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channel-sensing
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Distributed multiuser sequential channel sensing schemes in multichannel cognitive radio networks
, Article IEEE Transactions on Wireless Communications ; Volume 12, Issue 5 , 2013 , Pages 2055-2067 ; 15361276 (ISSN) ; Sheikholeslami, F ; Nasiri Kenari, M ; Sharif University of Technology
2013
Abstract
Effective spectrum sensing strategies enable cognitive radios (CRs) to identify and opportunistically transmit on under-utilized spectral resources. In this paper, sequential channel sensing problems for single and multiple secondary users (SUs) networks are effectively modeled through finite state Markovian processes. More specifically, a model for single user case is introduced and its performance is validated through analytical analysis. Then, in order to address multiple SUs case, this model is extended to include the modified p-persistent access (MPPA) protocol. Since the scheme utilized experiences a high level of collision among the SUs, to mitigate the problem appropriately,...
Resource allocation using fragmented-spectrum synchronous OFDM-CDMA in cognitive radio networks
, Article IWCIT 2014 - Iran Workshop on Communication and Information Theory ; May , 2014 ; ISBN: 9781479948772 ; Poursaeed, O ; Salehi, J. A ; Sharif University of Technology
Abstract
This paper presents a fragmented-spectrum synchronous OFDM-CDMA modulation and utilize it as secondary users modulation in a cognitive radio-based network to provide high data rate by efficiently exploiting available spectrum bands in a target spectral range while simultaneously offering multiple-access capability. In particular, given preexisting communications in the spectrum where the system is operating, a channel sensing and estimation method is used to obtain information of subcarrier availability. Given this information, some three-level codes are provided for emerging new cognitive radio users. Furthermore, analytical results of the system performance in a typical cognitive radio...
Visible light for communication, indoor positioning, and dimmable illumination: a system design based on overlapping pulse position modulation
, Article Optik ; Volume 151 , 2017 , Pages 110-122 ; 00304026 (ISSN) ; Jamali, M. V ; Abdollahramezani, S ; Salehi, J. A ; Dargahi, A ; Sharif University of Technology
Abstract
In this paper, we design a dimming compatible visible light communication (VLC) system with asynchronous and optimum indoor positioning method in a standard office room in combination with asynchronous and optimum indoor positioning method according to illumination standards under channel constraints. We use overlapping pulse position modulation (OPPM) to support dimming control by changing the code weights. The system parameters such as a valid interval for dimming together with an upper bound for bit rate according to the channel delay spread are investigated. Moreover, considering the dispersive VLC channel and using Monte Carlo (MC) simulations, a method is proposed to determine the...