An emerging use of wireless local area networks (LANs) is to carry voice traffic, letting companies extend phone service to mobile workers inside a building or campus without paying for cellular service. Hospitals have spearheaded adoption, with retailers and facilities managers also using it.But voice over wireless IP has a security drawback: Any authentication technology more powerful than the wired equivalency privacy (WEP) will cause delays of several seconds as users roam from one access point to another. However, WEP is easily hacked and is not considered appropriate for business, education or government deployments.Fortunately, there are several techniques to get around these limits. The simplest is to use virtual LANs (VLANs), which separate the voice and data traffic. In this case, the voice traffic's VLAN would use WEP encryption, while the data traffic's VLAN would use a better method such as IEEE 802.11i. That's what the HP Pavilion sports arena in San Jose, Calif., did when it deployed a wireless LAN for its facilities and events staff, notes General Manager Jim Goddard.Another option would be to build a second wireless LAN using a different radio spectrum, again using WEP for the voice network and a better technology for the data network. This approach allows more network traffic, but it is more costly.