Wireless Device NAV Duration Alignment for OFDMA Fairness
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Solution Overview
Problem
In wireless communication systems using OFDMA, non-target terminals experience unfairness in accessing the wireless medium due to longer EIFS periods, leading to inefficient resource allocation and reduced throughput.
Innovation Solution
A wireless communication device that identifies and decodes resource blocks in received physical packets, sets a Network Allocation Vector (NAV) based on the Duration field of the MAC frame, allowing non-target terminals to correctly receive and decode packets not destined for them, thereby preventing the setting of EIFS periods and ensuring fair access to the medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDMA communication is performed in an environment where non-target terminals reside, then resource allocation efficiency is improved, but access fairness deteriorates due to longer EIFS periods for non-target terminals
Solution Approach 1:
The patent segments the wireless communication system into target terminals (OFDMA communication participants) and non-target terminals (other terminals). By identifying and separately handling these two groups through different carrier sensing periods (DIFS/AIFS for target terminals, EIFS for non-target terminals), the system maintains resource allocation efficiency while ensuring access fairness. This segmentation allows the base station to allocate resources efficiently to target terminals while preventing non-target terminals from experiencing unfair access delays.
Solution Approach 2:
The patent changes the carrier sensing period parameter dynamically based on the terminal type. Target terminals use shorter carrier sensing periods (DIFS/AIFS) to access the medium quickly, while non-target terminals use the standard EIFS period. This parameter differentiation resolves the contradiction by allowing efficient resource allocation to target terminals without preventing non-target terminals from accessing the medium fairly when the channel is idle.
2Reliability
If EIFS period is set for non-target terminals to handle reception errors, then reliability is improved, but access speed deteriorates due to longer waiting time
Solution Approach 1:
The patent introduces dynamic behavior where non-target terminals adapt their carrier sensing period based on whether the medium is occupied by OFDMA communication. When OFDMA communication is detected, non-target terminals use EIFS for reliable error handling. When the medium is idle, they switch to shorter carrier sensing periods for faster access. This dynamic adaptation resolves the contradiction between reliability and access speed.
Solution Approach 2:
The patent implements periodic carrier sensing with different periods (EIFS when OFDMA is active, DIFS/AIFS when idle) for non-target terminals. This periodic switching between sensing periods allows the system to maintain reliability during OFDMA communication while providing faster access opportunities when the channel is available, thus resolving the contradiction between reliable error handling and access speed.
3Measurement precision
If non-target terminals decode all resource blocks to ensure fair access, then processing accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by having non-target terminals perform preliminary decoding of resource blocks to identify whether packets are destined for them. Instead of fully decoding all resource blocks, they perform initial checks (such as checking destination addresses or identifiers) to determine if further decoding is necessary. This preliminary action ensures accurate identification of relevant packets while reducing overall decoding complexity.
Solution Approach 2:
The patent implements partial action where non-target terminals decode only sufficient portions of resource blocks to determine packet destination, rather than fully decoding all packets. They perform partial decoding to check addressing information or identifiers, and only proceed with full decoding if the packet is relevant to them. This partial action maintains decoding accuracy for relevant packets while significantly reducing device complexity and processing load.
Data Source
AI summary
According to one embodiment, a wireless communication device includes a transmitter configured to transmit a first field containing information to identify a plurality of wireless communication terminals, and configured to multiplex and transmit a plurality of second fields in each of which a first frame containing an address of any of the wireless communication terminals is set; and a controller configured to determine, for the first frames, values pertaining to lengths of durations to suppress access to a wireless medium to the wireless communication terminal having an address different from the address contained in each of the first frames. The transmitter is configured to set the values in the first frames, the second fields, or the first field. The controller is configured to determine the values so that the durations have an end at an identical time.