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Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) is an integral part of Orthogonal Frequency division multiplexing (OFDM) systems. This forms the physical layer architecture of wireless systems and is designed to consume low power. This paper presents a low power and area efficient architecture for the FFT implementation. FFT involves more complex addition and multiplication...
The main goal of this work is to use the Cuckoo Search (CS) algorithm to optimize Fractional Frequency Reuse (FFR) of cellular network systems. FFR is an interference management technique well suited to OFDMA based cellular network systems, such as Long Term Evolution system (LTE). This paper proposes a mechanism that selects the optimal value of inner cell region radius in strict FFR that maximize...
The mechanisms of allocating the resources in Long Term Evolution (LTE) cellular networks are very critical issues, because scheduling algorithms have the main responsibility for determining how to allocate radio resources for different users. In this work a dynamically adopted Proportional Fair (PF) scheduling strategy for capacity enhancement of LTE system is proposed. Performance comparison with...
This paper presents a new eight-parallel multi-path delay commutator (MDC) FFT processor based on the novel modified radix-26 FFT algorithm. The proposed FFT processor can achieve a high throughput and a low hardware complexity by using the efficient scheduling scheme that reorders data-paths. The proposed scheduling scheme and CSD approach can reduce the number of complex multipliers.
:In today scenario, with increasing number of user fair Resource Allocation has become a problem. The purpose of Resource Allocation is to allocate sub-carrier and power to users to meet their service requirements while maintaining fairness among users and maximize resources utilization. In this paper resources are allocated in such a way to maximize the throughput while minimize the power consumption.
Long Term Evolution (LTE) is treated as a mainstream wireless communication technology from the 3G to 4G. The Orthogonal Frequency Division Multiple Access (OFDMA) is introduced to solve the innercell interference in the downlink of LTE. However the intercell interference especially for the edge users is still remain unsolved. In this paper, we propose a novel and general interference coordination...
This paper proposes a downlink mapping algorithm for two-level requests in Orthogonal Frequency Division Multiple Access based IEEE 802.16e systems under the Adaptive Modulation and Coding (AMC) mode by which the modulation and coding scheme (MCS) of a user may be different for available subchannels. Given a set of requests each with two priorities, the proposed algorithm efficiently allocates a two-dimensional...
In this paper, we propose an optimal resource allocation algorithm that maximizes the energy efficiency (EE) of a downlink (DL) multi-user orthogonal frequency division multiplexing (OFDM) system subject to a constraint on the total transmit power of the base station (BS). We show that the optimal EE is obtained by first allocating each subcarrier to the user equipment (UE) with the best channel power...
Opportunistic spectrum access in Cognitive Radio (CR) systems significantly improves spectrum efficiency by allowing secondary users (SUs) to opportunistically use licensed spectrum without causing harmful interference to primary users (PUs). However, as a prevailing transmission scheme, OFDM introduces unwanted interference to the primary user due to its side-lobe leakage. Meanwhile, miss detection...
LTE uses the SC-FDMA radio access technology for its uplink transmission. As a result, resources assigned to the same user must be contiguous in the frequency domain. Several uplink scheduling algorithms were proposed in the literature to fit that constraint. These algorithms take as input a matrix which is used by the Packet Scheduler for an efficient resource allocation. The performance of these...
We consider power allocation in OFDM based underlay cognitive radio networks with partially known inter-system CSI (Channel State Information). Under a given total transmit power limit at the SU (Secondary User) transmitter, the goal is to assign a certain amount of power for signal transmission in each OFDM sub-channel, such that the SU's overall throughput can be maximized, and the average interference...
In Cognitive Radio (CR) networks, it is common that the spectrum holes are too narrow to support high-speed communications. Discontinuous Orthogonal Frequency Division Multiplexing (DOFDM) is a good way for a secondary user to access several spectrum fragments simultaneously with one Radio Front (RF). In this paper, a novel Channel Characteristic Aware Spectrum Aggregation (CCASA) algorithm which...
Dedicated Short Range Communication (DSRC) designed to be built in to every vehicle for safety and commercial non-safety application, is a robust technology that is supported by IEEE 802.11p standard due to the mobility of vehicle that cannot be avoidable. High data rate is one of the requirements for devices operating in this category. As with such, there is need for vehicles to change data rate...
Towards the MAC design of the dynamic sharing spectrum communication system, this paper proposed a new MAC frame structure which can be used in centralized networks. And design a Slotted ALOHA access control algorithm based the feedback competition CSI (channel state information) of access users. Then through analyzing the delay features and the stability, we propose a new MFpBA to assure the system...
Link Adaptation can dynamically adjust a number of transmission parameters, most often modulation and coding, to reflect the characteristics of the wireless link to improve throughput and maintain link reliability. Most LA algorithms require only an estimate of the signal-to-noise ratio (SNR) to select an appropriate PHY mode, relying on the assumption of an AWGN channel. For channels experiencing...
We identify relaying as one of the most effective and enabling components of the LTE-A standard. However, this standard suffers from a major weakness that results from the assumptions that the relaying nodes are static, their locations are known and their number is fixed. While these assumptions facilitate the design of the cellular system, they limit the scope of relay usability. As an alternative,...
In this paper, we propose a distributed adaptive interference coordination algorithm for a practical orthogonal frequency division multiple access (OFDMA)-based mobile cellular systems. The designed algorithm can achieve an efficient frequency reuse for any user distribution and traffic load. Since no a priori frequency planning is required, the minimal coordination between base stations is also achieved...
The frequency resource of mobile communication systems is intensive and it needs to combine with cognitive radio technology. The mobile telecommunication system subscribers are sensitive to interference, making the interference problem need prompt solution. This paper analyzes the inter-system and intra-system interference and proposes the approach of utilizing spectrum holes classification. The spectrum...
In fourth generation wireless communication standards, the throughput enhancement for cell edge users is a main issue so that various inter-cell interference (ICI) coordination techniques have been suggested. Since the coordination between different cells requires the resources of cooperating cell, its use should be determined carefully. In this paper, we consider two basic handover schemes (Fast...
The problem of resource allocation in multiuser OFDM system is a combinatorial optimization problem, difficult to solve in polynomial time. For the sake of reducing complexity, it can be solved either by relaxing constraints and making use of linear algorithms or by metaheuristic methods. In this paper, ant colony optimization, a typical algorithm of metaheuristic methods, is applied to solve the...
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