This article is an extension of the "Jurassic Telecommunications" series written by Don Kimberlin for NARTE News about the various radio technologies. In fact, it was Don who contacted me and suggested I write about the next generation of radios. In compliance with his request, I will briefly discuss the next generation of radios in this article.

What is the next generation radio? Well we know the first one was hardware-driven radio. The hardware performs all transmit and receive functions via specifically designed Radio Frequency (RF) hardware. The transmit frequencies, modulation type and other RF parameters are determined by hardware and cannot be changed without actually altering the hardware. That means your 450 MHz two way radio cannot become a 1900 MHz PCS phone without drastically changing out the hardware. Hence, the radio operation is limited by its design.
The subsequent generation brought the digital radio. Part of the design is based on hardware; the other part based on the signal processing or transmission. However, it is not programmable in the field. Though the signal processing may be done by digital signal processors, it is still limited to its operation based on firmware and some of the hardware.
So now we come to the next generation. This is a fully software-driven, or software-defined radio that performs all signal processing in the digital domain using programmable digital signal processors, general purpose type microprocessors, or a series of field-programmable gate arrays. All functions, modes and applications can be reconfigured by the end user through software.

FCC NPRM
Since most radio operations are limited by regulatory agencies, the agencies first must agree to allow these types of systems. The FCC has recently released the Notice of Proposed Rule Making DA00-47 on Software Defined Radios (SDR). This rule is now out for public comments from the industry on this proposal. An overview of the proposal follows.
Under the current FCC Part 2 rules, a radio transmitter is approved for a specific set of technical parameters, including the operating frequencies, output power, and types of radio frequency emission. If the grantee of the equipment authorization changes these parameters after a piece of equipment has been authorized, the grantee must apply for a new approval and wait until the approval is issued before the unit may be marketed with the changes. These rules were developed to address radio characteristics defined by hardware.
The operating parameters of a software-defined radio, however, can be changed in the field by modifying its software. Implementing such change could possibly violate the terms of the transmitter’s equipment authorization by causing it to operate on frequencies or in modes that were not approved as part of the original equipment grant of authorization. In addition, the current FCC rules do not allow parties other than the grantee of the equipment authorization to make modifications to approved equipment. A software-defined radio’s operating parameters, such as the frequency and modulation type, are determined by software. The fact that these parameters are determined by software means that a software-defined radio could be programmed to transmit and receive on any frequency and to use any desired transmission format within the limits of its design. This provides the user substantial flexibility to operate in multiple radio services. Thus, the operating parameters of a software-defined radio could be altered by the end user in the field by a simple change to software. Under the current Part 2 FCC rules, this change in frequency and modulation type would be illegal, especially if done by the end user. The introduction of software-defined radios that can be reprogrammed to new operating parameters in the field could have far reaching implications for the way the FCC currently allocates and licenses the frequency spectrum, as well as how it authorizes radio equipment. The implementation of software-defined radios could actually allow a more efficient use of spectrum by facilitating spectrum sharing and also allowing radio equipment to be reprogrammed to more efficient modulation types.
The use of SDR could also enhance interoperability between different radio services by allowing them to select the most efficient mode of operation.

FCC Proposed Rule Changes
The FCC will define what an SDR radio is under the Part 2 rules, stated as follows:

2.1 Terms and definitions:
(c) Software defined radio. A radio that includes a trans-mitter in which the operating parameters of the transmitter, including the frequency range, modulation type and maximum radiated or conducted output power can be altered by making a change in software without making any hardware changes.

(e) Manufacturers must take steps to ensure that only software that has been approved by the FCC or a TCB can be loaded into a transmitter. The software must not allow the user to operate the transmitter with frequencies, output power, modulation types or other parameters outside of those that were approved. Manufacturers may use authentication codes or any other means to meet these requirements, and must describe the methods in their application for equipment authorization.

Any changes to the software that alter the operation of the radio from what was granted under the original application will be done under a Class III Change. Under the proposed new rules to include the SDR, the FCC defines a new Class of modifications. A Class III permissive change will include any modification to the software of a software-defined radio transmitter that will affect the frequency, modulation type, output power or maximum field strength. The Class III permissive changes may only be made by the original grantee.

Conclusion
The possibilities for the Software-Defined Radio could be endless. Think of a PCS phone that also could operate as a 2.4 Ghz wireless LAN device or in the cellular band or even as a two-way pager. Other possibilities include being able to use your PCS phone overseas without having to buy a dual mode phone or a separate GSM phone. Hopefully the comments from industry will support this change to the rules, allowing this new technology to be placed on the market and usher in this latest generation of radios.

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