BAHAMA Wireless ATM LAN NTT’s Wireless ATM Access

WIRELESS ATM SYSTEMS 343 this method uses preestablished multiple virtual channels, which require more bandwidth even though only one of them is used at a time.

12.2.4 BAHAMA Wireless ATM LAN

A wireless ATM LAN called BAHAMA was proposed at Bell Laboratories w x 6 . The basic characteristic of the network is its ad hoc nature. The network is self-organizing, that is, a predetermined topology does not exist. The BAHAMA network consists of two types of network elements: portable base Ž . stations PBSs and mobile endpoints. Each PBS combines ATM switching functionality with wireless access interfaces. The PBSs communicate to determine the network topology after changes due to the addition or deletion of network elements. PBSs are designed with simplicity in mind, and the ATM segmentation and reassembly are carried out in the portable units. In order to support mobility in the simplest possible way, a new VPIrVCI concept is defined that supports routing based on the destination address. Mobility is supported by means of an adaptive homing algorithm. The advantages of this homing algorithm include preservation of FIFO cell Ž sequence within a connection, and fast handoffs achieved by eliminating . node-by-node connection setup . The network employs a wireless data link layer that provides high reliability, based on both automatic repeat request Ž . Ž . ARQ and forward error correction FEC . Multiple access is provided by Ž . w x distributed-queuing request update multiple access DQRUMA 18 . w x SWAN is another prototype system proposed at Bell Laboratories 5 . This system is an experimental indoor wireless ATM network based on off-the-shelf 2.4-GHz ISM band radios that operate 625 kbitrs between a base station and a mobile terminal.

12.2.5 NTT’s Wireless ATM Access

A system proposed at NTT Wireless System Laboratories called ATM Ž . Wireless Access AWA concentrates on wireless access to an ATM network w x Ž . 2 . It operates in the superhigh-frequency band 3᎐30 GHz for public and private access at data rate between 30 and 80 Mbitrs. Highly directive antennas help alleviate serious shadowing effects that are apparent at these frequencies. The system is designed as a dual wireless ATM LAN with access to an ATM-based public multimedia network. The AWA system is designed for high-speed access with limited terminal mobility and incorporates dy- namic reservation TDMA, FECrARQ, and QPSK modulation with differen- tial detection.

12.2.6 Other European Projects