Most studies investigated the effectiveness of virtual reality (VR) for healthcare and educational purposes, but little is known on the effectiveness of VR in social interaction. Our aim was to examine whether VR would be similar to in-person interaction in reducing loneliness. A total of 73 participants participated in this study. They were randomly assigned to in-person or VR condition and interacted for 15 minutes about a tourist landmark. Participants completed a set of questions that measured belonging - acceptance and exclusion, positive and negative affect, wellbeing, trust, and mood before and after the interaction. Results showed that in both conditions, loneliness was significantly lower, with higher wellbeing, higher positive and lower negative affect, feeling happier and had more fun post task. Trust was higher in the VR condition post task but not for in-person. Our regression analyses showed that having higher wellbeing was a significant predictor in reducing loneliness for in-person condition and that being older and higher belonging - acceptance were significant predictors on feeling lonelier for the VR condition. In sum, our results demonstrated some success in reducing loneliness in VR but may not be sufficient to develop lasting friendship.

This study proposes a video retargeting method using deep neural network-based object detection. First, the meaningful regions of the input video denoted by bounding boxes of the object detection are extracted. In this case, the area is defined considering the size and number of bounding boxes for objects detected. The bounding boxes of each frame image are considered as regions of interest (RoIs). Second, the Siamese object tracking network is used to address high computational complexity of the object detection network. By dividing the video into scenes, object detection is performed for the first frame image of each scene to obtain the first bounding box. Object tracking is performed for the next sequential frame image until a scene change is detected. Third, the image is resized in the horizontal direction to alter the aspect ratio of the image and obtain the 1D RoIs of the image by projecting bounding boxes in the vertical direction. Then, the proposed method computes the grid map from the 1D RoIs to calculate new coordinates of each column data of the image. Finally, the retargeted video is obtained by rearranging all retargeted frame images. Comparative experiments conducted with various benchmark methods show an average bidirectional similarity score of 1.92, which is higher than other conventional methods. The proposed method was stable and satisfied viewers without causing cognitive discomfort as conventional methods.

This study deals with the study on the performance of the hybrid transmission scheme combining both beamforming and spatial multiplexing for multiple spatial streams. The capacity of the hybrid scheme is evaluated and compared with that of the beamforming scheme for a single spatial stream in both line‐of‐sight and multi‐path channels. Two kinds of hybrid schemes are considered: the shared antenna architecture, where each antenna processes all spatial streams and the split antenna architecture, where each antenna processes only one spatial stream. The effects of the channel parameters, such as the antenna spacing, the existence of reflected paths etc. On the capacity and the optimal beams and powers are examined. The frequency‐selective property of the capacity and optimal beams and powers are also investigated. In this study, a scenario is assumed, where the same analogue radio frequency (RF) beamforming vector (or matrix) is applied to all subcarriers whereas the digital baseband power allocation is executed individually at each subcarrier.

This article deals with the study on the performance of the hybrid transmission scheme combining both beamforming and spatial multiplexing. Specifically, the capacity of the hybrid scheme is evaluated and compared to that of the just beamforming scheme in line-of-sight and multi-path channels. Two kinds of the hybrid schemes are considered: the shared antenna architecture where each antenna processes all data streams and the split antenna architecture where each antenna processes only one data stream. The effects of the channel parameters such as the antenna spacing, the existence of reflecting paths, etc. on the capacity and the optimal beams and powers are examined. The frequency-selectivity property of the capacity and the optimal beams and powers is also investigated. In this study, a scenario is considered where the same analog RF beamformer is applied to all subcarriers but the digital baseband power allocation is executed individually at each subcarrier.

In Rayleigh block fading channels which represent fast-varying channels, long-term rate adaptation is required instead of instantaneous rate adaptation because the channel information fed back may be outdated. We maximize the long-term average transmission rate (LATR) in a two-hop relay network which adopts Chase combining (CC) type Hybrid Automatic-Repeat-reQuest (HARQ). The round transmission rate, i.e. the transmission rate of each HARQ round in each hop, is optimally selected based on the channel statistics of two hops. Two constraints are considered: the outage probability and the maximum number of HARQ rounds, L. In an infinite L case, we show that the optimal round transmission rate of one hop is determined only by the channel statistics of that hop, and can be expressed as a Lambert W function. In a finite L case, we propose a numerical search algorithm to find the optimal round transmission rate. If HARQ is not adopted, the LATR performance becomes very poor. As L increases in the two-hop relay with CC-based HARQ, the LATR performance becomes close to the LATR performance in the infinite L case. We also show the benefits of the proposed rate selection method compared to a non-optimal rate selection method in terms of the LATR.

Based on the ray-tracing technique, the 2×2 multiple-input multiple-output (MIMO) channel capacity is examined for millimetre-wave propagation channels between two stations on a table in a conference room. This study focuses on the contributions of reflectors in enhancing the MIMO capacity with small antenna spacings. The effect of each class of reflectors (front/rear/left/right wall or ceiling) on the capacity is investigated. For reflection, both cases are considered: the reflection without scattering (where there are only deterministic specular central rays) and the reflection with scattering (where there are stochastic pre-cursor and post-cursor rays as well). Both vertical and horizontal antenna polarisations are considered. Since the capacity is frequency dependent in multi-path channels, the capacity averaged over a range of frequency, as well as the capacity at a specific frequency, are examined for performance evaluation. This study relys on a theoretical evaluation of the capacity based on IEEE802.11ad 60 GHz channel model comprising idealised reflections and statistically modelled scattering effects. The dimension of the conference room and most of the other channel parameters are also employed, as suggested by the channel model.

The 2×2 MIMO channel capacity is studied for millimeter wave radio propagation between two stations (STA-STA) on a table in a conference room. It is focused on whether a small antenna spacing enables a high MIMO channel capacity or not. The effect of reflection is also investigated on the MIMO channel capacity. For reflection, both two cases are considered: the reflection without scattering (where there are only deterministic central rays) and the reflection with scattering (where there are stochastic pre-cursor and post-cursor rays as well). The dimension of the conference room and other most channel parameters are employed, as suggested in the IEEE802.11ad 60 GHz channel model. It is shown from the simulation results that the scattering of such power as suggested in IEEE802.11ad 60 GHz channel model does not have significant effect on the MIMO channel capacity. The capacity is shown to depend on the multiple antenna orientation and the orientation of reflectors (that is, whether the reflector is either wall or ceiling). It is found that there is a locally optimal value in the region of small antenna spacings to maximize the MIMO channel capacity over that region.

To overcome the problem that the transmission rate of a multicast channel is limited by the user with the worst channel quality, which causes the total system throughput to be low, the use of both multicast and unicast channels for multicast service is considered in this letter. Unicast channels, in addition to a multicast channel, are allocated to users with signal-to-noise ratios (SNRs) lower than a predefined threshold in order to enable the increase of the transmission rate of the multicast channel. The used unicast channels consume additional radio resource. It is examined whether use of such unicast channels can raise the spectral efficiency defined as the total system throughput normalized by the total consumed bandwidth. The optimal value of the threshold SNR is derived by maximizing the spectral efficiency. When a unicast channel is additionally allocated for multicast service, two decoding schemes are considered: one is to use only the signal of a unicast channel, and the other is to use and combine both the signals of multicast and unicast channels. Numerical examples are presented to show the performance gains obtained by using unicast channels in addition to a multicast channel.

To overcome the problem that the transmission rate of a multicast channel is limited by the user with the worst channel quality, which causes the total system throughput to be low, the use of both multicast and unicast channels for multicast service is considered in this paper. Unicast channels, in addition to a multicast channel, are allocated to users with signal-to-noise ratios (SNRs) lower than a predefined threshold in order to enable the increase of the transmission rate of the multicast channel. The used unicast channels consume additional radio resource. It is examined whether use of such unicast channels can raise the spectral efficiency defined as the total system throughput normalized by the total consumed bandwidth. The optimal value of the threshold SNR is derived by maximizing the spectral efficiency. When a unicast channel is additionally allocated for multicast service, two decoding schemes are considered: one is to use only the signal of a unicast channel, and the other is to use and combine both the signals of multicast and unicast channels. Numerical examples are presented to show the performance gains obtained by using unicast channels in addition to a multicast channel.

Recently, researches on space-time codes deploying multiple transmit and receive antennas have abruptly emerged due to its potential to greatly improve spectral efficiency. Particularly, space-time bit-interleaved coded modulation (ST-BICM) gives rise to very reliable bit error rate (BER) performance with quite flexible rate compatibility. In this paper, we propose an iterative linear minimum-mean-squared-error (LMMSE) channel estimation, detection, and decoding for ST-BICM systems over block fading channels in order to resolve more practical problems concerned with the performance degradation due to imperfect channel state information (CSI). The LMMSE channel estimation and detection are performed using a priori information fed back from the soft-input / soft-output (SISO) channel decoder in a computational efficient manner. The simulation results demonstrate that the performance of our proposed algorithm approaches to the matched filter bound (MFB) with an SNR loss of less than 1 dB at BER of 10-6, and its convergence of behavior is presented with the extrinsic information transfer (EXIT) charts.

The performance of non-data-aided feedback-loop symbol timing synchronization operating with the raised-cosine (RC) and the "better than" raised-cosine (BTRC) pulses is investigated. The individual effects of additive channel noise, self noise, and their product on the variance of the jitter are studied for the two pulses. The BTRC pulse is shown to have better synchronization performance than the conventional RC pulse, except when the signal-to-noise ratio is very large and the excess bandwidth is large. Furthermore, in the case where a prefilter removing self-noise is employed, the BTRC pulse always has a performance gain over the RC pulse. The gain is, for example, as much as 1.4 dB for excess bandwidth of 0.35 without a prefilter and is larger when the excess bandwidth is smaller or a prefilter is employed.

It is known that the "better than" raised-cosine pulse has several advantages over the conventional raised-cosine pulse. In addition to the advantages previously reported, this letter reports that the "better than" raised-cosine pulse enables better performance of symbol timing estimation than the raised-cosine pulse. Both Cramer-Rao lower bounds and simulations of practical synchronizers show the superiority of the new pulse. The performance gain can be as much as 3.4 dB for a practical system.

A new optimal pulse is derived considering both the symbol timing estimation performance and the mean squared error of intersymbol interference corrupted data recovered in timing error. The new pulse design minimizes the mean squared error of the recovered data averaged over the timing error, accounting for the fact that the distribution of the timing error is also affected by the pulse shape. The new pulse resembles the Franks' double-jump pulse, but has different slope than the Franks' double-jump pulse in the spectral rolloff region. Although the new pulse has greater mean squared error than the Franks' pulse for a fixed small timing error, it has better symbol timing estimation performance and better overall performance as measured by the Cramer Rao lower bound and by the mean square error of the recovered data accounting for both timing recovery effects and data recovery distortion, respectively. An optimal pulse that minimizes the mean squared error of intersymbol interference corrupted data recovered in the presence of fixed but arbitrary timing error is derived as an intermediate result.

The performances of non-data-aided feedback-loop symbol timing synchronization operating with the raised-cosine and the "better than" raised-cosine pulses are investigated. In terms of the jitter variance, modified Cramer-Rao bounds are compared and the individual effects of additive channel noise, self-noise, and their product on jitter variance are also investigated for the two pulses. The better than raised-cosine pulse is shown to have better synchronization performance than the conventional raised-cosine pulse. The gain is, for example, as much as 1.4 dB for excess bandwidth of 0.35 without a prefilter and is larger when the excess bandwidth is smaller or a prefilter is employed.

A new optimal pulse is derived considering both the symbol timing estimation performance and the mean squared error of intersymbol interference corrupted data recovered in timing error. The new pulse resembles the Franks' double-jump pulse, but has different slope than the Franks' double-jump pulse in the spectral rolloff region. Although the new pulse has greater mean squared error than the Franks' pulse for a fixed small timing error, it has better symbol timing estimation performance and better overall performance as measured by the Cramer Rao lower bound and by the mean square error of the recovered data accounting for both timing recovery effects and data recovery distortion, respectively. An optimal pulse that minimizes the mean squared error of intersymbol interference corrupted data recovered in the presence of fixed but arbitrary timing error is derived as an intermediate result.

It is known that the "better than" raised-cosine pulse has several advantages over the conventional raised-cosine pulse. In addition to the advantages previously reported, this paper reports that the "better than" raised-cosine pulse enables better performance of symbol timing estimation than the raised- cosine pulse. Both Cramer-Rao lower bounds and simulations of practical synchronizers show the superiority of the new pulse. The performance gain can be as much as 3.4 dB for a practical system.

A precise bit-error probability analysis method for multicode DS-CDMA systems in Rayleigh fading is derived. The proposed method applies to a multicode DS-CDMA system with an arbitrary number of multiple code sequences and any selection of multiple code sequences. The method gives accurate results for Rayleigh fading while requiring only a single numerical integration of an integrand involving the well-known Q-function. The solution discriminates the effect of the selection of different multiple code sequences on the bit-error probability, whereas Gaussian approximations do not. The numerical examples show that the differences between methods for a multicode DS-CDMA system operating over Rayleigh fading channels may be more significant than for a single code system in Rayleigh fading channels or a multicode system in AWGN channels when the spreading factor is not large compared to the number of multiple code sequences.

A precise bit-error probability (BEP) analysis method is derived for a multicode direct-sequence code-division multiple-access (DS-CDMA) system in an additive white Gaussian noise channel. The method is applicable to a multicode DS-CDMA system with an arbitrary number of multiple code sequences, and any selection of multiple code sequences. The precise method gives results that discriminate the effect of the selection of different multiple code sequences on the BEP, whereas Gaussian approximations (GAs) do not. Thus, the new method can be used to select the best multicode set for a given system, a task that cannot be achieved using GAs. A two-step analytical procedure enables deriving an explicit, compact form for the CF of the receiver decision statistic in a DS-CDMA system with an arbitrary number of multiple code sequences, and for any selection of multiple code sequences.

We analyze the computational complexity of sphere decoding (SD) for maximum likelihood detection (MLD) according to initial radius selection schemes, and also propose an efficient initial radius reduction scheme that reduces further the initial radius. As the initial radius for SD, we use the Euclidean distance between the received signal vector and the lattice vector corresponding to a suboptimum initial estimate. The proposed initial radius reduction scheme selects a new lattice vector closer to the received signal vector than the initial lattice vector in order to reduce the initial radius further. From our analyses, the reduction in the overall complexity due to further reduction of initial radius gets more significant as the SNR decreases. The ZF-DFE scheme in a combination with the proposed radius reduction scheme has the fewest computations over practical SNR range for communications, and its computations are less than that of the vertical Bell-labs layered space-time (V-BLAST) detection scheme with optimal ordering, even at low SNR values achieving an uncoded bit error rate (BER) of 0.1.

A precise bit-error probability analysis method is derived for a multicode DS-CDMA system in an additive white Gaussian noise channel. The method is applicable to a multicode DS-CDMA system with an arbitrary number of multiple code sequences and any selection of multiple code sequences. The precise method gives results that discriminate the effect of the selection of multiple code sequences on the bit-error probability, whereas Gaussian approximations do not. Thus, the new method can be used to select the best multicode set for a given system, a task that cannot be achieved using Gaussian approximations. A two-step analytical procedure enables deriving an explicit, compact form for the characteristic function of the receiver decision statistic in a DS-CDMA system with an arbitrary number of multiple code sequences, and for any selection of multiple code sequences.

Many techniques for calculating bit-error probabilities (BEPs) of direct-sequence spread-spectrum multiple-access systems (DS-SSMA) have been reported. Among them are the following three techniques: (1) the standard Gaussian approximation; (2) the improved Gaussian approximation; (3) and the simplified improved Gaussian approximation. We extend these techniques to derive the BEPs of multicode DS-SSMA systems. We assess the three techniques by comparing their results with the result of computer simulation.

We calculate the capacity of DS-CDMA systems supporting multi-class services with different transmission rates and bit error rates. Two techniques, a single-code scheme using a variable processing gain and a multi-code scheme, are considered to provide multi-rate services. The capacity is expressed by an inequality to which the number of accepted calls of each class should conform. The inequality is the necessary and sufficient condition satisfying the requirement of the bit energy-to-interference power spectral density ratio. The optimal received power is derived to cause the least interference to other signals while maintaining the acceptable bit energy-to-interference power spectral density ratio. Finally, the capacity is also derived in a dynamic multiple cell environment.

To accommodate multimedia and broadband mobile services, future mobile communication networks are likely to be integrated with broadband fixed networks. Previous MAN-based architectures may be rather complex to provide various isochronous/non-isochronous services due to complicated slot generation processings. We propose a broadband personal communication network (BPCN) architecture based on B-ISDN/ATM. We employ simple cell based add-drop multiplexers (ADMs) instead of rather complex medium access control systems. We also suggest a ring management scheme. After describing call processing procedures, we calculate and compare the signaling processing loads at the various nodes and the signaling loads on the various links for six types of configurations according to the locations of basestation controller (BSC), visitor location register (VLR), and mobile switching center (MSC). These results may be utilized in designing BPCNs in the given conditions, such as PCN subscriber environments and the capabilities of network entities. A 150 Mbps-dual ring can support the maximum carried traffic load of about 5,500 on-off voice traffic in the case that 300 connections are supported in the ring node (RN). This ring capacity corresponds to covering approximately 180 cells, if we assume 30 connections per cell.