VoIP and Voice over WLANs
VoIP and WLANs

802.11e is an emerging standard that will bring QoS capabilities to 802.11WLANs to enable reliable voice conversations. The IEEE 802.11e standard is a MAC level enhancement that works with 802.11b and 802.11a physical layers, as well as the upcoming 802.11g physical layer. In addition to multimedia and QoS support, 802.11e also adds security enhancements. The standard is scheduled for completion during 2003.

The 802.11e standard will carry implications for enterprise networks, as well as for small business and home environments. Aside from VoIP, the standard is expected to support video on demand and audio on demand.

One device that is likely to emerge from this standard is the multimode NIC. Multimode NIC will be able to handle voice calls over either wireless IP or mobile WAN. Cisco SoftPhone products will support 802.11e.

A number of wireless AP vendors, including Cisco, have adopted a temporary solution for improving the quality of voice calls over wireless IP. Known as SpectraLink Voice Priority (SVP), this proprietary protocol handles voice and data conflicts by letting network managers and end users prioritize voice in the wireless data environment.

SVP enhances packet filtering, which is a mechanism already present in most APs, to be able to identify both voice and data packets. By setting the AP to support no more than four simultaneous calls, at least half of the wireless bandwidth will be available for data. This is considered an interim solution, until 802.11e products are introduced.

SpectraLink has made SVP publicly available to 802.11 companies at no charge. Cisco has implemented SVP in Cisco Aironet APs.

Figure illustrates the integration of wireless voice and data, which is only part of Cisco Architecture for Voice, Video, and Integrated Data (AVVID).