COSSAP simulation model of DS-CDMA indoor microwave ATM LAN

This thesis presents an original work in the area of designing and implementing a simulation testbed for modelling a high speed spread spectrum Asynchronous Transfer Mode (ATM) Local Area Network (LAN). The spread spectrum technique used in this LAN model is Direct Sequence Code Division Multiple Access (DS-CDMA). The simulation model includes at least a physical layer of such a LAN, embedded into the COSSAP1 simulation environment, and has been fully tested. All the newly developed building blocks are comprised of standard blocks from the COSSAP libraries or compatible user-built primitive blocks (only where it is absolutely necessary), and are flexible enough to allow the modification of simulation or model parameters; such as the number of signal channels, modulation method used, different spreading code sequences and so on. All these changes can be made with minimal effort. Another significant contribution made in this thesis is the extended research into evaluating the Bit Error Rate (BER) performance of different spread spectrum COMA coding schemes for an indoor microwave A1M LAN [8]. Different spread spectrum CDMA coding schemes are compared for their transmission error rate in Additive White Gaussian Noise (AWGN) channel with varying transmitted signal power and at different channel Signal to Noise Ratio (SNR) levels. Since a wireless microwave channel is very prone to transmission errors, a major contribution of the simulation testbed developed in this thesis is its use in the finding of an optimal physical layer transmission scheme with the best Bit Error Rate (BER) performance in an indoor environment

Realization of a CDMA-based RFID system using a semi-active UHF transponder

RFID systems may increase the efficiency of logistic systems, e.g., inventory of stocks. Unfortunately, present existing systems come fast to their limits if a great amount of RFID transponder must be inventoried in very short time, as the channel access method of current RFID systems is Time Division Multiple Access. To shorten the inventory process, this work shows a first realization of an RFID-based semi-active UHF transponder using a Code Division Multiple Access method. The work concentrates on the uplink channel (tag to reader) that covers the transponder's backscattered signals. This channel access method enables simultaneous transfer of data, meaning that all transponder in the field may respond at the same time within the same frequency band. The data transfer realized for the uplink channel, uses a certain set of orthogonal spreading sequences (modified Gold codes) being different for every transponder. The RFID reader used in this work despreads the backscat tered signals and decodes the data of the different transponder. Briefly, this work shows, in principle, the opportunity for a simultaneous data transfer on the uplink channel in RFID systems, which in turn may shorten very much the time for a complete inventory round