To meet the strong demand for broadband multimedia services by both nomadic and mobile users, it is important to increase the bit rate of future mobile communications systems. To enhance system capacity, novel technologies or new concepts for improving bandwidth efficiency are indispensable. In this paper, an adaptive downlink modulation using OFDM and MC-CDMA is presented for maximizing the sy...

Multi-carrier code division multiple access (MC-CDMA) is modulation method for high speed data communication. The usage of MIMO MCCDMA can significantly improve the performance of wireless communication system. This paper presents the analysis of Multi Input Multi Output MultiCarrier CDMA system performance for BPSK, QPSK, MSK modulation over AWGN channel and Rayleigh channel. This represents t...

In this paper we propose a new bounded delay retransmission scheme that enhances the reliability of compressed video transmission in multicode DS-CDMA (MCCDMA) systems. We consider H.263/H.263+ video at low data rates (i.e., <64 kbps) in an IS-95B system over slow fading Rayleigh channels. Our approach is designed to reduce not only packet loss, time delays, and complexity, but also interferenc...

Low density signature orthogonal frequency division multiplexing (LDS-OFDM) and low density parity-check (LDPC) codes are multiple access and forward error correction (FEC) techniques, respectively. Both of them can be expressed by a bipartite graph. In this paper, we construct a joint sparse graph combining the single graphs of LDS-OFDM and LDPC codes, namely joint sparse graph for OFDM (JSG-O...

This paper proposes novel application of the Bees algorithm to multi objective optimization problems for the uplink of a multi carrier code division multiple access (MCCDMA) system based on orthogonal frequency division multiplexing (OFDM). The multiple input multiple output (MIMO) channel from users, which moves at vehicular speed, to the base-station (BS) is time variant. For time varying cha...

A new subcarrier combining technique is proposed for MC-CDMA receiver in mobile Rayleigh fading channel. It exploits the structure formed by repeating spreading sequences of users on different subcarriers to simultaneously suppress multiple access interference (MAI) and provide implicit channel tracking without any knowledge of the channel amplitudes or training sequences. This is achieved by a...

For a few years, multicarrier modulations have been proposed as valuable alternatives with respect to state-of-the-art single carrier ones due to their resilience against interference and channel distortion effects. In particular, many studies are arising about multicarrier-CDMA (MC-CDMA) techniques that provide improved robustness and flexibility with respect to single-carrier spread-spectrum ...

For Wireless Personal Area Network (WPAN) systems, resource allocation between several users within a piconet and the coexistence of several piconets are very important points to take into consideration for the optimization of high data rate Ultra Wide Band (UWB) systems. To improve the performance of the Multi Band OFDM (Orthogonal Frequency Division Multiplex) solution proposed by the Multi B...

The effect of two different pilot-assisted channel estimation techniques on BER in Multi-Carrier CDMA (MCCDMA) is considered. The first technique involves sending both data and pilot symbols in the same OFDM symbol. The second technique involves sending data and pilot symbols in separate OFDM symbols. In both cases multi-access interference is present. Simulations of both systems in a UMTS mult...

This paper examines a novel digital modulation/multiple access technique called Multi-Carrier Code Division Multiple Access (MC-CDMA) where each data symbol is transmitted at multiple narrowband subcarriers. Each subcarrier is encoded with a phase offset of 0 or π based on a spreading code. Analytical results are presented on the performance of this modulation scheme in an indoor wireless multi...