Wireless topologies exist through air and space by way of radio, microwave and infrared frequencies. Since they rely on access points, wireless topologies essentially can be classified as star, mesh, or hybrid topologies.

Three common situations follow that vary by mobility and complexity:

• Mobile Communications
  
  Mobile communications include any communications over public carrier facilities by way of radio, cellular and satellite stations. Mobile data connections began primarily with laptops and notebooks but usage has “exploded” recently with advances in cell phone technology. For example, the FCC estimated in 2009 that 42% of cell phone users in the U.S. were using smartphones, which was nearly three times as many as usage in 2006.

  Cellular (mobile) telephones use radio frequencies in an overlapping, honeycomb-shaped cellular pattern to provide coverage throughout a region. As a full-duplex device that allows separate frequencies for speaking and listening, a cell phone allows both people to talk simultaneously.

The Global System for Mobile communications (GSM) is an international standard that uses digital technology (TDMA) for worldwide connection. GSM has established many helpful features:

• More secure phone calls using encryption
• Paging and text messaging capability
• Caller ID
• Multi-party conferencing

Common technologies used by modern third generation cell phones include:

• CDMA2000
• Wideband Code Division Multiple Access (WCDMA)
• Time-division Synchronous Code-division Multiple Access (TD-SCDMA)

To connect with the Internet cell phones use the Wireless Application Protocol (WAP), an international standard developed by Nokia, Motorola, Erickson, and Phone.com. WAP can work with a variety of wireless services, including:

• General Packet Radio Service (GPRS)
• Short Message Service (SMS)
• High-Speed Circuit-Switched Data (CSD)
• Unstructured Supplementary Services Data (USSD)

• Wireless LAN Communications
  
  

  Wireless LAN communications act like radio communications that connect devices within a single office or floor of a building (or within a home). This is done primarily through a wireless router that connects with a wireless access point (WAP). Essentially this router performs much like a modem that can link a LAN together as well as provide a gateway to the Internet.

  Industry LANs may connect to one WAP or multiple WAPs as part of a wireless distribution system (WDS). In these cases WAPs can function as routers, bridges, or clients. This allows the network to expand without a wired backbone like traditional networks. The major advantage of WDS over other systems is that it preserves the MAC addresses of all client packets across links between all access points.

  Each IEEE 802.11 networked computer will need to have a wireless adapter as well.

  Security will be a major concern to prevent outsiders from accessing the LAN. Options include:

  • Wired Equivalency Privacy (WEP) – widely used but susceptible to hacking software programs
  • WiFi Protected Access (WPA) – more recent WPA2 version fully implements the IEEE 802.11i standard
  • Media Access Control (MAC) address filtering – requires more manual configuration using the 48-bit address assigned each NIC to determine network access

• Wireless Bridging and Internetworking
  
  

  Radio or satellite communications can also be used to connect separate buildings in a more complex network. A wireless bridge device can be used to connect wired Ethernet LANs together through a browser based administrative interface. This is simpler and less expensive than employing more access points.

  The type of WLAN bridge can vary:

  • Workgroup bridge – most often used to connect WLANs to larger wired LANs
  • Ethernet to Wireless – uses Ethernet port to connect to a single device, which in turn connects to an access point
  • Access Point / Wireless Bridge combination – requires configuring an access point as a bridge

Advantages


• Cabling needs are reduced or essentially eliminated
• Connections can be made to remote locations and through environments proven too rigorous for physical media (e.g., mountainous, rocky terrain)
• Penetrates through barriers without drilling holes (e.g., radio waves)
• Less expensive that physical media
• Transmits voice, video and data
• Can transmit in analog and digital
• Mobility without restriction by a cable
• Can be “self healing” since the network makes adjustments to find more reliable paths
• Versatility: easier to adapt and expand as needed

Disadvantages


• Atmospheric interference
• Clear line-of-site needed for infrared wireless connections
• Frequency licensing from the Federal Communications Commission (FCC)
• Requires more security vigilance