A data rate at which data can be transmitted is adapted in real-time to power fluctuations. Bits of data to be sent by a transmitter are mapped to physical symbols, where a first modulation uses a first number of bits per pulse and a second modulation uses a second number of bits per pulse. Both modulations are sent, with one nested inside the other. A receiver decodes one or both bit streams, depending on a signal to noise ratio (SNR). In this regard, the data rate traces the received power, and higher data rates may be used despite periods of power fluctuations. This technique enables rapid, or even instantaneous, changes by using nested modulation. Moreover, a fast feedback mechanism is used to inform the transmitter when to change its modulation and to retransmit bits lost during an initial transmission.