In a new series of features, WorldDAB members review the latest transmission technologies and trends. The second article comes from IZT and looks at virtualization and DAB.
In the first, Paneda looked at Cloud DAB and this can be found here.
Operating DAB multiplexer systems in IT data centres
Arne Borsum, IZT GmbH
Broadcast infrastructures have become more and more IT-centric. Broadcasters and platform operators benefit from harmonised infrastructure and connectivity – including flexibility regarding physical locations. With virtualization, the functionality is handled not by dedicated devices but by software applications being operated as a virtual machine (VM) on standard server hardware.
In the broadcast industry, technical processes of production and distribution are increasingly being operated on standard IT servers. At the same time, software applications have taken over the role from dedicated hardware devices for processes such as encoding and multiplexing, making it straight-forward to implement broadcast head-ends based on standard IT server hardware.
New technology makes it possible to incorporate all essential elements of a DAB head-end in one system, including multi-stream real-time audio encoding, handling of data applications and multiplexing. So it’s not a big step to virtualize this.
According to VMware, “Virtualization is the process of creating a software-based (or virtual) representation of something rather than a physical one.” Based on computer architectures, virtual machines provide the functionality of a physical computer.
Virtualization can make IT systems more efficient, flexible and scalable, simplifying the management of IT data centres by building a software-defined infrastructure. It also makes it possible to operate and combine applications on generic IT hardware platforms.
Non-virtualized DAB head-ends
Traditional DAB head-ends were designed using several dedicated devices for different purposes. In contrast, now we can incorporate audio encoding, data service handling and multiplexing in one entity – including configuration and monitoring capabilities. The software system is installed on a standard IT server, saving rack-space and energy costs as well as facilitating the replacement of defective or obsolescent hardware. The use of standard hardware and integrated audio encoding bring the benefits of lower hardware costs, cost-efficient maintenance and a significantly lower risk of failure.
There have been good reasons to operate each multiplexer instance on dedicated server hardware, including:
Virtualized DAB head-ends
Having all essential elements of a DAB head-end in one system, it is straightforward using virtual machines to operate several multiplexer instances in a virtualized environment. As a consequence, virtualization can provide further benefits:
This means virtualization can help optimise the infrastructure for DAB encoding and multiplexing. However, these processes require a permanent consumption of CPU, memory and network performance. Therefore, the gain in sharing capacities with other applications in order to facilitate peak demand is limited.
IZT recommends using VMware ESXi as hypervisor to set up a virtualized DAB head-end. The VMware hypervisor is a bare-metal hypervisor that virtualizes servers so that the user can consolidate its applications on less hardware.
Each DAB service or ensemble multiplexer requires a separate ContentServer instance. The ContentServer software system includes and integrates an operating system (Linux Ubuntu-based) which makes the installation straight-forward. Additional virtual machines can be installed, for example software to analyse the EDI output streams of the multiplexers.
VMware ESXi lets the operator configure physical and virtual network interfaces via a web interface. Each multiplexer system in the setup can be accessed via its primary IP address. In addition, it is reasonable to use additional interfaces and VLANs, e.g. for EDI streams, Audio over IP (AoIP) or for different service providers. The host system and VMs can be monitored using SNMP.
Running multiple VMs on a single hardware requires careful considerations regarding the performance and network traffic – especially with respect to timing.
It is important to regard the data rates of streams between virtual machines as well as streams over the physical network interfaces from and to the virtual machines’ host. In addition, it is useful to define separate VLANs and/or network interfaces, e.g. for different kinds of data streams or for different origins.
Broadcasters and network operators can benefit from building DAB head-ends based on virtualization – especially in case of complex setups, such as multi-regional DAB networks. However, virtualization requires careful system planning and monitoring. Accordingly, a system supplier should involve the operator’s technical experts and system architects for the integration of the system into the IT infrastructure.