There have been some notable live broadcast outages in the past few years–but much of the coverage of such incidents has tended to focus on cybersecurity and IT infrastructure failures. However, there is another growing risk factor that broadcasters need to start prioritising as part of their crisis planning: GPS jamming of satellite-related broadcast services.
It’s hardly unexpected to find that the potential for broadcasting to be deliberately disrupted has expanded as the world has become significantly more unstable recently. With geopolitical and military tensions as a backdrop to various technological developments, the notion that a bad ‘state actor’ or extremist group might seek to employ GPS jamming to disrupt broadcast production is one that can no longer be ignored.
The threat is generally regarded to be especially high in live and/or remote production scenarios, where GPS jamming can variously disrupt transmission site synchronisation, affect transport stream timing in SFNs (Single Frequency Networks), and impair remote production tools and satellite uplink coordination. Broadcast centres that utilise GPS for their internal synchronisation needs – as with the use of Precision Time Protocol (PTP) in ST 2110 IP standards – can also suffer synchronisation problems or sudden time changes when the GPS signal is no longer being jammed.
It’s important to note that many broadcasters and service providers have already taken proactive steps on this issue – especially those operating in some of the world’s most turbulent areas. For instance, it’s reported that broadcasters working in parts of the Middle East and near the borders of Russia are now, as a matter of routine, deploying GPS jamming detection tools and identifying redundant time sources in case of disruption.
However, there are other scenarios that should give broadcasters cause for pause, such as planned and highly sensitive events like a Papal or US Presidential visit. In this case, to help protect the VIPs involved, GPS jamming would be utilised by the security services – albeit only when the individual(s) are in close proximity to the venue. But with the broadcast set-up for such events usually beginning at least several days in advance, there would be ample time to establish connections and achieve synchronisation with GNSS (Global Navigation Satellite System). So as long as all SPGs (Sync Pulse Generators) have previously locked to GNSS, they will transition into ‘Stay-In-Sync’ or holdover mode once GNSS is lost.
For single OB truck operations, internal timing remains stable so there is unlikely to be a problem there. But with multiple OB truck productions, it’s vital that each truck’s SPG is synchronised with the others. This presents an unavoidable extra level of complexity that requires scrupulous planning to guarantee that timecode and genlock remain consistent across all units.
Mitigation strategy
There are other steps that broadcasters can take to mitigate the threat of GPS jamming – and to help get the show back on the road as quickly as possible if they do suffer disruption. Principal among these is the acquisition of a sync pulse generator, such as Leader’s own LT4670 ‘True Hybrid’ IP and SDI SPG, with multiple constellation GNSS receivers that – in addition to the US-owned GPS – can use other satellite navigation systems including Galileo (EU), BeiDou (China), GLONASS (Russia) and QZSS (Japan).
Use of a multi-GNSS receiver brings welcome robustness into the set-up; after all, jamming all GNSS simultaneously is far harder than jamming one of them. Additionally, SPGs like the LT4670 also use an internal OCXO (Oven Controlled Crystal Oscillator) that can frequency- and phase-lock to a GNSS. Consequently, if and when connection is lost, the LT4670 can continue to provide reference signals based upon the internal OCXO.
The name for this particular functionality is ‘Stay-in-Sync’ mode or PTP Clockclass 7. Another feature that can benefit broadcasters wishing to minimise their GPS jamming exposure is ‘Slow Sync’, which reduces the shock when synchronisation is re-established based on stay-in-sync. Thanks to its application to BB/TLS, SDI, digital audio and PTP references, ‘Slow-Sync’ supports the construction of a very reliable synchronisation system by gradually bringing the timing in-line when GNSS contact is resumed.
For a variety of reasons, these are challenging times for broadcasters, and so it’s perfectly understandable if news of this further risk to operations does not receive the warmest of welcomes. However, it’s also an issue where the threat can be dramatically reduced if the correct steps are taken – ensuring that you have the best possible chance of keeping those all-important live and remote productions on the air.
This article is taken from the July/August issue of TVBEurope, which is free to download here.
