KR100281098B1 - System synchronizer using internal network of mobile communication system - Google Patents

Abstract

In the mobile communication system, a network interface unit for receiving reference time information through a network inside the system, a GPS receiver for receiving the reference time information from the outside of the system, and time information input from the network interface unit or the GPS receiver are calculated. A reference clock generator for generating a reference clock, a delay compensator for compensating for a transmission delay error between an upper system or a lower system connected through the network, and time information and a reference clock compensated for the upper system or a lower system, respectively. It consists of a line interface for distributing.

Description

System synchronizer using internal network of mobile communication system

The present invention relates to a synchronization device of a mobile communication system, and more particularly, to a system synchronization device using an internal network of a mobile communication system suitable for obtaining synchronization information of an internal network.

FIG. 1 is a block diagram of a synchronization signal holding device in a conventional digital exchange, and FIG. 2 is a block diagram showing the BSC / BTS synchronization device of FIG.

Referring to FIG. 1, a conventional synchronizing signal holding device includes a mobile switching center (MSC) 10 including a digital processing PLL 11, a mobile switching center (MSC) 10, and the like for a mobile terminal of a mobile terminal. It consists of a base station control / base station transmission system (BSC / BTS) 20 that is interfaced and includes a global positioning system (GPS) receiver 21.

In addition, in the synchronization signal holding device using the time information and clock information provided by the national backbone network, such a synchronizer block of the MSC (10) in order to prevent the slip caused by the mismatch of the clock frequency between the exchange in the digital switching network. The basic clock of the MSC 10 is synchronized with the reference clock provided in the digital switching network using a PAMS synchronization scheme to maintain internal synchronization of the mobile communication system.

At this time, up to three reference clocks are accepted and selected as system reference clocks according to a predetermined priority, and the self-oscillation mode using a digital-PLL method using a highly accurate OVCXO (Ovenized voltage controlled X-tal oscillator) Maintain stability of around 3 × 10 ^-9 /day~1.08 × 10 ^-10 / day.

However, the above-described conventional synchronization signal holding device is very accurate in its own stability, but does not meet the level of precision of time synchronization required in a code division multiple access (CDMA) mobile communication system, so that it can be used as a synchronization device in a CDMA mobile communication system. Inadequate Here, the time synchronization is a kind of method of ensuring the mobility of the terminal by maintaining the same time information for each system based on the universal time.

The core technologies of the CDMA mobile communication system are the separation between users using code through accurate time synchronization and soft handoff through accurate time synchronization. Such a CDMA system operates based on accurate time synchronization between base stations, and the GPS time accuracy is absolutely effective in handoff between base stations. At this time, the performance of GPS has an error between GPS receivers less than 300ns in normal operation.

The MSC synchronizer 10 receives the synchronization reference signal inputted from the digital relay line matching device, generates a clock synchronized with the distributed RS, and distributes the clock to the distribution device that needs the clock. The system clock distribution is supplied through the optical transmission device. Each subsystem operates by extracting timing from the received data. It also has the function to generate the real time clock necessary for software operation and store it in the software block to visualize the time in hardware to the operator.

Meanwhile, referring to FIG. 2, the conventional BSC / BTS system 20 includes a GPS clock control and distribution unit 31 and 32, and the GPS receiver 33 is an antenna connected to a coaxial cable with time information from a satellite. It receives through the TOD (time of date) (time), 10MHz (clock), 1PPS (pulse per second) signals are separated and provided as a system clock for system synchronization through the bus line (30).

The synchronization method of the conventional BSC / BTS system 20 mentioned above is effective in maintaining time synchronization by the synchronization maintaining method using the GPS receiver 21, but the cell radius of the base station becomes narrower with the development of the mobile communication system. Accordingly, the number of base stations is increased, thereby increasing the installation cost of using a GPS system for each base station.

In addition, since the GPS system itself is a system of a different nationality, there is a problem in maintaining a network in an emergency station, and it is expected to increase the cost of charging a GPS fee. In addition, the failure of the GPS receiver may degrade the performance of the entire system. The failure of the GPS receiver is difficult to detect the occurrence of the failure itself, and the GPS receiver failure immediately generates a time error between base stations. This is expected to be a problem that the time error between adjacent GPS receivers located at a considerable distance cannot be accurately measured.

Therefore, the present invention has been made in view of the problems of the prior art as described above, the object of the present invention is to give a GPS receiver to the MSC or BSC to select the GPS output as a reference clock as a system, MSC / BSC The present invention provides an internal network synchronization method in a mobile communication system so that an upper or lower system can be synchronized with a clock supplied from the system.

In addition, another object of the present invention is to provide a DP-PLL device to the mobile communication system in a mobile communication system to maintain the time synchronization required for the mobile communication system without using a GPS receiver which is used for each existing BSC / BTS An internal network synchronization method is provided.

1 is a block diagram of a synchronization signal holding device in a conventional digital exchange.

2 is a block diagram showing the BSC / BTS synchronizer of FIG.

3 (a) and 3 (b) are block diagrams illustrating an internal network synchronizer in a mobile communication system according to the present invention.

4 is a block diagram according to the operation of the synchronization device of FIGS. 3 (a) and 3 (b).

5 is a layout diagram according to the synchronization delay compensation of FIG.

* Explanation of symbols for main parts of the drawings

10: Mobile Switching Center (MSC) 11,45,55: Digital Processing PLL

20: base station control / base station transmission system 21,33,41,51,61: GPS receiver

30: bus line 31: TRMA

32: TMPA 40: MSC / BSC

42: network interface (NIU) 43, 53, 62: reference clock selector

44, 54: TOD generator 46, 56: distributor

47,72: Line Interface (LIU) 47-1: With delay compensation function

63, 73: clock generator 64: delay compensation and clock distribution

74: code generator 80: MSC / BSC delay compensation device

In the mobile communication system of the present invention for achieving the above object, a network interface unit for receiving reference time information through a network inside the system, a GPS receiver for receiving the reference time information from outside the system, the network interface unit or the A reference clock generator for generating a reference clock by calculating time information input from a GPS receiver, a delay compensator for compensating for a transmission delay error between an upper system or a lower system connected through the network, and a higher level system or a lower system. A mobile communication control system comprising a line interface for distributing compensated visual information and a reference clock, respectively.

Hereinafter, a preferred embodiment of an internal network synchronization method in a mobile communication system according to the present invention will be described in detail with reference to the accompanying drawings.

3 (a) and 3 (b) are block diagrams showing an internal network synchronizer in a mobile communication system according to the present invention, and FIG. 4 is an operation of the synchronizer of FIGS. 3 (a) and 3 (b). And FIG. 5 is a layout diagram according to the synchronization delay compensation of FIG.

Referring to FIG. 3 (a), in the mobile communication system of the present invention, the internal network synchronizer generates visual information and synchronization information to compensate for time error or synchronization error between the respective systems. / BSC) 40, and each base station transmission system (BTS) 50 for synchronizing signals in accordance with the time information and synchronization information corrected in the MSC / BSC 40.

Referring to FIG. 3 (a), the MSC / BSC 40 is a GPS receiver 41 which transmits TOD data generated from the TOD generator 44 at 10 MHz and 1 PPS clocks, 2048 MHz and 8 KHz, and FE, respectively. A network interface (NIU) 42 for constructing an internal network with a clock, and a reference clock selector (RSU) 43 for selectively supplying reference clocks input from the GPS receiver 41 and the NIU 42. And a divider 46 for distributing TOD data, a system reference clock, and a system frame pulse for system synchronization, and a line of an internal network according to the TOD data, system reference clock, and system frame pulse distributed at the divider 46. It consists of a line interface (LIU) 47 to interface them. In this case, the line interface 47 includes a delay compensation function unit (DCF) 47-1 for delay compensation of time information and synchronization information between the upper system and the lower system. Further, a digital processing PLL 45 is connected between the RSU 43 and the divider 46 to synchronize phase synchronization.

3 (b) shows an example in which a synchronization device according to the present invention is added to a base station test apparatus.

The operation of the internal network synchronizer in the mobile communication system according to the present invention configured as described above will be described with reference to FIG.

Referring to FIG. 4, the MSC synchronizer 10 of FIG. 1 selects a GPS clock so that TOD data is received from the GPS receiver 61 and supplied to each system to provide accurate visual information on operation and maintenance. Can provide. In addition, TOD data can be delivered to the subsystem to achieve time synchronization using the GPS clock.

In addition, the frame synchronization timing in the system is maintained by referring to the 1PPS clock provided by the GPS receiver 61, so that the synchronization clock is provided using the DP-PLL (45) 55 to the clock provided by the network based on the frame synchronization. To create it.

In addition, a delay error compensator is installed in the delay compensation and clock distribution unit 64 to compensate for the delay error according to the distance between each subsystem and the transmission medium generated when the synchronization clock is transmitted to the subsystem. Avoid time and sync errors.

The synchronization method centering on the MSC / BSC 70 maintains the internal synchronization of the MSC or BSC by adopting the DP-PLL method, which is conventionally used to maintain synchronization of each system in the backbone network in the synchronization method using only GPS. The receiver 61 is selectively used to set synchronization information at system initialization, maintains synchronization with a clock provided by the DP-PLL during system operation, and accommodates GPS in the system as necessary. In addition, when the synchronization and time information are transmitted to the BTS 70, a delay compensator is provided in the code generator 74 so that the synchronization and time information at the base station BTS are matched.

In addition, the BTS 70 is provided with a line interface 72 to receive time and synchronization information provided from the MSC / BSC 70 to maintain synchronization. In this way, during the normal operation of the mobile communication system, the DP-PLL is used to converge to the synchronization information of the upper system, and if necessary, a GPS receiver may be attached to the system for operation.

In this case, the delay of synchronization information propagation is different for each lower base station when the system initial synchronization information is set, and the delay compensation method is also very important. The correction method for this is shown in FIG.

The maximum delay possible length of the delay compensator 80 may be set larger than the maximum value of the delay time of each base station (Tx ≥ τ _max ), and the delay compensation value for each base station may be expressed as follows.

T _D ≒ T _X -τ _x (X = a, b, c)

Therefore, if the delay value is corrected by calculating the compensation value as in the above expression, the delay error according to the transmission distance of each base station can be corrected, and time synchronization and clock synchronization between each base station can be maintained. To implement this, it is possible to use a looping function existing between the transmitter and the control unit of each subsystem. That is, in order to measure the delay time in the LIU control unit (A) (B) (C) of the delay compensation device 80, the LlU control unit of the subsystem is looped using the control channel on the transmission path, and the acceptance information When receiving the delay time data is sent, and the same data is received to measure the transmission / reception time difference, that is, the transmission delay time. These measurements are made several times to maintain reliability, and then the average value is obtained and used as a correction value.

In another embodiment, there is a method of performing time correction using a test GPS of a base station. When the time controller of the base station requests TOD data from the host system's time controller and receives the TOD data from the host system, the received TOD data of the base system is compared with the received TOD data of the base station's test GPS. The more accurate time synchronization can be maintained by a method of requesting a delay correction to the control unit in the delay compensation device 80 of the higher system by measuring the error. After the base station time information is set, the upper system synchronization clock is delay-compensated from the upper system and the synchronization of the system is properly maintained.

As described in detail above, in the mobile communication system according to the present invention, the internal network synchronization method can stably operate the system by selectively using the synchronization reference clock as the GPS clock and the synchronization reference clock received from the backbone network.

In addition, the GPS system at the base station, the last subsystem, can be eliminated and operated, reducing system installation costs.

In addition, since the system is operated using the synchronization device DP-PLL and GPS, there is an advantage that can increase the reliability and flexibility of the synchronization of the internal network.

In addition, since the system does not depend entirely on the synchronization of the GPS, it can be operated as the reference synchronization of the backbone network in case of an emergency, and can be applied to the difference of the wireless transmission method, that is, to be applied to both the synchronous and asynchronous environments.

Claims (2)

In the mobile communication system, a network interface unit for receiving reference time information through an internal network, a GPS receiver for receiving reference time information from the outside of the system, and visual information input from the network interface unit or the GPS receiver A reference clock generator for generating a reference clock, a delay compensator for compensating for a transmission delay error between an upper system or a lower system connected through the network, and a system synchronization for transmitting corrected visual information to the upper system or a lower system, respectively And a system synchronization device using an internal network of a mobile communication system. The apparatus of claim 1, wherein the delay compensation unit requests time information (TOD) data for a date from a higher system, and receives the time information (TOD) data from the higher system. TOD) data and the time information (TOD) data for the date received from the test GPS of his own, and the delay compensation unit of the delay compensation unit of the upper system by the error measured according to the comparison result, characterized in that System synchronizer using an internal network of a mobile communication system.

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