Chapter 19 – Catch a Wave-Guide and You are Sitting on Top of the World

The Beach Boys are going to hate me for this but I’ve been waiting for years to use that line. I also wanted to title it, “Look Ma, no mesh” but I should have used that one several articles ago. It’s not that I have anything against mesh as there is an application for almost every technology. At this point in the industry and the economy, however, it’s time to get past a word very few non-technical people understand and the excessive associated cost of it. Anyway, this article is about wave-guide antennas so let’s get back to that.

Vivato was a wave-guide based antenna. I have had Securawave wave-guide antennas installed for about 7 years. I became a believer when I connected a car at 2 miles and my laptop inside a Jack-in-the-Box at 1 mile. The horizontal polarity was a huge advantage since most wireless APs were vertical polarity. Securawave is no longer in business so I’m hoarding the last few units I have to support units I have in the field. Not that solid aluminum blocks have a tendency to fail as I suspect they will last longer than the buildings they are mounted to (they just don’t make them like this anymore), but in case of physical damage. I don’t need dual-polarity and 2x2 MIMO yet in these areas because Qwest hasn’t figured out how to get more then 3Mbps over the so-called HD Internet services and I’m not ready to mortgage my house for their other service offerings. Of course it’s hard to dial the phone when your eyes are tearing up from laughter when they advertise their new 40Mbps service. 18 months ago they couldn’t even keep a 640Kbps DSL line running properly in the middle of Phoenix less than 1 mile from Sky Harbor Airport.

Historically, wave guide antennas were expensive to make which is probably why it didn’t have more popularity. Ubiquiti seems to be bringing it back with its new omni-directional dual-polarity antennas. We know that dual-polarity has better penetrating and range capability than single polarity. So the idea of extending that into an omni-directional antenna seems like a great idea. Since there isn’t any other 2x2 MIMO omni-directional dual-polarity antennas that I know about, this is really cool from a technical, design, and financial standpoint. It’s also how we are going to keep Guerilla WiFi cost-effective and make it better.

The new Ubiquiti omni-directional antenna isn’t a true wave-guide antenna. Since it needs both polarities, half the antenna is basically two 180 degree vertical polarity sector antennas back to back with dual 180 degree wave guide antennas. Since it’s not out yet, I haven’t tested the unit but the pre-spec guess is it’s around 12-13dbi. That means the effective LOS range with dual polarity is going to be about 30% farther than an omni with 15dBi of gain for a couple of reasons. However, real world performance is going to be significantly better since dual-polarity will definitely penetrate vegetation better, reduce noise off-polarity, and reduce fading. If the client is using a dual-polarity indoor radio, then not only will range be better, noise will be significantly reduced even further. I smell a huge performance improvement in the air for Guerilla WiFi.

Let’s go back to Chapter 1 of Tales where we designed a $10K per square mile system. In that design, we used a 15dBi omni-directional antenna with a single polarity omni-directional. This design was using a single stream 802.11 b/g/n design. With the new dual-polarity omni-directional antenna, we still use a single radio for our AP but we have doubled the throughput with a 2x2 MIMO stream. In addition, we have doubled the throughput of every hop and added an additional hop. Even at the 4rd hop we are still delivering up to 10Mbps. Keep in mind that at a 10-1 oversell rate, that means that you can sell twenty clients 5Mbps at the end of the chain. Although pricing hasn’t been released, I’m pretty sure this antenna with a Rocket M2 radio will still cost less than $300. Double the performance of the original Guerilla WiFi at no additional cost and it’s better than triple coupon day at my local grocery.

Think about that for a moment. If we only had one egress point for our network, our base network was limited to 3 hops with the same capacity at the end. This single antenna, which allows us to change from a single stream 802.11b/g/n radio to a 2x2 AP, doubles that throughput, thus extending our single AP model out even further and doubling bandwidth down the chain. Our egress point can also use multiple radios which can triple the throughput to 3 times that for $300-$600 more without even getting into out next topic, GPS Synchronization. So for less than $11K per square mile, the system now supports 180-300Mbps, depending on the clients. So if your town is 20 square mile and this whole system cost $250K to put in, then it’s a no-brainer simply for cameras, security, mobile access, and department efficiency. Of course, if it goes through federal funding, has government engineers add in the fact that it has to support mesh (pointless in this and most designs but adds significant costs), throws in ridiculous temperature requirements like -30C for Phoenix or 80 degrees centigrade when -75 degrees centigrade would work fine, and requires copious amounts of paperwork to tell 14 different government agencies that you are paying wages equal to union scale even though you pay your guys more than that, then it’s going to cost $1,000,000 (my English teachers just had heart attacks over that sentence). If you can sense my frustration with federal rules that require union contractor shops to do work that is clearly better suited to IT companies, then you are very astute. This is why projects involving the government cost so much and take so long.

If this is a for profit network, $250,000 to cover 20 square miles with this level of bandwidth is pretty impressive. It’s fairly easy and cheap to add 100Mbps backhaul to each square mile for a total of 2GBps for the entire system. Realistically, I would guess that you would get about 500Mbps before the price starts going up for full-duplex links. Keep in mind that we are back to the core idea of an inexpensive municipal deployment.

Using numbers from previous articles, let’s assume 800 potential clients per square mile. If we get 10% of that base at $30 per month, that’s $48,000 per month. With this type of system, only a very small percentage of clients are going to need truck rolls. Total revenue on this network is almost $600K per year. If users have to get client radios, then they start at $30 for 802.11n 1x1 Vertical Polarity CPE’s. For about $80, you can include a window mount and get 2x2 MIMO. In most environments, I would be surprised if truck rolls needed to be done on more than 10% of the clients. Even if you add in the cost of the client radios, this system should be cash flow positive at 800 clients and should pay for itself at 2400 clients within 12 months. This just covers residential and doesn’t even get into business revenue. The numbers are now speaking to me so it’s time to kick the venture capital market back into high gear.

Also consider this, the 16 AP per square mile strategy now covers a higher percentage of deployments, especially profit oriented ones. If you live in the middle of high-density city, then you would want more APs per square mile for density or you fall back on the super AP concept described in previous articles. Since WiFi is far more unpredictable that PTP RF modeling, there is nothing wrong with installing 16 AP’s and then site surveying to see if there are coverage gaps than hinder more revenue.

Cell phone companies don’t cover every square inch of every house on the planet. It’s not cost effective. They deploy with the best models they have and then decide if it’s profitable after field testing to fix poor signal areas. WiFi should be deployed the same way. Put up 16 AP’s, field test, check the areas with poor coverage, and then decide if it’s worth another $300 in equipment to cover that area. If an area has higher usage, add in a triple radio AP upgrade for a few hundred dollars more. If an area really just needs more signal gain, look at adding a beam-forming AP just for a specific direction. There are many options but all of them would be based on sound profitability principals. There is nothing wrong with walking away from 2 customers that might cost $3000 to add additional infrastructure to cover.

I have 2 “Peeves of week” I have to get off my chest. The second is 99.999% uptime. I was asked to design a system where I have to guarantee the CPE’s have 99.999% uptime. Since the wireless industry has new equipment out every few months, very little of what I would deploy today has enough history for me to put my reputation behind that request. I’m not talking about PTP full-duplex $10K and put links but $50-$400 CPE’s. First off, anything less than 802.11N is too old and too slow for this type of video application. Second, anything that’s 802.11N hasn’t been around long enough to know how it’s going to run 3 years from now. It’s kind of a catch-22 situation. That means using cameras with built-in recorders that are going to cost three times as much or more than using lower priced cameras with CPE’s. Unfortunately there is no product history out there than guarantees that. The reality is that all the radios I work with rarely, if ever, just simply go offline if installed correctly. That doesn’t mean that they aren’t going to down for planned firmware upgrades or other system changes. However, the 99.999% uptime request didn’t stipulate whether planned maintenance was included.

I’ve already mentioned my first pet peeve, municipal bids that ask for mesh when every AP connected has a directional antenna. To everyone who keeps adding this expensive request into these bids, it’s a waste of money taxpayers’ money and costs the city a lot more to support in the long run. When you add a directional antenna to an AP or CPE, it’s a PTP or PTMP design, regardless of what firmware is on there. There is no mesh because the radio can’t connect to anything it’s not pointed at. By adding the mesh requirement, you are either getting the most expensive product out there or White Box APs with custom open-source mesh firmware that is cheaper. I’m not saying there isn’t a place for mesh, but don’t eliminate other options like WDS. It’s not your money you are spending; it’s ours, the taxpayers. Let the industry and a wireless engineer decide what the best product for the design is. It shouldn’t be the salesperson that took you out to lunch last week and has shiny brochures. If mesh is appropriate and the best fit, let the companies bidding on the project put that down. If WDS will work just as well or a PTMP design is better, they will bid that. So can anyone guessed what crossed my desk again this week? I know I’m beating my head against the wall on this since arguing with government is like trying to tell a 3 year old that candy isn’t good for them.

So we have come full circle on Guerilla WiFi from $10K per square mile to $50K per square mile and now back to $10K per square mile with double the performance. If this doesn’t kick the industry back into high gear, I’m not sure what will. Next we will cover GPS sync and how that affects deployments strategies.

Chapter 18 - Demystifying Beam-Forming

Based on some of the emails I’m getting, the biggest complaint is not enough details and without them, it’s difficult to implement the idea. Fair enough, I’m definitely guilty of that. In my defense, please understand that I want to have a personal life. Not that I have one now, as most WISP’s can attest, but if I had to put down every single detail on every single project or idea, I would be writing from here to Kingdom come. Except for the 6 guys on the planet like me that think they ought to make a movie out of every article in EETimes (I think a lower noise figure on a 741 OP-Amp makes a compelling plot line), most of you would be cancelling your Ambien prescriptions. The reality is that the details only matter to technical people and those are called White Papers. I’ve written a couple but I can’t sit still long enough to finish dinner, let alone do a 20 page technical document. My wife says that if I had put as much time into my homework as I have these articles, I would have my Master Degree by now. Of course, if University of Phoenix gave me real life credit for standing in a man-lift hanging antennas 80 feet in the air, I could get my Doctorate without ever attending class.

Let’s get back to the really cool stuff like beam-forming. We covered 900MHz and both the positive and negative aspects. Let’s move on to the category of what’s old is now new again, beam-forming. Vivato pioneered the idea several years ago but the financial model, coupled with irresponsible pre-marketing, didn’t really work in the real world. However, they did get the FCC to change the rules which is going to be a very good thing moving forward. The difference is how the different implementations of beam-forming are implemented and the effect in the real world, technically and financially.

Long before Vivato, the Super Scanner antenna from Antenna specialist tried to get an antenna to function in both a directional and omni-directional mode with the turn of a knob. Some of the manufacturers such as Wavion and Netronics sort of copied this model by using a ring of vertical omni-directional antennas. They can get up to 12dBi of antenna gain off of 7-9dBi antennas. Currently these units are limited to 802.11b/g bands and vertical polarity.

The next kind of design was done by SkyPilot where they simply rotated connection to one of 8 integrated sector antennas at any one time. This gave them up to 44dBm of EIRP in the 4.9-6.0 GHz bands. Ruckus, Netgear (with Ruckus helping), Cisco, and others are now integrating the antennas on circuit boards but at a lower gain. There will be several antennas cut into the boards or some other internal antenna hardware to add vertical and/or dual-polarity to the board that provide directional coverage. These designs are achieving up to 10dBi in gain with the bigger advantage being the noise reduction from other directions. They use the model of picking the 2 best signal antennas to receive the signal simultaneously since doubling antenna capture area provides up to a 3dB increase.

Vivato is still the technical King here in this realm though, although they weren’t covering 360 degrees. Vivato achieved 24dBi of gain in a 100 degree pattern in 2.4GHz. The catch is they did it for $8,000-$15,000, which meant I could either buy a new van for my company or 2 APs. That sort of limited the market for the product to the point that they are no longer in business, which is also what happens when you don’t listen to your vendors trying to sell the equipment. However, that 24dBi of gain is a huge advantage for reaching underpowered smartphones. Since Ubiquiti has now announced that they are releasing a beam-forming product over the next 2-4 months, the question is, does that have value for a municipal design?

Getting back to today, Wavion’s newest product, the WBS-2400 is probably the closest to the Ubiquiti beam-forming radio. It’s also very similar to Altai A8-Ei product with multiple radios, sectored antennas, and one enclosure. Both products tighten up the beam and assign a single radio per antenna. Unfortunately, both these products are still b/g.

Going back to the formula that distance doubles for every 6dBi of gain, if a 2.4GHz beam-forming AP has 21dBi of gain, or what I’m guessing the new Ubiquiti units are going to be, that almost quadruples the range of most omni-directional AP’s. Throw in the fact that noise will be reduced by at least -20dB, and the s/n ratio goes berserk. The effective range increase, and this is only my best estimate in the worst scenarios, is probably a factor of 8-16 in open air environments. This means hitting a smartphone at 3000-4000 feet or more is possible.

Here is where it gets interesting though. Based on past experience, I’m guessing the Ubiquiti beam-forming AP will be less than $300. That is 10 times less than other beam-forming products, none of which support 802.11N 2x2 MIMO. Heck, it’s less than I paid for a baseball bat last season.

We were all trained to think in terms of APs needing to cover 360 degrees for municipal deployments. Every product out there is designed for that. The end result of this is when the density reaches a certain level, the self-interference is basically self-defeating. I’ve seen proposals that suggest 60 APs per square mile for example. Central management systems can dynamically adjust power output between APs to reduce the interference and can simultaneously adjust power output on a per packet basis to reduce the interference even further. However, all this costs which effectively drives the price up to $150,000 per square mile or more for this level of performance. However, what in the playbook says that every AP has to have omni-directional coverage?

Throughout this series, we’ve been driving towards a low-cost, high-capacity design that can be commercially deployed. The original idea was trying to develop an inexpensive Super AP. I’ve gone from $200 to $2000 and was working on an idea that would have driven the cost to a retail level of $4000. It supported 1Gbps per AP and 700+ simultaneous clients, but still it got away from my original idea which was to lower the bar on the per mile cost, which it didn’t accomplish. It basically comes down to the following, are you trying to compete with cable which can deliver up to 50Mbps or delivering Internet to people who have to suffer with dial-up, or worse, DSL delivered by Qwest in Arizona (okay, bad joke).

Beam-forming lets us start with a new playbook. The first thing you do in a playbook is define your assets (okay, I never played organized football so I’m making this part up.). Using the Ubiquiti beam-forming product (2.4GHz version), we know roughly that we will have about 21dBi of gain, 90 degree coverage zone, 16 degree beam pattern, GPS synchronization, and 2x2 dual-polarity 802.11N MIMO. Since we can now hit a phone at 2500 feet without much of a problem in open air, the design mentality changes. Even with 21dBm of gain, we still aren’t going to penetrate several buildings. However, we probably bought ourselves another house or two. By changing the angle of transmission, ala cell towers, and to be fair to Vivato’s deployment design in Spokane, tops of buildings aiming down, and all of a sudden we are hitting several houses down the street. Throw in 2x2 MIMO dual-polarity, and the connection distance goes way up.

Because of the price point, I’m guessing Ubiquiti’s product uses the same type of design as SkyPilot in terms of switching between multiple feed points on the antenna. The difference is that each feed generates a different angle of radiation versus being a completely separate physical antenna. Ruckus hits multiple feeds also with circuit board based antennas.

Although the tops of buildings aren’t ideal for sector antennas due to amount of AP’s that are going to get picked up, if you aim it towards the horizon, angle it down 60 degrees or more, you still get coverage down the street and pretty impressive building coverage. At that angle, you are reducing attenuation from outer wall penetration and even taking the route of shooting through the roof. This doesn’t work all that well in areas with trees, but if the buildings are made out of concrete, brick, or stucco, then this might be the best option. There are a lot of cities where the street lights are decorative and there is no way to install an AP down at ground level, so secondary options are a must. Beam-forming makes this design more useable by effectively reducing the beam pattern down way down.

This model might work in a different way also. Think in terms of 3 dimensions instead of 2. Larger buildings or apartments in downtown areas might be 10 floors or more. Placing these antennas on the side of one building several stories up and aiming into another building let’s you build a vertical WiFi Although attenuation has been a killer, 21dB of gain makes up for a lot of wall and window attenuation. In addition, dual polarity will improve penetration even further. If you pick up 30 customers in a building at $20 per month, 3-4 antennas pointing into the building get paid for in a couple of months. I would have also said it’s significantly cheaper than AP’s in the building until I saw another product that I’m testing (to be discussed later). However, when you add in the savings on pulling cable, it’s a no-brainer.

Irregular areas with streets curving all over the place are another option for this type of design. Intermixed homes and small business areas with mostly 1-2 story homes and 2-5 story buildings work well for this design. Outdoor coverage is universal with indoor coverage hitting around 80% or more with careful planning. Keep in mind I’m assuming everyone wants to give you free vertical assets to enhance the system.

Bringing us back to earth gives us most of the real-world deployments, street lights. This is where the GPS synchronization really kicks in and is now the direct comparison to Wavion or Ruckus. Placement of four of these radios on a pole to cover 360 degrees provides the absolute farthest range of any AP on the market. This is only possible with GPS synchronization to keep them from interfering with each other. It effectively provides twenty four 16 degree beams shooting out in 360 degree pattern. The cost of this super AP will be about $1500 which isn’t a lot less than Wavion or other beam-forming 360 degree APs. It does have significantly longer range through, by a factor of 9dBi and dual-polarity which is worth another 3dB in my field testing. With the IPad supporting 802.11n and the Beam-Forming antenna supporting dual-polarity, this would be a potent combination for off-loading some bandwidth.

If we duplicate this design with Altai or Ruckus, the cost is now over $10K per AP. There are other manufacturers such as Motorola that use sector antennas but then the antenna gain drops back to 12dBi or less and their beam patterns are 120 degrees. The best way to reduce noise is to decrease the beam pattern which it also doesn’t do. Effectively we get a 9dBi increase and 20+dB of noise reduction for a cumulative 29dBm improvement in s/n ratio. Regardless of what wireless philosophy you follow, that’s huge.

Here is one of my philosophies though, “If you spend too much, all you have lost is a little money. If you spend too little, you could lose everything.” Guerilla WiFi is based on the concept of being the most cost-effective way to deploy and what I feel is the only way to make municipal wireless a self-sustaining profitable model. That doesn’t mean it’s the best way in every situation. I’m describing equipment that isn’t even out on the market yet and isn’t field tested. Wavion, Ruckus, Altai, Bel-Air, Motorola, FireTide, Cisco, Enterasys, and a host of other vendors are proven products that have been deployed and tested. I do think these vendors are making it difficult to meet the financial needs of a profitable municipality model which is where Guerilla WiFi comes in, but the products are solid. This models works for me and others who are willing to spend the time to work through early firmware issues and fine-tune the models during deployment. It’s kind of like the difference between Linux and Windows. Since Ubiquiti uses a common firmware platform across all of their outdoor products and has made great strides towards stability and features, I expect the new products to use the same firmware base which means , the firmware. However, there is still a long way to go towards a turn-key municipal deployment without a lot of engineering intervention. Based on the cost/performance ratio, I believe it’s worth it. But realistically I spend a lot of time testing and adjusting. Most customers are going to expect a more turn-key solution. However, if it’s your money, then this solution provides the best chance of financial success.

With this AP design, $1500 per AP is getting pretty pricey. However, it will also combine with our next article, the 360 degree dual-polarity 2x2 MIMO AP for under what I’m guessing is going to be $300. I’ll try not to wait 3 weeks to make this happen.

One other note that I want to mention is that Mike Ford is no longer at Ubiquiti. Mike was a central figure that seemed to have his hands in everything from testing to customer support. Over the last 3 years, he has become a friend that always went the extra mile to make sure I had the resources I needed for my clients. He was also instrumental in some of my decisions on my deployments. Although I don’t know his future plans, I am very sorry to see him go.

Chapter 17 - Who needs White Space?

It’s time to step up our game. There is no problem generating massive bandwidth from an AP location. We have proven that fact. What we haven’t figured out yet is how to leap tall trees in a single bound or walk through brick walls. If you are willing to add in another 20Mhz of super-powerful, wall-penetrating, obstruction busting, tree smashing signal, then we have solved the problem.

You are thinking I’m going to jump on the White Space bandwagon. I’m sure I will someday but there’s a lot of work that has to happen before that option is available. However, the infrastructure we have designed is pretty flexible and inexpensive. When White Space becomes feasible and cheap (my favorite word), we can add it. In the meantime, we have two other options. I think I will save the best for last though.

White Space is touted for 2 reasons, extended range and building penetration. It also has one big disadvantage. In major cities, there may not be a lot of channels available according to Spectrum Bridge, for White Space to operate. In addition, limited power output from clients is still going to limit high-bandwidth range back to the AP. I also see the 6MHz channels being an issue with bonding being the same problem as trying to run 40MHz outdoors.

Before we jump into this though, let me make note that Ubiquiti just released a stack of new products that are game changers in WiFi, indoor and outdoor, Video Surveillance, and cellular service. These technologies cover everything from Beam-Forming to GPS sync to dual-polarity omni’s. I’ve had to hold back due to NDA’s but we will now start covering how these technologies can be integrated into our Guerilla WiFi design to take the systems to a whole new level. Most of these products are several weeks away from shipping so we have time to develop our system. I do a have a pair of the 900MHz M series 802.11N 2x2 MIMO AP’s in my hands and that is the topic of this article.

Option one is 900MHz. Yes, it’s crowded, noisy, and seriously overused. So is a Japanese subway but people still use it because it’s the best option. Until now though, the best WISPs systems limited users to about 3Mbps under ideal conditions with APs limited to about 7Mbps. There really wasn’t a lot of development in that frequency band due to the interference and reduced band size as compared to all the other unlicensed options.

900MHz has close to the broadcast properties as White Space except for the vastly higher interference. In a municipal system with 16 AP’s per square mile, AP’s are within 600’ so range of everybody. Unfortunately, 2.4GHz can’t penetrate obstructions very well. Brick or Stucco buildings that will suck the life out of 2.4GHz are merely a few dB of loss to a 900MHz signal. At that range, trees effectively disappear. Junior’s frequency hopping baby monitor and the SCADA transmitter hanging on your water meter is now more of a problem than obstructions. In 900Mhz, with 802.11N 2x2 MIMO now being applied, bandwidth isn’t the issue any longer. The biggest problem is interference.

Everything has a threshold though and you just have to find it. With parents, it’s how low your grades can go before you become the prisoner of the bedroom Alcatraz and your friends start filing missing person’s reports. With RF, it’s the difference between the signal and the noise and how efficiently we use the bandwidth. Now toss in a very narrow band, 26MHz, and the total bandwidth throughput from any AP is going to be limited. Oh, yea, did I mention that we only have to go 600 feet?

802.11N isn’t just for 2.4GHz and 5.8GHz. It just hadn’t been applied before in the 900MHz band. Ubiquiti just released several new 900MHz products with 802.11N 2x2 MIMO protocol. Using a 5MHz channel will allow up to 4 APs to operate on one pole, which each one providing up to 20Mbps. However, using buildings and some shielding, might allow up to 4 channels of 10-20MHz in more remote areas to allow up to 300Mbps. I’m sort of guessing here but when I get one of the base station sector antennas in, I will do some testing to determine what would be needed for isolation.

Keep in mind through all of this that we are still dealing with an AP/sector antenna combination that cost less than $500. If budget is an issue and the city thinks that a several 4’ antennas on a pole aren’t their idea of aesthetically pleasing, then look at using 4 of the Nanostation M900 Loco’s. They are very small, and although rated at a 60 degree beam pattern, they can easily cover 90 degrees with a small drop off in antenna gain. In fact, the beam pattern for these radios is way over 90 degrees at 7.5dBi of gain.

The only problem here is that you need one of these radios in or on the house since there is no portable device that can support 900MHz. That starts getting expensive at $200 for the radio and another $50-$150 for an indoor WiFi device for wireless coverage. However, the problem of building penetration is completely solved.

If I haven’t mentioned it before, we only have to go 600’ from an AP location if we have 16 poles per square mile. Realistically though, if we have 16 APs per square mile, I would probably only use a maximum of 4 AP locations with the 900MHz radios for budget reasons. That means we might have to go 1300’. Of course, we are using a proprietary polling scheme and a dual-polarity signal to go that far. If the noise floor starts at -65, the signal level needs to be at -55 or better. At 1300’, even with obstructions, our signal level should easily exceed that.

Trilliant and other Smart Grid companies are releasing MOAB (Mother of All Bombs) 900MHz radios that are up to 1W for residential installations. If you think that a few towers can cause interference, try fighting tens of thousands of radios dropped into the middle of your coverage zones. Motorola 900MHz WISPS from here to Canada are getting hammered and there isn’t a lot they could do about it. There are going to be cities where running 900MHz WiFi may not be feasible. Don’t panic yet, we will take our 2.4GHz game up a notch also.

There are two advantages to the Ubiquiti 900MHz radios to fight interference. One is the dual-polarity MIMO design. In the city though, most radios are using antennas with such low gain, polarity isn’t going to make a lot of difference. However, the M900 product line came out simultaneously with the ability to frequency hop. That means you have 4, 5MHz channels to jump around with at 300ms rates to avoid noise try and punch a signal through. If the Smart Grid density is too high, then even that isn’t going to matter but right now it’s the best option available.

The second advantage is AirMax. AirMax will simply ignore other packets in the band and also eliminate the hidden node problem. Although interference is interference, AirMax AP’s won’t slow down acknowledging other APs in the band.

Ahh, but what works for city folk works even better for country folk. The dreaded trees of death for 2.4GHz and 5.8GHz are merely pin pricks to 900MHz. Toss in the dual-polarity 2x2 MIMO design and now signal will punch through the forests like Ray Lewis through an NFL helmet. Expand out the channel to 10 or even 20MHz, and throughput for a single AP could go as high as 80Mbps.

On the muni-wireless issue, we can assume that designating 4 AP sites per square mile will add about $1000 or about $4000 per square mile. It also adds 320Mbps of total capacity per square mile. Add in the CPE Capex of $200 per client, assume 25 clients need this radio to avoid a truck roll, and you have an additional $5000. If you truck roll, add another $3750 in the Capex column for those of you keeping track.

Based on those numbers with a $30 per month fee and a free install, it will take 17 months to recoup the Capex. Of course, we want to charge $100-$200 for an install to offset some of those costs. In areas where municipal staff thinks antennas are cool and interference is minimal, we could even use four 900MHz dual-polarity sector antennas with 13dBi of gain. That will provide over 6 times the coverage area which might reduce the AP locations from 4 to 2 but it will more than double the cost per AP, which is a wash. There will be scenarios where either option will be more appropriate.

Our second option is the new beam-forming radios. I’ll cover that in more detail in the future. Since the 2.4GHz versions of these units won’t be out for another 4 months or so, there is no hurry. However, they add another 4-6dBi of gain over a sector antenna and 8-9dB of antenna gain over any other beam-forming AP other than Vivato. Add in dual-polarity, which my field testing shows to be worth up to 3dBi more useable gain, and a 16 degree beam pattern to reduce noise (I’m extrapolating from the 5.8GHz beam-forming unit that was announced. The final specs may vary.) and that that’s enough gain to penetrate an extra wall or almost quadruple the coverage distance to a client. I’ll go into the difference between between all the beam-forming units on the market in our next article.

Now we have even more tools to play with for Guerilla WiFi. Theoretically, it wouldn’t be hard to build a 1Gbps AP to work across multiple frequencies with beam-forming and GPs for less than $4000. Taking this concept even further, it also wouldn’t be hard to create a load-balanced, business quality, multi-frequency design that could bond these frequencies together for very high-capacity throughput. There are other variations of this for backhaul, redundancy, and uptime. It’s possible, with a little networking work, to create a mission critical design capable of delivering tens or hundreds of MB’s to a CPE for less than $400 on the CPE side. This type of system could easily deliver 99.999% uptime using unlicensed frequencies, even with scheduled maintenance. And don’t get me started on 900MHz mobile options. The hits just keep on coming.