Bit interleaving for orthogonal frequency division multiplexing in the transmission of digital signals

• US 20010030939A1
• Filed: 05/10/2001
• Published: 10/18/2001
• Est. Priority Date: 06/19/1997
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Vijayan, Rajiv, Lee, Chong U., Odenwalder, Joseph P., Zehavi, Ephraim, Wolf, Jack K.
• Granted Patent: US 6,717,908 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H03M 13/27 using interleaving techniques
• CPC Class Codes: H03M 13/2707 Simple row-column interleaver, i.e. pure block interleaving
• CPC Class Codes: H03M 13/2936 comprising an outer Reed-Solomon code and an inner convolutional code
• CPC Class Codes: H03M 13/31 combining coding for error detection or correction and efficient use of the spectrum without error detection or correction H03M5/14 , H03M5/145
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/0059 Convolutional codes
• CPC Class Codes: H04L 1/0065 Serial concatenated codes
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/26526 with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002

Abstract

In an orthogonal frequency division multiplexing (OFDM) system which uses an outer Reed-Solomon encoder and interleaver an inner convolutional encoder, after the inner convolutional encoding the data bits are interleaved, and then grouped into symbols, each symbol having “m” bits. After grouping, the symbols are mapped to a complex plane using quadrature amplitude modulation (QAM). Thus, bits, not symbols, are interleaved by the inner interleaver. A receiver performs a soft decision regarding the value of each bit in each complex QAM symbol received.

Claims

1. For a receiver receiving “

n”

substreams of an orthogonal frequency division multiplexed (OFDM) signal containing complex phase-adjusted symbols, each symbol representing “

m”

data bits, a device, comprising;

for each substream, a soft decision quantizer for determining a binary value of each bit represented by each symbol in the substream.

2. The device of

claim 1

, wherein the soft decision quantizer comprises:

means for determining a first set of possible values for each symbol, each value in the first set having a binary value of “

0”

in a predetermined bit;

means for determining, for each symbol, a magnitude difference between the symbol and each possible value in the first set of possible values; and

means for determining the smallest magnitude difference an generating a first signal representative thereof.

3. The device of

claim 2

, wherein the soft decision quantizer further comprises:

means for determining a second set of possible values for each symbol, each value in the second set having a binary value of “

1”

in a predetermined bit;

means for determining, for each symbol, a magnitude difference between the symbol and each possible value in the second set of possible values; and

means for determining the smallest magnitude difference an generating a second signal representative thereof.

4. The device of

claim 3

, wherein the soft decision quantizer further comprises means for returning a binary “

1”

when the first signal is greater than the second signal, and otherwise returning a binary “

0”

.

5. The device of

claim 4

, wherein the soft decision quantizer further comprises means for returning a confidence value proportional to the magnitude of the difference between the first and second signals.

6. The device of

claim 4

, in combination with the receiver, the receiver further comprising a guard period deleter for deleting guard periods in the OFDM signal, prior to inputting the OFDM signal to the soft decision quantizer.

7. For an orthogonal frequency division multiplex (OFDM) signal receiver for receiving complex symbols in the OFDM signal, each symbol representing “

m”

data bits, a computer logic device comprising;

a computer logic storage device readable by a digital processing system; and

instructions embodied in the logic storage device, the instructions being executable by the digital processing system for performing method steps for undertaking a soft decision regarding a value of each symbol, the method steps comprising;

determining a first set of possible values for each symbol, each value in the first set having a binary value of “

0”

in a predetermined bit;

determining, for each symbol, a magnitude difference between the symbol and each possible value in the first set of possible values; and

determining the smallest magnitude difference an generating a first signal representative thereof.