Transmission Rounds Research Articles

Optimal Power Allocation for CC-HARQ-based Cognitive Radio with Statistical CSI in Nakagami Slow Fading Channels

Abstract This paper addresses the power allocation problem for cognitive radio (CR) based on hybrid-automatic-repeat-request (HARQ) with chase combining (CC) in Nakagamimslow fading channels. We assume that, instead of the perfect instantaneous channel state information (CSI), only the statistical CSI is available at the secondary user (SU) transmitter. The aim is to minimize the SU outage probability under the primary user (PU) interference outage constraint. Using the Lagrange multiplier method, an iterative and recursive algorithm is derived to obtain the optimal power allocation for each transmission round. Extensive numerical results are presented to illustrate the performance of the proposed algorithm.

Fuzzy based energy efficient sensor network protocol for precision agriculture

Today’s, wireless sensor network have become a more emerging technology in precision agriculture. This paper proposes a novel approach based on sensor network technology to control the irrigation in agricultural field automatically. All sensor nodes deployed in the field, continuously sense soil temperature, soil moisture and air humidity of the agricultural field and transmit this information to base station only when the user defined periodic timer or sensed attributes values exceed desired threshold. In the proposed routing protocol, region-based static clustering approach is used to provide efficient coverage over entire agricultural area and threshold sensitive hybrid routing is used for transmitting sensed data to base station. The proposed protocol uses fuzzy logic technique to select the best cluster head among other sensor nodes in a particular round which minimizes the energy consumption of nodes in every data transmission period. The proposed energy-efficient protocol is compared with existing benchmark EEHC, DEEC, DDEEC and RBHR routing protocols. The analysis and experimental results show a significant decrement in data transmission rate due to user-defined transmission thresholds. The balanced use of fuzzy logic technique, static clustering and hybrid routing approach efficiently reduce energy consumption of sensor nodes in every data transmission round and prolongs the overall network lifetime by 173.16%, 149.22%, 99.49% and 47.39% as compared to EEHC, DEEC, DDEEC and RBHR protocol respectively.

A Novel HARQ Scheme for SCMA Systems

This letter considers the hybrid automatic repeat request (HARQ) scheme for sparse code multiple access (SCMA) systems, where the message passing algorithm (MPA) is adopted in the multiuser detection. In MPA, the reliability can be improved when parts of messages are pre-known. Motivated by this fact, a novel HARQ scheme for SCMA systems is proposed, where some correctly decoded codewords are still retransmitted in the next round of transmission. Analysis and simulation results show that, compared with the traditional HARQ scheme, the reliability of the proposed scheme is enhanced obviously, while the latency increases slightly. Hence, in the proposed scheme, an affordable tradeoff between the reliability and latency can be achieved.

Autonomous fault-diagnosis and decision-making algorithm for determining faulty nodes in distributed wireless networks

In this paper, we address fault-diagnosis agreement (FDA) problems in distributed wireless networks (DWNs) with arbitrary fallible nodes and healthy access points. We propose a new algorithm to reach an agreement among fault-free members about the faulty ones. The algorithm is designed for fully connected DWN and can also be easily adapted to partially connected networks. Our contribution is to reduce the bit complexity of the Byzantine agreement process by detecting the same list of faulty units in all fault-free members. Therefore, the malicious units can be removed from other consensus processes. Also, each healthy unit detects a local list of malicious units, which results in lower packet transmissions in the network. Our proposed algorithm solves FDA problems in 2t+1 rounds of packet transmissions, and the bit complexity in each wireless node is O(n t+1).

An energy efficient encryption method for secure dynamic WSN

AbstractClustering methods have been developed to improve network life of wireless sensor network (WSN), yet the dynamic nature of sensor clusters and limited memory and processing power make security a much more challenging problem, and most conventional cryptography methods are ill suited to WSNs. In this paper, we propose a novel encryption method to secure data transmission in WSN with dynamic sensor clusters. Our method leverages elliptic curve cryptography algorithm to generate binary strings for each sensor and combines with node ID, distance to the cluster head, and the index of transmission round to form unique 176‐bit encryption keys. Using exclusive OR, substitution, and permutation operations, encryption and decryption are achieved efficiently. Compared with the state‐of‐the‐art methods, our simulation results demonstrated that the proposed method exhibited much improved network lifetime and reduced the energy consumption most evenly among all sensor nodes. More importantly, it overcame many security attacks including brute‐force attack, HELLO flood attack, selective forwarding attack, and compromised cluster head attack. Copyright © 2016 John Wiley & Sons, Ltd.

Interactive function computation via polar coding

In a series of papers (2011---2013) N. Ma and P. Ishwar considered a range of distributed source coding problems that arise in the context of interactive computation of functions, characterizing the region of achievable communication rates. We consider the problems of interactive computation of functions by two terminals and interactive computation in a collocated network, showing that the rate regions for both these problems can be achieved using several rounds of polar-coded transmissions.

A Novel Energy Efficient Clustering Mechanism in Wireless Sensor Network

The area of wireless sensor networks (WSNs) is one of the emerging and fast growing fields in the scientific world. This has brought about developing low cost, low-power and multi-function sensor nodes. However, the major fact that sensor nodes run out of energy quickly has been an issue and many energy efficient routing protocols have been proposed to solve this problem and preserve the longevity of the network. This is the reason why routing techniques in wireless sensor network focus mainly on the accomplishment of power conservation. Most of the recent publications have shown so many protocols mainly designed to minimize energy consumption in sensor networks. This paper proposes a hierarchical routing technique which shows energy efficiency. Our technique selects cluster head with highest residual energy in each communication round of transmission and also takes into account, the shortest distance to the base station from the cluster heads. Simulation results show that hierarchical routing technique with different level of hierarchy prolongs the lifetime of the network compared to other clustering scheme and the energy residual mean value after some communication rounds of simulation increases significantly.

Steadfast Energy Proficient Sensor Node Activation System in Wireless Networks Lifetime Enhancement

The wireless sensor network (WSN) is one of the budding exploring areas and fast rising fields in wireless communications. The sensor nodes in the network are generally small-size, low-cost, low-power and multi-function capabilities. Wireless sensor networks (WSNs) are used for various applications; since numerous sensor nodes are usually deployed on remote and inaccessible places, the employment and preservation should be easy and scalable. Sensor nodes in the field being run out of energy quickly has been an issue and many energy efficient routing protocols have been proposed to solve this problem and preserve the long life of the network. This paper work proposes a hierarchical based node activation routing technique which shows energy efficiency. This technique selects cluster head with highest residual energy in each communication round of transmission to the base station from the cluster heads. Hierarchical based node activation routing technique with different levels of hierarchy simulation results prolongs the lifetime of the network compared to other clustering schemes and communication rounds of simulation increase significantly.

Connected Dominating Set based Optimized Routing Protocol for Wireless Sensor Networks

Wireless Sensor Networks(WSNs) have problem of energy starvation in their operations. This constraint demands that the topology of communicating nodes should be limited. One of the ways of restraining the communicating nodes is by creating a Connected Dominating Set(CDS) of nodes out of them. In this paper, an Optimized Region Based Efficient Data(AORED) routing protocol for WSNs has been proposed. CDS has been employed in AORED to create a virtual backbone of communicating nodes in the network. The empirical study involving extensive simulations show that the proposed routing protocol outperforms the legacy DEEC and SEP protocols. AORED has increased number of transmission rounds, increased number of clusterheads and reduced number of packets sent to the basestation as compared to DEEC and SEP protocols.

Multipacket Hybrid ARQ: Closing Gap to the Ergodic Capacity

In this work, we consider incremental redundancy (IR) hybrid automatic repeat request (HARQ), where the transmission rounds are carried over independent block-fading channels. We analyze the multipacket HARQ, where the transmitter allows two different packets to share the same channel block; this stands in contrast with the conventional HARQ, where each packet occupies the entire block. We then optimally assign resources within the block to each packet and in each transmission round. We study superposition coding and time-sharing encoding strategies, and we optimize their parameters to maximize the throughput. Besides the conventional, one-bit (ACK/NACK) signaling we also consider a multibit feedback. We formulate our problem as a Markov decision process (MDP), where the decisions concerning the encoding strategies and their parameters are taken using additional information obtained from the receiver via feedback channel. In the case of the one-bit (ACK/NACK) signaling, the partial state information Markov decision process (PSI-MDP) framework is used to obtain the optimal policies. Numerical examples obtained in a Rayleigh-fading channel indicate that, the proposed multipacket HARQ outperforms the conventional one, by more than 5 dB for high-spectral efficiencies.

Approximate closed‐form power allocation scheme for multiple‐input–multiple‐output hybrid automatic repeat request protocols over Rayleigh block fading channels

In this study, the outage-limited optimal power allocation problem for hybrid automatic repeat request (HARQ) protocol over multiple-input–multiple-output (MIMO) block Rayleigh fading channels is addressed. Considering three typical HARQ protocols, the authors first derive the approximate outage probabilities of the MIMO HARQ protocols at the high signal-to-noise ratio region. On the basis of the approximations, they then formulate an optimisation problem of minimising the average total power usage with the constraints of the targeted outage probability and the maximum number of transmission rounds. A closed-form optimal power sequence is obtained by solving the outage-limited optimisation problem. Applying the solutions, the monotonicity of the optimal power sequence is further investigated. It is found that the optimal power sequence is monotonically increasing when the targeted outage probability is smaller than a threshold. They also study the impacts of the system parameters on the optimal power sequence and the power allocation gain under various conditions. Finally, the numerical and simulation results are presented to verify the theoretical derivation.

Joint Cooperative Beamforming, Jamming, and Power Allocation to Secure AF Relay Systems

The idea of multiuser (nodes) cooperation is an efficient way to improve the physical-layer security of a wireless transmission in the presence of passive eavesdroppers. However, due to the half-duplex constraint of the practical transceivers, two phases are required for one round of data transmission, which grants the eavesdroppers two opportunities to wiretap the information. Therefore, protecting the data transmissions in both phases is critical. Toward this end, we propose a joint cooperative beamforming, jamming, and power-allocation scheme to enhance the security of an amplify-and-forward (AF) cooperative relay network in this paper. Different from the existing works assuming that the source node always uses its total power, we show that the secrecy rate is a quasi-concave function of the power of the source node so that allocating its total power may not be optimal. The beamformer design and power optimization problem can be solved by a bisection method together with a generalized eigenvalue decomposition, which has a semiclosed form and is computationally very convenient. Simulations show that the joint scheme greatly improves the security.

Energy Efficient Smart Sensor Network Routing Protocol using Node Scheduling

needs are going more technology dependent in last decade. Technology touches live everywhere and also reach the area where humans unable to reach. One of Such important application is Wireless Sensor Networks (WSNs). This helps to collect data from different conditions where human faces challenges to gather information about atmosphere or environment. Apart of its advantage, WSN suffer from many different challenges like limited sensor node electric capacity, pattern of node deployment, data sending mechanism etc. To manage WSN with optimum resource utilization various data transmission methods have been given in recent years. This paper proposed another better method for improving network life span and increase stability of WSN. Proposed method manages all sensor nodes energy power within intelligence manor by using ON-OFF scheduling of node data transmission. Few nodes in ON state sense data and send to base station for one round of data transmission while other nodes are in power saving OFF mode by doing nothing neither sense nor transmit data. But for next round nodes are in ON status nodes goes to OFF power saving modes to save power and OFF mode nodes sense and send data to base station. This method is compared with other technique using same parameter while simulation and proposed method outperform better in all aspects of WSN comparison. Keywordsefficient, Data transmission protocol, ON mode, OFF mode, WSN, scheduling

Joint Bandwidth Optimization and Media Access Control for Multihop Underwater Acoustic Sensor Networks

Multihop underwater acoustic sensor networks (UASNs) suffer from low throughput caused by low channel utilization and unreasonable bandwidth allocation. The existing media access control (MAC) protocols for UASNs mainly aim to improve channel utilization but neglect to optimize bandwidth, so that they cannot achieve high throughput in miltihop networks. We propose the idea of joint bandwidth optimization and MAC in this paper. We first present a system model to optimize bandwidth for miltihop UASNs. Both the complicated interference relations between links and the different transmission demands of nodes are modeled. Thus, it can accurately reflect the characteristics of miltihop UASNs. By analyzing a 1-D linear miltihop network, we find and formulate a maximum hop number which is determined by nodes' traffic load and channel capacity. The other finding is that an optimal scheduling needs to allocate the bandwidth based on traffic load, and the nodes with more traffic load should be allocated more bandwidth. This finding inspire us to develop a distributed traffic-based scheduling MAC protocol. This protocol can optimize bandwidth allocation by letting the older packet to be transmitted preferentially. To improve channel utilization, multiple packets are allowed to be transmitted in each data transmission round. Simulation results have confirmed that our protocol can achieve excellent performance owing to its core idea of joint bandwidth optimization and MAC.

Saturation Throughput Analysis of the Slotted BiC-MAC Protocol for Underwater Acoustic Networks

Unlike most existing underwater medium access control (MAC) protocols that use unidirectional data exchange, the recently proposed BiC-MAC protocol allows each sender-receiver pair to exchange multiple rounds of bidirectional-concurrent data transmissions. Via simulations, it was shown that BiC-MAC greatly improves channel utilization. In this paper, we propose a novel analytical framework based on an absorbing Markov chain to analyze the single-hop saturation throughput for slotted BiC-MAC, under error-prone channel conditions. Motivated by the insight that time-slotting loses its effects when inter-nodal delay is longer than packet transmission time, the presented results can serve as a close approximation for the original, unslotted BiC-MAC protocol. We model the protocol behavior for a sender-receiver pair that attempts to bidirectionally exchange their backlogged batch of packets. To compute saturation throughput from batch service time, we systematically derive both the state transition probabilities and the expected time spent in each Markov chain. Via comparison against the simulation results of unslotted and slotted BiC-MAC in both small and large topologies with channel errors, we show that the model approximates unslotted BiC-MAC reasonably well. We also present another approach that uses the actual inter-nodal delay information and offers even closer approximation to the throughput of unslotted BiC-MAC.

On Power Allocation for Incremental Redundancy Hybrid ARQ

We study the power allocation for incremental redundancy (IR) hybrid automatic repeat request (HARQ) in block fading channel where causal channel state information is known at both the transmitter and the receiver. In IR-HARQ, the traffic is assigned into consecutive transmission rounds, and at each round, the instantaneous mutual information that is required for successful decoding is upper bounded by the data rate that is to be delivered. We propose an HARQ power allocation method that maximizes the average of incremental mutual information at each round, and its throughput quickly converges to the ergodic capacity as the number of retransmissions increases. The numerical results show that the proposed power allocation method achieves almost the full channel capacity with moderate average transmission delay and that it maintains good throughput under stringent delay requirement.

A Handshake Based Ordered Scheduling MAC Protocol for Underwater Acoustic Local Area Networks

Underwater acoustic local area networks (UA-LANs) can be used to improve the coverage of an underwater network by introducing a tier of local area communications. Media access control (MAC) is a crucial issue for UA-LANs. Existing MAC protocols for terrestrial WLANs cannot be directly applied to UA-LANs due to the acoustic channel features of limited bandwidth and high and variable propagation delay. In this paper, we propose a handshake based ordered scheduling MAC (HOSM) protocol for UA-LANs. The nodes with data packets to be transmitted first reserve the channel in a channel reservation phase. Then an order list is calculated, and the data packets of these nodes are transmitted according to this order list. We develop a control packets transmission adjustment mechanism to reduce collisions of control packets. The key idea of this mechanism is to utilize the information of propagation delay to adjust the time instant of control packets transmitting. To improve channel utilization, we present a variant Max-Min Ant System algorithm to calculate an optimal order for each data transmission round. Simulation results have confirmed that the proposed protocol can achieve high throughput with low delay and good spatial fairness.

Packet Error Rate Analysis and Power Allocation for CC-HARQ Over Rayleigh Fading Channels

In this letter, a novel approach is developed to evaluate the average packet error rate (PER) for chase combining (CC) based hybrid automatic repeat request (HARQ) protocol over block Rayleigh fading channels for the long packet system. A simple approximated expression for the average PER at the high signal-to-noise ratio (SNR) region is further proposed. Based on the approximation, the optimal power allocation (OPA) scheme for CC-HARQ is studied. The closed-form optimal assignment solution at the high SNR is derived to minimize the average total power consumption under packet loss rate (PLR) and maximum number of transmission rounds constraints. Furthermore, the impact of transmission parameters on the OPA scheme is investigated. It is found that the ratios among the optimal power sequence just depend on the targeted PLR and the maximum number of transmission rounds.

Virtual Nodes-Based Wavelet Compression Algorithm for Wireless Sensor Networks

除了能量受限以外,有限的存储容量也是无线传感器网络的基本特征.研究传感器网络中节省存储的数据传输问题,提出了一种基于虚拟节点的渐进数据传输方法.首先定义虚拟节点并建立各级虚拟节点之间的对应关系,充分利用传感数据的相关性;然后,设计基于此映射关系的传感数据调度算法,单轮传送数据的节点总数由相应簇头的实际存储容量决定,虚拟节点对每轮收集到的数据进行联合编码,形成节省存储的渐进数据传输.模拟实验表明,所提出的算法比DIMENSIONS有更小的网络耗能和延时,而且具有存储有效性.

Green Communication via Power-Optimized HARQ Protocols

Recently, the efficient use of energy has become an essential research topic for green communication. This paper studies the effect of optimal power controllers on the performance of delay-sensitive communication setups that utilize hybrid automatic repeat request (HARQ). The results are obtained for repetition time diversity (RTD) and incremental redundancy (INR) HARQ protocols. In all cases, the optimal power allocation, minimizing the outage-limited average transmission power, is obtained under both continuous and bursting communication models. Also, we investigate the system throughput in different conditions. The results indicate that the power efficiency is substantially increased if adaptive power allocation is utilized. For example, assume a Rayleigh fading channel with a maximum of two (re)transmission rounds with rates {1, [1/2]} nats-per-channel-use and an outage probability constraint 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Then, compared with uniform power allocation, optimal power allocation in RTD reduces the average power by 9 and 11 dB in the bursting and continuous communication models, respectively. In INR, these values are obtained to be 8 and 9 dB, respectively.