Message retrieving system with signal collision mitigation and a method thereof

• US 9,680,512 B2
• Filed: 07/11/2013
• Issued: 06/13/2017
• Est. Priority Date: 07/11/2013
• Status: Active Grant

• Current Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Original Assignee: Hong Kong Applied Science And Technology Research Institute Co., Ltd.
• Inventors: Chen, Jun, He, Song
• Primary Examiner(s): Cadeau, Wednel
• Application Number:
  US13/940,238
• Publication Number:
  US 20150016572A1
• Time in Patent Office: 1,433 Days
• Field of Search: None
• CPC Class Codes: H04B 1/12 Neutralising, balancing, or compensation arrangements
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

A message retrieving system and method for signal collision mitigation and the method thereof are disclosed. The message retrieving system transmits two orthogonal signals over two isolated antenna during a time period that it expects to receive the response. Two virtual channels are artificially created and the collision of response signals originated from the respondents is mitigated.

Claims

1. A method for isolating response signals from colliding response signals of multiple radio frequency identification (RFID) tags by a RFID reader, the method comprising:

transmitting, from the RFID reader to the multiple RFID tags, a first waveform from a first antenna of the RFID reader;

transmitting, from the RFID reader to the multiple RFID tags simultaneously with transmitting the first waveform, a second waveform from a second antenna of the RFID reader, wherein the first waveform is orthogonal to the second waveform, and wherein the first antenna is orthogonal to the second antenna;

receiving, at the first antenna of the RFID reader while the RFID reader is transmitting the first waveform, response signals that collide at a time slot from two or more RFID tags of the multiple RFID tags, the multiple signals received at the first antenna including a signal from a first RFID tag responsive to the first waveform and a signal from a second RFID tag responsive to the first waveform, wherein the first and second RFID tags each include an antenna, and wherein the first RFID tag antenna is randomly disposed in a different orientation than the second RFID tag antenna, and wherein a polarization angle of the antenna of the first RFID tag aligns with a polarization angle of the first antenna and the first antenna receives a stronger signal responsive to the first waveform from the first RFID tag than from the second RFID tag;

receiving, at the second antenna of the RFID reader while the RFID reader is transmitting the second waveform and simultaneously with receiving the response signals at the first antenna, response signals that collide at the time slot from the two or more RFID tags of the multiple RFID tags, the multiple signals received at the second antenna including a signal from the first RFID tag responsive to the second waveform and a signal from the second RFID tag responsive to the second waveform, wherein a polarization angle of the antenna of the second RFID tag aligns with a polarization angle of the second antenna and the second antenna receives a stronger signal responsive to the second waveform from the second RFID tag than from the first RFID tag, and wherein the response signals received at the first antenna and the response signals received at the second antenna collide at the time slot;

isolating, by a first receiver of the RFID reader, the signal from the first RFID tag from the signal from the second RFID tag based at least in part upon orthogonality of the different orientations of the first and second RFID tags and the orthogonality of the first and second waveforms;

isolating, by a second receiver of the RFID reader, the signal from the second RFID tag from the signal from the first RFID tag based at least in part upon orthogonality of the different orientations of the first and second RFID tags and the orthogonality of the first and second waveforms; and

decoding a message in the signal from the first RFID tag to recover an identification (ID) of the first RFID tag and a message in the signal from the second RFID tag to recover an ID of the second RFID tag, wherein the signals from the first RFID tag and the second RFID tag are received simultaneously.

2. The method of claim 1, wherein the isolating the signal from the first RFID tag from the signal from the second RFID tag comprises:

filtering weaker signals received at the first antenna to mitigate the signal collision and to retrieve message data in the multiple signals sent from the first RFID tag.

3. The method of claim 1, wherein the polarization angle of the first antenna and the polarization angle of the second antenna are orthogonal to each other.

4. The method of claim 1, further comprising:

analyzing different signal strengths of the multiple signals received at the first antenna and different signal strengths of the multiple signals received at the second antenna.

5. The method of claim 2, wherein the isolating the signal from the first RFID tag from the signal from the second RFID tag further comprises:

filtering the multiple signals received at the first antenna with a first matched filter unit, wherein the decoding the message in the signal from the first RFID tag includes

converting filtered signals from the first matched filter unit into the ID of the fist RFID tag.

6. The method of claim 5, wherein the isolating the signal from the second RFID tag from the signal from the first RFID tag comprises:

filtering weaker signals received at the second antenna to mitigate the signal collision and to retrieve message data in the multiple signals sent from the second RFID tag.

7. The method of claim 6, wherein the isolating the signal from the second RFID tag from the signal from the first RFID tag further comprises:

filtering the multiple signals received at the second antenna with a second matched filter unit, wherein the decoding the message in the signal from the second RFID tag includes

converting filtered signals from the second matched filter unit into the ID of the second RFID tag.

8. A system for isolating response signals from colliding response signals of multiple radio frequency identification (RFID) tags by a RFID reader, the system comprising:

an antenna system, of the RFID reader, having a first antenna and a second antenna, wherein the first antenna is orthogonal to the second antenna, and wherein the RFID reader is operable to transmit to the multiple RFID tags a first waveform from the first antenna and a second waveform from the second antenna, wherein the first waveform is orthogonal to the second waveform;

a first receiver, of the RFID reader, coupled to the first antenna and operable to receive response signals that collide at a time slot from two or more RFID tags of the multiple RFID tags while the RFID reader is transmitting the first waveform, wherein the multiple signals received at the first antenna include a signal from a first RFID tag responsive to the first waveform and a signal from a second RFID tag responsive to the first waveform, wherein the first and second RFID tags each include an antenna, wherein the first RFID tag antenna is randomly disposed in a different orientation than the second RFID tag antenna, wherein a polarization angle of the antenna of the first RFID tag aligns with a polarization angle of the first antenna and the first antenna receives a stronger signal responsive to the first waveform from the first RFID tag than from the second RFID tag, and wherein the first receiver is further operable to isolate the signal from the first RFID tag from the signal from the second RFID tag based at least in part upon orthogonality of the different orientations of the first and second RFID tags and the orthogonality of the first and second waveforms;

a second receiver, of the RFID reader, coupled to the second antenna and operable to receive response signals that collide at a time slot from the two or more RFID tags of the multiple RFID tags while the RFID reader is transmitting the second waveform and simultaneously with the first receiver receiving the response signals from the first antenna, wherein the multiple signals received at the second antenna include a signal from the first RFID tag responsive to the second waveform and a signal from the second RFID tag responsive to the second waveform, wherein a polarization angle of the antenna of the second RFID tag aligns with a polarization angle of the second antenna and the second antenna receives a stronger signal responsive to the second waveform from the second RFID tag than from the first RFID tag, wherein the response signals received at the first antenna and the response signals received at the second antenna collide at the time slot, and wherein the second receiver is further operable to isolate the signal from the second RFID tag from the signal from the first RFID tag based at least in part upon orthogonality of the different orientations of the first and second RFID tags and the orthogonality of the first and second waveforms; and

a retrieving module that is coupled to first and second demodulators and that is operable to resolve the colliding signals and retrieve at least one message of the first RFID tag to recover an identification (ID) of the first RFID tag and the second RFID tag to recover an ID of the second RFID tag based on a first component of the response signals and a second component of the response signals, wherein the colliding signals from the first RFID tag and the second RFID tag are received simultaneously.

9. The system of claim 8, wherein the first receiver comprises the first demodulator that is coupled to the first antenna and is operable to extract, based on an analysis of signal strengths of the multiple colliding signals, the first component from said response signals, and wherein the second receiver comprises the second demodulator that is coupled to the second antenna and is operable to extract, based on the analysis of the signal strengths of the multiple colliding signals, the second component from said response signals.

10. The system of claim 8, wherein the polarization angle of the first antenna and the polarization angle of the second antenna are orthogonal to each other.

11. The system of claim 8, further comprising:

a first waveform generator, coupled to the first antenna through a first transmitter, operable to generate a first time domain waveform comprising the first waveform transmitted from the first antenna; and

a second waveform generator, coupled to the second antenna through a second transmitter, and operable to generate a second time domain waveform comprising the second waveform transmitted from the second antenna, wherein the signal received from the first RFID tag comprises a carrier signal modulated by said first time domain waveform and the signal received from the second RFID tag comprises a carrier signal modulated by said second time domain waveform.

12. The system of claim 8, further comprising:

a first matched filter unit coupled to the first receiver and configured to extract a first filtered signal from an output of the first receiver; and

a second matched filter unit coupled to the second receiver and configured to extract a second filtered signal from an output of the second receiver.

13. The system of claim 8, wherein the first antenna and the second antenna are spatially isolated.

14. The system of claim 8, wherein the first antenna and the second antenna are isolated by radiation isolation.

15. The system of claim 11, wherein the first time domain waveform is a first modified Hermite pulse and the second time domain waveform is a second modified Hermite pulse.