The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Femtocells are a promising solution for the provision of high indoor coverage and capacity. Furthermore, OFDMA-based femtocells have proven to be highly versatile when dealing with cross-layer co-channel interference; however, concerns still exist related to the impact of the different access methods to femtocells in an overlaid network. Femtocells based on a Closed Subscribers group, where only device...
Time varying channel breaks the orthogonality between the subcarriers of Orthogonal Frequency Domain Multiplexing (OFDM). This introduces Intercarrier Interference (ICI). One of the ways to mitigate ICI is to first estimate the channel and then equalize it. In this paper we propose to estimate the channel using Discrete Proplate Spheroidal Sequences (DPS) using pilot carriers interleaved with data...
The effect of a power amplifier nonlinearity on multi-antenna orthogonal frequency division multiplexing (OFDM) transmitters utilizing subcarrier beamforming is investigated. Theoretical analysis and simulation shows that such systems can exhibit significant performance degradation due to the power amplifier nonlinearity when there are channel state feedback errors. The SINR degradation under solely...
This paper presents results from a novel OFDMA multi-cell mobile broadband system level simulator. The tool is used to statistically characterize uplink and downlink inter-cell interference. Without suitable interference management, multi-billion dollar networks can collapse under the strain of heavy traffic loads. Fully loaded interference studies cannot be performed on the network until it has been...
Current communication schemes rely on instantaneous adaptation, which increases the system complexity and is memoryless. We propose a scheme for adapting system parameters based on a priori knowledge of the channel statistics to reduce feedback requirements. As a vital parameter in OFDM system, cyclic prefix (CP) length depends mainly on two channel characteristics: the channel gains and the root...
This article addresses the signal distortion caused by receiver phase noise (PN) on OFDM waveforms in direct-conversion radio receivers. A closed-form solution for the observed signal-to-interference-plus-noise ratio (SINR) is derived, describing the level of intercarrier interference (ICI) stemming from PN. Compared to existing literature, the analysis is valid for arbitrary oscillator spectral shape,...
In this paper, we study how the downlink received signal quality and throughput will be affected by deploying the Open Subscriber Group (OSG) Femtocell [1] using Location-Dependent Power Setting (LDPS) scheme with spectrum allocation (1, 3, 3) in the next generation mobile network. The LDPS scheme aims to use a suitable power for femtocell base station to maintains its indoor user coverage. The design...
In this paper we propose three different frequency resource management strategies that, working together with FFR and open-loop Fractional Power Control (PFC), succeed on mitigating both uplink inter-cell interference (ICI) and ICI fluctuations, that usually reduce the performance of SC-FDMA cell-based systems. Simulations are carried out with real-time traffic patterns at different loading scenarios,...
Cognitive radio networks are receiving a lot of research attention lately. Most user equipment in state-of-the-art wireless communication systems are equipped with two antennas. In this paper, we take advantage of the two transmit antennas in an underlay cognitive radio network scenario. Secondary users use the two transmit antennas in order to insert a null in the direction of the primary base station,...
In this paper, we present a novel approach to evaluate the downlink Erlang capacity of a cellular Orthogonal Frequency Division Multiple Access (OFDMA) system with 1:1 frequency reuse. Erlang capacity analysis of traditional cellular systems like Global System for Mobile communications (GSM) cannot be applied to cellular OFDMA because in the latter, each incoming call requires a random number of subcarriers...
In this paper, we address the problem of optimal relay placement in cellular networks for maximum extension of coverage area. We present a novel definition of the coverage radius after the introduction of relays. Using this, we determine the optimal relay positions to maximize the coverage radius and estimate the number of relays required per cell. We also analyze relay placement in the multi-cell...
As an alternative to the OFDM transceiver, single carrier frequency domain equalization (SC FDE) based transceiver has received much attention because of its simple implementation and low peak to average power ratio (PAPR). In this paper, a minimum mean square error (MMSE) FDE for single carrier block transmission is presented to effectively equalize the channels with high frequency selectivity such...
In this paper, a cellular optical wireless communication system based on orthogonal frequency division multiplexing (OFDM) is simulated inside an aircraft cabin. Asymmetrically clipped optical OFDM (ACO-OFDM) and direct-current-biased optical OFDM (DCO-OFDM) transmission schemes are compared in terms of throughput and cell coverage. Cellular networks with wavelength reuse factors of 1 (full reuse),...
Femtocells that use co-channel allocation with macrocells can considerably increase wireless coverage and system capacity, especially for indoor and cell-edge users. However, the benefit is realized only when cross-tier interference between femtocells and macrocells is well managed. We propose a power allocation algorithm for femtocells in downlink OFDMA systems that effectively reduces cross-tier...
Inter-cell interference (ICI) is responsible for user throughput degradation and especially for users found near cell border which additionally experience serious path-losses. Efficient methods for ICI mitigation are ICI coordination (ICIC) schemes which allocate certain resources among users in different cells. In this paper we propose a decentralized ICIC scheme in order to mitigate the ICI and...
In the uplink, while macrocell mobile stations (mMSs) are synchronized to the macrocell base station (mBS), their signals will arrive asynchronously at the femtocell base station (fBS). For OFDMA, if the timing misalignment among the mMSs is greater than the cyclic prefix duration, intersymbol interference (ISI) and intercarrier interference (ICI) will occur in the received signal at the femtocell...
In this paper, we propose a novel equalization method for OFDM systems without guard interval (GI). The performance of GI-free OFDM system is usually limited by inter-symbol interference (ISI) and inter-carrier interference (ICI). The proposed method is to firstly detect the tail part of transmitted OFDM symbol, then eliminate the ISI and ICI to recover the whole symbol. We find that the tail part...
Interference management is a fundamental issue of a wireless network. In this paper, an interference management scheme based on partial loading is presented. The advantage of partial loading is that it does not require any protocol changes and renders an easy implementation. The partial loading scheme can be combined with other interference management techniques. In this paper, we present various...
Fractional frequency reuse (FFR) is an interference coordination technique well-suited to OFDMA based wireless networks wherein cells are partitioned into spatial regions with different frequency reuse factors. This work focuses on evaluating the two main types of FFR deployments: Strict FFR and Soft Frequency Reuse (SFR). Relevant metrics are discussed, including outage probability, network throughput,...
The optimal detector for CP (Cyclic Prefix)-OFDM (Orthogonal Frequency Division Multiplexing) signal with inherent periodic pilots in low signal to noise ratio environments relies on perfect time synchronization. In this paper, we modify the optimal detector and propose a new suboptimal sensing scheme based on pilots estimation (SSS-BPE). In the proposed SSS-BPE, the likelihood criterion and periodicity...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.