KR100537550B1 - Wide-band Transmission System and Signal Transmission Method In the System - Google Patents

Abstract

The present invention provides a broadband transmission system and a signal transmission method for reducing a time delay of a system by optically transmitting a signal by omitting a separate digital signal processing process in addition to a process of aligning a signal according to an optical transmission capacity at a transmitter. will be. In the broadband transmission system of the present invention, after converting an input analog signal into a digital signal, the transmission means for aligning and transmitting the converted digital data according to an optical transmission capacity and down-converting the digital data received from the transmission means. And receiving means for later filtering, interpolating, up-converting, and converting into analog data.

Description

Broadband Transmission System and Signal Transmission Method {Wide-band Transmission System and Signal Transmission Method In the System}

The present invention relates to a broadband transmission system and a signal transmission method, and more particularly, in order to reduce the efficiency and cost of the system configuration, the transmitting end directly transmits analog / digital converted digital data within the optical transmission capacity without exceeding the optical transmission capacity. In addition, the receiving end receives the filtering, and relates to a broadband transmission system and a signal transmission method suitable for implementing an optical distribution system for IMT-2000.

1 is a general configuration diagram of an optical dispersion system for IMT-2000 as a general broadband transmission system.

As shown in the figure, the forward direction receives a signal of 2GHz band from the base station 10, down-converts (Down Conversion) to the IF (Intermediate Frequency) band from the donor device 20 and converts it into a digital signal. After the signal processing and optical transmission to the remote device (30), the remote device (30) receives the optical conversion and signal processing, and then converted to the 2GHz band after the digital / analog conversion (Up Conversion) to the antenna Radiate.

In the reverse direction, the 1.9 GHz band signal from the terminal is transmitted to the base station 10 through the same process as the forward direction.

Since the optical transmission capacity between the donor device 20 and the remote device 30 is 2.5 Gbps, the capacity of each sector is limited to 600 Mbps.

FIG. 2 is a conventional configuration diagram of the donor device and remote device shown in FIG.

As shown in the figure, the donor device 20 converts an analog signal transmitted from the base station 10 into a digital signal in the analog / digital converter 21, and converts the digitally converted signal into a digital signal processor 22. Digital down-conversion to baseband I / Q (In-phase / Quadrature) signal, filter it, lower the data rate through decimation, and then send it to the remote device in the optical transmitter 23 Light transmission to 30 is made. In addition, the donor device 20 photoelectrically converts a signal transmitted from the remote device 30 to the optical receiver 24, and interpolates, filters, and digitally upstage the digital signal processor 25. After the conversion process, the digital-to-analog converter 26 converts the analog signal to the base station 10 for transmission.

In addition, the remote device 30 photoelectrically converts a signal transmitted from the donor device 20 to the optical receiver 31, and then performs interpolation, filtering, and digital up-conversion processing on the digital signal processor 32. The digital-to-analog converter 33 converts the analog signal and radiates it to the terminal through the antenna. The remote device 30 converts the analog signal received from the terminal through the antenna into a digital signal in the analog / digital converter 34, and digitally down-converts the digital signal in the digital signal processor 35. After the baseband I / Q signal is generated, the filter is filtered and decimated to transmit the light from the optical transmitter 36 to the donor device 20.

In this case, the digital signal processors 22, 25, 32, and 35 are generally implemented with a field programmable gate array (FPGA).

In the conventional donor device 20 and the remote device 30, the digital signal processors 22 and 35 at the transmitting end are configured as shown in FIG.

The signal input to the analog / digital converters 21 and 34 is an IF signal having a center frequency of 12.5 MHz. The analog / digital converters 21 and 34 convert the analog signal to a digital signal processor 22 or 35 at the transmitting end by analog-to-digital converting at a rate of 50 MHz. The digital signal processors 22 and 35 multiply the input digital signal with the frequency signal generated by the direct digital synthesizer (DDS) 41 in the mixers 42 and 43, respectively. After the digital down-conversion process is performed by separating the I component signal and the Q component signal, the processed I component signal and Q component signal are respectively filtered by the digital low pass filters 44 and 45. Here, when the I component signal (50 MHz) and the Q component signal (50 MHz) are multiplexed, the signal is 100 MHz. Therefore, it is necessary to reduce the data rate. Therefore, the decimators 46 and 47 pass the decimation signals of the I component signals and the Q component signals that have passed through the digital low pass filters 44 and 45, respectively, to reduce the data rate to 25 MHz. After the processing, the multiplexer 48 processes the I component signal and the Q component signal to have a data rate of 50 MHz, which is a transmission capacity. This signal is optically converted and transmitted to the donor device 20 when the transmitting end is the donor device 20, and transmitted to the donor device 20 when the transmitting end is the remote device 30.

4A to 4E show the frequency spectrum of the signal in the main part of the transmitter. That is, FIG. 4A is an analog signal waveform input to the digital / analog converters 21 and 34, FIG. 4B is a signal waveform after analog / digital conversion, and FIG. 4C is a signal waveform after downconversion to baseband. 4D is a signal waveform after passing through the low pass filter, and FIG. 4E is a signal waveform after decimation processing.

In the conventional donor device 20 and the remote device 30, the digital signal processor 32, 25 at the receiving end is configured as shown in FIG.

When the receiving end is the remote device 30, the optical signal transmitted from the donor device 20 is received, and when the receiving end is the donor device 20, the optical signal is received from the remote device 30. The digital signal processors 32 and 25 of the receiving end demultiplex the photoelectrically converted signal from the optical receiver in the demultiplexer 51 to separate the I component signal and the Q line signal and double each signal. After interpolation, the images are removed from the digital lowpass filters 54, 55 and multiplied by the frequencies coming from the direct digital synthesis (DDS) 56 in the mixers 57, 58. Thereafter, the I component signal and the Q component signal are synthesized by the adder 59 and subjected to upconversion processing, and then converted into an analog IF signal by the digital / analog converters 33 and 26.

6a to 6c show the frequency spectrum of the signal in the main part of the receiver. That is, FIG. 6A is a signal waveform after demultiplexing a received signal and performing double-interpolation, FIG. 6B is a signal waveform after passing a low pass filter, and FIG. 6C is a signal waveform after passing a mixer and an adder.

As described above, the same spectrum of the signal as the input to the transmitting end can be obtained at the output of the receiving end.

However, since the conventional technology uses a decimation filter at the transmitting end, as shown in the system configuration and the donor device / remote device description, the image signal approached by the decimation process is removed. The receiver must remove the image using a high tap interpolation filter. As a result, this increases the time delay of the overall system, which has a detrimental effect on the hand-off with neighboring base stations or repeaters. Accordingly, the distance between the donor device and the remote device is inevitably shortened. It also presents difficulties in cell planning.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in addition to the process of aligning the signal to the optical transmission capacity at the transmitting end, the optical signal is transmitted by omitting a separate digital signal processing process, thereby reducing the time delay of the system. It is an object of the present invention to provide a broadband transmission system and a signal transmission method.

In order to achieve the above object, a wideband transmission system according to a preferred embodiment of the present invention comprises: transmitting means for converting an input analog signal into a digital signal and then aligning and transmitting the converted digital data according to an optical transmission capacity; ; It characterized in that it comprises a receiving means for converting the digital data received from the transmission means after the down-conversion processing, filtering, interpolation processing, up-conversion and then converted into analog data.

In order to achieve the above object, the broadband transmission system according to the present invention is a broadband transmission system for signal relay between a base station and a mobile station, and after converting an analog signal input from the base station into a digital signal, Transmitting means for aligning and transmitting digital data to optical transmission capacity, down-converting, filtering and interpolating digital data received from the following remote device, up-converting and converting to analog data A donor device including a receiving means for transmitting; Receiving means for down-converting the digital data received from the donor device, filtering, interpolating, up-converting, converting the analog data, and transmitting the analog data to the mobile station, and converting the analog signal input from the mobile station into a digital signal. And converting the converted digital data according to the optical transmission capacity and transmitting the converted digital data to the donor device.

Here, the transmitting means includes an analog / digital converter for converting an input IF analog signal into a digital signal, a bypass unit for aligning the converted digital signal according to an optical transmission capacity, and the aligned single. And an optical transmitter for converting and transmitting digital signals into optical signals.

The receiving unit may include: a down conversion processing unit for digitally down converting the single digital signal input by multiplying the frequency signal generated by the first digital synthesizer by two mixers and separating the baseband I component signal and the Q component signal; A digital low pass filter for removing an image signal included in the processed I component signal and Q component signal; An interpolator for performing double interpolation processing on the I component signal and the Q component signal which have passed through the digital low pass filter; A digital low pass filter for filtering again the I component signal and the Q component signal that have passed through the interpolator; An up-conversion processing unit for multiplying the filtered I component signal and the Q component signal by the two mixers and the frequency signal generated by the second digital synthesizer, respectively, and then synthesizing these two signal components; And a digital / analog converter for converting the up-converted digital signal into an analog signal to restore the IF signal.

In addition, the signal transmission method according to the present invention in order to achieve the above object, in the signal transmission method in a broadband transmission system, after converting the input analog signal to a digital signal and converts the converted digital data into an optical transmission capacity A first step of aligning and transmitting accordingly; And a second step of receiving the digital data transmitted in the first step, performing down-conversion processing, filtering, interpolating, filtering and up-converting again, and converting the analog data into analog data.

Hereinafter, a broadband transmission system and a signal transmission method according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

7 is a configuration diagram of a donor device and a remote device in an optical dispersion system for IMT-2000 as a broadband transmission system according to the present invention.

As shown in the figure, the donor device 20A converts an analog signal transmitted from the base station 10 into a digital signal in the analog / digital converter 21, and aligns the digital converted signal with the optical transmission capacity. In addition to the processing, the signal is directly transmitted to the optical transmitter 23 through the bypass unit 22A without any signal processing, and the optical transmitter 23 receives the optical transmission from the optical transmitter 23 to the remote device 30A. The donor device 20A photoelectrically converts a signal transmitted from the remote device 30A (ie, a signal bypassed without a separate digital signal processing as described above) in the optical receiver 24, and After digital down-conversion in the digital signal processor 25A to form a baseband I / Q (In-phase / Quadrature) signal, it is filtered, interpolated, and then filtered and digital up-converted. In step 26), the signal is converted into an analog signal and transmitted to the base station 10.

In addition, the remote device 30A photoelectrically converts the signal transmitted from the donor device 20A (that is, the signal bypassed without separate digital signal processing as described above) in the optical receiver 31, and digitally converts it. After digital down-conversion by the signal processor 32A to make a baseband I / Q signal, filtering and interpolating it, performing filtering and digital up-conversion again, and converting the analog-to-analog signal by the digital-to-analog converter 33 Radiate to the terminal side through the antenna. The remote device 30A converts the analog signal from the terminal received through the antenna into a digital signal in the analog / digital converter 34, and aligns the digital converted signal with the optical transmission capacity. As it is directly transmitted to the optical transmitter 36 through the bypass unit 35A without additional signal processing, the optical transmitter 36 transmits the light to the donor device 20A.

In the donor device 20A and the remote device 30A according to the present invention, the transmitting end (forward and backward) is configured as shown in FIG. Here, the bypass units 22A and 35A may be configured as FPGAs, and serve only to align the digital data converted by the analog / digital converters 21 and 34 according to the optical transmission capacity.

For example, if the resolution bit of the analog-to-digital converters 21 and 34 is 14 bits and the sampling frequency is 50 MHz, the data rate is 700 Mbps, so that the optical transmission rate per sector is increased. Is exceeded. Therefore, it converts it into 12bit and makes 600Mbps. This applies to forward processing of donor device 20A and reverse processing of remote device 30A, respectively.

The signal waveform passing through the bypass units 22A and 35A is the same as in FIG. 4B.

On the other hand, in the donor device 20A and the remote device 30A according to the present invention, the receiving end (forward and backward) is configured as shown in FIG.

As shown in Fig. 9, it can be seen that a part of the transmitting end in the prior art has moved to the receiving end of the present invention (i.e., the downker version blocks 60, 61, 62 and the low pass filters 63, 64). ].

If the receiving end is the remote device 30A, the optical signal transmitted from the donor device 20A is received. If the receiving end is the donor device 20A, the optical signal is received from the remote device 30A.

The signal which is photoelectrically converted and input to the digital signal processor 32A or 25A of the receiving end is a single 12-bit signal having a rate of 50 MHz, and the digital signal processor 32A or 25A is a single input signal. Is multiplied by the frequency signal generated by the direct digital synthesizer (DDS) 60 in the mixers 61 and 62 to digital downconvert to separate the baseband I component signal and the Q component signal, and then process the The I component signal and the Q component signal are removed from the digital low pass filters 63 and 64, respectively. Thereafter, the signals passing through the digital low pass filters 63 and 64 are twice interpolated by the interpolators 65 and 66, and then filtered by the low pass filters 67 and 68 again. The frequency interval between the baseband signal of the component and the Q component and the image signal is further increased. Subsequently, the signal passing through the low pass filters 67 and 68 is multiplied by the frequency coming from the direct digital synthesis (DDS) 69 in the mixers 70 and 71, and then the I component signal and the Q component signal are added. 72, up-conversion is performed, and then the digital / analog converters 33 and 26 convert the analog IF signals.

As described above, since the decimation process is not performed at the transmitting end of the present invention, the distance between the image signals is not close at the receiving end so that the number of taps of the interpolation filter can be reduced. This can significantly reduce hardware size and system time delay than in the prior art.

10A to 10E show the frequency spectrum of the signal in the main part of the receiving end of the present invention described above. That is, FIG. 10A is a signal waveform input to the digital signal processors 32A and 25A, FIG. 10B is a baseband I component and Q component signal waveform with the input signal down-converted, and FIG. 10C is a low pass filter. 10D is a signal waveform after passing the low pass filter again after interpolation processing, and FIG. 10E is a signal waveform after up-conversion processing.

The receiving end of the system of the present invention lowered the frequency of the first DDS (60) to the baseband using 12.5MHz, and raised the frequency of the second DDS (69) to the IF band using 25MHz.

The final output of the digital / analog converter 33, 26 is shown in FIG. 10E, with signals at 25 MHz, 75 MHz, and so forth. However, it is important to note that the signal at 25 MHz and the signal at 75 MHz are out of phase in the waveform after upconversion. Therefore, either 25MHz or 75MHz should be used, and using a 25MHz signal at the RF interface is complicated because it requires the use of a double conversion and a SAW filter on an RF board. However, using signals above 100 MHz degrades the waveform quality a lot, so it is best to use a 75 MHz signal. Therefore, if the I component + Q component is applied at the rear end of the second mixers 70 and 71, that is, the I / Q summing, the 75 MHz phase becomes the same as that of the input signal. Will be.

On the other hand, the present invention is not limited to the above-described typical preferred embodiments, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions are common in the art Those who have knowledge will easily understand. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

As described in detail above, according to the present invention, the time delay of the overall system can be reduced, so that the remote device can be located at a greater distance, thereby facilitating cell planning, and smooth handing with the adjacent base station or repeater. It is possible to provide a handoff. In addition, since the analog SAW filter is not used, the waveform quality does not deteriorate, and many things that were performed in the existing analog are performed digitally so that there is no deterioration due to changes in the environment. As there is no change in characteristics due to Aging, it will play a part in establishing 3G mobile communication network.

1 is a conceptual diagram of a configuration of an optical dispersion system as a general broadband transmission system.

2 is a conventional configuration diagram of a donor device and a remote device shown in FIG. 1;

FIG. 3 is a block diagram illustrating the transmitting end of the donor device and the remote device shown in FIG. 2; FIG.

4A to 4E are signal waveform diagrams in the main part of the transmitting end shown in FIG.

FIG. 5 is a configuration diagram of a receiving end of the donor device and the remote device shown in FIG. 2; FIG.

6A to 6E are signal waveform diagrams of main parts of the receiving end shown in FIG.

7 is a block diagram of a broadband transmission system according to the present invention.

8 is a block diagram of a donor device and a remote device according to the present invention.

9 is a block diagram of the receiving end of the donor device and the remote device according to the present invention.

10A to 10E are signal waveform diagrams of main parts of the receiving end shown in Fig. 9;

※ Explanation of code for main part of drawing

10: base station 20,20A: donor device

21: analog / digital converter 22: digital signal processor

22A: Bypass Unit 23: Optical Transmitter

24: optical receiver 25: digital signal processor

26: digital / analog converter 30,30A: remote device

31: optical receiver 32: digital signal processor

33: digital / analog converter 34: analog / digital converter

35: digital signal processor 35A: bypass unit

36: optical transmitter 41: direct digital synthesizer

42,43: Mixer 44,45: Digital Low Pass Filter

46,47: Decimator 48: Multiplexer

51 demultiplexer 52,53 interpolator

54,55: digital lowpass filter 56: direct digital synthesizer

57,58: mixer 59: adder

61,62: Mixer 60: Direct Digital Synthesizer

63,64: digital lowpass filter 65,66: interpolator

67,68: Digital Low Pass Filter 69: Direct Digital Synthesizer

70,71 Mixer 72: adder

Claims (8)

delete A broadband transmission system for signal relay between a base station and a mobile station, After converting the analog signal input from the base station into a digital signal, the transmission means for aligning and transmitting the converted digital data according to the optical transmission capacity, and the digital data received from the following remote device after down-conversion processing and filtering A donor device including receiving means for performing interpolation, upconverting, converting the analog data, and transmitting the same to the base station; Receiving means for down-converting the digital data received from the donor device, filtering, interpolating, up-converting, converting the analog data, and transmitting the analog data to the mobile station, and converting the analog signal input from the mobile station into a digital signal. And a remote unit including transmission means for transmitting the converted digital data to the donor device after the conversion by aligning the converted digital data to an optical transmission capacity. The method of claim 2, And said receiving means performs double conversion on said digital data, and then performs filtering again and then up-converts. The method of claim 2, The transmitting means, An analog / digital converter for converting an input IF analog signal into a digital signal; Bypass unit for aligning the converted digital signal to the optical transmission capacity, And an optical transmitter for converting the aligned single digital signal into an optical signal and transmitting the optical signal. The method of claim 4, wherein And if the resolution bit of the analog / digital converter is 14 bits and the sampling frequency is 50 MHz, the bypass unit converts the 14 bit digital signal into 12 bits. The method of claim 3, wherein The receiving means, A down-conversion processing unit for multiplying an input single digital signal by a frequency signal generated by a first digital synthesizer in two mixers, separating the baseband I component signal and Q component signal, and digitally down converting the digital signal; A digital low pass filter for removing an image signal included in the processed I component signal and Q component signal; An interpolator for performing double interpolation processing on the I component signal and the Q component signal which have passed through the digital low pass filter; A digital low pass filter for filtering again the I component signal and the Q component signal that have passed through the interpolator; An up-conversion processing unit for multiplying the filtered I component signal and the Q component signal by the two mixers and the frequency signal generated by the second digital synthesizer, respectively, and then synthesizing these two signal components; And a digital / analog converter converting the up-converted digital signal into an analog signal to restore an IF signal. The method of claim 6, And a signal frequency generated by the first digital synthesizer is 12.5 MHz, and a signal frequency generated by the second digital synthesizer is 25 MHz. delete