| http://dbpedia.org/ontology/abstract
|
Carrier Interferometry (CI) is a spread sp … Carrier Interferometry (CI) is a spread spectrum scheme designed to be used in an Orthogonal Frequency-Division Multiplexing (OFDM) communication system for multiplexing and multiple access, enabling the system to support multiple users at the same time over the same frequency band. Like MC-CDMA, CI-OFDM spreads each data symbol in the frequency domain. That is, each data symbol is carried over multiple OFDM subcarriers. But unlike MC-CDMA, which uses binary-phase Hadamard codes (code values of 0 or 180 degrees) or binary pseudonoise, CI codes are complex-valued orthogonal codes. In the simplest case, CI code values are coefficients of a discrete Fourier transform (DFT) matrix. Each row or column of the DFT matrix provides an orthogonal CI spreading code which spreads a data symbol. Spreading is achieved by multiplying a vector of data symbols by the DFT matrix to produce a vector of coded data symbols, then each coded data symbol is mapped to an OFDM subcarrier via an input bin of an inverse fast Fourier transform (IFFT). A block of contiguous subcarriers may be selected, or to achieve better frequency diversity, non-contiguous subcarriers distributed over a wide frequency band can be used. A guard interval, such as a cyclic prefix (CP), is added to the baseband CI-OFDM signal before the signal is processed by a radio front-end to convert it to an RF signal, which is then transmitted by an antenna. A significant advantage of CI-OFDM over other OFDM techniques is that CI spreading shapes the time-domain characteristics of the transmitted waveform. Thus, CI-OFDM signals have a much lower peak-to-average-power ratio (PAPR), or crest factor, compared to other types of OFDM. This greatly improves power efficiency and reduces the cost of power amplifiers used in the radio transmitter. A CI-OFDM receiver removes the cyclic prefix from a received CI-OFDM transmission and performs OFDM demodulation with a DFT (e.g., an FFT) typically used in OFDM receivers. The CI-spread symbol values are collected from their respective subcarriers in an inverse-mapping process and may be equalized to compensate for multipath fading or processed for spatial demultiplexing. The CI de-spreader performs an inverse-DFT on the spread symbols to recover the original data symbols. Since CI coding can shape the time-domain characteristics of the transmitted waveform, it can be used to synthesize various waveforms, such as direct-sequence spread spectrum and frequency shift key [4] signals. The advantage is that the receiver can select time-domain or frequency-domain equalization based on how much scattering occurs in the transmission channel. For rich scattering environments, frequency-domain equalization using FFTs requires less computation than conventional time-domain equalization and performs substantially better.ization and performs substantially better.
|
| http://dbpedia.org/ontology/thumbnail
|
http://commons.wikimedia.org/wiki/Special:FilePath/CI_Transceiver_copy.jpg?width=300 +
|
| http://dbpedia.org/ontology/wikiPageID
|
13131203
|
| http://dbpedia.org/ontology/wikiPageLength
|
13129
|
| http://dbpedia.org/ontology/wikiPageRevisionID
|
1049503768
|
| http://dbpedia.org/ontology/wikiPageWikiLink
|
http://dbpedia.org/resource/Category:Channel_access_methods +
, http://dbpedia.org/resource/Subcarrier_multiplexing +
, http://dbpedia.org/resource/Fiber-optic_communication +
, http://dbpedia.org/resource/Hadamard_code +
, http://dbpedia.org/resource/Fading +
, http://dbpedia.org/resource/Multiple_access +
, http://dbpedia.org/resource/Spectral_interferometry +
, http://dbpedia.org/resource/Cyclic_delay_diversity +
, http://dbpedia.org/resource/Pseudonoise +
, http://dbpedia.org/resource/Multi-carrier_code-division_multiple_access +
, http://dbpedia.org/resource/Mode-locking +
, http://dbpedia.org/resource/MIMO +
, http://dbpedia.org/resource/Multiplexing +
, http://dbpedia.org/resource/Phased_array +
, http://dbpedia.org/resource/File:CI_Transceiver_copy.jpg +
, http://dbpedia.org/resource/Frequency-shift_keying +
, http://dbpedia.org/resource/Orthogonality +
, http://dbpedia.org/resource/Equalization_%28communications%29 +
, http://dbpedia.org/resource/Orthogonal_frequency-division_multiplexing +
, http://dbpedia.org/resource/Distributed_antenna_system +
, http://dbpedia.org/resource/Fast_Fourier_transform +
, http://dbpedia.org/resource/Direct-sequence_spread_spectrum +
, http://dbpedia.org/resource/Discrete_Fourier_transform_%28general%29 +
, http://dbpedia.org/resource/Software-defined_radio +
, http://dbpedia.org/resource/Spread_spectrum +
, http://dbpedia.org/resource/Crest_factor +
, http://dbpedia.org/resource/Spatial_multiplexing +
|
| http://dbpedia.org/property/wikiPageUsesTemplate
|
http://dbpedia.org/resource/Template:Reflist +
, http://dbpedia.org/resource/Template:Overly_detailed +
, http://dbpedia.org/resource/Template:Context +
, http://dbpedia.org/resource/Template:More_footnotes +
, http://dbpedia.org/resource/Template:Multiple_issues +
|
| http://purl.org/dc/terms/subject
|
http://dbpedia.org/resource/Category:Channel_access_methods +
|
| http://purl.org/linguistics/gold/hypernym
|
http://dbpedia.org/resource/Scheme +
|
| http://www.w3.org/ns/prov#wasDerivedFrom
|
http://en.wikipedia.org/wiki/Carrier_interferometry?oldid=1049503768&ns=0 +
|
| http://xmlns.com/foaf/0.1/depiction
|
http://commons.wikimedia.org/wiki/Special:FilePath/CI_Transceiver_copy.jpg +
|
| http://xmlns.com/foaf/0.1/isPrimaryTopicOf
|
http://en.wikipedia.org/wiki/Carrier_interferometry +
|
| owl:sameAs |
http://dbpedia.org/resource/Carrier_interferometry +
, http://www.wikidata.org/entity/Q5046371 +
, https://global.dbpedia.org/id/4g8Fx +
, http://yago-knowledge.org/resource/Carrier_interferometry +
, http://rdf.freebase.com/ns/m.02z7xyg +
|
| rdf:type |
http://dbpedia.org/ontology/Organisation +
|
| rdfs:comment |
Carrier Interferometry (CI) is a spread sp … Carrier Interferometry (CI) is a spread spectrum scheme designed to be used in an Orthogonal Frequency-Division Multiplexing (OFDM) communication system for multiplexing and multiple access, enabling the system to support multiple users at the same time over the same frequency band.he same time over the same frequency band.
|
| rdfs:label |
Carrier interferometry
|
