Interleaver

• US 7,529,307 B2
• Filed: 03/30/2005
• Issued: 05/05/2009
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Intel Corporation
• Inventors: Cheung, David, Sandhu, Sumeet
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Ghulamali; Qutbuddin
• Application Number:
  US11/093,743
• Publication Number:
  US 20060242475A1
• Time in Patent Office: 1,497 Days
• Field of Search: 375/260, 375/229, 375/240, 375/248, 375/285, 370/468, 370/328
• US Class Current: 375/260
• CPC Class Codes: H03M 13/27 using interleaving techniques

Abstract

An interleaver and scheme for interleaving in which highly correlated bits are maximally separated. The scheme involves interleaving a set of bits to be delivered to a modulation system that utilizes a quantity of N carrier frequencies. A first block of N consecutive bits is assigned to each of N bins, on a one-bit-per-one-bin basis. The aforementioned assignment proceeds in a particular sequence. A second block of N consecutive bits is assigned to each of the N bins, on a one-bit-per-one-bin basis. The second block is assigned in the same sequence the first block was assigned. The second block is consecutive to the first block.

Claims

1. A method for encoding and interleaving data bits for OFDM transmission comprising:

encoding a set of bits with an encoder having a constraint length that generates encoded bits having a code-word length;

selecting, from the set of encoded bits, an encoded bit designated by an index;

assigning the selected bit sequentially to one of N carrier frequencies that does not yet have a bit assigned thereto;

incrementing the index, and repeating the selecting and assigning acts, until each of the N carrier frequencies has an encoded bit assigned to it; and

for each of the N carrier frequencies, assigning another encoded bit thereto, wherein the other encoded bit is designated by an index value equal to the sum of the index of the encoded bit already assigned thereto and an integer multiple of N,

wherein, for each of the N carrier frequencies, the bits assigned thereto at least partially jointly determine a symbol to be modulated upon the carrier frequency,

wherein the encoded bits are assigned to each carrier frequency to provide a bit separation distance of N,

wherein the index of any of the encoded bits assigned to a single one of the carrier frequencies, when divided by N, exhibits a constant remainder, and

wherein N is greater than a product of the constraint length and the code word length.

2. The method of claim 1,

further comprising:

accessing a look-up table to determine a carrier frequency assignment based on the index of the encoded bit;

storing encoded bits in an addressable array of memory bins associated with each of the carrier frequencies, and

parsing, by a parser, to select encoded bits from the memory bins.

3. The method of claim 1, further comprising:

determining a symbol, for each carrier frequency, based upon the bits assigned thereto.

4. The method of claim 3, further comprising:

for each carrier frequency, modulating the corresponding determined symbol thereupon.

5. A device to transmit orthogonal frequency division multiplexed (OFDM) signals comprising:

an encoder having a constraint length configured to encode a set of data bits and yield encoded bits having a code-word length;

an interleaver in data communication with the encoder, the interleaver configured to receive and resequence the encoded bits;

a modulation system in data communication with the interleaver, the modulation system configured to receive the resequenced encoded bits, and based thereupon, to modulate symbols upon each of a quantity of N carrier frequencies to generate an OFDM symbol;

wherein the interleaver is adapted to;

select, from the set of encoded bits, an encoded bit designated by an index;

assign the selected bit sequentially to one of N carrier frequencies that does not yet have a bit assigned thereto;

increment the index, and repeat the selection and assignment of encoded bits until each of the N carrier frequencies has an encoded bit assigned to it;

for each of the N carrier frequencies, assign another encoded bit thereto, wherein the other encoded bit is designated by an index value equal to the sum of the index of the encoded bit already assigned thereto and an integer multiple of N;

wherein, for each of the N carrier frequencies, the bits assigned thereto at least partially jointly determine a symbol to be modulated upon the carrier frequency,

wherein the encoded bits are assigned to each carrier frequency to provide a bit separation distance of N, and

wherein the index of any of the encoded bits assigned to a single one of the carrier frequencies, when divided by N, exhibits a constant remainder, and

wherein N is greater than a product of the constraint length and the code word length.

6. The device of claim 5, wherein each bin comprises a memory space.

7. The device of claim 5, wherein each bin corresponds to one of the N carrier frequencies.

8. The device of claim 5, wherein each bin is of a size to store two or more bits.