As LTE goes Gigabit, how to build today’s networks

[Note: This item comes from friend David Burstein <>. DLH]

For the list, if interesting

I published the below summary of the latest in wireless tech as a Version 0.1 with a Creative Commons License because I still have a lot to learn and this is hard stuff. I think this is useful, especially because it goes beyond the GiG LTE, Massive MIMO, and mmWave that are drawing headlines. ​Eightfold way to Wireless Age of Abundance. I’ve also written lately
Sprint, T-Mobile Fighting to be First to Gig LTE in U.S.

John Saw of Sprint will “push 1 Gbps speed boundaries very soon.” Later, he specifically said, “in 2017.” Neville Ray of T-Mobile replied, “T-Mobile will absolutely be first to Gigabit speeds!

​ They are using the techniques I describe in For non-engineers. How LTE gets to the gigabit: 4×4 MIMO, 4 Band Carrier Aggregation, 256 QAM. A gigabit, shared across the cell site, is the goal of the new Qualcomm 835 chip, about to ship.

​Dave Burstein​

​​Eightfold way to Wireless Age of Abundance Version 0.1
Eightfold way 18010,000 engineers are producing remarkable advances in wireless. As 2017 begins, AT&T, BT, DT, and a dozen other telcos are racing to Gig LTE. Thousands of Massive MIMO cells are deploying at Softbank Japan and China Mobile. 10X to 25X are possible many places in 2017 & 2018. 5G mmWave in 2017 will run at 5 gig and I’ve seen demos at 20 gig. Verizon, KT, and AT&T have begun fixed mmWave trials to move to commercial service starting in 2018. Those are the headline moves, but I’m learning from folks like Telus CTO Ibrahim Gedeon to look at another half-dozen tools soon coming out of the labs. To get the conversation moving, I’m publishing this vision 0.1, really just a draft.

We’re at an inflection point on the path to the 50X to 100X wireless capacity growth. World class engineers – Paulraj, Samueli, Cerf, Goldsmith, Rappaport – explained at Marconi events in 2014 this would happen. Nobody but engineers believed them. Real networks are now proving them right.

Gig LTE, MIMO and millimeter waves just part of what’s coming.

Gedeon got me thinking when he said SON/HetNet improvements for his small cells may be more important than for his customers than “5G.” We were at Huawei’s MBBF in Tokyo, listening to speeches extolling the latest fads. As I walked the exhibit floor, I could see 20 gig mmWave and Gig LTE running flawlessly and Massive MIMO as deploying at Softbank and China Mobile. But Huawei’s $10B annual research budget is deep; they had examples of many other tools network builders will be using.

I’m calling this the Eightfold way to emphasize the many choices. Jennie and I are working on a related video. Here’s some of what I’m researching, best known first. Gig LTE isn’t included as a separate category because its prime components, 4×4 MIMO and 3-4 channel carrier aggregation, are simply early versions M-MIMO and CA, below. Ideas welcome.

Massive MIMO went commercial in 2016 when Softbank opened 100 cells in Japan. Capacity improved 9 times in Shinjuku and 6.7 times on average in company measurements. Presumably, they chose the more promising locations first; China Mobile is reporting 3 times for now. Speeds will vary by terrain, and are likely to go up further as the software and antennas are refined.

Millimeter wave high frequency works and almost surely will be important. As I write early in 2017, AT&T and Verizon intend to do fixed mmWave to hundreds of homes in 2017, probably. Verizon CEO Lowell McAdam is a true believer on fixed mmWave as a competitor to fiber and forecasts wide deployment very early. Korea Telekom and SK Telecom will showcase 5G at the Korean Olympics in 2018. They almost certainly will include mobile mmWave, although not necessarily in volume. Qualcomm and Intel will have mobile phones chips in 2018.

Almost everyone expects mobile mmWave to be rare until after 2020 when the standard is set. Seizo Onoe, NTT CTO and often a pioneer, doesn’t expect any volume before 2022-2023. Ted Rappaport disagrees, telling me Millimeter wave “Will come sooner and reach longer distances.” We all hope he is right. mmWave costs and ideal technology are unclear until far more reaches the field.

HetNets and SON for interference reduction between cells. Telus, like Verizon, is running fiber deep into neighborhoods. They have a large fiber home network, are working on, and adding LTE small cells. Dense cells interfere with each other, a well-known problem that severely limits efficiency. There’s massive literature on how to approach this problem and much practical engineering, but comprehensive solutions are just starting to appear. Gedeon is working with Huawei and likes the early results. (HetNets – heterogeneous networks – received that name because the original commercial offerings focused on problems like small & femtocells interacting with cell towers. SON – Self-organizing networks – try to solve the impracticality of human analysis to organize many small cells, much less adapt to the constant changes.) This was one of the most talked about technologies a few years ago and is finally starting to make a difference. Telus & Huawei have a paper.

Sharing spectrum Wi-Fi proves that shared spectrum can deliver more capacity. The U.S. is moving ahead on sharing 3.5 GHz frequencies now mostly used by the military; the navy doesn’t use the spectrum in the middle of the country. December 2016, a major British government report recommended sharing licensed spectrum as well. Telcos led by Verizon, working with Qualcomm, have demonstrated LTE can share spectrum with Wi-Fi in LAA. (The LAA specs do not protect Wi-Fi adequately so are very controversial.) There are numerous techniques that need to be perfected. The U.S. 3.5 GHz incorporates an online registry. Wi-Fi has dynamic mechanisms for each unit to check what others are doing, hunting for a chance to transmit without interference. LAA works with a control channel in licensed spectrum. The academics have a slew of proposals that need to be tried in the real world.

Sharing the spectrum in the 3.5 GHz band is now beginning after four years of work led by John Leibowitz at the FCC and Larry Strickling of NTIA. The White House PCAST Report has a strong recommendation to share more spectrum. While the telcos generally try to block programs that release spectrum, they went along with this one because they expected to get most of it. Their massive lobbying team will scream holy hell if they have to share the spectrum they have but it’s the right thing to do. If Verizon and Sprint had an agreement to use the other’s spectrum that’s currently occupied, each would see an increase in capcity of 20-30% (my estimate, but really a guess.) They have different customer bases in different regions and often different demand peaks. Often, one will have capacity while the other is close to congestion.

Contrary to general belief, a strong majority of even low band spectrum is not in use even at peaks in a busy city like Chicago. (See data by Professor Dennis Roberson.) Putting more to use through sharing would be very powerful.

Full Duplex uses the same spectrum for both upstream and down, yielding a likely throughput increase of 50% or more. Moore’s Law has brought the cost of processing power down enough for the many calculations needed for interference cancellation. It’s being actively tested by companies like Telecom Italia. I believe Kumu Networks will have product on the market in 2017 for certain uses. Expanding that to mobile four channel and 4×4 MIMO isn’t ready yet.

Reducing the capacity demands of the billions of IoT devices. NB-IoT, starting to deploy in LTE networks, allows connection while using less spectrum. Most IoT devices send only limited data, often for brief periods. NB-IoT is a partial solution, with advances possible beyond that.

Better carrier aggregation to put more spectrum to use. Both Verizon and AT&T recently told Wall Street they have 40 MHz of unused spectrum each, enough to double their current capacity. That would require aggregating four or five bands. 2016 brought three band aggregation, with more needed. Most countries have hundreds of megahertz unused around 3.5 GHz, just now being made available. One newly shared 3.5 GHz band in the U.S. could support four Verizon-sized networks. 3.5 GHz spectrum is more efficient than 4.9 GHz, the target of LAA. As spectrum becomes available at 600 MHz and around 6 GHz, efficient ways to go beyond 5 bands will be needed.

Several techniques I’m combining into item eight because I like the title Eightfold way. Murray Gell-Mann’s Eightfold Way unified sub-atomic physics. He took the name from the Buddhists. The Noble Eightfold path is Right Understanding, Right Intent, Right Speech, Right Action, Right Livelihood, Right Effort, Right Mindfulness and Right Concentration. They include better antennas in phones and base stations; power tweaks such as HPUE; analog improvements that allow going beyond 256 QAM; and more.

There will be generations of technology still to come. They will be called “6G,” which will again be a near-meaningless marketing term. “Cell free” systems will reconfigure the physical network on the fly, optimizing for the actual demand at that moment. Huawei’s CloudAir looks like an actual instance of the long sought software defined radio.TCP/IP is not efficient for mobile and replacements have been proposed. Local radio coordination is being pioneered in Wi-Fi and automotive DSRC. Moore’s Law isn’t dead yet, and faster chips open new possibilities.


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