Maximum likelihood sequence estimation of quadrature amplitude modulated signals
AssigneeZte Corporation
InventorsYi Cai, Zhensheng Jia, Jianjun Yu
Life of this patent
Estimating the term…
Abstract
In a receiver of Quadrature Amplitude Modulation (QAM) signal, the received QAM signal is divided into multiple Quadrature Phase Shift Keying (QPSK) symbol streams. A Maximum Likelihood Symbol Estimation (MLSE) is performed on each QPSK symbol stream to recover information bits in the received QAM signal. In one advantageous aspect, complexity of implementation can be reduced by performing MLSE on QPSK signals instead of QAM signals.
Claims20
A method of recovering data from a received Quadrature Amplitude Modulation (QAM) signal, comprising:
- performing a first stage of receiver-side processing to produce a stream of digitized QAM symbols from the received QAM signal;
- generating, from the stream of digitized QAM symbols, multiple digitized Quadrature Phase Shift Keying (QPSK) symbol streams;
- processing each of the multiple digitized QPSK symbol streams through a partial response filter, thereby resulting in multiple partially filtered symbols streams;
- and
- recovering data bits by performing maximum likelihood sequence estimation (MLSE) algorithm over the partially filtered symbols streams.
An optical signal receiver apparatus, comprising:
- a memory;
- electronic circuitry that performs a first stage of processing to recover a stream of digitized QAM symbols from the received QAM signal;
- a digital signal processor that generates, from the stream of digitized QAM symbols, multiple digitized Quadrature Phase Shift Keying (QPSK) symbol streams;
- electronic circuitry that processes each of the multiple digitized QPSK symbol streams through a partial response filter, thereby resulting in multiple partially filtered symbols streams;
- and
- electronic circuitry that recovers data bits by performing maximum likelihood sequence estimation (MLSE) algorithm over the partially filtered symbols streams.
A program product comprising a processor-readable storage medium holding processor-readable instructions, the instructions, when executed by a processor, causing the processor to implement a data reception method, comprising:
- separating a stream of 8-Quadrature Amplitude Modulation (8-QAM) symbols into a first stream of Quadrature Phase Shift Keying (QPSK) symbols and a second stream of QPSK symbols;
- for each of the stream of QPSK symbols:
- applying a partial response filter to generate a filtered symbol stream;
- and
- performing maximum likelihood sequence estimation (MLSE) on the filtered symbol stream to generate bit decisions;
- merging the bit decisions of the first and the second QPSK symbols streams;
- and
- recovering data bits by performing forward error correction on the merged bit decisions.
Dependencies are inferred from the claim text.