الفهرس 
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Abstract
The primary goal of fourth generation (4G) wireless systems is not only providing new technologies to cover the need for higher data rates and new services, but also the integration of existing technologies in a common platform. Hence, the selection of a generic air-interface for future generation wireless systems will be of great importance. Although the exact requirements for 4G have not yet been commonly defined, its new air interface will fulfill at least some requirements such that it helps the 4G systems have a generic architecture that enables the existing technologies to integrate. It will use spectrum in an efficient manner and offer higher data rates in a given spectrum. It will be also a highly scalable system that enables the design of different cell configurations (hot spot, cellular system). This provides better coverage using software defined radio (SDR). Besides, it will be a highly adaptive and reconfigurable system which can support different standards and technologies. It is cost efficient which makes marketing faster and offers future basis for new technologies.
A new wireless communication system denoted as Orthogonal Frequency Code Division Multiple Access (OFCDMA), which is the combination of Orthogonal Frequency Division Multiplexing (OFDM) and mean of two dimensional spreading namely time domain and frequency domain spreading, is analyzed in this thesis.
The broadband OFCDMA becomes a very promising technique to be used as multiple access technique for 4G high speed wireless communications requirements due to its advantages over OFDM as it has many degrees of freedom for system adaptability and the spreading which has been offered to OFDM to provide frequency diversity and facilitate one-cell reuse.
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Here, in order to focus much attention on the OFCDMA concept, a MC-CDMA system, OFDM system and a conventional DS-CDMA system are introduced for a comparison purpose.
MATLAB programs were written to compute the bit error rate (BER) for OFCDMA system and other mentioned systems for comparison. This comparison is made for different systems configurations and different environmental models like frequency selective fading model.
The BER results proved that OFCDMA outperforms MC-CDMA, OFDM and DS-CDMA systems under the same applied conditions for each system. This is because of the utilization of two dimensional spreading.