HIPERLAN type 2 for broadband wireless communication

The key drivers of demand for radio-based broadband access networks are massive growth in wireless and mobile communications, the emergence of multimedia applications, demands for high-speed Internet access, and the deregulation of the telecommunications industry. Present-day wireless telecommunications networks, which are primarily narrowband, are mostly used for circuit-switched voice services. The evolution of second-generation and the development of third-generation mobile wireless systems aim to enable networks to provide instantaneous user bit rates of up to 2 Mbit/s per radio channel. This capacity will significantly improve packet-data and mobile multimedia applications. In addition, even higher data rates can be obtained for local area networks using novel short-range wireless technologies. Bandwidth-hungry, realtime and interactive multimedia services, such as high-quality video distribution, client/server applications, and data-bank access, are typical applications for this technology. Therefore, new wireless networks with broadband capabilities are being sought to provide high-speed integrated services (data, voice, and video) with costeffective support for quality of service (QoS). Considerable research and standardization efforts have been expended to devise appropriate transmission and networking technologies. The Internet Engineering Task Force (IETF), the International Telecommunication Union (ITU) and the ATM Forum are defining the fixed core network. Similarly, the Broadband Radio Access Networks (BRAN) project of the European Telecommunications Standards Institute (ETSI) is working on standards for different kinds of wireless broadband access network. One of these standards, called highperformance radio local-area network, type 2 (HIPERLAN/2) will provide high-speed communications access to different broadband core networks and moving terminals (portable as well as mobile). In Japan, a system that is very similar to HIPERLAN/2 has also been specified. The main difference between it and HIPERLAN/2 is that the spectrum-sharing rule of the Japanese system introduces a carrier-sensing mechanism. Before beginning standardization work on HIPERLAN/2, ETSI had developed the HIPERLAN/1 standard for ad hoc networking of portable devices. This standard mainly supports asynchronous data transfer and applies a multiple access mechanism—from the carrier-sense multiple access (CSMA) family—with collision avoidance (CA). Using the CSMA/CA technique for resolving contention, the scheme shares available radio capacity between active users who attempt to transmit data during an overlapping time span. Although HIPERLAN/1 provides a means of transporting timebounded services, it does not control or guarantee QoS on the wireless link. It is thus considered a system for best-effort delivery of data. This is what motivated ETSI to develop a new generation of standards that support asynchronous data and timecritical services (for example, packetized voice and video) that are bounded by specific time delays.