local-area network (LAN), the case T3≠T4 might correspond to an ad hoc configuration among the terminals, whereas the case T3=T4 might correspond to an infrastructure configuration, where T3 serves as an access point. The broadcast nature of the wireless medium is the key property that allows for cooperativediversity among the transmitting terminals: transmitted signals can, in principle, be received and processed by any of a number of terminals. Thus, instead of transmitting independently to their intended destinations, T1 and T2 can hear each other’s transmissions first and then jointly communicate their messages. Inspite of the fact that these extra observations of the transmitted signals are available for free (except, possibly, for the cost of additional receive hardware) wireless network protocols often ignore or discard them.
Cooperativediversity protocols are designed with the assumption that terminals always help each other in a socially eﬃcient manner. This assumption may not be valid in commercial wireless networks where terminals may misbehave for selfish or malicious intentions. The presence of misbehaving terminals creates a social-dilemma where terminals exhibit uncertainty about the cooperative behavior of other terminals in the network. Cooperation in social-dilemma is characterized by a suboptimal Nash equilibrium where wireless terminals opt out of cooperation. Hence, without establishing a mechanism to detect and mitigate eﬀects of misbehavior, it is diﬃcult to maintain a socially optimal cooperation. In this paper, we first examine eﬀects of misbehavior assuming static game model and show that cooperation under existing cooperative protocols is characterized by a noncooperative Nash equilibrium. Using evolutionary game dynamics we show that a small number of mutants can successfully invade a population of cooperators, which indicates that misbehavior is an evolutionary stable strategy (ESS). Our main goal is to design a mechanism that would enable wireless terminals to select reliable partners in the presence of uncertainty. To this end, we formulate cooperativediversity as a dynamic game with incomplete information. We show that the proposed dynamic game formulation satisfied the conditions for the existence of perfect Bayesian equilibrium.
This paper presents an energy efficient and cooperative congestion control protocol to control the congestion in mobile adhoc networks (MANETs). The proposed scheme overcomes the disadvantages of existing multicast congestion control protocols which depend on individual receivers to detect congestion and adjust their receiving rates. In the first phase of the proposed protocol, it builds a cooperative multicast tree rooted at the source, by including the nodes with higher residual energy towards the receivers. In the second phase of the proposed protocol, it proposes an admission control scheme in which a cooperative multicast flow is admitted or rejected depending upon on the output queue size. In the third phase of the proposed protocol, it proposes a scheme which tests whether the relay node has the potential path to the required destination, if not then choose the another node which has the second most highest residual energy as a new relay node. That is more generally introduction of cooperativeness and making it. In the fourth phase, we propose a scheme which adjusts the multicast traffic rate at each bottleneck of a multicast tree. Because of the on-the-spot information collection and rate control, this scheme has very limited control traffic overhead and delay. Moreover, the proposed scheme does not impose any significant changes on the queuing, scheduling or forwarding policies of existing networks. Simulation results shows that the proposed protocol has better delivery ratio and throughput with less delay and energy consumption when compared with existing protocol.
We use simulation to evaluate the performance of our protocol. Network simulator ns2 is used for simulating the results and multi-hop scenario. Considering the x-dimension of topography as 500 and y-dimension of topography as 500, simulation time of 200 sec, total number of nodes in the network=100 and initial energy = 100J. Nodes are placed randomly and the numbers of cooperative nodes m is 7.The source and sink node are picked randomly. The metrics that we use for evaluation are: transmission power and energy consumption. Our protocol curves are shown as “CwR”, the CAN protocol curves are shown by “CAN”, disjoint paths schemes curves are shown as “noc” and One-path schemes curves as “One”. These curves are plotted in graph with different colours. We analyse different values of packet failure probability (P f ) for different values of
Therefore, answering the question posed in the title, we can assume that niche divergence is not a necessary condition for the formation of community species diversity. The number of species in the community and the width of their niches are determined by diversity optimization, when competition and divergence of species niches modify the structure depending on environmental conditions, the regional species pools characteristics, successional stages, etc. In very “reach” and stable environment when niche mechanisms are of little importance, the observed differences in species niches may be the result of a random combination of various factors. For example, it has been shown that small differences in niches of previously mentioned grass and moor frogs are determined not by competition in the modern community, but by the specific history of speciation [14, 47].
Firstly, SSD is introduced into a two-way cooperative relaying system with three-phase two-way decode-and-forward (DF) protocol. In this system, four sym- bols are exchanged in three time slots, thereby doubling the spectral efficiency and the data rate compared to the conventional three-phase two-way DF relaying system that uses six time slots to exchange the same four symbols. Next, SSD is employed in a dual-hop relaying system using DF protocol without a direct link between the source and the destination. In this system, two symbols are transmitted in three time slots as compared to four time slots to transmit the same two symbols in the conven- tional dual-hop DF relaying system. These proposed systems are designed to exploit the inherent diversity in the modulation signal-space by rotating and expanding the ordinary constellation. The improvement in spectral efficiency is achieved without adding extra complexity, bandwidth or transmit power. A comprehensive analysis of these proposed systems is carried out over Rayleigh fading channels, and closed- form expressions for various performance metrics, including error probability, outage probability and channel capacity, are derived and illustrated. An asymptotic approx- imation for the error probability is obtained and is used to illustrate the impact of system parameters and diversity gain on the system performance. The optimization of relay location and power allocation in these systems is also examined. Extensive Monte Carlo simulations are performed to ascertain the accuracy of the analytical re- sults presented in the thesis. Indeed, it is observed that the use of SSD in cooperative relaying can play a major role in the system design and performance improvement.
Ad Hoc network is the structure-less system. It does not depend upon the pre-existing infrastructure. One node sends the data to other node dynamically on the basis of network connectivity. Vehicular Ad Hoc Network is the collection of vehicles that connect with one another through DSRC. The communication between VANET may be V2V or V2I unit. The basic problem faced by VANETs is security . When some malicious vehicle enters into the network, then many type of attacks may occur like Eavesdropping, Sybil attack, malware, black hole attack etc. In this paper, to prevent the vehicles from malicious vehicles we introduced Bacterial Foraging Optimization in VANETs. There are various security and verification methods used. These methods are all used to prevent the intrusion. Identity based batch verification scheme is introduced . It can improve the performance of the system by verifying number of message-signature at once instead of verifying one message-signature after the other. It helps in fast verification of the messages, less time is utilized for this process thus, system performance is improved . In Cooperative Message authentication method, the user cooperatively authenticates a group of message-signature without the
The German cooperative banks’ down-to-earth approach to banking has left them least exposed to the financial crisis. They did not hold assets that were considered ‘toxic’ and therefore had no need to take write- downs. Most of them were even able to raise more deposits from their former clients and attract firms as new clients for their lending operations. The second-largest Volksbank, the one in Frankfurt, even reported that 2008 was the best year in its history. However, prospects may be less benign since with their heavy involvement in retail and SME lending, they now have to fear that in 2010 credit losses might increase as a result of rising numbers of corporate and private bankruptcies. However, there are reasons to believe that private bankruptcies will not go up very much, since employment hardly shrank during the crisis so far, and mid-sized firms now seem better equipped with equity cushions to weather the storm than in the last crisis in the early years of this decade.
WSN has gained significant attention to enable low cost communication solution for Internet of Things (IoT) ecosystem, primarily in Low Power Lossy Network (LLNs) . The decentralized and infrastructure-less nature of WSN make it a dominating solution to meet major communication demands. To fulfill quality of service (QoS) demands and energy efficient communication, numerous efforts have been made on achieving higher bandwidth utilization, minimal end-to-end delay, minimum data loss and energy consumption, reliable communication etc. However, limited energy and continuous sensory communication forces WSN to undergo exhaustion and node-dead condition. Additionally, factors like channel fading, interference, and spectrum irregularity introduce significant problems in enabling QoS and energy efficient routing. Among major solutions, Multiple-Input Multiple-Output (MIMO) technique has been found potential  to support efficient routing, it plays vital role in alleviating the key issues of low transmission rates and low reliability. Constructing WSN nodes having multiple antennas could be difficult because of the size and complexity related constraints. To deal with this situation, WSNs can apply MIMO in cooperative way that can assure reliable communication but also energy efficient
three-phase two-way decode-and-forward (DF) protocol. Signal space diversity (SSD) is incorporated into the two-way cooperative relaying system in the proposed scheme that exploits the inherent diversity in the modulation signal space by rotating and expanding the ordinary constellation. The proposed SSD-based three-phase two-way DF relaying scheme exchanges four symbols in three time slots and thus doubles the spectral efficiency as compared to the conventional three-phase two-way DF relaying system, where six time slots are required to exchange the same four symbols. This improvement in spectral efficiency is achieved without adding any extra complexity, bandwidth, or transmit power. A comprehensive analysis of the proposed scheme is carried out in this paper, and closed-form expressions for various performance metrics, including error probability, outage probability, and channel capacity, are derived. It is shown that the proposed scheme provides a diversity gain equal to one higher than the number of relays. The paper also studies different schemes for the optimization of relay position and power allocation. Finally, Monte Carlo simulations are performed which confirm the validity and accuracy of the analytical framework.
The quality signal in a wireless transmission occasionally suffers from severe bad channel quality due to effects like fading caused by multi-path propagation. Diversity is one of the methods that used to reduce such effect whereby different samples of the same signal are transferred over essentially independent channels. Cooperative wireless communication it resolves this problem by transmitting a message to a destination with the assistance of a relay. Upon receiving the message from the transmission source, the relay retransmits the message to the destination. Therefore, the combination of the direct and relay transmissions, improves signal reception at the receiver whereby the signal is clearer and better. As such, this paper compares and evaluates the performance of different relays and combining methods in cooperative relay network under noisy and Rayleigh fading channel. This paper examines the Amplify and Forward (AAF) and Decode and Forward (DAF) relay protocols using Maximal-Ratio Combining (MRC), Fixed-Rate Combining (FRC) and Equal-Rate Combining (ERC) methods with BPSK and QPSK modulation based on simulations. The result of the simulations, show that AAF performs better than DAF in terms of Bit Error Rate (BER) without the introduction of error correcting code. Another finding reveals that the relative distances between the relay and the stations affect the performance of BER. The unique of this work is, presented different combining methods with different distance channels between users, distention and relay using different modulation technique. The best performance is achieved when the relay is located in the middle between the source and destination. Finally, the combination of FRC and BPSK shows the best BER performance for SNR up to 20 dB.
In this paper, we focus on nonregenerative (amplify- and-forward) dual-hop cooperativediversity network to study their end-to-end performance using the best-relay selection scheme over independent nonidentical Rayleigh fading channels. The main contribution of this paper is the derived novel closed-form expressions for the probability density function (PDF), the cumulative distribution function (CDF), and the moment generating function (MGF) of a tight lower bound value of SNR of the relayed signal at the destination. Moreover, the average symbol error probability (SEP) and the capacity outage (C out ) are determined using
fading, and significantly improve the capacity of channel and the throughput of network below the premise that has not increased power and frequency, MIMO technology based on the idea of spatial diversity was gradually adopted by mainstream protocol of the next generation wideband wireless communication. The perfect MIMO technology may move haltingly in the process of practice because of many problems, especially challenge of setting multi-antenna in mobile wireless sensor terminal. So, cooperativediversity, which is a new technology of space diversity, is proposed by Sendonaris and others, as shown in Figure 1. The basic idea is to create virtual multi-antenna array by the form of sharing antenna and other network resources between multi-user construction, and achieve certain spatial diversity gain through the distributed processing. In this sense, cooperativediversity provides a new path in order to apply MIMO technology to engineering practice.
In search of diversity and scalability, one inevitably reaches a point where general testbed management be- comes a challenge in itself. This can be exacerbated by the goals of the research and the researcher’s expe- rience. To begin operating and re-configuring various aspects of the testbed requires some basic knowledge, for instance, which configuration software packages are required. Where more complex research goals are pro- posed, additional devices may be required. For instance, capturing network traffic centrally across all manufactur- ing zones would require the configuration and implemen- tation of additional network components. Here we pro- vide four lessons learnt from managing this complexity, based on experience of experimental work utilising the testbed, examples of which can be seen in [21, 22, 23, 24]. These works also provide insights into the type of experimentation facilitated by the testbed.
Note that the transmission power of each relay in (7) is proportional to its incoming and outgoing channel coefficients, which fits the intuition that more power should be allocated to relaying nodes with better quality links. The exact expression of the distributed beamformer was obtained from simulation experiments which showed that in (7) achieves the perfor- mance close to the optimal solution. To get the insights of such performance superiority, some information-theoretic metrics, such as the outage probability and the diversity-multiplexing tradeoff, will be developed for the proposed beamformer in the next section.
the cognitive mapping takes place which list the dimensions of intellectual physical motor social and emotional development for the life ahead. Heyneman and Loxley (1983) concluded that emotional intelligence is directly proportional to the performance and creativity. Gardner (1992) also narrated that the education can be imparted to different children in the way it is meant to be imported to them so that the information can be utilised in the best possible way. Gray and Viens (1994) witnessed that the pupils who attended the MI class were found to possess all the eight intelligences in higher but varied degrees. The results emphasized the importance of blue film multiple intelligences in the classroom and also highlighted the importance of Cooperativediversity in school according to the study it was suggested that physical motor emotional and social intelligence are important in the cognitive development of children. Phillips and Shonkoff (2000) explained the importance of scientific modes of education during early childhood the results revealed that during the early years child education it is very important to constructive and conducive activities which would lead to success in the later years of life. The study also emphasised the importance of playful educational activities which would include cognitive and academic based education. The results further found that the overall development of children is very important aspect of school education. This important aspect cannot be ignored if the best development is desired out of children. Berk et.al (2006) investigated that the children who have good social skills and good emotional health are more likely to succeed academically.
In this paper we consider the AF relay network where the multiple users are moving in very high speed. OFDMA uplink system in such network consists of different users with different CFO due to different Doppler frequency of each user channel. We investigate the cooperativediversity together with Doppler diversity for the relay based network. Considering the high mobility of the user, first an appropriate system model is developed. The system model presents an effective channel model as well as received OFDMA signal structure. Based on the introduced model, we develop signal detection algorithm. Next, we analyze how the proposed methods can achieve both cooperative and Doppler diversity at the same time. Simulation results are provided to demonstrate performance improvement in practical situations.
In this paper, we specifically study the fair scheduling scheme for combining cooperativediversity and multiuser diversity in multi-source multi-relay networks. Round robin scheduling guarantees each user has the same transmission opportunity in both long term and short term transmission. Best relay to help the worst source’s transmission can be obtained with round robin scheduling.
extended the equalization methods for conventional space time system to cooperative space time systems for frequency selective channel. The authors in  have investigated diversity for a system having multiple antennas at source and destination and single antenna relay terminal with no CSI available at the destination. In  authors have given framework for cooperativediversity scheme using regenerative and non-regenerative relaying over slow Rayleigh fading channel. They have proposed simulation for cooperative downlink CDMA system and cooperative space time system with single antenna terminal and compare system performance for bit error rate. In , authors have considered a wireless relay network with multiple antenna elements deployed at relay nodes and imperfect channel state information is presented at the receiver end. They found that AF relaying techniques always achieves maximal diversity while in DF relaying, diversity increases with the number of antenna at the relay nodes. Similar work for wireless multi-hop network is presented in .