Ofdm Based Modem

The main objective of this thesis is to design and implement an OFDM based modem. This thesis improves upon previous work done in this field. Most of the literature found with regards to OFDM contains work done on the basis of FFT or fast fourier transform but the transform is limited to radix-2 which severly limits the OFDM division capabilities of the main channel. By using radix-2 the main channel can be split only into 3 sub-carriers wherear by using radix-4 the main channel can be split into 31 sub carriers. By using FFT demodulation can be achieved and by using its inverse demodulation can be achieved. By joining these two parts a modem can be made that can be used for wireless or wire-based communication in an efficient way.

Stephen Brown and Jonathan Rose [1] This paper provides a tutorial survey of architectures of commercially available high-capacity field-programmable devices (FPDs). The paper first defines the relevant terminology in the field and then describe the recent evolution of FPDs. The three main categories of FPDs are delineated: Simple PLDs (SPLDs), Complex PLDs (CPLDs) and Field-Programmable Gate Arrays (FPGAs). Then there are details of the architectures of all of the most important commercially available chips, and give examples of applications of each type of device. This paper was used to build the core system of this thesis.

Karen Parnell & Nick Mehta [2] The book details the history of programmable logic, where and how to use them, how to install the free, full functioning design software and then guides you through your first of many designs. There are also sections on VHDL and schematic capture design entry and finally a data bank of useful applications examples. This resource helped in design with discrete logic, base all of your designs on microcontrollers, or simply want to learn how to use the latest and most advanced programmable logic software, you will find this book an interesting insight into a different way to design.

IEEE Standard VHDL Language Reference Manual [3] VHSIC Hardware Description Language (VHDL) is defined. VHDL is a formal notation intended for use in all phases of the creation of electronic systems. Because it is both machine readable and human readable, it supports the development, verification, synthesis, and testing of hardware designs; the communication of hardware design data; and the maintenance, modification, and procurement of hardware. Its primary audiences are the implementors of tools supporting the language and the advanced users of the language. The logical design and synthesis of all components that employ VHDL in this thesis were deigned by referring to key section of this manual.

Bushida Hirosaki [4] An orthogonally multiplexed QAM (O-QAM) system is a multichannel system with a baud rate spacing between adjacent carrier frequencies; this property is desirable to digitally implement the system using the discrete Fourier transformation (DFT). This paper provides a novel digital signal processing method based on anN/2-point DFT processing in the O-QAM system. A complexity comparison between a digital O-QAM system and a digital singlechannel QAM system shows that the digital O-QAM system using the new method is more economical than the digitally implemented conventional single-channel data transmission system. This resource has all the mathematical explanations required for impmentation of 4 Quadrature Amplitude Multiplexing. 4 QAM is used in the thesis to modulate the base band signal to split it into radix – 4 form. This generated a total of 31 subcarrier channels.

Ben Saltzberg [5] A parallel quadrature AM data transmission system may be implemented with a number of overlapping channels, each carrying a signaling rateb, spacedb/2apart in frequency. When a large number of channels are used, the system allows transmission speeds very close to the Nyquist rate, with little sensitivity to delay and amplitude distortion of the transmission medium. The receiver requires precise phasing of the demodulating carriers and sampling times in order to keep crosstalk between channels small. In the presence of delay and amplitude distortion, better results are obtained when half cosine roll-offs are used for shaping each channel than for full cosine roll-off. This transmission scheme appears to be a promising technique for achieving good performance at high information rates over bandlimited dispersive transmission media.

John A. C. Bingham [6] The state of the art of multicarrier modulation for the transmission of high-speed data With DSL technology poised to provide the fastest means of Internet access for years to come, there is a growing need for practical information on running xDSL services over existing telephone lines. Communications expert John Bingham draws on three decades of intimate involvement with data transmission research to provide a complete guide to the state of the art and future direction of multicarrier modulation (MCM)-one of the key methods for high-speed data transmission today. Geared to designers and system planners working with DSL modems, Internet access, and telephony, ADSL, VDSL, and Multicarrier Modulation presents everything engineers and programmers need to design MCM modems, understand current implementations, and formulate strategies for future improvements and research.

Yun Wei, Huaiwei Lu and Zhaohui He [7] The communication based train control (CBTC) system is an advanced train control system. It uses high accuracy of train locating, realizes a continuous automatic train control system. DCS system plays an important role in the information interaction between ground equipment and vehicle equipment in CBTC. Based on OPNET simulation console, this paper designs a DCS network, simulates its communication process, analyzes the simulation data of sending and receiving, evaluates the entire performance of the network, which can offer reference to designing and optimizing the DCS network. This thesis presents many different digital communication systems and their base ideas for ideal implementation.

Martin L Doelz, Erin Heald and Darren Martin [8] The linearity and highly stable frequency characteristics of modern single-sideband equipment make possible improvements in the frequency spectrum utilization and performance of binary data transmission systems. Problems associated with fully utilizing the binary data transmission potential of an SSB voice channel are discussed. These problems include consideration of frequency and phase stability of the SSB equipment and the propagation media, multipath reception of signals, delay distortion within the voice channel, maximum performance in the presence of noise, and maximum spectrum utilization. Equipment designed to transmit 3000 bits per second over a SSB voice channel is described. Comparative performance data with standard systems are included.