Publication Detail

High Rate Acoustic Link for Underwater Video Transmission

Costas Pelekanakis, Milica Stojanovic, Lee Freitag
7 pp.
MITSG 03-25J
$2.00 DOM

A high bit rate acoustic link for video transmission over an underwater channel is investigated. The key to achieving this objective lies in two approaches: use of efficient data compression algorithms and use of high-level bandwidth-efficient modulation methods. Currently available video encoding standards allow video transmission at bit rates as low as 64 kbps. While this rate is still above the limit of commercially available acoustic modems, prototype acoustic modems on phase coherent modulation / detection have demonstrated successful transmission up to 30 kbps over a deepwater vertical path. To bridge the final gap and provide acoustic transmission capability needed for near real-time video, the authors focus on the use of high-level bandwidth-efficient modulation methods. An experimental system, based on discrete cosine transform and Huffman entropy coding for video compression, and variable rate M- ary QAM was implemented. Phase-coherent detection is accomplished by decision-directed synchronization and adaptive equalization. System performance is demonstrated experimentally, using 25000 symbols/sec at a carrier frequency of 75 kHz over a short vertical path. Excellent results were obtained using modulation methods of 8, 16, 32 and 64-QAM, thus achieving bit rates as high as 150 kbps, which are sufficient for real-time transmission of compressed video.

type: Technical reports

Parent Project

Project No.: 2002-RD-17
Title: High Rate Acoustic Link for Video Transmission from Autonomous Underwater Vehicles (AUVs)