An Efficient Backoff Algorithm for IEEE 802.15.4 Wireless Sensor Networks

IEEE 802.15.4 is one of the most prominent MAC protocol standard designed to achieve low-power, low-cost, and low-rate wireless personal area networks. The contention access period of IEEE 802.15.4 employs carrier sense multiple access with collision avoidance (CSMA/CA) algorithm. A long random backoff time causes longer average delay, while a small one gives a high collision rate. In this paper, we propose an efficient backoff algorithm, called EBA-15.4MAC that enhances the performance of slotted CSMA/CA algorithm. EBA-15.4MAC is designed based on two new techniques; firstly, it updates the contention window size based on the probability of collision parameter. Secondly, EBA-15.4MAC resolves the problem of access collision via the deployment of a novel Temporary Backoff (TB) and Next Temporary Backoff (NTB). In this case, the nodes not choose backoff exponent randomly as mentioned in the standard but they select TB and NTB values which can be 10–50 % of the actual backoff delay selected by the node randomly. By using these two new methods, EBA-15.4MAC minimizes the level of collision since the probability of two nodes selecting the same backoff period will be low. To evaluate the performance of EBA-15.4MAC mechanism, the network simulator has been conducted. Simulation results demonstrate that the proposed scheme significantly improves the throughput, delivery ratio, power consumption and average delay.     

Face-Based Mobile Target Tracking Technique in Wireless Sensor Network

Wireless Personal Communications - A prediction-based method is presented to track mobile object and its location in a sensor network area. In recent years, energy consumption and high accuracy...     

MIMO-Terahertz in 6G Nano-Communications: Channel Modeling and Analysis

With the development of wireless mobile communication technology, the demand for wireless communication rate and frequency increases year by year. Existing wireless mobile communication frequency tends to be saturated, which demands for new solutions. Terahertz (THz) communication has great potential for the future mobile communications (Beyond 5G), and is also an important technique for the high data rate transmission in spatial information network. THz communication has great application prospects in military-civilian integration and coordinated development. In China, important breakthroughs have been achieved for the key techniques of THz high data rate communications, which is practically keeping up with the most advanced technological level in the world. Therefore, further intensifying efforts on the development of THz communication have the strategic importance for China in leading the development of future wireless communication techniques and the standardization process of Beyond 5G. This paper analyzes the performance of the MIMO channel in the Terahertz (THz) band and a discrete mathematical method is used to propose a novel channel model. Then, a channel capacity model is proposed by the combination of path loss and molecular absorption in the THz band based on the CSI at the receiver. Simulation results show that the integration of MIMO in the THz band gives better data rate and channel capacity as compared with a single channel.     

Review of Energy Conservation Using Duty Cycling Schemes for IEEE 802.15.4 Wireless Sensor Network (WSN)

Energy conservation is one of the crucial issues in wireless sensor network (WSN). A significant solution to conserve energy is done by deploying duty cycle management mechanisms in the WSN applications. This paper reviews several duty cycle mechanisms in WSN such as Duty Cycle Learning Algorithm, adaptive media access control (MAC) protocol for efficient IEEE 802.15.4 (AMPE), distributed duty cycle management (DDCM), distributed duty cycle management low power broadcast (DDCM + LPB) and distributed beacon only period. These mechanisms change their parameters such as idle listening, packet accumulation and delay in the end device transmitting queue to improve the energy conservation in WSN. The performances of these different energy conservation mechanisms have been compared at the MAC layer of IEEE 802.15.4 standard. It is found that the DDCM + LPB has made approximately 100 % enhancement in terms of average energy efficiency as compared to the other mechanisms. DDCM + LPB has significant enhancements by adapting the duty cycle according to the network traffic load condition. Using this mechanism, the duty cycle is increased when the traffic load increases and vice versa. Its energy efficiency also outperforms the conventional DDCM by the average of 10 %.     

Reduction of Outage Probability due to Handover by Mitigating Inter‐cell Interference in Long‐Term Evolution Networks

The burgeoning growth of real‐time applications, such as interactive video and VoIP, places a heavy demand for a high data rate and guarantee of QoS from a network. This is being addressed by fourth generation networks such as Long‐Term Evolution (LTE). But, the mobility of user equipment that needs to be handed over to a new evolved node base‐station (eNB) while maintaining connectivity with high data rates poses a significant challenge that needs to be addressed. Handover (HO) normally takes place at cell borders, which normally suffers high interference. This inter‐cell interference (ICI) can affect HO procedures, as well as reduce throughput. In this paper, soft frequency reuse (SFR) and multiple preparations (MP), so‐called SFRAMP, are proposed to provide a seamless and fast handover with high throughput by keeping the ICI low. Simulation results using LTE‐Sim show that the outage probability and delay are reduced by 24.4% and 11.9%, respectively, over the hard handover method — quite a significant result.     

A Review on Hierarchical Routing Protocols for Wireless Sensor Networks

The routing protocol for Wireless Sensor Networks (WSNs) is defined as the manner of data dissemination from the network field (source) to the base station (destination). Based on the network topology, there are two types of routing protocols in WSNs, they are namely flat routing protocols and hierarchical routing protocols. Hierarchical routing protocols (HRPs) are more energy efficient and scalable compared to flat routing protocols. This paper discusses how topology management and network application influence the performance of cluster-based and chain-based hierarchical networks. It reviews the basic features of sensor connectivity issues such as power control in topology set-up, sleep/idle pairing and data transmission control that are used in five common HRPs, and it also examines their impact on the protocol performance. A good picture of their respective performances give an indication how network applications, i.e whether reactive or proactive, and topology management i.e. whether centralized or distributed would determine the network performance. Finally, from the ensuring discussion, it is shown that the chain-based HRPs guarantee a longer network lifetime compared to cluster-based HRPs by three to five times.     

Low Complexity Iterative-QR (IQR) Precoder Design Based on Structure Blocks for Massive MIMO System

Massive multiple-input multiple-output (MIMO) technology is a promising technique having a high spectral efficiency for future wireless systems. Counterintuitively, the practical issues of transmitted signals are being attenuated by fading, propagation limitations, and implement non-linear precoding are solved by enlarging system dimensions. However, the computational complexity of precoding grows with the system dimensions. The existence block diagonalization (BD) precoding, which completely pre-cancels the multiuser interference is very complicated to implement with the use of a large number of BS antennas, since it considers full multiplexing order. Motivated by the high performance of the BD and generalized for the case when the users have multiple antennas, we propose a structure blocks based on iterative QR decompositions (IQRDs) to compute the precoding scheme. The proposed BLIQR-based precoder designed partitioned the channel matrix into capable square-wise blocks matrix and the IQRDs are applied to the blocks channel matrix. The channel matrix is partitioned such that it can fulfill the multiplexing order for the use in Massive MIMO. The computational complexity of the proposed design is effectively reduced and the sum-rate performance is improved, especially in large number of BS antennas. The performance of the proposed scheme achieves a good trade-off between throughput and computational complexity.     

Channel Coding Scheme for 5G Mobile Communication System for Short Length Message Transmission

Wireless Personal Communications - Some channel coding schemes for 5G mobile communication system is facing difficulty in satisfying the user requirements in machine-type communication. This paper...     

Hybrid channel gain prioritized access‐aware cell association with interference mitigation in LTE‐Advanced HetNets

LTE‐Advanced heterogeneous networks deployment is meant to address the increasing demand for quality of service, high data rates and coverage extension. Load balancing is among the primary challenges, especially when the user equipments (UEs) associate with diverse transmission power network tiers using received signal strength. The low‐power network tier's spectrum will be underutilized, and UEs associated with them will be inflicted by interference from the high‐power network tier. The proposed hybrid channel gain prioritized access (HCGPA)‐aware cell association scheme stresses the importance of combined metrics with interference mitigation to simultaneously achieve load balancing and enhance performance among the network tiers. The high‐priority UEs associate with the tier that gives the maximum channel gain being higher than a given threshold. While the low‐priority UEs association is based on the maximum joint metrics (channel gain, channel access probabilities of low‐priority UEs and high‐priority UEs). The HCGPA scheme has 1.72 times the number of UEs connected to low‐power networks, 8% better load balancing fairness, compared with the conventional reference signal receive power and RSRP + 6 dB bias cell associations. Although the susceptibility of HCGPA to interference led to the poor signal to interference to noise ratio (SINR) performance of the cell‐edge UEs, the cell‐centre UEs exhibited the best spectral efficiency performance. Copyright © 2016 John Wiley & Sons, Ltd.