Fast frequency hopping with a code division multiplexed pilot in an OFDMA system

• US 8,102,832 B2
• Filed: 12/21/2006
• Issued: 01/24/2012
• Est. Priority Date: 05/12/2003
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Agrawal, Avneesh, Teague, Edward Harrison
• Primary Examiner(s): Ho, Chuong T
• Application Number:
  US11/614,470
• Publication Number:
  US 20070211790A1
• Time in Patent Office: 1,860 Days
• Field of Search: 370/342, 370/345, 370/341, 370/335, 370/347, 370/324, 370/328, 370/331, 370/343, 370/377, 375/377
• US Class Current: 370/342
• 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, by a pilot generator, at least one pilot symbol with a pseudo-random number (PN) code to obtain a sequence of pilot chips for the wideband pilot;

processing, by a modulator, data symbols on different ones of a plurality of subbands in different time intervals as determined by a frequency hopping (FH) sequence and processing the data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

time division multiplexing, by a multiplexer, 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 sequences of data chips are provided between periods for sequences of pilot chips; and

transmitting, by a transmitter, the TDM sequence of pilot and data chips, wherein a time between periods for the sequences of pilot chips comprises a period less than a coherence time for a channel through which the sequences of pilot chips are being transmitted, 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).

2. 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.

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

4. 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.

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

6. 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 on different ones of a plurality of subbands in different time intervals as determined by a frequency hopping (FH) sequence and 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 providing a plurality of periods for sequences of data chips between periods for sequences of pilot chips; and

means for transmitting the TDM sequence of pilot and data chips, wherein a time between periods for the sequences of pilot chips comprises a period less than a coherence time for a channel through which the sequences of pilot chips are to be transmitted, 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).

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

a modulator operative to process data symbols on different ones of a plurality of subbands in different time intervals as determined by a frequency hopping (FH) sequence and to process the 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, the multiplexer operative to provide a plurality of periods for sequences of data chips between periods for sequences of pilot chips; and

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

wherein a time between periods for the sequences of pilot chips comprises a period less than a coherence time for a channel through which the sequences of pilot chips are to be transmitted, 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).

8. A terminal comprising the apparatus of claim 7.

9. A base station comprising the apparatus of claim 7.

10. A processor readable media for storing computer executable instructions which is executed by the computer processor 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 on different ones of a plurality of subbands in different time intervals as determined by a frequency hopping (FH) sequence and process the data symbols in accordance with a multi-carrier modulation scheme to obtain a sequence of data chips;

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; and

provide a plurality of periods for sequences of data chips between periods for sequences of pilot chips, wherein the TDM sequence of pilot and data chips is to be processed and transmitted over a communication channel in the system, and wherein a time between periods for the sequences of pilot chips comprises a period less than a coherence time for a channel through which the sequences of pilot chips are to be transmitted, 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).