Volume Number: 16 (2000)
Issue Number: 1
Column Tag: Hardware
by Neil Ticktin, Publisher
Every once in a while, a technology so grabs my attention, I just want to dive right in and play with it. In short, wireless is one of those technologies and it's just plain cool!
Today, connectivity is no longer a luxury - it's a requirement. It's not a matter of if you're connected at a specific location, but instead how much bandwidth and the type of connection you have. There are many options for bandwidth. Wireless has really matured and is frankly, an excellent, cost effective solution that should be put into play whenever it makes sense.
This article is going to take you through a real life scenario for replacing dedicated Frame Relay lines with wireless. Because wireless is relatively simple, this article will focus on the process and the results. If you are interested in the 802.11 standard and more technical information, look at the article in the December, 1999 MacTech which covers these in depth.
Why We're Running Away from Wires and Tel-Cos
For years, I've relied on Frame Relay to connect my home to the office, and the office to the Internet. For us, PacBell's Frame Relay network has been, let's say, less than reliable. So, we were eager to find a new solution. At the time we put in our Frame Relay WAN (1995), it was really the only option that made sense for us. Today, VPNs, DSL and wireless have really eliminated the benefits that Frame Relay had for us. And, most of these give you the opportunity to get away from phone companies, monthly fees, and more... a big plus in my book.
Some Wireless Basics
Spread-spectrum radio based systems like the Lucent WaveLAN are cost effective solutions that don't require an FCC license. The range can vary substantially - up to 40 miles with amplifiers, and easily within several miles. You can transmit at up to 11 Mbps using a signal that has a high resistance to interference.
Without encryption, there's still a fairly high level of security due to the spread-spectrum nature of the transmission algorithm. First, an interceptor would have to be in the line of sight. Then, they would have to find a matching frequency. They would also need to know network names, MAC addresses, and more, making things relatively secure. If that isn't enough for you, 64-bit key encryption is available, with 128-bit coming soon.
Getting the Right Help
If you are just setting up a short distance outdoor point-to-point connection, it will be easy. Why? There's so much extra signal, problems just don't show their face much.
Likewise, if you are going to set up an indoor wireless LAN with a Apple's AirPort or Lucent's WavePOINT, it's easy to do, and you should proceed without worry.
But, if you are going to do anything more complex than that, a tougher line of sight, or longer distance than 1/2 a mile, you should really look to have advice available to you.
One of the most knowledgeable wireless distributors out there is Winncom Technologies. They were recommended by several folks that I spoke to, and have solid relationships with Lucent, Aironet, BreezeCom, and others. They have everything and anything you need, from connectors to cables to antennas to the bridge and radio hardware itself. They will help you with site analysis, signal loss calculations, equipment choices, etc... A lot of what you learn in this article comes from what I learned from them. If this sounds like a commercial, it's because they were incredibly helpful, and knowledgeable and I would just assume that you have the same experience. Don't hassle me for touting them - believe me, they deserve the recognition.
You can reach them at: Winncom Technologies, Inc., 30700 Carter Street, Suite A, Solon, OH 44139, Toll Free: 888-WINNCOM (888-946-6266), 440-498-9510, Fax: 440-498-9511, <firstname.lastname@example.org>, <http://www.winncom.com/>
The Wireless Solution: Dollars and Sense.
With an off the shelf wireless setup, we were able to replace our Internet connection with an 11 Mbps wireless connection fairly easily. The bigger challenge was in connecting my home to the office... which didn't have line of sight.
For the Internet connection, we've been paying $500+ per month for a T1 Frame Relay (not including any costs for the Internet access itself), plus the initial cost of hardware. 11 Mbps point-to-point wireless connections, can be done for as little as $2000-$3000 in hardware and installation - giving us a payback time of 6 months compared to just the T1. One more thing: The wireless connectivity roughly equates, in real life, to three to four T1s worth of bandwidth... with no monthly costs.
For a WAN connection (such as my home to the office), we were doing a 56 Kbps Frame Relay connection (yeah, yeah, I know it's slow - but remember, 56k was a lot 4.5 years ago). This cost $125 per month, plus the cost of a router ($2500 then, probably $1000 now) and the Frame Relay installation ($1000).
Since we didn't have line of sight from my home to the office, we put in a relay point up on a hill that did have line of sight to both my home and the office. In our case, we mounted the antennas on this house up on the hill (giving them great Internet access in the process). Even in this more expensive scenario, this can be done for as little as $5000. That may sound like a lot, but when Frame Relay is unreliable, dedicated T1s are $1000, 128K DSL is the max, and there are no cable modems... it looks like a pretty good option if you need the bandwidth.
We took a look at two product lines - the Lucent WaveLAN <http://www.wavelan.com/> and the Aironet <http://www.aironet.com/>. As a side note, Aironet was recently acquired by Cisco. Both of these products are solid products that do the job well and are welcomed in our network.
There are a few primary differences between the Aironet and the WaveLAN. The Aironet is a point-to-multipoint bridging solution which allows one antennae and one Ethernet connection on each bridge. In addition, the radio is integrated into the bridge, so there's not an easy upgrade path. This is a nice, clean product that is pretty simple to use. The product uses a telnet interface for configuration.
Lastly, the Aironet radio is about two times the strength of the Lucent WaveLAN. By contrast, the WaveLAN tends to be a more sensitive radio not requiring as much power. Either approach works very well. In case you are curious, all of these are low power devices. While they are microwave, they are only putting out 30mW or so... so don't plan on cooking your chicken on stick in front of them. :) By contrast, my Nokia cell phone outputs up to 600mW nominal.
The WaveLAN separates the radios from the chassis and can have two radios per bridge. The radios are actually just PC Cards.
WavePOINT-II Access Point / Point-to-Point Bridge.
In fact, you can take the PC Cards out and just put them in your laptop. This allows for easy upgrades (e.g., from 2 Mbps to 11 Mbps), and swapping of equipment as well. The one downside is that to attach an external antennae or an extender antennae, you have to use a "pigtail" that you need to be careful with. We accidentally broke the tabs off of one and had to replace it. To me, dealing with this connector is worthwhile trade off to be able to use the PC Cards in the chassis and in my laptop. Given how small a PC Card is, and that you have to plug the antennae into the side of the card, it would be difficult for the connector to be anything more than it is.
Because it can have two radios, the WavePOINT-II allows you to use it as both an access point for your indoor wireless LAN at the same time as your external point-to-point connection - as we did. Or, you can use it as a relay point using two external antennas to get signal to a third location not in line of sight with the first - as we did as well. In general, I prefer the WaveLAN design approach which gave us incredible flexibility.
WaveLAN PC Card.
Before you go spending a bunch of time in looking at wireless equipment, your first step should be to figure out whether you can do wireless with a basic "site survey".
The primary thing with wireless is making sure that you can have a good signal path. This not only means visual line of sight, but radio line of sight. And, you need to make sure that you have enough height, and won't have issues with interference.
Visual line of sight means exactly what you think - can you see clearly from one point to the other. While it is possible to get the radio signal to bend around things, it is something that you really want to avoid (and leave to the professional radio installers). Optimally, you want to have a completely clear path. (See Radio Line of Sight diagram). to take into account the path of the signal.
Visual Line of Sight Diagram.
Radio line of sight takes into account the shape of the zone that the radio waves travel in. This is called the "Freznel" zone. Basically, the radio waves travel between the antennas covering an area that is shaped long an elongated football. (See Radio Line of Sight diagram). In other words, the clearance that you need halfway between the antennas is greater than right at each antennae. In many cases, this means that you are at an advantage if one of the antennae locations is at a higher elevation than the other.
Radio Line of Sight Diagram.
If you are doing a very short distance point to point setup, you have a lot of things running in your favor. There's not as much distance, therefore opportunity, for things to get in your way. Your signal strength is higher because the signal doesn't have to go very far. And, it's very easy to align the signal. In the case of our Internet connection, this is exactly what we did - less than a 1/2 mile is all that we needed to cover. In fact, the signal even goes through the branches of a tree.
Antennae Location, Type and Cable Length
One of the greatest challenges that we faced with our installations was the location of the antennas. Line of sight is an obvious contributing factor, but the one you may not be expecting is how close the antennae needs to be to your wired network. Typically, you want the length of the antennae cable to be 100 feet or less to the bridge hardware (the entry point to your wired network). 100 feet may sound like a lot, but it's not.
Antennas come in many shapes and gains (antenna gain is a measure of signal strength). The two that we looked at were the 14 dBi Yagi Directional and the 24 dBi Parabolic Directional antennas. Essentially, these numbers represent antenna gain. In addition, the Yagi and Parabolic have different characteristics. For example, the Yagi has a beam focus of 30 degrees. In other words, when aiming the antennae, the signal you are sending has a spread of 30+ degrees (15 to each the left and right, and up and down of the center point of the antennae). By contrast, the Parabolic antennae is more focused with only a 7 degree (total) spread.
When you are figuring out the type of equipment, the bottom line is that more signal is better... always. To determine the amount of signal that you'll have, you take the antennae signal strength (e.g., 14 dBi for the Yagi above), and then subtract out the cable and connector loss.
The cable that you will want to use is either LMR400 (good) or LMR600 (even better). In short, every foot of cable represents signal loss. For LMR400, there's 7 dBi of loss per 100 feet. For LMR600, it's 4.1 dBi loss per 100 feet. Each connector is 1 dBi of loss - in other words, a cable with a connector at each end would have 2 dBi of loss plus the loss from the length of cable. By the way, these cables typically use something called an "N-connector". They are not the type of thing that you would want to try and do yourself - so if you are considering cutting the cable and putting a new connector, forget it. This is not like 10BASET or ThinNet cables. Proper connections require soldering and skill.
In our example here, let's say that we have a 14 dBi Yagi and 100 feet of LMR 400. This means that we'll have 14 dBi minus 7 dBi for the cable minus 2 dBi for the connectors for a total of 5 dBi. This is not a lot, and we would be better off to use a Parabolic antennae here for decent connection.
By far, for me, the hardest part about putting in a wireless network is figuring out the mounting logistics. Technically, these things are easy, but it's easy to suck up hours looking for the right mounting bracket, fishing a wire through something, etc...
If you listen to one piece of advice in this article, assemble your complete wireless network on a table indoors first before climbing up on the roof. Make sure that you can make all the connections easily and that you have all the pieces and tools you need.
Lucent's WaveLAN Point to Point bridge is managed using a piece of Windows software. At first, this might bother you, but in reality, you'll almost never have to touch this piece of software once you are installed. Don't let it bother you, just throw a copy of VirtualPC from Connectix <http://www.connectix.com/> on your machine and leave it at that.
A couple of features to take advantage of in VirtualPC. First, let it share your Mac's IP configuration. It will save you the nightmare of configuring an IP connection under windows. Second, test this connection using a web browser - just to eliminate any unfamiliarity with Windows that you might have. Lastly, you can quit from VirtualPC without shutting down windows. VirtualPC can save the "state" that it's in, so that you don't have to repeatedly wait through a Windows 98 boot time.
Aside from one minor bug, I found the WaveMANAGER software to be intuitive and very easy to use. And the one bug was not that big a deal... once I realized it. In the version, we used for testing, entering in the wrong password for the bridge can an erroneous "timeout" error.
Timeout Error in WaveMANAGER.
Of course, once I figured this out, it was no big deal. Aside from this, I liked the application - it just made sense to me and I never even bothered to read the docs for this Windows app.
One of the nice features to WaveMANAGER is the graphical feedback that you get to use when aligning antennas. This is one of the strengths that the Lucent package has over the Aironet package (which uses a telnet interface).
Aironet's telnet interface does allow you to configure without using Windows. And, while that is a plus, I like Lucent's GUI approach better and it was much easier to understand and configure.
Remote Link Test in WaveMANAGER.
One of the interesting things that happened when we were aligning the antennas is that once the first antennae was set up, I realized that it sends a pretty strong signal in a pretty wide spread. That in combination with the Lucent PC Card's sensitivity (listening ability) made it such that 1/2 mile away, I had good signal (about 40% SNR) using the PC Card alone before we hooked up the second antennae.
WaveMANAGER considers SNR levels higher than 20% to be "Good". In speaking to the experts, their feeling, again, was that "more is always better". That said, once they reach the 60-70% SNR levels, they don't really try to get anything more out of it as that is quite good.
You may wonder what tricks you use to align an antennae. Actually, it's pretty basic... you use your eyes in conjunction with how the Link Test performs. You'll find that certain things may cause interference. In our case, we found that when we moved 5-10 feet away from a chimney, we gained about 10% SNR because the top of the chimney has a metal flashing causing interference.
Remember, higher speed connections, longer distances, and interference require better signal strength to get the job done. This is where your choice of higher gain antennas, shorter cable lengths, better quality cable, etc. ...all come into play.
Water... the enemy
The folks at Winncom Technologies tell me that the number one enemy to your wireless signal is actually water. It's not a matter of if, but when you are going to get water into the connections... unless you take the right precautions. Water will seriously degrade your connection.
To prevent water from being a problem, wrap the connection neatly with everyday electrical tape. The tape should extend from the insulation before the connector to the insulation beyond the other connector. In other words, you should completely cover the connection and the connectors with the tape. Then, cover all of the electrical tape with outdoor grade silicon (e.g., GE's Silicon II). If the cable is going to be lying on a roof, make sure that the connector has a block underneath it to keep it out of the water.
Bluntly, wireless is just plain cool. Thanks to 802.11 and Apple, the wireless market has become very competitively priced. Competitive here means it that it competes with wired and wireless solutions.
Personally, I like connections that if there's a problem, I can walk up to it myself and fix. Wireless is that way - it's all within your control, not that of a TelCo.
I love the fact that these things are blazing fast, and hassle free - oh yeah, and there's no monthly fee!
The Lucent product is simply an excellent product, well thought out and versatile. I like the Aironet product as well. If you are interested in wireless, contact a distributor like Winncom, and figure out which of the products fits your needs best... as each situation is different. But, don't be afraid of wireless. It's just too cool... and practical... to pass up.
Many thanks to the following who helped with the research of this article: Steve Wozniak (who turned me on to wireless to begin with), Marty Staudenmaier and Mark Shapiro from Lucent, Mike Maly and Gregory Raskin at Winncom Technologies (who all educated me a bunch on wireless); and Justin Newton, Director of Networks at NetZero (who helped me play with everything <g>).
Neil is the Publisher of MacTech Magazine and the CEO of Xplain Corporation. He's been around the Mac developer community for many years - with his first Mac program shipping in 1985. And, while he doesn't get to do as many technical projects as he would like, he does occasionally get to be a geek on projects like this wireless article.