JP2013115561A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide technology which can transmit and receive using the same frequency at the same time of day.SOLUTION: A transmission signal output from a transmitting unit 101 is radiated as a transmission wave 301 from a transmission antenna 102. A receiving antenna 103 has a reception desired wave 303 from a distant station input thereto. Also the receiving antenna 103 has part of the transmission wave 301 input thereto as a local station transmission interference wave 302 by isolation between antennas or as a reflection wave 304 reflected at a reflection object, etc. which is not shown. The reception wave received by the receiving antenna 103 is input to a cancellation unit 105 as a received signal via a receiving unit 104. The cancellation unit 105 executes a cancellation process by acquiring the transmitted signal from the transmitting unit 101 and cancelling the transmitted signal of the local station included in the received signal. Thus, when transmission and reception are performed using the same frequency at the same time of day, interferences of the transmitted signal of the local station on the receiving side of the location station are minimized.

Description

  The present invention relates to a wireless communication system including a wireless device that performs two-way communication using the same frequency band for reception and transmission.

  Conventionally, in wireless communication, if transmission / reception of the local station is performed at the same frequency and the same time axis, a signal of the transmission system of the local station is input to the reception system of the local station, and interference is caused to the reception system and communication cannot be performed. become.

  Therefore, normally, FDD (Frequency Division Duplex) that transmits and receives transmission frequency and reception frequency separately, TDD (Time Division Duplex) that time-divides one frequency into transmission and reception, etc. Thus, wireless communication is performed so as to eliminate interference between the transmission system and the reception system (see, for example, Patent Document 1).

JP 2003-229784 A

  By the way, the radio frequency is limited, and in recent years, a shortage of frequencies used for radio communication has become a problem, and it has become difficult to secure a frequency band.

  However, in the technique of Patent Document 1, FDD wireless communication requires twice as many frequency resources for transmission and reception, whereas TDD wireless communication reduces the amount of information transmitted and received by time division and increases the communication speed. There was a problem of lowering.

  This invention is made | formed in view of the said subject, and it aims at providing the technique which can transmit / receive using the same frequency at the same time.

  The wireless communication system of the present invention is a wireless communication system including a wireless device that performs two-way communication using the same frequency band for reception and transmission, and the wireless device transmits a signal transmitted from a wireless device that is a communication partner. Based on the signal transmitted from the receiving unit, the transmitting unit that transmits a signal to the wireless device that is the communication partner, and the signal transmitted from the transmitting unit, the signal transmitted by the receiving unit is canceled. And a cancel unit.

  According to the present invention, transmission and reception can be performed using the same frequency at the same time.

It is a functional block diagram which shows the structure of the radio | wireless machine X of embodiment which concerns on this invention. It is an image figure which shows the signal structural example in which the reference signal is contained in the desired reception wave 303 shown in FIG. It is an image figure which shows the example in case the desired reception wave 303 shown in FIG. 1 is a CDMA system. It is an image figure which shows the example in case the desired reception wave 303 shown in FIG. 1 is a FDMA system. It is a functional block diagram which shows the structure of the radio | wireless machine Y of embodiment which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a functional block diagram showing the configuration of the wireless device X of the present embodiment. The wireless device X includes a transmission unit 101, a transmission antenna 102, a reception antenna 103, a reception unit 104, and a cancellation unit 105.

  The transmission signal is generated by the transmission unit 101 and radiated from the transmission antenna 102 as a transmission wave 301.

  A reception desired wave 303 having the same frequency as that of the transmission wave 301 is input to the reception antenna 103 as a reception signal. At this time, transmission by the transmission antenna 102 and reception by the reception antenna 103 are performed simultaneously. Therefore, the local transmission interference wave 302 in which a part of the transmission wave 301 is circulated by the isolation between the transmission antenna 102 and the reception antenna 103 is also input to the reception antenna 103 as a reception signal. Therefore, as it is, the wireless device X cannot receive (demodulate) normally due to the influence of the local transmission interference wave 302.

  Therefore, the cancel unit 105 performs a cancel process on the local transmission interference wave 302. The cancellation unit 105 receives a reception signal obtained by performing a predetermined reception process on the reception signal of the reception antenna 103 by the reception unit 104. Here, it is assumed that the transmission wave 301 is Tx (t), the isolation between the antennas is ISO, and the delay time is Δt. ISO ([dB]) indicating isolation between antennas includes individual characteristics such as a frequency deviation depending on antenna characteristics and space characteristics. In this case, the local station transmission interference wave 302 is a signal slightly delayed from the transmission wave Tx (t), and is represented by ISO × Tx (t−Δt). If the desired reception wave 303 is Rx (t), a signal input to the reception antenna 103 is expressed by the following equation.

  Signal input to receiving antenna 103 = Rx (t) + ISO × Tx (t−Δt) (1)

The cancel unit 105 acquires the transmission signal from the transmission unit 101, that is, the transmission wave Tx (t) transmitted simultaneously with the desired reception wave Rx (t), and receives the reception signal and the transmission signal acquired from the reception unit 104. Compare The cancel unit 105 estimates the ISO which is the propagation path characteristic of the isolation between the antennas, adjusts Δt, and performs a cancel process so as to cancel the local transmission interference wave 302. Specifically, for example, the cancel unit 105 estimates the ISO by taking the correlation between the amplitude / phase of the received signal and the amplitude / phase of the transmission signal stored in the storage unit (not shown) to separate the direct wave and the delayed wave. To do.
Further, the cancel unit 105 obtains Δt based on the correlation result.
The cancel unit 105 uses the stored transmission signal, the ISO and Δt, generates a cancellation signal having the same amplitude and opposite phase with respect to the local transmission interference wave 302, and combines the cancellation signal and the reception signal. Self-station transmission interference wave 302 is canceled. The delay due to Δt is realized using a digital delay circuit (not shown).
As a result, the signal output from the cancel unit 105 is the Rx (t), which is the desired reception wave 303, with the own-station transmission interference wave 302 removed, and is a received signal that can be normally received. It is assumed that a demodulating unit (not shown) is provided after the canceling unit 105, and the demodulating unit demodulates the received signal that has been canceled by the canceling unit 105.

  Another configuration example is shown below. In a real environment, a reflected wave 304 that is generated when the transmission wave 301 is reflected by a reflecting object (not shown) is also input to the receiving antenna 103. Here, when the transfer function including the delay of the reflected wave 304 is RH (i), the local transmission interference wave 302 due to the isolation between the antennas can be regarded as equivalent to the reflected wave 304. From this, the signal input to the receiving antenna 103 can be expressed by the following equation.

  The cancel unit 105 applies a filter for extracting individual reflected waves to the received signal and uses a method for estimating a transfer function for each reflected wave, or applies a filter for extracting the reflected waves in a lump to apply each reflected wave. The transfer function portion is estimated by using a method for estimating the propagation path characteristic of the signal as a transfer function. And the cancellation part 105 produces | generates the cancellation signal of the same amplitude and reverse phase with respect to the reflected wave 304 with the estimated transfer function part and the transmission signal acquired from the transmission part 101, for example, and synthesize | combines with a received signal, Cancel processing is performed so as to cancel the reflected wave 304. As a result, the signal output from the cancel unit 105 is only Rx (t), which is the desired reception wave 303, and is a received signal that can be normally received.

  It should be noted that a reference signal such as a synchronization signal or a known signal on the reception side is included in the transmission signal transmitted from another wireless device, that is, the reception desired wave 303 in order to facilitate acquisition of the reception desired wave 303 on the reception side. It may be inserted. For example, as shown in FIG. 2, a transmission signal from another radio device, that is, a partner station may be time-divided and configured by a reference signal 501 and a free transmission section 502. Based on the reference signal 501 that is a known signal, the canceling unit 105 uses the phase amplitude information of the reference signal 501 at the time of transmission of the counterpart station to determine the phase based on the propagation characteristics, etc. Amplitude fluctuation amount can be acquired. Thereby, the cancellation part 105 can isolate | separate the reception desired wave 303 from a received signal by correct | amending the phase amplitude of the reception desired wave 303 based on the phase amplitude variation | change_quantity of the received reference signal 501. FIG. The cancel unit 105 can easily cancel the interference wave (the local station transmission interference wave 302, the reflected wave 304, etc.) due to the transmission signal of the local station, and can improve the accuracy of the cancellation process.

  As shown in FIG. 3, the communication method of the wireless device X may be a CDMA (Code Division Multiple Access) method. The reference signal 501 is multiplexed on the desired reception wave 303 by a spreading code. Even in this case, the canceling unit 105 can estimate the propagation path characteristic based on the phase amplitude fluctuation amount of the reception phase amplitude of the reference signal 501 that is actually received. Therefore, the reception desired wave 303 having the same propagation path characteristic is used as the reference signal. It becomes easy to specify and separate from the received signal based on 501 and improve the estimation and accuracy in the cancellation process. As shown in FIG. 4, the communication method of the radio device X may be an FDMA (Frequency Division Multiple Access) method. In this case, the reference signal 501 may be inserted at any location in the frequency band of the desired reception wave 303. Similarly, the canceling unit 105 can estimate the propagation path characteristic based on the phase amplitude fluctuation amount of the received phase amplitude of the received reference signal 501, so that the received desired wave 303 having the same propagation path characteristic is based on the reference signal 501. Identification and separation from the received signal can be facilitated, and estimation and accuracy associated with the cancellation process can be improved.

  In this embodiment, an example in which each of the transmission antenna 102 and the reception antenna 103 is configured separately is described. However, there are a plurality of transmission antennas 102 and reception antennas 103, respectively. Also good. Further, the transmission antenna 102 and the reception antenna 103 may be configured as a single unit. For example, FIG. 5 is a functional block diagram illustrating a configuration of a wireless device Y in which a transmission antenna and a reception antenna are integrated. Here, the same functions as those of the wireless device X of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted, and portions different from the wireless device X will be described.

  In FIG. 5, the wireless device Y is provided with a transmission / reception shared antenna 112 as an alternative to the transmission antenna 102 and the reception antenna 103 shown in FIG. Radio Y is provided with a circulator 111 that outputs a transmission signal from transmission section 101 to transmission / reception shared antenna 112 and outputs a reception signal from transmission / reception shared antenna 112 to reception section 104. In this case, by providing the circulator 111, the transmission signal of the local station affects the reception system of the local station depending on the isolation amount of the circulator 111. For this reason, it is necessary to consider the amount of isolation of the circulator 111, but in the same way as in the above processing, the cancel unit 105 causes interference of the transmission signal of the own station in the received signal based on the transmission signal acquired from the transmission unit 101. By canceling, a reception signal that can be normally received can be generated. The circulator 111 only needs to be able to perform transmission and reception with a single antenna, and may be configured with, for example, a directional coupler or a distributor.

  As described above, in this embodiment, when the radio wave transmitted by the local station and the radio wave received by the local station are used at the same frequency and the same time axis, the transmission signal of the local station is input to the reception system of the local station. Even so, interference can be minimized by canceling the transmission signal of the local station in the reception system of the local station. Therefore, in the present embodiment, there is no problem that frequency resources are twice required for transmission and reception as in FDD, and communication speed is reduced as in TDD. Thereby, in this embodiment, transmission / reception of the own station can be performed at the same frequency and the same time, and the frequency efficiency can be improved without reducing the communication speed.

As mentioned above, when this embodiment is outlined,
(1) The wireless communication system of the present embodiment is a wireless communication system including a wireless device that performs two-way communication using the same frequency band for reception and transmission, and the wireless device transmits from a wireless device that is a communication partner. Based on the signal transmitted from the transmission unit, the transmission unit that transmits the signal to the wireless device that is the communication partner, and the signal included in the signal received by the reception unit And a cancel unit for canceling the signal.
(2) The cancel unit according to (1) may cancel interference of the transmission signal by a reference signal included in the reception signal.
(3) The transmission antenna and the reception antenna described in (1) or (2) may be configured as a single unit.

  The present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention. Note that, in the above-described embodiment, the same reference numerals are given to configurations showing similar functions.

101: transmitting unit 102: transmitting antenna 103: receiving antenna 104: receiving unit 105: canceling unit 111: circulator 112: transmission / reception shared antenna 301: transmission wave 302: local transmission interference wave 303: reception desired wave 304: reflected wave X, Y: Radio

Claims (1)

A radio communication system comprising a radio that performs two-way communication using the same frequency band for reception and transmission,
The radio is
A receiving unit that receives a signal transmitted from a wireless device as a communication partner;
A transmitter for transmitting a signal to the wireless device serving as the communication partner;
Based on the signal transmitted from the transmission unit, a cancellation unit for canceling the signal transmitted by itself included in the signal received by the reception unit,
A wireless communication system comprising:

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