Deprecated: htmlspecialchars(): Passing null to parameter #1 ($string) of type string is deprecated in /var/www/ojs/plugins/generic/dublinCoreMeta/DublinCoreMetaPlugin.php on line 220
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PSD estimation in Cognitive Radio systems: a perform
| Instrumentation Viewpoint
All papers presented at Martech will be published in both the UPCommons and the Martech organization web sites, the former being the institutional digital deposit of Universitat Politècnica de Catalunya (https://upcommons.upc.edu). This difussion will be made through the Creative Commons License Attribution-NonCommercial-NoDerivs 2.5 or similar (http://creativecommons.org/licenses/by-nc-nd/2.5/deed.en).
When sending the final paper, the author must agree to the conference having non-exclusive rights on this operation. The author will maintain his/her right to diffuse the paper elsewhere.
Warning: mkdir(): Permission denied in /var/www/ojs/lib/pkp/classes/file/FileManager.php on line 424
Warning: file_put_contents(/SAN/files_ojs/usageStats/salt): Failed to open stream: No such file or directory in /var/www/ojs/lib/pkp/classes/statistics/PKPStatisticsHelper.php on line 158
Warning: filemtime(): stat failed for /SAN/files_ojs/usageStats/salt in /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php on line 213
Warning: file_put_contents(/SAN/files_ojs/usageStats/salt): Failed to open stream: No such file or directory in /var/www/ojs/lib/pkp/classes/statistics/PKPStatisticsHelper.php on line 158
Warning: mkdir(): Permission denied in /var/www/ojs/lib/pkp/classes/file/FileManager.php on line 424
Warning: fopen(/SAN/files_ojs/usageStats/usageEventLogs/usage_events_20260926.log): Failed to open stream: No such file or directory in /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php on line 104
Fatal error: Uncaught TypeError: flock(): Argument #1 ($stream) must be of type resource, false given in /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php:105
Stack trace:
#0 /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php(105): flock(false, 2)
#1 /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php(53): PKP\observers\listeners\LogUsageEvent->logUsageEvent('{"time":"2026-0...')
#2 /var/www/ojs/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Events/Dispatcher.php(512): PKP\observers\listeners\LogUsageEvent->handle(Object(APP\observers\events\UsageEvent))
#3 /var/www/ojs/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Events/Dispatcher.php(319): Illuminate\Events\Dispatcher->Illuminate\Events\{closure}('APP\\observers\\e...', Array)
#4 /var/www/ojs/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Events/Dispatcher.php(299): Illuminate\Events\Dispatcher->invokeListeners('APP\\observers\\e...', Array, false)
#5 /var/www/ojs/lib/pkp/lib/vendor/laravel/framework/src/Illuminate/Foundation/helpers.php(505): Illuminate\Events\Dispatcher->dispatch(Object(APP\observers\events\UsageEvent))
#6 /var/www/ojs/pages/article/ArticleHandler.php(366): event(Object(APP\observers\events\UsageEvent))
#7 [internal function]: APP\pages\article\ArticleHandler->view(Array, Object(APP\core\Request))
#8 /var/www/ojs/lib/pkp/classes/core/PKPRouter.php(327): call_user_func(Array, Array, Object(APP\core\Request))
#9 /var/www/ojs/lib/pkp/classes/core/PKPPageRouter.php(249): PKP\core\PKPRouter->_authorizeInitializeAndCallRequest(Array, Object(APP\core\Request), Array, false)
#10 /var/www/ojs/lib/pkp/classes/core/Dispatcher.php(157): PKP\core\PKPPageRouter->route(Object(APP\core\Request))
#11 /var/www/ojs/lib/pkp/classes/core/PKPApplication.php(429): PKP\core\Dispatcher->dispatch(Object(APP\core\Request))
#12 /var/www/ojs/index.php(21): PKP\core\PKPApplication->execute()
#13 {main}
thrown in /var/www/ojs/lib/pkp/classes/observers/listeners/LogUsageEvent.php on line 105
