OFDM wireless mobile communication system and method for estimating SNR of channel thereof
In a method for estimating a signal-to-noise ratio (SNR) of an orthogonal frequency division multiplexing (OFDM) wireless mobile communication system, noise is estimated from adjacent received signals of at least two adjacent subcarriers and received signals of subcarriers, noise power is calculated by calculating a mean square value of the estimated noise by summing squares of the estimated noise, a mean square value of the received signals is calculated by summing squares of the received signals, signal power is calculated by subtracting the noise power from the mean square value of the received signals, and the SNR is calculated using the signal power and the noise power. Thus, the method of the present invention having low complexity can estimate an SNR efficiently regardless of channel changes on a frequency axis when one OFDM symbol includes preamble data.
1. A method for estimating a signal-to-noise ratio (SNR) of a wireless mobile communication system, comprising:
estimating noise by using adjacent received signals of at least two adjacent subcarriers and received signals of subcarriers;
calculating noise power by calculating a mean square value of the estimated noise by summing squares of the estimated noise;
calculating a mean square value of the received signals by summing squares of the received signals;
calculating signal power by subtracting the noise power from the mean square value of the received signals; and
calculating the SNR using the signal power and the noise power,
wherein estimating the noise includes:
deriving components of adjacent received signals from adjacent received signals of adjacent subcarriers; and
subtracting the components of the adjacent received signals from received signals of subcarriers,
wherein the subcarriers are sck, the received signals are yk, the adjacent subcarriers are sck−1 and sck+1, and the adjacent received signals are yk−1 and yk+1, and
wherein the noise power is calculated using a first expression:
N
pow
=
2
3
(
N
-
2
)
∑
k
y
k
-
1
2
(
y
k
-
1
+
y
k
+
1
)
2
,
where N pow denotes the noise power, and ⅔ denotes a scaling down value.
2. The method of claim 1 , wherein the wireless mobile communication system is an orthogonal frequency division multiplexing (OFDM) system that transmits a preamble using one OFDM symbol.
3. The method of claim 2 , wherein the OFDM system is a Wireless Broadband (WiBro) system or a Worldwide Interoperability for Microwave Access (WiMAX) system.
4. The method of claim 1 , wherein the wireless mobile communication system is an 802.11 wireless local area network (WLAN) system that transmits a preamble using one OFDM symbol.
5. The method of claim 1 , wherein the signal power is calculated using a second expression:
S
pow
=
1
N
-
2
∑
k
y
k
2
-
N
pow
[
Expression
B
]
where S pow denotes the signal power.
6. A method for estimating a signal-to-noise ratio (SNR) of a wireless mobile communication system, comprising:
estimating noise by using adjacent received signals of at least two adjacent subcarriers and received signals of subcarriers;
calculating noise power by calculating a mean square value of the estimated noise by summing squares of the estimated noise;
calculating a mean square value of the received signals by summing squares of the received signals;
calculating signal power by subtracting the noise power from the mean square value of the received signals; and
calculating the SNR using the signal power and the noise power,
wherein estimating the noise includes:
deriving components of adjacent received signals from adjacent received signals of adjacent subcarriers; and
subtracting the components of the adjacent received signals from received signals of subcarriers,
wherein the subcarriers are sck, the received signals are yk, the adjacent subcarriers are sck−2, sck−1, sck+1, and sck+2, and the adjacent received signals are yk−2, yk−1, yk+1, and yk+2, and
wherein the noise power is calculated using a first expression:
N
pow
=
18
35
(
N
-
4
)
∑
k
y
k
-
(
2
3
(
y
k
-
1
+
y
k
+
1
)
-
1
6
(
y
k
-
2
+
y
k
+
2
)
)
2
,
where, N pow denotes the noise power, and ⅔, ⅙, and 18/35 denote scaling down values.
7. The method of claim 6 , wherein the signal power is calculated using a second expression:
S
pow
=
1
N
-
4
∑
k
y
k
2
-
N
pow
[
Expression
D
]
where S pow denotes the signal power.