ng a corner may take the MS out of one cell quality. The power radiated by the MS can be reduced by command into another with almost no overlap in which a handover can be from the BS in 13 steps of 2dB each. The reduction is one step at a set up. time. The decision to reduce the MS power is based on measure- Co-channel interference. Placing a large number of microcells ments of the signal level (RXLEV) and bit error rate (RXQUAL) in one area may ultimately lead to difficulties with frequency which are made by the MS and reported to the BS. re-use. It becomes much more difficult to predict the carrier to interference ratio when the coverage is dominated by buildings rather than distance, and hence the maximum microcell density 48.9.3.6 Multipath equalisation is not easy to forecast. Network loading. The increased number of handovers inherent Very high bit rates are used over the air interface between the in the microcell environment lead to a greater requirement for handset and the base station. When a signal is reflected from a signalling capacity in the network. building, it may arrive at the receiver slightly after the direct wave, and cause interference. The time delay may be small (up to 10us or Solutions to these problems exist, and are being developed by so) but the bit period of the baseband data is also very short (3.7us), PCN operators and manufacturers. Only when microcells are SO multipath equalisation is needed to demodulate the signal widely implemented will the advantages of PCN be fully apparent. 48/12 Personal communications networks 48.11 Bibliography Lindell, F., Swerup, J. and Uddenfeldt, J. (1987) Digital cellular radio for the future, Ericsson Review, (3). Balston, D.M. (1989) Pan-European cellular radio: or 1991 and all Macaris, R.C.V. (1991) Personal and Mobile Radio Systems, Peter that, Electronics and Communications Eng. J., January/Fe- Peregrinus Ltd. bruary. Marnick, P.J. (1991) Transmission network issues involved in the Cox, D.C. (1987) Universal digital portable radio communications,