By Art Reisman, CTO, www.netequalizer.com
The trend to go all wireless in high density housing was seemingly a slam dunk just a few years ago. The driving forces behind the exclusive deployment of wireless over wired access was two fold.
- Wireless cost savings. It is much less expensive to strafe a building with a mesh network rather than to pay a contractor to insert RJ45 cable throughout the building.
- People expect wireless. Nobody plugs a computer into the wall anymore – or do they?
Something happened on the way to wireless Shangri-La. The physical limitations of wireless, combined with the appetite for ever increasing video, have caused some high density housing operators to rethink their positions.
In a recent discussion with several IT administrators representing large residential housing units, the topic turned to whether or not the wave of the future would continue to include wired Internet connections. I was surprised to learn that the consensus was that wired connections were not going away anytime soon.
To quote one attendee…
“Our parent company tried cutting costs by going all wireless in one of our new builds. The wireless access in buildings just can’t come close to achieving the speeds we can get in the wired buildings. When push comes to shove, our tenants still need to plug into the RJ45 connector in the wall socket. We have plenty of bandwidth at the core , but the wireless just does can’t compete with the expectations we have attained with our wired connections.”
I found this statement on a Resnet Mailing list from Brown University.
“Greetings,
Despite the tremendous economic pressure to build ever faster wireless networks, the physics of transmitting signals through the air will ultimately limit the speed of wireless connections far below of what can be attained by wired connections. I always knew this, but was not sure how long it would take reality to catch up with hype.
Why is wireless inferior to wired connections when it comes to throughput?
In the real world of wireless, the factors that limit speed include
- The maximum amount of data that can be transmitted on a wireless channel is less than wired. A rule of thumb for transmitting digital data over the airwaves is that you can only send bits of data at 1/2 the frequency. For example, 800 megahertz ( a common wireless carrier frequency) has 800 million cycles per second and 1/2 of that is 400 million cycles per second. This translates to a theoretical maximum data rate of 400 megabits. Realistically though, with imperfect signals (noise) and other environmental factors, 1/10 of the original frequency is more likely the upper limit. This gives us a maximum carrying capacity per channel of 80 megabits on our 800 megahertz channel. For contrast, the upper limit of a single fiber cable is around 10 gigabits, and higher speeds are attained by laying cables in parallel, bonding multiple wires together in one cable, and on major back bones, providers can transmit multiple frequencies of light down the same fiber achieving speeds of 100 gigabits on a single fiber! In fairness, wireless signals can also use multiple frequencies for multiple carrier signals, but the difference is you cannot have them in close proximity to each other.
- The number of users sharing the channel is another limiting factor. Unlike a single wired connection, wireless users in densely populated areas must share a frequency, you cannot pick out a user in the crowd and dedicate the channel for a single person. This means, unlike the dedicated wire going straight from your Internet provider to your home or office, you must wait your turn to talk on the frequency when there are other users in your vicinity. So if we take our 80 megabits of effective channel bandwidth on our 800 megahertz frequency, and add in 20 users, we are no down to 4 megabits per user.
- The efficiency of the channel. When multiple people are sharing a channel, the efficiency of how they use the channel drops. Think of traffic at a 4-way stop. There is quite a bit of wasted time while drivers try to figure out whose turn it is to go, not to mention they take a while to clear the intersection. Same goes for wireless users sharing techniques there is always overhead in context switching between users. Thus we can take our 20 user scenario down to an effective data rate of 2 megabits
- Noise. There is noise and then there is NOISE. Although we accounted for average noise in our original assumptions, in reality there will always be segments of the network that experience higher noise levels than average. When NOISE spikes there is further degradation of the network, and sometimes a user cannot communicate at all with an AP. NOISE is a maddening and unquantifiable variable. Our assumptions above were based on the degradation from “average noise levels”, it is not unheard of for an AP to drop its effective transmit rate by 4 or 5 times to account for noise, and thus an effective data rate for all users on that segment from our original example drops down to 500kbs, just barely enough bandwidth to watch a bad video.
Long live wired connections!
NetEqualizer News Blog 
Deja Vu, IVR, and the Online Shopper’s Bill of Rights
December 16, 2012 — netequalizerBy Art Reisman
CTO
www.apconnections.net
www.netequalizer.com
My Bill of Rights for how the online shopping experience should be in a perfect world.
1) Ship to multiple addresses. This means specifically the ability to ship any item in an order to any address.
2) On the confirmation page, always let the user edit their order right there, delete, change quantity, ship to address, shipping options, etc. All buttons should be available for each item.
3) Never force the user to hit the back button for any mistake, assume they need to edit everything from every page, as if in a fully connected matrix. Let them navigate to anywhere from anywhere.
4) Don’t show items out of stock or on back order UNLESS the customer requests to see that garbage.
5) You had better know what is out of stock. :)
6) The submit button should immediately disappear when it is hit, it is either hit or not hit, and there should be no way for a customer to order something twice by accident or to be left wondering if they have ordered twice. The system should also display the appropriate status messages while an order is being processed.
7) If there is a problem on any page in the ordering process, a detailed message on what the problem was should appear at the top of page, along with highlighting the problem field, leaving a customer to wonder what they did wrong is just bad.
8) Gift wrap available or not when selecting an item, not at the end of the ordering process.
9) If the item or order is not under your inventory control then don’t sell it or pretend to sell it without a disclaimer.
10) Remember all the fields when navigating between options. For example, a user should never have to fill out an address twice unless it is a new address.
Why is it so hard to solve these problems ?
Long before the days of Internet, I was a system architect charged with designing an Integrated Voice Response product called Conversant (Conversant was one of the predecessors to Avaya IP Office). Although not nearly as wide-spread as the Internet of today, most large companies provided automated services over the phone throughout the 1990’s. Perhaps you are familiar with a typical IVR – Press 1 for sales, press 2 for support, etc. In an effort to reduce labor costs, companies also used the phone touch tone interface for more complex operations such as tracking your package or placing an order on a stock. It turns out that most of the quality factors associated with designing an IVR application of yesterday are now reflected in many of the issues facing the online shopping experience of today.
Most small companies really don’t have the resources to use anything more than a templated application. Sometimes the pre-built application is flawed, but more often than not, the application needs integration into the merchants back-end and business processes. The pre-built applications come with programming stubs for error conditions which must be handled. For small businesses, even the simplest customizations to an on-line application will run a minimum of 10k in programmer costs, and to hire a reputable company that specializes in customer integration is more like 50k.
Related Internet users bill of rights
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