KR19990058832A - How to Set Up a Synchronous Wireless Link in a Wireless Communication System - Google Patents

Abstract

The present invention relates to a method for establishing a synchronous radio link in a wireless communication system. In particular, in a wireless communication system such as a CT-2 base station and a terminal, a mobile terminal synchronously calls a TDD timing of a wireless link when establishing a wireless link between the terminal and a base station. A method for sending a request message to establish a wireless link.

The present invention relates to a base station connected to a public switched telephone network (PSTN) and providing a service to a mobile terminal through a wireless link, comprising: an antenna for transmitting and receiving a high frequency modulated signal, and a plurality of transmit and receive paths coupled to the antenna And a plurality of high frequency transceivers, each of which is connected to the distribution / combiner, the high frequency modulation signal and the digital signal, and the high frequency transceiver to perform the physical connection with the wireless link. A plurality of multiplexers to perform, a digital switch for selectively connecting the plurality of multiplexers to a desired path, a codec for mutual conversion between a digital signal selected by the digital switch and an analog signal in a public switched telephone network, the digital Is connected to the switch, A central processing unit (CPU) that controls various devices, a program read-only memory (ROM) that stores the operating program of the CPU, and the CPU are connected, and signal conversion is performed during data communication between the base station and the base station host device. Contains the modem used for this purpose.

In addition, in the second embodiment of the present invention, the base station selects an idle channel having the least interference among all available channels, and transmits state information of the base station to the mobile terminal in its area in the TDD multiplexing mode, and power is applied. Searching for received channel strengths of all available wireless channels by a mobile station in a closed state to find a channel appearing at a predetermined level or more, and when the mobile terminal detects an idle channel having a predetermined level or more, the idle channel information is stored in its memory. The mobile terminal detects the synchronization signal of the base station in the detected idle channel, The mobile terminal which detects the synchronization signal of the base station synchronizes the TDD timing with the burst of the base station and maintains the TDD timing. If a call request is made, the wireless terminal uses the idle channel information stored in memory. Checking the received electric field strength to select an idle channel if it is below a predetermined level, and transmitting the call request message on the transmission window at the TDD timing of the base station; Investigating the received field strength of all traffic channels except the wireless channel being used and the previously linked radio channels, and the base station examines whether a call request message is received from the mobile terminal when the received field strength is detected above a certain level. And transmitting, by the base station receiving the call request message, the call request response message to the mobile terminal, and establishing a radio link with the base station and stopping the call request when the mobile terminal receives the call request response message.

Description

How to Set Up a Synchronous Wireless Link in a Wireless Communication System

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a synchronous radio link establishment method in a radio telecommunication system, and more particularly, to establish a radio link between a terminal and a base station in a wireless communication system such as a cordless telephone (CT) -2 base station and a terminal. The present invention relates to a method for enabling a mobile station to establish a wireless link by transmitting a call request message synchronously with respect to the TDD (Telecommunication Device for the Deaf) timing of the wireless link.

1 illustrates a network configuration of a conventional wireless communication system. As shown, a plurality of base stations (110a) (110b) (110c) connected to a Publish Switched Telephone Network (PSTN) 130; A plurality of mobile terminals (100a) (100b) (100c) connected by radio links with the base stations (110a) (110b) (110c); And a regular telephone connected to a public switched telephone network.

Each base station 110a, 110b, 110c is connected to a public switched telephone network 130 using a regular telephone line.

The base stations 110a, 110b and 110c may provide a voice service by forming a wired / wireless interface between many mobile subscriber stations 100a, 100b and 100c such as a mobile terminal and a public switched telephone network. The base stations 110a, 110b and 110c are mainly installed in public places used by many people, such as offices, department stores, airports and subway stations.

Also, since the base stations 110a, 110b and 110c have a high frequency transceiver, the mobile terminal can establish a radio link. In the prior art, in order to establish a radio link between the base stations (110a) (110b) (110c) and the mobile terminal (100a) (100b) (100c), a call request message is transmitted asynchronously with respect to the TDD timing of the radio link.

2 is a flowchart illustrating a method for establishing a radio link between a base station and a mobile terminal according to the prior art. Hereinafter, a method for establishing a radio link between a base station and a mobile terminal according to the prior art will be described in detail with reference to FIG. 2.

The mobile subscriber uses the mobile terminals 100a, 100b and 100c to request a call from their location. The mobile terminal selects a traffic channel having the least interference (200) and transmits a call request message to the base station (215).

The base station scans all available traffic channels and checks whether the received signal strength indicator (RSSI) is detected above a certain level (205). If the received electric field strength is detected to be above a predetermined level, the base station fixes the channel to the corresponding traffic channel and then checks whether there is a call request from the mobile terminal in the received high frequency signal (220).

If there is no call request from the mobile terminal, the base station continues to examine the received field strength of all available traffic channels. If there is a call request from the mobile terminal, the base station transmits a call request response message to the mobile terminal (230).

If the mobile terminal does not receive the call request response message from the base station, the mobile terminal reselects (210) a traffic channel with low interference and transmits the call request message back to the base station (215). When the mobile terminal receives a call request response message from the base station, the mobile terminal establishes a radio link with the base station. The traffic channel is fixed through the established wireless link and a handshake message is transmitted to the base station (235).

When the base station receives the handshake message from the mobile terminal (240), the base station fixes the traffic channel with the wireless link established, and transmits the handshake message of the base station to the mobile terminal (250).

When the mobile terminal receives a handshake message from the base station (245), the mobile terminal and the base station maintain a radio link while exchanging handshake messages with each other. Call progress is continued using the radio link configured as described above.

As described above, the base station itself examines the received field strength of all used traffic channels other than the traffic channel being served. As a result of the investigation, it is checked whether there is a call request from the subscriber station for the traffic channel detected above a certain level.

Since the method for establishing a radio link according to the prior art configured as described above transmits a call request message asynchronously, the mobile terminal and the base station should always check whether a message is received from the other party. Therefore, there is a problem in that an influence due to interference occurs in the outgoing signal, and a delay may occur in setting up a link.

Therefore, in order to solve the above problems, the present invention continuously transmits a synchronization signal from a base station to a mobile terminal, and receives a synchronization signal from the mobile terminal to synchronize the TDD timing with the burst of the base station. An object of the present invention is to provide a synchronous radio link establishment method in a wireless communication system configured to transmit a call request message in a multiplex mode.

1 is a network configuration diagram of a conventional wireless communication system.

2 is a flowchart illustrating a method for establishing a radio link between a base station and a mobile terminal according to the prior art.

3 is a block diagram of a base station for a wireless communication system.

4 is a flowchart illustrating a method for establishing a radio link between a base station and a mobile terminal according to the present invention.

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

300 antenna 305 splitter / combiner

310,315: high frequency transceiver 320,325: multiplexer

330: digital switch 340: CPU

350: program ROM 360: voice ROM

370: modem 380,385: codec

390: public switched telephone network interface

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

A base station connected to a public switched telephone network (PSTN) and serving a mobile terminal through a wireless link,

An antenna for transmitting and receiving high frequency modulated signals;

A splitter / combiner coupled to the antenna to connect a high frequency modulated signal to a plurality of transmit and receive paths;

A plurality of high frequency transceivers connected to the distribution / combiner and performing modulation / demodulation between high frequency modulated signals and digital signals;

A plurality of multiplexers, each connected to the high frequency transceiver, to perform a physical connection with a wireless link;

A digital switch for selectively connecting the plurality of multiplexers to a desired path;

A codec for mutual conversion between a digital signal selected by the digital switch and an analog signal in a public switched telephone network;

A central processing unit (CPU) connected to the digital switch and controlling various devices constituting the base station;

A program read-only memory (ROM) storing an operation program of the CPU;

It is connected to the CPU, and includes a modem (MODEM) used for the conversion of the signal in the data communication between the base station and the base station host device.

In one embodiment of the present invention, it is preferable that up to six high frequency transceivers are mounted.

Preferably, the multiplexer performs a layer 1 function in a public air interface (CAI) protocol.

Preferably, the codec performs conversion between an analog voice signal and a pulse code modulation (PCM) signal.

The CPU may sequentially enable the plurality of high frequency transceivers, examine the received field strengths (RSSI) of all traffic channels available at the current location of the base station, and list and store traffic channels with low interference.

The list of traffic channels is preferably stored in static RAM (SRAM),

When the CPU receives a call request message from the mobile terminal, the CPU selects a traffic channel having the least interference and proceeds with the call.

A second embodiment of the present invention for achieving the above object,

A first step of the base station selecting an idle channel having the least interference among all available channels and transmitting state information of the base station to the mobile terminal in its area in a Telecommunication Device for the Deaf (TDD) multiplexing mode;

A second step of searching for a channel appearing above a predetermined level by examining the received electric field strength of all available wireless channels by a mobile terminal in a power-on state;

A third step of storing, by the mobile terminal, idle channel information in its memory when an idle channel having a received electric field strength of a predetermined level or more is detected;

The mobile terminal detects a synchronization signal of the base station in the detected idle channel;

Detecting a synchronization signal of the base station, the mobile terminal synchronizing the TDD timing with the burst of the base station and maintaining the TDD timing;

A sixth step of, when the subscriber requests a call, the wireless terminal selects an idle channel if the wireless terminal uses the idle channel information stored in the memory to investigate the received electric field strength and is less than a predetermined level;

The mobile terminal transmits a call request message on a transmission window at a TDD timing of the base station;

An eighth step of examining, by the base station, the received field strengths of all traffic channels except the radio channel it is using and the previously linked radio channels in a reception window of its TDD timing;

A base station, if the received electric field strength is detected to be higher than a predetermined level, checking the call request message from the mobile terminal;

A tenth step of, by the base station receiving the call request message, transmitting a call request response message to the mobile terminal; And

And an eleventh step of establishing a radio link with the base station and stopping the call request when the mobile terminal receives the call request response message.

In a second embodiment of the present invention, if the wireless terminal does not receive a call request response message from the base station, it is preferable to further include reselecting the traffic channel with low interference and resending the call request message to the base station.

Receiving, by the mobile terminal, base station state information from the base station to synchronize the TDD timing, detecting a received electric field strength of the base station in the reception window of the TDD timing, and confirming whether a synchronization signal is detected;

Switching to a continuous mode without division of a transmission / reception window if a synchronization signal of a base station is not detected in a reception window of a wireless terminal; And

Preferably, the method further includes detecting a synchronization signal in a continuous mode and resynchronizing with the base station's TDD timing.

Preferably, the mobile terminal and the base station where the wireless link is established maintain the wireless link while periodically sending and receiving handshake messages.

In the fifth step, it is preferable that the wireless terminal examines the received electric field strength in the reception window of the synchronized TDD timing,

In the tenth step, the base station preferably transmits a call request response message to the wireless terminal in the transmission window of the TDD timing.

The present invention continuously transmits a synchronization signal at a base station and receives a synchronization signal at a mobile station periodically to minimize the influence of interference when making an outgoing signal and to establish a faster link, thereby synchronizing the TDD timing to a burst of the base station. The call request is sent in the synchronous multiplexing mode instead of the asynchronous multiplexing mode.

3 shows a configuration diagram of a base station for a wireless communication system. As shown, an antenna 300 for transmitting and receiving signals, and a divider / combiner 305 for distributing and combining the paths of the transmitted and received signals; Radio transceivers 310 and 315 for receiving high frequency signals; A multiplexer (320) (325) for multiplexing the transmitted and received signals; A digital switch 330 for performing digital modulation; A voice read only memory (Voice ROM) 360 for storing modulation information of the digital switch; A central processing unit (CPU) 340 for controlling the digital switch; A program ROM (350) for storing program data of the CPU; A modem (MOdulation and DEModulation: MODEM) 370 for converting between digital data of the CPU and analog for transmission; Coded and DECoding (CODEC) 380 and 385 for modulating the digital data of the digital switch to analog; And a public switched telephone network (PSTN) interface 390 that connects data of the modem and codec with a public switched telephone network.

The antenna 300 is connected to the splitter / combiner 305 as a port for transmitting / receiving a modulated radio frequency (RF) signal. The distributor / combiner 305 combines the modulated high frequency output signals of up to six high frequency transceivers 310 and 315 and transmits them to the subscriber mobile terminal through the antenna 300. In addition, the high frequency modulated signal transmitted from the subscriber mobile terminal is received by the antenna 300, distributed into six signals, and then supplied to up to six high frequency transceivers 310 and 315.

For the above operation, the high frequency transceiver 310, 315 receives a digital signal from the multiplexer 320, 325, modulates it into a wireless signal, and sends the digital signal to the distribution / combiner 305. It also demodulates the high frequency modulated signal from the splitter / combiner 305 and sends it to the multiplexer 320,325.

The multiplexers 320 and 325 perform the function of Layer 1 for the physical connection in the Common Air Interface (CAI) protocol so that the base station and the subscriber mobile terminal communicate with each other wirelessly.

A public switched telephone network connected to a base station can connect analog signals from ordinary telephone subscribers. Therefore, the base station embeds codecs 380 and 385 for digitally modulating analog voice signals. The analog voice signal via the public switched telephone network interface 390 is encoded as a Pulse Code Modulation (PCM) signal at the codecs 380 and 385 and the corresponding multiplexer 320 at the digital switch 330. Switch to 325.

The various devices are controlled by the CPU 340, and the operating program of the base station is stored in the program ROM 350. The CPU 340 sequentially enables the high frequency transceiver in the base station by a program stored in the program ROM 350 and examines the received field strength of all traffic channels available at the current position of the base station. Traffic channels having a low interference among the received received field strengths are stored in a list in a static random access memory (SRAM) inside the base station. Then, when the call request is received from the mobile terminal, the call is selected by the traffic channel according to the radio link establishment method.

When the base station talks to the mobile subscriber, the base station stores the mobile subscriber information and the call information in the static RAM. This information is sent to the base station host device via the modem 370 when requested by the base station host device.

The modem 370 converts the digital signal of the base station into an analog signal and sends it to the base station host apparatus via the public switched telephone network interface 390. In addition, the analog signal sent from the base station host device is converted into a digital signal and supplied to the base station. That is, the modem 370 is used for data communication between the base station and the base station host apparatus.

The place to process the radio link setting according to the present invention is the high frequency transceivers 310 and 315 shown in FIG. The transceiver 310 is referred to as a radio frequency part (RFP1), and the transceiver 315 is referred to as a radio frequency part 2 (RFP2). The high frequency parts 1 and 2 are controlled by the CPU 340. 4 is a flowchart illustrating a method for establishing a radio link between a base station and a mobile terminal according to the present invention. Hereinafter, a method for establishing a radio link according to the present invention will be described in detail with reference to FIG. 4.

First, the RFP1 selects an idle channel with less interference (400), and transmits the state information of the base station to the mobile terminal in its area in the TDD multiplexing mode (402).

The mobile terminal which is in a power-on state checks whether the received electric field strength (RSSI) appears above a predetermined level by sequentially changing wireless channels (404). At this time, when the idle channel with less interference is detected, the mobile terminal stores the idle channel information in its memory. If a synchronization signal is detected in a wireless channel in which the received electric field strength is detected above a predetermined level, the mobile terminal synchronizes the TDD timing with the burst of the base station and maintains the TDD timing (408).

When the subscriber requests a call (411), the mobile terminal again checks the received electric field strength by using the idle channel information stored in the memory in the reception window of the TDD timing synchronized in step 408. If the received received electric field strength is less than or equal to a predetermined level, the idle channel is selected (410), and the call request message is transmitted to the base station in the transmission window of the TDD timing (412).

The base station's RFP2 examines the received field strength of the radio channels excluding the radio channel it is using and the radio channels that were previously on the radio link on its TDD timing reception window (414). If the received electric field strength is detected to be above a certain level, it is checked whether a call request message is received from the mobile terminal (416).

The base station receiving the call request message transmits the call request response message to the mobile terminal in the transmission window of the TDD timing (418). If the mobile terminal does not receive the call request response message from the base station, it reselects the traffic channel with low interference (421) and sends the call request message back to the base station (410). When the mobile terminal receives the call request response message from the base station, it establishes a radio link with the base station and stops the call request (420). The mobile station also locks the traffic channel and sends a handshake message to the base station (424).

When the base station receives the handshake message from the mobile terminal (426), the base station determines that the radio link is established, locks the traffic channel, and then transmits the handshake message of the base station to the mobile terminal (428). If it does not receive the handshake message from the mobile terminal, the base station again checks the received field strength of the wireless channels (414).

When the mobile terminal receives a handshake message from the base station (436), the mobile terminal and the base station periodically exchange messages with each other to maintain the radio link and continue the call progress.

When the mobile terminal receives base station state information from the base station and synchronizes the TDD timing, the mobile station detects the received electric field strength of the base station in the reception window of the TDD timing and checks whether a synchronization signal is detected. If the synchronization signal of the base station is not detected in the reception window, the mobile terminal detects the synchronization signal in the continuous mode without the transmission / reception window classification. When the synchronization signal of the base station is detected in the reception window, the TDD timing information is corrected.

According to the present invention operating as described above, the base station periodically sends a synchronization signal and the mobile terminal receives the synchronization signal and synchronizes the TDD timing with the burst of the base station, so that the asynchronous multiplexing mode is required when the mobile terminal subscriber requests a call. By sending the call request message in the synchronous multiplexing mode, it minimizes the influence of the interference in the outgoing call and enables faster link setup.

Claims (13)

A base station connected to a public switched telephone network (PSTN) and serving a mobile terminal through a wireless link, An antenna for transmitting and receiving high frequency modulated signals; A splitter / combiner coupled to the antenna to connect a high frequency modulated signal to a plurality of transmit and receive paths; A plurality of high frequency transceivers connected to the distribution / combiner and performing modulation / demodulation between high frequency modulated signals and digital signals; A plurality of multiplexers, each connected to the high frequency transceiver, to perform a physical connection with a wireless link; A digital switch for selectively connecting the plurality of multiplexers to a desired path; A codec for mutual conversion between a digital signal selected by the digital switch and an analog signal in a public switched telephone network; A central processing unit (CPU) connected to the digital switch and controlling various devices constituting the base station; A program read-only memory (ROM) storing an operation program of the CPU; And And a modem connected to the CPU, the modem being used to convert a signal during data communication between a base station and a base station higher level device. The apparatus of claim 1, wherein up to six high frequency transceivers are mounted. The apparatus of claim 1, wherein the multiplexer performs a layer 1 function in a public air interface (CAI) protocol. 2. The apparatus of claim 1, wherein the codec performs conversion between an analog voice signal and a pulse code modulation (PCM) signal. 2. The CPU of claim 1, wherein the CPU sequentially enables the plurality of high frequency transceivers to examine received field strengths (RSSI) of all traffic channels available at the current location of the base station, and lists and stores a low interference traffic channel. A device for establishing a synchronous radio link in a wireless communication system. 6. The apparatus of claim 5, wherein the list of traffic channels is stored in a static RAM. The apparatus of claim 1, wherein the CPU selects a traffic channel having the least interference when the call request message is received from the mobile terminal. A first step of the base station selecting an idle channel having the least interference among all available channels and transmitting state information of the base station to the mobile terminal in its area in a Telecommunication Device for the Deaf (TDD) multiplexing mode; A second step of searching for a channel appearing above a predetermined level by examining the received electric field strength of all available wireless channels by a mobile terminal in a power-on state; A third step of storing, by the mobile terminal, idle channel information in its memory when an idle channel having a received electric field strength of a predetermined level or more is detected; The mobile terminal detects a synchronization signal of the base station in the detected idle channel; Detecting a synchronization signal of the base station, the mobile terminal synchronizing the TDD timing with the burst of the base station and maintaining the TDD timing; A sixth step of, when the subscriber requests a call, the wireless terminal selects an idle channel if the wireless terminal uses the idle channel information stored in the memory to investigate the received electric field strength and is less than a predetermined level; The mobile terminal transmits a call request message on a transmission window at a TDD timing of the base station; An eighth step of examining, by the base station, the received field strengths of all traffic channels except the radio channel it is using and the previously linked radio channels in a reception window of its TDD timing; A base station, if the received electric field strength is detected to be higher than a predetermined level, checking the call request message from the mobile terminal; A tenth step of, by the base station receiving the call request message, transmitting a call request response message to the mobile terminal; And And an eleventh step of establishing a radio link with the base station and stopping the call request when the mobile terminal receives the call request response message. 10. The method of claim 8, further comprising reselecting a traffic channel with low interference if the wireless terminal does not receive a call request response message from the base station and retransmitting the call request message to the base station. Way. The method of claim 8, Receiving, by the mobile terminal, base station state information from the base station to synchronize the TDD timing, detecting a received electric field strength of the base station in the reception window of the TDD timing, and confirming whether a synchronization signal is detected; Switching to a continuous mode without division of a transmission / reception window if a synchronization signal of a base station is not detected in a reception window of a wireless terminal; And Detecting the synchronization signal in a continuous mode and resynchronizing with the base station's TDD timing. 10. The method of claim 8, wherein the mobile terminal and base station on which the wireless link is established maintain a wireless link while periodically sending and receiving handshake messages. 9. The method of claim 8, wherein the fifth step examines the received field strength in a reception window of a synchronized TDD timing. 9. The method of claim 8, wherein in the tenth step, the base station transmits a call request response message to the wireless terminal in a transmission window of TDD timing.