OFDM Receiver Soft-Bit Combining for Lower Bit Error Rates
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Solution Overview
Problem
Existing OFDM signal decoding methods struggle with accuracy due to noise and interference, particularly in extended range applications, leading to unreliable bit error rates.
Innovation Solution
A receiver apparatus and method that combines soft-bit sequences from two OFDM symbols with frequency and time diversity, using interleaved or non-interleaved states, to improve decoding accuracy and reduce bit error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If soft decision decoding is used instead of hard decision decoding, then decoding accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent segments the decoding process by separating soft decision decoding into multiple independent stages: receiving multiple OFDM symbols, performing soft decision decoding on each symbol separately to generate soft-bit sequences, and then combining these sequences. This segmentation allows the system to achieve improved decoding accuracy through soft decision decoding while managing computational complexity by processing symbols in discrete, manageable units rather than as a single complex operation.
2Reliability
If multiple OFDM symbols are combined to improve decoding reliability, then bit error rate is reduced, but processing time increases
Solution Approach 1:
The patent applies preliminary action by performing soft decision decoding on each OFDM symbol immediately upon reception, generating soft-bit sequences in advance before the combining operation. This preliminary processing of individual symbols allows the system to prepare multiple independent decoding results that can be quickly combined using simple addition operations, rather than requiring complex real-time processing of all symbols simultaneously, thus reducing overall processing time while maintaining improved reliability.
3Reliability
If interleaving is applied to provide frequency diversity, then resilience to fading is improved, but device complexity increases
Solution Approach 1:
The patent merges the benefits of interleaving and soft decision decoding by combining multiple soft-bit sequences that have undergone different interleaving patterns. Instead of implementing complex interleaving and de-interleaving operations for each symbol separately, the system receives multiple symbols with inherent frequency diversity, performs soft decision decoding on each, and then combines the resulting soft-bit sequences through simple addition. This merging approach achieves frequency diversity resilience while avoiding the complexity of multiple interleaving stages.
Data Source
AI summary
A receiver apparatus for receiving an OFDM radio signal comprising a first plurality of subcarrier-symbols, modulated on a corresponding plurality of subcarriers, and a second plurality of subcarrier-symbols, modulated on the corresponding plurality of subcarriers, to generate first and second bit sequences, the first bit sequence being an interleaved version of the second bit sequence according to a predetermined interleave function. Soft-output decoder logic generates a first soft-bit sequence for the first plurality of subcarrier-symbols, and a second soft-bit sequence for the second plurality of subcarrier-symbols. Combiner logic combines the soft-bit sequences, with the soft-bit sequences either both in an interleaved state or both in a non-interleaved state, by combining a respective soft-bit having a bit position in the first soft-bit sequence with a respective soft-bit having a same bit position in the second soft-bit sequence. Hard-output decoder logic outputs a hard-bit sequence representing the transmitted bit sequence.