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Browsing by Author "Abouei, J."

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    Cache replacement scheme based on sliding window and TTL for video on demand
    (IEEE, 2018-09-25) Raouf, Amir Hossein Fahim; Abouei, J.; Raouf, Amir Hossein Fahim
    In this paper, we propose a novel two-phased cache replacement algorithm based on the dataset obtained from a typical wireless mesh network. In the first phase, we aim to make a trade-off between the networks resources and refresh the cache content. To deal with this issue, we apply a sliding window to propose a new parameter, called equivalent active time, to forecast the user's behaviour pattern, i.e., make a decision whether to update the cache contents or utilize the network's resources for other services. In the second phase, we introduce, for the first time, the parameter time to live (TTL) that shows the video popularity lifetime. Our proposed cache replacement strategy uses frequency counters and the TTL information in the victim selection process to prevent the cache pollution and make better use of the cache space. Numerical results show that our replacement algorithm outperforms some existing cache replacement strategies in term of a portion of satisfied requests.
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    Delivery phase in cache-based wireless networks with modified LT codes
    (Springer Nature, 2020-10) Raouf, A. H. F.; Abouei, J.; Jaseemuddin, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
    Caching has emerged as an efficient technique to reduce delivery latency and network congestion. The focus of this paper is on content delivery in the caching-based wireless systems. In view of the fact that in such systems, users store fractional of popular contents during off-peak hours, we propose a modified version of the Luby Transform (MLT) encoding for the delivery phase to take the advantage of channel coding. The novelty of our proposed MLT encoding lies in employing the user’s partial information to create an appropriate degree distribution. To evaluate our proposed scheme, this study considers a realistic channel model inspired by the Gilbert-Elliott channel including the erasure mode and a binary symmetric channel model. The effectiveness of our MLT encoding is analyzed by the average degree and the number of encoding symbol. A comprehensive simulation evaluation is performed which shows that MLT encoding outperforms conventional LT coding in terms of the required number of encoding symbols and demonstrates a better performance on the recovered symbols. In particular, the MLT encoding, compared to the conventional LT encoding, reduces the amount of required symbols to recover the original file for at least 20%, when the user stored more than half a file.
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    Design and implementation of VLC-based smart barrier gate systems
    Rasti-Meymandi, A.; Madahian, A.; Abouei, J.; Mirvakili, A.; HajiAkhondi-Meybodi, Z.; Mohammadi, A.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
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    DMT analysis and optimal scheduling for two-hop parallel relay networks
    (Elsevier, 2021-06) Khayatian, H.; Parvaresh, F.; Abouei, J.; Saberali, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
    Two-hop parallel networks with half-duplex relays over quasi-static Rayleigh fading channels are considered. Assuming relays have only local channel state information, optimal communication schemes for these networks in terms of the diversity multiplexing trade-off (DMT) are obtained. It is shown that the dynamic quantize-map-and-forward (DQMF) and the static quantize-map-and-forward (SQMF) communication strategies achieve the optimal DMT at different ranges of the multiplexing gain. In the DQMF scheme, a relay sets its transmitting/listening times according to the instantaneous source-relay channel condition. However, in the SQMF scheme, a relay sets its transmitting/listening times to be a constant independent of the instantaneous source-relay channel gain. Essentially, we calculate the DMT of the network under the general setting for arbitrary average signal-to-noise ratios over links and it is shown that the DMT of the proposed schemes matches the upper bounds. Moreover, the optimal transmitting/listening times of the half-duplex relays as functions of the instantaneous channel realizations are derived for different communication strategies in the general setting. Finally, various simulation scenarios are considered and the DMT of the proposed schemes and the dynamic decode and forward communication strategy are compared.
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    Fast-decodable MIMO HARQ systems
    (IEEE, 2015-05) Hosseini, S. S.; Abouei, J.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
    This paper presents a comprehensive study on the problem of decoding complexity in a Multi-Input Multi-Output (MIMO) Hybrid Automatic Repeat reQuest (HARQ) system based on Space-Time Block Codes (STBCs). We show that there exist two classes of fast-decodable MIMO HARQ systems: independent and dependent STBC structures. For the independent class, two types of protocols namely, fixed and adaptive threshold-based are presented and their effectiveness in both computational complexity reduction and spectral efficiency preservation are discussed. For the dependent class, a fast Sphere Decoder (SD) algorithm with a low computational complexity is proposed for decoding process of HARQ rounds. Two new concepts are introduced to leverage the fast-decodable notion in MIMO HARQ systems. Simulation results show that the proposed fast-decodable MIMO HARQ protocols in both classes provide a significant reduction in the decoding complexity as compared with the original MIMO HARQ method.