WLAN - Wireless communications for the mobile business community

As globalization grows, more professionals are travelling on business, creating a fast expanding need for remote broadband access to data. Business professionals now anticipate high-speed, mobile broadband access that is as quick and easy to use when travelling as it is in the office. All these users need wireless LAN access and they need it in public places, wherever they happen to be.

Providing fast wireless data access for laptops is one of the most cost-effective and quickest ways for mobile operators to boost ARPU from business users. Hotspots, such as airports, hotels and conference centres, are prime locations for users wanting broadband data connectivity to access large files and synchronize their e-mails. WLAN is a short range packet data communication between base stations and user terminals and direct communication between terminals is possible. WLAN allows the business professionals to access their company's Intranet.

Wireless LAN access is all about using data, which makes it vital to stimulate the mobile corporate sector to use broadband data and applications. Public Wireless LAN is becoming a mobile business that complements 2G and 3G services. Operator Wireless LAN is a way to complement the service offering and in this way differentiate from the competition. It is a way to attract new subscribers and an opportunity to increase average revenue per user (ARPU). Mobile operators can also offer global roaming via the 25,000 agreements between the members of the GSM association.

A working example of WLAN is O2 Ireland who has employed the Nokia Operator Wireless LAN solution to provide it's customers with flexible wireless broadband access to Internet and corporate intranet services in public 'Wi-Fi Zones(TM)', such as the hotspots mentioned above. It is not difficult to see why this solution has been so successful when the technical capabilities and the convenience it offers are taken into consideration.

The Nokia solution uses 11Mbit/s IEEE802.11 Wireless LAN technology and complements the mobile operator's other data services, combining HSCSD, GPRS and Wireless LAN into a single service. Accompanied by the easy to use D211 multimode radio card, which supplies the key to accessing these services, it provides an excellent solution by extending the reach of local area networks (LANs). Instead of plugging into a wired LAN wall outlet, you can quickly connect to the corporate network through your PC and wireless LAN card for easy access to broadband data rates without wires.

Wireless LAN Technologies

Narrowband technology

A narrowband radio system transmits and receives user information on a specific radio frequency. The narrowband radio keeps the radio signal frequency as narrow as possible just to pass the information. Undesirable crosstalk between communications channels is avoided by carefully coordinating users on different channel frequencies.

A private telephone line is much like a radio frequency. When each house has its own private telephone line, people in one house cannot listen to calls made to the other house. In a radio system, privacy and non-interference are accomplished by using separate radio frequencies. The radio receiver filters out all radio signals except the ones on its designated frequency.

Spread spectrum

Most wireless LAN systems use the spread spectrum technology, a wideband radio frequency technique developed by the military for use in reliable, secure, mission-critical communications systems. Spread spectrum is designed to trade off bandwidth efficiency for reliability, integrity, and security. In other words, more bandwidth is consumed than in narrowband transmission, but the trade-off produces a signal that is louder and thus easier to detect, provided that the receiver knows the parameters of the spread spectrum signal being broadcast. If the receiver is not tuned to the right frequency, a spread spectrum signal looks like background noise. There are two types of spread spectrum radio: frequency hopping and direct sequence.

Frequency hopping spread spectrum technology

Frequency hopping spread spectrum (FHSS) uses a narrowband carrier that changes frequency in a pattern known to both the transmitter and the receiver. Properly synchronised, the net effect is to maintain a single logical channel. To an unintended receiver, FHSS appears to be short-duration impulse noise.

Direct sequence spread spectrum technology

Direct sequence spread spectrum (DSSS) generates a redundant bit pattern for each bit to be transmitted. This bit pattern is called a chip (or chipping code). The longer the chip, the greater the probability that the original data can be recovered (and, of course, the more bandwidth required). Even if one or more bits in the chip are damaged during transmission, statistical techniques embedded in the radio can recover the original data without the need for retransmission. To an unintended receiver, DSSS appears as low-power wideband noise and is rejected or ignored by most narrowband receivers.

With DSSS, the normal data rates in IEEE802.11 are 1, 2, 5.5 and 11 Mbps. The 11 Mbps rate also enables the use of multimedia solutions.

The difference between WLAN and other wireless technologies

Wireless LANs provide all the functionality of wired LANs, but without the physical constraints of the wire itself. Wireless LAN configurations include independent networks offering peer-to-peer connections, and infrastructure networks supporting fully distributed data communications. Point to- point local area wireless solutions, such as LAN-to-LAN bridging and personal area networks (PANs), may overlap with some WLAN applications, but they fundamentally address different user needs. A wireless LAN-to-LAN bridge is an alternative to a cable that connects LANs in two separate buildings. A wireless PAN typically covers the few feet surrounding a user's work space and enables synchronising computers, transferring files, and accessing local peripherals.

New security measures eliminate concerns

For years, wireless LAN systems have been dogged by security concerns from corporate users. Wireless LANs demand strong measures to prevent security breaches because it is easy to intercept radio data traffic.

In the Nokia example, these concerns are overcome by a combination of security measures - secure SIM (and EAP/SIM) authentication; security features in network elements; enhanced wireless LAN security protocols such as 802.11I; and by Virtual Private Networks (VPN). A VPN is a private data network that uses the public telecommunications infrastructure, maintaining privacy with tunnelling protocols and security procedures. In wireless LAN networks, VPNs create virtual tunnels for secure communications.

The business user authenticates with a SIM-card to the Internet and is charged by the mobile operator. The user then establishes a VPN tunnel back over the Internet and is authenticated to access the corporate network. In addition to a traditional user ID/password, the Nokia solution deploys a regular GSM SIM card for identifying, authenticating and accounting users. The SIM card stores a standard IMSI code identifying the user and the home operator.

BENEFITS OF WLANS
- Wireless LANs provide flexible installation and configuration and mobility in network environment. Key issues in implementing a wireless LAN are: Range and coverage, Throughput, Interoperability with wired infrastructure, Interoperability with wireless infrastructure, Interference and co-existence, Simplicity and ease of use, Security, Network management, Cost, Scalability, Battery life for mobile platforms and Safety.

- Wireless LAN offers the user more flexibility and security. It is seamless to use; no new software is needed. Wireless LAN enables mobility in campus areas with the same data rate and services of a wired LAN but without attached cables.

- Wireless LAN offers the user more flexibility and security. It is seamless to use; no new software is needed. Wireless LAN enables mobility in campus areas with the same data rate and services of a wired LAN but without attached cables.

- A wireless LAN is not much more expensive than a wired LAN, and the maintenance costs are even lower.

- There is no other network solution that is as flexible, secure and easy to implement as the wireless LAN.