The Potential Value of Decentralized Trunking as Regulatory Precedent for the Introduction of Dynamic Spectrum Access Technology

One important way of obtaining the necessary regulatory permissions for dynamic spectrum access ("DSA") technologies from domestic government agencies and the International Spectrum Management Community is to demonstrate that there are policy and legal precedents for their introduction. A recent precedent centers on efforts in the U.S. to allow Unlicensed National Information Infrastructure devices to operate in the 5.25- 5.35 GHz and 5.47-5.725 GHz bands without causing interference to existing radio frequency operations (government radars) through the use of dynamic frequency selection ("DFS") and Transmit Power Control ("TPC"). Another, slightly older precedent is the U.S. Federal Communications Commission's policies and rules that permit the utilization of "decentralized trunking" in the VHF and UHF private land mobile radio ("PLMR") service bands. Under these rules, adequate "monitoring" (a.k.a., "listen-before-talk" or "LBT") is required in order to share spectrum under a decentralized trunking approach. This paper analyzes the potential value of this older precedent in advocating for broader regulatory acquiescence and near-term deployment of DSA technology. Arguably, in the U.S., a DSA radio system using technology to achieve decentralized trunking capabilities could be introduced onto shared channels in the PLMR bands without any major changes in the Commission's existing rules or policies. Using LBT functionality with advanced sensing algorithms, together with DFS and TPC capabilities, could promote shared access via decentralized trunking in the VHF PLMR band, where licensees often employ non-standard channel pairs or un-paired (simplex) channels, and the UHF PLMR band, which is often characterized as overcrowded but underutilized. However, some economic and regulatory barriers to the development of robust secondary market access to these spectrum bands may hinder the full potential of DSA technologies in these bands.