Full- and half-square cell plans in urban CDMA microcellular networks

The Erlang capacity per cell and per unit area in urban code-division multiple-access (CDMA) microcellular environments is evaluated. Special emphasis is given to the effect of breakpoint distance and cell size on the system Erlang capacity. Two different cell plans are considered in which the communication between the base station (BS) and the mobile unit always occurs in a line-of-sight (LOS) condition: the full- and half-square cell plans. Our main result has been to obtain analytical expressions for the Erlang capacity, which are evaluated through a cell radius-normalization procedure, as a function of the breakpoint to the cell radius ratio (R_b/R_c). This has allowed us to notice some important facts not previously reported in the literature. In particular, we observe that the Erlang capacity is a monotonically decreasing function of R_b/R_c and that close to the highest reuse efficiency is achieved for R_b<0.7R_c. Thus, given a breakpoint distance, higher Erlang capacity per cell can be achieved with greater cell radius. Or, equivalently, given a cell radius, higher system capacity can be achieved with smaller breakpoint distances; that is, with smaller base-station antenna heights and/or smaller frequencies. Also, we show that the capacity increase due to the BSs doubling or cell radius-reduction depends on the antenna heights, frequency of operation, and distance between streets. It ranges from 64 to 100%.