NEC’s WATMnet Prototype System

WIRELESS ATM SYSTEMS 341 Ž . Ž . access layer WAL , which includes wireless physical PHY , MAC, and LLC layers. The control plane includes the necessary signaling enhancements as well as the WAL. An APCP is used between the AP and the mobility-support ATM switch. This protocol is needed for the communication of information related to the status of the radio resources from the access point to the switch. The mobility-support ATM switch connected to the access point includes not only APCP but also changes to the UNI, B-ICI, and PNNI Ž . UNI q M, B-ICI q M and PNNI q M . InB-ICI q M, UNI q M, and PNNI q M, qM represents supplemental signaling information to support mobility.

12.2 WIRELESS ATM SYSTEMS

12.2.1 NEC’s WATMnet Prototype System

w x The research reported in 1 proposes an ATM cell relay paradigm to be adopted as the basis for the next-generation wireless transport architectures. It is argued that in addition to its regular advantages, the use of ATM switching for intertransmission cell traffic also avoids the crucial problem of developing a new backbone network with sufficient throughput to support intercommunication among the base stations. A protocol layering strategy, harmonized with the standard ATM protocol stack, was proposed. The wireless-specific PHY, MAC, and DLC layers below the ATM layer are added to the standard ATM protocol stack. The baseline ATM network and signaling protocol will have to be augmented to support specific mobility- related functions such as address registration, roaming, handoff, and QoS renegotiation in response to the channel impairment. These imply that the regular ATM network layer and control services such as call setup, VCIrVPI addressing, cell prioritization, and flow control indication will continue to be used for the mobile services. w x The research presented in 11 describes an experimental wireless ATM Ž . network prototype WATMnet system, which was developed at NEC C C Research Laboratories in Princeton, NJ. The prototype system operates in Ž . the 2.4-GHz industrial, scientific, and medical ISM band at a channel rate of 8 Mbitrs. Wireless network protocols at portable terminal and base Ž . station interfaces support available bit rate ABR , unspecified bit rate Ž . Ž . Ž . UBR , variable bit rate VBR , and constant bitrate CBR transport ser- vices compatible with ATM, using a dynamic time-division multiple Ž . accessrtime division duplex TDMArTDD MAC protocol for channel shar- ing and a DLC protocol for error recovery. All network entities, including portable terminals, base stations, and switches, use a mobility-enhanced Ž . Ž . version of ATM signaling Q.2931 q for switched virtual circuit SVC connection control functions, including handoffs. WIRELESS ATM SWITCHES 342 w x Hardware and software implementation details are given in 12 for the second version of the WATMnet system operating at 25 Mbitrs in the 5 GHz w x ISM band. Some experimental results in 13, 14, 15 show the validation of major protocol and software aspects, including DLC, wireless control, and mobility signaling for handoffs.

12.2.2 Olivetti’s Radio ATM LAN