Pilot reference transmission for a wireless communication system

• US 9,118,387 B2
• Filed: 09/20/2007
• Issued: 08/25/2015
• Est. Priority Date: 11/03/1997
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Padovani, Roberto, Black, Peter J., Sindhushayana, Nagabhushana T.
• Primary Examiner(s): Pezzlo, John
• Application Number:
  US11/858,840
• Publication Number:
  US 20080008136A1
• Time in Patent Office: 2,896 Days
• Field of Search: 370/252, 370/278, 370/329, 370/503
• US Class Current: 1/1
• 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. A method for transmitting pilot references from a plurality of transmission sources, the method comprising:

generating at a first transmission source of the plurality of transmission sources a first pilot burst;

transmitting the first pilot burst during a time period during which no user data is transmitted by the plurality of transmission sources, the transmission of the first pilot burst being synchronized with a common system time reference, and wherein the time period of the transmission of the first pilot burst at least partially overlaps with a transmission time period of a second pilot burst from a second transmission source of the plurality of transmission sources;

receiving a connection request from an access terminal based on link conditions between the plurality of transmission sources and the access terminal, the connection request comprising a requested data rate for transmissions to the access terminal, the requested data rate representing a maximum data rate for the transmissions to the access terminal; and

transmitting user data to the access terminal at the requested data rate.

2. The method of claim 1, wherein the first pilot burst is transmitted at predetermined time intervals.

3. The method of claim 1, wherein the first pilot burst has a predefined width.

4. The method of claim 1, wherein the first pilot burst is transmitted at or near a maximum transmit power level.

5. The method of claim 1, further comprising:

withholding data transmission during transmission of the first pilot burst.

6. The method of claim 1, further comprising:

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

7. The method of claim 6, wherein the processing comprises:

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

8. The method of claim 1, further comprising:

continuing transmission of the first pilot burst even if no data is to be transmitted.

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

10. The method of claim 9, wherein each slot includes two pilot bursts.

11. The method of claim 9, wherein each pilot burst is associated with a respective portion of a slot and positioned in the center of the associated portion.

12. The method of claim 9, further comprising:

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

13. The method of claim 1, further comprising:

receiving one or more signals from a Global Positioning System (GPS) satellite constellation; and

deriving the common system time reference using the one or more received signals.

14. The method of claim 1, further comprising:

selecting a duration of a first transition period immediately preceding the first pilot burst and a duration of a second transition period immediately following the first pilot burst, the duration of the first transition period and the duration of the second transition period being selected to ensure that each pilot burst reaches a steady state value associated with the pilot burst for the duration of the pilot burst; and

transmitting data during the first transition period immediately preceding the first pilot burst and during the second transition period immediately following the first pilot burst.

15. The method of claim 14 wherein selecting the duration of the first transition period and the duration of the second transition period comprises selecting the duration of the first transition period and the second transition period based at least in part on a step response of at least one filter used to filter pilot data prior to transmission.

16. A method for transmitting pilot references from a plurality of transmission sources, the method comprising:

generating at a first transmission source of the plurality of transmission sources a first pilot burst;

transmitting the first pilot burst at predetermined time intervals during which no user data is transmitted by the plurality of transmission sources, the transmission of the first pilot burst being synchronized with a common system time reference, and wherein a time period of the transmission of the first pilot burst at least partially overlaps with a transmission time period of a second pilot burst from a second transmission source of the plurality of transmission sources;

receiving a connection request from an access terminal based on link conditions between the plurality of transmission sources and the access terminal, the connection request comprising a requested data rate for transmissions to the access terminal, the requested data rate representing a maximum data rate for the transmissions to the access terminal; and

transmitting user data to the access terminal at the requested data rate.

17. An access point comprising:

a processor; and

memory in electronic communication with the processor, the memory having instructions stored thereon that when executed by the processor cause the processor to;

generate a first pilot burst;

transmit the first pilot burst at predetermined time intervals during which no user data is transmitted by a plurality of transmission sources including the access point, the transmission of the first pilot burst being synchronized with a common system time reference, and wherein a time period of the transmission of the first pilot burst at least partially overlaps with a transmission time period of a second pilot burst from a second transmission source of the plurality of transmission sources;

receive a connection request from an access terminal based on link conditions between the plurality of transmission sources and the access terminal, the connection request comprising a requested data rate for transmissions to the access terminal, the requested data rate representing a maximum data rate for the transmissions to the access point; and

transmit user data to the access terminal at the requested data rate.

18. The access point of claim 17, wherein the 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 and to provide a signal indicative of the common system time reference using the one or more received signals.

19. The access point of claim 17, wherein the access point comprises:

a controller configured to receive the common system time reference and generate the first pilot burst.

20. The access point of claim 17, wherein the access point is configured to transmit the first pilot burst at or near a maximum transmit power level for the access point.

21. An apparatus, comprising:

means for generating a first pilot burst;

means for transmitting the first pilot burst at predetermined time intervals during which no user data is transmitted by a plurality of transmission sources including the apparatus, the transmission of the first pilot burst being synchronized with a common system time reference, and wherein a time period of the transmission of the first pilot burst at least partially overlaps with a transmission time period of a second pilot burst from a second transmission source of the plurality of transmission sources;

means for receiving a connection request from an access terminal based on link conditions between the plurality of transmission sources and the access terminal, the connection request comprising a requested data rate for transmissions to the access terminal, the requested data rate representing a maximum data rate for the transmissions to the access terminal; and

means for transmitting user data to the access terminal at the requested data rate.