Virtual Mimo

Recently, There are increasing number of studies that apply multi-carrier method, a land mobile communication method, to underwater channel environment in order to enhance the performance of underwater communication. Therefore, in this paper, in order to design a new system with improved communication performance compared to the multi-carrier method in underwater communication, we present that the RS(Resource Spreading) FMT-OFDM system has a diversity and repetition effect from resource spreading. Moreover, we verify the performance of RS FMT-OFDM system and existing FMT-OFDM system through simulations after modeling communication channels and setting the system parameter based on the data measured from the real sea. Our result indicate that, compared to the existing FMT-OFDM system, there has been an improvement in communication performance by 12dB based on BER    we also discovered that communication performance improves as the resource spreading rate increases.

Virtual multiple-input multiple-output (V-MIMO) technology promises significant performance enhancements to cellular systems in terms of spectral efficiency (SE) and energy efficiency (EE). How these two conflicting metrics scale up in large cellular V-MIMO networks is unclear. This paper studies the EE-SE trade-off of the uplink of a multiuser cellular V-MIMO system with decode-and-forward type protocols. We first express the trade-off in an implicit function and further derive closed-form formulas of the trade-off in low and high SE regimes. Unlike conventional MIMO systems, the EE-SE trade-off of the V-MIMO system is shown to be susceptible to many factors including protocol design (e.g., resource allocation) and scenario characteristics (e.g., user density). Focusing on the medium and high SE regimes, we propose a heuristic resource allocation algorithm to optimize the EE-SE tradeoff. The fundamental performance limits of the optimized V-MIMO system are subsequently investigated and compared with conventional MIMO systems in different scenarios. Numerical results reveal a surprisingly chaotic behavior of V-MIMO systems when the user density scales up. Our analysis indicates that low frequency reuse factor, adaptive resource allocation, and user density control are critical to harness the full benefits of cellular V-MIMO systems.

Deployment of sensor nodes has become a major challenge in improving network coverage dynamically in wireless sensor networks. Hence different spatial multiplexing techniques are experimented to provide energy efficiency in sensor networks. At the primary deployment level it is evident that the multiple input single outputs (MISO) consumes lesser energy than the other techniques. However implementing STBC based MIMO (SCHCT) technique in wireless sensor network further reduces the energy to large extent. This paper exploits this method for a group of sensor nodes those are divided into many clusters where multiple cluster heads cooperatively manages the transmission activity with less energy consumption and enhanced network life span. The network lifetime of WSN has also further increased by employing a different approach with the SCHCT technique even to a Heterogeneous sensor Network

A novel Phase Center Motion (PCM) based technique for discriminating angle-Doppler signatures within Multiple-Input-Multiple-Output (MIMO) radars using Frequency Modulated Continuous Wave (FMCW) has been explored in this work. The PCM technique induces angle dependent Doppler shifts in the back-scattered signal, wherein a modified Doppler post processing for FMCW leads to joint angle-Doppler processing. Specifically, we intend to design unique spatialtemporal motion of the phase center on each individual MIMO radar channel in an effort to synthesize nearly orthogonal angle-Doppler signatures. Subsequently, we also develop a MIMO radar receiver design, which would be capable of discriminating between these induced angle-Doppler signatures. The asymptotic investigation provides a Bessel function characteristic. Simulation results demonstrate a significant side-lobe suppression of 8.5 dB for an individual PCM trajectory and 7 dB over distinct PCM trajectories, in an attempt towards realization of nearly orthogonal MIMO radar channels.

Many of the current successful commercial recommender systems utilize collaborative filtering techniques. This technique recommends products to the active user based on product preference history of the neighbor users. Those users with similar preferences to the active user are typically named his/her neighbors. Hence, finding neighbors is critical to performance of the system. Although much effort for developing similarity measures has been devoted in the literature, there leaves a lot to be improved, especially in the aspect of handling subjectivity or vagueness in user preference ratings. This paper addresses this problem and presents a novel similarity measure using fuzzy logic for selecting neighbors. Experimental studies are conducted to reveal that the proposed measure achieved significant performance improvement.

In this paper, a combined error control coding and network coding (NC) scheme is proposed for performance improvement of wireless sensor networks (WSNs) in terms of throughput and Bit error rate (BER). A suggested network model is conserved in simulations, which integrates the characteristics of; mesh, stare, and tree network models with eleven nodes. Reed-Solomon (RS) code is considered as a Forward Error Control (FEC) coding scheme in simulations. The simulation results shows that BER may slightly increases using NC, while at high Signal to Noise power Ratios (SNRs), throughput performance is improved by about 64%. This improvement is obtained even when the transmission experience a frequency selective fading environments.

This paper considers the performance analysis of M-ary phase shift keying industrial cooperative relaying system in Nakagami-m multipath fading channel with Gamma shadowing, which is known as the Generalized-K composite fading channel. Since the paper deals with the industrial environment, the communication channel is also affected by the additive Middleton's Class-A impulsive noise. The bit error rate is used as a performance measure and the closed-form average bit error rate expression was derived. The influence of different fading and noise parameters on the system performance is investigated. The obtained results may be used for the improvement of the present and future industrial wireless communication systems.

In this paper, we consider a distributed virtual multiple-input multiple-output (MIMO) coalition formation algorithm. Energy savings are obtained in the reverse link by forming multi-antenna virtual arrays for information transmission. Virtual arrays are formed by finding a stable match between two sets of single antenna devices such as mobile stations (MSs) and relay stations (RSs) based on a game theoretic approach derived from the concept of the college admissions problem. Thus, power savings are obtained through multi-antenna arrays by implementing the concepts of spatial diversity and spatial multiplexing for reverse link transmission. We focus on optimizing the overall consumed power rather than the transmitted power of MSs and RSs. Furthermore, it is shown analytically and by simulation that when the overall consumed power is considered, the energy efficiency of the single antennas devices is not always improved by forming a virtual MIMO array. Hence, single antenna devices may prefer to transmit on their own when channel conditions are favorable. In addition, the simulation results show that the framework we propose provides comparable energy savings and a lower implementation complexity when compared to a centralized exhaustive search approach.

The performance of multi-hop Virtual Multiple-Input-Multiple-Output (V-MIMO) systems, when Slotted Aloha is used to select the radio resource at each hop, is investigated. Source, destination and relaying nodes, cooperate with neighboring devices (distributed according to a Poisson Point Process) to exploit spatial diversity by means of the concept of Virtual Antenna Array (VAA). Performance is evaluated in terms of outage probability, defined as the probability that the capacity between source and destination is smaller than a given threshold. It is computed as a function of the density of cooperating nodes, and the number of relaying VAAs. It is shown that depending on the level of required capacity, the optimum number of slots per frame in the slotted structure may differ. The performance degradation with Slotted Aloha with respect to a deterministic centralised re-use of radio resources, is assessed.

This study presents an approach to predict insulation resistance failure of multilayer ceramic capacitors (MLCCs) using non-linear modeling. A capacitance aging model created by non-linear modeling allowed for the prediction of insulation resistance failure. The MLCC data tested under temperature-humidity-bias testing conditions showed that a change in capacitance, when measured against a capacitance aging model, was able to provide a prediction of insulation resistance failure.

In the presence of spoofing signal the GPS signal having the same PRN with the spoofer is hard to be acquired since the power of spoofing signal is usually stronger than that of GPS signal. If a spoofing signal exists for the same PRN, there are double peaks in two-dimensional space of frequency and code phase in acquisition stage. Using double peak information it is possible to detect spoofing signal and acquire GPS information through separate channel tracking. In this paper we introduce an anti-spoofing method using double peak detection, and thus can acquire GPS navigation data after two-channel tracking for the same PRN as the spoofing signal.

This paper explores the spatial multiplexing gain in a relay assisted distributed wireless network, where multiple relays, each with a single antenna, form a virtual antenna array to transmit to a receiver with multiple antennas. Using a transmission scheme called Randomized Distributed Spatial Multiplexing (RDSM), the transmission rate between the relays and the destination is boosted to a level that is several times higher than the rate that can be achieved through a single relay. As a result, the end-to-end data rate between a source and a destination can be greatly improved. Consequently, in a wireless network, where multiple sources compete for channel access, the overall system aggregated throughput is also improved. An opportunistic rate adaptation algorithm is adopted to achieve the optimal average end-to-end performance. Randomized signal processing at the relays fundamentally changes the way how cooperation is established. Instead of picking nodes with good links or fast paths, our algorithm picks a transmission mode (modulation, coding, and number of streams). Any node that correctly receives from the source can act as a relay and participate in forwarding. We present the performance of RDSM with practical modulation and channel coding, and evaluate its performance in a fully distributed wireless scenario.

The development of wireless communication systems is focusing to provide a link with a high capacity and good quality. The multi-hop communication system using relay's diversity with a reliable coding is designed to fulfil the above requirements. Using multiuser WCDMA system, this research applies the above multi-hop technique using a relay with Alamouti code which can be defined as Distributed-Space Time Block Code or D-STBC. Therefore it does not need multi antenna but act like MIMO and that is why it is also called virtual MIMO using a cooperative multi-hop system. The simulation results show that the 2x1 virtual MIMO multi hop system performs better than a single hop system. Targeting BER of 10-3 , the multi hop system give 12 dB gain compared with a single hop system.

Interference reduction method of vehicle collision avoidance sensor which is used for the low speed electric vehicle has been investigated. Various methods were attempted for the vehicle collision avoidance distance sensor, which received a transmitted signal from a front driving vehicle to measure the distance between two vehicles, to avoid interference by the own transmitter signal toward the rear following vehicle. In this study,-12dB of interference cancellation ratio was realized by using the phase cancellation method to the transmitted signal from the own vehicle. Proposed phase cancellation method is regarded to have the advantage of continuous monitoring in comparison to the conventional time sharing transmitting and receiving method.

This paper presents a method for developing a TM (Traversability Map) from a DTM (Digital Terrain Model) collected by remote sensors of autonomous mobile robots. Such a map can be used to plan traversable paths and estimate navigation speed quantitatively in real time for robots capable of performing autonomous tasks over rough terrain environments. The proposed method consists of three parts: a DTM partition module which divides the DTM into equally spaced patches, a terrain information module which extracts the slope and roughness of the partitioned patches using the curve fitting and the fractal-based triangular prism method, and a traversability analysis module which assesses traversability incorporating with extracted terrain information and fuzzy inference to construct a TM. The potential of the proposed method is validated via simulation works over a set of fractal DTMs.

Wireless networks continue to gain popularity over wired networks while their users do not stop to grow their demands for high data rates. The new researches in this field try to meet these demands with the new orientation of the industry towards low cost, low power consumption and multifunctional small devices. Therefore, designer and researchers face a compromise between these goals and the required quality of service (QoS). In wireless network, multipath fading severely corrupts the link performance. Indeed, as a signal propagates through a wireless channel, it incurs random fluctuations in time, reflections, and attenuation due to the wireless link nature and the arbitrarily movement of the users. Multiple input multiple output (MIMO) system is an effective countermeasure to combat multipath effects and to provide spatial diversity to the receiver. But it requires the implementation of physically separated antennas in order to have independent fading effects. Theoretically, MIMO systems increase the capacity of wireless links compared to systems with single transmit or receive antenna (SISO). In the same context, ultra wideband (UWB) technology offers unique qualities such as the unlicensed re-utilization of the allocated spectrum. This technology can underlay existing radio systems using signal with low power and quasi flat power spectral densities (PSD). In addition, UWB signals occupy wide bandwidth leading to fine time resolution which can be employed for localization applications as well as a high capacity and data rates. All these advantages make this technology a very interesting choice for low and high rate communication in different applications. Motivated by the aim to answer to the new demands in the field of wireless communication while preserving simplicity, low cost, and low power consumption; we propose to use cooperative diversity in conjunction with UWB technology in wireless networks. Cooperative diversity is indeed an alternative of the well-known diversity techniques where instead of installing multiple antennas on each node, these nodes can share their antennas to relay each other's signal in such a way that they form a virtual antenna array (virtual MIMO system). To show the benefits of the proposed solution, we study an UWB system with cooperation schemes in multipath environment using decode-and-forward (FD) relaying protocol. Next, we compare the bit error performance of the proposition with the case of non-cooperative UWB communication in same environment. We consider, respectively, time hopping pulse position modulation (TH-PPM) and direct sequence binary phase shift keying (DS-BPSK) systems. Due to the high number of multipath components (MPCs) in UWB channel, we refer to use partial Rake (P-Rake) receiver in our simulation. We analytically analyze the decision variable at the output of Rake receiver and present simulation results of the BER performance of these two systems under different UWB channel considering the IEEE 802.15.4a standard, more precisely, residential and office line-of-sight (LOS) and non-line-of-sight (NLOS) channel environments. Our results show that the relay cooperation significantly improves the performance of the two systems under different scenarios, and that the diversity gain increases proportionally with the number of cooperative relays. Increasing the number of fingers in a RAKE receiver will enhance the systems performance but will, unfortunately, increase the complexity of the design. In order to remedy this problem, we can use selective Rake (S-RAKE) receiver, which combines the best MPCs of the received signal. In presence of multiple access interference (MAI), our results show that the overall system performance degrades significantly, but the benefit of cooperation is still moderately effective. The performance in this case is limited in terms of attainable diversity that the source-relay link becomes worse when MAI is present. Hence, if better reliability is achieved at the relay nodes, the diversity may be improve, or may even be maintained. In light of this, we propose to employ antenna selection at the relay receiver in order to improve the reliability of the source-relay link. We assume that the relay node is equipped with multiple antennas and the receiver selects the best antenna which corresponds to the best sub-channel between the source and the relay out of the available sub-channels. The proposal based on the principle of antenna selection can maintain a good performance in the presence of AMI. The consequence of this is that, while leveraging the benefits of the available antennas at the relay, the number of radio frequency (RF) chains is reduced to the number of selected antennas, which leads to reduced cost and complexity.

A dual-user multiplexing scheme for a pair of mobiles equipped with single antenna is proposed which incorporates time-delay diversity employing a rotation-based D-BLAST-like layered code. A low-dimension equivalent of the existing partial interference cancellation based group decoder is also proposed for the corresponding receiver. The BER performances of the proposed scheme and those of the ideal scheme are studied comparatively through Monte Carlo simulations.

In this paper, we consider a distributed virtual multiple-input multiple-output (MIMO) coalition formation algorithm. Energy savings are obtained in the reverse link by forming multi-antenna virtual arrays for information transmission. Virtual arrays are formed by finding a stable match between two sets of single antenna devices such as mobile stations (MSs) and relay stations (RSs) based on a game theoretic approach derived from the concept of the college admissions problem. Thus, power savings are obtained through multi-antenna arrays by implementing the concepts of spatial diversity and spatial multiplexing for reverse link transmission. We focus on optimizing the overall consumed power rather than the transmitted power of MSs and RSs. Furthermore, it is shown analytically and by simulation that when the overall consumed power is considered, the energy efficiency of the single antennas devices is not always improved by forming a virtual MIMO array. Hence, single antenna devices may prefer to transmit on their own when channel conditions are favorable. In addition, the simulation results show that the framework we propose provides comparable energy savings and a lower implementation complexity when compared to a centralized exhaustive search approach.

In this paper, we aim to reduce the power expenditure in the reverse link during low network load periods, by allocating extra resource blocks (RBs) to the mobile users. Thereby, the user's rate demands are split among its allocated RBs in order to transmit in each of them by using a low level modulation order. We model the bandwidth expansion (BE) process by a game theory framework derived from the concept of stable marriage with incomplete lists (SMI). We focus on the optimization of the circuit consumed power rather than on the transmitted power. Thus, the power consumption of the radio frequency (RF) circuits and the base band (BB) system module is taken into account. Our proposed framework works in a distributed way, hence each RB and mobile user in the system are considered as an independent entity which takes an active role in the decision making process. Additionally, we show that when circuit power consumption is used as an optimization metric, transmitting in more than one RB may not become an energy efficient solution for users experiencing favorable propagation conditions in the reverse link.

The development of wireless communication systems is focusing to provide a link with a high capacity and good quality. The multi-hop communication system using relay's diversity with a reliable coding is designed to fulfil the above requirements. Using multiuser WCDMA system, this research applies the above multi-hop technique using a relay with Alamouti code which can be defined as Distributed-Space Time Block Code or D-STBC. Therefore it does not need multi antenna but act like MIMO and that is why it is also called virtual MIMO using a cooperative multi-hop system. The simulation results show that the 2x1 virtual MIMO multi hop system performs better than a single hop system. Targeting BER of 10-3 , the multi hop system give 12 dB gain compared with a single hop system.

A Wireless Sensor Network (WSN) consists of a hundred of sensor nodes deployed in sensing fields in order to serve various applications. The limited resources of sensor nodes such as energy source, computational ability and communication bandwidth are the most important challenges in designing a reliable smart WSN which guarantees the connectivity and maximizes the lifetime of sensor's batteries. One of the available solutions for improving the energy efficiency of smart WSNs is by using the Virtual Multiple Input Multiple Output (V-MIMO) technology adapted to sensor nodes. In this paper, we proposed a high energy efficiency smart WSN in which we exploited the advantages Provided by the virtual MIMO technique (i.e. by reducing the multipath fading channel). Our network transmission has two scenarios. The first scenario is based on deploying one rechargeable relay node at the center of the sensing field which is responsible for receiving data packets from the source node, decoding and forwarding them to a destination node, while the second scenario is based on dividing the sensing field into clusters where each cluster has a rechargeable relay node which transfers data packets to a destination node in the same cluster or in any other cluster. In this work, we studied the effects of Rayleigh flat fading channels which increase the re-transmission error of data packets. Our simulation results show that the use of the advantages of virtual MIMO and one central/rechargeable relay node achieves only low energy efficiency for the Signal to Noise Ratio (SNR) range between-20 to 20dB over the Rayleigh flat fading channel. However, the second scenario achieves high energy efficiency due to the clustering technique and the central relay nodes with direct transmission in each cluster.