KR20050060764A - Method for checking link-state in communication system, and apparatus for the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a method and apparatus for checking a link state of a communication system, which enables an online test of a link state in a relay line between a local station and a large station, and a device for the same. It is possible to identify the presence or absence of the loop on the link line between the end lines online. Especially, the transmission equipment provided between the near end and the far end provides the E1 transmission interface of 2.048Mbps. When used, it does not interfere with user available bandwidth for user data transmission, and it is possible to identify whether there is a loop between the own station and the large station regardless of the data transmission method used. The present invention provides an inspection method and an apparatus therefor.

Description

Method for checking link-state in communication system, and apparatus for the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system, and more particularly, to a method and apparatus for checking a link state of a communication system, which enables an online test of a link state in a relay line between a local station and a large country.

In general, a communication system includes a repeater for transmitting and receiving a signal to and from a user terminal, and a controller for transmitting a signal to or receiving a signal from the repeater and controlling the repeater. do. The communication system also includes an exchanger for connecting its network with an external network.

For example of mobile communication, a mobile communication system includes a base station for transmitting and receiving radio signals to and from a mobile station, and a base station controller for transmitting and receiving wired signals to and controlling the base station. and a switching station (Mobile Switching Center) for connecting to various base station controllers or to an external network (such as a network of another service provider or a public switched network).

In the configuration of the above communication system, signal transmission between each component is defined by a communication protocol, and in particular, a transmission interface between each component having a predetermined transmission rate is defined by a physical layer protocol.

As an example of a transmission interface, E1 is a 2.048 Mbps digital transmission line that multiplexes several low-speed digital lines, and E1 is a distance between a near end and a far end that are several kilometers away from each other. Used as a transport interface.

As an example of using E1 as a transmission interface in the mobile communication system, E1 is used as a transmission interface between the base station and the base station control period or between the base station controller and the switching center. In order to actually use E1 as a transmission interface, multiplexing equipment is provided between the base station and the base station control period or between the base station controller and the switching center. The multiplexing equipment of a mobile communication system that is commonly used is a Digital Subscriber Line Access Multiplexor (DSLAM).

Techniques related to the E1 transport interface described above are specified in ITU-T G.704.

On the other hand, in a communication system, a physical logical path is defined between two points (host and power) to send and receive signals by a transmission interface. This is called a link.

In the case of a mobile communication system, equipment such as a Digital Subscriber Line Access Multiplexer (DSLAM) serves to form a link between the home and the country as an E1 transmission interface. Transmission links, such as digital subscriber line access multiplexers (DSLAMs), can form multiple links between the home country and the power.

On the other hand, it is necessary to manage whether the links between the home country and the big country are normal.

Accordingly, methods for checking whether the link status between the own country and the large country is normal or abnormal are proposed. Here, the base station, the base station controller and the switching station of the mobile communication system may be a local station or a large station, and the station and the station correspond to the base station and the base station control period or between the base station controller and the switching station.

In the prior art, there has been a method of performing a loop inspection for each link between the own station and the large station. On the other hand, it should also be possible to check whether or not the above-described loop check was executed normally.

Accordingly, in the related art, the local station and the large station generate specific data (loop identification data) for each link on a predetermined time basis and transmit the generated data to the transmission line. The counterpart (large station and self station) checks the status of each link by searching the transmission lines on a predetermined time basis and confirming the mutually promised data (loop identification data).

The loop state checking method according to the prior art will be described in more detail.

The local station transmits the loop identification data in units of time. The transmitted loop identification data then crosses the relay line.

The player receives the loop identification data and retrieves the loop identification data.

On the contrary, the large island also transmits the loop identification data by a certain time unit. The transmitted loop identification data then crosses the relay line.

The host then receives loop identification data and retrieves the loop identification data.

When the conventional loop state checking method is applied to a communication system using an E1 transmission interface, the method varies depending on the data transmission method. Detailed description thereof is as follows.

If the A1 transfer line uses the Asynchronous Transfer Mode (hereinafter, simply abbreviated as ATM) transmission system, the local station shall check for the presence of a loop at intervals of 30 ATM cells (53 bytes). ) To the powers. As a result, the power station searches for one cell received every 30 ATM cell intervals.

On the contrary, the large station also transmits one cell (53 bytes) to the local station to check the loop at every 30 ATM cell intervals, so that the local station searches for one cell received every 30 ATM cell intervals. .

Accordingly, the loop state of the transmission link Tx and the reception link Rx formed in the E1 transmission line are checked.

In case of using the packet transmission method in the next E1 transmission line, 1 byte is allocated for loop presence identification.

In addition, the self or large station inserts 1 byte of loop identification data allocated to the user packet in a predetermined time (20 ms) unit for loop presence identification. As described above, a packet of 20 ms in which loop identification data for loop existence identification is inserted is transmitted through an E1 transmission line.

In the above, the loop identification data of 1 byte is composed of a 4-bit combination. More specifically, the first 4 bits are for determining whether the loop identification data is normally received, and the remaining 4 bits are used for actual loop identification.

For example, it is assumed that the self station sets "10011111" as loop identification data and the big station sets "10010000" as loop identification data.

The loop identification data is transmitted and retrieved in 20 ms packet units.

When searching for loop identification data in units of 20 ms packets, the large station first checks whether the first 4 bits of the received packet are “1001” to determine whether or not data for loop identification is normally received.

If the first 4 bits of the packet received at the station are not "1001", the station ignores the loop identification data inserted in the corresponding packet and waits for loop identification data after 20 ms.

On the other hand, if the first 4 bits of the received packet is "1001", the player checks the second 4 bits.

At this time, if the second 4 bits are retrieved as "1111", the game is determined to be a normal link. However, if the second 4 bits are found to be "0000" in the large station, the loop identification data transmitted by the large station is looped back somewhere in the E1 transmission line, and the large station determines that the link is abnormal. In other words, it is determined as a looped link. As a result, the Power reports to the parent that a Looped Link exists.

The own station also searches for loop identification data in the same manner as above, and determines a normal link and a looped link according to the search result.

As described above, the conventional technique has a disadvantage in that a scheme for identifying a loop state is different according to a transmission scheme adopted for data transmission in a transmission line using an E1 transmission interface.

For example, the ATM transmission method and the packet transmission method have different data formats transmitted through the E1 transmission line. Therefore, a different loop identification function should be configured for each transmission method.

In addition, the prior art inserts and transmits loop identification data into a user available bandwidth limited to 1.920 Mbps by using an E1 transmission interface. As a result, pure user available bandwidth is wasted to check the loop state.

For example, in the packet transmission scheme in which 1 byte of loop identification data is inserted into a user packet and transmitted in 20 ms units, the user effective bandwidth of “8 bits / 20 ms = 400 bps” is occupied to perform the loop identification function. Therefore, the usable bandwidth for purely user data transmission is reduced by the overhead of 400bps at 1.920Mbps.

An object of the present invention has been made in view of the above points, in particular, it is possible to identify whether there is a loop of a link online in a transmission line (transfer line) between a host and a large country. It is to provide a device for.

It is still another object of the present invention to provide user effective bandwidth for user data transmission when transmission equipment provided between a near end and a far end uses an E1 transmission interface of 2.048 Mbps as a physical layer. The present invention provides a method for checking a link state of an appropriate communication system and an apparatus therefor, which can identify whether a link loop exists between a local station and a large station regardless of a data transmission method used without any interruption in bandwidth.

A feature of the link state checking method according to the present invention for achieving the above objects is a user channel using a user available bandwidth and a framing channel using a bandwidth excluding the user available bandwidth. inserting and transmitting loop identification data into a Not Frame Alignment Signal (NFAS) field of the framing channel in an E1 multi-frame consisting of a framing channel; And determining a link (Normal Link) and a looped link (Looped Link).

The loop identification data is inserted into a field into which national bits of a sick frame alignment signal (NFAS) field are to be inserted.

In addition, the framing channel corresponds to the first time slot of E1 multi-frames consisting of 32 time slots.

For example, in the case of a 16E1 frame supporting 16 E1 transmission lines, the loop identification data is inserted into a field of the framing channel corresponding to the first time slot of even-numbered E1 frames among the 16E1 frames.

A feature of the loop state inspection apparatus according to the present invention for achieving the above object is a user channel using a user available bandwidth (user available bandwidth) and a framing channel using a bandwidth other than the user available bandwidth ( In a system for transmitting and receiving a multi-frame consisting of a framing channel at a predetermined transmission rate, the first insertion unit for inserting and transmitting the first loop identification data in the free field of the framing channel and the free field of the received framing channel A device of a first end including a first searcher for searching and determining a link state, a second inserter for inserting and transmitting second loop identification data into a spare field of the framing channel, and a received framing The second end device includes a second search unit that searches a free field of a channel to determine a link state. To be configured.

More preferably, the devices of the first end and the second end transmit an E1 multiframe composed of a plurality of E1 frames. At this time, the framing channel corresponds to the first time slot of the E1 multi-frames. The margin field is a Not Frame Alignment Signal (NFAS) field of the E1 multi-frame.

The first and second loop identification data may have different values.

In addition, when the devices of the first end and the second end are searched for the same value as the loop identification data transmitted by being inserted into the spare field of the framing channel, a looped link is performed. Determined.

Other objects, features and advantages of the invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, a preferred embodiment of a link state checking method and apparatus therefor of a communication system according to the present invention will be described with reference to the accompanying drawings.

The present invention also provides a transmission line without affecting the bandwidth used for user data transmission in a transmission line (relay line) between a near end and a far end using a transmission interface of a predetermined transmission rate as a physical layer. Regardless of the transmission method used, the link status between the own station and the large station is checked in the same manner.

In particular, the present invention will be described as an example a loop state inspection procedure and apparatus therefor to be applied to an E1 transmission line (relay line) of 2.048Mbps. In addition, a mobile communication system will be described as an example.

Accordingly, the base station, the base station controller and the switching station of the mobile communication system may be the own station or the large station, and the station and the station have a corresponding meaning with the base station and the base station control period or between the base station controller and the switching station. The invention also applies to digital subscriber line access multiplexers (DSLAMs) using the E1 transport interface.

Once in the present invention, the E1 multi-frame framing channel is used to transmit loop identification data without using a user channel of the E1 multi-frame. This has the same meaning as using a band excluding a pure user available bandwidth for transmitting a user channel.

1 is a block diagram illustrating a link state checking procedure of a communication system according to the present invention.

Referring to FIG. 1, the loop state checking apparatus according to the present invention is provided in a device for transmitting E1 frames, that is, E1 multi-frames, by a physical layer protocol. The structure of the apparatus is that the local station inserting unit 10 and the local station searching unit 30 are provided in the first device of the local station, and the national station searching unit 20 and the national station inserting unit 40 are provided in the second device of the major country. .

The local station inserting unit 10 and the country inserting unit 40 insert loop identification data generated in the physical layer into a framing channel constituting an E1 multi-frame and transmit the same to the counterpart.

The power station searching unit 20 and the own station searching unit 40 then search for loop identification data in the framing channel constituting the E1 multi-frame to determine the link state.

In more detail, the E1 multi-frame consists of a user channel using a user available bandwidth and a framing channel using a bandwidth for control purposes other than the user available bandwidth.

The local station inserter 10 inserts loop identification data into a not frame alignment signal (hereinafter, referred to as NFAS) field, which is a free field of the framing channel, and transmits the loop identification data to the counterpart.

Accordingly, the power searching unit 20 searches for loop identification data in the NFAS field of the received framing channel to determine a normal link and a looped link. An example of the determination is described in detail below.

In addition, the player inserting unit 20 inserts loop identification data having a different value from the loop identification data transmitted from the local station inserting unit 10 into the NFAS field, which is a free field of the framing channel, and transmits the loop identification data to the counterpart.

Accordingly, the local station search unit 30 searches for loop identification data in the NFAS field of the received framing channel to determine a normal link and a looped link. An example of the determination will also be described in detail below.

The E1 multi-frame used in the present invention uses a plurality of E1 frames shown in FIG.

2 is a view showing the structure of an E1 frame used in the present invention.

Referring to FIG. 2, an E1 frame consists of 32 time slots.

Each time slot consists of 8 bits, and 30 of the 32 time slots correspond to the user channel, and the other two time slots correspond to the framing channel.

The time slots of the user channel are for transmitting voice or data, and the time slots of the framing channel are for signaling and framing in the E1 frame transmission. In FIG. 2, the time slot for signaling among the time slots of the framing channel is represented by “S”, and the time slot for the other framing is indicated by “F”.

The configuration of the E1 multi-frame in which a plurality of the above-mentioned E1 frames are combined is shown in FIG. 3.

3 is a diagram illustrating a structure of a sub multi-frame (SMF) used in the present invention, wherein a combination of 16 E1 frames is referred to as sub multi frame 1 (hereinafter referred to as SMF1) and sub multi frame 2 ( Sub multi frame2 (hereinafter abbreviated as SMF2).

In FIG. 3, SMF1 is the first eight E1 frames (Frame 0 to Frame 7), and SMF2 is the next eight E1 frames (Frame 8 to Frame 15). SMF1 and SMF2 are called one E1 multi-frame.

A framing channel consisting of a combination of the first time slots of each E1 frame in an E1 multi-frame is divided into a Frame Alignment Signal field and an NFAS field according to a number assigned to the E1 frame. .

That is, the field of the framing channel corresponding to the first time slot of the odd-numbered E1 frames Frame0, 2, 4, 6, 8, 10, 12, 14 in the E1 multi-frame is a FAS field, and the even ( The field of the framing channel corresponding to the first time slot of the even) th E1 frames Frame1, 3, 5, 7, 9, 11, 13, and 15 is an NFAS field.

The configuration of the NFAS field is shown in FIG.

Four bits of the eight bits of the NFAS field shown in FIG. 4 are used for the loop identification data transmission of the present invention.

The first three bits of the NFAS field are international bits, which are essential bits for composing an E1 frame, and the second five bits are national bits, which can be used by the user for driving / management and maintenance. Part.

More specifically, in FIG. 4, the first bit "Si / M", the second bit "1" and the third bit "A" are international bits necessary for composing an E1 frame, and the fourth to last. Up to five bits (Sa4, Sa5, Sa6, Sa7, Sa8) are national bits.

In the present invention, the latter four bits (Sa5, Sa6, Sa7, Sa8) of the spare field into which the national bits are inserted are used to transmit loop identification data.

The following describes a procedure for checking a loop state using the framing channel of the E1 multi-frame described above.

The localization inserter 10 inserts first loop identification data into the NFAS field of the framing channel corresponding to the first time slot of the even-numbered E1 frames Frame1, 3, 5, 7, 9, 11, 13, and 15. Insert it. At this time, '1' is set as the first loop identification data, respectively, to an initial value of the last four bits Sa5, Sa6, Sa7, Sa8 of the NFAS field of the framing channel.

Accordingly, the combination of the first loop identification data transmitted through one E1 multi-frame is composed of " 1111 " and is transmitted to the counterpart via the transmission equipment of the E1 transmission line.

The power searching unit 20 searches for the values of four bits Sa5, Sa6, Sa7, Sa8 inserted in the NFAS field in the received E1 multi-frame framing channel at a predetermined period.

At this time, if the combination " 1111 " of the 4-bit first loop identification data set by the local station inserting unit 10 is found, this is a normal E1 multi-frame transmitted from the local station inserting unit 10, so that the large station searching unit 20 Is determined to be a normal link state. In other words, the link status from the local station to the large station through the transmission equipment is determined to be normal.

On the other hand, if " 0000 " is searched instead of the 4-bit value set by the local station inserter 10, since the 4-bit value set by the power station inserter 40 is searched, the power search unit 20 is looped. It is determined as (looped link) state. In other words, the link status from the own station to the large station through the transmission equipment is determined to be abnormal.

Meanwhile, the power insertion unit 40 identifies the second loop in the NFAS field of the framing channel corresponding to the first time slot of the even-numbered E1 frames Frame1, 3, 5, 7, 9, 11, 13, and 15. Insert data. At this time, '0' is set as the second loop identification data in the initial values of the last four bits Sa5, Sa6, Sa7, Sa8 of the NFAS field of the framing channel.

Accordingly, the combination of the second loop identification data transmitted through one E1 multi-frame is composed of " 0000 " and transmitted to the counterpart via the transmission equipment of the E1 transmission line.

The local search unit 30 searches for the values of the four bits Sa5, Sa6, Sa7, Sa8 inserted in the NFAS field in the framing channel of the received E1 multi-frame at predefined intervals.

At this time, if the combination " 0000 " of the 4-bit second loop identification data set by the power station inserting unit 40 is found, this is a normal E1 multi-frame transmitted from the power station inserting unit 40, and thus the local station search unit 30 Is determined to be a normal link state. In other words, the link status from the large station to the local station through the transmission equipment is determined to be normal.

On the other hand, if " 1111 " is searched instead of the 4-bit value set by the power station inserter 40, this means that the 4-bit value set by the own station inserter 10 is searched, so that the local search unit 30 loops the loop. It is determined as (looped link) state. In other words, the link status from the large station to the local station through the transmission equipment is determined to be abnormal.

 Thereafter, the search units 20 and 30 report the determined link state to the upper level.

When the present invention is applied to a mobile communication system, a device supporting an E1 transmission interface is provided on an assembly board mounted on a base station controller of the mobile communication system. The device included in the assembly board of the base station controller further includes a local station inserting unit and a local station searching unit.

In addition, the assembly board mounted in the base station also includes a device supporting the E1 transmission interface. The device provided in the assembly mode of the base station further includes a power insertion section and a power search section.

The device of the E1 transmission interface provided in each base station controller and each assembly board of the base station supports 16 E1 transmission lines 16E1. The host insertion section and the power insertion section insert and transmit loop identification data of "1111" or "0000" to each other using four bits of one byte of the NFAS for each E1. That is, if the local station inserter uses the loop identification data of "1111", the station inserter uses the loop identification data of "0000", and if the local station inserter uses the loop identification data of "0000", the station inserter uses the "1111" loop identification data. Loop identification data.

In addition, the local search unit and the large country search unit extract and search loop identification data from each received E1 frame, and determine a normal link and a looped link according to the search result.

The device supporting the 16E1 transmission line is a physical layer device, and is mounted in an ATM low speed subscriber physical layer board assembly-ASIC (ALPA-A) supporting the E1 transmission interface in the base station controller, and also supports the E1 transmission interface in the base station. Is mounted on the Line Interface Control board Assembly (ASIC). Also, firmware is inserted and searched by using a device supporting 16E1 transmission line.

According to the present invention described above, in checking a link state between a station and a station using the E1 transmission interface as a physical layer, the data transmission method is correlated when identifying a loop in a transmission line (relay line) between the station and the station. Because it uses E1 frame without it, it has wide compatibility.

In addition, in the present invention, some fields of the NFAS of the framing channel, which is overhead for E1 control, are used for the transmission of loop identification data without occupying a user effective bandwidth of 1.920 Mbps, so that transmission of user data is not impeded. That is, using the link state checking method and apparatus therefor according to the present invention does not reduce the user effective bandwidth of 1.920 Mbps.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

1 is a block diagram for explaining a link state checking procedure of a communication system according to the present invention.

2 is a view showing the structure of an E1 frame used in the present invention.

3 is a diagram showing the structure of a sub multi-frame (SMF) used in the present invention.

4 is a diagram illustrating a structure of a sickle frame alignment signal (NFAS) field of a sub multi-frame (SMF) according to the present invention.

Claims (12)

In a multi frame including a user channel using a user available bandwidth and a framing channel using a bandwidth excluding the user available bandwidth, a predetermined frame of the framing channel Inserting and transmitting loop identification data into the field; And determining the link state by searching the loop identification data of the field. The method of claim 1, wherein the multi-frame is an E1 multi-frame. 2. The method of claim 1, wherein the field is a Not Frame Alignment Signal (NFAS) field. 4. The method of claim 3, wherein the loop identification data is inserted into a field into which national bits of the sick frame alignment signal (NFAS) field are to be inserted. The method of claim 1, wherein the framing channel corresponds to a first time slot of an E1 multi-frame consisting of 32 time slots. The method of claim 5, wherein the loop is identified in a field of the framing channel corresponding to the first time slot of even-numbered E1 frames among the 16E1 frames as the multi-frame is a 16E1 frame supporting 16 E1 transmission lines. Link status checking method of a communication system, characterized in that for inserting data. In a system for transmitting and receiving a multi-frame consisting of a user channel using a user available bandwidth (framing channel) using a user channel using a user available bandwidth and the bandwidth excluding the user effective bandwidth, at a predetermined transmission rate, A first station including a first inserting unit inserting and transmitting first loop identification data into the spare field of the framing channel, and a first search unit searching for the spare field of the received framing channel to determine a link state; Device); Second end including a second insertion unit for inserting and transmitting the second loop identification data in the free field of the framing channel, and a second search unit for searching the free field of the received framing channel to determine the link state (Second end) Link state inspection apparatus of a communication system, characterized in that it comprises a device of). 8. The apparatus of claim 7, wherein the devices of the first end and the second end transmit an E1 multiframe including a plurality of E1 frames. 9. 10. The apparatus of claim 8, wherein the framing channel corresponds to a first time slot of the E1 multiframes. 9. The apparatus of claim 8, wherein the margin field is a Not Frame Alignment Signal (NFAS) field of the E1 multi-frame. 8. The apparatus of claim 7, wherein the first and second loop identification data have different values. 8. The method of claim 7, wherein the devices of the first end and the second end are looped when the same value as loop identification data transmitted by being inserted into the spare field of the framing channel is detected. Link state inspection apparatus of a communication system, characterized in that determined by the (looped link).