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The LOS components of the base station (BS) can provide a high SNR to mobile stations (MSs), but they cannot achieve a high spatial multiplexing gain in the MIMO-OFDMA system. The spatial multiplexing gain is obtained by degrees of freedom between MIMO antenna arrays. MIMO channels should be uncorrelated to achieve the maximum degrees of freedom, and it depends on rich scattering environments which...
Performance of next generation OFDM/OFDMA based Distributed Cellular Network (ODCN) where no cooperation based interference management schemes are used, is dependent on four major factors: 1) spectrum reuse factor, 2) number of sectors per site, 3) number of relay station per site and 4) modulation and coding efficiency achievable through link adaptation. The combined effect of these factors on the...
We propose a cross-layer strategy that jointly optimizes user scheduling and resource allocation for adaptive modulation and coding (AMC) based orthogonal frequency multiple access (OFDMA). The objective of this paper is to maximize the system throughput as a function of the bit error rate (BER) and the spectral efficiency based on selected modulation and coding schemes (MCSs). The proposed optimal...
In this paper, we undertake a comparison of LDPC (768,384) and convolutional (171,133) codes for 60-GHz OFDM-based wireless communication systems. The comparison is based on two parameters: Frame Error Rate (FER) for 60-GHz channels and decoding hardware complexity for a required throughput of more than 1 Gbps. Additionally, we provide performance parameters of a fully parallel LDPC decoder chip,...
Inter-cell interference coordination (ICIC) is one of the key technologies in the multi-cell radio resource management of mobile systems. It plays a vital role in mitigating strong inter cell interference and guaranteeing proper quality of services for in-progress sessions. Because heterogeneous deployment is adopted in LTE-Advanced, and interference problem becomes serious. In this paper, we propose...
This paper studies the performance of a superposition based approach for multi-user access in the uplink of a wireless cell. The approach uses non-orthogonal signaling and multi-user detection on top of an orthogonal multiple-access method like OFDMA. Path losses depending on the distance between a terminal and the base station and cancellation errors during multi-user detection are taken into account...
Femtocells are being deployed for coverage extension and higher data rates. However, interference problem between macrocell and femtocells should be solved before massive deployment. In this paper, we analyze the possible cases of frequency resource allocation in the OFDMA femtocell systems using Fractional Frequency Reuse (FFR) in order to minimize the interference between both cells. Under the assumed...
We have already proposed a hybrid single-carrier (SC) and multi-carrier (MC) system for next-generation mobile communication system. A SC signal has low peak-to-average power ratio (PAPR), which yields high power output for wide coverage. A MC signal is robust against frequency-selective fading and has high data rate with quadrature amplitude modulation (QAM). By appropriately selecting SC and MC...
In this paper, a joint channel-and-queue-aware relay selection and resource allocation scheme at the scheduling phase in an OFDMA downlink cellular network is proposed. The scheme can choose the best relay to cooperate and allocate subchannels and power for the source and the relay for the selected packet which can maximize the proposed utility function waiting in the base station. Under the premise...
In this paper, a new joint scheduling and hybrid resource allocation method is derived and investigated for a multi-user downlink Orthogonal Frequency Division Multiple Access (OFDMA) system that provides Time Delay-Sensitive services (TDS) and Time Delay-Insensitive services (TDI). A three sectored multi-cellular heterogeneous traffic environment is considered where users are randomly distributed...
In the multi-cell environment, the approaches that are suitable for the single cell scenario may cause excessive interference to other cells and become suboptimal. In this paper, we present a number of receiver-centric power allocation schemes that take into account the detrimental impact of allocated resources to the neighboring cells, and use it as a guideline in determining the appropriate power...
This paper presents a link adaptation strategy for non-binary LDPC code over a time-variant frequency-selective channel. The algorithm is based first on the adoption of waterfilling technique to wisely adapt the transmitted power. It is shown that as long as best subchannels are identified with the waterfilling algorithm, an equal power distribution can be applied with performance comparable to the...
In current wireless standards like 3GPP LTE or IEEE 802.16 / WiMAX multiple access is based on orthogonal signalling using single-carrier frequency-division multiple access (SC-FDMA) or orthogonal frequency-division multiple access (OFDMA). Links between a base station and different terminals use mutually orthogonal radio resources. This paper studies potential gains in average cell throughput by...
In this work we consider the allocation of buffer space to data streams sharing a common high-speed wireless transmitter. As an example, we focus on an OFDMA-based downlink system scenario. Scheduling for maximum throughput has been extensively studied in the literature. However, the practically interesting case of a finite buffer has not been sufficiently addressed before. Especially in the case...
We consider joint cross-layer resource allocation and inter-system interference avoidance in OFDMA-based multiuser cognitive radio (CR) systems, where the secondary users (SU) can share spectrum with the primary users (PU) without causing unacceptable interference. The objectives are to provide quality of service (QoS) to both real-time and non-real-time services for SUs, and optimize the system throughput...
We present an orthogonal frequency division multiple access (OFDMA) cognitive radio medium access control using multichannel ALOHA (OCR MAC). The performance of an infinite population based OCR system is numerically as well as theoretically analyzed in terms of throughput, delay, and data capacity. We evaluate the throughput versus delay tradeoff of OCR MAC with an agile OFDM channel selection. Especially,...
This paper demonstrates the usage of novel cognitive methods that improve the throughput of a WIMAX network by minimizing packet loss. The effects of the ant colony and fastest path routing algorithms on the throughput are investigated. a combination of Time Division Multiple Access (TDMA) and Orthogonal Frequency Division Multiple Access (OFDMA) spectrum sharing techniques is used. Data packet loss...
For the issue of resource allocation in a heterogeneous multi-user downlink OFDMA system with both delay-constrained (DC) and non-delay-constrained (NDC) traffic, this paper proposes suboptimal joint subcarrier and power allocation (JSPA) for channel-aware queue-aware(CAQA) scheduling. The objective is to maximize the sum of all NDC users' logarithmic utility functions (achieving proportional fairness)...
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 presents a novel adaptive video streaming framework designed for OFDM-based mobile networks. The proposed adaptation algorithm exploits the benefits of the Scalable Video Coding (SVC) extension of the H.264/AVC standard together with cross-layer information from the mobile terminals in performing adaptation that maximizes streaming qualities amongst all participating users. Simulations...
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