Uplink signal receiving method and apparatus using successive interference cancellation in wireless transmission system based on OFDMA

Abstract

An uplink signal receiving method and apparatus using successive interference cancellation (SIC) in a wireless transmission system based on Orthogonal Frequency Division Multiple Access (OFDMA) are provided. The uplink signal receiving method includes storing in a provisional storage each uplink intermediate frequency (IF) signal received through an antenna of a base station and subjected to analog-to-digital conversion; analyzing the uplink IF signals stored in the provisional storage and determining a terminal to be restored; converting a data symbol of the determined terminal to be restored from a time domain into a frequency domain; performing channel/phase correction on the converted data symbol; demodulating the corrected data symbol; determining if there is a terminal to be restored; and when there is a terminal to be restored, removing the demodulated data symbol of the terminal to be restored from the temporarily stored uplink IF signals and then updating the uplink IF signals; thereby, to reducing interference between sub-carriers of the terminals caused by deviation of a center frequency of the sub-carriers of terminals constituting the uplink signal in the OFDMA-based wireless transmission system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by i 5 reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 illustrates the construction of an uplink signal receiving apparatus using successive interference cancellation (SIC) in a wireless transmission system based on Orthogonal Frequency Division Multiple Access (OFDMA) in accordance with the present invention;

FIG. 2 illustrates a processing procedure of the symbol processor of the uplink signal receiving apparatus using SIC in the OFDMA-based wireless transmission system;

FIG. 3A illustrates uplink intermediate frequency (IF) signals transmitted from first and second terminals;

FIG. 3B illustrates the data symbol of a first terminal;

FIG. 3C illustrates the data symbol of a second terminal;

FIG. 3D illustrates an uplink IF signal from which the data symbol of a first terminal is removed;

FIG. 4 is a flowchart illustrating an uplink signal receiving method using SIC in an OFDMA-based wireless transmission system in accordance with the present invention;

FIG. 5 is a flowchart illustrating a process of the uplink signal receiving method using SIC in the OFDMA-based wireless transmission system illustrated in FIG. 4;

FIG. 6A illustrates demodulated -data symbols of first and second terminals that both have a center frequency of 2345.005 MHz in an uplink signal receiving method and apparatus using SIC in a conventional OFDMA-based wireless transmission system;

FIG. 6B illustrates demodulated data symbols of first and second terminals that both have a center frequency of 2345.005 MHz in the uplink signal receiving method and apparatus using SIC in the OFDMA-based wireless transmission system illustrated in FIGS. 1 and 4;

FIG. 6C illustrates demodulated data symbols of first and second terminals that have center frequencies of 2344.995 MHz and 2345.005 MHz respectively in an uplink signal receiving method and apparatus using SIC in a conventional OFDMA-based wireless transmission system; and

FIG. 6D illustrates demodulated data symbols of first and second terminals that have center frequencies of 2344.995 MHz and 2345.005 MHz respectively in the uplink signal receiving method and apparatus using SIC in the OFDMA-based wireless transmission system illustrated in FIGS. 1 and 4.

Claims

1. An uplink signal receiving method using successive interference cancellation (SIC) in a wireless transmission system based on Orthogonal Frequency Division Multiple Access (OFDMA), the uplink signal receiving method comprising the steps of: storing in a provisional storage each uplink intermediate frequency (IF) signal received through an antenna of a base station and subjected to analog-to-digital conversion;analyzing the uplink IF signals stored in the provisional storage and determining a terminal to be restored;converting a data symbol of the terminal to be restored from a time domain into a frequency domain;performing channel/phase correction on the converted data symbol demodulating the corrected data symbol;determining if there is another terminal to be restored; andwhen there is a terminal to be restored, removing the demodulated data symbol of the terminal to be restored from the temporarily stored uplink IF signals and then updating the uplink IF signals.

2. The uplink signal receiving method according to claim 1, wherein the step of removing the demodulated data symbol comprises: receiving an output raw data symbol of the terminal;distorting the raw data in the frequency domain by an amount corresponding to estimation channel/phase correction information and offset estimation frequency of the restored terminal;converting the raw data distorted in the frequency domain into the time domain;distorting the raw data symbol in the time domain by an amount corresponding to the offset estimation frequency of the terminal, and restoring the demodulated data symbol of the terminal; andremoving the restored demodulated data symbol of the terminal from the uplink IF signals stored in the provisional storage, and then updating the uplink IF signals at the provisional storage.

3. The uplink signal receiving method according to claim 2, wherein the offset estimation frequency is expressed as in

4. The uplink signal receiving method according to claim 2, wherein the channel/phase correction information of the restored terminal is given

5. The uplink signal receiving method according to claim 2, wherein the raw data is distorted in the frequency domain according to exp(−j2πΔ{circumflex over (f)}CniTS)

6. The uplink signal receiving method according to claim 2, wherein in the raw data symbol is distorted in the time domain according to exp(−j2πΔ{circumflex over (f)}CnTS)

7. An uplink signal receiving apparatus using successive interference cancellation (SIC) in a wireless transmission system based on Orthogonal Frequency Division Multiple Access (OFDMA), the uplink signal receiving apparatus comprising: a provisional storage for temporarily storing each uplink intermediate frequency (IF) signal that is received through an antenna of a base station and subjected to analog-to-digital conversion;a terminal selector for selecting a terminal that has a data symbol to be demodulated from the uplink IF signals stored in the provisional storage;a digital signal processor (DSP) for converting the data symbol of the selected terminal from a time domain into a frequency domain, correcting the data symbol which is converted into the frequency domain, demodulating the corrected data symbol into raw data, and outputting the demodulated raw data; anda symbol restorer for restoring the data symbol from the demodulated raw data, removing the restored data symbol from the uplink IF signals stored in the provisional storage, and then updating the uplink IF signals at the provisional storage.

8. The uplink signal receiving apparatus according to claim 7, wherein the DSP provides channel/phase correction information to the symbol restorer.

9. The uplink signal receiving apparatus according to claim 8, wherein the channel/phase correction information is given by

10. The uplink signal receiving apparatus according to claim 7, wherein the DSP provides information on an offset estimation frequency to the symbol restorer.

11. The uplink signal receiving apparatus according to claim 10, wherein the offset estimation frequency information is a difference between center frequencies of a base station and the terminal.

12. The uplink signal receiving apparatus according to claim 11, wherein the offset estimation frequency is expressed as

13. The uplink signal receiving apparatus according to claim 7, wherein the symbol restorer distorts the raw data in the frequency domain according to exp(−j2πΔ{circumflex over (f)}CniTS)

14. The uplink signal receiving apparatus according to claim 7, wherein the symbol restorer distorts the raw data symbol in the time domain according to exp(−j2πΔ{circumflex over (f)}CnTS)