Fatma Newagy

Joint complex regularised zero-forcing equalisation and CFO compensation for MIMO SC-FDMA systems

In single carrier frequency division multiple access (SC-FDMA) systems, frequency domain equalisers suffer performance degradation due to several channel impairments such as inter-symbol interference, inter-carrier interference (ICI), especially in multiple access/multiple input multiple output (MIMO) systems. This study presents a joint complex regularised zero forcing (JCRZF) equaliser that is able to compensate the channel impairments and to mitigate the ICI induced by the carrier frequency offset (CFO) in mobile channel environments. JCRZF equaliser is also able to eliminate the inter antenna interference resulting from the MIMO channel coupling by transforming the MIMO channel into equivalent SISO channels. Simulation results show that the JCRZF equaliser outperforms ZF based equalisers in terms of bit error rate while preserving their potential complexity and appropriate robustness to CFO estimation errors.

Novel technique for scaling down LDPC code lengths in DVB-T2 standard

The paper proposes an approach to scale-down the LDPC code length, thus saving memory and processing power, without significantly sacrificing the code robustness. the paper describes how to use specific Low Density Parity Check (LDPC) codes for Digital Video Broadcasting Terrestrial Second Generation DVB-T2. While the original LDPC codes are rather long 16200 bits and 64800 bits, we propose to reduce their size (about 3k instead of 16k). To reduce the encoder/decoder complexity, the scaled down LDPC codes based on DVB-T2 of length 16200 are proposed in this paper. Scaling the codes may lead to the problems of girth-4 and low weight codes. This paper analyzed the possible reasons leading to the problems, and proposed the optimum scaled down LDPC codes of DVB-T2 that avoid girth-4 and low weight codes. The simulation results in the AWGN channel show that for code rate ½ at BER = 10-5, LDPC DVB-T2_3240 requires only additional 0.5dB above that required by DVB-T2_16200 and the proposed scaled down code by 5 still has no error floor as well as the former codes in [10]. The impact of the paper is not restricted to DVB-T2 systems, but also to DVB-S2 and all future technologies which are to adopt LDPC.

Complexity reduction for GPS acquisition algorithms using Sparse Fourier Transform

The global navigation satellite system (GPS) receiver has to lock on the satellites signals to calculate its position. The process of locking on the satellites is quite costly and requires millions of hardware multiplications, leading to high power consumption. In order to reduce the GPS receivers cost, acquisition time and power consumption; the complexity of the acquisition process should be reduced. In this paper, A modified algorithm is proposed to reduce the complexity of the time parallel acquisition algorithm with transition detection (TPATD) by using the Sparse Fourier Transform. The acquisition process is considered to two signals −24 dB (weak signal) and −30 dB (very weak signal) in presence of data bit-sign transitions. The complexity of the proposed algorithms without losing the sensitivity will be O (Np+ N/p log N/p) for very weak signals and O (N/p log N/p) for weak signals where p is the down sampling factor. The reduction in complexity because of the proposed algorithm is calculated for the mentioned cases. Simulation results show the performance of the proposed algorithm with the receiver operative characteristic curves using Monte Carlo simulations.

Modified Square Rooting Companding Technique to Reduced PAPR for FBMC/OQAM

Multicarrier modulation (MCM) have become a fast developing area in wireless communication system. The filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) system may be the most popular multicarrier modulation technique used for next generation wireless communication technology 5G. It has several advantages such as supporting high data rate, low impulse noise and eliminating inter symbol interference (ISI), inter-carrier interference. However, the main challenging problems of FBMC/OQAM system is the high peak to average power ratio (PAPR). In this paper, we used Square Rooting Companding Technique (SQRT) to reduce the PAPR in the FBMC system, then we modified the SQRT scheme to new scheme which namely by Rooting Companding Technique (RCT). Moreover, new techniques are analyzed with CCDF characteristics and BER Performances. However, the simulation result shows the proposed RCT schemes given significant improvement in the PAPR reduction and increasing BER performance.

PAPR Reduction of FBMC/OQAM Systems Based on Combination of DST Precoding and A-law Nonlinear Companding Technique

The filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is considered as a most efficient technique for next wireless communication systems 5G due to its higher spectral bandwidth efficiency, robustness to frequency-selective fading channels, etc. However, the biggest disadvantage to working with FBMC system is its high peak-to-average power ratio (PAPR) leads to severe intercarrier interference, out-of-band radiation, and poor bit error rate performance because of the nonlinearity of the high power amplifier. In this paper, we investigate a low complexity hybrid scheme using the combination of the Discrete Sine Transform (DST) Precoding technique and A Law Nonlinear companding technique to reduce PAPR in FBMC system. The numerical results verify that the FBMC systems with our proposed schemes can improve PAPR performance of the signals greatly with satisfying the performance of BER condition. It can reduced PAPR about 84% of original PAPR.

Global Energy-Efficiency Metric for Coordinated Cognitive Radio Networks

Energy-efficiency is a significant parameter contributing to the performance of coordinated cognitive radio networks (CCRNs). To estimate the average value of sensing and reporting energy efficiency of CCRN, a new metric is proposed. This paper presents a new metric based on the gain from the coordination of missed detection and false alarm probabilities that minimize the interference on the primary users and maximize the throughput for cognitive terminals (CTs), respectively. Furthermore, the proposed maximum metric is placed by analytically figuring out the optimum number of coordinated CTs. The global average value of energy efficiency of sensing and reporting process among coordinated CTs with various probabilities of missed detection and false alarm is formulated. In addition, a new iterative CTs assignment strategy is proposed. Finally, the average energy-efficiency results are significantly enhanced as shown by simulations.

Energy efficient cooperation scheme for self-organized femtocells

Cooperation among self-organized femtocells (SOFs) becomes an optimization technique to induce a fair resource allocation. However, cooperation performance is restricted by backhaul limitations. In this paper, an energy efficient system design for cooperative SOFs is proposed. A new spectral resource management is used to avoid the uplink co-tier interference depending on less signaling overhead resulting from cooperation organization among SOFs. A model is built to the cooperation among the SOFs for resource allocation with minimum backhaul signaling traffic. The simulation results show that the proposed model guarantees different radio blocks allocation for femto-users affected by the co-tier interference. In addition, the proposed model will reduce the traffic of the cooperation by 45% of that of the conventional model. Finally, the proposed model performance in terms of latency and power consumption for different backhaul technologies is simulated. It is found that the signaling power consumption can be reduced from 814w to 159w. Therefore, our proposed cooperation model can be considered energy efficient.

Probability of error and ergodic capacity of switch-and-examine combining diversity over the α-μ fading channel

In this paper, we consider a switch-and-examine combining (SEC) diversity scheme operating over independent and identically distributed (i.i.d) branches assuming an α-μ fading channel. We derive expressions for the average symbol error rate (ASER) for a class of coherent modulation techniques considering this fading model as well as expressions for the ergodic capacity under the same assumptions. The results for the ASER and the ergodic capacity are shown to reduce to those previously reported in the literature for other channel models such as the Weibull model as a special case, which confirms the validity of the obtained expressions. Different aspects are studied including the effect of fading severity, the number of branches and the modulation scheme used. Also, insights on the optimal choice of the switching threshold are provided.