Cooperative Multiple Input Multiple Output Technique Research Articles

Energy-Efficient Cooperative MIMO Formation for Underwater MI-Assisted Acoustic Wireless Sensor Networks

The energy problem has become one of the critical factors limiting the development of underwater wireless sensor networks (UWSNs), and cooperative multiple-input–multiple-output (MIMO) technology has shown advantages in energy saving. However, the design of energy-efficient cooperative MIMO techniques does not consider the actual underwater environment, such as the distribution of nodes. Underwater magnetic induction (MI)-assisted acoustic cooperative MIMO WSNs as a promising scheme in throughput, signal-to-noise ratio (SNR), and connectivity have been demonstrated. In this paper, the potential of the networks to reduce energy consumption is further explored through the joint use of cooperative MIMO and data aggregation, and a cooperative MIMO formation scheme is presented to make the network more energy efficient. For this purpose, we first derive a mathematical model to analyze the energy consumption during data transmission, considering the correlation between data generated by nodes. Based on this model, we proposed a cooperative MIMO size optimization algorithm, which considers the expected transmission distance and transmission power constraints. Moreover, a competitive cooperative MIMO formation algorithm that jointly designs master node (MN) selection and cooperative MIMO size can improve energy efficiency and guarantee the connectivity of underwater nodes and surface base station (BS). Our simulation results confirm that the proposed scheme achieves significant energy savings and prolongs the network lifetime considerably.

A multi-channel cooperative MIMO MAC protocol for clustered wireless sensor networks

Recently, several multi-channel MAC protocols have been proposed for wireless sensor networks (WSNs) to improve network capacity and boost energy efficiency. In addition, cooperative multiple-input multiple-output (MIMO) technique has been shown to be able to significantly enhance the energy efficiency of WSNs if properly configured. However, these two promising techniques have not been jointly considered in clustered WSNs. In this paper, we explore such a joint design by proposing a novel MAC protocol for clustered WSNs that takes advantage of both multiple channels and cooperative MIMO to further boost network performance. Specifically, sensor nodes in a WSN are organized into clusters and each cluster head selects some cooperative nodes to help forward traffic to or receive from other clusters by utilizing a cooperative MIMO technique. For intra-cluster communications, different channels are assigned to adjacent clusters to reduce collisions, while for inter-cluster communications, cooperative MIMO links are scheduled to improve energy efficiency and concurrent transmissions are enabled by assigning different channels to them. We also provide a network-wide time synchronization approach to facilitating the functionality of this protocol. We carry out extensive simulations and the results demonstrate that the proposed protocol can significantly increase throughput and improve energy efficiency compared to other schemes. For example, for a WSN with 150 sensors in a 250×250m2 field, with five available channels, the protocol can achieve three times saturated throughput while saving 14% energy per bit for inter-cluster communications.

MIMO-Based Secret Key Generation Strategies

Over the last decade, physical layer secret key generation (PHY-SKG) techniques that exploit reciprocity of wireless channels have attracted considerable interest among researchers in the field of wireless communication. Compared to traditional cryptographic methods, PHY-SKG techniques offer the following advantages: a computationally bounded adversary does not need to be assumed; PHY-SKG avoids the requirement of key management, and secret keys can be dynamically replenished. Additionally, PHY-SKG can enhance existing security schemes because it operates independently of higher layer security schemes. However, a key drawback of PHY-SKG is low secret key generation rate (SKGR), a critical performance metric. Therefore, the role of advanced network technologies (e.g., multiple input multiple output (MIMO) and cooperative MIMO) must be explored to enhance SKGR. This paper describes how MIMO and cooperative MIMO techniques can enhance SKGR.

Energy Efficient Multi-Hop Wireless Sensor Networks with Cooperative MIMO Scheme

For wireless sensor networks, energy efficiency is one of the most important subjects in recent research. In this paper, an energy-efficient multi-hop scheme based on cooperative MIMO (multiple-input multiple-output) technique is proposed for wireless sensor networks. Different from other papers, we consider a single cluster transmission scenario in which energy consumption is optimized by selecting the hop length and modulation constellation size. The optimal energy consumption formula is derived and proved mathematically. In addition, the minimum energy consumption per bit is calculated numerically.

Cooperative MIMO Communication at Wireless Sensor Network: An Error Correcting Code Approach

Cooperative communication in wireless sensor network (WSN) explores the energy efficient wireless communication schemes between multiple sensors and data gathering node (DGN) by exploiting multiple input multiple output (MIMO) and multiple input single output (MISO) configurations. In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed where low density parity check (LDPC) code is used as an error correcting code. The rate of LDPC code is varied by varying the length of message and parity bits. Simulation results show that the cooperative communication scheme outperforms SISO scheme in the presence of LDPC code. LDPC codes with different code rates are compared using bit error rate (BER) analysis. BER is also analyzed under different Nakagami fading scenario. Energy efficiencies are compared for different targeted probability of bit error pb. It is observed that C-MIMO performs more efficiently when the targeted pb is smaller. Also the lower encoding rate for LDPC code offers better error characteristics.

An Energy-Efficient Multi-Hop Scheme Based on Cooperative MIMO for Wireless Sensor Networks

An energy-efficient multi-hop scheme based on cooperative MIMO (multiple-input multiple-output) technique is proposed for wireless sensor networks, taking into consideration the modulation constellation size, transmission distance, and extra training overhead requirement. The scheme saves energy by selecting the hop length. In order to evaluate the performance of the proposed scheme, a detailed analysis of the energy and delay efficiencies in the proposed scheme compared with the equidistance scheme is presented. Results from numerical experiments indicate that by use of the proposed scheme significant savings in terms of total energy cousumption can be achieved.

Channel Estimated Cooperative MIMO in Wireless Sensor Network

Energy efficient data transfer is the key factor for the design of energy efficient wireless sensor network (WSN). In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed in the WSN where fixed constellation size is considered in transmitting both the local and long-haul communication. A selection criterion is used based on the channel conditions where a selected number of sensors in a cluster is used to form a multiple input multiple output (MIMO) structure wirelessly connected with multiple antennas of a data gathering node (DGN). The selected approach is tested on the correlated data scenario. Experimental results show that the selected C-MIMO structure outperforms the unselected C-MIMO in terms of total energy consumption and they show energy efficient performance over existing one when they are compared with SISO structure. Energy models are evaluated for this scenario while energy consumption and efficiency are compared for different combination of cluster sizes and selected number of sensors. Comparisons are shown for different fixed number of constellation sizes. The effect of correlation coefficient and intersensor distance are analyzed. Later, a delay analysis is shown considering optimal constellation size.

Dual Frequency Single Aperture Microstrip Patch Antenna Element for SAR Applications

This paper presents the design of a dual frequency microstrip patch antenna. The design is presented at C and X band with centre frequency at 5.35 and 9.6 GHz respectively.The radiating element at C band is a microstrip patch while the radiating element at X band is a slot. Simulated and measured data are presented as a function of geometrical parameters.Energy efficient data transfer is the key factor for the design of energy efficient wireless sensor network (WSN). In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed in the WSN where fixed constellation size is considered in transmitting both the local and long-haul communication. A selection criterion is used based on the channel conditions where a selected number of sensors in a cluster is used to form a multiple input multiple output (MIMO) structure wirelessly connected with multiple antennas of a data gathering node (DGN). The selected approach is tested on the correlated data scenario. Experimental results show that the selected C-MIMO structure outperforms the unselected C-MIMO in terms of total energy consumption and they show energy efficient performance over existing one when they are compared with SISO structure. Energy models are evaluated for this scenario while energy consumption and efficiency are compared for different combination of cluster sizes and selected number of sensors. Comparisons are shown for different fixed number of constellation sizes. The effect of correlation coefficient and intersensor distance are analyzed. Later, a delay analysis is shown considering optimal constellation size.

Experimental Investigation on Ride through Capability of Closed Loop Controlled Matrix Converter Fed Cage Drive

Three phase matrix converters have received considerable attention in recent years because they may become a good alternative to voltage-source inverter pulse widthmodulation (VSI-PWM) converters. In fact, the matrix converter provides bidirectional power flow, sinusoidal input/output waveforms, and controllable input power factor. Furthermore, the matrix converter allows a compact design due to the lack of dc-link capacitors for energy storage. The matrix converters are more sensitive to input power disturbances than conventional PWM voltage source inverters due to the absence of dc-link. With the rapid increase of adjustable speed drives (ASDs) in commercial and industrial facilities, the susceptibility of ASDs under power disturbances such as sags, swells, transients and short term power interruption (STPI) has become more important issue. A matrix converter laboratory prototype of 250 VA, 230 V capacity has been developed with the embedded PWM VSI part, to investigate the ride through capability. The ride through approach has been shown to maintain the rotor flux and keep synchronization between the motor and matrix converter during momentary power interruption. It has been shown that by regenerating the mechanical energy stored in load inertia and transferring it to dc-link capacitor within the embedded PWM VSI part, successful ride-through operation is accomplished. The duration of the ride-through operation depends on initial motor shaft speed level, load torque type and load inertia and so the approach is more effective for applications with sufficient load inertia. The ride-through capability has been achieved by the minimal addition of hardware and software into the matrix converter.Energy efficient data transfer is the key factor for the design of energy efficient wireless sensor network (WSN). In this paper, an energy efficient cooperative MIMO (C-MIMO) technique is proposed in the WSN where fixed constellation size is considered in transmitting both the local and long-haul communication. A selection criterion is used based on the channel conditions where a selected number of sensors in a cluster is used to form a multiple input multiple output (MIMO) structure wirelessly connected with multiple antennas of a data gathering node (DGN). The selected approach is tested on the correlated data scenario. Experimental results show that the selected C-MIMO structure outperforms the unselected C-MIMO in terms of total energy consumption and they show energy efficient performance over existing one when they are compared with SISO structure. Energy models are evaluated for this scenario while energy consumption and efficiency are compared for different combination of cluster sizes and selected number of sensors. Comparisons are shown for different fixed number of constellation sizes. The effect of correlation coefficient and intersensor distance are analyzed. Later, a delay analysis is shown considering optimal constellation size.

Cross-layer design of energy-constrained networks using cooperative MIMO techniques

We consider networks where energy is a limited resource so that energy consumption must be minimized while satisfying given throughput requirements. For such networks, cross-layer design coupled with node cooperation can significantly reduce both energy consumption and delay. In this paper, we propose a cooperative multiple-input multiple-output (MIMO) technique where multiple nodes within a cluster cooperate in signal transmission and/or reception. In our scheme, local information exchange within the cluster is not necessary if Alamouti codes are used with appropriate transmission scheduling. A cross-layer design framework is then applied that optimizes routing to minimize the energy consumption and delay. For the cooperative MIMO scheme, routing is optimized based on an equivalent single-input single-out (SISO) system, where each cooperating cluster is treated as a super node. We derive the best energy-delay tradeoff curve under this optimization model and show that the cooperative MIMO approach dramatically improves energy and delay performance, especially when link layer adaptation is used.