US 7,609,609 B2 · Apparatus and method for processing digital signal in an OFDMA wireless communication system

Abstract

An apparatus and method is provided to process a digital signal in an orthogonal frequency division multiple access (OFDMA) wireless communication system. In the apparatus, a memory stores the number of subcarriers allocated to a mobile terminal and stores an inverse discrete Fourier transform (IDFT) coefficient. A controller outputs a mode selection signal indicating a transmission mode or a reception mode. An inverse fast Fourier transform (IFFT) block multiplies a first result obtained by determining a bitwidth for the IDFT coefficient according to the number of subcarriers by a second result obtained by determining a bitwidth for data according to the number of subcarriers.

Claims15

Dependent claims

An apparatus for processing a digital signal in a transmitter of an orthogonal frequency division multiple access (OFDMA) wireless communication system, the apparatus comprising:

a memory for storing a number of allocated subcarriers and an inverse discrete Fourier transform (IDFT) coefficient;
an inverse fast Fourier transform (IFFT) block for determining each of a bitwidth for the IDFT coefficient and a bitwidth for data according to the number of the allocated subcarriers, and performing multiplication calculations on the IDFT coefficient and the data;
and
a controller for outputting a mode selection signal indicating a transmission mode or a reception mode to the IFFT block, wherein the IDFT coefficient is defined by the following equation:
x
⁡
[
n
]
=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
⁢
ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn
≤
∑
k
=
0
N
-
1
⁢

s
⁡
(
k
)

⁢

ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn

=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
≤
N
⁢
⁢
max
⁢
⁢

s
⁡
(
k
)

wherein x[n] denotes the IDFT coefficient, n denotes an orthogonal frequency division multiplexing (OFDM) symbol index, N denotes the number of the allocated subcarriers, s(k) denotes an input signal to the IFFT block, and k denotes a subcarrier index.

89 more elements

An apparatus for processing a digital signal in a transmitter of an orthogonal frequency division multiple access (OFDMA) wireless communication system, the apparatus comprising:

a memory for storing a number of allocated subcarriers and an inverse discrete Fourier transform (IDFT) coefficient;
a first bitwidth adjuster for determining a bitwidth for data according to the number of the allocated subcarriers;
a second bitwidth adjuster for determining a bitwidth for the IDFT coefficient according to the number of the allocated subcarriers;
a multiplier for performing multiplication calculations on the data and the IDFT coefficient output from the first and second bitwidth adjusters;
and
a controller for outputting a mode selection signal indicating a transmission mode or a reception mode to the first bitwidth adjuster and the second bitwidth adjuster,
wherein the IDFT coefficient is defined by the following equation:
x
⁡
[
n
]
=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
⁢
ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn
≤
∑
k
=
0
N
-
1
⁢

s
⁡
(
k
)

⁢

ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn

=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
≤
N
⁢
⁢
max
⁢
⁢

s
⁡
(
k
)

wherein x[n] denotes the IDFT coefficient, n denotes an orthogonal frequency division multiplexing (OFDM) symbol index, N denotes the number of the allocated subcarriers, s(k) denotes an input signal to an inverse fast Fourier transform (IFFT) block, and k denotes a subcarrier index.

92 more elements

A method for processing a digital signal by a transmitter in an orthogonal frequency division multiple access (OFDMA) wireless communication system, the method comprising the steps of:

checking, by the transmitter, a number of allocated subcarriers which is stored in memory;
determining, by the transmitter, a bitwidth for an inverse discrete Fourier transform (IDFT) coefficient according to the number of the allocated subcarriers;
determining, by the transmitter, a bitwidth for data and which varies number of data bits used according to the number of the allocated subcarriers during an inverse fast Fourier transform (IFFT) process at the transmitter;
and
performing, by the transmitter, multiplication calculations on the IDFT coefficient and the data N−1 to implement the N−1 IFFT process at low power, wherein the IDFT coefficient is defined by the following equation:
x
⁡
[
n
]
=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
⁢
ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn
≤
∑
k
=
0
N
-
1
⁢

s
⁡
(
k
)

⁢

ⅇ
j
⁢
⁢
2
⁢
⁢
π
/
Nkn

=
∑
k
=
0
N
-
1
⁢
s
⁡
(
k
)
≤
N
⁢
⁢
max
⁢
⁢

s
⁡
(
k
)

wherein x[n] denotes the IDFT coefficient, n denotes an orthogonal frequency division multiplexing (OFDM) symbol index, N denotes the number of the allocated subcarriers, s(k) denotes an input signal to an inverse fast Fourier transform (IFFT) block, and k denotes a subcarrier index.

90 more elements

Dependencies are inferred from the claim text.

Apparatus and method for processing digital signal in an OFDMA wireless communication system

Life of this patent

Apparatus and method for processing digital signal in an OFDMA wireless communication system

Life of this patent

Abstract

Claims15