Power Control Mechanism Research Articles

LQG Control via Wireless Sensor Networks with Minimal Transmission Power

This study concerns control of dynamical systems via wireless sensor nodes with minimal transmission power. In particular, we jointly design a controller and a transmission power control mechanism that adjusts the transmit power of a wireless sensor node. We develop a framework for achieving the minimum expected transmit power required for a specific level of the LQG control performance. We model the communication channel between the wireless sensor node and the controller by an AWGN channel compatible with the IEEE 802.15.4 standard, which was formed for the specification of low-data-rate and low-power wireless communication. We use dynamic programming to characterize the optimal policies, and show that there exists a separation between the designs of the optimal estimator, optimal controller, and optimal transmission power control mechanism.

Resource Allocation for Cellular-based Inter-Vehicle Communications in Autonomous Multiplatoons

With the significant population growth in megacities everywhere, traffic congestion is becoming a severe impediment, leading to long travel delays and large economic loss on a global scale. Platooning is a promising intelligent transportation framework that can improve road capacity, on-road safety, and fuel efficiency. Furthermore, enabling inter-vehicle communications within a platoon and among platoons (in a multiplatoon) can potentially enhance platoon control by keeping constant inter-vehicle and inter-platoon distances. However, an efficient resource allocation (RA) approach is required for the timely and successful delivery of inter-vehicle information within multiplatoons. In this paper, subchannel allocation scheme and power control mechanism are proposed for LTE-based inter-vehicle communications in a multiplatooning scenario. We jointly consider the evolved multimedia broadcast multicast services and device-to-device (D2D) multicast communications to enable intra- and inter-platoon communications such that a desired tradeoff between the required cellular resources and the imposed communication delay can be achieved. Simulation results are given to demonstrate that the proposed approaches can reduce the communication delay comparing to D2D-unicast based RA scheme, especially in a multiplatoon scenario with a large number of vehicles.

Massive MIMO-Enabled Full-Duplex Cellular Networks

In this paper, we provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the self-interference (SI) channels follow the Rician distribution and other channels are Rayleigh distributed. To facilitate bi-directional wireless functionality, we adopt (i) a downlink (DL) linear zero-forcing with self-interference-nulling (ZF-SIN) precoding scheme at the FD base stations (BSs), and (ii) an uplink (UL) self-interference-aware (SIA) fractional power control mechanism at the FD user equipments (UEs). Linear ZF receivers are further utilized for signal detection in the UL. The results indicate that the UL rate bottleneck in the baseline FD single-antenna system can be overcome via exploiting massive MIMO. On the other hand, the findings may be viewed as a reality-check, since we show that, under state-of-the-art system parameters, the spectral efficiency (SE) gain of FD massive MIMO over its half-duplex (HD) counterpart largely depends on the SI cancellation capability of the UEs. In addition, the anticipated two-fold increase in SE is shown to be only achievable with an infinitely large number of antennas.

A Power Control and Anticolision Mechanism for RFID Systems

RFID (Radio Frequency IDentification) applications require identification of large number of tags, which results in increased collisions and degradation in the performance of traditional DFSA (Dynamic Frame slot ALOHA) algorithms. This paper proposes a power control mechanism to estimate the amount of tags in RFID networks. The mechanism is based on the division of the interrogation zone in sub-areas called clusters. This division is used to interrogate in a single slot all tags of a cluster, perform measurements of RSSI and, with it, estimate the amount of tags per cluster. The mechanism is simulated and evaluated using our own simulator developed in C/C ++ programming language. We compared the results of number of slots, identification time and energy consumption with that obtained from the use of the optimal DFSA algorithm and Q algorithm of the EPCglobal standard. From the simulation results, one can see that the proposed mechanism provides performance 99% close to the ideal DFSA in dense networks, where there are large amount of tags.

Joint Scheduling and Transmission Power Control in Wireless Ad Hoc Networks

In this paper, we study how to determine concurrent transmissions and the transmission power level of each link to maximize spectrum efficiency and minimize energy consumption in a wireless ad hoc network. The optimal joint transmission packet scheduling and power control strategy are determined when the node density goes to infinity and the network area is unbounded. Based on the asymptotic analysis, we determine the fundamental capacity limits of a wireless network, subject to an energy consumption constraint. We propose a scheduling and transmission power control mechanism to approach the optimal solution to maximize spectrum and energy efficiencies in a practical network. The distributed implementation of the proposed scheduling and transmission power control scheme is presented based on our MAC framework proposed in [1]. Simulation results demonstrate that the proposed scheme achieves 40% higher throughput than existing schemes. Also, the energy consumption using the proposed scheme is about 20% of the energy consumed using existing power saving MAC protocols.

A Hybrid MAC Protocol with Multi-slot Reservation for Dense Wireless Ad-Hoc Networks

Dense wireless ad-hoc networks (DWAN) is developed with explosive growth of users and traffics, which means that the future network will bear more frequent and intensive communication services under the condition of limited spectrum resource. To meet the requirement of DWAN, an efficient medium access control (MAC) design has been a hot research topic. Towards the current MAC protocols, we mainly focus on addressing two issues in DWAN: (1) serious collisions; (2) low efficiency of spectrum utilization. In this paper, we propose a hybrid MAC with multi-slot reservation for DWAN, called MRPMAC, which is based upon the architecture of the carrier sense multiple access/collision avoidance and time division multiples access. In the proposed MRPMAC protocol, the network collisions are alleviated by using multi-slot reservation (MSR) scheme, and the frequency spectrum efficiency is improved through power control mechanism. Concretely, just with one handshake in the proposed MRPMAC protocol, multiple slots are reserved and multiple concurrent data transmissions are periodically initiated over single channel without collisions. Therefore, spectrum reusing can be achieved, the network throughput is greatly improved as well as quality of service can be ensured in DWAN. Furthermore, the upper bound of slot utilization in MRPMAC is analyzed. Through simulations using ns-2 simulator, we validate that the upper bound of throughput gain brought by power control scheme in MRPMAC is twice as high as pure MSR scheme, and demonstrate that system throughput of MRPMAC outperforms IEEE 802.11 DCF and POWMAC about 150 and $$67\%$$ , respectively.

Resource Allocation Based on Channel Sensing and Spatial Spectrum Reuse for Cognitive Femtocells

A cognitive femtocell is a new small cell based on a smart home base station to solve the spectrum-scarcity problem. Recently, dedicated resource allocation for cognitive femtocell to mitigate co-channel interference is extensively researched. However, the cognitive femtocell may suffer from the lack of frequency resource for its users due to high data traffic load of the macrocell. We propose a novel resource allocation and power control mechanism using spatial frequency reuse and spectrum sensing, which enables femto users in the cognitive femtocell to obtain more feasible resource. We analyze and evaluate the performance gain of the proposed scheme. Although data traffic load of the macrocell increases, the capacity of the cognitive femtocell can be maintained appropriately by the proposed resource allocation and power control scheme and it is shown that the performance is improved compared to that of the conventional scheme.

Distributed Power Control for Delay Optimization in Energy Harvesting Cooperative Relay Networks

We consider cooperative communications with energy harvesting (EH) relays, and develop a distributed power control mechanism for the relaying terminals. Unlike prior art which mainly deal with single-relay systems with saturated traffic flow, we address the case of bursty data arrival at the source cooperatively forwarded by multiple half-duplex EH relays. We aim at optimizing the long-run average delay of the source packets under the energy neutrality constraint on power consumption of each relay. While EH relay systems have been predominantly optimized using either offline or online methodologies, we take on a more realistic learning-theoretic approach. Hence, our scheme can be deployed for real-time operation without assuming acausal information on channel realizations, data/energy arrivals as required by offline optimization, nor does it rely on precise statistics of the system processes as is the case with online optimization. We formulate the problem as a partially observable identical payoff stochastic game (PO-IPSG) with factored controllers, in which the power control policy of each relay is adaptive to its local source-to-relay/relay-to-destination channel states, its local energy state as well as to the source buffer state information. We derive a multi-agent reinforcement learning algorithm which is convergent to a locally optimal solution of the formulated PO-IPSG. The proposed algorithm operates without explicit message exchange between the relays, while inducing only little source-relay signaling overhead. By simulation, we contrast the delay performance of the proposed method against existing heuristics for throughput maximization. It is shown that compared with these heuristics, the systematic approach adopted in this paper has a smaller sub-optimality gap once evaluated against a centralized optimal policy armed with perfect statistics.

Mitigating Uplink Interference in Femto–Macro Coexisted Heterogeneous Network by Using Power Control

In the femto–macro coexisted heterogeneous network, the uplink transmission of femtocell user equipment (FUE) interferes with the macrocell base station (MBS) and deteriorates the capacity of macrocell user equipments (MUEs). To mitigate the cross-tier interference, a power control mechanism is proposed to adjust transmission power of FUE. The approach of this paper is to derive the minimum transmission power to achieve the required modulation and coding scheme and the maximum transmission power without violating the maximal tolerable interference of MBS, respectively. By selecting the minimum one among the two derived transmission power and the maximum allowable transmission power of an FUE as the transmission power of each FUE, the cross-tier interference from FUEs to MBS are alleviated. Simulation results show that when femtocells and macrocell are operated in the co-channel allocation approach, the average capacity of MUEs by using the proposed power control mechanism can be increased by 53.4% as compared to that without power control when 40 femtocells are deployed. The cost for the improvement is a reduction in the average FUE capacity by 7.3%. When the hybrid channel allocation approach is employed, the average capacity of MUEs can be further increased by 21.3%. Hence, the proposed power control mechanism is an efficient solution to mitigate the cross-tier interference and improve the average capacity of MUE with an acceptable reduction in the capacity of FUEs for the femto–macro coexisted heterogeneous network.

A Novel Resource Allocation and Power Control Mechanism for Hybrid Access Femtocells

LTE Small cells like Femto cells are being deployed in enterprises and residential buildings to improve data rates of indoor users who experience low Signal-to-Interference plus Noise Ratio (SINR) from Macro Base Stations (MBSs). Deployment of Femto cells inside a building can lead to signal leakage at the edges/corners of the buildings. This causes cross-tier interference and degrades the performance of users in High Interference Zone (HIZone) around the building area, who are connected to one of the MBSs in LTE Heterogeneous Networks (HetNets). Hybrid Access Femto cells (HAFs) can ensure QoS for paid Subscriber Group (SG) users by giving them preferential access to resource blocks over non-SG (NSG) users and also improve the throughput of LTE HetNet system by serving nearby NSG users. In this work, we address various challenges involved in deployment and operation of HAFs in indoor environments by proposing an Optimal Placement of Femto cell (OPF) model, a dynamic Bandwidth Allocation (BWA) mechanism for splitting resource blocks between SG and NSG users, a dynamic power control mechanism to mitigate co-tier and cross-tier interference in HetNets and an Enhanced Priority (EP) scheduling mechanism to give more priority to SG users over NSG users.During peak traffic load scenarios, HAFs may not be able to guarantee QoS of both indoor and HIZone users connected to them. As HAFs are primarily meant for indoor users, HAFs employ an Optimal Power Control (OPC) mechanism to tune their transmit powers so that HIZone users are offloaded to near-by MBSs. Since the OPC is a Mixed Integer Non-linear Programming (MINLP) problem, we put forth a Sub-Optimal Power Control (SOPC) mechanism. The SOPC mechanism boosts the throughput of MBSs by almost 62% over the traditional 3GPP proposed enhanced Inter-Cell Interference Co-ordination (eICIC) mechanism for 300 users in the HetNet system. Also, the proposed EP scheduling mechanism maintains Jain’s fairness index of 0.99 for both SG and NSG users while providing a 40% higher per user throughput than that obtained with the legacy proportional fair and Priority Set schedulers.

Outage Probability of Device-to-Device Communications in Frequency Reuse-1 Networks

In this paper, we analyse the outage probability of Device-to-Device (D2D) communications in a multi-cell frequency reuse-1 (FRF-1) system. We derive a formula for outage probability of a D2D link in the FRF-1 system when uplink resource sharing between cellular users and D2D users is enabled in the network. Based on this analysis, we propose a location-based power control mechanism for D2D which can enhance the outage performance of the D2D link, and at the same time, reduce the transmit power required for communication.

다중셀 상향링크 네트워크에서 기밀 전송률 향상을 위한 전력조절 기법

본 논문에서는 무선 다중셀 다중 사용자 네트워크에서 전송용량과 도청용량의 차로 정의되는 기밀용량을 증대시키기 위한 단말의 전력조절 기법을 제안한다. 모의실험 결과를 통해 제안 전력조절 기법과 임계값 기반의 스케줄링의 결합이 다중셀 환경에서 기밀 전송률을 상당히 향상시킬 수 있다는 것을 확인하였다. In this letter, we propose a power control mechanism in order to improve secrecy rate defined as the difference between capacity of main link and wiretap link in a wireless multi-cell multiuser network. Through simulations, we verify that the proposed power control mechanism with threshold based user scheduling can significantly increase secrecy rate in a multi-cell environment.

GreenCoMP: Energy-Aware Cooperation for Green Cellular Networks

Switching off base stations (BSs) is an effective and efficient energy-saving solution for green cellular networks. The previous works focus mainly on when to switch off BSs without sacrificing the traffic demands of current active users, and then enlarge the coverage of the stay-on cells to cover as many users as possible. Based on this objective, both constant power and transmission power of each BS become the major energy consumption sources. However, the transmission powers of enlarged cells, which have not been taken into account in previous research, are not negligible as compared to other energy consumption sources. To tackle this problem, we observe that the transmission power of one specific BS could be reduced via cooperation among two or more BSs, which is typically used to improve the throughput or enhance the spectrum efficiency in wireless systems. The challenges come mainly from how to jointly consider which BSs to switch off and how to cooperate among active-mode BSs. In this paper, we design energy-aware cooperation strategies that ensure that our system is energy-saving while satisfying user demands. To cope with sleep-mode BSs and perform cooperation among active BSs, we formulate this problem as a binary integer programming problem, and prove it is NP-hard. Based on our formulation, we derive a performance lower bound for this problem via Lagrangian Relaxation with search enumeration. Furthermore, we propose two heuristic algorithms accounting for the properties of energy savings and the constraints of bandwidth resources. The simulation results show that our algorithms outperform pure power control mechanisms that do not consider the transmission power and pure cooperation without power control in terms of the total consumed energy. We also observe that larger cooperative size does not imply a better strategy under different scenarios. Compared to the total consumed energy given that all BSs are turned on, our algorithms can save up to 60 percent of energy. This demonstrates that our methods are indeed efficient energy-saving cooperation strategies for green cellular networks.

Power Control in Mac Protocol for Wireless Networks using Hybrid Optimization Techniques

Objectives: To propose power control techniques used in MAC protocol for wireless networks. Methods/Statistical Analysis: Energy reductions techniques are essential for wireless networks, as battery powered wireless hosts have limited energy. Hence energy aware techniques with power saving mechanisms are restored to conserve energy of nodes in wireless networks. Power based connectivity is an ad-hoc implements power control mechanisms to enhance network life by improving throughput, cost effective routes and spatial reuse. This study proposes hybrid optimization for “Medium Access Control (MAC)” protocol to implement coordination functions and power control mechanisms. Hybrid optimization is based on “Genetic Algorithm (GA)” and “Gravitational Search Algorithm (GSA)”. Findings: Experiments with hybrid optimization are compared to GA fuzzy rules and Fuzzy methods. The result reveal that two hop power control with GA fuzzy logic method lowers route discovery time, increases cache replies, minimizes simulation time and end to end delay in contrast to DSR routing and two hop routing protocols. Application/Improvements: The new hybrid GA-GSA has a throughput of 8.89% and 1.62% and low end to end delay of 13.66% and 2% compared to Fuzzy and GA based Fuzzy respectively.

On the spectral coexistence of GSO and NGSO FSS systems: power control mechanisms and a methodology for inter‐site distance determination

SummaryThe coexistence of geostationary satellite orbit (GSO) and non‐GSO (NGSO) fixed satellite service systems within the same spectrum to enhance the spectrum efficiency in Ka band has attracted many interests lately. However, the coexistence of GSO‐NGSO satellite systems with limited shared spectrum can cause in‐line interference from a satellite to other satellite's earth terminals. In this context, this contribution investigates three possible power control approaches to mitigate the in‐line interference caused by an NGSO satellite to the GSO earth terminal, while the NGSO satellite is crossing the GSO satellite's illumination zone. Moreover, three types of interference mitigation techniques, namely, range‐based, traffic‐aware, and cognitive power control techniques are investigated. Furthermore, to increase the spectrum efficiency of the GSO‐NGSO fixed satellite service terrestrial network, we formulate and solve an optimization problem with the objective of minimizing the inter‐site distance between earth user‐terminals. More specifically, we find the minimum distance from a GSO earth terminal, where an NGSO earth terminal can be implemented subject to minimizing received interference level at the victim system. Finally, our comparative results show that the cognitive power control technique performs the best in protecting the victim receiver from the in‐line interference. Copyright © 2016 John Wiley & Sons, Ltd.

Bounds on achievable degrees of freedom in blind cellular networks

Cellular networks are of particular interest when communication takes place. The main barrier of employing cellular networks to reach broad access everywhere is interference. Although interference alignment has by theory raised hopes to leap this last hurdle, however, no operator will show interest for practical implementation of the complicated algorithms proposed so far, especially considering the need for global channel knowledge. Besides, there is no measure to appraise the performance of existing algorithms. In this study, the authors study blind cellular networks to characterise their achievable degrees of freedom. As it is very hard – if not impossible – to obtain its exact value, they provide related upper and lower bounds for this special scenario when power control mechanism is applied in the network. They also propose constructive proof for the lower bound and offer their seminal blind resource allocation algorithm in which they utilise concepts of both frequency alignment and fractional frequency reuse. Analytical upper bounds are also proposed and proved to be tight with respect to simulated results.

Analytical Modeling of Interference Aware Power Control for the Uplink of Heterogeneous Cellular Networks

Inter-cell interference is one of the main limiting factors in current Heterogeneous Cellular Networks (HCNs). Uplink Fractional Power Control (FPC) is a well known method that aims to cope with such limiting factor as well as to save battery live. In order to do that, the path losses associated with Mobile Terminal (MT) transmissions are partially compensated so that a lower interference is leaked towards neighboring cells. Classical FPC techniques only consider a set of parameters that depends on the own MT transmission, like desired received power at the Base Station (BS) or the path loss between the MT and its serving BS, among others. Contrary to classical FPC, in this paper we use stochastic geometry to analyze a power control mechanism that keeps the interference generated by each MT under a given threshold. We also consider a maximum transmitted power and a partial compensation of the path loss. Interestingly, our analysis reveals that such Interference Aware (IA) method can reduce the average power consumption and increase the average spectral efficiency. Additionally, the variance of the interference is reduced, thus improving the performance of Adaptive Modulation and Coding (AMC) since the interference can be better estimated at the MT.

Adaptive Power-Control Based Energy-Efficient Routing in Wireless Sensor Networks

Efficient utilization of energy is a hot topic of research in the field of wireless sensor networks. Limited battery resource at a sensor node coupled with the hostile multi-path fading propagation environment makes the task of the network to provide reliable data services with an enhanced lifetime, challenging. In order to achieve this goal, a number of efforts have been made by the researchers; one such key strategy is an energy-aware routing embedded with transmission power control mechanism. In this strategy, every sensor node in a network transmits at a lowest possible power level to maintain on one hand reliable wireless links with other neighboring nodes and saves the energy on the other. In this paper, we propose a novel routing technique embedded with transmission power control for wireless sensor networks while considering a realistic radio fading environment. The proposed strategy considers channel fading in the propagation environment and mitigate it through transmission power control mechanism. The main aim of the proposed protocol, APCEER, is to reduce the communication interference among sensor nodes, establish energy-efficient routes from source to sink and thus, to save energy of each and every sensor node in the network. This results in an overall increase of network lifetime, transmission throughput, energy saving and reduce communication interference and collision. Simulation and experimental results show that the proposed scheme outperforms the existing energy-aware routing strategies that are not equipped with a power control mechanism. The proposed protocol thus utilizes in urban applications of wireless sensor networks that need ultra efficient utilization of energy by power-constrained nodes operating in severe fading conditions.

Throughput reliability analysis of cloud-radio access networks

This paper develops a stochastic geometry-based analytical approach for calculating the throughput reliability of a cloud-radio access network (C-RAN) comprising randomly distributed remote radio heads (RRHs) and randomly located users. A tunable distance-based RRH transmit power control mechanism along with cooperative joint transmissions by the RRHs is employed to achieve power savings and high throughput reliability. The analytical result for the throughput reliability serves as input to analysis of per user achievable average rate and C-RAN network-level performance metrics of spectral efficiency and energy efficiency. The analytical results are validated by Monte Carlo simulation results with good agreement, thus confirming the accuracy of the developed analytical approach. The key finding from the analysis is that by carefully tuning the RRH transmit power and cooperation parameter (cluster radius), it is possible to realize a threefold improvement in the energy efficiency along with 108% enhancement in the spectral efficiency of C-RANs. Copyright © 2016 John Wiley & Sons, Ltd.

On the Performance Analysis of Underlay Cognitive Radio Systems: A Deployment Perspective

We study the performance of cognitive Underlay System (US) that employ power control mechanism at the Secondary Transmitter (ST) from a deployment perspective. Existing baseline models considered for performance analysis either assume the knowledge of involved channels at the ST or retrieve this information by means of a band manager or a feedback channel, however, such situations rarely exist in practice. Motivated by this fact, we propose a novel approach that incorporates estimation of the involved channels at the ST, in order to characterize the performance of the US in terms of interference power received at the primary receiver and throughput at the secondary receiver (or \textit{secondary throughput}). Moreover, we apply an outage constraint that captures the impact of imperfect channel knowledge, particularly on the uncertain interference. Besides this, we employ a transmit power constraint at the ST to classify the operation of the US in terms of an interference-limited regime and a power-limited regime. In addition, we characterize the expressions of the uncertain interference and the secondary throughput for the case where the involved channels encounter Nakagami-$m$ fading. Finally, we investigate a fundamental tradeoff between the estimation time and the secondary throughput depicting an optimized performance of the US.