KR20030060675A - Transmitter in multi-carrier communications system and signal transmitting method thereby - Google Patents

Abstract

PURPOSE: A transmitter of a multicarrier communication system and a signal transmitting method thereby are provided to support carriers according to various communication methods using a TRXA and reduce the number of TRXAs. CONSTITUTION: A channel combiner(310) divides an input bit row for transmission into channel signals having different frequency bands corresponding to the number of carriers. The channel combiner(310) combines the channel signals with each other and outputs a digital signal. A digital/analog converter(320) converts the digital signal from the channel combiner(310) into an analog signal. A modulator block(330) modulates the analog signal from the digital/analog converter(320) into a high frequency signal according to an oscillating frequency by carriers and outputs the modulated signal. The channel combiner(310) includes a plurality of filters(311,312,313), a plurality of frequency synthesizers(314,315), an adder(317), and an oscillator(316).

Description

Transmitter of Multicarrier Communication System and Signal Transmission Method {TRANSMITTER IN MULTI-CARRIER COMMUNICATIONS SYSTEM AND SIGNAL TRANSMITTING METHOD THEREBY}

The present invention relates to a transmitter of a mobile communication system, and more particularly, to a transmitter for use in a multicarrier communication system and a signal transmission method by the transmitter.

A mobile communication system based on a code division multiple access (CDMA) scheme, which is a typical mobile communication system, includes a mobile switching center (MSC), a base station system (BSS), and a terminal (or mobile station). (MS: Mobile Station). The base station system includes a base station controller (BSC) and a base station transceiver system (BTS), which are connected to each other by wire. The base station system wirelessly communicates with the mobile station, and is connected to a public switched telephone network (PSTN) by wire to enable communication between the mobile station and the public switched telephone network.

The mobile communication system may be classified into a digital cellular system (DCS), a personal communications system (PCS), an international mobile telecommunication 2000 (IMT-2000) system, and the like according to the scheme. These mobile communication systems can be classified into various criteria. Typically, the mobile communication systems may be classified into transmission frequency bands. For example, DCS is a method of allocating 869 to 894 MHz as a transmission frequency band, PCS is a method of allocating 1840 to 1870 MHz as a transmission frequency band, and the IMT-2000 system uses 2110 to 2170 MHz of a transmission frequency band. This is a method of assigning and using.

In the meantime, the base station system considers a type that supports only one communication method, but the recent base station system considers a type that supports various communication methods. In order to revive this trend, a transceiver block (eg, a TRXA (Transceiver) block) of a base station must be designed to support frequency allocation (FA) according to each communication scheme. The base station may be simply designed to include all of the transceiver blocks supporting the respective communication schemes.

However, it cannot be said that this design approach is very inefficient. This is because, each time the number of FA increases, a new transmission path must be additionally increased, and thus the number of TRXA blocks must increase. In addition, different TRXA blocks are required depending on the service providers as the frequency bands serviced by the mobile communication service providers are different.

Accordingly, an object of the present invention is to provide a transmitter and a signal transmission method of the multicarrier communication system supporting carriers according to various communication schemes.

Another object of the present invention is to provide a transmitter and a signal transmission method by which a base station of a mobile communication system can support an allocated frequency band according to various communication schemes by one transmitter block.

The transmitter of the multicarrier communication system according to the present invention for achieving these objects includes a channel combiner. The channel combiner separates the input bit string for transmission into channel signals having different frequency bands corresponding to the number of carriers, and combines the separated channel signals to output the digital signals. A digital to analog converter converts the digital signal into an analog signal. The modulator block directly converts the analog signal into a signal of a high frequency band according to a preset carrier-specific oscillation frequency and outputs a modulated signal for transmission.

Advantageously, the channel combiner comprises: a plurality of filters corresponding to the number of carriers and finite field impulse response (FIR) filtering the input bit stream, and the bit stream filtered by the respective filters in the carrier; A plurality of frequency mixers that mix according to one less than the number of channel frequency signals and generate the channel signals corresponding to the number of carriers, and a summer that sums the channel signals and generates the combined digital signal. Include. The channel combiner further comprises an oscillator for oscillating signals of the channel frequency. The signals at the channel frequency are exponential signals. And an interpolator connected between the channel combiner and the digital to analog converter, for interpolating the digital signal and providing the digital signal to the digital to analog converter.

Preferably, the modulator block, the oscillator for generating the set frequency of the carrier-specific carrier, and converts the analog signal directly into a signal of a high frequency band according to the set frequency of the carrier-specific carrier and outputs the modulated signal for transmission Includes a direct converter.

The signal transmission method of the multicarrier communication system according to the present invention comprises the steps of: separating the input bit stream for transmission into channel signals having different frequency bands corresponding to the number of carriers; Outputting a digital signal, converting the digital signal into an analog signal, directly converting the analog signal into a signal of a high frequency band according to a preset oscillation frequency for each carrier, and outputting a modulated signal for transmission It includes.

Advantageously, said separating comprises: filtering said input bit string by a plurality of finite field response (FIR) filters corresponding to the number of carriers, and filtering said bit string filtered by said respective filters. Mixing according to one less channel frequency signals than the number of carriers and generating the channel signals corresponding to the number of carriers. The signals at the channel frequency are exponential signals. And interpolating the digital signal to provide the digital signal for conversion to the analog signal.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that those skilled in the art may better understand the detailed description of the invention that follows.

Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. Those skilled in the art should recognize that the disclosed concepts and specific embodiments of the invention may be readily used as a basis for modifying or designing other structures for achieving the same purposes of the present invention. Those skilled in the art should also recognize that structures equivalent to the invention do not depart from the spirit and scope of the broadest form of the invention.

1 is a diagram illustrating a transmitter configuration of a general mobile communication system.

2 illustrates a transmitter configuration of a multicarrier communication system according to an embodiment of the present invention.

3 is a block diagram illustrating a specific block configuration of a TX RF CIRCUIT shown in FIG. 2.

4 is a diagram illustrating the frequency characteristics of a signal input to the digital channel combiner (DCC) shown in FIG.

FIG. 5 is a diagram showing frequency characteristics of a signal output from the digital channel combiner shown in FIG. 2; FIG.

FIG. 6 is a diagram showing frequency characteristics of a signal output from a modulator shown in FIG. 2; FIG.

DETAILED DESCRIPTION A detailed description of preferred embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that reference numerals and like elements among the drawings are denoted by the same reference numerals and symbols as much as possible even though they are shown in different drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

First, prior to describing the embodiment of the present invention in detail, the terms to be described below are summarized in Table 1 below.

DU: DIGITAL UNITIFDA: INTERMEDIATE FEQUENCY DIGITAL ASSEMBLYRFU: RADIO FREQUENCY UNITTRXA: TRANSCEIVERHPA: HIGH POWER AMPLIFIERAFEB: ANTENNA FRONT END BLOCKDCC: DIGITAL CHANNEL COMBINERFIR: FINITE IMPULSE LOCAL CONTROL

Hereinafter, the multicarrier communication system according to an embodiment of the present invention will be described in the form of supporting three communication schemes (DCS, PCS, and IMT-2000). However, it should be noted that the present invention is not limited to this embodiment. That is, the embodiment of the present invention is a structure that can accommodate three carriers in one TRXA transmission path, and the frequency band to use up to the frequency of DCS, PCS, IMT2000 from 800MHz to 2170MHZ without replacing TRXA It can be implemented by one transmitter.

1 is a diagram illustrating a transmitter configuration of a general mobile communication system to which the present invention is applied.

Referring to FIG. 1, a transmitter includes a digital unit 100, a radio frequency unit 200, and an antenna.

The RFU 200 is a part of a base station. The RFU 200 is a device for performing a wireless connection between a digital unit (DU) 100 and a mobile station through forward and reverse links. The RFU 200 includes a transceiver unit (TRXA: Transceiver) 300, a high power amplifier (HPA) 400, an antenna connection unit (AFEB: Antenna Front End Block) 500, and a base station test unit (BTU: BS Test Unit) ( Not shown). The main function of the transceiver unit (TRXA) 300 is to up-convert an intermediate frequency (IF) signal from an intermediate frequency digital assembly (IFDA) 110 of the DU 100 to an ultra high frequency (UHF) signal. Conversely, down-conversion of the UHF signal to the IF signal. The forward link passes from the transceiver section 300 through the transmit high power amplifier 400 and the antenna connection 500 and finally connects to the transmit antenna. The reverse link starts from the receiving antenna, passes through the antenna connection unit 500, and is down-converted into the IF signal by the transceiver unit 300 and input to the DU 100.

2 is a diagram illustrating a transmitter configuration of a multicarrier communication system according to an exemplary embodiment of the present invention. This transmitter corresponds to the digital transmitter included in the TRXA 300 shown in FIG. 1.

Referring to FIG. 2, the overall structure of the digital transmitter is composed of a digital processing circuit block, a modulator circuit block, and a transmit high frequency circuit block. The digital processing circuit block includes a digital channel combiner (DCC) 310 and a two-channel interpolating digital-to-analog converter (IDAC) 320.

The DCC 310 includes finite impulse response (FIR) filters 311 to 313, frequency mixers 314 and 315, a digital local oscillator 316 and a summer 317. do. The DCC 310 separates an input bit stream for transmission into channel signals having different frequency bands corresponding to the number of carriers, and combines the separated channel signals and outputs them as digital signals. Here, the number of carriers will be described as three. The finite impulse response (FIR) filters 311 to 313 of the DCC 310 correspond to the number of carriers 3 and FIR filter the input bit stream. The frequency mixers 314 and 315 mix the bit strings filtered by the respective filters 311 to 313 according to the number 2 channel frequency signals, one less than the number 3 of the carriers. The signals of the channel frequency are oscillated by oscillator 316. At this time, the signals of the channel frequency are exponential signals {exp (jωt), exp (-jωt)}. The signals of the channel frequency can be rejected by the oscillator 316 by generating the exponential functions exp (jωt) and exp (-jωt) rather than the cosine function. have. Operation of the frequency mixers 314,315 generates channel signals corresponding to the number three of the carriers. Here, the three channel signals refer to two signals having the center frequencies -fo and fo by the frequency mixers 314 and 315, respectively, and a signal having the center frequency 0 output directly from the FIR filter 312. The summer 317 sums the generated channel signals and generates a combined digital signal. Each component of the DCC 310 processes both an I component signal and a Q component signal in processing the signals. However, it should be noted that for convenience of explanation, the description is uniformly described as a signal. In addition, all the functions performed by the components of the DCC 310 may be implemented by a FPGA (Format Programmable Gate Array).

The IDAC 320 includes an interpolator 321 for inserting a signal and DACs 324 and 325 for digitally / analog converting input I and Q signals, respectively. The interpolator 321 consists of FIR filters 322, 323. That is, the interpolator 321 is interpolated as 2 × FIR filter 322 and 3 × FIR filter 323. In the bandwidth of 1.2288 MHz, a sampling rate of 4.9152 MHz is used. Since the total 6 times of interpolation is performed by the FIR filters 322 and 323, a signal having a sampling rate of 29.4912 MHz is input to the DACs 324 and 325. . As a result, aliasing between sampling bandwidths does not occur.

The modulator block 330 includes a direct converter 331 and a transmitting local oscillator 332. The modulator block 330 directly converts the analog signal from the IDAC 320 into a signal of an RF band according to the carrier-specific oscillation frequency generated by the oscillator 332, and outputs the modulated signal for transmission. In the modulator block 330, a direct conversion operation may be performed using RF local oscillation signals (869 to 894 MHz and 1810 to 2170 MHz) for each carrier for each of the I and Q signals having a center frequency of -fo, 0, and fo. At this time, the RF local oscillation signal for each carrier may be generated in the form of 869 to 894 MHz (for DCS), 1840 to 1870 MHz (for PCS), and 2110 to 2170 MHz (for IMT-2000).

The transmit high frequency circuit block 340 is configured as shown in FIG. Referring to FIG. 3, the transmission high frequency circuit block 340 is divided into transmission paths (Path 1, Path 2, Path 3) for processing the transmission high frequency signals from the modulator block 330 corresponding to each carrier for each carrier. Lose. The transmission path Path 1 is a transmission path for the DCS, the transmission path Path 2 is a transmission path for the PCS, and the transmission path Path 3 is a transmission path for the IMT-2000.

The transmit high frequency circuit block 340 consists of a signal divider 341, filters 342, 344, 346, amplifiers 343, 345, 347 and a combiner 348. The splitter 341 provides the directly converted signal from the modulator block 330 to a corresponding transmission path for each carrier. In each of the transmission paths, the filtering operation by the filters 342, 344 and 346 and the amplification operation by the amplifiers 343, 345 and 347 are performed. The combiner 348 combines the high frequency transmission signals filtered and amplified in each transmission path and outputs the combined high frequency transmission signals to the HPA 400 illustrated in FIG. 1.

4 is a diagram illustrating a frequency characteristic of a signal input to the digital channel combiner 310 illustrated in FIG. 2, and FIG. 5 is a diagram illustrating a frequency characteristic of a signal output from the digital channel combiner 310 illustrated in FIG. 2. . 4 and 5, the bit string input to the DCC 310 has a center frequency of 0, but the bit string output from the DCC 310 is divided into bands of frequencies corresponding to the number 3 of carriers. Able to know. That is, it can be seen that channel signals having a center frequency of -fo, 0 and fo occur.

FIG. 6 is a diagram illustrating frequency characteristics of a signal output from a modulator block 330 shown in FIG. 2. Referring to FIG. 6, it can be seen that the high frequency signal for transmission is carried on the carrier frequency f1, f2, f3. That is, one transmitter enables transmission of high frequency signals corresponding to three carriers.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention implements a transmitter of a multi-carrier TRXA covering all mobile communication service bands currently in service in preparation for SDR (Software Definable Radio). The present invention can reduce the number of TRXA by simply using the TRXA to accommodate the multi-carrier in the base station of the mobile communication system, it is possible to simply implement the base station, the cost reduction effect by using a single TRXA for all frequency service bands There is an advantage to that.

Claims (10)

In the transmitter of a multicarrier communication system, A channel combiner for dividing an input bit string for transmission into channel signals having different frequency bands corresponding to the number of carriers, combining the separated channel signals, and outputting them as digital signals; A digital / analog converter for converting the digital signal into an analog signal; And a modulator block for directly converting the analog signal into a signal of a high frequency band according to a preset oscillation frequency for each carrier and outputting a modulated signal for transmission. The method of claim 1, wherein the channel combiner, A plurality of filters corresponding to the number of carriers and filtering the input bit stream with a finite field impulse response (FIR); A plurality of frequency mixers for mixing the bit stream filtered by the filters according to one less channel frequency signals than the number of carriers and generating the channel signals corresponding to the number of carriers; And a summer for summing the channel signals and generating the combined digital signal. 3. The transmitter of claim 2, further comprising an oscillator for oscillating signals of the channel frequency. 3. The transmitter as claimed in claim 2, wherein the signals of the channel frequency are exponential signals. The transmitter of claim 1, further comprising an interpolator connected between the channel combiner and the digital-to-analog converter and interpolating the digital signal to provide the digital-to-analog converter. The method of claim 1, wherein the modulator block, An oscillator for generating the set oscillation frequency for each carrier; And a direct converter for directly converting the analog signal into a signal of a high frequency band according to the oscillation frequency for each carrier and outputting a modulated signal for transmission. In the signal transmission method of a multicarrier communication system, Dividing an input bit string for transmission into channel signals having different frequency bands corresponding to the number of carriers, Combining the separated channel signals and outputting the digital signals; Converting the digital signal into an analog signal; And directly converting the analog signal into a signal of a high frequency band according to a preset oscillation frequency for each carrier and outputting a modulated signal for transmission. The method of claim 7, wherein the separating process, Filtering the input bit string by a plurality of finite field response (FIR) filters corresponding to the number of carriers; Mixing the bit stream filtered by the filters according to one less channel frequency signals than the number of carriers and generating the channel signals corresponding to the number of carriers. Way. 9. The method of claim 8, wherein the signals of the channel frequency are exponential signals. 8. The method of claim 7, further comprising interpolating the digital signal and providing the analog signal for conversion into the analog signal.