Method and system for adaptive control of sub-carriers
View Patent ↗A method and system for adaptive control of sub-carriers is useful for increasing frequency diversity gain to improve bit error rate performance in an Interleaved Frequency Division Multiple Access (IFDMA) system. The method includes selecting a combination of a Repetition Factor (RF) and a repetition block size (Q), from possible combinations of a RF and a Q, based on a number of users (N u ) (step 1405 ). A Spreading Factor (SF), Forward Error Correction (FEC) coding rate (R), or modulation order (M) based on the N u is then determined (step 1410 ). Control signals are then provided based on the RF and Q, and based on the SF, R, or M (step 1415 ).
1. A method for providing control signals for adaptive control of sub-carriers comprising:
selecting a combination of a Repetition Factor (RF) and a repetition block size (Q) from possible combinations of the RF and the Q based on a number of users (N u ) of an Interleaved Frequency Division Multiple Access (IFDMA) system;
determining a Spreading Factor (SF), a Forward Error Correction (FEC) coding rate (R), or a modulation order (M) based on the N u ; and
providing control signals for adaptive control of the sub-carriers based on the RF and Q, and based on the SF, R, or M.
2. The method of claim 1 wherein the combination of RF and Q is selected using the following equation:
I
n
=
CEIL
[
log
2
(
N
sub
N
u
)
]
(
n
=
0
,
1
,
⋯
,
N
u
-
1
)
,
where I n denotes a rate index for a user n, and N sub is a total number of sub-carriers.
3. The method of claim 2 wherein the rate index is decremented by one user until the total sum of Q(I n )=N sub .
4. The method of claim 2 wherein an SF for the user n is determined by the following equation:
SF
(
n
)
=
Q
(
I
n
)
W
(
n
)
,
where W(n) is a requested number of sub-carriers for the user n and Q(I n ) is the repetition block size for the rate index for the user n.
5. The method of claim 2 wherein a coding rate R for the user n is determined by the following equation:
R
(
n
)
=
W
(
n
)
Q
(
I
n
)
where R(n) is the FEC coding rate for the user n, Q(I n ) is the repetition block size for the rate index for the user n, and W(n) is a requested number of sub-carriers for the user n.
6. The method of claim 2 wherein a modulation order M for the user n is determined by the following equation:
M
(
n
)
=
W
(
n
)
Q
(
I
n
)
where M(n) is the number of bits per modulated symbol for the user n, Q(I n ) is the repetition block size for the rate index for the user n, and W(n) is a requested number of sub-carriers for the user n.
7. The method of claim 1 wherein the combination of RF and Q is selected based on both N u and on a requested number of sub-carriers W(n) for a user n by a mobile station using the IFDMA system.
8. The method of claim 7 wherein the combination of RF and Q is selected using the following equation:
I
n
=
CEIL
[
log
2
(
W
(
n
)
∑
j
=
0
N
u
-
1
W
(
j
)
×
N
sub
)
]
(
n
=
0
,
1
,
…
,
N
u
-
1
)
,
where I n denotes a rate index for the user n, and N sub is a total number of sub-carriers.
9. The method of claim 8 wherein the rate index is decremented by one user until the total sum of Q(I n )=N sub .
10. An Interleaved Frequency Division Multiple Access (IFDMA) base station comprising:
a controller adapted to provide a Repetition Factor (RF) and a repetition block size (Q) based on a number of users (N u ) of the base station, and also adapted to provide a Spreading Factor (SF), a Forward Error Correction (FEC) coding rate (R), or a modulation order (M) based on the N u ; and
a signal processor adapted to receive the RF and Q, and the SF, R, or M from the controller so as to increase a number of active sub-carriers.
11. The base station of claim 10 wherein the provided RF and Q, and the SF, R, or M are transmitted using sub-channels from the base station to a signal processor in a mobile station.
12. The base station of claim 10 wherein the RF and Q are selected using the following equation:
I
n
=
CEIL
[
log
2
(
N
sub
N
u
)
]
(
n
=
0
,
1
,
…
,
N
u
-
1
)
,
where I n denotes a rate index for a user n, and N sub is a total number of sub-carriers.
13. The base station of claim 12 wherein the rate index is decremented by one user until the total sum of Q(I n )=N sub .
14. The base station of claim 12 wherein an SF is determined by the following equation:
SF
(
n
)
=
Q
(
I
n
)
W
(
n
)
,
where W(n) is a requested number of sub-carriers for the user n and Q(I n ) is the repetition block size for the rate index for the user n.
15. The base station of claim 12 wherein a coding rate R is determined by the following equation:
R
(
n
)
=
W
(
n
)
Q
(
I
n
)
where R(n) is the FEC coding rate for the user n, Q(I n ) is the repetition block size for the rate index for the user n, and W(n) is a requested number of sub-carriers for the user n.
16. The base station of claim 12 wherein a modulation order M for the user n is determined by the following equation:
M
(
n
)
=
W
(
n
)
Q
(
I
n
)
where M(n) is the number of bits per modulated symbol for the user n, Q(I n ) is the repetition block size for the rate index for the user n, and W(n) is a requested number of sub-carriers for the user n.
17. The base station of claim 10 wherein the RF and Q are selected based on both N u and on a requested number of sub-carriers W(n) for a user n by a mobile station that is in radio communication with the base station.
18. The base station of claim 17 wherein the RF and Q are selected using the following equation:
I
n
=
CEIL
[
log
2
(
W
(
n
)
∑
j
=
0
N
u
-
1
W
(
j
)
×
N
sub
)
]
(
n
=
0
,
1
,
…
,
N
u
-
1
)
,
where I n denotes a rate index for the user n, and N sub is a total number of sub-carriers.
19. The method of claim 18 wherein the rate index is decremented by one user until the total sum of Q(I n )=N sub .
20. An Interleaved Frequency Division Multiple Access (IFDMA) system for providing control signals for adaptive control of sub-carriers comprising:
means for selecting a combination of a Repetition Factor (RF) and a repetition block size (Q) from possible combinations of the RF and the Q based on a number of users (N u ) of the system;
means for determining a Spreading Factor (SF), a Forward Error Correction (FEC) coding rate (R), or a modulation order (M) based on the N u ; and
means for providing control signals for adaptive control of the sub-carriers to signal processors based on the RF and Q, and based on the SF, R or M.