Radar Detect and DFS on MikroTik

welcome to the first mum in the United Kingdom here in London and I hope you're going to enjoy today for those who've gone to any of the European mums they've been absolutely fantastic and the beer is free at five o'clock ish after the raffle lots of free gifts it's going to be fun okay so why am i here up at the front is because of an announcement that was made by my critique about DFS becoming mandatory on their latest version of Route OS which caused a ripple throughout the industry in the UK for those who use DFS so that's why I decided to choose this hot 2 topic so where have I come from one of the words that you might find up there as to where I've come from in my history and my career is I came from Ofcom whoops and before that it was the radio communications agency and I was part of the radio investigation service which meant that I was part of a team throughout the whole of the UK that went out resolving interference problems either legitimate users affecting other legitimate users or quite often illicit users users that were operating outside the terms and conditions of a an appropriate licence of some kind causing interference to some other service usually a safety of life service so that's the emergency services aircraft that sort of thing kept us very very busy during that time it might in my time in the government I got loads of pieces of paper which was fantastic for covering up the holes in the wall no examinations required you just had to be awake by the end of the week and you got given a certificate anyone who's ever gone on those training courses will remember those I'm sure and that's basically what I did for 25 years gaining an enormous amount of experience and knowledge about wireless I first got wind of mikrotik Reuter OS in around 2005 2006 because I was assisting a very close friend and family colleague now at dining Guernsey and he put a Wi-Fi hotspot in down on his marina for his boat so that when he was on the boat before he went to sail he could pick up what the latest weather was because there was no 3G there was no 4G in those days and in in the bottom of the hole of a granite marina you're not gonna pick up any mobile signal anyway so he put a little Wi-Fi access point up and then he found that everyone else realized that he had Wi-Fi up there and they all wanted a share of it and he then he suddenly thought I can make some money from this how the hell am I going to do it and that's when I did some research for him and I came up with this my critique routes aboard it was a 5-3 - Wow it's amazing what can it do except make the coffee I then realized after about a year but I didn't really understand it very well I mean I got a good idea of what I was doing I wasn't stupid but I found after about a year there was so much potential to this product there was so much things you could tinker with and play and make it stop working that I kind of guessed I could do with some training on this to be honest and that's when I went to my critique who were actually doing the training in those days and I got myself the certification in my critique and then they then said to me you know what Ron you need to become a trainer says why what's in it for me no no you you need to be a trainer didn't quite realize what was in store for me because I then subsequently then became a trainer and I've got all the mikrotik certifications and working for Lyn ITX we provide all the certifications for mikrotik and a couple other vendors as well which we can't be allowed to mention here today so you just get this to work yeah it's a layer 8 problem as I call it OSI 7 layer model and it's a layer 8 problem ok so we're proud to mention then that we are the largest UK distributor we shift the largest amount of stock we've got the largest number of certified consultants and the largest number of trainers were too but anyway we've got two trainers and we've been doing that since about 2010 2011 DFS don't we just love DFS it's that furniture company isn't it always got a sale on all the time that ends tomorrow and then you know the day after it starts again so it's not true well I think it's a quite a good analogy because I think that when it comes to DFS and mikrotik the sale is finished there isn't going to be another sale after this one so if you're going to be using new versions of microchip or s and you're going to be using Wi-Fi or wireless for point-to-point links you're going to have to come across this DFS problem why do many of you not use DFS there are problems with it let's have a bit of honesty no one's filming you there any filming me how many of you are using outdoor wireless for point to point and point to multi-point services on five gigs and have taken some step or some measure to turn DFS off totally honest yeah bout a third of you to about half excellent I'll just pass the names on to my colleagues at Ofcom it'll be fine so what's the problem with DFS the problem is is that we weren't there first the five gigahertz band was given to us as a freebie under some very very tight control some terms and conditions that came with it in the small print and in the actual paperwork that came with the allowance around the world to use five gigs for Wi-Fi or for point-to-point links indoors or outdoors it came with a caveat that we had to make sure that the new users of those five gigahertz services had to protect the legacy users who were there before and had been there since the first international world conference just after the Second World War which was an idea that got formed from the League of League of Nations and the United Nations they thought it'd be a good idea to start regulating the radio spectrum and five gigs was allocated for radar and for satellite services set aside for it and so what they said was we'll go to these users and we'll double-check with them what they want to enable Wi-Fi to be used and the Wi-Fi vendors the people who are actually physically going to be manufacturing the equipment and selling the kits were saying well it's very low-power most of the time is going to be indoors anyway so there's going to be quite high levels of attenuation from the brickwork and the roof it's not really going to make it's all way up to the satellites so the satellites community those who are using satellite links earth to satellite was saying okay that's fine but we will have one stipulation which is that we want the spectrum to be used evenly we don't want everyone to just use one frequency so you can have a nice good chunk of radio spectrum but you've got to even out you've got to have a method you've got to have some kind of a system to make sure that the spectrum the energy that's going to end up going upwards is fairly evenly flattened out across the band so that was put into the spec the other users was some radar users and that was maritime and military and they also said well we'd like to have it flattened out across the band but also we want to make sure that if they pick up a radar signal then they go and pick another frequency randomly from some other part of the band so they don't interfere with our radar systems that have been there since the 1950s and it was rubber-stamped and agreed and the vendors said that they will implement DFS and it will all stop that from happening everyone everyone was happy and the problem is as we found out that life wasn't quite that wonderful why have things changed now if you actually look at the technical specifications for DFS the Etsy specifications they have changed significantly in the sort of 1517 years that five gigs has been operational but DFS has always been there it's just what's been happening over the last 17 years is that the technical spec for it has been tightening and tightening and tightening and the wording of the relent of the legislation has been getting stronger it's no longer saying things like you should use DFS which in legal terms means basically you can avoid it and don't have to do it it now says you shall which now means it's mandatory you can't have a choice in the matter anymore and then they found that people were finding that was a tick box you could UNTAC or tick or ask or a drop-down menu that they could choose to have it on or off so they've now changed the wording of the spec again and said that that controlled by the end-user shall not be possible they've actually now put that into the wording of the regulations so what's been happening over the years slowly piece by pieces they've been shutting the doors and making it more and more difficult to circum to to get around these problems so what's actually happened then over the last 17 years is that those original legacy users have been getting more and more interference five gigs has taken off we know how rubbish 2.4 is Internet of Things are going to make it even worse so 2.4 gigs is just a noisy mess of garbage but 5 gigs is getting very very busy as well especially for you guys who are running outdoor wisps if you are certainly in an area that you're competing with other companies who are operating 5 gig services in the same patch that you are operating in is getting more and more difficult to find clear spectrum that you can operate your services to your customers in so it's getting more crowded that's increasing the amount of energy in the 5 gigahertz band so perfectly than the noises is going up and also it's increasing the chances of somebody treading on top of a radar signal and being seen because there's just sheer numbers there's more of you out there there's more signals so the level of chance has now increased the other major problem that happened was that when they brought in the legislation for five geeks nobody bothered asking the biggest user of five gigs radar nobody actually thought it'd be a good idea to talk to the meteorological departments around the world and they were oblivious to this and didn't really realize what was going in but that was going on around the world until it started affecting their radar signals and then they started asking questions how the hell did this happen well you didn't get invited to the meeting how we're gonna get invited to the next one and in fact they went to enormous lengths to make sure that they got the regulations tightened up to their benefit one of the things that then happened was that because they complained to the regulators about the levels of interference that they were getting from us guys was that they called upon the regulators to do something about it now they the beauty of the way in which the legislation was written within the EU is that the directives have got a very very powerful clause there is an article 9 statement that basically says that if there's a problem they can come down on the manufacturer the importers and anyone shifting the equipment around in Europe like a ton of bricks and stop it dead in its tracks they can basically give an order to anyone involved in the supply chain from manufacturer to the person who sells it to the end-user and say you can't sell it anymore that hurts you imagine if you're the manufacturer of a device and the EU comes to you with a little nice little letter from Brussels and says if you don't do something about this by this date you are now being banned from being able to sell this equipment anymore now all of a sudden you wake up and you and you pay attention and you do things the carrot to that religious legislation is that there is no barriers to trade and we've always heard this phrasing there within the EU that there's no barriers to the free movement of goods within the EU that's allowed as long as you play ball as long as you abide by the regulations no one will do anything with you with nobody will touch you you can just crack on and sell and shift as much kit as you like but the minute that the EU gets wind of the fact that there's a technical problem with the equipment not complying with the regulations and therefore is not compliant with the SI e-mart that is applied upon it the ultimate sanction is to cut you off I'm not saying that's what's happened but that is the power that the EU have got so I'll quickly go over the the history I've actually got a hell of a lot more slides and I will they'll get printed up on the website as a PDF and you'll see there's a lot more technical information in there because I've actually got a good hour and a half to two hours I can do on this and I don't want to bore you with all the technical detail you're probably waiting for me to get onto the tips and tricks bit so how you get around this how did it start off it started off back in 1991 and there was a recommendation that five gigs that should be used for Wi-Fi there was also thinking there about 17 gigs which made it into the mostly European Union but we here in the United Kingdom have got legacy users on 17 gigs who put their foot down and said we're not having 17 gigs used for Wi-Fi so I know you can buy 17 gigs microwave link equipment and you can use it in places like Ireland and in quite a few countries in Europe but here in the UK 17 gigs is not available but the magic one was five gigs and what they said was is we think that Etsy is a good body to come up with the technical standards required so they then consulted with Etsy and came up with a specification and a recommendation and they then published and said yep go ahead you can use five gigs indoors now outdoors at all just indoors because then you've got the attenuation of the building and the satellite users will not get upset but then they said in 1998 we want more and it's like Fagin you know please sir I want some more and they realized that the vendors realized that five gigs was fantastic but they needed more spectrum they wanted more radio channels so they went back to the legislators and said we want more and there about a year later they got given more but on the understanding that we still had this catch which is that it has to have DFS to protect military radar and satellite uplinks no mention of weather radar whatsoever at all if you actually then read the actual clause that got put into the final spec you can see there is no mention at all about weather radar and yet it's the weather radar that's the biggest losers in this at the moment because remember DFS is not just about radar detection it is also about the random selection of a radio channel which is a killer for you because if you're doing point-to-point links you've probably nailed it to one frequency because you thought that's a good one I like that frequency and yet in fact it's in the spec that you have to allow it to work it out for itself across the whole of the band you're not supposed to be able to override the choice and we all know that we can then there was a World Conference the whole of the world then gained five gigs but the thing was that they still tied it all back to an original ITU recommendation for how DFS worked recommendation M 16:52 which was something from like the 50s or the 60s it was a very very very old DFS specification and it was not fit for purpose they didn't realize that at the time not until the interference reports started one of the cools things one of the cool things though however about the actual technical specification was it was actually all written into it that they should continue to modify the specification it has she had it written in there that it wasn't a static specification they said that further studies should be made and you know she'd get feedback from from users and from legacy users and it should therefore keep in touch with the real world of what's actually going on so that's what happened if you look at the Etsy specification for this it's now 2 1 or 8.1 and it started off at version 1 so we've had about nearly a dozen different versions that have come out over the years is being constantly being changed all the time yes we should have radar detection and that was the problem the by the time it actually went live it was already out of date with the type of radar technology that was being used at the time when it came out that's what said just now that taking into account practical experience this is the thing about the standard taking into account what's actually happening on the ground what's really happening and as a result of that feeding it back into the system so that the the spec was constantly being changed the problem was that the meteorological organizations were never consulted especially in Europe and they were the ones who were getting most of the grief at the original conference in 2003 there were some countries who had representatives which was Australia America and Canada and their meteorological services did not like the idea of any kind of DFS solution they looked at the DFS solution that was put into the technical spec but they didn't like it and they didn't feel that there was enough protection mechanisms in there in the spec to make sure that their radar systems would remain uninformed you can't use the same slot of frequencies that's used by all the weather radar which is why we have this you know if you have a Google anything about weather radar you get a lot of information from the states the TD twr information the weather radar that's at nearly every American airports and the band is actually locked out you're not allowed to use 5600 256 50 at all the sub band is is notched out it isn't in Europe we can use it because of course we believe that the DFS works there again we didn't actually ask the Meteorological organizations if it works found out soon enough so the Americans the Australians the Canadians they all banned it and we just carried on blindly going on with it to the point now where even the Meteorological organizations know that they can't put the genie back in the bottle they can't they can't request the European standard to be modified now it's too late they come asked for that band to be notched out and removed from the Wi-Fi band because it's just too heavily used now it's too late should have done it back in 2003 but it's too late now visit is it important do we even need to worry about the interference that may be potentially caused to the Weather Service's very much so they are actually seen by the UK government as an emergency service in the same way as you want the emergency services to come to your aid as quickly as possible if you require them to come to you we want the police the fire ambulance to come to you as quickly as possible anything that impedes their progress can cause lives to be lost and the same thing applies to whether we get quite a bit of rain in the UK for some weird reason I think there's a large lump of water in there between us in the United States and we get a large amount of water and therefore the ability for the UK Meteorological Office and other European countries as well to be able to predict many many hours in advance where the rain is going to fall and by how much means that they can then warm those emergency services they can warm the Environment Agency that then in turn means that they can put flood alerts out and they can then warn us in our homes to be better prepared for anything that might happen in the next few hours or over the next 24 hours or so it can alert the utility companies because then they know when there's going to be a gap in the rain they know when there's going to be a chance for it to stop at long last so that the engineers can get to the locations to fix the problems where lightning has taken some kind of service out it's a very very important service which is why when the Meteorological Office gets interference they ring off calm and Ofcom will immediately respond it's a safety of life service which is why when you get the phone call from Ofcom which is usually done on a very gentleman Airy very diplomatic and very pleasant way there is there any chance that you might be using 5625 and it has this SSID name which is the same as your company name could it be you possibly any chance and you go might be why well just because you're interfering with the weather radar and you're thinking are okay but it really is important and you do need to do something about it because the ultimate sanction is Ofcom will eventually come and knock on your door and they give you a beautiful little piece of paper there's a little receipt for all the stuff that used to be on your roof at one time and then your business has gone down the pan so they do it softly softly you know you can always ramp up the enforcement you don't go in heavy-handed gung-ho or guns blazing you start at the bottom you do it polite do it gentleman airy you do the request and if the problems gone away within 15-20 minutes case closed excellent on to the next job whereas if you don't respond and you don't do anything about it right okay we're gonna have to go and visit them now it starts to become a little bit more aggressive the next one after that is they get warrants magistrates will issue warrants 24 hours a day seven days a week even Christmas Day New Year's Day whatever there's a duty magistrate available he'll sign the warrant off and then there'll be a knock on your door at some ungodly hour and you've now got to find keys you've got to find key holders you've got to get to the kit you've got to now deal with it and it then becomes more inconvenient there's also really clever piece of legislation which says that they can nominally seize the equipment what they then do is they say right you've got to turn that piece of equipment off you can't turn it back on again if you do it's contempt of court we've seized it so if you turn it back on you are now you know in contempt of the courts because you're now modifying the evidence the evidence is there leave it alone don't touch it it must stay as it is now until we see you in court which could be six nine months down the line can you survive an outage for that amount of time be nice to them okay they've got a hard job to do there's not very many of them left and they're absolutely struggling to keep up with it so be kind to them aircraft need to know about the weather CAA needs to be notified the mo D do their own air traffic control so the mo D need to know about the weather they don't use weather radar themselves they don't like have like they have in the United States they don't have a five gig weather radar at every single Airport they rely upon the Met Office's system to provide them with the weather reports we don't also have the same problem they have in the States with wind shear highways agency they need to know about the motorways you know is it going to be a real really terrible massive sudden downpour in a certain month in which case they can put the warning signs up to say slow down which we then all ignore because we can't see the rain so we may just keep going at 17 Coast Guard agency they need to be knowing about the weather out at sea and therefore keep the shipping safe and put out announcements to shipping out at sea that there's going to be really bad storms it's really really important it's definitely safety of life so because of all the interference the European organisation called EU metnet really sexy name they got involved in working out how can we fix this interference problem and they took upon it in two ways they actually did a practical study they literally went to the kit looks at it and found out what could you do and they found that it was really easy to circumnavigate around the DFS settings and they found that in the vast majority of vendors at that time we're not making DFS mandatory and yet in the in the regs it said DFS was mandatory not optional so that upset them a bit but it also illuminated them and it made it explained to them as to why we've got the problem because you can turn it off the other thing they discovered was that the radar systems that they did installed for many many years did not match the radar signatures that were built into the etsy spec there was no real correlation with it at all so therefore even if you had enabled DFS detection you wouldn't have seen the Met Office's system you wouldn't have triggered you wouldn't have turned off that radio channel the system would not have been automatically avoiding them anyway so didn't work the major problem was was the pulse-width wasn't small enough and the PRF was wrong the pulse repetition frequency how many pulses of radar energy are going out every second was completely askew from reality so they came up with a whole load of modified changes the etsy spec got modified again year upon year over the next few years it kept getting tighter and tighter and the other thing that they did in a big way was they said you're not listening for long enough a weather radar does not work like a air traffic control radar you've seen the thing that goes round really really fast usually paint your bright red or orange which is a primary surveillance radar which is what's just looking for aircraft looking for lumps are metal in the sky and that is spinning around quite fast a Meteorological Office weather radar doesn't do that it actually goes around very slowly indeed in incremental steps in a helical shape in a spiral and so therefore the radar is only looking at you or your base station maybe for just one minute in an entire 30 minute window because for the other twenty nine minutes the dish is pointing the other way and you don't see it that's a completely different animal so they said 60 seconds is not enough time for other for the receiver in the Wi-Fi unit to pick up the radar pulses so they want that increased for a staff so they said we want that increase to 10 minutes the other thing is they found is it's just not accurate enough in the actual meteorological office band the the 5600 256 50 band we want it to have a much higher probability of being able to detect the radar pulses in the spec at the time it was a 60% chance of it of it being successful we want it up to 99.99% big leap anyone has ever tried to do reliability of links from say what they call four nines to five nines reliability just going one extra nine on the end is a massive amount of extra reliability the other thing that they realized was that they do a noise floor calibrations spin the radar goes round the whole of the sky measuring just the background noise level it's not transmitting at all and so what they agree was what they'll do is every now and again they will transmit test pulses out into the air as they're doing the noise calibration procedure so as to increase your chances of picking up their radar when they're doing the receive only path the receive the receive only bit so we're now on eight dot one dot 8.1 and on the top band c-section we're up to 1.2 DeLand that ones hardly gone through any changes at all I will flip through these because you can read these later so after making all these massive changes did it make the slightest bit of difference now twelve countries in the EU are regularly reporting interference to their regulatory authorities and in the UK that would be Ofcom it is a major problem hungary reported for one entire month their system was down it was getting so much interference they couldn't pick up any rain they couldn't tell the difference to being a Wi-Fi signal and whether it was a lump of water in the air what does it look like if you can you can go to any of these countries websites and you can see it every single day for yourself that's the check one that is not rain that is a Wi-Fi signal you can see the pulsed transmissions from the WLAN system and it's then seen as lumps of water in the air in a single line going away from the radar there's the radar site so the interfering signal is somewhere along that line like a direction finder beam the Czech Republic has got so much interference that they actually publish a bad list they actually now using their radar to receive the SSIDs and they're publishing all the SSID names MAC addresses SSID and radio name is being published on their website every single day and I looked at it the other day and those all there was 40 40 different links that were being on that URL Spanish radar nice good beam of garbage they're coming through that's not a block of rain Spanish again nice good beam of interference Belgian radar definitely interference that's not rain the French getting it Latvia as well loads of interference from five gigs users here's one in real time you can actually see here how the bands of interference keep appearing and they're all pointing back towards where the radar site is near Bucharest you see them there how about the good old UK yep UK gets it as well okay look sexy there's another one just towards the end so this one's affecting an Irish radar site which is teed in with the UK system they get shared with the UK authorities they get the data fed through to them it'll come up again just towards the end so somebody somewhere in the Irish Republic down there is causing interference to the Met Office and what's the name of the regulator down there alright comrade so they'll end up making phone calls and ringing around and try and find out who the guilty person is it come up again in a second so what's happening is the radar is going round slowly over a 30 minute window so it's taken quite a long time you can see here in five minute increments the next time the radar is coming around and looking at the point-to-point length is causing it here we go okay that's going to make it difficult for the weather analysts to actually work out whether there's any really any root you know rain there or not so there was a working group and they came up with just said right in a typical year can you send us a report into the EU of what you've had to put up with and this is a list so in Latvia for example there's been 23 reports of interference up to 20 kilometers away from the actual radar site in the United Kingdom they've had thousands of reports the UK Ofcom has had so many reports that they lost count they didn't bother sending them to the EU of every single report they just said trust us we've had thousands of them we actually physically went out the door and chased down and found the source of 24 of them because they were on the air long enough for us to be able to get the Land Rover out and find where it was actually really coming from because we couldn't figure out who it was we had to go and do it the hard way but you can see up to 100 kilometers range those radar have actually got about 150 200 kilometers range so in in the Ofcom one what do they actually discover they found two wireless point-to-point you know two wireless cameras so they just educated the engineer to retune it to the different frequency in five gigs they came across eight wisp point-to-point links three of them had DFS enabled because they had them disabled and five will just simply retune so that's the eight of those sorted a cell phone enhancer that's not Wi-Fi that's someone using an illegal amplifier it was causing interference on five gigs so that was removed by the Enforcement Team and they were left with a pretty little piece of paper which said we own it now if you really want it see us in court masthead amplifier you know mastered amplifier on the top of a UHF TV erial they go quite often into local they're going to like a self-oscillation mode there's such a high gain amplifier inside them if water gets into them at all it affects like shorts it out and the thing will actually take off it's not self oscillating and if you look at it the spectrum analyzer on downs you'll drive down the street you is not very difficult to find strongest in the direction of where the aerial is pointing because that's what's now amplifying the direction where it's feeding so CC there was a mastered amplifier that was causing interference there was a military raid armed it was non-standard if non-compliance it did not actually comply with the regulations so even though it's the military Ofcom still have got the ability to say to the military no no no you can't do that there was an unknown military one again and ten that they never did find where where they were they just couldn't get to the bottom of it and there comes a point where you just have to call the dogs off you know you just they're not causing interference anymore we can just write this off we're never gonna find it we're spending more and more time looking for them and not getting anywhere so where are all the radars well in the UK you can get that from the Met Office website and also from a really good one which is the EU Met net site they list every single radar site in their organization with their frequencies and everything here is the UK list of the EU met nets you can see the exact frequency that they're operating on Jersey has declined to comment but every other one all of the others have all got their frequencies in their lap Long's so you can then plot them on your own whatever system that you've got for where you know where you where you got all your base stations located you can then figure out whether an antenna is pointing in that direction or not that is the spec of a radar look at the size of the dish it's a four meter dish they're running 250 kilowatts on the transmit side 150 200 corners of range it's a helical scan that I was saying before it is not just a spinning round around very very fast it's a very very slow scan so it picks about quarter of a an hour to do one scan and they use two different pulse repetition systems one slow one fast how wide is a Met Office radar it's about 30 Meg's wide can't see on this graph because it's just off the edge unfortunately off the right but there's another lump of energy about 100 megahertz higher up so you've got the main lobe of energy on the frequency that they're licensed for and also 100 makes further up so that would be 5,700 ish there'll be another lump of radar energy so if you're operating in bands see or write the top end of the band you can still get radar detection hits from a radar that is not on your frequency but is actually on 5600 something that is just magnetrons that's the way they are it's the nature of the beast magnetrons will generate the majority of the RF on their design frequency but they will also generate RF about plus 100 mix off common the Met Office are slowly organizing a way of tightening up the specifications so that they can filter out with a cavity filter the 100 Meg's but it's a bit difficult we're talking about plumbing now this is real mechanics this is big-boy stuff you know it's not just a case of making the capacitor a resistor and creating a filter this is 250 kilowatts of RF and needs large amounts of tubing oops quickly go over the DFS process there's two attention please attention please please leave the building thank you one two three we can settle down thank you for your patience part two well what we just suffered there was a radar detection and we had a 10-15 minute outage didn't we thank you for that demonstration so what does DFS do DFS has two two major component parts which is that before it becomes operational before it allows the wireless to start transmitting it just listens only different amounts of time usually a minute for the mess for the majority of the band but in the 5600 256 50 slot it listens for 10 minutes because it takes a while for though remember for the dish to come around so after 10 minutes if it has not received any radar pulses then it will bring the transmitter up alive on that frequency it will then continue to listen in between transmissions every time the thing is receiving the usually a throg ship set in the case of mikrotik root or s the a thorough skip set is constantly looking out for radar pulses and if the earth rose chips are chipset gets a hit it would then pass that information through to route OS and then Rooter s can then make a decision as to what to do about it if DFS is disabled it ignores it if DSS DFS is enabled which is it is now mandatory setting then it will kill the operation of the transmitter it just goes off air and it will now go to the next frequency in the scan list and see if there's any radar on that for a kak time and if you're in the 5600 256 50 section every single time it will listen for 10 minutes that can be quite a lot of outreach time one of the things about the way the regulations has been written is the regulation says you don't have to do a channel availability check if you've already done one recently so in theory what the regulations say you can do is that whilst you're actually operating on the frequency you're actually on at the moment you can actually conceive as well so in parallel you can hop off in the spare airtime and you're allowed to check the other frequencies to see if there is any radar on those so you can do the CAC the channel availability check thing during an operational is M phase Rooter s doesn't do that but the regulations allow you to do that so that means that when you do hop because of a radar you don't have to be forced into doing a whole brand new ten minute wait and have to the regulations say if you've already done it already because you've looked ahead then you can use that information to start going straight into is M the in service monitoring state what's the biggest problems with DFS is basically is false positives false positives is the biggest problem that has caused so many operators of wireless links to disable DFS you don't know whether they're pole that they're they're false or true you don't know if you've really picked it's not like in the log it says detected meteorological office Thurley radar site on this frequency and you look at it and go oh yeah that's it yeah that's the frequency they're on as well it just simply just says radar detected but was it what it really means is is we think radar was detected because that's what the chipsets told us the chipsets told us that it's receiving these pulses which matches the signatures that are embedded within the HC specification so I'll believe it if it says is radar there I'll take its word for it and it will then trigger a DFS change of frequency the problem is is that these triggers can cause quite long outages times you can be having a link gone off air for easily half an hour especially with other vendors equipment they can be offline for a long period of time and if that's a backhaul link and a few hundred megabits of traffic and you've got no other links running in parallel we've got no redundancy built into the system that's a very long embarrassing silence well it won't be completely silent because your phone will be ringing all the time from customers saying you've got no internet so that's why a lot of them ended up hacking the firmware or finding ways to get around it the other problem is is using older firmware meant that then became vulnerable to virus attack we all know about an event that happened over the last year it actually also happened a couple of years back as well it was the same firmware the same vulnerability just got hit twice one-eyes pete was out for over a week fighting desperately to get their systems back up and running again because they just get wiped part of the virus attack is that it wipes the whole config and that's your whole network just gone down the tube very very quickly indeed within minutes the whole network was was around their knees so that has caused the industry to look at it and go we don't like DFS I'm turning it off but why are you getting false positives one of the biggest reasons that I have seen four pol for false positives is because you're all running those who are getting it are running far to hire a transmitter power easily I've seen point-to-point links being used with 30 DB I or greater dishes they're running at the maximum output power of the radio and that actually calculates in at about one-and-a-half kilowatts I'm glad I'm not climbing the tower and walking past the front of that dish one and a half kilowatts is there's a very very high level and it's illegal anyway you're only allowed four watts as a massive jump in difference between four watts erp and one and a half kilowatts and the downsides are running these high powers is yes you can do a link that's 20 30 miles long and you can get some decent throughput out of it and you think that's fantastic this kit is brilliant this stuff the downside is is the reflections you're getting from nearby reflective objects the end of the transmission that the radio is transmitting with goes off air it then switches into receiving mode because a half-duplex system and what it then picks up is it picks the tail end of itself reflected back off some object nearby and then thinks that's a radar pulse it's a it's a miss diagnosis it isn't really radar but that's enough we're out here we're gone DFS result you know that's it we've triggered we go off air so by just simply turning the power down two things will happen we've found consistently that by turning the transmitter power down you won't get any DFS triggers anymore the second thing we found is the link drops out and doesn't work anymore but that because it was engineered wrong in the first place okay if you're going to design a system that's illegal it is going to come back and bite you in the backside at some time in the future you are you know working on borrowed time but that's the problem very very very common problem reflective surfaces solar panels on rooftops the edge of a building if you're mounting it too close to things they reflect and you will get that RF come back to you and because you're running such a high amount of power the reflection may be only very very weak but it's enough for it to think that it is a incoming radar pulse so by turning the power down you then make the reflections go down you don't hear them anymore so you don't get the triggers anymore the other thing of course is keep up-to-date with the latest firmware revisions because the vendors the actual manufacturers of the equipment are getting wise to these false alerts and they are writing new code you know if you complain if you raise support tickets they can then look into it and try and find a way of making it less sensitive but still trigger legitimately with legitimate radar but less so often with false alert right type transmissions so make sure you keep yourself up to date so where are we at now we've now have got it on 637 the announcer went out in the changelog which I have to applaud the verbosity of the changelog is fantastic I was one of the ones that for many years kept complaining about the changelog and it would say we fixed something I found a change log going back it's very very very very very to the early days and it just said we fixed some bugs that really helps me but now we've got a cracking brilliant system now where everything is listed and in one of those DFS is now mend a tree so what do we do the problem is is that when it now turns on the operating system when it boots up the transmitter will stay offline and it will do a kak if you're inside the 5600 256 50 then it will sit there for 10 minutes if it's anywhere else in the band it will do it for one minute if it finds radar on the frequency that you've got programmed into the frequency field it will then start going to the scan list now the scan list if you haven't edited it it will have the first entry is 51 80 if you set outdoor point-to-point link what are you doing operating on 51 80 not permitted but it will operate on 51 80 no DFS no kak time she'll come up straight away and you'll suddenly find that all your links are on 51 80 so edit your scan list and make sure that the scan list has actually got legit frequencies in it for in the UK Ofcom bands b and c not band aid the other thing is that the DFS checks in root RS are only performed on the AP so the actual AP or AP bridge will bridge mode is going to actually be doing the DFS checks not the station and this has come about because in the regulations it says that you have a master and a slave if the master is in control of the frequency that the channels going to be operating on then the slave does not need to actually do a DFS by itself so the slave is getting the information from the master for your quick response to our emergency situation which now has been dealt with we apologize for the inconvenience caused and we sure love eBay thank you hang in so if you have got a radio operating in any of the station modes station bridge pseudo bridge all the other wonderful modes that you've got they do not do a DFS check make sure that you are not operating in the actual band itself where the vast majority of weather radars are try and avoid those frequencies if you can try and stay out of fifty six hundred two fifty six fifty if you're going to be deploying a new link have a look at the direction in which the antenna is going to be pointing in remember are giving you the links you'll see them on the PDF when you download them from mikrotik the eve net net best of three right this is what you get with DFS isn't it constant interruptions this a beautiful example but it's not what I wanted not what I wanted okay so make sure which direction you're firing the antenna in check against the map look to see if you've got a weather radar in that direction if there is one don't use it or flip the link around so that the AP and the station is the other way around you're still potentially going to be causing interference remember because the antenna at one end is still pointing towards the radar station there is still a risk of damage being caused by interference but you won't know about it until you get the phone call but at least it won't keep getting triggered so it's not the best advice but you know if your backs up against the wall you know sometimes you've got to do these things to get you out of trouble quickly and then you think that I'll try and sort out next week which then becomes next month which becomes never but I know what it's like ultimately I can see this being a real bad bad bad thing for five gigs a DFS is a danger I think to the five gigs usage because we're going to end up having to just push more and more stuff on to other radio bands we're gonna have to leave five gigs we're going to have to actually we can use it for some parts of the radio spectrum but certainly in very very congested areas you're going to have to start using other other kit so 24.1 the E and the V bands light license scheme stuff very very low cost fifty pound a year and very very very suitable bands to use or you can go over to licenced equipment yes there is off comm legitimately license to six gigahertz equipment there are two bands in six gigs 6l and 6u six lower and six upper I'm not aware of any low cost equipment being used on six gigs I've checked the Ofcom register and all I have found is very very very very very expensive kit being used on six gigs but there is spectrum available you can use six gigs if somebody wants to be the first one to give it a go to try and get a license for use lower-cost equipment on six gigs feel free to try otherwise you're gonna have to use the higher frequency bands 13 15 18 24 and then you're now talking about professional carrier grade kit but that link will stay up once it's deployed it will stay up and you can get like five nines reliability out of it if you're not making it too long a distance if it's longer distance links you'll get it you can get it to four nines reliability but you know you're talking about easily a ground a couple of grand license fee every year on top of the capital costs for the kit itself the price we're going to have to pay bottom line last thing of all is if you really really really are sure that you don't want DFS and you are able to sleep at night without any worries or concerns about the phone call from the regulators you've always got super channels but remember how the system works there's a latency involved in it every time we find a workaround the regulators will shut the door on it at some point in time in the future so even though you can use super channels which then turns all that off there will come a time ultimately when that will get taken away as well the last remaining thing what about caps man that's a Wi-Fi controlling system it's a fantastic Wi-Fi controller system what's changed without noting because it doesn't do DFS anyway but again for how long mikrotik are not stupid they are going to be looking into this at some time in the future it's on their work list and Katzman will also then have DFS implement upon implemented it on it as well but for the moment if you're using caps man to do a Wi-Fi deployment say in a school DFS is not going to be of a concern to you so good luck and let's be careful out there thank you very much any questions I can't answer any questions I can answer cracking next thank you very much Weldon McRoberts here

Channel: MikroTik

Views: 21,908

Keywords: mikrotik, routerboard, routeros, latvia

Id: ZbrbRUAfpac

Length: 73min 8sec (4388 seconds)

Published: Wed Nov 16 2016