JP2015185916A - Communication device and communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device capable of accurately removing an interference signal.SOLUTION: A communication device comprises: a transmission modem 12 that performs spreading processing for a transmission signal and outputs the result as an output signal; a transmitting/receiving unit 15 that emits the output signal as a radio wave, and receives an arriving radio wave to output it as a reception signal; and a reception modem 13 that, when a signal from a communication partner via a communication satellite is regarded as a desired signal, a signal when a relay wave is received is regarded as an interference signal, the relay wave being produced when the communication satellite relays an output signal transmitted by the transmitting/receiving unit 15, and at least the desired signal and the interference signal are included in the reception signal from the transmitting/receiving unit 15, generates a cancel signal corresponding to the interference signal, removes the interference signal from the reception signal using the cancel signal, and executes de-spreading processing to perform demodulation. The reception model 13 generates the cancel signal based on the transmission signal.

Description

  The present invention relates to a communication device and a communication system.

  In communications via satellites, parabolic antennas are sometimes used to transmit and receive radio waves. At this time, an antenna having a large diameter may be used in order to improve reception sensitivity for weak radio waves.

  FIG. 3 is a diagram schematically showing such a communication system. The communication system 100 includes an earth station 110, a communication satellite 120, and a plurality of communication partner stations 130 (130A and 130B) mounted on a ship or the like.

  Since the communication partner station 130 has limited installation space and power supply capacity, the diameter of the antenna 131 (131A, 131B) is small, and a transceiver (not shown) having a small transmission capability and reception capability is provided. ing. On the other hand, since the earth station 100 has fewer restrictions on the installation space and power supply capacity than the communication counterpart station 130 and must receive weak radio waves from the communication counterpart station 130, the diameter of the antenna 112 is There are cases where large and large capacity transceivers are installed.

  Then, the earth station transmission wave E1 transmitted from the earth station 110 is relayed by the communication satellite 120, transmitted from the communication satellite 120 as the earth station relay wave E2, and received by the communication partner station 130. The communication partner station transmission wave E3 transmitted from the communication partner station 130 is relayed by the communication satellite 120, and the communication partner station relay wave E4 is received by the earth station 110.

  However, when both the earth station 110 and the communication partner station 130 are located within the reach of the earth station relay wave E2, the earth station 110 may receive the earth station relay wave E2. Hereinafter, the earth station relay wave E2 received by the earth station 110 is referred to as a return relay wave E5.

  Since the earth station 110 transmits the high-power radio earth station transmission wave E1, the return relay wave E5 also becomes high power. Originally, the earth station 110 is provided with a large antenna in order to receive the low-power communication partner station relay wave E4 from the communication partner station 130 with high sensitivity. As a result, the earth station 110 receives the high power return relay wave E5 at the same time as the low power communication partner station relay wave E4 with a large antenna, and when performing spread communication, the difference in signal level between the received signals. Misdetection caused by

  This will be described with reference to FIG. FIG. 4A is a diagram showing the time dependence of the correlation value when the level of the return relay wave (interference signal) E5 is relatively small compared to the communication partner station relay wave (desired signal) E4. FIG. 5 is a diagram illustrating time dependency of a correlation value when the signal level of an interference signal is relatively higher than that of a desired signal.

  When the signal level of the interference signal is relatively small compared to the desired signal, the autocorrelation value has a steep peak as shown in FIG. Can do. On the other hand, when the signal level of the interference signal is relatively high compared to the desired signal, the cross-correlation value due to the interference signal becomes large, and it becomes difficult to determine the autocorrelation time with high accuracy.

  Therefore, as a technique for removing the interference signal, Japanese Patent Laid-Open No. 2003-209535 removes the interference signal (corresponding to the signal from the return relay wave E5) from the desired signal (corresponding to the signal from the communication partner station relay wave E4). Technology has been proposed.

JP 2003-209535 A

  However, in Japanese Patent Laid-Open No. 2003-209535, since a cancel signal for removing an interference signal is generated using a received signal, the interference signal is removed with high accuracy in the case of FIG. 2B. It was difficult to do. That is, since the received signal includes external noise, the cancel signal generated based on the received signal includes the influence of external noise. Therefore, there is a problem that the removal accuracy cannot be improved even if the interference signal is removed by the cancel signal including the influence of the external noise.

  Therefore, a main object of the present invention is to provide a communication device and a communication system that can remove interference signals with high accuracy.

  In order to solve the above problems, an invention relating to a communication apparatus that transmits and receives a relay wave from a communication satellite that relays radio waves performs a spreading process on a transmission signal, and outputs a transmission modem as an output signal. A transmission / reception unit that radiates an output signal as a radio wave, receives an incoming radio wave and outputs it as a reception signal, and a signal from a communication partner via a communication satellite is a desired signal, and an output signal transmitted from the transmission / reception unit is A signal relayed by a communication satellite and receiving the relay wave is used as an interference signal, and a cancellation signal corresponding to the interference signal is generated when the received signal from the transmitter / receiver includes at least a desired signal and an interference signal. And a receiving modem that removes an interference signal from the received signal using the cancel signal and demodulates the signal by performing a despreading process. The receiving modem is based on the transmitted signal. And generating a cancellation signal.

  In addition, a communication system that transmits and receives a relay wave from a communication satellite that relays a radio wave performs a spreading process on the transmission signal, and transmits the output signal as an output signal, and radiates the output signal as a radio wave. A transmission / reception unit that receives an incoming radio wave and outputs it as a received signal, and a signal from a communication partner via a communication satellite is a desired signal, and the output signal transmitted from the transmission / reception unit is relayed by the communication satellite, and the relay wave is When the received signal is an interference signal and at least the desired signal and the interference signal are included in the received signal from the transmission / reception unit, a cancel signal corresponding to the interference signal is generated and received using the cancel signal. A reception modem that removes an interference signal from the signal and demodulates the signal by performing despreading processing, and the reception modem generates a cancel signal based on the transmission signal. A communication device that communicates with the communication device, a communication satellite that relays radio waves from the communication device to the communication counterpart station, and relays radio waves from the communication counterpart station to transmit to the communication device. It is characterized by providing.

  According to the present invention, since the cancel signal is generated based on the transmitted transmission signal, the interference signal can be removed with high accuracy.

It is a block diagram of the communication system using the communication apparatus which concerns on embodiment. It is a block diagram of a communication apparatus. It is the figure which showed typically the communication system applied to description of a related technique. FIG. 6 is a diagram for explaining a problem in a related communication device, in which (a) shows the time dependence of a correlation value when a signal level difference between a communication partner station relay wave (desired signal) and a return relay wave (interference signal) is small. FIG. 4B is a diagram showing the time dependence of the correlation value when the signal level difference between the desired signal and the interference signal is large (when the interference signal is large).

  An embodiment of the present invention will be described. FIG. 1 is a block diagram of a communication system 2 using a communication device 11 according to the present embodiment. The communication device 2 is composed of a plurality of communication partner stations 30 (30A, 30B) mounted on the earth station 10, the communication satellite 20, a ship or the like.

  The earth station 10 and the communication partner station 30 include communication devices 11 and 31 (31A and 31B) and antennas 17 and 32 (32A and 32B), respectively. At this time, it is assumed that the antenna 17 of the earth station 10 is larger than the antenna 32 of the communication partner station 30.

  FIG. 2 is a block diagram of the communication apparatus 11 according to the present invention, which includes a transmission modem 12, a reception modem 13, a line control unit 14, and a transmission / reception unit 15. Note that the transmission modem 12 and the reception modem 13 are connected by a signal line 16 so that a transmission signal G1 described later can be output from the transmission modem 12 to the reception modem 13.

  The transmission modem 12 includes a modulation unit 12a, a spreading unit 12b, and a power adjustment unit 12c. The receiving modem 13 includes a signal delay unit 13a, a modulation unit 13b, a gain adjustment unit 13c, a spreading unit 13d, an interference removing unit 13e, a despreading unit 13f, and a demodulation unit 13g. The signal delay unit 13a, the modulation unit 13b, the gain adjustment unit 13c, the spreading unit 13d, and the interference removal unit 13e constitute an interference signal removal unit, and generate a cancel signal according to a successive interference removal (SIC) method to generate an interference signal. Remove.

  Then, when the earth station 10 transmits, the transmission signal G1 (t1) is modulated by the modulation unit and modulated by PSK (Phase Shift Keying) or QAM (Quadrature Amplitude Modulation) to generate a transmission symbol sequence. , And output as a modulation signal G2 (t1). Thereafter, the spreading unit 13d performs a spreading process on the modulation signal G2 (t1) with a spreading code sequence having a predetermined spreading factor, and outputs this to the power adjustment unit 12c as a coded signal G3 (t1).

  The power adjustment unit 12c amplifies the input encoded signal G3 (t1) (sets as a gain coefficient α) and outputs the amplified signal to the transmission / reception unit 15 as an output signal G4 (t1). The transmission / reception unit 15 transmits the output signal G4 (t1) from the antenna 17 as the earth station transmission wave E1.

  The earth station transmission wave E1 is relayed by the communication satellite 20 and received by the communication partner station 30 as the earth station relay wave E2.

  On the other hand, the radio wave (communication partner station transmission wave E3) transmitted from the communication partner station 30 is relayed by the communication satellite 20 and received by the earth station 10 as the communication partner station relay wave E4. At this time, the earth station 10 also receives a relay wave (returning relay wave E5) of the earth station transmission wave E1 by the communication satellite 20.

  In this way, the communication partner station relay wave E4 and the return relay wave E5 are received by the antenna 17 and input to the transmission / reception unit 15. The reception signal G5 (t2) from the transmission / reception unit 15 is input to the interference removal unit 13e.

The received signal G5 (t2) is given as the sum of the desired signal S by the communication partner station relay wave E4 and the interference signal P by the return relay wave E5. That is,
G5 (t2) = S (t2) + P (t2) + n (t2) (1)
Here, n (t2) is external noise.

The interference signal P (t2) is based on the output signal G4 (t1). Radio waves are attenuated by propagating in the air, so if the attenuation coefficient at this time is β,
P (t2) = β · G4 (t1 + Δ1) (2)
It becomes.
This delay time Δ1 corresponds to the time from when the earth station transmission wave E1 is output from the antenna 17, relayed by the communication satellite 20, and received by the antenna 17 as the return relay wave E5. Instructed by a quantity indication signal. Δ1 is a delay time for adjusting the timing with respect to the interference signal P (t2) and the transmission signal G1 (t1).

Now, the cancel signal G9 (t2) is input from the diffusion unit 13d to the interference removal unit 13e. Therefore, the interference removal unit 13e separates the desired signal S (t2) by removing the cancellation signal G9 (t2) from the reception signal G5 (t2) (removes the interference signal). That is, from Equation 1,
G5 (t2) −G9 (t2) = S (t2) + P (t2) + n (t2) −G9 (t2) (3)
In the present embodiment, the signal line 16 is provided so that the transmission signal G1 (t1) input to the transmission modem 12 is also input to the signal delay unit 13a.

  The delay time Δ1 delayed by the signal delay unit 13a is instructed from the line control unit 14 by a signal delay amount instruction signal. The signal delay unit 13a generates a signal G6 (t2) = G1 (t1 + Δ1) obtained by delaying the transmission signal G1 (t1) by a predetermined delay time Δ1, and outputs it to the modulation unit 13b.

  The signal G6 (t2) from the signal delay unit 13a becomes a signal G7 (t2) modulated into a symbol-sequence signal by the modulation unit 13b, and gain adjustment is performed by the gain adjustment unit 13c (the gain coefficient at this time is γ). And output to the diffusion unit 13d as a signal G8 (t2).

  The spreading unit 13d spreads the signal G8 (t2) and outputs the signal G8 (t2) to the interference removing unit 13e as a cancel signal G9 (t2).

Therefore, the cancel signal G9 (t2) is
G9 (t2) = C · G8 (t2) = C · γ · G7 (t2) = C · γ · G6 (t2)
= C · γ · G1 (t1 + Δ1) (4)
It becomes. Here, C is a spreading code.

Here, P (t2) is
P (t2) = β · G4 (t1 + Δ1) = β · α · G3 (t1 + Δ1)
= Β · C · α · G2 (t1 + Δ1) = β · C · α · G1 (t1 + Δ1) (5)
So, if you organize the above formulas,
G5 (t2) -G9 (t2) = S (t2) + P (t2) + n (t2) -G9 (t2)
= S (t2) + β · C · α · G1 (t1 + Δ1) + n (t2) −C · γ · G1 (t1 + Δ1) (6)
Thus, the interference component can be removed by selecting γ = β · α.

  The signal G10 (t2) obtained by removing the interference component in this way is input to the despreading unit 13f. The despreading unit 13f performs despreading processing on G10 (t2) and outputs the result to the demodulation unit 13g as a signal G11 (t2). The demodulator 13g demodulates the signal G11 (t2) to output the signal G12 (t2) as an output signal of the receiving modem 13.

  In the known technique, the cancellation signal is calculated using the received signal including the external noise, so that the separation accuracy of the desired signal is lowered. However, the reception signal G5 (t) in Equation 6 is an actual measurement value, and the cancel signal G9 (t) is a value calculated based on the transmission signal G1 (t) that is actually transmitted. For this reason, in the method according to the present embodiment, the cancellation signal is calculated based on the transmission signal G1 (t) that does not include external noise, so that it is possible to improve the separation accuracy of the desired signal.

2 Communication device 10 Earth station 12 Transmitting modem 12a Modulating unit 12b Spreading unit 12c Power adjusting unit 13 Receiving modem 13a Signal delay unit 13b Modulating unit 13c Gain adjusting unit 13d Spreading unit 13e Interference removing unit 13f Despreading unit 13g Demodulating unit 14 Line control unit 15 Transmission / reception unit 16 Signal line 17, 32 (32A, 32B) Antenna 20 Communication satellite 30 (30A, 30B) Communication partner station

Claims (4)

A communication device that transmits and receives relay waves from a communication satellite that relays radio waves,
A transmission modem that performs spreading processing on the transmission signal and outputs it as an output signal;
A transmitter / receiver that radiates the output signal as a radio wave, receives the incoming radio wave, and outputs it as a received signal;
A signal from a communication partner via the communication satellite is set as a desired signal, the output signal transmitted from the transmission / reception unit is relayed by the communication satellite, and a signal when the relay wave is received is set as an interference signal, and the transmission / reception is performed. When the received signal from the unit includes at least the desired signal and the interference signal, a cancel signal corresponding to the interference signal is generated, and the interference signal is generated from the received signal using the cancel signal. And a receiving modem that demodulates by performing despreading processing,
The communication apparatus, wherein the reception modem generates the cancel signal based on the transmission signal. The communication device according to claim 1,
The receiving modem is
A signal delay unit that delays the transmission signal for a predetermined time;
A modulation unit that modulates a signal from the signal delay unit;
A gain adjuster for adjusting the gain of the signal from the modulator;
A spreading unit that performs spreading processing on the signal from the gain adjustment unit to generate and output the cancellation signal;
An communication apparatus comprising: an interference signal removal unit including an interference removal unit that receives the reception signal and the cancellation signal and removes the interference signal from the reception signal by the cancellation signal. The communication device according to claim 1,
The communication apparatus according to claim 1, wherein the first-term receiving modem generates a cancel signal according to a successive interference cancellation method to remove the interference signal. A communication system that transmits and receives relay waves from a communication satellite that relays radio waves,
A transmission modem that performs a spreading process on a transmission signal and outputs the signal as an output signal; a transmission / reception unit that radiates the output signal as a radio wave; A signal from a communication partner via a satellite is set as a desired signal, the output signal transmitted from the transmission / reception unit is relayed by the communication satellite, and a signal when the relay wave is received is set as an interference signal. When the received signal includes at least the desired signal and the interference signal, a cancel signal corresponding to the interference signal is generated, and the interference signal is removed from the received signal using the cancel signal. A receiving modem that demodulates by performing despreading processing, and the receiving modem generates the cancel signal based on the transmission signal. And location,
A communication partner station communicating with the communication device;
A communication satellite comprising: a communication satellite that relays radio waves from the communication apparatus and transmits the radio waves to the communication counterpart station, and relays radio waves from the communication counterpart station and transmits the radio waves to the communication apparatus.

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