System capacity of F-TDMA cellular systems

We study the system capacity of cellular systems with time-division multipl e access, slow time-frequency hopping (F-TDMA), and conventional single-use r processing at the receivers. System capacity is formally defined as the m aximum of the product of the number of users per cell times the user spectr al efficiency for a given maximum outage probability. We adopt an informati on-theoretic definition of outage as the event that the mutual information of the block-interference channel resulting from a finite number of signal bursts spanned by the transmission of a user code word falls below the actu al code rate, because of fading, shadowing, and interference. Starting from this definition, we develop a general framework which naturally takes into account many different aspects of F-TDMA cellular systems like channel reu se, channel utilization, waveform design, time-frequency hopping, voice act ivity exploitation, handoff, and power control strategies. Most importantly , our analysis does not rely on the choice of a particular coding scheme an d can be applied to a very large class of systems in order to find guidelin es for capacity-maximizing system design. A numerical example based on a ty pical urban mobile environment shows that there is a considerable capacity gap between actual F-TDMA systems and the limits predicted by our analysis, However, this gap can be filled by carefully designed "practical" systems, which make use of conventional single-user processing and simple coded mod ulation schemes.