MIMO Channel Estimation Circuit Using Dynamic LTF Symbol Allocation
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Solution Overview
Problem
Existing technologies lack effective solutions for MIMO channel estimation in Extremely High Throughput (EHT) WLAN, which requires support for up to 16 spatial streams, as current Long Training Fields (LTF) in existing technologies only support up to 8 spatial streams.
Innovation Solution
The proposed solution involves generating Long Training Fields (LTF) in Physical Layer Protocol Data Units (PPDU) that support up to 16 spatial streams by determining the number of LTF symbols (NLTF) based on the maximum number of space-time streams for each resource unit (RU), using a PLTF matrix to spread space-time streams across LTF symbols, and incorporating user-specific resource allocation information in multiuser PPDUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of spatial streams is increased from 8 to 16 to achieve higher throughput in EHT WLAN, then the peak throughput and capacity are improved, but the existing LTF structure cannot support this increase as it only supports up to 8 spatial streams
Solution Approach 1:
The patent applies dynamics by making the LTF structure adaptable through the `NLTF` parameter that dynamically adjusts based on the number of spatial streams. The controller determines `NLTF` according to `NSTSMAX` (maximum number of space-time streams), allowing the LTF to transition from fixed 8-stream support to dynamic 16-stream support, resolving the contradiction between higher throughput capability and LTF adaptability
Solution Approach 2:
The patent changes the parameter `NLTF` (number of LTF symbols) from a fixed value to a variable that depends on `NSTSMAX`. By establishing `NLTF` as a function of the maximum number of space-time streams, the system can adjust the LTF configuration to match different spatial stream requirements, enabling support for up to 16 spatial streams while maintaining backward compatibility
2Measurement precision
If the number of LTF symbols (NLTF) is increased to support more spatial streams, then the channel estimation accuracy is improved, but the PPDU structure complexity increases
Solution Approach 1:
The patent uses dynamics by making `NLTF` adjustable rather than fixed. The controller dynamically sets `NLTF` based on the actual number of spatial streams being transmitted, so that channel estimation resources are allocated efficiently - more LTF symbols when more spatial streams are needed, fewer when fewer are used, thereby avoiding unnecessary structural complexity in common cases
3Productivity
If the maximum number of space-time streams (NSTSMAX) is increased to 16, then the capacity for multiuser MIMO transmissions is improved, but the existing LTF generation method becomes insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the LTF generation parameters to accommodate up to 16 spatial streams. The controller establishes `NLTF` based on `NSTSMAX`, and the LTF generator uses updated parameters (`NLTF`, `NSTSMAX`) to generate appropriate LTF sequences. This enables the system to maintain feasibility in LTF generation while supporting the increased capacity of 16 spatial streams for multiuser MIMO transmissions
Data Source
AI summary
Disclosed is an integrated circuit for a communication apparatus. The integrated circuit includes a receiver, which, in operation, receives a physical layer protocol data unit (PPDU) with a single frequency resource, and circuitry, which, in operation, processes the PPDU. The PPDU includes a first field that indicates a first number of symbols of a long training field (LTF) for Multiple Input Multiple Output (MIMO) channel estimation in the PPDU. The first number is larger than or equal to a second number of the symbols of the LTF. The second number is determined according to a number of spatial streams (Nss) for the PPDU. The circuitry processes the PPDU based on the first number.