Modified fast Fourier transform in FBMC for satellite communications

The use of sharing channel simultaneously has become the trend in telecommunication technology particularly in network with distributed users as the allocation of frequency spectrum becomes more crowded. The proposed power control method in cognitive femtocell network is based on game theory (commonly known as power control game, PCG). This method uses utility function formula as the goal of game theory for power strategy in power update process. Utility function formula of Proposed PCG includes channel sharing factor that aimed to accommodate the system requirement of channel sharing. The result showed that the implementation of channel factor is inversely proportional to the signal to noise and interference ratio (SINR) and transmit power, but proportional to utility function. In comparison of user transmit power and SINR with two other methods, can also be conclude that Proposed PCG was able to achieve SINR of 5.49 dB and above the SINR target 5 dB, while the Thalabani (TB) and Koskie-Gajic (KG) were only able to achieve respective SINR of 4.87 dB and 4.98 dB. It can be concluded that the Proposed PCG was better in achieving the SINR target. It means that the quality of service in this system can be fulfilled properly.

As one of the most important components of the wideband wireless access technique, orthogonal frequency division multiplexing (OFDM) has a high usage rate of spectrum and combats inter-symbol interference (ISI) in multi-path fading channel. However, when there are frequency offsets during the signal transmission, the inter-carrier interference (ICI) is introduced, which significantly degrades the performance. The existing ICI self-cancellation schemes such as PCC-OFDM are not optimum to minimize the interference considering both noise and ICI. In this paper, a new metric named SINR (signal-to-interference-and-noise ratio) is proposed. We discuss the optimization issue when a constant frequency offset exists and in time-varying channels. The optimum weighting-coefficient-pair (OWCP) is obtained, which maximizes SINR theoretically through the alternant iteration algorithm. Simulations show that the performance of OWCP-OFDM is better than that of PCC-OFDM, especially when the frequency offset is large. Although the ICI self-cancellation scheme suffers bandwidth inefficiency, from the simulation results we can also see that the performance of OWCP-OFDM is much better than that of the standard OFDM systems with the same bandwidth efficiency when a frequency offset exists. Moreover, since the redundant modulation provides the capability to suppress ICI as well as a receiving SNR gain, it can be considered as exchanging the bandwidth for SNR.

In recent years, attentions have been focused on 3D (three-dimensional) beamforming which can improve cell average and cell edge throughput and eliminate the interference to adjacent cells. In the work towards calibration of 3D channel model, it seems that elevation beamforming with fixed electrical downtilt of 102 degrees has a good SINR (signal to interference and noise ratio) performance in 3D-UMI (Urban Micro) and 3D-UMa (Urban Macro) scenarios. In order to improve the user's SINR of elevation beamforming, in this paper, two user-specific elevation beamforming methods are proposed to improve the performance, one (method I) selecting the EoD (elevation angle of departure) as the electrical downtilt for each user, the other (method II) selecting the optimal electrical downtilt by considering user signal strength and inter-cell interference. Simulation results with the 3D channel model show that method I achieves a little improvement in 3D-UMI scenario but poor performance in 3D-UMa scenario compared with the fixed 102-degree elevation beamforming method from SINR. Method II in both scenarios outperforms the fixed downtilt method from SINR.

Performance evaluation of channel inversion precoding for downlink multi-user MIMO system

An efficient frequency domain soft interference cancellation (FD-SIC) scheme is proposed for turbo frequency domain equalization (FDE) in multiple-input multiple-output (MIMO) system. It is designed that at the receiver the inter-antenna interference (IAI) is cancelled by prior information in terms of data expectation. It can improve the input signal to interference and noise ratio (SINR) for the equalizer. Then block (data of one transmit antenna) wise frequency domain minimum mean square error (MMSE) equalization is implemented. Later a low complexity algorithm on the basis of single frequency tone (SFT) is deduced. Symbol Log-likelihood ratio (LLR) is calculated from the output of equalizer. Simulation results show that the proposed scheme has better link performance than traditional algorithms.

The paper studies the capacities of time hopping ultra wideband (TH-UWB) systems by adopting orthogonal pulse-based modulation schemes in a multipath environment with the consideration of multiple access interference (MAI) and inter symbol interference (ISI). Recently, orthogonal pulse-based modulation schemes such as pulse shape modulation (PSM), biorthogonal PSM (BPSM) and the combination of orthogonal pulse position modulation (OPPM) and BPSM have been proposed for UWB system to reduce ISI and MAI. In this paper, we first investigate the influences of ISI and MAI on the capacities of TH-UWB systems in terms of signal-to-interference and noise ratio (SINR) for high-order modulation schemes based on various sets of orthogonal pulses. How mutual information varies with the number of multipath components (MPCs) is then analyzed. The complete mathematical analysis and simulation results are provided in detail. When maximizing the mutual information, the Gaussian distribution approximate is assumed to describe the characteristics of MAI and ISI. Simulation results are provided to verify the theoretical analysis. Some conclusions are drawn thereafter, such as that capacity depends on the pulse patterns adopted and mutual information varies with inversely proportional to the number of MPCs. We also observed that the capacities of UWB systems for OPPM-BPSM schemes are larger than those of PSM and BPSM schemes.

This paper presents the impact of synchronization errors on the performance of a downlink multicarrier two-dimensional spreading OFDM-CDMA system. This impact is measured by the degradation of the signal to interference and noise ratio (SINR) obtained after despreading and equalization. The contribution of this paper is twofold. First, we use some properties of random matrix and free probability theories to derive a new expression of the SINR. This expression is then independent of the actual value of the spreading codes while still accounting for the orthogonality between codes. This model is validated by means of Monte Carlo simulations. Secondly, the model is exploited to derive the SINR degradation of OFDM-CDMA systems due to synchronization errors which include a timing error, a carrier frequency offset, and a sampling frequency offset. It is also exploited to compare the sensitivities of MC-CDMA and MC-DS-CDMA systems to these errors in a frequency selective channel. This work is carried out for zero-forcing and minimum mean square error equalizers.

Future communication systems employing massive multiple input multiple output will not have the ability to use channel state information at the mobile user terminals. Instead, it will be necessary for such devices to evaluate the downlink signal to interference and noise ratio (SINR) with interference both from the base station serving other users within the same cell and other base stations from adjacent cells. The SINR will act as an indicator of how well the precoders have been applied at the base station. The results presented in this paper from a 32 x 3 massive MIMO channel sounder measurement campaign at 2.4 GHz show how the received bit error rate and error vector magnitudes can be used to obtain a prediction of both the average and dynamically changing SINR.

This paper addresses first the problem of max-min fair (MMF) link transmissions in wireless sensor networks (WSNs) and in a second stage studies the joint link scheduling and transmission power assignment problem. Given a set of concurrently transmitting links, the MMF link transmission problem looks for transmission powers of nodes such that the signal-to-interference and noise ratio (SINR) values of active links satisfy max-min fairness property. By guaranteeing a “fair” transmission medium (in terms of SINR), other network requirements may be directly affected, such as the schedule length, the throughput (number of concurrent links in a time slot), and energy savings. Hence, the whole problem seeks to find a feasible schedule and a power assignment scheme such that the schedule length is minimized and the concurrent transmissions have a fair quality in terms of SINR. The focus of this study falls on the transmission power control strategy, which ensures that every node that is transmitting in the network chooses a transmission power that will minimally affect the other concurrent transmissions and, even more, achieves MMF SINR values of concurrent link transmissions. We show that this strategy may have an impact on reducing the network time schedule.

This paper proposes an enhanced decision feedback equalizer (DFE) for filter bank multicarrier (FBMC) systems over offset quadrature amplitude modulation (OQAM) based on a minimal mean square error (MMSE) criterion. For each subcarrier, besides one feedforward (FF) filter and one feedback (FB) filter, we add two intercarrier interference (ICI)-suppressing filters, which feed back detected precursors extracted from neighboring subchannels to enhance ICI suppression in the presence of multipath channels. Our simulation results indicate our proposal makes a considerable improvement comparing with MMSE-DFE under a severe ICI and ISI scenario despite few extra costs in computational complexity.

Space-time adaptive process(STAP) is an advanced anti-jamming method for GNSS receiver. It is widely used and researched. Normally the array output signal to interference and noise ratio(SINR) is used to measure the performance of STAP method, while de-spread output carrier to noise density ratio(CNR) performance is more concerned for GNSS receiver practical application. The weight frequency response in satellite signal direction is obtained through theoretical derivation and simulation. The difference between array output SINR performance and de-spread output CNR performance is deeply analyzed and explained by weight frequency response. Based on the analysis, a new space-time process method is proposed. The valuable reference is provided through research in this paper for space-time anti-jamming method theory research, performance evaluation and engineering practice.

Software-defined Internet of Vehicles (SDIoV) has emerged as a promising field of study as it could overcome the shortcomings of traditional vehicular networks, such as offering efficient data transmission and traffic shaping in different vehicular scenarios to satisfy all the requirements of applications on the fly. Although routing solutions are lightly addressed for SDIoV, there are many limitations of routing protocols unaddressed in such environment. More precisely, shortest path routing algorithms are mostly focused in the state of the arts. This paper presents quality of service aware routing algorithm that forwards packets toward the most reliable and connected path to the destination. Particularly, candidate routes should satisfy metrics, such as signal to interference and noise ratio (SINR) constraint and have the highest probability of connectivity. To address these issues, we have formulated a discrete optimization problem to favor the best route among candidate paths and proposed the modified laying chicken algorithm (LCA) that results better results than the traditional approaches. We have mathematically analyzed the probability of connectivity along with the SINR metric. Moreover, a multiscore function based on traffic density and greediness factor is proposed to make intelligent decision at the intersections. Simulation results are used to validate the superiority of the proposed routing approach over the existing solutions.

Implementing an efficient frequency reuse (FR) plan is significantly important to meet the demand on high data rates and the required quality of service for 5G. In this paper, we use the direction of arrival algorithms and the correlator to determine the directions of the desired user and the interferers in the cell. Then, we use the beamformer to produce a beam towards the desired user and nulls in the direction of the interferers. Moreover, we implement the synthesizer to smartly form the desired beam shape and make the nulls deeper. We take the advantage of the smart antennas, beamforming capabilities, and the radiation pattern synthesizing techniques to build up an efficient FR plan for 5G. In addition, we develop a formula for calculating the signal to interference and noise ratio (SINR) in terms of the desired and the interferers directions. Our objective is to maintain the SINR at the minimum levels required for data calls with accepted quality while reducing the beam sizes, and hence increase the FR factor. Our simulation results show that with a uniform linear antenna of 11 elements, we can achieve the desirable SINR levels using beams of 10° width, which raises the FR factor from 1 to 18 and subsequently increases the number of mobile users by 18 times.

In a real cellular system, existence of a number of multi-antenna schemes in neighboring cells means that different multi-antenna schemes will experience co-channel interference (CCI) from the same or other multi-antenna schemes. In this work, we have summarized our analysis and simulations related to cellular interference of some specific multiple input multiple output (MIMO) schemes on the same and other MIMO schemes. The goal is to study the impact of interference from MIMO schemes at a user located in the cell edge. Semi-Analytical evaluations of signal to interference and noise ratio (SINR) is done to find out the SINR statistics of different combinations of desired and interfering links. We have studied linear combining receivers for all the link combinations. Based on the current analysis, it is found that space-time block code (STBC) is a severe interferer compared to others, and specific attention is needed to counter the interference introduced by STBC interfering link.

In wireless ad hoc networks, PHY-layer interference is highly dependent on link scheduling schemes, and in turn heavily affects the performance of link scheduling. However, most existing link scheduling schemes ignore such relationship between the PHY and network layers, and hence fail to achieve the optimal end-to-end throughput due to large co-channel interference. This paper proposed a general framework for optimal TDMA (time division multiple access) link scheduling in multi-hop wireless ad hoc networks with general topology. In contrast to existing work, we maximizes the end-to-end throughput by taking into consideration the explicit relationship between the transmission rate of a link and its PHY-layer SINR (signal to interference and noise ratio). In particular, the authors formulate the scheduling problem into a LP (linear programming) problem based on the rate matrices with each entry being a function of SINR. With this formulation, the cross-layer link scheduling problem can be solved in polynomial time. To further reduce the computational complexity the authors proposed an algorithm to effectively reduce the size of the LP problem. Furthermore, to handle large-scale wireless networks, the authors present a decentralized scheduling algorithm that achieves a suboptimal TDMA scheduling solution with dramatically lower computational complexity comparing to the original LP formulation. Numerical results show that the proposed cross-layer link scheduling schemes outperform the existing schemes that assume a simplistic PHY-layer interference model by 59.45%.