09-07-2012, 10:02 AM
Software Defined Radio
Software Defined Radio.pdf (Size: 1.18 MB / Downloads: 126)
Abstract
A software defined radio is a transmitter and receiver system that uses digital signal
processing (DSP) for coding, decoding, modulating, and demodulating data. This project
focused on using the IEEE 802.11a specification to create a software radio. The
feasibility of using Mathworks’ Simulink and Texas Instrument’s Code Composer Studio
to design, test, and prototype an OFDM software radio system on a Texas Instruments
CDSK6713 DSP development board was studied. Among the subjects examined were
communication with the board through real time data exchange (RTDX), quadrature
amplitude modulation (QAM), orthogonal frequency division multiplexing (OFDM),
frame and carrier synchronization, and issues with Simulink DSP code generation for
prototyping.
Introduction
This project focused on the design and implementation of a digital software radio. Digital
signal processing (DSP) was used to implement the transmitter and receiver. This
allowed for greater flexibility and accuracy when designing the radio. The project is a
scaled down version of the IEEE 802.11a standard that uses QAM (Quadrature
Amplitude Modulation) with OFDM (Orthogonal Frequency Division Multiplexing) to
create the coding and modulation scheme. The project also focused on rapid development
and prototyping by using Simulink block diagrams to program the Texas Instruments
TMDSK6713 evaluation board.
Functional Description
A software defined radio is a transmitter and receiver system that uses digital signal
processing (DSP) for coding, decoding, modulation, and demodulation. This allows much
more power and flexibility when choosing and designing modulation and coding
techniques. The Texas Instruments TMDSK6713 evaluation board with the
TMS320C6713 DSP chip was selected to implement the radio. The system functions are
shown in Figure 1.
Demultiplexing & Modulation
The demultiplexing block takes a byte of binary data and then breaks the byte into
four 2-bit streams. These 2-bit streams are each fed into a QAM modulation
channel. Once the QAM channels have modulated the input data, a buffer
collects a group of 20 QAM symbols that represent 5 bytes of data. The group of
symbols is then passed into the OFDM block. The OFDM system multiplexes the
QAM signals together to produce the final modulated output.
OFDM Modulation
Orthogonal Frequency Division Multiplexing or OFDM is a way to transmit many
modulated signals at once by multiplexing them over a large number of frequencies.
OFDM is different from normal frequency multiplexing because the individual frequency
carriers are orthogonal to each other. This allows them to be closely space and not
interfere with each other. Leon Couch in his book Digital and Analog Communication
Systems [1] gives the complex envelop for OFDM in equation 1.
Software Defined Radio.pdf (Size: 1.18 MB / Downloads: 126)
Abstract
A software defined radio is a transmitter and receiver system that uses digital signal
processing (DSP) for coding, decoding, modulating, and demodulating data. This project
focused on using the IEEE 802.11a specification to create a software radio. The
feasibility of using Mathworks’ Simulink and Texas Instrument’s Code Composer Studio
to design, test, and prototype an OFDM software radio system on a Texas Instruments
CDSK6713 DSP development board was studied. Among the subjects examined were
communication with the board through real time data exchange (RTDX), quadrature
amplitude modulation (QAM), orthogonal frequency division multiplexing (OFDM),
frame and carrier synchronization, and issues with Simulink DSP code generation for
prototyping.
Introduction
This project focused on the design and implementation of a digital software radio. Digital
signal processing (DSP) was used to implement the transmitter and receiver. This
allowed for greater flexibility and accuracy when designing the radio. The project is a
scaled down version of the IEEE 802.11a standard that uses QAM (Quadrature
Amplitude Modulation) with OFDM (Orthogonal Frequency Division Multiplexing) to
create the coding and modulation scheme. The project also focused on rapid development
and prototyping by using Simulink block diagrams to program the Texas Instruments
TMDSK6713 evaluation board.
Functional Description
A software defined radio is a transmitter and receiver system that uses digital signal
processing (DSP) for coding, decoding, modulation, and demodulation. This allows much
more power and flexibility when choosing and designing modulation and coding
techniques. The Texas Instruments TMDSK6713 evaluation board with the
TMS320C6713 DSP chip was selected to implement the radio. The system functions are
shown in Figure 1.
Demultiplexing & Modulation
The demultiplexing block takes a byte of binary data and then breaks the byte into
four 2-bit streams. These 2-bit streams are each fed into a QAM modulation
channel. Once the QAM channels have modulated the input data, a buffer
collects a group of 20 QAM symbols that represent 5 bytes of data. The group of
symbols is then passed into the OFDM block. The OFDM system multiplexes the
QAM signals together to produce the final modulated output.
OFDM Modulation
Orthogonal Frequency Division Multiplexing or OFDM is a way to transmit many
modulated signals at once by multiplexing them over a large number of frequencies.
OFDM is different from normal frequency multiplexing because the individual frequency
carriers are orthogonal to each other. This allows them to be closely space and not
interfere with each other. Leon Couch in his book Digital and Analog Communication
Systems [1] gives the complex envelop for OFDM in equation 1.