Philip Nobles

A Novel Indoor Location Sensing Mechanism for IEEE 802.11 b/g Wireless LAN

Wireless LAN, now a day exists in most of the organizations. Hardware is inexpensive to buy and easily available off-the-shelf. More and more offices, organizations and public places are installing it for its ease of utilization. Developing location aware services using WLAN has therefore gained tremendous interest in recent years. It is however, still a daunting challenge for the research community to improve location accuracy inside a building to a few meters by means of computing path loss to find distances based on signal strength of a received RF signal. The accuracy offered by various top-of the-range products using signal strength methods within the indoor environment is not very good. This paper presents a novel method to achieve improved consistency in received signal strength of an RF signal by effectively reducing the multi-path affect on RF propagation inside the building, thus enabling development of better location estimation system.

Knowing who to watch: Identifying attackers whose actions are hidden within false alarms and background noise

Insider attacks are often subtle and slow, or preceded by behavioral indicators such as organizational rule-breaking which provide the potential for early warning of malicious intent; both these cases pose the problem of identifying attacks from limited evidence contained within a large volume of event data collected from multiple sources over a long period. This paper proposes a scalable solution to this problem by maintaining long-term estimates that individuals or nodes are attackers, rather than retaining event data for post-facto analysis. These estimates are then used as triggers for more detailed investigation. We identify essential attributes of event data, allowing the use of a wide range of indicators, and show how to apply Bayesian statistics to maintain incremental estimates without global updating. The paper provides a theoretical account of the process, a worked example, and a discussion of its practical implications. The work includes examples that identify subtle attack behaviour in subverted network nodes, but the process is not network-specific and is capable of integrating evidence from other sources, such as behavioral indicators, document access logs and financial records, in addition to events identified by network monitoring.

Indoor radiowave propagation measurements at frequencies up to 20 GHz

Wideband radiowave propagation measurements were performed within a building at 2, 5 and 17 GHz using a vector network analyser. The exponent of the path-loss law n and the statistics of the rms delay spread were evaluated for line-of-sight (LOS) and obstructed (OBS) paths. Values of n for LOS paths were similar for all three frequencies whilst increasing attenuation with frequency was observed for OBS paths. Mean rms delay spread values were found to decrease with frequency.<<ETX>>

Channel estimation for layered space-time systems

Space-time techniques for multiple-input multiple-output (MIMO) systems potentially provide vast increases in capacity. In order to achieve the quoted capacity gains the MIMO channel impulse response (CIR) must be known or estimated. Thus far, existing MIMO channel estimation techniques have been limited to the narrowband case or cater specifically for coded space-time systems. In this paper, we present a novel training-based MIMO channel estimation scheme for an uncoded layered space-time system that operates in the wideband frequency-selective fading environment. The method uses a pilot matrix consisting of pilot symbols derived from the Paley-Hadamard matrix in order to jointly estimate the individual CIR of the MIMO channel. The orthogonal property of the pilot matrix is utilized to resolve both intersymbol interference and intercarrier interference of the multiple transmit and received signals. The Paley Toeplitz structure is also exploited in order to minimise the length of the pilot sequence for a given length of CIR and thus maximise the effective data throughput. Results are presented which demonstrate the accuracy of the proposed channel estimation scheme and its performance in a layered space-time system.

Wideband propagation measurements onboard HMS Bristol

A modern warship has many complex systems for onboard communications, command and control. At present, all of these systems are hard-wired and are expensive to modify or replace for the many upgrades that occur during the lifetime of the ship. It would be advantageous to replace much of this cabling with wireless links and to use COTS wireless local area network (WLAN) technology. Very little previous research has been carried out, however, to investigate the nature of the propagation environment onboard a ship or to determine whether existing WLAN technologies will have sufficient range and bandwidth. This paper describes wideband propagation measurements carried out onboard a warship. A vector network analyser was used to obtain a frequency domain characterisation of the radio channel at 2 GHz and 5 GHz within several compartments and passageways aboard HMS Bristol. Results are presented that demonstrate multipath fading and path loss. The attenuation caused by the closing of watertight doors is also considered. Comparisons are made with the authors previous measurements taken in typical office buildings (P. Nobles, et al., (1997)). The conclusions provide a fascinating insight into the propagation mechanisms onboard a warship and the challenges of implementing wireless systems in this environment.

A Deployment Value Model for Intrusion Detection Sensors

The value of an intrusion detection sensor is often associated with its data collection and analysis features. Experience tells us such sensors fall under a range of different types and are diverse in their operational characteristics. There is a need to examine some of these characteristics to appreciate the value they add to intrusion detection deployments. This paper presents a model to determine the value derived from deploying sensors, which serves to be useful to analyse and compare intrusion detection deployments.

Networking Recon: Network reconnaissance

Along with its wider reach in society, in the form of both mobility and relatively affordable access, the internet has transformed the world we live in, serving as bedrock for electronic commerce and other digital and communication services. It has become an integral part of the personal, professional, and economic spheres of our daily life. Global organisations, whether official, commercial, or social, are relying on it ever more to function, bringing an increasing need for a secure electronic infrastructure. The pervasive nature of the internet, one major factor behind its success, is also proving to be its main threat. Once connected to this global network, no one is more than a few clicks away from servers hosting websites that transact commerce worth millions or critical state-run networks that run sensitive operations.

Optimising IDS Sensor Placement

In large network environments multiple intrusion detection sensors are needed to adequately monitor network traffic. However, deploying and managing additional sensors on a large network can be a demanding task, and organizations have to balance their desire for detecting intrusions throughout their network with financial and staffing limitations. This paper investigates how intrusion detection system (IDS) sensors should best be placed on a network when there are several competing evaluation criteria. This is a computationally difficult problem and we show how Multi-Objective Genetic Algorithms provide an excellent means of searching for optimal placements.

Channel estimation for layered space-time systems in time-varying frequency selective wireless channels

A novel training-based channel estimation scheme is presented for an uncoded layered space-time system that operates in a wideband frequency selective fading environment of a time-varying multiple-input multiple-output (MIMO) channel. The method uses a pilot matrix consisting of pilot symbols derived from the Paley-Hadamard matrix to estimate the MIMO channel impulse response. The orthogonality of the pilot matrix resolves both the intersymbol interference and the cochannel interference of the wideband MIMO channel. The Toeplitz-like structure of the Paley-Hadamard matrix is exploited to minimise the length of the pilot sequence, reducing pilot symbol overhead. A decision feedback algorithm is used to track the time-varying MIMO channel. Results are presented which demonstrate the performance of the proposed MIMO channel estimator in a layered space-time system for different mobile velocities and system configurations.

Intrusion Detection: Towards scalable intrusion detection

We raise some questions that need to be addressed to overcome the scalability challenges that intrusion detection systems face. We also take this opportunity to highlight some of the recent related work and put it in context.