Miroslav Peric

Traffic Protection Method in IP Radio Networks above 70 GHz

Terrestrial radio signals at frequencies above 70 GHz are vulnerable to atmospheric absorption by rain. In order to prevent traffic loss in radio network, caused by finite duration of rerouting algorithm convergence, protection method based on pre-calculated backup routes is proposed. Using two-dimensional rain cell model, a performance analysis is held out for different rain parameters in network with adaptive modulation/capacity links. It is shown that under influence of moderate rain intensity, a network protected by proposed method can have performance very close to that of a rerouted network.

Direct QPSK modulator for point-to-point radio link at 23 GHz

The design and characteristics of a simple direct QPSK modulator for a terrestrial point-to-point radio link is presented. This modulator enables a compact, low cost and high efficiency transmitter. Good sideband suppression, greater then 25 dB is obtained in the frequency range 21.0 to 24.0 GHz, without tuning. The insertion loss is less than 8 dB in 3 GHz bandwidth and the carrier suppression is about 22 dB.

Securing data on fiber optic transmission lines

Speed, bandwidth, cost efficiency, reliability and security are some of the demands placed on telecommunication today. Fiber optic systems have the advantage of most of these requirements over standard telecommunications solutions and make up the base of all modern communications networks. Although it was initially believed that fiber optic systems would be inherently secure it has been discovered that the unauthorized extraction of information from optical fibers is relatively simple. There are various tapping methods, which are discussed in the paper. Optical taping methods enable the extraction and analyses of large volumes of data transmitting over optical fiber. In response to this problem we propose implementation of advanced encryption standard (AES) algorithm, supported with block chaining method, which is necessary for high capacity systems. The problem of AES implementation at the data rates of 1 Gbps or higher is discussed and one scheme with parallelized structure is proposed for practical FPGA implementation.

A New Approach to Performance analysis of Point-To-Point Radio Links at Frequencies above 70 GHz

A New Approach to Performance analysis of Point-To-Point Radio Links at Frequencies above 70 GHz In this paper we discuss high throughput fixed point-to-point radio links in frequency bands above 70 GHz. These links are interesting as a commercial alternative to fiber connections in IP computer networks. Characteristics of equipment used for radio transmission above 70 GHz are presented. As rain is being the predominant propagation effect that causes link outages, standard rain model is described. Performance analysis in the case of adaptive radio equipment is presented. A new approach to point-to-point radio link performance analysis, that uses two dimensional rain cell models and performance criterion based on end-user experience, is proposed. This approach is compared with the standard point-to-point radio link performance analysis procedure, based on calculation of percentage of time when link is unavailable and percentage of time when link has reduced capacity. It is shown on characteristic examples that proposed performance analysis gives better insight into how rain event would really affect end-user.

High speed random number generator for section key generation in encryption devices

This paper describes hardware implementation of random number generator for session key generation in multiuser high capacity encryption systems. The generator is implemented by non-uniform quantization of avalanche diode noise samples which are modulo 2 added with pseudo random sequence. Physical process statistics stability is achieved by wide dynamic range automatic gain control circuitry of noise amplification stage. Statistic tests of measured results prove the correct operation of implemented device up to 320Mbit/s.

Some aspects of practical implementation of AES 256 crypto algorithm

In this paper some interesting aspects of practical implementation of AES crypto algorithm, performed by using elements of digital electronics, are described. Also, one example for practical realization of the most complex variant of this algorithm, AES 256, is analyzed in detail through the context of selected realization platform, and achieved results are given.

Improving Costas loop pull in range using pseudo BER detector

This paper describes a method for improving pull in range for the four-phase version of a Costas loop. The basic idea is that a pseudo bit error ratio (PBER) detector is used for fast detection of loop synchronization loss, and to trigger the frequency-sweeping circuitry. After synchronization is achieved the PBER detector detects the small BER and switches off the sweeping circuitry. Several types of PBER detector are considered and experimentally tested. One version is implemented in IMTELs (Institute for Microwave Techniques and Electronics) digital radio relay systems (DRRS) RRU13A and RRU23A.

Dynamic Rain Attenuation Model for Millimeter Wave Network Analysis

In millimeter wave networks, a received signal level and interference dynamically vary due to rain attenuation. These physical layer variations have influence on upper communication layers, which yield to variable network capabilities to serve traffic demands. Standards and agreements between service providers and users usually specify performance objectives at annual level. In order to make realistic annual level performance analysis of such networks, a new computationally efficient dynamic rain attenuation model is proposed and analyzed. The model reproduces assumed rain statistics at annual level: cumulative distribution function (cdf) of rain intensity, number of rain events in which specified rain intensity threshold is exceeded, rain advection vector intensity, and rain advection vector azimuth. Derivation of model parameter tolerances is based on the experimental results from dense rain gauge network. As an example of model application, annual level cdfs of node-to-node connection capacity in a test network are calculated.

An experiment with real-time data transmission over global scale mobile voice channel

This paper presents a details of experiment for real-time transmission of low bit rate data over global scale mobile voice channel. The emphasize is on high availability and low delay variations, rather then channel capacity. Since 3G and LTE technologies are still not predominantly deployed on global scale, the experiment is performed on GSM channel. Although this technology provides low bit rate data transmission by GPRS, voice traffic has higher priority than data traffic and hence data transmission is not suitable for interactive applications due to large delay variations. In order to enable data transmission over voice channel, a special type of modem that would be robust to speech compression algorithm is necessary. We have designed special modulation scheme whose symbols are combination of carrier frequency and anvelope changes. Both simulation and experimental results are presented. It is shown that cascading of certain amount of standard codecs, like EFR or AMR, is not sufficient for real world scenario simulation, so additional processing, like noise reduction, should be also included.

Laboratory environment for verification of protected multi-gigabit transmission systems

In order to prevent various types of attacks to ICT systems, techniques of path diversity and data encryption are used. In multi-Gbps channels propagation, delay and transmission errors are always present. These introduce difficulties in protected systems operation, especially in compensation of delay variation and system synchronization. The authors have developed laboratory environment for analyzing system stability in the presence of variable propagation delay and bit error rate. Bit error occurrence is emulated by customized error generator, while delay variation is emulated by variable delay lines. This environment consists of: hardware channel simulator based on FPGA platform, PC control software, and QoS measurement instrument. Test environment emulates fiber optic or digital radio-relay channel. Experimental results of testing emulated SDH STM-16 and Ethernet 1000BaseFx transmission channels are presented.