scholarly journals Analysis of Multiple-Access Discrimination Techniques for the Development of a PSD-Based VLP System

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1717 ◽  
Author(s):  
Álvaro De-La-Llana-Calvo ◽  
José-Luis Lázaro-Galilea ◽  
Alfredo Gardel-Vicente ◽  
David Rodríguez-Navarro ◽  
Borja Rubiano-Muriel ◽  
...  
Keyword(s):  
Visible Light ◽  
Multiple Access ◽  
Error Rates ◽  
Integration Time ◽  
Optical Signals ◽  
Positioning Systems ◽  
Advantages And Disadvantages ◽  
Positioning Errors ◽  
High Measurement ◽  
Code Division Multiple

There are several technologies and techniques available when developing indoor positioning systems (IPS). Recently, the development of positioning systems based on optical signals has aroused great interest, mainly those using visible light from the lighting infrastructure. In this work, we analyze which techniques give better results to lay the foundations for the development of a Visible Light Positioning system (VLP). Working only with a receiver, it is analyzed what the result of determining the position of different emitters is when they emit simultaneously and without any synchronism. The results obtained by Frequency Division Multiple Access (FDMA) (with digital bandpass filters, I/Q demodulation, and FFT) and Code Division Multiple Access (CDMA) are compared. The interference between signals when emitted simultaneously from multiple emitters is analyzed as well as the errors they cause and how these effects can be mitigated. As a result of the research, the advantages and disadvantages using different multiple-access determination techniques are determined. In addition, advantages and disadvantages of using FDMA and CDMA techniques as well as hardware requirements that make one more feasible than the other are presented. The system behavior, in terms of errors, is established using FDMA and different configurations such as: I/Q, RMS, or FFT. The work also determines the error rates that can be obtained with the different FDMA and CDMA configurations, considering different error scenarios and integration time. Synthetic emulations and empirical tests were performed, which concluded that IPS systems based on optical signals and PSD sensors can achieve very high measurement accuracies and a high measurement rate. Obtained positioning errors in a room of 3 m height are less than 1 cm when working in noisy environments.

scholarly journals Doubly Orthogonal Wavelet Packets for Multi-Users Indoor Visible Light Communication Systems

Photonics ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 85 ◽  
Author(s):  
Arslan Khalid ◽  
Hafiz Muhammad Asif ◽  
Konstantin I. Kostromitin ◽  
Sattam Al-Otaibi ◽  
Kazi Mohammed Saidul Huq ◽  
...  
Keyword(s):  
Visible Light ◽  
Communication Systems ◽  
Multiple Access ◽  
Visible Light Communication ◽  
Wavelet Packets ◽  
Easy Access ◽  
Line Of Sight ◽  
Detection Scheme ◽  
Time Frequency ◽  
Code Division Multiple

Visible Light Communication (VLC) is a data communication technology that modulates the intensity of the light to transmit the information mostly by means of Light Emitting Diodes (LEDs). The data rate is mainly throttled by the limited bandwidth of the LEDs. To combat, Multi-carrier Code Division Multiple Access (MC-CDMA) is a favorable technique for achieving higher data rates along with reduced Inter-Symbol Interference (ISI) and easy access to multi-users at the cost of slightly reduced compromised spectral efficiency and Multiple Access Interference (MAI). In this article, a multi-user VLC system is designed using a Discrete Wavelet Transform (DWT) that eradicates the use of cyclic prefix due to the good orthogonality and time-frequency localization properties of wavelets. Moreover, the design also comprises suitable signature codes, which are generated by employing double orthogonality depending upon Walsh codes and Wavelet Packets. The proposed multi-user system is simulated in MATLAB software and its overall performance is assessed using line-of-sight (LoS) and non-line-of-sight (NLoS) configurations. Furthermore, two sub-optimum multi-users detection schemes such as zero forcing (ZF) and minimum-mean-square-error (MMSE) are also used at the receiver. The simulated results illustrate that the doubly orthogonal signature waveform-based DWT-MC-CDMA with MMSE detection scheme outperforms the Walsh code-based multi-user system.

scholarly journals Comparison of a Ring On-Chip Network and a Code-Division Multiple-Access On-Chip Network

VLSI Design ◽  
2007 ◽  
Vol 2007 ◽  
pp. 1-14 ◽  
Author(s):  
Xin Wang ◽  
Jari Nurmi
Keyword(s):  
Code Division Multiple Access ◽  
Multiple Access ◽  
Data Transfer ◽  
Performance Estimation ◽  
Description Language ◽  
Advantages And Disadvantages ◽  
Globally Asynchronous Locally Synchronous ◽  
Hardware Description ◽  
On Chip ◽  
Code Division Multiple

Two network-on-chip (NoC) designs are examined and compared in this paper. One design applies a bidirectional ring connection scheme, while the other design applies a code-division multiple-access (CDMA) connection scheme. Both of the designs apply globally asynchronous locally synchronous (GALS) scheme in order to deal with the issue of transferring data in a multiple-clock-domain environment of an on-chip system. The two NoC designs are compared with each other by their network structures, data transfer principles, network node structures, and their asynchronous designs. Both the synchronous and the asynchronous designs of the two on-chip networks are realized using a hardware-description language (HDL) in order to make the entire designs suit the commonly used synchronous design tools and flow. The performance estimation and comparison of the two NoC designs which are based on the HDL realizations are addressed. By comparing the two NoC designs, the advantages and disadvantages of applying direct connection and CDMA connection schemes in an on-chip communication network are discussed.

PERFORMANCE EVALUATION OF ADAPTIVE MEDIA ACCESS CONTROL PROTOCOLS FOR PERVASIVE WIRELESS NETWORKS

2002 ◽  
Vol 03 (03n04) ◽  
pp. 253-272 ◽  
Author(s):  
ALVIN LIM ◽  
KUI MOK
Keyword(s):  
Wireless Networks ◽  
Access Control ◽  
Multiple Access ◽  
Error Rates ◽  
High Density ◽  
Media Access Control ◽  
Slotted Aloha ◽  
Media Access ◽  
Control Protocols ◽  
Code Division Multiple

As pervasive and high-density wireless networks become increasingly common, it is critical to address the problems of intermittent disconnection, high error rate and collision that cause degradation in the performance of wireless media access control protocols, such as slotted ALOHA Time Division Multiple Access (slotted ALOHA/TDMA) and Direct Sequence Code Division Multiple Access (DS/CDMA). We propose adaptive techniques for improving performance of media access protocols through awareness of the mobile communication environment. These techniques involve detection of intermittent disconnection, high error rates, and collisions. Upon detection and notification of these conditions by snooping devices, the media access control layer adapts its operation and synchronization accordingly to reduce delay and loss of bandwidth. Results from our simulation studies show that adaptive TDMA improves performance by as much as 12 times over basic TDMA and adaptive CDMA improves by as much as 4 times over basic CDMA in wireless network with high density cells. Overall, adaptive CDMA still performs better than adaptive TDMA by about 4 times.

scholarly journals A New Code Family for QS-CDMA Visible Light Communication Systems

2018 ◽  
Vol 3 ◽  
pp. 5-8 ◽  
Author(s):  
Mouad Addad ◽  
Ali Djebbari
Keyword(s):  
Visible Light ◽  
Communication Networks ◽  
Communication Systems ◽  
Multiple Access ◽  
Multipath Propagation ◽  
Multiple Access Interference ◽  
Visible Light Communication ◽  
Wireless Communication Networks ◽  
Strong Candidate ◽  
Code Division Multiple

Visible light communication (VLC) is a promising technology for wireless communication networks. Optical code division multiple access (OCDMA) is a strong candidate for VLC-based applications. The predominant source of bit error in OCDMA is the multiple access interference (MAI). To eliminate MAI in synchronous OCDMA, zero cross correlation (ZCC) codes have been proposed. However, synchronization problems and multipath propagation introduce relative non-zero time delays. Therefore, the zero correlation zone (ZCZ) concept was introduced. In this paper, we propose a new method for generating ZCC codes. The proposed construction can accommodate any number of users with flexible Hamming weight. The numerical results obtained show that the proposed codes significantly reduce MAI, compared to ZCC, as well as ZCZ codes.

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