Free-space directional communication links (FSO) experience short-term link outages or fades because of atmospheric turbulence, and longer term link outages because of obscuration resulting from either atmospheric conditions, beam pointing errors, or temporary line-of-sight obstructions for links from mobile or static nodes. Various approaches can be used to mitigate these effects. Physical-layer techniques, such as dynamic thresholding, time delayed diversity, and data encoding can significantly reduce the effects of short term (millisecond scale) outages caused by deep turbulenceinduced fades. Outages on a longer term (second scale) producing large data loss can be mitigated by packet-layer largeblock, error protection techniques. In this paper, we will first introduce physical-layer mitigation techniques. Second we present experimental data comparing the latencies and throughput of different means of packet-based error protection techniques. We will discuss the influence of error protection techniques to quality of service issues like error probability and delay and further compare this with service requirements given by the application.

Date Published: 19 August 2008
PDF: 9 pages
Proc. SPIE 7091, Free-Space Laser Communications VIII, 70910C (19 August 2008); doi: 10.1117/12.798305

Published in SPIE Proceedings Vol. 7091:
Free-Space Laser Communications VIII
Arun K. Majumdar; Christopher C. Davis, Editor(s)