Several potential technologies have been evaluated for wireless access, including CT-2, DECT and a number of proprietary systems. In most cases it is clear that the system architecture can be independent of the radio technology. To meet the objective of low costs, the proposed system has been based upon a standard radio interface thus allowing volume of scale cost reductions to be achieved. The prototype wireless access system is based on CT-2 as this technology is already in volume production. The architecture of the wireless access system is compatible with DECT and, when this technology is commercially available, it would be possible to upgrade the wireless access system to provide basic rate ISDN. The CT-2 radio distribution point (DP) provides 6 radio channels which can support up to 30 customers by employing demand assignment. The 6 radio transceivers communicate with the supporting exchange interface equipment via 3 copper pairs using digital transmission based on the ISDN U interface. A key requirement when designing the radio DP is to minimise the power consumption so that the unit can be powered over the same three copper pairs used for transmission. To achieve this it is necessary to minimise the functionality at the radio DP and make best use of the signalling channel on the U interface to control the transceivers from the exchange interface.
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