294 research outputs found
Analysis and Implementation of New Techniques for the Enhancement of the Reliability and Delay of Haptic Communications
No full textHaptic communication is a science that recreates the feeling of touch or tactile sensation, which can be controlled by computer applications allowing interaction. The users receive feedback through different vibrations or forces in form of felt sensations in specific parts of the human body, such as hands. Typically used for games, haptic communications take advantage of vibrating joysticks or controllers to enhance on-screen activity, allowing the user to feel the outcome of having depressed a button. However, it can be also used in many other fields.
The most sophisticated touch technology is found in industrial, military and medical applications, where training people for tasks that require hand-eye coordination is needed. For instance, in surgery, medical students are able to master delicate surgical techniques using a computer, whilst feeling the real sensation of dealing with muscles, suturing blood vessels or injecting Botox into a virtual face or body. Besides, it is widely used in teleoperation, where a human controls the movement of a device or a robot and, at the same time, a homologous unit is recreating the motion in real time. Once these techniques have been mastered in a near future, the medical industry will benefit from virtual surgeries that provide a revolutionary concept for medical care. Furthermore, haptic technology shall establish emergent industries that had not been feasible for the time being.
In order to achieve the transmission of data in haptic communications, we need a master/slave model where a device had control over one or several devices. Also known as primary/secondary model, both parts have to be connected via network, and in this communication, we have to deal with different challenges such as delay, jitter or packet loss, which cause troublesome effects on the system. Additionally, we have to consider that the error rate of the packet shall be increased by fading in wireless communications. In order to overcome these harsh effects, error correcting technologies are used, and, specifically in this thesis, some Forward Error Correction (FEC) techniques have been applied, such as BCH or LDPC codes. Moreover, multipath diversity methods will be used for the purpose of the enhancement of delay and reliability. In terms of delay, some techniques will have to be dismissed since they make impossible a real-time communication despite they exhibit good behavior against errors.
This thesis mainly focuses on studying, proposing and implementing new approaches of transmittin
Effects of handoff algorithms on the performance of multimedia wireless networks
No full textAbstractHandoff is the procedure providing the connection to the backbone network while a mobile terminal is moving across the boundaries of coverage of two wireless points of connection. The complexity of the handoff decision process has led to the examination of a number of traditional and pattern recognition handoff decision algorithms for wireless networks. Traditional algorithms use a received signal strength measurement and an optional threshold, hysteresis, or a dwell timer to determine the handoff decision. Degradation of the signal level, however, is a random process, and simple decision mechanisms result in a ping–pong effect whereby several consecutive handoffs degrade the service provided by the network. Consequently, more complex pattern recognition algorithms are needed to decide on the optimal time for handoff. In these algorithms, the handoff decision receives off line training to create a reference database of possible handoff locations in an environment with an associated handoff "fingerprint" at those locations. This dissertation introduces newly designed neural network and adaptive network based fuzzy inference system (ANFIS) pattern recognition algorithms. To select appropriate algorithms for a specific wireless network, we need to create an analytical framework for performance evaluation. The design of a framework for comparative performance evaluation of different handoff algorithms is a complex problem as different networks have different performance evaluation criteria.This dissertation divides wireless networks into three categories according to their topology and wireless service application: traditional cellular phone networks, heterogeneous wireless data networks, and rate adaptive wireless data networks. For each category of wireless networks we define a performance evaluation scenario and using Monte Carlo simulations, Monte Carlo calculations, and direct mathematical analysis we analyze the effects of different handoff decision algorithms. The Manhattan micro-cellular scenario is used for traditional cellular phone networks. Using Monte Carlo simulations on this scenario, the performance of traditional and our neural network and ANFIS handoff decision algorithms are compared. A moving-in moving-out performance evaluation scenario for heterogeneous wireless data networks is defined to characterize intertechnology roaming between two networks with substantially different data rates. We use Monte Carlo calculations to define the optimum handoff location for a mobile terminal in this scenario. Using Monte Carlo simulations and the optimal handoff location, we perform comparative performance evaluation of newly introduced asymmetric traditional and pattern recognition algorithms designed for intertechnology handoff. Finally, we introduce two performance evaluation scenarios for rate adaptive wireless networks to characterize user mobility in rate adaptive networks with random and grid deployments. For the first scenario we provide mathematical analysis for the effects of handoff using relative power to calculate the average throughput observed by the mobile terminal for different distances between the two wireless points of connection. For the second scenario designed for grid deployment we present a comparative performance analysis using Monte Carlo calculations for four handoff decision algorithms.Academic dissertation to be presented, with the assent of the Faculty of Technology of the University of Oulu, for public defence in Raahensali (Auditorium L10), Linnanmaa, on June 26th, 2008, at 12 noonAbstract
Handoff is the procedure providing the connection to the backbone network while a mobile terminal is moving across the boundaries of coverage of two wireless points of connection. The complexity of the handoff decision process has led to the examination of a number of traditional and pattern recognition handoff decision algorithms for wireless networks. Traditional algorithms use a received signal strength measurement and an optional threshold, hysteresis, or a dwell timer to determine the handoff decision. Degradation of the signal level, however, is a random process, and simple decision mechanisms result in a ping–pong effect whereby several consecutive handoffs degrade the service provided by the network. Consequently, more complex pattern recognition algorithms are needed to decide on the optimal time for handoff. In these algorithms, the handoff decision receives off line training to create a reference database of possible handoff locations in an environment with an associated handoff "fingerprint" at those locations. This dissertation introduces newly designed neural network and adaptive network based fuzzy inference system (ANFIS) pattern recognition algorithms. To select appropriate algorithms for a specific wireless network, we need to create an analytical framework for performance evaluation. The design of a framework for comparative performance evaluation of different handoff algorithms is a complex problem as different networks have different performance evaluation criteria.
This dissertation divides wireless networks into three categories according to their topology and wireless service application: traditional cellular phone networks, heterogeneous wireless data networks, and rate adaptive wireless data networks. For each category of wireless networks we define a performance evaluation scenario and using Monte Carlo simulations, Monte Carlo calculations, and direct mathematical analysis we analyze the effects of different handoff decision algorithms. The Manhattan micro-cellular scenario is used for traditional cellular phone networks. Using Monte Carlo simulations on this scenario, the performance of traditional and our neural network and ANFIS handoff decision algorithms are compared. A moving-in moving-out performance evaluation scenario for heterogeneous wireless data networks is defined to characterize intertechnology roaming between two networks with substantially different data rates. We use Monte Carlo calculations to define the optimum handoff location for a mobile terminal in this scenario. Using Monte Carlo simulations and the optimal handoff location, we perform comparative performance evaluation of newly introduced asymmetric traditional and pattern recognition algorithms designed for intertechnology handoff. Finally, we introduce two performance evaluation scenarios for rate adaptive wireless networks to characterize user mobility in rate adaptive networks with random and grid deployments. For the first scenario we provide mathematical analysis for the effects of handoff using relative power to calculate the average throughput observed by the mobile terminal for different distances between the two wireless points of connection. For the second scenario designed for grid deployment we present a comparative performance analysis using Monte Carlo calculations for four handoff decision algorithms
Multi-hop cognitive radio networking through beamformed underlay secondary access
No full textThis paper introduces a transmit beamforming strategy taking into account the positions of primary, secondary victim and intended secondary receivers, to achieve underlay secondary access in multihop cognitive radio networking. The transmit beamforming strategy defines a novel path optimization scheme that deviates from a preselected path given by the routing module, based on local information and according to a relay selection metric. This metric is designed to improve both coexistence with primary/secondary victim receivers and performance of the secondary cognitive network. Simulations compare the proposed strategy with a baseline solution that does not adopt beamforming, and with a strategy that applies beamforming on each hop without modifying the original path. Results show that the proposed strategy is capable of improving coexistence with primary/secondary victims, and highlight that a trade-off exists between the meeting of coexistence constraints and maximisation of secondary network performance. © 2013 IEEE
An investigation of the impact of mobility on the protocol performance in wireless sensor networks
No full textMobility has introduced a new dimension to the wireless research areas such as IP mobility management protocols and wireless ad hoc networks. In this paper we take a closer look at the issues related to the mobility in wireless sensor networks (WSNs). The aim of this work is to identify improvements that can be obtained considering mobility, recognize its research challenges. We describe different levels of mobility in WSNs and highlight the effect of the mobility on the performance of WSN protocols
On Radio Resource Allocation in LTE Networks with Machine-to-Machine Communications
No full textThe introduction of Machine-to-Machine (M2M) communications in cellular networks creates a whole new set of challenges due to the unique service requirements and features of M2M devices. One such challenge is the radio resource management, particularly on the uplink. The requirements of high energy efficiency coupled with diverse QoS requirements of M2M devices and conventional Human-to-Human (H2H) users complicate the resource allocation problem. In this paper, we address the issue of energy efficient radio resource allocation for M2M/H2H co-existence scenarios in LTE networks, while meeting the QoS requirements for different users. Our proposed algorithm shows encouraging performance in achieving the desired objectives, compared to existing algorithms in literature
Load balancing through dynamic partitioning for hierarchical cellular networks
No full textA novel autonomic area reconfiguration mechanism is proposed that complements hierarchical QoSR protocols in wireless access networks. The proposed mechanism revises the border between adjacent areas based on handover rates and on resource consumption in terms of bandwidth and user population. Its objectives are concentrated on reducing the overhead related with frequent inter-area handovers as well as providing bandwidth and user balancing on per area basis. This paper focuses on the load balancing aspects, exploring the contribution and effects of mobility through a simulation study
A PRMA based MAC protocol for cognitive machine-to-machine communications
No full textM2M communications enables devices with an ability to communicate autonomously and thus acts as the enabling technology for Internet-of-Things. It is expected that a multitude of connected devices will exist in near future. In order to avoid any spectrum scarcity issues, there is a need to explore alternate spectrum opportunities. Thus the need of cognitive radio technology for M2M communications will be indispensable. On the other hand, the unique features of M2M communications create a number of challenges for existing communication networks, especially at the MAC layer. We aim to design a MAC protocol for generic M2M communications that uses cognitive radio technology at the physical layer. For this purpose, we propose PRMA, carry out its feasibility study, adapt and significantly enhance it with modifications especially tailored for M2M communications. Analytical and simulation results show a promising combination for application in practical M2M scenarios
A cross-layer optimisation solution to improve routing protocol performance for dense wireless sensor environment
No full textIn unreliable communication environments, traditional routing protocols designed for static wireless sensor networks may fail to deliver data timely since link/node failures can be found out only after trying multiple transmissions. The main goal of the proposed protocol is to find more stable paths and to control the flooding overhead which will lead to higher level of scalability. This mechanism considers link stability for the route selection, which makes routing data more reliable and decreases the probability of retransmission, thus saves the energy and prolongs the lifetime of the whole network. In this work, we propose a cross-layer solution which utilises MAC layer information to improve routing mechanisms reliability and scalability in network layer
Mobility to improve efficiency of data collection in wireless sensor networks
No full textIn mobile communication environments, traditional routing protocols designed for static wireless sensor networks may fail to deliver data timely. The aim of this work is to identify improvements that can be obtained considering mobility and to recognize its research challenges. We briefly describe different levels of mobility in wireless sensor networks (WSNs) and highlight the efficiency ofrouting in the presence of the mobility
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