KR101224297B1

KR101224297B1 - Apparatus and method for controlling timing and mobile telecommunication system for the same

Info

Publication number: KR101224297B1
Application number: KR1020090032842A
Authority: KR
Inventors: 김정훈
Original assignee: 에릭슨 엘지 주식회사
Priority date: 2009-04-15
Filing date: 2009-04-15
Publication date: 2013-01-18
Also published as: KR20100114350A

Abstract

The present invention relates to an apparatus and method for matching time and frequency between remote base stations. The timing control device determines whether synchronization is possible through the GPS signal, switches the synchronization mode during the holdover, and transmits a timing packet between the master base station and the slave base station set on the neighbor list to maintain synchronization and receive GPS. Switch to GPS sync during state recovery.

GPS, timing packet, base station synchronization

Description

A timing control device and method and a mobile communication system using the same {APPARATUS AND METHOD FOR CONTROLLING TIMING AND MOBILE TELECOMMUNICATION SYSTEM FOR THE SAME}

The present invention relates to a mobile communication system, and more particularly, to a timing control apparatus and method for matching time and frequency between base stations.

A-GPS (Assisted GPS) is a method designed for in-building use, but uses a conventional GPS (Global Positioning System) receiver to acquire position information and synchronization signals from satellites after cold start. Various information about the satellite is required (eg Almanac, ephemeris data, etc.). Assisted-GPS (A-GPS) technology receives data from the A-GPS server over the network, which solves the low sensitivity problem during initialization, resulting in higher performance sensitivity and synchronization of time. Time to First Fix (TTFF) can be significantly reduced.

However, in the method of acquiring synchronization using the GPS receiver, the signal is weak enough due to reflection and absorption until the signal generated from the satellite reaches the earth's surface, so that the signal cannot be sufficiently transmitted in the building. There is a problem. Therefore, the degree of quality deterioration varies depending on the material, thickness, number of floors, height of adjacent buildings, viewing angle, and the like.

In addition, since the GPS receiver is a moving object whose position changes with time, there is a problem in that the reception state of the satellite signal is constantly changing, and even if the installation position or direction of the GPS satellite signal receiver changes, it may affect the RF (Radio Frequency) reception environment. As a main factor, a holdover state can occur frequently.

If the holdover state persists in the mobile communication system, the handoff failure rate gradually increases, which may result in a state in which the handoff is not performed. As the frequency shift increases, RF interference with neighboring base stations occurs, resulting in a decrease in throughput. A situation may arise in which the call becomes impossible.

Other methods of synchronization acquisition include IEEE 1588 standard time protocol (PTP) and network timing protocol (NTP). PTP, NTP, etc., designed as a method for synchronizing asynchronous networks such as ethernet, have a timing server transmitting timing packets and a client extracting frequencies and synchronization signals included in the received timing packets. That's the way it is. However, in asymmetric networks such as DSL, the error is not easy to use because the error increases according to the degree of asymmetry, and the timing packet increases the load on the network, thereby reducing the efficiency of the network, and the error increases only as the network size increases. However, there is a problem in that it requires a remarkably large number of servers (eg, assuming about 100 clients can connect to the timing server, and about 10,000 servers are needed for 1 million base stations).

The present invention provides a timing control apparatus and method for matching time and frequency between base stations in a mobile communication system.

The timing control apparatus of the present invention determines whether the synchronization is possible through the GPS signal, switches the synchronization mode during the holdover, and transmits a timing packet between the master base station and the slave base station set on the neighbor list to maintain the synchronization state. Switch to GPS sync when GPS reception is restored.

The timing control method of the present invention includes the steps of: a) forming a neighbor list including addresses of base stations adjacent to a specific base station, and arranging addresses to set a master base station and a slave base station; b) determining whether synchronization is possible through a GPS signal, switching a synchronization mode during a holdover, and transmitting a timing packet between the master base station and the slave base station set on the neighbor list to maintain a synchronization state; And c) switching to GPS synchronization during GPS recovery.

The mobile communication system of the present invention determines whether the synchronization is possible through the GPS signal, switches the synchronization mode during the holdover, and transmits a timing packet between the master base station and the slave base station set on the neighbor list to maintain the synchronization state. And a base station for switching to GPS synchronization during GPS reception state recovery, wherein the base station is either one of the master base station and the slave base station, or the master base station and the slave base station.

According to the present invention, it is possible to offset the shortcomings of the A-GPS dependent on the RF environment and the packet timing protocol dependent on the network for timing and synchronization signal acquisition of the base station.

It is possible to facilitate the use of base stations in buildings and homes by enabling synchronization acquisition and maintaining high quality indoors. Since Pico / Femto acts as a server and client in a master / slave structure, no separate server is required. Timing packets can be used to prevent quality deterioration caused by holdovers that occur frequently in buildings. In addition, it is possible to prevent deterioration in synchronization acquisition quality that occurs as the size of the network increases. The visual information does not generate visual synchronization errors resulting from up / down asymmetry. Adjacent Pico / Femto optimizes the number of packets per unit time, reducing the load on the network as much as possible. Timing packet masters are automatically configured, maintained, and switched within the network by specific algorithms, reducing system complexity.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions will not be described in detail if they obscure the subject matter of the present invention.

As wireless data services such as Code Division Multiple Access (CDMA) 2000, EV-DO, WCDMA, WLAN, etc. have been commercialized, the use of mobile phones and mobile data in homes is continuously increasing. A method for providing a mobile communication service has been proposed by installing a mobile communication base station at home to access a mobile communication core network. Such a mobile communication base station is called a femto cell or a pico cell. Femto is a unit representing 10 ^-15 and a femtocell radius is several tens of meters, and Pico is a unit representing 10 ^-12 and a picocell has a cell radius of 100 m or less. Femtocells have a smaller radius than picocells. The main characteristics and advantages of femtocells / picocells are femtozones / picos, which are the same as existing mobile phones, unlike fixed mobile convergence (FMC) services based on unlicensed mobile access (UMA), which requires dual-mode terminals. Is available in the zone. Accordingly, femtocells / picocells are expected to be able to act as a gateway for home network services in the home as well as effects such as rate cuts, increased coverage of mobile communication networks, and reduced network operating costs.

A femtocell / picocell is a base station with all functions minimized compared to a macrocell (i.e., an outdoor base station (NodeB; 3G broadband base station, eNodeB (evolved NodeB); 4G EPS)). It can accommodate up to 10 subscribers and can be installed directly by the network operator or subscriber. In addition, the connection with the mobile communication core network (public IP network) may be connected via a separate communication network connecting femtocell / picocell, or even through the Internet in a general home using a high-speed Internet service.

The femtocell / picocell is connected to the wired IP network, which is connected to the mobile communication network. There are two ways to access the mobile communication network, one to be connected to the mobile communication line network and the other to be connected to the mobile communication IP network.

When connected to a mobile communication line network, the RNC (Radio Network Controller) can be used as it is via a mobile communication core network. Therefore, there is no need to install a special device in the mobile communication network, but data communication is difficult as much as using a voice communication network.

There are two ways to connect to mobile IP network: UMA (Unlicensed Mobile Access) type and IMS & SIP type. The UMA can use voice (VoIP) and data communication services while connected to the wired IP network. In this case, a separate corresponding terminal is required. The UMA type femtocell is connected to the mobile IP network via the wired IP network. In this case, the user can use the existing terminal as it is, but the mobile communication company should install a device called UMA compliant network controller (UNC) separately. In the IMS & SIP type, it is premised that the mobile communication network corresponds to the All IP type IMS (IP Multimedia System).

Mobile communication systems require time synchronization, which uses GPS technology. The GPS receiver outputs a pulse per second (PPS) signal synchronized with the GPS time, and all base stations synchronize phase synchronization with the on time edge of the PPS signal. If the normal signal is not received due to the weak GPS signal according to the RF environment, the exact timing cannot be extracted. This state is called holdover. In the holdover state, the reliability of the output PPS signal accuracy decreases with time. If this condition persists, the terminal loses mobility and normal service is not achieved.

1 is a block diagram schematically illustrating a configuration of a mobile communication system to which a timing control device according to an embodiment of the present invention is applied.

At least one femto / pico base station 120 is connected to the timing server 110. The timing server 110 transmits assistant data to each femto / pico base station 120 to improve reception performance and to quickly induce initial operation. In addition, the femto / pico base station 120 receives auxiliary data from the timing server 110.

2 is a flowchart showing a procedure of a timing control method according to an embodiment of the present invention, FIG. 3 is an exemplary view showing a neighbor list according to an embodiment of the present invention, and FIG. 4 is a PPS according to an embodiment of the present invention. An illustration showing a control method. The timing control method of the present invention has the following procedure.

1. Femto / Pico base station neighbor list acquisition (S110)

First, a specific femto / pico base station 120 forms a neighbor list including an IP (internet protocol) address of neighboring femto / pico base stations 120 after system initialization. The neighbor list formation is an operation for checking whether each femto / pico base station 120 is adjacent to another femto / pico base station 120. That is, the femto / pico base station 120 forms an IP (internet protocol) address list of the adjacent femto / pico base station 120 to confirm the presence of another adjacent femto / pico base station 120 (get neighbor list). .

The femto / pico base station 120 simultaneously performs synchronization using GPS signals and synchronization using timing packets on a network. First, synchronization using the GPS signal is performed, and when the state in which the GPS signal cannot be received continues for a predetermined time or more, the synchronization state is maintained using the timing packet. The femto / pico base station 120 performs an auto-configuration process for performing synchronization by timing packets (Auto-configuration). The automatic setting process will be described later.

2. Timing Master / Slave Auto-Configuration (S120)

The femto / pico base station 120 forms an arrangement of a predetermined rule by using a method such as sorting the neighbor list. In one embodiment, each femto / pico base station 120 is ordered according to an IP address order and automatically configured as a master and a slave according to a predetermined rule. For example, referring to FIG. 2, the femto / pico base station 120 having the fastest IP address among the two femto / pico base stations 120 of consecutive IP addresses on the sorted neighbor list may be set as a master, and the IP address order. May set a late femto / pico base station 120 as a slave. In addition, the femto / pico base station 120 set as a slave may become a master, and the femto / pico base station 120 of a next IP address may have a continuous structure in which it is set as a slave. Thus, a particular femto / pico base station 120 can be both a slave and a master at the same time. That is, the femto / pico base station 120 having an IP address of 150.150.43.77 is a master of the femto / pico base station 120 having an IP address of 150.150.43.78 and has a femto / pico base station having an IP address of 150.150.43.78 ( 120 is a slave to femto / pico base station 120 with an IP address of 150.150.43.77 and a master of femto / pico base station 120 with an IP address of 150.150.43.79. In addition, the femto / pico base station 120 with an IP address of 150.150.43.79 does not have a master function and only has a slave function of the femto / pico base station 120 with an IP address of 150.150.43.78 (single master) / Slave structure). In the case of a multi-master / single-slave in which multiple masters are configured in one slave, the slave may consider selecting a master of higher quality (QoS) among the multiple masters. There is an advantage to selectively motivating a master of good quality. For example, a dual-master / single slave may transmit timing packets by two masters to one slave, and one slave may transmit timing packets by selecting from two masters.

For automatic master / slave configuration, obtain the neighbor list, sort the obtained neighbor list, and set the master / slave configuration rules between adjacent IPs in the sorted list as 1: 1, 2: 2, 3: It is automatically configured as a single or multi master / single or multi slave structure like 3, 4: 4. The advantage of having multiple masters is that you can choose a good quality master or trade off each other because the network load increases somewhat because multiple masters have to send all the timing packets to one slave. Consider relationships. When there is no other femto / pico base station around the specific femto / pico base station 120, the corresponding femto / pico base station 120 is requested by the timing server 110 to be assigned.

3. Switch over (S130) in synchronization using timing packet in holdover state

(1) Time synchronization using timing packet

When the master and the slave of the femto / pico base stations 120 is set, the master and slave transmit and receive timing packets with each other (S140). The timing packet includes time stamp data representing time information. The time stamp data is time information included in the timing packet, which is hardware stamped when the timing packet is transmitted. The femto / pico base station 120 calculates and synchronizes the time at which the timing packet was transmitted and the time at which the packet was received (S150). Timing packets to send and receive are composed of a minimum number of packets to maintain synchronization to minimize the load on the network.

(2) PPS (Packets Per Second) control of timing packet

The purpose of controlling the PPS of the timing packet is to find an optimal price / performance ratio. The higher the number of timing packets per unit time transmitted from the master to the slave, the better the synchronization quality can be maintained. However, the cost increases by increasing the load on the network. In contrast, the use of a small number of timing packets degrades the quality of synchronization (accuracy of phase error and frequency). At the time of synchronization by GPS, since the quality of the synchronization depends on the GPS signal, high quality can be obtained, and thus a large number of timing packets are not required. On the other hand, in the holdover state, degradation of synchronization quality gradually occurs, and it is necessary to induce stabilization using timing packets within a short time. Therefore, enough timing packets (e.g. 128 PPS) are sent from master to slave, and the slave sends information on the synchronous quality to the master so that the timing packets transmitted from master to slave are 64PPS-> 32PPS-> 16PPS-> Decreases in the order of 8PPS-> 4PPS-> 2PPS. This unnecessarily reduces the load on the timing packets in the network.

4. Switch to GPS sync when GPS reception is restored

Thereafter, when the GPS signal is normally received, the mode is switched back to the synchronization mode by the GPS signal. This is because the synchronization by GPS signal can be more stably obtained and when the synchronization by timing packet is maintained for a long time, very low period phase drift may be affected by Systematic Delay Variation (G.8261) in the network. Because there is.

While the above methods have been described through specific embodiments, the methods may also be implemented as computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disks, optical data storage devices, and the like, which are also implemented in the form of carrier waves (for example, transmission over the Internet). Include. In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily deduced by programmers of the present invention.

While the invention has been described in connection with certain embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention . It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

2 is a flowchart showing a procedure of a timing control method according to an embodiment of the present invention.

3 is an exemplary view showing a neighbor list according to an embodiment of the present invention.

4 is an exemplary view showing a PPS control method according to an embodiment of the present invention.

Claims

As a timing control device,

Determining whether synchronization is possible through GPS signal, the synchronization mode is switched in case of Holdover, and the timing packet is transmitted between the master base station and the slave base station set on the neighbor list to maintain the synchronization state. Switch,

And a timing control unit capable of changing the number of timing packets per unit time transmitted from the master base station to the slave base station according to the quality of the synchronization state.

The method of claim 1,

Forming the neighbor list including addresses of the base stations adjacent to a specific base station, arranging addresses to set the master base station and the slave base station, and transmitting and receiving the timing packet including time information between the master base station and the slave base station; The timing control device which keeps the said synchronous state.

delete

The method according to claim 1 or 2,

And the timing control device is either one of the master base station and the slave base station or the master base station and the slave base station.

5. The method of claim 4,

And the master base station and the slave base station have a multi-single structure.

The method of claim 5,

In the multi-single structure, at least one slave base station can select one of a plurality of master base stations.

5. The method of claim 4,

And the slave base station is assigned to the master base station by requesting a timing server when there is no adjacent base station.

As a timing control method,

a) forming a neighbor list including addresses of base stations adjacent to a specific base station, and arranging addresses to set a master base station and a slave base station;

b) determining whether synchronization is possible through a GPS signal, switching a synchronization mode during a holdover, and transmitting a timing packet between the master base station and the slave base station set on the neighbor list to maintain a synchronization state; And

c) switching to GPS synchronization upon recovery of GPS reception,

And in step b), the number of timing packets per unit time transmitted from the master base station to the slave base station can be changed according to the quality of the synchronization state.

delete

9. The method of claim 8,

The timing control device is either one of the master base station and the slave base station, or the master base station and the slave base station;

And the master base station and the slave base station have a multi-single structure, and in the multi-single structure, at least one slave base station can select one of a plurality of master base stations.

The method of claim 10,

A mobile communication system,

Determining whether synchronization is possible through GPS signal, the synchronization mode is switched in case of Holdover, and the timing packet is transmitted between the master base station and the slave base station set on the neighbor list to maintain the synchronization state. Including a base station to switch to,

The base station is either one of the master base station and the slave base station, or the master base station and the slave base station, and the number of timing packets per unit time transmitted from the master base station to the slave base station according to the quality of the synchronization state. Changeable, mobile communication systems.

The method of claim 12,

And a timing server for allocating the master base station at the request of the slave base station when there is no neighbor base station.

delete

The method according to claim 12 or 13,

The master base station and the slave base station has a multi-single structure,