KR20120106474A - Rf repeater and method of processing signal for mobile communication - Google Patents

Abstract

PURPOSE: An RF relay and an RF signal processing method are provided to linearize a power amplifier and to increase power consumption efficiency of a wireless power amplifier. CONSTITUTION: A signal converting unit(20) converts a received digital modulated wave into a baseband signal. The signal converting unit reproduces digital data. A modulator(30) modulates the reproduced digital data. The modulator generates a transmission signal. A power amplifying unit(40) amplifiers the transmission signal.

Description

Radio repeater and method of processing signal for mobile communication

The present invention relates to a mobile communication technology, and more particularly, to a mobile communication wireless relay device and a wireless relay signal processing method.

A mobile communication system such as a digital TRS, PCS, cellular or IMT-2000 basically consists of an exchange station, a base station, and a terminal (or mobile station). The entire communication service area of the mobile communication system is divided into cells, which are several small service areas, and a base station is installed in the center of the cell so that the base station serves as a relay between the terminals in the cell and the switching center. However, there may be a radio wave shadow area or a mixed signal area in the cell. In this case, at least one digital mobile communication relay device for relaying signals between the base station and the terminal may be used to secure the call quality and the communication area of the base station. Can be.

The digital mobile communication relay device includes a wireless relay device (or an RF relay device), an optical relay device, a microwave relay device, or a laser relay device according to a link method with a base station. The dual radio relay apparatus relays a signal by compensating for propagation path loss between the base station and the mobile station by linking the base station and the mobile station using the RF signal. Recently, due to the increase in the number of subscribers, the mobile communication service allocates and transmits several carriers (carriers) to one base station. Therefore, in order to suppress intermodulation of signals that may appear while amplifying a plurality of carriers in a relay device, the power amplifier of the wireless relay device should have excellent linearity. If the radio relay device has nonlinearity, it may result in adjacent channel interference (ACI), in which the transmitted signal spectrum is extended to the adjacent channel, which uses CDMA, WCDMA, Wibro, and especially digital modulation schemes. It is a cause of deterioration of communication quality in digital TRS.

Conventionally, the repeater is designed to operate in an area where linearity is ensured by backing off the power amplifier so that linear amplification is possible. For example, in the Terestrial Trunked Radio System (TETRA) specification for digital TRS requiring adjacent channel leakage power of -60 dB or less, a power amplifier is used with backoff of 10 dB or more. As described above, the amplification method of the conventional relay apparatus using the backoff not only consumes a lot of power, but also causes problems of enlargement and stability of the relay apparatus due to the use of a large output amplifier.

On the other hand, the more the propagation path loss of a radio signal, the higher the power amplification of the relay device requires. Conventional repeaters are structurally unable to selectively control the gain of each receiving channel, so when the output of the relay is set based on a signal having a low signal level, a signal of a large signal level may be saturated, and a large signal level When the output of the relay device is set based on the signal of, a problem occurs that a low level signal still has a low output level. In addition, since the method of amplifying the received wireless signal only the size, since the multipath fading and noise due to buildings and obstacles in the downtown area are transmitted to the terminal as it is, the quality of the relay signal is deteriorated.

The problem to be solved by the present invention, when the gain is adjusted to compensate for the propagation path loss, through the appropriate gain control for each of the plurality of receiving channels has a constant output level, such as a base station, multiplexed channel amplification without intermodulation is possible, By linearizing the power amplifier and improving the power consumption of the wireless power amplifier, it is possible to reduce the size and operation economics of the wireless repeater and, optionally, eliminate the noise included in the wireless transmission section to achieve the same signal quality as that of the base station. It is to provide a mobile communication wireless relay device that can be transmitted to.

In addition, another object of the present invention is to provide a wireless relay signal processing method having the above-described advantages.

According to an aspect of the present invention, there is provided a mobile communication wireless relay apparatus including: a receiver configured to receive a digital modulated wave transmitted from a base station; A signal converter converting the received digital modulated wave into a baseband signal to reproduce digital data; A modulator for modulating the reproduced digital data to generate a transmission signal; And a power amplifier for amplifying the transmission signal. A part of the output signal of the power amplifier is fed back to the input of the modulator so that the power amplifier is linearized. The feedback may be performed by a Cartesian feedback loop.

In some embodiments, the digital modulated wave may have a plurality of channel frequencies, and the modulator and the power amplifier may be allocated to each of the plurality of channel frequencies. The mobile communication wireless relay device may further include an error correction unit configured to correct an error of the converted digital data between the signal converter and the modulator.

The mobile communication wireless relay device may comply with the digital TRS standard. In the digital TRS specification where stringent transmission quality is required, the advantages in terms of transmission quality and power efficiency of embodiments of the present invention become more apparent.

Wireless relay signal processing method according to an embodiment of the present invention for solving the other technical problem, the step of receiving a digital modulated wave transmitted from the base station; Reproducing digital data by modulating the received digital modulated wave into a baseband signal; Generating a transmission signal by modulating the reproduced digital data; Amplifying the transmission signal to an output level; And linearizing the amplifying by feeding back a portion of the amplified transmission signal during the generation of the transmission signal.

In some embodiments, the linearizing may be performed by a Cartesian feedback loop. In addition, after the reproducing of the digital data, the step of correcting an error of the digital data may be further performed.

According to embodiments of the present invention, the digital modulated wave received from the base station by the signal converter is converted into a baseband signal, thereby enabling linearization of the power amplifier using a linearization mechanism such as a Cartesian feedback system. When the gain is adjusted to compensate for propagation path loss, the power efficiency may be improved, thereby providing a wireless relay device capable of miniaturizing and operating economics of the wireless relay device. In addition, since the radio relay apparatus uses the reproduced digital data, multiplexed channel amplification can be performed without intermodulation, and signal transmission to the mobile station can be performed at the same level as the base station in response to multipath fading.

In addition, according to an embodiment of the present invention, a wireless relay signal processing method having the above-described advantages and features can be provided.

1A is a flowchart illustrating a wireless relay signal processing method according to an embodiment of the present invention, and FIGS. 1B and 1C are diagrams illustrating an internal configuration for forward signal relay of mobile communication wireless relay devices according to various embodiments of the present disclosure. It is a block diagram showing.
2 shows a circuit diagram of a Cartesian feedback system in accordance with one embodiment of the present invention.
3 is a block diagram illustrating a mobile communication wireless relay device according to another embodiment of the present invention.
Figure 4 is a block diagram showing a mobile communication wireless relay device according to another embodiment of the present invention.
5 is a block diagram illustrating a mobile communication wireless relay device according to another embodiment of the present invention.
6 is an image illustrating an output signal measured at a service side of a mobile communication wireless relay device according to an embodiment of the present invention.

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

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In addition, in the following drawings, the thickness or size of each layer is exaggerated for convenience and clarity of description, the same reference numerals in the drawings refer to the same elements. As used herein, the term “and / or” includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, "comprise" and / or "comprising" specifies the presence of the mentioned shapes, numbers, steps, actions, members, elements and / or groups of these. It is not intended to exclude the presence or the addition of one or more other shapes, numbers, acts, members, elements and / or groups.

1A is a flowchart illustrating a wireless relay signal processing method according to an embodiment of the present invention, and FIGS. 1B and 1C are diagrams illustrating a forward signal relay of mobile communication wireless relay devices 100 according to various embodiments of the present disclosure. It is a block diagram showing the internal configuration.

Referring to FIG. 1B together with FIG. 1A, the wireless relay apparatus 100 is wirelessly linked to the base station BS to transmit a service signal of the base station BS to the mobile station MS in the radio range. The digital relay device 100 has a reception signal processor RX for receiving and processing digital modulated waves received from the base station BS. The received signal processor RX may include a receiver 10 and a signal converter 20.

The receiver 10 may receive a digital modulated wave transmitted from the base station BS (S100). The receiver 10 receives an RF signal transmitted from the base station BS through the base station counter antenna BA, and removes an unnecessary band signal other than a predetermined reception band. And a low noise amplifier (not shown) coupled to an output terminal of the band pass filter to amplify the received digital modulated wave. In some embodiments, the signal amplified by the low noise amplifier is a frequency down converter for converting the intermediate frequency (IF) into an intermediate frequency (IF) for easier signal processing and amplification. H) may be further included.

The digital modulated wave output through the receiver 10 is converted into a baseband signal by the signal converter 20 and restored to data sent from the base station (S200). The signal converter 20 may include, for example, a phase shifter and an orthogonal regenerator. The quadrature recoverer may include two mixers for respectively multiplying a carrier signal having a 90 ° phase difference generated by a phase shifter with an input digitally modulated wave. If desired, a low pass filter may be coupled to the output of the mixers. The digital modulated wave is demodulated by signal processing of the mixers, and an in-phase (I) channel signal (I _d ) and a quadrature-phase (Q) channel signal (Q _d ), which are orthogonal to each other, are baseband signals. have.

In another embodiment, the baseband signal may be composed of only one of the I channel signal I _d and the Q channel signal Q _d , in which case, the signal converter 20 may be connected to one mixer. It may consist of only one low pass filter.

The baseband signal reproduced by the signal conversion unit (20), I _d and Q _d is the mobile station opposed to the antenna after the gain control in the transmission signal processing portion (TX) in order to compensate for transmission loss of the downlink process of the digital modulated wave ( MS). The transmission signal processor TX may include a modulator 30 and a power amplifier 40. The modulator 30 modulates the reproduced digital data to generate a transmission signal (S300), and the power amplifier 40 amplifies the transmission signal to an output level (S400).

Specifically, the modulator 30 is a phase shifter for providing a phase shifted carrier signal, and a carrier signal provided from the phase shifter is mixed with an I channel signal and a Q channel signal to form an I channel RF signal and a Q channel RF signal. Up-converting mixers, the I-channel RF signal and the Q-channel RF signal output from the mixer may be composed of a power synthesizer for generating a transmission signal having the same frequency as the digital modulation wave of the base station (BS). The configuration of the above-described modulator 30 is exemplary, but the present invention is not limited thereto.

The power amplifier 40 may include, for example, a high power amplifier (HPA) capable of amplifying at a high output level. If necessary, high output transistors can be balanced to achieve high output levels.

A portion of the amplified transmission signal may be fed back during the generation of the transmission signal to linearize the amplification step (S500). To this end, the mobile communication wireless relay device 100 may include a feedback circuit 50 for feeding back the output signal of the power amplifier 40 to the input terminal of the modulator 30. The feedback circuit 50 may be a Cartesian Feedback System (CFS), and FIG. 2 illustrates a circuit diagram of a Cartesian Feedback System (CFS) according to an embodiment of the present invention.

Referring to FIG. 2, a part of the transmission signal output through the power amplifier 40 is demodulated after power branching through the combiner 50c in the Cartesian feedback system CFS, and the signal converter 20 The power amplifier 40 is linearized by feeding back the I channel signals I _d and the Q channel signal components Q _d received from the respective channels. The combiner 50c has an appropriate value of coupling ratio so as not to affect transmission power. The Cartesian feedback system CFS may include one or more down conversion mixers 50m1 and 50m2 for demodulating the signal of the power amplifier 40. If necessary, a phase shifter (not shown) may be provided between the mixers 50m1 and 50m2 and the combiner 50c. The phase shifter is for phase adjustment of the signal of the forward path of the Cartesian feedback system (CFS) and the signals of the feedback path.

The baseband I channel signal I 'and Q channel signal Q' output through the downconversion mixers 50m1 and 50m2 are input to the subtractors 50d1 and 50d2, respectively, and the subtractors 50d1 and 50d2. ) Subtracts the I-channel signals I _d and Q-channel signals Q _d , which are baseband signals input from the modulator 20, and the error signals e _i , e _o corresponding to the baseband signals are subtracted from the modulator 30. The output signal of the power amplifier 40 may be linearized by being input to the up-conversion mixers 30m1 and m2.

Although the signal processing described above with reference to FIG. 1B is for a baseband signal having a single channel frequency, the digital data output by the signal converter 12 may include a plurality of channel frequencies, for example, F ₁ , F. _{May have 2} , ..., F _N. In this case, as shown in FIG. 1C, the transmitter TX of the mobile communication wireless relay apparatus 100 includes a plurality of modulations assigned to each channel frequency F ₁ , F ₂ , ..., F _N. It may also include the parts 30, the power amplifiers 40, and the feedback circuits 50. Each channel is frequency-linearized to _{(F 1, F 2, ...} , F N) amplified signals are transmitted to the mobile station opposing antenna (MA) combined by a summer (60).

According to the above embodiments, by converting the digital modulated wave received from the base station into a baseband signal, linearization by the Cartesian feedback system (CFS) is possible, and distortion that may occur in the power amplifier 22 is removed. Can be. In addition, the gain of the output level can be determined at the same level and / or separately for each channel frequency, thereby allowing multiplexed channel amplification without intermodulation between signals having neighboring channel frequencies, resulting in multipath fading. Corresponding to the mobile station, the same level of signal transmission as that of the base station is possible.

Compared with the power amplification process of simply power amplifying and transmitting the digital modulated wave received from the base station as in the related art, according to the embodiment of the present invention, the power amplifier does not need to be operated by backing off the power amplifier for linearization of the power. The efficiency is improved, whereby the relay device can be miniaturized, and the reliability of the device can be increased. Experimentally, the Cartesian feedback system (CFS) according to the present embodiment eliminates at least 30 dB of distortion signal and achieves the same level of linearization effect as back off by 10 dB when compared with a conventional simple power amplifier. Could.

The mobile communication wireless relay apparatus according to the above-described embodiment may comply with the TETRA radio standard of Table 1, in which case, the relay apparatus converts and modulates the digital modulated wave transmitted from the base station to the Pi / 4 DQPSK scheme. The power is amplified and relayed to the mobile station.

TETRA Wireless Specifications Item Contents Remarks Frequency band 806 to 870 MHz Multiple access method TDMA 4-Time Slot, FDD Transmit and receive frequency interval 45 MHz Channel bandwidth 25 kHz Data rate 7.2 kbps (28.8 kbps for TETRA R1 MSPD) Modulation method Pi / 4 DQPSK Output power 1, 3, 5, 10, 20 watts Adjacent Channel Leakage Power -60 dBc Voice codec ACELP security TEA1,2,3 & E2EE

3 is a block diagram illustrating a mobile communication wireless relay device 200 according to another embodiment of the present invention. The features and advantages of the illustrated components having the same reference numerals as the above-described components may refer to the foregoing disclosure as long as there is no contradiction.

Referring to FIG. 3, the mobile communication wireless relay device 300 may further include an error correction unit EC for error correction of a digital modulated wave received from the base station BS, unlike the wireless relay device of FIG. 1A. have. The error correction unit EC may be disposed between the signal converter 20 and the modulator 30 to perform error correction in the base band.

The baseband signals I _d and Q _d output from the signal converter 20 may include error components due to multipath fading and noise. The error correction unit EC may analyze the phase points of the signals in the baseband signals I _d and Q _d , and identify the signal points at the time of transmission from the base station, and correct the error component based on these.

4 is a block diagram showing a mobile communication wireless relay device 300 according to another embodiment of the present invention.

Referring to FIG. 4, the mobile communication wireless relay device 300 is a donor unit DU linked to a base station, and remote service units RU1 and RU2 separated from the donor unit DU and disposed remotely and linked with the mobile station. It may include. As illustrated in FIG. 4, two or more remote service units RU1 and RU2 may be provided. In this case, the donor unit DU and the remote service units RU1 and RU2 may be configured as 1: N (where N is two or more). Integer) relationship can be satisfied. In another embodiment, the remote service unit can be one.

The donor unit DU may be provided with a reception signal processor RX including the receiver 10 and the signal converter 20 described above, and the transmit signal processor TX is provided in the remote service units RU1 and RU2. The above-described modulator 30, power amplifier 40, and a Cartesian feedback system 50 for linearization may be disposed. The donor unit DU and the remote service units RU1 and RU2 may each communicate with each other by means of a transmission medium 60 such as an Ethernet cable, optical cable, microwave, or a radio link by frequency conversion. Interface circuits (DI, SI) may be included. The donor side interface circuit (DI) and the service side interface circuit (SI) may be appropriately selected according to the transmission medium 60. Preferably, the baseband digital data is connected at low cost by connection via an Ethernet cable. It can be minimized.

Although not illustrated, when the digital modulated wave has a plurality of channel frequencies, the modulator 30, the power amplifier 40, and the Cartesian feedback system 50 also refer to FIG. 1B in the embodiment shown in FIG. 4. As described above, each channel frequency may be allocated. In addition, the donor unit DU may further include an error correction unit (see EC of FIG. 2) for correcting an error of the digital data converted as described above.

5 is a block diagram illustrating a mobile communication wireless relay device according to another embodiment of the present invention.

Although the mobile communication wireless relay apparatuses described above with reference to FIGS. 1A to 4 are disclosed in terms of forward signal relaying, this is merely to simplify the description, and the actual mobile communication wireless relay apparatus performs reverse signal relay from the mobile station to the base station. It may further include a signal processing circuit for. The signal processing circuit for reverse signal relay may be implemented symmetrically with components RX, TX for forward signal processing, as is well known in the art. The component for reverse signal processing also has a reception signal processing unit RX 'and a transmission signal processing unit TX'.

Referring to FIG. 5, the signal processing circuits RX 'and TX' for reverse signal relay may low-noise amplify and demodulate and reproduce a signal input from a mobile station counter antenna MA, and then modulate and output the signal to a base station. There will be. However, this is exemplary, and the signal processing circuit for the reverse signal relay low noise amplifies the RF signal received from the mobile station, gains it back to a predetermined output level, and simply filters by using a band filter having a high selectivity to transmit the signal. You could do it. The signal processing circuit for the reverse signal relay may adopt another configuration suitable for satisfying the required standard and ensuring ease of signal processing, but the present invention is not limited thereto.

The signal processing circuit for forward signal processing and the signal processing circuit for reverse signal processing may independently configure or share some signal processing circuits according to a frequency division duplex (FDD) or time division duplex (TDD) scheme. Since the TETRA radio standard defines the FDD scheme, in this case, a frequency filter (link duplexer) 70A and a service duplexer 70B may be combined and shared at both ends of the forward and reverse signal processing circuits. In some embodiments, the mobile communication wireless relay device 400 may be configured as a donor unit and a remote service unit with components separated from each other as indicated by a dotted line DL as described above with reference to FIG. 4.

6 is an image showing an output signal measured at the service unit side of a mobile communication wireless relay device according to an embodiment of the present invention.

The output signal was analyzed with a TETRA signal analyzer. The output signal displayed in the dotted rectangle DR of FIG. 6 is completely outputted through the service unit after the error components due to multipath fading and noise are completely removed and completely restored to the signal point of the base station without mixing between adjacent channel frequencies. Able to know.

The above-mentioned components, for example, a receiver, a signal processor, an error corrector, a converter, and a power amplifier may include a set of one or more codes that can be read and executed by a computer; Hardware such as a microprocessor, field programmable gate array (FPGA) or digital signal processor; Or as a set of codes and hardware. The signal processing method described above may likewise be implemented by a set of one or more codes, hardware or a set thereof that can be read and executed by a computer, at least some of which being stored on a computer readable storage medium. Can be. The above-described storage media is also an embodiment of the present invention, and the storage media may be other memory devices such as RAM, ROM, EEPROM, flash memory or phase change memory (PcRAM), CD-ROMs and DVDs. Optical or holographic media such as (DVD), magnetic tape, hard disk, solid state disk device (SSD), which are exemplary and may be other suitable recording media.

It is to be understood that the present invention is not limited to the above-described embodiments and the accompanying drawings, and that various substitutions, modifications, and changes can be made without departing from the spirit of the present invention, having ordinary skill in the art. It will be obvious to him.

Claims (8)

A receiver which receives a digital modulated wave transmitted from a base station;
A signal converter converting the received digital modulated wave into a baseband signal to reproduce digital data;
A modulator for modulating the reproduced digital data to generate a transmission signal; And
A power amplifier configured to amplify the transmission signal,
And a part of an output signal of the power amplifier is fed back to the input of the modulator so that the power amplifier is linearized. The method of claim 1,
And the feedback is performed by a Cartesian feedback loop. The method of claim 1,
The digital modulated wave has a plurality of channel frequencies,
And the modulator and the power amplifier are allocated for each of the plurality of channel frequencies. The method of claim 1,
And an error correcting unit configured to correct an error of the converted digital data between the signal converter and the modulator. The method of claim 1,
And the mobile communication wireless relay device complies with the digital TRS standard. Receiving a digital modulated wave transmitted from a base station;
Reproducing digital data by modulating the received digital modulated wave into a baseband signal;
Generating a transmission signal by modulating the reproduced digital data;
Amplifying the transmission signal to an output level; And
Linearizing the step of amplifying by feeding back a portion of the amplified transmission signal during the generation of the transmission signal. The method according to claim 6,
And said linearizing is performed by a Cartesian feedback loop. The method according to claim 6,
And after correcting the digital data, correcting an error of the digital data.

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