KR20010065931A - Apparatus for Transmitting Radio Frequency in a Radio Interface Unit of Wireless Local Loop System - Google Patents

Abstract

PURPOSE: An RF transmitting apparatus of an RIU(Radio Interface Unit) in a WLL(Wireless Local Loop) system is provided to improve the signal/noise ratio of an RF transmitting apparatus so as to increase the isolation of the front end of the RF transmitting apparatus in a WLL terminal. CONSTITUTION: In order to reduce the output noise of a system to the minimum, an amplifier(210), of which the gain is larger than '1', is installed in the input port of a mixer(200) in the front end of a transmitting unit. Accordingly, the whole front end of the transmitting unit becomes an amplifier, not a modulator. In case that the amplifier(210), of which the gain is larger than '1', is installed in the input port of the mixer(200), a receiving band noise generated from a transmitting output port is reduced remarkably because a total noise factor is reduced.

Description

Apparatus for Transmitting Radio Frequency in a Radio Interface Unit of Wireless Local Loop System in wireless subscriber network system

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio frequency (RF) transmitting apparatus of a radio interface unit (RIU) in a wireless local loop network (hereinafter referred to as WLL) system. The present invention relates to an RF transmitter of a subscriber access device in a WLL system in which an output signal-to-noise ratio of a transmitter is improved to improve isolation of the device.

In general, the WLL system has a merit that it is much better than the radio wave environment of the mobile communication network in terms of use as a communication medium through a wireless channel.

In addition, the line-of-sight environment is secured, and the propagation path loss is about 20 dB / decade, so that it can serve a wider area with the same transmission power. Fading due to multipath is much less than that of point-to-point mobile communication network.

Due to these advantages, the development and research of the WLL system is actively underway, and the accompanying drawings of FIG. 1 show a schematic configuration of a general WLL network having the above advantages.

As shown in Fig. 1, network components include network subscriber station 10, 10 ', subscriber access devices 20, 20', base station 30, 30 ', base station controller 40, WLL switching station ( 50), a base station operating device 60, and the like, and additionally, a data communication matching device 70 (IWF: inter-working function) for data service, a home location register (HLR: Home Location Resister / Authentication Center) ( 80).

In addition, the billing center 100 connected to the network management sensor 90, the WLL switch 50 and the data communication matching device 70 is connected to the base station operating device 60 and the WLL switch 50 is further provided.

Let us explain the interface between the network components in the WLL system network configured as described above.

The subscriber access devices 20 and 20 'and the base stations 30 and 30' use the standard WLL radio access standard as the access standard, and the channel bandwidth is 10 MHz. The connection standard between the base stations 30 and 30 'and the base station controller 40 selects and uses E1 or HDSL, and the signaling method uses LAPD (Link Access Protocol D).

The base station controller 40 and the WLL switch 50 use E1 as a connection standard and use ITU-T.G965 as a signaling method.

In addition, the connection standard between the base station controller 40 and the base station operating device 60 uses Ethernet, and as a signaling method, Simple Network Management Protocol (SNMP), File Transfer Protocol (FTP), and Telecommunication Network (TELNET). Etc.

On the other hand, the base station controller 40 and the data communication matching device 70 uses E1 as the connection standard, and uses LAPD as the signaling method. In addition, the connection between the WLL switch 50 and the data communication matching device 70 uses E1 as the connection standard and R2 is used as the signaling method.

The connection standard between the WLL switch 50 and the home position register 80 uses E1, and IS-41C is used as the signaling method.

Let's look at the operation of the WLL system network connected through the connection standard and the signaling method in more detail.

First, the base station (30, 30 ') is a base station control module (RCP) that performs the overall management function for one base station, a modem module performing a signal processing function related to the CDMA channel, high power / low noise amplification and transmission and reception frequency conversion function RF module for performing the step, and a line connection module for performing the relay line (E1) connection function for matching with the base station controller 40, amplification of the transmission signal in the RF module, low noise amplification of the received signal, frequency down / up It performs conversion, reception of diversity through two antennas, high power / low noise amplification, and transmission / reception frequency conversion.

In addition, the modem module provides CDMA channels (pilot channel, sync channel, paging channel, access channel, signaling channel, traffic channel, packet traffic channel, packet access channel), digital baseband function processing, CDMA channel coding and decoding related functions. Do this.

The line connection module performs data communication with the base station controller 40 with respect to traffic and control information, and performs a relay line (E1 / HDSL) function for matching the base station controller 40.

The base station controller 40, which controls the base stations 30 and 30 ', is composed of a transcoder module, a call processing module, a switching module, and a matching module. The transcoder module is a 64 Kbps Pulse Code Modulation (PCM) voice coding signal. It includes a transcoder that performs the conversion function, and echo cancellation is implemented. In addition, the call processing module performs various call processing functions such as incoming / outgoing call processing support and message processing of the base station, subsystem status management in the base station controller 40, and control signal format between the WLL switch 50 and the subscriber access device. It is a processor that has a redundant structure for system reliability. The switching module also provides a traffic path between the base station matching device and the transcoder in the base station controller 40.

In addition, the matching module is composed of a WLL switch matching module, a base station matching module and a base station operating device (60) matching module, dual WLL switch (50) matching module for installing the base station controller 40 remotely with the WLL switch (50) If so, perform the E1 / G.965 digital heavy accounting function. In addition, the base station matching module performs the E1 / LAPD, HDSL relay line matching function between the base station and the base station control, and the base station operating device matching module performs the Ethernet / SNMP, FTP, TELNET matching function during the base station operating device-base station control period.

Next, the base station operating device 60 operates the base station controller 40, the base stations 30 and 30 ', and the subscriber access devices 20 and 20', and is responsible for maintenance and repair of each device.

In addition, as shown in FIG. 2, the subscriber access devices 20 and 20 ′ are composed of a large high frequency processing module 210, a digital processing modem 22 for processing a digital signal, and a subscriber interface module 23.

Here, the high frequency processing module 21 performs amplification of the transmission signal, low noise amplification of the reception signal, and frequency up / down conversion function. That is, the high frequency processing module 21 is responsible for transmitting and receiving data with the base station (30, 30 ') through the antenna, the subscriber interface module 23 is composed of BRI, SLIC and SIO.

BRI provides ISDN U-interface function for physical connection with ISDN subscribers. SLIC performs A / D conversion and D / A conversion function by performing matching function with analog line, and has line feed function, ring signal and various tone signal providing functions. The SIO connects to the RS-232C for serial port connection and provides digital data terminal access.

Next, the modem 22, which is a digital processing block, is connected to the high frequency processing module 21 in the searcher 22a to extract only a desired channel signal from the received signal, and the power control unit 22b is a channel obtained from the searcher 22a. Power control is performed by detecting the strength of the signal. The phase tracking unit 22c tracks the phase from the channel signal obtained from the searcher 22a and is responsible for the automatic frequency control function to compensate for the phase error. In addition, the automatic gain control unit 22d variably controls the gain of the amplifier according to the strength of the received signal obtained from the searcher 22a.

In addition, the receiver 22c converts the CDMA signal of the RF band through the searcher 22a into a baseband signal. The converted baseband signal is demodulated, deinterleaved, and decoded by the channel decoding and encoding unit 22f. After channel decoding is performed, it is passed to the subscriber interface module 23.

On the contrary, the subscriber data transmitted from the subscriber interface module 23 is modulated into a CDMA signal by the channel decoding and encoding unit 22f, interleaved and channel encoding, and then spread by the spreader 22g. This is done.

The spread spectrum signal is filtered by the FIR filter unit 22h into the set band, and then transmitted to the high frequency processing module 21 and transmitted as an RF signal.

3 is a diagram illustrating the first stage configuration of a transmitter of a conventional RF processing apparatus, and FIG. 4 is a diagram illustrating reception band noise of a transmission signal at a final output stage according to the structure of a conventional high frequency transmitter. The first stage is usually made of a modulator, and many of the modulators currently commercially made of a passive mixer 210 as shown in FIG. 3 have a gain less than one. In other words, rather than amplifying the signal, the signal is reduced.

The signal attenuation at the first stage increases the noise factor of the entire system, which causes a lot of noise at the final output stage.

Since such noise occurs in a wide band, much noise is generated in the reception band as shown in FIG.

The noise of the reception band is introduced into the receiver from the current terminal, which is not completely separated from the transmission and reception path, and degrades the reception performance of the terminal.

In other words, at the final output of the terminal, not only the signal we want, but also the noise is emitted at the same time. Since this noise has a wideband characteristic, it occurs not only in the transmission band but also in the reception band.

Increasing the transmission power of the WLL terminal means that the distance from the base station is that far, so the received signal received by the terminal is very weak.

As shown in FIG. 4, the noise of the reception band generated by the transmitter has a greater signal strength than the desired reception signal, and thus, when the noise of the reception band flows into the receiver, the reception performance of the WLL terminal is degraded.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an output signal-to-noise ratio of a transmitter so as to improve the isolation ion of an RF transmitter in a WLL terminal. The present invention provides an RF transmitter of a subscriber access device in a WLL system having an improved performance.

In the WLL system according to the present invention for achieving the above object, a feature of the RF transmitter of the subscriber access unit is the ultra short configuration of the RF transmitter in the WLL subscriber matching device having a frequency synthesizer having a gain less than one. In order to reduce the overall noise factor for the RF transmitter and to reduce the size of the reception band noise to a minimum, an amplifier having a gain greater than 1 is installed at a frequency synthesizer input having a gain less than 1.

1 is a block diagram illustrating a general broadband wireless subscriber network system;

2 is a block diagram illustrating a detailed block configuration of the subscriber access device shown in FIG. 1;

3 is a diagram illustrating an ultra-short configuration of a high frequency transmission apparatus of a subscriber access device in a wireless subscriber network system according to the prior art;

4 is a diagram illustrating reception band noise of a transmission signal at a final output terminal according to a structure of a high frequency transmission apparatus according to the prior art;

5 is a view showing a structure of a high frequency transmission apparatus of a subscriber access device in a wireless subscriber network system according to the present invention;

6 is a diagram illustrating reception band noise of a transmission signal at a final output terminal according to the structure of the transmission apparatus according to the present invention.

<Explanation of symbols for main parts of drawing>

200: mixer 210: amplifier

Hereinafter, an RF transmitter of a subscriber access device in a WLL system according to the present invention will be described in detail with reference to the accompanying drawings.

5 is a diagram illustrating a structure of a high frequency transmission apparatus of a subscriber access apparatus in a wireless subscriber network system according to the present invention, and FIG. 6 is a diagram illustrating reception of a transmission signal at a final output terminal according to the structure of the transmission apparatus according to the present invention. A diagram illustrating band noise.

First, the basic principle of the RF transmitter of the subscriber access device in the WLL system according to the present invention for reducing the reception band noise in the prior art described above, N elements are connected in parallel in any communication system. If present, the signal-to-noise ratio (S / N ratio) at the final output is determined as in Equation 1 below.

Where S / N _in is the signal-to-noise ratio at the system input and F is the system-specific noise factor. In other words, the smaller F is, the less noise is generated at the output.

This F may be calculated as shown in Equation 2 below.

Here, fN and GN are noise factors and gains inherent to the Nth device, respectively. That is, it can be seen that the noise factor of the entire communication system is mostly determined by the noise factor and gain of the first stage (N = 1).

Therefore, in order to reduce the output noise of the system, it is essential to use a device having a small noise factor and a large gain at the beginning of the system.

Accordingly, the present invention is designed to minimize the output noise of the system as described above. As shown in FIG. 5, an amplifier 210 having a gain greater than 1 is installed at the input of the mixer 200 at the first stage of the transmitter. Therefore, the first stage of the entire transmitter is an amplifier rather than a modulator.

As such, when the amplifier 210 having a gain greater than 1 is installed at the input of the mixer 200, the overall noise factor is reduced, so that the reception band noise generated at the transmission output is remarkably enjoyed as shown in FIG. Able to know.

For example, the reception band reduction amount is simplified as shown in Equation 3 below.

That is, in the conventional structure shown in FIG. 3 and the structure of the present invention shown in FIG. 5, f1 and f2 are the same, f1 = f2 >> 1, much smaller than the existing structure G1 and G1 of the structure of the present invention Assuming a much larger ratio, the ratio of the noise factor F1 of the existing structure to the noise factor F2 of the structure of the present invention becomes as shown in Equation 4 below.

That is, if the loss of the modulator is 10 dB, F1 / F2 = 10 because G1 = 0.1, and the noise generated in the structure of the present invention shown in FIG. 5 is reduced to 1/10 of the existing one.

In the WLL system according to the present invention as described above, the RF transmitter of the subscriber access unit is provided with an amplifier having a gain greater than 1 at the mixer input stage of the transmitter stage. The receiver of the transmitter generates a high output of the WLL terminal. By reducing the effect on the terminal, it is possible to contribute to the improvement of the reception sensitivity, the communication quality and the stabilization of the terminal.

In addition, by increasing the isolation of the transmitter, the use of high-performance components can be reduced, resulting in cost savings and other effects of increasing the efficiency of the power amplifier.

In addition, there is an advantage that can be expected to extend the use time of the WLL terminal and reduce heat generation.

Claims (1)

In an ultra-short configuration of an RF transmitter in a WLL subscriber matching device having a frequency synthesizer having a gain less than 1, Subscriber access in the WLL system, characterized in that an amplifier with a gain greater than 1 is installed at the input of the frequency synthesizer having a gain less than 1 to reduce the total noise factor of the RF transmitter to minimize the size of the reception band noise. RF transmitter of the device.