Further description for Contract on lease and operation of DR FM/DAB distribution network Transmission service for Audio Signals

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Introduction

The primary distribution of radio signals from DR Byen to all the FM transmitters and DAB transmitters have been based on 2 Mbit/s E1 circuits for more than 2 decades. The audio programmes to the FM transmitter sites are carried on E1 circuits from DR Byen to each main transmitter in DK using MPEG-2 audio compression. To the DAB transmitter sites the ETI streams are carried on other E1 circuits lines from DR Byen to all these sites. The number of FM Main transmitter sites are 16, distributed all over DK, while the number of DAB transmitter sites are 66, of which 14 of these are major High Tower/High Power transmitters. Few of the DAB transmitters are placed at the same geographical position as the FM-transmitters, but most of the DAB-sites are stand-alone transmitters. By end of 2020 the Danish operator TDC has announced, that all their E1 circuits will be phased out by end of 2021, and no options for postponing this termination is possible. Consequently, since DR is using TDC’s E1 circuits and has to maintain distribution and transmission of our radio programmes to the FM and DAB transmitters in DK without any interruptions, DR has to move away from E1 primary distribution towards other more modern transmission technologies, such as IP/MPLS. When moving to IP transmission, the old E1 audio codecs must be substituted by new Audio-over-IP codecs that are able to carry the audio signals over IP using a robust transmission protocol, good error protection and very high redundancy. RDS signals for station info, traffic announcement and TMC must also be carried to the FM-transmitters, now using IP transport, also with a robust transmission protocol, good error protection and very high redundancy. Finally, the transport of the DAB ETI signals needs to move to EDI over IP transmission, again using a robust transmission protocol, good error protection and very high redundancy. Due to the emergency obligations that DR has as a national public broadcaster, the transition from E1 primary distribution toward IP/MPLS must be done without any major transmission interruptions.

Description of the existing FM distribution network The existing distribution network for transporting DR’s radio signals to the FM transmitters consists of Mandozzi CombiMUX 2 Mbit/s audio codecs for 3 MPEG-2 compressed audio downstream channels (DR P1/P2, DR P3 and DR P4) plus one MPEG-2 upstream channel for monitoring purposes (return to MCR, DR Byen). The distribution network is implemented as a star-shaped network architecture to the FM transmitter sites with DR Byen at the center. There are two identical playouts at DR Byen, the primary equipment placed at the Server Room 1 (basement SK1) and fully identical spare/protection secondary equipment placed at the Server Room 2 (basement SK2).

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At each transmitter site there is only one E1 CombiMUX codec. It is equipped with two E1 ports (G.704), and it can automatically select the E1 input that is valid (based on frame loss alarms on port A primary and B secondary). RDS information is carried in a narrow (192 kbit/s) channel within the E1 payload in the CombiMUX codecs from the RDS server (main + spare) in DR Byen to the 2wcom RDS encoder at each transmitter station. The RDS information is then inserted with the left+right audio channel in the Omnia.SG stereo generator that generates an FM MPX signal to the FM transmitter. DARC signals (for bus arrival information) is also carried in the same 192 kbit/s channel. In case of faults on the primary and secondary E1 lines, the transmitter can be fed by signals either from the regional DR studio close to the transmitter, from ISDN or from the Cibicom Ball empfang chain starting from the main Copenhagen GLX transmitter site. The selection between these sources is done by the Cibicom PLC control based on GPIO alarms from the different receivers. The CombiMUX terminal equipment in DR Byen is connected to the Cibicom network via firewalls, and controlled, supervised and managed by Cibicom personnel. It should be noted that each radio programme is processed by an Omnia 9 processor placed centrally at DR Byen – one for P1, P2, P3 and one for each of the 10 P4 regions shown in figure 1. This processor is not shown in the drawing below (figure 1). It should also be noted that E1 CombiMUX terminals also are used today for audio contribution between DR Byen and the regional DR studios, but this equipment will soon be changed to newly purchased Video-MADI-IP Link terminal equipment running over new 10G WAN connections to/from the regional DR studios. Thus, so the distribution network is purely separated from the contribution network. The audio contribution in the WAN network is outside the scope of this tender.

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Figure 1. Existing E1 distribution to FM transmitters.

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Figure 2: FM-transmitters and their regional coverage.

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Description of the existing DAB distribution network The DAB headend in DR Byen comprise of 3 relatively new DAB+ ensembles that transmit 3 different ETI streams via E1 circuits to 3 different regions in Denmark, DAB2 North, South and East, respectively. The DAB ensembles are based on Content Server technology from AVT/ Fraunhofer GmbH. Each stream comprises 4-5 regional DR programmes of DR P4 and DR P5 as well as the national programmes DR P1, P2, P3, P6, P8 plus a programme from another public broadcasting station, Radio4, totally approx. 15-17 programmes in each ensemble. Single Frequency Network (SFN) operation is used in each of these 3 regions, each of which consists of 17-26 synchronous DAB transmitters. The DAB headend in DR Byen is fully redundant with a 100% identical setup and playout from both server rooms SK1 and SK2. The DAB+ playout in DR Byen is prepared for EDI output via IP, but presently this type of output is not activated, and only ETI 2 Mbit/s coaxial outputs are used for the primary distribution. The DAB distribution network is implemented as a tree-shaped network architecture to the local telephone exchanges in the Copenhagen area, that feed the DAB2 East region and from there to 2 other main TDC exchanges in Aarhus, that feed the DAB transmitters in the North region, and to Kolding, that feed the DAB transmitters in the South region, respectively. DAB transmitters placed at the sites, where Cibicom has their own fiber connections, are fed directly from DR Byen via coaxial ETI through Cibicoms fiber network to these transmitter sites – not via E1 lines from the 3rd party network operator TDC. The ETI outputs from the two DAB+ playouts in DR Byen are transmitted to all major DAB transmitter sites as main + protection connections from the two server rooms in DR Byen with separate routes (tracés) all the way throughout to these transmitter sites. Minor DAB transmitters have fully redundant routes to the nearest telephone exchange, but only a single circuit from there for the “last mile” to the local DAB transmitter site. The DAB headend in DR Byen is connected to the DR network and controlled and supervised by DR personnel.

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* DR P5 with regional news

Figure 3: DAB-transmitters and their regional coverage.

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1.1. General description The establishment of audio and data transmission through an IP/MPLS distribution network requires purchase of new audio transmission equipment, and also requires establishment of new connections for carriage of IP/MPLS signals from DR Byen to all the FM and DAB transmitters. The new Audio-over-IP codecs are mainly used for permanent connections through the IP/MPLS network. Since the network connections are almost permanent (however with protection), simple unicast transmission to each of the FM-transmitter stations is preferred, compared to multicast methods that are more complex during fault finding and risk of “broadcast storms” are not negligible. This tender is both related to the Audio-over-IP terminal equipment and related to control and supervision towards the FM-transmitters, transport of RDS- messages to the same FM-transmitters, and transport of DAB/EDI signals to all the DAB transmitters, and finally – not at least - establishment of the connection lines between DR Byen and the FM and DAB transmitter sites. Earlier the E1 transmission circuits were established by DR through 3rd party agreements with a network provider, but with this tender, the connection lines are also included. Thus, the tender can be considered as a total system delivery of audio, RDS and DAB/EDI services from DR Byen to all DR’s FM and DAB transmitters in DK, and the Tenderer will then have the full responsibility of the service delivery from DR Byen all the way throughout to the transmitter stations. DR has investigated multiple solutions with the help of the UK based broadcast network operator Arqiva and a simple approach has been chosen in order to employ traditional audio-over-IP codecs carrying at least 3 bidirectional audio channels instead of the CombiMUX E1 codecs. In DR Byen identical Audio-over-IP codecs should be placed in both SK1 and SK2, just like the existing CombiMUX’es. The IP signals should be transported over IP/MPLS connections from SK1 to each transmitter site via two simultaneous routes for high protection and seamless change-over, such as SMPTE 2022-7 based on RTP or similar principles. At the transmitter site two sets of audio codecs are necessary, and the 2nd codec should then be connected to DR Byens SK2, also with two simultaneous routes from SK2 and SMPTE 2022-7 switching as the codec no. 1. The two codecs at the transmitter site should be synchronized to a common clock reference, so the audio latency from audio input at DR Byen to audio output at the transmitter site becomes identical in the two codecs within few ms, resulting in a switching that becomes inaudible. Similarly, the transport of RDS and DARC signals from DR Byen to the FM-transmission sites should have the redundancy and passed through the IP/MPLS connections like regular data streams. Finally, it seems realistic that the transition from E1 transmission to IP/MPLS can be done – by careful planning - with almost no impact of the DR’s on- air broadcasting FM and DAB services. In figure 4, the red, green and blue boxes are new equipment that is covered in this tender. The white boxes are new equipment that is outside the scope of this tender, and the grey boxes are reuse from the existing system. The establishment of this new audio transmission principle gives the following advantages: • The solution is relatively easy to establish since the changes at the transmitter sites are modest. • Very high reliability of audio, RDS and DAB EDI services is expected.

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• Separate playout from DR Byen’s Server Room 1 (SK1) and Server Room 2 (SK2) is maintained. • Unicast transmission will be used for the audio and RDS connections to/from the FM-sites in order to ensure simplicity and easy fault finding, while multicast transmission will be used for the distribution of EDI signals from the 3 DAB ensembles to the DAB transmitters in each of the 3 different regions, i.e. the North, South and East ensemble, respectively. • Two physical Audio-over-IP codecs will be installed at each the FM-transmitter site in order to ensure very high reliability, no single-point-of- failure and seamless change-over between main and protection routes. • Two physical EDI/ETI converters at DAB-transmitter sites to ensure firmware updates don’t cause service outage. Note not all DAB-sites will be equipped with redundant IP/MPLS connection at the beginning but could be established at a later point in time as an option in the contract. • All the current functions on the FM-transmitter sites are maintained, including RDS and DARC. • Changes of PLC “auto-shifting” functionality at the FM-transmitter sites are modest, since most of the new codecs and processor on the transmitter site can provide “old-fashioned” GPIO, that can communicate with the existing PLC. • All new IP codecs and the IP/MPLS terminals in the distribution chain are solely connected and managed via the Tenderers network, in order to obtain a well-defined responsibility of the system operation. DR has no direct access of the codec units and the transmission equipment. • DR will have a total overview of the system operation of selected parameters, transferred via firewalls from the Tenderers supervision system to DR’s MCR, preferably in a system map drawing using PRTG, a Dashboard or similar.

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Figure 4. Proposal for new Audio-over-IP distribution to FM and DAB transmitters using IP/MPLS.

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