• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.1
• /
• pp.30-35
• /
• 2010

As of today, Frequency Hopping techniques are widely used for over-channel interference and anti-jamming communication systems. In this paper, analysis the performance of robustness on the focus of some general jamming channel. In FH/SS systems, usually SFH(Slow Frequency Hopping) and FFH(Fast Frequency Hopping) are took up on many special communication systems, the SFH, FFH are also combined with a channel diversity algorithm likes NED(Normalized Envelop Detection), EGC(Equal Gain Combines) and Clipped Combines to overcome jammer's attack. This paper propose Adaptive-NED and shows A-NED will be worked well than the others in the some general jamming environments.

• ETRI Journal
• /
• v.38 no.3
• /
• pp.455-462
• /
• 2016

Frequency hopping (FH) is a common characteristic of a wide variety of communication systems. On the other hand, software-defined radio (SDR) is an increasingly utilized technology for implementing modern communication systems. The main challenge when trying to realize an SDR FH system is the frequency tuning time, that is, the higher the hopping rate, the lower the required frequency tuning time. In this paper, significant universal hardware driver tuning options (within GNU Radio software) are investigated to discover the tuning option that gives the minimum frequency tuning time. This paper proposes an improved SDR frequency tuning algorithm for the generation of a target signal (with a given target frequency). The proposed algorithm aims to improve the frequency tuning time without any frequency deviation, thus allowing the realization of modern communication systems with higher FH rates. Moreover, it presents the design and implementation of an original GNU Radio Companion block that utilizes the proposed algorithm. The target SDR platform is that of the Universal Software Radio Peripheral USRP-N210 paired with the RFX2400 daughter board. Our results show that the proposed algorithm achieves higher hopping rates of up to 5,000 hops/second.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.4
• /
• pp.789-796
• /
• 2013

It is known that the detection of hopping signals without any information about hopping duration and hopping frequency is rather difficult. This paper considers the blind detection of hopping signal's information such as hopping duration and hopping frequency from the sampled wideband signals. In order to find hopping information from the wideband signals, multiple narrow-band filters are required in general, which leads to huge implementation complexity. Instead, this paper employs the polyphase DFT(discrete Fourier transform) filterbank to reduce the implementation complexity. This paper propose hopping signal detection algorithm from the polyphase DFT filterbank output. Specifically, based on the binary image processing, the proposed algorithm is developed to decrease the memory size and H/W complexity. The performance of the proposed algorithm is evaluated through the computer simulation and FPGA (field programmable gate array) implementation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.2
• /
• pp.237-241
• /
• 2005

In Bluetooth version 1.0, the frequency hopping algorithm was such that there was one piconet, using a specific frequency, resolving the frequency depending on the part of the digits of the device clock and the Bluetooth address. Basic pattern was a kind of a round-robin using 79 frequencies in the ISM band. At this point, a problem occurs if there were more than two devices using the same frequency within specific range. In this paper, we proposed a software-based adaptive frequency hopping method so that more than two wireless devices can stay connected without frequency crash. Suggested method was implemented with HDL(Hardware Description Language) and automatically synthesized and laid out. Implemented adaptive frequency hopping circuit operated well in 24MHz correctly.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.4 no.4
• /
• pp.475-490
• /
• 2010

Cognitive Radio is an advanced enabling technology for the efficient utilization of vacant spectrum due to its ability to sense the spectrum environment. It is important to determine accurate spectrum utilization of the primary system in a cognitive radio environment. In order to define the spectrum utilization state, many CR systems use what is known as the quiet period (QP) method. However, even when using a QP, interference can occur. This causes reduced system throughput and contrary to the basic condition of cognitive radio. In order to reduce the interference time, a frequency-hopping algorithm is proposed here. Additionally, to complement the loss of throughput in the FH, a HMM-based channel prediction algorithm and a channel allocation algorithm is proposed. Simulations were conducted while varying several parameters. The findings show that the proposed algorithm outperforms conventional channel allocation algorithms.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.9 no.4
• /
• pp.24-31
• /
• 2006

To reduce the interferences between the radio equipments which are operated in frequency hopping mode, the frequency resource should be assigned to each equipment without overlapping when several groups of radio equipments operate in the same area. If the radio equipments are in a different area, the partial frequency overlaying can be permitted. From the isotropic multi-dimensional array, several frequency assignment tables can be extracted for a same area. Also several tables can be extracted for different areas. Since there can be no overlapped frequencies between the tables for the same area, no interference between the radio equipments in an area is guaranteed. The frequencies overlapped between 2 tables for 2 different areas are pre-planed as required. The interference performance in frequency hopping radio can be controlled as desired using the proposed Frequency Resource Assignment Algorithm using Isotropic multi-dimensional Array.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.9B
• /
• pp.604-611
• /
• 2007

In this paper, we present an analysis of the throughput when there are multiple piconets and WLAN sharing the ISM bands. The analysis takes channel propagation characteristics and the capture effect. We also propose an algorithm which can be used to reduce the amount of channel scanning. By using traffic prediction of the interfering WLAN, we are able to maintain a reasonable performance in terms of fraction of time channel is wasted due to collisions or unused channel. Through computer simulation, we demonstrate that the proposed algorithm achieves reduced scanning frequency.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.240-240
• /
• 2000

This paper presents two algorithms based on the concept of the frequency domain adaptive filter(FDAF). First the frequency domain recursive least squares(FRLS) algorithm with the overlap-save filtering technique is introduced. This minimizes the sum of exponentially weighted square errors in the frequency domain. To eliminate discrepancies between the linear convolution and the circular convolution, the overlap-save method is utilized. Second, the sliding method of data blocks is studied Co overcome processing delays and complexity roads of the FRLS algorithm. The size of the extended data block is twice as long as the filter tap length. It is possible to slide the data block variously by the adjustable hopping index. By selecting the hopping index appropriately, we can take a trade-off between the convergence rate and the computational complexity. When the input signal is highly correlated and the length of the target FIR filter is huge, the FRLS algorithm based on the block processing technique has good performances in the convergence rate and the computational complexity.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.10 no.3
• /
• pp.129-138
• /
• 2007

Recently, Direction Finding(DF) System is using switching DF algorithm to reduce system-weight by eliminating RF cable as much as possible. Also, Correlation Vector Direction Finding(CVDF) algorithms is being used for Fast Direction finding in tactical environment. In this paper, I will give you burst error elimination algorithms and compare the performance in case we use switching CVDF algorithm. Although antenna array is not working, we will successfully perform direction finding when we use this burst error elimination algorithms. Also, we will be completely capable of DF mission despite of meeting the unwanted situation that the monitoring signal disappear in case we use Switching Direction Finding algorithms. That situation frequently occurs under the Frequency Hopping signal circumstances.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.7B
• /
• pp.469-476
• /
• 2008

In this paper we analyze the packet interference probability and the aggregated throughput of a WPAN in which a number of Bluetooth piconets share the ISM band with WLANS. Using an Adaptive Frequency Hopping algorithm, when the AFH is employed, the number of hops available to the Bluetooth piconets varies depending on the number of independent WLANs within the piconet's radio range. Using a packet collision model in a piconet cluster, we give an analysis of the packet interference probability and the aggregated throughput as a function of the available hops for the AFH algorithm. We also present an analytical model of packet interference with multi-path fading channel in a cluster of piconets. Through analysis, we obtain the packet collision probability and aggregated throughput assuming capture effect. Numerical examples are given to demonstrate the effect of various Parameters such as capture ratio, Rice factor and cluster size on the system performance.