Reverse Link Research Articles

The Endpoint Application Execution Control Scheme based on the Whitelist

Under the situation that existing information protection systems adopt an approach that tackles malicious codes based on already known signatures or analyzed behavior/feature, they are limited in detecting and identifying the unknown and the deformation of the malicious code. The present study, as a means of overcoming such a shortcoming, proposes a way of endpoint application control capable of more securely protecting endpoint devices (PCs) from intrusion of malicious codes and attacks through exploitation of an application or operating system vulnerability, by implementing a hybrid of technology such as whitelist-based application execution control via authentication of integrity, media access control, prevention of modification of important files, and control over IP/port attempting for process access or reverse link.

The peripheral circulation in patients with acute coronary syndrome

Purpose. The aim of this study was to evaluate the microcirculation in patients with acute coronary syndrome over the course of the disease. Design/methodology/approach. 48 patients were examined with average age of 65.3±5.1 years. The patients were delivered in an intensive care unit with a diagnosis of acute coronary syndrome. Analysis of clinical, instrumental and laboratory parameters was made depending on the final diagnosis: «myocardial infarction» - 26 patients, «unstable angina» - 22 patients. In addition, both linear and volume blood flow were evaluated on the distal phalanx of second finger of the right hand in all patients using the method of high-frequency (25 MHz) ultrasound Doppler study. Findings. At admission, in patients with acute myocardial infarction the linear velocity of blood flow was 10.27±1.18 mm/s, the volume rate of flow 4.67±0.55 ml/min; in the subgroup of patients with unstable angina these figures were 14.09±1.50 mm/s and 6.64±0.71 ml/min, respectively (p<0.05). After 12-24 hours on a background of the therapy in patients with myocardial infarction an increase of the studied parameters is registered (12.3±1.7 mm/s and 6.33±0.96 ml/min for linear and volumetric blood flow velocity). The inverse correlations between the indices of the peripheral circulation and the size of the left and right atria, and end-diastolic size of left ventricular were identified. Originality/value. Patients with acute myocardial infarction in the start of disease showed significantly lower rates of microcirculation with their subsequent growth, in comparison with the patients with unstable angina, where the opposite dynamic is registered at the initially higher values of the microcirculation. The statistical correlation analysis was made. In patients with acute coronary syndrome it defined a reverse reliable link of microcirculation parameters with the end-diastolic size of the left ventricle, the size of the left and right atrium, as well as the level of sodium in blood plasma.

A distributed virtual MIMO coalition formation framework for energy efficient wireless networks

In this paper, we consider a distributed virtual multiple-input multiple-output (MIMO) coalition formation algorithm. Energy savings are obtained in the reverse link by forming multi-antenna virtual arrays for information transmission. Virtual arrays are formed by finding a stable match between two sets of single antenna devices such as mobile stations (MSs) and relay stations (RSs) based on a game theoretic approach derived from the concept of the college admissions problem. Thus, power savings are obtained through multi-antenna arrays by implementing the concepts of spatial diversity and spatial multiplexing for reverse link transmission. We focus on optimizing the overall consumed power rather than the transmitted power of MSs and RSs. Furthermore, it is shown analytically and by simulation that when the overall consumed power is considered, the energy efficiency of the single antennas devices is not always improved by forming a virtual MIMO array. Hence, single antenna devices may prefer to transmit on their own when channel conditions are favorable. In addition, the simulation results show that the framework we propose provides comparable energy savings and a lower implementation complexity when compared to a centralized exhaustive search approach.

An Efficient Link Establish Scheme for Device to Device Communications in Wireless USB Systems

In this paper, we propose an efficient link establish scheme among wireless USB devices. When a wireless USB host establishes a default link with a wireless USB slave device, the proposed scheme allocates resources for its reverse link at the same time. After this, when the role of wireless USB host is changed to the wireless USB device, the proposed scheme can prevent the failure of reverse link establish by guaranteeing the early resource allocation for reverse link. Also, the proposed scheme can reduce delay and the energy consumed by the wireless USB host scan to set up a new reverse link, because the proposed scheme scans only medium access slots already allocated for reverse link. From the simulation results for throughput, delay and energy consumption, it is shown that the performance of the proposed scheme is superior to that of the legacy WUSB standard, for device to device communications.

Cognitive Transmit Beamforming From Binary CSIT

Transmit beamforming is used to steer radiated power towards a receiver of interest and to limit interference to unintended receivers, thereby facilitating coexistence. Transmit beamforming requires accurate channel state information (CSI) at the transmitter, which is often difficult to acquire, particularly in cognitive underlay settings, where the primary receiver cannot be expected to cooperate with the secondary system to enable it to learn the secondary to primary crosstalk channel. This paper considers cases where it is not realistic to assume channel reciprocity, or that the receivers are capable of accurate CSI estimation and feedback-because they are legacy systems, or have limited computation/energy resources. Transmit beamforming from binary and infrequent CSI is first considered for an isolated link. An online beamforming and learning algorithm is developed using the analytic center cutting plane method and is shown to asymptotically attain optimal performance. A robust maximum-likelihood formulation is next developed to handle feedback errors and correlation drift. The setup is then generalized to a cognitive underlay setting, also exploiting the standard acknowledgement/negative-acknowledgement feedback on the reverse primary link. This is the first solution to jointly tackle secondary signal-to-noise ratio maximization and primary interference mitigation from only rudimentary CSI, without assuming channel reciprocity.

Опыт использования возможностей спутниковой системы Argos-3 для передачи информации и определения координат морских дрейфующих буев

The technical characteristics of the new satellite communication system are investigated with reference to the drifter experiments in the World Ocean and the Black Sea. A comparison of the standards of satellite communication systems Argos-2 and is carried out. The distinctive features of the from the previous generations of the system are greatly increased bandwidth and a significant reduction of the data equipment power consumption through the use of the reverse link for the guarantee of prediction of the satellite transmission and acknowledgment during the message transferring. In the context of the international pilot project Argos-3 Pilot Project the equipment performance is evaluated and its configuration is determined according to the insitu operation as a part of the marine drifting buoys (drifters). The results of in-situ experiments with new drifters and traditional Argos-2 drifters are compared and the performances of both systems are analyzed. The recommendations on the optimum configuration of the equipment as part of drifting buoys are given. The results of the laboratory and long-term field experiments have shown the efficacy of the solutions to adapt the surface drifting buoys to the satellite system Argos-3, developed in MHI и Marlin-Yug Ltd and which is now widely used to improve the global drift-monitoring network.

Bflinks: Reliable Bugfix Links via Bidirectional References and Tuned Heuristics.

Background. Data from software version archives and defect databases can be used for defect insertion circumstance analysis and defect prediction. The first step in such analyses is identifying defect-correcting changes in the version archive (bugfix commits) and enriching them with additional metadata by establishing bugfix links to corresponding entries in the defect database. Candidate bugfix commits are typically identified via heuristic string matching on the commit message. Research Questions. Which filters could be used to obtain a set of bugfix links? How to tune their parameters? What accuracy is achieved? Method. We analyze a modular set of seven independent filters, including new ones that make use of reverse links, and evaluate visual heuristics for setting cutoff parameters. For a commercial repository, a product expert manually verifies over 2500 links to validate the results with unprecedented accuracy. Results. The heuristics pick a very good parameter value for five filters and a reasonably good one for the sixth. The combined filtering, called bflinks, provides 93% precision and only 7% results loss. Conclusion. Bflinks can provide high-quality results and adapts to repositories with different properties.

Blind Transmission and Detection Designs With Unique Identification and Full Diversity for Noncoherent Two-Way Relay Networks

This paper considers blind detection for a two-way relay system in which two source nodes exchange information with each other via a relay node using an amplify-and-forward (AF) protocol. The channel coefficients are assumed to be nonreciprocal, i.e., the channel gain between two nodes is not identical to that in the reverse link between the same nodes. An effective signaling and transmitting scheme using four M-ary phase-shift keying (M-PSK) constellation sets is proposed to achieve a unique identification of the transmitted symbols and the channel coefficients in a noise-free transmission. Blind receivers with full diversity are derived for Rayleigh fading channels with Gaussian noise by the generalized likelihood ratio test (GLRT) and least squares error (LSE) criteria. Constellation selections are investigated for the source nodes to transmit at a uniform bit rate in each time slot. Power-allocation schemes are discussed to improve further the average error probability of the source nodes in the blind detection. Simulation results are provided to validate the proposed designs.

Overhead and Spectral Efficiency of Pilot-Assisted Interference Alignment in Time-Selective Fading Channels

The spectral efficiency achievable by interference alignment (IA) in a K-user multiple-input-multiple-output interference channel is studied in the face of time-selective continuous fading explicitly estimated through pilot-symbol observations. The robustness of IA in such operationally relevant conditions is assessed through a joint optimization of the pilot overhead and the IA update interval, which are characterized - in high-power conditions - as solutions of a fixed-point equation. Variations of the formulation are given for both frequency-division duplexing (FDD) and time-division duplexing, the former requiring explicit feedback of the fading estimates and the latter relying on fading reciprocity. For the FDD variation, analog feedback is considered. In addition to arbitrary numbers of users and antennas and arbitrary temporal fading correlation functions, the derivations accommodate forward and reverse links with asymmetric power levels.

Power Control for Cellular Communications with Time‐Varying Channel Uncertainties

AbstractPower control in a code‐division multiple access (CDMA) based cellular network is a challenging problem because the communication channels change rapidly because of multipath fading. These rapid fluctuations cause detrimental effects on the control efforts required to regulate the signal‐to‐interference plus noise ratios (SINRs) to the desired level. Thus, there is a need for power‐control algorithms that can adapt to rapid changes in the channel gain caused by multipath fading. Much of the previous work has either neglected the effects of fast fading, assumed that the fading is known, or assumed that all the link gains are known. In this paper, we model the effects of fast fading and develop practical strategies for robust power control based on SINR measurements in the presence of the fading. We develop a controller for the reverse link of a CDMA cellular system, and use a Lyapunov‐based analysis to prove that the SINR error is globally uniformly ultimately bounded. We also utilize a linear prediction filter that utilizes local SINR measurements and estimates of the Doppler frequency that can be derived from local SINR measurements to improve the estimate of the channel fading used in the controller. The power‐control algorithm is simulated for a cellular network with multiple cells, and the results indicate that the controller regulates the SINRs of all the mobile terminals (MTs) with low outage probability. In addition, a pulse‐code‐modulation technique is applied to allow the control command to be quantized for feedback to the transmitter. Simulation results indicate that the outage probabilities of all the MTs are still within the acceptable range if at least 3‐bit quantization is employed. Comparisons to a standard algorithm illustrate the improved performance of the predictive controller.

Symbolic Number Abilities Predict Later Approximate Number System Acuity in Preschool Children

An ongoing debate in research on numerical cognition concerns the extent to which the approximate number system and symbolic number knowledge influence each other during development. The current study aims at establishing the direction of the developmental association between these two kinds of abilities at an early age. Fifty-seven children of 3–4 years performed two assessments at 7 months interval. In each assessment, children's precision in discriminating numerosities as well as their capacity to manipulate number words and Arabic digits was measured. By comparing relationships between pairs of measures across the two time points, we were able to assess the predictive direction of the link. Our data indicate that both cardinality proficiency and symbolic number knowledge predict later accuracy in numerosity comparison whereas the reverse links are not significant. The present findings are the first to provide longitudinal evidence that the early acquisition of symbolic numbers is an important precursor in the developmental refinement of the approximate number representation system.

A Optimum Resource Allot for Data in Code Division multiple access Contrary Link

The optimum resource apportionment standpoint is studied for non-real-time users CDMA (code division multiple access) overturn link. A resource apportionment standpoint of concern includes channel coding, out strectching gain control and power allocation under the conventional receive operation. The restriction in the optimization include peak transmit power of the mobile station, total received power at the base station and QoS in the form of minimum SINR (Signal-toInterference-plusNoise-Ratio) for each user. The coding and flattening gain control can be share from the power apportionment strategy. Our results show that the optimal power allotment standpoint depends on the purpose function: avaricious standpoint is optimal to maximize the sum of throughput from each user, whereas a fair standpoint is optimal to maximize the product of throughput from each user. A unified approach is taken to derive the optimal policies, and it can also be applied to other power apportionment problems in CDMA (code division multiple access) reverse link. Numerical results of the channel volume which can be held are presented for both objectives along with the effect of QoS constraints Code division multi access, information rates land(arrive on the ground, alight) mobile radio cellular systems, nonlinear programming resource (source of wealth) management.

Performance Analysis of Turbo Codes In CDMA Under AWGN and Fading

In order to have reliable communications, channel coding is often employed. Turbo code as a powerful coding technique has been widely studied and used in communication systems. Turbo code decoder algorithm is studied in details in this paper. The performance of Turbo code used in IS-2000 Code Division Multiple Access (CDMA) reverse or forward link under Additive White Gaussian Noise (AWGN) and slow fading channels is evaluated. The bit error rates (BER) of Turbo code at low signal-to-noise ratio (SNR) are obtained by simulations. Index terms: IS-2000 CDMA, RSC encode, Interleaver, Output puncturing, Fading, AWGN channel, Rayleigh fading channel, Uncorrelated Rayleigh fading generator, Correlated Rayleigh fading generator

Orthogonal Multicarrier Division Multiple Access for Multipoint-to-Multipoint Networks

We develop new transmission schemes for multipoint-to-multipoint (M2M) networks which, unlike the existing approaches, address duplexing/multiplexing and multiple access jointly and possess true M2M characteristics in the physical layer. In the proposed schemes, all forward and reverse links of the M2M network share the overall spectrum concurrently in an orthogonal frequency division manner. This provides increased degrees of freedom and enhanced diversity in scheduling and resource allocation, thus leading to performance enhancement. We first discuss practical implementation issues. Next, we develop our proposed schemes for both centralized and distributed access scenarios. Under the centralized access, we illustrate advantages of the proposed approach for M2M networks using a scheduling algorithm and provide a closed-form analytical throughput upper-bound. Next, we extend the proposed approach to multicasting and present a new scheduling strategy and its closed-form analytical approximate throughput expression. Under the distributed access, we develop a generalized multi-channel carrier sensing multiple access/collision avoidance scheme for M2M networks and propose a new scheme which exploits local channel information. Closed-form analytical throughput expressions for a specific scenario are also presented. Simulation results corroborate substantial performance gains of the proposed schemes over the conventional schemes in both centralized and random access scenarios.

페이딩 채널에서 최선 릴레이 선택을 갖는 네트워크 코딩의 성능

Recently, network coding has been actively studied to increase the spectral efficiency of two-way relay wireless channels such as cellular systems as well as broadcasting systems. In this paper, we derive the average transmission capacity and the outage probability of a network coding system, which utilizes two-way data transmission via the best relay rather than multiple relays. Since the data unbalance between the forward and the reverse link in two-way communication systems exists, we include the asymmetric link as well as the symmetric link in the analysis. It is noticed that the space diversity gain increases as the increase of the number of relays. Also we obtain 11.4 dB signal-to-noise ratio (SNR) gain with 9 relays compared to that with single relay in symmetrical link at the given conditions. In asymmetrical links, we denotes that the outage probability is more sensitive to the number of relays rather than data unbalance between the links.

Space time frequency coding for dual polarization MIMO in hybrid mobile satellite system

The hybrid mobile satellite system operating in a single frequency network (SFN) mode is increasingly becoming attractive. The combination of satellite component (SC) and terrestrial component (TC) promises a better quality of service (QoS). Multimedia broadcast and multicast services (MBMS) are expected to be prevailed in this kind of system. Several space frequency (SF) or space time (ST) codes have been proposed to enhance the system performance due to the lack of reverse link and omni-directional transmission. However, they mostly consider the system with only one SC and one TC and fail to make full use of available diversities. This paper presents a novel way to realize the dual polarization multiple input multiple output (MIMO) transmission by using the space time frequency (STF) code. The theoretical analysis and simulations indicate that the application of STF code can improve the system performance dramatically. A higher diversity gain can be achieved due to the cooperative transmission of SC and TC, while the coding gain can be enhanced by the reusing of STF code between SCs or TCs. Even if some of the links are lost, it can still work properly and benefit from the STF code. The relative relay can result in a degradation up to 0.5 dB in the coding gain.

Rate Assignment in Wireless Networks: Stability Analysis and Controller Design

In this brief, data-rate assignment in IS-856 uplink (reverse link) is studied. The problem is first formulated using an interference model, and then a dynamic control strategy is developed for efficient rate assignment. In the first step, the controller is designed for the special case when the number of users in the network is fixed. Then, the designed controller is further developed for a dynamic network (where the number of users is subject to change) to achieve the desired performance. To this end, the network is formulated in the framework of switched systems, where any new activation or deactivation of users is considered as switching from one system to another. The controllers obtained are then modified properly to retain network stability and performance in the presence of time-delay. Simulation results are presented to elucidate the effectiveness of the proposed approach.

Comparative Study of OFDM and CDMA Technique

Orthogonal frequency division multiplex (OFDM) modulation is being used more and more in telecommunication both in wired and wireless. This modulation technique has several advantages, reason for its increasing usage in communication. OFDM can provide high data rates, it can be implemented easily, it is spectrally efficient and with sufficient robustness to channel imperfections. On the other hand most third generation mobile phone systems are using Code Division Multiple Access (CDMA) as their modulation technique. For this reason, CDMA is also investigating so that the performance of both CDMA and OFDM can be compared. It is found that OFDM performs extremely well when compared with CDMA, and provide very high tolerance to multipath delay spread, channel noise, and peak power clipping. In addition to this it provides a high spectral efficiency The noise performance of OFDM is found to depend solely on the modulation technique used for modulating each carrier of the signal. The OFDM signal performance is found to be the same as for a single carrier system, using the same modulation technique and can provide large data rates with sufficient robustness to radio channel impairments The minimum signal to noise ratio (SNR) required for BPSK was ~7 dB, where as it was ~12 dB for QPSK and ~25 dB for 16PSK. CDMA was found to perform poorly in a single cellular system, with each cell only allowing 7-16 simultaneous users in a cell, compared with 128 for OFDM.1.25 MHz bandwidth and 19.5 kbps user data rate was used for it. This low cell capacity of CDMA was attributed to the use of non-orthogonal codes used in the reverse transmission link, leading to a high level of inter-user interference.

Enhancement of TCP congestion control based on relative delay and Bandwidth Estimation

The traditional TCP assumes that all packet losses result from the congestion even in networks with high bit error rates (BER), and this causes a significant performance degradation. In this paper, we propose a novel end-to-end congestion control mechanism called TCP VenoDB, which joins the relative delay and bandwidth estimation together as a judgment condition to distinguish the network states, and refines the traditional fast retransmit and fast recovery phase with partial ACK mechanism. Simulation results by NS-2 show that TCP VenoDB provides more significant performance improvement in throughput, bandwidth utilization and fairness than TCP Veno, TCP Westwood and TCP NewReno in networks with high BER, and has minimal influence of reverse link congestion. Furthermore, TCP VenoDB is friendly towards TCP NewReno for practical purpose.

Signal-to-Noise Ratio Estimation Algorithm for Advanced DVB-RCS Systems

This paper presents a signal-to-noise ratio (SNR) estimation algorithm for advanced Digital Video Broadcasting-Return Channel via Satellite (DVB-RCS) systems using adaptive coding and modulation (ACM) in the reverse link of broadband satellite systems. Due to the absence of a repetitive pilot symbol structure, SNR estimation has to be performed using the fixed symbol preamble data. Moreover, sporadic nature of data traffic on the return link causes variation in interference level from slot to slot and, therefore, the estimation has to be done within one traffic slot duration. Hence, it becomes necessary to use a combination of data-aided (DA) and decision-directed (DD) algorithms so as to make use of traffic data. A non-data-aided (NDA) estimator that was previously proposed by the authors for binary phase shift keying (BPSK) and QPSK schemes is extended to 8-PSK in a decision directed manner. This estimator shows improved performance over existing estimators. The inherent bias of DD approach at low values of SNR is reduced by using a hybrid approach, i.e., using the proposed estimator at moderate/high values of SNR and the moments-based estimator ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> ) at low values of SNR. Overall improved performance of the proposed hybrid estimator, in terms of accuracy and complexity, makes it an attractive choice for implementing ACM in advanced DVB-RCS systems.