JP2017017394A - Radio repeater and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio repeater capable of maintaining or improving user throughput by preventing influences of interference even when an interference problem occurs in such a case when close frequency bands are used in an identical frequency bandwidth.SOLUTION: A radio repeater in an embodiment relays a communication between a radio base station radio communication terminal apparatus as a moving body. When relaying the communication, a signal processing section monitors signal level of interference wave and updates a weight coefficient for performing weighting on a signal of received wave to lower the signal level interference wave.SELECTED DRAWING: Figure 2

Description

  Embodiments described herein relate generally to a wireless relay apparatus and method.

  In 3GPP (3rd Generation Partnership Project) Release 12 whose specifications are currently being developed, specifications focusing on small cells are being studied. When small cells are frequently used, it becomes necessary to discuss how to secure a backhaul line for small cells.

  One solution is to use a wireless backhaul line, especially under conditions where it is difficult to secure a wired backhaul line, such as optical fiber or ADSL, due to topographical difficulties or inadequate cost. Construction is being considered as one of the effective means to solve the future backhaul line problem in the small cell system.

  For wireless backhaul lines, in addition to those using microwaves (Microwave: so-called P to P wireless) that are already in use, methods using the wireless relay device (Relay) that appeared in Release 10 are being studied. .

In addition to having an access line function that a normal base station has, a wireless relay device can also have a backhaul line function.
It is effective as a means to expand the coverage area (Coverage) of existing macro base stations, but it can also be used to improve communication capacity even in hot spots where traffic is tight. Is possible. For this reason, the use of a wireless relay device is one means for realizing a small cell.

On the other hand, in order to use a wireless relay device, depending on how the frequencies on the access line side and the backhaul line side are used, the type of the wireless relay device is an in-band relay device (In-band Relay), A distinction is made between two types of out-band relay devices.
Here, the in-band radio relay device (In-band Relay) is a radio relay device that uses the same frequency on the access line side and the backhaul line side, and the out-band radio relay device (Out-band Relay) The wireless relay device uses different frequencies on the access line side and the backhaul line side.

JP 2004-048196 A

However, although the reason is different in each wireless relay device, there is a problem that the user throughput is lowered, and it has not been possible to easily realize a small cell.
By the way, in the out-band wireless relay device, since different frequencies are used on the access line side and the backhaul line side, in general, no frequency interference occurs between the access line side and the backhaul line side. However, an interference problem arises in an actual operation case, such as when using adjacent frequency bands within the same frequency band (for example, assigned frequency band). When interference is not avoided, the user throughput decreases.

  The present invention has been made in view of the above, and suppresses the influence of interference and maintains user throughput even when an interference problem occurs as in the case of using adjacent frequency bands within the same frequency band. Or providing a radio relay apparatus and method that can be improved.

  The radio relay apparatus of the embodiment relays communication between a radio base station and a radio communication terminal apparatus that is a mobile body. When relaying communication, the signal processing unit monitors the signal level of the interference wave, and updates the weight coefficient that weights the signal of the reception wave so that the signal level of the interference wave decreases.

FIG. 1 is a schematic configuration block diagram of a wireless communication system according to an embodiment. FIG. 2 is a functional configuration block diagram at the time of reception (downloading) of the wireless relay device of the first embodiment. FIG. 3 is an explanatory diagram of the allocated frequency band allocated to the macro base station and the radio relay apparatus. FIG. 4 is an explanatory diagram of an interference image at the time of downloading. FIG. 5 is an explanatory diagram of an interference image at the time of uploading. FIG. 6 is a functional configuration block diagram at the time of reception (during download) of the wireless relay device of the second embodiment.

Next, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration block diagram of a wireless communication system according to an embodiment.
A radio communication system 10 includes a macro base station 11 corresponding to a macro cell capable of constructing a communication area having a radius of several hundred meters to several tens of kilometers, and a radio relay apparatus that communicates with the macro base station 11 and relays communication of the macro base station 12 and a plurality of wireless communication terminal devices 13 configured as a mobile phone, a smartphone, or the like that performs communication via the macro base station 11 or the wireless relay device 12.
Here, the service area of the macro base station 11 is the service area SA11, and the service area of each wireless relay device 12 is the service area SA12.

[1] First Embodiment FIG. 2 is a functional configuration block diagram at the time of reception (downloading) of the wireless relay device of the first embodiment.
The wireless relay device 12 includes an access antenna (service antenna) for performing communication between the donor antenna 21 for performing communication with the macro base station 11, the relay device main body 22, and the wireless communication terminal device 13. 23.

  In the above configuration, it is assumed that the transmission signal X (z) transmitted by the macro base station 11 reaches the radio relay apparatus 12 via the propagation path of the propagation path parameter Bz.

  The relay apparatus main body 22 amplifies the output (= X (z) · B (z)) of the donor antenna 21 with an amplification factor K1 and outputs it as a transmission RF signal RF1, and a first transmission RF signal. The first mixer 32 mixed with the first carrier signal corresponding to the frequency f1 and output as the received baseband signal SB1, and the analog / digital conversion of the received baseband signal output from the first mixer 32 is performed to obtain the digital baseband. And an A / D converter 33 that outputs the data DB1.

  Further, the relay apparatus main body 22 includes a DSP (Digital Signal Processor) 34 that performs a cancellation process of a sneak wave (interference wave) R (z) that wraps around from the access antenna 23 based on the digital baseband data DB1, and a process that is output by the DSP 34. And a D / A converter 35 that performs digital / analog conversion of the completed digital baseband data DB2 and outputs an analog transmission baseband signal SB2.

  Further, the relay apparatus main body 22 mixes the analog transmission baseband signal SB2 with the second carrier signal corresponding to the second frequency f2, and outputs it as the relay transmission RF signal RF2, and the relay transmission RF signal RF2. Is amplified with an amplification factor K2 and output as an amplified relay transmission RF signal ARF2, and is transmitted to the wireless communication terminal device 13 existing in the relay area via the access antenna 23. .

  The DSP 34 adds the white noise data N (z) to the digital baseband data DB1, the subtractor 42 by subtracting the weight W (z) from the output of the adder 41, and the output of the subtractor 42. A weight generation coefficient generator 43 that outputs a weight generation coefficient α for generating a weight W (z) from the transfer function Y (z), and a weight that generates a weight W (z) based on the weight generation coefficient α. A generation unit 44 and a demodulation / modulation unit 45 that demodulates and modulates the digital baseband data DB1 to which the transfer coefficient Y (z) is applied and outputs the processed digital baseband data DB2.

Here, prior to describing the operation of the embodiment, conventional problems will be described.
FIG. 3 is an explanatory diagram of the allocated frequency band allocated to the macro base station and the radio relay apparatus.

  In this case, the frequency band F allocated to the radio communication system 10 includes a frequency band whose center frequency is the first frequency f1, a frequency band whose center frequency is the second frequency f2, and a frequency band whose center frequency is the third frequency f3. I have. Furthermore, the frequency band of the first frequency f1 is adjacent to the frequency band of the second frequency f2, the center frequency is the frequency band of the second frequency f2, and the center frequency is the third frequency f3. It is assumed that the frequency band is adjacent.

  In the following, the macro base station 11 uses the frequency band whose center frequency is the first frequency f1, the radio relay apparatus 12 uses the frequency band whose center frequency is the second frequency f2, and the radio relay apparatus 12 uses the macro base station 11. An example of downloading from will be described.

FIG. 4 is an explanatory diagram of an interference image at the time of downloading.
Normally, the wireless relay device 12 receives a weak level download (DL) signal (= X (z) · B (z)) from the macro base station 11, and once demodulates and amplifies it. Output.

  For this reason, when the isolation between the donor antenna 21 and the access antenna 23 is insufficient, the signal level of the second frequency f2 that goes around from the access antenna to the donor antenna that receives the download signal of the first frequency f1 is very high. Adjacent channel leakage power (ACL: Adjacent Channel Leakage) in the frequency band of the second frequency f2 as an adjacent channel increases, and as a result, adjacent channel leakage power ratio (ACLR) increases, resulting in interference. Will occur.

FIG. 5 is an explanatory diagram of an interference image at the time of uploading.
The above description is about the download signal, but the same applies to the upload (UL) signal from the wireless communication terminal device 13 which is a mobile device. That is, as shown in FIG. 5, the radio relay apparatus 12 that receives the weak frequency f2 ′ (= upload signal corresponding to the frequency f2 of the download signal) from the radio communication terminal apparatus 13 receives the carrier frequency f1 ′ after demodulation. The output is amplified with the frequency changed. For this reason, the wraparound from the donor antenna 21 to the access antenna 23 occurs, and interference similarly occurs.

  Therefore, in the present embodiment, in the above configuration, the DSP 34 realizes interference removal by an ICS (Interference Cancellation System) function.

  That is, a desired wave (in the case of the above example, the center frequency is the first frequency f1 at the time of download) and an interference wave (in the case of the above example, the center frequency is the second frequency f2 at the time of download) are mixedly input. In this state, the DSP 34 forms a loop for canceling the interference wave by the weight generation coefficient generation unit 43 and the weight generation unit 44, and subtracts it from the input signal.

  Then, in the output of the subtractor 42, a weight which is a coefficient for monitoring the signal level of the second frequency f2 with the center frequency being the interference wave and weighting the signal so that the signal level of the second frequency f2 is lowered with the center frequency. Interference cancellation is realized by continuing to update (weight) W (z).

Hereinafter, the case where the macro base station 11 transmits to the wireless communication terminal device 13 will be specifically described as an example.
When the macro base station 11 transmits to the wireless communication terminal device 13, the transmission wave is received by the relay device body 22 via the donor antenna 21.

  As a result, the first amplifier 31 of the relay apparatus main body 22 amplifies the output (= X (z) · B (z)) of the donor antenna 21 with the amplification factor K1 and outputs it to the first mixer 32 as the transmission RF signal RF1. To do.

The first mixer 32 mixes the transmission RF signal with the first carrier signal corresponding to the first frequency f1, and outputs the mixed signal to the A / D converter 33 as the reception baseband signal SB1.
The A / D converter 33 performs analog / digital conversion of the received baseband signal output from the first mixer 32, and outputs the result to the DSP 34 as digital baseband data DB1.

As a result, the adder 41 of the DSP 34 adds the white noise data N (z) to the digital baseband data DB1 and outputs the result to the subtractor 42.
The subtracter 42 subtracts the weight W (z) from the output of the adder 41 and outputs the result.

Accordingly, the demodulation / modulation unit 45 demodulates and modulates the digital baseband data DB1 to which the transfer coefficient Y (z) is applied, and outputs the processed digital baseband data DB2 to the D / A converter 35.

In parallel with this, the weight generation coefficient generation unit 43 generates a weight generation coefficient α for generating the weight W (z) from the transfer function Y (z) that is the output of the subtractor 42, and the weight generation unit 44. Output to.
The weight generation unit 44 generates a weight W (z) based on the weight generation coefficient α and outputs it to the subtractor 42.

As a result, the processed digital baseband data DB2 in which the influence of the interference wave is reduced is input to the D / A converter 35.
Then, the D / A converter 35 performs digital / analog conversion of the processed digital baseband data DB2 output from the DSP 34 and outputs an analog transmission baseband signal SB2 to the second mixer 36.

The second mixer 36 mixes the analog transmission baseband signal SB2 with the second carrier signal corresponding to the second frequency f2, and outputs the mixed signal as the relay transmission RF signal RF2 to the second amplifier 37.
The second amplifier 37 amplifies the relay transmission RF signal RF2 with the amplification factor K2 and outputs it as an amplified relay transmission RF signal ARF2, and transmits it to the wireless communication terminal device 13 existing in the relay area via the access antenna 23. To do.

  In the above operation, the transfer function Y (z) at the observation point Y in FIG.

  Since the influence of the interference wave can be canceled by always setting the denominator of the transfer function Y (z) to 1, Equation (2) is established as an ideal weight W (z) t.

  Further, a weight difference E (z) that is a difference between an ideal weight W (z) t = R (z) K2 and an actual weight W (z) is defined as shown in the following equation (3).

この（３）式を（１）式に代入すると、以下の（４）式が導かれる。

Substituting this equation (3) into equation (1) leads to the following equation (4).

  Here, when the SNR (Signal-Noise Ratio) of the input signal is high, the value of the noise N (z) is very small with respect to the value of the transfer function Y (z). (= N (z) / Y (z)) can be regarded as 0.

  The variable amplification factor K1 is known. Further, X (z) / Y (z) can be estimated when there is no interference wave and propagation channel fading, and can be estimated during a training period using a pilot signal or the like.

Therefore, the weight difference is converged by updating the current weight W _n (z) with the previous weight W _n−1 (z) as in the following equation (5).

  As described above, according to the first embodiment, even when an interference problem occurs as in the case of using adjacent frequency bands in the same frequency band, the influence of interference can be suppressed. The user throughput can be maintained or improved.

[2] Second Embodiment FIG. 6 is a functional configuration block diagram at the time of reception (during download) of the wireless relay device of the second embodiment.
In FIG. 6, the same parts as those in FIG. 2 are denoted by the same reference numerals.
6 is different from the wireless relay device 12 of the first embodiment in that the wireless relay device 12A transmits to the wireless communication terminal device 13 existing in the relay area via the access antenna 23. The output of the second amplifier 37 is input via the attenuator 51, and the multiplier 53 that down-converts at the same frequency synchronized by the PLL 52 to the same frequency as the output of the second amplifier 37, and the output A of the multiplier 53 A level adjustment unit 46 that multiplies a point at which digital feedback data is generated by the / D converter 54, a level adjustment K for adjusting the level of the output of the demodulation / modulation unit 45, and a predetermined delay d to the output of the level adjustment unit 46 Is provided with a delay circuit 47 that outputs and subtracts the output data of the delay circuit 47 from the digital feedback data. The configuration is such that the output of the subtractor 48 of the subtractor 48 is subtracted from the digital feedback data, thereby canceling the main signal component and outputting only the adjacent channel leakage power component to the weight generation coefficient generation unit 43. .

  According to the configuration of the second embodiment, in addition to the effects of the first embodiment, the influence of adjacent channel leakage components included in the output of the wireless relay device 12 is further suppressed, and the influence of interference is further suppressed. The user throughput can be maintained or improved.

[3] Modification of Embodiment In the above description, the interference between the signal having the center frequency of the first frequency f1 and the signal having the center frequency of the second frequency f2 has been described. Can be configured to control the weight W (z) so that interference between the signal of the second frequency f2 and the signal of the center frequency of the third frequency f3 is also removed in parallel. .

  With this configuration, even in a wireless communication system in which a plurality of wireless relay devices 12 are provided, the influence of interference can be further suppressed, and the user throughput can be maintained or improved.

In the above description, the configuration in which the interference cancellation process is performed by the DSP is adopted, but the same process may be performed by a hardware circuit.
Although the above description mainly explained the weight (weighting coefficient) at the time of transmission of the radio relay apparatus 12 from the macro base station 11 to the radio communication terminal apparatus 13, the radio relay from the radio communication terminal apparatus 13 to the macro base station 11 The same applies to the weight (weighting factor) at the time of reception by the device 12.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Wireless communication system 11 Macro base station 12, 12A Wireless relay apparatus 13 Wireless communication terminal apparatus 21 Donor antenna 22 Relay apparatus main body 23 Access antenna 31 1st amplifier 32 1st mixer 33 A / D converter 34 DSP
35 D / A Converter 36 Second Mixer 37 Second Amplifier 41 Adder 42 Subtractor 43 Weight Generation Coefficient Generation Unit 44 Weight Generation Unit 45 Demodulation / Modulation Unit 46 Level Adjustment Unit 47 Delay Circuit 48 Subtractor 51 Attenuator 52 PLL
53 Multiplier 54 A / D Converter SA11, SA12 Service Area W (z) Weight

Claims (8)

A radio relay device that relays communication between a radio base station and a mobile radio communication terminal device,
A signal processing unit that monitors a signal level of the interference wave and updates a weight coefficient that weights the signal of the reception wave so that the signal level of the interference wave decreases;
Wireless relay device. The signal processing unit reduces the signal level of the interference wave by reducing the adjacent channel leakage power component,
The wireless relay device according to claim 1. When the signal processing unit relays the received wave and outputs it as a transmission wave, the signal processing unit cancels the main signal component by matching the phase while inverting the transmission wave component, and the obtained adjacent channel leakage Updating the weighting factor based on the power component;
The wireless relay device according to claim 1. The weight coefficient is a transmission weight coefficient or a reception weight coefficient.
The wireless relay device according to claim 1. A method executed by a radio relay apparatus that relays communication between a radio base station and a mobile radio communication terminal apparatus,
The process of monitoring the signal level of the interference wave;
Updating a weighting factor that weights the received wave signal so that the signal level of the interference wave decreases;
With a method. The signal processing unit reduces the signal level of the interference wave by reducing the adjacent channel leakage power component,
The method of claim 5. The process of updating the weight coefficient was obtained by canceling the main signal component by reversing the transmitted wave component and matching the phase when relaying the received wave and outputting it as a transmitted wave. Updating the weighting factor based on the adjacent channel leakage power component;
The method of claim 5. The weight coefficient is a transmission weight coefficient or a reception weight coefficient.
The method of claim 5.

Images