{"id":877,"date":"2021-06-12T13:32:53","date_gmt":"2021-06-12T20:32:53","guid":{"rendered":"https:\/\/www.apsubsea.com\/?p=877"},"modified":"2021-06-12T13:32:54","modified_gmt":"2021-06-12T20:32:54","slug":"testing-2-4ghz-wi-fi-underwater-and-between-boundaries","status":"publish","type":"post","link":"https:\/\/www.apsubsea.com\/?p=877","title":{"rendered":"Testing 2.4GHz Wi-Fi underwater and between boundaries"},"content":{"rendered":"\n<p>In air our WiFi system provides stable radio link at distances 500 meters (tests conducted at 0-2 meters height above the water surface), which is good for AUV and many ASV applications. Distance is much longer if antennas elevated above the water surface and water does not attenuate the signal.  <\/p>\n\n\n\n<p>This spring 2021, we complete extensive tests in real environment of our recently made \u201cSubsea (submersible 6000 m) compact 2.4GHz Wi-Fi radio transceiver\u201d (<a href=\"https:\/\/www.apsubsea.com\/?page_id=824\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/www.apsubsea.com\/?page_id=824<\/a>).<\/p>\n\n\n\n<p>Major question we asked ourselves \u2013 is it possible by using standard 3-5 dBi omnidirectional antennas organize Ethernet communication in the way:<\/p>\n\n\n\n<ul type=\"a\"><li>2-way subsea Wi-Fi band radio communication when antennas submersed;<\/li><li>2-way Wi-Fi band radio communication when one of the antennae submersed and another \u2013 above the water;<\/li><li>What would be maximum distance of signal propagation and bitrate, latency in both scenarios;<\/li><li>What is the application for that and how\/where it can be helpful?<\/li><\/ul>\n\n\n\n<p>AP Subsea Inc. is giving answers, thank you for staying tuned.<\/p>\n\n\n\n<p>So, in short \u2013 the answer is <strong><u>YES<\/u><\/strong>! Bidirectional radio datalink underwater and as well as between air-water boundaries is not just possible, it is fast, low latency, secure. To be honest, we watched live Full HD video stream using our system! So, we are super excited.<\/p>\n\n\n\n<p>Now, details.<\/p>\n\n\n\n<p><strong>Theory<\/strong><br>For many people it sounds obvious (or even more &#8211; like an axiom) that there is no radio comms in water and between boundaries at such high frequencies. Also, that there is no practical use for that. By doing theoretical study we found that there is neither many sources of information, no details about radio signal propagation thru\/ (or in) water. One problem is that water is not a uniform substance: turbidity, temperature and salinity may play significant role in RF signal propagation. Another \u201cfeature\u201d that fresh and seawater have different radio transparency properties. Also due to significant RF signal attenuation and conductivity properties of water &#8211; much, much higher than air, almost all the radio signal energy used to interact with water \u201csnow\u201d, particles, water molecules. This effect we can watch by warming water in the microwave oven.<\/p>\n\n\n\n<p>To compare water and air as media we found that these two parameters in the equation are playing main role:<\/p>\n\n\n\n<ul><li>relative dielectric permittivity (dielectric constant)<\/li><li>electrical conductance<\/li><\/ul>\n\n\n\n<p>See parameters in table below for 2.4 GHz signal<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td><strong>Parameters<\/strong><\/td><td><strong>Fresh water<\/strong><\/td><td><strong>Sea water<\/strong><\/td><td><strong>Air<\/strong><\/td><\/tr><tr><td>Relative dielectric permittivity (dielectric constant)<\/td><td>60<\/td><td>80<\/td><td>~1<\/td><\/tr><tr><td>Electrical conductivity, S\/m<\/td><td>1<\/td><td>4<\/td><td>3  to 8 * 10^-15<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>If lower dielectric constant and smaller electrical conductivity \u2013 then further radio wave can travel. These limitations are true for high frequency (short wavelength) radio signals. For low frequency and long wavelength radio signals this is less critical. More important becomes to provide enough transmit power and tune sensitive receiver to detect signal. However, for long wavelength signals, i.e. 10kHz (~30 km wavelength) classic E-antennas dimensions would be at least 7.5 km long (1\/4 of wavelength). The only option to minimize antenna (but sacrifice signal transmission distance) is to account on magnetic component of the RF and use magnetic loop type of antenna.<\/p>\n\n\n\n<p><strong>Testing<\/strong><br>By doing tests we have confirmed that our system, which is equipped by common use 3-5 dBi omnidirectional antennas, can establish solid, low latency, reliable wireless radio connection at frequency 2.4 GHz.<br>We complete tests in freshwater lakes and seawaters around beautiful Vancouver metro area, British Columbia, Canada.<br>Table below demonstrates what we achieved during the tests<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><tbody><tr><td>&#8212;&#8212;<\/td><td><strong>Link distance, inches<\/strong><\/td><td><strong>Datalink speed, Mbit\/s<\/strong><\/td><td><strong>Latency, ms<\/strong><\/td><\/tr><tr><td><strong>Antennas in water<\/strong><\/td><td>4-6<\/td><td>50-100<\/td><td>1-2<\/td><\/tr><tr><td><strong>One of antenna in air another in water<\/strong><\/td><td>30-40<\/td><td>10-100<\/td><td>1-2<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>So, why to use 2.4 GHz radio datalink underwater if distance is that short?<\/p>\n\n\n\n<p><strong>First <\/strong>\u2013 at short distance \u2013 Pretty good baud rate: 50-100 Mbit\/s<\/p>\n\n\n\n<p><strong>Second <\/strong>\u2013 security \u2013 Modern ciphering protocols are used and no data leak due to nature of environment<\/p>\n\n\n\n<p><strong>Third <\/strong>\u2013 integration \u2013 Ease to add number of payload onto highly integrated vehicles with limited amount of \u201cGuest ports\u201d, i.e. setup access point with antennas basket<\/p>\n\n\n\n<p><strong>Forth<\/strong> \u2013 standard interfaces \u2013 Well known interface Ethernet (POE) and TCP\/IP protocol are used<\/p>\n\n\n\n<p><strong>Fifth <\/strong>&#8211; signal latency \u2013 It is low enough and compatible to provide payload NTP clock synchronization.<\/p>\n\n\n\n<p><strong>Sixth <\/strong>\u2013 speed in water \u2013 2.4 GHz radio wave propagation in water is faster then acoustic.<\/p>\n\n\n\n<p>In conclusion we would like to say thank you everyone who have shown interest to what we do and waited for the interesting results.\u00a0<\/p>\n\n\n\n<p>Specification is on the page: <a href=\"https:\/\/www.apsubsea.com\/?page_id=824\" target=\"_blank\" rel=\"noreferrer noopener\">https:\/\/www.apsubsea.com\/?page_id=824<\/a> <\/p>\n\n\n\n<p>Contact us: +1 (604) 363-3862, <a href=\"mailto:sales@apsubsea.com\">sales@apsubsea.com<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>In air our WiFi system provides stable radio link at distances 500 meters (tests conducted at 0-2 meters height above the water surface), which is good for AUV and many ASV applications. Distance is much longer if antennas elevated above the water surface and water does not attenuate the signal. This spring 2021, we complete &hellip; <a href=\"https:\/\/www.apsubsea.com\/?p=877\" class=\"more-link\">Continue reading<span class=\"screen-reader-text\"> &#8220;Testing 2.4GHz Wi-Fi underwater and between boundaries&#8221;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v20.4 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Testing 2.4GHz Wi-Fi underwater and between boundaries - AP Subsea Inc.<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.apsubsea.com\/?p=877\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Testing 2.4GHz Wi-Fi underwater and between boundaries - AP Subsea Inc.\" \/>\n<meta property=\"og:description\" content=\"In air our WiFi system provides stable radio link at distances 500 meters (tests conducted at 0-2 meters height above the water surface), which is good for AUV and many ASV applications. 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