HiperLAN2 is one of a number of new generation standards supporting both asynchronous data and time critical services (e.g. packetised voice and video) that are bounded by specific time delays to achieve an acceptable Quality of Service (QoS) being developed under the auspices of the ETSI’s Project BRAN (Broadband Radio Access Networks).
The HiperLAN2 standard is nearly identical to 802.11 in terms of its physical layers – both use OFDM technology to achieve their data rates, for instance – but is very different at the MAC (Media Access Control) level and in the way the data packets are formed and devices are addressed. On a technical level, whereas 802.11 can be viewed as true wireless Ethernet, HiperLAN2 is more akin to wireless Asynchronous Transfer Mode (ATM). It operates by sharing the 20MHz channels in the 5GHz spectrum in time, using Time Division Multiple Access (TDMA) to provide QoS through ATM-like mechanisms. It’s this ability to guarantee specific bandwidth to specific users that proponents cite as its major advantage over 802.11h.
HiperLAN2 relies on cellular networking topology combined with an ad-hoc networking capability. It supports two basic modes of operation: centralised mode and direct mode. The centralised mode is used in the cellular networking topology where each radio cell is controlled by an access point covering a certain geographical area. In this mode, a mobile terminal communicates with other mobile terminals or with the core network via an access point. It is mainly used in business applications – both indoors and outdoors – where an area much larger than a radio cell has to be covered. The direct mode is used in the ad-hoc networking topology – mainly in typical private home environments – where a radio cell covers the whole serving area. In this mode, mobile terminals in a single-cell home network can directly exchange data.
HiperLAN2 support came mainly from European telecommunications equipment vendors – with Ericsson Telephone Co. and Nokia Corp. amongst the founding members of the HiperLAN2 Global Forum – and it was in Europe that HiperLAN2 and 802.11h were expected to compete. However, such is the dominance of US markets and standards committees that support for HiperLAN2 had evaporated well before the first products had been expected to reach the market in mid-2002, leaving the various IEEE 802.11 standards to battle it out in the mobile communications arena.