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Beamforming is a signal processing technique in which multiple antennas are used to weight the signals so that they can be added constructively in the desired direction, and destructively in the interference direction. In this paper, adaptive beamforming based on subband decomposition structure is investigated in smart antenna arrays and the performance of the proposed adaptive beamforming scheme...
First, the paper analyzes the basic principle of the uplink MU-MIMO and gives the user matching conditions and application suggestion. Then, an estimation method of uplink MU-MIMO gain is presented based on the tests analysis. At last, the performance of uplink MU-MIMO in the current user condition is also given.
We produced two Raman-laser beams with a frequency offset of 6.834GHz by injection-locking of a master diode-laser to a slave diode-laser. The master laser was phase-modulated at 6.834 GHz with an Electro-Optic Modulator and then injected into the slave laser that was oscillating around one of the side-bands. The relative linewidth of the two lasers was less than 1 Hz. Utilizing these laser beams,...
In this paper, we consider a collaborative routing strategy in cognitive radio network. We define a system model and a pricing scheme as a means to stimulate cooperation in users. Assuming that cognitive radio base station sets prices for the network profit maximization according to the interferences caused by secondary users to primary users, we propose an iterative price adaptation algorithm to...
In wireless networks, mutual interference prevents wireless devices from correctly receiving packages from others and becomes one of the challenges in the design of protocols for wireless networks. Spatial-reuse time division multiple access (STDMA) has been used to cope with this problem. In this scheme, links are assigned to several time slots and in each slot all the links can transmit simultaneously...
Improving frequency interference is the primary purpose of network planning and optimization in TD_SCDMA. In this paper, a new algorithm to improve frequency interference, named Ant Colony Algorithm (ACA), was put forward to; in addition existent methods were enriched. We described ACA principle, and then a new specific scenario was investigated and introduced into the frequency planning. Afterwards,...
This paper presents another look at the problem of frequency spectrum sensing based on energy detection in OFDM. OFDM is one of the most important techniques to improve the capacity of the channel in 3G and 4G. In order to detect the presence of the spectrum holes and utilize them efficiently without causing interference to primary users in OFDM, spatial spectrum estimation is considered as the key...
In this paper, we consider that cooperative frequency spectrum sensing based on the spatial spectral estimation in cognitive radio sensor networks. We propose an algorithm that estimates the interference temperature of this model using a generalization of the DOA (direction of arrival) algorithm. From this, we find the interference temperature and show that it does become smaller. We compare our method...
Majority of evaluation methods on interference temperature algorithms are based on the assumption that either the interference signals or the user's signals are no directions. This is a mathematical constraint that is not satisfied in many applications. In fact, without consideration the signal directions increase estimation interference temperature, that is, reduce the frequency utilizing chance...
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