OFDM GENERATION APPARATUS IN A MULTI-CARRIER DATA TRANSMISSION SYSTEM
The present invention relates to OFDM generation apparatus and methods for generating OFDM transmission signals from OFDM symbols, each comprising a plurality of OFDM subcarriers, for transmission in a multi-carrier data transmission system. An embodiment of the proposed apparatus and method are adapted for using a selected mixing frequency for mixing said complex time-domain samples of said OFDM symbol from a baseband frequency up to a passband frequency by use of a mixing frequency to obtain said OFDM transmission signal, wherein the mixing frequency is selected such that common phase rotations of the OFDM subcarriers of said OFDM symbol with respect to adjacent OFDM symbols of said OFDM transmission signal are avoided or compensated after said mixing. Further embodiments for avoidance or compensation of such common phase rotations are provided.
1 . (canceled)
2 . An Orthogonal Frequency-Division Multiplexing (OFDM) generation apparatus for generating OFDM transmission signals from OFDM symbols, each comprising a plurality of OFDM subcarriers, for transmission in a multi-carrier data transmission system, said apparatus comprising:
circuitry configured to
inverse Discrete Fourier Transform (DFT) an OFDM symbol into complex time-domain samples; and
mix said complex time-domain samples of said OFDM symbol from a baseband frequency up to a passband frequency by use of a mixing frequency f c to obtain an OFDM transmission signal, wherein
the circuitry selects the mixing frequency f c such that common phase rotations of the OFDM subcarriers of said OFDM symbol with respect to adjacent OFDM symbols of said OFDM transmission signal are avoided or compensated after said mixing.
3 . The OFDM generation apparatus as recited in claim 2 , wherein
the circuitry selects the mixing frequency f c as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c fulfilling a condition that
k
c
·
(
Δ
T
U
)
is an integer,
T U is the useful OFDM symbol duration, and
Δ is the duration of the guard interval.
4 . The OFDM generation apparatus as recited in claim 2 , wherein
the circuitry selects the mixing frequency f c as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected to be close to a central subcarrier among the subcarriers of said OFDM symbol, and
T U is the useful OFDM symbol duration.
5 . The OFDM generation apparatus as recited in claim 2 , wherein
the circuitry selects the mixing frequency f c as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected as
k
c
=
⌊
K
ma
x
+
K
m
i
n
2
·
Δ
T
U
+
1
2
⌋
·
1
(
Δ
T
U
)
,
T U is the useful OFDM symbol duration, Δ is the duration of the guard interval, K min is the carrier index of first active carrier having the lowest frequency, and K max is the carrier index of last active carrier having the highest frequency.
6 . The OFDM generation apparatus as recited in claim 2 , wherein the circuitry stores the mixing frequency f c .
7 . The OFDM generation apparatus as recited in claim 2 , wherein
the circuitry selects the mixing frequency f c with respect to a standard mixing frequency.
8 . An Orthogonal Frequency-Division Multiplexing (OFDM) generation apparatus for generating OFDM transmission signals from OFDM symbols, each comprising a plurality of OFDM subcarriers, for transmission in a multi-carrier data transmission system, said apparatus comprising:
an inverse transformation circuit that performs an inverse Discrete Fourier Transform (DFT) of an OFDM symbol into complex time-domain samples; and
a frequency mixing means configured to mix said complex time-domain samples of said OFDM symbol from a baseband frequency up to a passband frequency by use of a mixing frequency f c to obtain an OFDM transmission signal, wherein
the mixing frequency f c is selected such that common phase rotations of the OFDM subcarriers of said OFDM symbol with respect to adjacent OFDM symbols of said OFDM transmission signal are avoided or compensated after said mixing.
9 . The OFDM generation apparatus as recited in claim 8 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c fulfilling a condition that
k
c
·
(
Δ
T
U
)
is an integer,
T U is the useful OFDM symbol duration, and
Δ is the duration of the guard interval.
10 . The OFDM generation apparatus as recited in claim 8 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected to be close to a central subcarrier among the subcarriers of said OFDM symbol, and
T U is the useful OFDM symbol duration.
11 . The OFDM generation apparatus as recited in claim 8 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected as
k
c
=
⌊
K
ma
x
+
K
m
i
n
2
·
Δ
T
U
+
1
2
⌋
·
1
(
Δ
T
U
)
,
T U is the useful OFDM symbol duration, A is the duration of the guard interval, K min is the carrier index of first active carrier having the lowest frequency, and K max is the carrier index of last active carrier having the highest frequency.
12 . The OFDM generation apparatus as recited in claim 8 , further comprising a storage means configured to store the mixing frequency f c .
13 . The OFDM generation apparatus as recited in claim 8 , wherein
the mixing frequency f c is selected with respect to a standard mixing frequency.
14 . An Orthogonal Frequency-Division Multiplexing (OFDM) generation method for generating OFDM transmission signals from OFDM symbols, each comprising a plurality of OFDM subcarriers, for transmission in a multi-carrier data transmission system, said method comprising:
inverse discrete Fourier transforming, by circuitry, an OFDM symbol into complex time-domain samples; and
mixing, by the circuitry said complex time-domain samples of said OFDM symbol from a baseband frequency up to a passband frequency by use of a mixing frequency f c to obtain an OFDM transmission signal, wherein
the mixing frequency f c is selected such that common phase rotations of the OFDM subcarriers of said OFDM symbol with respect to adjacent OFDM symbols of said OFDM transmission signal are avoided or compensated after said mixing.
15 . The OFDM generation method as recited in claim 14 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c fulfilling a condition that
k
c
·
(
Δ
T
U
)
is an integer,
T U is the useful OFDM symbol duration, and
Δ is the duration of the guard interval.
16 . The OFDM generation method as recited in claim 14 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected to be close to a central subcarrier among the subcarriers of said OFDM symbol, and
T U is the useful OFDM symbol duration.
17 . The OFDM generation method as recited in claim 14 , wherein
the mixing frequency f c is selected as
f
c
=
k
c
T
U
with the OFDM subcarrier k c at the mixing frequency f c being selected as
k
c
=
⌊
K
ma
x
+
K
m
i
n
2
·
Δ
T
U
+
1
2
⌋
·
1
(
Δ
T
U
)
,
T U is the useful OFDM symbol duration, Δ is the duration of the guard interval, K min is the carrier index of first active carrier having the lowest frequency, and K max is the carrier index of last active carrier having the highest frequency.
18 . The OFDM generation method as recited in claim 14 , further comprising storing the mixing frequency f c .
19 . The OFDM generation method as recited in claim 14 , wherein the mixing frequency f c is selected with respect to a standard mixing frequency.
20 . A receiving method, comprising:
mixing a received OFDM transmission signal, generated according to the method of claim 14 , from the passband frequency down to the baseband frequency.