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A particular problem in satellite communications is the estimation of the current operating point of a bent-pipe transponder. Various special effects aggravate this estimation problem, among which the capture effect, gain compression, unknown attenuation in the transmission channel, or noisy received signals are the most prominent. In most practical cases, operators desire a fully blind estimator...
In order to attain high data rate in underwater acoustic communication the use of a high carrier frequency is inevitable due to the limited ratio between the bandwidth and the center frequency. Recently studies on communication systems using carrier frequencies of a few hundred kHz have been done for this purpose. Currently Korea Research Institute of Ships and Ocean Engineering (KIRSO) is also developing...
Ultra wideband (UWB) communication is a promising technology for achieving high data rate transmission. For any system design process and testing, understanding the wireless channel behavior is essential in situations where the communication system parameters can be designed to match the studied behavior. Due to its high bandwidth, UWB channel has its own characteristics. Therefore, measurement and...
This paper deals with noise effect on control systems. It uses the principle of spread spectrum to reduce the noise effect on deteriorating system performance. The proposed technique can be applied to networked control systems and conventional control systems which is the scope of this paper. Numerical example is introduced to ILC controlled system due to its well known sensitivity to noise measurement...
Cyber attacks are a major threat to today's Internet services. Most of these attacks utilize IP spoofing to conceal the actual source of the attack. In this paper, Hop Count Filtering (HCF), presented by Wang et al., is extended by utilizing both Round Trip Time (RTT) and Hop Count (HC) to detect IP spoofing where RTT calculation is possible. Based on one month traceroute data from 6 different sources...
Performance of communications systems receivers is generally estimated by the bit error rate (BER) which is computed using the Monte Carlo (MC) simulation (Bit Error Counting). In a previous paper, an alternative new method based on an estimation in an iterative and nonparametric way, of the probability density function (pdf) of the soft decision of the received bit, was suggested. It was shown that...
In this paper, the statistic characteristics of the digital channelized receiver are studied in the context of additive white Gaussian noise. Based on the statistic characteristics, the automatic censored mean level (ACML) detector is proposed and its performance is analyzed by simulation. The results show that the simulated performance curves are very similar to the theoretical curves for the detection...
The presence of undetected direct path conditions in the TOA (Time of Arrival)-based indoor geolocation introduces major errors into distance measurements. In the proposed location estimation, an improved procedure is introduced in Ultra-wideband (UWB) systems in Line of Sight (LOS) and Non-Line of Sight (NLOS) multipath environments by incorporating the skewness as new statistic information of multipath...
Underlay ultra wideband (UWB) systems have to be able to detect the presence of primary systems operating in the same band for detect-and-avoid (DAA) operation. In this paper, the performances of joint and independent detection of multiple primary systems are investigated assuming that the primary systems are potentially dependent (e.g., frequency division duplex uplink-downlink communications). Joint...
A time-hopping (TH) multiple access ultrawideband (UWB) system combined with a large modulation level of M-ary pulse position modulation (PPM) is considered and analyzed. Unlike the conventional TH method that the number of the provided TH slots becomes fewer as the adopted modulation level of M-ary PPM is lager and the data rate is fixed, a feasible TH scheme that utilizes the whole frame duration...
The conventional DPLLs (digital phase-locked loops) are designed for Gaussian noise environment, and play important roles in carrier and clock recoveries. However, in power line communication (PLC), the power line noise is often impulsive, and then its statistical feature is different from Gaussian one. Therefore, we introduced Class A noise model in PLC first, and then proposed an optimum DPLL for...
Analog-to-digital conversion at the receiver is known to be a stumbling block to the implementation of high data rate communications systems. It is desirable to answer the question of how the performance of a communications system is actually bounded when the analog-to-digital conversion stage is becoming its bottleneck. This paper studies the limits to communications with analog-to-digital conversion...
We designed a specific router which can provide the required level of QoS over NGN (next generation network) in this paper. We called this router 'QoS-Aware router', which consists of two parts, a class-based routing part and a flow-based routing part. QoS-Aware router enables data taking broad bandwidth or requiring high-level QoS to be processed immediately and not to be affected by other services...
Application-level multicast suffers some disadvantages in terms of high multicast delay, overloading at rendezvous point (RP) and single-point of failure. In this paper, we propose DINCast to optimize application-level shared-tree multicast. The general idea of DINCast is to form a special logical data loop and use this loop instead of the RP as multicast sources. To demonstrate its effectiveness,...
The increasing user density and higher data rate demands of future wireless networks are to be met with new technologies under the scope of IMT-advanced. The required high data rates can be provided by wide transmission bandwidths and a high density of access points in local area scenarios. Carefully coordinated network deployment and high performance RF front-ends are envisioned infeasible due to...
We propose a new TCP-friendly multicast congestion control for very large groups of receivers. This protocol named M2C is layered and receiver-driven. Like TCP, M2C is composed of a congestion avoidance and a slow start state. However, M2C can re-activate the Slow Start when the current rate is far below the fair one. This protocol is well designed for continuous and long lived data streams, such...
This paper considers the practical implementation of low-resolution digital receivers in impulse radio ultra-wideband (IR-UWB) communication systems for low complexity and low power consumption. The performance of 1-bit digital receivers is investigated. The maximum mutual information per sample is derived and the structure of the maximum likelihood receiver is analyzed. The bit error rate performances...
As the UWB regulations have not been finalized in many parts of the world, spectral flexibility is a key requirement for an UWB system to win in the global marketplace. The unlicensed nature of the UWB spectrum makes it imperative for these devices to have the capability to coexist with existing services. The multi-band OFDM UWB communication system, standardized by ECMA for high-speed WPAN, has the...
In this paper we derive closed-form expressions for the single-user capacity of selection combining diversity (SCD) system, taking into account the effect of imperfect channel estimation at the receiver. The channel considered is a slowly varying spatially independent flat Rayleigh fading channel. The complex channel estimate and the actual channel are modelled as jointly Gaussian random variables...
In this paper we develop network protection strategies against a single link failure in optical networks. The motivation behind this work is the fact that %70 of all available links in an optical network suffers from a single link failure. In the proposed protection strategies, denoted NPS-I and NPS-II, we deploy network coding and reduced capacity on the working paths to provide a backup protection...
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