Lezione 6 Communications Blockset

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1 Corso di Tecniche CAD per le Telecomunicazioni A.A Lezione 6 Communications Blockset Ing. Marco GALEAZZI 1

2 What Is Communications Blockset? Communications Blockset extends Simulink with a comprehensive library of blocks to design and simulate the physical layer of communication systems and components. The key features of the blockset are Blocks for designing and simulating the physical layer of communications systems, including modulation, source and channel encoding, channels, and equalization The ability to tune models and visualize the results Hierarchical, block-based models for visually conveying complex designs Integration with Communications Toolbox for postsimulation analysis 2

3 QPSK vs. MSK Demo The QPSK vs. MSK demo, my_qpskvsmsk, enables you to visually compare quadrature phase shift keying (QPSK) and minimum shift keying (MSK) modulation schemes. 3

4 Structure of the Demo (1) 4

5 Structure of the Demo (2) This demo uses various Communications and Signal Processing Blockset blocks to model QPSK and MSK modulation. The demo includes these blocks: Sources of uniformly distributed random integers between 0 and M-1, where M is the constellation size of the modulation scheme. Two sources are required, because QPSK is a quaternary modulation method, while MSK is a binary modulation method. QPSK Modulator Baseband MSK Modulator Baseband AWGN Channel Discrete-Time Eye Diagram Scope Discrete-Time Signal Trajectory Scope 5

6 Results and Displays The demo includes these visual aids to illustrate the difference between the two modulation schemes: Eye diagram blocks that show the eye diagrams of QPSK and MSK signals plus noise. In QPSK, the values of both the in-phase and quadrature components of the signal are permitted to change at any symbol interval. However, for MSK, the symbol interval is half that for QPSK but the inphase and quadrature components change values in alternate symbol epochs. Therefore, the ideal sampling time for QPSK is 0.5, 1.5, 2.5,..., while the ideal sampling period for MSK is 0.5, 1.5, 2.5,... for the in-phase signal and 1, 2, 3,... for the quadrature signal. 6

However, for MSK, the symbol interval is half that for QPSK but the inphase and quadrature components change values in alternate symbol epochs.

7 Cosa contiene Comms Blockset Il Communication Blockset contiene (ad oggi) 13 sottolibrerie. Si può accedere alla finestra mostrata a lato digitando il comando commlib nella Command Window di MATLAB. 7

8 Comm Sources Blocks in the Comm Sources library can Generate random data (bit or integer) Uniform, Bernoulli, Poisson Generate random noise to simulate channels Uniform, Gaussian, Rayleigh, Rician Generate sequences that can be used for spreading or synchronization in a communication system PN sequences, Gold sequences, Hadamard codes... 8

Uniform, Gaussian, Rayleigh, Rician Generate sequences that can be used for spreading

9 Comm Sinks Comm Sinks library contains Error Statistics Error Rate Calculation block. It calculates these error statistics: Error rate Number of error events Total number of input events Scopes Discrete-Time Eye Diagram Scope Discrete-Time Scatter Plot Scope Discrete-Time Signal Trajectory Scope 9

It calculates these error statistics: Error rate Number of error events

10 Source Coding Analog-to-digital conversion and data compression are two categories of source coding. Source encoding converts a source signal into a digital signal using a quantization method. Source decoding recovers the original information from the source-coded signal. Source Coding library contains Encoders and Decoders Scalar quantization and differential coding Companders A-Law and Mu-Law Compressor/Expander 10

Source decoding recovers the original information from the source-coded signal.

11 Error Detection and Correction Questo blocks library si divide in: Block Coding Binary linear and cyclic, BCH, Hamming, Reed- Solomon Convolutional Coding Convolutional Encoder, Viterbi Decoder Cyclic Redundancy Check (CRC) Coding General CRC Generator and Syndrome Detector CRC-N Generator and Syndrome Detector 11

Coding Convolutional Encoder, Viterbi Decoder Cyclic Redundancy Check (CRC)

12 Interleaving An interleaver permutes symbols according to a mapping. Interleaving can be useful for reducing errors caused by burst errors in a communication system. This blockset provides interleavers in two broad categories: Block interleavers. This category includes matrix, random, algebraic, and helical scan interleavers as special cases. Convolutional interleavers. This category includes a helical interleaver as a special case, as well as a general multiplexed interleaver. 12

This blockset provides interleavers in two broad categories: Block interleavers.

13 Modulation Questo blocks library si divide in: Analog Modulation Amplitude modulation (DSB, DSB-SC, SSB) Digital Modulation Pulse Amplitude Modulation (PAM) Quadrature Amplitude Modulation (QAM) Phase Shift Keying (PSK) Differential Phase Shift Keying (DPSK) Frequency Shift Keying (FSK) Minimum Shift Keying (MSK) Gaussian Minimum Shift Keying (GMSK) Continuous Phase Frequency Shift Keying (CPFSK) 13

Shift Keying (PSK) Differential Phase Shift Keying (DPSK) Frequency Shift Keying (FSK) Minimum Shift

14 Comm Filters The Comm Filters library includes several blocks that you can use for filtering (Rx) or pulse shaping (Tx). Gaussian FIR filter Raised Cosine Transmit and Receive filters Integrate and Dump These operations are necessary to control bandwidth, intersymbol interference, and signal-to-noise ratio. 14

Gaussian FIR filter Raised Cosine Transmit and Receive filters Integrate and

15 Channels (1) Communication channels introduce noise, fading, interference, and other distortions into the signals that they transmit. Simulating a communication system involves modeling a channel based on mathematical descriptions of the channel. In a simulation, the channel model usually fits directly between the transmitter and receiver, as shown below. 15

Simulating a communication system involves modeling a channel based on mathematical

16 Channels (2) This blockset provides several channel models for binary, real, and complex signals. Binary Symmetric Channel: Add binary errors to the input signal. AWGN Channel: Add white Gaussian noise to the input signal. The input and output signals can be real or complex. Multipath Rayleigh Fading Channel: For complex baseband signals, multiplies the input signal with samples of a Rayleigh distributed complex random process. Rician Fading Channel: For complex baseband signals, multiplies the input signal with samples of a Rician distributed complex random process. The spectrum of the both Rayleigh and Rician process is given by the Jakes Power Spectral Density (PSD). 16

Multipath Rayleigh Fading Channel: For complex baseband signals, multiplies the input signal with samples of a Rayleigh distributed complex random process.

17 RF Impairments The RF Impairments library contains blocks that model impairments to a baseband signal caused by the radio frequency (RF) components in the receiver. Nonlinearity and I/Q imbalances Phase/frequency offsets and phase noise Receiver thermal noise and free space path loss 17

18 Synchronization In order to interpret information correctly, a communication receiver must be synchronized with the corresponding transmitter. The Synchronization library contains: Components Voltage Controlled Oscillator (VCO) Phase-Locked Loop (PLL) Timing Phase Recovery Carrier Phase Recovery (CPM, M-PSK) 18

The Synchronization library contains: Components Voltage Controlled

19 Equalizers An equalizer attempts to mitigate ISI and thus improve the receiver s performance. This blockset supports these distinct classes of equalizers, each with a different overall structure: Linear equalizers, a class that includes symbol-spaced equalizers and fractionally spaced equalizers Decision-feedback equalizers MLSE (maximum-likelihood sequence estimation) equalizer that uses the Viterbi algorithm 19

$Linear equalizers, a class that includes symbol-spaced equalizers and fractionally spaced equalizers$

20 Sequence Operations This library contains: Repeat/Derepeat input samples N times. Scrambler/Descrambler Puncture/Insert Zero Interlacer/Deinterlacer 20

21 Utility Blocks This library contains: Integer Bit Converters Data Mapper (Binary Gray, User Defined) db Conversion Bipolar Unipolar Converters {-M+1, -M+3, -M+5,..., M-1} {0... M-1} Align Signals Find Delay Complex Phase Difference Complex Phase Shift 21

22 FINE 22

MODULATION Systems (part 1)

MODULATION Systems (part 1) Technologies and Services on Digital Broadcasting (8) MODULATION Systems (part ) "Technologies and Services of Digital Broadcasting" (in Japanese, ISBN4-339-62-2) is published by CORONA publishing co.,