Method and apparatus for pilot signal transmission

• US 20050226140A1
• Filed: 03/30/2004
• Published: 10/13/2005
• Est. Priority Date: 03/30/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Baum, Kevin L., Zhuang, Xiangyang, Nangia, Vijay, Vook, Frederick W.
• Granted Patent: US 7,426,175 B2
• Time in Patent Office: Days
• US Class Current: 370/203
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 2001/6912 using chirp
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04L 27/2613 Structure of the reference signals

Abstract

Pilot sequences are constructed from distinct “classes” of chirp sequences that have an optimal cross correlation property. Utilization of chirp sequences for pilot sequences results in pilot sequences that have optimal or nearly-optimal cross correlation and auto-correlation properties.

Claims

1. A method for assigning a pilot sequence to communication units within a communication system, the method comprising the steps of:

assigning a first communication unit a first pilot sequence, wherein the first pilot sequence is selected from a group of pilot sequences constructed from a set of Generalized Chirp-Like (GCL) sequences; and

assigning a second communication unit a second pilot sequence taken from the group of pilot sequences constructed from the set of GCL sequences.

2. The method of claim 1 wherein the step of assigning the first communication unit the first pilot sequence comprises the step of assigning a first base unit the first pilot sequence, and wherein the step of assigning the second communication unit the second pilot sequence comprises the step of assigning a second base unit the second pilot sequence.

3. The method of claim 1 wherein the step of assigning the first communication unit the first pilot sequence comprises the step of assigning a first remote unit the first pilot sequence, and wherein the step of assigning the second communication unit the second pilot sequence comprises the step of assigning a second remote unit the second pilot sequence.

4. The method of claim 1 wherein the step of assigning the first communication unit the first pilot sequence comprises the step of assigning a first sector of a base station the first pilot sequence, and wherein the step of assigning the second communication unit the second pilot sequence comprises the step of assigning a second sector of the base station the second pilot sequence.

5. The method of claim 1 wherein the step of assigning the first communication unit the first pilot sequence comprises the step of assigning a first antenna of a sector of the base station the first pilot sequence, and wherein the step of assigning the second communication unit the second pilot sequence comprises the step of assigning a second antenna of a sector of the base station the second pilot sequence.

6. The method of claim 1 wherein prior to assigning the first and the second communication units the first and the second pilot sequences, performing the step of determining a length of the pilot sequences (N_G) based on a number of pilot sequences needed in the communication system (K) and a desired pilot sequence length (N_p).

7. The method of claim 6 further comprising the step of:

choosing N_G to be equal to N_p if the smallest prime factor of N_p excluding “

1”

is larger than K.

8. The method of claim 6 further comprising the step of:

choosing N_G to be a smallest integer that is greater than N_p and whose minimum prime factor excluding “

1”

is larger than K and generating the set of GCL sequences by truncating sequences in the set to N_p;

or

choosing N_G to be a largest integer that is smaller than N_p and whose minimum prime factor excluding “

1”

is larger than K, and generating the set of GCL sequences set by repeating beginning elements of each sequence in the set to append at an end of each sequence to reach the desired length N_p.

9. The method of claim 1 wherein the first and the second pilot sequences are constructed from the GCL sequences or from sequences resulting from taking a size-N_G unitary transformation of the GCL sequences;

and the GCL sequences are generated as

S_u=(a_u(0)b, a_u(1)b, . . . , a_u(N_G−

1)b),

where b is any complex scalar of unit amplitude and

10. The method of claim 9 wherein the step of assigning the first communication unit the first pilot sequence comprises the step of assigning the first communication unit a pilot sequence constructed from the class-u₁ GCL sequence;

and

wherein the step the assigning the second communication unit the second pilot sequence comprises the step of assigning the second communication unit a pilot sequence constructed from the class-u₂ GCL sequence that satisfies the requirement of |u₁−

u₂| being relatively prime to N_G.

11. A method comprising the steps of:

receiving a pilot sequence as part of an over-the air transmission, wherein the pilot sequence is constructed from a set of Generalized Chirp-Like (GCL) sequences; and

utilizing the pilot sequence for at least one of the following;

acquisition and tracking of timing and frequency synchronization, estimation and tracking of desired channels for subsequent demodulation and decoding, estimation and monitoring of characteristics of other channels for handoff purposes, and interference suppression.

12. The method of claim 11 wherein the step of receiving the pilot sequence comprises the step of receiving the pilot sequence at a base unit.

13. The method of claim 11 wherein the step of receiving the pilot sequence comprises the step of receiving the pilot sequence at a remote unit.

14. The method of claim 11 wherein the step of receiving the pilot sequence comprises the step of receiving a pilot sequences constructed from GCL sequences or from sequences resulting from taking a size-N_G unitary transformation of the GCL sequences, and the GCL sequences are generated as

S_u=(a_u(0)b, a_u(1)b, . . . , a_u(N_G−

1)b),

where b is any complex scalar of unit amplitude and

15. A communication unit comprising:

pilot channel circuitry for transmitting or receiving a pilot channel sequence, wherein the pilot channel sequence comprises a sequence unique to the communication unit and is constructed from a GCL sequence.

16. The communication unit of claim 15 wherein the GCL sequence is equal to

S_u=(a_u(0)b, a_u(1)b, . . . a_u(N_G−

1)b),

where b is a complex scalar of unit amplitude and

17. The communication unit of claim 15 further comprising:

data channel circuitry for transmitting data, wherein a peak to average power ratio (PAPR) of the pilot channel sequence is lower than a PAPR of data transmitted over the data channel circuitry.

18. The communication unit of claim 17 wherein the pilot channel sequence is transmitted at a higher power than the data.