An allocation of radio resources is signaled with a multi-user multiple-input-multiple-output MU-MIMO field indicating whether MU-MIMO is enabled in the allocation. The structure of the signal allocating the resources changes depending on whether the MU-MIMO field indicates enabled or not. For downlink signaling, an additional length field indicates a length of another component of the allocation apart from that listing user identifiers. A component listing which resource blocks are allocated for MU-MIMO is one embodiment, and it may be split to indicate per-stream. Multiple embodiments are shown with various assumptions as to mapping between components of the resource allocation and tradeoffs of flexibility and signaling overhead, for method, apparatus, program, and chip.