This phase difference Phi is then converted to a frequency offset. The locatePreamble method of the object, which is responsible for this operation, uses a normalized minimum peak height, and a minimum number of required peaks to provide a possible preamble match.Ģ) Carrier Frequency Recovery: Frequency estimation is accomplished by calculating the phase difference in the time domain between halves of the long portion of the 802.11a preamble. This identification method is based upon. The preamble itself is designed to produce this specific shape in the time domain. The cross-correlated data will contain a specific peak arrangement/spacing which allows for identification. More specifically, it utilizes a known preamble sequence in the received frame found through a cross-correlation. It is divided into four primary operations in this order:ġ) Timing Recovery: This component is responsible for determining the sample location of the start of a given frame. This OFDMReceiver System object recovers the original transmitted payload message. The noise level of the AWGN is given in dB. It degrades the transmitted signal with both phase and frequency offset, a delay to mimic channel delay between transmitter and receiver, and AWGN. This component simulates the effects of over-the-air transmission. Frames are padded to fill the OFDM grid when necessary. Identical frames are repeated by the transmitter based on the value supplied. Each transmission frame is made up of several OFDM symbols, including preamble and data symbols. The OFDMTransmitter System object generates an OFDM signal based upon the IEEE 802.11a standard with a supplied ASCII payload. Description of the Individual Components and Algorithms The output of the OFDMReceiver object's step method is the decoded bit stream from those detected frames.Ĥ) calculateOFDMBER: calculate the system frame error rate (FER) and bit error rate (BER) based on the original payload message in each frame and the bit output from the OFDMReceiver System object. The object can also be configured to show multiple scopes to visualize the receiver processing.
Ofdm transceiver design using matlab simulink series#
The object models a series of components at the receiver, including timing recovery, carrier frequency recovery, channel equalization, and demodulation. The transmitter repeats this frame numFrames times.Ģ) applyOFDMChannel: models the channel with carrier offset, timing offset, and additive white Gaussian noise (AWGN).ģ) receiveOFDMSignal: set up and step an OFDMReceiver System object. The object converts the payload message into a bit stream which is first PSK modulated, then OFDM modulated, and finally prepended by preamble OFDM symbols to form an individual frame. The system is broken down into four functions: generateOFDMSignal, applyOFDMChannel, receiveOFDMSignal, and calculateOFDMBER.ġ) generateOFDMSignal: set up and step an OFDMTransmitter System object. This example models a digital communication system based upon the IEEE 802.11a standard. Transmitter and receiver functions will be compiled for additional simulation acceleration.
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