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Distributed sparse random projections

A second method modifies the randomized gossiping approach by limiting the number of communications each node must perform, in order to reduce overall power consumption  [link] . Each data node takes M projections of its data, passing along information to a small set of L neighbors, and summing the observations; the resulting CS measurements are sparse, since N - L of each row's entries will be zero. Nonetheless, these projections can still be used as CS measurements with quality similar to that of full random projections. Since the CS measurement matrix formed by the data nodes is sparse, a relatively small amount of communication is performed by each encoding node and the overall power required for transmission is reduced.

Centralized algorithms

Decentralized algorithms are used when the sensed data must be routed to a single location; this architecture is common in sensor networks were low power, simple nodes perform sensing and a powerful central location performs data processing.

Compressive wireless sensing

Compressive wireless sensing (CWS) emphasizes the use of synchronous communication to reduce the transmission power of each sensor  [link] . In CWS, each sensor calculates a noisy projection of their data sample. Each sensor then transmits the calculated value by analog modulation and transmission of a communication waveform. The projections are aggregated at the central location by the receiving antenna, with further noise being added. In this way, the fusion center receives the CS measurements, from which it can perform reconstruction using knowledge of the random projections.

A drawback of this method is the required accurate synchronization. Although CWS is constraining the power of each node, it is also relying on constructive interference to increase the power received by the data center. The nodes themselves must be accurately synchronized to know when to transmit their data. In addition, CWS assumes that the nodes are all at approximately equal distances from the fusion center, an assumption that is acceptable only when the receiver is far away from the sensor network. Mobile nodes could also increase the complexity of the transmission protocols. Interference or path issues also would have a large effect on CWS, limiting its applicability.

If these limitations are addressed for a suitable application, CWS does offer great power benefits when very little is known about the data beyond sparsity in a fixed basis. Distortion will be proportional to M - 2 α / ( 2 α + 1 ) , where α is some positive constant based on the network structure. With much more a priori information about the sensed data, other methods will achieve distortions proportional to M - 2 α .

Distributed compressive sensing

Distributed Compressive Sensing (DCS) provides several models for combining neighboring sparse signals, relying on the fact that such sparse signals may be similar to each other, a concept that is termed joint sparsity  [link] . In an example model, each signal has a common component and a local innovation, with the commonality only needing to be encoded once while each innovation can be encoded at a lower measurement rate. Three different joint sparsity models (JSMs) have been developed:

  1. Both common signal and innovations are sparse;
  2. Sparse innovations with shared sparsity structure;
  3. Sparse innovations and dense common signal.

Although JSM 1 would seem preferable due to the relatively limited amount of data, only JSM 2 is computationally feasible for large sensor networks; it has been used in many applications  [link] . JSMs 1 and 3 can be solved using a linear program, which has cubic complexity on the number of sensors in the network.

DCS, however, does not address the communication or networking necessary to transmit the measurements to a central location; it relies on standard communication and networking techniques for measurement transmission, which can be tailored to the specific network topology.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, An introduction to compressive sensing. OpenStax CNX. Apr 02, 2011 Download for free at http://legacy.cnx.org/content/col11133/1.5
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