KR20010058972A - Wll system using smart antenna - Google Patents

Abstract

PURPOSE: A WLL(Wireless Local Loop) using a smart antenna is provided to increase capacity, and improve sound quality, by reducing interference on a reverse link using a switched-beam array antenna that is a kind of the smart antenna. CONSTITUTION: Switched-beam array antennas(60-1 - 60-4) emit beams having fixed direction and phase. A 4-by-4 butler matrix(61) removes a crossover of transmission lines for signals received from the beams applied from the switched-beam array antennas(60-1 - 60-4). Directional couplers(62-1 - 62-4) couples some of the signal output from the 4-by-4 butler matrix(61) with others. An RSSI(Received Signal Strength Indicator) detection part(63) detects the RSSI of the signals applied from the directional couplers(62-1 - 62-4). Three-way splitters(64-1 - 64-4) divide each signal output from the directional couplers(62-1 - 62-4) into three signals having the same level. A cell-site receiver(110) selects three of the signals output from the three-way splitters(64-1 - 64-4).

Description

Wireless subscriber network system using smart antenna {WLL SYSTEM USING SMART ANTENNA}

The present invention provides a switched-beam array antenna which is a kind of smart antenna at the receiving end of a radio frequency (RF) unit in a base station of a wireless local loop (WLL) system. The present invention relates to a WLL system using a smart antenna capable of reducing interference in a reverse link using a switched-beam array antenna.

In general, the WLL system is a telephone system that wirelessly connects subscriber lines that are about 2 to 6 km away from a base station without using a conventional telephone line. The WLL system is composed of a subscriber matching device, a base station, a base station controller, and a wireless subscriber exchange. In addition, it is a backbone network with an installation cost that is inexpensive and short installation period compared to a conventional wired system.

The WLL system adopts a wideband code division multiple access (W-CDMA) method as a standard communication method, and utilizes infinite application technology of the W-CDMA method. Depending on the wired network can provide services.

The RF unit in the base station of the WLL system employing the W-CDMA scheme includes a baseband modem 10, an I & Q modulator 20, an up converter card (UCC) -α, β, γ, as shown in FIG. R (30-1 to 4), HPA (High Power Amplifier) -α, β, γ, R (40-1 to 4), transmit antenna 50, receive antenna 60, low noise amplifier (LNA) α, β, γ, R (70-1 to 4), DCC (Down Converter Card) -α, β, γ, R (80-1 to 4), I & Q demodulator 90, RFC (RF Control card) It consists of 100.

In the RF unit configured as described above, the signal modulated by the baseband modem 10 is combined through the I & Q modulator 20, and then the frequency is increased in each UCC-α, β, γ, and R (30-1 to 4). It is then converted and then amplified through each HPA-α, β, γ, R (40-1 to 4), and then transmitted to the subscriber matching device through the air interface by the transmitting antenna 50.

On the contrary, the signal of the subscriber matching device received through the receiving antenna 60 is amplified low by LNA-α, β, γ, R (70-1 to 4) and then DCC-α, β, γ, R (80- 1 through 4), the frequency down-conversion is performed, and the I & Q demodulator 90 separates the I and Q signals, respectively, and then demodulates the signals in the baseband modem 10 and transmits them to the base station controller.

In this case, in order to eliminate interference on the reverse link in the conventional reception path, a spatial diversity scheme that receives signals from two independent radio paths is used, or the signal is temporally decomposed again by the baseband modem 10. A rake receiver is used.

That is, the spatial diversity technique selects and demodulates a higher quality signal from signals received from two independent radio paths, and the method using a rake receiver provides real-time strength of several signals separated in time. In this method, the largest signal is used for demodulation.

However, such a conventional method alone is not easy to cope with high quality service and subscriber increase within a limited frequency spectrum, and thus it is necessary to search for various methods for interference cancellation and capacity increase.

The present invention has been made to solve the above problems, the object of which is a kind of smart antenna in the base station RF unit of the WLL system, without adding a built-in modem ASIC or a separate DSP The purpose of the present invention is to provide a WLL system using a smart antenna that can increase capacity and improve sound quality by using an in-switched-beam array antenna to reduce interference on a reverse link.

1 is a block diagram of an RF unit in a base station of a general wireless subscriber network system;

2 is a view showing a difference between a conventional omnidirectional antenna and a smart antenna of the present invention;

3 is a block diagram of an RF unit receiving end in a base station of a wireless subscriber network system using a smart antenna according to the present invention;

4 is a flowchart illustrating a control operation for a smart antenna in a wireless control unit in an RF unit in a base station of a wireless subscriber network system using a smart antenna according to the present invention;

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

10: baseband modem 20: I & Q modulator

30-1 to 4: UCC-α, β, γ, 40-1 to 4: HPA-α, β, γ, R

50: transmit antenna 60: receive antenna

60-1 to 4: first to fourth switched-beam array antennas

61: 4 × 4 Butler Matrix

62-1 to 4: 1st to 4th directional coupler 63: RSSI detector

64-1 to 4: 1 to 4 3-way splitter 65: RF switch

70-1 to 4: LNA-α, β, γ, 80-1 to 4: DCC-α, β, γ, R

90: I & Q demodulator 100: RFC

110: Cell Site Receiver

The WLL system using the smart antenna of the present invention for achieving this object is to radiate a beam having a fixed direction and phase in the four first to fourth switched-beam array antennas installed in one sector area to the desired direction When receiving the signal of the corresponding subscriber matching device, after removing the crossover of the transmission line for the signal received from the first to fourth switched-beam array antenna through the 4 × 4 Butler matrix, the first to fourth directory The RSSI detector detects the strength of the received signal by coupling a portion of the received signal through the coupler, and then RSSI is applied to the signal coupled and output by the first to fourth directional couplers in the RSSI detector. RF switch by detecting and separating the signal output through the first to fourth directional coupler from the first to fourth three-way splitter into three equally sized signals Value, the RF switch switches by the switching control signal of the RFC output according to the strength of the received signal detected by the RSSI detector, so that the three signals having the largest magnitude are output from the first to fourth three-way splitters. Select to output to the cell-site receiver.

Hereinafter, with reference to the accompanying drawings will be described in detail the configuration and operation of the WLL system using a smart antenna according to the present invention.

FIG. 2 is a diagram for illustrating a difference between a conventional omnidirectional antenna and a smart antenna of the present invention, and employs a technique of pseudo-space division multiple access (P-SDMA). The difference between the omnidirectional antenna and the smart antenna of the present invention is shown. As shown in FIG. 2, the smart antenna may have a higher transmission gain and a transmission range than the omnidirectional antenna, and has less interference. The interference of the reverse link can be more efficiently excluded.

Here, having a high transfer gain means an advantage that power consumption can be greatly reduced because the size of the output can be reduced in the subscriber matching device.

3 is a block diagram of an RF unit receiving end in a base station of a WLL system using a smart antenna according to the present invention, i.e., a receiving antenna system of an RF unit receiving end is installed in one sector area, so that a signal of a subscriber matching device is provided only in a desired direction First to fourth switched-beam array antennas 60-1 to 4 and radiating beams having a fixed direction and a fixed phase to receive the first and fourth switched-beam array antennas 60 4 × 4 Butler Matrix 61 for eliminating crossover of transmission lines for signals received in each beam radiated at −1 to 4), and the 4 × 4 Butler Matrix A first to fourth directional couplers 62-1 to 4 for coupling a part of the signal output through the second terminal 61 to detect the strength of the received signal; and the first to the fourth By the directional couplers 62-1 to 4 The RSSI detector 63 detects the strength of the received signal, that is, the received signal strength indicator (RSSI), and the first through fourth directional couplers 62-1 through 4, respectively. The first to fourth three-way splitters 64-1 to 4 for dividing the signal into three equally sized signals and outputting the same; and the strength of the received signal detected by the RSSI detector 63; The switching operation is performed by the switching control signal of the RFC 100 which is output according to the cell-site by selecting three signals having the largest magnitude among the signals output from the first to fourth three-way splitters 64-1 to 4. The RF switch 65 outputs to a receiver (Cell-Site Receiver) (110).

The cell-site receiver 110 is a part of an RF unit receiving end including an LNA and a DCC. The RF unit receiving end according to the present invention configured as described above is located in front of the LNA, and the RFC 100 is a wireless radio. Control array patterns for your environment.

4 is a flowchart illustrating a control operation for the smart antenna in the RFC 100 in the RF unit in the base station of the WLL system using the smart antenna according to the present invention.

The operation of the RF unit receiving end in the base station of the WLL system using the smart antenna configured as described above will be described with reference to the flowchart of FIG. 4.

First, the first to fourth switched-beam array antennas 60-1 to 4 installed in one sector area radiate a beam having a fixed direction and a fixed phase to signal a subscriber matching device only in a desired direction. Receive.

Subsequently, in the 4 × 4 butler matrix 61, after removing the crossover of the transmission line with respect to the signal received in each beam emitted from the first to fourth switched-beam array antennas 60-1 to 4, Each received signal from which crossover is removed is outputted to the first to fourth directional couplers 62-1 to 4.

Then, the first to fourth directional couplers 62-1 to 4 couple a part of the received signal output through the 4x4 butler matrix 61 so that the RSSI detector 63 adjusts the strength of the received signal. To be detected.

Accordingly, the RSSI detection unit 63 detects the strength of the received signal, that is, RSSI, with respect to the signal coupled and output by the first to fourth directional couplers 62-1 to 4, and outputs the detection result. Output to RFC (100).

In the first to fourth three-way splitters 64-1 to 4, signals output through the first to fourth directional couplers 62-1 to 4 are divided into three signals having the same magnitude. To the RF switch 65.

Subsequently, the RFC 100 inputs the strength of the received signal detected by the RSSI detector 63 as shown in the flowchart of FIG. 4 (S1) to select the three signals having the largest size (S2), and then selects the selected signals. The corresponding switching control signal is output to the RF switch 65 so that three signals can be transmitted to the cell-site receiver 100 through the RF switch 65 (S3).

Accordingly, in the RF switch 65, the first to fourth three-way splitters are switched by the switching control signal of the RFC 100, which is output according to the strength of the received signal detected by the RSSI detector 63. Three signals having the largest magnitude among the signals output from 64-1 to 4 are selected to be output to the cell-site receiver 110.

Then, the RFC 100 adjusts the gain of the DCC in the cell-site receiver 100 to make a reception gain for each sector commanded from the top (S4).

As described above, the present invention compensates the receiving end of the RF unit in the base station by using a smart antenna having a high transmission gain and a transmission range to receive the signal of the subscriber matching device only in a desired direction, thereby reducing the interference of the reverse link. It becomes smaller, which in turn leads to an improvement in sound quality, thereby providing a quality service.

As described above, the present invention, in the reverse link using a switched-beam array antenna which is a kind of smart antenna without adding a separate DSP or a separate DSP in the base station RF unit of the WLL system By reducing the interference, the effect of increasing capacity and sound quality can be achieved.

In other words, by using the smart antenna to reduce the interference on the reverse link, a base station installed in an urban area can serve more people at the same time, and in a suburban or rural area, a single base station can serve a wider area. This can reduce the cost of constructing a backbone network for a given region.

In addition, by using a smart antenna having a higher transmission gain than in the related art, it is possible to extend the battery life of the subscriber matching device by inducing the subscriber matching device to transmit less power for link formation.

Claims (1)

In a base station RF unit receiver of a WLL system including a receive antenna using an omnidirectional antenna, an LNA, a DCC, an I & Q demodulator, and a baseband modem, A receiving antenna system of an RF unit receiving end located in front of an LNA in a cell-site receiver composed of the LNA, DCC, I & Q demodulator, and baseband modem is installed in one sector area to receive a signal of a subscriber matching device only in a desired direction. Signals received at each of the first to fourth switched-beam array antennas emitting a beam having a fixed direction and a fixed phase so as to be received, and at each beam radiated from the first to fourth switched-beam array antennas First to fourth coupling a 4 × 4 butler matrix for eliminating crossover of the transmission line with a portion of a signal output through the 4 × 4 butler matrix to detect the strength of the received signal. An RSSI detector configured to detect an intensity of a received signal with respect to a signal coupled and output by the directional coupler and the first to fourth directional couplers; First to fourth three-way splitters that separate the signals output through the first to fourth directional couplers into three equally sized signals and output the signals according to the strength of the received signal detected by the RSSI detector; It is composed of an RF switch switching operation by the switching control signal of the RFC to select the three signals having the largest magnitude among the signals output from the first to fourth three-way splitter to output to the cell-site receiver Wireless subscriber network system using smart antenna.