MOTOTRBO: Why Digital Two-Way?
Why Two-way Radio?Before we look at the advantages of digital, there's a more fundamental question. With alternative and emerging technologies – such as cellular, push-to-talk over cellular, and Voice-over-WLAN – is there any reason for enterprises to stick with two-way radio at all? While there's no single answer to this question for every organization, two-way radio offers certain advantages that make it the clear choice for the vast majority of mobile professionals who require an affordable, flexible, highly reliable solution – along with the power and range available only in licensed bands. Advantages of two-way radio include:
- Low total cost of ownership.
- Customizable coverage and features.
- Simple, reliable implementation.
Digital Two-way Radio: A Modern Solution for Modern NeedsAnalog radio works well, and proves itself every day in countless deployments around the world. However, analog two-way radio has reached the limits of innovations. Virtually everything that can be imagined using analog radio has been already been attempted or achieved over more than a half-century of experimentation and innovation. Today, a new platform is required to break through to new levels of performance and productivity. Many enterprises are finding they need more than the fundamentals that analog two-way radio delivers. Perhaps their licensed channels are becoming crowded and they need more capacity. Perhaps they need more flexible ways to communicate with users both inside and outside the work team. Perhaps they need access to data in combination with voice to improve responsiveness and productivity. Digital radio provides a powerful, flexible platform that professional organizations can adapt to meet these needs and more. By migrating from analog to digital two-way radio communications, these organizations can fill many of these needs immediately and build a strong technical foundation for adding new functionality to meet new needs in the future. Let's take a look at each of these enterprise mobility needs in turn, and explore how digital radio technology can support a more responsive and adept mobile team.
Need: Efficient Use of RF SpectrumFor many two-way users, the most important benefit of digital radio is to make more efficient use of licensed 25 kHz and 12.5 kHz channels. The airwaves are becoming more and more crowded, and the old licensed channel structures – originally designed with the principal goal of serving a handful of broadcasters – are no longer adequate to carry the increasing broadcast and private radio traffic projected in the future. Regulatory agencies are responding to an impending crisis in RF congestion by mandating more efficient use of licensed spectrum. For example, in the U.S., the FCC is requiring manufacturers to offer only devices that operate within 12.5 kHz channels by 2011. By the year 2013, all users will be required to operate in 12.5 kHz – making it possible for twice as many users to share the airwaves as compared with today's 25 kHz licenses. The next logical step is to further improve the effective capacity of 12.5 kHz channels. It's only a matter of time before the ability to carry two voice paths into a single 12.5 kHz channel, also known as 6.25 kHz equivalent efficiency, becomes a requirement. But with digital radio, there's no need to wait for a mandate. Devices that incorporate Time-Division Multiple Access (TDMA) can achieve 6.25 kHz equivalency today – doubling the capacity of a currently licensed 12.5 kHz channel or quadrupling the capacity of a 25 kHz channel. That means many more people can communicate over an enterprise's existing licensed channels, without worrying about interference. And because each TDMA "slot" works independently, these virtual 6.25 kHz channels can be used flexibly according to the organization's needs. For example, two slots within one channel can be used to carry two separate and private conversations, or else one slot could be used for data or priority signaling in conjunction with a conversation on the other slot.
Digital radio offers:
- The ability to expand digital voice, data and control capabilities.
- Lower licensing and equipment costs.
What is Narrowbanding?Private land mobile radio (LMR) systems - including municipal government and State and local public safety systems - use blocks of radio spectrum called channels. Historically, LMR systems have used 25 kHz-wide channels. In December 2004, the Federal Communications Commission mandated that all private LMR users operating between 150 and 512 MHz move to 12.5 kHz narrowband voice channels and highly efficient data channel operations by January 1, 2013. This migration complements a National Telecommunications and Information Administration mandate for more rapid Federal agency migration to 12.5 kHz narrowband operation by January 1, 2008. The earlier Federal deadline affects State and local FCC licensees that interface or share frequencies with Federal radio systems.
Need: Improved Fundamentals, Including Voice Quality, Privacy, Battery Life and Additional FeaturesProfessional two-way radio users depend on clear, unbroken, reliable voice communications. A missed call, user error, garbled message or dead battery can mean lowered productivity, wasted time and money, unsatisfied customers, and lost business. Due to the inherent nature of RF physics, analog radio can suffer from several limitations that affect the range and clarity of voice. In an analog system, everything in the environment that disrupts or interferes with the signal itself directly impinges on the voice quality at the receiving end. Although it's possible to boost and retransmit a degraded signal, there's no way to reconstitute the original voice quality. The most common result of this degradation is an increase in static and artifacts that makes the signal increasingly unintelligible as the user approaches the margins of the radio's effective range. Signal strength falls off exponentially as the distance from the transmitter increases, following the inverse square law. At the same time, the background RF "noise" level remains constant, so the signal-to-noise ratio declines by a factor of four with each doubling of the distance between transmitter and receiver. Environmental factors – such as line-of-sight obstacles and RF interference – can also severely degrade performance, further shortening the effective range at which analog radio performs with acceptable voice quality. The only way to retain analog voice quality at the edge of the radio's effective range is to boost signal strength. But this quickly becomes impractical due to the added battery size and drain, the risk of cross-talk and other interference, and regulations governing radio power and spectrum use in various applications. Moreover, techniques that are applied to the analog transmission – such as compounding or voice scrambling for security – alter the quality of the voice signal itself, coloring the sound and adding artifacts that can make it difficult to understand what's being said. Digital systems, by contrast, incorporate built-in error-correction techniques that reconstitute the voice at nearly its original fidelity throughout most of the RF coverage area. Depending on the device design, digital systems can also improve field operations through longer battery life and additional features. For example, TDMA-based systems that provide 6.25 kHz equivalency in a 12.5 kHz channel use only half their transmit time to carry a single half-duplex conversation. Since transmitting RF signals is very power-intensive, this means digital systems place less drain on the battery than their analog counterparts. In fact, conversation-for-conversation, TDMA-based digital radios function about 40 percent longer on a battery charge than analog systems. Moreover, the two-for-one channel capacity of a TDMA-based system can be used to carry a second conversation, to provide dispatch data in parallel with verbal instructions, to enable enhanced call-control and emergency pre-emption, and for a variety of other existing and future applications. In the same way that digital technology is creating new possibilities for wired and cellular communications, digital two-way radio gives mobile workgroups flexible access to more kinds of information – so they can work faster and more effectively than ever before.
Digital radio offers:
- Enhanced voice communications over a greater range.
- Static and noise rejection.
- Privacy without loss of quality.
- Longer battery life.
Need: Integrated, Rapid Data AccessMobile workers who depend on analog two-way radio are realizing that they can work even more effectively in the field if they also have wireless access to applications and data. For example, construction contractors that have relied on two-way radio for decades are now adding on-site access to work schedules, materials ordering systems, and other tools that can't be accessed effectively through a voice call. It's just as common these days to see a site foreman using a wirelessly connected laptop as a radio. But as mobile enterprises increasingly adopt wireless data solutions, they face a dilemma: Should they acquire and maintain separate voice and data systems, or adopt a converged system that provides both voice and data in a single unit? And for organizations that already have multiple systems in deployment, how can they preserve their current investment without committing to a continuing investment in incompatible, side-by-side technologies in the years ahead? A complete system change-out scenario is impractical for most organizations in the short term. But going forward, it's wise to invest in backward-compatible systems that don't require an ongoing commitment to separate acquisition, training and maintenance costs. If it meets the needs of your business, moving to a converged voice and data platform over time can simplify system administration, and empowers users with systems that are more portable, flexible, and much easier to use than two different and incompatible systems.
Digital radio offers:
- Enhanced operational control, capacity and efficiency,
- Leverage the power of two-way for voice and data.
- More applications, simplified integration.
- Flexibility to allocate channels to voice and/or data as needed.
Need: Ease of Migration from Analog to Digital, While Helping to Preserve InvestmentNobody can afford so-called "disruptive technology" to disrupt their day-to-day operations or their IT budget. Fear of disruption is probably the biggest deterrent to organizations that have used analog radio for years, even when they realize that digital capabilities could greatly enhance their productivity and responsiveness. Once the benefits of digital systems become impossible to ignore, organizations must choose a viable migration path. One option is to deploy separate digital systems for data, while retaining analog radio for voice communications. While this helps preserve the existing investment in analog radios, the drawback to this approach is that it entails an indefinite commitment to analog, preventing the organization from enjoying the benefits of digital radio for the foreseeable future. Another option is to plan for an extended period in which analog and digital systems – including two-way radio devices – exist side-by-side, with the goal of phasing out the analog systems over time. This enables the organization to maximize the return on investment (ROI) of legacy systems, control the budget and ease the IT burden associated with transitioning end users. Such a migration strategy must be implemented carefully in order to achieve the intended benefits. This means choosing devices that are specifically designed for flexibility – so that digital and analog systems don't just exist side-by-side, but work together to provide the optimum communication method for any situation.
Digital radio offers:
- Available devices that provide analog and digital voice side-by-side in the same unit.
- Immediate enhancement of operations,
- A flexible, future-facing architecture.
Need: Appropriate Standards and Technology for Professional UsersWith the emergence of digital two-way radio technologies, professional users can expect to be offered an increasing variety of systems, both proprietary and standards-based. Professional organizations selecting systems based on widely accepted standards will benefit from reliable operation, as well as to ensure compatibility and interoperability among competitively priced products from multiple manufacturers. Multiple standards and technologies exist to meet the varying needs of the radio communications marketplace, from consumer and light industrial applications to professional business-critical applications and to first-responders engaged in mission-critical public safety applications. The most relevant standard for professional, business critical applications of digital mobile radio is the European Telecommunications Standards Institute Tier-2 standard for licensed, conventional, unit-to-unit and repeater-based radio operations. Developed by ETSI, this globally recognized standard provides spectral efficiency, advanced features and integrated packet data services in licensed bands for professional users.
eContact SAS-Norsat Communications for further details and a demonstration of the Digital Radio Systems.