System-level performance evaluation of winner system

In multi-user multiple input multiple output (MIMO) systems, the non-orthogonal multiple access (NOMA) method based spatial modulation (SM) and generalized spatial modulation (GSM) can mitigate inter-user interference. However, the spectral efficiency of these methods is restricted because of antenna configuration. In this paper, a combination of the variable active antenna spatial modulation (VASM) scheme with the downlink power domain NOMA system, so-called NOMA-VASM, is proposed to improve spectral efficiency while main-taining mitigation of inter-user interference. In the novel NOMA-VASM, the antenna configuration is arbitrary and the number of enabled transmitting antennas (TAs) can be altered, so it is easier to increase spectral efficiency compared to NOMA-SM and NOMA-GSM. Monte Carlo simulations were performed under various scenarios, and the results showed that NOMA-VASM outperformed conventional NOMA-SM and NOMA-GSM in terms of spectral efficiency, average bit-error-rate (ABER) performance, and required number of TAs.

Adaptive orthogonal frequency division multiplexing (OFDM) has been shown to have significant improvement over basic OFDM in terms of spectral efficiency and bit error rate performance. However, the most important condition to achieve these benefits is the availability of accurate channel state information (CSI) at the transmitter. Imperfect CSI arises from noise at the receiver and due to a delay in providing the CSI from the receiver to the transmitter for the next data transmission. In this paper, we have studied the impact of imperfect CSI on the spectral efficiency of adaptive OFDM systems. We have proposed a robust loading algorithm to improve the performance of such systems. This algorithm applies the bit under loading phenomenon and makes efficient use of M-ary Phase Shift Keying (MPSK) modulation. Plots of spectral efficiency via simulations are provided.

Femto cell deployment creates a pre-dominate effects in the world of Long Terminal Evolution-Advanced (LTE-A). Such deployment in Marco cell will enhance the coverage up to a large extends into building premise. Also, it doesn't need any frequency planning. However, major concern with respect to the Femto deployment is its resource allocations along with Marco and mobility of Home evolved NodeB (HeNodeB) at the building premises. This Paper suggests a method of scheduling in Femto-Marco cell when frequent handover occur at the pedestrian speeds. This demands an improved scheduling in Marco cell and Femto cell. Hence, in this paper we investigate scheduling techniques, namely, Fair Proportion (FP), Modified-Largest Weighted Delay First (MLWDF) and Exponential Scheduling (ES). The performance of the network is analyses in term of spectral efficiency, throughput and delay, found to be more effective compare to existing method used in literature. Combined MLWDF-ES has 38% better spectral efficiency compared to the literature value.

Due to directional propagation of light signals, visible light communication (VLC) channel quality is sensitive to the distance and the angle between a VLC access point (AP) and a VLC terminal. When a terminal is mobile, VLC channel gain varies with the position of the terminal. Considering rotations of a terminal during mobility, channel variations are even more severe. As a result, data rates need to be adapted according to variable link qualities. The commonly used feedback-based adaptive modulation and coding (AMC) scheme cannot catch up with channel variations in VLC, resulting in staircase-shaped adaptation results. Smoother adaptation can be achieved by the seamless rate adaptation (SRA) scheme via rate compatible modulation (RCM). However, SRA does not provide an effective way to increase symbol distances, so the improvement on spectral efficiency is small. To address the shortcomings in the existing schemes, rateless adaptation (RLA) is developed for VLC systems in this paper based on spinal codes. With RLA, smooth rate adaptation is accomplished without channel state information (CSI) feedback, and spectral efficiency is also greatly improved. Simulation results show that, in mobile scenarios, RLA achieves at least 46% improvement over AMC and 19% improvement over SRA in terms of spectral efficiency.

Adaptive M-QAM systems with maximal-ratio diversity (MRD) over composite arbitrarily correlated Nakagami-m fading and log-normal shadowing channels are analyzed. The slow adaptive modulation (SAM) technique is considered which adapts the constellation signaling to slow channel variations and achieves good performance in terms of spectral efficiency (SE) and bit error outage (BEO) despite its low feedback rate. Non-ideal channel estimation (CE) based on pilot symbols is assumed. Analytical expressions and tight bounds for the bit error probability are obtained which are used for deriving analytical expressions and tight bounds for the BEO and achieved SE (ASE). Performance evaluation results have shown that fading correlation and CE errors degrade the performance of SAM systems. The partition of resources for CE and information data requires a careful definition of the ASE and results have shown the tradeoff between CE quality and ASE.

In this paper, the spectral efficiency (SE) of an uplink hardware-constrained cell-free massive multi-input multi-output (MIMO) system with maximal ratio combining (MRC) receiver filters in the context of superimposed pilots (SPs) is investigated. Tractable closed-form SE expressions for the considered system are derived, which share us with opportunities to explore the impacts of the hardware quality coefficient, the length of coherence interval, and the power balance factor between pilot and data signals. Numerical results indicate that the achievable SE deteriorates as the hardware quality decreases and is more susceptible to the hardware impairments at the user equipments (UEs). Besides, we observe that SPs outperform regular pilots (RPs) in terms of SE and this performance gain is heavily dependent on the values of power balance factor and coherence interval. However, the superiorities of SPs over RPs have vanished when severe hardware imperfections are considered.

We propose a superposition-based adaptive modulated STBC (SPAM-STBC) for MIMO-OFDM systems to improve adaptive modulation optimization of space time block coding (STBC). When transmit antennas have the different channel conditions, the previous adaptive modulated STBC selects the same modulation based on averaging of the multiple channel gains. If the different modulation is selected to each transmit antenna, the STBC decoding problem occurs. In this letter, we select the optimal modulation corresponding to each channel condition by the superpositioned space time encoding and decoding. Simulation shows the proposed SPAM-STBC scheme outperforms both the fixed and adaptive modulated STBC schemes by the maximum 0.407 bits/sec/Hz in terms of spectral efficiency.

Recently, technological developments have enhanced, the use of Millimeter-wave (mm-Wave) Multiple Input Multiple Output (MIMO) system in various communication applications and wireless sensor networks as channel estimation efficiency can be immensely improved with the help of this technological developments in Millimeter-wave MIMO system and wireless sensor network as well. Moreover, they can improve quality of communication services to a great extent. However, cell interference in Millimeter-wave (mm-Wave) MIMO system can produce a massive impact on spectral efficiency. Therefore, a Routing Enabled Channel Estimation (RECE) technique is presented in this article to minimize interference between cells. The proposed Channel Estimation technique improves channel capacity as well as spectral efficiency. Moreover, Normalized Mean Square Error (NMSE) is minimized heavily using proposed RECE technique. Here, main aim of this article is to reduce cell interference and channel estimation inside a cell by using route selection, beam selection, and spatial frequency estimation. Here, different scenarios and parameters are considered to evaluate performance efficiency of proposed RECE technique in terms of spectral efficiency, NMSE and SNR and compared against varied traditional channel estimation techniques. Moreover, it is clearly evident from performance results that the proposed channel estimation technique performs better than the other two methods.

The use of Millimeter-wave (mm-Wave) has recently immensely enhanced in various communication applications due to massive technological developments in wireless communications. Furthermore, mm-Wave consists of a high bandwidth spectrum that can handle large demands of data transmission and internet services. However, high interference is observed in previous research at the time of spectrum handover from secondary (unlicensed) users to primary (licensed) users. Thus, interference reduction by achieving high spectral efficiency and an easy spectrum handoff process with minimum delay is an important research area. Therefore, a Hybrid Pre-coder Design based Spectrum Handoff (HPDSH) Algorithm is proposed in this article to increase spectrum efficiency in Cognitive Radio Networks(CRNs) and to access the large bandwidth spectrum of mm-Wave systems to meet the high data rate demands of current cellular networks. Moreover, a HPDSH Algorithm is presented to enhance spectral efficiency and this algorithm is utilized to take handover decisions and select backup channels. Here, different scenarios and parameters are considered to evaluate the performance efficiency of the proposed HPDSH Algorithm in terms of spectral efficiency and Signal to Noise (SNR) ratio. The proposed HPDSH Algorithm is compared against precoding methods like the OMP algorithm and SIC based methods.

In this paper, we delve into the maximized spectral efficiency (SE) of millimeter-wave (mmWave) multicell multiuser massive MIMO Systems for uplink transmission with low-resolution phase shifters (LRPSs). Millimeter-wave massive multiple-input multiple-output (mMIMO) is an important technology for upcoming cellular networks which will provide higher bandwidth and throughput than current wireless systems and networks. LRPSs are commonly used to minimize power consumption, maximize spectral efficiency and diminish the complexity of hybrid precoder and combiner. In this paper, we consider a hybrid analog-digital precoder and combiner design with LRPSs for mmWave multi-cell multiuser mMIMO systems for uplink transmission to spectral efficiency in terms of iterations. The proposed technique outperforms when compared to traditional optimization approaches concerning spectral efficiency and bit error rate (BER). We show through simulation results that our designs with LRPSs outperform standard iteration procedures.

Spectrum prediction based sensing schemes minimize the overall energy consumption of the sensing module in cognitive radio networks (CRNs) by predicting the status of spectrum before performing actual physical sensing. But, the performance of independent or local prediction models suffer from inaccuracies. Cooperative mode of spectrum prediction is found to be suitable to overcome the issues of local prediction models. In this work, we propose a cooperative spectrum prediction-driven sensing scheme for energy constrained cognitive radio networks to reduce the energy consumption while maintaining the spectral efficiency. The proposed scheme first employs a long short term memory network technique to perform local spectrum prediction, which identifies the status of a channel before actual sensing to improve energy efficiency. Thereafter, a parallel fusion based cooperative spectrum prediction model is applied to minimize the errors induced in local prediction model. Finally, the resultant cooperative prediction model is combined with a spectrum sensing framework to perform sensing operation when the cooperative spectrum prediction results to an indeterminate state in order to enhance the spectral efficiency. Simulation results show the efficacy of the proposed scheme in terms of spectral efficiency and energy efficiency compared to similar schemes from literature.

Device-to-device (D2D) communication plays an important role in the next generation of communication systems. Enabling D2D communication decreases latency and expands the coverage of a cell in cellular networks. In addition, D2D underlaying cellular users benefit from high spectral efficiency. However, it creates interference to cellular communications. In this paper, we propose a genetic algorithm-based method to minimize the interference and maximize the spectral efficiency. One of the advantages of genetic algorithm is that it escapes from local maximums and evolves toward global maximum by searching different parts of search space simultaneously. Since D2D underlay cellular network degrades the signal-to-interference plus noise ratio (SINR), a minimum SINR is considered for cellular users. Numerical evaluations demonstrate the superior performance of the proposed technique in terms of spectral efficiency and interference mitigation.

Successive Interference Cancellation (SIC) is a potentially powerful technique for improving the performance of multi-hop wireless networks, owing to its ability to enable concurrent receptions from multiple transmitters as well as interference rejection. In this paper, we address the problem of finding the route with maximal end-to-end spectral efficiency in multi-hop wireless networks, under the constraint of optimal bandwidth sharing. By taking advantage of SIC, more transmission opportunities are exploited by the nodes along the selected path. We formulate a cross-layer optimization framework to quantify the spectral efficiency improvement with SIC and then make use of several structural properties to derive exact solutions. Additionally, three SIC-based routing alternatives with low computational complexity are proposed, on the basis of the conventional shortest path algorithm, to obtain spectrum-efficient routes. Numerous simulation results verify that SIC can bring significant gains in terms of spectral efficiency.

Relay networks face a fundamental challenge in terms of spectral efficiency, because relays must repeat the source information. To address this key problem, this paper presents two relay selection protocols that salvage spectral efficiency by adroitly leveraging the multiple relays. Both protocols have the feature of letting the source transmit all or most of the time. The diversity-multiplexing tradeoff (DMT) of Zheng-Tse is used to show the advantage of our protocols. The proposed protocols require minimal overhead and feedback, and have similar complexity compared to existing protocols.

Light fidelity (Li-Fi) systems based on the orthogonal frequency division multiplexing (OFDM) scheme have gained more attention in the communications circles, as a means to provide high spectral efficiency and ensure stricter data rate requirements for visible light communication (VLC) systems. However, common OFDM schemes employ Hermitian symmetry to obtain a real-valued signal which is necessary in intensity modulation and direct detection (IM/DD) optical systems, at the expense of doubling the required bandwidth. In this paper, a novel transmission scheme for an OFDM-based Li-Fi system is proposed to tackle the issue in question. A new approach to complex signal mapping (CSM), based on the pairing function method, has been developed for Li-Fi systems. It does not require Hermitian symmetry and, hence, saves about 50% of the required bandwidth. Unlike existing OFDM-based VLC approaches, the proposed scheme employs CSM to ensure a real and positive signal without Hermitian symmetry in order to fully utilize the bandwidth available to Li-Fi networks. Simulation results show that the proposed scheme significantly outperforms other systems in terms of spectral efficiency. The CSM-OFDM based Li-Fi system also achieves a good peak-to-average power ratio (PAPR) reduction with acceptable bit-error-rate (BER) performance, compared to conventional approaches.