Sphere Detector Depth-First Search for MIMO Symbol Detection
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Solution Overview
Problem
In wireless communication, the detection of multiple symbols transmitted in parallel from multiple antennas becomes infeasible due to the exponential increase in possible combinations, especially with higher order modulation and a large number of antennas, leading to inefficiencies in evaluating all possible combinations for maximum-likelihood detection.
Innovation Solution
A system utilizing a sphere detector that performs a depth-first search, pruning nodes based on distance evaluations and maintaining a bounding value to reduce the search space, allowing for efficient detection of symbols by terminating the search when a result is requested and selecting the node with the lowest distance, thereby improving processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all possible symbol combinations are evaluated for maximum-likelihood detection, then detection accuracy is improved, but computational complexity increases exponentially
Solution Approach 1:
The patent segments the exhaustive search space into a structured tree with multiple levels, where each level corresponds to a transmitting antenna. The depth-first search algorithm processes nodes level by level, evaluating partial distances at each stage. This segmentation allows the detector to systematically explore candidate symbol combinations without evaluating all possible combinations, thereby reducing computational complexity while maintaining detection accuracy through progressive refinement of candidate paths.
Solution Approach 2:
The patent extracts and evaluates only the most promising candidate paths through the depth-first search algorithm. By maintaining a current best distance metric and comparing partial distances during traversal, the system extracts relevant candidate symbol combinations while discarding unlikely paths early in the search process. This extraction principle enables the detector to focus computational resources on evaluating only those symbol combinations that have a reasonable probability of being the correct detection, significantly reducing the overall computational burden.
2Productivity
If the number of transmitting antennas and modulation order increase, then data transfer rate is improved, but the number of possible symbol combinations becomes infeasible to evaluate
Solution Approach 1:
The patent implements dynamic adaptation of the search process through the depth-first search algorithm, which adaptively explores the search space based on partial distance evaluations. The algorithm dynamically adjusts which candidate paths to pursue by comparing partial distances at each node and backtracking when promising paths are exhausted. This dynamic approach allows the system to handle increased numbers of antennas and modulation orders efficiently, as the search effort automatically scales with the problem complexity rather than evaluating all possible combinations regardless of their likelihood.
Solution Approach 2:
The patent changes the parameter of search evaluation from exhaustive to selective by introducing partial distance metrics at each tree level. Instead of evaluating complete symbol combinations only at the final stage, the system computes partial distances incrementally during the depth-first traversal, allowing early elimination of unlikely paths. This parameter change in the evaluation process enables the detector to efficiently handle higher order modulations and more antennas by pruning the search space based on intermediate distance measurements rather than requiring complete combination evaluation.
Data Source
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AI summary
Systems and methods detect a communication received at receiving antennas (112-118) from transmitting antennas (102-108). Each transmitting antenna transmits a symbol in a constellation. A sphere detector (140) performs a depth-first search until the depth-first search terminates in response to a terminate signal (160) requesting the result from the sphere detector. The depth-first search evaluates respective distances of one or more leaf nodes in response to the communication received at the receiving antennas (206). The depth-first search selects the result from these nodes in response to the respective distances (210). The result includes a selected leaf node that identifies a corresponding symbol in the constellation for each transmitting antenna, with this symbol detected as transmitted by the transmitting antenna (212).