WO2017037202A1

WO2017037202A1 - Surveillance and access control system

Info

Publication number: WO2017037202A1
Application number: PCT/EP2016/070663
Authority: WO
Inventors: Andreas Bayer; Norbert Blissenbach; Dimitri Korobkov
Original assignee: DSP Algorithms GmbH
Priority date: 2015-09-02
Filing date: 2016-09-01
Publication date: 2017-03-09
Also published as: DE102015216816A1

Abstract

The disclosed device and associated method relate, in particular, to a surveillance system (100) having a number of surveillance stations (200) and a number of monitoring stations (300). Furthermore, the surveillance stations (200) and the monitoring stations (300) are connected to each other in a bus structure by means of a 2-wire cable (400). Furthermore, the surveillance stations can have cameras (601) and microphones (501) in order to capture video data and audio data. The monitoring stations (300) can have displays (604) and loudspeakers (507) in order to play back the video data and the audio data. Upon request by a surveillance station (200), an audio channel and a video channel are reserved for the transmission of video data and audio data from the surveillance station (200) to a monitoring station (300). Video data and audio data are transmitted by means of an orthogonal frequency-division multiplexing (OFDM) method.

Description

Monitoring and access control system

This document relates to a monitoring system with a number of

Monitoring stations and a number of monitor stations or a

Access control system that monitors and controls access to a protected area, such as a building. Further disclosed is a method for audio and video communication in an access control system between a number of monitoring stations and a number of monitoring stations.

Known surveillance or access control systems, such as

Door intercoms allow bidirectional audio communication between a monitoring station, also called an outdoor station, and a monitor station, also called an indoor station. Such systems are widespread in residential buildings as well as in the commercial or industrial sector. Often, there is a desire to provide unidirectional video communication so that the user of the monitor station can also see the person requesting admission at the monitoring station before deciding on the entry request. To transfer the

bandwidth-intensive video data (a video transmission with a PAL resolution of 15 frames per second, for example, requires one

Transfer rate of 10 Mbit per second) are then usually special

Cabling systems required, such as those used for the construction of Ethernet-based packet networks, for example, according to the Cat.7 specification. Here, the problem is that when retrofitting a bell system with a video capability, the wiring in the building, which usually consists only of a 2-wire bell line, must be changed, which leads to high costs. There is therefore a need for a monitoring and access control system that enables video communication over pre-existing 2-wire lines that allow signal transmission only with a very limited bandwidth (typically less than 1 MHz). Often, such wiring is also implemented as a bus system with branches, which has additional reflections of the signals at the cable ends result. This problem is exacerbated when multiple simultaneous video transmissions should be possible.

The present document proposes a solution that provides for a very efficient transmission of video and audio data, so that retrofitting existing systems while continuing to use existing ones

Wiring is possible.

According to one aspect of the present disclosure, a monitoring system having a number of monitoring stations and a number of

Monitor stations provided. The monitoring stations and the

Monitor stations are connected to each other by means of a 2-wire line in bus structure (for example by means of bell wire). The monitoring stations may have cameras and microphones to capture video and audio data. The monitor stations may have displays and speakers to play the video and audio data. Upon request by a monitoring station, an audio channel and a video channel become

Transmission of video and audio data from the monitoring station to a monitor station occupied. The transmission of video and audio data can be carried out by means of an Orthogonal Frequency Division Multiplexing (OFDM). However, other transmission methods are conceivable for transmitting video and audio data between monitoring and monitoring stations.

Under a bus structure comprising the monitoring and monitoring stations of the monitoring system according to the invention via a 2-wire line

connects to each other, is a system structure for data transmission between multiple participants to understand a common transmission path, the separate data transmission between two participants allows, ie in which two participants are not involved in the data transfer between other participants. In other words, in the monitoring system according to the invention, the monitoring stations and the monitoring stations are connected to one another in such a way that communication between a pair of monitoring and monitoring stations is made possible in each case. The monitoring system according to the invention can have a number of MO

Monitoring stations and a number of Ml monitor stations, which are interconnected via the bus structure. In particular, the number M1 of the monitoring stations can exceed the number MO of the monitoring stations.

The monitoring system according to the invention is also configured to be activated by a monitoring station, i. H. by initiating a data transmission from the monitoring station, a transmission channel having an audio and / or a video channel between the initiating one

Monitoring station and a selected monitor station to open and occupy.

A transmission channel is associated with a separate frequency resource that can be used to transmit video and / or audio data from the monitoring station to the monitor station. A frequency resource is to be understood as one or more frequency bands which are assigned to the transmission channel or the audio and / or video channel for data transmission and reserved for it. Each transmission channel may thus be assigned a first frequency band for transmission of audio data in an audio channel by means of a first OFDM signal and a second frequency band for transmission of video data in a video channel by means of a second OFDM signal. The transmission of audio and video data is thus carried out by means of separate signals which are transmitted in dedicated frequency ranges directly from the transmitter of the monitoring station to the receiver of the monitor station (and possibly also vice versa). The frequency bands of different transmission channels are generally different. This is therefore a one-to-one communication between the stations the 2-wire line, wherein for different data (audio and video) and different communication partners each separate frequency bands are dynamically assigned. The frequency bands of a transmission channel for transmission of audio and video data from the monitoring station to the monitor station may be contiguous or separate. Each

(physical) channel is assigned its own OFDM signal for data transmission between the stations. In other words, for each busy channel, a separate OFDM signal is generated from the transmitter for transmission on the 2-wire line to the receiver. Audio and video signals are each detected by a microphone or a camera of the monitoring station. an audio channel means a physical channel having a frequency range for the OFDM signal to be transmitted for audio data having a predetermined width, for example, the audio channel

corresponding frequency range has a width between 10 kHz and 20 kHz, in particular 16 kHz. Analogously, a video channel means a physical channel having a frequency range for the OFDM signal to be transmitted for video data of a predetermined width, for example, the one corresponding to a video channel

Frequency range have a width between 200 kHz and 300 kHz, in particular 256 kHz. Each pair of monitoring station and monitor station are dynamically an audio channel with appropriate

Frequency range and a video channel with appropriate frequency range assigned for communication. Accordingly, another couple uses a different audio and video channel for communication, so a

Frequency division arises.

After occupying an audio channel and / or a video channel by a monitoring station is a data transfer on the occupied

Transmission channel or channels. This means in more detail that the monitoring station selects from a plurality of the transmission channels, ie the frequency intervals of a certain width, an audio channel and / or a video channel by means of which the data transmission is to take place and transmits video and / or audio data on these selected channels using Orthogonal Frequency Division Multiplexing (OFDM).

In the transmission of the signal by means of orthogonal frequency division multiplexing (OFDM) according to the invention, the information to be transmitted in the high data rate video and audio data is divided among a plurality of low data rate partial data streams. Each of these partial data streams is modulated with low bandwidth and then the modulated signals are added together. It is necessary that the carrier signals in

Functions space are orthogonal in order to achieve the least possible influence on the partial data streams and to distinguish the partial data streams in the demodulation in the receiver can.

A particular advantage of OFDM data transmission is that, for example, the influence of narrowband interference can be reduced or eliminated by excluding carriers affected by the interference from the data transmission. The whole

Data transmission rate thus decreases only by a small part, whereas in the case of a broadband modulation with only one carrier, a narrow-band disturbance can considerably influence or even prevent the complete data transmission. Furthermore, OFDM is very robust with pulse interferers, as they often occur on 2-wire cables such as bell wire. The power of the individual pulses is distributed by the FFT between the individual carriers of the OFDM signal quasi-uniformly and thus by the factor N (FFT length)

weakened. In addition, OFDM is an optimal solution for channels with intersymbol interference. In this case, they are reflections that lengthen the impulse response of the channel and thus cause intersymbol interference. In other words, divides the OFDM modulation in the inventive

Data transfer in the modulation phase on the existing wideband signal in many modulated orthogonal narrowband signals. The so modulated

Data signal consists in the arithmetic sum of all narrowband signals. The modulated data signal is thus given with a much smaller bandwidth than the original signal from the monitoring station to the 2-wire line. This has the effect that attenuation effects of the signal, which increase with high frequencies, as well as reflection effects, which can arise in particular with 2-wire-like bus structures, have less influence on the

Have transmission.

Thus, it is possible to use in the monitoring system according to the invention, a 2-wire bus system for data transmission, are provided in the data transfer and power supply via a simple 2-wire cable without reflection or attenuation effects disturb the transmitted signal too much. In particular, the cable length used can thus be increased, which contributes to the ease of installation of audio and video data transmission systems. In addition, the monitoring system according to the invention allows use of existing 2-wire cable infrastructure for audio and video signal transmission in building complexes, which saves additional costs and labor.

Furthermore, in the monitoring system according to the invention, a plurality of transmission channels may be provided for the transmission of video and / or audio data from the monitoring stations to the monitoring stations. A

Monitor station may also dynamically select a free transmission channel from the plurality of transmission channels for transmission to the monitor station. This has the advantage that audio and video data transmissions to a monitor station can be initiated from a monitoring station and a user of a monitoring station can easily initiate a request to a selected monitor station.

In particularly preferred and useful embodiments, the monitoring system may include a return channel for transmitting audio data from the monitor station to the monitoring station (also called audio return channel) and / or control data (e.g., a video data return channel) from the monitor station

Monitor station to the monitoring station have. Furthermore, in the monitoring system according to the invention, each

Audio forward channel for transmission of audio data from one

Monitoring station to a monitor station a corresponding

Be assigned to audio return channel and / or each video forward channel for transmitting video data from a monitoring station to a

Monitor station associated with a corresponding data return channel. The

Monitor station can use the associated return channel for communication with the monitoring station. This has the advantage that on the selected channel between monitoring station and monitor station forward data transmission, i. from the monitoring station to the monitor station, as well as in the reverse direction, i. from the monitor station to the monitoring station. This allows interactive communication between

Monitor station and monitoring station.

In addition, when establishing the connection between the monitoring station and the monitor station, a call signal and / or an address signal of the selected monitor station can be transmitted in a frequency band of a transmission channel on the 2-wire line. This has the advantage that it is possible by initiation of the call and / or address signal to address a particular monitor station. In other words, this allows a selective selection of a specific monitor station from the set of monitor stations Ml from one of the monitoring stations from the set MO. Preferably, in the monitoring system according to the invention

Ring signal and / or the address signal in the form of selected OFDM subcarriers in the frequency band of the audio channel are transmitted. This allows efficient coding of call signal and / or address signal during data transmission. In particular, a transmission of the call and / or address signal in the form of selected OFDM subcarriers allows the

Information regarding an initiation of a call signal and the information to which the monitoring station is directed the initiated call signal can be easily transmitted to all monitor stations. This allows it to be centralized Dispensing infrastructure in the overgrowth system to select the call signals according to their addressing and channeling. Thus, the complexity of the monitoring system is reduced and costs are saved. Furthermore, in the monitoring system according to the invention, the

Monitoring stations easily monitor the free channels on the 2-wire line to detect a call signal and / or an address signal which is coded by means of one or more sub-carriers of the OFDM signal for the corresponding channel on a forward channel. By coding the address signal and the address by selecting OFDM subcarriers, they can be easily detected without requiring complete OFDM decoding by the receiver. This allows the receiver to monitor all channels (or all free channels) with little effort, since only the presence of one or more uncoded subcarriers in a respective channel must be detected. In other words, a receiver of a monitor station that is not in any communication is in a monitoring state in which it broadband the presence of

Monitored carrier signals on all or all free channels. Become

Detected carrier signal in a channel, it is first determined whether the received carrier signals correspond to a call signal, i. if she

correspond to expected carriers. In a next step, it is then determined whether the received carrier signals correspond to the own address of the monitor station. All of this can be done without OFDM demodulation and requires, for example, only the detection of unmodulated carriers, i. Sinusoidal oscillations.

A monitor station detecting an address signal associated therewith may set a data receiver of the monitor station for OFDM demodulation to the forward channel and decode the subsequent audio and / or video data on the forward channel. Thus, it allows only the

Target monitor station, ie the monitor station for which the audio and / or video data are determined, responds to a call and address signal and enforces the corresponding forward channel for data transmission. Furthermore, in the monitoring system, the monitor station, which detects an address signal associated therewith, transmits data on the associated return channel to the monitoring station, for example to confirm receipt of the ringing signal.

Preferably, in the monitoring system, the audio data and / or the video data may be coded prior to transmission by means of a source coder. Source encoding allows the messages from digital sources to be transmitted digitally, with the amount of data at the output of the analogue sources being transmitted

Source coding is minimized to the number of channels on the

band to maximize limited line. This task provides a trade-off between the data rate and the quality (usually subjectively estimated) of the recovered analog audio or video signal on the other side of the channel.

Furthermore, the audio data and / or the video data can be encrypted before transmission by means of an encryption algorithm. A

Encryption of the data increases security during data transmission. For example, it is more difficult to get information between

Monitoring station and monitor station is read by a third party.

Furthermore, in the monitoring system according to the invention, the

Monitoring stations and / or monitor stations to authenticate received signals to prevent unauthorized access to the system. This has the advantage that security in the

Data transfer is additionally increased by preventing that

Unauthorized persons can read or feed data from the system.

In particularly preferred and expedient embodiments of the monitoring system according to the invention, this can be a Recording station include which audio and / or video data

recorded between the monitoring stations and monitoring stations. This has the advantage that the information regarding the data signals can be stored centrally and can be retrieved at any time. For example, this allows an assessment of the recorded data signals at any time after the data acquisition by cameras and microphones.

Preferably, the monitoring system according to the invention as

Access control system may be formed, wherein the monitoring stations can be arranged at inlet areas to be monitored and allow the selection of a desired monitor station. It can be a

Monitor station in response to the selection a channel request and an address signal with the address of the selected monitor station generate. Such access control system according to the invention, for example, in buildings, especially in multi-party residential buildings, find application to the access to the building interior at various

To monitor and control entrance areas. Preferably, in the monitoring system according to the invention, the selected monitor station can send an opening signal to the monitoring station by means of a data return channel to cause the monitoring station to allow access to a protected area. Thus, the security monitoring system of the present invention may be enhanced in restricted access areas of facilities

Safety requirements such as industrial plants, nuclear power plants, banks, etc. contribute. The use of an opening signal sent to the monitoring station has the further technical advantage that the inlet to restricted access areas can be controlled from the monitor station. This has the particular advantage that the security of the person who controls the access by means of the opening signal from the monitor station, can be increased. Further, a monitoring station may include user identification means to enable identification of a user at the monitoring station. The user identification means may comprise, for example, a fingerprint scanner, a face or eye scanner or a card reader. In addition, it is possible the different

User identification means for identifying a user at the

Monitor station to combine. Thus, an additional

Level of access to sensitive areas of facilities with increased security requirements. For example, through the use of additional user identification means

be excluded that access to security-related areas inadvertently, for. B. is activated by inattentiveness of the user of the monitor station. In accordance with another aspect of the present disclosure, a method for audio and video communication is between a number MO of

Monitoring stations and a number M l provided by monitor stations. The MO monitoring stations and the M1 monitor stations can be interconnected by means of a 2-wire line in bus structure. A plurality of transmission channels having a number K1 of audio channels and one

Number K2 of video channels may be provided. An audio channel with an associated frequency band is for the transmission of audio data from a monitoring station to a monitor station, and a video channel with an associated frequency band is provided for the transmission of video data from the monitoring station to the monitor station. By a

Monitoring station can be a free transmission channel or a free audio channel and a free video channel for communication between the

Monitoring station and a selected monitor station can be determined or determined, for example by monitoring the corresponding

Frequency bands regarding the existence of certain signals.

In the particular free audio channel and / or specific free

Video channel can transfer data from the monitoring station to a selected one Monitor station to be sent. For this purpose, a first OFDM signal is generated for the transmission of audio data in the audio channel and a second OFDM signal for the transmission of video data in the video channel. The first OFDM signal and the second OFDM signal are then sent over the 2-wire line from the monitoring station to the selected monitor station.

A return channel associated with the transmission channel used may be monitored to receive a response from the selected monitor station, e.g. an acknowledgment of the incoming call signal. The

Data transmission in both directions can take place by means of an Orthogonal Frequency Division Multiplexing (OFDM).

A monitor station may further control data in the return channel to the

Send monitoring station to set audio or video settings on the monitoring station or to trigger an action on the monitoring station.

A second transmission channel for transmitting audio and / or video data from another monitoring station to another monitoring station uses a different frequency range. The transmission of audio and or

Video data is provided by means of a frequency division multiplexing method in which the frequency bands assigned to the transmission channels are allocated dynamically. The monitoring station may determine a free transmission channel by checking the available frequency bands to determine if a signal is being transmitted on a respective frequency band. For example, the monitoring station determines a free transmission channel by detecting predetermined OFDM pilot tones in the associated frequency band.

In particularly preferred and expedient embodiments of the method according to the invention for audio and video communication, the monitoring station can receive a call signal and / or an address signal of the selected one Monitor station in the particular free transmission channel on the 2-wire transmission to initiate the communication between monitoring station and monitor station and occupy a channel. Preferably, in the inventive method for audio and

Video communication the monitor stations free transmission channels i. monitor free audio channels and free video channels to receive paging signals and / or address signals. Furthermore, the monitor stations can check whether received address signals correspond with the own address, and in such a case, a response via a return channel to the sending one

Send monitoring station.

In addition, in the inventive method for audio and

Video communication, a monitor station that receives a call signal and / or an address signal with its own address, an audible or visual notification issue to inform a user about the input of the signal. This has the particular advantage that a user does not have to continuously monitor the monitor station in order to detect the input of a signal. The user can thus carry out other work until notification of a signal input.

In particularly preferred and expedient embodiments of the method according to the invention for audio and video communication, a monitoring station can send control data in the return channel to the monitoring station in order to set audio or video settings at the monitoring station or to trigger an action at the monitoring station. This can make it possible, for example, the information content of the audio and video data by changing the camera setting and / or

Microphone setting to zoom in or out. For example, the camera may zoom in on a particular object to present a captured subject in close-up, or the camera may be adjusted to represent an object in the total shot. In the methods and devices according to the invention can thus be a reliable video and audio data transmission between a

Monitoring station and a monitor station using OFDM-modu Herten signals are carried out by means of a 2-wire in a

Bus infrastructure are interconnected.

According to a further aspect, a computer program product with computer program means may be provided here, which is based on a

computer-readable medium and may be executable by a computer, the computer program means executable

May include instructions that may cause the computer to perform the steps according to at least one of the aforementioned method aspects. It should be noted that the methods described in this document,

Devices and systems can be used both alone, as well as in combination with other methods, devices and systems described in this document. Furthermore, any aspects of the methods, apparatus, and systems described herein may be combined in a variety of ways. In particular, the features of the claims can be combined in a variety of ways.

The apparatus and the method described here will be described below by way of example with reference to the attached, schematic

Drawings described. Show it

Fig.lA is a schematic representation of one described here

Monitoring system with monitoring stations using a

Bus infrastructure can be connected to monitor stations,

1B is a partial section of the monitoring system according to the invention with each paired monitoring stations and monitoring stations, FIG. 1C is a schematic illustration of the network topology of the partial section of the monitoring system according to the invention, FIG.

2 shows a schematic representation of an exemplary embodiment of an audio module of a monitoring or monitoring station of the monitoring system according to the invention for the transmission of audio data,

3 shows a schematic representation of an exemplary embodiment of a video module of a monitoring or monitoring station of the video data transmission monitoring system according to the invention,

4 is a schematic representation of the division of the frequency range in audio and video channels, Fig. 5 is a schematic representation of the frequency range in audio and video channels when occupied,

Fig. 6 is a schematic representation of the establishment of a channel for

Data transmission between a monitoring station of a monitor station,

7 shows a schematic representation of the transmission of call signal and address of a monitoring station to a monitoring station, as well as a schematic representation of the time sequence of the transmission of a call signal to a specific monitor address for establishing a data transmission between a monitoring station and a monitoring station.

In the following, various examples will be described in detail and with reference to the figures. Identical or similar elements in the figures are denoted by the same reference numerals. However, the present system and method are not limited to the described combinations of features. Rather, also other modifications and

Combinations of features of different examples in the framework of the

Scope of the independent claims includes. 1A shows a schematic representation of a monitoring system 100 described here with monitoring stations 200, which are connected to monitoring stations 300 by means of a 2-wire line 400 in a bus infrastructure. The number of monitor stations 300 in the example shown is greater than the number of monitoring stations 200.

The 2-wire line 400 is a line of two insulated wires (not shown). The two wires are twisted together. The twisting ensures that interference voltages caused by inductive coupling largely cancel each other out. As a result, crosstalk can be avoided. The 2-wire line 400 serves as

Transmission medium for data signals between the monitoring stations 200 and the monitor stations 300.

The illustrated bus infrastructure enables the transfer of data between pairs of monitor stations 300 and monitoring stations 200

Initiation of a signal transmission by one or more of the

Monitoring stations 200. The monitoring system 100 according to the invention operates independently of possible other existing systems due to the bus structure. For this reason, for example, an application in residential buildings with a lower standard of construction is possible. Advantages of the bus structure of the monitoring system 100 according to the invention are

For example, the significantly smaller wiring and installation costs, as well as simplified troubleshooting and easy expandability of the entire system. Furthermore, existing systems can be easily converted in buildings.

FIG. 1B shows a partial section of the monitoring system 100 according to the invention according to FIG. 1A. Shown are two

Monitoring stations 200A, 200B and two monitor stations 300A, 300B, which are coupled to the bus of the monitoring system. In particular, in Figure 1C, a possible connection structure is shown between the monitoring stations 200A, 200B and the monitor stations 300A, 300B of Figure 1B. In the illustrated connection configuration, the

Monitoring station 200A with the monitor station 300B and the

Monitoring stations 200B coupled to the monitor stations 300A. However, it is possible to connect each of the monitoring stations 200A, 200B to each of the monitor stations 300A, 300B for data transmission. A

On the other hand, connection between the monitor stations 300A, 300B or between the monitoring stations 200A, 200B is not established.

The representations in FIG. 2 schematically show the structure of an audio module 500, which is provided, for example, by the monitoring stations 300 and the

Monitoring stations 200 of Figures 1 and 2 may be included. The transmission of an audio signal from a monitoring station 200 to a monitor station 300 will be outlined below on the basis of the schematic representation of FIG.

Audio data is acquired at an audio module 500 of a monitoring station by means of a microphone 501. A microphone 501 is here a sound transducer, the sound pressure fluctuations in a corresponding analog

Converts microphone signal. This signal is then digitally coded by means of an analog-to-digital converter and an audio codec 502. In other words, the analog microphone signal is converted into a digital signal. The audio codec may also be capable of compressing and decompressing the audio data flow using an algorithm, whereby the audio signal is represented with a minimum number of bits, thereby preserving the quality of the audio signal

Audio signal is obtained as possible. All types of audio codecs can be used, i. a restriction to a specific audio codec is not necessary.

The coded, d. H. digital audio data is then OFDM modulated by a digital signal processor 503. When orthogonal

Frequency division multiplexing becomes the information to be transmitted, for example, the audio data, with high data rate to several

Split partial data streams with low data rate. Each of these partial data streams is modulated with low bandwidth and then the modulated signals are added together. It is necessary that the carrier signals in the function space are orthogonal in order to achieve the least possible effect on the partial data streams and to be able to distinguish the partial data streams in the demodulation in the receiver.

Following the OFDM modulation of the encoded digital audio data, these become analog signals in a digital-to-analog converter 504

The digital-to-analog converter 504 converts the quantized information, which is present as binary information, into a continuous analog-technical signal. Subsequently, the OFDM modulated analog data signal is passed to a low-pass filter 505. The low-pass filter may for example consist of resistors, coils and capacitors. However, it is also possible to use active components, such as operational amplifiers or transistors. The analog OFDM modulated signal is filtered by the low pass filter 504 to attenuate high frequency signal components. Subsequently, the data signal is passed to a hybrid circuit 506, which allows undisturbed signal transmission in both directions via the 2-wire line 400. From the hybrid circuit, the OFDM modulated audio data signal is routed to the 2-wire line 400 and transported to a monitor station 300 via the bus structure. The incoming OFDM modulated audio data signal from a monitor station 300 is coupled out at the hybrid 506, filtered in a low-pass filter 505 of the audio module, and converted into a digital signal in an analog-to-digital converter 504B. In the digital signal processor 503, the digital signal is OFDM-demodulated, ie the individual carriers are separated from the signal mixture and demodulated. The demodulated signal is then transcoded by the audio codec and the digital-to-analog converter 502 and converted into an analog signal. Thus, the digital demodulated audio signal is converted into an analog signal and on a Speaker 507 is output. The receiving monitor station 300 may also include an audio module 500 as shown in FIG.

In addition, it is possible to collect information for authenticating a user on an audio module 500 of a monitoring station 200. The

Information acquisition may be performed on a console 508, for example. An authentication may be that a code needs to be entered at console 508 or an electronic one

Identification card must be provided. In addition, another type of authentication may include a fingerprint sensor or an iris scanner that collect biometric data. It is also possible to combine two or more of the above types of authentication at the console 508. The acquired authentication data may be given to the digital signal processor 503 after being acquired to be processed together with the audio data.

The illustrations in FIG. 3 schematically show the structure of a video module 600, which can be used, for example, by the monitoring stations 300 and the

Monitoring stations 200 of Figures 1 and 2 may be included. The illustrated video module 600 is a generic video module. This means that it is to be understood as an abstracting representation of a video module according to the invention. Individual embodiments of the video modules at the monitor and monitoring stations may differ. A video module 600 comprises, in addition to the audio data processing means as described in connection with FIG. 2, a camera which records static or moving images and an interface

can transmit. In addition, the video module may include an electrically driven display 604 for optically displaying variable information, such as images or characters. In addition to the audio data transfer described in connection with FIG. 2, a video module 600 thus also makes it possible to capture video data on a camera 601 Monitoring station 200. Audio and video data can thus be recorded and transmitted simultaneously.

The video data is encoded in a video encoder 602, passed to a video chip 603, and thereafter sent to a digital signal processor 503. The digital video data is then OFDM modulated by the digital signal processor 503. In addition, in the signal processor, audio data acquired by a microphone 501 of the video module and converted into digital data may also be OFDM-modulated together with the video data. The OFDM modulated data is applied to a signal processing chip 603B. The signal processing chip 603B can be used for digital

Signal processing in the context of digital filters or for fast Fourier transformation can be used. However, the coding of the digital signals, the encryption of data and error correction methods can also be carried out by means of the signal processing chip 603B.

Following the OFDM modulation of the encoded digital data, these are converted into analog signals in a digital-to-analog converter 504. Subsequently, the OFDM modulated analog data signal is set to one

Low pass filter 505 passed and filtered by the low pass filter 504. Subsequently, the data signal is passed to a hybrid 506, which allows undisturbed signal transmission in both directions via the 2-wire line. From the hybrid circuit, the OFDM modulated data signal is passed to the 2-wire line 400 and to a monitor station 300 by means of the bus structure

transported.

In the other direction, the incoming OFDM modulated data signal is coupled out to the hybrid 506, filtered in a low pass filter 505, converted to a digital signal in an A / D converter 504B, applied to the signal processing chip 603B and stored in the digital signal processor 503 OFDM. demodulates, wherein the individual carriers are separated from the composite signal and decoded. In addition, a separation of the

Data signal in audio data and video data portion instead. The audio data share The data signal is then converted by means of the audio codec and the digital-to-analog converter 502 into an analog signal and at a

Speaker 507 is output. The video portion of the demodulated data signal is from the digital

Signal processor 503 given to the video encoder / decoder chip 603 and forwarded to a decoder 602B. The decoder 602B decodes that

Digital signal and outputs it on a display 604. The receiving monitor station 300 may also include a video module 600. Usually, however, there is no camera in the monitor station 300 and no monitor in the monitoring station 200, since usually a video data transmission only in the direction of the monitoring station

Monitor station is implemented. However, video module 600 of FIG. 3 shows all possible video components for the sake of simplicity.

A video module 600 may also provide the ability to authenticate a person at a monitoring station 200. Analogous to

Description of Figure 2 may be the information gathering for

Person authentication, for example, be performed on a console 508. Authentication may include entering a code at the console 508 or providing an electronic identification card. In addition, authentication may include biometric data acquisition by means of a fingerprint sensor or an iris scanner. It is also possible to combine two or more of the above types of authentication at the console 508. The acquired authentication data may be given to the digital signal processor 503 after being acquired to be processed together with the audio data. Figure 4 shows a schematic representation of the channels of the

Monitoring system 100 according to the invention can be used for data transmission. In the forward direction is a data transfer from a

Monitoring station 200 to a monitor station 300, selecting a Audio channels and / or a video channel for each pair of monitor station 300 and monitoring station 200. In a corresponding manner, the

Backward data transfer from a monitor station 300 to a monitoring station 200, selecting an audio channel and / or video channel for each pair of monitor station 300 and monitoring station 200.

The proposed communication structure does not need a central element, so it works decentralized, and allows all stations to participate without special registration. Unlike Ethernet packet transmission in the prior art, no network element such as a router or switch is required. A transmitter transmits its OFDM signal in a particular frequency band over the bus directly to all receivers. The audio and / or video data is encoded directly onto the transmission signal by OFDM without using

Packages with addresses. The desired receiving station recognizes when establishing the connection by the transmitter, a corresponding call signal and its own identifier in an address signal in a frequency band and sets its receiver to this frequency to receive the OFDM signal and to decode. Other receiving stations with a different identifier simply ignore the transmission on that channel after they have recognized the call signal and have determined that they are not the desired receiver. By agreeing on a common identifier, several or all recipients can be addressed and selected. Access to communication resources (i.e., transmission channels) is done by the transmitter by checking that the corresponding channel (i.e., the allocated frequency band) is idle or busy and occupying a vacant channel. The channels (frequency bands) are not permanently assigned but are allocated dynamically if a transmitting station wants to establish a connection to a receiving station. This way becomes an effective one

Implemented frequency division multiplex access method. After completion of the communication, the corresponding channel is released in which no more OFDM signals are transmitted on it. Alternatively, too a special signal in the frequency band are transmitted to the

To notify receivers (and possibly all other stations) that the transmission has ended on this channel and the channel is enabled. Ordinary digital data transmission for audio and video data on a 2-wire cable requires a certain bandwidth, which is generally in the range of 20 MHz for 8 audio channels and 3 video channels. However, as explained above, with such a bandwidth, there are considerable problems with attenuation and reflection in data transmission by means of a 2-wire line connected in bus structure. The OFDM modulation of the

However, data signal allows efficient transmission of the data, so that the required bandwidth can be limited to a frequency range which is less than or equal to 1 MHz and thus better suited for transmission by means of simple 2-Draftleitungen.

The diagram a) of Figure 5 shows to clarify the proposed frequency division multiplexing a possible spectral distribution of the channels in a frequency range from zero to about 1MHz, in different

Frequency bands is divided. These frequency bands correspond to the audio and video channels used for data transmission in the monitoring system 100 according to the invention. In particular, a first

Audio frequency range 700 shown, the bandwidth is between 10 and 170 kHz. The audio frequency range 700 represents the bandwidth for forward data transmission, i. The transmission of data signals from the monitoring stations 200 to the monitor stations 300. In a similar manner, a second audio frequency range 800 is shown, the bandwidth is between 170 and 330 kHz. The second audio frequency range 800 represents the bandwidth for reverse data transmission, i. the transmission of

Data signals from the monitor stations 300 to the monitoring stations 200 of the bus infrastructure. In addition, a frequency band 900 to

Data transmission in the reverse direction shown, whose bandwidth is 48kHz. Furthermore, three frequency ranges are 1000 with a respective one

Bandwidth of 256 kHz is shown as video data transmission channels between monitoring stations 200 and monitor stations 300 are to be understood. Furthermore, a frequency range 750 between zero and 5 kHz is shown, which can be used for data transmission, for example for the transmission of analog audio data.

In particular, the diagram b) of Figure 5 shows an enlarged view of the frequency range between 10 and 170 kHz from diagram a). Of the

Frequency range is divided into 10 equidistant bands 701 -710 with a width of 16 kHz each. These ten bands 701-710 correspond to ten physical audio channels that can be occupied by the monitoring stations 200 of the monitoring system according to the invention. Diagram b) shows an assignment of the frequency ranges 701, 702, 705, 706 and 708. In other words, it is shown that out of five

Monitoring stations 200, the said channels for the transmission of

Audio signals are occupied in the forward direction. The remaining

Frequency ranges / audio channels are available for occupancy, ie. are free. In the occupied channels, a separate OFDM signal for direct 1-to-1 transmission to the corresponding receiver is generated by the corresponding transmitter.

Correspondingly, it is shown in diagram c) that the corresponding audio channels, i. H. the frequency ranges 801, 802, 805, 806 and 808 are used by the monitor stations to transmit audio data in the reverse direction. The other audio channels are free. In other words, in the diagrams b) and c), an audio data transfer between five

Monitor stations 200 and five monitor stations 300 shown.

Furthermore, three channels 1100 with a respective width of 16 kHz are shown in diagram d). These channels are associated with the video channels 1000 to convey additional data regarding video data transmission from the monitor station to the monitoring station. For example, via the channels 1100 data for controlling the camera, z. B. for adjusting the camera lens (zooming) and / or moving the camera to be transmitted. An allocation of different audio and video channels for data transmission is made as needed. That is, if between one

Monitoring station 200 and a monitor station 300 is a demand for audio and / or video transmission, a corresponding audio and / or video channel is claimed, if this is still available.

FIG. 6 is a graphical representation of the initiation of a call signal from a monitoring station 200 to a monitoring station 300. The essential working steps at a monitoring station 200 are shown in flowchart a).

The monitoring station 200 is initially in the idle state (step: 1100). At the monitoring station 200, a call signal is then activated to a specific monitor station 300. In other words, by one

User of the monitoring station triggered a call signal, for example by pressing a bell button at an interface of the monitoring station 300, which corresponds to a specific address or number of a monitor station 300.

The monitoring station 200 then searches for a free channel for

Data transmission (step 1200). Thus, the available frequency band is scanned for a free audio channel and / or video channel. The

Monitor station 200 may also be configured to

Operation of a pure audio signal button only audio channels are scanned for availability and that only video channels are scanned for availability by pressing a pure video call signal button at the monitoring station 200. Once one or more channels are detected by the monitoring station 200 as not busy, the monitoring station 200 randomly selects an available audio channel and / or video channel and sends information regarding the ring signal and the address of the monitor station 200, with the Contact to be made on the randomly selected audio and / or video channel (step 1300). For the details regarding the coding of call and address signal, reference is made to FIG. The monitoring station 200 then waits a predetermined period of time for a response of the controlled monitor station 300 on the associated one

Reverse channel of the randomly selected audio and / or video channel. If the predetermined time period is exceeded, the step of random

Selecting a channel and the transmission of call signal and

Monitor station address repeated. Upon a response of the monitor station 200 on the reverse channel of the randomly selected video and / or audio channel, the channel (s) will be occupied and the monitoring station 200 will start transmitting the OFDM modulated data to the monitor station 300 (step 1500).

Flowchart 6 b) explains the individual steps for establishing a

Communication between a monitoring station 200 and a

Monitor station 300 from the perspective of the monitor station 300. The monitor station 300 permanently monitors all free channels, i. all free audio and video frequency bands looking for ring signals (step 2100). Once monitor station 300 detects a paging signal and an address signal on a channel, monitor station 300 determines whether the address transmitted on the channel matches the address of monitor station 300 (step 2200). Vote the transfer address and the own address of the

Monitor station does not match, the call signal is ignored and the monitor station returns to the state of continuous monitoring of all channels. If the transmitted address and the address of the monitor station 300 match, the monitor station 300 sends a response in the form of a

Acknowledgment signal on the reverse channel of the audio and / or video channel on which the call signal and the address signal were received to

Monitor station 200 (step 2300). Thus, the audio and / or video channel will pass through monitor station 200 and monitoring station 300 occupied and an OFDM data transmission in the form of audio and / or

Video data between the monitoring station 200 and the monitor station 300 may be performed (step 2400). FIG. 7 shows in more detail the principle according to which a specific monitor station 300 is addressed by a monitoring station 200 by means of a call signal. A paging signal sent from a monitoring station 200, i. a request to establish a data transfer between

Monitoring station 200 and monitor station 300, will be within the

Bus system to all monitor stations 300 transferred. Thus, the problem arises as to how a monitor station 300 can detect that a call signal initiated by a particular monitoring station 200 is directed to this monitor station 300 to establish a data transmission, so that an occupancy of a channel for data transmission can be initiated.

Diagram 7a) shows how a call signal can be transmitted on a specific audio channel. First, there is the

Monitoring station in retirement (step 3100). Upon initiation by a user, a paging signal to a particular monitor station 300 is initiated at the monitoring station 200. For example, as described above, this can be done by selecting and pressing an address button on a console of the monitoring station 300. Analogously, a video channel or a combination of audio and video channels can also be used.

As shown, the coding of the ringing signal may be implemented by means of a selection of two carriers of the OFDM signal (step 3200). In an analogous manner, the address of the addressed monitor station 300 can also be represented as coding by means of two carriers of the OFDM data signal in the channel selected by the monitoring station (step 3300). The information thus encoded is then transmitted on the channel to all monitor stations 200 (step 3400). In Diagram 7b) the timing of the establishment of a data transmission between a monitoring station 200 and a monitor station 300 is shown schematically. The first step is on the part of a

Monitoring station 200 a call signal and the address of a called

Monitor station 300 and transmitted to all monitor stations on a randomly selected channel (step 4100).

Monitor station 300 continuously monitors all channels for paging signals associated with the call station address identifier. Upon receipt of a paging signal with the correct address on a particular channel, i. the address corresponding to the address of the monitor station, the monitor station 300 sends an acknowledge signal on the corresponding return channel to the

Monitor station 200 back (step 4200). Thus, a channel pair to

Communication between monitoring station 300 and monitor station 200 established. Data may then be transmitted between the monitor station 300 and the monitoring station 200 in an OFDM modulated manner (steps 4300, 4400).

In summary, the monitoring system 100 described herein has a number of monitoring stations 300 and a number of

Monitor stations 200, which are connected in a bus infrastructure by means of a 2-wire line and pairwise transmit each other OFDM-modulated signals, the technical advantage that due to the OFDM data transmission, a lower bandwidth is required, so that damping effects and reflection effects, especially in 2 wire-like bus structures can arise play a lesser role. As a result, an already existing 2-wire line structure can be used for data transmission and, moreover, enlargement of existing 2-wire line lengths is enabled.

The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the Figures illustrate only the principle of the proposed methods, devices and systems.

Claims

claims

A monitoring system comprising a plurality of monitoring stations and a plurality of monitoring stations, the monitoring stations and the monitoring stations being connected in a bus structure by means of a 2-wire line, the monitoring stations having cameras and microphones for capturing video and audio data, the monitor stations displaying and Speakers to reproduce the video and audio data, upon request by a monitoring station, a transmission channel for transmitting video and / or audio data from the

Monitoring station is assigned to a monitor station, where a

Transmission channel is assigned to a separate frequency resource, which is used for the transmission of video and / or audio data from the

Monitoring station is occupied to the monitor station, and the transmission of video and audio data in the transmission channel by means of an Orthogonal Frequency Division Multiplexing (OFDM) is performed.

The monitoring system of claim 1, wherein a plurality of

Transmission channels are provided for transmitting video and / or audio data from the monitoring stations to the monitoring stations and the one monitoring station determines a free transmission channel from the plurality of transmission channels and selects for transmission to the one monitoring station.

3. Monitoring system according to claim 1 or 2, wherein a return channel for the transmission of audio data from the monitor station to the

Monitoring station and / or control data from the monitor station to the monitoring station is provided.

4. Monitoring system according to one of the preceding claims, wherein

each transmission channel is assigned a first frequency band for transmission of audio data in an audio channel by means of a first OFDM signal and a second frequency band for transmission of video data in a video channel by means of a second OFDM signal, the assigned frequency bands of the transmission channels being different.

5. Monitoring system according to one of the preceding claims, wherein when establishing the connection between the monitoring station and

Monitor station a call signal and / or an address signal of the

Monitor station is transmitted in a frequency band of a transmission channel on the 2-wire line / are.

6. Monitoring system according to claim 5, wherein the call signal and / or the address signal is transmitted in the form of selected OFDM subcarriers in the frequency band.

7. Monitoring system according to claim 5 or 6, wherein the

Monitoring stations monitor the free channels on the 2-wire line to detect a call signal and an address signal on a transmission channel, wherein a monitor station that detects an address signal associated with it, sets a data receiver of the monitor station on the transmission channel and the audio and / or decodes video data on the transmission channel.

8. The monitoring system of claim 7, wherein the monitor station detecting an address signal associated therewith, data on the

assigned return channel to the monitoring station transmits.

9. Monitoring system according to one of the preceding claims, wherein the audio data and / or the video data before transmission by means of a Source coder coded and / or by means of a

Encrypted encryption algorithm.

10. Monitoring system according to one of the preceding claims, wherein

Monitoring stations and / or the monitoring stations one

Authenticate received signals to prevent unauthorized access to the system.

11. Surveillance system according to one of the preceding claims, which is designed as an access control system, wherein the monitoring stations are arranged to be monitored inlet areas and allow the selection of a desired monitor station, wherein a

Monitoring station generated in response to the selection of a channel request and an address signal with the address of the selected monitor station.

The monitoring system of claim 11, wherein the selected one of

Monitor station sends an opening signal to the monitoring station by means of a return channel to the monitoring station

to allow access.

13. A method for audio and video communication between a number MO of monitoring stations and a number M1 of monitor stations in an access control system connected by means of a 2-wire line in

Bus structure are interconnected, with a variety of

Transmission channels with a number Kl of audio channels and a number K2 of video channels are provided, wherein an audio channel with an associated frequency band for the transmission of audio data from a monitoring station to a monitor station and a

Video channel are provided with an associated frequency band for the transmission of video data from the monitoring station to the monitor station, with

Determining a free transmission channel having an audio channel and a video channel through a monitoring station, Generating a first OFDM signal for transmission of audio data in the audio channel and a second OFDM signal for transmission of video data in the video channel;

Transmitting the first OFDM signal and the second OFDM signal over the 2-wire line from the monitoring station to the selected one

Monitor station, and

Monitoring a return channel associated with the used transmission channel to receive a response from the selected monitor station.

14. The method of claim 13, wherein the monitoring station a

Ring signal and / or an address signal of the selected monitor station in the particular free transmission channel on the 2-wire line transmits.

15. The method of claim 14, wherein the monitor stations are free

Monitor transmission channels to receive paging signals and / or address signals, check whether received address signals correspond to the own address, and in such a case send an answer via an associated return channel to the transmitting monitoring station.

16. The method according to any one of claims 13 to 15, wherein a

Monitor station control data in the return channel to the

Monitoring station sends to set audio or video settings on the monitoring station or an action on the

Trigger monitoring station.

17. The method according to any one of claims 13 to 16, wherein a second

Transmission channel for transmitting audio and video data from another monitoring station to another monitor station uses a different frequency range.

18. The method according to any one of claims 13 to 17, wherein the transmission of audio and or video data by means of a Frequency division method takes place, in which the

Transmission channels associated with frequency bands are assigned dynamically.

19. The method of claim 18, wherein the monitoring station determines a free transmission channel by examining the available frequency bands to determine whether on a respective one

Frequency band a signal is transmitted.

The method of claim 19, wherein the monitoring station determines a free transmission channel by detecting predetermined OFDM pilot tones in the associated frequency band.