Wireless Device NAV Control for OFDMA Access 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 set for carrier sensing, leading to inefficient resource allocation and reduced access opportunities compared to target terminals and base stations.
Innovation Solution
A wireless communication device that decodes and identifies resource blocks in received physical packets, even if not destined for it, and sets a Network Allocation Vector (NAV) based on the medium reservation period, allowing non-target terminals to correctly decode packets and prevent EIFS period setting, thereby equalizing access opportunities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-target terminals perform carrier sensing using EIFS period after receiving OFDMA packets not destined for them, then error detection is achieved, but access fairness deteriorates due to longer waiting time compared to target terminals
Solution Approach 1:
The patent changes the carrier sensing parameter from EIFS period to DIFS/AIFS period specifically for non-target terminals. When a non-target terminal receives an OFDMA packet not destined for it, it extracts the Length field from the physical packet header and sets its Network Allocation Vector (NAV) to this value, then performs carrier sensing using the shorter DIFS/AIFS period instead of the longer EIFS period. This parameter change resolves the contradiction by maintaining error detection capability while reducing access waiting time to achieve fairness with target terminals.
2Reliability
If non-target terminals set EIFS period for carrier sensing, then reception error is detected, but access opportunity is reduced compared to target terminals using DIFS/AIFS
Solution Approach 1:
The patent applies parameter change by switching the carrier sensing period from EIFS to DIFS/AIFS for non-target terminals. The terminal detects that it is not the intended recipient by checking the RA field in the MAC header, then uses the Length field from the physical packet header to set NAV and performs subsequent carrier sensing with DIFS/AIFS period. This allows non-target terminals to detect reception errors reliably while increasing their access opportunity frequency to match target terminals.
Solution Approach 2:
The patent uses the Length field from the physical packet header as an intermediary to set the NAV value. This intermediary mechanism allows non-target terminals to obtain accurate medium occupation time information from the transmitted packet without needing to decode the entire packet or wait for error confirmation, enabling them to plan their access timing appropriately and increase access opportunities.
3Reliability
If non-target terminals decode physical packets to detect errors, then reliable error detection is achieved, but processing complexity increases
Solution Approach 1:
The patent extracts only the essential information needed for error detection and access timing from the physical packet. Specifically, non-target terminals extract the Length field from the physical packet header to set their NAV value, without needing to fully decode or process the entire packet content. This extraction approach maintains reliable error detection capability while significantly reducing processing complexity compared to complete packet decoding.
Data Source
AI summary
According to one embodiment, a wireless communication device, includes a receiver configured to receive a first field, receive at least one of a plurality of second fields having been multiplexed and transmitted, and decode the one of the second fields to obtain a frame in a case where first information identifying the wireless communication device is not set in the first field, and a controller configured to suppress access to a wireless medium during a period indicated by a value set in the frame.