133 research outputs found

    On the Modelling of the Mobile WiMAX (IEEE 802.16e) Uplink Scheduler

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    Packet scheduling has drawn a great deal of attention in the field of wireless networks as it plays an important role in distributing shared resources in a network. The process involves allocating the bandwidth among users and determining their transmission order. In this paper an uplink (UL) scheduling algorithm for the Mobile Worldwide Interoperability for Microwave Access (WiMAX) network based on the cyclic polling model is proposed. The model in this study consists of five queues (UGS, ertPS, rtPS, nrtPS, and BE) visited by a single server. A threshold policy is imposed to the nrtPS queue to ensure that the delay constraint of real time traffic (UGS, ertPS, and rtPS) is not violated making this approach original in comparison to the existing contributions. A mathematical model is formulated for the weighted sum of the mean waiting time of each individual queues based on the pseudo-conservation law. The results of the analysis are useful in obtaining or testing approximation for individual mean waiting time especially when queues are asymmetric (where each queue may have different stochastic characteristic such as arrival rate and service time distribution) and when their number is large (more than 2 queues)

    CIR Performace of One-third ICI-SC Subcarrier Mapping Technique with STFBC in MIMO-OFDMA System

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    In multiple input multiple output (MIMO) with orthogonal frequency division multiple access (OFDMA) system, intercarrier interference (ICI) is one of the major drawback in the system. This is due to the orthogonality of the subcarrier which has been destroyed by frequency offset (FO) and thus degrades the system performance. In order to overcome this problem, one-third intercarrier interference selfcancellation (ICI-SC) subcarrier mapping method with space time frequency block codes (STFBC) is proposed. Average power desired (APD) signal, ICI and carrier to interference ratio (CIR) are derived theoretically and the proposed signal is analyzed with other previous methods. As a result, it is proven that by choosing the suitable subcarrier mapping with ICI-SC method, MIMO-OFDMA system performance which affected by FO can be improved with maximum diversity order

    Robust Schemes to Enhance Energy Consumption Efficiency for Millimeter Wave-Based Microcellular Network in Congested Urban Environments

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    Future wireless communication networks will be largely characterized by small cell deployments, typically on the order of 200 meters of radius/cell, at most. Meanwhile, recent studies show that base stations (BS) account for about 80 to 95 % of the total network power. This simply implies that more energy will be consumed in the future wireless network since small cell means massive deployment of BS. This phenomenon makes energy-efficient (EE) control a central issue of critical consideration in the design of future wireless networks. This paper proposes and investigates (the performance of) two different energy-saving approaches namely, adaptive-sleep sectorization (AS), adaptive hybrid partitioning schemes (AH) for small cellular networks using smart antenna technique. We formulated a generic base-model for the above-mentioned schemes and applied the spatial Poisson process to reduce the system complexity and to improve flexibility in the beam angle reconfiguration of the adaptive antenna, also known as a smart antenna (SA). The SA uses the scalable algorithms to track active users in different segments/sectors of the microcell, making the proposed schemes capable of targeting specific users or groups of users in periods of sparse traffic, and capable of performing optimally when the network is highly congested. The capabilities of the proposed smart/adaptive antenna approaches can be easily adapted and integrated into the massive MIMO for future deployment. Rigorous numerical analysis at different orders of sectorization shows that among the proposed schemes, the AH strategy outperforms the AS in terms of energy saving by about 52 %. Generally, the proposed schemes have demonstrated the ability to significantly increase the power consumption efficiency of micro base stations for future generation cellular systems, over the traditional design methodologies

    MIMO-OFDMA Subcarrier Mapping Improvement by using Quarter ICI-SC with STFBC Technique

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    Many wireless communication systems rely on Orthogonal Frequency Division Multiple Access (OFDMA) to guarantee reliable transmission and better performance. However, the orthogonality of the subcarriers has been destroyed by frequency offset (FO) and thus leads to intercarrier interference (ICI) which reduces the system performance. In order to overcome this problem, quarter ICI self-cancellation (ICI-SC) subcarrier mapping scheme using data allocation in space-time-frequency block codes (STFBC) for MIMO-OFDMA system is proposed. The technique is then evaluated through Pairwise Error Probability (PEP) and Bit Error Rate (BER) performance. From the results, proposed quarter ICI-SC subcarrier mapping scheme technique with STFBC shows the best result for MIMO-OFDMA system

    On the robustness of measurement of reliability stopping criterion in turbo iterative decoding

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    Measurement of reliability (MOR) stopping criterion is able to terminate early in the low and high signal-to-noise ratio (SNR) while maintaining the bit error rate (BER) performance. However, the performance of MOR is only based on one code structure and hence, the robustness of MOR is still unknown in turbo iterative decoding. Thus, this paper will test the robustness of MOR based on the following parameters: frame size, code structure, channel reliability and code rate. Then, we analyse and compare the average iteration number (AIN) and the BER performance of MOR with the benchmark stopping criterion known as Genie to determine the robustness of MOR. From the analysis, MOR has a BER degradation for low code rate. MOR also fails to perform well if the corret channel reliability is not available at the receiver and this results a large degradation in BER performance. However, MOR has close performance to Genie in terms of BER for various frame sizes, code structures and high code rate with the assistance of correct channel reliability. MOR is also able to save AIN at low SNR as compared to Genie and this can reduce delay and complexity of turbo codes

    Investigation of QoS Performance Evaluation over 5G Network for Indoor Environment at millimeter wave Bands

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    One of the key advancement in next-generation 5G wireless networks is the use of high-frequency signals specifically those are in the millimeter wave (mm-wave) bands. Using mmwave frequency will allow more bandwidth resulting higher data rates as compared to the currently available network. However, several challenges are emerging (such as fading, scattering, propagation loss etc.), when we propagate the radio signal at high frequencies. Optimizing propagation parameters of the mm-wave channels system are much essential for implementing in the realworld scenario. To keep this in mind, this paper presents the potential abilities of high frequencies signals by characterizing the indoor small cell propagation channel for 28 GHz, 38 GHz, 60 GHz and 73 GHz frequency band, which is considered as the ultimate frequency choice for many of the researchers. The most potential Close-In (CI) propagation model for mm-wave frequencies is used as a Large-scale path loss model. The results have been collected concerning the capacity of users to evaluate the average user throughput, cell-edge user throughput, average cell throughput, spectral efficiency and fairness index. The statistical results proved that these mm-wave spectrum gives a sufficiently greater overall performance and are available for use in the next generation 5G mobile communication network

    EVALUATING A NEW SUBCARRIER MAPPING ICI-SC SCHEME USING LINEAR MAXIMUM LIKELIHOOD ALAMOUTI COMBINER (LMLAC) DECODING TECHNIQUE

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    This paper presents a new subcarrier mapping scheme ICI-SC technique that use Linear Maximum Likelihood Alamouti Combiner (LMLAC) as a decoding technique to mitigate intercarrier interference (ICI) problem with low complexity decoding system for space time frequency block codes (STFBC) orthogonal frequency division multiplexing (OFDM) in the frequency selective environments. We provide details of the mathematical models of the proposed scheme and simulate its error performance caused by frequency offset (FO). We also analyze the impact of the STFBC of the system. The simulation results showed that the scheme has the ability to reduce ICI effectively with a low decoding complexity and maximum diversity in terms of bandwidth efficiency and also in the bit error rate (BER) performance especially at high signal to noise ratio

    Optimal generator matrix G

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    Multiple antenna transmission methods are currently being developed all around the world for evolving 3G wireless standards. Space–Time Trellis Code (STTC) has been proven to use transmit diversity efficiently. It effectively exploits the effects of multipath fading to increase the information capacity of the multiple antenna transmission systems. STTC is a channel coding technique that maximises the ‘distance’ between different symbol matrices such that the probability of transmission errors are decreased when transmitting redundant symbol or in other words, to maximise the minimum determinant. Maximising the minimum determinant is equivalent to obtaining optimal generator matrix G. Instead of using state diagrams, optimal generator matrix G discussed in this paper is obtained using an improved algorithm which is based on Lisya tree structure. Optimal generator matrix G in this paper has a minimum determinant of 48 which is the highest coding gain obtained so far

    Performance analysis of stopping turbo decoder iteration criteria

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    The invention of turbo codes has attracted many researchers to explore various fields regarding turbo codes since it provides better error rate performance compared to the existing codes. Good error rate performance gives a penalty to the complexity of the codes. It includes the complexity of decoding algorithm and iterative decoding. This paper reviews the history of turbo codes and its structures. This paper also discusses the turbo decoding stopping criteria algorithm and analyses the performance of fixed and cross-entropy (CE) based stopping criteria. From the results, both criteria fail to terminate early in low SNR. However, CE-based stopping criteria outperform the fixed stopping criterion at high SNR and able to save more iteration and delay. This leads to an energy saving preservation while maintaining the performance of turbo codes
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