As first-generation SDRs are successfully deployed, innovations and interoperability testing continue to improve these flexible, programmable radios.
Battlefield radios are essential tools for tactical communications, but many older radios are simply wearing out. The US military needs more radios and communications channels. To fulfill that need, it is focusing on systems that are flexible, efficient, and cost effective. Work continues on both the Joint Tactical Radio Services (JTRS) program and continued development of software-defined-radio (SDR) platforms as a result. Some maintain that SDR technology has not progressed quickly enough in the past decade. Filling the gap are JTRS battlefield radios that are optimized for size, weight, power, and cost (SWaP-C).
Despite the strengths of such radios, the military is still determining its exact needs. For example, it is engaging in tests that are likely to influence near- and long-term designs. This past July, the US Army conducted the Network Integration Evaluation (NIE)a six-week test of communications network capabilities held at the White Sands Missile Range, NM. The second exercise, scheduled for October and November, will involve nearly 3800 soldiers and 1000 vehicles.
A key player in this test, the Boeing Co., is the prime contractor for the JTRS ground-mobile-radio (GMR) program for US Army vehicles. (Other members of the project team include Northrop Grumman, Rockwell Collins, BAE Systems, and Harris' RF Communications Division.) As explained by Matthew P. Billingsley, a spokesman for Boeing, "Boeing is preparing for the second Network Integration Evaluation this fall and awaiting a decision from the JPEO JTRS and the US Army on lowrate initial production of the JTRS GMRs. During the Network Integration Evaluation conducted in June and July, JTRS GMR provided forces with the secure, multi-channel communications system that they need to share data and communicate in areas without traditional infrastructure."
Brad Curran, Industry Analyst at Frost & Sullivan, projects some of what will be learned from these tests: "I think you will see more commercial-off-the-shelf (COTS) -based technologies used by the Army on a more widespread basis. The advantages are that it saves money and gets systems out to the troops faster. There is still an issue with collaboration between platforms, but these are nowhere nearly as bad as the problems that civilian agencies have. During the last 10 years of constant warfare, they've made enormous improvements, and COTS-based wireless networking technologies have helped."
Tom Keen, Business Development at ITT CFPS, reports that his company uses COTS/standard components extensively. In fact, ITT has been using commercial modules and processors in its radios for more than 15 years. For its part, Harris RF Communications "operates on a commercial basis model that's unique to government and defense markets," explains Ed Maier, Vice President and General Manager, Operations and Engineering. "The ready availability of outstanding COTS/standard components allows us to continue to reduce cycle times and get these new products in the hands of users."
Frost & Sullivan's Curran expects the military-electronics market in generaland battlefield radios in particularto continue to be robust. The radios are in constant use, there are still not enough of them, and they get worn out by operating in harsh environments. "We see good volume and good replacement rates for battlefield radios, as compared to ship or aircraft electronics," he notes.
BATTLEFIELD CHALLENGES
For military electronics, reducing SWaP while driving down costs remains the highest priority and one of the biggest challenges. Keen explains that ITT uses "extensive microelectronic integration" to address SWaP and cost issues. As part of the SWaP equation, improved battery charge density would lead to smaller batteries with longer run times. In addition, finding ways to ruggedize parts and protect them from dust using lighter-weight materials would be advantageous.
In his analysis of SDR and the use of field-programmable gate arrays (FPGAs), Curran notes that thermal management also is a big challenge: "We are trying to get these FPGAs to be multifunctional and flexible, but they produce an enormous amount of heat. Any technology that can help reduce or solve the heat problem would be welcome." Among other trends noted by Curran are rising concerns over counterfeit parts and the need for embedded cryptography/ security.
"The last major issue is standardization," adds Curran. "Most systems are still proprietary, so they do not work together without a lot of extra training and coding. The DoD wants things to be standardizedCOTS designs as well as standardized interfaces and software so components can be bought inexpensively and upgraded quickly without the need for new code."
According to Harris' Maier, the greatest challenges involve providing legacy interoperability, high performance, and wideband-networking data-communications capability in a small package with missionlength battery life. "From an RF standpoint, new SDRs must be multiband with broadband design from 30 MHz to over 2 GHz, be frequency agile, and be able to perform in both narrowband and wideband modes," says Maier. He also cites the challenges of compressed design periods.
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An additional challenge is the increasingly complex processing and networking waveforms that are required due to the demand for high levels of real-time data interchange, points out Troy Brunk, Senior Director of Airborne and Fixed Site Communications at Rockwell Collins. "The design of communications products capable of enabling these operations while retaining legacy capability to achieve interoperabilityall within the SWaP-C constraintsremains a key challenge across the industry," he explains.
At Rockwell Collins, designers approach these market challenges by enhancing many core products with advanced capabilities. Brunk notes that they also leverage innovations from the firm's Advanced Technology Center to "bring to market affordable, leading-edge communications products in the areas of SDRs and advanced networking solutions." Recent advancements in electronics packaging, power-efficient components, and multi-layer printed-circuit boards (PCBs) with embedded components have led to a significant reduction in SWaP. Yet they still allow designers to improve on overall performance and capability.
At Harris, Maier says that SWaP dictates key design constraints right from the start. "We leverage existing commercial technologyparticularly in the semiconductor product areato achieve high performance with minimum power consumption. We employ low-weight, rugged materials throughout. We have key supplier partnerships in areas like semiconductor integrated circuits (ICs) and discretes, battery technology, and antennas."
SOFTWARE-DEFINED RADIO
Without a doubt, first-generation SDRs have been very successful and are battlefield proven. Radios with upgradable software allow the addition of new features as needed. While it is true that work remains to support wideband waveforms, SDR seems well on its way to fulfilling its early promise for battlefield radios.
"SDR is already deployed by companies like Rockwell Collins, Thales, and Harris. A specific example would be the Harris PRC-152 radio," observes Ian Land, Senior Manager of Altera Corp.'s Military Business Unit. "Companies like Boeing and General Dynamics are offering SDR in JTRS-capable radios."
Maier adds, "SDR is an extraordinary success for both government and industry and is here to stay." Keen agrees while cautioning, "Software radios will not be designed to do everything; they will be a more intelligent device with reasonable flexibility for a basic task area. In terms of deployment, the budget will prevent the widespread deployment of new equipment for the next decade."
Early SDRs for the military focused on replacing traditional point-to-point radios with SDRs that were capable of emulating a number of distinct, secure, digital, point-to-point, narrowband radio-transmission waveforms. "A casual observer may wonder why the military doesn't just adopt a militarized version of commercial wireless networks," says John L. Shanton, MILCOM System Architect, Xilinx, Inc. "But these networks require cell towers to work, and cell towers are hard to come by on the modern battlefield. This is the fundamental difficulty of modern tactical wireless networks. They must be peer-to-peer (MANET) in topology with relayed links to bridge one network to another."
In fact, some of the latest SDRs are running newer, wideband-networking waveforms like the Soldier Radio Waveform (SRW). "There have been many improvements in networking during the last decade of evolution in military SDR platforms," adds Shanton.
WHAT'S AVAILABLE NOW
Although it is always exciting to look into the future, many impressive radio developments are already available. For instance, Thales Communications, Inc. continues to deliver the AN/PRC-148 JTRS enhanced JEM radio, which is the next generation of its MBITR radio (Fig. 1). The company reports that approximately 200,000 AN/ PRC-148s are deployed globally. For its part, Harris offers the AN/PRC-117G multiband manpack radio (Fig. 2); RF- 7800W high-capacity line-of-sight radio; RF-7800V VHF combat net radio; and RF-7800S secure personal radio.
ITT offers its Soldier Radio, Rifleman Radio, SpearNet, SideHat ER (Fig. 3), and RO Tactical Radio. Rockwell Collins recently released the next-generation airborne VHF/UHF transceiver in its ARC- 210 product family. "The ARC-210 Gen5 radio provides the military with a first-tomarket, affordable, software-defined radio with cryptographic modernization features," says Brunk. "It retains form, fit, and functionality while enabling new capabilities, such as crucial networking waveforms to connect air and ground assets."
FPGA companies have been busy supporting military SDRs as well. Altera released a suite of products to meet the cryptographic needs of suite A and B cryptographic systems, known as Single FPGA Cryptography. Those products are the Cyclone III LS, Security Supervisor IP, and Altera Separation and Verification Tool. For military radios, the firm offers the Arria V while the Stratix V is for infrastructure.
For its part, Xilinx has built three families on its generation 7 series FPGA devicesall on a common 28-nm silicon geometry. They include the Artix-7 (for portable, battery-powered radios); Kintex-7 (for moderate-power, higher-performance radios); and Virtex-7 (for higher-end devices). Xilinx also released the Zynq-7000 family. This Extensible Processing Platform (EPP) integrates a Dual ARM Cortex-A9 MPCore with programmable logic and I/O peripherals and memory controllers on a single chip. The various elements on the chip are tied together with the AMBA AXI interconnect. "A single Z-7040 can host almost any military wideband waveform in a vehicular or airborne radio," says Shanton. "Combining a Zynq EPP Z-7020 with a single Artix device would provide a level of processor and FPGA resources well beyond any existing man-portable radio in existence today. This approach enables a whole new wave of networking radio capabilities. Future generations of military radios will continue the trend of more resources for less power, thus pushing to new levels of radio waveform sophistication and application-layer capabilities."