What's New in the Modulation Toolkit 3.1

The latest release of the Modulation Toolkit, the industry's most powerful open communications software, introduces many new features to augment and simplify designing and testing communications systems. The following lists the major features integrated into the software.

OFDM Web Example

The OFDM example generates baseband complex waveform based on OFDM modulation. This is a very general tool that simulates most of OFDM systems currently in use or under development.

LabVIEW Modulation Toolkit OFDM Example

Interleavers/Deinterleavers

The Modulation Toolkit 3.1 features two new blocks to our digital communication system; Interleaver and its counterpart named Deinterleaver. An interleaver is a device that ensures the symbols from several different code words are well separated during transmission over a single path, so that the symbols from any given code word are clearly received in time-division sequence.

Interleavers are used in conjunction with error-correcting codes (encoding) to counteract the effects of bursty errors.  The type of Interleavers we have added are the Block Interleaver and the Convolutional Interleaver.  Interleavers are used in a variety of wireless standards.  Refer to the following theoretical example for an illustration of the interleave operation.

Interleave input: 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,…

0	1	2	3	4
5	6	7	8	9
10	11	12	13	14

Interleave output: 0,5,10,1,6,11,2,7,12,3,8,13,4,9,14

Puncturing

The process of puncturing data is used to artificially increase the code-rate of the data stream that is output from a block or convolutional encoder by selectively deleting certain elements in the data stream.
The process of depuncturing data is the reverse of the puncturing process: erasure values are inserted into the input data stream prior to its input to the decoder.

Generic I/Q Symbol Map

The toolkit also introduces a utility to create generic, user-defined, symbol maps. The user can use this utility to create any symbol map pattern that they want.  Some of the wireless standards including the new wireless television standard, DVB, use a non-uniform spacing of I/Q symbols.  This utility shows first-hand the flexibility and power of a software-defined approach to RF design and test.

Figure 1:  VI Demonstrating Custom 64-QAM Constellation for DVB using I/Q Generic Symbol Map Utility

The following example demonstrates 8-QAM symbol map creation.  Define the symbol values as
Define the I symbol amplitude array as.  
Define the Q symbol amplitude array as   .
Define gain as 1.0.  These settings result in the following symbol map.

Bit Packing

Pack Bits (Unpack Bits) is a very simple utility yet very useful one to perform packing a set of bits into integer symbols and unpacking an integer symbol into bits. For example, if you specify bits per integer as 3, and packed bit order as MSB First, the bits [1 0 0] are mapped to the integer 4. If packed bit order is specified as LSB First, the bits are mapped to the integer 1.

Phase-Locked Loop (Baseband)

This VI simulates the operation of the PLL in response to an input waveform with an unknown phase and frequency offset. The PLL is a feedback control system which employs a phase detector, loop filter, and a voltage-controlled oscillator (VCO) for its operation. The PLL tracks the instantaneous phase and frequency of the input waveform and returns an estimate of the carrier phase and frequency. You can use these estimates to adjust/correct the phase of the input waveform (for example, carrier phase/frequency offset correction in M-ary PSK digital communication systems). You can also use this functionality to determine the incidental FM signal present on RF signals.

Bit Generation

Two different techniques of bit generation namely Galois and Fibonacci pseudonoise (PN) have been added to the software. The Modulation Toolkit also features the ability to generate bit sequences based on a user-defined pattern. The selected pattern is repeated until the user-specified number of total bits is generated.

Related Products

NI LabVIEW
The National Instruments PXI-5660 is a modular 2.7 GHz RF vector signal analyzer optimized for automated test. It provides high-throughput RF measurements in a compact, 3U PXI package.

NI Modulation Toolkit
The National Instruments Modulation Toolkit extends the built-in analysis capability of LabVIEW with functions and tools for signal generation, analysis, visualization, and processing of standard and custom digital and analog modulation formats.

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