Wi-Fi Spectrum Analyzers: Configure and troubleshoot optimally 802.11 Wireless Networks
Wi-Fi wireless networks have grown in popularity in recent years and are found ubiquitously in the economy, industry and at home. Wi-Fi at 2.4 GHz industrial, scientific and medical (ISM) – a public that is not licensed by the FCC. Many types of wireless devices to compete with Sky in the 2.4 GHz ISM band – and that brings disorder that affects negatively the performance of a wireless network. A 2.4-GHz spectrum analyzer is the tool of choice forDetection and identification of sources of interference and delivery of information, the optimal configuration of a Wi-Fi allows.
Overview
With wireless systems, it is very difficult to predict the propagation of radio waves and the presence of interfering signals without the use of testing equipment. Radio waves do not travel the same distance in all directions – instead of walls, doors, lift shafts, people and other obstacles offer varying degrees ofDamping, the radio frequency (RF) radiation that causes irregular and unpredictable. To ensure maximum reliability and throughput for Wi-Fi (802.11b) wireless network is necessary to recognize and identify sources of interference that can impair its performance.
There are a variety of electronic devices, transmitting RF energy in the air. Wi-Fi (802.11 b / g) operates at 2.4 GHz Industrial, Scientific and Medical (ISM).This particular range of frequencies (2.401 GHz to 2.473GHz) is public and their use does not require approval by the FCC. As a result of this band tends to get almost full – not just with 802.11 devices, but also microwave ovens, Bluetooth devices, cordless phones, baby monitors, audio / video transmitters, wireless cameras, etc.
Optimizing professional installers of wireless computer networks to try their customers Wi-Fi strategic choice of a subset of 2.4GHz, for the use of wireless network devices. 2.4-GHz, 2,401-2,473 GHz is subdivided into 11 another, 22 MHz channels. Note that 2.473GHz – 2.401GHz MHz 72 = 11, times 22 MHz or 242 MHz So, as a measure of 242 MHz to 72 MHz? Answer – the channels intersect. Installationsprogramm kann die ein oder Wireless Router Access Point (AP) so konfigurieren, dass Kanal 6, the benutzt und dann über den Daten-Kommunikation wird der Bereich mit Frequenzen Kanal 6 (z. B. 2.426 GHz – 2.448 GHz verbunden auftreten).But if other wireless devices (802.11 and 802, 11) are also transmitting on this frequency range is suffering from a wireless network between them. Thus, if a wireless network or troubleshooting a performance is weak, it is important that a channel that is not subject to interference from other devices select – that is, do not want your wireless network with other devices compete for the same range of frequencies.
Wi-Fi DiagnosticsTools
There are two categories or types of tools to help choose the best channel for Wi-Fi wireless network – WiFi Scanner (ie, 802.11 discovery tools), and 2.4 GHz spectrum analyzers:
Wi-fi, or 802.11 (WLAN) discovery utility. The best known of this category is NetStumbler (http://www.netstumbler.com/). The instrument of discovery is the Service Set Identifier (SSID), report for each access point (AP) points out, along withChannel used by AP. This works is that roughly every 100 ms, an AP sends an "I'm here," Beacon – and the means of detection (on a laptop, and with its 802.11 wireless adapter) takes the lighthouse and adds the SSID his list. In addition, the discovery could Utility SNR (signal to noise ratio) for each AP, and as an indication of how close the AP is your current position. Although this is information is useful, is that it says nothingNon-802.11-or even devices such as access points are used. This is your laptop could be sitting next to a microwave oven, sending all types of radio in the room, and the instrument of discovery would have been aware of its existence. The Discovery program knows only about 802.11 devices – devices that transmit RF signals to the 802.11 protocol – and can not see, not-802, 11 transfers. Here is an analogy – you are in a large auditorium and you hear someone shouting across the room, sometimes"Hello, I am Joe." Joe is an Access Point, and from time to time sends a signal to leave, who's out there know that he is there. It could be that Joe is very busy talking with many people, or it can be with him. Or are there a lot of noise in the hall would be difficult to carry on a conversation with Joe from a distance. The instrument of discovery can not help you with that – just occasionally hears lighthouse Joe's "Hello, I am Joe."
2.4 GHz Spectrum Analyzer.This is the tool of choice for detection and identification of sources of RF interference. Spectrum analyzer is an essential tool for monitoring radio frequency (RF) are used – they give you a clearer picture of the RF environment to help identify and find devices interfering with the wireless LAN (WLAN). Basieren In der Regel werden sie auf einer 2-Darstellung dimensionalen, wo die vertikale Achse (Y-Achse) entspricht der Größe eines Signals und die horizontale Achse (X-Achse) ist die Frequenz eines Signals.Dedicated hardware spectrum analyzers can be in the tens of thousands of U.S. dollars obtained (using arrays of many analog-digital converter). Recently, PC-based analyzers have appeared on the market. But they are also quite expensive – close to $ 4000 AirSleuth is a convenient 2.4 GHz spectrum analyzer shows available on Nuts Nets, LLC, the RF data in a variety of diagnostic help, once the presence of interfering with the devices and then choose the bestChannel for your wireless network.
Examples
Click here to see examples of measures including 5 with AirSleuth 2.4-GHz spectrum analyzer. In each photo there are 3 items to take note of:
a. The maximum value for the y-axis
b. White horizontal lines indicate the limits of the 11 channels are superimposed 802.11
c. Place (ie the frequency) and height (signal on) the big top HF
Figure 1 In thisNumber of white horizontal lines show the limits of 11, 22 MHz channels in 2.4 GHz band to note how many adjacent channels overlap.
Figure 2 The airspace is relatively quiet and there are wireless devices transmitting in the 2.4 GHz band Note: The maximum value of the y-axis is '3 .0 'drive signal respect – which is small. The reason you see peaks (and starting) is not flat enough, the display uses the automatic scaling, so that thehigher peak (no matter how it is really small), fills the screen. We know what it looks like the background noise, since the maximum value of the y-axis in Figure 3 A microwave oven is running. Here you can see that radiate radio frequency energy across the band 2.4 GHz
Figure 4 2.4 GHz cordless phone is switched on. Note: the height of the peak near the channel 1 is about "140" units and the peak near channel 11, as '110 'Units. These are strong enough to knock out wireless networks are configured to use channel 1 or channel 11. Moreover, because of the way channels overlap the first peak probably also interfere with a wireless network with channel 2, and the second summit could also interfere with wireless networks on channels 9 or 10.
Figure 5 shows the course of a wireless network (set to channel 6) to be used, since it is actively transmitting aimportant flow.
Computer-network 