# Improving Spatial Reuse of Wireless LAN Uplink Using BSS Color and Proximity Information
## 5 Conclusions and Future Work  
In this paper, we proposed a spatial reuse method for uplink communication in wireless LANs. The proposed method, PSC-UL, allows concurrent transmissions when the estimated SNR at the receiver is sufficient to receive both the packets. In order to estimate the SNR, APs and stations maintain RSSI of neighboring APs. An AP periodically sends its neighbor table to its associated stations, so that a station has both its neighbor table and the neighbor table of the AP. When a node transmits a packet, it includes its BSS color and proximity information in the preamble. The proximity information is an indication of the distance between the transmitter and its destination AP. When a node in a different BSS receives this preamble, it uses the BSS color, the proximity information, and its neighbor tables to determine whether both packets will be successfully received at the receivers if the node chooses to transmit concurrently. If either of the packets is expected to be lost, the node pauses backoff and defers its transmission. Simulation results have shown that PSC-UL achieves a considerable amount of throughput improvement using legacy, OBSS/PD, and Dual-CST methods without causing significant unfairness as in PSR. While the proposed method has merit, many limitations exist that need further research. First, the proposed method can only be used with UL traffic. The major reason for this is that it is difficult to estimate SNR at the receiver if the receiver is a user station. An AP cannot keep track of all user stations in the vicinity because the user stations are mobile and they do not send out beacons. Still, improving spatial reuse for DL traffic is very important. Achieving high spatial reuse for DL may require cooperation between APs, which is an important feature in the upcoming standard, IEEE 802.11 be. Second,  
Figure 12: Performance of methods varying margin. (**a**) Total throughput; (**b**) Bottom 50% throughput; (**c**) Bottom 25% throughput; (**d**) Fairness; (**e**) Non-starvation Ratio; (**f**) Delivery Ratio. we assumed that MCS levels were fixed. However, a node may choose to send a packet using a lower MCS level if the SNR at the receiver is expected to be low. Concurrently sending a packet at a lower rate can increase the throughput by allowing more parallel transmissions, but at the same time can degrade the throughput by having lower rate transmissions occupy the channel. A spatial reuse method combined with rate control is an important topic for future study. Third, we only considered a single channel in this paper. In practice, multiple channels exist, and APs and stations can be assigned channels in a way that the spatial reuse of each channel is maximized. A spatial reuse method combined with channel assignment is another interesting topic for further study. Fourth, machine learning approaches can be used to obtain optimal parameter values, such as margin, adequate for the environment. We plan to pursue these problems in the near future. Conceptualization, H.K. and J.S. ; methodology, H.K. and J.S. ; software, H.K., validation, H.K. and J.S. ; writing--original draft preparation, H.K. and J.S. ; visualization, H.K. ; supervision, J.S. All authors have read and agreed to the published version of the manuscript. This work was supported in part by the NRF (National Research Foundation) of Korea under grant no. 2019R1A2C1005881. Not applicable. The authors declare no conflicts of interest. The following abbreviations are used in this manuscript: