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In this paper, we present a pilot design for an OFDM cellular system based on Costas arrays. The design provides pilot symbols for both common and dedicated pilots for MIMO transmission. The pilot symbols are designed so that pilots from different cells intersect minimally. The design results in a large number of available distinct pilot symbol patterns with minimally overlapping resource elements...
Power control is one of the key functions which are able to co-ordinate the system interference. In this paper, several power control schemes are investigated for a hybrid LTE system, which combines the direct device-to-device (D2D) mode communication and the normal cellular mode communication. In the system study, the power control for the D2D mode communication is emphasized. In general, the utilization...
Inter-cell interference is a major problem in multi-cell OFDMA systems and can severely degrade the system throughput, particularly for cell-edge users. An efficient technique to mitigate inter-cell interference (ICI), is interference coordination that allocates certain resources among users in different cells. In this paper, we propose a novel and distributed algorithm in order to mitigate the inter-cell...
Orthogonal Frequency Division Multiplexing (OFDM) is very sensitive to carrier frequency offsets (CFO). The CFO results in intercarrier interference (ICI). This drawback of OFDM is inherited to Orthogonal Frequency Division Multiple Access (OFDMA). In this paper, we propose a new ICI model for an uplink OFDMA system that takes into account the presence of the cyclic prefix which is usually ignored...
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...
Careful management of inter-cell interference is important in OFDMA based systems such as LTE. In this paper, we study an uplink ICIC (Inter-cell Interference Coordination) mechanism, which fully utilizes the flexibility of frequency selective scheduling and rate adaptation, while dynamically limiting the interference experienced by the neighboring cells. This technique can be seen as an extension...
In cellular OFDMA networks, there exists a fundamental trade-off between the achievable cell capacity and the degree of fairness among the users in the cell. Several scheduling algorithms have been proposed which try to balance this tradeoff. The parameterization of these scheduling algorithms to achieve a certain desired fairness level is non-trivial. We show that the optimal fairness parameter settings...
The opportunistic beamforming (OB) technique in multicellular OFDMA networks is investigated in this paper. For this reason, three cross-layer radio resource management (RRM) algorithms for OFDMA operational scenarios that are based on typical resource allocation targets such as minimization of transmit power, maximization of throughput and interference averaging are considered. The OB concept is...
In this paper, a new space-frequency combination technique is proposed for Alamouti coded Orthogonal Frequency Division Multiplexing (OFDM) in the context of cooperative communications. Since cooperative antennas are distributed, there may exist multiple carrier frequency offsets (MCFOs) which cause problems for conventional space-frequency decoding. The proposed algorithm, taking cues from existing...
In this paper we propose a novel hybrid multicarrier architecture for wireless LAN (WLAN) applications. We refer to this architecture as hybrid filtered multitone (HFMT). Depending on the experienced channel condition, H-FMT switches between short orthogonal FMT (SO-FMT) modulation, and adaptive orthogonal frequency division multiplexing (A-OFDM). Extensive numerical results show that H-FMT could...
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...
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...
In this paper, we focus on the guarantee of inter-cell fairness in OFDM femtocell systems. To solve this problem, we formulate an optimization problem to maximize the summation of logarithmic cell capacity. Based on analytic results, we propose an enhanced modified iterative water-filling algorithm which improves inter-cell fairness compared to a modified iterative water-filling algorithm. The key...
This paper addresses the effect of timing synchronization errors for two different multicarrier techniques CPOFDM and FBMC. Such errors degrade the performance of the reference receiver by causing multi user interference. This interference occurs when the signals from different transmitters arrive at a given receiver with arbitrary timing misalignments, leading to the destruction of orthogonality...
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...
The Wireless over Cable (WoC) paradigm is a new technique to enable distributed antennas systems. WoC is based on the relay of radio frequency wireless signals over a cable infrastructure through a bidirectional (analog) amplify and forward device that translates the bandwidth of wireless signals to comply with the specifications of the wired links. Following the WoC concept, here the xDSL connection...
This paper addresses the problem of theoretical characterization of the joint effect of a transmitter I/Q imbalance and nonlinear amplification on OFDM. We prove a theorem about a linear representation of the distorted signal and apply it to error rate analysis. In view of the structure of the distorted signal, the proven theorem can be referred to as an extension of Bussgang's theorem.
Multi-carrier modulation and especially CP-OFDM is widely used nowadays in several radio communications. However, FBMC is a potential alternative to CP-OFDM since it does not require cyclic prefix, and thus, it has a higher spectral efficiency. One of the characteristics of FBMC is that the received data are accompanied by a two dimensional inter-symbol interference term (2D ISI), which complicates...
In this work, we analyze the performance of a multi-user sectored MIMO/OFDMA system under the limited feedback constraint. Dynamic radio resource management methods are used to a reuse-one sectorized cell in order to reduce the cross-sector interference. Simulation results show that the proposed strategy reduces the co-channel interference and maintain at the same time high spectral efficiency.
This paper proposes a decentralized interference control scheme for an OFDMA (Orthogonal Frequency Division Multiple Access) cellular scenario where multiple macrocells and femtocells are deployed. In particular, we model the distributed resource allocation problem by means of a potential game, which is demonstrated to converge to a unique and pure Nash equilibrum. In this game, the femto base stations...
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