Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
Line Number: 143
Backtrace:
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 143
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 209
Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 994
Function: getPubMedXML
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3134
Function: GetPubMedArticleOutput_2016
File: /var/www/html/application/controllers/Detail.php
Line: 574
Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
Line: 488
Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
Line: 316
Function: require_once
In a practical light emitted diodes (LEDs)-based visible light communication (VLC) system, high-speed transmission is generally limited by the LED bandwidth. To address the bandwidth limitation, a hybrid digital linear and decision-feedback equalization (DFE) is investigated to improve the transmission performance (or spectral efficiency) in the carrier-less amplitude phase modulation (CAP)-based VLC systems. A real-time CAP-VLC transceiver with the hybrid digital equalization is designed, based on which 200 Mb/s transmission is successfully demonstrated over a 15 m VLC link with the commercial red LEDs (bandwidth: 6.5 MHz). In the real-time CAP-VLC system, the baseline wander (BLW) is observed, due to the removal of the low-frequency components with a direct current (DC) block. The BLW effect can be mitigated by increasing the roll-off factor. However, this roll-off factor affects the equalization performance, due to an increased loss in the signal spectrum beyond the system bandwidth. Optimization of the roll-off factor and filter length is required. Experimental results show that, with the optimized real-time transceiver design, the hybrid Wiener/recursive least squares (RLS) and DFE significantly improves the error vector magnitude (EVM) performance compared with the DFE. In addition, the digital signal processing (DSP) complexity is discussed.
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1364/OE.27.009382 | DOI Listing |
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!