Ultra-low power data transmission method and apparatus
An ultra-low power data transmission method and apparatus are disclosed. An ultra-low power data transmission method to be performed by a user terminal of an ultra-low power data transmission system includes performing channel coding on a payload included in a transmission packet; interleaving a payload obtained through the channel coding, spreading the interleaved payload using a gold code and an orthogonal variable spreading factor (OVSF), combining a synchronization header spread using the gold code and the OVSF with the spread payload, and modulating a transmission packet in which the payload and the synchronization header are combined.
1. An ultra-low power data transmission method to be performed by a user terminal of an ultra-low power data transmission system, the ultra-low power data transmission method comprising:
receiving downlink signals through a satellite network and a terrestrial network, respectively;
identifying received power of each of the received downlink signals; and
transmitting, to a gateway, collected data through one of the satellite network and the terrestrial network based on the identified received power of the downlink signals,
wherein the transmitting is performed using a different channel code and a preamble sequence based on a type of the network to be used for the transmitting;
wherein the transmitting comprises:
when the collected data is transmitted through the satellite network, estimating channel error information corresponding to a Doppler frequency error and a carrier frequency error through a downlink signal comprising control information and a pilot signal that is received from a satellite;
determining a transmission method for correcting the Doppler frequency error and the carrier frequency error based on the estimated and computed channel error information; and
transmitting, to the gateway, the collected data through the satellite network by first correcting the estimated and computed channel error information using the determined transmission method;
wherein the transmission method comprises at least one of a modulation method, a channel code rate-based method, or a transmission power-based method; and
wherein the ultra-low power data transmission method further comprises:
selecting, as the modulation method and the channel code, respectively, a differential binary phase-shift keying (BPSK) modulation method and a convolution code, based on a first amount of variation in the Doppler frequency error and a first amount of received signal-to-noise ratio (SNR); and
selecting, as the modulation method and the channel code, respectively, a coherent modulation method and a turbo code, based on a second amount of variation in the Doppler frequency error and a second amount of received SNR;
wherein the first amount is greater than the second amount.
2. The ultra-low power data transmission method of claim 1 , wherein the transmitting comprises:
transmitting the collected data through a network corresponding to a downlink signal having greater received power based on the identified received power of the downlink signals.