HIPERLAN/2 is a European-standard high-speed wireless local area network (WLAN) operating in the 5 GHz band. In order to support broadband multimedia communications, it can provide data rates up to 54 Mbps. The HIPERLAN/2 standard specifies a flexible radio-access network that can be used with a variety of core networks, including UMTS. It is likely that HIPERLAN/2 will become an important complementary technology to 3G cellular systems, typically used for `hot-spot' coverage. In this paper, the use of HIPERLAN/2 in conjunction with UMTS is discussed. Software-simulated physical layer performance results are presented and an evaluation given of the impact of the use of sectorised antennas at access points. Results are shown for statistical channel models and real channel measurements taken in both indoor and outdoor environments in the 5 GHz band.