School’s back in session
Last year in this publication we authored a series of land-mobile-radio system engineering articles that we like to call the “LMR 100” series. In this article, we kick off the LMR 200 series. The first series examined many of the concepts behind the design of a good radio system. Now that we have gone through these preliminary steps, new series of articles will cover some of the more intricate system design criteria and will include more emphasis on budgets and real-world situations. This information can be used by engineers new to the LMR field or with limited experienced, in order to learn the nuances of how to design systems while avoiding many of the pitfalls.
There are limited resources in the LMR sector as we enter a third year of difficult financial times for both enterprises and government agencies. Accordingly, this series will focus in large measure on identifying resource management issues and opportunities. From spectrum efficiency to “green” system design to the radio frequency link, our goal is to help system designers, engineers and technicians better understand how resources can be utilized best in order to cost effectively deliver a well-functioning radio system.
The following offers an overview of the series.
The first article will examine the most important component of any LMR system: spectrum. It will discuss the advantages and disadvantages of specific bands, provide a more in-depth look at the FCC and its auctioning processes, and look at the factors that affect spectrum management.
This article specifically will explore when and where to use each frequency band. It also will examine the impact of the following factors:
- System architecture
- Power levels
- Subscriber-unit utilization
- Antenna systems
- Transmission lines
- Radio frequency interference
- Link budgets
- Radio system coverage
- Noise floor
- Atmospheric environments
- Data and other non-voice communications, such as video
Finally, this article will provide specifics that a competent engineer should know when planning a new — or troubleshooting an existing — radio system.
The next article in the series will look at infrastructure and is a direct extension of the spectrum-management and efficiency discussion, as it will explore how spectrum is applied to real-world communications sites.
The state of the art in system topologies has evolved from straight conventional and simple trunking systems to wide-area zoned trunking, IP-interconnected wireless access networks and self-healing mesh networks. These topologies have the ability to preserve resources. Moreover, different topologies can be mixed together for the most efficient use of the system.
From system design comparisons to a discussion on lower utility costs, this article will help radio system engineers better understand the impact of their designs on operating expenditures and environmental and resource management. The discussion of managing resources is an entry point into the next article on power systems and green radio.
One of the most expensive costs of operating and maintaining an LMR system concerns electrical power for the communications sites and server farms. With the advent of the smart grid, as well as advanced metering and solar and wind generation technologies, electric customers can now reduce their energy costs significantly — both when using the services and when idle.
The engineer of tomorrow will need to fully understand all aspects of power management and consumption in order to keep operating expenses under control. For instance, the communications site design must take into account the heat dissipation of the equipment in order to best manage the air-conditioning and heating requirements. Meanwhile, the batteries of tomorrow will be more efficient and as such will force a different approach to power system design and management. Smart metering will enable end-users to best manage their system’s communications power consumption to drive down their utility bills. All of these areas of power consumption and green radio will be highlighted in the third article of the series.
Here’s a summary of the remaining articles.
Mobile systems. Mobile and vehicular systems can be used to increase efficiency and lower the dependence on communication sites in an LMR system. This article will discuss the advantages of dynamic power control within the subscriber units, similar to the cellular industry, as a means of resource management for land-mobile radio.
Antenna systems. This article will look at antenna system infrastructure and is an extension to the discussions of spectrum management and infrastructure deployment. A special emphasis will be placed on shared facilities that use antenna-combining and cross band-coupling techniques. A closer look at how antenna systems can be used to contour the coverage to the user requirements will allow the engineer to minimize the spectrum and number of communications sites required.
Transmission lines. This article will explore transmission line technologies that connect antenna system infrastructure and also is an extension to the discussion of spectrum management and infrastructure deployment. Shared facilities again will be a highlight. Transmission line technology has not changed over the past few years. However, the way that they are analyzed — as well as the performance metrics that are used to display information to the engineer and maintenance technicians — has changed and will be discussed. What was thought to be a good transmission line measurement 20 years ago has been found to be very inefficient using today’s technology.
Radio coverage and interference. LMR system efficiency is dependent on clean and clear use of the spectrum. Radio frequency interference robs the system of the ability to perform as predicted and causes additional spectrum and communications sites to be used to cover the same area as originally designed. This article takes an advanced look at several interference cases and details methods for mitigation. It also will discuss link budgets and receiver sensitivity implications that affect system range and efficiency. Radio coverage is vital to spectrum resource management, not to mention capital expenditure and system performance, and will be addressed.
Licensing. With an emphasis on spectrum efficiency, this article discusses methods for working with regional planning committees, frequency coordinators and the FCC. Advanced techniques for managing co-channel and adjacent channel interference also will be addressed, with suggestions regarding how to overcome the inefficiencies of the Carey and R6602 curves. Finally, the issues associated with close-spaced spectrum also will be addressed in this article.
Data/CAD/location/video. Today’s technologies allow improved data communications with IP connectivity. For example, console positions are now Internet connected and can be located securely anywhere on the network. In the future, Internet and intranet access connected via new wireless services that utilize the 700 MHz band and Long-Term Evolution technologies will allow more efficient operations. This article will discuss these new technologies and how they can be leveraged to achieve operational and situational efficiencies. It also will explain what other infrastructure must be in place for the advanced technology to work as intended.
Specifications. This article will look at the art of specifications management from a user perspective. Understanding how manufacturers and vendors display technical features, which leads to the pricing of goods and services, enables an efficient bidding process and potentially cost savings. Often, specification nuances can make the difference between a mediocre system that barely meets the user’s needs and a system that operates as the user wants and expects it to work.
Project management techniques. In the final article of the series, we will examine such techniques from both the practitioner and vendor perspectives. Proper planning is the cornerstone to resource management and a successful implementation and cutover will minimize overlapping services and wasted utilities. Proper staging and deliveries are all key functions in this regard and as such require careful planning.
Ira Wiesenfeld, P.E., is a consulting engineer who has been involved in the radio communications business since 1966. He is a senior member of the IEEE and has been a licensed amateur radio operator since 1963. He can be reached at [email protected].
Robert C. Shapiro, P.E, is a consulting engineer who has been in Land Mobile Radio since 1984. He serves on the TIA TR8 committee (TSB-88) as vice chair and is a senior member of the IEEE. He can be reached at [email protected].
LMR 100 Series
- Part 1: Class is in session: Basic LMR and FCC definitions
- Part 2: Start at the beginning: Understanding LMR user needs
- Part 3: The devil’s in the details: Conducting a user-needs survey
- Part 4: Decisions, decisions: Understanding the LRM procurement process
- Part 5: Let’s get started: System engineering begins with RF planning
- Part 6: The lynchpin: Receiver planning and noise interference
- Part 7: Connecting the dots: How to connect LMR sites
- Part 8: The next piece of the puzzle: Understanding dispatch communications
- Part 9: Now the real work begins: How to select a suitable LMR site
- Part 10: The bane of your existence: How to deal with RF interference
- Part 11: Winning the battle: More causes of RF interference
- Part 12: Now the fun begins: Installing the LMR system
- Part 13: Dotting Is and crossing Ts: Choosing the LMR project, program managers
- Part 14: Now you’re done: Maintaining the LMR system