In one embodiment, a device in a network receives, at its wireless receiver, a preamble of a spatially modulated packet. The device analyzes the preamble of the packet to identify a transmit antenna index of the packet. The device determines that the packet was not destined for the device, based on the transmit antenna index of the packet. The device depowers, prior to decoding the complete packet, the wireless receiver of the device, based on the determination that the packet was not destined for the device.