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The multiband orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) system suffered from the narrowband interference (NBI) due to the presence of coexistence communication system, such as worldwide interoperability for microwave access (WiMAX). If we deal with the NBI before the receiver, the performance of MB-OFDM UWB system can be significantly improved. The NBI cancellation algorithms...
From the mathematic expression, we can see that sidelobe power of multi-band orthogonal frequency-division multiplexing (MB-OFDM) signal is a function of the data symbols loaded on the sub-carriers. Through the derivation of the minimum of the function, relationships among data symbols, which help to suppress sidelobes, are obtained. Two types of methods, referred as sub-carrier adding (SA) method...
Orthogonal frequency division multiple access (OFDMA), which is known as one of the most promising physical techniques for advanced wireless communications system, generally has a guard interval (GI) to mitigate the inter-symbol interference (ISI) and inter-carrier interference (ICI) caused by delay paths. However, the intra-cell interference (ISI and ICI) may be severe, when GI becomes insufficient...
We address the problem of frequency reuse schemes in the downlink of the fixed two-hop orthogonal frequency division multiple access (OFDMA) cellular relaying networks. There has been little work on specific frequency reuse schemes for this system in the literatures, although this is the key element for realizing the potential capacity and coverage increase offered by the relay. Therefore, we propose...
Two points need to be considered on power loading policy of cognitive radio (CR) systems. The first is to maximize the channel capacity over the given frequency band, which is detected usable for CR systems. The second is the out-of-band interference suppression of the CR systems. In the paper based on the mathematical expression of the interference power caused by MB-OFDM based CR systems, the relationship...
In orthogonal frequency division multiplexing (OFDM) systems, channel power delay profile can be acquired by an IFFT of pilot-aided channel estimate which is used for fine timing. However, an ambiguous channel impulse response (CIR) estimate is induced by coarse timing errors. In this paper, a simple CIR adjustment algorithm is proposed to correct the CIR order which can hold with large coarse timing...
This paper addresses aspects of routing strategy of a cellular network enhanced with two-hop fixed relay nodes. The routing strategy for each user is important design parameter because the terminal is energy-limited. To enhance the radio resource utility, a utility maximization framework via pricing is adopted for multi-cell distributed power allocation. Under the optimization physical layer transmission...
A mathematical expression of side-band interferences caused by sub-carriers of multi-band (MB)-OFDM UWB based cognitive radio is derived. Based on this expression, the constraint relationship among transmitted symbols, which is satisfied to suppress the interferences, is obtained. Combined with this constraint, the design process of a type of LDPC-like modulation scheme is described. With modulation...
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