تحليل و افزايش كارايي سيستمهاي مخابراتي TiR-UWB در شرايط تخمين‌گر غير ايده‌آل كانال
محورهای موضوعی : مهندسی برق و کامپیوتر
حسين خالقي بيزکي
1
(دانشگاه صنعتي مالک اشتر)
سجاد عليزاده
2
(دانشگاه امام حسين (ع))
مجيد اخوت
3
(دانشگاه امام حسين (ع))
کلید واژه: تخمين‌گر MMSE بهينه تکنیک TiR سیستم‌های TiR-UWB فيلتر منطبق ساده,
چکیده مقاله :
روش ارسال معكوس زماني (TiR) به دليل توانايي منحصر به فرد آن در كاهش پيچيدگي ساختار گيرنده در سيستمهاي UWB در سال‌هاي اخير مورد توجه بسياري واقع شده است. با اين حال، داشتن اطلاعات ناقص از شرايط كانال (CSI غير كامل)، عملكرد اين روش را كاهش مي‌دهد. در این مقاله ابتدا فرم بسته‌اي براي روابط احتمال خطاي يك سيستم UWB مبتني بر TiR با گيرنده شامل فيلتر منطبق ساده و در شرايط CSI غير كامل محاسبه مي‌گردد. سپس به‌منظور بهبود عملكرد سيستم TiR-UWB در چنين شرايطي، يك الگوريتم بهينه‌سازي دومرحله‌اي مبتني بر تكرار پيشنهاد مي‌شود. در مرحله اول به كمك کواریانس خطای تخمین کانال، ضرایب پيش فيلتر بر اساس سيستم شامل تخمين‌گر MMSE بهينه محاسبه شده و در مرحله دوم به كمك اين ضرایب، الگوريتم تكرارشونده‌اي براي سيستم شامل فيلتر منطبق ساده طراحي مي‌شود كه قادر است عملكرد سيستم TiR-UWB را در 3 گام پياپي بهبود دهد. همچنين با کمک شبیه‌سازی، صحت روابط احتمال خطاي محاسبه‌شده در حالت تئوري با نتايج حاصل از شبيه‌سازي مورد تأييد قرار گرفته است.
Time reversal method has been recently considered with great interest due to its ability of the receiver complexity mitigation in the UWB communication systems. However, the channel imperfection (Imperfect CSI) has the destroyed effects on the time-reversed UWB communication system performance. In this paper, at first the BER equations have been calculated in the TiR-UWB systems with the simple matched filter receiver in an imperfect CSI scenario. Then, a two-stage algorithm is proposed to improve the TiR-UWB in such conditions. First stage of mentioned algorithm provides the pre-filter coefficients derivation based on MMSE criteria via channel estimation error covariance matrix and then, an iterative routine is obtained in second stage via the simple matched filter receiver based on the derived coefficients in first stage. Finally, exhaustive simulations are done to demonstrate the performance advantage attained by the improved algorithm. As an especial case, the TiR-UWB system performance is improved by the proposed algorithm in 3 steps.
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