WLAN PPDU CSD Value Determination for 16 Transmit Chains
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing WLAN systems face challenges in maintaining efficient transmission and backward compatibility when dealing with a large number of transmit chains, particularly in next-generation WLAN systems that support up to 16 chains, as the Cyclic Shift Delay (CSD) values are not defined for chains beyond 8, leading to potential unintended beamforming and power imbalance issues.
Innovation Solution
A method is proposed to determine and apply CSD values for each transmit chain in the legacy field of the PPDU, specifically by minimizing the difference in reception powers between the L-STF and data fields, using criteria that consider the power ratio's Cumulative Distribution Function (CDF) to ensure efficient transmission and prevent beamforming, while maintaining compatibility with legacy systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If CSD values are not defined for transmit chains beyond 8, then legacy system compatibility is maintained, but unintended beamforming occurs and power imbalance arises in next-generation systems supporting up to 16 chains
Solution Approach 1:
The patent extends the CSD value definition from 8 transmit chains to 16 transmit chains by defining new CSD values for chains 9-16. Specifically, it sets CSD values as: 0 for chain 1, 220.5 degrees for chain 2, 441 degrees (equivalent to 0) for chain 3, and so on, creating a periodic pattern that maintains power balance and prevents unintended beamforming while supporting the increased number of chains in next-generation WLAN systems.
2Adaptability or versatility
If CSD values are arbitrarily assigned for chains 9-16, then support for 16 chains is achieved, but power imbalance between L-STF and data fields occurs
Solution Approach 1:
The patent carefully selects specific CSD values (0, 220.5, 441, 661.5, 882, 1102.5, 1323, 1543.5 degrees for chains 1-8, and corresponding values for chains 9-16) that create a periodic pattern with a period of 4 chains. This specific parameter selection ensures that the cumulative phase shifts result in balanced power distribution across the L-STF and data fields, preventing power imbalance while enabling support for 16 transmit chains.
Data Source
AI summary
A method and an apparatus for transmitting a PPDU in a WLAN system are proposed. Specifically, a transmitter generates a PPDU and transmits the PPDU to a receiver. The PPDU includes a legacy field and an EHT field. The legacy field includes an L-STF. The EHT field includes a data field. The legacy field is configured on the basis of a CSD value per a transmission chain. The CSD value is determined by a candidate CSD value that is the minimum of the sums of a first absolute value and a second absolute value on the basis of a power ratio. The power ratio is a ratio of received power of the L-STF to received power of the data field. The first absolute value is an absolute value of a value related to 5 percent of a CDF relative to the power ratio. The second absolute value is an absolute value of a value related to 95 percent of the CDF relative to the power ratio.