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  2. Zigbee - Wikipedia

    en.wikipedia.org/wiki/Zigbee

    Zigbee is an IEEE 802.15.4-based specification for a suite of high-level communication protocols used to create personal area networks with small, low-power digital radios, such as for home automation, medical device data collection, and other low-power low-bandwidth needs, designed for small scale projects which need wireless connection.

  3. 2.4 GHz radio use - Wikipedia

    en.wikipedia.org/wiki/2.4_GHz_radio_use

    Many Zigbee/IEEE 802.15.4-based wireless data networks operate in the 2.4–2.4835 GHz band, and so are subject to interference from other devices operating in that same band. The definition is for 16 channels numbered 11–26 to occupy the space, each 2 MHz wide and spaced by 5 MHz.

  4. Line-of-sight propagation - Wikipedia

    en.wikipedia.org/wiki/Line-of-sight_propagation

    R is the radius of the Earth, h is the height of the ground station, H is the height of the air station d is the line of sight distance In the case, when there are two stations involve, e.g. a transmit station on ground with a station height h and a receive station in the air with a station height H , the line of sight distance can be ...

  5. List of wireless network protocols - Wikipedia

    en.wikipedia.org/wiki/List_of_wireless_network...

    True 3G systems such as EV-DO, W-CDMA (including HSPA and HSPA+) provide combined circuit switched and packet switched data and voice services from the outset, usually at far better data rates than 2G networks with their extensions. All of these services can be used to provide combined mobile voice access and Internet access at remote locations.

  6. Radio propagation - Wikipedia

    en.wikipedia.org/wiki/Radio_propagation

    Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]

  7. Satellite Internet access - Wikipedia

    en.wikipedia.org/wiki/Satellite_Internet_access

    A radio signal takes about 120 milliseconds to reach a geostationary satellite and then 120 milliseconds to reach the ground station, so nearly 1/4 of a second overall. Typically, during perfect conditions, the physics involved in satellite communications account for approximately 550 milliseconds of latency round-trip time.

  8. Urgency mounts in search for survivors of powerful Tibet ...

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    800-290-4726 more ways to reach us. Sign in. Mail. 24/7 Help. For premium support please call: 800-290-4726 more ways to reach us. ... No avalanches have been observed on Everest so far, state-run ...

  9. Ground conductivity - Wikipedia

    en.wikipedia.org/wiki/Ground_conductivity

    Ground conductivity is an extremely important factor in determining the field strength and propagation of surface wave (ground wave) radio transmissions. Low frequency (30–300 kHz) and medium frequency (300–3000 kHz) radio transmissions are particularly reliant on good ground conductivity as their primary propagation is by surface wave. [1]