KR19990058826A - Pilot Transmitter in Code Division Multiple Access System - Google Patents

Abstract

The present invention relates to a pilot transmitter of a code division multiple access system, and more particularly, to a pilot transmitter for guaranteeing service continuity between neighboring base stations in which the total number of frequency allocations of a cellular and personal mobile communication system using a code division multiple access technique is different. It is about.

One preferred embodiment of the present invention comprises: a sector interface card apparatus for modulating an output signal on a forward link to an intermediate frequency; A transmitter device for converting the modulated intermediate frequency signal into a high frequency signal; A large power amplifier for amplifying the frequency converted high frequency signal to a signal level suitable for an output terminal; And a transmission band filter for filtering the amplified signal and transmitting the filtered signal to a transmission antenna.

Using this structure, it is compatible by replacing only the relevant high frequency modules to suit the frequency of use of the cellular system or personal mobile communication system, and since one transmitter device serves one frequency allocation / 3 sectors, the multi-frequency It is possible to design pilot transmitters with allocation and multi-sector structures.

In addition, a pilot transmitter having a compact structure according to the capacity can be designed, and the transmission output can be controlled for each frequency allocation and sector by using a transmission path power attenuator.

Description

Pilot Transmitter in Code Division Multiple Access System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pilot transmitters in Code Division Multiple Access (CDMA) systems, and in particular to the frequencies of cellular and personal communication systems (PCS) using CDMA technology. The total number (Pie) of Frequency Assignment (FA) relates to a pilot transmitter for ensuring service continuity between different neighbor base stations.

According to the International Organization for Standardization (IS-95), a conventional mobile communication system using a code division multiple access technology uses a mobile station provided with a service and a base station transceiver subsystem (BTS) providing a service. It is configured to include.

Currently, a CDMA system operating in Korea includes a base station controller (BSC) for controlling the base station, a base station manager system (BSM) for operating and managing various base station controllers, in addition to a mobile terminal and a base station. A mobile switching center (MSC) for connecting a base station to a public switched telephone network (PSTN), and a home location register (HLR) for connecting to the switching center system and managing a service state of a mobile terminal.

The area serviced by each base station is called a cell, and each base station may have an omni-cell structure, a sector-cell structure, or a micro-cell structure.

The base station is connected to an existing Public Switched Telephone Network (PSTN), and a mobile terminal in each cell forms a radio channel with a base station serving a corresponding cell and performs communication. In this case, a channel formed in the direction of the mobile station from the base station is called a forward channel, and a channel formed in the direction of the base station from the mobile station is called a reverse channel.

The mobile station and the base station transmit and receive voice information and data by using a traffic channel, and pilot, synchronous, and paging channels except for the traffic channel are transmitted and received. It is called an additional channel, ie an overhead channel. Each base station and mobile terminal determines whether it should receive the data through pilot or paging (or code) transmitted on additional channels.

Each base station is assigned several frequencies according to system capacity and uses as many frequency channels, and each frequency channel is called frequency assignment (FA). CDMA systems can include multiple access channels per frequency channel with different frequency offsets and sequences.

Wireless telephones (mobile terminals) aim to ensure that there are no obstacles in communication when traveling in different areas. Therefore, when the mobile terminal is in an idle state, it is necessary to regularly re-register with the system according to various parameters. When the call is in operation, the mobile station and the base station and the switching station manage communications between the base station and the mobile station to maintain good radio link efficiency.

In CDMA technology, one system can simultaneously receive mobile transmissions from two or more base stations. One terminal may simultaneously receive signals transmitted from two or more base stations. Having such a function, it is possible to handle handoffs from one base station to another, or from one antenna area to another within one base station.

The handoff here refers to a process in which a mobile station moves from one base station to a new base station or within one base station to a new antenna allowance area, i.e., to a new traffic channel. It is very important to ensure that the success of the moving call and the quality of the voice information are not degraded during the handoff.

Various types of handoffs have been provided to ensure call continuity in CDMA cellular and PCS systems. Depending on the method and implementation, the handoff may have a difference in efficiency in terms of reliability of call continuity and system load. The setting of the channel by the handoff is called ADD, and the release of the channel by the handoff is called DROP.

There are two major handoff methods: soft handoff and hard handoff. Soft handoff is a method of making a call before making a call, and hard handoff is a method of cutting an arc before creating a new call. -before-make) method. When handoff is required due to the movement of a mobile station, the CDMA system preferentially handles soft handoff. However, if it is inevitable, hard handoff ensures call continuity.

Soft handoff is a method of stably establishing call continuity by simultaneously setting up a call path by two or more channels for a single call. Since CDMA can be configured simultaneously by different codes through different frequency bands in the same time zone because of its characteristics, the soft handoff method is a CDMA-specific handoff that can configure multiple call paths for a single call. Technique.

Hard handoff is provided when the two base stations to which the mobile station is affected are not synchronized or not at the same frequency, and when interruptions occur in voice or data communications. In other words, hard handoff is a method of guaranteeing continuity of a call by setting a new channel within a short time that is difficult for a caller to recognize after cutting an existing channel.

Hard handoff may be provided when more than one frequency band (frequency allocation or channel) is used in each cell or two base stations are not synchronized. Another kind of hard handoff is provided when there is no CDMA base station to serve effectively and the mobile station must be assigned to an analog cellular channel. In hard handoff, it is very important to consider the decision and decision criteria of the cell to be handoffed.

Hard handoffs include inter-MSC hard handoffs and Inter FA (Frequency Assignment) handoffs, inter-frame offset hard handoffs, and the like.

The base station of a mobile communication system using a code division multiple access technique uses a different number of frequency allocations depending on the capacity of the system. For example, base station A is operating three frequency assignments, FA # 1, FA # 2, FA # 3. Base station B also operates two frequency assignments, FA # 1 and FA # 2. In this case, if the mobile station in the mobile station using FA # 3 in the base station A moves to the area of the base station B, since the base station B cannot serve the frequency originally used by the subscriber, handoff between frequencies occurs.

In addition, in order to recognize that the mobile terminal to which the FA # 3 channel is connected has moved to the area of the base station B, the base station B operates the frequency of the FA # 3 as a dummy pilot. Then, the mobile terminal receives the FA # 3 pilot transmitted from the base station B, and can recognize that the mobile station has moved to the area of the base station B.

Therefore, an additional device called a pilot transmitter is required to perform inter-frequency hard handoff. Each base station has a pilot transmitter that detects a frequency allocation situation of a neighboring base station and generates a corresponding frequency signal.

1 shows a structural diagram of a pilot generator according to the prior art. As shown, an I channel short code generator for receiving absolute time and generating an I channel spread sequence at a time offset, and a first band pass filter for receiving and filtering the I channel spread sequence; A first mixer receiving the filtered I channel spreading sequence and supplying a modulated I output signal; A Q channel short code generator for receiving absolute time and generating a Q channel spread sequence at a time offset; A second band pass filter for receiving and filtering the Q channel spreading sequence; A second mixer receiving the filtered Q channel spreading sequence and supplying a modulated Q output signal; A summer (Summer) for summing the modulated I output signal and the modulated Q output signal to generate a summed modulation signal; And an upconversion and amplifier receiving the summed modulation signal to generate a pilot signal to be sent.

The pilot generator configured as described above is installed in the CDMA base station together with a searcher and a demodulator for classifying cells or sectors by the pilot signal and performing demodulation of the CDMA signal. The prior art pilot generator configured as described above is disclosed in US Patent 5,680,395, "METHOD AND APPARATUS FOR TIME DIVISION DUPLEX PILOT SIGNAL GENERATION."

The code division multiple access cell has a multi-frequency allocation (Multi-FA) or a multi-sector structure as needed. Therefore, it is necessary to configure a pilot transmitter that can be applied according to the structure of the cell.

In addition, a structural change is required for application to cellular and personal communication service (PCS) systems using a code division multiple access technology, and it is not possible to control transmission frequency for each frequency allocation or sector. That is, the pilot transmitter according to the prior art configured as described above has various problems described above in application to actual communication services using code division multiple access technology.

Therefore, the present invention can be used interchangeably for code division multiple access cellular and personal mobile communication systems with a simple module replacement in order to solve the above problems, to apply to the actual communication service using code division multiple access technology. An object of the present invention is to provide a pilot transmitter of a code division multiple access system having an internal configuration according to a cell structure.

1 is a structural diagram of a pilot generator according to the prior art.

2 is a block diagram of a pilot transmitter according to the present invention.

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

100: sector interface card device (SICA)

200 transmitter unit (TXU)

210: frequency rising converter

220: frequency synthesizer (FSB)

230: controller (CNT)

300: high power amplifier (HPAU)

400: TX bandpass filter (TX BPF)

One preferred embodiment of the present invention devised to achieve the object as described above,

A sector interface card device for modulating the output signal on the forward link to an intermediate frequency;

A transmitter device for converting the modulated intermediate frequency signal into a high frequency signal;

A large power amplifier for amplifying the frequency converted high frequency signal to a signal level suitable for an output terminal; And

And a transmission band filter for filtering the amplified signal and transmitting the filtered signal to a transmission antenna.

In one embodiment of the present invention, the above structure is preferably used to ensure service continuity between neighboring base stations having different frequency pis,

Preferably, the sector interface card device analog-summing six I, Q baseband signals, which are output signals on a forward link, in respective channel units, converts them into intermediate frequencies, and then sums and outputs them for each sector.

The I, Q baseband is preferably in the range of 0 ~ 630KHz,

The conversion to the intermediate frequency is preferably using a quadrature phase shift keying (QPSK) method,

Preferably, the transmitter device covers one frequency allocation (FA) / 3 sectors,

The transmitter apparatus includes a frequency rising converter for converting an intermediate frequency signal into a high frequency signal; It is preferable to include a frequency synthesizer for supplying a local oscillation frequency to the frequency rising converter and a control board for controlling and monitoring the frequency rising converter,

It is preferable that the three frequency rising transducers share the local oscillation frequency generated by the frequency synthesizer,

Preferably, the output of the frequency rising converter is changeable, and the frequency rising converter may change the output using a built-in power attenuator, and the attenuation value of the power attenuator is adjusted by the control board. Preferably, the control board stores characteristic curve calibration data in order to control the output of the frequency rising converter, and the characteristic curve calibration data is stored in an EEPROM. It is preferable to store data by assigning a unique address to each rising converter.

Preferably, the frequency rising converter includes a band pass filter for improving transmission characteristics, and the band pass filter is a surface acoustic wave (SAW) filter.

Preferably, the frequency rising converter is mounted one by sector,

Preferably, the frequency synthesizer generates a local oscillation frequency using a phase locked loop (PLL) scheme.

Preferably, the control board stores high frequency channel frequency setting data for controlling and monitoring the frequency rising converter.

The high power amplifier is preferably a linear amplifier in consideration of phase linearity.

The pilot transmitter of the code division multiple access system according to the present invention is as follows.

1) Sector Interface Card Assembly (SICA)

2) Transmitter Unit (TXU)

3) High Power Amplifier Unit (HPAU)

4) Transmit Band Pass Filter (TX BPF)

Here, the transmitter device TXU includes a frequency up-converter, a frequency synthesizer board (FSB), and a control board.

2 shows a block diagram of a pilot transmitter according to the present invention. As shown, the sector interface card apparatus 100 for modulating the output signal on the forward link to an intermediate frequency (IF) for each sector; A transmitter device for converting the modulated intermediate frequency signal into a radio frequency (RF) signal; A large power amplifier 300 suitable for amplifying the frequency converted high frequency signal at an output terminal; And a transmission band filter 400 for filtering the amplified signal and transmitting the filtered signal to a transmission antenna.

Hereinafter, the operation of the present invention will be described in detail with reference to the accompanying drawings. The sector interface card apparatus 100 performs analog summing of six I and Q baseband signals (0 to 630 KHz), which are output signals on a forward link connected from a base station to a mobile terminal, in units of channels. do. The summed signal is modulated to an intermediate frequency using Quadrature Phase Shift Keying (QPSK). The modulated signal is summed and output for each of α, β, and γ sectors.

The transmitter device 200 controls a frequency rising converter 210 for converting an intermediate frequency signal into a high frequency signal, a frequency synthesizer 220 for supplying a local oscillation frequency to the frequency rising converter, and the frequency rising converter and the frequency synthesizer. And a control board 230 for monitoring.

The frequency up converter 210 performs frequency up conversion on the modulated intermediate frequency signal transmitted from the sector interface card device 100 to convert a high frequency signal corresponding to a specific carrier frequency of the base station transmission frequency band. Each frequency rising converter 210 has a SAW (Surface Acoustic Wave) filter having a bandwidth of 1.23 MHz for CDMA transmission characteristics, and a power attenuator (Tx Flower Attenuator) capable of changing the transmission output if necessary. ). Each frequency up converter 210 takes one for each FA / sector.

The frequency synthesizer 220 generates a local oscillation frequency signal to be added to the transmission intermediate frequency signal. The frequency rising converter 210 generates the high frequency signal by adding the local oscillation frequency to the transmission intermediate frequency signal. A phase locked loop (PLL) is used to generate the local oscillation frequency. The signal generated by the frequency synthesizer 220 is divided into power and supplied to the three sector-specific frequency rising converters 210.

The controller 230 interworks with the control module of the base station to control and monitor each frequency rising converter 210 in the transmitter device 200. The controller 230 is composed of a microprocessor and a peripheral circuit, and performs functions such as setting a high frequency channel frequency, adjusting attenuation values of a transmission path power attenuator, and storing characteristic curve calibration data.

The large power amplifier 300 receives a high frequency signal from the transmitter device 200 and amplifies the signal with a constant gain. The large power amplifier 300 used in the present invention is a linear amplifier considering phase linearity.

The transmission band pass filter 400 suppresses the out-of-band unnecessary radiation wave of the high frequency signal amplified by the high power amplifier 300 and transmits it to the transmission antenna.

The present invention operating as described above can obtain the following effects.

First, it is possible to design a pilot transmitter for a code division multiple access cellular and personal mobile communication system. In other words, it is compatible by replacing only the relevant high frequency modules to suit the frequency of use of the cellular system or personal communication system.

Second, since one transmitter device serves one frequency allocation / 3 sectors, a pilot transmitter having a multi-frequency allocation and a multi-sector structure can be designed.

Third, a compact pilot transmitter can be designed according to the capacity.

Fourth, transmission path power attenuators can be used to control transmission power for each frequency allocation and sector.

Claims (20)

A sector interface card device for modulating the output signal on the forward link to an intermediate frequency; A transmitter device for converting the modulated intermediate frequency signal into a high frequency signal; A large power amplifier for amplifying the frequency converted high frequency signal to a signal level suitable for an output terminal; And And a transmission band filter for filtering the amplified signal and transmitting the filtered signal to a transmission antenna. 2. The pilot transmitter of claim 1 wherein the structure is used to ensure service continuity between adjacent base stations with different frequency pis. The apparatus of claim 1, wherein the sector interface card apparatus analog-summing six I, Q baseband signals, which are output signals on a forward link, in units of channels, converts the signals to intermediate frequencies, and then adds them by sector. , Pilot transmitter of code division multiple access system. 3. The pilot transmitter of claim 2 wherein the I and Q basebands range from 0 to 630 KHz. 3. The pilot transmitter of claim 2 wherein the method of converting to an intermediate frequency uses a quadrature phase shift (QPSK) modulation scheme. The pilot transmitter of claim 1, wherein the transmitter device covers one frequency allocation (FA) / 3 sectors. The method of claim 1, wherein the transmitter device, A frequency rising converter for converting the intermediate frequency signal into a high frequency signal; A frequency synthesizer for supplying a local oscillation frequency to said frequency rising converter; And a control board for controlling and monitoring the frequency rising converter. 8. The pilot transmitter of claim 7, wherein the three frequency up converters share a local oscillation frequency generated by a frequency synthesizer. 8. The pilot transmitter of claim 7 wherein the output of the frequency up converter is changeable. 10. The pilot transmitter of claim 9 wherein the frequency ramping up converter uses a built-in power attenuator to alter the output. 11. The pilot transmitter of claim 10 wherein the attenuation value of the power attenuator is adjusted by the control board. 10. The pilot transmitter of claim 9 wherein the control board stores characteristic curve calibration data to control the output of the frequency rising converter. 13. The pilot transmitter of claim 12 wherein the characteristic curve calibration data is stored in an EEPROM. 13. The pilot transmitter of claim 12, wherein the control board stores data by assigning a unique address to each frequency rising converter. 8. The pilot transmitter of claim 7 wherein the frequency up converter incorporates a band pass filter to improve transmission characteristics. 16. The pilot transmitter of claim 15 wherein the band pass filter is a Surface Acoustic Wave (SAW) filter. 8. The pilot transmitter of claim 7 wherein the frequency up converter is mounted one sector by sector. 8. The pilot transmitter of claim 7 wherein the frequency synthesizer generates a local oscillation frequency using a phase locked loop (PLL) scheme. 8. The pilot transmitter of claim 7 wherein the control board stores high frequency channel frequency setting data for control and monitoring of the frequency up converter. 8. The pilot transmitter of claim 7, wherein the high power amplifier is a linear amplifier in consideration of phase linearity.