| 摘要 |
<p>A frequency hopped cellular mobile radio system, comprising a plurality of base stations each affording a cellular region, or cell, within which communication is facilitated with a plurality of mobile units, each of which mobile units is free to move from cell to cell, the system having in combination the following features: a synchronisation system which serves to bring all mobile units within a cell into synchronisation, as observed from the base station of that cell, whereby orthogonal frequency hopping between mobile units of the cell is facilitated, frequency hopping between mobile units in different cells being non-orthogonal; an affiliation strategy which tends to constrain each mobile unit to maintain communication with a base station selected in dependence upon received signal strength; mobile unit transmission power control in dependence upon received signal/noise ratio at a base station, whereby transmitted mobile power tends towards the minimum necessary for acceptable communication; a frequency hopping strategy, wherein the number of bits per hop is limited to a few bits per hop, the actual number of hops being chosen having regard to performance and overall framing delay constraints; Nyquist filtering of signals effective to constrain interference between hops both in the time domain and in the frequency domain, hopped dwells being arranged to extend in time beyond a nominal bit transmission period (before and after the period) so as to overlap; differential phase shift keying (DPSK) modulation combined with randomised quadrature phase shift keyed (QPSK) modulation to decorrelate interference between cells; and, a system of error control coding.</p> |
