March 4, 2014
As part of its centennial celebration, the American Radio Relay League (ARRL) re-published in the March 2014 issue of QST Magazine a copy of the “special bulletin” sent out by the ARRL in April 1919 to radio amateurs as World War I was winding down. The bulletin is interesting on several levels, one of which is that it gives us a glimpse into the state of the radio art as it existed almost a century ago.
Regenerative receivers, spark gap motors, oscillation transformers, etc. were still common. Vacuum tubes, or “VTs,” were used by the military during WWI, edging out the De Forest “Audion” that were more common before the war but proved inconsistent and unreliable. ARRL’s editors in 1919 pondered in the special bulletin whether VTs would find their way into amateur radio as hobbyists hung up their uniforms and went on air as civilians; of course these and many more advances would radically change the radio art over the next 95 years. VTs would dominate the radio art for the next four decades, eventually replaced by transistors and then integrated circuits.
So what will the next 100 years bring? Given the current rapid pace of technical advancement, it would be hard to predict what radio will look like 20 years from now much less in a century. Asked to predict the future in 1919, even David Sarnoff himself would not have been able to describe anything resembling a basic first-generation handheld P25 public safety radio. Nevertheless, it’s interesting to explore some current trends in enabling technologies and extrapolate based on those.
Probably the most promising enabling technology in 2014 is the move towards widespread adoption of LTE data systems such as FirstNet. I tend to agree with the notion held by some that push-to-talk (PTT) Voice-over-LTE (VoLTE) for critical situations is not something we’ll see widely adopted for many years. Public safety leaders and incident response commanders have been hesitant to adopt even more traditional APCO P25 systems for use in critical situations because of concerns about RFI/EMI blocking, channel contention, and vocoder overload from sirens, pumps, concrete saws, etc.
The digital radio system at NAVSEA failed during the September 2013 active shooter incident because people activated the fire alarms and the noise overwhelmed the vocoders of the responder’s radios. Because of these concerns, I don’t see PTT VoLTE replacing traditional LMR any time soon. Given rapid advances in processor technology (which has driven huge advancements in digital signal processing) we may someday be able to build a vocoder that can intelligently filter human voice from ambient noise, but we’re not there yet.
Even if LTE is never used for voice, data transfer of critical information such as photos, maps, documents, etc. is useful and LTE is our best current solution. I expect we’ll also see some adoption of PTT VoLTE for sub-critical and daily operations. LTE will become even more valuable once 3GPP implements LTE Direct - allowing LTE user equipment to form ad hoc networks in locations without LTE site infrastructure. There are also competitive, complimentary, and/or alternate solutions to 3GPP's approach to LTE Direct and PTT VoLTE.
SocialMesh Network is an emerging industry consortium that builds on mesh and peer-to-peer networking technologies such as Open Garden. These technologies use decentralized and distributed networking to form peer networks that provide data connectivity in the absence of infrastructure. It’s possible that Open Garden, SocialMesh, etc. or similar technologies may find their way into 3GPP’s future standard for LTE Direct. Mesh networks, however, tend to be inefficient, so until new algorithms are developed I expect mesh/peer wireless to be useful only in low-bandwidth applications.
In cases where network infrastructure already exists, apps running on handheld computing devices can complement or even replace traditional radios. Like Twitter was used by Iranian students during the 2009 “Orange Revolution,” Zello is a PTT voice app for iOS and Android that was the communications tool of choice for Venezuelan protesters during the February 2014 uprisings against the Maduro-led government. Zello has become so widely used by protesters that CANTV (the ISP owned by the Venezuela government that carries 90% of all domestic IP traffic) took steps to block Zello data streams, prompting Austin, TX-based Zello to release updates that allow the app to work around the CANTV blocks. VPN encryption services have also played a role in restoring Zello service. While likely not suitable for mission-critical use in its current state, Zello is proving that apps on consumer devices can provide a reasonable replacement for PTT radio.
Search for Standardization
So, is the future of LMR going to be IP-based apps running on “smartradios,” self-forming networks over dynamic peer-to-peer mesh connections? Or will LMR lag behind, staying within the safe, if somewhat inefficient, confines of traditional analog or digital radio? I think the answer is that we’ll see both, with the mission critical users tending to remain on older proven technologies.
The downside of all this new technology is: How will we achieve standardization? The proliferation of new digital LMR standards has led to less, not more, interoperability. If fire chiefs in one county are running Zello over LTE, and their counterparts in the adjoining county are running PTT smartphones with a proprietary mobile carrier app, then we’ll be no closer to interoperability than we were in 1985. We need to start thinking about standardizing apps and data stream APIs, not just radios. We need to think about standardizing mobile VPNs, because the same tactics employed by the Maduro government at CANTV against the protesters could be applied by criminals seeking to shut down public safety IP networks.