Electronic and Communication - Engineering

Abstract: The orthogonal frequency division multiple access (OFDMA) scheme adopts orthogonal frequency division multiplexing (OFDM) subcarriers, which are particularly suited for transmition over broadband frequency selection channels, to support multiusers. The scheme considered usually assigns a subset of subcarriers to each user and adopted adaptive techniques for the allocation of available resources/subcarriers according to the channel state information (CSI) estimated at the transmitter using a reverse link.

Abstract: In this thesis, an adaptive modulation and coding (AMC) scheme is applied to OFDM wireless communication systems. This scheme offers an alternative wireless link adaptation approach that promises to raise the overall system capacity. The AMC provides the flexibility to match the modulationcoding scheme to the average channel conditions. With AMC, the power of the transmitted signal is held constant over a frame interval while both the modulation and coding formats are changed to match the received signal quality.

Abstract: Support for voice communications using the Internet Protocol , usually called “voice over IP (VoIP)”, has become especially attractive given the low cost, flatrate pricing of the Internet. In fact, toll quality telephony over IP has now become one of the key steps leading to the convergence of the voice, video and data communications industries. VoIP telephony or IP telephony is the transportation of voice traffic over the Internet protocol (IP) .The Internet is an interconnection between networks that use IP.