Security Transmission with Modulator Structure Hopping in Cooperative System with Untrusted Relay

In this research work, the effect of ReformedReed Muller Encoded Data (RRMED) on Peak to Average PowerRatio (PAPR) of Multicode Code Division Multiple Access(MC-CDMA) systems was studied under Minimum Shift Keying(MSK) modulation. Simulation studies revealed thatimplementation of RRMED on PAPR with MSK modulation cansave up to 7dB of transmitter power compared to the un-codedPAPR of MC-CDMA systems.Simulation results further proved that MSK modulation alsoplays an important role in reducing PAPR as compared to binaryPhase Shift Keying (PSK).

Although MSK (minimum-shift keying) modulation has been well investigated and applied widely to wireless communications, while its performance analysis over fading environment is few in the literature up to now. In this paper, the characteristic of MSK signal is studied, and two types of MSK quadrature modulator structures are presented. The performance of these two types of MSK modulation systems over flat Rayleigh fading channel environment are analyzed, and the corresponding BER (bit error rate) expressions are obtained. Their BER performance over different fading channel environments are simulated using MATLAB software. The simulation results are in good agreement with the theoretical analysis, which shows that our analysis is accurate. In addition, the theoretical analysis results obtained in this paper can be regarded as the performance bounds of MSK modulation over actual wireless communication channels.

Linear and nonlinear distortion effects in direct detection 40 Gb/s MSK modulation formats multi-span optically amplified transmission

Since the existing full-rate cooperative transmission schemes have a serious defect in low Bit Error Rate (BER) performance while the existing high-rate cooperative transmission schemes have a serious defect in low spectral efficiency, a distributed high-rate cooperative relay transmission scheme based on full-rate cooperative communication model is proposed in this paper, in which Cyclic Delay Diversity (CDD) technology and Linear Constellation Precoding (LCP) technology are employed. Moreover, the proposed scheme addresses the issue of obtaining maximum spatial and multipath diversity with low decoding complexity and high transmission reliability. The BER performance of the proposed scheme is contrasted to that of the full-rate transmission scheme where better performance is achieved, and is improved when the number of the multipath or the relay nodes increases.

Considering a nonregenerative untrusted relay network, we investigate three different secure transmission strategies, for example, noncooperative strategy, conventional amplify-and-forward (AF) strategy, and cooperative jamming (CJ) strategy. To thoroughly assess the secrecy performance achieved by the three strategies, we derive the closed-form expressions for the connection outage probability and secrecy outage probability regarding each strategy. Based on these expressions, the reliability and security tradeoff (RST) is examined to facilitate the design of the transmitting parameters. We then present the closed-form expression for the effective secrecy throughput (EST) and characterize the overall efficiency of these transmission strategies. Furthermore, we conduct the asymptotic analysis for the secrecy throughput, which enables us to determine the optimal transmission strategy under different scenarios. Our analytical and numerical results demonstrate that compared with the noncooperative and AF strategies, the CJ strategy possesses the best performance in terms of RST. Additionally, we also find that the EST performance of the AF strategy is nearly invariable when the quality of the second hop changes.

This paper introduces a cooperative orthogonal frequency division multiplexing (CO-OFDM) based on amplify and forward (AF) relay and utilizing a fast low complexity T-transform as a subcarriers modulation scheme. The proposed cooperative system is developed by changing the modulation/demodulation algorithms which significantly enhanced the immunity of the system to deep notches of the multipath channels. Thereafter, the paper presents a mathematical analytic model for the proposed amplify and forward CO-T-OFDM scheme. The use of T-transform in the transceiver of the proposed system enhances the signal diversity. Therefore, the presented AF cooperative system is efficient in enhancing the signal diversity, mitigating the effects of multipath fading channels and achieving more reliable bit-error-rate (BER) performance than the state-of-the-art cooperative system. It also moderates the peaks power of the signal. The BER of the developed AF cooperative system is evaluated by Monte Carlo simulation over frequency-selective multipath channels when AF relay is used, and compared with the BER performance of the standard AF cooperative system. The results show that the developed AF cooperative technology achieves better BER than the classic CO-OFDM under different transmission scenarios.

Low-resolution ADC MIMO-Constant Envelope Modulation, MIMO-CEM, is one of the alternative candidates to the well-known MIMO-OFDM, suitable for wireless backhaul networks. One of the major problems withstands the real application of MIMO-CEM is the channel estimation. This comes from the low resolution ADC used in MIMO-CEM receiver. Intermediate Frequency (IF) based Adaptive channel estimator was previously proposed for MIMO-CEM. This channel estimator is based upon replicating the received preamble signal to exactly match the effect of high quantization error ADC upon the received MIMO signal. Because MIMO-CEM ADC is IF sampled, the whole IF MIMO-CEM transceiver is replicated to exactly replicate the received preamble signal. Although this channel estimator has an excellent estimation performance, its computational complexity is very high. This high complexity comes from the IF (high frequency) calculations. In this paper, a low complexity MIMO-CEM adaptive channel estimator is introduced. The proposed channel estimator is based upon linearly modeling the quantization error occurred at the low resolution IF sampled ADC in baseband. Hence, a baseband adaptive channel estimator can be designed, which has a much lower complexity than the IF estimator (previously designed). The effectiveness of the proposed estimator is proven under different channel scenarios using Minimum Shift Keying (MSK) and Gaussian MSK (GMSK) modulations.

Orthogonal frequency division multiplexing (OFDM) systems suffer from high sidelobes level. In some applications, as cognitive radios, this phenomenon can be a serious matter. This paper proposes Minimum shift keying (MSK)-OFDM to address this problem. The proposed method is an OFDM system using MSK modulation in each subcarrier. The corresponding transmitter and receiver are introduced. The method doesn't entail great changes in the main parts of OFDM. Like OFDM systems, the transceiver can be implemented using DFT/IDFT. Simulation results show great reduction in out of band radiation in comparison with conventional OFDM.

It is considered by some that minimum shift keying (MSK) is spectrally more efficient than quaternary phase-shift keying/offset quadrature phase-shift keying (QPSK/OQPSK). An analytical method is presented here for determining the detection efficiencies of MSK and QPSK/OQPSK when the constant-envelope signal is passed through a set of filters and when the resulting signal is corrupted by Gaussian noise. The detection efficiency of MSK is compared with that of QPSK/OQPSK when a four-pole Butterworth filter is used as a transmit filter and for two different receive filter functions. When the two-sided 3-dB bandwidth of the transmit filter is between approximately 1.00/T and 1.50/T, it is shown that the detection efficiency of MSK is not substantially different from that of QPSK/OQPSK. For more severe bandlimiting of the signal, the performance of MSK is shown to be inferior to that of QPSK/OQPSK. It is, therefore, concluded that MSK does not have significantly better detection efficiency when the effect of bandlimiting filters is taken into account.

In this paper, we study three cooperative transmission schemes by use of amplify-and-forward (AF) relaying strategies. It is assumed that there is one source, one destination and several AF-relays. First, a parallel-relay strategy is considered wherein the transmitted message from the source is received by each relay independently. Then, the relay retransmit the message by use of AF relaying to the destination. Next, we consider the case where the message is being sent through the whole relays sequentially to the destination. Finally, we consider a general case, where we have multi-branches such that on each branch, there exist several relays sequentially cooperating to transmit the message to the destination. For each cooperative transmission scheme, we are looking for minimizing the symbol-error rate (SER) subject to sum-relay power (SRP). Hence, for each cooperative transmission schemes, we analyze the optimization problem and analytically derive the optimal power allocation at the relays to minimize the SER. Finally, we numerically show that when the SRP is low, we can optimize the number of active relays. That is, at low SRP increasing number of relays does not monotonically decrease the SER. On the other hand, at high SRP, employing more number of relays is more beneficial than allocating more power to a limited number of relays.

In this research work, we have developed a communication system (transmitter / receiver) to control peak to average power (PAPR) with small bit error rate (BER) for a 4G system called multicode code division multiple access (MCCDMA). Proposed communication system works on modified Reed Muller encoded data (MRMED) string. In MRMED data is first encoded with Reed Muller (RM) code. Thereafter, encoded RM message is XORed with optimal binary string, which results lower Peak to Average Power ratio (PAPR). A well-known fact is that, bit error rate (BER) is the best performance measurement tool for a communication system. To check the integrity of our communication system, we have run the simulation for monitoring BER using MRMED sequence. Simulation work conducted, with multipath Rayleigh fading, Minimum Shift Keying (MSK) modulation and several orders of RM codes. Our results show that implementing MRMED sequences of the suggested MCCDMA communication structure, returns noticeable lower BER. For instance, in case of RM(1,4), that has error improvement proficiency of 3 (three) errors , returns BER = 8.2x10−5 adopting MSK, at SNR = 12dB. Similarly, for RM(2,3), which has error improvement efficiency of 0 error and shows distinct BER of 4.9x10−4 at 12dB (SNR).In addition to using simulation for checking BER performance of our communication system, we have also shown in our results that, as the error improvement capability of different RM codes surges, correspondingly we get a lower BER.

This paper deals with the design of non-regenerative relays in cooperative transmission schemes. The conventional nonregenerative approach is the amplify and forward (AF) approach, where the signal received at the relay is simply amplified and retransmitted. In this paper, we propose an alternative design which maximizes the capacity for nonregenerative cooperative transmission, when channel state information is available at the relay station. Therefore, the relay units are not simple amplify and forward units, but still they are not required to demodulate or remodulate the symbols transmitted by the base station as in regenerative relaying schemes. We compare the performance so obtained with the performance for the conventional AF approach, and also with the performance of regenerative relays and direct noncooperative transmission.

Underwater acoustic channels normally have low data rate, long propagation delay, severe multipath effect, and time varying fading. Cooperative transmission is a new wireless communication technique in which diversity gain is achieved by utilizing relay nodes as virtual antennae. In this paper, we investigate cooperative transmission techniques for underwater acoustic communications. First, we study the performance of several cooperative transmission schemes, originally designed for radio communications, in an underwater scenario. Second, by taking advantage of the low propagation speed of sound, we design a new wave cooperative transmission scheme. In this scheme, the relay nodes amplify the signal received from the source node, and then forward the signal immediately to the destination. The goal is to alter the multipath effect at the receiver. Third, we derive the performance upper bound for the proposed wave cooperative transmission scheme. The simulation results show that the proposed wave cooperative transmission has significant advantages over the traditional direct transmission and the existing cooperative transmission schemes originally designed for radio wireless networks.

This paper proposes a cross-layer design which combines adaptive modulation and coding (AMC), cooperative diversity at physical layer (PHY) and hybrid automatic repeat request (HARQ) at data link layer (LL) for wireless ad-hoc networks. First, we provide theoretical analyses of conventional direct transmission scheme and cooperative transmission scheme with AMC and HARQ that include analytical expressions for the packet error rate (PER) and spectral efficiency. Then we propose a novel hybrid transmission scheme which invokes cooperation based on the feedback AMC information. Numerical results demonstrate that the performance of the hybrid transmission scheme is equivalent to the cooperative transmission scheme while its cooperation cost is kept much lower compared with that of the cooperative transmission scheme.

Since classical time-division-multiple-access based cooperative scheme suffers from lower data rate due to two time-slots based transmission approach, superposition modulation has recently gained huge research attention which enables single time-slot cooperative transmission. Therefore, in this paper we propose a novel superposition modulation based regenerate-and-forward cooperative transmission scheme with M-ary phase shift keying constellation signals. Closed-form expressions for average symbol error probability (SEP) and maximum power allocation for relay data are derived for proposed scheme. Simulation results show that proposed scheme outperforms classical cooperative scheme by providing higher spectral efficiency and lower SEP.