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Multiuser diversity combined with Orthogonal Frequency Division Multiple Access (OFDMA) are a promising technique for achieving high downlink capacities in new generation of cellular and wireless network systems. The total capacity of OFDMA based-system is maximized when each subchannel is assigned to the mobile station with the best channel to noise ratio for that subchannel with power is uniformly...
(WiMAX) Worldwide Interoperability for Microwave Access is a promising broadband wireless technology that promises high-speed data services. Mobile WiMAX is a broadband wireless solution that enables junction of mobile and fixed broadband networks through a common wide area broadband radio access technology and flexible network structural design. Mobile WiMAX is based on orthogonal frequency division...
The growing demands for advanced mobile multimedia let the wireless mobile Internet access be developed rapidly. The Mobile WiMAX (IEEE 802.16e) is capable of providing high data rate and flexible Quality of Service (QoS) mechanisms. However, one of killer applications, mobile streaming video service from mobile station (MS) to fixed internet network can't still avoid a traditional QoS degradation...
In this paper, cell searching and DoA (Direction of Arrival) estimation methods are proposed for mobile relay stations with a uniform linear array in OFDM-based cellular systems. The proposed methods can improve the performance of cell searching and DoA estimation, even when there exist symbol timing offsets among the signals received from adjacent base stations and Doppler frequency shifts caused...
Spectrum awareness is one of the most challenging tasks in cognitive radio (CR). To adequately adapt to the changing radio environment, it is necessary for the CR to be able to perform joint detection and classification of low signal-to-noise ratio (SNR) signals without requiring much a priori information on the signal parameters. In this paper, we propose a joint detection and classification algorithm...
In this paper, an area-efficient FFT processor is proposed for IEEE 802.16m mobile WiMAX systems. The proposed scalable FFT processor can support the variable length of 512, 1024, 2048 and 4096. By reducing the required number of non-trivial multipliers with mixed-radix (MR) and multi-path delay commutator (MDC) architecture, the complexity of the proposed FFT processor is dramatically decreased without...
In this paper, we focused on the physical layer of mobile-WiMAX and showed the performance of a WiMAX base station in the field using the EVM and BER performance measures. We obtained the theoretical performance, the performance using computer simulations and the performance from field experiments and evaluated the overall performance for WiMAX/OFDM systems. As a result, we could show the effectiveness...
The Simultaneous Transmit and Receive (STR) relaying is the most important feature as a Multi-hop Relay solution in WiMAX technologies to improve performance and extend coverage. This article contributes to the performance on unalignment modes in OFDM-based relay framework and applying in WiMAX standard which refer as IEEE 802.16j STR MAC. We proposed a cut-through scheme based on unalignment approach...
The mobile WiMAX standard (802.16e) uses multiple-input multiple-output (MIMO) limited feedback linear precoding to exploit the channel state information at the transmitter. Although the performance of limited feedback linear precoding in relation to traditional open-loop MIMO-OFDM has been extensively studied in the literature, these studies commonly assume perfect channel estimation at the receiver...
In this paper, channel estimation for Space-Time Block Code (STBC) - Orthogonal Frequency Division Multiplexing (OFDM) is investigated for Mobile WiMax systems. A new channel estimation approach is proposed using the dedicated pilot subcarriers defined at constant intervals by the WiMax standard. The estimation method has low computation as only linear operations are needed due to orthogonal pilot...
The present article describes the experimental result of victim system detection by UWB wireless system to contribute for Japanese UWB regulatory discussion, in which a mitigation, including detect-and-avoid (DAA), technology implementation in the frequency range of 3.4 to 4.8 GHz is a major technical topic. A FPGA based MB-OFDM UWB receiver with 528 MHz sampling rate and 128 points FFT capability...
We propose a strategy that optimally schedules and allocates users for adaptive modulation and coding based orthogonal frequency multiple access systems (AMC-OFDMA). This strategy aims to maximize the average system throughput as a function of bit error rate (BER) and spectral efficiency by exploiting the user diversity. It sorts the available users of an assigned base station (BS) in queues based...
This paper addresses the issue of wireless resource allocation of a Mobile WiMAX cell based on OFDMA access technique. We compare two strategies: the MAX SNR which is the most used channel assignment technique and our proposal which is based on channel condition learning. As we distinguish four IEEE 802.16e-2005 service classes: UGS, rtPS, nrtPS and ErtPS, we combine these strategies with a scheduler...
Hardware implementation of WiMAX systems using field programmable gate array (FPGA) technology is a very important task for mobile communication and wireless network researchers. As a first step, a careful simulation of the system performance has been done using the simulation link platform of matlab_2009. The performance of the simulated system was evaluated using the bit-error-rate (BER). In this...
In this paper, the performance evaluation of the Mesh-based PHY of IEEE 802.16e standard (a.k.a Mobile WiMax) for above the sea propagation is presented. For a Mesh OFDM system, the independent bursts transmission among different communicating nodes compels the receiving nodes to perform frame locking using the preamble with size of only one OFDM symbol interval, short preamble length is used in favour...
Mobile WiMAX is a broadband wireless solution that enables convergence of mobile and fixed broadband network through a common wide area broadband radio access technology and flexible network architecture.Performance evaluation of mobile WiMAX under varying channel is one of the convincing research interest.Most of the existing works,based on performance evaluation under channel condition are limited...
In this paper several hints to be considered in the design of a commercial broadband wireless network are presented. The case of study is based in Worldwide Interoperability for Microwave Access (WiMAX) networks, but the general concepts are also valid for Long Term Evolution (LTE). The information presented here is not only valid for the task of designing a broadband wireless network, but also it...
The novel proposed method as a combination of Time Division Multiple Access (TDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) called Orthogonal Frequency Division Most Congested Access First (OFDMCAF) provides spectrum sharing, buffer management and improves the throughput. In this work the power consumed by activating each cognitive method is analyzed in addition to the throughput...
In this paper, we consider Mobile WiMAX and LTE as the future technologies for primary OFDMA systems and study dynamic spectrum access (DSA) for unlicensed systems coexisting with primary OFDMA systems. We propose an effective DSA scheme that allows an unlicensed system to statistically and opportunistically access the whole spectrum bandwidth during the last consecutive symbols of each primary OFDMA...
Orthogonal frequency division multiple access (OFDMA) has been adopted by all the proposals which have been considered for the fourth generation (4G) wireless technologies. Specifically, the two main contenders in the 4G marketplace are likely to be evolutions of WiMAX and LTE. In this work, we compare the use of OFDMA in these standards.
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