CHAPTER 1 REVIEW ON CHANNEL EQUALIZATION 1.1 INTRODUCTION Communication systems comprise three fundamental elements: transmitter, channel and receiver. When signals are transmitted through a communications system, they are obstructed by some distortions which are mainly intersymbol interference (ISI) and noise. The transmitted signal is distorted by ISI which is caused by multipath effect in band limited (frequency selective) time dispersive channels and is the cause of bit errors on the receiver side. ISI is considered the main factor negatively affecting fast transmission of data over wireless channels. In order to eliminate or minimize these distortions, equalizers are employed in these systems. Equalization is the method of compensating for, eliminating or reducing the amplitude and phase distortion introduced by the transmission medium in communications systems. In a general meaning, the term refers to any signal processing operation equalization which minimizes ISI. An equalizing filter overcomes the ISI caused by individual received symbols of a transmitted data stream, as well as the crosstalk that for example occurs due to coupling of a transmitted pulse or that results from the capacitive coupling of the transmitted pulse on an outgoing pair interfering with the received pulse on an incoming pair. The task of equalizers is to provide efficient and error free communications by ensuring that signals transmitted through the channel are recovered as original at the end of the receiver that communications system has. Distortions may be linear or nonlinear depending on the channel characteristics of channel. When transmitting information through a physical channel, various mechanisms distort the transmitted signal significantly, causing degradation or even failure in the communications. These mechanisms can be classified as additive thermal noise, man-made noise and atmospheric noise. In practice, many of the physical channels are characterized by various channel models. The most frequently encountered channel of communications is that with additive noise. An additive random noise process is involved in this channel model. The factors causing the additive noise process are amplifiers and electronic components on the
CHAPTER 1 REVIEW ON CHANNEL EQUALIZATION 1.1 INTRODUCTION Communication systems comprise three fundamental elements: transmitter, channel and receiver. When signals are transmitted through a communications system, they are obstructed by some distortions which are mainly intersymbol interference (ISI) and noise. The transmitted signal is distorted by ISI which is caused by multipath effect in band limited (frequency selective) time dispersive channels and is the cause of bit errors on the receiver side. ISI is considered the main factor negatively affecting fast transmission of data over wireless channels. In order to eliminate or minimize these distortions, equalizers are employed in these systems. Equalization is the method of compensating for, eliminating or reducing the amplitude and phase distortion introduced by the transmission medium in communications systems. In a general meaning, the term equalization refers to any signal processing operation which minimizes ISI. An equalizing filter overcomes the ISI caused by individual received symbols of a transmitted data stream, as well as the crosstalk that for example occurs due to coupling of a transmitted pulse or that results from the capacitive coupling of the transmitted pulse on an outgoing pair interfering with the received pulse on an incoming pair. The task of equalizers is to provide efficient and error free communications by ensuring that signals transmitted through the channel are recovered as original at the end of the receiver that communications system has. Distortions may be linear or nonlinear depending on the channel characteristics of channel. When transmitting information through a physical channel, various mechanisms distort the transmitted signal significantly, causing degradation or even failure in the communications. These mechanisms can be classified as additive thermal noise, man-made noise and atmospheric noise. In practice, many of the physical channels are characterized by various channel models. The most frequently encountered channel of communications is that with additive noise. An additive random noise process is involved in this channel model. The factors causing the additive noise process are amplifiers and electronic components on the
Channel%20Equalization%20of%20QAM%20Signals%20Using%20a%20Neuro-Fuzzy%20Equalizer.docx