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Block diagram of a simple OFDM transreceiver. 

Block diagram of a simple OFDM transreceiver. 

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This paper gives an overview of Power Line Communications(PLC) and the different prevailing standards in PLC. The implementation of an OFDM transmitter - receiver system using MATLAB and Xilinx ZYNQ has been covered in detail in this paper. Additional links for tutorials on Hardware in loop testing and hardware software co-design can be found withi...

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... Line Communication (PLC) uses AC power lines to send data, this technology started showing up in the year 1922, where the first carrier frequency system (CFS) started using high-tension lines for sending data. It was found that open-wire equipment with few cross connections was an excellent medium for transmitting/carrying RF energy; transmissions up to 500 Km could be achieved with a 10 Watts transmitter. Due to higher number of cross- connection and noise CFS system was not practical on Low Voltage (LV) or Medium Voltage (MV) lines [1]. The basic principle of PLC is to couple a high-frequency power line communication signal to the AC line. Various modulation techniques have been researched over the years and various protocols have been developed to address the different problems put forth by the noisy power lines. Recent advancement in semiconductor technology has enabled the use of high-speed Digital Signal Processors (DSP) and Field Programmable Gate Arrays (FPGA) to implement complex modulation/demodulation techniques to make signals immune to noise and for efficient use of the available spectrum. This paper addresses the various effects found on the power line, protocols, standards and techniques used. It also presents an implementation of a hardware PLC modem using OFDM on a Zedboard with a Xilinx Zynq 7000 SoC. This Paper goes through various effects seen on Power Line communications and how then problems can be eliminated with the use of various Protocols and Modulation schemes. Orthogonal Frequency Multiplexing is the common denominator in most PLC technology and is covered in detail in this paper. An depth analysis of PHY (physical) layer is always essential to design a communication system every physical channel has unique characteristics and determining transfer characterizes by sounding the channel helps us to understand this effects and ways to overcome them. PLC data has to overcome various noise effects on the power line , transfer characteristics determined by field tests show in-home channels have high frequency selectivity and low attenuation. Outdoor channels have high attenuation but negligible fading [2], Error! Reference source not found. figure 1 show these characteristics as function of path loss, on an AC power line at home. These dynamic characteristics of the channel were similar to problems faced by mobile communications. With the use of OFDM, the mobile carriers have achieved higher reliability and higher bandwidths in a very noisy channel. Similar techniques have been also tested with PLC and have proved to be efficient, to send data reliably over noisy Power Lines. The applications of efficient power line communication are farfetched, from remote monitoring/metering system to Automobile charging stations. There several PLC standards that can be used in commercial and industrial applications; this section briefly explains PRIME and G3 standards that are two of the most widely accepted standards in PLC. These Protocols and standards are implemented using various DSP blocks. The most widespread modulation technique used in most PLC is Orthogonal Frequency Division Multiplexing (OFDM). OFDM provides noise immunity to the signal being transmitted into the power line, to test the working of OFDM on hardware, we have used Xilinx 7000 SoC along with Xilinx Simulink DSP toolbox to perform a Hardware Co-simulation of the OFDM algorithm on FPGA. OFDM is a modulation technique that is best suited for high data rate in a delay-dispersive channel. This technique splits data into low rate stream and this is transmitted over orthogonal narrow bands. This is a very primitive concepts dating back to 1940s but is currently back in the lime light due to advancement in DSP and processor technology. These OFDM systems were not previous feasible due to complexity in the hardware and software to perform such operation. OFDM is also currently being used in most wireless communication system and have proved its feasibility in an extremely noisy environment. The diagram (Figure 2) below shows how the spectra of each carrier overlap with the spectra of the other carrier, but this will not cause any interference since they are orthogonal in nature [7]. This also reduces the inter symbol interference of the signal. This OFDM transceiver can be an analog system or a digital system, the scope of this paper covers the design of digital OFDM transceivers and later focuses on the implementation of OFDM receiver on FPGA. Figure 3 show a high-level block diagram of the OFDM transceiver. The S/P Converter converts the Serial Stream of data from the data source to parallel data that is fed into the IFFT block, The Cyclic Prefix is added later to detect errors due to multipath at the receiver side. The receiver section uses an FFT block to do the reverse and get transmitted data back. This system design is inferred from the following mathematical representation of OFDM [7]. Digital Modulation and demodulation divides the data stream in groups of N symbols. The EQ1 represents a complex symbol at a time instant of i on the nth carrier. Symbols are data groups from the source, mapped over a 2D ...