ADJACENT CHANNEL INTERFERENCE MITIGATION DURING THE ACQUISITION PHASE IN OFDM COMMUNICATIONS

• US 20120177095A1
• Filed: 01/12/2011
• Published: 07/12/2012
• Est. Priority Date: 01/12/2011
• Status: Abandoned Application

• Current Assignee: Autotalks Ltd. (Qualcomm, Inc.)
• Original Assignee: Autotalks Ltd. (Qualcomm, Inc.)
• Inventors: HARAN, ONN, TSODIK, GENADIY
• Application Number:
  US13/005,001
• Publication Number:
  US 20120177095A1
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H03G 3/3078 Circuits generating control signals for digitally modulated signals

Abstract

Methods and apparatuses for adjacent channel interference mitigation during the acquisition phase in OFDM communications use a Discrete Fourier Transform (DFT) to detect the energy of a received channel without adding latency. In particular embodiments, the communications are vehicular OFDM communications and the DFT is a sliding DFT of variable length. In a typical acquisition procedure, RF gain is set based on received total energy, which includes energies of the received and adjacent channels. A modified state machine waits until the energy of a received channel is detected, then the RF gain is adjusted to fulfill an enhanced adjacent channel rejection criterion requirement.

Claims

1. A method for adjacent channel interference mitigation during the acquisition phase in OFDM communications, comprising the steps of:

a) setting an RF gain based on received total energy;

b) waiting until energy of a received channel is detected; and

c) adjusting the RF gain based on the detected energy of the received channel, thereby fulfilling an enhanced adjacent channel rejection criterion requirement in the OFDM communications.

2. The method of claim 1, wherein the step of waiting includes waiting while using a discrete Fourier transform (DFT) to detect the received channel energy.

3. The method of claim 2, wherein the DFT is a sliding DFT.

4. The method of claim 2, wherein the DFT is a dynamic DFT with variable length.

5. The method of claim 2, wherein the using a DFT includes calculating a subset of the DFT for the duration of a short preamble (SP).

6. The method of claim 4, wherein the subset is selected from the group consisting of a subset of 4 subcarriers and a subset of 2 subcarriers.

7. The method of claim 1, wherein the OFDM communications are vehicular OFDM communications.

8. A method for adjacent channel interference mitigation during the acquisition phase in OFDM communications, comprising the steps of:

a) using a DFT to detect the energy of a received channel; and

b) adjusting an RF gain based on the detected energy of the received channel, thereby fulfilling an adjacent channel rejection criterion requirement in the OFDM communications.

9. The method of claim 8, wherein the DFT is a sliding DFT.

10. The method of claim 8, wherein the DFT is a dynamic DFT with variable length.

11. The method of claim 8, wherein the using a DFT includes calculating a subset of the DFT for the duration of a short preamble (SP).

12. The method of claim 11, wherein the subset is selected from the group consisting of a subset of 4 subcarriers and a subset of 2 subcarriers.

13. The method of claim 8, further comprising the step of performing a stability test which demands a substantially constant result representing stable energy, thereby separating the received channel transmission from out-of-band emission of an adjacent channel.

14. An apparatus for adjacent channel interference mitigation during the acquisition phase in OFDM communications, comprising:

a) a receive signal strength indicator (RSSI) estimator for measuring total energy of input signals;

b) a Discrete Fourier Transform (DFT) for measuring energy of a received channel; and

c) a state machine used for processing the measured total energy and received channel energy to fulfill an enhanced adjacent channel rejection criterion requirement in the OFDM communications.

15. The apparatus of claim 14, wherein the DFT is a sliding DFT.

16. The apparatus of claim 14, wherein the DFT is a dynamic DFT with variable length

17. The apparatus of claim 14, wherein the OFDM communications are vehicular OFDM communications.

18. The apparatus of claim 14, wherein the DFT includes a DFT subset calculated during a short preamble period.

19. The apparatus of claim 18, wherein the DFT subset includes four subcarriers.

20. The apparatus of claim 18, wherein the DFT subset includes two subcarriers.