What type of connection to use for the STL?

The bit rate of the data stream of a full MUX (e.g. 12 broadcasters at 96 kbps) is 1.2 Mega bits per second (Mbps). It is therefore very important to choose a connection that can handle this data stream.

If more than 1 transmitter site is used, the ETI stream will have to be sent to all transmitter sites. For example, if there are 3 transmitter sites and the multiplexer is at yet another location, 3.6 Mbps will be uploaded (1.2 Mbps per transmitter site). It is also very important to provide enough reserve and choose a connection that can handle more than what is actually needed. Why we will explain later in a subsequent article.

A stable connection is then also something that needs to be thought about very carefully. After all, if the connection is not stable enough, “synchronization” problems can quickly occur, which will cause different transmitters to interfere with each other.

Therefore, we list briefly which solutions can be considered to transport the EDI (ETI over IP) stream.

1. Private VPN connection

This is always an “IP connection”, a private Internet connection based on the MPLS protocol (PE and CE routers).

It is a private IP network where a piece is reserved for a user. Everything else is identical to the public Internet. SLA’s (Service Level Agreements) on throughput are possible but will have an additional cost.

It can also be over a LAN (switch on the sites) one calls this service VPLS (Virtual Private Lan Service). In this case you connect to a switch (not a router) at the different sites. The network then looks like a switch that you connect to with Ethernet. We know that this service is more expensive because of the rental price of Catalist switches.

2. Radio link (ex: wireless data links)

The main condition for using a (professional) radio link is that the “antennas can see each other”. This has mainly to do with the frequency band used.

At best, a good radio link can span several kilometers. Tests proved that this kind of data link can be perfectly used for an STL for DAB. Best to use professional equipment for this.

3. Fiberglass network

Renting fiber is expensive as is lighting it (putting up a signal). Dedicated fiber is out of the question for local radios because of its cost. One will therefore have to concentrate on shared solutions such as SDH.

4. The public Internet

This is a public network (public Internet). No SLA’s (Service Level Agreements) apply here. The basic principle is “best effort.” So using public Internet involves certain risks.

The throughput is primarily a function of usage. If many people use the Internet, throughput may drop to a level where ETI signals no longer arrive in time to keep the SFN transmitters in sync.

Using public Internet should be seen as accepting risk. One can NEVER achieve 100% availability with it.