KR19990058986A - Intra-Network Synchronization Method in Mobile Communication System - Google Patents

Abstract

In the mobile communication system, an intra-network synchronization method may include: a GPS that generates time information (TOD) and a reference clock generator that generates a reference clock according to the time information. A mobile switching sensor comprising a clock generator for generating a system synchronous clock according to the time information and a reference clock, a delay compensation and a clock distribution unit for preventing a delay error due to networking with a higher system and a lower system and distributing a clock required for the system. Base station control unit (BSC / BSC); And a base station transmission system (BTS) for receiving time information and synchronization information provided through the switching center / base station controller to maintain synchronization of each base station.

Description

Intra-Network Synchronization Method in Mobile Communication System

The present invention relates to a synchronization device of a mobile communication system, and more particularly, to an intra-network synchronization method in a mobile communication system suitable for obtaining intra-network synchronization information.

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 synchronization signal maintaining apparatus includes a mobile switching center (MSC) 10 including a digital processing PLL 11, a mobile switching center (MSC) 10, and a mobile terminal for a mover. It consists of a base station control / base station transmission system (BSC / BTS) 20 that is interfaced and includes a global positioning system (GPS) 21 and manages the base station.

The MNC block of the MSC 10 uses a MSC (preferred alternate master slave) PAMS synchronization scheme to prevent slippage caused by mismatches in the switching clocks in the digital switching network. The internal clock of 10) is synchronized 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 suitable for use as a synchronization device in a CDMA mobile communication system because its stability is very accurate but the time synchronization aspect required in a code division multiple access dl (CDMA) mobile communication system is not considered at all. Do. 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.

Meanwhile, referring to FIG. 2, the core technology of the conventional CDMA mobile communication system is a sort handoff through separation between users using a code and accurate time synchronization. The CDMA system operates on the basis of accurate time synchronization between base stations, so that the accuracy of GPS time is absolutely effective in handoff between base stations. At this time, the performance of the GPS there is an error between the GPS 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 needed for software operation and store it in the software block to visualize the time in hardware to the operator.

BSC / BTS synchronizer 20 is composed of GPS clock control and distribution unit 31, 32, GPS receives time information from satellite, TOD (time of date), 10MHz, 1PPS using coaxial cable Receive and provide it as a system clock for system synchronization.

The conventional synchronization method of the BSC / BTS 20 mentioned above is effective to maintain the time synchronization by the synchronization maintaining method using the GPS 21, but as the cell radius of the base station becomes narrower with the development of the mobile communication system, As the number increases, the installation cost of using the GPS system for each base station increases.

In addition, since the GPS system itself is a system of different nationalities, there is a problem in maintaining the network in an emergency situation, and the cost of the GPS fee is expected to increase. 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 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.

Accordingly, the present invention has been made in view of the above-mentioned point, and an object of the present invention is to provide a GPS to the MSC and select the GPS output as the reference clock as the system, and synchronize the system to the clock supplied from the MSC / BSC. In one mobile communication system to provide an intra-network synchronization method.

In addition, another object of the present invention is to provide a DP-PLL device to the mobile communication system, thereby enabling intra-network synchronization in a mobile communication system to maintain the TOD synchronization required for the mobile communication system without using a GPS receiver of a conventional BSC / BTS. In providing a method.

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

FIG. 2 is a block diagram illustrating a BSC / BTS synchronizer of FIG. 1. FIG.

3A and 3B are block diagrams illustrating an intra-network synchronization apparatus 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. 3A and 3B.

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, 71: GPS

30: bus line 31: TRMA

32: TMPA 40: MSC / BSC

42: network interface (NIU) 43, 53, 62, 72: reference clock selector

44, 54: TOD generator 46, 56: distributor

47, 52: line interface (LIU) 47-1: delay compensation function

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

74: clock divider 80: MSC / BSC delay compensation device

In the mobile communication system of the present invention for achieving the above object, the intra-network synchronization method includes a GPS for providing time information (TOD), a reference clock generator for generating a reference clock according to the time information, and the time information and the reference clock. A mobile switching center / base station controller (BSC / BSC) consisting of a clock generator that generates a system synchronous clock, a delay compensation due to networking with a higher system and a lower system, and a delay compensation and a clock distribution unit for distributing the clock required for the system. And a base station transmission system for receiving time information and synchronization information provided through the switching center / base station control unit and maintaining synchronization of each base station.

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

3A and 3B are block diagrams illustrating an intra-network synchronization apparatus in a mobile communication system according to the present invention, FIG. 4 is a block diagram according to the operation of the synchronization apparatus in FIGS. 3A and 3B, and FIG. 5 is synchronization in FIG. A layout diagram according to delay compensation.

Referring to FIG. 3A, the MSC / BSC 40 includes a GPS 41 for transmitting the TOD data generated from the TOD generator 44 to the 10 MHz and IPPS clocks, 2048 MHz and 8 kHz, respectively, and the FE clock. System synchronization with a network interface (NIU) 42 for constructing an intra-network, and a reference clock selector (RSU) 43 for selectively supplying reference clocks to the GPS 41 and the NIU 42. A divider 46 for distributing TOD data, a system reference clock, and a system frame pulse for each interface; and interfaces of lines of an intra-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. 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.

The base station transmission system (BTS) 50 also provides a 2048 MHz and 8 kHz, a line interface (LIU) 52 for connecting the lines of the intra-network to the FE clock, and a reference clock to the LIU 52. A reference clock selector (RSU) 53 for selectively supplying, and a divider 46 for distributing and outputting TOD data, system reference clock, and system frame pulse for system synchronization, respectively. In this case, a GPS 51 for transmitting the TOD data generated from the TOD generator 54 to the RSU 53 at 10 MHz and 1 PPS clock is connected to an input terminal of the RSU 53, and the RSU 53 is connected to the RSU 53. A digital processing PLL 55 is connected between the divider 56 to synchronize phase synchronization.

An operation of the intra-network synchronization method 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, thereby receiving TOD data from the GPS 61 and supplying each system to provide accurate visual information on operation and maintenance. can do. 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 61, and the synchronization clock is generated using the DP-PLL 45 and 55 at the clock provided by the network based on the frame synchronization. Do it.

In addition, a delay error compensator is provided in the clock distribution unit 64 to compensate for the delay error between the sub-systems generated when the sync clock is transmitted to the sub-systems so that time and sync errors between the sub-systems do not occur. do.

The BSC synchronization maintains the internal synchronization of the BSC by adopting the DP-PLL method used in the MSC in the conventional synchronization method using only GPS, and the GPS 61 is used to set the synchronization information at the system initialization. The system maintains synchronization with the clock provided by the DP-PLL and accommodates GPS in the system as needed. In addition, when transmitting synchronization and time information to the BTS 70, a delay compensator is provided in the clock divider 74 similarly to the MSC so that the synchronization and time information at the base station are matched.

In addition, DP-PLL is also installed in the BTS 70 to maintain synchronization by receiving time and synchronization information provided from the MSC / BSC 60, and set the time information and synchronization information by using GPS at the initial setting of the system. To be referenced. However, during 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, the GPS can be attached to the system and operated.

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. A correction method for this is shown in FIG. 5.

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 ≒ Tx-τ _χ (χ = 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) in the delay compensation device 80, the LIU 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, the intra-network synchronization method in the mobile communication system according to the present invention can use the same synchronization clock and time information when the synchronization reference clock is applied to the system by synchronizing the GPS clock and the synchronization reference clock received from the backbone network. As a result, slips can be reduced when data is transmitted and received between systems.

In addition, the GPS system of the base station, the final subsystem, can be selectively operated to reduce the system installation cost.

In addition, since the system is operated using the DP-PLL and GPS, the synchronization device has the advantage of increasing the reliability and flexibility of the intra-network synchronization.

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

Claims (2)

GPS for generating time information (TOD), a reference clock generator for generating a reference clock according to the time information, a clock generator for generating a system synchronization clock in accordance with the time information and the reference clock, networking with a higher system and a lower system. A mobile switching center / base station controller (BSC / BSC) consisting of a delay compensation and a clock distribution unit that prevents delay errors and distributes clocks necessary for the system, and visual information and synchronization information provided through the switching center / base station controllers. An intra-network synchronization method in a mobile communication system comprising a base station transmission system (BTS) for receiving and maintaining synchronization of each base station. The system of claim 1, wherein the base station transmission system (BTS) is configured to generate a GPS that generates time information (TOD), a reference clock generator that generates a reference clock according to the time information, and a system synchronization clock according to the time information and the reference clock. An intra-network synchronization method in a mobile communication system, comprising: a clock generator for generating a clock divider for distributing a system synchronization clock of the clock generator to each system.