Terms Of Signal-to-interference-plus-noise Ratio Research Articles

User-Centric Cluster Design and Analysis for Hybrid Sub-6GHz-mmWave-THz Dense Networks

The terahertz (THz) waves with enormous bandwidth can be used along with the existing sub-6GHz and millimeter wave (mmWave) bands to achieve the ever evolving ecosystem of applications that need to be supported by the modern wireless networks. This paper investigates a user-centric dynamic base station (BS) clustering design for a hybrid network where THz, mmWave, and sub-6GHz BSs coexist. Invoking the proposed clustering model, the BS cooperation within each band is made possible by considering long term channel variations and all the surrounding BSs within a cluster with tunable size. A typical user is associated with the best BS cluster, from either a sub-6GHz, mmWave or THz tier based on the maximum signal-to-interference-plus-noise-ratio (SINR) criterion or the maximum rate criterion. Using tools from stochastic geometry, we assess the performance of the proposed user-centric hybrid system in terms of SINR and rate coverage performances, while accounting for: band specific propagation models, directional beamfroming, and BSs random locations. The accuracy of the analytical results is validated with Monte-Carlo simulations. The obtained results recognize a clear coverage/rate trade-off where a high fraction of THz BSs improves the rate significantly but may degrade the coverage performance. Thus, with carefully planned networks, enabling user-centric BS cooperation for hybrid wireless systems can achieve ultra-high rates while maintaining sufficient coverage in sixth-generation (6G) networks.

Low-Complexity Power Allocation in Pilot-Pouring Superimposed-Training Over CB-FMT

Pilot-pouring superimposed training (PPST) is a novel channel estimation technique specially designed for cyclic block filtered multi-tone (CB-FMT), where the pilot symbols are poured into the subcarriers taking advantage of the power left unused by the data symbols. Hence, since this technique is based on superimposed training (ST) principles, the data rate is not reduced, unlike the pilot symbol assisted modulation (PSAM). Besides, it exploits a weighted average at the receiver side that is capable of minimizing the mean squared error (MSE) of the channel estimation, and then enhancing the performance of the system. However, the existing proposal on PPST is limited to the minimization of the MSE to improve channel estimation for a given power allocation factor, without solving the joint optimization of channel estimation and data detection procedures. With this aim, this work addresses the whole problem to reach the best performance for both tasks, thus taking into account also the power allocation factor in the optimization process, where the spectral efficiency must be maximized through the signal-to-interference plus noise ratio (SINR). Two optimization approaches are proposed, where the first one, referred as pilot-pouring optimization (PPO), is focused on performance at the expense of a high complexity, while the second one, denoted as low-complexity PPO (LPPO), is able to trade-off between performance and execution time. Numerical results are provided in order to show the validity of our proposal, where the different optimization problems are compared in terms of SINR and execution time.

Low-Complexity Data Collection Scheme for UAV Sink Nodes in Cellular IoT Networks

Owing to the nature of battery-operated sensors, the residual energy of their battery should be considered when a sink node collects sensory data from them. If a sink attempts to collect data from a sensor that does not have sufficient residual energy to transmit data, the utilization of wireless communication resources may be degraded. However, requiring a periodic residual energy report of the sensors considerably reduces the energy efficiency of them. Consequently, the sink node must be able to estimate the residual energy of the sensors without additional information exchange before attempting to collect data. To tackle this problem, we propose a data collection scheme for mobile sinks in cellular Internet-of-things (IoT) networks. The scheme consists of two phases. In the first phase, the mobile sink estimates the residual energy of the surrounding sensors. To reduce the complexity, we design a state diagram composed of three states based on the Markov chain of the sensor. The sink node calculates the communicable likelihood of each sensor based on the state diagram and collects data from the sensor with the highest likelihood. In the second phase, a cellular base station (BS) selects the appropriate mobile sink to improve the signal-to-interference-plus-noise ratio (SINR) of the signal from a cellular user. Each sink node delivers the bidding price to the BS based on the likelihoods of the sensors. The BS determines an appropriate sink node to allocate resources based on the received bidding prices. Moreover, we show the performance of the proposed method in terms of SINR and IoT network utilization through simulation.

New Weight Function for Adapting Handover Margin Level over Contiguous Carrier Aggregation Deployment Scenarios in LTE-Advanced System

In this paper, an Adaptive Handover Margin algorithm based on Novel Weight Function (AHOM-NWF) is proposed through Carrier Aggregation operation in Long Term Evolution—Advanced system. The AHOM-NWF algorithm automatically adjusts the Handover Margin level based on three functions, $$f(SINR), \; f(TL)\; {\text{and}}\; f(v)$$ , which are evaluated as functions of Signal-to-Interference-plus-Noise-Ratio (SINR), Traffic Load $$(TL)$$ , and User’s velocity $$(v)$$ respectively. The weight of each function is taken into account in order to estimate an accurate margin level. Furthermore, a mathematical model for estimating the weight of each function is formulated by a simple model. However, AHOM-NWF algorithm will contribute for the perspective of SINR improvement, cell edge spectral efficiency enhancement and outage probability reduction. Simulation results have shown that the AHOM-NWF algorithm enhances system performance more than the other considered algorithms from the literature by 24.4, 14.6 and 17.9%, as average gains over all the considered algorithms in terms of SINR, cell edge spectral efficiency and outage probability reduction respectively.

Robust Optimum and Near-Optimum Beamformers for Decode-and-Forward Full-Duplex Multi-Antenna Relay With Self-Energy Recycling

In this paper, we consider the full-duplex decode-and-forward wireless-powered relaying system, which employs energy harvesting protocol with power splitting. The robust joint optimum relay transmit beamformer and power splitting factor are obtained for the quality of service (QoS)-aware problem for the first time in the literature. The optimum solution is found by analyzing the Karush–Kuhn–Tucker conditions, thanks to the effective reformulation of the problem in an equivalent and simplified manner. In addition, the signal-to-interference-plus-noise ratio (SINR) maximization problem is investigated in order to find the robust optimum solution. The simulation results verify the optimality of the proposed method compared with the sub-optimum one which is presented by Zhao et al. . In the next part of this paper, the considered system is generalized by employing multiple receive antennas at the relay. Both QoS-aware and SINR maximization problems are considered. The near-optimum relay transmit and receive beamformers as well as power splitting factor are found by optimizing the variables alternately. First, transmit beamformer and power splitting factor are found optimally for a given initial receive beamformer. Then, the optimum receive beamformer is obtained. Relay with multiple-receive antennas is shown to perform better than the single receive antenna relay in terms of SINR and transmission power.

How Much FBMC/OQAM Is Better than FBMC/QAM? A Tentative Response Using the POPS Paradigm

A major trend of the current research in 5G is to find well time and frequency localized waveforms, dedicated to non‐orthogonal wireless multi‐carrier systems. The ping‐pong optimized pulse shaping (POPS) paradigm was proposed as a powerful technique to generate a family of waveforms, ensuring an optimal signal to interference plus noise ratio (SINR) at the receiver. In this paper, we derive, for the first time, the analytical expression of the SINR for FBMC/OQAM systems. We then adopt the POPS algorithm in the design of optimum transmit and receive waveforms for FBMC/OQAM, with respect to the SINR criterion. For relatively high dispersions, numerical results show that the optimized waveforms provide a gain of 7 dB, in terms of SINR, compared to the PHYDYAS waveform. They also show that the obtained waveforms offer better out‐of‐band (OOB) emissions with regard to those of the IOTA waveform. Furthermore, we notice that FBMC/OQAM systems present a gain of 4 dB in SINR, compared to FBMC/QAM systems, when both operate at their time‐frequency lattice critical densities. However, FBMC/QAM systems can guarantee, with a reduced computational complexity, a comparable performance to FBMC/OQAM systems, in terms of SINR, when their spectral efficiency is relatively reduced by less than 5%.

Analytical evaluation of heterogeneous cellular networks under flexible user association and frequency reuse

Offloading mobile users from highly loaded macro base stations (BSs) to lightly-loaded small cell BSs is critical for utilizing the full potential of heterogeneous cellular networks (HCNs). However, to alleviate the signal-to-interference-plus-noise ratio (SINR) degradation of so called biased users, offloading needs to be activated in conjunction with an efficient interference management mechanism. Fractional frequency reuse (FFR) is an attractive interference management technique due to its bandwidth efficiency and its suitability to orthogonal frequency division multiple access based cellular networks. This paper introduces a general mathematical model to study the potential benefit of load balancing in conjunction with two main types of FFR interference coordination: Strict-FFR and soft frequency reuse (SFR)- in the downlink transmissions of HCNs. For some special but realistic cases we were able to reduce the rather complex general mathematical expressions to much simpler closed-forms that reveal the basic properties of BS density on the overall coverage probability. We show that although Strict-FFR outperforms the SFR mechanism in terms of SINR and rate coverage probability, it fails to provide the same spectral efficiency. Finally, we present a novel resource allocation mechanism based on the BSs bias values and FFR thresholds that achieves an even higher minimum user throughput and rate coverage probability.

A Novel Algorithm for Improving the SINR of D2D Communication in the Cellular Network

In this paper, we investigate the interference scenario where multiple Device-to-Device (D2D) pairs reuse the spectrum resources allocated to one cellular user, and propose a novel algorithm for improving the signal-to-interference-plus-noise ratio (SINR) of D2D communication. We call this D2D SINR improvement algorithm as DSIA, and design it from the perspective of precoding and decoding. With the DSIA, each D2D pair involved in the network can obtain the corresponding precoding and decoding vectors which make the SINR of its receiver being maximized. In order to clearly describe the design procedure of the proposed algorithm, we first formulate an optimization problem with multiple variables to maximize the SINR of each D2D receiver, then simplify the objective function through mathematical derivation and seek out the relationship between the optimized variables which can transform the optimization problem to one of solving nonlinear equations, and finally propose the DSIA to work out the nonlinear equations. Numerical results show that the DSIA will enable D2D to achieve significant performance gains in terms of SINR and bit-error rate (BER) compared with the traditional spectrum orthogonal scheme.

Be Cautious When Analyzing the Sampling Clock Offset in OFDM Systems

Many studies have analyzed the effects of sampling clock offset (SCO) on orthogonal frequency-division multiplexing (OFDM) systems. The results of these studies are based on one of two discrete representations of continuous time-domain OFDM signals: (1) a subcarrier set consisting of both negative and positive frequencies, or (2) a subcarrier set comprising only positive frequencies. This paper discusses whether there is any difference between the two representations in the presence of SCO. When SCO is not considered, both representations are equivalent because of aliasing. In the presence of SCO, we derive a closed form of signal-to-interference-plus-noise ratio (SINR) expressions for both cases and compare their performances in terms of SINR by numerical analysis. The latter representation shows worse SINR performance compared to the former representation because the effect of SCO is more relevant for high frequencies and the latter representation has complex exponentials with high frequencies. Therefore, for fair comparisons of performance, caution is needed when analyzing SCO in OFDM systems.

Distributed Synchronization and Beamforming in Uplink Relay Asynchronous OFDMA CoMP Networks

In this paper, we use delay-amplify-and-forward relays in the uplink direction of a coordinated multi-point network based on orthogonal frequency division multiplexing. The key novelty is that we assume delay from users to different base stations (BSs), in general, may exceed cyclic prefix (CP) length as might be the case in large cells and cannot be completely compensated by traditional timing advance strategies. Consequently, interchannel interference and intersymbol interference may arise under such assumptions. We first optimize the adjustable delays added at users, relays and BS nodes in order to reduce the effective delay spread at the receive sites, then we optimize relays' weights and post-processing matrices at BS nodes to reduce the residual interference. For this purpose, we propose an iterative method that at each step first fixes either the relay weights or the post-processing matrices and then optimizes the signal-to-interference-plus-noise-ratio (SINR) over the other variable. Furthermore, we investigate the optimization problem of minimizing sum mean square error (SMSE) at the receive side under total relay power constraint. Simulation results show significant improvement in terms of SINR and SMSE in comparison with traditional systems in which no relay is deployed and the limited CP length is not addressed properly.

Analysis of receiver algorithms for lte LTE SC-FDMA based uplink MIMO systems

This letter derives mathematical expressions for the received signal-to-interference-plus-noise ratio (SINR) of uplink Single Carrier (SC) Frequency Division Multiple Access (FDMA) multiuser MIMO systems. An improved frequency domain receiver algorithm is derived for the studied systems, and is shown to be significantly superior to the conventional linear MMSE based receiver in terms of SINR and bit error rate (BER) performance.