6.4 Wireless Communications Media

>Electromagnetic spectrum of radiation is the basis of all telecommunications signals, wired and wireless.

>Radio-frequency (RF) spectrum is the part of the electromagneticc spectrum that carries most communications signals.

Bandwidth : range (band) of frequencies that a transmission medium can carry in a given period of time

•Analog bandwidth is expressed in hertz, digital bandwidth usually in bits per second (bps)

•Narrowband (voiceband) : used for regular telephone communications

•Transmission rate 1.5 megabits per second or less

•Broadband : For high-speed data and high-quality audio and video; wide band of frequencies

•Transmission rate 1.5 megabits per second to 1 gigabit per second or more

•TC/IP (Ch. 2) is the protocol for getting wired devices connected to the Internet

•WAP (wireless application protocol) : Wireless handheld devices such as cellphones use the Wireless Application Protocol for connecting wireless users to the Web. Just as the protocol TCP/IP was designed to provide a wired connection to your Internet access provider, WAP is a standard designed to link nearly all mobile devices telecommunications carriers’ wireless networks and content providers. 

Five Types of Wireless Communications Media

       >Infrared Transmission

•Sends signals using infrared light (TV remotes)

•Frequencies are too low to see (1-16 megabits per second)

      >Broadcast Radio

•AM/FM, CB, ham, cellphones, police radio

•Sends data over long distances using a transmitter and a receiver (up to 2 megabits per second)

       >Cellular Radio

•Form of broadcast radio

•Widely used in cellphones and wireless modems

•Transmits voice and digital messages

       >Microwave Radio

•Superhigh-frequency radio transmit voice and data at 45 megabits per second

•Requires line-of-sight transmitters and receivers

•More than ½ of today’s telephones systems use microwave

       >Communications Satellites

•Microwave relay stations in orbit around the earth

•Basis for Global Positioning Systems (GPS)

•Cover broad service area

Communications Satellites - Can be placed at different heights: GEO, MEO, LEO

>GEO – geostationary earth orbit

1. 22,300 miles above earth; travel at the same speed as the earth and so appear to us to be stationary
2. Always above equator
3. Transmission delay (latency) can make conversations difficult; not good for applications requiring real-time user input

>MEO – medium-earth orbit

1. 5,000 – 10,000 miles up

>LEO – low-earth orbit

1. 200 – 1,000 miles up
2. Has no signal delay

Long-Distance Wireless: One-Way Communication

>GPS (Global Positioning System)

1. 24 to 32 MEO satellites continuously transmitting timed radio signals to identify Earth locations
2. Each satellite circles earth twice each day at 11,000 miles up
3. GPS receivers pick up transmissions from up to 4 satellites and pinpoint the receiver’s location
4. Accurate within 3 – 50 feet, with a norm of 10 feet accuracy
5. Not all services based on GPS technology are reliable

GPS

>One-way Pagers : radio receivers that receive data sent from a special

radio transmitter

1. Radio transmitter sends out signals over the special frequency; pagers are tuned to that frequency
2. When a particular pager hears its own code, it receives and displays the message
3. Often used in hospitals and areas where smartphones are not allowed

Long-Distance Wireless: Two-Way Communication

>1G: First-Generation Cellular Service

1. Analog cellphones
2. Designed for voice communication using a system of hexagonal ground-area cells around transmitter-receiver cell towers
3. Good for voice – less effective for data because of handing off

>2G: Second-Generation Cellular Service

1. Uses digital signals
2. First digital voice cellular network

>3G: Third-Generation Cellular Service

1. Broadband technology
2. Carries data at high speeds: 144 kilobits per second up to 3.1 megabits per second
3. Accepts e-mail with attachments
4. Displays color video and still pictures
5. Plays music 

>4G: Fourth-Generation Cellular Service

1. A nationwide 4G network is in development; up to 100 megabits/second
2. Enables faster Internet surfing

>LTE (Long Term Evolution) , an international standard widely adopted in the United States and several countries in Europe and Asia. LTE supports data transfer rates of up to 100 megabits per second over cellular networks.

Cellphone Connections

Short-Range Wireless: Two-Way Communication 

>Local Area Networks

1. Range 100 – 228 feet
2. Include Wi-Fi (802.11) type networks
3. Wi-Fi n is the latest and fastest Wi-Fi technology

>Personal Area Networks

1. Range 30 – 33 feet
2. Use Bluetooth, ultra wideband, and wireless USB

>Home Automation networks

1. Range 100 – 150 feet
2. Use Insteon, ZigBee, and Z-Wave standards

Two-Way Communication

Short-Range Wireless: Wi-Fi b, a, g, & n for local area networks (LANs)

1. Named for variations on the IEEE 802.11 standard
2. Data ranges: 11 megabits per second up to 228 feet
3. Wireless devices must use the same communications standard to communicate. Many products conform to the 802.11a, 802.11b, 802.11g, or 802.11n wireless standards. People have Wi-Fi networks in their homes, and go online through wireless hot spots at cafes and other establishments, including airports and hotels.
4. Be sure the Wi-Fi connection is secure against cyberspying. Also, Wi-Fi connections can be made without your knowledge, so disable your Wi-Fi software, instead of leaving it on to auto connect, whenever you’re not using it. This can keep you from unknowingly connecting to a fraudulent network.
5. Use cellphone security software!
6. WiMax is similar to Wi-Fi but has a greater range (10 – 30 miles).

Wi-Fi set up in a restaurant

General Wi-Fi Network

>Personal Area Wireless

-Bluetooth

1. Short-range wireless standard to link cellphones, computers, and peripherals at distances usually up to 33 ft.
2. Often used with headsets
3. Transmits up to 24 Mbps per second
4. When Bluetooth devices come into range of each other, they negotiate. If they have information to exchange, they form a temporary wireless network.

-Ultra Wideband (UWB)

1. Operates in 480 megabits - 1.6 gigabits per second, range up to 30 ft.
2. Uses a low power source to send out millions of bursts of radio waves each second

-Wireless USB

1. USB is the most used interface on PCs
2. Range of 32 ft. and maximum data rate of 110 - 480 megabits per second; used in game controllers, printers, scanners, digital cameras, MP3 players, hard disks, and flash drives

>Short-Range Wireless for Home

-Insteon

1. Combines electronic power line and wireless technology
2. Can send data at 13.1 kilobits per second with 150 ft. range

-ZigBee

1. Entirely wireless sensor technology
2. Can send data at 128 kilobits per second with 250 ft. range

-Z-Wave

1. Entirely wireless power-efficient technology
2. Can send data at 127 kilobits per second to range of 100 ft.

UNIT 6B: Cyberthreats: Trolls, Spies, & Hackers & Thieves

The ongoing dilemma of the Digital Age is balancing convenience against security.

>Security consists of safeguards for protecting information technology against unauthorized access, system failures, and disasters that can result in damage or loss.

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