The multi-carrier code division multiple access (MC-CDMA) is becoming a very attractive technique for high-rate data transmission in the future wireless communication systems. MC-CDMA systems transmitting over multipath channels suffer from inter-symbol interference (ISI) and (MAI). Recently, with equalisation has attracted much attention its ability to obtain an excellent performance even strong frequency-selective fading channels. In this study, proposed architecture uses minimum...

Drastic increase in throughput and link reliability requirements over high frequency (HF) long-distance communication backhaul necessities the exploitation of HF ionospheric channels with wider spectrum. While there exist substantial work modeling narrowband (3KHz) channel, bandwidth did not gain same attention. Present paper introduces an OFDM system design a concatenation eight standard 3KHz resulting overall 24KHz channel. First, we provide accurate channel model for such wideband that...

Turbo codes have been shown to approach the Shannon limit for error correcting capability at low signal-to-noise ratios given large sized frames. Extensive research efforts examining ways enhance performance of turbo short frames (e.g., voice transmission). One way enhancing is optimize energy allocated each bit stream achieve best possible. In standard codes, all bits are transmitted with equal energy. Changing allocation strategy can frame lengths. Using computer simulation and analytic...

In this paper, an OFDM scheme for image transmission is proposed. The based on unequal cyclic time guard (UTG) of conventional OFDM. performance the UTG_OFDM compared with results show better former at lower average extension period. To enhance signal-to-noise ratio, convolution coding combined method, where error protection (UEP) overlayed scheme. remarkable improvement in quality to equal (EEP) over multipath channels.

The low complexity receiver structure based on discrete cosine transform for a downlink multicarrier code division multiple access (DCT‐MC‐CDMA) system is proposed. It employs an interference cancellation scheme with linear equaliser to suppress the and caused by multipath fading channel performance of proposed receivers analysed compared conventional DFT‐MC‐CDMA system. Simulation results show large improvement when using such relative DCT equalisation receiver,

The key to the efficient operation of turbo codes is interleaver design. With proper design, pairing low-weight sequences input encoders can be avoided. Circular shift interleavers used ensure that minimum distance due weight-2 grows roughly as /spl radic/2N, where N block length. We generalized mapping function circular suitable for both equal and unequal error protections. Also, we present results a unique examination behavior general protections using code with short frames.

Recently wireless sensor networks have been shown to be very attractive for many communications applications. A large number of tiny sensors spread over the area under consideration constitute networks. These limited power resources. Due built-in battery life-time at each sensor, minimizing consumption in is an important issue reliable and sustainable network operation. Error control coding (ECC), such as turbo codes Low Density Parity Check (LDPC), a classic approach used increase link...

Orthogonal frequency division multiplexing (OFDM)is an excellent technique to reduce the effect of selective in time varying multipath channels by dividing transmission bandwidth into many narrow-band subcarriers, each which exhibits approximately flat fading. Cyclic extensions are added OFDM symbols allow for mutipath signals from previous symbol die away before information current is gathered. In this paper, a modified scheme image proposed. The new proposal based on modification structure...

This paper presents a comparative study between orthogonal frequency division multiplexing (OFDM) and the single carrier with cyclic prefix (SCCP) communication systems over wideband high (HF) ionospheric channel. HF has advantages of long distance coverage, low cost, simplified infrastructure. Meanwhile, limited bandwidth (3KHz) standard channels restricts operation modern applications which requires relatively higher data rates. In an attempt to evaluate utility for rate applications, this...

Relay communications channels have been shown to be used achieve combined diversity and coding gain in wireless networks. To enhance the performance of relay network some cooperation distributed schemes introduced. In networks signals transmitted from one terminal another through a number relays. Embedding turbo code (DTC) technique into has approach theoretical bound capacity applications, availability power required at source device satisfy level quality destination is not available, like...

The average upper bound for punctured turbo codes is derived from knowledge of the conditional weight enumerating function original low-rate code. A novel approach to generating these bounds, hypergeometric puncturing, introduced, which enables performance be averaged over all possible puncturing positions at a required code rate.

The OFDM technique with cyclic time guard, which has been proposed for broadband communications, is an increasing approach to combat the frequency selectivity of channel.In this paper, a modified scheme image transmission proposed.The new proposal based on modification structure through using unequal power allocation successive symbols.Unequal guard also applied allocation.The method compared conventional OFDM.Results show that performance improved at lower average extension periods and when...

The Multi-Carrier Code Division Multiple Access (MC-CDMA) is becoming a very attractive multiple access technique for high-rate data transmission in the future wireless communication systems.MC-CDMA systems transmitting over multipath channels suffer from intersymbol interference (ISI) and (MAI).Recently, MC-CDMA with equalization has attracted much attention its ability to obtain an excellent performance even strong frequency selective fading channels.In this paper, proposed architecture...

The Multi-Carrier Code Division Multiple Access (MC-CDMA) is becoming a very attractive multiple access technique for high-rate data transmission in the future wireless communication systems.The advantage of MC-CDMA systems that work frequency domain.Recently, with any equalization scheme has attracted much attention its ability to obtain an excellent performance even strong selective fading channels.In this paper, two proposed architecture downlink based on regularized zero forcing...

In future wireless communication systems such as 3rd generation mobile systems, increasing the downlink capacity from base stations to remote units becomes more important due high data rate applications internet access.Turbo Codes and Space-Time Transmit Diversity (STTD) are two of most recently techniques improve system performance capacity.In this paper, turbo codes with transmit diversity is studied.The effect number transmits antennas, puncturing, frame length investigated over Rayleigh...

Performance degradation of uplink OFDMA and MC-CDMA under Wiener phase jitter is pointed out in this paper using theoretical simulation results. Beginning by characterizing the process, signal to noise presented waveforms derived. Under assumption full load small jitter, shown be varying with variance time. The main conclusion that can achieved strong may occur frequency locked multicarrier systems presence jitter.

This paper considers the performance enhancement of a space-time turbo codes processing system employing combined code and antenna transmission diversity scheme for direct sequence spread spectrum communication system.Turbo have been shown to approach Shannon limit error correcting capability at low signal-to-noise ratios given large sized frames.Extensive research efforts examining ways enhance short frames (e.g., voice transmission).The proposed is investigated over Rayleigh fading...

The most exciting and potentially important development in coding theory recent years has been the dramatic announcement of "Turbo codes".Turbo codes are constructed by applying two or more component to different interleaved versions same information sequence.Then, encoded bits decoded through an iterative decoding algorithm relatively low complexity.Turbo code decoder consists soft-input/soft-output convolutional decoders that work together fashion.Turbo process is complex part turbo...