input bit stream specifies the bit sequence representing the code word to decode. You can use the MT Convolutional Encode VI to generate the encoded bit stream. The default is empty.

rate (k/n) specifies the convolutional code rate as a ratio k/n, where k is the input data word length and n is the output code word length. Use a generator matrix instance of this VI to specify a different rate. The default is 1/2.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the survivor state resulting from the Viterbi hard decision decoding operation after decoding the entire input bit stream.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

input bit stream specifies the bit sequence representing the code word to decode. You can use the MT Convolutional Encode VI to generate the encoded bit stream. The default is empty.

generator matrix (n x k) specifies the generator connection polynomial matrix used for setting the convolutional feedforward decoder connections in octal format. The convolutional decoder is modeled as a linear feedforward shift register arrangement consisting of k rows with K-1 shift registers per row, where k denotes the data word length and K denotes the constraint length. If a _ij {0 ≤ i ≤ n-1, 0 ≤ j ≤ k-1} denotes a particular element in the generator matrix, the row index i corresponds to the convolutional decoder output y _i that is affected by this element, while the column index j corresponds to the jth row in the k row shift register arrangement. Thus a _ij specifies how the K bits in the jth row of the feedforward shift register matrix affects the ith output of the convolutional decoder. The default is

For a rate 2/3 convolutional decoder, the generator matrix is specified as

Notice that the preceding matrix represents the elements in octal format. Zeros are padded at the end of the corresponding code generator sequences such that the total length of the sequences is a multiple of three.

Tip   Ensure that the convolutional encoder and decoder receive the same generator matrices.

The following diagram depicts the rate 2/3 convolutional decoder corresponding to the generator matrix shown previously, with a constraint length of 4. In this diagram, D represents a shift register or memory element.

Here, y _i ^j, 0 ≤ j ≤ n-1 denotes the jth output of the convolutional decoder in the ith decoding instance.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the survivor state resulting from the Viterbi hard decision decoding operation after decoding the entire input bit stream.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

input integers specifies integers representing bit metrics for quantized demodulated BPSK symbol data. These demodulated BPSK symbols are quantized to n _soft bits of precision, such that an integer value of 0 represents a strong logic 0 and a value of 2ⁿ _soft represents a strong logic 1. The default is empty.

Note   To generate the integer-valued quantized BPSK demodulated data from the Modulation Toolkit, decimate and quantize the oversampled data at the output of the PSK demodulator/matched filter. For higher-order M-PSK/QAM schemes, convert the I/Q symbol values into corresponding quantized bit metrics using a suitable algorithm/heuristic.

rate (k/n) specifies the convolutional code rate as a ratio k/n, where k is the input data word length and n is the output code word length. Use a generator matrix instance of this VI to specify a different rate. The default is 1/2.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

soft decision bits specifies the number of bits used for quantizing the BPSK modulated symbols to integers. The default is 1.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the final state for the k(K-1) shift registers as the right-aligned (least significant) k(K-1) bits, where K is the constraint length, and k is the data word length in bits.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

input integers specifies integers representing bit metrics for quantized demodulated BPSK symbol data. These demodulated BPSK symbols are quantized to n _soft bits of precision, such that an integer value of 0 represents a strong logic 0 and a value of 2ⁿ _soft represents a strong logic 1. The default is empty.

Note   To generate the integer-valued quantized BPSK demodulated data from the Modulation Toolkit, decimate and quantize the oversampled data at the output of the PSK demodulator/matched filter. For higher-order M-PSK/QAM schemes, convert the I/Q symbol values into corresponding quantized bit metrics using a suitable algorithm/heuristic.

generator matrix (n x k) specifies the generator connection polynomial matrix used for setting the convolutional feedforward decoder connections in octal format. The convolutional decoder is modeled as a linear feedforward shift register arrangement consisting of k rows with K-1 shift registers per row, where k denotes the data word length and K denotes the constraint length. If a _ij {0 ≤ i ≤ n-1, 0 ≤ j ≤ k-1} denotes a particular element in the generator matrix, the row index i corresponds to the convolutional decoder output y _i that is affected by this element, while the column index j corresponds to the jth row in the k row shift register arrangement. Thus a _ij specifies how the K bits in the jth row of the feedforward shift register matrix affects the ith output of the convolutional decoder. The default is

For a rate 2/3 convolutional decoder, the generator matrix is specified as

Notice that the preceding matrix represents the elements in octal format. Zeros are padded at the end of the corresponding code generator sequences such that the total length of the sequences is a multiple of three.

Tip   Ensure that the convolutional encoder and decoder receive the same generator matrices.

The following diagram depicts the rate 2/3 convolutional decoder corresponding to the generator matrix shown previously, with a constraint length of 4. In this diagram, D represents a shift register or memory element.

Here, y _i ^j, 0 ≤ j ≤ n-1 denotes the jth output of the convolutional decoder in the ith decoding instance.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

soft decision bits specifies the number of bits used for quantizing the BPSK modulated symbols to integers. The default is 1.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the final state for the k(K-1) shift registers as the right-aligned (least significant) k(K-1) bits, where K is the constraint length, and k is the data word length in bits.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

input symbols specifies the unquantized BPSK demodulated soft symbol data. The default is empty.

Note   To generate the unquantized BPSK demodulated data from the Modulation Toolkit, decimate the oversampled data at the output of the PSK demodulator/matched filter. For higher order M-PSK/QAM schemes, convert the I/Q symbol values into corresponding bit metrics using a suitable algorithm/heuristic.

rate (k/n) specifies the convolutional code rate as a ratio k/n, where k is the input data word length and n is the output code word length. Use a generator matrix instance of this VI to specify a different rate. The default is 1/2.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the survivor state resulting from the Viterbi hard decision decoding operation after decoding the entire input bit stream.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

input symbols specifies the unquantized BPSK demodulated soft symbol data. The default is empty.

Note   To generate the unquantized BPSK demodulated data from the Modulation Toolkit, decimate the oversampled data at the output of the PSK demodulator/matched filter. For higher order M-PSK/QAM schemes, convert the I/Q symbol values into corresponding bit metrics using a suitable algorithm/heuristic.

generator matrix (n x k) specifies the generator connection polynomial matrix used for setting the convolutional feedforward decoder connections in octal format. The convolutional decoder is modeled as a linear feedforward shift register arrangement consisting of k rows with K-1 shift registers per row, where k denotes the data word length and K denotes the constraint length. If a _ij {0 ≤ i ≤ n-1, 0 ≤ j ≤ k-1} denotes a particular element in the generator matrix, the row index i corresponds to the convolutional decoder output y _i that is affected by this element, while the column index j corresponds to the jth row in the k row shift register arrangement. Thus a _ij specifies how the K bits in the jth row of the feedforward shift register matrix affects the ith output of the convolutional decoder. The default is

For a rate 2/3 convolutional decoder, the generator matrix is specified as

Notice that the preceding matrix represents the elements in octal format. Zeros are padded at the end of the corresponding code generator sequences such that the total length of the sequences is a multiple of three.

Tip   Ensure that the convolutional encoder and decoder receive the same generator matrices.

The following diagram depicts the rate 2/3 convolutional decoder corresponding to the generator matrix shown previously, with a constraint length of 4. In this diagram, D represents a shift register or memory element.

Here, y _i ^j, 0 ≤ j ≤ n-1 denotes the jth output of the convolutional decoder in the ith decoding instance.

constraint length (K) specifies the maximum number of encoded bits that can be affected by a single input bit. This value represents (1 + maximal memory order), where maximal memory order refers to the length of the longest shift register chain in the convolutional encoder. The default is 3.

initial state specifies the initial parent state for the decode operation. When reset? is set to TRUE (default), the trellis structure is set to this state, thereby initializing the Viterbi decoding operation. On the first call to this VI, and thereafter when reset? is set to FALSE, the survivor state from the previous iteration is used to continue performing Viterbi decoding and this parameter is ignored. The default is 0.

traceback depth (D) specifies the number of trellis stages used in the Viterbi decoding process. The default is 15.

reset? specifies whether the decoder state is reset on each call to this VI. By default, the VI resets on the first call. When reset? is set to TRUE, the VI clears any buffered bits from the previous iterations, and the Viterbi hard decision decoding algorithm is initialized to start decoding from the specified initial state. In this case, the relationship of the length of the output decoded bit stream, L _out, to the input encoded bit stream length, L _in, is described by the following equation:

L _out = k × [floor(L _in/n) – D]

where k/n specifies the code rate, and D specifies the decoder traceback depth in symbols. When reset? is set to FALSE, the VI continues performing convolutional decoding from the previous iteration. In such a case, the length of the output decoded bit stream is given by the following equation:

L _out = k × floor(L _in/n).

Tip   If the length of the encoded bit stream is L in, and reset? is set to TRUE, the Viterbi decoding algorithm (for a rate k/n code) returns a total of L out=k×[floor(L in/n)–D] decoded bits in a single iteration, implying that a total of k×D message bits are buffered inside the VI. To recover the entire message of length k×floor[L in/n] in a single call to the MT Convolutional Decoder VI with reset? set to TRUE, choose one of the following options: Append max(D,K–1)×k zeros to the end of the message prior to performing convolutional encoding. Here k represents the message word length. Append D×n zeros to the end of the encoded bit stream prior to calling the MT Convolutional Decoder VI. Here D is the traceback depth employed in the convolutional decoder, and n is the code word length.

The default is TRUE.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

output bit stream returns the decoded code word. Wire this parameter to the MT Calculate BER VI to perform bit error rate measurements.

final state returns the survivor state resulting from the Viterbi hard decision decoding operation after decoding the entire input bit stream.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.