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wireles network hacks mods - briere D.

briere D. wireles network hacks mods - Wiley publishing, 2005. - 387 p.
ISBN: 0-7645-9583-0
Download (direct link): wirelesnetworkhacks.pdf
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To maximize your Wi-Fi system’s performance, you want to ensure that your received signal is above the receiver sensitivity for the highest speed that your system supports. In Chapter 6, we talk about network monitoring software that can help you do just this.
Understanding Wi-Fi Antennas
Wi-Fi equipment (access points, network adapters, media adapters, bridges, and repeaters — any bit of Wi-Fi gear) comes standard with some sort of antenna. What kind of antenna your gear comes with — and more importantly, how it is mounted or connected to your system — makes a big difference in the performance and upgradeability of the equipment.
Counting your antennas
The first thing you might notice on many Wi-Fi systems (particularly on APs and Wi-Fi routers) is that they sport a pair of antennas. If you’ve skipped ahead to the end of this chapter and read about MIMO, you might think that there’s something MIMO-ish going on here. In fact, there is not. Many systems use two antennas in what’s known as an antenna diversity system. This means that both antennas receive a signal and the AP (or other device, although it’s usually an AP) chooses the antenna with the strongest signal and uses it. Figure 7-1 shows the popular Linksys WRT54G Wi-Fi router with its pair of non-MIMO antennas.
Other types of Wi-Fi gear (like the Apple AirPort Extreme router) have no visible antennas — everything is hidden inside away from view (and prying fingers). Although such an approach is more aesthetically pleasing (and safer from accidental antenna snap-off incidents), it can sometimes reduce the performance of the system and also make upgrades a pain.
112 Part II: Boosting Performance on Your Wireless Network
Figure 7-1:
Two antennas, but only one is used at any given time.
You can upgrade the antenna of most “internal” antenna system APs (as well as many laptops with internal antennas), but it often means getting inside your individual hardware and doing a bit of hardware modification. In many cases, you can find kits that include all the pieces and parts you need as well as very specific instructions on what and how to modify your hardware. An example is the QuickerTek 27 dBm transceiver for the Apple AirPort or AirPort Extreme (shown in Figure 7-2). This unit includes both an amplifier (discussed later in the section titled “Adding Amplification”) and an external antenna connector for the AirPort. (The latest versions of AirPort Extreme already have an external antenna connector, but many existing AirPort Extreme base stations do not.)
Going external
You can really boost the signal of your Wi-Fi equipment when you connect an external antenna to the device. Despite a few glaring exceptions, most APs (and many other Wi-Fi devices like PCI card network adapters, bridges and repeaters, and media adapters) now come with external, removable antennas.
This is a great thing because a wealth of different antennas are now available on the market designed to supplement or replace the factory-installed antennas on your gear.
Chapter 7: Boosting Signal Strength Where You Need It 113
Figure 7-2:
Adding an antenna to an Apple AirPort or AirPort Extreme.
JUNG/
Understanding the connectors
The following discussion may quite possibly turn your brain into jelly. Connectors are not fun, and they are obscure. Anything you learn about Wi-Fi connectors most likely will not ever help you again in your life.
Before you can add an antenna to your Wi-Fi equipment, you need to ascertain what type of antenna connection is available on that equipment. Dozens of different antenna connectors are used in the Wi-Fi world. (It’s not simple like the connectors used for TV signals, where the F-connector is used for satellite, cable TV, and even most over-the-air antenna connections.)
A few of the most commonly used connectors are listed below (and shown in Figure 7-3):
^ N-type ^ SMA ^ RP-SMA ^ MC ^ MC-X ^ MMX
114 Part II: Boosting Performance on Your Wireless Network
Figure 7-3:
A cornucopia of Wi-Fi antenna connectors.
^ TNC ^ RP-TNC ^ BNC ^ APC-7
Male RP-SMA connector Female MC (Lucent proprietary) connector
Some important facts to remember about Wi-Fi antenna connectors are
^ RP stands for reverse polarity.
The N connector is the most commonly found connector on the external antennas themselves.
Almost all come in both male and female versions. The one big exception is the APC-7 connector, which is sexless.
Pay attention to whether you need a male or female connector when you’re buying an antenna or antenna cable. Nothing is more frustrating than getting your shiny new antenna and not being able to hook it up because you got the wrong type of connector.
A few pieces of equipment go even further down the road to obscurity by offering standard connectors with reverse threads — making them even harder to find the proper cables to match!
Chapter 7: Boosting Signal Strength Where You Need It
115
Rather than spending a lot of time trying to figure out different connectors, we recommend that you just focus on those connectors that are installed on your equipment. A great online resource for determining connector types is
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