A computationally efficient optimal discrete bit allocation algorithm is proposed for medium and high target bit rate discrete multitone (DMT) transmissions. Unlike conventional greedy bit-loading algorithms, which compare the incremental transmission power of multicarriers bit-by-bit and allocate one bit at a time, the proposed algorithm is based on parallel bit-loading with reference to a virtual equal power assignment bit allocation. After maximum bit rate allocation, the algorithm achieves the target bit rate by two types of parallel bitloading. If the target bit rate allocation is not optimal, bit swapping is performed to obtain the optimal solution. Simulation results using the standard asymmetric digital subscriber line (ADSL) test loops demonstrate the reduced computational load of the proposed algorithm compared to the existing optimal discrete bit allocation algorithm when the target rate is between 60% and 99% of the loop's maximum bit rate.

High precision of the inter-satellite ranging is very important for the realization of system function for the formation of satellite constellation. The delay of transmitter is a key parameter relating to range. A high accurate delay calibration algorithm of V-band transmitter is developed. The ranging signal and the 1PPS (1 Pulse Per Second) are sampling in synchronization. The sampling frequency is lower than the frequency of inter-satellite link ranging signal. The duration of ranging signal data to process is less than a period of the PRN (Pseudo-Random Noise) sequence. Using carrier-phase acquisition, the start point of the PRN sequence is obtained and absolute delay of transmitter can be calculated. The absolute uncertainty with the proposed algorithm is less than 0.2ns with the sampling frequency is 10 G Sa/s.

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