Method and system for the transmission, reception and processing of 4-level and 8-level signaling symbols

• US 6,567,475 B1
• Filed: 12/29/1998
• Issued: 05/20/2003
• Est. Priority Date: 12/29/1998
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul W., Ramesh, Rajaram
• Primary Examiner(s): Vo, Don N.
• Assistant Examiner(s): Nguyen, Dung X
• Application Number:
  US09/222,617
• Time in Patent Office: 1,603 Days
• Field of Search: 375/286, 375/288, 375/264, 375/272, 375/279, 375/308, 375/261, 375/280, 375/281, 375/284, 332/112, 332/144, 332/103, 332/104, 341/17, 341/55, 341/56, 341/61, 341/102
• US Class Current: 375/286
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/186 in which the information is carried by both the individual signal points and the subset to which the individual signal points belong, e.g. coset coding or related schemes

Abstract

A method and system for the transmission, reception, and processing of 4-level and 8-level signaling symbols is provided. An inventive modulator is provided for modulating 4-level signaling symbols using an 8-level modulator. Further, this inventive modulator is able to produce 4-level modulation when modulating 4-level signaling symbols using an 8-level modulator, where the 4-level modulation represents the 4-level symbol sequence modulated. Further, a constrained/unconstrained demodulator is provided which is able to demodulate both 4-level signaling symbols and 8-level signaling symbols. The inventive demodulator accomplishes this by limiting the number of new symbol hypotheses and path histories to 4 when working with 4-level signaling symbols, and setting the number of new symbol hypotheses and path histories to 8 when working with 8-level signaling symbols. Additionally, an error correction decoder is provided which is also able to decode a demodulated signal which contains both 4-level and 8-level signaling symbols. The inventive error correction decoder accomplishes this by utilizing an interleaver that only places bits in the 2-bit positions of the 3-PSK soft values that correspond to the 2-bits of QPSK to decode 4-level signalling symbols, and utilizing an interleaver that places bits in all three of the possible bit positions of a symbol to decode 8-level signalling symbols.

Claims

1. A method of modulating 4-level signaling symbols using an 8-level modulator, the method comprising:

receiving 4-level signaling symbols to be modulated, each 4-level signaling symbol containing 2-bits of information;

expanding said 4-level signaling symbols into expanded 4-level signaling symbols, each expanded 4-level signaling symbol containing 3-bits of information and constrained to one of four possible values corresponding to four points of an 8-point signaling constellation; and

modulating said expanded 4-level signaling symbols using an 8-level modulator.

2. The method of claim 1, wherein the step of expanding said 4-level signaling symbols into expanded 4-level signaling symbols includes manufacturing a third bit for each 4-level signaling symbol and appending said third bit to said 2-bits of information.

3. The method of claim 2 wherein said third bit is the exclusive-OR of said 2-bits.

4. The method of claim 1 further comprising performing a progressive 45°

phase shift between a modulation of consecutive symbols.

5. The method of claim 1 wherein modulating an expanded 4-level signaling symbol with the 8-level modulator causes the 8-level modulator to produce 4-level modulation.

6. The method of claim 1 wherein said 4-level signaling symbols are a subset of said 8-level signaling symbols.

7. The method of claim 1 further comprising the step of sending an indication signal indicating which of expanded 4-level signaling symbols and 8-level signaling symbols are being transmitted.

8. A system for modulating 4-level signaling symbols using an 8-level signaling symbol modulator comprising:

a processor for processing information into a plurality of 4-level signaling symbols to be modulated;

an expander coupled to said processor for expanding said plurality of 4-level signaling symbols each containing 2-bits of information to expanded 4-level signaling symbols each containing 3-bits of information; and

constrained to one of four possible values corresponding to four points of 8-point signaling constellation and

an 8-level modulator coupled to said expander for modulating said expanded 4-level signaling symbols.

9. The system of claim 8 wherein said expander expands said plurality of 4-level signaling symbols by XORing said 2-bits of information to generate a third bit and appends said third bit to said 2-bits of information.

10. The system of claim 8 wherein said 8-level modulator applies a progressive 45°

phase shift between a modulation of consecutive symbols.

11. The system of claim 8 wherein said 4-level signaling symbols are a subset of said expanded 8-level signaling symbols.

12. The system of claim 8 wherein said 8-level modulator produces 4-level modulation when modulating said expanded 8-level signaling symbols.

13. The system of claim 8 wherein said information processed by said processor indicates a presence of said expanded 8-level signaling symbols.

14. The system of claim 8 wherein said processor processes information into a plurality of 8-level signaling symbols.