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Re: [802.19] Microsoft/Harvard Protocols to Fix WhiteSpace Interference

Ed and all,
 
Your observation is right on, from both a technical and practical standpoint.  Having spent over 10 years messing with the DAA (Detect And Avoid) debate for worldwide ultrawideband regulations, I can say without equivocation that simple energy detection, no matter how it is performed, is not adequate.
 
If one examines the initial premise of 47 CFR Part 15 type non-interfering operation, you are always protecting a receiver.  This fact essentially begs the question... how do I detect a receiver, particularly one that is specifically designed to recover a complex modulation scheme that may look like almost zero dB of uncorrelated power rise in the broad spectrum seen by a typical amplitude detector?  What am I going to look for, the local oscillator leakage?  All I can reasonably detect is an operating transmitter because any other detection operation is way too complex in both implementation and expense (Ed's point).
 
Over the last several years, the Office Of Engineering Technology at the FCC, and particularly their Labs in Gaithersburg, MD, have examined practically all of the devices being evaluated for use in the so-called white space.  I strongly suggest that the IEEE coordinate with the FCC resources in this matter, to achieve an acceptable solution that allows growth and innovation in the areas of new standard based devices operating in the allocated bands.
 
One last comment.  The revelation that Microsoft and Harvard have solved the time - space - frequency - communication problem through an asynchronous open loop sampling and planning technique is absurd.  This group (IEEE 802 et seq.) has more experience in this technology space than any other in history.  The universal axiom that no two objects can occupy the same space in our know dimension still exists, and that applies to energy which occupies spectral regions, as detected by a "victim" receiver.
 
I'm not saying that you can't fashion a solution for the problem.  However, I am saying that the FCC, EU and other worldwide regulators as well as the ITU have solicited significant input on the same subject matter we are dealing with here, and we now have an opportunity to dispel the myths and actually propose a framework that may lead to a workable solution.
 
Best regards,
 
Gregg Rasor 
----- Original Message -----
From: Reuss, Ed
Sent: Thursday, August 20, 2009 11:21 AM
Subject: Re: [802.19] Microsoft/Harvard Protocols to Fix WhiteSpace Interference

So as per Section 4.2.1, this system uses simple amplitude detection [sqrt(I^2 + Q^2)] above a predefined threshold in the time domain to detect the presence of another network. This might be fine for existing wireless technologies, such as simple OFDM (most people don?t normally characterize OFDM as ?simple? J), but beamformed networks may be nearby that simple amplitude detection won?t detect unless it implements a beamformed receiver in the opposite direction, which I suspect would be unlikely.

 

Furthermore, modulation techniques may be developed for these bands, using lots of coding, that permit data transmission close to 0 dB SNR. These transmissions will not be detected either, regardless of which direction you point the beam.

 

I don?t wish to sound like a curmudgeon, and I recognize that such fancy modulation systems may never be developed for these bands, but if we accept such a simple detection system, then it guarantees that we will never be able use them even if we wanted to. On the other hand it?s unrealistic to require every device in this band to include a full-blown SDR with wide-band I-Q spectrum analysis capability.

 

-- Ed Reuss, Principal Engineer, Advanced Technology Group, Plantronics, Inc.

 

From: Bruce Kraemer [mailto:bkraemer@xxxxxxxxxxx]
Sent: Thursday, August 20, 2009 7:25 AM
To: STDS-802-19@xxxxxxxxxxxxxxxxx
Subject: Re: [802.19] Microsoft/Harvard Protocols to Fix WhiteSpace Interference

 

Richard et al,

The technology description can be found here.

 

http://research.microsoft.com/pubs/80952/whitefi.pdf

 

 

Bruce

From: Richard Paine [mailto:richard.h.paine@xxxxxxxxx]
Sent: Thursday, August 20, 2009 9:45 AM
To: STDS-802-19@xxxxxxxxxxxxxxxxx
Subject: [802.19] Microsoft/Harvard Protocols to Fix WhiteSpace Interference

 

Everybody who has been working on TVWS in IEEE 802 should read this, the source document, and the related material.

 

From FierceBroadbandWireless:

 

-------------------------------------------

 

Microsoft claims new protocol fixes interference problem for white-space devices

 

By Lynnette Luna

http://static.fiercemarkets.com/public/newsletter/assets/comment_ico.gifComment | http://static.fiercemarkets.com/public/newsletter/assets/email_ico.jpgForward

Researchers from Microsoft and Harvard University say they have developed a protocol that could be the foundation for new white-space devices.

The researchers believe the protocol could enable devices to avoid interference in white-space spectrum--those unused slivers of spectrum in the 700 MHz band between spectrum used by broadcast TV stations. The FCC approved the use of white-space devices last November on the condition that they don't interfere with nearby services, such as broadcast TV and wireless microphones. White-space devices are supposed to undergo a rigorous certification process before it is authorized. The vision for white space is to create super WiFi technology. The broadcasting industry has vigorously opposed any use of white-space devices, citing interference concerns. It hasn't been satisfied with the FCC's conclusion that interference won't be a major problem.

Microsoft and Harvard researchers presented their ideas this week at the ACM SIGCOMM 2009, a communications conference held in Barcelona, Spain, according to an article published on MIT's Technology Review Web site. The set of protocols are called "White-Fi," which are designed to avoid interference and make efficient use of the white-space spectrum since much of the interference has to do with devices using the same frequency at the same time. The protocol enables each device to evaluate the spectrum around it, discover available frequencies and continually search for interference, the researchers said. Once the interference is found, the protocol enables the device to jump to a different piece of spectrum at any time.

Microsoft recently obtained an experimental license from the FCC to build a prototype White-Fi system on the Microsoft Research Campus in Redmond, Wash., Microsoft researcher Ranveer Chandra told Technology Review. Microsoft plans to share its findings with the FCC.

For more:
- read Cnet

Related articles:
White space: Dell to make laptops; Google downright giddy
FCC unanimously approves unlicensed white-space devices
Microsoft intensifies white-space lobbying efforts

Read more about: WiFi, White-Fi, white space, protocol

 

 

Richard Paine

Success is getting what you want, happiness is liking what you get!

Phone:  206-854-8199

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Email:  richard.h.paine@xxxxxxxxx