VoIP for Dummies 2005

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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 everfaster 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.

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Adding VoIP to the Wireless Network

The 802.11 standards make VoIP and IP telephony possible with nothing more than your laptop armed with a wireless interface card, perhaps a set of headphones, and IP telephony software from your VoIP provider. Theoreti-

cally, you can walk into any coffee shop or hotel that provides wireless Internet access and make a telephone call while you’re surfing the Web. There are many more scenarios for using wireless VoIP, but I think you get the picture.

The following sections provide an overview of some of the VoIP telephony devices you can use with a wireless network.

IP soft phones for pocket PCs

You already know that VoIP uses packets to transport phone calls from sender to receiver. Thus, any computer that uses IP protocols can theoretically connect to a VoIP network and make or receive telephone calls. This includes pocket PCs.

Many pocket PCs running the Windows operating system can connect to local area networks and exchange data. Provided the data rate for your pocket PC is high enough, you can use the device for your phone calls. The software used on the wireless pocket computer to make and receive phone calls is referred to as an IP soft phone for pocket PC. In most cases, the pocket PC can also operate as a cellular phone. This makes the device versatile in a mobile, wireless environment.

Wireless extension to cellular

When using a land line, the caller pays the regulated recurring per-minute charges involved with the call. The caller has to pay these charges whether the call is answered or goes into voice mail. Wireless extension to cellular (WEC) is a technique that enables an incoming call to ring at your hardwired telephone (land line) and your cell phone at the same time. It enables you to take the incoming call or send it to voice mail wherever you are at the time of the call. Plus, the call does not get billed to your cell phone plan. It is treated as an inbound call to your office number.

WEC requires the PRI transport service, as discussed in Chapter 5. The PRI transport line has proven to be a cost-effective way to support WEC because

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As mentioned, WiMax covers a distance of up to 30 miles, which is a large enough range to span a city the size of Chicago. The maximum range with WiFi is several thousand square feet, depending on which of the 802.11 standards you’re using. WiMax is being installed in a limited number of regions as a replacement for smaller WiFi hot spots because they cover a larger geographical area.

Putting WiMax to use

The evolution of WiMax has ushered in a new way of doing wireless. Although WiMax has not reached the marketplace to any great degree (as of this writing), manufacturers and service providers are developing models for how

to design and sell or lease wireless networks using WiMax technology. The increased bandwidth and flexibility offered by WiMax are influencing how the marketplace views wireless telephony.

When the 802.16 standard was formalized in 2001, it quickly became apparent that WiMax had the potential for seriously changing the way we establish networks in metropolitan areas. The traditional model for network development is to install a local loop at each site location (LAN) to be connected to the larger overall network (WAN). Instead of running a T1 local loop to each location (at an expense averaging $450 to $1200 per month per location), you could have one WiMax hub that wirelessly interconnects all four locations.

If you run VoIP over this WiMax network, you also reduce the cost of intersite telephony to $0. You can also reduce the cost of your off-net regional (intralata) telephony to the price of local calling. All VoIP on-net traffic would be carried on-net to the closest of the four LANs, and there it would go out to the PSTN as a local call.

If your company has other locations that are beyond the range of your WiMax infrastructure, you can interconnect them by connecting all the WiMax hubs at each metropolitan area. You can then run traditional dedicated transports between the regional WiMax hubs.

For example, suppose you have a WiMax hub covering four offices in Chicago. You could connect this hub via a dedicated line to a similar WiMax hub that covers your offices in Los Angeles, Pittsburgh, or any other metropolitan area. Figure 8-1 shows how such a network would look if you didn’t use WiMax. Figure 8-2 shows the same network redesigned to take advantage of WiMax.

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Getting Hip to WiSIP

Session initiation protocol (SIP) is a catalyst for the next phase of open communications using not only IP telephony and VoIP but also the full suite of IP-related protocols. SIP is an interoperable protocol designed to allow equipment from different vendors to communicate with each other. SIP enables new leading-edge VoIP calling features not available on traditional phones, including features such as LDAP directory access, presence, and multiple call appearance. (You find out about these features — and more — in Chapter 10.)

WiSIP is the flavor of SIP that delivers advanced telephony features to other WiSIP wireless phones or end-user devices. These devices can use WiFi and WiMax connectivity to the Internet to bypass the conventional cell phone and PSTN networks.

It is important to realize that you do not need a WiSIP phone to benefit from the advanced features of VoIP through the SIP protocols. A VoIP end-user with multiple endpoint devices such as a cell phone, a desk phone, a PC client, and a PDA can rely on SIP to permit all these devices to operate as a single system. SIP brings about increased efficiency and productivity.

In a VoIP converged network with SIP, organizations can choose from a variety of vendors to create a seamless converged communication network. For instance, some equipment vendors use SIP to support trunking functionality. (Trunking is a way to make a network support a protocol it might not otherwise support.) Other vendors may use SIP to control gateways and calling features. The way in which SIP is used is entirely up to the communications vendors. SIP allows their equipment to communicate with equipment from other vendors.

SIP enables smoother conversions

SIP does to traditional telephone service what the World Wide Web does to the Internet. In fact, SIP is a cousin of the main protocol of the Web, hypertext transfer protocol (HTTP); both are text-based protocols. SIP has emerged at the forefront of most if not all VoIP-related applications. SIP has been embraced by the leading VoIP telephony manufacturers and is being built into VoIP hardware and software, including IP-enabled telephones.

SIP integrates with traditional circuit-switched interfaces and IP-switched interfaces. This integration allows the user to easily convert from traditional circuit-switched telephony infrastructures to next-generation IP infrastructures, including wireless networks supported by WiFi and WiMax.