Wireless Capabilities

The availability of IP-Centrex, based on a common voice-data network, should remove management's inhibitions regarding Centrex-based contact centers. In the IP-based environment the physical locations of applications, including call management and customer relationship software, and of agents, are no longer significant concerns.

We can classify the solutions for in-building, wireless access to IP-Centrex into these three categories:

1. Wireless IP phones, based on the IEEE 802.11b standard, can communicate (as a data device) with wireless access points within the building. A few companies, such as Spectralink and Symbol, have been making this type of phone for a while.

2. Wireless-enabled data devices, such as PDAs, laptop PCs, and voice-capable pagers are available with IEEE802.11b and/or Bluetooth capability.

3. Multipurpose wireless handset that can work outside a building as cell phones (with GSM, CDMS, or TDMA systems), but that can also operate to proprietary in-building standards (e.g., Ericsson's Freephone) have not become widely accepted yet. These phones would need an IP gateway between the wireless access points and the IP-Centrex system.

The IEEE 802.11b standard, frequently known as "Wi-Fi," has become the dominant standard for high-rate wireless LANs and employs direct sequence spread spectrum at the physical layer. Wi-Fi operates in an unlicensed 2.4-GHz band in most countries, at a nominal bit rate of 11 Mbps, and delivers a throughput of from 5 to 7 Mbps. An extension known as 802.1 lg offers a nominal bit rate of 22 Mbps.

Although IEEE 802.11a was ratified at the same time as 802.11b (in 1999), this standard has not yet been widely adopted because it involves a radically different modulation technology. IEEE 802.11a wireless systems are intended to operate in the 5-GHz band, where 300 MHz of unlicensed spectrum should be available in most countries.

The disadvantage of moving to a higher radio frequency than that used for IEEE 802.11b is a reduced operating range, which means that the required number of APs may be quadrupled. To compensate for this, the 802.11a standard increases the recommended output to 50 mW and employs coded orthogonal frequency division multiplexing.

As the demand for wireless LAN access grows, it is likely that we will see a mixed-standard enterprise environment develop, where users' devices will be able to roam between 802.11b and 802.1la networks. As equipment prices fall, dual-mode clients and APs will become prevalent.

Equipment made to 802.11b standards can interoperate with earlier 802.11 devices, which may deliver only 1 or 2 Mbps. Most Wi-Fi transmitters radiate at a power level of 30 mW, but the standards do allow for an output of up lW, for use outdoors. There are always concerns regarding security when wireless transmission is used for telecommunications, but the 802. lx standard, which defines the authentication and encryption techniques to be employed, has strengthened the security walls around 802.11 systems.

For over a decade the widespread use of wireless LANs has been a promise for "next year" that never seems to be fulfilled. However, the combination of a powerful array of wireless voice terminals and the capabilities of IP-Centrex may lead to a growth in usage more like that of cellular radio than of wireless data networks.