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We study a cognitive channel reuse approach for autonomous femtocell deployment in an OFDMA-based cellular network. The objective is to manage the uplink interference from macrocell users to femtocell access points. Macrocell users are normally far away from the base station and may cause strong uplink interference to the close-by femtocells. By cognitive interference recognition, a femtocell access...
In the planning of cellular networks, link budget calculation is the first step to get the maximum allowable cell radius that guarantees a target signal to interference plus noise ratio (SINR) with a certain level of outage probability at the cell border. The interference margin as one of key inputs for link budget is used to compensate for co-channel interference. In this paper, a mathematical analysis...
Recent research on Frequency Reuse (FR) schemes for OFDM/OFDMA based cellular networks (OCN) suggest that a single fixed FR cannot be optimal to cope with spatiotemporal dynamics of traffic and cellular environments in a spectral and energy efficient way. To address this issue this paper introduces a novel Self Organizing framework for adaptive Frequency Reuse and Deployment (SO-FRD) for future OCN...
In the bistatic radar, it is important to suppress the undesired signals such as the direct propagated signal from transmitter and its multipath components. Conventionally, the suppression method by subtracting the replicas of the undesired signals is often used. However, it requires the precise delay times of the undesired signals. In this paper we propose a new method to detect the target without...
The promising spectrum sharing technology used to improve the spectrum usage may cause severe narrowband interference, which seriously degrades the timing synchronization. As noticed that only the auto-correlation based methods have been investigated in the literature, this paper examines the impairment of narrowband interference to the cross-correlation based timing synchronization, to obtain a comprehensive...
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...
Ultra Wide Band (UWB) and Cognitive Radio (CR) offer radically different approaches to efficiently use the seemingly scarce spectrum in wireless communications. In this paper, we study the combined cognitive multiuser spectrum sharing and power allocation problem in the context of Multiband OFDM. A proposed gradient power allocation scheme with a target based game strategy is investigated to solve...
Spectrum sharing is promising to improve the efficiency of spectrum usage. However, this technology may incur severe narrow band interference (NBI), which seriously complicates the synchronization problem. This paper investigates the timing synchronization problem in the presence of NBI for the OFDM-based spectrum sharing systems. We consider the cross-correlation based timing synchronization and...
In this paper we analyzed possibilities to adapt the DL-PUSC pilot grid in filters bank based multicarrier (FBMC) system. We showed that by applying certain designed pilot patterns especially for FBMC, the BER can outperforms in certain cases that achieved in conventional CP-OFDM system. The performance evaluations are done in hypothetical WiMAX scenario on which the FBMC system will substitute the...
This paper presents an interference mitigation algorithm for coexistence of Multiple-Input Multiple-Output (MIMO) Multiband OFDM ultra wideband (MB UWB) Cognitive Radio systems with other wireless communication systems. While other interference cancellation algorithms are applied for SISO system, an improved Active Interference Cancelation algorithm for MIMO MB-UWB systems is proposed with aims to...
We propose the use of simple full interference cancellation (FIC) and orthogonal frequency-division multiplexing (OFDM) within a two-hop asynchronous cooperative four relay network. This approach can achieve the full available diversity and asymptotically full rate. The four relay nodes are arranged as two groups of two relay nodes with offset transmission scheduling. Therefore, the source can serially...
Development of fair and efficient algorithms for resource allocation to secondary users (SUs) is one of the key issues in the design of cognitive radio (CR) systems. In this paper, we present a two-step resource allocation solution for multiuser based CR systems employing orthogonal frequency division multiplexing (OFDM). The solution allocates the subcarriers to SUs in the first step, considering...
We consider a cellular network MIMO OFDM system where cooperating base stations apply joint signal processing to the receive signals of several users. In this situation, due to geometry, the problem of unavoidable differences in time of arrival between the users' signals occurs. As a result, symbol timing offsets can be larger than the cyclic prefix, which leads to OFDM inter-symbol interference....
In this paper we propose three frequency reuse coordination schemes for interference management in OFDMA. The aim of these schemes, working together with time and frequency domain packet scheduling, is to achieve reuse of 1 at sector level in a trisectorized base station scenario. Inter-sector interference is strong at the frontier between sectors and a tight coordination scheme needs be applied....
We propose a novel distributed and low complexity joint channel and power allocation scheme for the uplink of multi-cellular multi-carrier systems. The algorithm is based on the min-sum message passing (MP) scheme that entails passing messages between the base station (BS) and mobile terminals (MTs) with the aim of achieving a low power consumption resource allocation while respecting rate constraints...
In this paper, we compare the performance attained by several scheduling policies when the resource allocation is performed in a per-user or in a per-frequency resource ordering. We test the capability of both approaches to deal with the quality of service (QoS) provisioning in a multi-service scenario in a mobile OFDMA network. We probe that the comparative performance of these two approaches depends...
A novel Narrowband Interference (NBI) suppression scheme using a Soft Limiter (SLM) is proposed for a digital noncoherent receiver in Time-Hopping Pulse Position Modulation Ultra Wideband (TH-PPM-UWB) communications. The NBI suppression is carried out in the analog domain (before the digital processing) via a feedforward structure. The suitability of this NBI suppression concept is confirmed by the...
In adaptive time division duplex (TDD) broadcast multi-antenna orthogonal frequency division multiplexing (OFDM) systems, non-reciprocal transceiver chains at the base station (BS) cause multi-user interference. This is due to the inappropriate spatial filter design at the BS based on the reverse link estimate. Hence, BS transceiver calibration is required. Provided that an estimate of the forward...
FBMC transmission system was proposed as an alternative approach to OFDM system since it has a higher spectral efficiency. One of the characteristics of FBMC is that the demodulated transmitted symbols are accompanied by interference terms caused by the neighboring transmitted data in time and frequency domain. The presence of this interference is an issue for the Maximum Likelihood (ML) implementation...
The algorithm of high capacity digital watermarks embedding into the speech signals using OFDM-technology has been worked out. For DWM embedding it is suggested to apply vector quantization of complex envelope of the narrow-band signal. DWM resistance against intersymbol interference, multiplicative and additive interferences are provided accordingly by means of: 1) OFDM-like forming the narrow-band...
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