Ryan Heaton Dick Al-Bayaty Wi-Fi How Wireless Communication works

Overview What is Wi-Fi History Ethernet IEEE standards (amendments a,b,g,n) 2.4GHz /5GHz differences

What is Wi-Fi Wi-Fi is a means which allows for electronic devices to talk to one another or exchange data through radio waves. Common devices utilizing Wi-Fi: Computers Smartphones Video game consoles Tablets

The History 1985: FCC releases ISM band 1991: Wi-Fi creates by NCR Corporation/AT&T 1992 & 1996: CISRO obtains patents for methods that were used to “Unsmear” the Wi-Fi signal 1999: Wi-Fi name trademarked

The History Initially meant for cashier systems, the first wireless products were brought on the market under the name WaveLAN with speeds of 1Mbps/2Mbps It is continually advancing under IEEE amendments a → b → g → n

The History Release Date Freq.Bandwidth Data rate per stream Allowable Modulation Approximate indoor range Approximate outdoor range protocol(GHz)(MHz)(Mbit/s)[7] MIMO stream s (m)(ft)(m)(ft) —Jun , 21DSSS, FHSS aSep , 9, 12, 18, 24, 36, 48, 54 1OFDM ——5,00016,000 bSep , 2, 5.5, 111DSSS gJun , 9, 12, 18, 24, 36, 48, 54 1OFDM, DSSS nOct-092.4/ , 14.4, 21.7, 28.9, 43.3, 57.8, 65, OFDM , 30, 45, 60, 90, 120, 135, ac (DRAFT)Nov up to up to up to 433.3

ISM Band ISM stands for industrial, scientific, and medical. ISM bands are set aside for equipment that is related to industrial or scientific processes or is used by medical equipment. The ISM band is license-free, provided that devices are low-power. The standard is contained by the ISM band.

ISM Band

U-NII (Unlicensed National Information Infrastructure) Bands n can operate at the 5G U-NII bands : U-NII Low (U-NII-1): GHz(indoor use only) U-NII Mid (U-NII-2): GHz. U-NII Worldwide: GHz. U-NII Upper (U-NII-3): to GHz.

2.4GHz vs. 5GHz 2.4 GHz band is divided into 11 overlapping channels spaced by 5 MHz. 5GHz band is less likely to be congested. 2.4GHz is more prone to interference, commonly used. The 5GHz band offers much higher throughput with the same channel width.

2.4GHz vs. 5GHz 2.4GHz covers a substantially larger range than 5GHz. Higher frequency wireless signals of 5GHz networks do not penetrate solid objects nearly as well as 2.4GHz. In general, the higher the frequency of a wireless signal, the shorter its range.

2.4GHz vs. 5GHz 5GHz and 2.4GHz are simply different frequencies, each with its advantages and disadvantages. To get the best of both worlds, some recent routers have the capability for dual-band operation in both ranges simultaneously. 5GHz offers higher throughput at a shorter distance, while 2.4GHz offers increased coverage and higher solid object penetration.

Protocol Stack

Wireless LAN Networks

Ad-Hoc Point-to-point Mesh Infrastructure Star topology

WLAN Architecture—Ad Hoc Ad-Hoc mode: Peer-to-peer setup where clients can connect to each other directly.

WLAN Architecture — Mesh Mesh: Every client in the network also acts as an access or relay point, creating a “self-healing” and (in theory) infinitely extensible network. Not yet in widespread use, unlikely to be implemented residentially.

Infrastructure network

Comparison of Two Structures Infrastructure Ad hoc ExpansionX FlexibilityX ControlX RoutingX CoverageX ReliabilityX

How does the RF propagate?

Antennas WLAN equipment usually comes with a built-in omni-directional antenna, but some select products will let you attach secondary antennas that will significantly boost range.

Antennas Antennas come in many shapes and styles: Omni-directional: Vertical Whip Ceiling mount Directional: Yagi “Pringles can” Wall mounted panel Parabolic dish

How Can Several Users Communicate Simultaneously? There is a difference between a network designed for voice conversation and one for data exchange. For voice conversations, like telephone and cell phone calls, each person has a dedicated channel during the entire conversation. For data exchange, many users can share one channel. A user sends information when no one else is sending e: QoS facilitates prioritization of data, voice, and video transmissions.

Share One Channel in Data Communication In data communication, data are grouped into packets/frames. Each packet/frame contains a number of bits of information. Devices (phones, computers, etc.) do not communicate simultaneously, similar to the concept of sharing a single connection (the air in this case); only one person can use it at one time.

Share One Channel in Data Communication Send RTS packet Receive CTS packet Send data packets Send EOB packet Receive EOBC packet No CTS packet Generate random wait time Resend RTS Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA)

Security i provides security enhancements WEP – Wired Equivalent Privacy Additional Security Measures WPA – Wi-Fi Protected Access WPA2

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