The demand for cellular radio service is growing rapidly, and in heavi
ly populated areas the need arises to shrink the cell sizes and ''scal
e'' the clustering pattern. The extension of the service into the PCN
domain, mostly in-buildings and in pedestrian areas, further enhances
this trend. The vision of the ''third generation'' cellular systems in
corporates micro- and picocells for pedestrian use, with macrocells fo
r roaming mobiles. Connectivity between all these cells, while maximiz
ing total system capacity, is the main challenge facing the ''third ge
neration architects.'' The CDMA cellular system, which shares the same
frequency channel across the system (reuse pattern of one) and applie
s soft handoff between the cells, has already shown, both by analysis
and by tests, to have full connectivity between the microcells and the
overlaying macrocells without capacity degradation. The parameters in
volved in the engineering of a heterogeneous CDMA network are discusse
d in this paper. Factors that determine the size of the cell, the soft
handoff zone, and the capacity of the cell clusters are analyzed, and
engineering techniques for overlay-underlay cell clustering are outli
ned.