It is fairly safe to say that wireless networking has caused a revolution in small networks and among the ranks of those perpetually on-the-go. Wireless networks allow computers to be positioned without regard for wires and make movement of computers to new locations painless. For those who are mobile, wireless networking means that they can easily connect almost anyplace they go.
At its simplest, WiFi networking is a method to extend Ethernet protocols over a limited area without the need for wires. Instead, the wireless signals become the medium by which communication happens. Before you can fully understand wireless (and how it relates to VoIP), you need to understand a bit about how wireless works. The following sections describe the basics of wireless networking.
Ethernet networking and VoIP
Ethernet comes in several flavors. When first standardized back in the mid-to-late 1980s, Ethernet was strictly a computer-data network technology that operated at 10 Mbps. Today there are 100 Mbps, 1 Gbps, and even 10 Gbps speeds. To support VoIP, each location in the network must use Ethernet as its network protocol. The network type may change as the VoIP packets traverse the distance between caller and receiver, but the network must be Ethernet at the point where the caller connects.
Ethernet, including its wireless forms, uses the Media Access Control (MAC) frame for carrying LAN traffic. The MAC frame is a way to organize the data, voice, or video bits so that they can be transported on the local network. Whenever the network traffic needs to go from the LAN to another location or to the Internet, the MAC frames on the LAN get repackaged through the LAN’s edge device as VoIP packets. As packets, they can travel either on the WAN or to another network to reach their destination.
Today, thanks to VoIP, wireless forms of Ethernet such as WiFi can support voice and video applications as well as data across multilocation networks.
Examining the IEEE 802.11 standard
WiFi was invented in the 1990s as a wireless method for connecting to the LAN. It was accepted by the IEEE in 1997 as the 802.11 standard. (The IEEE, or Institute for Electrical and Electronic Engineers, is the organization responsible for the set of networking standards known as the 802 series.)
WiFi is basically wireless Ethernet. The first version of 802.11 operated at 2 Mbps and supported only computer applications. Very much like the original Ethernet 802.3 standard, the 802.11 standard evolved to incorporate ever-faster speeds. Today, variations of 802.11 include the following:
802.11a: Operating at 54 Mbps, 802.11a is considered the hands-down favorite for IP telephony within a limited range. Although 802.11a is the wireless option with the best quality, it has the shortest distance limitations; you can use it up to 100 feet without the need to be connected via some wire.
V 802.11b: Operating at 11 Mbps, 802.11b operates up to 300 feet without the need for a wired network connection. 802.11b works great for coffee shops or even small campus-type environments. Voice quality over 802.11b is passable, almost like a long-distance cell phone connection.
V 802.11g: Operating at 54 Mbps, 802.11g is still relatively new, but is being touted as a high-speed replacement for 802.11b.
Notice that both 802.11g and 802.11a can transmit data at 54 Mbps. 802.11g has technical advantages over 802.11a, however. It is backwards compatible with 802.11b, which means that if you have an 802.11g network device, it will work in an 802.11b network (or vice versa). Thus, 802.11g provides a clear upgrade path for older 802.11b users, whereas 802.11a does not.
Newer, cheaper, faster, and better wireless transport alternatives are in the works. They follow the technology milestones completed by the 802.3 and 802.11 series of standards.
Moving up to wireless
Wireless networks take the idea of network access to a new, never-before-seen level of service, allowing more flexibility in how users may connect to the network. If your organization has already migrated to IP telephony, the LAN side of the enterprise (or the LAN side of each site location in a multilo-cation company) is running a standard Ethernet-based network. Because the LAN architecture is Ethernet, it is based on the IEEE 802 series of standards and is therefore compatible with WiFi.
To upgrade an Ethernet LAN running IP telephony to support wireless telephony, the only requirement is to add VoIP-compatible wireless access points (WAP). The WAP devices have a limited range, so they should be added to the network in a manner that is most useful for wireless VoIP users. All WAP devices should be connected to the LAN through switched ports as opposed to simple hubs. A hub merely provides a physical, plain-vanilla connection to the network, whereas Ethernet switches provide fault isolation at every port and therefore are more conducive with the wireless telephony application.
Finally, users need a wireless IP telephone. Such a phone looks a lot like a cell phone and operates within a few hundred feet of the WAP devices. However, users can avoid the expense of a separate phone by using VoIP soft phone on their WiFi-ready computers. Any computer that permits you to add a WiFi card can run VoIP. Wireless IP telephones and soft phones are discussed in more detail in topic 10.
