On the Allocation of Transmit Power for Coordinated Spatial Reuse in IEEE 802.11bn Multi-Access Point Coordination

Abstract

IEEE 802.11bn (11bn) introduces Coordinated Spatial Reuse (Co-SR), a Multi-AP Coordination (MAPC) scheme in which two Access Points (APs) coordinate to control the transmit power for a simultaneous transmission. This letter introduces a Proportional Fairness (PF)-driven framework for allocating Co-SR transmit power on a per-Transmission Opportunity (TXOP) basis. We prove that any Pareto-optimal power pair keeps at least one AP at its maximum power, reducing the joint two-dimensional search to two cheap one-dimensional line searches that fit comfortably within TXOP timing, and show that this collapses to an exact closed-form expression in a real, discrete-rate system. We validate the resulting policies, together with a low-complexity selfish baseline, against a brute-force oracle and through packet-level simulations in Kom8ndor, an 11bn network simulator. Results show that jointly evaluating both APs'links is key to unlocking Co-SR's spatial reuse gains, that the coordinated AP's fairness-optimal power depends critically on whether the rate is modeled continuously or through real, discrete Modulation and Coding Scheme (MCS) steps, and that current 11bn signaling supports the selfish policy but not the fairness-optimal ones, which would need additional per-TXOP channel reporting.