Apparatus and method for automatic gain control in a broadband wireless access communication system
An AGC apparatus and method in a BWA communication system are provided, in which a MAP interpreter detects a beamformed symbol period in an (n−1) th signal, a symbol power calculator measures an average signal level of a symbol in an n th signal, and a beamforming gain calculator calculates a beamforming gain of the n th signal by adding a beamforming gain of the (n−1) th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the n th signal using information about the beamformed symbol period of the (n−1) th signal and the average signal level of the symbol in the n th signal.
1. An Automatic Gain Control (AGC) apparatus in a wireless communication system, comprising:
a MAP interpreter for detecting a beamformed symbol period in an (n−1) th signal;
a symbol power calculator for measuring an average signal level of a symbol in an n th signal; and
a beamforming gain calculator for calculating a beamforming gain of the n th signal by adding a beamforming gain of the (n−1) th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the n th signal using information about the beamformed symbol period of the (n−1) th signal and the average signal level of the symbol in the n th signal.
2. The AGC apparatus of claim 1 , further comprising:
an energy detector for measuring an average signal level of a preamble symbol in the n th signal before the n th signal is processed by Fast Fourier Transform (FFT); and
an automatic gain controller for adding the beamforming gain of the n th signal to the average signal level of the preamble symbol, calculating the difference between the sum and a reference power, and outputting the difference as a gain control value.
3. The AGC apparatus of claim 1 , wherein the MAP interpreter detects the beamformed symbol period based on DownLink-MAP (DL-MAP) information.
4. The AGC apparatus of claim 1 , wherein the beamforming gain calculator calculates the beamforming gain of the n th signal by the following equation,
V G — BF ( N )=α V G — BF ( N− 1)+βΔ( N ) (1)
where V G — BF (N) denotes the beamforming gain of the n th signal, V G — BF (N−1) denotes the beamforming gain of the (n−1) th signal, Δ(N) denotes the power difference between the signal of the beamformed symbol period and the signal of the non-beamformed symbol period in the n th signal, and α and β denote reflection ratios of power differences.
5. An Automatic Gain Control (AGC) method in a wireless communication system, comprising the steps of:
detecting a beamformed symbol period in an (n−1) th signal;
measuring an average signal level of a symbol in an n th signal; and
calculating a beamforming gain of the n th signal by adding a beamforming gain of the (n−1) th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the n th signal using information about the beamformed symbol period of the (n−1) th signal and the average signal level of the symbol in the n th signal.
6. The AGC method of claim 5 , further comprising the steps of:
measuring an average signal level of a preamble symbol in the n th signal before the n th signal is processed by Fast Fourier Transform (FFT); and
adding the beamforming gain of the n th signal to the average signal level of the preamble symbol and calculating the difference between the sum and a reference power.
7. The AGC method of claim 5 , wherein the detection comprises detecting the beamformed symbol period based on DownLink-MAP (DL-MAP) information.
8. The AGC method of claim 5 , wherein the beamforming gain calculation comprises calculating the beamforming gain of the n th signal by the following equation,
V G — BF ( N )=α V G — BF ( N− 1)+βΔ( N ) (2)
where V G — BF (N) denotes the beamforming gain of the n th signal, V G — BF (N−1) denotes the beamforming gain of the (n−1) th signal, Δ(N) denotes the power difference between the signal of the beamformed symbol period and the signal of the non-beamformed symbol period in the n th signal, and α and β denote reflection ratios of power differences.
9. A receiver for automatic gain control in a wireless communication system, comprising:
a MAP interpreter for detecting a beamformed symbol period in an (n−1) th signal;
a symbol power calculator for measuring an average signal level of a symbol in an n th signal;
a beamforming gain calculator for calculating a beamforming gain of the n th signal by adding a beamforming gain of the (n−1) th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the n th signal using information about the beamformed symbol period of the (n−1) th signal and the average signal level of the symbol in the n th signal;
an energy detector for measuring an average signal level of a preamble symbol in the n th signal before the n th signal is processed by Fast Fourier Transform (FFT); and
an automatic gain controller for adding the beamforming gain of the n th signal to the average signal level of the preamble symbol, calculating the difference between the sum and a reference power, and outputting the difference as a power control value.
10. The receiver of claim 9 , further comprising
a gain control amplifier for controlling an amplification ratio for a signal received through an antenna according to the power control value received from the automatic gain controller;
an analog-to-digital converter for converting an amplified signal received from the gain control amplifier to a digital signal;
an FFT processor for processing the digital signal by FFT; and
a subcarrier demapper for demapping FFT signals mapped to subcarriers, received from the FFT processor and providing the demapped signals to the MAP interpreter.
11. The receiver of claim 9 , wherein the MAP interpreter detects the beamformed symbol period based on DownLink-MAP (DL-MAP) information.
12. The receiver of claim 9 , wherein the beamforming gain calculator calculates the beamforming gain of the n th signal by the following equation,
V G — BF ( N )=α V G — BF ( N− 1)+βΔ( N ) (3)
where V G — BF (N) denotes the beamforming gain of the n th signal, V G — BF (N−1) denotes the beamforming gain of the (n−1) th signal, Δ(N) denotes the power difference between the signal of the beamformed symbol period and the signal of the non-beamformed symbol period in the n th signal, and α and β denote reflection ratios of power differences.
13. A reception method for automatic gain control in a wireless communication system, comprising the steps of:
detecting a beamformed symbol period in an (n−1) th signal;
measuring an average signal level of a symbol in an n th signal;
calculating a beamforming gain of the n th signal by adding a beamforming gain of the (n−1) th signal to a power difference between a signal of a beamformed symbol period and a signal of a non-beamformed symbol period in the n th signal using information about the beamformed symbol period of the (n−1) th signal and the average signal level of the symbol in the n th signal;
measuring an average signal level of a preamble symbol in the n th signal before the n th signal is processed by Fast Fourier Transform (FFT); and
adding the beamforming gain of the n th signal to the average signal level of the preamble symbol, calculating the difference between the sum and a reference power, and outputting the difference as a power control value.
14. The reception method of claim 13 , further comprising, before the step of detecting the beamformed symbol period in the (n−1) th signal;
amplifying a signal received through an antenna by controlling an amplification ratio according to the power control value;
converting an amplified signal received from the gain control amplifier to a digital signal;
processing the digital signal by FFT; and
demapping FFT signals to subcarriers.
15. The reception method of claim 13 , wherein the detection comprises detecting the beamformed symbol period based on DownLink-MAP (DL-MAP) information.
16. The reception method of claim 13 , wherein the beamforming gain calculation comprises calculating the beamforming gain of the n th signal by the following equation,
V G — BF ( N )=α V G — BF ( N− 1)+βΔ( N ) (4)
where V G — BF (N) denotes the beamforming gain of the n th signal, V G — BF (N−1) denotes the beamforming gain of the (n−1) th signal, Δ(N) denotes the power difference between the signal of the beamformed symbol period and the signal of the non-beamformed symbol period in the n th signal, and α and β denote reflection ratios of power differences.