ارتباطات نوری فضای آزاد از راه دور
Abstract
1-Introduction
2-Atmospheric Optical Channel
3-Spinal Code Transmission Strategy Based on Q-Learning Algorithm
4-Performances Analysis
5-Conclusion
6-References
Abstract
In this paper, a spinal code transmission strategy based on Q-learning algorithm is proposed for long distance free space optical communication. The strategy adopts the Q-learning algorithm with the main objective of reducing the retransmission times to optimize the decoding waiting time and improve the transmission efficiency. The simulation results illustrate that, under the same turbulent conditions, the average retransmission times of the proposed transmission strategy is maintained at about one time, which is 94-99% less than the traditional spinal code transmission strategy and 78-92% less than the linear transmission strategy. Thus effectively improves the transmission efficiency of long-distance optical communication.
Introduction
Rate-adaptive FSO systems can provide reliable communication in different weather conditions while efficiently exploiting the channel capacity.In long-distance FSO communication, in order to improve the availability of FSO channels degraded by atmospheric turbulence, the effects of channel gain variations must be compensated [1] [2] .FEC technologies such as LDPC codes with excellent performance[3] are limited by the characteristics of fixed encoding rate. Rateless code is a kind of code without coding rate constraint. Due to its forward increasing redundancy, it can automatically adapt to the dynamic change of link without feedback and become an ideal means to make full use of channel transmission capacity under different weather conditions [4] .Spinal code[5] is a novel rate-free encoding method capable of near-capacity limited transmission in both BSC channel and AWGN channel [6] .