JP2011055359A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose a system capable of highly accurately predicting channel interference even when there is the nonlinearity of a power amplifier. <P>SOLUTION: In the wireless communication system 1 for exchanging radio signals between terminal devices sharing the same physical layer, in one terminal device 2, real data obtained by adding a synchronization sequence (SYNC) to real data to be transmitted are made into a pulse signal, amplified by a power amplifier after applying modulation to the pulse signal, and then transmitted wirelessly. Another terminal 2 acquires an auto-correlation coefficient based on the SYNC after demodulation of the received signal and before passing through a filter and the SYNC of the signal after passing through the filter and further, based on the auto-correlation coefficient acquired, predicts interference inside the same channel or between neighboring channels. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio communication system that transmits and receives radio signals having millimeter-order wavelengths between terminal apparatuses sharing the same physical layer.

  Compared to wired communication, wireless communication requires less space for cables, and portable terminals such as notebook personal computers (notebook PCs) connect to the network without compromising portability. There are advantages such as being able to. In particular, a millimeter-wave WPAN (Wireless Personal Area Network) that performs wireless communication using millimeter-order wavelengths is a wireless personal area network that realizes communication between terminal devices that transmit and receive wireless signals to each other up to about 10 m. (For example, refer to Patent Document 1). The frequency band allocated in this millimeter wave WPAN is 59 to 66 GHz in Japan, and 7 to 9 GHz is also allocated as the bandwidth. In other words, since the bandwidth of this millimeter wave WPAN is about 100 times that of the 2.4 GHz band wireless LAN, it is possible to perform ultra-high speed short-distance communication on the order of several Gbps, which could not be considered in the past wireless communication .

  In such millimeter-wave wireless communication, since a millimeter-order wavelength can be used, a terminal device that transmits and receives wireless signals can be realized extremely small, and it is possible to have a more portable device configuration. Become.

Special table 2009-500958

  By the way, in a radio communication system such as millimeter wave WPAN, it is possible to predict the coherence of a signal within the same channel or between adjacent channels, and to improve the performance of a received signal based on the predicted coherence. It has been done conventionally. In particular, in the prediction of coherence, signal energy is detected when determining whether a specific frequency band is occupied in a wireless communication system. In actual wireless communication, a terminal device on the transmission side amplifies a signal to be transmitted by a power amplifier (PA). However, this power amplifier generally has a nonlinear output with respect to the input. This nonlinearity at the time of input / output of the power amplifier becomes a factor of deteriorating prediction accuracy and reliability in predicting signal coherency within the same channel or between adjacent channels.

  Accordingly, the present invention has been devised in view of the above-described problems, and its object is to provide nonlinearity of a power amplifier in a wireless communication system that transmits and receives a wireless signal having a millimeter-order wavelength. Even in this case, it is an object to provide a wireless communication system capable of predicting the coherence of a channel with high accuracy.

  In order to solve the above-described problem, a wireless communication system according to the present invention is a wireless communication system that transmits and receives wireless signals between terminal devices that share the same physical layer. The real data to which the synchronization sequence (SYNC) is added is converted into a pulse signal, the pulse signal is modulated, then amplified by a power amplifier and wirelessly transmitted, and the other terminal device filters the received signal after demodulation. A cross-correlation coefficient is acquired based on the SYNC before passing and the SYNC of the signal after passing through the filter, and further, the coherence in the same channel or between adjacent channels is determined based on the acquired cross-correlation coefficient. It is characterized by prediction.

  In the wireless communication system having the above-described configuration, even in the case where the nonlinearity of the power amplifier exists in the wireless communication system that transmits and receives a wireless signal having a wavelength on the order of millimeters, the channel interference can be predicted with high accuracy. It becomes possible.

It is a figure which shows the system configuration | structure of the radio | wireless communications system to which this invention is applied. It is a block block diagram of a terminal device. It is a figure which shows an example of reception power in case the terminal device of a transmission side uses the carrier frequency around 60 GHz. It is a figure which shows an example of the cross-correlation coefficient normalized of the virtual pulse waveform output from the 1st amplifier.

  Hereinafter, as an embodiment of the present invention, a radio communication system for transmitting and receiving radio signals between terminal devices will be described in detail with reference to the drawings.

  FIG. 1 shows a system configuration of a wireless communication system 1 to which the present invention is applied. The wireless communication system 1 performs bidirectional wireless communication by transmitting and receiving radio waves between one terminal device 2a and the other terminal devices 2b, 2c,. System. The other terminal devices 2b, 2c,... 2n are assigned to each user. The wireless communication system 1 is assumed to transmit and receive a wireless signal having a wavelength on the order of millimeters, but the present invention is not limited to this.

  In particular, the wireless communication system 1 to which the present invention is applied may be applied to a millimeter wave WPAN that performs wireless communication using millimeter-order wavelengths. The millimeter wave WPAN is a wireless personal area network that realizes communication up to a distance of about 10 m between the terminal devices 2 that transmit and receive radio signals to each other, and is assigned a wide band extending from 59 to 66 GHz. For this reason, the millimeter wave WPAN enables ultra-high-speed short-range communication on the order of several Gbps.

  FIG. 2 shows a block configuration of the terminal device 2 that generates a signal necessary for such wireless communication and detects a signal transmitted from the other party.

  The terminal device 2 includes a pulse generation unit 21 that generates a pulse signal, a pulse shaping unit 22 that is connected to the pulse generation unit 21 and that receives the pulse signal generated by the pulse generation unit 21, and a pulse A mixer circuit 24 for performing frequency conversion on the pulse signal output from the shaping unit 22 based on a reference signal described later, a local transmitter 23 for generating a reference signal, and a signal frequency-converted in the mixer circuit 24 A filter 25 for limiting the pass band, a first amplifier 26 connected to the filter 25, a switching circuit 51 connected to the first amplifier 26, and an antenna 27 connected to the switching circuit 51. And. The terminal device 2 is connected to the filter 32 connected to the switching circuit 51, a low noise amplifier (LNA) 33 that performs high-frequency signal processing on the signal output from the filter 32, and the LNA 33 and the local oscillator 23. The mixer circuit 52, the filter 41, the second amplifier 43, and the ADC 45 are sequentially connected to the mixer circuit 52, and a signal detector 47 is connected to the ADC 45.

  The switching circuit 51 executes a switching process so that the first amplifier 26 and the antenna 27 are connected when transmitting a signal to another terminal device 2. The switching circuit 51 executes switching processing so that the antenna 27 and the filter 32 are connected when receiving a signal from another terminal device 2.

  The pulse generator 21 generates a pulse signal having a certain time width. When this pulse signal is actually generated, the pulse generator 21 sequentially generates a pulse train in which pulse signals having substantially equal amplitudes are arranged at a predetermined interval. The pulse signal generated by the pulse generator 21 is transmitted to the pulse shaping unit 22 as it is.

  The pulse shaping unit 22 performs a predetermined shaping process on each pulse signal constituting the pulse train of the spread sequence transmitted from the pulse generation unit 21.

  The local oscillator 23 generates a reference signal for modulation. The local oscillation frequency of the reference signal generated by the local oscillator 23 may be configured to be variable in the local oscillator 23. Further, the local oscillator 23 may be controlled so that the local oscillation frequency to be generated is increased and attenuated based on a PLL circuit (not shown) or the like.

  The mixer circuit 24 converts the frequency of each pulse signal subjected to the shaping process in the pulse shaping unit 22 based on the reference signal transmitted from the local transmitter 23. The mixer circuit 24 outputs the frequency-converted signal to the filter 25.

  The filter 25 passes only a desired band of the signal output from the mixer circuit 24 and cuts an unnecessary band. At this time, the pass band may be set so that the filter 25 can remove unnecessary frequency components generated during frequency conversion in the mixer circuit 24. The signal composed of the band component that has passed through the filter 25 is output to the first amplifier 26 as it is.

  The first amplifier 26 amplifies the signal output from the filter 25. At this time, the first amplifier 26 may further correct the frequency characteristics so as to be flat within the band.

  The antenna 27 converts the signal amplified by the first amplifier 26 into an electromagnetic wave and radiates it into the air. The antenna 27 receives radio waves transmitted from the other party.

  The filter 32 removes a signal outside a predetermined band from the radio wave received by the antenna 27. That is, in the process of transmitting radio waves between the terminal devices 2, a signal other than a desired signal may be superimposed, so that the signal is accurately removed by the filter 32.

  The LNA 33 amplifies the signal received by the antenna 27 and sent through the filter 32 with low noise. The signals amplified by the LNA 33 with low noise are supplied to the connected mixer circuits 52, respectively.

  The local oscillator 23 generates an in-phase signal (I signal) and a quadrature signal (Q signal) as baseband reference signals. The local oscillator 23 outputs the generated I signal and Q signal to the mixer circuit 52, respectively.

  The mixer circuit 52 demodulates the signal transmitted from the LNA 33 based on the I signal and Q signal output from the local oscillator 23.

  The filter 41 allows only a predetermined waveform component to pass through each signal demodulated by the mixer circuit 52.

  The second amplifier 43 amplifies the signal band-limited by the filter 41 and sends it to the ADC 45.

  The ADC 45 samples the analog baseband signal sent from the second amplifier 43 and converts it into a digital signal, and transmits the digitized signal to the signal detection unit 47.

  The signal detection unit 47 detects signals transmitted from the ADC 45.

  Next, a method for actually transmitting and receiving a radio signal in the radio communication system 1 to which the present invention is applied will be described in detail with reference to the drawings.

  First, the pulse generation unit 21 generates a pulse train composed of pulse signals under a predetermined communication method. At this time, the actual data obtained by adding the synchronization sequence (SYNC) to the actual data to be transmitted is converted into a pulse signal. Incidentally, this SYNC may be a Golay code or an m-sequence signal.

  Incidentally, this SYNC may be inserted in the preamble part provided in the preceding stage of the actual data part. This preamble is generated in the physical layer, and dummy information for preventing loss of frame data is written. The preamble 61 acquires a transmitted signal, evaluates it, and when it determines that a correct signal has been transmitted, initiates communication in synchronization based on SYNC. is there.

  The pulse signal on which the SYNC is superimposed is subjected to a shaping process in the pulse shaping unit 22. Further, this pulse train is modulated by a high frequency component based on the local oscillation frequency in the mixer circuit 24.

  The signal having such a configuration is amplified by the first amplifier 26 after removing unnecessary frequency components in the filter 25. The first amplifier 26 amplifies the input signal linearly or nonlinearly. The signal output from the first amplifier 26 is converted into an electromagnetic wave by the antenna 27 and radiated into the air. The radio wave radiated into the air is received by the antenna 27 in the destination terminal device 2 and reconverted into an electrical signal. The received signal is amplified with low noise by the LNA 33 and adjusted so that it can be distinguished from noise, and then supplied to the mixer circuit 52.

  The signal sent to the mixer circuit 52 is orthogonally modulated based on the I signal and the Q signal, and further passes through the filter 41, so that unnecessary components superimposed thereon are removed. Finally, these signals are analog-digital converted by the ADC 45 and then transmitted to the signal detection unit 47.

  The signal detection unit 47 detects the signal transmitted from the ADC 45 and analyzes it. In the actual detection processing in the signal detection unit 47, the transmitted signal is captured over a predetermined time, and a more detailed pulse signal analysis is performed on the signal captured in units of the predetermined time. That is, the signal detection unit 47 monitors the pulse train through a detection window configured with a predetermined time length, and performs a process equivalent to detecting this. A signal sent from another terminal device 2 is input to the detection window in time series. The signal detection unit 47 sequentially detects the input signals through the detection window and analyzes them.

  At this time, the signal detection unit 47 records the SYNC of the signal after being demodulated by the mixer circuit 52 and before passing through the filter 41. Hereinafter, the SYNC before passing through the filter 41 is referred to as SYNC before passing. Then, the SYNC after the signal passes through the filter 41 (hereinafter referred to as SYNC after passing) is acquired. The signal detection unit 47 acquires a cross-correlation coefficient based on the pre-pass SYNC and the post-pass SYNC. Further, the signal detection unit 47 predicts the coherence within the same channel or between adjacent channels based on the acquired cross-correlation coefficient.

In addition, the signal detection unit 47 calculates received power μ _{l, k} for the signal transmitted from the ADC 45. This detection of the received power μ _{l, k} corresponds to detection of so-called signal energy.

Here, the standardized received powers of the signals from the terminal devices 2b, 2c,..., 2n passing through the filter 41 are μ _{l, 0} , μ _{l, 1 ,.} Represented as: Here, l is a specific branch of the desired user, and k is a transmission user of the signal.

Further, μ _{l, k} is defined as the following equation (1).

Here, P _RRC (f) is the frequency response of the Root Raised Cosine (RRC) filter 41, that is, the Fourier transform of the time domain RRC pulse waveform Ψ _RRC (t). R _{l, k} (ff _k ) is the frequency content of the received signal (f _k is the center frequency of the user k signal), that is, the Fourier of the time domain received signal received from the user k in the l th branch of the desired user. The transformation r _{l, k} (t). In addition, “||” represents a size, and “′” represents a complex conjugate. As an ideal case, when there is no non-linearity with respect to the first amplifier 26, μl _{, k} described above is 1. In other cases, that is, when nonlinearity exists for the first amplifier 26, 0 ≦ μl _{, k} <1.

Here, P _RRC (f) and P ^′ _RRC (f) are known. In order to obtain R _{l, k} (ff _k ), the frequency is divided into a number of slots. In each divided frequency slot, R _{l, k} (ff _k ) is measured and satisfied, and R _{l, k} (ff _k ) can be obtained over the entire band.

Next, calculation of the cross-correlation coefficient ρ _{l, k} will be described. The pulse waveform output from the first amplifier 26 is important in analyzing the cross-correlation between a desired signal and an unnecessary signal, but this waveform is unknown. The first amplifier 26 is usually non-linear. In addition, since the input to the first amplifier 26 is not a single pulse but an infinite series of bits having a random polarity, it is difficult to obtain a highly accurate pulse waveform from the output. Note that the pulse waveform before being input to the first amplifier 26 is represented by Ψ _T (t). In addition, the pulse waveform output from the first amplifier 26 is Ψ _R (t) ≠ PA [Ψ _T (t)]. In the following description, a hypothetical pulse waveform Ψ _R (t), which is considered to produce all the effects of the present invention, is first used. How [psi _R (t) performs convolution operation including _R [psi in a situation where not known clearly (t) and [psi _RRC (t) will be described in detail later.

ρ _{l, k} can be defined as shown in the following equation (2).

(2)

Here, b _k ⁽ⁱ⁾ is the i-th data symbol of user k. In addition, Ψ (t) is actually a frequency domain behavior, that is, Ψ (t) is a cross-correlation between the frequency response of the filter 41 on the receiver side and the frequency content of the signal received in front of the filter 41. In the time domain.

Incidentally, for this time domain, the convolution operation between the time domain impulse response Ψ _RRC (t) of the filter 41 on the receiver side and the pulse waveform from the filter 41 received from each user Ψ _RE = Ψ _R (t) cos It can be expressed as (2πf _{Dl, k} t + φ _{l, k} ).

Here, for f _{Dl, k} = f ₀ -f _k and φ _{l, k} = θ _{l, 0} -θ _{l, k} , Ψ (t) = Ψ _RRC (t) * Ψ _RE (t). “*” Represents a convolution operation, and θ _{l, k} represents the phase of the kth user in the lth branch of the desired user 0.

The reason why it is difficult to obtain Ψ (t) based on the above-described method is that Ψ _R (t) is basically an unknown virtual pulse waveform. Here, the above method cannot be used mathematically accurately. For this reason, in the present invention, the cross correlation coefficient is obtained based on another method described below. In such a method, a cross-correlation is obtained using a SYNC code. All the user terminal devices 2b, 2c,..., 2n transmit a specific SYNC code. Here, the present invention applies CCI (Copy Control Information) prediction and ACI (Access Control Information) prediction performed for the same physical (PHY) layer. In the following, the case where a Golay code or an m-sequence signal is used as the SYNC code will be described.

  First, the case where a Golay code is used as the SYNC code is considered when two binary complementary Golay codes each having a length G are transmitted by each user. In practice, the processing described below is executed.

First, a complementary Golay code sequence transmitted from each user is converted into a pulse waveform by Ψ _T (t) in a pulse generation unit 21, carrier-modulated at a frequency f _k oscillated by a local oscillator 23, and This is amplified by the amplifier 26 of 1 and transmitted with 0 phase. The receiving side receives the signal and records the signal before the filter 41.

Incidentally, the received signal is down-converted based on the frequency f ₀ oscillated from the local oscillator 23, and the cross correlation coefficient is calculated by the filter 41. Actually, the cross-correlation coefficient is acquired based on the Golay code sequence after passing through the filter 41 and the Golay code sequence before passing through the filter 41. The cross-correlation coefficients obtained from the two series are aligned in time series and normalized by 2G.

Next, a case where an m-sequence signal is used as the SYNC code will be described. When an m-sequence signal having a length M is transmitted by each user, the m-sequence signal is first converted into a pulse waveform by Ψ _T (t) by the pulse generator 21, and the carrier wave is modulated at the frequency f _k oscillated by the local oscillator 23. Then, after this is amplified by the first amplifier 26, it is transmitted with 0 phase. The receiving side receives the signal and records the signal before the filter 41.

These received m-sequence signals are down-converted based on the frequency f ₀ oscillated from the local oscillator 23, and the cross-correlation coefficient is calculated by the filter 41. Actually, the cross-correlation coefficient is acquired based on the m-sequence signal after passing through the filter 41 and the m-sequence signal before passing through the filter 41. This cross-correlation output is Ψ (t).

The present invention is applicable to personal short-range wireless communication. FIG. 3 shows an example of received power when the terminal device 2 on the transmission side uses a carrier frequency around 60 GHz. As the filter 41, the first amplifier 26 of 60 GHz when an RRC filter having various output back-off and roll-off rates of 0.25 is used will be considered. FIG. 3 shows the relationship between μ _{l, k} and T _b f _{Dl, k} for an arbitrary user k whose OBO is 3, 10, and 20 dB. The OBO here is ₁₀ log ₁₀ (P _set / P _in ). Here, P _{The set} is the saturation voltage of the first amplifier 26, P _in is the input voltage at the first amplifier 26. Here, the smaller the OBO value, the closer the first amplifier 26 becomes non-linear, and the larger the OBO value, the closer the first amplifier 26 becomes linear.

  FIG. 4 shows an example of a normalized cross-correlation coefficient of a virtual pulse waveform output from the first amplifier 26 obtained based on the above-described method. The OBO in the first amplifier 26 is 3 dB and 20 dB. In addition to the received power, the cross-correlation coefficient is used to predict the coherency within the same channel or between adjacent channels. And based on this coherence, the performance degradation of a desired user's signal can be calculated accurately. According to the present invention, such a system can also be realized through hardware.

DESCRIPTION OF SYMBOLS 1 Radio | wireless communications system 2 Terminal device 21 Pulse generation part 22 Pulse shaping part 23 Local transmitter 24 Mixer circuit 25 Filter 26 1st amplifier 27 Antenna 32 Filter 33 Low noise amplifier (LNA)
41 Filter 43 Second amplifier 45 ADC
47 Signal Detection Unit 51 Switching Circuit 52 Mixer Circuit

Claims (4)

In a wireless communication system for transmitting and receiving wireless signals between terminal devices sharing the same physical layer,
In one terminal device, real data obtained by adding a synchronization sequence (SYNC) to real data to be transmitted is converted into a pulse signal, the pulse signal is modulated, amplified by a power amplifier, and wirelessly transmitted.
The other terminal apparatus acquires a cross-correlation coefficient based on the SYNC before the received signal passes through the post-demodulation filter and the SYNC of the signal after the filter passes, and further acquires the cross-correlation coefficient. A radio communication system characterized by predicting coherency within the same channel or between adjacent channels. The wireless communication system according to claim 1, wherein the other terminal device further improves the performance of the signal based on the predicted coherence. The wireless communication system according to claim 1, wherein the SYNC is a Golay code. The wireless communication system according to claim 1, wherein the SYNC is an m-sequence signal.