A wireless communication system can be more efficient if link-layer parameters such as modulation order, symbol rate and packet size, are (adaptively) optimised. Previously, we obtained a simple and robust characterisation of the link configuration that maximises bits per second or bits per Joule for data traffic: a set of possible link configurations can be ranked by the slope of a tangent line from zero to the graph of a scaled version of the packet-success rate function (PSRF): the steeper the tangent the better the configuration. However, this applies to a single communication link. We now analytically find for many mutually-interfering data-uploading terminals link configurations that satisfy the necessary conditions for throughput maximisation. A key observation: the tangent line common to 2 (scaled) PSRF tells us when to switch between them. We present a simple semi-decentralised algorithm implementable through pricing, and report very encouraging numerical results.