Transmitter and method for transmitting soft pilot symbols in a digital communication system

• US 8,750,407 B2
• Filed: 09/29/2008
• Issued: 06/10/2014
• Est. Priority Date: 06/17/2008
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Cheng, Jung-Fu, Fulghum, Tracy, Cairns, Douglas
• Primary Examiner(s): PATEL, DHAVAL V
• Application Number:
  US12/239,889
• Publication Number:
  US 20090310708A1
• Time in Patent Office: 2,080 Days
• Field of Search: 375/295, 375/298, 375/260, 375/262, 375/265, 375/267, 375/340, 375/346, 375/350, 370/203, 370/204, 370/205, 370/208, 370/209, 370/210
• US Class Current: 375/295
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0068 by puncturing
• CPC Class Codes: H04L 2001/0098 Unequal error protection
• CPC Class Codes: H04L 2025/03401 PSK
• CPC Class Codes: H04L 2025/0342 QAM
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 2025/03509 fractionally spaced H04L2025/03515 takes precedence
• CPC Class Codes: H04L 2025/03796 Location of reference signals
• CPC Class Codes: H04L 2027/0061 remodulation
• CPC Class Codes: H04L 2027/0093 Intermittant signals
• CPC Class Codes: H04L 25/021 Estimation of channel covariance
• 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 25/03044 using fractionally spaced delay lines or combinations of fractionally integrally spaced taps
• CPC Class Codes: H04L 25/03324 Provision of tentative decisions
• CPC Class Codes: H04L 25/061 providing hard decisions only; arrangements for tracking or suppressing unwanted low frequency components, e.g. removal of dc offset removal of dc offset in coupling arrangements H04L25/029, H04L25/0296
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04L 27/227 : using coherent demodulation
• CPC Class Codes: H04L 27/3455 : in order to facilitate carrier recovery at the receiver end, e.g. by transmitting a pilot or by using additional signal points to allow the detection of rotations
• CPC Class Codes: H04L 27/3818 : using coherent demodulation, i.e. using one or more nominally phase synchronous carriers H04L27/227 and H04L27/389 take precedence

Abstract

A transmitter, channel coder, and method for coding and transmitting a sequence of symbols in a digital communication system utilizing soft pilot symbols. In one embodiment, the transmitter transmits a set of soft pilot symbols with higher reliability than the remaining symbols in the sequence by modulating the soft pilot symbols with a lower order modulation such as BPSK or QPSK while modulating the remaining symbols with a higher order modulation such as 16 QAM or 64 QAM. The transmitter shares the modulation type and location (time/frequency/code) of the soft pilot symbols with a receiver. Unlike traditional fixed pilots, the soft pilots still carry some data. Additionally, the soft pilots are particularly helpful in establishing the amplitude reference essential in demodulating the higher order modulation symbols. In another embodiment, soft pilot symbols are inserted by low-level puncturing of channel encoded bits and replacing the punctured bits with known bit patterns.

Claims

1. A method of channel coding a radio signal for a High Speed Downlink Shared Channel (HS-DSCH) radio channel utilizing 16 QAM channel coding, wherein the method is performed in an I-Q coordinate system having an In-phase dimension and a Quadrature dimension, said method comprising the steps of:

channel interleaving the HS-DSCH radio signal; and

inserting soft pilot symbols selected from a 16 QAM constellation by low-level puncturing of channel coded bits to provide the soft pilot symbols with constant amplitude in only one dimension in the I-Q coordinate system, wherein the low-level puncturing includes one of the following;

providing constant Quadrature amplitude by replacing the punctured bits with known bit patterns having four bit labels in which a last bit label is fixed to a value of “

1”

;

or

providing constant In-phase amplitude by replacing the punctured bits with known bit patterns having four bit labels in which a third bit label is fixed to a value of “

1”

.

2. The method as recited in claim 1, wherein the inserting step is performed after modulation constellation rearrangement.

3. The method as recited in claim 1, wherein the radio channel is an Enhanced Dedicated Channel (E-DCH).

4. The method as recited claim 1, further comprising sending an indication to a receiver indicating locations in the sequence for the soft pilot symbols, said locations being defined in terms of time and code.

5. The method as recited in claim 1, further comprising sending an indication to a receiver indicating a modulation type for the soft pilot symbols.

6. The method as recited in claim 1, further comprising sending an indication to a receiver indicating the punctured bit label positions.

7. The method as recited in claim 1, further comprising pre-agreeing by a transmitter and a receiver upon locations of the soft pilot symbols, said locations being defined in terms of time and code.

8. The method as recited in claim 1, further comprising pre-agreeing by a transmitter and a receiver upon a modulation type for the soft pilot symbols.

9. The method as recited claim 1, further comprising pre-agreeing by a transmitter and a receiver upon bit label positions for puncturing.

10. A channel coder for channel coding a radio signal for a High Speed Downlink Shared Channel (HS-DSCH) radio channel utilizing 16 QAM channel coding, wherein the channel coding is performed in an I-Q coordinate system having an In-phase dimension and a Quadrature dimension, said channel coder comprising processing circuitry configured to:

channel interleave the HS-DSCH radio signal; and

insert soft pilot symbols selected from a 16 QAM constellation by low-level puncturing of channel coded bits to provide the soft pilot symbols with constant amplitude in only one dimension in the I-Q coordinate system, wherein the low-level puncturing includes one of the following;

providing constant Quadrature amplitude by replacing the punctured bits with known bit patterns having four bit labels in which a last bit label is fixed to a value of “

1”

;

or

providing constant In-phase amplitude by replacing the punctured bits with known bit patterns having four bit labels in which a third bit label is fixed to a value of “

1”

.

11. The channel coder as recited in claim 10, wherein the channel coder is configured to insert the soft pilot symbols after modulation constellation rearrangement.

12. The channel coder as recited in claim 10, wherein the radio channel is an Enhanced Dedicated Channel (E-DCH).