The Problem with Software Defined Radio
<html> <p>There’s a problem with software defined radio. It’s not that everyone needs to re-learn what TEMPEST shielding is, and it’s not that Bluetooth is horribly broken. SDR’s biggest problem is one of bandwidth and processing. With a simple USB TV Tuner, you can listen in on aircraft, grab Landsat images from hundreds of miles up, or sniff the low-power radios used in Internet of Things things. What you can’t do is make your own WiFi adapter, and you can’t create your own LTE wireless network. This is simply a problem of getting bits from the air to a computer for processing.</p> <p>At HOPE last weekend, the folks behind the very capable <a href=„https://www.crowdsupply.com/lime-micro/limesdr“ target=„_blank“>LimeSDR</a> and a new company working with Lime’s hardware laid out the possibilities of what software defined radio can do if you make a link to a computer very fast, and add some processing on the SDR itself.</p> <p/> <p>The key feature of the LimeSDR, and all boards derived from Lime Micro’s tech is the LMS7002M. It’s a Field Programmable RF transceiver with coverage from 100kHz to 3.8GHz, a programmable IF filtering from 600kHz to 80MHz, and — this one is important — on-chip reconfigurable ‘signal processing’ and a fast USB 3.0 interface to a computer.</p> <figure id=„attachment_215995“ style=„width: 260px“ class=„wp-caption alignright“><a href=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg“ target=„_blank“><img data-attachment-id=„215995“ data-permalink=„https://hackaday.com/2016/07/29/the-problem-with-software-defined-radio/dsc_0011-7/“ data-orig-file=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg“ data-orig-size=„600,600“ data-comments-opened=„1“ data-image-meta=„{"aperture":"5.6","credit":"","camera":"NIKON D5200","caption":"","created_timestamp":"1469364455","copyright":"","focal_length":"55","iso":"1800","shutter_speed":"0.033333333333333","title":"","orientation":"1"}“ data-image-title=„DSC_0011“ data-image-description=„“ data-medium-file=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=400“ data-large-file=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=600“ class=„wp-image-215995 size-thumbnail“ src=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=250&h=250“ width=„250“ height=„250“ srcset=„https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=250&h=250 250w, https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=500&h=500 500w, https://hackadaycom.files.wordpress.com/2016/07/dsc_0011.jpg?w=400&h=400 400w“ sizes=„(max-width: 250px) 100vw, 250px“/></a><figcaption class=„wp-caption-text“>The Fairwaves XTRX</figcaption></figure><p>Aside from the Lime, another company was also at HOPE showing off the latest SDR wares they have to offer. <a href=„https://fairwaves.co/“ target=„_blank“>Fairwaves</a> was there with the <a href=„https://xtrx.io/“ target=„_blank“>XTRX</a>, a software defined radio built around  the same Lime Micro LMS7002M chip in a miniPCIe form factor.</p> <p>This tiny card uses the same tech found in the LimeSDR with one key difference. Instead of a USB 3.0 port, the XRTX connects to a computer through the PCI bus, sending data to RAM at 8Gb/s. That’s fast.</p> <p>The miniPCIe form factor also has another interesting application. The folks at Fairwaves are working on putting this device in a miniPCIe to PCIe x1 adapter – that makes sense, it’s all the same signals, just a different form factor.</p> <p>This also means you can run four XTRX boards with a yet-to-be-designed PCIe 16x adapter. Putting four of these SDRs in a single card means phased array antennas, 8×8 MIMO, and other techniques that make this massive SDR very interesting. The Fairwaves team only had a handful of these boards assembled, but when this goes on sale, you’ll be able to build a rig that blows the roof off the price/performance ratio of any other SDR.</p> <p>In the talk presented at HOPE (not available independently of other talks yet, but <a href=„http://livestream.com/internetsociety3/hopeconf/videos/130824120“ target=„_blank“>starting 1:46:12 into this live recording</a>), the folks behind the LimeSDR talked about the possible applications of this hardware. In a year or two, you’ll be able to build a portable 3G or 4G base station for about $2500. That’s an incredible advancement in the state of the art, and something that’s only possible because of on-chip processing and very fast access to a computer’s memory.</p> </html>
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