Abstract: Provided is a wireless communication system using a single-carrier multi-value modulation scheme, the wireless communication system aiming at preventing erroneous transmission of data and securing a high data rate while utilizing a non-linear region of an amplifier. A reception apparatus acquires, from a transmission apparatus, a specification related to an input/output characteristic of a transmission signal amplifier and transmission power of data transmission. On the basis of the specification and the transmission power, a constellation of signal points is estimated. A reception point, which is a point in constellation coordinates, of a reception signal is detected, and likelihood calculation for the reception point is performed with respect to the signal points. A symbol intended by the reception point is identified on the basis of a result of the likelihood calculation.

Abstract: A channel estimation method in which a reception device performs channel estimation on the basis of a known signal transmitted by a transmission device divides and arranges a known signal having a predetermined length in frames, transmits the known signal divided and arranged in the frames together with a data signal as a radio frame, receives the transmitted radio frame, calculates a data signal component including a delay wave component from the received radio frame, extracts a plurality of known signal components each including a delay wave component of the divided and arranged known signal by subtracting the data signal component from the received radio frame, concatenates the plurality of extracted known signal components to restore a known signal having a predetermined length, and performs channel estimation on the basis of the restored known signal having a predetermined length.

Abstract: A wireless communication method according to an embodiment includes converting n+1 signals into n predetermined power signals obtained by setting a C/N to a predetermined value and into n divided signals obtained by setting the C/N to 1/n of a predetermined value and performing division into n, superimposing the n predetermined power signals and the n divided signals that have been converted, non-orthogonally so as to be n multiplexed signals for the n frequency channels, transmitting the n multiplexed signals, receiving n multiplexed signals, demodulating n predetermined power signals from the n multiplexed signals that have been received, creating replica signals of each of the n predetermined power signals, subtracting each of the n replica signals that have been created from each of the n multiplexed signals, and combining the n subtracted signals.

Abstract: A radio communication method according to an embodiment is a radio communication method for transmitting a signal from a transmitter to a receiver using a single carrier, in which the transmitter generates two or more training signals using a symmetric subcarrier at the time of training to perform an OFDM modulation, and shapes a spectrum of each of the OFDM-modulated training signals to be close to a single carrier spectrum, and in which the receiver adjusts the timing of two or more training signals, using a single carrier time domain correlation sequence at the time of training, estimates a channel response and an IQ imbalance from the two or more training signals whose timing is adjusted, compensates for the estimated IQ imbalance, and demodulates the compensated signal.

Abstract: A congestion control method in an IP telephone system includes acquiring a number of simultaneous calls in one line shared by a plurality of IP telephones, acquiring a call time order corresponding to length of a call time for each call, and controlling a packet discard rate of each call on the basis of the number of simultaneous calls and the call time order. The packet discard rate of each call is set to a predetermined first upper limit value or less. In addition, the packet discard rate is set higher as the call time is longer, and the packet discard rate is set lower as the call time is shorter. Further, the packet discard rate of the latest call having the shortest call time is set to be equal to or less than a predetermined second upper limit value lower than the predetermined first upper limit value.

Abstract: To avoid uniform deterioration of the voice quality of all the calls sharing an IP phone line at a time of congestion. The congestion control method in an IP phone system includes a call state acquisition process of acquiring the number of simultaneous call sessions in one line shared by a plurality of IP phones. A congestion control method further includes a packet loss control process of setting a priority ranking to each call session and dynamically controlling packet loss rates of the call sessions in accordance with the number of the simultaneous call sessions and the priority ranking. In the packet loss control process, the packet loss rate is set lower for call sessions ranked higher in priority, and higher for call sessions ranked lower in priority.

Abstract: A wireless communication method includes phase shift amount determination processing for determining a random phase shift amount for each of symbols of transmission data. The wireless communication method further includes modulation processing for modulating the transmission data and further shifting a phase according to the random phase shift amount for each of the symbols. The wireless communication method further includes precoding processing for performing precoding on the transmission data after the modulation processing, and transmission processing for transmitting the transmission data after the precoding processing from the transmission device to the reception device.

Abstract: A wireless communication method includes phase shift amount determination processing for determining a random phase shift amount for each of subcarriers of transmission data. The wireless communication method further includes modulation processing for modulating the transmission data and further shifting a phase according to the random phase shift amount for each of the subcarriers. The wireless communication method further includes precoding processing for performing precoding on the transmission data after the modulation processing, and transmission processing for transmitting the transmission data after the precoding processing from the transmission device to the reception device.

Abstract: The wireless transmission device includes a power amplifier that varies transmission power. An SNR degradation amount calculation unit calculates an SNR degradation amount {QAM} caused by QAM and an SNR degradation amount {APSK} caused by APSK on the basis of input/output characteristics of the power amplifier acquired from an input/output characteristic storage unit, a QAM modulated signal acquired from a QAM modulation unit, an APSK modulated signal acquired from an APSK modulation unit, and the transmission power of the power amplifier. A modulation scheme selection unit acquires a required SNR {QAM} of QAM and a required SNR {APSK} of APSK from a required SNR storage unit, compares “required SNR {QAM}+SNR degradation amount {QAM}” with “required SNR {APSK}+SNR degradation amount {APSK}”, and selects the modulation scheme with the smaller value.

Abstract: A wireless transmission device and a wireless receiver that support at least two multi-level modulation schemes are used. The multi-level modulation scheme includes a first modulation scheme (QAM) and a second modulation scheme (APSK) having a shorter minimum Euclidean distance on the constellation and a lower PAPR than the first modulation scheme. A power amplifier has a function of changing transmission power. A transmission power control unit determines transmission power, and the power amplifier changes the transmission power. A modulation scheme selection unit compares the transmission power with a threshold value set on the basis of a boundary point at which a linear region and a nonlinear region of the power amplifier are switched, selects the QAM when the transmission power is not greater than the threshold value, and selects the APSK when the transmission power is greater than the threshold value.

Abstract: An adjoint matrix adjH(z, t) of a transfer function matrix H(z, t) established between a transmission station and a reception station is defined as a transmission weight WT(z). A training signal multiplied by the transmission weight WT(z) is transmitted from transmission antennas toward a reception station. M sequence portions S included in the received training signals #1 and #2 are connected in series to generate a virtual training signal block. A communication path response R(m) implemented by using the transmission weight WT(z) is calculated by calculating a correlation between both an M sequence portion S and a comparison sequence portion at each position while sliding the comparison sequence portion with respect to the virtual training signal block. Based on the communication path response R(m), a reception equalization weight WR(z) corresponding to an inverse response det{H(z, t)}?1 of a determinant det{H(z, t)} of the transfer function matrix H(z, t) is calculated.

Abstract: A wireless communication method includes phase shift amount determination processing for determining a phase shift amount for each stream of transmission data, modulation processing for modulating the transmission data and further shifting a phase according to the phase shift amount for each stream, and precoding processing for performing precoding on the transmission data after the modulation processing. The transmission data after the precoding processing is transmitted from the transmission device to the reception device. A plurality of types of phase shift patterns prepared in advance define different phase shift amounts. The phase shift amount determination processing includes: selecting, from among the plurality of types of phase shift patterns, one that minimizes a PAPR of the transmission data after the precoding processing or one that maximizes a data reception quality in the reception device; and determining the phase shift amount for each stream according to the selected phase shift pattern.

Abstract: A wireless transmission device and a wireless reception device that support QAM and APSK are used. The wireless transmission device includes a power amplifier that varies transmission power. A constellation calculation unit calculates an estimated constellation {QAM} predicted to occur when a QAM-modulated signal is amplified by the power amplifier at desired transmission power on the basis of input/output characteristics of the power amplifier, and similarly calculates an estimated constellation {APSK} predicted to occur when an APSK-modulated signal is amplified at the desired transmission power. A modulation scheme selection unit compares an estimated minimum Euclidean distance on the estimated constellation {QAM} with an estimated minimum Euclidean distance on the estimated constellation {APSK}, and selects the modulation scheme having the longer distance.

Abstract: A wireless communication method includes phase shift amount determination processing for determining a phase shift amount for each symbol of transmission data, modulation processing for modulating the transmission data and further shifting a phase according to the phase shift amount for each symbol, and precoding processing for performing precoding on the transmission data after the modulation processing. The transmission data after the precoding processing is transmitted from the transmission device to the reception device. A plurality of types of phase shift patterns prepared in advance define different phase shift amounts. The phase shift amount determination processing includes: selecting, from among the plurality of types of phase shift patterns, one that minimizes a PAPR of the transmission data after the precoding processing or one that maximizes a data reception quality in the reception device; and determining the phase shift amount for each symbol according to the selected phase shift pattern.

Abstract: A wireless communication method includes phase shift amount determination processing for determining a random phase shift amount for each of streams of transmission data. The wireless communication method further includes modulation processing for modulating the transmission data and further shifting a phase according to the random phase shift amount for each of the streams. The wireless communication method further includes precoding processing for performing precoding on the transmission data after the modulation processing, and transmission processing for transmitting the transmission data after the precoding processing from the transmission device to the reception device.

Abstract: A transmission device includes: a transmission signal amplifier enabled to vary transmission power; a transmission power control unit 28 that controls the transmission power; an error rate characteristic estimation unit that estimates an error rate of a reception signal in a reception device of a communication partner, and a reception unit that receives information on an SNR in the reception device. The error rate characteristic estimation unit executes: processing of estimating a constellation corresponding to a modulation scheme and reflecting a specification regarding an input-output characteristic of the transmission signal amplifier on the basis of the transmission power, and processing of estimating the error rate on the basis of a characteristic of the constellation and the SNR. The transmission power control unit controls the transmission power such that the error rate satisfies a predetermined requirement.

Abstract: A distributed antenna system and aggregation station of the present disclosure may prevent or reduce radio wave interference when there is a positional relationship in which a plurality of base stations and a plurality of user terminals are arranged on a straight line. The distributed antenna system receives, from each of the base stations, communication path information with each of accommodated user terminals, for each user terminal; and calculates, in a case where it is determined that the plurality of the respective base stations and the plurality of user terminals are arranged on the straight line, transmission weights of respective transmission beams transmitted by the plurality of the respective base stations to the plurality of respective user terminals based on the communication path information for each user terminal received by the receiver. The base stations transmit the respective transmission beams based the respective transmission weights calculated.

Abstract: An accompanying matrix adjH(z, t) of a transfer function matrix H(z, t) established between a transmission station and a reception station is defined as a transmission weight WT(z). An M sequence part is divided into two blocks to obtain an M sequence first half part and an M sequence second half part. A training symbol #1 having the M sequence second half part and the M sequence first half part in that order and a training symbol #2 having the M sequence first half part and the M sequence second half part in that order are processed by the transmission weight WT(z). In the receiving station, a virtual training signal block having the M sequence part S and the M sequence first half part is generated. A communication path response R(m) is calculated by a slide correlation method for the virtual training signal block.

Abstract: A wireless communication method in a wireless communication system which includes a radio transmitting station apparatus having a plurality of antennas and a radio receiving station apparatus having an antenna and which performs transmission and reception of a radio signal with a single carrier. The wireless communication method includes: estimating a communication path matrix based on a training signal; transforming the estimated communication path matrix into a frequency domain, transforming a complex conjugate transposed matrix of each of a unitary matrix and an adjoint matrix obtained by performing singular value decomposition for each frequency with respect to the transformed frequency domain communication path matrix into a time domain, and adopting each as a reception weight matrix and a transmission weight matrix; performing transmission beam formation based on the transmission weight matrix; and performing reception beam formation based on the reception weight matrix.

Abstract: In a wireless communication system for performing single-carrier MIMO transmission, a transmitting station apparatus includes a training signal generation unit and a transmit beamforming unit that performs transmit beamforming processing using transmit weights and a receiving station apparatus includes a communication path estimation unit, an interference amount determination unit that determines whether or not a residual inter-stream interference exceeds a predetermined threshold value, a receive weight calculation unit that calculates a receive weight used for receive beamforming processing when the residual inter-stream interference exceeds the threshold value, and a receive beamforming unit that performs receive beamforming processing for suppressing residual inter-stream interferences using the receive weight.