Currently viewing the tag: "MIMO"


The future billboard Working on many things at the same time, the tunnel vision sets in, so every once in a while, I try to take a I step back and reflect on where we are in LTE land.

What I see is a early market that has yet to find it’s purpose in life. Yeah yeah, consumers are buying devices like Samsung Galaxy III/IV and Apple iPhones that are LTE enabled at a rapid clip in the US, but at this point the device is driving the sale not the LTE itself.  

There have been a couple of interesting developments, such as Audi and GM deciding to leverage LTE for in car data links and even going as far as choosing to use VoLTE for voice. That’s a major step towards finding the killer app for LTE.AudiLTE_connect

However, those developments are in progress and have not actually resulted in any traffic yet, both are expected in 2014.

Consumers are driving traffic today. Looking through some public data, like Root Metrics reports on average data speeds, I am reminded by how inefficient the networks are.

Verizon vs AT&T LTE

Here are some results from that more or less concur the performance observed by Root Metrics.
iPhone 5 Verizon 4G LTE Speed Test Results
  • 8.52 Mbps download, 13.87 Mbps upload, 39 ms ping
  • 7.47 Mbps download, 13.70 Mbps upload, 38 ms ping
  • 10.21 Mbps download, 13.81 Mbps upload, 38 ms ping

iPhone 5 on AT&T 4G LTE Speed Test Results

  • 9.32 Mbps download, 13.69 Mbps upload, 47 ms ping
  • 9.11 Mbps download, 13.88 Mbps upload, 47 ms ping
  • 9.69 Mbps download, 16.20 Mbps upload, 48 ms ping
  • 8.96 Mbps download, 15.83 Mbps upload, 40 ms ping
iPhone 5 over Wi-Fi (Comcast Blast 50 Mbps) Speed Test Results
  • 8.52 Mbps download, 13.87 Mbps upload, 39 ms ping

So it’s hard for me not to notice a couple of elements to this story. Firstly, the mad rush to provide LTE coverage (schedule driven) has been, understandably, at the expense of quality. Here’s the difference:



The peak throughout of a 10MHz 2×2 MIMO with 3 PDCCH symbols, 5% extra overhead and 10% retransmissions channel is 58Mbps, with SIMO at 35MBps. So practical rates in the field are 26.4% of the peak rates with retransmissions. 

It doesn’t take a math genius to realize that 26.4% efficiency is an ROI buster.

So with 50,000 eNBs they currently carry maximally 750GBs over their RAN instead of the 2.9TBs they have already paid for. Simply extrapolating from Cisco’s 2013 VNI report, I get a projected data explosion like this:


Uhhh, isn’t the datapcolypse supposed to need about 800GBps  per operator in 2017? They’re blowing 2x that amount with poor efficiency!


 Making matters worse, ATT and VZW are starting to throw some additional spectrum into the markets. VZW recently announced they are adding 5000 eNBs with AWS spectrum, most likely ‘hotspots’ costing them $3.9B in a one time AWS spectrum buy plus ~$15K/eNB = $75M annually for the additional carrier. ATT has done a series of multibillion dollar deals to add in more 700MHz spectrum. 

ATT has been spending something on the order of $22B to build out and maintain an extensive WiFi network they claim offloads their LTE networks.

Here’s the rub, improving the efficiency to move their average is not as expensive as the offloading or spectrum additions they are doing. One more thing, SON should be doing some of the work for them in a very OPEX friendly manner. 

By cleaning up the network, making it more efficient, there is going to be an induced demand, yes, however having users use your product is not necessarily a bad thing. (I’ve already complained about pricing.)

Let me just say this is crazy. Reducing the network efficiency effectively increases your cost to provide service thus degrading margins. There are tons of levers to pull in the protocol as it is written, with improvements on the horizon. Wake up!

Ladies and gentlemen, the captain has illuminated the fasten seatbelts sign as some turbulence and or distruption is expected in this market.. 

PS: Verizon and ATT, I will make myself available to send you an invoice for, say, $1-2B and will turnkey a project to give you another 800GBps. You can sell your recent investments and return the money to working capital or the investors, or hold them for getting to 1GBps over the air with carrier aggregation in the future… (ok time for me to get back to work…)



I’ll give you one guess why LTE usage in the US is about to explode? Say it together… ready… 

Yep, iPhone 5. If the rumors are true and they follow the precedent of implementing LTE in iPad, then it’s reasonable to assume that iPhone5 is going sport LTE. Now, per our previous discussions, the design choices will guide how many markets a single SKU can support (hopefully they chose wisely) but I am going to be optimistic and think it would support 700, 800, 950, 1800, 1900 and 2100 handily. The next challenge would be global roaming but let’s hash that out later. 

From a utilization perspective, if 50% of the iPhone users are in urbanized areas where LTE is deployed, it’s safe to assume that most of these will be using LTE instead of HSPA+/EVDO. The data model shows that iPhone users are averaging around 1GB per month currently so I would expect that to nearly double quickly given the new capabilities of the LTE channel.

Here is our previous discussion regarding how the iPad parts were chosen BTW.

Next, prediction, at the application level, video chatting may finally get BIG thanks to Apple’s Face Time.   They have done a good job of making video conferencing simple to the point I think people are likely to begin using this en masse’ soon. Ohhh yeah, Contrary to the doom and gloom types, Face Time over LTE will not crash the network. It’s really a small bandwidth service as compared to high definition streaming (gaining popularity) or downloading those huge work PPTs and PDFs. (uh huh) Factor in the general mobility and individual sectors won’t stay loaded…more likely people will go indoors anyway and end up on WiFi…but even when out and about, Face Time WILL NOT CRASH LTE NETWORKS. 

Simple example:

1 sector capacity= 70Mbps (10MHz 2×2 MIMO such as Verizon or ATT) … Toss out 50% for no SON, poor optimization etc… = 36Mbps…

1 FaceTime user bandwidth 175Kbps (peak) x2 (Uplink and downlink) = 350Kbps (numbers from fairly popular mouths range from 392Kbps to 150Kbps)

(See this interesting link on Face Time bandwidth and this one too… )

36Mbps/350Kbs = 102 simultaneous (instantaneous), non throttled, FaceTime users PER SECTOR. A typical site usually has 3 sectors, sometimes 4 or 6…

So if you are a tech blogger and go to a major conference or iUnveiling on campus, and there are more than 102 smokers outside since you are likely to be on WiFi inside, you may find yourself competing for bandwidth but the hogs are more likely to be YouTube streaming (have seen 3Mbps!) and not necessarily just FaceTiming…



 First ran across this story in After reading through the presentations and watching some of the video presentations, I was initially very skeptical. After thinking about it a while, it strikes me that this seems very sound approach even if the exact implementation for a commercial wireless networking infrastructure is different than what Dr. Amir Khandiani has outlined. So going a step further, I’m going to say this is a legitimate candidate for improving LTE and useful as a cornerstone to a 5G wireless. 

Firstly, there is a patent, Methods for spatial multiplexing of wireless two-way channels 7,817,641that covers most of the technology in this discussion.

From his presentation, the summary of the patent is: 

  • New methods for antenna design
  • New RF and base‐band processing brings degradation in SNR due to self‐interference close to zero.
  • Support for asynchronous clients (superimposed networking)
  • Support for MIMO
  • New applications for full‐duplex wireless
  • Hardware, RF and DSP complexities are virtually the same as half‐duplex units.
The technology is a layered approach that first utilizes a symmetrical antenna design including symmetrical pairings of multiple antennae to create nulls relative to TX and RX signals.

2D Symmetrical Antenna

MIMO Symmetrical Antennae

His presentation shows a null of around -15dB on a scope just for antenna nulls. This deserves a checkmark for simplicity.

The second layer of this technology involves active cancellation that is not-syncronized to the TX. He suggests if using a single TX chain, then just go to active interference cancellation. This is done today in multiple over the air technologies, comparable to Qualcomm’s QLIC etc… For multiple TX he suggests using ‘corrective’ beam forming. Beam forming allows a null (think of it as silence) to be created by the TX at the RX. He also suggests you can possibly have a mode where you use existing MIMO antenna and add an ‘auxiliary’ TX just for the purpose of interference nullling.

The last thing he shows in this layered approach is a final synchronous interference cancellation and equalization step in the base band. Performance example he gives is:

Residual Self Interference to Noise Ratio:

  • Antenna structure alone: about 40dB
  • After corrective beam‐forming: about 2dB
  • After base‐band subtraction: about 0.4dB 
So all in all this bit of technology is similar to, or can be thought of as, creating a electromagnetic set of ear muffs for the transmitter so the receiver can listen for distant signals at the same time the transmitter is singing. While there is nothing earth shattering about that as interference cancellation (IC) schemes are being employed on uplink and downlink in LTE today, it is important to note that this approach is a possible solution to the vexing self interference dilemma (If I shout, I can’t hear you at the same time…) with a repeatable, orderly system of layers. 
Lastly he mentions something I’ve been thinking of for some time, and that’s a shift from source based communications (unique signal stream including MIMO) The best way I can summarize it to be simple is, instead of using an isolated signal for transmission, focus on using the interference.

Media = The universe

Overall you can see the pieces of a wireless evolutionary step. I think the layered IC could be added after 3GPP Release 11 to further increase throughput/capacity and security of wireless transmissions. It’s very compelling if we shift to using mixed TDD/FDD modes and now you have the basis of a new range of applications including super low latency communications, extremely high security and so on. Throw in some cognitive radio and we are really capturing the lightning in a bottle. My hat is tipped to Dr. Amir K. Khandani, he found a good way to tie together different pieces of the puzzle to move the needle forward.

Links: E&CE Department, University of Waterloo, Qualcomm,,,

It may be very worthwhile attending his seminar 2PM on June 18th, 2012.

Dr. Amir K. Khandani
Department of Electrical and Computer Engineering, University of Waterloo

Shaping the Future of Wireless: Two-way Connectivity

Monday, June 18, 2012

2:00 pm

DC 1302

Their summary below.. 


Two-way (True Full-duplex) Connectivity: The Future of Wireless

Amir K. Khandani 
[email protected], 519-8851211×35324



Current wireless systems are one-way (similar to walkie-talkies), meaning that disjoint time or frequency segments are used to transmit and to receive. Realization of two-way wireless has challenged the research community for many years, generally believed to be impossible. This talk establishes the theory and presents practical realization of two-way wireless. In contrast to the widely accepted beliefs, it is shown that two-way wireless is not only possible, but is fairly simple, with virtually no degradation in signal-to-noise-ratio. More importantly, it is shown that two-way wireless can do much more than just doubling the rate. The innovation is in the antenna design and multiple levels for cancelling self-interference. Methods are developed to support multiple antenna (MIMO) two-way transmission, and asynchronous two-way links (useful in networking applications). These findings are expected to have a profound impact on wireless transmission, networking and security in the near future, more significant than other major breakthroughs in the last few decades.A number of new applications are introduced, showing that two-way wireless: (1) Facilitates wireless networking. (2) Enhances security through “desirable jamming”. (3) Provides the ground to realize unbreakable security (beyond computational or information theoretical security). (4) Enables a new method of wireless communications (to be introduced in this talk) based on embedding data in the transmission media by changing its RF properties in contrast to embedding data in the transmitted signal, and thereby significantly exceeding some of the known theoretical limits on channel capacity. (5) Enables realizing multi-node distributed & collaborative networking, which has been topics of extensive research in the context of Network Information Theory, but still far from practice. (6) Doubles the point-to-point throughput.

The developed hardware uses off-the-shelf components, antennas have a simple structure, are omnidirectional, do not suffer from bandwidth limitations, have a small size/spacing (comparable to current one-way systems), and the increase in signal processing complexity vs. one-way is virtually zero.

BIO: Amir K. Khandani is a professor of electrical and computer engineering at the University of Waterloo. He received his degrees from Tehran University, Iran, and McGill University, Canada, in 1984 and 1992, respectively. He joined uWaterloo in 1993. He currently holds the RIM-NSERC Industrial Research Chair on Network Information Theory and a Canada Research Chair (Tier I) on Wireless Systems. Prior to the RIM-NSERC Chair, he held an NSERC Industrial Research Chair funded by Nortel. He has supervised more than 40 PhD students, 30 master’s students, 30 post-doctoral fellows and 10 research engineers. His former team members have successful careers in industry and academia across the globe.



Presentation (Powerpoint with sound and PDF) 



Presentation-Powerpoint (Please run in full-screen mode for sound)


Frequently Asked Questions








Real-time Performance (4mins)
Right-click to download

Real-time Performance (4mins) – Lower Quality
Right-click to download

Summary of Presentation (17mins)
NOTE: This summary does not include technical details.
It is a subset (replica) of the complete presentation.
Please see the complete presentation for details.
Right-click to download

Summary of Presentation (17mins) – Lower Quality
NOTE: This summary does not include technical details.
It is a subset (replica) of the complete presentation.
Please see the complete presentation for details.
Right-click to download

Complete Presentation (80mins)
Right-click to download

Complete Presenstation (80mins) – Lower Quality
Right-click to download


 SkyCross has announced their device antenna technology and plans for world domination, which essentially shrinks the total space required for antennae in a device. They put it best…”The SkyCross VersiTune-LTE™ tunable antenna module leverages SkyCross patented ST-iMAT™ technology, enabling a single antenna structure to operate over up to 12 transmit and receive bands while providing optimized MIMO functionality crucial for 4G LTE speeds. This solution enables OEMs to deliver greater device performance, but shrinks the volume required for antennas inside advanced 4G LTE devices up to half that required for conventional antennas.” It’s a good technology. I wonder if it can be combined with the Taoglas efficiency? Good stuff… 


Links: SkyCross

Read Full Article →

Airspan announced the release of a pretty good piece of technology for the LTE network deployment puzzle a few days ago, their Air4G. The key things here are that it is a physically small outdoor package, capable of both WiMAX and LTE. The primary thing that caught my eye was as an LTE eNB it features 2×2 MIMO (Single User [SU] and Multi User [MU]!), built in 2x 40dBm TX power, support for 700MHz and the ability to connect a Remote Radio Head (RRH) with a CPRI connection for more RF power! Arghh!  Overall if they can reasonably offer these, make the sale and provide decent support for these boxes, this should be a hit for them.

Links: Airspan 

Read Full Article →

Let me preface this with I’m not hating on ATT, just irritated with the irrational exuberance of the press.

I read something the other day regarding ATT’s recent LTE demo. The author was claiming that ATT was going to blow away Verizon. I think they made that leap from this sentence of PR: US carrier AT&T has given a demonstration of its forthcoming LTE network, achieving download speeds of 28.7Mbps and uploads of 10.4Mbps. It’s simply not true.








Here’s why:

Read Full Article →

This lawsuit is one of those that irritate me. From what I can tell, the story begins after Gerard Joseph Foschini writes MIMO/BLAST papers in 1996 and gets the first MIMO patent at Bell Labs in 2002. Donald L Schilling, CEO of Linex Technologies, whom spent a lot of time making patents in wireless and is no slouch with respect to granted patents, filed Patents 6757322, Space diversity and coding, spread-spectrum antenna and method in 2004 and RE42,219  Multiple-Inout Multiple-Output (MIMO) Spread-Spectrum System and Method which just got printed in March of 2011. Now Donald wants to collect royalties from the computer industry and relax in Florida. It’s logical to me that next he is likely to turn his guns on the LTE market.


More details after the break…



Read Full Article →

So there is a EB (Elektrobit) Wireless Environment Solution (EB WES) that essentially consists of the EB Propsim F8 hardware that is capable of emulating MIMO, SIMO, fading, doppler and other radio conditions that are seen in the real world. From what I gather, the concept is to use maps and a mapping tool in combination with this HW tool to create the ‘drive test’ type of results. It’s a very intriguing concept that could be very beneficial change to the way things are done currently, specifically eliminating lots of drive testing. I want to learn more, but here is the information I have so far…






Link: Elektrobit





Voice over LTE (VoLTE) is the next big thing. In fact, in 24 months, virtually all LTE enabled smart phones will support it. Curious?
Small Cells

Small Cells

Small Cells, previously known as 'femto' or 'pico' cells are possibly a savior to network operators. They offer capacity and coverage to the end user and are inexpensive for the network operator. Why aren't they everywhere?
Public Safety

Public Safety

LTE is and ideal technology for Public Safety use. See Why.