TR Daily Unlicensed Devices Detect DSRC Signals in 5.9 GHz Band
Monday, October 29, 2018

Unlicensed Devices Detect DSRC Signals in 5.9 GHz Band

Prototype unlicensed devices were able to detect 5.9 gigahertz band dedicated short-range communications (DSRC) signals in testing in the FCC’s lab, the agency said in a long-awaited report released today.

The testing was conducted in Phase I of what is scheduled to be three phases of testing, with the last two in the field. The FCC had planned to complete all three phases by January 2017, but the second phases have yet to begin.

“As summarized in the report, we found the prototype devices reliably detected DSRC Signals,” the Office of Engineering and Technology said in a public notice released late today seeking comment on the report. “The report includes the results of the evaluation of the Wi-Fi sharing techniques since one of the proposed band sharing methods would require re-channelization of the DSRC spectrum. In brief, the test results show that the prototype U-NII-4 devices were able to detect a co-channel DSRC signal and implement post detection steps as claimed by the submitters. This Phase I test report was peer reviewed and the information is included in the record. The report was also coordinated with the NTIA and DoT.

“We recognize there have been a number of developments since the three-phase test plan was announced in 2016 — such as the introduction of new technologies for autonomous vehicles, the evolution of the Wi-Fi standards, the development of cellular vehicle-to-everything (C-V2X) technology, and the limited deployment of DSRC in discrete circumstances. We invite comment on how any of these factors or others should impact our evaluation of the test results, our three-phase test plan, or our pending proceeding on unlicensed use in the 5.9 GHz band,” OET added.

“Five parties — Cisco, Qualcomm, KEA Tech, Broadcom, and CAV technologies — submitted a total of nine devices in response to the U-NII-4 Public Notice for Phase I testing,” OET said. “In addition, Qualcomm, Cisco, KEA, Broadcom, and DoT submitted DSRC devices to use for the testing program. The prototypes were designed to prevent interference by detecting DSRC signals and then either vacating the spectrum entirely or sharing a portion of the spectrum with non-safety related communications using techniques similar to Wi-Fi sharing. We performed approximately 1,450 individual tests (more than one million data points collected), the results of which are summarized in the report.”

The two sharing proposals analyzed are known as detect and vacate and re-channelization.

Comments on the report are due Nov. 28 and replies Dec. 13 in ET docket 13-49.

“Test results show that the prototype U-NII-4 devices were able to detect a co-channel DSRC signal and implement post detection steps as claimed by the submitters. All of the prototype U-NII-4 devices were found to be capable of detecting a DSRC signal at a level of approximately -95 dBm. The receiver sensitivity level of the DSRC devices tested fell in the range of -95 dBm to -93 dBm. In other words, the detection threshold of the U-NII-4 devices was similar to that of the DSRC devices detecting its own signal,” according to the report.

“Data suggests that the two proposed interference mitigation methods, Detect-and-Vacate and Re-channelization proposals, offer a means for U-NII-4 devices to coexist with DSRC devices,” the report added. “For example, assuming a DSRC transmission at the maximum permissible EIRP level of 33 dBm along a 300-meter unobstructed line-of-sight propagation path, the theoretical received power level at a U-NII-4 device will be approximately -65 dBm. This calculation suggests that all of the prototype U-NII-4 devices tested would be capable of detecting this DSRC signal at a distance of 300 meters with significant margin (~30 dB) to account for additional signal attenuation associated with multipath and/or signal obstructions. The two proposals make different assumptions about the characteristics associated with: (1) the environment in which DSRC and U-NII-4 devices operate; (2) detection mechanisms of the U-NII-4 devices to sense the presence of a DSRC transmission; and (3) steps each U-NII-4 device will take upon detection of a DSRC signal (post detection process).”

Commissioner Mike O’Rielly and Jessica Rosenworcel, who have been pressing the FCC to consider uses of the 5.9 GHz band than DSRC, released statements on the results released today.

“While I appreciate release of the 5.9 GHz Phase I testing data, the results are not all that surprising given the simple questions posed,” Mr. O’Rielly said. “The reality is that the entire debate has gravitated away from the type of sharing regime envisioned in the testing. Instead, the Commission should move past this and initiate a rulemaking to reallocate at least 45 megahertz of the band, which is completely unused today for automobile safety.”

“Nearly two years after the deadline for completing a three-phase test plan to determine whether auto safety and Wi-Fi can share the 5.9 GHz band, this agency is releasing the results of its lab testing. These results are long overdue. But we need to do more than just make our work public. We need to start a rulemaking to take a fresh look at this band and its real possibilities,” Ms. Rosenworcel said.

WifiForward said, “The results of these tests prove that Wi-Fi can successfully operate in the 5.9 GHz band without causing harmful interference. But the facts on the ground have changed and further testing of co-channel operation with DSRC is no longer relevant. So while some parties will seek years of additional testing to try to stall FCC action, it is now time for the FCC to issue a new further notice that brings Americans Gigabit broadband and asks whether it should continue to support the failed DSRC experiment.”- Paul Kirby, [email protected]


Back to Top

Interested in submitting an article?

Submit your information to us today!

Learn More