Optimal Resource Allocation for Multicarrier NOMA in Short Packet Communications

This paper discusses the performance of radio-over-fiber systems in different channels for distributing gigabit-per-second wireless signals at millimetre wave frequencies. Nonlinear distortions (NLD) in the channel reduce the dynamic range (distortion-free range for the input signal) of radio-over-fibre (ROF) links. Performance comparison of RoF in different channels shows that the dynamic range is highest in AWGN channel (highest SNR) and lesser in Rayleigh channel than Rician channel. An Orthogonal Frequency Modulated(OFDM) signal is Mach Zehnder Modulated (MZM), the generated optical signal is amplified by an Erbium Doped Fiber Amplifier (EDFA), noises are filtered, transmitted to a Radio Access Point (RAP) through a single-mode optical fiber and reached at the end user passing AWGN, Rayleigh and Rician channels.

Rapidly growing demand for high data rates in wireless communication systems is the cause of the merging of Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) techniques. MIMO-OFDM technique needs Radio Frequency (RF) front end in each antenna, which is not effective for large dimensional antenna size. Therefore, RF front end on the receiver side will be simplified using a single RF technique based on the Electrically Steerable Parasitic Array Radiator (ESPAR) antenna. In real life, a channel cannot be ideal. Therefore, before the signal is transmitted, that signal must be coded to minimized errors when the data transmission process. Convolutional code is a coding technique that can detect and correct error bit (error control coding) and that it is expected to reduce the quantity of Bit Error Rate (BER). In this research, a simulation is designed to analyze single RF performance on the MIMO-OFDM system using Vertical Bell Laboratories Space-Time (VBLAST) detection for convolutional code encoder and Viterbi decoder. The result simulation shows that the channel estimation technique works well on the MIMO-OFDM system using single RF, which is shown in the magnitude and phase curves against the subcarrier index between the theory channel and the estimated channel are at almost the same points. VBLAST-ZF detector performance is shown in the BER curve against SNR, where the difference BER value for SNR value 10 dB between the theory channel and the estimated channel is 0.001499. Channel coding technique using convolutional code encoder and Viterbi decoder with a rate of ½ works well on the MIMO-OFDM system using single RF which is shown in the BER curve against SNR, where BER value with coding technique is smaller than BER value without coding technique.

We consider the performance comparisons of adaptive Minimum Variance Distortionless Response (MVDR) and received Least Squares (LS) beamforming on the downlink channel from High Altitude Platform (HAP) to high speed train. The channel, as modeled in CAPANINA project, is considered as time varying rician and flat fading process. Since the rician factor is moderate to high, adaptive MVDR beamforming is attractive in compensating for the rician fading channel. Due to the constraint in the cost function, MVDR beamforming neglects useful received signal particularly in the lower rician factors, hence, mismatch occurs. By implementing the LS beamforming, the receiver is able to adapt better to a more rayleigh fading channel case. The comparisons of the considered beamforming algorithms are given in terms of Mean Square Error (MSE) of beamforming weight tracking and Bit Error Rate (BER).

The Bit Error Rate (BER) expressions of Walsh-Hadamard Transform (WHT) aided Quadrature Amplitude Modulation (QAM) transmitted in impulsive noise environments are derived. It is found that there is a crossover point between the conventional and WHT-aided schemes' BER curves, above which WHT is beneficial in terms of the corresponding BER performance. The exact crossover SNR is analysed and its approximate closed-form expression is derived for a QPSK scheme based on the Chernoff bound. An adaptive WHT scheme is proposed for QAM systems, where the transmitter activates the WHT only when the instantaneous SNR at the receiver is higher than the crossover SNR. The theoretical BER of our adaptive WHT scheme is derived for QAM systems operating over Nakagami-m fading channels. It is found that our adaptive WHT scheme is effective in terms of mitigating the detrimental effects of impulsive noise over the entire SNR range.

The performance of encoded opportunistic transmission schemes in wireless channels affected by Rayleigh fading and additive white Gaussian noise (AWGN) is analyzed. In opportunistic transmission, the information is transmitted only when the fading amplitude is above a threshold. For this, the receiver with the knowledge of the channel state information notifies the instants the transmitter should transmit. Opportunistic systems with convolutional error correcting codes or with trellis coded modulation are analyzed in terms of closed-form bit error rate (BER) expressions. Nevertheless, the approach presented can be employed with any kind of error correcting codes. Hence, the performance of turbo codes is also presented in the simulations. Monte Carlo simulations verify the accuracy of the derived expressions and provide insights on the system performance. Performance results show that uncoded and encoded opportunistic systems are superior to uncoded and encoded ordinary systems (non-opportunistic), respectively. In particular, the BER curves of the opportunistic system decay exponentially when the signal-to-noise ratio (SNR) increases. On the other hand, BER curves for ordinary transmission decay linearly, where the slope is proportional to the diversity that depends on the error correcting code. Thus, opportunistic systems require less SNR to guarantee the same BER of ordinary transmission. The BER gain increases as the SNR increases. It is also observed that uncoded opportunistic systems are even superior to encoded ordinary ones. The results are validated guaranteeing the same spectral efficiency for all the scenarios. Finally, due to the exponential decay of the BER curves, coding gain expressions, used in ordinary systems over AWGN, can be used as approximations for opportunistic transmission in fading channels.

In this paper we propose a hybrid method to determine the positions and velocities of mobile stations (MSs) in a GSM (Global System for Mobile communication) network. The proposed method can be implemented within the existing GSM standard without any additional hardware changes. The hybrid method operates at two levels. At a lower level, time delay method (TDM) is used to obtain coarse values for distances between a MS and three or more Base Transceivers (BTSs). At a higher level, field strength method (FSM) uses the coarse distances estimates obtained using TDM as initial values to obtain refined values for distances. The accurate position of a MS then can be determined by the refined distance values. Subsequently, the velocity of the MS be can obtained using the FSM estimates of the sequential positions of the MS. Least mean square (LMS) method is used to determine the refined distances in the FSM algorithm and to estimate the actual position of the MS from the refined distance estimates. The proposed method was tested for several cases, including complex MS trajectories and varying speeds along the trajectory. The heights of the BTSs were allowed to vary between 20 m and 60 m. The convergence characteristics were found to be satisfactory. For a SNR of 20 dB, position measurements accuracy in a roughly 4 km2 cell is 30 m in a Gaussian channel, 60 m in a Rayleigh channel and 80 m in a Rician channel. The velocity accuracy for a MS traveling at 200 km/h is 15 km/h in a Gaussian channel, 30 km/h in a Rayleigh channel and 50 km/h in a Rician Channel.

Inter symbol interference and signal fading caused by multipath propagation are problems confronting wireless communication technology. For the UHF RFID system, multipath propagation can also reduce the system's readability and increase the bit error rate of the system. Therefore, the research of UHF RFID wireless channel is of great significance. Firstly, channel models of UHF RFID system has been analyzed in this paper. Then the maximum capacity of UHF RFID system is studied in Rician channel and Rayleigh channel with using different methods to transfer information. Water-injection method is also applied to this study. Using MATLAB simulation and two methods under the same signal to noise ratio, we found that Rician channel has a greater capacity and Rayleigh channel has a greater attenuation of the signal.

Wireless communication channels experience high variability in channel quality due to a variety of phenomenon, including multipath, fading, atmospheric effects, and obstacles. Due to this different wireless communication channels have different capacity for transferring the data. This paper studies the movements of nodes within channel environments using Ricean, Rayleigh and Free space channel models. Three performance metrics are used for this purpose. These metrics are throughput, end to end delay and link ratio. It is discovered that free space channel model performed better than Ricean channel which in turn perform better than Rayleigh channel model.

Diverse methodologies of Diversity combining schemes are used for performance improvements of Filter Bank Multicarrier (FBMC) by using Additive White Gaussian Noise and Rayleigh channels. These diversity combining schemes are Maximum Ratio combining and Selection Combining. The proposed schemes are implemented by using different channels of MIMO methodology, which results in high order diversity. This system simulation includes varying number of receiving antennas to analyzes the performance over AWGN and Rayleigh channel. The aim of the proposed schemes is to improve bit error rate (BER) performance with using two different diversity combining schemes. It observed through MATLAB simulations that the proposed schemes provides evident performance improvements.

The vulnerability of Global Positioning System (GPS) receivers to jammers is a major concern owing to the extremely weak received signal power of GPS. Researches have been conducted on a variety of antenna array techniques to be used as countermeasures to GPS jammers, and their antijamming performance is known to be greater than that of single antenna methods. However, the application of antenna arrays remains limited because of their size, cost, and computational complexity. This study proposes and experimentally validates a novel space-time-polarization domain adaptive processing for a single-element dual-polarized antenna (STPAPS) by focusing on the polarization diversity of a dual-polarized antenna. The mathematical models of arbitrarily polarized signals received by dual-polarized antenna are derived, and an appropriate constraint matrix for dual-polarized-antenna-based GPS antijam is suggested. To reduce the computational complexity of the constraint matrix approach, the eigenvector constraint design scheme is adopted. The performance of STPAPS is quantitively and qualitatively evaluated through experiments as follows. 1) The carrier-to-noise-density ratio (C/N0) of STPAPS under synthetic jamming is demonstrated to be higher than that of the previous minimum mean squared error (MMSE) or minimum variance distortionless response (MVDR) based dual-polarized antenna methods. 2) The strengths and weaknesses of STPAPS are qualitatively compared with those of the previous single-element dual-polarized antenna methods that are not based on the MMSE or MVDR algorithms. 3) The characteristics of STPAPS (in terms of the directions and polarizations of the GPS and jamming signals) are compared with those of the conventional two-element single-polarized antenna array method, which has the same degree of freedom as that of STPAPS.

In this paper, the performance of parallel interference cancellation (PIC) multiuser detector in orthogonal frequency division multiple access (OFDMA) mobile communication systems is investigated. In multiuser systems, the multi-user interference (MUI) degraded the system performance, especially in near-far effect environments. The PIC scheme is proposed to reduce the MUIs and to improve the bit error rate (BER) performance for uplink OFDMA systems. Simulation results show that under the near far problems for both block sub carrier assignment scheme (BCAS) and block-interleaved sub carrier assignment scheme (ICAS), the PIC scheme can improve the BER performance for all users.

An effective design of multistage parallel interference cancellation (PIC) receiver using blind adaptive (BA) despreader and pre‐respreader interference estimator for uplink CDMA is proposed and analysed. A novel algorithm is designed, which exploits constant modulus (CM) property of the users' transmitted signals and inherent channel condition to perform adaptive despreading based on minimum error variance criteria. This is carried out by BA weighting of each chip signal for accurate tracking of the desired user's signal power and hence for more improved data detection at the output of each stage of PIC. Furthermore, the despreader weights are used within the adaptive pre‐respreader interference estimation and cancellation to obtain online scaling factors during every symbol period, without any knowledge of users' channels or the use of training sequences. It is found that this way of estimation is optimal in minimum mean squared error sense, and hence, significant reduction in interference and noise variance is observed in detection and estimation of the desired users' signals compared with conventional PIC. Bit error probability of the proposed PIC is obtained using Gaussian Approximation method. Extensive simulation results are shown, which demonstrate impressive performance advantage in fading environments, high system loading, and severe near far conditions. Copyright © 2008 John Wiley & Sons, Ltd.

In this paper, the error performance analysis of an amplify-and-forward (AF) relay-aided cooperative multi-antenna system using spatial modulation (SM) over Rayleigh channels is presented. The SM is a simple and spectral efficient modulation technique that can increase the data rate by using input data bits to select a transmit antenna to send a constellation point. The relay transmission deploying SM not only can enhance the coverage and but also can improve the spectral efficiency. In the performance analysis, the overall average bit error rate (BER), which is related to the error probability of an antenna index detection ( $P_{a}$ ) and the error probability of symbol detection ( $P_{d}$ ) given transmit antenna index, is analyzed. With the derivation of the probability density function and the moment generating function of output signal-to-noise ratio (SNR), closed-form expressions of $P_{a}$ and $P_{d}$ are obtained to compute the overall BER. With the obtained BER expression, asymptotical BER expressions are derived to reveal the BER performance of the system at high SNR. By minimizing the asymptotical BER, a suboptimal power allocation (PA) scheme is developed. The diversity gain is analyzed at high SNR. The results indicate that the cooperative AF-SM can achieve full diversity order. Simulation results verify the effectiveness of the theoretical BER analysis, and the cooperative AF-SM with PA scheme outperforms upon the equal PA scheme.

The performances of direct-sequence spread-spectrum multiple-access (DS-SSMA) systems with M-ary differential phase shift keying (MDPSK) and differential phase detector (DPD) are estimated on the satellite mobile channel (SMC) which includes Gaussian and Rayleigh channels as the special cases. The numerical results are presented for the system with one of three types of chip waveforms (rectangular, cosine and root Nyquist filtering (RNF)), and binary or complex random signature sequences. They show that the system with the complex random signature sequences outperforms the system with the binary random signature sequences on Gaussian and Rician (K = 10) channels, while on a Rayleigh channel both systems perform similarly; the system with 2 × I users and BDPSK signalling format outperforms that with I users and QDPSK for Gaussian and Rician (K = 10) channels; and from the point view of both bandwidth efficiency and antimultipath effects, the cosine pulse shaping is the best choice of the three pulse shape functions, although the system with the RNF has the highest bandwidth efficiency.

Performance analysis of an adaptive two-stage PIC CDMA receiver in AWGN channels