Nec Corporation

Tomoki Osawa

Kazuhiro Okanoue

Yoshikazu Kakura

Takeshi Yamamoto

Kenichi Ishii

Kenji Takeda

Seiji Kachi

Yukie Mimura

A radio communication apparatus in a radio packet communication system constituted by a plurality of radio stations and having a plurality of radio channels is provided. To allow radio stations belonging to different radio links to directly communicate with each other, when a packet as data is to be transmitted, a channel control section () inquires of a channel registration section () about a radio channel used for reception by a radio station corresponding to the destination address in input transmission data, and a radio channel used for packet transmission is selected. The packet is then transmitted from a transmission/reception section () via the selected radio channel. When a packet is to be received, the radio channel in the transmission/reception section () is switched to the self-station radio channel stored in a self-station channel storage section ().

Radio communication device for radio packet communication system

A mobile terminal and method of controlling the same, each that can integrally move between an infrastructure network and an ad hoc network. The mobile terminal can interconnect an infrastructure network and an ad hoc network while moving. In an address management process, a connection network identification process, and a destination address capture process which are needed to establish communications with the terminal connected to a network, an infrastructure network connection procedure is integrated with an ad hoc network connection procedure. The integrated configuration consists of an ad hoc/infrastructure network address management means, an ad hoc/infrastructure integration move management means, an ad hoc/infrastructure network integration destination address capture means. In each process, it is identified whether or not the mobile terminal is connected to an ad hoc network or infrastructure network, so that the procedure corresponding to the connected network is used.

Mobile terminal and method of controlling the same

In data communication between a terminal equipment connected to a first network and a second network and a server terminal equipment via an interconnecting installation, there are provided a first communication controller in which data communication control is performed on the terminal equipment via the first network by a message group for functions of data transfer, transmission acknowledgment, flow control, and the like, and a second communication controller in which the data communication control is performed on the interconnecting installation with the terminal equipment via the first network by the message group, and the data communication control is performed with TCP module of the server terminal equipment according to TCP. By this, data communication efficiency is enhanced in a communication environment for communicating a communication terminal equipment on a cable network through a radio line or another access link.

Data Communication method, terminal equipment, interconnecting installation, data communication system and recording medium

A diversity receiver having n (integer of 2 or more) antenna branches for receiving a packet made up of a preamble field and data field includes n first switches, second switch, packet detection circuit, and demodulation section. The n first switches receive signals respectively received by the n antenna branches and a &ldquo;packet receive pulse&rdquo; representing that a packet is being received, and change the output destination based on the &ldquo;packet receive pulse&rdquo;. The second switch receives an antenna switching signal and outputs from the n first switches, and when no &ldquo;packet receive pulse&rdquo; is output, selects and outputs the outputs from the n first switches based on the antenna switching signal. The packet detection circuit receives an output from the second switch, and when a packet is being received, outputs a &ldquo;packet receive pulse&rdquo;. The demodulation section receives and demodulates all or some of the outputs from the n first switches when a &ldquo;packet receive pulse&rdquo; is input.

Diversity reception method and diversity receiver

An object of the present invention is to provide a diversity receiver having an excellent anti-multi-path fading characteristic in a further simple structure. A diversity receiver according to the present invention measures a reception level, delay spread and a phase of a burst OFDM modulates signal received by a plurality of antennas. Received signals of arbitrary antennas are combined for synthesization and demodulated in accordance with a result of measurement, thereby obtaining the excellent anti-multi-path fading characteristic.

Diversity receiver

In order to shorten delay time in a synchronization circuit in an OFDM demodulator, with respect to a preamble for estimating carrier frequency/channel characteristic, the synchronization circuit does not have a delay circuit and a frequency error compensation signal of a carrier frequency estimating circuit is supplied to a channel distortion estimating circuit connected to an output of an FFT. In the channel distortion estimating circuit, a carrier frequency deviation is compensated.

OFDM demodulator

In an OFDM demodulator, in order to stably perform a timing reproducing process with a simple configuration, a complex correlation circuit correlates sampled and quantized digital complex baseband signals outputted from A/D converters and a pattern of a preamble for timing/carrier frequency synchronization of a short symbol prestored in a reference signal storing circuit and outputs the correlation result. The correlation result is supplied to a timing detecting circuit and the timing of the short symbol is detected.

K sub-carrier components from an FFT circuit are output to a sub-carrier demodulating circuit . The sub-carrier demodulating circuit demodulates the k sub-carrier components and outputs a transmitted information bit to an output terminal . Further, the sub-carrier demodulating circuit outputs distortion correction coefficients C( )-C(k) that are used during demodulation of each sub-carrier, each of sub-carrier components S( )-S(k) in which distortion is corrected, and determination signal points R( )-R(k) for each sub-carrier to a phase estimating circuit . The phase estimating circuit receives C( )-C(k), R( )-R(k) and S( )-S(k), and outputs a phase error signal to an output terminal . The phase error signal output to the output terminal is integrated by a loop filter and so forth, and is fed back to a local oscillator, and thereby, phase tracking is conducted.

Receiver and receiving method

In a data communication network, a first connection is established over a wireless link between a terminal and a router and a second connection is established between the router and a server over a land-line network. Communication protocol data necessary for communication control with the server is transferred from the terminal to the router. A data signal from the terminal is received at the router and converted into a packet according to communication protocol defined by the transferred protocol data between the router and the server and then transmitted to the server. A data signal from the server is received at the router and converted into a packet according to communication protocol defined by the transferred protocol data between the router and the terminal and then transmitted to the terminal.

High throughput wireless data communication using transferred protocol data for communication across land-line network

A clock synchronizing circuit enables initial synchronization of clock in spite of the case of modulation system except for quadrature modulation with simple constitution. A cosine/sine output circuit inputs thereto an integration clock 'ICLK', a sampling signal 'SSAMP', a sign switching signal &lsquo;SPM&rsquo;, a cosine component integration signal &lsquo;SCCI&rsquo;, and a sine component integration signal, before obtaining a cosine signal &lsquo;SCOS&rsquo; corresponding to a cosine component of initial phase of a symbol clock and a sine signal &lsquo;SSIN&rsquo; corresponding to a sine component thereof. An angular detector inputs thereto the cosine signal &lsquo;SCOS&rsquo; and the sine signal &lsquo;SSIN&rsquo;, before obtaining initial phase of the symbol clock &lsquo;SCLK&rsquo;.

Clock synchronizing circuit

A transmission apparatus and method for a frequency division multiple access (FDMA) system that uses FSK (frequency shift keying) or OOK (On/Of keying) modulation. The apparatus includes a plurality of FSK (or OOK) modulators, each of which allocates a maximum frequency shift value in the FSK (or OOK) modulation for data to be transmitted for a respective one of a plurality of channels of the FDMA system. The apparatus also includes a frequency converter for converting modulated signals output from each of the FSK (or OOK) modulators to carrier wave frequencies, and for combining the frequency-converted signals by allocating a carrier wave frequency of at least one of the plurality of channels to be between two carrier wave frequencies of another of the plurality of channels. The apparatus further includes an amplifier for amplifying the power of signal output from the frequency converter.

System and method for allocating a carrier wave frequency of one channel between two carrier wave frequencies of another channel

A sign determination circuit is input with in-phase signal I, and outputs in-phase sign determination signal S to indicate the sign, positive or negative, of in-phase signal I. Another sign determination circuit is input with orthogonal signal Q, and outputs orthogonal sign determination signal S to indicate the sign, positive or negative, of orthogonal signal Q. A decoder is input with in-phase sign determination signal S and orthogonal sign determination signal S , judging which quadrant the vector represented by in-phase signal I and orthogonal signal Q belongs to, thereby determining I&thgr; , I&thgr; to indicate the 180&deg; bit and 90&deg;-bit, respectively, of angle information I&thgr;. Also, I&thgr; , I&thgr; to indicate the 45&deg;-bit and 22.5&deg;-bit, respectively, of angle information I&thgr; is given by the other decoders.

Angle calculation circuit

A message processing method is provided for transmitting a transmit message while adding a unique transmit ID to identify the transmission of a transmit message to the transmit message; registering the correspondence between the transmit message and the transmit ID into a storage when the transmit message is transmitted; and judging that a receive message is related with a previously-transmitted transmit message when the receive message to which ID identical with a transmit ID registered in the storage is added is received. Also disclosed is a message processing device which has a storage; a transmission-managing means for adding a unique transmit ID to identify the transmission of a transmit message to the transmit message, and for registering the correspondence between the transmit message and the transmit ID into the storage when the transmit message is transmitted; a message transmitter for transmitting a transmit message provided with a transmit ID by the transmission-managing means; and a transmission-related detector for judging that a receive message is related with a previously-transmitted transmit message when the receive message to which ID identical with a transmit ID registered with the storage is added is received.

Message processing method, device, system and recording medium

In a wireless local area network, each subnetwork is formed by a base host and several mobile hosts. The base host broadcasts a control packet at periodic intervals and the mobile hosts monitor the broadcast packet and interfering signals from other subnetworks. If any of the mobile hosts does not receive the control packet for a predetermined period or detects the interfering signal, it makes a search and selects a new channel. The parent host also monitors interfering signals from other subnetworks. If it detects an interfering signal, it selects a noiseless new channel. The channel number of the new channel may be broadcast using a channel assignment signal to allow the mobile hosts to select the new channel. Alternatively, no channel assignment signal is broadcast. In this case, it is up to the mobile hosts to select the new channel.

Wireless LAN for reestablishing wireless links between hosts according to monitored desired and undesired signals

A diversify receiver comprises an antenna selector for selecting signals received by diversity antennas. Detection circuitry detects respective strengths of the selected signals and produces first and second strength indication signals. A mode selector is provided for selecting a reference threshold or the second strength indication signal. A comparator compares the output of the mode selector with the first strength indication signal. The mode selector is controlled to select the reference threshold so that the first strength indication signal is compared with the reference threshold and then to select the second strength indication signal in response to a first output signal of the comparator indicating that the first strength indication signal is higher than the reference threshold, so that the first strength indication signal is compared with the second strength indication signal. The antenna selector is then controlled according to a second output signal of the comparator indicating the result of the comparison between the first and second strength indication signals.

Growing community of inventors

Tokyo, Japan

Tomoki Osawa