a predetermined time interval after the transmitting section starts transmission of the transmission data signal. When the receiving section does not correctly receive the reception data signal, the transmitting section stops the transmission of the transmission data signal and an alarm signal is supplied to the terminal. Alternatively, the transmission data signal may include another address signal representative of another address of another earth station.

In a communications system, a multiframe data signal is sent from a transmit end to a receive end of the system. The multiframe is composed of a series of submultiframes each containing a series of frames. Each frame in turn comprises a sync word for establishing the start timing of the frame, an identifier for uniquely identifying the submultiframe in which the frame is contained, and a specified number of data bits. A pseudo-random scrambling bit pattern, which repeats at intervals of multiframe and varies from one pattern to another at frame intervals, is generated as a scrambling bit pattern with which the data bits of each frame are scrambled prior to transmission. At the receive end, the sync word of each frame is detected to establish frame synchronization. A memory stores initial bit patterns each of which is identical to the pattern which was generated at the beginning of each submultiframe. The identifier is detected when frame sync is established and applied as a read address to the memory. The initial bit pattern of the submultiframe which is next to a one in which the establishment of frame sync occurred is read out of the memory into a pseudo-random sequence generator. The latter is activated at the beginning of the next submultiframe to generate a pseudo-random sequence, which successively varies at frame intervals and repeats the same pattern at multiframe intervals, for descrambling received data bits.

Scrambling/descrambling method using a memory for storing initial

In a satellite business communication system comprising a plurality of aperture terminals, a supervising station is coupled to the aperture terminals through a public communication network to centralize a monitoring operation of each aperture terminal. Each of the aperture terminals has a terminal directory number and a terminal indentification address while the supervising station has a primary directory number. A monitoring item is transmitting from the superivising station to a selected aperture terminal along with the terminal identification address of the selected aperture terminal and the primary directory number after a transmission path is formed by the terminal directory number through the public communcation network. A result of monitor in the selected aperture terminal is sent as a response signal back to the supervising station through a return path formed by the use of the primary directory number. The result of monitor may be stored in a status memory or be transmitted through a different path to the supervising station, if the return path is busy.

Satellite business communication system capable of monitoring a

In order to compensate for frequency deviation without using a pilot signal and associated apparatus, a channel number identification code is added to a transmit signal at an earth station transmitter. Each channel unit (e.g. demodulator) of a receiving earth station is arranged to extract a channel identification code from a received signal and to compare this with a preset code assigned to that channel. In the event that the recieved channel idenfication code does not coincide with that of the instant channel, the channel determines that number of channels by which deviation which has occured and adjusts its receiving frequency accordingly.

Transceiver for use in earth station in satellite communications system

A power control circuit comprises a signal input, a controllable attenuator, an amplifier, an output, a power detector, a reference circuit, a comparator, an external control input, an error detector, and a controller. The comparator, error detector, and controller are digital circuits realized by a microprocessor. The attenuator is between the signal input and the input to the amplifier to regulate the amplifier's output. The power detector couples to the amplifier output to generate a measurement signal representing the power at the output. The reference circuit generates a reference signal representing a predetermined minimum output when the signal input is nonzero. The comparator compares the measurement and reference signals and generates a decision signal indicating if the signal input is nonzero. The external control input receives an external control signal. The error detector is coupled to the power detector and the external control input and computes the difference between the external control signal and the measurement signal. When the measurement signal is at or above the minimum power, the controller provides an integral of the computed difference to control the variable attenuator. When the measurement signal is below the minimum power, the controller keeps the attenuator at a prior constant value.

Automatic electrical power control circuit

In a terrestrial station of a TDMA communication network, a TDMA frame includes a particular time slot shared by the station and other stations of the network. In order to increase communication traffic, each station can send a transmission burst in the particular time slot in addition to a preassigned time slot which is preassigned to the station. In response to a reception burst received through a prescribed time slot, the station determines whether or not it can send the transmission burst to the particular time slot. This makes it possible to change the communication traffic without causing overlap of bursts in the particular time slot.

Station of a TDMA communication network capable of quickly changing

In order to initially establish burst acquisition in a TDMA satellite communications system, at least one of multiple earth stations (a first station) is controlled to instruct one of the other earth stations (a second station) to transmit an acquisition signal. The acquisition signal is transmitted in a continuous manner and has lower power than normal or full power. The first station receives the acquisition signal transmitted via a satellite transponder and detects a reference time point included in the received acquisition signal. Thereafter, the first station obtains a time difference between the reference time point and a received reference burst time point. The time difference intelligence is sent to the second station, which in turn transmits a burst at a time point determined by the transmitted time difference information.

Method of initially establishing burst acquisition in TDMA satellite

A supervising and controlling system for a TDMA equipment in a TDMA station designates one of two control memories in the TDMA equipment as a spare one with the other as operating one by a memory selection signal from a supervisory and control apparatus. The content of the spare memory is periodically verified by the significant control data from the control apparatus. When non-coincidence is detected by the verification, the significant control data is transmitted to the TDMA equipment and is written into the spare control memory without interfering with other stations. Two similar TDMA equipments are provided in the station and controlled by the control apparatus in the similar manner. One of the equipments can be selectively used as an operating one by equipment selection signals from the control apparatus.

Supervising and controlling system for a communication station in a TDMA

On carrying out communication among a plurality of earth stations by the use of a satellite, super-frame time slots are specified on board the satellite at a super-frame period equal to a frame period multiplied by a predetermined natural number in order to synchronize the satellite and the earth stations with the super-frame time slots. The satellite informs each earth station of the super-frame time slots by generating super-frame bursts specifying the super-frame time slots. Alternatively, each earth station generates super-frame bursts to enter the super-frame time slots on the satellite. The satellite informs such earth station of the super-frame time slots by preventing the super-frame bursts from being returned to each station. At any rate, the satellite and each station change one on-line sequence of operation to the other in synchronism with a specified one of the super-frame time slots without any interruption of communication.

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Tokyo, Japan

Toshinori Hotta