Roaming for W-LAN revenue: the business case for public access W-LANs will strengthen once roaming becomes available - but it's going to take time to organise - Public Network Strategies

Telecommunications International, June, 2002 by Bob Emmerson

Thus, mobile professionals would be able to work on the LAN, disconnect, roam within the enterprise, move into a cellular environment (2.5 and 3G), enter a hotspot, go back to cellular and then hit other Wi-Fi access pipes at home or

in somebody else's office -- the profile and IP address would be retained. This concept also involves network intelligence; for example, this would allow messages with large attachments to be held back when users are on low-speed networks.

This scenario, however, is still some way off. After all, W-LAN roaming is still to be implemented and, as we have seen, while hotspots are easy to implement the business issues surrounding them are complex. Until they are resolved, there will be 'island solutions' and the market will live with these because high-speed wireless access is a must-have service. Payment, for example, could be mode using a credit cord, but users may not want to do this for security reasons. Alternatively, airtime could be obtained using vouchers or scratch cards as an interim solution.

RELATED ARTICLE: New acronym: VoWLAN

Yes, it's a dreadful term so let's pray for a quick death.

The main function of a Wi-Fi access point is the extension of IP connectivity to wireless clients, thereby enabling IP-based applications to be used when mobile. This also applies to applications that handle real time traffic such as voice, but only when the requisite QoS can be guaranteed over the wireless part of the link. This will came when the 802.11e standard is implemented sometime next year.

In the meantime companies such as SpectraLink and Symbol are marketing VoIP phones with proprietary QoS mechanisms. A computer server on the LAN manages these calls. This concept therefore combines mobility within the enterprise with toll bypass.

These phones can be used in hotspots. When employees set up sessions with the corporate intranet this server will set up and tear down calls in the same way. Thus, mobile calls are over the corporate intranet instead of the public infrastructure.

IP Telephony vendors have 'soft phone' solutions that run on notebooks and PDAs such as the iPAQ and these devices can be used in the same way. However, in this case there is no QoS mechanism.

The combination of IP telephony with hotspot access could therefore impact on the voice revenues of MNOs, which are already in decline.

Standards and security

IEEE 802.11 represents a set of standards designed to embrace different encoding methods, frequencies and data rates. 802.11b products were the first to emerge. The gross data rate is 11Mbps and this standard operates in the 2.4GHz band, which is unlicensed and somewhat crowded. The 802.11a standard operates at a higher frequency band (also unlicensed but not crowded) and this results in significantly higher data rates, typically 54Mbps.

802.1lb is today's de facto standard. 802.1lg aims to provide higher speeds while retaining compatibility, ie it uses the 2.4GHz frequency band. The goal is a data rote in the mid-20Mbps, which can be achieved using newer modulation techniques, but agreement has not been reached yet in the IEEE.