Building wireless infrastructure on a (really small) budget Network Startup Resource Center www.ws.nsrc.org These materials are licensed under the Creative Commons Attribution-NonCommercial 4.0 International license (http://creativecommons.org/licenses/by-nc/4.0/) Presentation Title (Arial 44) Network Startup Resource Center (Arial 32) www.ws.nsrc.org (Arial 32 and Hyperlink blue #0645AD) • 1.2/ Wireless connectivity for hard-to-reach areas • 2.1/ Building wireless infrastructure on a (small) budget • 3.1/ Measuring and monitoring wireless connectivity • These materials are licensed under the Creative Commons Attribution-NonCommercial 4.0 International license 4.1/ Building a(http://creativecommons.org/licenses/by-nc/4.0/) wireless community/campus network There are ... • Best practices • Acceptable practices • Fun experiments :) From a workshop in South Africa 2005 – this worked over ~6 km Link Budget / examples DIY cantenna point-to-point link TX + 020 dBm Cable + Connectors - 003 dB (not so good cabling) Antenna TX + 010 dBi (??? … not measured precisely) FSL (10 km at 2.4 Ghz) - 120 dB Antenna RX + 010 dBi (???) Cable + Connectors - 003 dB ---------------------------------------------------------------------- Result - 086 dBm Receive Sensitivity - 095 dBm (lowest data rate) ---------------------------------------------------------------------- TOTAL + 009 dB Link Margin hhmmm… that s (too?) tight ... Is it worth building your own? • You will need an AP or Wireless Router, in any case – This will be off-the-shelf equipment (you could build it yourself, but there s nothing to save there) • Antenna DIY? It all depends on – budget – time – skills – ambition Comparison: prices for commercial antennas • Small omni, indoors, “rubber ducks” $2 • Omni, strong (8-12 dBi), outdoor $30 • Patch/Panel $20 • Directional, grid/dish, strong (20+ dBi) $50 … $100s Always check quality! Need to have datasheet / measurement protocol! Three DIY antenna projects • Cantenna • Bi-quad • Collinear Cantenna • an empty can of right size ($0) • connector ($2) • cable ($2) One of the earliest DIY Antennas (July 2001, Rob Flickenger made the Pringles Antenna) source: wndw.net Cantenna ICTP 2005 Shopping for Cans, w Marco Zennaro, Rob Flickenger Cantenna: what to expect • (8-)10 (-12) dBi • 60 degs beamwidth • 2 hours of work, perhaps • Cost: $3 - $5 source: wndw.net Cantenna: video guide https://www.youtube.com/watch?v=prTKZXoTLgQ Bi-Quad • a metal plate, some wire • connector ($2) • cable ($2) A reasonably strong patch antenna (~10 dBi) source: qrznow.com Bi-Quad Bi-Quad Linksys DIY mesh node, Sengerema, Tanzania 2008 Collinear antenna ● 2 or 4 elements ● 5 / 7 dBi ● Difficult to make it precise! source: wndw.net Making Your Own Antennas Free, Open Source Designs Available Combine with Reflectors (Satellite Dishes) for high gain Learn Collinear & Cantenna with WNDW (multiple languages) http://wndw.net/book.html Make a BiQuad with Trevor Marshall (English) http://www.trevormarshall.com/biquad.htm Make a Parabolic Reflector & More with M. Erskine (English) http://www.freeantennas.com/projects/template/index.html Make a Collinear with Marty Bugs (English) http://martybugs.net/wireless/collinear.cgi Making Your Own Antennas http://martybugs.net/wireless/collinear.cgi http://www.dslreports.com/forum/remark,5605782~root=wlan~mode=flat http://www.trevormarshall.com/biquad.htm Recycling parts • Old dishes from TV, satellite, … • Kitchenware: woks, pans, … – WokFi – Pantenna • Often used to improve existing Wi-Fi gear, e.g. USB dongles, small APs By User:Mark0, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=23315173 Pro and Con for DIY antennas + it s fun and saves (a bit of) money + it s educational - prices for antennas dropped a lot – is it worth it? - antennas become smaller, integrated in routers and devices - newer Wi-Fi standards need more/advanced antennas (MIMO, beamshaping …) - those are more difficult Trend: Antenna and radio integrated New types of DIY antennas Antennas get more complex, move to PCB/print antennas This example for 868/915 MHz LoRaWAN source: Le Huy Trinh, Nguyen Vu Truong, and Fabien Ferrero https://www.mdpi.com/2079-9292/9/10/1564 Summary: DIY antennas, DIY wireless • Great fun and education • Whether it still makes sense in 2021, depends entirely on your budget, ambition • Free designs and guides are widely available • Interesting to develop DIY print antennas, new approaches.