Nippon Telegraph and Telephone Corporation

Tomoaki Kumagai

Shinya Otsuki

Kazuyoshi Saito

Satoru Aikawa

Kengo Nagata

Atsushi Ohta

Akinori Hirukawa

Masato Mizoguchi

Masahiro Morikura

Yasuhiko Inoue

Takeshi Onizawa

Koichi Ishihara

Tomoki Murakami

Riichi Kudo

Yusuke Asai

Takeo Ichikawa

Kengo Nataga

Tetsu Sakata

The number of training signals for channel estimation is reduced. A wireless communication method includes: a step of reading, by an access point apparatus, stored training weights for a station which performs channel estimation; a step of generating, by the access point apparatus, a weight training symbol by multiplying the training weights by a training symbol and transmitting the generated weight training symbol; a step of estimating, by a station apparatus, weight channel information from the received weight training symbol; a step of transmitting, by the station apparatus, the weight channel information to the access point apparatus; a step of calculating, by the access point apparatus, transmission weights using the received weight channel information and the stored training weights; a step of transmitting, by the access point apparatus, a data signal in accordance with the transmission weights; and a step of calculating and storing, by the access point apparatus, new training weights using the weight channel information and the stored training weights.

Wireless communication method and access point apparatus

When a transmission rate of each of lines that transmit data simultaneously between two STAs by using a plurality of radio channels and/or MIMO can be set independently, one data frame is fragmented in accordance with the transmission rates of the respective lines so as to generate a plurality of data packets having the same packet time length and data sizes equal to or smaller than a maximum data size. Those data packets are transmitted simultaneously by using a plurality of radio channels, or one radio channel and MIMO, or a plurality of radio channels and MIMO.

Wireless packet communication method

In retransmission processing due to a failure of transmission of data packets, a plurality of data packets are simultaneously transmitted between two STAs by utilizing multiple wireless channels and MIMO, and the number of idle channels and the number of retransmission packets are compared. Then, when both of the numbers are different or only when the number of idle channels is larger than the number of retransmission packets, the retransmission packets are reconstructed according to the number of idle channels, and the reconstructed retransmission packets are simultaneously transmitted by using the idle channels.

Wireless packet communication method and wireless packet communication apparatus

Data packets are transmitted between two STAs capable of using plural radio channels and MIMO together, by using idle channels and MIMO. When at least one idle channel has been detected, plural data packets are generated in the same number as the sum of MIMO numbers of the respective idle channels, in which the data packets are generated from one or plural data frames, and plural data packets having the same packet time length are transmitted simultaneously between the two STAs by using the idle channels and MIMO.

A plurality of types of available transmission rates to be used for transmission of data packets are individually managed for each receiver terminal. When there are a plurality of data packets to be transmitted onto a transmission buffer and when it is possible to transmit said plurality of data packets simultaneously, the packet sizes representative of the data amounts of the respective data packets are referred to as well as the transmission rates of the respective data packets associated with the receiver terminals. The packet time lengths (transmission times) defined by the packet sizes and transmission rates are checked for the respective data packets. A plurality of data packets whose packet time lengths are approximately equal to each other are selected regardless of their receiver terminals. The transmissions of the plurality of selected data packets are commenced simultaneously by use of a plurality of radio channels.

For data packet transmission in special format generated by connecting or patching data frames, a request packet and reply packet receivable only by STAs supporting the special format are transmitted/received before the data packet transmission, to check and manage the STA supporting the special format. Based on management information in own station, the data packet is transmitted in the special or standard format according to a receive-side STA. For generating plural data packets in special format in which plural data frames are patched, the plural data frames having subheaders added are connected and divided to data blocks. A main header including information necessary to restore patched data frames are added to each data block, and a control information field and a frame check field of a data packet are added before and after the data block having the main header added thereto, respectively, to generate data packets.

Wireless packet communication method and apparatus

A transmit-side STA transmits a wireless packet using a wireless channel which has been determined to be idle by both a physical carrier sense for determining based on received power whether the wireless channel is busy or idle and a virtual carrier sense for determining the wireless channel to be busy during set transmission inhibition time. At this time, the transmit-side STA sets transmission time used for the virtual carrier sense to a paired wireless channel which is affected by leakage from a transmitting wireless channel. This allows for setting transmission inhibition time to a paired wireless channel even when the paired wireless channel cannot successfully receive due to the effect caused by leakage from the transmitting wireless channel.

A plurality of data packets that contain sequence numbers, respectively, are transmitted simultaneously between two STAs by using a wireless channel and MIMO. An STA receiving the plurality of data packets transmitted simultaneously by using MIMO generates a single ACK packet containing information that corresponds to a sequence number of each data packet successfully received, and transmits the single ACK packet to a transmit-side STA without using MIMO. Thus, a ratio of successful ACK packet receptions to total receptions can be increased. An effect of improving throughput achieved by simultaneous transmission can also be ensured.

In a wireless packet communication method for transmitting a plurality of wireless packets simultaneously by using multiple wireless channels determined to be idle by carrier sense, a wireless channel determined to be idle and MIMO, or the multiple wireless channel and the MIMO, a mandatory channel that is always used for transmission is set. The wireless packets are transmitted by using the wireless channel(s) including the mandatory channel only when the mandatory channel is idle. That is, in case of transmitting a plurality of wireless packets simultaneously, transmission is performed by using the wireless channel(s) including the mandatory channel, and transmission is not performed when the mandatory channel is not idle.

In an OFDM packet communication receiver, the deterioration of received signal quality is suppressed, even when carrier frequency error and/or clock frequency error exists between a transmitter and a receiver, and/or phase noise and/or thermal noise is superimposed to a received signal in a receiver.

OFDM packet communication receiver

A preamble for synchronization, or a reference timing for operation of an OFDM packet communication receiver system is detected finely even under environment of large waveform distortion due to thermal noise and/or multi-path propagation, and/or large carrier frequency offset between a transmit side and a receiver side. A correlator ( ) detects a pattern of a short preamble (t -t ) in a preamble for synchronization. An output of the correlator ( ) is applied to a complex filter ( ) which separates a short preamble having a predetermined repetition period from uniformly distributed noise. A scalar filter ( ) integrates some period of short preambles which have distributed-delay by multi-path propagation as if a single short preamble with no delay were received for determining a reference timing. When a correlator output exceeds a predetermined threshold level a plurality of times for every repetition periods (T) of a short preamble, and an output of the correlator after time (T) from the last short preamble is decreased a predetermined ratio as compared with that of the last short preamble, it is determined that a preamble for synchronization is detected. Carrier frequency offset compensation is carried out either for each short preamble during reception of a short preamble, or based upon the last received short preamble during reception of an OFDM symbol after the last short preamble. As a preamble for synchronization is detected accurately, a guard interval of each OFDM symbol is removed accurately, or an FFT window is defined accurately, so that a demodulation is possible in spite of noise and/or interference.

OFDM packet communication receiver system

A coherent detection system for multicarrier modulation system capable of accurate channel estimation even in severe environment with high thermal noise and deep multipath fading, has been found with simple structure and small circuit size. The present coherent detection system comprises a channel estimation circuit ( ) for estimating a channel attenuation of a preamble part of each subcarriers, an adaptive filter ( ) for smoothing estimated channel attenuation among subcarriers, a divider ( ) for coherent detection of a data part by dividing a receive vector by smoothed estimated channel attenuation for each subcarriers, and a characteristic extraction circuit ( ) for extracting characteristic value of each subcarriers. The adaptive filter ( ) is controlled depending upon characteristic value of each subcarriers measured by the characteristic extraction circuit ( ). A characteristic value may be amplitude, phase rotation, vector difference, modulation system, of each subcarriers, and/or combination of those values.

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Kanagawa, Japan

Tomoaki Kumagai