The disclosed apparatus and methods can be used to provide an energy efficient Internet of Things (IoT) communication method that can be deployed on a city-wide scale using existing infrastructure and that can target individual sensors or devices. An example apparatus is a decoder including an energy detector and a processor. The energy detector is configured to detect average subframe energy levels of a plurality of subframes during reception of at least one frame of data defined by a first communications protocol (e.g., Long-Term Evolution (LTE)). The average subframe energy levels of the plurality of subframes form a pattern of relatively higher and lower energy levels. The processor is configured to interpret, according to a second communications protocol, the pattern of energy levels to decode a block of data represented by the pattern of energy levels. Another embodiment is a method producing index modulation signals of the second communications protocol.