Computational Intelligence - February 2014 - 48
The interference at TP i in the
downlink direction is from the active
BSs j i . That is, we only consider the
interference from the BSs which are
close to TP i . Then, the signal quality
constraint for each connection in the
downlink direction can be expressed as:
W
R di
~I
d
in, i
p dji g ijk s ij
= SIR di s ij (17)
+ I dout, i + h mi
for i ! I, j ! J , where
I din, i =
/
=
/
dv i
ilk
l
p g
l ! J i, l ! j
represent the intercell and intracell interferences in the downlink direction,
respectively. p dji is the power assigned
from BS j to a mobile station at TP i
and p dj vi is the total power of the sector
whose maximum influence region contains TP i of BS j . R di is the user data
rate provided that all the mobile stations
have the same value R di = 64 kbit/s.
SIR di = 4 db is the lower bound on SIR
in downlink. h mi = 108 dbm is the thermal noise at TP i and ~ = 0.5 is the
orthogonality loss factor. For any active
connection between a BS installed in CS
j and TP i, the summation term of I din,i
expresses the power distributed to the
TPs falling in the sector v i and severed
by CS j . tp j is the pilot signals of BS j .
I dout,i is the interference due to the signals
transmitted by the neighbor BSs J i .
Obviously, the power that a BS can
assign to a connection is nonnegative
and there exists an upper bound on the
maximum power p djimax . We have:
0 # p dji # p djimax 6 i ! I.
(18)
The limit on the total power that
each BS j can emit is given by the following inequality:
0 # p dj v = tp j +
/
p dji s ij # p djmax (19)
v
i ! C jk
for j ! J, v = 1, 2, 3 , where p djmax is the
upper bound on the total power emitted
by BS j in downlink.
48
Input: The state of each BS: X;
The set of the TP: I;
The set of the CS: J.
Output: I jkv, C jkv, J i .
for i d I do
for j d J do
if x jk =1 then
Compute the propagation gain
g ijk and the received pilot power
t ji = p
t j g ijk ;
p
t ji 2 p
t min then
if p
I jkvi: = I jkvi j i; J i: = J i j j;
end if
end if
end for
uj = arg max p
t ji by Eq. (7);
D. Fix S As Given X by Using the
Iterative Power Control Scheme
t ! C jk
= p dj vi g ijk - p dji g ijk
I
i!I
This model is a complex constrained
combinational optimization problem. To
solve this problem, we propose an iterative
power control method to compute the
power p ui and p dji, i ! I, j ! J , and then
check the constraints (12)-(19) to determine the state s ij of each connection.
Algorithm 1: Allocate TP to BS.
u dt p djt g ijk s tj - p dji g ijk + pt j g ijk
vi
d
out, i
Finally, we consider the rate of coverage as follows:
Tcap
(20)
/ u i $ 0.9 .
A subset J has been selected from the
set CS J and a definite configuration
parameters combination level k is chosen
for each BS installed at CS j ! J . That
is, x jk is determined. There are three basic
procedures to assign a TP i to a suitable
BS and determine the power in the
uplink and downlink directions.
jdJ
vi
vi
C ujk : = C ujk j i .
end for
Eq. (21) can be extended by the
equation c = /
u ut p ut g tjk s tj with an
t ! C jk
additional variable c . Substituting this
into Eq. (21) we have that
vi
p ui g ijk =
1) tp allocation
We first determine I vjk and C vjk for
j ! J, k ! K, v = 1, 2, 3 and j i for each
TP i . That is, we find the maximum
influence of each sector of every BS and
the cells. Specifically, it can be achieved
by Algorithm 1.
2) power Control in
uplink Direction
The problem is to determine the minimum transmit power for mobile station
such that constraint (15) is satisfied. Let
Q ij = W SIR uj R ui , then the Eq. (15)
can be converted into the following linear equations:
(1 + Q ij) p ui g ijk -
/
u ut p ut g tjk s tj = h bjvi
t ! C jki
v
(21)
for i ! I, j ! J , where
vi
h bj
= h bj + I uout, i = h bj +
/
vi
u ut p ut g tjk .
vi
t ! I jk, t g C jk
(22)
It is the system interference at the sector v i containing TP i of BS j , which
is composed of the thermal noise and
the interference from the mobile stations in the maximum influence region
of the sector v i at BS j , but not in the
same cell.
IEEE ComputatIonal IntEllIgEnCE magazInE | FEbruary 2014
and
c=
/
c + h vbji
1 + Q ij
u ut p ut g tjk s tj
vi
t ! C jk
= (c + h vbji)
/
t ! C jki
v
u tu s tj
.
1 + Q tj
Solving the above equation for c
yields c = bh vbji ^1 - b h with b =
/ u ut s tj ^1 + Q tjh. Hence, we have
t ! C jki
v
p ui =
vi
h bj
g ijk (1 + Q ij) e 1 -
/
t ! C jki
v
u ut s tj
1 + Q tj o
i ! C jk .
,
(23)
vi
From Eq. (23) we have that p ui
depends on the spreading gain Q ij, the
propagation gain g ijk, the system interference h vbji, and the connection state
s tj, t ! C vjki . It is independent of the variables p ui in the same cell. In addition, from
the third factor in the denominator of Eq.
(23), there is no feasible power allocation if
/
u ut s tj $ 1 + Q tj
vi
t ! C jk
and all user data rate and QoS parameters are equal, i.e. Q tj = Q for all
t ! C vjki . In WCDMA system, if W =
3.84 Mhz and the user data rate R ui =
12.2 kbit/s in uplink and SIR uj = 6 db
Table of Contents for the Digital Edition of Computational Intelligence - February 2014
Computational Intelligence - February 2014 - Cover1
Computational Intelligence - February 2014 - Cover2
Computational Intelligence - February 2014 - 1
Computational Intelligence - February 2014 - 2
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