There is a mis-print in the statement of problem 30.5.3 on page 755. The correct statement should read: "A mobile communication system is to be designed to the following specifications: the instantaneous received amplitude r shall not drop below a specified level rmin more than 10% of the time. The system shall be operational at the cell-boundary (maximum distance from base station) for 90% of the time. The signal experiences both small-scale Rayleigh fading and large-scale log-normal fading, with σF=6 dB. Find the required fading margin for the system to work".