Fast Frequency Hopping With a Code Division Multiplexed Pilot in an OFDMA System

• US 20070211790A1
• Filed: 12/21/2006
• Published: 09/13/2007
• Est. Priority Date: 05/12/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Teague, Edward
• Granted Patent: US 8,102,832 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03509 fractionally spaced H04L2025/03515 takes precedence
• CPC Class Codes: H04L 2025/03789 Codes therefore
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 25/03866 using scrambling
• CPC Class Codes: H04L 27/26134 Pilot insertion in the transmitter chain, e.g. pilot overlapping with data, insertion in time or frequency domain
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0041 Frequency-non-contiguous
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal

Abstract

Techniques are provided to support fast frequency hopping with a code division multiplexed (CDM) pilot in a multi-carrier communication system (e.g., an OFDMA system). Each transmitter (e.g., each terminal) in the system transmits a wideband pilot on all subbands to allow a receiver (e.g., a base station) to estimate the entire channel response at the same time. The wideband pilot for each transmitter may be generated using direct sequence spread spectrum processing and based on a pseudo-random number (PN) code assigned to that transmitter. This allows the receiver to individually identify and recover multiple wideband pilots transmitted concurrently by multiple transmitters. For a time division multiplexed (TDM)/CDM pilot transmission scheme, each transmitter transmits the wideband pilot in bursts. For a continuous CDM pilot transmission scheme, each transmitter continuously transmits the wideband pilot, albeit at a low transmit power level. Any frequency hopping rate may be supported without impacting pilot overhead.

Claims

1. A method of transmitting a wideband pilot in a wireless multi-carrier communication system, comprising:

processing at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for the wideband pilot;

processing data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips, wherein a plurality of periods for the sequences of data chips are provided between periods for the sequences of pilot chips; and

transmitting the TDM sequence of pilot and data chips.

2. The method of claim 1, wherein the wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system, and wherein the multi-carrier modulation scheme is orthogonal frequency division multiplexing (OFDM).

3. The method of claim 1, wherein the at least one pilot symbol is spectrally spread with the PN code in time domain using direct sequence spread spectrum processing to obtain the sequence of pilot chips.

4. The method of claim 1, wherein the PN code uniquely identifies a transmitting entity of the wideband pilot.

5. The method of claim 1, wherein the system includes a plurality of subbands, and wherein the data symbols are sent on different ones of the plurality of subbands in different time intervals as determined by a frequency hopping (FH) sequence.

6. The method of claim 1, further comprising:

scaling the sequence of pilot chips with a scaling factor to obtain a sequence of scaled pilot chips, wherein the scaling factor is indicative of a transmit power level for the wideband pilot, and wherein the sequence of scaled pilot chips is time division multiplexed with the sequence of data chips.

7. The method of claim 1, wherein the TDM sequence of pilot and data chips is transmitted on a reverse link in the system.

8. The method of claim 1, wherein a time between periods for the sequences of pilot chips comprises a period less than a decorrelation time for a channel through which the sequence of pilot chips are being transmitted.

9. An apparatus in a wireless multi-carrier communication system, comprising:

means for processing at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for a wideband pilot;

means for processing data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

means for time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips, wherein a plurality of periods for the sequences of data chips are provided between periods for the sequences of pilot chips; and

means for transmitting the TDM sequence of pilot and data chips.

10. The apparatus of claim 9, wherein a time between periods for the sequences of pilot chips comprises a period less than a decorrelation time for a channel through which the sequence of pilot chips are being transmitted.

11. An apparatus in a wireless multi-carrier communication system, comprising:

a modulator operative to process data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

a pilot generator operative to process at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for a wideband pilot;

a multiplexer operative to time division multiplex (TDM) the sequence of pilot chips with the sequence of data chips to obtain a TDM sequence of pilot and data chips, wherein the multiplexer provides a plurality of periods for the sequences of data chips between periods for the sequences of pilot chips; and

a transmitter unit operative to process and transmit the TDM sequence of pilot and data chips.

12. The apparatus of claim 11, wherein a time between periods for the sequences of pilot chips comprises a period less than a decorrelation time for a channel through which the sequence of pilot chips are being transmitted.

13. A terminal comprising the apparatus of claim 11.

14. A base station comprising the apparatus of claim 11.

15. A processor readable media for storing instructions operable to:

process at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for a wideband pilot in a wireless multi-carrier communication system;

process data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips; and

time division multiplex the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips, wherein the multiplexer provides a plurality of periods for the sequences of data chips between periods for the sequences of pilot chips and wherein the TDM sequence of pilot and data chips is processed and transmitted over a communication channel in the system.

16. An apparatus in a wireless multi-carrier communication system, comprising:

a rake receiver operative to process a sequence of received chips with a pseudo-random number (PN) code to obtain a plurality of channel gain estimates for a plurality of propagation paths for a transmitting entity, wherein the sequence of received chips includes a sequence of combined pilot and data chips transmitted by the transmitting entity and obtained by summing a sequence of pilot chips for a wideband pilot with a sequence of data chips at the transmitting entity;

a processor operative to process the plurality of channel gain estimates to obtain a plurality of channel response estimates for a plurality of subbands; and

a demodulator operative to process the sequence of received chips in accordance with a multi-carrier demodulation scheme and with the plurality of channel response estimates to obtain recovered data symbols for the transmitting entity.

17. A method of transmitting a pilot in a wireless multi-carrier communication system, comprising:

processing at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips;

processing data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips;

assigning data symbols for transmission on different ones of a plurality of subbands in different time intervals according to a frequency hopping (FH) sequence; and

transmitting the TDM sequence of pilot chips and data chips on the assigned ones of the plurality of subbands.

18. The method of claim 17, wherein the wireless multi-carrier communication system is an orthogonal frequency division multiple access (OFDMA) communication system, and wherein the multi-carrier modulation scheme is orthogonal frequency division multiplexing (OFDM).

19. The method of claim 17, wherein the at least one pilot symbol is spectrally spread with the PN code in time domain using direct sequence spread spectrum processing to obtain the sequence of pilot chips.

20. The method of claim 17, wherein the PN code uniquely identifies a transmitting entity of the pilot.

21. The method of claim 17, further comprising:

scaling the sequence of pilot chips with a scaling factor to obtain a sequence of scaled pilot chips, wherein the scaling factor is indicative of a transmit power level for the pilot, and wherein the sequence of scaled pilot chips is time division multiplexed with the sequence of data chips.

22. The method of claim 17, wherein the TDM sequence of pilot and data chips is transmitted on a reverse link in the system.

23. An apparatus in a wireless multi-carrier communication system, comprising:

means for processing at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips;

means for processing data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

means for time division multiplexing the sequence of pilot chips with the sequence of data chips to obtain a time division multiplexed (TDM) sequence of pilot and data chips;

means for assigning data symbols for transmission on different ones of a plurality of subbands in different time intervals according to a frequency hopping (FH) sequence; and

means for transmitting the TDM sequence of pilot chips and data chips on the assigned ones of the plurality of subbands.

24. The apparatus of claim 23, wherein the PN code uniquely identifies a transmitting entity of the pilot.

25. The apparatus of claim 23, further comprising:

means for scaling the sequence of pilot chips with a scaling factor to obtain a sequence of scaled pilot chips, wherein the scaling factor is indicative of a transmit power level for the pilot, and wherein the sequence of scaled pilot chips is time division multiplexed with the sequence of data chips.

26. The apparatus of claim 23, wherein the TDM sequence of pilot and data chips is transmitted on a reverse link in the system.

27. An apparatus in a wireless multi-carrier communication system, comprising:

a modulator operative to process data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

a pilot generator operative to process at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for a pilot;

a multiplexer operative to time division multiplex (TDM) the sequence of pilot chips with the sequence of data chips to obtain a TDM sequence of pilot and data chips; and

a transmitter unit operative to process and transmit the TDM sequence of pilot and data chips, wherein the data symbols are transmitted on different ones of a plurality of subbands in different time intervals according to a frequency hopping (FH) sequence.

28. The apparatus of claim 27, wherein the PN code uniquely identifies a transmitting entity of the pilot.