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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL. 50, NO. 3, MAY 2001
Fig. 3.
Capacity in the 27-cell CDMA network with three hot spots.
left corner is at (1600,
1000) m, and the upper right corner is
at (6100, 3500) m. All the hot spots have the same relative user
density per grid point, which is five times that of a grid point
with no hot spot.
The equal capacity of this network calculated from (8) is 13
users per cell, giving a network capacity of 351. The network
capacity obtained from (9) is 540 (the rounded-down capacity
is 528). The IP solution of (9) yields a network capacity of 536
(with 106 610 branches). The capacity in each cell is shown in
parentheses in Fig. 3. The capacity of cells 4, 15, and 19, which
are inside the hot-spot clusters, has decreased from 18 to 3, 17
to 1, and 17 to 9, respectively. These cells lose the most capacity
due to the increase in intracell and intercell interference because
of the nonuniform user distribution. The network capacity opti-
mization tries to increase the sum of the capacities of the cells
by adjusting the physical parameters of power compensation
factors, pilot-signal powers, and base-station locations. We now
examine the advantages of adjusting these parameters in our op-
timization.
1) Optimization Using Power Compensation Factors: From
(31), the maximization of network capacity with respect to PCFs
increases the network capacity to 560 (the rounded-down ca-
pacity is 546). The MIP solution of (31) yields a network ca-
pacity equal to 555 (with 129 357 branches) and the cell capaci-
ties given in Fig. 4. The values of the optimized PCFs are shown
in brackets and the cell capacities are shown in parentheses.
After optimization, the capacity of cells 4, 15, and 19 increases
from 3 to 12, 1 to 9, and 9 to 14, respectively. Even though the
capacity in a few cells has decreased, the smallest capacity in
any cell has increased from 1 to 9. Without the power compen-
sation optimization, the cells with high interference have very
small capacity.
The optimization increases the power compensation factors
of the cells with high interference. This results in a PCF of 1.64
for cell 4, 1.71 for cell 15, and 1.56 for cell 19. Increasing the
PCF of a cell increases its signal-to-noise ratio, thus increasing
the cell’s capacity.
Fig. 4.
Capacity in the 27-cell CDMA network, which is optimized using
power compensation factors.
Fig. 5.
Capacity in the 27-cell CDMA network, which is optimized using
pilot-signal powers.
