Kenji Leibnitz

Biologically inspired self-adaptive multi-path routing in overlay networks

Using randomness to find optimal solutions in selecting network paths.

Source Traffic Modeling of Wireless Applications

Summary Data applications are expected to play an increasingly important role in the next generation mobile communication services. To plan these networks, detailed models of data users with diverse applications are required. The purpose of this study is to provide practically usable traffic models for data users in wireless networks, e.g. GPRS. We start with a discussion of well-known models in the literature, where the focus is on their applicability in mobile networks. A practical model of mobile HTTP users, based on an extrapolation of WWW users in current wire-line networks, is presented; this model is expected to be accurate enough to be used in simulation studies for network planning purposes. Finally, models for other emerging data applications are also taken into account.

Approximating the othercell interference distribution in inhomogeneous UMTS networks

We present an analytical model for computing the othercell interference distribution in a third generation UMTS network with inhomogeneous user distribution. Our proposed model is based on an iterative calculation of a fixed-point equation which describes the interdependence of the interference levels at neighboring base stations. Furthermore, we develop an efficient algorithm based on lognormal approximations to compute the mean and standard deviation of the othercell interference. We show that our model is accurate and fast enough to be used efficiently in the planning process of large UMTS networks.

Estimating churn in structured P2P networks

In structured peer-to-peer (P2P) networks participating peers can join or leave the system at arbitrary times, a process which is known as churn. Many recent studies revealed that churn is one of the main problems faced by any Distributed Hash Table (DHT). In this paper we discuss different possibilities of how to estimate the current churn rate in the system. In particular, we show how to obtain a robust estimate which is independent of the implementation details of the DHT. We also investigate the trade-offs between accuracy, overhead, and responsiveness to changes.

Biological principles for future internet architecture design

Currently, a large number of activities on Internet redesign are being discussed in the research community. While todays Internet was initially planned as a datagram-oriented communication network among research facilities, it has grown and evolved to accommodate unexpected diversity in services and applications. For the future Internet this trend is anticipated to continue even more. Such developments demand that the architecture of the new-generation Internet be designed in a dynamic, modular, and adaptive way. Features like these can often be observed in biological processes that serve as inspiration for designing new cooperative architectural concepts. Our contribution in this article is twofold. First, unlike previous discussions on biologically inspired network control mechanisms, we do not limit ourselves to a single method, but consider ecosystems and coexisting environments of entities that can cooperate based on biological principles. Second, we illustrate our grand view by not only taking inspiration from biology in the design process, but also sketching a possible way to implement biologically driven control in a future Internet architecture.

Attractor selection and perturbation for robust networks in fluctuating environments

The heterogeneity of connected devices, technologies, and protocols anticipated in future-generation information and communication networks also requires the development of new approaches for robust and self-adaptive systems. Recently, methods observed from biological phenomena have gained much attention as viable alternatives or inspiration for the solution of networking problems. The main advantages of such dynamic mechanisms inspired by biology lies in their self-organizing properties, scalability to numbers of connected devices, simplicity in terms of control rules, as well as adaptability and robustness to changing and fluctuating environments. Dealing with fluctuations plays a key role in maintaining the stability of the system. In this article we propose a new framework for selecting among different networks and services based on the robustness of each network¿s performance metrics. The selection is only based on observations of the systems responsiveness to inherent fluctuations. This method is derived from biological experiments where the speed of fluorescence evolution of proteins in bacteria is observed to have a positive correlation with the phenotypic fluctuation of fluorescence over clone bacteria. Due to the explicit utilization of the inherent fluctuations in the system, the proposed selection scheme can operate smoothly to select the most suitable and robust network.

Resilient multi-path routing based on a biological attractor selection scheme

In this paper we propose a resilient scheme for multi-path routing using a biologically-inspired attractor selection method. The main advantage of this approach is that it is highly noise-tolerant and capable of operating in a very robust manner under changing environment conditions. We will apply an enhanced attractor selection model to multi-path routing in overlay networks and discuss some general properties of this approach based on numerical simulations. Furthermore, our proposal considers randomization in the path selection which reduces the selfishness and improves the overall network-wide performance.

ICEPT-an integrated cellular network planning tool

In this paper, we present ICEPT, a new mobile radio network planning tool that is based on an integrated design approach. The new approach starts with the analysis of the spatial distribution of the expected teletraffic within the service area of the cellular system. Employing this principle, the ICEPT tool considers concurrently the four major design areas of cellular networks: radio transmission, mobile subscriber, resource allocation, and system architecture. ICEPT uses these factors as input for the automatic network design algorithm ABPA which locates the base stations in the supplying area.

A uniform airdrop deployment method for large-scale wireless sensor networks

The performance of wireless sensor networks in terms of coverage, connectivity, lifetime and robustness is greatly influenced by the initial physical placement of the sensor nodes. In this paper we propose a novel deployment method for sensor nodes, when a large number of nodes is distributed from the air in a monitoring region that is inaccessible from the ground. In our deployment method, each sensor node is equipped with a parachute and a device to switch between its two falling behaviours (gliding and falling) in the air. After being dropped from midair, sensor nodes stochastically coordinate their falling behaviour in order to distribute themselves uniformly in the monitoring region. In addition, each sensor node exchanges messages with neighbouring nodes while being airborne and it changes its falling behaviour according to the density of the neighbouring nodes in order to reduce non-uniform areas. Through simulation evaluations, we confirm that our proposal can achieve a high uniformity in the placement of the nodes compared to a traditional airdrop method.

Peer-to-peer vs. client/server: reliability and efficiency of a content distribution service

In this paper we evaluate the performance of a content distribution service with respect to reliability and efficiency. The considered technology for realizing such a service can either be a traditional client/server (CS) architecture or a peer-to-peer (P2P) network. In CS, the capacity of the server is the bottleneck and has to be dimensioned in such a way that all requests can be accommodated at any time, while a P2P system does not burden a single server since the content is distributed in the network among sharing peers. However, corrupted or fake files may diminish the reliability of the P2P service due to downloading of useless contents. We compare a CS system to P2P and evaluate the downloading time, success ratio, and fairness while considering flash crowd arrivals and corrupted contents.