Interference-rejection coding method for an optical wireless communication system and the optical wireless communication system thereof

• US 7,689,132 B2
• Filed: 06/07/2005
• Issued: 03/30/2010
• Est. Priority Date: 06/07/2005
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Chen, Yuan, Tsai, Shang-Feng, Hung, Yung-Hua
• Primary Examiner(s): Vanderpuye; Ken N
• Assistant Examiner(s): LEUNG, WAI LUN
• Application Number:
  US11/146,546
• Publication Number:
  US 20060275039A1
• Time in Patent Office: 1,757 Days
• Field of Search: 398/127, 398202-214
• US Class Current: 398/189
• CPC Class Codes: H04B 10/11 Arrangements specific to free-space transmission, i.e. transmission through air or vacuum

Abstract

An interference-rejection coding method for an optical wireless communication system and such an optical wireless communication system are provided. The coding method uses delay modulation, block code techniques and filtering to reduce the low frequency interference from light sources. A plurality of codewords from the block codes are reserved for performing digital data recovery. The invention removes the need of analog clock data recovery circuit, and does not require complex hardware for realization. Therefore, it can be applied to a wide range of applications, such as optical WLAN, data transmission of medical facilities, wireless communication in the aircraft, encrypted data transmission network, and low-priced transmission interfaces.

Claims

1. An interference-rejection coding method for being used in an optical wireless communication system having an optical wireless transmitter and an optical wireless receiver, said method comprising the steps of:

(a) encoding a data signal for transmission using a block code encoder with a block code and generating an encoded block code;

(b) delay modulating said encoded block code into a modulated code using a delay modulation unit of delay modulation technique;

(c) converting said modulated code into an optical data signal for transmission;

(d) converting said optical data signal back to an electrical data signal;

(e) filtering out low frequency interferences in said electrical data signal to generate a filtered signal;

(f) over-sampling said filtered signal at the receiver'"'"'s end to generate a sampled signal, and selecting correct phase from said sampled signal to form a recovered data signal;

(g) delay demodulating said recovered data signal into a demodulated data signal using a demodulator of delay modulation technique; and

(h) decoding said demodulated data signal, thereby to obtain a corresponding original data signal;

wherein said block code encoder makes the number of bits 0 and 1 passing through said delay modulation unit equal.

2. The interference-rejection coding method as claimed in claim 1, wherein said transmitter reserves a plurality of codewords of said block code for controlling or transmitting messages.

3. The interference-rejection coding method as claimed in claim 2, wherein said receiver uses said codewords for phase selection to achieve said digital data recovery.

4. An optical wireless communication system, comprising an optical wireless transmitter and an optical wireless receiver, said optical wireless transmitter further comprising:

a block code encoder for encoding a data signal for transmission with a block code and generating an encoded block code;

a delay modulation unit for modulating said encoded block code into a modulated electrical data signal; and

an electrical-to-optical converter for converting said modulated electrical data signal into an optical data signal for transmission through a wireless channel;

and said optical wireless receiver further comprising;

an optical-to-electrical converter and receiver for receiving and converting said optical data signal into an electrical data signal;

a band-pass filter for filtering out low frequency interferences in said electrical signal to generate a filtered signal;

a delay demodulator for demodulating said filtered signal into a demodulated data signal; and

a block code decoder for decoding said demodulated data signal to thereby obtain a corresponding original data signal;

wherein said optical wireless receiver further comprises an over-sampling unit and a phase selector placed between said filter and said delay demodulator.

5. The system as claimed in claim 4, wherein said block code encoder reserves a plurality of codewords for controlling or transmitting messages.

6. The system as claimed in claim 5, wherein said codewords are used by said over-sampling unit and said phase selector to select correct sample phase to achieve digital data recovery.