KR20030040778A - A bandwidth efficient modulation method for transmitting 155Mbps baseband data signals in 50 MHz RF bandwidth - Google Patents

Abstract

PURPOSE: A modulation system is provided to be capable of transmitting a 155Mbps baseband signal using 50MHz band. CONSTITUTION: A plurality of serial to parallel modulation converters(100) perform a serial-parallel conversion operation of a 155Mbps input signal. A buffer part(200) temporally stores output signals of the serial to parallel converters by a data size of a predetermined frame. A modulation part(300) multiplies an orthogonal code with each signal from the buffer part, groups output signals by a predetermined number and performs an SSB(Single SideBnad) filtering of grouped signals so as to be modulated to a radio signal below a 50Mbps.

Description

A bandwidth efficient modulation method for transmitting 155 megabits baseband signal using a 50 MHz band and a system therefor {A bandwidth efficient modulation method for transmitting 155 Mbps baseband data signals in 50 MHz RF bandwidth}

The present invention relates to a band modulation method and a modulation system for transmitting 155 Mbps baseband data signal wirelessly in a 50 MHz band.

Recently, as the exchange of data between individuals or groups through computer communication and mobile communication has rapidly increased, the amount of data to be processed is increasing exponentially. As e-commerce and wireless Internet are activated in the future, more data will need to be processed. One of the data processing speeds for processing such data at high speed is 155 Mbps. Currently, these data rates are possible with wired networks, but they are very difficult to process with wireless networks.

The reason for this is that not only is it difficult to obtain a wide-band license such as 155 MHz in the spectrum, but also a hardware system that can handle data of 155 MHz or 155 Mbps is not easy.

However, if there is an available band of 50 MHz in the 23 GHz band and can transmit 155 Mbps signals in the 50 MHz band, it is very useful to use these bands when radio transmission is required rather than wired in mountainous areas such as Korea. will be.

As a conventional method, a modulation method called quadrature amplitude modulation (QAM) may be used. However, this method requires an expensive power amplifier with good performance because the output level of the signal is constantly changing, and the cost of the system hardware is very high because the receiver must judge the signal of multiple levels rather than the general binary signal level. There is a problem of getting expensive.

The present invention has been made to solve such a problem, and when a high-speed data signal of 155 Mbps is to be transmitted wirelessly in a 50 MHz band, the 50 MHz band can be used to transmit a high speed signal in a small band in consideration of the efficiency of the frequency band. A band modulation method for transmitting a 155 Mbps baseband signal is provided to provide a modulation system thereof.

1 is a configuration block diagram of a modulation system for bandwidth efficient modulation according to the present invention.

FIG. 2 is a detailed block diagram of a modulator shown in FIG. 1; FIG.

3 is an exemplary diagram of spectral forms in a transmission step after a modulation process in accordance with the present invention.

4 is an operational flow diagram for performing bandwidth modulation in accordance with the present invention.

<Description of the symbols for the main parts of the drawings>

100: serial-parallel conversion unit 200: buffer unit

300: modulator 310: multiplier

320: D / A converter 330: adder

340: carrier modulator 350: adder

360: SSB filter 370: Adder

In order to achieve the above object, the present invention uses a small orthogonal code, carrier orthogonality, spectral symmetry, and the like to transmit a signal having a band of 155 MHz within a 50 MHz band at an economical cost. do.

According to one aspect of the modulation system according to the present invention, in the modulation system for modulating the baseband signal of 155Mbps, a plurality of serial-to-parallel conversion unit for serial-parallel conversion of the 155Mbps input signal and a serial-to-parallel conversion unit Multiplying orthogonal codes for each signal outputted from the buffer section by temporarily buffering each signal divided by and converted in parallel to a data size of a predetermined frame, and grouping the output signals by a predetermined number And a modulator for performing SSB filtering on each grouped signal to modulate the radio signal band of 50 Mbps.

In addition, according to one aspect of a band modulation method for transmitting a 155 Mbps baseband signal using a 50 MHz band according to the present invention, in the method for modulating a 155 Mbps baseband signal, serial-to-parallel conversion of a 155 Mbps input signal Reducing the processing speed by dividing the signal into a plurality of signals, buffering each of the divided and parallel-converted signals to a predetermined size, and processing a signal using an orthogonal code for each of the signals buffered to a certain size. Increasing the speed, grouping the output signal by a predetermined number, and performing SSB filtering on each grouped signal to perform modulation to a 50Mbps wireless signal band.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

1 is a block diagram of a modulation system according to the present invention.

Referring to FIG. 1, a serial-parallel conversion unit 100 for serial-parallel conversion of an input signal of 155 Mbps, a buffer unit 200 temporarily storing signals converted in parallel through the serial-parallel conversion unit 100, and The modulation unit 300 is configured to perform modulation for transmitting a signal stored in the buffer unit in the 50 MHz band.

High-speed data of 155 Mbps is first converted by the serial-to-parallel converter 100. The number of parallel paths by the serial-parallel converter can be any number. The reason for dividing the paths is to reduce the speed. The higher the data speed, the wider bandwidth is required. That is, a signal of 155 Mbps in the time domain requires a signal bandwidth of 155 MHz in the frequency domain. Since the given bandwidth is 50 MHz, it cannot pass a signal of 155 MHz.

Here, 16 is described as an example. That is, as described below, it is preferable to use a quadrature orthogonal code when divided into 16 paths, and if it is divided into 32 paths, it is preferable to use an orthogonal code of eighth order. One buffer (for example, 211a) for temporarily storing a signal exists, and data of a certain length is stored in each buffer, for example, a data signal of one frame length may be stored. Currently in Synchronous Transfer Mode (STM), 14990 bits make up a frame and are 125 x 10 ^-6 seconds (sec) in time.

The data rate is slowed down by the number of buffers and thus the bandwidth. The 155 Mbps signal is exactly 155.52 Mbps. When the signal is divided into 16 paths, the data rate in each path is 155.52 Mbps / 16 = 9.72 Mbps.

Each path is considered a group of four paths. These four bundles are referred to as small bundles 211, 212, 221, and 222, and two bundles of four, that is, eight bundles, are referred to as large bundles 210 and 220. The four groups of 16 paths are grouped to apply orthogonal codes, such as four-dimensional Walsh or Hadamard codes, to each path. Since there are 16 paths in all, four-dimensional orthogonal codes are applied to each small bundle at the same time. The signals stored in each buffer are transferred to the modulator 300 at the same time when all data is input to the 16 buffers to start the modulation process.

2 is a detailed block diagram of the modulator 300 illustrated in FIG. 1. A detailed configuration and operation of the modulation block will be described with reference to FIG. 2.

As shown in FIG. 2, the modulation block according to the present invention includes a multiplier 310 for multiplying a signal output from the buffer by an orthogonal code, and a D / A converter for D / A converting the output signal of the multiplier 310. 320, an adder 330 that collects signals from parallel branches into one, a carrier modulator 340 capable of shifting a band of signals to a required radio band, and an adder that gathers output signals of the carrier modulator 340 into one; 350, an SSB filter 360 for removing one of the symmetrical signal spectra, and an adder 370 for adding the signal of the SSB filter 360.

Orthogonal code through a multiplier (311, 312, 313, 314) to multiply the four-dimensional orthogonal code consisting of four symbols to each data symbol when it is input to the modulator 300 for the signal output from each buffer 200 Is multiplied. An example of an orthogonal code may be a Walsh code. This results in a data throughput rate of 9.72 Mbps × 4 = 38.88 Mbps.

Accordingly, the data processing speed is improved, and the data is converted into an analog signal form through the D / A converter 320, and the four analog signals forming one small bundle are added by one adder 330. Is added. That is, the signals of 16 paths are added to each of four smaller bundles. Thus, there are four adders for all 16 paths.

The output signals from the four adders 330 are modulated by the carrier in the modulator 340. The carriers multiplied by these four signals are all different. An example of the method is as follows. The signals in the small batch are added by one adder, so there are four adder output signals, cos w ₁ t (341) for the _first adder output signal, sin w ₁ t (342) for the second adder output signal, and third Cos w ₂ t (343) is added to the adder output signal, and sin w ₂ t (344) is multiplied to the fourth adder output signal.

Since the cosine function and the sine function are orthogonal to each other, they can be added to each other in the adder 350 and transmitted. The signals of two small groups in a large bundle can be received by the receiver, and the signals in the small bundle are multiplied. Orthogonal codes are distinguished in the receiver.

Two large packed signals may exist without interference from each other on the RF band by a single sideband (SSB) filter. As mentioned above, the bandwidth of the modulated signal is 38.88 MHz. Thus, within a given 50 MHz band, the spectra overlap. However, if one half of the spectrum is removed by the SSB filter prior to transmission, the calculation is 38.88 MHz / 2 = 19.44 MHz.

The spectrum of the signal is symmetrical and has the same information on both sides, so if the half is removed, no information is lost, so the SSB filter can be used. Since the signal passing through the SSB filter becomes a signal of about 20 MHz, there can be two spectra within 50 MHz, so that the spectrum can be properly positioned within a given band to minimize interference with each other.

3 is an example of a spectral form in a transmission step after a modulation process. Although the shape of the main lobe and side lobe of the spectrum varies depending on the modulation scheme, for example, in FIG. 3, the selected center frequency fc1 is fc1 = (x + x + 25) / 2 = (x + 12.5) MHz, and the center frequency fc2 of the second spectrum is fc2 = (x + 25 + x + 50) / 2 = (x + 37.5) MHz.

Considering these results, the modulation frequencies w ₁ and w ₂ are determined. Since the carrier frequencies for the two large packed signals are different, the corresponding SSB filter also has a different center frequency. Therefore, the SSB filter for the first large bundle signal is referred to as SSB filter 1 361 and the SSB filter for the second large bundle signal is referred to as SSB filter 2362. The signal passing through each filter is added by the adder 370 and transmitted through an amplifier, an antenna, or the like. However, the SSB filter may be present at any position during signal processing for modulation.

4 is an operational flowchart of a modulation system according to the present invention. 4, a band modulation method for transmitting a 155 Mbps baseband signal in a 50 MHz band according to the present invention will be described.

When a signal of 155Mbps is input into the modulation system, first, the serial-to-parallel converter 100 divides the input signal by the number of divided paths (S1). When splitting using 16 paths, the 155 Mbps signal (accordingly 155.52 Mbps) is split at 155.52 Mbps / 16 = 9.72 Mbps. The divided signals are transmitted to each buffer 200 and stored in the buffer 200 at a size of a predetermined frame (S2). The multiplier 310 multiplies the data stored in each buffer 200 by the orthogonal codes generated in the order of a predetermined orthogonal code. The D / A converter 320 performs a D / A conversion on the output signal of the multiplier 310 (S3). At this time, the orthogonal code is formed by the correlation between the given bandwidth and the signal bandwidth. Since there are 16 paths, orthogonal codes such as Walsh codes or Hadamard codes should be applied.

The adder 330 adds the signals in small groups of small groups to the respective output signals of the D / A converter 320 with respect to the D / A conversion signal (S4). At this time, all 16 paths are applied to each small bundle as the four-dimensional orthogonal code is applied, and each path is grouped into four paths to be considered. The 16 paths are grouped by 4 because each orthogonal code such as Walsh code or Hadamard code is applied to each path. This results in a data throughput rate of 9.72 Mbps × 4 = 38.88 Mbps.

The carrier modulator 340 modulates the added signal by using a cosine function and a sine function using the RF frequency in order to move the band of the signal to the required radio band (S5). The output signal of the carrier modulator 340 is added by the adder 350 in units of large bundles, i.e., at the same frequency (S6), so that the spectrums located at the same frequency have the same bandwidth, and thus the SSB filter prior to transmission. The filtering is performed through 360 (S7). If half of the spectrum is removed by the SSB filter 360, the calculation is 38.88 MHz / 2 = 19.44 MHz. In the embodiment, since two different frequencies are considered, a process of adding the filter output signals of the two SSB filters 361 and 362 is required, which is performed by the adder 370 (S8). If there are more filter outputs, you will need to add all of these signals. Finally, all modulation processes are terminated by transmitting the added signal (S9).

According to the present invention, when a high-speed data signal of 155Mbps is to be transmitted wirelessly in a 50MHz band, the high-speed signal can be transmitted in a small band in consideration of the efficiency of the frequency band. This simplifies the system and makes it cheaper.

Claims (5)

A modulation system for modulating a baseband signal of 155 Mbps, A plurality of serial-to-parallel converters for serial-parallel conversion of 155Mbps input signals; A buffer unit which temporarily stores each signal divided by the serial-to-parallel conversion unit and converted in parallel as a data size of a predetermined frame; And a modulation unit for multiplying orthogonal codes for each signal output from the buffer unit, grouping the output signal by a predetermined number, and performing SSB filtering on each grouped signal to modulate the radio signal band of 50Mbps or less. Band modulation system for transmitting 155 Mbps baseband signals using the 50 MHz band. The method of claim 1, wherein the modulator, A multiplier for multiplying orthogonal codes by a signal output from the buffer; A plurality of adders for grouping a predetermined number for each signal multiplied by an orthogonal code, A carrier modulator for modulating the grouped signal into a wireless band of 50 Mbps or less required; And a band modulation system for transmitting a 155 Mbps baseband signal using a 50 MHz band including an SSB filter unit to remove one of a symmetrical signal spectrum modulated by the radio signal. The method of claim 2, wherein the carrier modulator, Band modulation system for transmitting a 155 Mbps baseband signal using a 50 MHz band to select and modulate a frequency capable of positioning the spectrum of the transmission signal within a given frequency band. In the method for modulating a baseband signal of 155Mbps, Reducing the processing speed by dividing the 155 Mbps input signal into serial-to-parallel conversion into a plurality of signals; Buffering each of the divided and parallel converted signals to a predetermined size; The signal processing speed is increased by using an orthogonal code for each signal buffered to a predetermined size, and the output signal is grouped by a predetermined number to perform SSB filtering on each grouped signal to modulate the radio signal band of 50Mbps or less. Band modulation method for transmitting a 155Mbps baseband signal using a 50MHz band performing the step. The method of claim 1, wherein the modulating step, Multiplying an orthogonal code with each signal buffered by the constant magnitude; Grouping a predetermined number for each signal multiplied by an orthogonal code; Modulating a radio band of 50 Mbps or less for the grouped signal; And performing a SSB filtering on the signal modulated by the radio signal to remove one of a symmetrical signal spectrum, thereby transmitting a 155 Mbps baseband signal using a 50 MHz band.