نوع مقاله : پژوهشی

نویسنده

استادیار - دانشگاه آزاد اسلامی، واحد جهرم

چکیده

تخصیص توام بیت، انتخاب رله و تخصیص زیر کانال برای دستیابی به مزایای کامل شبکه‌های رله‌ای مشارکتی مبتنی بر OFDM ضروری می‌باشد. در این مقاله ابتدا این مسأله در یک شبکه مشارکتی OFDM مطالعه می‌شود. این شبکه شامل چندین زوج گره مبدأ ـ مقصد و چندین گره رله با روش کدگشایی و ارسال مجدد (DF) می‌باشد. هدف، کمینه‌سازی توان ارسالی کل تحت شرایط نرخ خطای بیت (BER) و نرخ داده می‌باشد. با این حال، راه حل بهینه مسأله بهینه‌سازی بسیار پیچیده است و ممکن است غیرمنصفانه باشد. سپس با فرض آگاهی از بهره‌های لحظه‌ای کانال برای تمامی لینک‌ها در تمام شبکه، یک الگوریتم بازگشتی سه مرحله‌ای برای تخصیص منصفانه منابع با پیچیدگی کم پیشنهاد شده است. در این الگوریتم، ابتدا کاربر برتر بر اساس معیار انصاف انتخاب می‌شود؛ سپس رله و زیرکانال تحت شرایط مفروض به کاربر برتر اختصاص داده می‌شود. در پایان، بیت و توان براساس الگوریتم water-filling به زیرکانال‌های کاربر برتر تخصیص می‌یابد. علاوه بر این، برای تضمین انصاف میان کاربران، معیارهای مختلفی با هدف تحقق معاوضه موثر میان طول عمر کاربران و احتمال خاموشی آنها پیشنهاد شده است. مطالعات عددی به منظور ارزیابی کارایی الگوریتم پیشنهادی در دو سناریوی عملی انجام گردیده است. نتایج شبیه سازی نشان می‌دهد که الگوریتم تخصیص منابع پیشنهادی، به یک معاوضه موثر میان کارآیی شبکه و انصاف میان کاربران دست می یابد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Resource Allocation for OFDMA Two-Hope Cooperative Cellular Networks: Considering QoS and Fairness Constraints

نویسنده [English]

  • Hemed Bani Zaman

Assistant Professor - Islamic Azad University of Jahrom

چکیده [English]

Abstract – Joint bit allocation, relay selection and subcarrier assignment are critical for achieving full benefits of OFDM-based cooperative relay networks. In this paper, first such a problem is studied in a dual hop OFDMA cooperative network consisting in multi source nodes, multiple decode-and-forward (DF) relays and a single destination node. The aim is to minimize overall transmission power under the bit-error-rate (BER) and data rate constraints. However, the optimal solution to the optimization problem is computationally complex to obtain and may be unfair. Assuming knowledge of the instantaneous channel gains for all links in the entire network, an iterative three-step resource allocation algorithm with low complexity is proposed. It performs the privileged user selection based on fairness criterion first, and then allocates subcarrier-relay with the given constraints. Finally, power and bit are assigned to the selected subcarriers based on the water-filling algorithm. In order to guarantee the fairness of users, several fairness criteria are also proposed to provide attractive trade-offs between network performance (i.e. overall transmission power, average network lifetime and average outage probability) and fairness to all users. Numerical studies are conducted to evaluate the performance of the proposed algorithm in two practical scenarios. Simulation results show that the proposed allocation algorithm achieves an efficient trade-off between network performance and fairness among users.

کلیدواژه‌ها [English]

  • Dynamic resource allocation
  • Multi-user Orthogonal Frequency Division Multiplexing
  • Cooperative Relaying
  • Fairness
  • Quality of Service
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