Method for adjusting FFT window positioning in MB-OFDM UWB system

• US 20070133392A1
• Filed: 12/07/2006
• Published: 06/14/2007
• Est. Priority Date: 12/09/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Choi, Sung-Woo, Kang, Kyu-Min, Choi, Sang-Sung, Cho, Sang-In, Park, Kwang-Roh, Shin, Cheol-Ho
• Granted Patent: US 7,729,238 B2
• Time in Patent Office: Days
• US Class Current: 370/210
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04L 27/2605 Symbol extensions, e.g. Zero Tail, Unique Word [UW]
• CPC Class Codes: H04L 27/2651 Modification of fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators for performance improvement
• CPC Class Codes: H04L 27/2665 Fine synchronisation, e.g. by positioning the FFT window

Abstract

Provided is a method for adjusting Fast Fourier Transform (FFT) window positioning in a Multi Band Orthogonal Frequency Division Multiplexing Ultra-Wideband (MB-OFDM UWB) system. The method includes the steps of acquiring an initial FFT window position and a frequency hopping position, demodulating a received signal by using the initial FFT window position and the frequency hopping position acquired in the acquiring step, transmitting received data information to a Media Access Control (MAC) layer with a reception frame (RX frame) structure and judging at the MAC layer whether or not a packet error is occurred based on Frame Check Sequences (FCSs), and if no packet error is occurred, returning to the demodulating step, and if the packet error is occurred, changing a register map by using a predetermined interface line in a MAC-physical layer (MAC-PHY) interface to thereby adjust the FFT window position and the frequency hopping position, and then returning to the demodulating step.

Claims

1. A method for adjusting Fast Fourier Transform (FFT) window positioning in a Multi Band Orthogonal Frequency Division Multiplexing Ultra-Wideband (MB-OFDM UWB) system, the method comprising the steps of:

(a) acquiring an initial FFT window position and a frequency hopping position;

(b) demodulating a received signal by using the initial FFT window position and the frequency hopping position acquired in said step (a);

(c) transmitting received data information to a Media Access Control (MAC) layer using a reception frame (RX frame) structure and judging at the MAC layer whether or not a packet error is occurred based on Frame Check Sequences (FCSs); and

(d) if no packet error is occurred, returning to said step (b), and if the packet error is occurred, changing a register map by using a predetermined interface line in a MAC-physical layer (MAC-PHY) interface to thereby adjust the FFT window position and the frequency hopping position, and then returning to said step (b).

2. The method as recited in claim 1, wherein said step (d) adjusts the FFT window position within a guard interval (32 zeros) based on the register map information.

3. The method as recited in claim 2, wherein the predetermined interface line is a “

SERIAL_DATA”

line in the MAC-PHY interface.

4. The method as recited in claim 3, wherein said step (d) reads out the status of a modem from the register map by using the “

SERIAL_DATA”

line among the MAC-PHY interface lines at the MAC layer, and changes the modem status of the register map at the MAC layer.

5. The method as recited in claim 4, wherein when the error is continuously detected by checking the FCSs at the MAC layer, said step (d) changes an “

RXCTL”

register map by using the “

SERIAL_DATA”

line presented by the MAC-PHY interface protocol to cause the modem to change the FFT window position in sequence, and repeats the process of again checking the FCSs for the changed FFT window position at the MAC layer to thereby adjust the FFT window position.

6. The method as recited in claim 2, wherein the FFT window is configured in such a manner that the frequency hopping position is set to be placed more than 5 samples ahead of the FFT window position.

7. The method as recited in claim 1, wherein the FFT window is configured in such a manner that zeros are transmitted before an OFDM symbol and a sum of maximum 32 samples from the end part of a 128-point FFT window and samples of the front part of the FFT window is used as an FFT input.

8. The method as recited in claim 7, wherein the FFT window is configured in such a manner that the FFT window position and the frequency switching position to be placed minimum 5 samples ahead of the FFT window position are adjusted and set depending on an amount of a sampling clock offset, a transmission mode, a payload transmission length and a fading by an ultra-wideband channel model.

9. The method as recited in claim 7, wherein said step (a) determines the initial FFT window position and the frequency hopping position with packet sequence symbols of a preamble through a symbol timing estimation synchronization process that is a first process in a synchronization algorithm.

10. The method as recited in claim 9, wherein said step (a) detects a cross-correlation value between a packet sequence symbol within a reception preamble and a reference packet sequence to thereby decide a point where a peak is detected as the initial FFT window position.