SlideServe
Télécharger Obtenir Pro
Menu
Accueil Pro
Préférences
ApparenceLight Aide et commentaires
© SlideServe · v2026

11/26/13

margot avatar
margot
8 diapositives · 280 Views · Jul 25, 2014

P14251 Underwater Acoustic Communication. Framing Parameters Sentinels and Header Information Control frame data Frame sizes Frame transmission times Error Detection/Correction. 11/26/13. Rochester Institute of Technology. 1. P14251 Underwater Acoustic Communication. Frame Sentinels

11/26/13 - slide 1
01 / 811/26/13
1 / 17

Télécharger la présentation

11/26/13
Une image / un lien ci-dessous est fourni (tel quel) pour télécharger la présentation

Politique de téléchargement : le contenu du site vous est fourni TEL QUEL pour votre information et votre usage personnel ; il ne peut être vendu, concédé sous licence ni partagé sur d’autres sites sans l’accord de son auteur.Le contenu vous est fourni TEL QUEL, pour votre information et votre usage personnel uniquement. Téléchargez la présentation en cliquant sur ce lien. Lors du téléchargement, si vous ne parvenez pas à télécharger une présentation, l’éditeur a peut-être supprimé le fichier de son serveur.Pendant le téléchargement, si vous ne parvenez pas à obtenir une présentation, le fichier a peut-être été supprimé par l’éditeur.

F I N

Plus de contenu associé

Transcription de la présentation

  1. P14251 Underwater Acoustic Communication • Framing Parameters • Sentinels and Header Information • Control frame data • Frame sizes • Frame transmission times • Error Detection/Correction 11/26/13 Rochester Institute of Technology 1

  2. P14251 Underwater Acoustic Communication • Frame Sentinels • Sentinels are a unique pattern of bits that signify the start and end of the framei.e. 01110 –data– 01110 • When preparing the frame for transmission, if the pattern appears anywhere in the data, bit stuffing is used to eliminate it (i.e. 01110 -> 011010) • Commonly used sentinel which we’ll use is 01111110 • Frame Header • 1 bit to signify the type of frame: control or message • 1 bit that gets flipped each time a new frame is sent 11/26/13 Rochester Institute of Technology 2

  3. P14251 Underwater Acoustic Communication • Control frame formats • Since it’s especially important to interpret control frames correctly, 4 bits are used to display the unique patterns • 0000 – Request to Send (RTS) • 0110 – Clear to Send (CTS) • 1001 – Acknowledgement (ACK) • 1111 – Done (Signifies that all frames have been sent) 11/26/13 Rochester Institute of Technology 3

  4. P14251 Underwater Acoustic Communication • Frame Sizes • - 15kbits per second, after compression and encoding = 9kbits • - 9kbits = Number of Frames * Message Bits/Frame • Minimum frame sizes:- Control Frame: 18 (overhead) + 4 (type) = 22 bits- Message Frame: 18(overhead) + X (message) = 18+X bits 11/26/13 Rochester Institute of Technology 4

  5. P14251 Underwater Acoustic Communication • Frame Transmission Times • (per 2 bits) • Frames that get transmitted for a message: • Send RTS – 22 bits • Receive CTS – 22 bits • Send all message frames – 18+x bits/frame • Receive all acknowledgements – 22 bits/frame • Send Done – 22 bits • Receive Acknowledgement – 22 bits • - Tx time for x bits = 20ms + (40μs/2)*(18+x) 11/26/13 Rochester Institute of Technology 5

  6. P14251 Underwater Acoustic Communication • Frame Transmission Times • - Tx time for x bits = 20ms + (40μs/2)*(18+x) • Frames that get transmitted for a message: • Send RTS = 20.4 ms • Receive CTS = 20.4 ms • Send all message frames (20ms + (40μs/2)*(18+x))*Y • Receive all acknowledgements 20.4 ms * Y • Send Done = 20.4 ms • Receive Acknowledgement = 20.4 ms • Where x = number of bits, Y = number of frames, and x*Y = 9000 11/26/13 Rochester Institute of Technology 6

  7. P14251 Underwater Acoustic Communication • Frame Transmission Times • -From (40ms + (40μs/2)*(40+x))*Y and x*Y = 9000, with the maximum time left for transfer being under 0.9s: • Maximum number of frames Y = 15, • where x = 600 bits/frame, • and the total transmission time = 0.792s • - This is much better than a 9kbit frame, but is still a risk area for error correction/detection- The propagation delay is by and large the biggest limiting factor (ignoring frame sizes, it takes 40ms per message/ACK pair, * 15 frames = 0.6s) 11/26/13 Rochester Institute of Technology 7

  8. P14251 Underwater Acoustic Communication • Brief note Error Detection/Correction • If a 600 bit codeword takes too long to decipher: • - Partition the frame into five 120 bit codewords (or possibly smaller) • - If necessary, use multi-threading to try and decode all five 120 bit codewords at the same time • - Alternatively, it may be possible to send fewer frames, if the propagation time reduction grants enough code execution time • - Either BCH or Reed-Solomon will be used 11/26/13 Rochester Institute of Technology 8