Wireless Communication Apparatus Exposed Terminal Problem
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Solution Overview
Problem
In overcrowded wireless LAN environments, the 'exposed terminal problem' leads to reduced throughput due to interference from adjacent devices, making it difficult to avoid throughput reduction in CSMA/CA-based systems.
Innovation Solution
A wireless communication apparatus that receives a frame indicating the start of medium protection, acquires BSS identification information, and determines whether to initiate a transmission based on this information, allowing it to avoid interfering with adjacent devices by adjusting its transmission operations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a wireless LAN device transmits a frame in an overcrowded environment, then the device can utilize the wireless medium, but interference from adjacent devices causes the exposed terminal problem and reduces throughput
Solution Approach 1:
The invention applies preliminary action by having the transmitting device send an RTS (Request to Send) frame before the actual data transmission. This RTS frame reserves the wireless medium in advance, allowing the transmitting device to proceed with data transmission without being blocked by interference from adjacent devices that would otherwise cause the exposed terminal problem.
Solution Approach 2:
The invention uses feedback through the CTS (Clear to Send) frame mechanism. When a receiving device sends a CTS frame in response to an RTS frame, it provides feedback that confirms the medium reservation. This feedback loop allows transmitting devices to adjust their behavior based on the medium status, enabling them to transmit data even when adjacent devices are present, thus improving throughput while managing interference.
2Object-affected harmful factors
If a wireless LAN device restricts access to the wireless medium to avoid interference, then interference is reduced, but the utilization efficiency of radio resources decreases
Solution Approach 1:
The invention applies dynamics by making the medium access control adaptive rather than static. Devices dynamically adjust their transmission behavior based on real-time medium conditions and BSS identification. When the medium is reserved and conditions are favorable, devices can transmit; when not, they defer. This dynamic approach allows the system to maximize radio resource utilization while keeping interference at acceptable levels.
Solution Approach 2:
The invention uses local quality by applying different access rules to different BSSs (Basic Service Sets). By identifying the BSS of the transmitting device and comparing it with the reserved medium's BSS, the system allows more aggressive access for devices in the same BSS (where interference is already managed) while being more conservative for devices in overlapping BSSs. This localized differentiation improves overall resource utilization without causing excessive interference.
3Reliability
If a wireless LAN device monitors preambles and PLCP headers with high accuracy, then detection reliability is improved, but the complexity of the receiving operation increases
Solution Approach 1:
The invention applies segmentation by dividing the frame reception process into distinct stages: preamble detection, BSS identification extraction, and data reception decision-making. The receiving device first detects the preamble, then extracts and processes only the necessary BSS identification information from the PLCP header, and finally makes a reception decision based on this segmented processing. This segmentation improves detection reliability while managing complexity by processing only essential information at each stage.
Data Source
AI summary
A decrease in access rate to a wireless medium caused by an exposed terminal apparatus is improved. A wireless communication apparatus of the present invention includes a reception unit that receives a frame indicating start of a medium protection operation, and acquires, from the frame indicating the start of the medium protection operation, BSS identification information for identifying a BSS to which a transmission-source wireless communication apparatus of the frame indicating the start of the medium protection operation belongs, and a transmission unit that determines whether or not to start a transmission operation of a frame addressed to another wireless communication apparatus belonging to a BSS to which the wireless communication apparatus belongs based on the BSS identification information.