Attenuation | Psiber Data Systems RF3D instruction

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2.4.1Omnidirectional Antennas Omnidirectional antennas are generally used to in- crease the communication range within offices or homes. The antennas commonly sup- plied with access points are omnidirectional. Omnidirectional antennas have a beam angle of 360° in the horizontal plane.Vertically, their radiation pattern is compressed, and may cover an angle of 80°. These antennas can have a gain of 2 to 5 dB, and may be used to increase an access point’s horizontal range.

Please see appendix A: The Antenna Library

2.4.2Patch Antennas Patch antennas typically offer gain of 4 to 6 dB, with horizontal and vertical beam angles of 80° to 65°.A patch antenna can increase the communica- tion range by up to 100%.

2.4.3Yagi Antennas Yagi antennas are extremely directional antennas,and are used to set up point-to-point radio links, bridging distances of up to 300 m at 54 Mbit/s, 1 km at 11 Mbit/s, or 2 km at 2 Mbit/s for example using 2.4 GHz WLAN. In this way separate buildings can be interconnected using WLAN equipment.

Please see appendix A: The Antenna Library

2.5 Attenuation

Once the signal leaves the access point’s antenna, it is subject to attenuation, or loss: that is, it becomes weaker. In the ideal case, the signal attenuation with increasing distance from the antenna is called free-space loss.The theoretical rate of free space loss is different for the different frequency bands, 2.4 GHz and 5 GHz. A 5 GHz signal is subject to greater loss than a 2.4 GHz signal. Indoors, the actual attenuation depends on the given build- ing. The signal loss through wooden walls is clearly different from the loss through stone or reinforced concrete. It is therefore important to determine the building materials involved and their specific properties.

Please see appendix B: The Wall and Floor Library

2.6 Theoretical Throughput Rates

Signal strength is one of the factors that determine the theoretical throughput of a wireless LAN.Wireless LAN components lower their data rate automatically when the received signal power is no longer sufficient for a higher throughput. Furthermore, the received signal must also be greater than the noise due to interference, typically by 10 dB. Thus the signal quality is characterized in terms of the signal-to-noise ratio (SNR).