The robustness of subnetworks for the interconnection network of a computer system is an important consideration for the system performance. It can be measured by the extent to which subnetworks can stay fault-free when faults are present in the system. In this paper, we evaluate the subnetwork robustness for then-dimensional split-star network$S_{n}^{2}$. Let$S_{n-m}^{2}, 1 \leq m \leq n-3$, be a subnetwork of$S_{n}^{2}$, and letpbe the node reliability, the probability that a single node remains fault-free. We determine two values that reflect how robust$S_{n-m}^{2}$subnetworks are, from two perspectives. We first establish the upper/lower bounds for$\mathcal{F}_{m} (S_{n}^{2})$, the minimum number of faulty nodes to make all$S_{n-m}^{2}$subnetworks faulty. Then, we determine the subnetwork reliability, denoted by$\mathcal{R}_{m} (S_{n}^{2}, p)$, which is the probability that at least one fault-free$S_{n-m}^{2}$subnetwork exists in$S_{n}^{2}$, given the node reliabilityp. The upper/lower bounds and an approximation expression for$\mathcal{R}_{m} (S_{n}^{2}, p)$are obtained. We also propose a simulation method to estimate$\mathcal{R}_{m} (S_{n}^{2}, p)$. The experimental results show that a) whenpis relatively low,$\mathcal{R}_{m} (S_{n}^{2}, p)$can be approximated by the mean value of its upper and lower bounds, or the estimation value by the approximation expression; b) whenpis high,$\mathcal{R}_{m} (S_{n}^{2}, p)$can be more accurately estimated by our simulation method.

It is often a challenging task to build Machine Translation (MT) engines for a specific domain due to the lack of parallel data in that area. In this project, we develop a range of MT systems for 6 European languages (English, German, Italian, French, Polish and Irish) in all directions and in two domains (environment and economics).

Contact tracing apps used in tracing and mitigating the spread of COVID-19 have sparked discussions and controversies worldwide. The major concerns in relation to these apps are around privacy. Ireland was in general praised for the design of its COVID tracker app, and the transparency through which privacy issues were addressed. However, the ”voice” of the Irish public was not really heard or analysed. This study aimed to analyse the Irish public sentiment towards privacy and COVID tracker app. For this purpose we have conducted sentiment analysis on Twitter data collected from public Twitter accounts from Republic of Ireland. We collected COVID-19 related tweets generated in Ireland over a period of time from January 1, 2020 up to December 31, 2020 in order to perform sentiment analysis on this data set. Moreover, the study performed sentiment analysis on the feedback received from a national survey on privacy conducted in Republic of Ireland. The findings of the study reveal a significant criticism towards the app that relate to privacy concerns, but other aspects of the app as well. The findings also reveal some positive attitude towards the fight against COVID-19, but these are not necessarily related to the technological solutions employed for this purpose. The findings of the study contributed to the formulation of useful recommendations communicated to the relevant Irish actors.

Contact tracing apps used in tracing and mitigating the spread of COVID-19 have sparked discussions and controversies worldwide with major concerns around privacy. COVID Tracker app used in the Republic of Ireland was praised in general for the way it addressed privacy and was used as baseline for other contact tracing apps worldwide. The success of the app is dependent on the general public uptake, hence their voice and attitude is the one that really matters. This paper focuses on developing a survey and the methods aiming to examine the attitudes toward privacy during COVID-19 of the general public in the Republic of Ireland and their impact on the uptake of the COVID tracker app. Various privacy models are used and health belief model as well in this purpose. A pilot study with 286 participants show a change in attitude towards privacy during COVID-19 pandemic, with more people willing to share their data in the interest of saving lives. However, privacy attitudes are shown to have impacted the adoption of the app in Ireland.

Generation and detection of millimeter-wave carrying orbital angular momentum (OAM) have been of growing interest. In this paper, we evaluate patch antenna arrays with different arrangements as OAM generators and receivers by simulation. We compare beam evolution processes and steering performance for circular and ring-antenna-array based OAM links. Mode purity of the generated OAM +1 beam fluctuates between 10% and 99% for ring antenna arrays with 10 cm diameters while it remains >99% for circular antenna arrays. Compared to a ring-antenna-array based link, the circular-antenna-array based link could have an ~10 dB lower power loss at the distance up to 0.5m. We also show that a 5cm diameter circular antenna array could steer an OAM +1 beam up to 80° with a mode purity degradation of <;1%, while ring antenna arrays have ~10% mode purity degradation. OAM spectrum analysis shows both the lattice shape and the boundary shape of an antenna array could cause power leakage to harmonic OAM orders. Such power leakages would increase as the designed OAM order or the lattice period d increases, while it would decrease as the array diameter D increases.

Detecting moving objects is of great importance for autonomous unmanned vehicle systems, and a challenging task especially in complex dynamic environments. This paper proposes a novel approach for the detection of moving objects and the estimation of their motion states using consecutive stereo image pairs on mobile platforms. First, we use a variant of the semi-global matching algorithm to compute initial disparity maps. Second, assisted by the initial disparities, boundaries in the image segmentation produced by simple linear iterative clustering are classified into coplanar, hinge, and occlusion. Moving points are obtained during ego-motion estimation by a modified random sample consensus) algorithm without resorting to time-consuming dense optical flow. Finally, the moving objects are extracted by merging superpixels according to the boundary types and their movements. The proposed method is accelerated on the GPU at 20 frames per second. The data which we use for testing and benchmarking is released, thus completing similar data sets. It includes 812 image pairs and 924 moving objects with ground truth for better algorithms evaluation. Experimental results demonstrate that the proposed method achieves competitive results in terms of moving-object detection and their motion state estimation in challenging urban scenarios.

Line-of-sight wireless communications can benefit from the simultaneous transmission of multiple independent data streams through the same medium in order to increase system capacity. A common approach is to use conventional spatial multiplexing with spatially separated transmitter/receiver antennae, for which inter-channel crosstalk is reduced by employing multiple-input-multiple-output (MIMO) signal processing at the receivers. Another fairly recent approach to transmitting multiple data streams is to use orbital-angular-momentum (OAM) multiplexing, which employs the orthogonality among OAM beams to minimize inter-channel crosstalk and enable efficient (de)multiplexing. In this paper, we explore the potential of utilizing both of these multiplexing techniques to provide system design flexibility and performance enhancement. We demonstrate a 16 Gbit/s millimeter-wave link using OAM multiplexing combined with conventional spatial multiplexing over a short link distance of 1.8 meters (shorter than Rayleigh distance). Specifically, we implement a spatial multiplexing system with a 2 × 2 antenna aperture architecture, in which each transmitter aperture contains two multiplexed 4 Gbit/s data-carrying OAM beams. A MIMO-based signal processing is used at the receiver to mitigate channel interference. Our experimental results show performance improvements for all channels after MIMO processing, with bit-error rates of each channel below the forward error correction limit of 3.8 × 10-3. We also simulate the capacity for both the 4 × 4 MIMO system and the 2 × 2 MIMO with OAM multiplexing. Our work indicates that OAM multiplexing and conventional spatial multiplexing can be simultaneously utilized to provide design flexibility. The combination of these two approaches can potentially enhance system capacity given a fixed aperture area of the transmitter/receiver (when the link distance is within a few Rayleigh distances).

This paper reports an experimental investigation of using orthogonal frequency division multiplexing (OFDM) on orbital-angular momentum (OAM) channels when there is intersymbol interference (ISI) caused by multipath effects. The impulse response measurement indicates that due to the divergence of OAM beams, channels of larger OAM number are more affected by the ISI caused the reflections from surrounding objects. Channel performance of three different OAM numbers l = 0, +1 and +3 are studied. When a single QPSK channel is used, the more channel performance degradation in term of BER and EVM is observed for higher OAM channels. OFDM with 4 sub-carriers is used on the OAM channels to help reduce the ISI and improve the channel performance to some extent.

In this paper, the generation and steering of beams carrying orbital angular momentum utilizing a custom-designed circular antenna array has been demonstrated at 28 GHz. A steering angle as large as 30 degrees for an orbital angular momentum (OAM) beam has been achieved. The effect of number of antennas and the distance from antennas to the array center to the quality of beam generation and beam steering is investigated through both experiments and simulations. Our results indicate that: (1) As the steering angle increases, the mode purity of the generated OAM beams decreases; (2) Increasing the number of antennas improves the OAM mode purity; (3) For a fixed number of antennas, high mode purity is observed for lower order OAM modes; (4) Placing the antennas farther away from the array center allows for reduced divergence of the generate OAM beams.

This paper reports an experimental demonstration of a 32-Gbit/s wireless link using orbital angular momentum (OAM) and polarization multiplexing in a millimeter-wave regime at 60 GHz. Results of the analysis show that a higher carrier frequency reduces the propagation loss as well as the size of the transmitter and receiver, particularly for OAM channels with higher OAM values. Further, two different OAM channels (with l = +1 and l = +3) on each of the two polarizations are spatially multiplexed, and each channel carries 2-Gbaud signals with 16-QAM modulation. Spiral phase plates are used to generate 60-GHz OAM beams. The simulation results show that a higher carrier frequency plays a more significant role in reducing both the aperture size and the transmission loss for channels with higher OAM values. The bit error rates (BERs) of 4 channels are measured, and the raw BERs are found to be less than 3.8 × 10−3

We present a short-range experimental orbital-angular-momentum (OAM) multiplexing millimeter-wave communication system using patch antenna arrays. The dependence of the evolution of OAM beams on the number of array elements and array radius are analyzed. We also find phase delay deviation of 30 degrees leads to mode purity degrading to ∼1% and power deviation of 6 dB reduces the purity by <40%. An obstruction of size <10mm has not much influence on the evolution of OAM beams generated from antenna arrays with r = 8mm, which enables the stacking of multiple antenna arrays. We also use these patch antenna arrays to demonstrate a 60 GHz wireless communication link using two multiplexed OAM modes, each carrying a 500-Mbaud 16-QAM or 2-Gbaud QPSK signal. A channel crosstalk of less than −20 dB and bit-error-rates (BER) of less than 3.8 × 10−3 are achieved.

This paper reports on an experimental measurement and analysis of multipath-induced intra- and interchannel crosstalk effects in a mm-wave communications link using orbital angular momentum multiplexing at 28 GHz. The reflection is from an ideal reflector parallel to the propagation path. The intra-channel crosstalk effect is measured when a single OAM beam is transmitted, and inter-channel crosstalk effect is measured when 2 multiplexed OAM beams are transmitted. Both simulation and experimental results show that OAM channels with larger OAM number ℓ tend to have stronger intra-channel crosstalk because less power is received from the direct path and more power is received from the reflected path. This effect is caused by OAM beam divergence, as OAM beams with larger ℓ spread into a larger beam size and have less power in the beam center. For the same reason, OAM beams of larger ℓ lead to stronger inter-channel crosstalk with the other OAM channels.

We present the design and performance characterization of a thin metamaterial plate for generation of orbital angular momentum (OAM) modes of a millimeter-wave beam, which can carry independent data streams over the same physical medium. The plate has a thickness of 1.56 mm, and consists of 3.06 × 0.68 mm rectangular apertures with spatial variant orientations. It generates OAM beams l = +1 and l = +3 with mode purity larger than 77.5% over a bandwidth of 6 GHz (25-31 GHz). We then use these streams to experimentally demonstrate a 16-Gbit/s millimeter-wave wireless communications link using two multiplexed OAM modes, each carrying a 2-Gbaud 16-QAM signal. A channel crosstalk less than -20 dB over a bandwidth of 4 GHz (26-30 GHz) and biterror-rates (BER) less than 3.8 × 10-3are achieved.

This paper reports an experimental demonstration of a 16 Gbit/s millimeter-wave communication link using MIMO processing of 2 OAM modes on each of two transmitter/receiver antenna apertures. Two groups of multiplexed OAM beams, each containing OAM beams of ℓ =1 and +3 are generated and transmitted through two transmitter apertures respectively. The two transmitter apertures are separated with a certain distance such that the two groups of OAM beams are spatially overlapping at the receiver aperture plane. Each channel carries 1-GBaud 16-QAM signals at the same carrier frequency of 28 GHz. Our experimental results show that MIMO equalization processing can help mitigate the interferences from the other OAM channels and the BER performance of each channel improves significantly after MIMO processing. Our results indicate that OAM multiplexing and traditional spatial multiplexing combined with MIMO processing can be compatible and complementary with each other.

This paper reports an experimental demonstration of modal multiplexing using orbital angular momenta (OAM) in the millimeter-wave regime (28 GHz). Using 1 GBaud/s signals with 16-QAM modulation, a data rate of 32 Gbit/s is obtained by employing 4 different OAM modes (l= -3,-1,+1 and +3) on two orthogonal linear polarization states. Without any digital post-processing, the receiver can separate the different data streams since crosstalk among the OAM channels is low: measured to be better than -23dB with a 28 GHz narrowband carrier on a single polarization, and better than -16dB on both polarization states. The bit-error rate (BER) of 8 channels is measured, and found the raw BER is below 3.8×10-3, thus allowing efficient use of forward error correction (FEC) codes.

Free-space-optical (FSO) coherent communication is a cost-effective, license-free, high-sensitivity and wide-bandwidth access technique for high date rates applications, whereas its performance strongly suffers from the turbulent atmosphere for the reason of both intensity scintillation and phase fluctuation. In this paper, the intensity scintillation is modeled as a multiplicative random process following the Gamma-Gamma distribution while the phase fluctuation is proved to satisfy Gaussian distribution. And the slow varying characteristic of the power spectrum destiny of the atmosphere is verified. In our research the Mach-Zehnder-interferometer (MZI) based coherent differential-phase-shift-keying (DPSK) transmission system is employed. And its bit-error-rate (BER) performance is studied with BER expression given by Meijer-G function substitution. Besides, a novel simulation model of the atmosphere channel is established based on which effects of the atmosphere to BER performance of the system are simulated. From the simulation, we know over FSO links, to guarantee the performance of the coherent system, measures should be taken to compensate the intensity of the signal when the Rytov variance is over 1.0, and the statistical standard deviation of the received signal frequency should be compensated to less than 100MHz when the transmission rate is 1Gbit/s. By comparing performances of MZI-DPSK and traditional PSK, the advantages of MZI-DPSK are presented.

In this paper, we investigate a cooperative system consisting of one source-destination pair equipped with single antenna and L relays equipped with M antennas as wireless access points. We propose a new relay selection scheme for this system based on partial relay selection, where the best relay is selected according to the instantaneous and one-hop channel state information (CSI). We use maximal ratio combining (MRC) and maximal ratio transmitting (MRT) at relays to obtain the maximal achievable received signal-to-noise ratio (SNR). Close-form expressions for the outage probability and symbol error rate (SER) are derived. High SNR analysis is tightly approximated to explicitly characterize the diversity order and array gain. Monte Carlo simulations verify our analytical results. Results show that the diversity order increases with the antenna numbers at the selected relay according to M. For partial relay selection, two available relays are enough to get the array gain, and impacts of relay locations are also discussed in this paper.

A combination of statistical and rule methods has been developed for Chinese spoken language analyzing. The analyzing result is a middle semantic frame, which can be converted to different language according people’s needs. We adopt the statistical method in the stage of extracting semantic meaning and the rule method in the stage of mapping the semantic units to middle semantic frame. Experiment shows this method has high robustness and can analyzing Chinese spoken language effectively. 1.