The wireless broadband industry is fighting to prevent sharing conditions in unlicensed spectrum, but utilities, railroads and others insist such safeguards are necessary to prevent interference in existing and future unlicensed frequencies.
The Federal Communications Commission rejected Cellnet Technology Inc.’s request that a spectrum etiquette-any combination of steps and protocols a device must follow before accessing spectrum-be imposed in the 915 MHz band, the agency conceded the approach may offer benefits even though the existing unlicensed regulatory scheme has proved largely successful. The difference now, according to Cellnet and others, is the growing emergence of wireless broadband services in the 915 MHz band.
“However, we note Cellnet’s observations regarding emerging products and its concerns that digitally modulated 915 MHz devices operating under [current regulations] have no duty cycle limitation and may therefore transmit continuously at the maximum power permitted by the rules,” the FCC stated in June when it denied Cellnet’s petition for reconsideration and concurrently solicited public comment on using a spectrum etiquette in that band as well as the 2.4 GHz and 5.8 GHz bands. “Additionally, we observed that there is no limitation on the maximum transmit bandwidth for digitally modulated 915 MHz devices other than the requirement to maintain the fundamental emissions within the authorized band of operation. Thus, there appears to be a potential for a digitally modulated device or a group of digitally modulated devices to essentially occupy the entire 915 MHz band, leaving little or no opportunity for other devices to gain access to the spectrum.”
The FCC approved use of a spectrum etiquette developed by industry for unlicensed PCS devices in the 1920-1930 MHz band. In addition, the high-tech industry and the Department of Defense agreed to shared government-commercial use of the 5 GHz band so long as new Wi-Fi devices are capable of identifying and avoiding transmissions on channels occupied by military radar. Debate over whether Wi-Fi devices can be introduced in unoccupied TV spectrum-white spaces-turns on whether wireless broadband products can be engineered to avoid interference to broadcasters.
Cellnet and Hunt Technologies L.L.C., which provide real-time wireless automated meter-reading for utilities, said spectrum sharing conditions are needed to prevent disruption of the balance whereby multiple unlicensed devices have been able to co-exist without any one kind of device gaining an unfair share of unlicensed bands. The two companies, GE MDS L.L.C., Freewave Technologies Inc. and Dataradio Inc. as well as utility companies and railroads with internal unlicensed operations in the 915 MHz band fear expanded Wi-Fi usage will do just that.
“An appropriate spectrum etiquette can provide an environment in which numerous users may operate in the same geographic area simultaneously, using only the minimum power and bandwidth they need for the particular application,” Cellnet and Hunt told the FCC. “Such an approach protects current users in the band and ensures that the band will continue to be available to future innovation.”
The Software Defined Radio Forum said it generally supports the concept of a spectrum etiquette so long as federal regulators avoid narrowly proscribed spectrum-sharing requirements, but it declined to take a position on making such a policy applicable to the frequency bands at the center of the current controversy.
A better way
Wireless broadband players, particularly manufacturers that sell Wi-Fi gear, and others reply innovation will be one of the casualties of a spectrum etiquette in unlicensed frequencies. They argue there is a better way forward.
The Wireless Communications Association International said it “continues to support voluntary frequency coordination and other best practices among unlicensed users, approaches that do not undermine the flexibility and technological innovation that has been critical to the success of unlicensed services over the past decade.” Indeed, the trade group noted, the FCC previously refused to mandate a spectrum etiquette in unlicensed spectrum.
“We believe a good part of this spectacular success of Wi-Fi devices can be attributed to the fact that the development of these devices was encouraged by having unlicensed spectrum with minimum regulatory restrictions,” stated the Wi-Fi Alliance. “It is our belief that, in the interest of both the consumer and the industry, that we maintain a regulatory environment that is conducive to the creation of new wireless technologies.”
Cisco Systems Inc., whose Lynksis unit is a global Wi-Fi equipment giant, said extending a spectrum etiquette to the 2.4 GHz and 5.8 GHz bands would economically degrade them.
The Telecommunications Industry Association, representing telecom vendors, the Consumer Electronics Association and the IEEE wireless networking standards committee also oppose the imposition of a spectrum etiquette in unlicensed airwaves, warning that doing so “will unnecessarily constrain innovation.”
