Method and apparatus for closed loop transmission

• US 20060035643A1
• Filed: 12/03/2004
• Published: 02/16/2006
• Est. Priority Date: 08/12/2004
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Baum, Kevin L., Zhuang, Xiangyang, Vook, Frederick W., Thomas, Timothy A.
• Granted Patent: US 7,773,535 B2
• Time in Patent Office: Days
• US Class Current: 455/450
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 2025/03796 Location of reference signals
• CPC Class Codes: H04L 2025/03815 Transmission of a training request
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0026 Division using four or more dimensions
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 72/04 Wireless resource allocation

Abstract

In a wireless communication system, a method and apparatus for closed loop transmission is disclosed. In accordance with the preferred embodiment of the present invention, a time frequency portion of an uplink frame is dynamically reserved as a sounding zone for uplink channel sounding. A first message is transmitted to a first subscriber station in a downlink frame assigning a time-frequency resource within the sounding zone, and a sounding waveform. Furthermore, a signal is received from the subscriber station within the assigned time-frequency resource, a partial channel response is determined from the received sounding signal, and the subsequent transmission to the subscriber station is tailored based on the at least partial channel response.

Claims

1. A method for enabling a base station (BS) to determine a BS-to-subscriber station (SS) channel response under an assumption of channel reciprocity, the method comprising the steps of:

determining an uplink sounding zone within a frame; and

instructing the SS to transmit a specific sounding signal at one or more specific symbol intervals within the sounding zone, and specifying a specific sounding frequency to be occupied within each sounding symbol interval.

2. The method of claim 1 wherein the step of determining the uplink sounding zone comprises the step of determining one or more OFDM/OFDMA symbol intervals in the frame that is used by the SS to transmit the sounding signal and enables the BS to determine a channel response between the BS and the SS.

3. The method of claim 2 wherein the step of determining the uplink sounding zone comprises the step of determining non-overlapping frequency bands, wherein each frequency band comprises a plurality of consecutive OFDM/OFDMA subcarriers.

4. The method of claim 2 wherein the step of determining the uplink sounding zone comprises the step of determining non-overlapping frequency bands, wherein each frequency band comprises 18 consecutive OFDM/OFDMA subcarriers.

5. The method of claim 1 wherein the step of instructing the SS to transmit the specific sounding signal additionally comprises the step of instructing the SS to transmit the sounding signal on consecutive subcarriers or decimated subcarriers.

6. The method of claim 1 wherein the step of instructing the SS to transmit the specific sounding signal additionally comprises the step of providing the SS with a total number of sounding symbols to transmit.

7. The method of claim 1 wherein the step of instructing the SS to transmit the specific sounding signal additionally comprises the step of instructing the SS to transmit the sounding signal on consecutive subcarriers or decimated subcarriers and providing the SS with a decimation value (D) instructing the SS to sound every Dth subcarrier.

8. The method of claim 1 further comprising the step of instructing a second SS to transmit a specific sounding signal at the same symbol interval within the sounding zone, and specifying a specific sounding frequency to be occupied by the second SS within each sounding symbol interval.

9. The method of claim 8, further comprising the steps of

receiving a composite of a first and second sounding signal transmitted from the first and second subscriber station within the assigned time-frequency resource;

determining at least a partial channel response for the second subscriber station from the received composite sounding signal; and

tailoring a characteristic of a subsequent transmission to the second subscriber station based on the at least the partial channel response of the second subscriber station.

10. The method of claim 1 further comprising the steps of:

receiving the sounding signal transmitted from the SS within the assigned sounding zone;

determining at least a partial channel response from the received sounding signal; and

tailoring a characteristic of a subsequent transmission to the SS based on the at least partial channel response.

11. The method of claim 10 where the step of tailoring comprises the step of tailoring at least one of:

a frequency characteristic of the subsequent transmission, and a spatial characteristic of the subsequent transmission.

12. The method of claim 1 further comprising the step of assigning a time-frequency resource in the downlink frame for the SS to receive downlink data, and wherein a frequency part of the time-frequency resource within the sounding zone is assigned implicitly based on the time-frequency resource in the downlink frame for the SS to receive downlink data.

13. A method for a subscriber station to transmit a sounding signal with desired characteristics, the method comprising:

receiving a message from a base station in a downlink frame, the message assigning a time-frequency resource in an uplink frame and a sounding waveform; and

transmitting a sounding signal based on the assigned sounding waveform within the assigned time-frequency resource in the uplink frame.

14. The method of claim 13 where the step of receiving the message from the base station in the downlink frame comprises the step of receiving a separability mode, and a separability parameter.

15. The method of claim 14 where the step of receiving the message from the base station in the downlink frame comprises the additional step of receiving a sounding sequence index.

16. The method of claim 13 where the step of transmitting the sounding signal comprises the step of transmitting a specific sounding signal based on a base station identification number.

17. A base station comprising:

a reservation unit for dynamically reserving a time-frequency portion of a frame as a sounding zone for channel sounding;

a sounding message unit for generating a channel sounding assignment message specifying a time-frequency resource within the sounding zone, and a sounding waveform to be used; and

a transmitter for transmitting the channel sounding assignment message.

18. The base station of claim 17, further comprising:

a receiver unit for receiving a sounding signal transmitted from a subscriber station within the time-frequency portion of the frame;

a channel response unit for determining at least a partial channel response from the sounding signal; and

a signal tailoring unit for tailoring a characteristic of a transmission to the subscriber station based on the at least partial channel response to provide closed loop transmission to the target communication unit.

19. The base station of claim 17 further comprising an identification number known to a subscriber station, and where the subscriber station determines the sounding waveform to be transmitted from at least the base station identification number, a separability mode, a separability parameter, and a sounding sequence index.

20. The base station of claim 17 wherein the time-frequency portion comprises an integer number of OFDM (Orthogonal Frequency Division Multiplex) symbol periods by an integer number of OFDM subcarriers.

21. The base station of claim 17 where the channel sounding assignment message further comprises a multi-antenna sounding mode for indicating a set of one or more antennas for sounding and a sounding waveform for each of the antennas.

22. The base station of claim 17 wherein the channel sounding assignment message further comprises a separability mode indicating that the subscriber station shall transmit on every subcarrier in the time frequency resource.

23. The base station of claim 22 wherein the channel sounding assignment message further comprises a separability parameter indicating a per-subcarrier incremental phase shift value that the subscriber station shall use.

24. The base station of claim 17 wherein the channel sounding assignment message further comprises a separability mode indicating that the subscriber station shall transmit on a decimated set of subcarriers in the time-frequency resource

25. The base station of claim 20 wherein the channel sounding assignment message further comprises a separability parameter indicating an index of a set of subcarriers on which the subscriber station shall transmit in the time-frequency resource.

26. The base station of claim 17 wherein the channel sounding assignment message further comprises a sounding sequence index indicating the waveform that shall be transmitted on the subcarriers in the time frequency resource

27. An apparatus comprising:

a receiver unit for receiving a channel sounding assignment message;

a sounding message decoding unit for determining from the channel sounding assignment message, a time-frequency resource in a frame, and a sounding signal; and

a transmitter unit for transmitting the sounding signal within the assigned time-frequency resource in the frame.

28. The apparatus of claim 27 wherein the time-frequency resource comprises an integer number of OFDM (Orthogonal Frequency Division Multiplex) symbol periods by an integer number of OFDM subcarriers.

29. The apparatus of claim 27 where the channel sounding assignment message further comprises a multi-antenna sounding mode for indicating a set of one or more antennas for sounding and the sounding signal for each of the antennas.

30. The apparatus of claim 27 wherein the channel sounding assignment message further comprises a separability mode indicating that the subscriber station shall transmit on consecutive subcarriers in the time frequency resource.

31. The apparatus of claim 30 wherein the channel sounding assignment message further comprises a separability parameter indicating a per-subcarrier incremental phase shift value that the subscriber station shall use.

32. The apparatus of claim 27 wherein the channel sounding assignment message further comprises a separability mode indicating that the subscriber station shall transmit on a decimated set of subcarriers in the time-frequency resource.

33. The apparatus of claim 32 wherein the channel sounding assignment message further comprises a separability parameter indicating which portion of the subcarriers on which the subscriber station shall transmit in the time-frequency resource.

34. The apparatus of claim 27 wherein the channel sounding assignment message further comprises a sounding sequence index indicating the specific waveform that shall be transmitted on the subcarriers in the time frequency resource.