KR20160080828A - Digital transmission overflow processing device - Google Patents

Abstract

According to the present invention, provided is an apparatus for processing overflow in digital transmission. The apparatus comprises: an excessive input detection unit which detects an overflow of a digital signal digitally transmitted via a transport medium from an adjacent node constituting a distributed antenna system, wherein the excessive input detection unit is disposed in a digital part installed in a corresponding node receiving the digital signal transmitted from the adjacent node, and the digital part performs digital processing of a relay signal adapted to relay a mobile communication signal in the corresponding node; and a digital gain control unit which is disposed on a signal transmission path of the digital signal, and controls gain based on at least one of information about whether the digital signal has been excessively input and an excessive input level, transferred as a result of the detection of the excessive input detection unit, so that the digital signal which has been excessively input is converted into a level equal to or lower than a predetermined allowable level.

Description

[0001] DIGITAL TRANSMISSION OVERFLOW PROCESSING DEVICE [0002]

The present invention relates to a digital transmission overflow processing apparatus, and more particularly, to a digital transmission overflow processing apparatus which monitors whether a digital signal transmitted through a transmission medium from a neighboring node constituting a distributed antenna system And to a digital transmission overflow processing apparatus capable of solving the problem caused by digital transmission overflow and digital spurious transmission.

In general, a repeater is installed in a mobile communication system to expand a service area of a base station or to solve a shadow area. At this time, a distributed antenna system (Distributed Antenna System) is also commercially available as a method capable of appropriately accommodating various requirements of the installation of the repeater depending on the installation area and characteristics. In recent years, demands for a digital system for performing digital processing on a relay signal such as a digital distributed antenna system are also increasing.

In a digital distributed antenna system, when saturation occurs in a digital part performing a digital calculation and processing on a relay signal at a specific node, the saturated signal and digital spurious are transmitted to a neighboring node through a transmission medium, Or may cause deterioration in the system characteristics and / or service of the adjacent node.

Accordingly, with respect to a digital signal transmitted from a specific node in a distributed antenna system through a transmission medium, the receiving node monitors whether the received digital signal is input or not by inputting a digital signal, thereby deteriorating the system characteristics due to digital transmission overflow, And the like.

The present invention monitors whether a digital signal transmitted through a transmission medium from a neighboring node constituting a distributed antenna system (DMB) is input or output, thereby solving the problem of digital transmission overflow and digital spurious transmission The present invention provides a digital transmission overflow processing apparatus capable of solving the above problems.

According to an aspect of the present invention, there is provided an AND detector for detecting an overflow of a digital signal digitally transmitted from a neighboring node constituting a distributed antenna system through a transmission medium, Wherein the overhead detection unit is arranged in a digital part mounted in a corresponding node receiving the digital signal transmitted from the adjacent node and the digital part performs digital processing on the relay signal for relaying the mobile communication signal at the corresponding node, ; And a control unit that is disposed on a signal transmission path of the digital signal and controls the overdrive digital signal based on at least one of the overdelivery and overdelivery levels transmitted as a detection result of the overdrive detection unit There is provided a digital transmission overflow processing apparatus including a digital gain control section for controlling gain.

In one embodiment, the digital gain control section includes:

Wherein a transmission delay from a signal detection point of the over-input detection unit to a placement position of the digital gain control unit is longer than a transmission delay time of the over- And a value larger than the delay.

In one embodiment, a transmission delay, which is disposed on the signal transmission path, is located at a rear end of the input detection section and at a front end of the digital gain control section, and from the signal detection point of the over-detection detection section to the placement position of the digital gain control section, And a delay element for giving a time delay to be larger than the time delay required for overdetection detection in the input detection section.

In one embodiment, the over-input detecting unit detects, based on the signal transmission path,

The digital signal processing apparatus according to claim 1, further comprising: a controller for receiving a digital signal from a neighboring node, the digital signal being processed in a format suitable for digital transmission and converted into a form that can be processed in the digital part, And at least one of the degree of input can be determined.

In one embodiment, the over-

Detecting whether or not a digital signal input from the analog / digital converter to the digital part exceeds a predetermined maximum bit overflow or whether an output level of the digital signal exceeds a predetermined peak value, Or not.

In one embodiment, the digital filter may further include a digital filter that removes signals other than the frequency band of the relay signal in order to remove digital spurious signals generated by the overflow of the digital signal output from the analog / digital converter have.

In one embodiment, the digital filter may be disposed at a rear end of the digital gain control unit with respect to the signal transmission path.

According to an embodiment of the present invention, whether or not a digital signal transmitted through a transmission medium from a neighboring node constituting a distributed antenna system is digitally transmitted is monitored to determine a digital transmission overflow and a digital spurious It is possible to prevent damage due to digital transmission overflow and PAU at a corresponding node due to digital spurious emission, system characteristics and / or deterioration of service.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an example of a topology of a distributed antenna system to which the present invention can be applied; FIG.
2 is a block diagram of an embodiment of a remote unit in a distributed antenna system to which the present invention may be applied;
Figure 3 illustrates an example of forwarding to a neighboring node in accordance with a digital transmission overflow due to digital part saturation of a particular node;
4 is a diagram for explaining a digital transmission overflow processing apparatus according to the first embodiment of the present invention.
5 is a diagram for explaining a digital transmission overflow processing apparatus according to a second embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following description of the present invention, detailed description of known related arts will be omitted when it is determined that the gist of the present invention may be unnecessarily obscured. In addition, numerals (e.g., first, second, etc.) used in the description of the present invention are merely an identifier for distinguishing one component from another.

Also, in this specification, when an element is referred to as being "connected" or "connected" with another element, the element may be directly connected or directly connected to the other element, It should be understood that, unless an opposite description is present, it may be connected or connected via another element in the middle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an example of a topology of a distributed antenna system to which the present invention can be applied.

1, a distributed antenna system (DAS) includes a base station interface unit (BIU) 10, a main unit (MU) 20, (Hub Unit) 30, which is an extension node, and a plurality of RUs (Remote Unit) 40, which are arranged at remote service locations. Such a distributed antenna system may be implemented as an analog DAS or a digital DAS, and in some cases may be implemented as a mixed type (i.e., some nodes perform analog processing and the remaining nodes perform digital processing).

1 shows an example of a topology of a distributed antenna system, and a distributed antenna system may be used in an installation area and an application field (for example, an in-building, a subway, a hospital, Stadiums, etc.), various topology modifications are possible. In this case, the number of BIU 10, MU 20, HUB 30, RU 40, and the connection relationship of the upper and lower ends of the BIU 10, the HUB 30, and the RU 40 may differ from those of FIG. Also, in the distributed antenna system, the HUB 20 is utilized when the number of branches to be branched from the MU 20 to the STAR structure is limited, compared to the number of RUs 40 required for installation. Therefore, the HUB 20 may be omitted when the number of the RUs 40 required to be installed can be sufficiently satisfied even with a single MU 20, or when a plurality of MUs 20 are installed.

Hereinafter, with reference to the topology of FIG. 1, each node in the distributed antenna system applicable to the present invention and its function will be described in turn.

A Base Station Interface Unit (BIU) 10 serves as an interface between a Base Station Transceiver System (BTS) such as a base station and an MU 20 in a distributed antenna system. In FIG. 1, a plurality of BTSs are connected to a single BIU 10, but the BIU 10 may be separately provided for each service provider, for each frequency band, and for each sector.

Generally, since the RF signal transmitted from the BTS is a high power signal, the BIU 10 generally transmits a RF signal of a high power level to the MU 20 And transfers it to the MU 20. 1, the BIU 10 receives a signal of a mobile communication service for each frequency band (or for each service provider, sector) as shown in FIG. 1, combines the signals, ), As shown in FIG.

If the BIU 10 lowers the high power signal of the BTS to a low power and then combines the mobile communication service signals and transmits them to the MU 20, the MU 20 combines the received mobile communication service signals Relay signal ") for each branch. In this case, when the distributed antenna system is implemented as a digital DAS, the BIU 10 includes a unit that performs a function of converting a high-power RF signal of the BTS into a low-power RF signal, and a unit that performs an IF (Intermediate Frequency) And converted into a unit for performing a digital signal process and combines them. Alternatively, if the BIU 10 only performs a function of lowering the high power signal of the BTS to low power, the MU 20 may combine the transmitted relay signals and distribute the relay signals for each branch.

As described above, the combine relay signal distributed from the MU 20 is directly transmitted to the RU 40 or the HUB 20 via the branch, and each RU 40 transmits the combined combine relay signal to the frequency band (Analog signal processing in case of analog DAS, digital signal processing in case of digital DAS). Accordingly, each RU 40 transmits a relay signal to a user terminal in its service coverage through a service antenna. The specific functional configuration of the RU 40 will be described later in detail with reference to FIG.

1, a case where an RF cable is connected between the BTS and the BIU 10 and a case where the BIU 10 and the MU 20 are connected by the RF cable, and all the connections from the MU 20 to the lower end are connected by the optical cable, The signal transport medium between each node can also be modified in various ways. For example, the BIU 10 and the MU 20 may be connected through an RF cable, but may be connected through an optical cable or a digital interface. As another example, an optical cable is connected between the MU 20 and the HUB 30 and an RU 40 directly connected to the MU 20, and an RF cable, a twisted cable, a UTP Cable, or the like. As another example, in another example, the RU 40 directly connected to the MU 20 may also be implemented in such a manner that they are connected via an RF cable, a twisted cable, a UTP cable, or the like.

However, the following description will be made with reference to Fig. Therefore, in this embodiment, the MU 20, the HUB 30, and the RU 40 may include optical transceiver modules for all-optical conversion / photoelectric conversion, and when interconnecting nodes with a single optical cable, Wavelength Division Multiplexing (WDM) devices. This can be clearly understood from the functional description of the RU 40 in FIG. 2, which will be described later.

The distributed antenna system can be connected to an external management apparatus (NMS (Network Management Server or System) in FIG. 1 via the network.) Accordingly, the manager can remotely monitor the status and problem of each node of the distributed antenna system through the NMS And can control the operation of each node remotely.

2 is a block diagram of an embodiment of a remote unit in a distributed antenna system to which the present invention may be applied. Here, the block diagram of FIG. 2 illustrates one implementation of an RU 40 within a digital DAS in which the inter-node connection is via an optical cable.

Referring to FIG. 2, the RU 40 includes an optical to electrical converter 50, a serializer (SERDES) 50, and a serial-to-serial converter A deserializer 44, a deframer 52, a digital signal processor (DSP) 70, a digital / analog converter (DAC) 54, an up converter 56, (Amplification Unit) 58.

Thus, in the forward path, the optical relaying signal digitally transmitted through the optical cable is converted into an electric signal (serial digital signal) by the optical / electrical converter 50, and the serial digital signal is converted by the SERDES 44 into parallel digital And the parallel digital signal is reformatted by the de-framer 52 so that the digital signal processor 70 can process the frequency band. The digital signal processing unit 70 performs functions such as digital signal processing, digital filtering, gain control, and digital multiplexing for each frequency band with respect to the relay signal. The digital signal processor 70 may be implemented as an FPGA (Field Programmable Gate Array). The digital signal that has passed through the digital signal processing unit 70 is converted to an analog signal via the digital / analog converter 54 constituting the final stage of the digital part based on the signal transmission path. At this time, the analog signal is an IF signal, and is up-converted to an analog signal of the original RF band through the up-converter 56. In this way, the analog signal converted into the original RF band (i.e., the RF signal) is transmitted through the PAU 58 and transmitted through the service antenna (not shown).

The RU 40 includes a Low Noise Amplifier (LNA) 68, a down converter 66, an analog-to-digital converter (ADC) 68, A digital signal processor (DSP) 70, a framer 62, a SERDES 44, and an electrical to optical converter 60. The digital signal processor (DSP)

Thus, in the reverse path, the RF signal (i.e., the terminal signal) received via the service antenna (not shown) from the user terminal (not shown) in the service coverage is low noise amplified by the LNA 68, 66, and the converted IF signal is converted into a digital signal by the analog-to-digital converter 64 and transmitted to the digital signal processing unit 70. [ The digital signal passed through the digital signal processing unit 70 is formatted into a format suitable for digital transmission through the framer 62 and converted into a serial digital signal by the SERDES 44, And is transmitted to the upper end through the optical cable.

Although not clearly shown in FIG. 2, when the RUs 40 are cascade-connected to each other as in the example of FIG. 1, when a relay signal transmitted from an upper end is transmitted to a neighboring RU of a cascaded lower end The following method can be used. For example, when an optical relay signal digitally transmitted from an upper stage is transmitted to a neighboring RU of a lower stage cascaded, the optical relay signal digitally transmitted from the upper stage is transmitted to the optical / electrical converter 50 -> SERDES 44 - The descrambler 52, the framer 62, the SERDES 44, and the photodetector 60 in that order.

Although the SERDES 44 and the digital signal processor (DSP) 70 are shown as being shared in the downlink and uplink signal propagation paths in FIG. 2, they may be separately provided for each path. In addition, although the optical / electrical converter 50 and the optical / electrical converter 60 are shown separately in Fig. 2, they may be implemented in a single optical transceiver module.

1 and 2, a configuration example of one form of topology and RU of the distributed antenna system has been described. The digital transmission overflow processing apparatus described below can be implemented in the MU 20 and / or the RU 40 constituting the above-described distributed antenna system (in particular, the digital DAS). Hereinafter, a case where a digital transmission overflow occurs will be described with reference to FIG.

FIG. 3 is a diagram illustrating an example of transmission to a neighboring node according to a digital transmission overflow due to digital part saturation of a specific node. In particular, in FIG. 3, it is assumed that a digital transmission overflow occurs. The overflow and digital signals are applied to a digital signal converted by an ADC (Analog to Digital Converter) And a case where spurious waves are generated is illustrated.

In this way, when a digital part of a specific node is saturated and a digital signal overflow and digital spurious are generated, it is transmitted as it is to the adjacent node connected to the corresponding node and branch, and the deterioration And service degradation problems. In addition, when a digital transmission overflow occurs, if a bit overflow occurs due to insufficient bit margin during digital computation in the digital part of the node, or if an error occurs in the reference clock, There are various causes such as the case where the

Therefore, each embodiment of the present invention proposes a solution to overcome this digital transmission overflow problem. This will be clearly understood from the following description of FIG. 4 and FIG.

4 is a diagram for explaining a digital transmission overflow processing apparatus according to the first embodiment of the present invention.

Referring to FIG. 4, the apparatus for processing digital transmission overflow according to the first embodiment of the present invention may include an over input detection unit 210, a digital gain control unit 220, and a digital filter 230. At this time, the digital transmission overflow processing apparatus is mounted on a node unit constituting a specific node of the distributed antenna system and is responsible for digital processing required for relay signals (that is, downlink or uplink mobile communication signals) May be implemented in the digital part 200. FIG. 4 (also described later in FIG. 5) illustrates a case where a digital transmission overflow is transmitted from an upper-layer MU to a lower-layer RU. That is, in FIG. 4, it is exemplified that the neighboring node that caused the digital transmission overflow is an MU. Therefore, for convenience and concentration of the description, it is assumed that the digital transmission overflow device is implemented in the digital part 200 of the corresponding RU based on FIG.

And the input detection unit 210 detects an overflow of a digital signal transmitted through a transmission medium from a neighboring node constituting the distributed antenna system based on the signal transmission path.

When a digital signal digitally transmitted from a neighboring node through a transmission medium is an over input, digital saturation may also occur in the digital components in the digital part 200 that are responsible for digital processing of the relay signal in the node. In addition, a spurious wave may also be present in the input digital signal transmitted from the adjacent node through the transmission medium.

Accordingly, the over-input detecting unit 210 monitors whether an overflow has occurred in the digital signal transmitted from the adjacent node. Since the digital signal transmitted from the adjacent node is a signal framed in a format suitable for digital transmission, the over-input detecting unit 210 detects the digital signal transmitted in the digital part 200 It is possible to monitor whether or not an overflow has occurred in the digital signal signal, which is disposed at the rear end of the deframer 205 to be converted. An example of this is shown in FIG. 4 (a).

The detection as to whether or not the over-input by the over-input detection unit 210 can be performed, for example, by monitoring whether or not the input digital signal exceeds a pre-designated (that is, allowed) maximum bit overflow. For example, when the digital signal is a 14-bit signal, it is possible to detect whether or not an overflow occurs by checking whether an overflow has occurred in the total of 13 bits of data excluding the sign bit of the 14 bits. As another example, the detection as to whether or not the overdrive by the overdetection detector 210 may be performed by monitoring whether or not the digital output level of the digital signal exceeds a predetermined peak value.

 In the above-described manner, the over-input detection unit 210 can determine whether or not the input digital signal is over-input. If it is determined that the over-input is present, The gain control unit 220 can output a gain change control signal. Also, depending on the implementation method, the over-input detection unit 210 may detect the degree of input and the degree of input (i.e., the input level) as to how much the input digital signal is input. In this case, as the determination result, the over-input detection section 210 may output the variable gain change control signal according to the over-input level exceeding the allowable range to the digital gain control section 220. [

The input detection unit 210 may be implemented as a separate component for only the corresponding function, but may be implemented in a digital signal processor (DSP), a field programmable gate array (FPGA), or a central processing unit (CPU) The corresponding function may be implemented.

The digital gain control unit 220 is disposed on the downstream side of the above-described input detection unit 210 on the basis of the signal transmission path of the digital signal. Based on the gain change control signal transmitted from the over-input detection unit 210, And performs gain control so that the digital signal is gain-changed below a predetermined allowable level.

As a gain control method through the digital gain controller 220, the following methods can be applied. For example, the digital gain control unit 220 may apply a fixed attenuation rate to lower the signal level of the digital signal. At this time, if the signal level can not be lowered below the predetermined allowable level by only a single gain change using the fixed signal attenuation rate, the gain changing operation may be repeatedly performed. In another example, the digital gain control unit 220 may be implemented as a variable attenuator so that the signal attenuation can be made as much as the input level exceeding the allowable level according to the variable gain change control signal transmitted from the over- have. In this case, the digital gain controller 220 may be implemented as a variable attenuator.

The digital gain control unit 220 may control the transmission delay from the signal detection point of the over-input detection unit 210 to the placement position of the digital gain control unit 220 in consideration of the signal transmission delay on the signal transmission path of the digital signal (See Delay A in Fig. 4) has a value larger than a time delay (see Delay B in Fig. 4) required for over-input detection in the over-input detecting section 210. [ This is to increase the effectiveness of the gain control on the input digital signal.

In FIG. 4, other digital components are shown as being absent between the over-input detector 210 and the digital gain controller 220, but there may be other digital components between them. In the latter case, the delay time required for the digital operation in the other digital constituent units, which may be interposed between the input detection unit 210 and the digital gain control unit 220, It is sufficient that the total transmission delay has a larger value than the detection delay by the input detection section 210. [ Therefore, the arrangement position of the digital gain control section 220 can be selected as an appropriate position on the signal transmission path in consideration of the detection delay by the over-input detection section 210.

When the gain control process is performed through the digital gain controller 220, a signal in which overflow of the overdriven digital signal is removed can be obtained. An example of this is shown in FIG. 4 (b).

The digital signal output in a state in which the over and input problems are solved through the gain control process of the digital gain controller 220 is input to the digital filter 230 disposed at the rear stage of the digital gain controller 220, .

 The digital filter 230 plays a role of eliminating the digital noise transmitted together with the digital signal transmitted from the adjacent node as described above. For example, the digital filter 230 may be implemented to remove unwanted waves existing in a band other than the frequency band of the relay signal that should normally be transmitted. An example of this is shown in FIG. 4 (c).

4, the digital filter 230 is disposed at the rear end of the digital gain controller 220. However, the digital filter 230 may be disposed at a position different from that in FIG. 4 It is possible. For example, it may be disposed between the signal detection point by the over-input detection unit 210 and the digital gain control unit 220 based on the signal transmission path. However, in a state where an excessive overflow has occurred, the filter function may also deteriorate. In FIG. 4, the digital filter 230 is disposed at the rear end of the digital gain control unit 220 in consideration of this case.

Through the above-described configuration, the digital transmission overflow processing apparatus according to the first embodiment of the present invention

System and / or service deterioration of the downstream PAU or the like can be prevented by appropriately removing over-input and digital unnecessary waves of the digital signal transmitted from the adjacent node through the transmission medium (see Fig. 4 (d)) .

5 is a view for explaining a digital transmission overflow processing apparatus according to a second embodiment of the present invention.

In the following description of the second embodiment of the present invention, the same elements as those in the first embodiment are not described again, and the following description will focus on functions and roles related to the components added through the second embodiment do. Referring to Fig. 5, in the second embodiment of the present invention, a delay element 215 is further added as compared with the digital transmission overflow processing apparatus of the first embodiment illustrated in Fig.

The delay element 215 is disposed between the signal detection point of the input and detection section 210 and the digital gain control section 220 on the basis of the signal transmission path and forcibly gives a delay of a predetermined time to the digital signal to be transmitted. The reason for this is as follows.

The delay of the self-transmission according to the path between the signal detection point of the over-input detection unit 210 and the digital gain control unit 220 is greater than the detection delay of the over- , Long) may be difficult to implement. The transmission delay from the signal detection point of the over-input detection section 210 to the digital gain control section 220 is controlled by the over-input detection section 210, Can be made larger than the detection delay in the case of FIG.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims And changes may be made without departing from the spirit and scope of the invention.

200: Digital Part
205: Framer / Diff Framer
210: an output detector
215: Delay element
220: digital gain control section
230: Digital filter

Claims (7)

An overflow detection unit for detecting an overflow of a digital signal digitally transmitted from a neighboring node constituting a distributed antenna system through a transmission medium, wherein the overflow detection unit comprises: The digital part performs a digital process on a relay signal for relaying a mobile communication signal from the corresponding node; And
And a gain control unit which is disposed on a signal transmission path of the digital signal and outputs a gain control signal for changing the overdriven digital signal based on at least one of the over- A digital gain control section
The digital transmission overflow processing apparatus comprising:
The method according to claim 1,
Wherein the digital gain control unit comprises:
Wherein a transmission delay from a signal detection point of the over-input detection unit to a placement position of the digital gain control unit is longer than a transmission delay time of the over- And the delay time is set to a value larger than a delay.
The method according to claim 1,
A transmission delay from the signal detection point of the over-input detection unit to the arrangement position of the digital gain control unit is provided on the signal input path of the over- Further comprising a delay element for giving a time delay so as to be larger than a time delay required for input detection.
The method according to claim 1,
Wherein the over-detection detecting unit detects, based on the signal transmission path,
The digital signal processing apparatus according to claim 1, further comprising: a controller configured to detect whether the digital signal is overflowed or not, And judges at least one of the input degree and the input degree.
The method according to claim 1,
The over-
Detecting whether or not a digital signal input from the analog / digital converter to the digital part exceeds a predetermined maximum bit overflow or whether an output level of the digital signal exceeds a predetermined peak value, The digital transmission overflow processing apparatus comprising:
The method according to claim 1,
Further comprising a digital filter for removing signals other than the frequency band of the relay signal in order to eliminate digital spurious signals generated by an overflow of the digital signal output from the analog / Device.
The method according to claim 6,
Wherein the digital filter is disposed at a rear end of the digital gain control unit with respect to the signal transmission path.

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