Adaptive Deinterleaver Memory Allocation for Soft-Decision Receivers
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Solution Overview
Problem
Wireless communication systems, such as T-DMB and ISDB-T, require significant receiver memory for deinterleaving, which is costly and performance-degrading, especially in fast fading conditions, due to the need for representing soft decisions with a large number of bits.
Innovation Solution
An adaptive technique that adjusts the number of bits per soft decision based on subchannel organization and available memory, allowing for variable allocation of memory to optimize performance by utilizing unused memory for enhanced Viterbi decoder input, thereby reducing overall receiver memory requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of bits per soft decision (N) is increased to improve receiver performance in fast fading channels, then the Viterbi decoder performance is improved, but the receiver memory size increases significantly
Solution Approach 1:
The patent applies dynamics by making the number of bits per soft decision (N) variable rather than fixed. The processor dynamically adjusts N based on the number of occupied subchannels, allowing the system to adapt memory allocation to actual usage conditions. When fewer subchannels are occupied, N is reduced to decrease memory requirements while maintaining adequate performance.
Solution Approach 2:
The patent changes the parameter N (number of bits per soft decision) based on the operational conditions. The processor determines N by dividing the total available memory by the number of soft bits required for occupied subchannels, thereby changing the memory allocation parameter to optimize the balance between performance and memory usage.
2Reliability
If a fixed large memory size is allocated for deinterleaving to ensure sufficient performance, then receiver reliability is maintained, but the device complexity and cost increase
Solution Approach 1:
The patent applies local quality by allocating memory resources differently based on the specific conditions of subchannel occupation. Instead of uniformly allocating maximum memory throughout, the system allocates memory locally to only the occupied subchannels, adjusting the bit depth N according to the actual number of active subchannels, thereby reducing overall memory requirements while maintaining performance where needed.
Solution Approach 2:
The memory allocation is made dynamic rather than static. The processor continuously monitors which subchannels are occupied and adjusts the number of bits per soft decision accordingly, allowing the receiver to use less memory when fewer subchannels are active while ensuring sufficient memory when more subchannels are occupied.
3Volume of stationary object
If the number of bits per soft decision is reduced to decrease memory requirements, then receiver cost is reduced, but the Viterbi decoder performance deteriorates especially in fast fading conditions
Solution Approach 1:
The system changes the parameter N dynamically based on the number of occupied subchannels. When fewer subchannels are occupied, the processor reduces N to decrease memory requirements. When more subchannels are occupied, the processor increases N to maintain performance, thereby optimizing the trade-off between memory usage and decoder performance under varying conditions.
Solution Approach 2:
The bit depth N is made dynamic rather than fixed. The processor adjusts N in real-time based on the actual number of active subchannels, allowing the receiver to use lower bit depths (reducing memory) when conditions permit while increasing bit depth to maintain performance when more subchannels are active.
Data Source
AI summary
A receiver for use in a wireless network comprising a communications channel and a method of allocating deinterleaver memory usage in the receiver, wherein the receiver comprises a processor adapted to organize subchannels of the communications channel and set a number (N) of data bits per soft decision, wherein the soft decision is represented by N data bits; an address decoder adapted to decode the subchannels; a demapper adapted to receive QAM symbols and demap the QAM symbols to soft decisions; a deinterleaver adapted to perform deinterleaving on the soft decisions, wherein the deinterleaver comprises a memory component having a storage size that is a function of the number (N) of bits per soft decision; and a Viterbi decoder adapted to decode the deinterleaved soft decisions.