The industry is being swamped with the likes of IEEE 802.11b, IEEE 802.11a, Infrared, HiperLAN, HiperLAN II, OpenAir, Home RF & SWAP and Bluetooth, each having its own data transfer rates, modulation methods and power limitations.

Different Air Routes
The completion of the IEEE 802.11 standard in 1997 for WLANs signalled the birth of wireless networking. The primary goal of the standard was to optimise interoperability between differing brands of WLANs as well as introduce improved performance.

Later in 1999, 802.11 High Rate (HR), also known as the IEEE 802.11b standard, was ratified. Most implementations of IEEE 802.11 used the RF-based spread spectrum-either Direct Sequence Spread Spectrum (DSSS) or Frequency Hopping Spread Spectrum (FHSS). The DSSS physical layer specified a 2 Mbps data rate with optional fallback to 1 Mbps in noisy environments while the FHSS physical layer was defined to operate at 1 Mbps and allowed for 2 Mbps in clean environments.

For the high rate 802.11b (11 Mbps) standard, most vendors across Asia have chosen to implement DSSS, which provides greater throughput while maintaining the 802.11 protocol. Fortunately, the migration from the 2 Mbps DSSS to the current 11 Mbps is a simple task akin to moving the wired Ethernet 10 Mbps to the Fast Ethernet 100 Mbps where protocols are maintained.

In addition to faster speed, 802.11b-still the current prevailing protocol-also offers multi-vendor interoperability amongst products within the same physical layer, allowing customers to mix and match vendor products. An added benefit is that the standardisation has also lowered the cost of components.

This cross-vendor interoperability is maintained by the Wireless Ethernet Compatibility Alliance (WECA), which certifies products with a Wi-Fi interoperability badge. Another driver for 802.11b is its strong support from telecom and IT gear manufacturers like Cisco, Lucent, Enterasys, Nokia and 3Com.

However, the FHSS OpenAir standard, developed by Proxim, is fast losing market share in the Asia- Pacific-largely constrained by its slower speed and proprietary nature. Nevertheless, Proxim has rallied a number of companies behind OpenAir by supplying many OEMs with products operating on this standard and even plans to deliver 10 Mbps FHSS soon.

Interestingly, Proxim and other traditional FHSS players like Symbol and BreezeCOM, have also started offering DSSS-based 802.11b products in a bid to remain competitive as typical markets for FHSS, like securities, diminish.

Infrared
Perhaps the least used of all available WLANs is the infrared (IR) system. First used in the military, infrared WLANS use very high frequencies-just under visible light in the electromagnetic spectrum-to transport data.

As with light beams, IR cannot penetrate solid objects so its mode of communication is limited to a line-of-sight or diffused connectivity. The line-of-sight IR range is limited to approximately 3 ft (less than 1m) and is typically used for personal area networks and specific WLAN applications. It is not practical for roaming mobile users and better used as a fixed network.

On the other hand, diffuse or reflective IR WLANs do not require line-of-sight, but cells are limited to individual rooms, allowing the spectrum to ‘bounce off’ the plains to provide network facilities. Thus, diffuse IR communications are more appropriate for offices. However, both these technologies are fast disappearing from the commercial WLAN market place.

HiperLAN II vs IEEE802.11a
RadioLAN and Proxim were the only 5 GHz players in 2000. Proxim had products for the outdoor market while RadioLAN delivered primarily indoor products. Both products were proprietary in nature.

From our examination, 5 GHz will become the technology for the next wireless wave, promising speeds of up to 54 Mbps and potentially more. Frost & Sullivan expects most major players to introduce 5 GHz products in 2002 with networking giants already striding confidently into this arena. Cisco, for instance, acquired the Australian 5 GHz chip manufacturer Radiata in late 2000 to emphasise its commitment to this technology. Lucent, and more recently 3Com, are expected to join the bandwagon.

This in mind, both 802.11a and the European HiperLAN II are vying to be recognised as the 5 GHz standard. Let’s take a look at how they differ.

The 802.11a was developed on the back of Ethernet-based networks while the European equivalent gave due consideration to access to asynchronous transfer mode (ATM), third generation (3G) mobile telephone networks and IP networks in its design. Another distinguishing factor lies in the media access control (MAC) layer, where HiperLAN II readily supports QoS features, paving the way for video and multimedia content delivery.

Both 5 GHz technologies use orthogonal frequency-division multiplexing (OFDM)-the allocated radio spectrum is divided into eight separate 20 MHz channels, which can each provide 54 Mbps of bandwidth. Although all devices connected to any one-channel share its bandwidth, the devices can, however, roam from one channel to another seamlessly.

There is talk in the industry that these two standards could be unified and the common physical layer makes this a possibility. One initiative is by leading chip maker Atheros, which is backing a unified protocol.

In any case, the 5 GHz adapter cards and access points will not be able to communicate with 2.4 GHz-based 802.11b systems and this has given rise to the development of an 802.11b-compatible standard called 802.11g that doubles the operating speed to 22 Mbps. Thus, while 5 GHz is positioned at the future WLAN frequency band, the current 2.4 GHz may still hold its installed base for some time to come.

5 Ghz Friendly Bluetooth
Because both Bluetooth and 802.11b WLANs operate in the 2.4 GHz frequency range, there is an issue of interference. With the 5 GHz WLAN, this will become a non-issue. With its expected broad device support, Bluetooth has the potential to provide short-range networks for devices including PDAs, PCs, refrigerators and cars.

Bluetooth is the codename for an open frequency hopping specification for short-range wireless communication of data and voice between electronic devices. It is based on a small, low-cost, low-power radio frequency module, which can be integrated into products, enabling ad-hoc point-to-point and point-to-multi-point communications.

The technology will initially offer connections from 10-100m with throughputs between 1 Mbps and 2 Mbps. Vendors including Ericsson and Toshiba are now designing products that engage two separate chips. This would allow mobile phone makers to use the Bluetooth chip solely for transmission and rely on the cell phone’s existing processor for computing capabilities, thereby driving down the costs.

In addition, most vendors are already planning a single-chip solution that combines the radio transmitter, memory functions, and other components on a single piece of silicon. British-based Cambridge Silicon Radio (CSR) has manufactured an integrated chip which is likely to be much more flexible and affordable. CSR has garnered investments from Compaq Computer, Intel, Sony and chipmaker ARM.

Sony’s high-end Vaio notebook models are amongst the first to be shipped with built-in Bluetooth chips designed by CSR, while other vendors such as Samsung Electronics, Motorola, National Semiconductor, Qual-comm and Texas Instruments are also developing single-chip Bluetooth products.

In-line with this trend, the Bluetooth Special Interest Group (SIG)-whose main charter is to ensure interoperability-also has a long-term initiative to integrate the mobile and computing chips. The SIG body also addresses Bluetooth security, versatility and reliability issues.

Thus, although much controversy has surrounded Bluetooth since its creation, it is on its way in becoming a networking standard.

Who Will Win?
The key success factor that will decide which standards will be successful will largely depend on how well the technologies serve the different customer needs and applications. While the current 802.11b products have gained a reputation for high performance and reliability, the emergence of 5 GHz technology push WLAN performance almost five-fold and will be a major consideration moving forward.

Very soon, discussions should shift from the lack of interoperability and speed in wireless access networks, to the killer applications that will ride on it.

— www.asiacomputerweekly.com