Nec Corporation

Siemens Aktiengesellschaft

Huawei Technologies Co., Limited

Telefonaktiebolaget Lm Ericsson (Publ)

Nortel Networks Corporation

Nokia Solutions and Networks Gmbh & Co. Kg

Hizuru Nawata

Shousei Yoshida

Toshifumi Sato

Jacob Österling

Susumu Otani

Armin Splett

Hiroki Tsuda

Jacob Kristian Osterling

Eric Georgeaux

Thomas Ostman

Thomas Östman

Kenichiro Yagawa

Werner Korte

Hans Kröner

Lin Zhibin

Lan Haiqing

Yang Ganghua

Patrick Lagrange

Peter Merz

Bernd Hassler

Torbjörn Aarflot

Yozo Hirata

Torbjöm Aarflot

Hans KRÖNER

An interface, apparatus, and method are described for communication between a radio control (REC) node and first and second radio equipment (RE) nodes in a radio base station that transceives information over radio interface using multiple antenna carriers. The REC node is separate from and coupled to the first RE node by a first transmission link, and the second RE node coupled to the first RE by a second transmission link. Both control information and user information intended for communication between the REC node and the first RE node and the REC and the second RE node are conveyed over the first transmission link. The first RE node also conveys information between the REC and second RE node. Many advantageous features are described.

Interface, apparatus, and method for communication between a radio equipment control node and one or more remote radio equipment nodes

A communication amount monitoring circuit () monitors a transmission buffer () to which communication data () is input, and discriminates the magnitude of the amount of communication data. If the amount of information per unit time is relatively large, information is read out from the transmission buffer in accordance with a chip clock. This information is modulated as communication data () by a modulator () and transmitted. If the amount of information is relatively small, information is read out from the transmission buffer () in accordance with a clock obtained by frequency-dividing the chip clock. This information is exclusive-ORed with a spreading code generated by using the chip clock and is then modulated by a modulator (). The resultant data is transmitted as communication data (). Since there is no change in the frequency of the communication data (), there is no need to provide any resynchronization on the reception device side at the time of switching between the large and small amounts of information. There is therefore no need to provide any buffer area for resynchronization.

Variable communication system

A satellite communication transmission control system includes one central station, a plurality of small aperture terminals, and one communication satellite serving as a repeater for the central and aperture terminals. This system performs communication via a frequency division multiple access communication channel. The central station includes a modulator for transmitting via a common channel a signal for controlling/monitoring the small aperture terminals on the basis of a stable clock signal. Each aperture terminal includes a modulator, transmission frequency converter, antenna/RF device, reception frequency converter, demodulator, and frequency comparator. The modulator modulates communication information. The transmission frequency converter frequency-converts a modulated wave from the modulator into a carrier signal (modulated carrier). The reception frequency converter frequency-converts the modulated carrier. The demodulator demodulates a signal received via the common channel and outputs a reception clock. The frequency comparator detects the frequency error of a local oscillator, and generates a control signal for stopping transmission of the modulated carrier until the frequency error falls within a preset tolerance range.

Satellite communication transmission control system and small aperture terminal

A VSAT station and a VSAT communication system have a demand assign multiple access function for keeping a transmission path only for a required period of time to effectively use frequencies. The VSAT station has a transmission controller for temporarily reading and storing communication datato be transmitted in bufferand outputting the stored communication data as transmission dataafter elapsed of a given period of time. Communication traffic monitoring circuitmonitors the stored amount of communication data in bufferand outputs communication path selecting signal. Transmission data switching circuitselects a transmission circuit to transmit the transmission data. If the communication traffic between communicating stations is increased, then dedicated lineis established in another frequency band. If CSC lineis congested, then dedicated lineis established to reduce the burden on CSC line. Thus, frequencies are effectively used and expenses for using the satellite repeater are reduced.

VSAT station and VSAT communication system

In a digital satellite communications system for communicating data between a HUB station and a plurality of VSATs (Very Small Aperture Terminals) or between the VSATs via a communications satellite, each VSAT comprises: a digital signal processing section for demodulating signals received by the VSAT; ROM for storing a default program for letting the digital signal processing section execute signal demodulation at start-up of the VSAT; rewritable memory for storing an operation program for letting the digital signal processing section execute signal demodulation after the start-up of the VSAT; an operation program download section for obtaining the operation program by downloading the operation program from the HUB station; an error check/rewriting section for conducting error check to the downloaded operation program until an errorless operation program is obtained by the download and storing the errorless operation program in the rewritable memory; and a switching control section for switching a program which is loaded into and used by the digital signal processing section from the default program to the operation program.

System and method for digital satellite communication

Radiated from each orbiting satellite of a satellite communication network to M cells (M representing an integer, such as thirty-seven) covered with a predetermined solid angle on the earth, M spot beams are identified by M identification codes. In an earth station which may be a portable unit, a burst signal transmitter device (31) comprises a receiver part (35) receiving one of the spot beams as a received beam at a reception time, to recognize as a recognized code one of the identification codes that identifies the received beam, and a transmitter part (45) for transmitting burst signals at a transmission time delayed from the reception time by an offset amount selected by the recognized code from M offset amounts predetermined for the identification codes. Preferably, the M offset amounts are stored in a memory (43).

Burst signal transmission from an earth station to an orbiting satellite

A frequency error occurring in a repeater station and a receiving side radio station is determined by using a dummy signal received from the repeater station, and is stored as frequency control data corresponding to the frequency error into a memory. By controlling a reception frequency based on the stored frequency control data, a data signal received from the repeater station is compensated for the frequency error. A relatively large frequency error such as the common frequency error occurring in the satellite and the downconverter of the receiving side can be eliminated effectively.

Radio communication apparatus and method

In a control system being provided with a local oscillator (42) and being for controlling a demodulating arrangement (43, 44, and 45) demodulating a desired one of modulated signals in accordance with a demodulating frequency, produced by a sweeping operation of the local oscillator, into a demodulated signal having a unique word and an identification number which are carried by the desired modulated signal, a unique word detecting circuit (47) detects the unique word to produce a unique word detection signal. A number comparing circuit (48) compares the identification number with a desired one of predetermined numbers to produce a number coincidence signal when the identification number coincides with the desired number. In response to presence and absence of each of the number coincidence and the unique word detection signals, an oscillator control circuit (49) controls the sweeping operation of the local oscillator.

Demodulator control system and a receiver capable of quickly acquiring a

An available frequency range previously assigned to the communication system is divided into a plurality of subranges each including a plurality of frequency channels to which channel identifiers are assigned, respectively. The channel identifiers are repeatedly assigned to all the frequency channels in the subranges. In such a channel assignment, a transmitting side transmits a signal including a desired channel identifier corresponding to a desired frequency channel. At a receiving side, after detecting a frequency acquisition of the demodulator, the desired channel identifier is detected based on the received signal when the frequency acquisition of the demodulator is detected. When the frequency acquisition of the demodulator is detected and the desired channel identifier is detected, a local oscillation frequency sweeping for demodulator is locked to receive the signal from the transmitting side.

Communication system with repeatedly allocated channel ID numbers

In a communication system for transmitting and receiving burst signal between a round-trip satellite and a ground station, upon transmission of a transmitting burst signal from the round-trip satellite, a standard time upon transmission is added to the transmitting burst signal. In the ground station, the time data added to the transmitting burst data is extracted and compared with the standard time upon reception to derive a transmission delay period. A transmission timing of a burst signal to be transmitted from the own station is controlled depending upon the transmission delay period. By this, even when a distance between the ground station and the round-trip satellite is varied, overlapping of the burst signals in the time slots on the same time axis can be successfully avoided. Also, a guard time can be shortened to contribute for improvement of the transmission efficiency.

Communication system for varying timing offset to accommodate variation

A transmission apparatus for an orbiting satellite which can establish stabilized frame synchronization even if the distance between the round-trip satellite and a communications terminal varies and which can minimize the displacement between a frame signal received on the ground and another frame signal generated in a communications terminal. The transmission apparatus comprises M (M is an integral number equal to or greater than 2) composers for forming frame signals, M transmitters for outputting M spot beams having different radiation directions, and M delay circuits interposed between the composers and the transmitters. The delay times of the delay circuits are set so that they are long where the radiation angles of the corresponding spot beams are small, but they are shorter where the radiation angles are larger.

Transmission apparatus for orbiting satellite

At the transmit end of a communications system, a convolutional code of a multiplex of an information-bearing signal and a unique word is modulated upon a transmitted carrier. At the receive end, the transmitted carrier is demodulated with a local carrier to detect the convolutional code. The error rate of a decoded version of the convolutional code is determined, and an out-of-FEC-sync signal is produced when the error rate is higher than a threshold value. Unique words are detected from the decoded signal and counted during a prescribed time interval to produce an out-of-frame-sync signal when the count falls below a threshold. The frequency of the local carrier is swept in the presence of the out-of-FEC-sync signal. When the signal ceases to exist, a timeout period is set, and the local carrier frequency is swept again when the timeout period expires during the presence of the out-of-frame-sync signal.

Carrier recovery control with sequential FEC sync detection and frame

A unique word detection apparatus for detecting a unique word out of a demodulated signal resulting from the demodulation of a burst signal consisting of a carrier recovery section, a bit timing recovery section, a unique word section and a data section. The magnitude of the D.C. component of the demodulated signal is extracted, and the timing of the transition of this D.C. component from large to small is detected. An aperture signal designating the period in which to detect the unique word on the basis of the transition timing of the D.C. component generated, and the unique word out of the demodulated signal entered during the period designated by the aperture signal is accurately detected.

Unique word detection apparatus

In a burst demodulator, an APSK burst signal containing a preamble of alternating '1' and '-1' symbols, followed by a data field is received and quasi-coherently demodualted into a baseband complex signal, which is converted to digital form such that each symbol of the complex signal yields N digital samples, with N being selected such that at least one of the N digital samples is closest to a signal point of the burst signal. A clock recovery circuit is responsive to the arrival of the burst for estimating the symbol timing of the burst signal from digital samples of the preamble. A digital sample is extracted from every N samples of the preamble in response to the estimated symbol timing so that it is most likely to be closest to the signal point. A carrier recovery circuit responds to the estimated symbol timing by estimating the carrier frequency and phase of the burst signal from the extracted digital samples to produce a complex carrier signal, which is multiplied with the extracted digital samples to recover the original signal. Memories are preferably provided to store the received burst signal. By repeatedly reading the preamble from the memories, the same symbols of the preamble can be used for clock timing and carrier phase recovery operations.

Burst demodulator for establishing carrier and clock timing from a

In a satellite communications system, a time slot assignment signal and a reference timing signal are transmitted from a central station to terminal stations to allow them to send bursts on assigned time slots and to establish the frame timing. In the central station, first and second self-resettable counters increment their respective binary counts at clock intervals and reset their counts to an initial value at time-slot intervals. A local timing signal is generated synchronously with the reference timing signal and delayed by an amount corresponding to a minimum round-trip propagation delay to reset the first counter. In an initial, wide aperture mode, the output of the first counter is used to generate control signals for recovering a carrier and clock and widely opening an aperture gate for detecting unique words of a burst that is affected by satellite drift. If a unique word is detected, the central station switches to a narrow aperture mode in which the output of the second counter is used instead to generate control signals for recovering the carrier and clock and narrowly opening the gate to reduce the possibility of detecting false unique words. In a preferred embodiment, the output of the second counter is stored in a memory in response to the detection of a unique word and an average value of the stored counts is derived to optimize the reset timing of the second counter.

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Tokyo, Japan

Hizuru Nawata