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Data centers are used to host computation-intensive distributed applications. Since all the applications are distributed in nature, their performance is significantly affected by the communication network. These applications generally create two kinds of flows: large data flows that require high throughput and small control flows that require low delay. These two contradictory requirements are not...
This paper presents a low power clock and data recovery (CDR) circuit for a wireless body sensor node. The proposed circuit interfaces the RF receiver output with the digital processing. It consumes 50nW at 100kbps. It uses a delay locked loop (DLL) that is calibrated in one-shot fashion to save power, locking over 18X faster than prior art. The proposed circuit is fabricated in a 0.13?m CMOS technology...
Both Galileo E1 OS and GLONASS L1 signals require a wider pre-correlation bandwidth than GPS C/A. The GLONASS channels are uniformly spaced on a frequency division grid, and occupy some 8MHz in total, whereas Galileo E1 OS has sidebands that are separated by about 2MHz. Being wideband is an advantage because of sharper correlation peak (Galileo) and better interference rejection; however it also exposes...
Deployed high-latency anonymous communication systems conceal communication patterns using pool mixes as building blocks. These mixes are known to be vulnerable to Disclosure Attacks that uncover persistent relationships between users. In this paper we study the performance of the Least Squares Disclosure Attack (LSDA), an approach to disclosure rooted in Maximum Likelihood parameter estimation that...
Multiple Input Multiple Output (MIMO) radars transmit partially coherent or noncoherent waveforms for improving spatial resolution or spatial diversity. While waveform design for SIMO radars concentrate on improving the delay and Doppler resolution characteristics, waveform design for MIMO radars involve optimization of delay, Doppler and spatial resolution characteristics. MIMO radar ambiguity function...
It is known that signal acquisition can be treated as a two-dimensional search and all the possible results are located in the search plane as different cells. In this paper, the theoretical expression of the cross-ambiguity function (CAF) is analyzed, and the property of the approximate expression is exploited, while it is seldom addressed in previous GNSS receiver architectures. Based on the property...
The Double Estimation Technique (DET) is a GNSS signal-tracking concept. DET has the capability to produce reliable unambiguous, full-precision delay estimates from the Binary Offset Carrier (BOC) signals which have been adopted by the modernized and new GNSS, including the European Galileo constellation. DET is robust, being able to function under conditions of low C/N0, strong multipath and filtering...
In this paper, we study a hybrid positioning system working with two GNSS satellites and two DVB-T transmitters in a SFN. By calculating the TDOA between the two satellites, the receiver clock error can be eliminated and a hyperboloid surface can be generated. The user location will result on a line generated by intersecting the hyperboloid surface with the earth surface. A similar approach is used...
Pre-correlation differential detection (PDD) scheme is studied for global navigation satellite systems (GNSS) receiver design. By performing a differential detection at the chip or sample level before correlation process, the effect of both data and residual carrier is eliminated which in turn allows for frequency independent code phase acquisition. Hence the search space and computational complexity...
A myriad of applications are based on the positioning and timing information provided by GNSS systems. Protecting the system against any kind of interference has been always on the focus of researchers and manufacturers. Unintentional and intentional interferences are two well known ways to mislead the results of GNSS receivers. However, it has been recently, with the mass-market production of Software...
Advances in computation and signal processing technologies allow the implementation sophisticated non-linear synchronization techniques that can be integrated in the acquisition and tracking modules, estimating both Line Of Sight Signal (LOSS) and multipath (MP) echoes. Instead of using an ordinary DLL/PLL, advanced DLLs as the Multipath Estimating Delay Lock Loop (MEDLL), based on maximum likelihood...
Quantification of the multipath-induced error in GNSS code-based range measurements is usually entrusted to curves as the multipath error envelope (MEE). Although very useful for comparative evaluations, these metrics do not include any realistic information on the propagation channel statistical characterization and consequently cannot be used to quantify the multipath error in an absolute way. A...
This paper proposes a cross-layer control mechanism to stream efficiently scalable videos to mobile receivers. Its goal is to maximize the quality of the received video while accounting for the variations of the characteristics of the transmitted content and of the channel. The control problem is cast in the framework of Markov Decision Processes. The optimal actions to apply to the system are learned...
An alternative implementation of the filter bank multicarrier (FBMC) concept is introduced. It is based on an FFT whose size is the length of the prototype filter. The approach clarifies the connection with OFDM and its main benefit is in the receiver, where high performance sub-channel equalization and timing offset compensation are achieved in a straightforward manner without additional delay. The...
The Pre-FFT minimum mean square error (MMSE) antenna array (AA) can depress the large delay paths signal in multi-path fading channel by performing the spatial filtering to desired/undesired signals in time domain. For mobile OFDM application, the conventional AA scheme cannot render the system less sensitive to Doppler effects. In this paper, an AA scheme is derived to suppress both Doppler shift...
In smart metering systems, when the density of node is high or distance of communication range is large, the adjacent node number becomes large. If routing based on the number of hop from the sink node is used in such a network, the deviation of load will become large and it will shorten the network lifetime, also degrades other network performance. In this paper, we proposed the techniques solving...
In-band spectrum sensing requires that the secondary users (SU) periodically suspend their communication in order to determine whether the primary user (PU) has started to utilize the channel or not. In contrast, in spectrum monitoring the SU can detect the emergence of the PU from its own receiver statistics such as receiver error count (REC). Previously it is shown that in AWGN channels, a hybrid...
Conventional frequency-domain receivers require a fixed channel within the block duration being the performance severely affected in presence of strong Doppler effects. In this paper we propose an iterative receiver for SC-FDE schemes (Single Carrier with Frequency-Domain Equalization) that is able to mitigate strong Doppler effects. This receiver can be regarded as a modified turbo equalizer, implemented...
Providing integrated network functionality in VHF tactical networks has been problematic for many years. Modern MANET routing techniques can swamp the limited bandwidth of ground-based tactical networks while legacy techniques are inefficient. In this paper, we expand on our previous work using a cross-layered approach and propose a new technique for Multicast Enhanced Opportunistic Routing (MEOR)...
In this paper, we introduce a novel multipath mitigation technique for binary offset carrier signals in global navigation satellite system (GNSS). The proposed technique is based on nonlinear operator called Teager - Kaiser Operator, which initially has been used to obtain energy of physical process. Moreover, the proposed multipath mitigation technique tries to reduce or remove the error caused by...
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