Methods and apparatuses for synchronization and modulation type detection

• US 6,463,107 B1
• Filed: 07/01/1999
• Issued: 10/08/2002
• Est. Priority Date: 07/01/1999
• Status: Expired due to Term

• Current Assignee: Optis Cellular Technology LLC (Brevet Capital)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Khullar, Anders, Lindoff, Bengt, Stenstrom, Niklas
• Primary Examiner(s): Ghayour, Mohammad H.
• Application Number:
  US09/340,254
• Time in Patent Office: 1,195 Days
• Field of Search: 375/343, 375/224, 375/220, 375/213, 375/340, 375/354, 375/365, 375/368
• US Class Current: 375/343
• CPC Class Codes: H04L 2025/03401 PSK
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/2017 in which the phase changes are non-linear, e.g. generalized and Gaussian minimum shift keying, tamed frequency modulation H04L27/201 takes precedence
• CPC Class Codes: H04L 27/2067 with more than two phase states H04L27/2064 takes precedence

Abstract

In a communication system including a transmitter and a receiver, the receiver is synchronized with the transmitter, and a modulation type in a signal transmitted by the transmitter and received by the receiver is detected. A first portion of the received signal is correlated with one or more signals representing modulation types used by the communication system to detect the type of modulation being used in the received signal. Synchronization is established between the transmitter and the receiver. The first portion may be correlated with each of one or more different signals representing various modulation types used in the communication system to detect the type of modulation used. Alternately, the first portion of the received signal may be derotated by different amounts to produce a plurality of derotated signals that are correlated with the signal representing modulation used by the communication system in order to detect the type of modulation used. If the correlation does not result in a determination of the modulation type, either a predetermined modulation type is selected as the modulation type, or the decision of the modulation type is made at a later stage based, e.g., on a comparison of signal qualities or equalization results.

Claims

1. In a communication system including a transmitter and a receiver, an apparatus for synchronizing the receiver with the transmitter and detecting a modulation type in a signal transmitted by the transmitter and received by the receiver, the apparatus comprising:

a detector for detecting the type of modulation being used in the received signal by correlating a first portion of the received signal with one or more signals representing modulation types used by the communication system to; and

a synchronization unit for synchronizing the receiver with the transmitter.

2. The apparatus of claim 1, wherein the detector correlates the first portion of the received signal with each of one or more different signals representing various modulation types used in the communication system to detect the type of modulation used.

3. The apparatus of claim 1, further comprising a derotator for derotating the received signal by different amounts to produce a plurality of derotated signals, wherein the detector correlates the signal representing a modulation used by the communication system with each derotated signal in order to detect the type of modulation used.

4. The apparatus of claim 1, further comprising a channel estimator for estimating a channel of the received signal based on the detected modulation type.

5. The apparatus of claim 1, further comprising a derotator for derotating a second portion of the received signal to compensate for offsets introduced by the transmitter.

6. The apparatus of claim 4, further comprising an equalizer for equalizing channel estimate and the second portion of the received signal.

7. The apparatus of claim 1, wherein modulation type detection and synchronization are performed simultaneously.

8. The apparatus of claim 1, wherein the first portion of the received signal is a training sequence, and a second portion of the received signal is an information sequence.

9. The apparatus of claim 1, further comprising a decision unit, wherein if the type of modulation is not detected by the detector, either a predetermined modulation type is determined to be the modulation type used or a decision of the modulation type is made by the decision unit.

10. The apparatus of claim 9, wherein the decision unit decides the modulation type based on a comparison of signal qualities.

11. The apparatus of claim 9, further comprising an equalizer, wherein the decision unit decides the modulation type based on equalization results.

12. In a communication system including a transmitter and a receiver, a method for synchronizing the receiver with the transmitter and detecting a modulation type in a transmitted signal received by the receiver, the method comprising the steps of:

detecting the type of modulation being used in the received signal by correlating a first portion of the received signal with one or more signals representing the type of modulation used by the communication system; and

synchronizing the receiver with the transmitter.

13. The method of claim 12, wherein the step of detecting includes correlating the first portion with each of one or more different signal representing various modulation types used in the communication system to detect the type of modulation used.

14. The method of claim 12, further comprising a step of derotating the first portion by different amounts to produce a plurality of derotated signals, wherein the step of detecting includes correlating the signal representing the modulation used by the communication system with each derotated signal in order to determine the type of modulation used.

15. The method of claim 12, further comprising estimating a channel of the received signal based on the detected modulation type.

16. The method of claim 12, further comprising derotating a second portion of the received signal to compensate for offsets introduced by the transmitter.

17. The method of claim 15, further comprising equalizing the channel estimate and the second portion of the received signal.

18. The method of claim 12, wherein the steps of detecting and synchronizing are performed simultaneously.

19. The method of claim 12, wherein the first portion of the received signal is a training sequence, and a second portion of the received signal is an information sequence.

20. The method of claim 12, wherein if the type of modulation is not detected by the detecting step, either a predetermined modulation type is determined to be the modulation type used or the method includes a further step of deciding the modulation type.

21. The method of claim 20, wherein the deciding step decides the modulation type based on a comparison of signal qualities.

22. The method of claim 20, further comprising a step of equalizing, wherein the deciding step decides the modulation types based on equalization results.