The Regulation of Software-Defined and Cognitive Radios

David A. Case

Obtaining compliance for spectrum use and frequency band technologies is important, as they hold promise for spectrum sharing among various services.

Two technologies are often noted in discussions about spectrum use and frequency bands: cognitive radios and software-defined radios. Because these technologies hold promise for spectrum sharing among various services, the issue of obtaining compliance for these systems is important.

FCC adopted the original regulations for software-defined radios in 2001 and recently updated them in 2004, before any software-defined radios were approved. The 2004 updated regulations also mentioned cognitive radios. To understand the regulatory process, it is essential to define cognitive and software-defined radios.

A cognitive radio is also referred to as a smart radio. It can adapt to its environment to avoid interfering with other services operating in the same band. One cognitive-radio technique is dynamic frequency selection (DFS). Basically, with DFS functionality, a cognitive radio checks on the availability of a channel before using it. During quiet periods, the radio determines whether a radar signal is present. It also works to ensure that the channels are evenly loaded to reduce interference.

A software-defined radio is essentially a radio controlled by software. With modification to the software alone, it can be programmed to operate on various bands. An example would be an 802.11a/b/g radio that can be upgraded to include the new 5.4 GHz band or the 4.9 GHz band. In addition, under the current regulations, an end-user can update the radio to the new bands without having to ship the radio back to the factory.

FCC Regulations

FCC rules state that the software for a radio, or a description of the software, must be submitted along with an application for certification. The rules also require that the manufacturer provide information to FCC on the security measures being used to ensure that only the correct software can be uploaded.

This information must be filed as confidential to keep it out of the public domain. The manufacturer cannot provide information to end-users that would enable them to modify the software themselves.

Under Section 2.1043, a Class III change covers the incorporation of new software to add bands or features. A Class III change can be done only when no hardware changes are incorporated; any hardware changes fall into the Class II category for FCC upgrades.

It is important to note that a software-defined radio can go through only one Class II change, including the addition of antennas. Although a Class II change can be used to upgrade radio software to include new bands as well, the major difference is that under Class III, software upgrades can be done by the end-user. No further updates to a software-defined radio are allowed after the Class II change is done. Additional Class II changes can be done from that point on as part of the approval process only, but no further Class III changes are allowed, which limits upgrades in the field.

Although the rules in Part 2 do not specifically address cognitive radios, features such as DFS may be incorporated as part of the FCC product-specific rules, as was done for the requirement for the updated U-NII band under Part 15.407 in 2003. This is partly because some of the requirements are band specific.¹

Approval Process

For software-defined radios, there are no specific test requirements other than addressing the questions posed by FCC. FCC concerns include software security, limiting which versions can be uploaded to the system, and controlling software uploads.

Because very few software-defined radios have been approved, FCC has yet to iron out the pertinent review requirements. FCC also has not fully worked out the issues related to full module approval of software-defined radios. At this time, a product must be submitted to an FCC lab for approval, because telecommunication certification bodies (TCBs) may not review and issue FCC grants for software-defined radio products.

The same issue, in part, applies to cognitive radios, which have features that may require testing (such as required for verification of DFS). FCC has adopted a procedure developed by the U.S. International Telecommunication Advisory Committee Radiocommunication Sector (ITAC-R) working group to test the capabilities of DFS. Because of that, FCC must review products that are required to have DFS detection capabilities, like the U-NII radios that operate in the 5250–5350 MHz and 5470–5725 MHz bands.²

Most nations have adopted the requirements for DFS. So, by default, they have also adopted at least one cognitive-radio technique. As more techniques are developed, it is very likely that there will be some test requirements for these radios, specifically required for sharing the band.

During recent TCB training courses, FCC engineers have started to address in detail the issue of approving these types of products. As FCC establishes its policies and is satisfied that the industry understands the technical requirements, it will allow the TCBs to start reviewing software-defined and cognitive radios.

Depending on the complexity of the reviews, it will probably be a year or so before a TCB can review a software-defined radio or a cognitive radio with DFS features.

Conclusion

Discussions of software-defined radio and cognitive radio are being raised in a number of countries. The U.S. work groups addressing mobile services requirements in the Inter-American Telecommunication Commission (CITEL) and International Telecommunications Union Radiocommunication Sector (ITU-R) arenas have submitted papers on the respective topics. Japan’s regulatory authorities have started a discussion on the issue of software-defined radio and have even asked for some industry input. Industry Canada has talked with members of the industry on the subject as well.

Whether countries adopt special regulations, as FCC has done, for software-defined and cognitive radio, or whether they just accept software-defined radio as part of the evolution of existing radio products, remains to be seen.

References

1. Code of Federal Regulations, 47 Part 0–19 (2005).
2. Revision of Parts 2 and 15 of the Commission’s Rules to Permit Unlicensed National Information Infrastructure (U-NII) Devices in the 5 GHz Band (ET Docket No. 03-122).

David A. Case, NCE, NCT, is senior regulatory engineer, corporate compliance EMC standards and operations, for Cisco Systems Inc. (Richfield, OH). He can be reached at davecase@cisco.com.