# A Survey of Wi-Fi 6: Technologies, Advances, and Challenges
## 5 SR in Wi-Fi 6
### Related Works
#### 5.4.1 Threshold Manipulation
[129] also adopted a multi-armed bandit approach for the same objective. They proposed a Gaussian mixture to sample new network configurations and computed a reward to avoid starvation to select the best configuration. NS-3 simulations validated the model. Some papers aimed to compute the OBSS PD value efficiently. The authors of [130] exploited the RSSI of the beacon to directly compute the OBSS PD threshold. The transmission power is calculated by subtracting a value from a beacon's RSSI. A station close to the access point will use a large OBSS PD value. [PERSON] et al. [131] proposed a Control OBSS PD Sensitivity Threshold (COST) algorithm. First, the access point collects the moving average of the stations' RSSIs and the interference levels from all the stations. Then, it derives the sensitivity threshold value to respect a minimum margin. The OBSS PD value may directly affect the network throughput. Interference-Based Dynamic Channel Access (IB-DCA) [132] maximized the aggregate throughput of the WLAN. Each station keeps a record of the maximum RSSI level of all the overlapping BSSs, i.e., BSSs with a different color. More precisely, it measures the maximum RSSI separately for uplink and downlink transmissions. These values are advertised to other stations periodically as well as the transmission power of the issuer. Thus, any station can compute the expected RSSI level at the expected destination based on these values. The station defines its SR flag accordingly; it knows it will not provoke any collisions since the expected receiving RSSI will be sufficient to be robust against transmissions in overlapping BSSs. As an extension, the authors of [133] focused on the performance of each end-user in dense networks. [PERSON] et al. [134] proposed an analytical model to find the suitable OBSS PD threshold and transmission power that optimizes the throughput. They proved that the throughput depends on the interference range of the BSSs. The model was based on the received power, transmission power, MCS, distance, and path loss. The authors of [135] improved the aggregated throughput by tuning the OBSS PD threshold and transmission power. They utilized the RSSIs of beacons and overlapping BSSs. The former keeps the connection with the access point and the latter prevents interference in overlapping BSSs. The threshold is computed based on the recorded RSSIs and uses an exponentially weighted moving average (EWMA) [136] for updating the threshold during runtime. [PERSON] et al. [137] proposed a link-aware SR algorithm to select the appropriate links for simultaneous transmissions and the MCS without interfering with the ongoing transmission. The mechanism tunes the transmission power for transmission protection and applies EWMA to select the link and MCS that compute the achievable throughput. A distributed OBSS PD mechanism was proposed to improve the fairness in the network [138]. Taking into account the history of transmission opportunities, it tunes the OBSS PD threshold. It prioritizes stations that did not access the medium in earlier time slots and downgrades the other stations.