استخراج پیام در استاندارد پالس نهم سیستم ناوبری eLoran
محورهای موضوعی : مهندسی برق و کامپیوترمهری لطفعلی زاده 1 , مرتضی شفیعی نیستانک 2 * , محمد باقر نظافتی 3
1 - دانشکده مهندسی برق و کامپیوتر، دانشگاه صنعتی مالک‌اشتر، تهران، ایران
2 - دانشکده مهندسی برق و کامپیوتر، دانشگاه صنعتی مالک‌اشتر، تهران، ایران
3 - پژوهشگاه دانش‌های بنیادی، تهران، ایران
کلید واژه: پالس نهم, شیفت پوش, شیفت فاز, لورن بهبودیافته (eLoran), مدولاسیون مکان پالس (PPM).,
چکیده مقاله :
در سیستم لورن بهبودیافته (eLoran) مبتنی بر پالس نهم، به‌منظور افزودن سازوکار انتقال داده به سیستم ناوبری، پالسی به گروه پالس‌های ناوبری افزوده شده که حاوی پیام است. استخراج پیام از سیگنال لورن شامل دو مرحله محاسبه تأخیر زمانی پالس داده نسبت به محل اصلی آن و کدبرداری داده است. در این مقاله روشی برای استخراج پیام سیگنال لورن در استاندارد پالس نهم پیشنهاد شده است. برای این منظور تأخیر زمانی پالس داده در دو مرحله شیفت پوش و شیفت فاز با استفاده از فیلترهای منطبق و تأخیر کسری محاسبه می‌شود. سپس کدبردار رید سولومون (RS) بر روی سمبل‌ها اعمال و نهایتاً پیام استخراج می‌گردد. همچنین در مقاله به منظور بهبود تخمین تأخیر پالس، به‌خصوص در محیط‌های نویزی و در حضور تداخلات، پالس مرجع به صورت میانگین هشت پالس قبل از پالس داده پیشنهاد شده و به این ترتیب پالس مرجع برای استخراج هر سمبل متفاوت خواهد بود. مطابق نتایج ارزیابی، نرخ خطا قبل از کدبرداری حدود 08/0 تا 003/0 در نسبت سیگنال به نویزهای 7 تا 15 دسی‌بل است که بعد از تصحیح خطای کدبرداری به طور محسوسی کاهش می‌یابد.
In the Standard of 9th pulse enhanced Loran (eLoran) system, an additional pulse is incorporated into the navigation pulse group for data transmission. The process of extracting messages from the Loran signal involves two stages: first, determining time delay of the data pulse relative to its original position, and second, decoding the data. This paper proposes a method for message extraction using the 9th pulse standard. Time delay of the data pulse is calculated in two steps, involving envelope shift and phase shift utilizing matched and fractional filters, respectively. Following this, Reed-Solomon (RS) decoding is applied, leading to final message extraction. Furthermore, to enhance pulse delay estimation, particularly in noisy and interference conditions, the reference pulse is chosen as average of the eight pulses preceding the data pulse, resulting in a unique reference pulse for each symbol extraction. Evaluation results show that the error rate before decoding decreases from 0.08 to 0.003 as the signal-to-noise ratio increases from 7 to 15 dB, with a significant reduction in errors after RS correction.
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