Guidelines & Requirements for Next-Generation IP-Based Intercom Systems
Written by Fredrik Borjesson (RTS) and John Ball (Microsoft Production Studios)
Intercom systems are used in fixed and mobile broadcasting, entertainment, houses of worship and other applications that require coordination of real-time production. Systems consist of a central audio router, the matrix, plus user devices connected to the matrix, such as keypanel control interfaces. In this article, we will be focusing on the matrix itself, in particular how current and future needs translate into requirements on the products themselves.
Connecting a Wired Matrix
Even today, analog connections are a very common way of connecting keypanels to matrix intercom systems. Since each keypanel requires a dedicated connector, the size of breakout panels and the number of required physical connectors grows in linear proportion with the scale of the system. In addition, without additional equipment, it is not easy to concentrate the traffic from multiple analog keypanels into a single cable. That means every keypanel requires its own homerun cable all the way back to the matrix. Cabling and installation man-hour costs add up quickly as a result.
With the advent of digital audio over IP, that has changed. Switches can be used to decentralize traffic. The matrix no longer requires a dedicated physical connector for each keypanel. Two standards dominate digital audio over IP. Today, Audinate’s Dante™ is the dominant standard, supported by hundreds of hardware vendors. Recently, AES67 has been introduced to allow interoperability between various standards, including Dante.
Requirement 1 The matrix must support digital audio over IP, in a ubiquitous format.
Bridging the Distance
In broadcast applications, remote reporters are often connected to the intercom system through IP audio. For remote connections, digital audio over IP must be compressed and/or transmitted in a format that accommodates higher network latencies. Most suppliers offer technologies that compress the original audio from several Mbit/s down to a few tens of kbit/s. One supplier, RTS, has a fully Dante-compatible solution for high-quality audio over IP that accommodates up to 20 ms of network latency. This technology expands the range to where it may be possible to connect field reporters with CD-quality audio.
Requirement 2 System must provide mechanism for digital audio to be sent over long distances.
Requirement 3 If Requirement 2 can be fulfilled with retained audio quality, that is preferable.
Audio over IP offers countless advantages over traditional analog technologies, but this view ignores one very important reality: there is a huge base of legacy analog keypanels out there. Keypanels make up somewhere between two thirds and three quarters of the total intercom system investment, so users need to know if their analog keypanels can work on a new matrix.
Requirement 4 My analog keypanels have to work on the new matrix.
In many markets, two-wire technology is still used in many applications. To connect a two-wire system to a matrix, a special converter box is typically required, unless the matrix has two-wire ports.
Requirement 5 It should be possible to connect two-wire, without the need for special adapters.
As a consequence of digitalization, analog-only keypanels will slowly phase out. Matrices need fewer connectors for analog keypanels, but they still need some.
Requirement 6 The matrix needs to have some analog connectors, without a breakout panel.
Space is Scarce, and so is Cooling
Everything gets smaller. New products have perhaps ten times the processing power of older generation products. That frees up some rack space. Both rack space and cooling are concerns in a truck or a broadcast equipment room. We’ll formulate three requirements based on these insights: smaller rack space footprint, low power consumption, and cool running temperatures.
Requirement 7 Space is a scarce resource. The less rack space needed for the matrix, the better. A single rack unit is ideal.
Requirement 8 New equipment should use less power than old equipment. Users should expect a new matrix to use less than half of the power of an older system. Switching power supplies should operate at 120 or 240 V AC, 50 or 60 Hz.
Requirement 9 Significantly reduce empty rack space required around matrix for cooling.
Setup, Configuration & Maintenance
Installing the matrix hardware is only part of the work. After it has been installed into the rack and cabling connected, it needs to be configured. Configuration is usually done on a separate computer, connected to the matrix over IP, running dedicated software from the matrix vendor. In the US, Windows-based computers still dominate. A simpler work flow could also consolidate setup, configuration, and maintaining, into a single application – or better yet, through secure webpage access.
Requirement 10 Setup, configuration, and maintenance software should run on a normal Windows-based computer or be available through secure webpage access.
Ethernet-enabled devices must address potential vulnerability to hacking to prevent them from being used as gateways for people wishing to access sensitive data or cause disruptions.
Requirement 11 Ethernet-enabled equipment must have built in state-of-the-art IP security to prevent illicit access, loss of data, and system disruption.
In a house of worship, theater, or small television station, full-blown configuration software might cater to advanced options that are not required in a simple setup with just a matrix and a few keypanels.
Requirement 12 An optional simplified configuration should be available through a web interface or on the front panel interface of the matrix itself.
Scaling the System
Intercom matrix products are almost always designed to allow for system expansion. A modular intercom typically consists of a frame and card-slots. Cards can be added to the frame as more ports are required. However, modular frames typically use two or more rack units. As a result, true modularity is hard to reconcile with Requirement 7. A matrix designed to fit in a single rack unit can still be expandable. First, it may be possible to enable more ports without adding hardware. Second, it may be possible to achieve larger capacity by interconnecting multiple units.
Requirement 13 My matrix capacity should be able to grow by enabling additional ports, provided the hardware can support it.
Once the system reaches the maximum capacity of a single matrix, there should be a mechanism for expanding further.
Requirement 14 When the hardware limit is reached in a single rack unit, there should be an option to grow further by adding more hardware.
Today, an intercom matrix investment assumes you know exactly what you need 6-12 months from now. An intercom user has to purchase a card specific to one format, often for a specific number of ports. That is not really user-centric; it’s hardware-centric and it limits the maximum frame expandability.
Requirement 15 The system should offer the flexibility to reallocate ports, independent of hardware type. If ports are no longer needed for one hardware standard, they should be reclaimable for use via another.
In a truly cost-effective solution, it should be possible to grow simply by adding another matrix, without first having to spend money on a new box or card to make the interconnection possible.
Requirement 16 Ideally, a user should be able to expand their system by simply connecting another matrix to my existing one. No additional boxes or cards should be required.
High reliability can be achieved through redundancy. Any of the following subsystems can be redundant: power converters, main processor, switching fabric, expansion cards, and connectors – up to and including the frames themselves.
Requirement 17 My matrix has to have redundancy.
The backup unit should take over automatically if the primary fails.
Requirement 18 If my primary matrix suffers a catastrophic failure, the backup matrix should take over automatically.
It should be noted that for devices that use an analog connection – such as analog keypanels – automatic switchover is not usually possible. In case of a failure, a technician would have to move those connectors from one frame to the other.
Future-Proofing Your Investment
A matrix should have a long useful life. In a modular matrix, it is possible to add new cards to accommodate new technologies. In a single rack unit form factor, it may be more realistic to consider new firmware as a means of “teaching” a matrix new functions. To support modern IP networks, all NICs (Network Interface Controllers) should be gigabit-speed at a minimum.
Requirement 19 A matrix is a long-term investment. It has to be future-proof, with the expectation of improved firmware as new technologies become available.
Requirement 20 All NICs should support gigabit-speed at a minimum, preferably more.
Dynamic Trunk Allocation
Matrix technology must support a solution for distributed networks where the total number of ports exceeds the limits of a single matrix. The inter-matrix signaling required is vendor-specific, as is any additional hardware required. Transmission capacity between matrices is often referred to as trunks. Special nodes may be required to calculate the optimum path between two matrices, to allow calls to get through via an alternate path, even if all direct trunks are busy. This is referred to as trunking.
Requirement 21 If the existing intercom system uses trunking to interconnect multiple sites, the new matrix should be able to communicate with its trunked matrix infrastructure.
The advantages of IP-based intercom systems are clear. The needs of your particular intercom installation should cover the 21 basic requirements proposed in this article, plus any specific needs dictated by your productions.
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