Sophisticated Wireless Interference Analysis: A Case Study for Spectrum Sharing Policy
University of Colorado at Boulder
Kenneth R. Baker
University of Colorado at Boulder - Interdisciplinary Telecommunications Program
March 19, 2014
Access to sufficient wireless spectrum is important for sustaining the growth of wireless broadband and enabling next-generation wireless technology. However, freeing additional spectrum for wireless broadband is often a difficult and contentious process. As policymakers look to new mechanisms of sharing spectrum to meet growing wireless needs, the specific terms of sharing are central to the utility of the wireless resource. For this reason, nuanced understanding of interference risks - which drive spectrum sharing policies - is needed to maximize the productive use of the spectrum.
Commonly proffered interference analyses are static and simplified, while the real world of wireless is dynamic and ever-changing. Improving the technical information on which policymakers rely is therefore critical to the success of spectrum sharing as a policy strategy.
In this paper, we demonstrate how sophisticated simulation of wireless coexistence can yield important insights, in contrast to simplified models normally offered by advocates. We focus on a portion of the 5 GHz Wi-Fi band, which is crucial for enabling capacity and throughput, and is the global home to the next-generation mass market Wi-Fi standard known as 802.11ac.
In this analytic context, outdated FCC rules designed to protect mobile satellite service (MSS) from harmful interference render Wi-Fi access to 100 megahertz of the band, known as UNII-1, unsuitable for wide-scale deployment. Today, only one MSS company, Globalstar, occupies this entire 100 megahertz, and a far lower level of MSS utilization exists than what the FCC assumed when establishing rules many years ago. Nonetheless, Globalstar has repeatedly argued that updating UNII-1 technical rules to allow for outdoor use and higher power levels would cause harmful interference to its satellite phone system. Our paper develops a sophisticated coexistence simulation, which shows that satellite phone users are extremely unlikely to experience any service diminution (harmful interference) as a result of expanded Wi-Fi access to UNII-1.
This analysis was submitted to the FCC in January 2014, and served as the primary basis for action to expand Wi-Fi access to UNII-1 in March. Our goal at TPRC is to provide greater exposure to methods of sophisticated interference analyses and discuss how to leverage this work to the benefit of spectrum sharing efforts more broadly.
Keywords: spectrum, wireless, FCC, TPRC, interference, Wi-Fi, Globalstar, 5 GHzworking papers series
Date posted: March 21, 2014
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