Steven J. Crowley, P.E.
The interaction of radio waves in free space has never been much of a concern to this wireless engineer. Propagation models do a pretty good job of estimating received signal strength. Receivers are designed to select desired signals and reject undesired ones, within limits. “Interference takes place in the receiver,” I’ve heard more than once. Yes, there are a lot of signals in the air at once, but I’m more interested in the end result.
Once a year the Telecommunications Industry Association (TIA) holds a membership meeting that looks forward to tomorrow’s networks. Last week I moderated a spectrum panel at the “Network of the Future” conference in Dallas, and stayed for the rest of the wireless track (parallel tracks I didn’t attend related to software-defined networking and big data).
Sinclair Broadcast Group, the country’s largest TV group owner, is also a communications technology proponent. With partner Coherent Logix, a developer of software defined radio (SDR) technology, it’s behind one of several systems up for consideration in the Advanced Television Systems Committee (ATSC) for next-generation television in the U.S.. The new standard will be known as ATSC 3.0.
Update March 27, 2014: A few days after this application was filed, it was apparently withdrawn. The links below to the application form and exhibits no longer work, and I see no trace of the application. The essential application information is still in my original post below. I don’t know why the application was withdrawn. The application was apparently prepared by an engineer based at a Google office in Seattle. To me, it seemed incomplete in some aspects. Usually, such applications are prepared by Google’s attorneys; I speculate this caught the attorneys unaware, they didn’t like it, and they pulled the application for their review. Look for it to be recast and filed again.
Google yesterday filed an application with the FCC for an experimental radio license that apparently involves connected-car technology. No specific location for the experiment is indicated; it’s to take place in the “Seattle and San Francisco areas.” A total of 10,000 transmitting units are involved, with 5,000 being custom experimental devices manufactured by Google, and 5,000 consisting of off-the-shelf CSR CSR8311 Bluetooth ICs, which the manufacturer describes as the “first Wideband Speech IC qualified for the automotive market” and “the first Bluetooth low energy IC ready for automotive use.” I speculate the IC will be used in combination with the Google device, for a total of 5,000 experimental radio systems. There’s only one frequency band (2402-2480 MHz) and one emission designator (1M00F1D) specified in the application; these parameters are consistent with Bluetooth, so the custom Google transmitter would seem to have Bluetooth-like emissions.
Supporting exhibits are usually filed with experimental applications. Google has done so, but designated them “not available,” presumably invoking confidentiality provisions of the FCC’s Rules. It’s standard FCC practice to have the applicant make the confidentiality request visible to the public. Google has not. Furthermore, from the exhibit descriptions, it appears Google has not even filed a confidentiality request. I expect the FCC to ask Google to do so and to make it public. If there are updates to this application, I’ll update this post.
On January 22 Google filed an experimental radio application at the FCC. The company has requested confidential treatment of the application, so significant portions aren’t publicly available.
As part of the filing, Google filed a request for confidentiality, which is public. It contains a few technical details. Two separate transmitter types are identified, both operating at low power in the range 76-77 GHz, and using FM and BPSK modulation. The 76-77 GHz band is used for short-range vehicular radar and, knowing Google’s interest in vehicles, it’s reasonable to assume that is what the experiment involves.
A study commissioned by UK telecom regulator Ofcom examines tradeoffs among many mobile indoor-coverage technologies, and suggests the agency help consumers learn more about them.
LTE Direct, now being standardized in 3GPP as part of Release 12, is a platform for directly discovering and connecting nearby peers. Qualcomm and Samsung sponsored an LTE Direct workshop earlier this year in which several major operators participated. A few days ago Qualcomm made available a white paper, prepared jointly by some of the participants, that summarizes key points from the workshop.
The FCC has adopted a Report and Order that raises the power limit for outdoor links operating in the 57-64 GHz band on an unlicensed basis. The average equivalent isotropically radiated power (EIRP) limit is raised from 40 dBm (10 watts) to a maximum of 82 dBm (158,489 watts) depending on how high the antenna gain is. The peak power limit is 3 dB higher. The new power limit is comparable to others the FCC has in the fixed microwave services.This increase is expected to enable higher-capacity outdoor links extending to about one mile. Connection of buildings on a campus is one application, as is connections of small cells within a 4G macrocell. In addition to higher power limits, the FCC also changed the way 60 GHz emissions are specified for consistency with other rules, and it eliminated the need for certain 60 GHz devices to transmit an identifier.
The FCC has issued a Report and Order amending its rules to allow foreign object debris (FOD) detection radar equipment at airports. FOD covers a variety of debris that can collect on airport surfaces, possibly damaging aircraft. These systems will be permitted to operate in the 78-81 GHz band on a licensed basis. The FCC says it is considering other uses of the band in other proceedings. Mitchell Lazarus at the CommLawBlog provides a summary of this proceeding’s history and main issues.
LightSquared has asked the FCC for extension of experimental authority to conducts tests in support of a proposed frequency swap, saying it needs more time.
In March, I wrote about the original request for this experiment. That authority expires July 20. On the new application form, LightSquared says it expects experimental operation to be completed by September 30, 2013.
The form is accompanied by a supporting exhibit, similar to the first, but with LightSquared taking the opportunity to “clarify” a few points:
- When LightSquared says “continental United States,” it includes Alaska
- LightSquared emphasizes that its cooperation with federal agencies extends to NOAA
- Having had some coordination discussions with federal agencies, LightSquared says it won’t conduct experimental operation at certain specified locations, but will at others if they are acceptable to the FCC, NTIA, and NOAA.
The law firm of Fletcher, Heald & Hildreth has a post that’s unsettling to engineers such as I who don’t expect very different radio technologies on very different frequencies to interfere with one another.
It seems that 700 MHz base station receivers have become so sensitive they’re susceptible to 8th-order harmonic interference from FM broadcast stations. This is the case even though the FM transmitters meet FCC emission requirements. LTE receivers have become better than the FCC’s Rules.
The lawyers make several good arguments in support of the broadcasters. Unfortunately for the FM stations, Section 73.317(a) of the FCC’s Rules, which governs FM emissions, includes this provision: “. . . should harmful interference to other authorized stations occur, the licensee shall correct the problem promptly or cease operation.” We’re not lawyers, but that seems to be an overarching broad requirement that, until now, hasn’t been much of a concern.
These cases of interference are now being handled on an ad hoc basis, with some encouraging cooperation between broadcasters and the mobile industry. As mobile broadband receivers continue to improve and become even more sensitive, however, they will be even more susceptible to interference from FM harmonics. This should be looked at more formally by the FCC, perhaps in an inquiry or in a rulemaking proceeding.
Rearden LLC filed an application for experimental license with the FCC on May 24. That caught my eye as as it’s the same company that created a splash in 2011 with its announcement of Distributed-Input-Distributed-Output (DIDO) wireless technology, said to achieve capacity 1000-times the Shannon Limit with sub-millisecond latency. The company issued a white paper authored by company president Steve Perlman and the company’s principal scientist Antonio Forenza, but it didn’t have a lot of details for an engineer. DIDO seemed to be a form of network MIMO, whereby each user is served by all base stations in its vicinity through a complex coordination process. (Various forms of network MIMO will be appearing in successive releases of 3GPP’s LTE Advanced specifications.) Aside from the white paper, there are patents that supported the notion of DIDO as network MIMO.
In the FCC’s incentive spectrum auction proceeding, Information Age Economics (IAE) complains about the reliance of some in the industry (CTIA and Verizon, to name a couple) on a spectrum efficiency metric that simply divides an operator’s nationwide spectrum holdings by the number of subscribers. This results, in one example they give, of Sprint having 3.57 Hz per subscriber and Verizon having 1.05 Hz per subscriber. Some take this as Verizon using spectrum more efficiently, and perhaps being at a disadvantage. As IAE points out, however, spectrum is not partitioned to users this way: cellular infrastructure allows for frequency reuse. If one wants to compare the spectrum efficiency of Sprint and Verizon, don’t look at it nationwide — look at, say, Washington, D.C.
Today the FCC granted Google’s application to conduct a radio experiment in Mountain View, California. When I looked at the application in January, I noted Google withheld some information it felt was confidential, and I took a crack at trying to figure out what was going on based on available information. A couple of days later, the FCC asked Google to provide additional information, and Google responded. Then things sat with no apparent activity for a couple of months.
The experimental license issued today gives Google the authority it sought: use of the 2524-2546 MHz and 2567-2625 MHz bands. In January I noted those bands might be used by Clearwire. In January the FCC asked Google if it had consent from the license holder. Google responded that it “understands that a grant will be conditioned on coordination with affected licensees, and is engaged in discussions to satisfy that obligation.”
Apparently Google hasn’t furnished such consent to the FCC, as the experimental license contains the following “special condition:”
Prior to operation, licensee must successfully coordinate with existing and future Broadband Radio Service/Educational Broadband Service (BRS/EBS) licensees or lessees (as applicable).
So, the FCC is relying on the honor system, which isn’t unusual for experimental authorizations.
Last month I wrote about the Jarvinian Wireless Investment Fund and its application to the FCC to test its proposed terrestrial low-power service (TLPS). TLPS would use both the upper 2.4 GHz unlicensed band and Globalstar’s terrestrial-use spectrum (2473-2495 MHz all in all). That test would take place in Cambridge, Massachusetts.
Jarvinian is back with a second application, similar to the first, but with testing taking place at three locations in Silicon Valley (Sunnyvale and Cupertino, California). The supporting technical exhibit appears essentially the same. Different is the equipment to be used. The Cambridge application specified 50 Linksys WRT54GL access points, 10 Ubiquity UniFi access points, 10 Ubiquity XR2 client cards, and 10 Ubiquity SR-71-12 client cards. The Silicon Valley application specifies 10 TP-LINK TL-WA5110G access points, 20 TP-LINK TL-WR1043ND access points, and 20 Ubiquity SR-71-12 client cards.
This application was received by the FCC on March 6. The Cambridge application was received February 13 and is still pending.