Transmission Of Symbols Research Articles

Measuring social media brand community success: the roles of media capability and organisational support

By integrating the perspectives of the DeLone and McLean information systems success model, media synchronicity theory, and organisational support, this study develops a theoretical model to examine the factors affecting the success of a social media brand community. Data collected from 220 users of a social media brand community in Taiwan were used to test the model. The results showed that transmission velocity, symbol sets, and reprocessability are the factors that affect social media brand community quality. The results also showed that technology resources support is a predictor of social media brand community quality and user satisfaction, whereas business resources support only has a significant effect on social media brand community quality. Finally, the results revealed that social media brand community quality and user satisfaction exerted significant influences on continuance intention. This paper discusses the theoretical and managerial implications of the study.

Energy-Efficient SWIPT: From Fully Digital to Hybrid Analog–Digital Beamforming

Simultaneous wireless information and power transfer (SWIPT) enables the transmission of information symbols and energy simultaneously. In this paper, we study the multiple-input-multiple-output SWIPT systems with limited RF chains at the base station. We focus on the scenario where there is one information decoder with a target signal-to-interference-plus-noise-ratio and several separate energy-harvesting receivers with harvested energy thresholds. To motivate our energy-efficient hybrid analog–digital beamforming strategy, the fully digital power minimization problem is first analyzed, where we mathematically show that the optimal beamformer consists of only the information beamformer, and derive closed-form beamformers for a number of special cases. Based on this result, we further consider hybrid beamforming and propose an iterative scheme where the analog and digital beamformers are alternately updated. For the proposed scheme, in each iteration we design the analog beamformer by minimizing the difference between the fully digital beamformer and the hybrid beamformer. Based on our above-mentioned analysis for fully digital case, the optimal solution for the analog beamformer can be obtained via a geometrical interpretation. We further design the robust beamformers for the proposed schemes, when only imperfect channel state information is available. The numerical results show that the proposed iterative designs achieve a close-to-optimal performance with significant gains in the total power consumption over fully digital SWIPT.

Modulation Over Nonlinear Fourier Spectrum: Continuous and Discrete Spectrum

Nonlinear frequency division multiplexed (NFDM) systems are considered when data are modulated in both parts of the nonlinear Fourier spectrum: Continuous spectrum and discrete spectrum. An efficient algorithm is introduced to generate a time-domain signal from a given nonlinear spectrum. The transmission of such NFDM symbols is experimentally demonstrated over 1460 km standard single-mode fiber with EDFA-only amplification. In each NFDM symbol, the continuous spectrum is modulated by 64 $\times$ 0.5 Gbaud orthogonal frequency-division multiplexing (OFDM) symbols with 32-QAM format whereas the discrete spectrum contains four eigenvalues with the same imaginary part, each one is modulated by 8-PSK format, resulting a line rate of 55.3 Gb/s. The cross-talk between different nonlinear modes is quantified in terms of cross-correlation and the performance loss is computed in terms of mutual information when each nonlinear modes is detected individually.

Expected distortion of simultaneous transmission of multiple source symbols with multicarrier frequency hopping modulation

In this paper, we consider the problem of transmitting a Gaussian source over a slow-fading channel, when the aim is to adjust system parameters so that the source is reconstructed with minimum expected distortion. In the considered scenario, the spatial distribution of users is modelled by a homogeneous Poisson point process. These users transmit their symbols by means of multicarrier frequency hopping modulation in which the frequency diversity characteristic is implemented by dividing the available bandwidth into several subbands where each subband consists of several subchannels. The number of subbands has a significant effect on the improvement of the system’s performance. We can have as many descriptions as the number of available subbands. In this way, we consider a combination of symmetric multiple description coding as the source coding and direct channel transmission coding as the channel coding so as to code the source signal into several descriptions which have the same number as the subbands. Considering separate source-channel coding strategy, we compute the expected distortion and evaluate the effects of system parameters on it. Furthermore, with the goal of minimizing the expected distortion, the optimum values of some system parameters in general and also for the case where the bandwidth expansion ratio is equal to one, are calculated. Through the optimization process, the optimum number of subbands and the optimum value of source coding rate are determined which lead to a significant improvement in the network performance.

Burst transmission symbol synchronization in the presence of cycle slip arising from different clock frequencies

In digital communication systems, different clock frequencies of transmitter and receiver usually are translated into cycle slips. Receivers and transmitters may experience different sampling frequencies due to manufacturing imperfection, Doppler effect introduced by channel or having error in estimation of symbol rate. Timing synchronization in presence of cycle slip for a burst sequence of received information leads to severe degradation in system’s performance. Therefore, the necessity of prior detection and elimination of cycle slip is obvious. Accordingly, the main idea introduced in this paper is to employ the Gardner detector (GaD) not only to recover a fixed timing offset, but also its output is processed such that timing drifts can be estimated and corrected. By deriving a two-step algorithm, first the cycle slips arising from symbol rate offset is eliminated, and then symbol’s timing offset is synchronized in an iterative manner. GaD structure is used in a feedforward structure with the additional benefit that convergence and stability problems, which are typical challenges of the systems with feedback, are avoided. The proposed algorithm is able to compensate considerable symbol rate offsets at the receiver side. Results in terms of BER confirm the algorithm’s proficiency.

Theoretical Performance of Coherent and Incoherent Detection for Zero-Forcing Receive Antenna Shift Keying

Receive antenna shift keying (RASK) is a multiple-input multiple-output transmission scheme that applies the spatial modulation concept at the receiver. Zero-forcing (ZF) precoding can be used at the transmitter side to steer the signal toward the targeted antenna. Different detection schemes can be implemented in order to detect the RASK information. Moreover, for the sake of low complexity and low power consumption, decreasing the number of RF chains by the use of switched antennas can also be implemented. In this paper, we lead a theoretical analysis of the transmission of spatial symbols in RASK, using the ZF precoding. Two detection schemes relying on maximum likelihood (ML) detection are presented and proved to be implemented as a simple single-tap detector. One, called coherent ML (CML), needs one RF chain per receive antenna and the other one, named incoherent ML (IML), is based on an envelope detector and needs only one RF chain for the entire antenna array. Theoretical expressions of the bit error rate (BER) are derived for each scheme and validated through simulation. The CML detector is demonstrated to obviously outperform the IML detector in terms of the BER but at the cost of higher complexity and power consumption. We then proposed to use switches to reduce the number of RF chains, thus trading off some performance against complexity. At some point, IML is shown to outperform CML, depending on the number of switches, RF chains, and system configuration. This turning point is analytically calculated and validated through simulations, and so can be used for further system comparison studies.

Iterative equalization algorithm based on modified matrix for asynchronous MIMO OFDM

Aiming to co-antenna interference and multipath interference in the downlink multiple input multiple output orthogonal frequency division multiple multiplexing (MIMO-OFDM) asynchronous communication system, a low complexity iterative equalization algorithm based on precoding matrix is proposed. At the transmitter, the algorithm utilizes precoding matrix to spread the symbols over all the subcarriers, which relieve the influence of deep fading in part of the subcarriers. At the receiver, the algorithm adopts Soft input soft output(SISO) interference elimination algorithm based on the minimum mean square error sorted QR decomposition (MMSE-SQRD) to avoid the complexity of solving inverse matrix, which is always involved in the traditional parallel soft interference elimination algorithm based on minimum mean square error(MMSE)equalization. Utilizing a sorted QR decomposition of the channel matrix, on the other hand, the algorithm has the priority for detection transmission symbol with maximum noise-signal ratio (SNR) to improve detection accuracy. Furthermore, the error of reconstructed signals is spread by the precoding matrix, which decreases the error propagation in iteration processing. Simulation results show that the performance of the proposed algorithm is improved compared with the existing iterative interference cancellation algorithm, that is, when the system is equipped with 2 transmitters and 2 receivers and the Bit error rate is 10-3, the performance of the system is improved about 2dB.

Generalized Blind Detection of OOK Modulation for Free-Space Optical Communication

For optimal detection of ON – OFF keying symbols in free-space optical (FSO) communication, the receiver requires the instantaneous channel fading coefficient. In this letter, to increase the bandwidth efficiency of the FSO channel, we propose a blind data detection method, i.e., without requiring transmission of any training symbols. The proposed blind detection is a two-step method that performs block-by-block detection. Simulation results show that the proposed receiver can achieve a significantly lower bit-error-rate performance compared with the existing blind methods in the context of FSO communications. In addition, the proposed blind method has a simple structure, which makes it particularly suitable for fast FSO communications.

An efficient network coding scheme for reliable multicast power line communications

Nowadays, Power Line Communication (PLC) technology is receiving a renewed attention for a wide class of innovative applications and services, mainly thanks to the advantage of using the existing electrical infrastructures, thus reducing the deployment costs. However, such electrical infrastructures have been originally conceived for power distribution and not for data. Hence, signal propagation is affected by more severe impairments than traditional media, such as impulsive noise and frequency selectivity. Furthermore, new emerging PLC applications need more efficient information delivery schemes that encompass both unicast and multicast mode. Towards this end, this paper deals with an efficient Network Coding (NC) based multicast reliable PLC scheme that makes use of (i) a decision direct impulsive noise mitigation approach and of (ii) a scheme based on multiple transmissions of a same symbols in the frequency domain. A suitable optimization procedure is also proposed here with the aim of improving the performance of the proposed scheme, under the constraint of a specified maximum data flow delivery failure probability. Finally, comparisons with alternative solutions are provided in order to highlight the significant advantages of the proposed scheme in terms of data flow delivery delay and overall transmission energy cost, under specific service constraints.

Laser phase noise impact on optical DP-MQAM: experimental investigation

Advances in optical technologies, modulation formats, and symbol transmission rates became paramount for today’s agile high spectral efficiency optical networks. Nonetheless, laser phase noise (PN) has played a major impact on the performance of these systems due to the employment of moderate-quality lasers that significantly affect the implementation of high-order modulation schemes starting from existing QPSK and growing to MQAM, $$M=16$$ , 32, and 64. In this paper, we report an optical dual-polarization (DP) transmitter prototype that digitally emulates the effect of the laser phase noise, according to Wiener process, applied to a different types narrow-linewidth laser sources. This enables the generation of an arbitrary laser linewidth ranging from kilohertz up to tens of megahertz. Our experimental study evaluates the effect of PN on the performance of tracking algorithms commonly implemented on practical coherent receivers. The experimental results show that, for laser linewidth $$\le $$ 1 MHz, practical filter recovery algorithm succeeds to make appropriate tracking for both DP-QPSK and 16 QAM at 16- and 32-Gbaud system rates. However, for 10 MHz linewidth, correct recovery is possible only for DP-QPSK.

Lagrangian Detection for Generalized Space-Shift Keying MIMO Systems

Generalized space-shift keying (GSSK) has recently established itself as a promising technology for massive multiple-input multiple-output (MIMO) systems. However, the computational complexity of maximum likelihood (ML) detection is too high, and it increases significantly as the number of transmit antennas and active antennas increases. In this correspondence, we propose a low-complexity suboptimal detection for massive GSSK-MIMO systems. The ML detection of GSSK can be posed as a 0-1 quadratic programming with an equality constraint. First, we employ the Lagrange multiplier to transform the 0-1 quadratic programming with a linear equality constraint into a standard 0-1 quadratic programming. Most of the conventional methods for determining the Lagrange multiplier are derived from Karush-Kuhn-Tucker (KKT) conditions, which are usually valid for continuous variable programming rather than the discrete one. However, in our problem, the optimization variables are binary. Therefore, we propose a theorem that can determine the Lagrange multiplier iteratively by an 1-D binary search rather than KKT conditions and, finally, detect the GSSK transmission symbols. Simulation results demonstrate that the proposed method can achieve an excellent signal detection performance for massive GSSK-MIMO systems with low computational complexity.

An Improved Dual-Hop Transmission Method for High Reliability in Wireless Communication Networks

In this paper, a new dual-hop transmission scheme based on MIMO-OFDM is proposed in order to enhance the performance of cooperative scheme. This paper proposes improved cooperative dual-hop scheme which handles transmission schemes for three areas of the cell by changing transmission symbols. Since performance of wireless communication depends on channel states of cell area, the transmission can have flaws because of deep fading or heavy shadowing. Therefore, in order to overcome these flaws, a cooperative dual-hop scheme is used to construct virtual MIMO system and get spatial diversity gain. In addition, the usage of CDD and STBC scheme redeems the cooperative dual-hop scheme by obtaining high reliability.

Dynamic Resource Allocation for Energy Efficient Transmission in Digital Subscriber Lines

Linear matrix precoding, also known as vectoring, is a well-known technique to mitigate multiuser interference in the downlink digital subscriber line (DSL) transmission. While effective in canceling interference, vectoring does incur major communication overhead and computational overhead in terms of the transmission of idle symbols and precoder-data multiplications at each data frame, resulting in significant energy consumption when the number of lines is large. To facilitate energy efficient transmission, it has been recently proposed (in the G.fast standard) that each data frame is divided into a normal operating interval (NOI) and a discontinuous operating interval (DOI). In the NOI, all lines (or users) are involved in a common vectoring group, which requires a large matrix precoder, whereas in the DOI, the lines are subdivided into multiple small nonoverlapping vectoring subgroups and are transmitted in a time division multiple access manner, requiring small matrix multiplications and, thus, improving the energy efficiency. In this paper, we consider the key dynamic resource allocation problems in downlink DSL: given the real-time demands, determine the optimal transmission scheme: The optimal NOI and DOI size in each data frame as well as the optimal grouping strategy in the DOI, and optimally adjust the transmission scheme. We formulate these optimal dynamic resource allocation problems and propose efficient real-time algorithms to solve them to global optimality. Simulation results are shown to demonstrate the efficiency and the effectiveness of the proposed algorithms.

Effects of CEE and Feedback Error on Performance for AF-ORS with PSA-CE Schemes Over Quasi-Static Rayleigh Fading Channels

In this paper, we propose the analytical approach for amplify-and-forward (AF) opportunistic relaying schemes (ORS). When operation of AF-ORS consists of relay selection and data transmission phases based on pilot symbol assisted-channel estimation (PSA-CE) methods over quasi-static Rayleigh fading channels, we show that the relay selection phase can be implemented by pilots symbols transmission for source-relay and relay-destination. Moreover, the feedback method for the selected relay index is proposed to have a simple fashion. Then, we investigate the effects of both a channel estimation error and an estimated noise variance, which are obtained by PSA-CE methods, on the received signal-to-noise ratio (SNR). The average SNR loss is also derived in terms with the number of pilots in PSA-CE methods. Moreover, the average symbol error rate, the outage probability, and the normalized channel capacity of the ORS are derived in approximated closed-form expressions for an arbitrary link SNR when the channel state information in the source-relay-destination link is estimated based on transmitted pilots symbols. As the number of pilot symbols, the derived analytical approach is verified, and by comparing it with simulation results, the accuracy is demonstrated. In addition, it is verified that the effect of the feedback error can be neglected for PAS-CE methods over quasi-static fading channels.

Application, Effect and Value of the Cultural Transmission of Game Visual Symbol in Game Character Design

Application, Effect and Value of the Cultural Transmission of Game Visual Symbol in Game Character Design

Performance comparison of dual‐hop hybrid decode‐or‐amplify‐forward relay schemes for M‐ary quadrature amplitude modulation burst transmission over Rayleigh fading channels

SummaryThis paper shows the analytical performance expressions of M‐ary quadrature amplitude modulation burst symbol transmission for hybrid decode‐or‐amplify‐forward (HDAF) relay schemes over quasi‐static Rayleigh‐fading channels. First, we derive the probability density function of the received instantaneous signal‐to‐noise ratio as the simplified form, which is related to all the possible occurrence probabilities of error‐events for M‐ary quadrature amplitude modulation burst transmission. On the basis of the derived probability density function, we express average bit error probability, average symbol error probability, and average burst error rate as closed forms, which can be also applied to both amplify‐and‐forward and adaptive decode‐and‐forward (ADF) schemes. The analysis and simulation results show that HDAF scheme for burst transmission can achieve the performance of ADF scheme with symbol‐by‐symbol transmission, which is the achievable lower bound. Furthermore, the outage probability, the normalized channel capacity, and the goodput performance are also derived as closed forms. The analysis shows the superiority of HDAF scheme to ADF scheme. Comparison with simulations confirms that the derived analytical expressions are accurate over all signal‐to‐noise ratio regions and for different numbers of relays and modulation orders.

Rola muzeów w budowie konkurencyjności samorządów lokalnych województwa podkarpackiego

Under globalisation the transmission of symbols between social fields is shaped by relations of domination and subordination between different centres. Those engaged on a local level in joining in the global processes adapt to the rules set by supranational organisations and their own states. Economic changes force local governments to compete for resources that enable their existence, while the increase in importance of the service sector and corresponding decrease in the role of industry compel local powers to seek new sources of funds supplying regional development. Mobility growth, being one of the results of globalisation, appears simultaneously with the popularity of tourism and territorial units concentrate resource acquiring strategies on that field. It is accompanied by the professionalisation of promotional, public relations and marketing activities. Local governments considering the existence of groups interested in cultural heritage are entering the territorial marketing arena to compete with other centres for the attention of these tourist. During this process the commoditisation of community, borough or voivodeship cultural achievements occurs. Museums are one element of the discussed actions and, depending on situation, their subject or object. As resources they are treated in a complex or a selective way. In the first case they make a ready product while in the second a local government may use different museum components beginning from the architectural qualities of their buildings to their employees’ knowledge and skills. In the paper I distinguish these elements and analyse them as components of the role played by museums participating in territorial unit actions focused on competitive advantage building.

Differential Space Time Frequency Codes for MIMO OFDM Systems

In general coherent detection, channel estimation requires huge number of symbols for transmission in Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) Ultra Wide Band (UWB) system, due to this bandwidth efficiency reduces. The proposed Differential Space-Time-Frequency Code (DSTFCs) for multiband-OFDM Ultra-WB communications is increases the efficiency of bandwidth. DSTFC system does not require Channel State Information (CSI). Due to this, the system bandwidth efficiency is possible to increase with DSTFCs. The proposed DSTFCs are derived both coding and decoding algorithms for 64 QAM (Quadrature Amplitude Modulation). The Simulation outcomes show that the use of DSTFCs can improve the coherent MB-OFDM (without STFC), differential MB-OFDM (without OFDM) bit error performance. The performance of DSTFCs almost reaches the STFCs performance even in the absence of channel state information.

Differential frequency hopping performance in doubly spread underwater acoustic communication channels

Underwater acoustic communication requires waveforms that are robust to the signal distortions caused by the channel. Many waveforms used for this purpose require the transmission of training symbols that span the inter-symbol interference (ISI) to compensate for these channel effects. Differential frequency hopping (DFH) is a fast frequency hopping, digital signaling technology that requires minimal information at the transmitter to communicate in the underwater channel. The relationships between the parameters of Doppler spread‐inducing underwater environments and DFH bit‐error performance are characterized. Wind speed determines the nature of the effect that the water surface imposes on acoustic DFH waveforms with low wind speeds resulting in an essentially flat, low‐absorption sea surface. In this case, strong surface reflections and little frequency spreading make ISI the dominant effect on the received waveforms. At high wind speeds, air bubbles in the surface layer absorb almost all energy incident...

QoS-Aware Forward Error Correction Cooperating with Opportunistic Routing in Wireless Multi-hop Networks

QoS provisioning in wireless multi-hop networks is always a hot researching issue, and QoS is mainly influenced by symbol error rate and transmission delay. Conventional adaptive forward error correction and opportunistic routing cannot perceive the wireless networks' condition well for improving the QoS performance, because the transmission delay and reliability are contradictory for each other, and both of adaptive forward correction and opportunistic routing only focus on optimizing one side. In this paper, we propose QoS-aware forward error correction cooperating with opportunistic routing (QFEC-OR), which balances the reliability and effectiveness to improve QoS performance. Then we adopt a better QoS performance perception parameter--20---80 perception parameter to make QFEC-OR superior for QoS experience. We compare QFEC-OR with two kinds of encoding schemes combined with OR to illustrate QFEC-OR's efficiency, and compare QFEC-OR employing 20---80 perception parameter with two kinds of perception parameters employed in QFEC-OR to illustrate the 20---80 perception parameter makes QFEC-OR provide better QoS performance. Simulation results demonstrate the higher effectiveness of QFEC-OR with 20---80 perception parameter for QoS provisioning in wireless multi-hop networks.