Multiple User Access Research Articles

A joint subcarrier and power allocation technique with pro-rata fairness and unequal error protection for video transmission over OFDMA downlink

In this paper, we investigate the video quality fairness issue experienced during the transmission of video traffic from base station (BS) to users in orthogonal frequency division multiple access (OFDMA) networks. Assurance of video quality fairness is a cross-layer optimization problem when fairness is required among users in the application layer and it is achieved through resource optimization in the physical layer. For this we develop a non-iterative joint subcarrier assignment and power allocation algorithm for downlink transmission. Also we define pro-rata video quality fairness, where users are assigned video quality proportional to their demand and formulate a pro-rata fairness index to measure the fairness of the proposed algorithm. The rate compatible punctured codes (RCPC) used in the proposed work compliments video quality fairness through unequal error protection (UEP) of users based on their priority at the physical layer. The physical layer channel state information (CSI) and application layer rate distortion (RD) information of each user are used to allocate power and spectrum resources. Extensive simulation studies show that in comparison with methods which utilize only the physical layer information available at the BS, the proposed algorithm ensures significantly better video quality fairness and spectral efficiency.

Abstract B06: HTSvis: An user-friendly application for analysis of arrayed high-throughput experiments by interactive data representations

Abstract The presented application HTSvis provides an user-interface tool for interactive analysis of arrayed high-throughput screening experiments. Arrayed formats are broadly used for cell-based screens which help to reveal mechanisms of complex diseases such as cancer. Technological advances allow to screen tens of thousands experimental conditions in a single experiments resulting in large datasets with complicated annotation files. Software packages for standardized analysis with a minimized programming effort have been developed accordingly. Even though such pipelines provide comprehensive analysis options, interpretation of the results remains a challenge as the user has to manually compare files and possibly re-run the analysis to prosecute certain hypotheses. Here we present HTSvis, a web application that visualizes data from arrayed screens. The data can be read-in as result files of the established R package CellHTS2 or as any spreadsheet table. This enables the user to feed in data which has been statistically analyzed whilst preserving flexibility to analyze data independent of the CellHTS2 package. The application provides several informative data representations like heatmaps, scatter plots and tables. Within the application, the data can be browsed in an ad hoc manner via the implemented user interface. This allows the user to assess data quality, compare experiments, identify measurements of interest and to verify generated hypotheses in an exploratory manner. The direct allocation of data points to experimental conditions is preserved in all representations facilitating an intuitive interpretation. HTSvis is easy to install, data input is straight forward and no programming skills are required for the usage. The application is compatible with common web browsers and can be set up on local computers as well as on server clusters which allows parallel access for multiple users. Summarized, HTSvis provides a helpful tool for interactive data analysis and interpretation for both, users with and without programming skills. Thereby, the application also promotes the cooperation and exchange of ideas between bioinformaticians and experimental biologists or between collaborators. Citation Format: Christian Scheeder, Florian Heigwer, Michael Boutros. HTSvis: An user-friendly application for analysis of arrayed high-throughput experiments by interactive data representations [abstract]. In: Proceedings of the AACR Precision Medicine Series: Opportunities and Challenges of Exploiting Synthetic Lethality in Cancer; Jan 4-7, 2017; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2017;16(10 Suppl):Abstract nr B06.

Fast Water-Filling Method for Sum-Power Minimization in OFDMA Networks

In this letter, we investigate the problem of sum-power minimization for the users in orthogonal frequency division multiple access (OFDMA) networks subject to the target rate constraint. To address this problem, two fast water-filling (WF) methods are developed under two scenarios: without and with considering the peak-power constraint on the subchannels, which are referred to as FWF and FWF-PP, respectively. We show that our proposed methods converge to the optimal solution, while the computational complexity is reduced compared to the existing WF methods. Our results are also confirmed via simulations.

Secure Degrees of Freedom of One-Hop Wireless Networks With No Eavesdropper CSIT

We consider three channel models: the wiretap channel with $M$ helpers, the $K$-user multiple access wiretap channel, and the $K$-user interference channel with an external eavesdropper, when no eavesdropper's channel state information (CSI) is available at the transmitters. In each case, we establish the optimal sum secure degrees of freedom (s.d.o.f.) by providing achievable schemes and matching converses. We show that the unavailability of the eavesdropper's CSIT does not reduce the s.d.o.f. of the wiretap channel with helpers. However, there is loss in s.d.o.f. for both the multiple access wiretap channel and the interference channel with an external eavesdropper. In particular, we show that in the absence of eavesdropper's CSIT, the $K$-user multiple access wiretap channel reduces to a wiretap channel with $(K-1)$ helpers from a sum s.d.o.f. perspective, and the optimal sum s.d.o.f. reduces from $\frac{K(K-1)}{K(K-1)+1}$ to $\frac{K-1}{K}$. For the interference channel with an external eavesdropper, the optimal sum s.d.o.f. decreases from $\frac{K(K-1)}{2K-1}$ to $\frac{K-1}{2}$ in the absence of the eavesdropper's CSIT. Our results show that the lack of eavesdropper's CSIT does not have a significant impact on the optimal s.d.o.f. for any of the three channel models, especially when the number of users is large. This implies that physical layer security can be made robust to the unavailability of eavesdropper CSIT at high signal to noise ratio (SNR) regimes by careful modification of the achievable schemes as demonstrated in this paper.

A Virtual User Pairing Scheme to Optimally Utilize the Spectrum of Unpaired Users in Non-orthogonal Multiple Access

This letter proposes a strategy to efficiently utilize the spectrum of unpaired users in non-orthogonal multiple access (NOMA) systems. This is done by pairing multiple similar gain users to a single distant user in a nonoverlapping frequency band pairing fashion. We consider a case where the number of far users in a cell is larger than the number of near users. Thus, some far users cannot be paired and should get data using conventional multiple access (OMA). In such case, we propose a strategy where a near user can be paired with multiple (two) far users to optimally utilize the spectrum of unpaired users in the NOMA system. Performance of the proposed pairing scheme is evaluated in terms of ergodic sum capacity over independent Rayleigh flat fading channel. Analytical and simulation results show that significant increase in the capacity gain of the system is achieved by using the proposed strategy compared to OMA and conventional NOMA.

Modeling Cellular Networks With Full-Duplex D2D Communication: A Stochastic Geometry Approach

A network model is considered, where Poisson distributed base stations transmit to $N$ power-domain non-orthogonal multiple access (NOMA) users (UEs) each that employ successive interference cancellation (SIC) for decoding. We propose three models for the clustering of NOMA UEs and consider two different ordering techniques for the NOMA UEs: mean signal power-based and instantaneous signal-to-intercell-interference-and-noise-ratio-based. For each technique, we present a signal-to-interference-and-noise ratio analysis for the coverage of the typical UE. We plot the rate region for the two-user case and show that neither ordering technique is consistently superior to the other. We propose two efficient algorithms for finding a feasible resource allocation that maximize the cell sum rate $\mathcal {R}_{\mathrm{ tot}}$ , for general $N$ , constrained to: 1) a minimum throughput $\mathcal {T}$ for each UE, 2) identical throughput for all UEs. We show the existence of: 1) an optimum $N$ that maximizes the constrained $\mathcal {R}_{\mathrm{ tot}}$ given a set of network parameters and 2) a critical SIC level necessary for NOMA to outperform orthogonal multiple access. The results highlight the importance in choosing the network parameters $N$ , the constraints, and the ordering technique to balance the $\mathcal {R}_{\mathrm{ tot}}$ and fairness requirements. We also show that interference-aware UE clustering can significantly improve performance.

Outage capacity and source distortion analysis for NOMA users in 5G systems

This Letter analyses the impact of the outage probability on the outage capacity and the expected source distortion of information transmission to non-orthogonal multiple access (NOMA) users with a fixed set of power allocation coefficients. The analysis shows that the outage probability at which a strong user experiences the maximum outage capacity (and the minimum expected distortion) is characteristically different from that of a weak user. Moreover, the outage probability that maximises the outage capacity does not provide the minimum source distortion for both users. The analysis is validated against simulation.

High security chaotic multiple access scheme for visible light communication systems with advanced encryption standard interleaving

Chaotic sequences can be applied to realize multiple user access and improve the system security for a visible light communication (VLC) system. However, since the map patterns of chaotic sequences are usually well known, eavesdroppers can possibly derive the key parameters of chaotic sequences and subsequently retrieve the information. We design an advanced encryption standard (AES) interleaving aided multiple user access scheme to enhance the security of a chaotic code division multiple access-based visible light communication (C-CDMA-VLC) system. We propose to spread the information with chaotic sequences, and then the spread information is interleaved by an AES algorithm and transmitted over VLC channels. Since the computation complexity of performing inverse operations to deinterleave the information is high, the eavesdroppers in a high speed VLC system cannot retrieve the information in real time; thus, the system security will be enhanced. Moreover, we build a mathematical model for the AES-aided VLC system and derive the theoretical information leakage to analyze the system security. The simulations are performed over VLC channels, and the results demonstrate the effectiveness and high security of our presented AES interleaving aided chaotic CDMA-VLC system.

Performance Comparison of OFDM System with Different Modulation Methods

OFDM is a multicarrier technique for transmission, which divides the available spectrum into many carriers with each one of them being modulated by a data stream of low rate. OFDM is similar to FDMA in the sense that the multiple user access is achieved by further dividing the available bandwidth to multiple channels. These sub channels are then allocated to the users. But in OFDM, the spectrum is used much more efficiently by spacing the channels much close to one another. This is achieved by making all the carriers orthogonal to one another, preventing interference between these carriers. The digital data in serial form to be transmitted is split into different data streams, and each one of them is modulated by a separate carrier in the allotted bandwidth. The modulation done can be any one of the forms of modulation applied to digital data, but the most commonly used are quadrature phase shift keying (QPSK), and quadrature amplitude modulation (QAM). When these modulators are used, their outputs are summed linearly, and the output signal is sent to the channel. In this paper we will analyze the performance of different modulation techniques in AWGN channel. We conclude that a different modulation scheme has different bit error rate. General Terms OFDM Transmitter, OFDM Receiver, Performance of Modulation Techniques

Performance-Complexity Analysis for MAC ML-Based Decoding With User Selection

The rate-reliability-complexity limits of a quasi-static $K$ -user multiple access channel (MAC), with or without feedback, are explored in this paper. Using high-SNR asymptotics, bounds on the computational resources required to achieve near-optimal (ML-based) decoding performance are first derived. They, in turn, yield bounds on the (reduced) complexity needed to achieve any (including suboptimal) diversity-multiplexing tradeoff (DMT) performance. Similar complexity-bounds in the presence of feedback-aided user selection are also given. This latter effort reveals the ability of a few bits of feedback not only to improve performance, but also to reduce complexity. In this context, our analysis reveals the interesting finding that a proper calibration of user selection can allow for near-optimal ML-based decoding, with complexity that need not scale exponentially in the total number of codeword bits. The derived bounds constitute the best known performance-versus-complexity behavior to date for ML-based MAC decoding, as well as a first exploration of the complexity-feedback-performance interdependencies in multiuser settings.

Efficient Dynamic Provable Possession of Remote Data via Update Trees

The emergence and wide availability of remote storage service providers prompted work in the security community that allows clients to verify integrity and availability of the data that they outsourced to a not fully trusted remote storage server at a relatively low cost. Most recent solutions to this problem allow clients to read and update (i.e., insert, modify, or delete) stored data blocks while trying to lower the overhead associated with verifying the integrity of the stored data. In this work, we develop a novel scheme, performance of which favorably compares with the existing solutions. Our solution additionally enjoys a number of new features, such as a natural support for operations on ranges of blocks, revision control, and support for multiple user access to shared content. The performance guarantees that we achieve stem from a novel data structure called a balanced update tree and removing the need for interaction during update operations in addition to communicating the updates themselves.

A Lamarckian Hybrid Grouping Genetic Algorithm with repair heuristics for resource assignment in WCDMA networks

In this paper we propose a novel Lamarckian Hybrid Grouping Genetic Algorithm (LHGGA) with repair heuristics for a problem of resources assignment to mobile terminals (or, simply, users) in Wide-band Code Division Multiple Access (WCDMA) networks. We propose a novel problem formulation that takes into account all the interference terms, which strongly depend on the assignment to be done. The second contribution is a cost function (to be minimized) with weighted components, which is composed of not only the load factors (including the mentioned interference terms) but also other utilization ratios for aggregate capacity, codes, power, and users without service. The second group of contributions is related to the LHGGA approach. On the one hand, we propose a novel encoding scheme, suitable for the novel problem formulation. On the other hand, we present fully tailored operators. We emphasize the proposal of a repair operator of unphysical candidates (which are substituted by their repaired versions), and a crossover operator, able to acts on groups (users assigned to a base station) in a very efficient way. The proposed LHGGA exhibits a superior performance than that of the conventional method, since most of users receive the demanded services along with a more efficient use of resources per user. The LHGGA approach has been successfully applied to a variety of scenarios: different number of users, distributions, or users profiles.

스펙트럼 감지 무선 인지 네트워크에서 이차 사용자들의 다중 접속 성능 분석

 (cognitive radio network)%&'()*+, -./01)234 -56/&'(74894%:;. %  ((secondary user)+4?/(primary user)&'(7@ABCD)E6 )@(F% (multiple access))GHI.  .p-persistentJnon-persistent 2K) LM4NOP4Q4R. S 2TU3VWXYZ(throughput))(T5[\84R], 7^_`7[(Monte Carlo) abc)03de4R. abcfghi jklmUU:nopq7Lr4NstuXYZmU+v)j4 R.AbstractCognitive radio network technology is that secondary (unlicensed) users use the spectrum of primary (licensed) users without interfering primary communication. In this paper, we propose multiple access scheme for a cognitive radio network, where multiple secondary users access spectrum of one primary user. We consider two types of multiple access scheme, one is p-persistent and one is non-persistent, and apply these two schemes in the secondary network. For each multiple access scheme, total throughput of secondary network is derived and verified by Monte Carlo simulation. Simulation results show that maximum total throughput of the secondary network is achieved when channel access probability or the number of maximum waiting frames is chosen appropriately.Keyword : cognitive radio, spectrum sensing, multiple access, CSMA, p-persistent, non-persistent

Developing an On-Demand Cloud-Based Sensing-as-a-Service System for Internet of Things

The increasing number of Internet of Things (IoT) devices with various sensors has resulted in a focus on Cloud-based sensing-as-a-service (CSaaS) as a new value-added service, for example, providing temperature-sensing data via a cloud computing system. However, the industry encounters various challenges in the dynamic provisioning of on-demand CSaaS on diverse sensor networks. We require a system that will provide users with standardized access to various sensor networks and a level of abstraction that hides the underlying complexity. In this study, we aim to develop a cloud-based solution to address the challenges mentioned earlier. Our solution, SenseCloud, includes asensor virtualizationmechanism that interfaces with diverse sensor networks, amultitenancymechanism that grants multiple users access to virtualized sensor networks while sharing the same underlying infrastructure, and adynamic provisioningmechanism to allow the users to leverage the vast pool of resources on demand and on a pay-per-use basis. We implement a prototype of SenseCloud by using real sensors and verify the feasibility of our system and its performance. SenseCloud bridges the gap between sensor providers and sensor data consumers who wish to utilize sensor data.

Li-Fi: Light fidelity-a survey

Visible light communication (VLC), which uses a vast unregulated and free light spectrum, has emerged to be a viable solution to overcome the spectrum crisis of radio frequency. Light fidelity (Li-Fi) is an optical networked communication in the subset of VLC to offload the mobile data traffics which offers many advantages at indoor scenario. In this article, we survey the key technologies for realizing Li-Fi and present the sate-of-the-art on each aspect, such as: indoor optical wireless channel model, the VLC modulation techniques with user satisfaction, OFDM in VLC, optical MIMO, optical spatial modulation, multiple user access, resource allocation, interference management and hybrid Li-Fi schemes. Some challenges and future work that need to be solved in the area are also described.

Performance improvement of TH-CDMA UWB system using chaotic sequence and GLS optimization

The multi-user interference is an important factor that significantly affects the performance of ultra- wideband (UWB) system. Due to this assumption, we suggest a code optimization to reduce collisions with other users in time hopping-code division multiple access (TH-CDMA) for UWB system indoor communication with line-of-sight residential. To solve a code optimization problems, guided local search algorithm has been applied. To evaluate our method, we tackle the bit error rate (BER) performance analysis. Computer simulation results have shown that optimized skew tent map chaotic-TH-CDMA sequences achieve considerable improvement in terms of the BER that justifies the optimization process.

A green scheduling with adaptive spatial division multiple access grouping for multi‐user coordinated multi‐point networks

AbstractMulti‐User Coordinated Multi‐Point (MU‐CoMP), which couples CoMP with Multi User‐Multiple Input Multiple Output (MU‐MIMO), appears as a promising solution to enhance the Long Term Evolution‐Advanced (LTE‐A) system performance. However, some challenging issues in MU‐CoMP networks require more investigation. First, the set of users transmitting under CoMP mode should be properly identified. Secondly, time‐frequency resource should be efficiently partitioned between CoMP and non‐CoMP users in order to improve the system radio capacity. Thirdly, a fair and green scheduler is much needed for a more energy efficient system. This paper deals with these three issues. We propose an adaptive transmission mode selection according to the total load in the cluster and to users' quality of service. The adequate size of the Spatial Division Multiple Access users' groups is also analyzed. We finally propose a new scheduling algorithm to further enhance the radio capacity and the energy consumption in the cluster. Simulations results showed that significant improvements are obtained in terms of total system throughput and outage probability in the cluster with our proposed scheme. Moreover, energy efficiency has increased by four times with our proposed scheduling algorithm as compared to commonly used schedulers. Copyright © 2015 John Wiley & Sons, Ltd.

LMDS-based approach for efficient top-k local ligand-binding site search.

In this work, we propose a LMDS-based binding-site search for improving the search speed of the Patch-Surfer method. Patch-Surfer is efficient in recognition of protein-ligand binding partners, further speedup is necessary to address multiple-user access. Futher speedup is realised by exploiting Landmark Multi-Dimensional Scaling (LMDS). It computes embedding coordinates for data points based on their distances from landmark points. When selecting the landmark points, we adopt two approaches--random and greedy selection. Our method approximately retrieves top-k results and the accuracy increases as we exploit more landmark points. Although two landmark selection approaches show comparable results, the greedy selection shows the best performance when the number of landmark points is large. Using our method, the searching time is reduced up to 99% and it retrieves almost 80% of exact top-k results. Additionally, LMDS-based binding-site search+ improves the retrieval accuracy from 80% to 95% while sacrificing the speedup ratio from 99% to 90% compared to Patch-Surfer.

Color-Shift Keying and Code-Division Multiple-Access Transmission for RGB-LED Visible Light Communications Using Mobile Phone Camera

Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK–CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on–off keying (OOK) modulation.

System study on direct sequence spectrum of radio-frequency identification

This paper considers points of secure and anti-collision of the Radio-frequency identification (RFID) technology. Source symbols are represented by a special coding, termed Minimum Energy (ME) coding, which exploits redundant bits for saving power when transmitted via RF links with On-Off Keying (OOK). This ME coding is applied to Direct Sequence Spread Spectrum (DSSS) RFID tag in order to enhance security as well as to reduce collision. This synchronized DSSS RFID system is designed and simulation is conducted to verify the advantage of DSSS RFID and present the power efficiency enhance 4 dB, quantities are taken at Bit Error Rate (BER) of 10e-4. When the channel uses the ME coding combined with a DSSS code and OOK without FM0 encoding as is disclosed in the EPC-C1G2/ISO 18000-6 Type C standard. Finally, the maximum number of users in this Direct-Sequence Code Division Multiple Access (DS-CDMA) RFID system is calculated under the condition of successfully acquired.