Scheduling method in multiple access system and apparatus using the same
A method for transmitting data streams by a transmitter in a wireless communication system is provided. The transmitter performs Fourier transform for a data stream to generate a transformed stream. The transmitter repeats the transformed stream to generate a repeated stream. The transmitter maps the repeated stream on a plurality of subcarriers to generate a transmission signal. The transmitter transmits the transmission signal to a receiver. The plurality of subcarriers are selected by starting from a subcarrier having a predetermined index and hopping at a subcarrier interval.
1. A method for transmitting data streams in a wireless communication system, comprising steps of:
performing Fourier transform for a data stream to generate a transformed stream;
repeating the transformed stream to generate a repeated stream;
mapping the repeated stream on a plurality of subcarriers to generate a transmission signal, the plurality of subcarriers selected by starting from a subcarrier having a predetermined index and hopping at a subcarrier interval; and
transmitting the transmission signal to a receiver,
wherein the predetermined index is given by the following equation,
⌊
i
-
1
M
′
⌋
M
′
(
L
′
-
1
)
+
i
where i is an index of user, M′ is the subcarrier interval, L′ is a number of the plurality of subcarriers.
2. The method of claim 1 , wherein the step of mapping the repeated stream comprises steps of:
weighting the repeated stream based on a spectral weighting vector to generate a weighted stream; and
performing inverse Fourier transform for the weighted stream.
3. The method of claim 2 , wherein the spectral weighting vector f (i) f (i) is determined by using the following equation,
f
l
(
i
)
=
0
,
if
rem
(
l
-
⌊
i
-
1
M
′
⌋
M
′
(
L
′
-
1
)
-
i
,
M
′
)
≠
0
f
L
(
i
)
[
l
]
ℋ
f
L
(
i
)
[
l
]
=
1
,
∀
l
=
0
,
1
,
…
,
L
-
1
where, rem(a,b) is a remainder when a is divided by b, i is an index of user, M′ is the subcarrier interval, L′ is a number of the plurality of subcarriers, f l (i) is a l-th element of f (i) , f L (i) [l] is defined as the following equation
f
L
(
i
)
[
l
]
=
Δ
[
f
l
(
i
)
f
l
+
L
(
i
)
⋮
f
l
+
L
(
M
-
1
)
(
i
)
]
.
4. The method of claim 1 , wherein the subcarrier interval is larger than a coherence bandwidth of the wireless communication system.
5. The method of claim 1 , wherein the subcarrier interval is determined based on a channel condition in the wireless communication system.
6. The method of claim 1 , wherein a number of the plurality of subcarriers is determined based on a channel condition in the wireless communication system.
7. A base station for transmitting data streams in a wireless communication system, the base station comprising:
a radio frequency unit for receiving a radio signal; and
a processor, operatively coupled with the radio frequency unit, configured for:
performing Fourier transform for a data stream to generate a transformed stream;
repeating the transformed stream to generate a repeated stream;
mapping the repeated stream on a plurality of subcarriers to generate a transmission signal, the plurality of subcarriers selected by starting from a subcarrier having a predetermined index and hopping at a subcarrier interval; and
transmitting the transmission signal to a receiver,
wherein the predetermined index is given by the following equation,
⌊
i
-
1
M
′
⌋
M
′
(
L
′
-
1
)
+
i
where i is an index of user, M′ is the subcarrier interval, L′ is a number of the plurality of subcarriers.
8. The base station of claim 7 , wherein the processor is configured for mapping the repeated stream by:
weighting the repeated stream based on a spectral weighting vector to generate a weighted stream; and
performing inverse Fourier transform for the weighted stream.
9. The base station of claim 8 , wherein the spectral weighting vector f (i) is determined by using the following equation,
f
l
(
i
)
=
0
,
if
rem
(
l
-
⌊
i
-
1
M
′
⌋
M
′
(
L
′
-
1
)
-
i
,
M
′
)
≠
0
f
L
(
i
)
[
l
]
ℋ
f
L
(
i
)
[
l
]
=
1
,
∀
l
=
0
,
1
,
…
,
L
-
1
where, rem(a,b) is a remainder when a is divided by b, i is an index of user, M′ is the subcarrier interval, L′ is a number of the plurality of subcarriers, f l (i) f l (i) is a l-th element of f (i) , f L (i) [l] is defined as the following equation
f
L
(
i
)
[
l
]
=
Δ
[
f
l
(
i
)
f
l
+
L
(
i
)
⋮
f
l
+
L
(
M
-
1
)
(
i
)
]
.
10. The method of claim 7 , wherein the subcarrier interval is larger than a coherence bandwidth of the wireless communication system.
11. The method of claim 7 , wherein the subcarrier interval is determined based on a channel condition in the wireless communication system.
12. The method of claim 7 , wherein a number of the plurality of subcarriers is determined based on a channel condition in the wireless communication system.