NL1026149C1 - Method for operating a DAB communication network. - Google Patents

Description

TITLE Method for operating a DAB communication network.

The invention relates to a method for operating a DAB communication network. The method is particularly suitable for use in a T-DAB or DVB-T transmission network. DAB (Digital Audio Broadcasting) and DVB (Digital Video Broadcasting) transmission networks and communication technology for digital audio and video transmission using a digital format have been developed to replace the existing outdated radio and television analogue transmission technology such as e.g. FM (Frequency Modulation) and 10 VHF / UHF television signals. In Europe, the "Eureka 147 DAB" protocol has been agreed for DAB based on standard ETSI EN 300 401 V1.3.3.

Eureka DAB has been developed for good "mobile" reception and can be applied to frequencies between 30 MHz to 3 GHz. To ensure good "mobile" reception in moving objects such as e.g. To guarantee a moving car or train, time interleaving or guard interval and robust synchronization are applied to correct time-dependent interference and intersymbol interference (also known as own network disruption). The DAB transmission signal has a bandwidth of 1,536 MHz within which a large number of carriers are formed depending on the transmission mode to be selected (TM, Transmission Mode). For transmitting frequencies below 375 MHz, TM-I is generally used, with 1536 carriers being transmitted, on which the digital information is transmitted in low bit rates. This technique is known as OFDM (Orthogonal Frequency Division Multiplexing) and has the advantage that frequency interference is strongly suppressed, because only a part of the carriers will have disturbing interference, while the majority of the carriers can be received without interference.

The bits to be transmitted are transmitted as a transmission frame or symbol "with a fixed sequence of the symbols, distributed over the different carriers. Each DAB transmission frequency with a bandwidth of 1,536 MHz 30, or DAB ensemble or DAB block, can now contain a multiplex of audio and / or multimedia services depending on the desired and chosen configuration. The gross bit rate of a multiplex is approximately 2.3 Mbits / s, but due to redundancy, error correction and other overhead to improve reception, a net data stream of approximately 1.5 Mbits / s is available. The "transmission frame" can be flexibly, depending on the need, divided into segments such as data streams or audio transmitters, for example into six 192 Kbits / s digital audio data streams or into ten 100 Kbits / s multimedia data streams or any other S desired distribution or combination.

This TM-1 technology for DAB transmitters below 375 MHz is very suitable for an SFN (Single-Frequency NetWork, common frequency network or one frequency network). In particular, because interference problems such as intersymbol interference in transition areas between the different transmitters are also suppressed by the added robust redundancy and error correction for good "mobile" or moving reception.

For higher transmission frequencies such as the L-band, 2 other transmission modes are defined, TM-II and TM-IV. TM-11 and TM-IV in particular are suitable for use in the so-called L-band transmitters whose frequencies are between 1.452 and 1.402 GHz. The transmission signal is split into 384 (mode II) 768 (mode IV) carriers in this transmission mode. Due to the higher frequency of the carrier, the maximum transmitter distance is only approximately 25 km Mode II and approximately 50 Km mode IV, while for VHF-III (band-III) frequencies (174-230 MHz) this maximum transmitter distance is approximately 100 20 kilometers . As a result, the band-11 frequencies are often used for national DAB SFN broadcasting networks and L-band frequencies are only used on a very limited scale for regional SFN applications or for local one-transmitter applications.

The method according to the invention focuses in particular on transmission networks 25 formed from transmitters placed on the earth; the so-called Terrestrial or T-DAB networks to distinguish with e.g. cable transmission networks or satellite transmission networks.

In a T-DAB broadcasting network, transmitters are placed at a certain distance from each other. These either broadcast a different program each on their own transmission frequency, or the channels each broadcast the same program on the same frequency, whereby national reception can be created within the relevant block, multiplex or allotment.

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The currently implemented T-DAB transmission networks with national coverage use band-lll frequencies and TM-I. To this end, high-power transmitters are used on high transmission masts. The disadvantages of this are the disruption of the own transmission network and transmission networks in neighboring countries. Since transmission networks are often established per country and language area, they should preferably not extend beyond national or language borders. Since national borders are often very erratic, it is difficult to meet the requirement of good reception at the national border with simultaneous minimal disruption of other transmitter networks. High-power transmitters reach very far and disrupt service areas of other transmitters and often also cause disruption to their own network.

Furthermore, high power transmitters have the disadvantage that they produce a high field strength in an area with a radius of a few kilometers around the transmitter set-up point. This high field strength can cause malfunctions in electrical devices.

The invention therefore contemplates a method for operating a T-DAB communication network (T, terrestrial; DAB, Digital Audio Broadcast) for a service area, wherein the service area is greater than the maximum DAB-20 transmitter distance A, comprising the following step: sending DAB signals to the service area with the help of low power DAB transmitters mounted at fixed, ground-connected, low set-up points, where the mutual distance a between the DAB transmitters is less than half the maximum DAB transmitter distance A , or 25

Preferably, the T-DAB network is an SFN (single frequency network, one frequency network) of transmitters that broadcast on a DAB frequency in band III (174-240 MHz) and wherein the mutual distance a between the DAB transmitters on band III is equal to the maximum transmitter distance between DAB transmitters on the L ° 30 band, so that a <0.2A.

The mutual distance a between the DAB transmitters on band III is preferably between 5 and 25 kilometers; more preferably, the distance is approximately 10 kilometers.

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In particular, the low set-up points have a maximum height of approximately 50 meters and the transmitted power of each individual T-DAB station is less than 100 W.

For transmitters with a capacity of less than 100 W, no EIA (environmental impact assessment) needs to be carried out, at least for the moment, which results in a cost saving. By applying both L-band and band-III to the same set-up points, the project costs are reduced and a cost saving can also be achieved when applying the power supply signals.

Preferably, at least one T-DAB transmitter on band III and at least one T-DAB transmitter on the L-band are arranged at the low set-up points.

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Preferably, it holds that the DAB transmitter on band III and the DAB transmitter on the L-band are centrally controlled from a central DAB server.

The invention also relates to a communication system comprising at least one network of SFN T-DAB band-11 transmitters and at least one network of T-DAB L-band transmitters, the transmitters being called being centrally controlled from a central DAB server via a communication bus, a receiver adapted to receive T-DAB signals on band III and / or for T-DAB signals on the L-band.

The invention also relates to a method for obtaining information, such as for example: an Internet page, by a user with a receiver, wherein an SFN T-DAB band-III transmission signal covering the service area is offered by a central DAB server via a number of transmitters at set-up points, with data streams such as an EPG (electronic program guide) being transmitted in the frame of the DAB signal, as a result of which the user can select further information from the received EPG by sending a request signal to a bi-directional network as a mobile telephony network such as a GRPS or UMTS network, whereafter via a mobile telephony service provider the request signal supplemented with geographic data from the receiver is received by a central DAB server and the relevant information can be retrieved, for example from 1026149

Internet, after which the central DAB server makes a connection on the basis of the geographical data of the receiver via a communication bus to a T-DAB L-band transmitter in whose service area the receiver is located and to adjust the DAB frame in such a way, that bandwidth is now created for sending the requested information from the central DAB server via the communication bus and the T-DAB L-band transmitter via an on-demand segment of the frame to the user's receiver.

The invention will now be further elucidated with reference to the drawing.

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Figure 1 shows a schematic high power network with high set-up points and a low power low set-up network;

Figure 2 shows a diagram of the information and signal flows according to the invention.

Fig. 1 schematically shows two different embodiments of a transmission network. This is, for example, a state of the art high-power network in the VHF-III (band III) with high set-up points 1 which emit a high field strength V. The high set-up points 1 are at a large maximum distance A relative to each other, as a result of which the field strength 3 strongly decreases with an increase in the distance to the high set-up point 1. In the case of a band III DAB network, the transmitters have, for example, a capacity of 4 kW and the mutual maximum distance A between the transmitters is 1 80-100 kilometers. Due to interference within the own network, the resultant field strength of the own network transmitters at a greater distance, field strength 5, is at the disturbed level. It can clearly be seen that a very high field strength 3 is present in the vicinity of the high set-up point 1, as a result of which disturbances can occur e.g. in other electrical appliances. While in the middle, between the two high masts, the field strength of the own network transmitters reach a disturbing field strength.

The embodiment of the transmission network according to the invention is also shown in Fig. 1.

I.p.v. two high-power transmitters at high set-up points, a larger number of low set-up points 2 are now used, each provided with a low power 4026149 6 transmitter, which leather generates a low field strength 4. The mutual distance a between the low positioning points 2 In this example, a factor 10 is smaller than the mutual distance A between the high positioning points 1. As can be seen, the field strength is much more homogeneous due to the use of the low positioning points and 5 no areas with a very high field strength and areas with a low field strength. This also makes it much easier to take erratic land borders into account, so that catchment areas of other transmission networks in neighboring countries are less disturbed. By using low antenna set-ups in combination with low-power transmitters, the 10 transmitting antennas radiate less far, so that their own network disturbance is suppressed. By placing the transmitting antennas on low antenna set-up points in valleys in areas with hills and / or mountains, instead of at high set-up points on mountains and / or hills, disruption of one's own network is suppressed. By using existing infrastructure infrastructure that is already in use for mobile telephony, GSM, GRPS, UMTS and C2000, the costs for a national DAB SFN network can even be lower than for a high infrastructure network. The above-mentioned advantages already occur when a smaller or equal 1 / aA is taken, so as a A.

Moreover, the same low set-up points can still be used advantageously for L-band T-DAB low power transmitters. This provides the advantage that the costs for the infrastructure, connection and control can be shared by the: different networks.

If now both the band III and the L-band T-DAB transmitters are arranged at the same set-up points, mutual synergy between the two networks is advantageously created. Although the mutual distance between the T-DAB band III transmitters is now much smaller than the maximum distance and consequently many more transmitters have to be installed in order to be able to provide a certain service area with a signal, the total project costs for the total network do not have to be to be higher due to cost savings realized with this method such as the disappearance of the EIA requirement, integration of supporting equipment, reduction of assembly costs and maintenance costs.

Fig. 2 shows how the synergy benefits can be obtained by the connected operation of Band-11 and L-band networks. With reference numeral 1026149 7, a receiver of a user is shown in a diagram, which can be moving as desired, e.g. a receiver in a moving car or train. This receiver 10 is arranged within the transmission range of T-DAB band III low power transmitter 11 at low set-up point 2. According to the invention, a low-set point 2 also includes a T-DAB L-band transmitter 12 and optionally a mobile telephone transmitter and receiver 13 for GSM, but preferably for GPRS and / or UMTS bi-directional communication. The two T-DAB transmitters 11, 12 receive via communication bus 15 e.g. an SFN T-DAB signal 33 for the band III transmitter 11 with national coverage and a local signal 34 for the L-band transmitter 12. In the diagram of figure 2, one band III transmitter and one L-band transmitter are shown, others configurations with more T-DAB transmitters are also considered within the scope of protection .; this patent application. The communication bus 15 can be a satellite connection, a cable connection or a beam connection which is in contact with the central DAB server 16. From this central DAB server 16, the entire entire band III and L-band transmitter network within the service area of signal and data provided eg in this example multiplex 37 for L-band transmitter 12! and SFN multiplex or allotment 38 for band-11 transmitter 11. This configuration and the central control from the central DAB server 16 give rise to many possibilities for sending central and decentralized information flows to the receiver 10 of the user.

First of all, the receiver 10 can receive a T-DAB block or multiplex 20 with e.g. Digital audio channel including program associated data (PAD) 21, and service information (SI) 22. For the sake of clarity, these two data streams are indicated by a separate arrow; in reality, these data streams are included in the digital transmission frame or 'symbol' within the Eureka-DAB protocol and are only separated from each other again in the different data streams in the receiver 10. According to the invention, a separate data stream 23 can also be included in the transmission frame with e.g. an electronic program guide (EPG).

This data stream can then provide the connection, coupling and synchronization between the band-lll transmission network and the L-band transmission network. By sending data on the L-band network in the EPG data stream 23, the L-band network can be used for on-demand (on request) data flows 26 or for 1026149 8 warnings of data flows 27. The central SFN network does not have to be burdened with the mostly local data flows, for this bandwidth can be kept free on the much more flexible L-band network to be configured and configured.

L-band transmitter 12 may, for example, be a local transmitter that broadcasts L-DAB block or multiplex 24 from e.g. three local stereo channels, each with a data stream of 128 Kbiis / s. In addition, local data is also transmitted such as PAD 25. As a result, space remains free within the frame for data flows such as data flows 26 and 27.

Therefore, this configuration can be used for on-demand delivery of information to the user of receiver 10. e.g. In EPG data stream 23, a basic set of Internet pages can be sent to the receiver 10. When the receiver e.g. is connected to a GPRS / UMTS service provider 14 via a mobile telephony transmitter / receiver system, e.g. by clicking on 15 a link on one of the basic Internet pages a specific page is requested via connection 32. This request is sent via connection 36 to the service provider 14, after which the request as request 39 together with the geographical data of the recipient 10, i.e. the geographic data from GPRS / UMTS receiver 13 or geographic data obtained in another way, sent to the central DAB server 16. The central DAB server is connected to Internet 28 and retrieves the relevant page. On the basis of the geographical data from the receiver 10 transmitted, the frame is now reconfigured for at least one T-band T-DAB transmitter and an on-demand data stream 26 is added to the frame, on which the requested Internet page is sent to the receiver 10 sent. Thanks to this method, a very large bandwidth can be offered per set-up point for additional data traffic. Since little bandwidth is available within the frame for the SFN band-III blocking and the same signal must be offered over the entire service area, this service is hardly suitable for additional data traffic to users. By using local L-band T-DAB transmitters for this purpose, a large number of requests for information, such as an Internet page, can be processed and sent to the user per set-up point. In this way use is made very efficiently of the DAB transmission bandwidth present. Since the T-DAB is extremely suitable for reception in moving receivers, this makes fast internet possible for a moving receiver at low costs. Costs for receiving the information can for example be settled via the GPRS / UMTS network and its service provider 14.

CONCLUSIONS

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Claims (8)

A method for operating a T-DAB communication network (T, 5 terrestrial; DAB, Digital Audio Broadcast) for a service area, wherein the service area is larger than the maximum DAB station distance (A), comprising the following step: sending of DAB signals to the service area with the help of low power DAB transmitters mounted at fixed, ground-connected, low set-up points (2), the distance (a) between the DAB transmitters being less than half of the maximum DAB station distance (A), or a ^ 4A. Method for operating a T-DAB communication network according to claim 1, characterized in that the network is an SFN (single frequency nefwork, one frequency network) of transmitters that broadcast on a DAB frequency on band-ill (174-240 MHz) and wherein the mutual distance (a) between the DAB transmitters on band III is equal to the maximum transmitter distance between DAB transmitters on the L-band, so that a £ 0.2A. 20 Method for operating a T-DAB communication network for a service area according to one of claims 1 or 2, characterized in that the mutual distance (a) between the DAB transmitters on band III is between 5 and 25 kilometers ; more preferably, the distance is approximately 10 kilometers. 25 Method for operating a DAB communication network for a service area according to one of claims 1-3, characterized in that the low set-up points have a maximum height of approximately 50 meters and that the transmitted power of each individual DAB transmitter is smaller is then 30 100W. 1026149 ________ I Method for operating a DAB communication network according to one of claims 2-4, characterized in that at the low set-up points there are at least one DAB transmitter on band III and at least one DAB transmitter on the L band 5 applied. 6. Method for operating a DAB communication network according to claim 5, characterized in that the DAB transmitter on band III and the DAB transmitter on the L band are centrally controlled from a central DAB server. A communication system comprising at least one network of SFN T-DAB band-11 transmitters (11) and at least one network of T-DAB L-band transmitters (12), the transmitters (11, 12) both being centrally controlled from a central DAB server (16) via a communication bus (15), a receiver (10) adapted to receive T-DAB signals on band III (20, 21, 22, 23) and for T-DAB signals on the L band (24.25.26.26). . .., ··· 1026149 Method for obtaining information, such as for example an Internet page, by a user with a receiver (10), wherein through a central DAB server (16) an SFN T-DAB band 11 covering the service area! 5 transmission signal (33) is supplied via a number of transmitters (11) at set-up points (2), data streams such as an EPG (electronic program guide) (23) being transmitted in the frame of the DAB signal, whereby further information is provided by the user can be selected from the received EPG (23) by sending a request signal (32) to a bi-directional network as a mobile telephony network (13) such as a GRPS or UMTS network, after which via a mobile telephony service provider (14) the request signal supplemented with geographical data from the receiver (10) = is received by a central DAB server (16) and the relevant information can be retrieved, for example from the Internet (28), after which the central DAB server is based on the geographical data from the receiver (10) establishes a connection via a communication bus (15) to a T-DAB L-band transmitter (12) in whose service area the receiver (10) is located and to adjust the DAB frame so that nowbandwidth is created for sending the requested information from the central DAB 20 server via the communication bus and the T-DAB L-band transmitter (12) via an on-demand segment (26) of the frame, to the receiver (10) of the user. 1026149