WLAN and Mobile Networks

The existing GPRS/GSM and newer 3G networks have for a long time offered data
services to their subscribers.
Original circuit-switching data at rates of 9.6 kbps do not allow a great deal
of flexibility and severely restrict the service and content that can be offered. The
advent of GPRS has improved this matter significantly. The packet-switching service
can offer much higher rates to the user and at the same time offer resource
efficiencies to the network operator. However, the data rates are still in the range 10
to 40 kbps. Even if EGDE is deployed in the network, the data rate will only be a
maximum of hundreds of kilobits per second. The advent of 3G networks improves
on this data rate, thus allowing a greater range of services to the users.

These data rates, no matter how impressive, are simply blown away by the rate
available through WiFi hotspots — where typical data rates can be as much a
2 Mbps. The obvious difference here is that the cellular networks are providing
wide area coverage for voice and data, whereas the WiFi service is limited to a very
specific place and does not yet offer mobility services. There may be advantages to
the cellular operators by allowing some form of interworking between the WiFi
systems and their own networks. It is likely that this can be achieved in several different
ways, depending on available technologies and potential agreements between
WiFi and cellular operators.

Some cellular operators have formed alliances with the WiFi service providers,
allowing the cellular subscriber access to the hotspots under the single mobile
subscription. Mobile phone manufacturers are already producing equipment that
supports the WiFi radio in multi-mode devices. This allows the phone itself to use
the WiFi hotspot for data download or even in some cases to make phone calls
using VoIP protocols.

In due course it may become common for the cellular operators themselves to
build and maintain their own WiFi infrastructure, connecting directly to the mobile
core network. Using mobile IP and a 3G core network, this offers users seamless
mobility between mobile networks and WiFi systems under a single subscription.
WiFi is illustrated as a stand-alone technology that connects
directly to the Internet, or as an integral part of the cellular operator’s network —
effectively providing alternative access. Note that IMS refers to the IP Multimedia
Subsystem that is designed to provide support for advanced multimedia services.