Wireless Lan Standards

Wireless LAN Standards

There are several wireless LAN solutions available today, with varying levels of standardization and interoperability. Two solutions that currently lead the industry are, HomeRF and Wi-Fi* (IEEE** 802.11b). Of these two, 802.11 technologies enjoy wider industry support and are targeted to solve Enterprise, Home and even public .hot spot. wireless LAN needs.

1. IEEE 802.11

The IEEE finalized the initial standard for wireless LANs, IEEE 802.11 [1] in June 1997.This initial standard specifies a 2.4 GHz operating frequency with data rates of 1 and 2 Mbps. With this standard, one could choose to use either frequency hopping or direct sequence (two non compatible forms of spread spectrum modulation). Because of relatively low data rates (as compared to Ethernet), products based on the initial standard did not flourish as many had hoped.

In late 1999, the IEEE published two supplements to the initial 802.11 standard: 802.11a and 802.11b (Wi-Fi*). The 802.11a [3] standard (High Speed Physical Layer in the 5 GHz Band) specifies operation in the 5 GHz band with data rates up to 54 Mb/s. The advantages of this standard (compared to 802.11b.Higher Speed Physical Layer Extension in the 2.4 GHz Band) include having much higher capacity and less RF (radio frequency) interference with other types of devices (e.g., Bluetooth), and products are just now becoming available throughout 2002. However, 802.11a isn't compatible with 802.11b and 802.11g products. As with the initial standard, 802.11b operates in the 2.4 GHz band, but it includes 5.5 and 11 Mb/s in addition to the initial 1 and 2 Mb/s. The 802.11b standard only specifies direct sequence modulation, but it is backward compatible with the initial direct sequence wireless LANs. The IEEE 802.11b standard is what most companies choose today for deploying wireless LANs.

The 802.11 working group is currently working to extend the data rates in the 2.4 GHz band to 54 Mb/s using OFDM (orthogonal frequency division multiplexing), which is the 802.11g [7] standard. This standard will hopefully be ratified by the end of 2002. Companies should be able to easily scale their existing 802.11b products to become 802.11g-compliant through firmware upgrades. This enables companies having existing 802.11b infrastructures to scale up their network via relatively simple cost-effective changes.

2. HiperLAN Ð...

European Telecommunications Standards Institute, ETSI, ratified in 1996 with High Performance Radio LAN (HiperLAN /1) standard to provide high speed communications (20Mbps) between portable devices in the 5GHz range. Similarly to IEEE802.11, HiperLAN/1 adopts carrier sense multiple access protocol to connect end user devices together. On top of that, HiperLAN/1 supports isochronous traffic for different type of data such as video, voice, text, etc. Later, ETSI, rolled out in June 2000, a flexible Radio LAN standard called HiperLAN 2, designed to provide high speed access (up to 54 Mbps at PHY layer) to a variety of networks including 3G mobile core networks, ATM networks and IP based networks, and also for private use as a wireless LAN system. Basic applications include data, voice and video, with specific QoS parameters taken into account. HIPERLAN/2 has a very high transmission rate up to 54 Mbps. This is achieved by making use of a modularization method called Orthogonal Frequency Digital Multiplexing (OFDM). OFDM is particularly efficient in time-dispersive environments,