No. 4 (2003)
Published:
2003-12-30
ARTICLES FROM THIS ISSUE
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Error probability and error stream properties in channel with slow Rician fading
Abstract
In a radio communication channel wave parameters fluctuate randomly. The signal envelope undergoes deep fades. When binary information is transmitted through such a channel, fading causes random variation of probabilities of error associated with the detection of individual elementary signals, which produces a clustering of errors. The paper presents an analytical description of the probability of bit error in the channel with very slow Rician fading and Gaussian noise for noncoherent and coherent detection. Digital systems employing error detection or error correction coding are generally based on the transmission of blocks of N sequential bits. Expressions are given for the probability of n errors occurring in N bits (weighted spectrum of errors) and the probability of more than n errors in a block of N bits (block error probability) for noncoherent frequency shift keying (NCFSK). Also the calculations are presented graphically.
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Remarks on improved inversion attacks on nonlinear filter generators
Abstract
The subject of this paper are inversion attacks on stream ciphers (nonlinear filter generators), which were first introduced by Golić [3] and extended by Golić, Clark and Dawson [4]. These original attacks have computational complexity O(2^M), where M is the so-called "memory size" - distance between outer taps to filter function. In [6] we have proposed improved inversion attacks which have computational complexity O(2^{r-m}), where r denotes the length of the shift register and m denotes the largest gap between cells with taps to filter function or to connection polynomial. In this paper we describe further extension of our previous results obtained by considering shifts of the feedback polynomial which maximise the largest gap between cells with taps to filter function or to connection polynomial. We show that the previously proposed set of design criteria [3, 6] does not prevent the new version of improved inversion attack and we propose an additional criterion based on the relationship between positions of taps to filter function and positions of taps to the multiples of the connection polynomial.
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The tactical Intranet IPSec security concept
Abstract
The IPSec protocols architecture that can be applied in tactical Intranet based on the IPv6 protocol stack for wireless environment is the subject of the paper. The potential usefulness of the new version of IP protocol is very important for tactical communication systems. Additionally, Internet Engineering Task Force (IETF) security working group proposes recommendations covering the RFC 2401, 2402, 2406, that describe the security architecture for Internet Protocol. These standards, published by IETF are discussed here in military requirements context. The NATO~C3 Technical mbox{Architecture} model also recommends these issues. The concept of the IPSec architecture in military systems is described in the paper. The position of the security applications designed for subscriber devices with reference to layered model is also presented. The concept presented here is defined for the tactical level.
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A study of differences between bent functions constructed using Rothaus method and randomly generated bent functions
Abstract
Bent functions, having the highest possible nonlinearity, are among the best candidates for construction of S-boxes. One problem with bent functions is the fact that they are hard to find among randomly generated set of Boolean functions already for 6 argument functions. There exist some algorithms that allow for easy generation of bent functions. The major drawback of these algorithms is the fact that they rely on deterministic dependencies and are only able to generate bent functions belonging to one specific class. In our paper we present an efficient generator of random bent functions of more than 4 arguments. Resulting functions are not bounded by constraints described above. The generator operates in algebraic normal form domain (ANF). We also present our result on comparing the performance of S-boxes build using our bent function generator versus a standard method of bent function construction. We also give some directions for further research.
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A comparison of ATM and IP QoS network capabilities for handling LAN traffic with QoS differentiation
Abstract
Now, a network operator must choose between two packet switched technologies for providing QoS in WAN networks, which are ATM and IP QoS [3, 4, 9]. As ATM has reached the maturity with capabilities for offering a number of different network services (i.e. CBR, VBR, ABR, UBR, GFR), the IP QoS with network services like expedited forwarding, assured forwarding, etc. is still at developing phase but nevertheless is commonly regarded as capable to guarantee in near future similar QoS level as ATM. This paper tries to compare the efficiency of the mentioned technologies (in case of IP QoS network the AQUILA network concept [1, 2] is investigated) for handling traffic generated by LANs with QoS differentiation. This is extremely required since the applications running in LAN differ in QoS requirements and emitted traffic profiles (streaming, elastic). Therefore, a classification process of outgoing LAN traffic into predefined sub-streams should be performed at the entry point to WAN network (edge ATM switch or IP router). Furthermore, particular sub-streams are submitted to adequate WAN network service, available in ATM or IP QoS. The paper presents the experimental results, measured in the test bed, corresponding to QoS level and QoS differentiation provided by ATM and IP QoS core. For this purpose, a set of representative applications currently available to a LAN user was selected demanding from the core different QoS level. They correspond to streaming applications like VoIP with QoS objectives represented mainly by packet delay characteristics and elastic applications controlled by TCP protocol with minimum guaranteed throughput/goodput as target.
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The Integrated Data Environment: a new tool for interoperability and effective data integration for command and control
Abstract
This paper describes an ongoing effort at NC3A to provide one integrated database which contains data from a number of different sources. Initially, these sources are legacy NATO systems. Later, other systems, including messaging interfaces of a wide variety, and national systems, will be added. A common data model is used as the lingua franca between systems. A COTS product has been identified that creates translator boxes to provide interfaces to and from the legacy systems.
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NATO automated information system co-operative zone technologies
Abstract
The core components of NATO`s automated information systems (AIS) include directory services (DS), e-mail, web services, and military message handling systems (MMHS) to exchange information with similar capabilities in NATO`s member nation systems or systems that are under control of multi-national coalitions. NATO has developed the concept of information exchange gateways (IEGs) to meet this requirement. This paper introduces the concept of combining symmetric co-operative zones (CZs) to form these information exchange gateways. A~generic framework for the co-operative zone network and security architecture is introduced in support of co-operative zone development. It is shown how a co-operative zone network interface can be integrated with the NATO general-purpose segment communications system (NGCS). Development of the NATO co-operative zones is based on an evolutionary approach. A~baseline co-operative zone configuration, supporting directory services, e-mail and web services, has been tested and validated on the allied systems interoperability testbed (ASIT). This paper reports the results of the test and validation program. The paper concludes with an overview of planned evolutionary steps for co-operative zone development. Subjects covered in this overview are extension of information services, enhancement of security architecture, and operational deployment (i.e., scalability and manageability).
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Military route planning in battlefield simulation: effectiveness problems and potential solutions
Abstract
Path searching is challenging problem in many domains such as simulation war games, robotics, military mission planning, computer generated forces (CGF), etc. Effectiveness problems in military route planning are related both with terrain modelling and path planning algorithms. These problems may be considered from the point of view of many criterions. It seems that two criterions are the most important: quality of terrain reflection in the terrain model and computational complexity of the on(off)-line path planning algorithm. The paper deals with two above indicated problems of route planning effectiveness. Comparison of approaches used in route planning is presented. The hybrid, terrain merging-based and partial path planning, approach for route planning in dynamically changed environment during simulation is described. It significantly increase effectiveness of route planning process. The computational complexity of the method is given and some discussion for using the method in the battlefield simulation is conducted. In order to estimate how many times faster we can compute problem for finding shortest path in network with n big squares (b-nodes) with relation to problem for finding shortest path in the network with V small squares (s-nodes) acceleration function is defined and optimized.
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Interfacing war game simulations with tactical C2 systems - dream or reality?
Abstract
Decision making process in current tactical C2 systems is base on planning process of commanders and their staff. Improving tactical decision making by interfacing war game simulations with tactical C2~systems is achievable. Commander can review the results of the simulation and subsequently modify the tactical plan. Previously, the use of "training" simulations was not a viable solution to real world decision making due to the lengthy time required to input all of the combat entities, the unit organizations and personnel dispositions, the equipment configurations, status of the units and equipment, and the distribution of the available supplies. Modern C2~systems have all of this information stored in the common system databases, and this information can be used to instantiate and populate the simulation through an electronic adaptation of the data structures to match the requirements of the constructive simulation. This paper will provide description of system approach of interfacing simulation and C2 system to improve decision-making.
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Web-based e-learning environment
Abstract
Using a progressive information technologies for development of web-based courses and their administration brings a lot of practical and theoretical problems. We know web course problem is only small solution concerning construction of a large entire web-based e-learning environment. One of a practical problem is how to construct web-based electronic courses that have to meet international AICC standards. Implementation of such strict statements resulted in a lot of small or larger difficulties if we had used an elementary HTML editor. Using a~special web course oriented editors can absolutely solve this problem. The second problem is construction of the web-based e-learning application that can administrate such web courses and takes into consideration AICC regulations. Development of such web applications is founded on the latest web technologies. This article introduces one approach to the modeling of the two most important components (web-based course, web-based application) of the web-based e-learning environment, convenient for Military Academy in Brno and Czech army. The article outlines the structure of web subject, e-learning environment and their implementation. The LMS`s structure and its functionality, based on a snaps algebra, belong to important results of the article.
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An effective method of channels assignment for third generation cellular system
Abstract
An original hybrid method of channels assignment for DS-CDMA system is discussed in the paper. This method combines standard PN codes assignment policy and dynamic channel assignment procedure that minimise the cost of channel assignment. OPNET simulation model DS-CDMA system was used for assessment of the hybrid method. The results of simulation presented in the paper confirmed that the proposed method importantly improves the quality of services in the third generation cellular system.
