Evolving to fast data

New technology promises to transport public safety communications to the next level, including spectrally efficient streaming video.

Following the US FCC mandate to limit most modulation formats to 2.5 kHz bandwidth after 1 January 2013, on the most commonly used public safety channels below 512 MHz, there have been some big changes in best engineering practices. Despite the doom and gloom of losing that almost studio-quality voice afforded us for years under the old analog, 5 kHz deviation (20K0F3E), recent updates in both audio recovery and data transfer designs have opened new possibilities.

Operators have settled on solutions for voice dispatch using the new narrowband analog standard or converted to one of the popular digital formats. LTE continues to evolve, and we now see some progress in the US on planning for the nationwide FirstNet system. Mandatory updates for push-to-talk dispatching have been a boom for the OEM and system providers, and the integrity and feature sets have actually improved on some systems. But what about mobile data?

We have also seen an evolution in Radio over Internet Protocol (RoIP) that demonstrates the possibility of using the same back-office infrastructure, plus end-user devices capable of good data-to-audio conversion. If perfected, they would serve both the PTT (voice) requirements and the transfer of data that holds so much promise for improved first-responder dispatching and communications.

Yes, these attributes were all promised by the now-popular P25 format, but how many applications have you seen in common use that access the rather slow data bandwidth of most available devices? The majority of P25 end-user offerings are not even compatible between vendors for simple text-style messaging.

Humble beginnings for public safety

There are multiple formats, but they all evolved from the ‘error corrected packet’ methodology originally running at speeds less than 5 Kbps. To meet that dated speed restriction, operating systems were greatly simplified and amounted to ‘fill in the blanks’ on most mobile computer terminals (MCT) and mobile data terminals (MDT). It worked for most applications, saved a lot of lives and put a lot of offenders on the path to a very rigid lifestyle. Those of us within the end-user community were essentially the ‘first texters’ long before Twitter and the other forms of SMS. We called them ‘AMs’, or administrative messages, and soon found they could be accessed by the local press and department administration. We developed some abbreviations that would impress the best of the ‘LOL, BFF, PIR’ crowd.

Complex matters were handled by the dispatchers using voice, usually the ‘teletype’ operators who had full access to a broadband data platform integrated into the local, state and national databases. It all worked, and many agencies in the United States dispatch the majority of their calls by data terminal, greatly increasing privacy and security… and incidents of minor vehicle mishaps! The latter issue still has to be addressed due to the common legislation against driving and texting. ‘Do as we say, not as we do!’ applies here. I couldn’t afford all of the fines if these laws were enforced on first responders.

Common carrier, cellular approach

The majority of public safety agencies — law enforcement, fire suppression/rescue and emergency medical — have adopted some form of mobile data to handle the complex file transfer formats demanded by first responders. We now commonly exchange photos, floor plans, GIS (mapping) information, criminal and call history, and verification of public records. For smaller agencies, and some larger ones, the ‘air card’ or mobile wireless Wi-Fi router has been their data gateway, with a level of performance and reliability adequate for most users. In addition, for small agencies, it is cost-effective.

Rather than have a dedicated channel or channels on substantial wireless sites, paired with the associated hardware and software infrastructure, the air card was developed for multiple applications and played well with most end-user devices and operating systems. Even when the only available data channels were the CDPD analog ‘control’ channels still used by some common carriers, it worked rather well. The cellular carriers were quick to identify this potential market as their capacity increased — first through the evolution to 3G, EVDO and EVDO(a), and more recently through the well-publicised 4G/LTE multiple formats. With preferred client tariffs ranging from US$15 to US$50 monthly per card or cellular modem, this made sense for many users.

Dedicated regional data channels

This was often not a viable approach for many service providers and first responders. If you operated an agency with hundreds or even thousands of mobile assets, that monthly billing became a large budget item. All agencies are feeling the effects of a prolonged downturn in local sales and property tax revenues. Grants have been greatly curtailed and are not likely to soon return.

Again, the OEMs and system vendors had an opportunity, and used this as a sales tool in persuading agencies to create their own bandwidth to serve their mobile devices. If properly engineered and maintained, this approach often gave the end users a superior quality of service within their normal geographic footprint. Since their operations were now on bandwidth assigned to the task, with no other subscriber competition, it offered certain advantages.

There have been some MDT and MCT systems in operation on public safety-category licensed channels since the 1970s. Most still use frequency-shift keying (FSK), now in emission standard 11K2F2D, or a variant approved by the FCC.

The evolution to fast data

First responders are not the only end users of fast data. The military and transportation industries use a multitude of devices. SCADA networks that control and monitor most of the publicly and privately owned utilities in the United States are major data clients and have spent a good bit of their budgets on these systems, motivating the industry OEMs to make it ‘better, faster and stronger’.

This has produced some greatly improved engineering and chipsets. We’re now seeing some demonstrated speeds that actually enable streaming video applications and error-corrected baud rates in excess of 128 Kbps. This has been demonstrated on VHF and UHF channels over kilometres, not metres.

With the right overall system design, using all of the rapidly developing technology, it actually challenges the current industry darling, LTE, in its multiple core offerings. When paired with technology already developed for other mobile communications, it has the range, capacity and speed necessary to meet the requirements of critical and essential applications.

Companies serving the SCADA, military and transportation sectors abound. We’ve seen solid system performance on narrow channels from multiple vendors, such as IP Mobilenet (IPMN), CalAmp (DCI), Data Radio, Electronic Systems Technology, Motorola Solutions and others. Based on their published specification sheets, they are still only delivering 32 to 64 Kbps raw data rates for narrowband 25 kHz channels. With FEC, the higher of these rates deliver approximately 48 Kbps to the user (Motorola and IPMN).

Meeting speed and capacity goals

In a rather complete paradigm shift, Australia’s CSIRO has introduced a methodology to obtain some substantial gains in both capacity and user speed, coupled with the ability to run substantial power levels and agile software-defined radios (SDRs), giving the correct propagation for extended coverage. Here’s the overall approach:

• Multi-user MIMO beamforming
• Antenna array and processing at the base station forms spatially separate beams to each mobile user
• Each beam uses the full spectrum all the time: simultaneous, independent, continuous transmission to each mobile user
• Simple mobile hardware and antenna
• Base station antenna array and processing maintains beam alignment with mobile users
• Dynamic selection and digital aggregation of non-contiguous spectrum, with no interference to adjacent channels

The hardware platform comprises:

• Software-defined RF front end that preserves signal phase and amplitude with minimal distortion
• High linearity, high dynamic range and FPGA processing, producing any modulation, narrowband or broadband
• Bandwidth up to 20 MHz
• Agile frequency tuning of 30 to 900 MHz
• High RF power
• Simultaneous voice and data/video, multiple protocols (P25, Ethernet, TETRA, DMR, DPMR) in one radio, with native simulcast
• Common front end for mobiles and base station

Delivering on public safety requirements

So what does all of this evolution mean to a typical public safety-grade communications system? Here’s an abbreviated list of the CSIRO system attributes:

• World’s highest data rate in 12.5 kHz (160 Kbps MAC throughput, raw data of 260 Kbps, up to 8 P25 channels) while travelling at 110 km/h currently achieved
• Ability to aggregate up to eight 12.5 kHz channels for increased bandwidth and data rate: 320 Kbps for 2 channels, multiplying up to a maximum of 2.5 Mbps for eight channels
• Predictable, video-capable performance for all users on the entire cell: no shared bandwidth, no reduced performance at cell edges
• One hardware platform from 30 to 900 MHz, and a common front end for mobiles and base station
• Incremental capital investment: no forklift upgrades of existing P25 equipment
• Voice and data/video in one radio
• Increased coverage = fewer towers
• Minimum greenfield cost: 25–40% vs LTE equivalent
• Spectrally efficient — uses all available existing narrowband public safety spectrum, contiguous and non-contiguous, scalable from 12.5 kHz to 10 MHz, dynamically allocated by base station or mobile (will later be compatible with broadband public safety spectrum, eg, FirstNet)
• High spectral efficiency and dynamic spectrum management means minimum spectrum use for the application
• Intelligent RF management means greater frequency re-use
• High security, sure delivery
• Physical separation from public network, and secure gateways
• RSA security, total visibility and control across the network
• RF modulation has built-in security to avoid snooping
• Targeted applications and services
• Native IP delivery equals easy customisation and efficient delivery of public safety applications

CSIRO has a commercialisation partner that will be deploying this technology.

With this much evolution arriving just before the start of some pilot wireless broadband systems, it might be time to evaluate the narrowband, frequency-agile approach to eliminate some of the major obstacles to system construction: access to enough sites, strategically located to meet the requirements of a low-power LTE network.

TF Smoak is an experienced emergency strike team commander and first responder who works as a project manager and compliance engineer on large wireless projects. He will give a presentation at Comms Connect Melbourne on 2 December 2015.

Image courtesy Electronic Frontier Foundation under CC