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.
Cognitive radios (CR) are proposed to alleviate the spectrum scarcity problems facing wireless service providers. In US, the FCC is considering spectrum regulation changes by allowing unlicensed operation in the TV broadcast bands provided that no harmful interference is caused. In this paper, we discuss the spectrum sensing aspects of cognitive radios. We particularly focus on the detection method...
In a practical OFDMA system, the terminal receiver often observes very low power in significant number of sub-carriers. The sparse energy distribution is because of the partial-load on sub-carriers, the beam-forming at basestation and the large amount of zero-sub-carriers obligated by communication standards. We present the algorithm and implementation of an energy-scalable OFDMA demodulator exploiting...
OFDM demodulation under fast fading radio channels is very computationally demanding, making the implementation of Software Defined Radio (SDR) solutions problematic. A sub-optimal demodulation algorithm based on QR decomposition of blocks of the channel transfer matrix offers near optimal performance at lower computational cost, but hardware support is still needed. We first propose a COordinate...
Orthogonal-Triangular Decomposition (QRD) is one of the most fundamental signal processing primitives based on complex matrix operations [1]. It forms the core of many advanced multi-dimension and statistical signal processing algorithms that utilize orthogonalization, projection, and rank-revealing principles. Especially in the domain of wireless signal processing, many emerging algorithms in MIMO...
Digital predistortion is a technique used to reduce the signal dynamic range in a multichannel system in order to improve power amplifier (PA) efficiency. These techniques have been developed for orthogonal frequency-division multi-plexing (OFDM) systems, but are not directly applicable to general frequency-division multiplexing (FDM) systems such as those used in broadcast. A modification to the...
Linear amplifier with nonlinear components (LINC) is a power amplifier (PA) linearization technique which offers both high PA efficiency and high linearity of wireless transmitters. But at the output stage, LINC uses a power combiner which results in low system efficiency. To solve this problem, we propose a multilevel out-phasing (MOP) scheme and a corresponding architecture, multilevel LINC (MLINC),...
This paper presents a novel multifunctional multiple-input multiple-output (MIMO) scheme that combines the benefits of the Vertical Bell Labs Layered Space-Time (V-BLAST) scheme, of Space-Time Codes (STC) as well as of beam-forming. Further system performance improvements can be attained by serially concatenated convolutional encoding combined with a unity-rate code (URC) referred to as a precoder...
The sphere decoding algorithm has been used for maximum likelihood detection in MIMO systems, and the K-Best sphere decoding algorithm is proposed for MIMO detections for its fixed complexity and throughput. However, to achieve near-ML performance, the K needs to be sufficiently large, which leads to large computational complexity and power consumption in hardware implementation. In this paper, we...
In multiple-input multiple output (MIMO) systems, maximum likelihood (ML) detection can provide good performance, however, exhaustively searching for the ML solution becomes infeasible as the number of antenna and constellation points increases. Thus ML detection is often realized by K-best sphere decoding algorithm. In this paper, two techniques to reduce the complexity of K-best algorithm while...
Motivated by the need for high throughput sphere decoding for multiple-input-multiple-output (MIMO) communication systems, we propose a parallel depth-first sphere decoding (PDSD) algorithm that provides the advantages of both parallel processing and rapid search space reduction. The PDSD algorithm is designed for efficient implementation on programmable multi-processor platforms. We investigate the...
Adaptive MIMO detection is used when knowledge of the channel is unavailable. We propose an efficient look-ahead LMS algorithm for MIMO systems which has no noticeable performance loss compared to the standard LMS procedure. In particular, the additional logic introduced into the feedback path can be retimed to reduce the critical path delay. We illustrate this by implementing both the retimed look-ahead...
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.