Abstract

The advantages of optics that include processing speed and information throughput, modularity and versatility could be incorporated into one of the most interesting and applicable topics of digital communication related to Viterbi decoders. We aim to accelerate the processing rate and capabilities of Viterbi decoders applied for convolution codes, speech recognition, inter symbol interference (ISI) mitigation problems. The suggested configuration for realizing the decoder is based upon fast optical switches. The configuration is very modular and can easily be increased to Viterbi decoder based upon state machine with larger number of states and depth of the trellis diagram.

©2007 Optical Society of America

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References

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  1. G. D. Forney, “The Viterbi Algorithm,” Proceedings of the IEEE, 61,268–278 (1973).
    [Crossref]
  2. J. G. Proakis, Digital Communications, (McGraw-Hill Science/Engineering/Math, 4th edition 2000).
  3. T. W. Parsons, Voice and Speech Processing, (McGraw-Hill, 1987).
  4. C.W. Therrien, Discrete Random Signals and Statistical Signal Processing, Signal Processing Series (Prentice-Hall, New-Jersy, 1992).
  5. J. E. Midwinter, Photonics in Switching , Vols.1 and2, (Academic press, 1993).
  6. Z. Zalevsky, D. Mendlovic, E. Marom, N. Cohen, E. Goldenberg, N. Konforti, A. Shemer, G. Shabtay, U. Levy, and R. Appelman, “Ultra fast all optical switching,” J. Opt. Netw. 1,170–187 (2002).

2002 (1)

1973 (1)

G. D. Forney, “The Viterbi Algorithm,” Proceedings of the IEEE, 61,268–278 (1973).
[Crossref]

Appelman, R.

Cohen, N.

Forney, G. D.

G. D. Forney, “The Viterbi Algorithm,” Proceedings of the IEEE, 61,268–278 (1973).
[Crossref]

Goldenberg, E.

Konforti, N.

Levy, U.

Marom, E.

Mendlovic, D.

Midwinter, J. E.

J. E. Midwinter, Photonics in Switching , Vols.1 and2, (Academic press, 1993).

Parsons, T. W.

T. W. Parsons, Voice and Speech Processing, (McGraw-Hill, 1987).

Proakis, J. G.

J. G. Proakis, Digital Communications, (McGraw-Hill Science/Engineering/Math, 4th edition 2000).

Shabtay, G.

Shemer, A.

Therrien, C.W.

C.W. Therrien, Discrete Random Signals and Statistical Signal Processing, Signal Processing Series (Prentice-Hall, New-Jersy, 1992).

Zalevsky, Z.

J. Opt. Netw. (1)

Proceedings of the IEEE (1)

G. D. Forney, “The Viterbi Algorithm,” Proceedings of the IEEE, 61,268–278 (1973).
[Crossref]

Other (4)

J. G. Proakis, Digital Communications, (McGraw-Hill Science/Engineering/Math, 4th edition 2000).

T. W. Parsons, Voice and Speech Processing, (McGraw-Hill, 1987).

C.W. Therrien, Discrete Random Signals and Statistical Signal Processing, Signal Processing Series (Prentice-Hall, New-Jersy, 1992).

J. E. Midwinter, Photonics in Switching , Vols.1 and2, (Academic press, 1993).

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Figures (9)

Fig. 1.
Fig. 1. Allocating the optimal path.
Fig. 2.
Fig. 2. (a).-(b). Interferometer module for extraction of the distance. (c). Schematic description of the spatial position of the 4 detectors on top of the interference fringes. (d). The description of the two-state machine, the commands required in order to move form one state to the next and the convolution code of the machine. (e). The Viterbi decoder.
Fig. 3.
Fig. 3. (a). The schematic sketch of the optical realization. (b). The constructed experimental setup that follows the schematic plot of Fig. 3(a).
Fig. 4.
Fig. 4. (a). The GUI. (b). The optical buffer loop (loop A or loop B). (c). The decision module. (d). The measurements of the VOA realizing the three possible attenuations.
Fig. 5.
Fig. 5. Interferometer module. (a). Fringes in the output plane. (b). Shift of the fringes when relative phase is introduced between the input and the reference beams.
Fig. 6.
Fig. 6. Realization of the optical buffer (loop A in Fig. 4(c)). Attenuation states that follow external commands coming according to the decisions made in every stage of the trellis diagram. In this example one may see 5 clear energy states.
Fig. 7.
Fig. 7. (a). The experimental configuration following Fig. 2(e). (b). The GUI if the unit that controls the optical setup. The GUI presents the example of transmission/receiving that was tested in the lab.
Fig. 9.
Fig. 9. The trellis diagram of the tested configuration. The trellis presents the decoding process of the incoming bits´ sequence. The corresponding weight is depicted on each branch. The accumulated attenuation is depicted on each node.
Fig. 9.
Fig. 9. The experimental results measured at the outputs of the various 2 by 2 switches. (a). The upper output of the first 2 by 2 switch (i.e. node M3 of Fig. 8). (b). The lower output of that switch (i.e. node M4 of Fig. 8). (c). The upper output of the second 2 by 2 switch (i.e. node M5 of Fig. 8). (d). The lower output of that switch (i.e. node M6 of Fig. 8). (e). The final output of the system at the detector (i.e. node M7 of Fig. 8).

Tables (1)

Tables Icon

Table 1. Shift of the interference fringes due to change in the input sequence and the allocation between the different inputs and the intensity levels read by the detectors. The columns of the table are the connection of the detectors while the rows are the input bit sequence.

Equations (8)

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P r { s 0 , , s T } = p 0 t = 1 T P r { s t s t 1 }
P r { s 0 , , s T o 0 = z 0 , , o T = z T } = P r { o 0 = z 0 , , o T = z T s 0 , , s T } P r { s 0 , , s T } P r { o 0 = z o , , o T = z T }
P r { o 0 = z 0 , , o T = z T M k }
P r { s 0 , , s T , o 0 = z 0 , , o T = z T } = t = 0 T P r { s t s t 1 } P r { o t = z t s t } ; P r { s 0 s 1 } = p 0
t = 0 T [ V i ( t ) + B j , i ( t ) ]
W i ( t ) = max j [ W j ( t 1 ) + B j , i ( t ) ] + V i ( t )
z t = l = 0 L 1 h l x t l + w t
W t ( s t ) = max s t log P r { o t = z t | s t } + W t 1 ( s t 1 )

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