VHT Channel Access via Bonding Subchannels
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Solution Overview
Problem
The existing IEEE 802.11n WLAN system is limited in achieving a data processing speed of 1 Gbps or more due to its single STA architecture and inefficiencies in the CSMA/CA channel access mechanism, which restricts throughput and channel usage efficiency.
Innovation Solution
A new channel access mechanism for a VHT system using a bonding channel with multiple subchannels, allowing for channel estimation without collision and enabling MIMO usage across the full channel bandwidth, with the method involving training information, RTS, and CTS frame exchanges to optimize channel access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CSMA/CA mechanism with binary exponential backoff is used for channel access, then collision avoidance is achieved, but channel usage efficiency and throughput are limited
Solution Approach 1:
The bonding channel is divided into multiple subchannels, allowing multiple STAs to perform channel estimation and RTS transmission simultaneously on different subchannels. This segmentation enables parallel channel access operations, improving overall channel usage efficiency while maintaining collision avoidance through the structured RTS/CTS handshake protocol on each subchannel.
2Device complexity
If single STA architecture is used in IEEE 802.11n, then system complexity is reduced, but data processing speed cannot reach 1 Gbps or more
Solution Approach 1:
Multiple subchannels are merged into a bonding channel to achieve aggregate throughput of 1 Gbps or more. The patent combines multiple 20 MHz subchannels into an 80 MHz bonding channel, allowing simultaneous data transmission across all subchannels, thereby multiplying the data processing speed while maintaining compatibility with the existing STA architecture.
Solution Approach 2:
The patent transitions from single-channel sequential access to multi-channel parallel access by utilizing the frequency dimension. Multiple STAs perform channel estimation and RTS transmission on different frequency subchannels simultaneously, adding a spatial-parallel dimension to the channel access process without increasing temporal complexity.
3Measurement precision
If channel estimation is performed on full channel bandwidth, then MIMO usage is optimized, but collision between training signals from multiple STAs occurs
Solution Approach 1:
The full channel bandwidth is segmented into multiple subchannels, and each STA is assigned to perform channel estimation on a specific subchannel. This segmentation allows multiple STAs to simultaneously conduct channel estimation without collision, as each STA operates on a dedicated frequency portion. The training offset value further refines this segmentation by assigning specific time-frequency resources to each STA.
Solution Approach 2:
The patent introduces training offset values as intermediaries that coordinate channel estimation timing across multiple STAs. These offset values act as mediators that schedule training signal transmissions on different subchannels at different time offsets, preventing collisions while enabling full bandwidth utilization for MIMO operations.
Data Source
AI summary
A channel access method for a very high throughput (VHT) system using a bonding channel having a plurality of subchannels is provided. The method includes receiving training information comprising a training offset value through a subchannel, performing channel estimation on a full channel bandwidth comprising all subchannels when a time corresponding to the training offset value is elapsed after the training information is received, transmitting a request to send (RTS) frame to a destination station through some subchannels selected from the plurality of subchannels by one or a plurality of source stations according to a result of the channel estimation, and transmitting a clear to send (CTS) frame to one source station selected from the plurality of source stations by the destination station in response to the received RTS frame. Accordingly, an effective channel access mechanism is provided for the VHT system, and collision among stations can be avoided.