Wireless communication method, transmitting device, receiving device, and wireless communication system

Abstract

A wireless communication method according to one embodiment of the present invention comprises transmitting a signal from a transmission device to a reception device using a single carrier. At the time of training, the transmission device generates two or more training signals in which a symmetrical subcarrier is used, subjects the training signals to OFDM modulation, and implements shaping such that the spectrum of each OFDM modulated training signal approaches the single carrier spectrum. During training, the reception device adjusts the timing of the two or more training signals using a single carrier time domain correlation sequence, estimates a channel response and an IQ imbalance from the two or more training signals for which the timing was adjusted, compensates for the estimated IQ imbalance, and demodulates the compensated signal.

Description

[Technical Field]

[0001] The present invention relates to a wireless communication method, a transmitting device, a receiving device, and a wireless communication system. [Background technology]

[0002] In single-carrier transmission using quadrature modulation and demodulation, the received quadrature components I and Q may be affected by different interferences, resulting in signals with different attenuation and phase rotation (IQ imbalance).

[0003] In subcarrier transmission such as OFDM (orthogonal frequency division multiplexing), when IQ imbalance occurs, it is possible to simultaneously estimate the channel response value and the IQ imbalance value using two or more pilot signals, and to compensate for the IQ imbalance (see, for example, Non-Patent Document 1).

[0004] For example, in OFDM, since symmetric subcarriers (indexes k and −k) have mutual leakage, it is possible to estimate IQ imbalance using symmetric subcarriers of two or more training OFDM symbols (see, for example, Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] T. Schenk, "RF imperfections in High-rate Wireless Systems", Impact and Digital Compensation, Springer, 2008, pp.139-145 [Non-patent document 2] Yoshimasa Egashira and two others, "IQ Imbalance Compensation Method Using Pilot Signals in OFDM Systems," IEICE Transactions on Information and Communication Engineers, Vol. J91-B No. 5, 2008, pp. 558-565. [Non-patent document 3] Part11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, Amendment3: Enhancements for Very High Throughput in the 60 GHz Band, IEEE Computer Society, IEEE Std. 802.11adTM-2012. Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the past, in single-carrier transmission under frequency-selective fading channels, symmetric subcarriers did not exist, so training allocation for symmetric subcarriers was not possible, and quality degradation due to IQ imbalance could not be prevented.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a wireless communication method, a transmitting device, a receiving device, and a wireless communication system that are capable of estimating and compensating for IQ imbalance even when single-carrier transmission is performed. [Means for solving the problem]

[0008] A wireless communication method according to one embodiment of the present invention is a wireless communication method for transmitting signals from a transmitting device to a receiving device using a single carrier, characterized in that the transmitting device generates two or more training signals using symmetric subcarriers during training, modulates the signals using OFDM, and shapes the spectrum of each of the OFDM-modulated training signals so as to approximate a single-carrier spectrum, and the receiving device adjusts the timing of the two or more training signals using a single-carrier time-domain correlation sequence during training, estimates a channel response and IQ imbalance from the two or more timing-adjusted training signals, compensates for the estimated IQ imbalance, and demodulates the compensated signals.

[0009] Furthermore, a transmitting device according to one embodiment of the present invention is a transmitting device that transmits a signal to a receiving device using a single carrier, characterized in that it has an OFDM modulation unit that generates two or more training signals using symmetric subcarriers during training and OFDM-modulates the generated training signals, and a shaping unit that shapes the spectrum of each of the training signals OFDM-modulated by the OFDM modulation unit so that it approaches the single carrier spectrum.

[0010] Moreover, a receiving device according to one embodiment of the present invention includes: The above A receiving device that receives a signal from a transmitting device is characterized by comprising: a timing adjustment unit that adjusts the timing of two or more training signals using a single-carrier time-domain correlation sequence during training; an estimation unit that estimates a channel response and an IQ imbalance from the two or more training signals whose timings have been adjusted by the timing adjustment unit; a compensation unit that compensates for the IQ imbalance estimated by the estimation unit; and a demodulation unit that demodulates the signal compensated by the compensation unit.

[0011] Moreover, a wireless communication system according to one embodiment of the present invention is a wireless communication system that transmits signals from a transmitting device to a receiving device using a single carrier, wherein the transmitting device has an OFDM modulation unit that generates two or more training signals using symmetric subcarriers during training and OFDM-modulates the signals, and a shaping unit that shapes the spectrum of each of the training signals OFDM-modulated by the OFDM modulation unit so that the spectrum approaches a single carrier spectrum, and the receiving device has a timing adjustment unit that adjusts the timing of the two or more training signals using a single-carrier time-domain correlation sequence during training, an estimation unit that estimates a channel response and an IQ imbalance from the two or more training signals whose timing has been adjusted by the timing adjustment unit, a compensation unit that compensates for the IQ imbalance estimated by the estimation unit, and a demodulation unit that demodulates the signal compensated by the compensation unit. [Effects of the Invention]

[0012] According to the present invention, it is possible to estimate and compensate for IQ imbalance even when single-carrier transmission is performed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates the functionality of a receiving device that allows estimating IQ imbalance using a training signal. [Figure 2] FIG. 10 is a diagram illustrating an example of a packet transmitted by a transmitting device. [Figure 3] FIG. 2 is a diagram illustrating functions of a transmitting device according to an embodiment. [Figure 4] FIG. 2 is a diagram illustrating functions of a receiving device according to an embodiment. [Figure 5] 5 is a diagram illustrating an example of signals that each function of the receiving device shown in FIG. 4 refers to when processing each packet. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] First, the background to the invention will be described. Fig. 1 is a diagram illustrating the functions of a receiving device that enables IQ imbalance to be estimated using a training signal.

[0015] The receiving device shown in FIG. 1 receives a received signal Rx by mixing a signal having a frequency emitted by an oscillator circuit 1 using two mixers 2.

[0016] A received signal Rx distorted by an IQ imbalance is expressed by the following equation (1).

[0017]

number

[0018] Also, S of the transmission signal Tx at time n n =1 (1st pilot) is expressed by the following equation (2).

[0019]

number

[0020] Also, S of the transmission signal Tx at time n n =j(2nd pilot) is expressed by the following equation (3).

[0021]

number

[0022] Here, the following equations (4) and (5) are designated as A and B, respectively.

[0023]

number

number

[0024] In this case, the estimated results of the channel response, the estimated results of the gain imbalance, and the estimated results of the phase imbalance are expressed by the following equations (6), (7), and (8).

[0025]

number

number

number

[0026] On the other hand, a phase compensation unit 3 is provided in the preceding stage of the mixer 2 to compensate for the phase imbalance of the symmetric subcarriers.

[0027] Of the two amplifiers 4, the amplifier 4 that amplifies the signal whose phase imbalance has been compensated for is adapted to compensate for the gain imbalance.

[0028] Then, the ADC 6 can output the I-Ch signal that has been AD converted via the LPF 5, and the Q-Ch signal that has been AD converted via the LPF 5 with phase imbalance and gain imbalance compensated for.

[0029] In this case, the compensated channel response at time n is given by the following equation (9).

[0030]

number

[0031] In this way, the IQ imbalance caused by the imbalance between the quadrature modulation and the demodulator can be simultaneously estimated and compensated for along with the channel response h from two or more training (pilot) signals (see Non-Patent Document 1).

[0032] Furthermore, when estimating IQ imbalance in OFDM transmission, for example, the signal of the following equation (10) on subcarrier k of the frequency domain received signal Rx and the signal of the following equation (11) on the symmetric subcarrier −k can be used.

[0033]

number

number

[0034] The frequency domain transmitted signal S in the first training OFDM symbol k =S -k =1 are expressed by the following equations (12) and (13), respectively.

[0035]

number

number

[0036] In this case, the following equations (14) and (15) are designated as A and B, respectively.

[0037]

number

number

[0038] Also, the frequency domain transmission signal S in the second training OFDM symbol k =S -k =-1 are expressed by the following equations (16) and (17), respectively.

[0039]

number

number

[0040] In this case, the following equations (18) and (19) are defined as C and D, respectively.

[0041]

number

number

[0042] In this case, the estimated results of the CFR (channel frequency response) of subcarrier k, the estimated result of the CFR of subcarrier −k, the estimated result of the gain imbalance, and the estimated result of the phase imbalance are expressed by the following equations (20) to (23).

[0043]

number

number

number

number

[0044] The compensation result at this time is expressed by the following equation (24).

[0045]

number

[0046] In this way, IQ imbalance can be estimated for mutual leakage between symmetric subcarriers (indexes k and -k) by using two or more training OFDM symbols. In other words, in a frequency-selective fading channel, IQ imbalance can be estimated simultaneously with channel estimation in the frequency domain in OFDM transmission (see Non-Patent Document 2).

[0047] Next, a wireless communication system according to an embodiment that can estimate and compensate for IQ imbalance even when single-carrier transmission is performed will be described. The wireless communication system according to the embodiment performs OFDM modulation training to estimate and compensate for IQ imbalance in a training stage in order to perform single-carrier transmission from a transmitting device to a receiving device.

[0048] For example, a transmitting device that performs single-carrier transmission generates a communication path (channel) estimation training field by OFDM modulation, and performs spectrum shaping to approximate the spectrum of a single carrier.

[0049] FIG. 2 is a diagram illustrating a packet transmitted by a transmitting device of a wireless communication system having a function conforming to IEEE 802.11ad-SC (see Non-Patent Document 3) and a function of estimating and compensating for IQ imbalance in single-carrier transmission.

[0050] A transmitting device according to one embodiment generates a channel estimation training field for single-carrier transmission by OFDM modulation and performs symmetric subcarrier (indexes k and −k) training. At this time, the transmitting device performs spectrum shaping (SS) to make the spectrum of the modulated signal closer to the spectrum of the single carrier.

[0051] That is, the transmitting device according to one embodiment changes the CEF (Channel Estimation Field) in IEEE 802.11ad-SC by OFDM modulation and spectrum shaping.

[0052] At this time, the CEF includes a first training signal and a second training signal, each of which is provided with a GI (Guard Interval).

[0053] In one embodiment, since it is difficult to synchronize symbol timing using symmetric subcarrier training, the receiving device synchronizes two training symbols using another single-carrier time-domain correlation sequence (STF (short training field) in Figure 2).

[0054] Next, functions of the transmitting device according to an embodiment will be described. Fig. 3 is a diagram illustrating functions of the transmitting device according to an embodiment.

[0055] As shown in Figure 3, during training, the transmitting device in one embodiment has the functions of an OFDM modulation unit 10, a shaping unit 12, an IFFT unit 14, a copy unit 16, and a DA unit 18, and generates a CEF including the first training signal and the second training signal shown in Figure 2.

[0056] The OFDM modulation unit 10 performs OFDM modulation of the first training and second training in the frequency domain. That is, the OFDM modulation unit 10 generates two or more training signals using symmetric subcarriers during training and performs OFDM modulation.

[0057] The shaping unit 12 performs spectrum shaping on the spectrum of each training signal that has been OFDM modulated by the OFDM modulation unit 10 so that the spectrum approaches a single carrier spectrum.

[0058] The IFFT unit 14 performs an inverse Fourier fast transform. The copy unit 16 copies the training signal and adds a GI to each. The DA unit 18 is a DAC that performs DA conversion on the first training signal and the second training signal.

[0059] Furthermore, when performing single-carrier transmission, the transmitting device has the functions of, for example, a QAM processing unit 20, a GI processing unit 22, a sampling unit 24, a shaping unit 26, and a DA unit 28.

[0060] The QAM processing unit 20 processes the signal to be transmitted as a single carrier into a constellation that conforms to a QAM map. The GI processing unit 22 processes the signal to be transmitted as a single carrier. The sampling unit 24 performs 2x upsampling. The shaping unit 26 shapes the pulses of the transmission signal. The DA unit 28 is a DAC that performs DA conversion of the transmission signal, and is shared with the DAC that constitutes the DA unit 18, for example.

[0061] Next, functions of a receiving device according to an embodiment will be described. Fig. 4 is a diagram illustrating functions of a receiving device according to an embodiment. Fig. 5 is a diagram illustrating signals that each function of the receiving device shown in Fig. 4 refers to when processing each packet.

[0062] As shown in FIG. 4, the receiving device according to one embodiment includes functions of a timing adjustment unit 30, an estimation unit 31, a noise estimation unit 32, a data formation unit 33, an equalization unit 34, a compensation unit 35, and a demodulation unit 36 ​​that operate during training, and estimates and compensates for the IQ imbalance between the first training signal and the second training signal.

[0063] The timing adjustment unit 30 adjusts the timing of two or more training signals using a single-carrier time-domain correlation sequence during training. For example, the timing adjustment unit 30 synchronizes the symbol timing of two or more training signals using a matched filter and an STF for the received signal that has been downsampled by 1 / 2 during training, excluding the CEF during data transmission, and performs packet detection and frequency correction (see FIG. 5).

[0064] The estimation unit 31 estimates a channel frequency response (CFR) and an IQ imbalance (IQI) in the frequency domain from two or more training signals whose timing has been adjusted by the timing adjustment unit 30, and outputs the estimation results to the noise estimation unit 32 and the data formation unit 33.

[0065] The noise estimation unit 32 performs noise estimation in the time domain and outputs the estimation result to the equalization unit 34 and the compensation unit 35 .

[0066] The data forming unit 33 extracts the data fields in the time domain, re-forms them into data blocks, converts them from the time domain to the frequency domain, and outputs them to the equalization unit 34.

[0067] The equalization unit 34 performs frequency domain equalization (FDE) on the data field in the frequency domain using the noise estimation result by the noise estimation unit 32 and the data block reconstructed by the data formation unit 33, and outputs the result to the compensation unit 35.

[0068] The compensation unit 35 performs conversion from the frequency domain to the time domain, and compensates for the IQ imbalance estimated by the estimation unit 31. More specifically, in the time domain, the compensation unit 35 compensates for the phase and gain of the IQ imbalance using the result of noise estimation by the noise estimation unit 32 and the data field equalized by the equalization unit 34.

[0069] The demodulator 36 performs OFDM demodulation on the signal compensated by the compensator 35. More specifically, the demodulator 36 performs bit recovery of the DMG data by demapping and decoding the DMG data.

[0070] In this way, in a wireless communication system according to one embodiment, the transmitting device generates two or more training signals using symmetric subcarriers during training, modulates them using OFDM, and shapes the spectrum of each OFDM-modulated training signal to approximate a single-carrier spectrum, thereby making it possible to estimate and compensate for IQ imbalance even when single-carrier transmission is performed. [Explanation of symbols]

[0071] 10...OFDM modulation unit, 12...shaping unit, 14...IFFT unit, 16...copying unit, 18...DA unit, 20...QAM processing unit, 22...GI processing unit, 24...sampling unit, 26...shaping unit, 28...DA unit, 30...timing adjustment unit, 31...estimation unit, 32...noise estimation unit, 33...data formation unit, 34...equalization unit, 35...compensation unit, 36...demodulation unit

Claims

1. A wireless communication method for transmitting a signal from a transmitting device to a receiving device using a single carrier, The transmitting device During training, two or more training signals using symmetric subcarriers are generated and OFDM modulated; The spectrum of each OFDM-modulated training signal is shaped to approximate a single carrier spectrum, The receiving device adjusting the timing of two or more training signals using a single-carrier time-domain correlation sequence during training; Estimating the channel response and IQ imbalance from two or more time-aligned training signals; Compensating for the estimated IQ imbalance; Demodulate the compensated signal A wireless communication method comprising:

2. A transmitting device that transmits a signal to a receiving device using a single carrier, an OFDM modulation unit that generates two or more training signals using symmetric subcarriers during training and performs OFDM modulation on the generated training signals; a shaping unit that shapes the spectrum of each training signal modulated by the OFDM modulation unit so that the spectrum approaches a single carrier spectrum; A transmitting device comprising:

3. A receiving device for receiving a signal from the transmitting device according to claim 2, a timing adjustment unit that adjusts timings of two or more training signals using a single-carrier time-domain correlation sequence during training; an estimation unit that estimates a channel response and an IQ imbalance from two or more training signals whose timings have been adjusted by the timing adjustment unit; a compensating unit that compensates for the IQ imbalance estimated by the estimating unit; a demodulation unit that demodulates the signal compensated by the compensation unit; A receiving device comprising:

4. In a wireless communication system in which a signal is transmitted from a transmitting device to a receiving device using a single carrier, The transmitting device an OFDM modulation unit that generates two or more training signals using symmetric subcarriers during training and performs OFDM modulation on the generated training signals; a shaping unit that shapes the spectrum of each training signal modulated by the OFDM modulation unit so that the spectrum approaches a single carrier spectrum; and The receiving device a timing adjustment unit that adjusts timings of two or more training signals using a single-carrier time-domain correlation sequence during training; an estimation unit that estimates a channel response and an IQ imbalance from two or more training signals whose timings have been adjusted by the timing adjustment unit; a compensating unit that compensates for the IQ imbalance estimated by the estimating unit; a demodulation unit that demodulates the signal compensated by the compensation unit; A wireless communication system comprising:

Images