68 research outputs found
SPECTRUM SENSING USING CYCLIC PREFIX IN COGNITIVE RADIO WIRELESS SYSTEM
The rapid growth of wireless communications has made the problem of spectrum utilization ever more critical. The increasing diversity (voice, short message, Web & multimedia) and demand of high quality-of-service (QoS) applications have resulted in overcrowding of the allocated (officially sanctioned) spectrum bands, leading to significantly reduced levels of user satisfaction. The concepts of GLRT algorithm and substantial improvement over the U-GLRT algorithm are explained. This paper presents a model which uses efficient CP method for CR in Wireless Systems. Primary signal has been detected in the OFDM transmission with both the CPCC and MP–based C-GLRT algorithms greatly outperform energy detection in multi path environment has been implemented using software design. The signal model in our analysis is to efficiently exploit the correlation among the transmitted signals due to the presence of CP. Proposed method of cognitive radio takes two steps of implementation .first named as MP based is to detect the noise and de-noise the signal and the second is cp based in which the signals are identified based on the cyclic prefix
Cooperative multiterminal radar and communication: a new paradigm for 6G mobile networks
The impending spectrum congestion imposed by the emergence of new
bandwidth-thirsty applications may be mitigated by the integration of radar and
classic communications functionalities in a common system. Furthermore, the
merger of a sensing component into wireless communication networks has raised
interest in recent years and it may become a compelling design objective for
6G. This article presents the evolution of the hitherto separate radar and
communication systems towards their amalgam known as a joint radar and
communication (RADCOM) system. Explicitly, we propose to integrate a radio
sensing component into 6G. We consider an ultra-dense network (UDN) scenario
relying on an active multistatic radar configuration and on cooperation between
the access points across the entire coverage area. The technological trends
required to reach a feasible integration, the applications anticipated and the
open research challenges are identified, with an emphasis on high-accuracy
network synchronization. The successful integration of these technologies would
facilitate centimeter-level resolution, hence supporting compelling
high-resolution applications for next-generation networks, such as robotic cars
and industrial assembly lines.publishe
Opportunistic Unsynchronized Cognitive Radio Networks
The challenge of opportunistic networks is to maximize the usage of the spectrum by offering quick and easy access to independent systems and their users. A physical layer able to operate efficiently in an unsynchronized environment is needed and it is shown that the filter bank multicarrier (FBMC) technique can meet the objectives in terms of performance and flexibility. Then, a protocol must be developed to ensure global convergence and an overall transmission capacity close to the optimal possible value at a given place and a given time. An approach called “good neighbour” is presented, which consists of building the capacity requested by the users through a threshold regulated local search and with minimum changes in frequency band allocation to reduce interference non-stationarity to other systems. Finally, potential applications of opportunistic networks are reviewed and the conditions for proliferation of this kind of network are discussed
Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals
Abstract-We consider spectrum sensing of OFDM signals in an AWGN channel. For the case of completely known noise and signal powers, we set up a vector-matrix model for an OFDM signal with a cyclic prefix and derive the optimal NeymanPearson detector from first principles. The optimal detector exploits the inherent correlation of the OFDM signal incurred by the repetition of data in the cyclic prefix, using knowledge of the length of the cyclic prefix and the length of the OFDM symbol. We compare the optimal detector to the energy detector numerically. We show that the energy detector is near-optimal (within 1 dB SNR) when the noise variance is known. Thus, when the noise power is known, no substantial gain can be achieved by using any other detector than the energy detector. For the case of completely unknown noise and signal powers, we derive a generalized likelihood ratio test (GLRT) based on empirical second-order statistics of the received data. The proposed GLRT detector exploits the non-stationary correlation structure of the OFDM signal and does not require any knowledge of the noise power or the signal power. The GLRT detector is compared to state-of-the-art OFDM signal detectors, and shown to improve the detection performance with 5 dB SNR in relevant cases
Data Transmission with Reduced Delay for Distributed Acoustic Sensors
This paper proposes a channel access control scheme fit to dense acoustic
sensor nodes in a sensor network. In the considered scenario, multiple acoustic
sensor nodes within communication range of a cluster head are grouped into
clusters. Acoustic sensor nodes in a cluster detect acoustic signals and
convert them into electric signals (packets). Detection by acoustic sensors can
be executed periodically or randomly and random detection by acoustic sensors
is event driven. As a result, each acoustic sensor generates their packets
(50bytes each) periodically or randomly over short time intervals
(400ms~4seconds) and transmits directly to a cluster head (coordinator node).
Our approach proposes to use a slotted carrier sense multiple access. All
acoustic sensor nodes in a cluster are allocated to time slots and the number
of allocated sensor nodes to each time slot is uniform. All sensor nodes
allocated to a time slot listen for packet transmission from the beginning of
the time slot for a duration proportional to their priority. The first node
that detect the channel to be free for its whole window is allowed to transmit.
The order of packet transmissions with the acoustic sensor nodes in the time
slot is autonomously adjusted according to the history of packet transmissions
in the time slot. In simulations, performances of the proposed scheme are
demonstrated by the comparisons with other low rate wireless channel access
schemes.Comment: Accepted to IJDSN, final preprinted versio
PLC for the smart grid: state-of-the-art and challenges
This paper aims to review systems and applications for power line communications (PLC) in the context of the smart grid. We discuss the main applications and summarise state-of-the-art PLC systems and standards. We report efforts and challenges in channel and noise modelling, as well as in state-of-the-art transmission technology approaches
Performance of a filterBank multiCarrier (FBMC) physical layer in the WiMAX context
This paper describes some of the outcome of the FP7 project
PHYDYAS, whose main objective was to propose a new physical layer that will
enable introduction of cognitive radios and dynamic access spectrum
management. During the project both a software simulator and a demonstrator
have been developed. A description of the demonstrator and some simulation
results that show the differences in spectral efficiency and the sensititvity to
synchronisation errors between OFDM and FBMC are given.
The simulator, which is written in Matlab, was used to evaluate the
performance of both OFDM and FBMC in a WiMAX context, i.e. the frame
format is kept as close as possible to WiMAX. From the simulation results it has
been possible to analyze the performance differences between the two systems.
In addition to that the simulator was used as a reference in the validation of the
demonstrator. The transmitter in the demonstrator is implemented in hardware
and operates in real time. The channel emulation and up-conversion to RF is
done using commercially available instruments from Agilent which have been
modified to fit to the task. In the demonstrator receiver the hardware front-end
converts the signal to baseband and digitizes it. The OFDM/FBMC signal
processing is done in near real time on a general purpose computer connected
to the front- end hardware.Postprint (published version
Timing and Carrier Synchronization in Wireless Communication Systems: A Survey and Classification of Research in the Last 5 Years
Timing and carrier synchronization is a fundamental requirement for any wireless communication system to work properly. Timing synchronization is the process by which a receiver node determines the correct instants of time at which to sample the incoming signal. Carrier synchronization is the process by which a receiver adapts the frequency and phase of its local carrier oscillator with those of the received signal. In this paper, we survey the literature over the last 5 years (2010–2014) and present a comprehensive literature review and classification of the recent research progress in achieving timing and carrier synchronization in single-input single-output (SISO), multiple-input multiple-output (MIMO), cooperative relaying, and multiuser/multicell interference networks. Considering both single-carrier and multi-carrier communication systems, we survey and categorize the timing and carrier synchronization techniques proposed for the different communication systems focusing on the system model assumptions for synchronization, the synchronization challenges, and the state-of-the-art synchronization solutions and their limitations. Finally, we envision some future research directions
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