While a clock generated by a built-in clock generator is used as a reference signal for determining a carrier frequency of a transmit signal, carrier frequency synchronization is achieved between base stations. A base station device is configured to perform wireless communication with a terminal device. In the base station device, accuracy of a carrier frequency of an OFDM signal is affected by accuracy of a clock frequency generated by a built-in clock generator 18. The base station device receives an OFDM signal transmitted from another base station device while transmission to the terminal device is stopped, estimates a carrier frequency offset of the OFDM signal, and corrects a carrier frequency of an OFDM signal to be transmitted to the terminal device.

Base station device

An error correction encoding rate selection table is provided in an error correction processing unit of a packet transfer apparatus, and the table stores an error correction encoding rate preset to maintain a desired QoS in correspondence with a protocol type and an application type. When a transmission packet is transferred to a wireless transmission path, an encoding control unit judges the protocol type and application type of a transmission packet from a header of the transmission packet, in accordance with a judgement result and the error correction encoding rate selection table, an error correction encoding rate is selected, and the transmission packet is subjected to error correction encoding and transferred.

Wireless packet transfer apparatus and method

A system, a method and computer product for synchronizing of a femto cell with a macro cell, the method comprising: placing a forward link receiver into the femto cell; receiving by a micro cellular network the femto cell transmission timing; and synchronizing the femto cell transmission timing with the macro cellular network transmission timing in reliance on the forward link receiver signal Further, a system, a method and computer product for allocating pilot phases to femto cells, the method comprising: creating at least as many new potential pilot phases for femto cells as there are for macro cells; and allowing a mobile device on a macro cell to search and find a femto cell pilot without explicitly listing femto pilot phases in the neighbor list

Femto cell synchronization and pilot search methodology

PROBLEM TO BE SOLVED: To solve the problem that time synchronization between base stations cannot be stably maintained with a predetermined precision for extended hours when any state preventing a GPS satellite from being captured occurs at an existing base station. SOLUTION: A base station 100 transmits alarm information when a GPS satellite cannot be captured. At a nearby base station 200, a 1PPS signal of accurate timing is sent to a calculation part 6 from a GPS receiver 1 to make comparison with the timing of the 1PPS signal sent from the base station 100 for calculation of time deviation between own and other base stations. The time deviation is sent by frame to the base station 100. The base station 100 confirms that no alarm information is contained in the frame and obtains correction information based on the time deviation. It determines whether the time deviation is within a tolerable range and then corrects the timing of the 1PPS signal. COPYRIGHT: (C)2011,JPO&INPIT

Time synchronizer and time synchronizing method

There is provided an optical transmitter including: a demultiplexer configured to divide a data frame of a transmission signal into subframes with a predetermined length so as to form the subframes in a plurality of signal lanes; an index generator configured to generate an index for indicating an order of the signal lanes; a lane rearrangement unit configured to rearrange the order of the signal lanes according to the index; a carrier controller configured to generate a frequency offset of a carrier corresponding to the index; a mapping unit configured to map the transmission signal in the plurality of signal lanes with the rearranged order to the transmission signal with a phase corresponding to the frequency offset; and a transmitting unit configured to optically modulate the mapped transmission signal so as to transmit the modulated transmission signal.

Optical transmitter, optical receiver, and optical transmission method

PROBLEM TO BE SOLVED: To obtain a communication system which is capable of sending out both control signals and IP packets by burst waves. SOLUTION: A process of inserting control signals into the data division of the frame format of upward burst signals and the other process of inserting IP packets into the data division are separately carried out by switching, and frequencies of the modulated burst waves which are outputted as control signals are set different from those of the other modulated burst waves which are outputted as IP packets by the switching. Moreover, when the IP packets are generated while the control signals are subjected to processings, the IP packets are sent out by the burst waves after the transmission of the control signals by the burst waves is finished. COPYRIGHT: (C)2005,JPO&NCIPI

Communication system and communication method

PURPOSE:To eliminate the degradation of synchronization accuracy by detecting a base station identification number from a reception signal and defining the reception timing of the reception signal as the transmission timing of a base station when the base station identification number coincides with a stored number. CONSTITUTION:TDMA signals transmitted by the base station are received and the TDMA signal reception timing of the base station is detected in a reception control circuit 107 based on clocks generated in the clock synchronization circuit 108 of a TDMA synchronization control part 104. Along with it, the base station identification number is detected in a base station identification number detection part 111 and whether or not the detected base station identification number coincides with the base station identification number stored in a storage part 112. In a frame timing generation circuit 109, when the identification numbers coincide, the reception timings of the TDMA signals from the base stations detected in the circuit 107 are defined as the respective transmission timing of the base stations and the average value is defined as the transmission timing of the present base station.

Frame synchronization method among base stations for mobile communication

PROBLEM TO BE SOLVED: To surely sweep carrier waves in order to prevent line disconnection from being caused following the frequency drift of all carrier waves to be received in parallel SOLUTION: The range of frequency sweep in the automatic frequency sweep circuit of a demodulating part is set small to a degree that any erroneous sweep can be prevented from being caused according to the symbol rate of carrier waves When the frequency sweep-out can not be completed in the range, the conversion frequency of a frequency converting part is shifted by fixed amounts, and the frequency sweep of the automatic frequency sweep-out circuit of the demodulating part is performed again, and this processing is repeated so that the sweep range can be widened as a result Furthermore, even when all carrier waves to be received in parallel at the time of multi-carrier communication are made to follow up frequency drift, the shift of the conversion frequency is used COPYRIGHT: (C)2005,JPO&NCIPI

Communication apparatus and communication method

PURPOSE:To improve the precision of frame synchronization between base stations while shortening the guard time of a mobile communication system which uses a time-division multiple access system and minimizing an increase in power consumption by placing only circuits, relating with frame synchronization control, in operation with a high-speed clock and placing others in operation with a low-speed system clock. CONSTITUTION:This circuit is provided with a high-speed clock generating circuit 40 which generates the clock faster than the system clock and the high- speed clock is supplied to a system clock generating circuit 13, a synchronization error detecting circuit 21, a reception timing control circuit 23, and a transmission timing control circuit 31. Namely, only the circuits relating with the frame synchronization control are placed in operation with the high-speed clock and others are placed in operation with the low-speed system clock. Therefore, the detection of the reception timing of a peripheral base station signal, the detection of a synchronization error in transmission frame timing between base stations, and the control of the transmission frame timing of this base station can be performed with high precision and the precision of frame synchronization between the base stations can be improved.

Frame synchronization control system

PROBLEM TO BE SOLVED: To provide a satellite communication modem capable of preventing line disconnection or short break during frequency changing. SOLUTION: At the transmission side, a signal branching means 12, two FIFOs (first in first out) 13, a multi-signal modulating means 31 capable of associating two signals with two communication channels and modulating them simultaneously, a frequency translating means 32, and a switch control means 33 for transmitting signals from two channels simultaneously according to a frequency switching instruction and stopping a carrier of a switching destination channel by a switching completion notification from a satellite communication reception station, are provided. At the reception side, the multi-signal demodulating means 31, two FIFOs 24 for processing two signals of two channels simultaneously, two synchronization detecting means 23 for detecting synchronization establishment of received signals, a signal selecting means 22 for outputting either of two received signals and switching the selection state using synchronization establishment detection as a trigger, and a switch control means 33 for starting signal reception at two channels according to a frequency switching instruction and notifying switching completion after synchronization establishment is detected at a switching destination communication channel, are provided. COPYRIGHT: (C)2004,JPO

Kazama Hiroshi

Papers

Communication system and communication method

Frame synchronization method among base stations for mobile communication

Communication apparatus and communication method

Frame synchronization control system

Satellite communication modem