Steven J. Crowley, P.E.
Archive for the ‘LTE’ Category
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.
Google filed an application at the FCC last week seeking permission to conduct testing of an experimental radio system. Portions of the application and accompanying exhibits have been designated confidential and are thus not available to the public. Even the request for confidential treatment has been redacted. Let’s try to infer what’s happening from the information available.
In the first of a series of webinars, Qualcomm today began reporting on the results of its “1000x Data Challenge,” an initiative to meet what it sees as the need, someday, to increase mobile capacity 1000-times. The webinar, conducted by Rasmus Hellberg, Qualcomm’s Senior Director of Technical Marketing, was an overview. He discussed spectrum, small cells, and other techniques to increase capacity. More-detailed webinars on each of these are forthcoming: spectrum initiatives on September 18, small cells and heterogeneous networks on October 18, and more efficient networks, applications, and devices on November 14. Today’s webinar should be posted tomorrow, and a white paper should appear in about a week.
4G Americas, a wireless industry trade association representing the 3GPP family of technologies, has released a report looking at broadband devices and applications, and their impact on HSPA and LTE networks. There’s quite a bit of interesting information; here I highlight the discussion on mobile broadband offload and mobile data growth.
In a recent blog post, CTIA compares some measures of the U.S. wireless industry to those in nine other countries. The purpose is two-fold; to show the U.S. is a leader in number of subscribers, lowest cost per voice minute, and spectrum efficiency, and to argue the need for getting more mobile broadband spectrum in the “pipeline.” These goals are somewhat at odds, and the spectrum-efficiency argument I don’t get, as I’ll explain, but within the constraints of a blog post I think CTIA makes the case that the U.S. is a clear leader in some areas, and that the prospects for more mobile spectrum in the U.S. are fuzzier than they should be today.
The following is my response to a query on LTE versus wired, and the user experience. It capsulizes my current thinking, which evolves.
To your point, I don’t see LTE being competitive with wired in terms of speed or reliability today or in the future. You take the hit there for the convenience of mobile or portable operation. There’s a notion that if we just add enough base stations and repurpose enough spectrum to LTE, we can replicate the home wired experience in the mobile environment, but I don’t think that’s practical. The throughput from an LTE sector is divided among all users in the sector. If everyone wants to watch the Super Bowl at once on LTE, forget it (unless the LTE broadcasting standard is implemented, which let’s everyone watch the same channel like today’s TV (cough)). On FIOS or cable, the Super Bowl is no problem.
A couple of days ago the Mobile Future coalition posted a short video on YouTube advocating the allocation of more spectrum for mobile broadband. As evidence of the need, it says that, compared to feature phones, smartphones use 24 times the spectrum and tablets 120 times the spectrum.
Recent contributions to the mobile broadband spectrum debate are reports from NAB and CTIA. I envisioned a “dueling reports” piece, but they mostly complement each other. Below I walk through the main points, adding some of my own views.
One of AT&T’s non-redacted arguments in support of its acquisition of T-Mobile USA is that data usage on AT&T’s network is projected to “skyrocket by a factor of eight to ten” over the next five years due in part to streaming HD video. AT&T’s vision is that T-Mobile’s resources would be used to relieve resulting capacity restraints.
Enabling an HD streaming service will be challenging because of the relatively-high and somewhat-constant bit rates required in a fading radio environment. Wondering how practical this is, I recalled a paper Motorola prepared last year reporting some of its simulation results on mobile broadband streaming video.
The FCC relies on Cisco’s forecast of mobile-broadband data demand as a basis for spectrum policy. Called the Visual Networking Index, it comes up many times in the National Broadband Plan, in other documents, and in speeches.
The debate won’t end but the volume is dropping on the what-is-4G controversy. Previously, I’ve written about the ITU’s characterization of 4G as only applying to the two radio technologies it has designated as IMT-Advanced: LTE-Advanced and WirelessMAN-Advanced (the latest version of WiMAX).