----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com Midwest Internet Exchange http://www.midwest-ix.com ----- Forwarded Message ----- From: "Jaime Fink" <[email protected]> To: [email protected] Sent: Friday, May 1, 2015 12:18:22 PM Subject: [WISPA Members] Mimosa update - "Why you owe it to yourself" to get real facts Speaking for Mimosa here, we’re concerned with the misinformation that is being spread about the B5/B5c radios, and we owe it to this community to get real facts out there to address these assertions since they’re being discussed extensively within WISPA. A large number of WISPs who have deployed our products properly were very easily able to see that the information and use case assertions presented recently were simply not correct. It did not reflect our publicly declared FCC filings, and most importantly did not match their real world experience with the radios in the field at all. I’d like to thank those of you for speaking up with facts and accurate information and bringing it to our attention. In simple terms, we are honest, straight shooters who want to build great products for the industry, and hopefully make some friends along the way. The B5/B5c represents over 30-man years of development at Mimosa, using a state-of-the-art chipset from Quantenna Communications. Quantenna is quickly becoming recognized as the worldwide leaders in Wi-Fi technology. At Mimosa, we have unprecedented levels of access to modify the firmware of the Quantenna chip, “down to the metal,” which allows us to offer a highly accurate GPS-timed TDMA protocol to address the unique needs of WISPs. In the specific application of the B5/B5c, we did an interesting trick of connecting two RF chips with a single baseband chip, tuning each RF chip to a different channel. By doing this, we map the four chains of a 4x4 radio into two polarizations on two channels: Channel 1 - vertical, Channel 1 – horizontal, Channel 2 – vertical, and Channel 2 – horizontal. Each of the chains are fed through separate power amplifiers , and the pairs of common polarization signals are combined through passive combiners . We had to use separate power amplifiers, because as someone pointed out in a prior posting, combining two OFDM signals on different channels through a common Wi-Fi power amplifier will result in intermodulation distortion. Our FCC test report, tested in a local Silicon Valley lab, speaks for itself with regard to our out-of-band emission levels. We exceed the performance specified by the Wi-Fi Alliance PSD mask by several dB as well. For those not familiar with this specification, it states that when you’re more than one bandwidth away from the edge of the OFDM signal (e.g. 40MHz away from the edge of a 40MHz OFDM signal), you need to be at least -40dBr relative to the OFDM power spectral density. We are between –45dBr and –50dBr as you move away from the band edge, which is equal to or better than other radios based on Wi-Fi silicon. For your reference, attached are a couple of spectra of our radio operating in 2x mode. Contrary to the misinformation posted by others, we do not have intermodulation spurs above and below the two active channels. What would have caused such spurs, you are probably wondering? If the person setting up the experiment were to directly inject a high-powered signal into the spectrum analyzer, they could cause a non-linear response in the LNA of the spectrum analyzer. The proper way to set up the experiment is by operating the radio through an attenuator rated for the specific load required, ensuring that the spectrum analyzer is always operating within its specified input power range. Simply put, our actual implementation approach in the radio and the proper spectrum analyzer results, are entirely contrary to the assertions made: It’s entirely possible that the “other product" has lower out-of-band emissions than the B5/B5c, but the relevant questions is, what effect will it have? Take for example a B5 operating at 17dBm. The off-axis antenna response is generally around –6dBi. Presuming a 2m spacing between a Mimosa radio and another radio, the free-space-path-loss is –53dB in the middle of the 5GHz band. Presuming the other radio has a high-performance dish as well, the out-of-band energy received on the adjacent radio is +17dBm – 50dBr(OOBE) - 6dBi(B5 antenna) – 53dB(FSPL) - 6dBi (Other antenna) = -98dBm. The thermal noise floor of a radio is kTB + NF = -174dBm/Hz + 73dB(20MHz) + ~4dB = -97dBm. So in this example at a 2m spacing, we are below the thermal noise floor by 1dB, increasing the cumulative noise floor by 2.5dB. In the real-world, however, chances are that the noise floor is already degraded by 10dB or more from other man-made noise sources. Net-net, the OOBE of Mimosa radios will not degrade your network performance. I’d ask that if you need help, contact us via our support page, we stand behind our product and have actual real technical support people that help tune links every day, often times delivering huge improvements with simple power reductions and channel usage suggestions. They can answer any of these questions and make sure the links are working properly. We absolutely support people doing these types of tests, but certainly hope that they truly are being done independently, fairly, correctly, evaluating all the features of products, and each vendor given at least the opportunity to validate results or express any methodology concerns. As always, if you know us at Mimosa at all, we are here to listen to you, you have been incredibly helpful in guiding our development efforts, and constantly adding new features and products based on your feedback. Please contact me directly if I can provide more information on this topic, or address any other concerns you have. Cheers, Jaime Fink • Mimosa • CPO & Co-Founder This email may contain confidential and privileged material for the sole use of the intended recipient(s). Any review, use, distribution or disclosure by others is strictly prohibited. If you are not the intended recipient (or authorized to receive for the recipient), please contact the sender by reply email and delete all copies of this message. _______________________________________________ Members mailing list [email protected] http://lists.wispa.org/mailman/listinfo/members
