摘要:
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.
摘要:
In order to compensate for chromatic dispersion caused by optical fiber transmission in a communication system with coherent detection using optical signals, specific frequency band signals are used to enable estimation of a chromatic dispersion value. The chromatic dispersion value calculating apparatus is provided with: a signal distributing circuit which distributes, into a plurality of signal sequences, an electrical digital signal converted from received optical signals of an optical signal transmitted by an optical signal transmitting apparatus, in which a known signal with concentrated frequency components of a plurality of specific frequencies is appended to a signal generated from a transmission data sequence; a plurality of frequency band pass filter circuits, each of which separating only each of a plurality of specific frequency components in which the known signal is included from each of the signal sequences distributed by the signal distributing circuit, and passing each of the specific frequency components therethrough; a plurality of power calculating circuits which are provided so as to correspond respectively to the plurality of frequency band pass filter circuits and which calculate power values of signals output from the corresponding frequency band pass filter circuits; a delay time calculating circuit which detects times at which power has the maximum value or times at which the power exceeds a predetermined threshold value, respectively from signal sequences of the power values output from the plurality of power calculating circuits, and which compares the detected times; and a chromatic dispersion value calculating circuit which calculates a chromatic dispersion value based on a comparison result of the times by the delay time calculating circuit.
摘要:
In a system which performs wireless communication from an access point to stations using group identification information, the frequency of uses of group identification information that overlaps with that of another access point is reduced. An association between a station apparatus included in a group that is a target for simultaneous transmission and group identification information is stored, each station apparatus included in the group is notified of the group identification information, group identification information that is being used in the other access point apparatus is acquired, and if group identification information that is being used by the access point apparatus itself overlaps with the group identification information used by the other access point apparatus, the group identification information is changed so as to reduce the number of pieces of overlapping group identification information.
摘要:
Provided is a frequency offset estimation apparatus that appropriately estimates and compensates for a frequency offset of a received signal when estimating the frequency offset which is the difference between a carrier frequency of the received signal and the frequency of an output signal of a local oscillator. The frequency offset estimation apparatus converts the received signal sampled in advance with a predetermined sampling frequency into a frequency spectrum having N frequency components, limits a frequency band of negative frequency components from 1 to N /2 of the frequency spectrum and a frequency band of positive frequency components from N /2+1 to N of the frequency spectrum, calculates the sum of the squares of the positive frequency components of the frequency spectrum that have been subjected to frequency band limitation and the sum of the squares of the negative frequency components of the frequency spectrum that have been subjected to frequency band limitation to calculate power of the positive frequency components and power of the negative frequency components, and cyclically shifts all frequency components of the frequency spectrum in a frequency domain until the absolute value of a power difference between the power of the positive frequency components and the power of the negative frequency components is less than or equal to a predetermined threshold value, and estimates the frequency offset based on a shift amount until the absolute value is less than or equal to the threshold value.
摘要:
The number of OFDM symbols for channel estimation is reduced, overhead due to a pilot signal and a feedback signal is reduced, and the throughput is improved. A wireless apparatus is provided with: an iterative coefficient setting unit which sets, for a plurality of transmission ports, an iterative coefficient representing the number of transmission ports which share a plurality of frequency channels of training signals for estimating the channel information; a training signal generating unit which allocates frequency channels to each transmission port so as to satisfy the set iterative coefficient and generates L training signals based on the allocated frequency channels; a channel information acquiring unit which acquires channel information estimated from the training signals from a communication partner for the frequency channels allocated to each transmission port; and a channel information interpolating unit which interpolates channel information of a remaining frequency channel other than the frequency channels allocated to each transmission port from the acquired channel information.
摘要:
Communication quality is prevented from being deteriorated due to interference caused by low accuracy of channel information or interference from another base station or another wireless communication system. A wireless communication system includes a first wireless station including a plurality of antenna elements, transmission units corresponding to the plurality of antenna elements, and a transmission directivity control unit that controls transmission directivity of the plurality of antenna elements, and a plurality of second wireless stations each including a reception power measurement unit that measures a reception power. The transmission directivity control unit determines the transmission directivity of each of the plurality of antenna elements so that a signal does not reach a particular second wireless station among the plurality of second wireless stations. The transmission units generate wireless signals using the transmission directivity. The plurality of antenna elements transmit the generated wireless signals. The reception power measurement unit measures the reception power in a period that is set so that a signal does not reach the particular second wireless station, and detect the presence or absence of interference.
摘要:
A polarization state of a transmission signal can be changed at a high speed based on a symbol-rate By switching a first switch, a second switch, and a third switch with time, one of an X-polarized wave_I-signal as a Y-polarized wave_I-signal, a signal caused by performing logical inversion for an X-polarized wave_I-signal, an X-polarized wave_Q-signal and a signal caused by logical inversion for an X-polarized wave_Q-singal is input to a second modulator. Further, by switching the first switch, the second switch and the third switch with time, the second modulator is input one of the X-polarized wave_I-singal as the Y-polarized wave_Q-signal, the X-polarized wave_I-signal, the signal caused by performing logical inversion for the X-polarized wave_I-signal, the X-polarized wave_Q-signal and the signal caused by performing logical inversion for the X-polarized wave_Q-signal. Thereby, a polarization state of a transmission signal can be changed at high speed based on a symbol-rate speed.