PILOT REFERENCE TRANSMISSION FOR A WIRELESS COMMUNICATION SYSTEM

• US 20080008136A1
• Filed: 09/20/2007
• Published: 01/10/2008
• Est. Priority Date: 11/03/1997
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Sindhushayana, Nagabhushana, Padovani, Roberto, Black, Peter
• Granted Patent: US 9,118,387 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 7/2687 Inter base stations synchronisation
• CPC Class Codes: H04J 3/0644 External master-clock
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels

Abstract

A pilot reference transmission scheme well suited for high data rate wireless communication systems is disclosed. To maximize the amount of interference from transmissions from neighboring transmission sources (e.g., access points or base stations) during the pilot interval, and hence minimize the amount of interference from non-transmitting sources during the data intervals, the pilot references are transmitted in bursts at predetermined time intervals, and the pilot bursts from the access points are synchronized. This results in maximum interference contributions from non-transmitting neighboring access points, facilitating reliable estimation of worst case carrier-to-interference (C/I), and further allows the receiving devices (e.g., access terminals) to easily recognize the bursts as pilot reference. In one embodiment, each access point transmits the pilot bursts at or near its maximum transmit power level and no user-specific data is transmitted during the pilot bursts.

Claims

1. In a wireless communication system, a method for transmitting pilot references from a plurality of transmission sources, the method comprising:

receiving at each transmission source one or more signals indicative of a time reference for the communication system;

generating at each transmission source a plurality of pilot bursts for a pilot reference; and

transmitting the plurality of pilot bursts in synchronization with the time reference from each transmission source.

2. The method of claim 1, wherein pilot bursts from the plurality of transmission sources are aligned in time at the time of transmission.

3. The method of claim 1, wherein the plurality of pilot bursts from each transmission source are transmitted at predetermined time intervals.

4. The method of claim 1, wherein each of the plurality of pilot bursts has a predefined width.

5. The method of claim 1, wherein each pilot burst is transmitted at or near a maximum transmit power level of the transmission source.

6. The method of claim 1, further comprising:

withholding data transmission at each access point during transmission of the pilot bursts.

7. The method of claim 1, further comprising:

processing at each transmission source pilot data in accordance with a particular processing scheme such that the pilot reference from each transmission source is differentiated from pilot references from other transmission sources.

8. The method of claim 7, wherein the processing at each transmission source comprises:

spreading the pilot data with a pseudo-noise (PN) sequence at a particular offset that is different from offsets for other transmission sources.

9. The method of claim 1, further comprising:

continuing transmission of the plurality of pilot bursts from a particular transmission source even if no data is to be transmitted from the transmission source.

10. The method of claim 1, wherein transmission from each transmission source occurs over slots, and wherein each slot covers a particular time period and includes a particular number of pilot bursts.

11. The method of claim 10, wherein each slot includes two pilot bursts.

12. The method of claim 10, wherein each pilot burst is associated with a respective portion of the slot and positioned in the center of the associated portion.

13. The method of claim 10, further comprising:

padding both sides of each pilot burst in an idle slot with additional transmissions of at least a particular minimum period.

14. The method of claim 1, further comprising:

transmitting immediately on both sides of each pilot burst to ensure that the pilot burst is received at or near its steady state value.

15. The method of claim 1, wherein the one or more signals used to derive the time reference for the communication system are received from a Global Positioning System (GPS) satellite constellation.

16. In a wireless communication system, a method for transmitting pilot references from a plurality of transmission sources, the method comprising:

at each transmission source

processing one or more received signals to derive a time reference for the communication system,

generating a plurality of pilot bursts for a pilot reference, and

transmitting the plurality of pilot bursts at predetermined time intervals and in synchronization with the time reference,

wherein pilot bursts from the plurality of transmission sources are aligned in time at the time of transmission.

17. A wireless communication system comprising:

a plurality of access points, each access point configured to

receive one or more signals indicative of a time reference for the communication system,

generate a plurality of pilot bursts for a pilot reference; and

transmit the plurality of pilot bursts in synchronization with the time reference.

18. The communication system of claim 17, wherein each access point comprises:

a Global Positioning System (GPS) receiver configured to receive and process one or more signals from a Global Positioning System (GPS) satellite constellation to provide a signal indicative of the time reference for the communication system.

19. The communication system of claim 17, wherein each access point comprises:

a controller configured to receive the time reference for the communication system and generate the plurality of pilot bursts.

20. The communication system of claim 17, wherein each access point is configured to transmit the plurality of pilot bursts at or near a maximum transmit power level for the access point.

21. An access terminal for use in a wireless communication system, comprising:

an RF module configured to receive a modulated signal over a wireless communication link and to condition the received signal to generate a conditioned signal; and

a modem block coupled to the RF module and configured to process the conditioned signal to recover a plurality of pilot references transmitted from a plurality of access points, wherein the pilot reference from each access point is transmitted in pilot bursts that are synchronized with a system time reference, and wherein the pilot bursts from the plurality of access points are aligned in time at the time of transmission.

22. The access terminal of claim 21, wherein the modem block is configured to generate samples from the conditioned signal and to despread the samples with a pseudo-noise (PN) sequence at a particular offset for each of the plurality of access points.

23. An access terminal, comprising:

means for receiving a pilot reference transmitted in pilot bursts that are synchronized with a time reference; and

means for determining a link condition based on the pilot reference.

24. An access terminal as in claim 23, further comprising:

means for determining an access point having a best signal quality based at least on the received pilot reference.

25. An access terminal as in claim 24, further comprising:

means for determining a highest data rate supported by the access point.