METHOD AND APPARATUS FOR CHANNEL QUALITY MEASUREMENTS

• US 20120219093A1
• Filed: 04/02/2012
• Published: 08/30/2012
• Est. Priority Date: 10/17/2001
• Status: Active Grant

• Current Assignee: Rockstar Bidco LP (Rockstar Consortium Inc.)
• Original Assignee: Rockstar Bidco LP (Rockstar Consortium Inc.)
• Inventors: JIA, Ming, MA, Jianglei, ZHU, Peiying, YU, Dong-Sheng, TONG, Wen
• Granted Patent: US 8,594,247 B2
• Time in Patent Office: Days
• US Class Current: 375/308
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0036 arrangements specific to the receiver
• CPC Class Codes: H04L 1/0631 Receiver arrangements
• CPC Class Codes: H04L 1/208 involving signal re-encoding
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 25/0236 using estimation of the other symbols
• CPC Class Codes: H04L 25/03318 Provision of soft decisions
• CPC Class Codes: H04L 25/067 providing soft decisions, i.e. decisions together with an estimate of reliability H04L25/068 and H04L25/069 take precedence; sequence estimation techniques H04L25/03178
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals

Abstract

A method and apparatus for measuring channel quality over which has been transmitted a sequence of symbols produced by encoding and constellation mapping a source data element sequence. A sequence of received symbols is received over the channel. The sequence of received symbols is de-mapped based on a first channel quality indicator previously transmitted to a transmitter of the sequence of symbols. The de-mapped symbols are decoded to produce a decoded output sequence. In some embodiments, the decoding may be based on the first channel quality indicator. The decoded output sequence is re-encoded to produce a re-encoded output sequence. The de-mapped symbols are correlated with the re-encoded output sequence to produce a second channel quality indicator. The second channel quality indicator is transmitted to the transmitter to adaptively select a type of mapping based on the second channel quality indicator.

Claims

1. A transmitter, comprising:

a plurality of transmit antennas; and

at least one transmit signal processor configured to;

apply forward error coding to a signaling message to generate a coded signaling message;

M-ary Phase Shift Key (MPSK) map the coded signaling message to produce an MPSK mapped coded signaling message;

encode symbols of the MPSK mapped coded signaling message using Differential Space-Time Block Coding (D-STBC) in a time direction to generate encoded symbols;

map the encoded symbols of the MPSK mapped coded signaling message onto a plurality of sub-carriers within an Orthogonal Frequency Division Multiplexed (OFDM) frame comprising a plurality of OFDM symbols; and

transmit the encoded symbols on a plurality of transmit antennas, with the encoded symbols being transmitted at an increased power level relative to other symbols within the OFDM frame as a function of channel conditions.

2. The transmitter of claim 1, wherein the at least one signal processor is further configured to transmit the encoded symbols in a scattered pattern.

3. The transmitter of claim 1, wherein transmitting the encoded symbols on a plurality of antennas comprises, on a selected sub-carrier, each antenna transmitting a respective plurality N of encoded symbols over N consecutive OFDM symbols, where N is the number of antennas used to transmit, for a total of N×

N transmitted encoded symbols, the N×

N symbols being obtained from D-STBC encoding L symbols of the MPSK mapped coded signaling stream, where L,N determine an STBC code rate.

4. The transmitter of claim 3, wherein the at least one signal processor is operable to transmit a set of pilot sub-carriers in at least one OFDM frame, using the pilot sub-carriers as a reference for a first set of D-STBC encoded symbols transmitted during subsequent OFDM frames.

5. The transmitter of claim 4, wherein transmitting a set of pilot sub-carriers in at least one. OFDM frame comprises transmitting a plurality of pilots on each antenna on a respective disjoint plurality of sub-carriers.

6. The transmitter of claim 5, wherein each disjoint plurality of sub-carriers comprises a set of sub-carriers each separated by N−

1 sub-carriers, where N is the number of antennas.

7. The transmitter of claim 5, wherein the at least one signal processor is further configured to transmit pilot sub-carriers for a number of consecutive. OFDM frames equal to the number of transmit antennas.

8. The transmitter of claim 1, wherein the signaling message contains an identification of one or more receivers which are to receive data during a current TPS frame.

9. A receiver, comprising:

at least one antenna configured to receive an Orthogonal Frequency Division Multiplexed (OFDM) signal containing Differential Space-Time Block Coding (D-STBC) encoded m-ary phase shift key (MP K) mapped coded signaling message symbols; and

at least one signal processor configured to;

recover received signaling message symbols from the OFDM signal;

determine from the signaling message symbols whether a current OFDM transmission contains data to be recovered by the receiver;

upon determining the current OFDM transmission contains data to be recovered by the receiver;

a) re-encoding, MPSK mapping and D-STBC coding the received coded signaling message symbols to produce re-encoded D-STBC encoded MPSK mapped coded signaling message symbols; and

b) determining a channel estimate by comparing the received D-STBC encoded mapped coded signaling message symbols with the re-encoded D-STBC encoded MPSK mapped coded signaling message symbols.

10. The receiver of claim 9, wherein the at least one signal processor is further configured to:

determine a channel estimate for each location (in time, frequency) in the OFDM signal containing D-STBC encoded MPSK mapped coded signaling message symbols; and

to interpolate to get a channel estimate for each remaining location (in time, frequency) in the OFDM signal.

11. The receiver of claim 10, wherein the at least one signal processor is further configured to receive pilot symbols which are not D-STBC encoded which are used as a reference for a first D-STBC block of D-STBC encoded MPSK mapped coded signaling message symbols.

12. The receiver of claim 9, wherein the at least one signal processor is further configured to extract the signaling message.

13. An apparatus for determining a channel response from an Orthogonal Frequency Division Multiplexed (OFDM) frame received at an OFDM receiver, the OFDM frame containing an encoded fast signaling message in the form of encoded symbols within the OFDM frame, the apparatus comprising at least one signal processor configured to:

process the encoded symbols based on a scattered pilot pattern to recover the encoded fast signaling message as a recovered encoded fast signaling message;

re-encode the recovered fast signaling message so as to produce known pilot symbols in the scattered pilot pattern;

processing the encoded symbols comprising;

differentially decoding the encoded symbols using Differential Space-Time Block Coding (D-STBC) decoding to recover the encoded fast signaling message;

applying Forward Error Correction decoding to the encoded fast signaling message to recover a fast signaling message; and

analyzing the fast signaling message to determine whether it includes a desired user identification;

if the fast signaling message includes the desired user identification, re-encoding the recovered fast signaling;

message comprises;

re-encoding the fast signaling message using Forward Error Correction coding to generate the encoded fast signaling message, and

re-encoding the encoded fast signaling message using D-STBC.

14. The apparatus of claim 13, wherein the at least one signal processor is further configured to apply a fast algorithm to compute a Discrete Fourier Transform based on the scattered pilot pattern to extract the combined pilot symbols and fast signaling message and to only proceed to recover the channel response if the fast signaling message indicates a current transmission contains content for the OFDM receiver.