Comparative Study of Power Saving and Delay in LTE DRX,Directional-DRX and Hybrid-Directional DRX

With integration of advanced long term evolution networks (LTE networks) in mobile technology, 5G networks are introduced due to broadband spectrum extension which requires higher power consumption. Discontinuous reception (DRX) sleep mode mechanism is provided to accommodate lower power consumption of user equipment terminals (UE_s). For mmWave directional communication air interface in LTE between UE and LTE eNB, UE performs beam searching and alignment with LTE eNB (4G base station) after every short/long DRX cycle during ON duration. Dual connectivity of UE to both LTE eNB and NR NodeB (5G New RAN base station) is a hybrid-directional system. This allows us to propose a sleep mode mechanism which is called hybrid directional-DRX (HD-DRX). In HD-DRX, UE performs beam searching and alignment with NR NodeB during ON duration only if data packet intimation. A semi-Markov chain process is introduced to describe UE state transition. Depending on this chain, power saving factor and average delay are calculated. HD-DRX power saving as compared to LTE DRX and Directional-DRX (D-DRX) is conducted. Due to different beam searching procedure, another comparison of average delay is assigned between D-DRX and HD-DRX. Data traffic model parameters are considered and numerical analysis is validated using MATLAB program simulations.     

Leakage rate analysis with imperfect channel state information for cooperative nonorthogonal multiple access networks

This paper investigates the imperfect channel state information that is caused by the channel estimation error and feedback delay effects on the leakage rate analysis for the cooperative nonorthogonal multiple access networks. The investigation considers a dual hop one‐/two‐way nonorthogonal multiple access‐based information exchange process with the aid of half‐/full‐duplex untrustworthy wireless relaying network for the leakage rate analysis. The channel estimation error causes system coding gain losses while the feedback delay does not have any effect on the users' outage performance at untrustworthy relay terminal in low signal‐to‐noise ratio regimes. Conversely, the channel estimation error effects become negligible while the feedback delay causes system coding gain losses on the users' outage performance at untrustworthy relay terminal in high signal‐to‐noise ratio. Results also reveal that the untrustworthy relay terminal, which is under the effect of the channel estimation error and feedback delay, is being active between and ‐  dB. Beyond ‐  dB, the untrustworthy relay terminal becomes out of order and saturates. The Monte Carlo–based simulation results are in agreement with the analytical and asymptotic derivations.     

Energy Saving Mechanism with a Route Prediction Based Intra-handover in LTE Networks

Long term evolution standard employs the discontinuous reception (DRX) technology to help user equipment (UE) in energy saving. After the UE received nothing from the base station for a predefined time span, it turns off the radio frequency module to enter sleep mode for energy saving. An UE may fail to handover or lost connection for late handover in case it enters sleep mode before handover and missed the optimal handover timing, therefore results in data loss. This paper proposes an energy saving mechanism with a prediction based intra-handover which predicts the next target handover base station and the optimal handover time according to the historical path data kept in a database. The UE would check whether the next sleep mode outlast the handover time point before entering sleep mode to reduce power consumption for handover failure caused by the long DRX cycle and base station reselection. Simulation results show that the DRX mechanism helps reduce power consumption of UE by 90–95 % over the conventional one more than 7 % handover failures. The energy saving mechanism combined with route prediction leads to 22 % more energy saving while cutting handover failures to 5 %.

     

Nonlinear performance evaluation model for throughput of AQM scheme using full factorial design approach

The performance of active queue management (AQM) is measured in terms of throughput, delay, queue size, and loss rate. We have carried out the optimized performance measure of throughput for AQM scheme random early detection (RED) using full factorial design (FDD) technique that is a new approach of performance analysis particularly for congestion control algorithms. We have considered the input factors, viz, buffer size, maximum threshold, and the number of file transfer protocol (FTP) sources for the evaluation of RED that can be used for other AQM schemes, viz, adaptive RED, three‐section RED (TRED), and adaptive queue management with random dropping (AQMRD). The effect of each input factor as well as their interactions are evaluated using factorial design technique that results to obtain the nonlinear equation for performance measure in terms of input factors buffer size, maximum threshold, and the number of FTP sources. Finally, we show the contour plots for variation of performance measure throughput (steady state) from minimum to maximum values with respect to the different setting of input parameters.     

Performance Evaluation of Sleep Mode on Power Saving in WiMAX IEEE 802.16m and LTE DRX

Power saving represents a vital role in mobile communications networks such as IEEE 802.16m and LTE. Modern user equipment (UE_s) require high data rates and low power consumption. It is found that arranging sleep mode mechanisms ensures UE battery longer lifetime. In this paper, different sleep mode mechanisms are investigated for both IEEE 802.16m and LTE networks. The analyses are based on Markov and Semi-Markov chains. It is focused on the determination of UE transition state. Web traffic model parameters were considered in MATLAB simulation and a comparison assessment was conducted between WiMAX IEEE 802.16m and LTE DRX. It was found that LTE DRX sleep mode provides more power saving than WiMAX IEEE 802.16m sleep mode. The study is now implemented for 5G networks with encouraging results.     

A deep learning based latency aware predictive routing model for network-on-chip architectures

Network on Chip (NoC) is an evolving platform for communications related applications, which are executed on a single silicon chip. There are several routing models in NoC architectures, but the accuracy of these models is limited, and the existing models are degraded because of over and under fitting issues. This research introduces the new deep learning-based latency aware predictive routing model for on-chip networks to route packets with better performance and power efficiency. The deep learning model used in this research is a new convolutional residual gated recurrent unit (CRGRU) with queuing theory. Moreover, the source and channel queuing delay is comprised of features to learn spatial and sequential information that improves the overall prediction accuracy. This router is modified by the intrusion of the Router States Monitor unit and the CRGRU hardware engine. The work is executed using the Xilinx platform, and the performance measures like latency and throughput are obtained by varying the network size as $4\times 4$, $8\times 8$, and $12\times 12$ and also varying the buffer space and length as $L=4,B=9$, $L=9,B=4$, and $L=14,B=3$, respectively. In addition, the squared correlation coefficient (SCC) and normalized root mean square error (NRMSE) are evaluated and compared with existing learning models to validate the proposed model.     

On the performance of energy harvesting-assisted Nth best relay cooperative networks in Nakagami-m fading

We study the energy harvesting (EH)-assisted system model based on the performance of a dual-hop cooperative communication system that is subjected to Nakagami- $m$ fading. Through the partial relay selection method, the selection of $N$th best relay (BR) is performed among $M$ amplify and forward (AF) relays, which can harvest energy from radio frequency signals. At the receiver, the selection combining scheme is considered to select between the signals of $N$th best relaying path and the direct path. For this considered system, we compute the closed-form expressions of outage probability (OP) and the average symbol error rate (ASER) for higher order quadrature amplitude modulation (QAM) techniques, especially for rectangular QAM, cross QAM, and hexagonal QAM. Further, a new moment-generating function expression is obtained which is used to derive the ASER expression related to the generalized non-coherent modulation technique. We also give the asymptotic expression of OP to find out the diversity order. Furthermore, we study the effect of fading parameters, $N$th BR, and other factors on system behavior. Finally, we verify the derived expressions with Monte Carlo simulations.     

Spectrum sensing performance of wireless cognitive radio sensor network with hard-decision fusion over generalized α−μ fading channels

The analysis of spectrum sensing performance of energy detection (ED)-based wireless cognitive radio sensor network (ED-WCRSN) with hard-decision combining (HDC) is presented in this paper. Particularly, several network parameters are derived to estimate the performance of ED-WCRSN, considering channel errors, noise, and generalized $\alpha -\mu$ fading. In the considered network, first, cognitive radio sensor (CRS) senses a primary user (PU), gets sensing data, and then uses an ED to make a local binary decisions about PU's active or inactive status. In both sensing and reporting channels, the channel error probability is also taken into account. Next, HDC technique is used at control center (CC) to combine the locally obtained decisions, and a final decision about the status of the PU is made. To do so, first, the expression for the novel and analytical, which incorporates noise and $\alpha -\mu$ fading, detection probability in a CRS is derived and validated using Monte Carlo simulations in MATLAB and using an experimental setup. Then, utilizing derived mathematical expressions, closed-form expressions of an average error rate (AER), optimal numbers of CRSs, and detection thresholds under noisy and $\alpha -\mu$ fading conditions are developed. The substantial influence of channel and network factors is assessed using receiver operating characteristics (ROC), complementary ROC, and AER. Finally, the impacts of channel and network parameters on ED-WCRSN performance are explored. For numerous parameters of the considered network, the optimal values detection threshold and number of CRSs are also found.     

A methodology to benchmark flexible payload architectures in a megaconstellation use case

This paper proposes a methodology to benchmark satellite payload architectures and find the optimal trade‐offs between high flexibility and low complexity. High flexibility would enable the satellite to adapt to various distributions of user terminals on the ground and fulfill the data rate demand of these users. Besides, low complexity is required to keep satellite networks competitive in the context of emerging 5G networks. To estimate the flexibility of a payload, an indicator to characterize the non‐uniformity of user distributions is proposed. Each benchmarked payload may be characterized by a graph relating the throughput to this parameter further denoted . The payload provides the same throughput trends for different scenarios of user distributions with the same parameter. As a consequence, the average capacity of the system may be estimated by (a) calculating the probability distribution of over the orbit and (b) integrating the throughput based on this payload response. It thus results in a straightforward way for benchmarking payloads directly on an estimation of the averaged capacity, accounting for the user distribution over the earth. A simulation platform has been developed to characterize the payload throughput including the implementation of a resource allocation algorithm that accounts for constraints of various payloads. Using this definition and the developed tool, we benchmark a bent‐pipe architecture, a beam hopping architecture and a hybrid beam‐steering architecture for a LEO megaconstellation use case. The methodology showcases the interest for investigating different payload architectures depending on realistic traffic scenario analysis.     

5G终端空闲态节能方案分析

由于大带宽、大规模天线、高速率等新特性的引入,5G终端的能耗问题比4G终端更加严峻,成为影响5G网络用户体验的重要原因之一。3GPP标准化组织开展了与NR终端节能课题相关的研究,R16协议版本主要面向连接态下的终端节能优化,R17协议版本则主要面向空闲态终端节能优化。首先分析了空闲态下的终端节能问题,同时与LTE终端能耗进行对比。针对寻呼检测和时频跟踪过程的能耗问题提出了节能优化解决方案,进行了节能增益分析,该方案可以降低5G终端的能耗,为后续5G商用终端空闲态的节能技术指明了方向。     

ASER analysis of generalized hexagonal QAM schemes for NOMA systems over Nakagami-m fading channels

To achieve high data rates expected from beyond 5G communications, higher-order modulation techniques have been explored. The energy-efficient modulation technique with a high data rate has encouraged researches towards an optimum two-dimensional hexagonal-shaped constellation, namely, hexagonal quadrature amplitude modulation (HQAM). Thus, in this work, we analyze the average symbol error rate (ASER) of HQAM schemes by considering a two-user nonorthogonal multiple access (NOMA) pair. Closed-form expressions for ASER of HQAM schemes for users are derived over generalized Nakagami- $m$ fading channels. Further, for the HQAM constellation feasibility in two-user downlink NOMA systems, the power allocation criterion for the users is presented. Furthermore, the impact of modulation order of the users over the systems ASER analysis is investigated and valuable insights are drawn.     

An application aware discontinuous reception mechanism in LTE-advanced with carrier aggregation consideration

3GPP Release 8 specifications define a mechanism named DRX (Discontinuous Reception) to save UE’s (User Equipment) energy consumption in LTE (Long Term Evolution). The DRX allow an UE to stop monitoring PDCCH (Physical Downlink Control CHannel) on a CC (Component Carriers) during some periods of the operation time. Obviously, the duration and the frequency of these non-monitoring periods are important parameters that can significantly impact the ES (Energy Saving) efficiency and the performance of applications running on the CC. In Release 9, 3GPP introduces an advanced technology named CA (Carrier Aggregation) for LTE-Advanced to achieve higher bandwidth and throughput: the UE may operate over up to 5 CCs. The conventional DRX operations are no longer appropriated in the CA case: applying the same DRX configuration for all the CCs is neither performance-optimal nor energy-efficient if applications with different QoS requirements operating simultaneously on the CCs in realistic environment. A DRX mechanism by taking both applications’ QoS requirement and CA into account to achieve reasonable ES might be an optimal choice. In this paper, based on the survey of various conventional DRX energy saving protocols in LTE networks, we propose a simple but efficient application aware DRX mechanism to optimize the performance in LTE-Advanced networks with CA consideration. The simulation results verify that the ES efficiency is conditioned to the fulfillment of the DRX parameters, and our proposed optimal scheme can significantly improve energy saving efficiency as compared to the conventional DRX mechanism.     

Pilot-aided 1 × 2 and 2 × 2 space-time line code systems with transmit antenna selection

The space-time line code (STLC), which has been recently proposed in the literature, assumes fully known channel state information at the transmitter and not the receiver. However, the effective channel gain is still required at the receiver to coherently detect $M$-ary quadrature amplitude modulation ( $M$QAM) symbols. In this paper, we propose pilot-aided STLC systems, which do not require the effective channel gain at the receiver to detect the $M$QAM symbols. In order to further improve the error performance of the proposed schemes, we present the pilot-aided STLC systems with transmit antenna selection (TAS). Using a more direct and simpler approach, we derive the average symbol error probability (ASEP) of the coherent $1\times 2$ STLC systems with TAS, which represents the lower bound of the pilot-aided $1\times 2$ STLC systems with TAS. For comparison, in a similar manner, we also derive the ASEP of the coherent $2\times 2$ STLC systems without TAS, which represents the lower bound of the pilot-aided $2\times 2$ STLC systems. For pilot-aided $1\times 2$ STLC systems with TAS, the gap between the simulated symbol error rate (SER) and the derived theoretical ASEP lower bound is very small. For a given number of transmit antennas, the simulated SER and theoretical ASEP also show that the error performance of the pilot-aided $2\times 2$ STLC systems with or without TAS is superior to the pilot-aided $1\times 2$ STLC systems with TAS by at least 1.8 dB.     

Path loss model based on exponential water cycle algorithm for wireless sensor network

Wireless sensor networks (WSNs) are frequently employed in the agriculture field to improve the quality and crop yield. The WSN might reduce the quality of the communication link because of the absorption, dispersion, and attenuation through the leaves of plants. Therefore, estimating the path loss due to signal attenuation before WSN deployment is crucial for the smooth operation of the network. In this research paper, three innovative path loss models are defined based on the MATLAB curve fitting tool: polynomial water cycle (PWC), exponential water cycle (EWC), and Gaussian water cycle (GWC) algorithm. Here, the path loss between the router node and the coordinator node is modeled on the basis of the received signal strength indicator (RSSI) and time of arrival (TOA) measurements in a sugarcane field. The correlation coefficient between the RSSI measurement and the distance must be increased to create a precise path loss model. This paper integrates the exponential, polynomial, and Gaussian functions with the water cycle algorithm (WCA) to evaluate the optimal coefficients that would lead to precise path loss models. The performance of the proposed models that determines the optimum linear fit between RSSI and distance is validated using the correction coefficient $R^2$. The results show that the proposed path loss model is superior to existing path loss models. The correlation coefficient $R^2$ of the proposed EWC model is 0.9993, whereas the existing PE-PSO, LNSM, and PSO-Exponential models yield 0.98, 0.87, and 0.93, respectively. Also, the proposed models attain the best mean absolute error (MAE) of 0.2187, 0.2951, and 0.3457 dBm for EWC, PWC, and GWC algorithms, respectively.     

4G与5G双网共存时能效最优策略

无线网络的能量效率逐渐成为评估网络的重要指标，4G与5G能效存在差别，双网共存时，如何提高无线网络能效至关重要。为分析4G与5G能效差异，从基站能耗组成出发，通过实测数据建立4G和5G基站能耗模型，然后进行仿真，计算其能效。结果表明，4G和5G存在各自能效占优区间，单站吞吐量小于500 Mbit/s时，4G效更优；单站吞吐量大于500 Mbit/s时，5G能效更优。双网共存时，吞吐量小于500 Mbit/s时只开4G；吞吐量大于500 Mbit/s，只开5G，单站功耗可降低53.4%，能效可提升116.4%。     

Multitier heterogeneous network using stochastic geometry and factorial moment approaches

The rapid growth of small cells is driving cellular network toward randomness and heterogeneity. Usually, cellular networks are modeled by placing each tier (eg, macro, pico, and relay nodes) deterministically on a grid. In such a heterogeneous cellular network, the rational approach to characterize the base stations (BSs), user, and relay locations is by using random spatial models. When calculating the metric performances such as coverage probability, these networks are idealized without consideration of interference. Therefore, interference modeling remains the key issue for the deployment of small cells. This paper developed a single and multitier cellular network model that captures the downlink heterogeneous cellular network with variable parameters such as the target signal‐to‐interference ratio (SIR), transmitted power, and deployment density. In particular, we model ‐tier transmission and compare it with a single‐tier and traditional grid model to obtain tractable coverage probability using stochastic geometry and factorial moment. The obtained results demonstrate the effectiveness and analytical tractability to study the heterogeneous performance.     

Outage analysis of SWIPT‐based full‐duplex cognitive NOMA downlink system over Nakagami‐m fading channels

Cognitive nonorthogonal multiple access (NOMA) technique allows multiple users to share the same time and same frequency resources to fulfil the reliability and spectral efficiency requirements of 5G communication standards. In this paper, simultaneous wireless information and power transfer (SWIPT)–based full‐duplex cognitive NOMA downlink system is proposed. In this system, secondary source (SS) serves as a relay to far primary user as there is no direct link from the primary source. NOMA technique is used at SS to transmit information to far primary user and secondary user. The time switching mechanism is adopted at SS for harvesting energy and information decoding. Analytical closed‐form expressions are derived for the outage probabilities of both primary and secondary users. Outage analysis is carried out in Nakagami‐ fading environment in the presence of self‐interference at SS. In addition to that, the optimal harvesting time to maximize the instantaneous throughput of the far primary user is also derived. Numerical results are plotted to validate the derived expressions. It is inferred that the outage probability of the proposed system depends on the fading environment, harvesting parameters, and self‐interference at SS.     

Optimal scheduling of coordinated multipoint transmissions in cellular networks

In this paper, we study the optimal scheduling problem in coordinated multipoint (CoMP) transmission–based cellular networks. We consider joint transmission and coordinated scheduling together in CoMP transmission–based cellular networks and develop an optimization framework to compute the optimal max‐min throughput and the optimal scheduling of the transmissions to the users. The optimization problem is found to be a complex linear program with number of variables in for a cellular network of N users and K cells. We solve the optimization problem for several network instances using an optimization tool. The numerical results show that the optimal CoMP transmission provides a significant throughput gain over a traditional transmission. We find that in optimal scheduling the fraction time of coordinated scheduling is higher than that of joint transmission. To solve the optimization problem without any optimization tool, we propose a heuristic algorithm. The performance of the heuristic algorithm is evaluated and found to be provided throughput around 97% of the optimal throughput. Further, we extend the optimization framework to study joint scheduling and power allocation (JSPA) problem in CoMP transmission–based cellular networks. We numerically solve the JSPA problem for the network instances and demonstrate that the optimal power allocation at the base stations is not binary for a significant fraction of time of scheduling. However, the gain in max‐min throughput by the optimal JSPA technique over the optimal scheduling technique is not significant.     

Performance analysis of intelligent reflecting surface-assisted mobile wireless networks subjected to generalized Gaussian noise

Different from the prior works, this paper presents the performance analysis of an intelligent reflecting surface (IRS)-assisted communication link in a static and mobile scenario impaired by Rayleigh fading and additive white generalized Gaussian noise (AWGGN). Precisely, the IRS is configured as an intelligent access point, and the mobile behavior of the nodes is characterized by the random waypoint (RWP) model. To this end, closed-form expressions of average bit error rate (BER), average channel capacity (ACC), and outage probability (OP) in both static and mobile scenarios are obtained. To gain further insight into the system performance at high signal-to-noise ratio (SNR), asymptotic expressions are obtained. Moreover, the effect of the number of reflective elements ( $N$) and the shaping parameter ( $\lambda$) on the system performance is thoroughly studied. The results indicate that introduction of IRS leads to significant improvement in the overall system performance. The derived results are corroborated with Monte Carlo simulations.     

Cooperation-enabled energy efficient base station management for dense small cell networks

Dense small cell networks are deployed for future wireless communication to meet the ever-increasing mobile traffic demand. However, network densification will significantly increase the energy budget and lead to energy inefficiency due to the constant operation of network hardware. In this paper, we consider cooperation-enabled dynamic base station (BS) management for downlink dense small cell networks. By introducing two traffic-aware sleep modes, i.e., deep sleep mode and opportunistic sleep mode which are operating in different time and energy consumption scales, the network hardwares are turned to be the resources that can be occupied and released dynamically. Small cell BSs (SBSs) with zero or low load are completely switched off and reside in deep sleep mode during a predefined time interval. At each time slot, SBS dynamically turn some antennas and associated physical components into opportunistic sleep mode according to the short term traffic distribution, and the users are jointly served by the remaining antennas via cooperative transmission. The corresponding sleep mode decision making are presented respectively to find the optimal number of SBS and antennas that should be switched off. Numerical results are then presented to illustrate the superior performance in terms of energy efficiency gain. In summary, the proposed cooperation-aided sleep strategies for dense small cell networks take both traffic features and optimal cooperative transmission into account, and can achieve great energy saving while maintaining required quality of service.