Rama Murthy Garimella

Cognitive cross-layer multipath probabilistic routing for cognitive networks

Mobile Ad-hoc NETworks (MANETs) is a set of mobile nodes that can move around arbitrarily, and communicate with others in a multi-hop fashion without any assistance of base stations. With recent advances in Cognitive Radio (CR) technology, it is possible to apply the Dynamic Spectrum Access model in MANETs. This introduces the concept of Cognitive Radio Ad Hoc Networks (CRAHNs). Applying CR techniques provides better throughput, even in congested spectrum along with better propagation characteristics. CRAHN is a kind of intelligent network that is aware of its surrounding environment, and adapts to the transmission or reception parameters to achieve efficient communication without interfering with primary users. Routing in CR environment is a challenging task as the availability of channel is constrained by the presence of primary user. The problem of routing in CRAHNs targets the creation and maintenance of wireless multi-hop paths among cognitive nodes by deciding both the spectrum to be used and the relay nodes of the path. This paper proposes a cognitive cross-layer multipath probabilistic routing for cognitive radio based networks. The proposed solution uses spectrum holes identified by MAC layer, decides the channel to be used and transmit power level for each hop in the path. The proposed solution is implemented in NS2, and performance of the proposed solution is compared with the existing solution from the literature. The paper also shows that the proposed solution outperforms existing solution in terms of packet delivery ratio, average end-to-end delay and energy consumed per data packet.

On the dynamics of a Recurrent Hopfield Network

In this research paper novel real/complex valued recurrent Hopfield Neural Network (RHNN) is proposed. The method of synthesizing the energy landscape of such a network and the experimental investigation of dynamics of Recurrent Hopfield Network is discussed. Parallel modes of operation (other than fully parallel mode) in layered RHNN is proposed. Also, certain potential applications are proposed.

Concurrent cyber physical systems: Tensor State Space Representation

In this research paper, state space representation of concurrent, linearly coupled dynamical systems is discussed. It is reasoned that the Tensor State Space Representation (TSSR) proposed in [Rama1] is directly applicable in such a problem. Also some discussion on synchronizing linearly coupled, concurrent systems evolving on multiple time scales is included. Briefly new ideas related to distributed signal processing in cyber physical systems are included.

LCSD: Leveling Clustering and Sectoring with Dissemination Nodes to Perform Energy Efficient Routing in Mobile Cognitive Wireless Sensor Networks

Mobility in wireless sensor networks is gaining popularity in recent years and has led a lot of researchers to work in this field [10, 11] due to tremendous real time applications which were otherwise not possible with static environment in WSNs. The issues which static WSNs faced with respect to power, storage capacity, etc. are faced by mobile environment too and thus it is very important to deal with them to produce the best out of the network. In this paper, we propose an energy efficient cognitive, mobility-aware routing protocol for wireless sensor networks with a major aim of increasing the lifetime of the network. It uses the concept of leveling, sectoring and clustering. Dissemination of data from mobile source to static base station is performed in such a way that the energy loss in finding a route is decreased to minimum. Route preservation (to support fault tolerance) is also proposed to support maximum lifetime of the network. The protocol when implemented in the static environment proves to be better than PASCAL[1], a leveling and sectoring protocol proposed for static environment. Thus, the proposed protocol is an enhancement over PASCAL and a proposed idea for mobile environment.

Simple and secure node authentication in wireless sensor networks

Wireless sensor network (WSN) comprises of several nodes usually called motes or sensors. These motes gathered together and collect data by observing the surroundings and reported the information to one or more reliable links. This valuable data only be accessible between two communicating parties. To secure the data that delivers between the two parties, we require a secure node authentication scheme. Wireless sensor networks are special networks which attract several researchers due to the variety of applications but at the same time it suffers from many hazards. There are many guaranteed solutions but authentication assumes to give the best result among them. But sometimes it would be an energy consuming process. So, we need a safe and energy efficient mechanism to secure the whole network. In this paper, we have proposed a mechanism to authenticate nodes in a WSN. The proposed mechanism is simple and secure.

Energy efficient cognitive cross-layer MAC protocol

The ever increasing demand for communication bandwidth and inefficient usage of the existing spectrum has led to spectrum scarcity. In this light, spectrum should be managed as a scare resource. For radio communication systems, efficient utilization of spectrum is the key requirement. The inefficient usage of the existing spectrum can be improved through opportunistic access to the licensed bands without interfering with the primary users. This introduces the concept of dynamic spectrum access and cognitive radio. This paper proposes a energy efficient medium access protocol for any cognitive network. For performance evaluation, proposed solution is implemented in NS2 and comparative analysis is also done against existing solution from the literature. The paper also validates that the proposed solution gives better results.

Simple Median based information fusion in wireless sensor network

The accuracy of a system is measured by the deviation of the systems results from the actual results. Information fusion deals with the combination of information from same source or different sources to obtain improved fused estimate with greater quality or greater relevance. As larger amount of sensors are deployed in harsher environment, it is important that sensor fusion techniques are robust and fault-tolerant, so that they can handle uncertainty and faulty sensor readouts. The sensor nodes in Wireless Sensor Network (WSN) are constrained with computation and communication resources, and efforts are required to increase the performance measures of the network. Thus sensor fusion techniques should be simple with less computation complexity. In this paper we propose a novel Median based sensor fusion function named D function. It is shown that the proposed D function satisfies the lipschitz condition. Paper also presents some of the ideas which can open new areas for research in fusion problem.

Dynamics of Ordinary and Recurrent Hopfield Networks: Novel Themes

In this research paper several interesting themes related to Hopfield network are explored and concrete results are derived. For instance, convergence in partial parallel mode of operation, convergence when synaptic weight matrix, W is row diagonally dominant case. Also, structured recurrent Hopfield network with companion matrix as W is studied. The dynamics when the activation function is a step function, the state space is asymmetric hypercube are also studied. Finally several experimental results are derived.

Dynamics of structured Complex Recurrent Hopfield Networks.

In this research paper, Complex Recurrent Hopfield Networks are introduced. Dynamics of a Structured Complex Recurrent Hopfield Network whose synaptic weight matrix is skew Hermitian is studied. It is proved that such a network when operated in parallel mode leads to a cycle of length 4. Two new types of complex matrices known as Braided Hermitian and Braided Skew Hermitian are defined and dynamics of a complex recurrent Hopfield network based on them is studied. It is reasoned that a cycle of length 8 is reached in parallel mode of operation. Experimental results for different types of Complex Recurrent Hopfield Networks are also discussed.

Primary user authentication in cognitive radio network using authentication tag

Todays wireless network is characterized by fixed spectrum assignment policy, which is known as licensed spectrum. But this licensed spectrum is not utilized properly and on the other hand due to enormously increase in wireless devices there is a problem of spectrum shortage. So a new technology, cognitive radio network (CRN) has been proposed by Mitola(2000) for efficient utilization of available spectrum and to overcome the problem of spectrum shortage. The aim of cognitive radio network technology is to use the license spectrum opportunistically without causing any harmful interference to primary user. But an attacker can mimic primary user signals to get unfair share of radio channels. Therefore, it is necessary to distinguish primary user signal from an attacker signal or secondary user signal. In this paper, we propose a mechanism to authenticate primary user by using authentication tag at physical layer.