Se conoce como banda ancha a la transmisión de datos en el cual se envían simultáneamente varias piezas de información, con el objeto de incrementar la velocidad de transmisión efectiva. En ingeniería de redes este término se utiliza también para los métodos en donde dos o más señales comparten un medio de transmisión.
Algunas de las variantes de los servicios de línea de abonado digital (del inglés Digital Subscriber Line, DSL) son de banda ancha en el sentido de que la información se envía sobre un canal y la voz por otro canal, pero compartiendo el mismo par de cables. Los modems analógicos que operan con velocidades mayores a 600 bps también son técnicamente banda ancha, pues obtienen velocidades de transmisión efectiva mayores usando muchos canales en donde la velocidad de cada canal se limita a 600 baudios. Por ejemplo, un modem de 2400 bps usa cuatro canales de 600 baudios. Este método de transmisión contrasta con la transmisión en banda base, en donde un tipo de señal usa todo el ancho de banda del medio de transmisión, como por ejemplo Ethernet 100BASE-T.
Es una tecnología de modems que permite el trafico de datos se realice a una velocidad extraordinaria a través de una línea telefónica convencional. Además se puede mantener una conversación por teléfono mientras se está navegando por Internet
Las comunicaciones pueden utilizar distintos canales físicos simultáneamente; es decir multiplexar para tener acceso múltiple. Tales canales pueden distinguirse uno de otro por estar separados en: tiempo (multiplexación por división de tiempo o TDM), frecuencia de portadora (multiplexación por división de frecuencia, FDM o multiplexación por división de longitud de onda, WDM), o por código(multiplexación por división de código, CDMA). Cada canal que toma parte en la multiplexación es por definición de banda estrecha (pues no está utilizando todo el ancho de banda del medio)
Aunque varias formas de transmisión de baja velocidad como los modems analógicos de más de 600 bps son de banda ancha, esta denominación se ha asociado más estrechamente con formas transmisión de alta velocidad tales como DSL y T/E-carrier. Por ello la denominación "banda ancha" también se utiliza para indicar velocidades relativamente altas, mientras que la denominación "banda estrecha" se utiliza para indicar velocidades relativamente bajas. Hoy en día es bastante común oír que a un método de banda ancha como un modem de 9600 bits se lo tilde de "banda estrecha", mientras que a un método de banda base como Ethernet 10BASE-T se lo denomine como de "banda ancha".
La recomendación I.113 de ITU-T, el sector de estandarización de la Unión Internacional de Telecomunicaciones, encuadra dentro de bancha ancha a las técnicas capaces de transmitir más rápido que un acceso primario de RDSI, sea éste a 2 ó 6 Mbps. Sin embargo las velocidades de 1512 kbps o incluso 1024 kbps se comercializan como de "banda ancha", convención que siguen tanto los proveedores de servicios de internet como los gobiernos en sus políticas.
NO TENIA IDEA DE QUE ESTABA CASADO
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Un australiano descubrió que su matrimonio era inválido porque ya se había casado durante una borrachera.
Un australiano de 67 años descubrió que su actual matromonio era ilegal ya que se había casado treinta años antes con otra mujer. Sólo que él no lo recuerda. "Me viene a la memoria una linda rubia que conocí en Arizona pero no tengo ninguna imagen de haberme casado con ella, o una ceremonia, o siquiera haber hablado de casarnos".El hombre explicó que el cielo se le vino abajo cuando las autoridades de Arizona le mostraron la libreta matrimonial. Intentaban mudarse a Hawaii y las autoridades de migración le dieron la noticia. Su actual esposa -que pasó a ser su novia- se mostró muy comprensiva. La jueza Sally Brown, sin embargo, anuló el matrimonio y la pareja ahora está en condiciones de casarse en serio.
Querian enseñar a su perro manejar
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Una pareja china recibió una multa cuando intentaba enseñarle a manejar a su perro caniche
La policía vial de Liunan, China, divisó un automóvil que se desplazaba demasiado despacio por la autopista local. Se colocaron con la patrulla detrás del auto y cuando hacían señas para que se detuviera se llevaron una sorpresa: el conductor era un perro caniche con sus dos patas delanteras sobre el volante.Las patas de atrás del animal se apoyaban en la falda de la señora que se ocupaba de maniobrar los pedales. La mujer explicó que ella y su novio tuvieron la idea de enseñarle a conducir al perro. Dijeron que era la oportunidad ideal para que "Niu Niu" aprendiera porque la autopista estaba vacía.No tanto como el coco de esta gente.
BROADBAND
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They may not agree on net neutrality or the Fairness Doctrine, but almost half a dozen advocacy groups from liberal to libertarian do concur on one issue: they hate Federal Communications Commission Chair Kevin Martin's proposal for a national broadband service with the porn filtered out.
"Unconstitutional and unwise," their Friday filing calls the plan, which they charge amounts to a "government mandated 'blacklist' of websites." The filtering component would limit the system "so dramatically that the usefulness of the service would be radically reduced." Plus, if the agency actually approved the scheme, it would face a tsunami of lawsuits.
Related StoriesFCC moves ahead with plan for smut-free wireless broadband
GOP pols oppose smut-free wireless network proposal
FCC sends mixed messages on free broadband wireless service
So contend the Center for Democracy and Technology (CDT), People for the American Way, Adam Thierer of the Progress and Freedom Foundation, the Public Interest Spectrum Coalition, the American Booksellers Association, the Von Coalition, the Electronic Frontier Foundation, and fifteen other groups. It was inevitable that this shoe would drop on a scheme that is already taking heavy incoming fire from the wireless industry for its alleged technical shortcomings.
Free smutless broadband
In late June the FCC launched a proceeding on an idea long advocated by M2Z Networks: a free, national wireless broadband service. The proposed system would work its magic way up there in the Advanced Wireless Services area number three region of the spectrum (AWS-3, 2155-2180 MHz). Bidders would compete for the zone in a public auction, then commit to rolling the plan out to 95 percent of the United States over a ten year period at 768Kbps, the FCC's new minimum rate for "high speed" broadband. The provider would make money on the service via ad revenue, paying five percent of its gross annual income to Uncle Sam.
The CDT et al filing doesn't have any issues with this. It's the filtering part that's the big problem, the 22 groups say. The FCC's proposal makes it pretty clear how it is supposed to work. The auction winner must provide a feature that "filters or blocks images and text that constitute obscenity or pornography and, in context, as measured by contemporary community standards and existing law, any images or text that otherwise would be harmful to teens and adolescents." The outline defines teens and adolescents as "children 5 through 17 years of age."
The CDT filing warns that not only does this plan violate the First Amendment, it repeatedly crosses the Supreme Court's interpretation of the First Amendment in its important indecency rulings.
A new standard for censorship
The FCC's filtering plan "would censor content far beyond anything ever upheld by any court for any medium," warns the CDT group. Vague and over broad, the proposal's provision to block out anything that might be disturbing to five year olds could deny access to a wide variety of content, including conventional news reports. "This prohibition would plainly infringe on the rights of adults to access broad categories of lawful speech," they write.
The idea also runs afoul of several key Supreme Court cases, CDT warns, most notably the crucial Reno vs. ACLU ruling of 1997. That decision bumped off a big chunk of the Communications Decency Act's prohibition against the "knowing" transmission of indecent images over the Internet to minors. The high court insisted that in regulating indecent speech, the government must mandate "the least restrictive" way to protect children from smut: client-side filtering software being the best candidate, then and now.
Don't count on Pacifica And so the FCC can't rely on that old standby, Pacifica vs. FCC (1978), to justify this proposal, argues CDT, because unlike terrestrial radio, undesired content on the Internet can be filtered out at the user end. Nor could an "opt-in" filtering system get around the fact that the FCC's proposal effectively creates a filtering blacklist. "The FCC cannot constitutionally serve as a censorship board that selects which Internet websites should be available to all Americans," CDT says. In addition, the Commission's plan violates an often forgotten part of Pacifica, its prohibition on government censorship in advance.
"Given the insurmountable constitutional problems raised by the filtering mandate," the CDT group observes, it would serve as target practice for First Amendment lawyers if actually approved by the FCC. Their filing concludes by suggesting that the FCC go back to square one on the idea and try it again, sans filtering.
This proposal isn't just getting piledriven by civil liberties groups. It's also drawing fire from just about every big wireless company around, with T-Mobile leading the pack. Its latest statement—over 100 pages long—charges that the AWS-3 plan will mess with mobile receivers running on the nearby AWS-1 band. "For consumers, the interference will be extensive, widespread, and unpredictable," T-Mobile warns, "significantly degrading their service."
The company says it wants the FCC to extend this proceeding and submit its proposed AWS-3 specs to independent testing. But it's obvious that the commercial wireless community hates the basic idea on principle. "The Commission's free service proposal would be of little or no help to those it is designed to support, given that the 'free' aspect of the service would be vastly inferior to any commercial service on the market and will not even be available for years," T-Mobile concludes.
FCC Chair Martin has been enjoying a good run of late, with the Sirius/XM merger in cement and a net neutrality order on Comcast due this Friday. But his "family friendly" broadband plan could definitely use a friend or two about now.
"Unconstitutional and unwise," their Friday filing calls the plan, which they charge amounts to a "government mandated 'blacklist' of websites." The filtering component would limit the system "so dramatically that the usefulness of the service would be radically reduced." Plus, if the agency actually approved the scheme, it would face a tsunami of lawsuits.
Related StoriesFCC moves ahead with plan for smut-free wireless broadband
GOP pols oppose smut-free wireless network proposal
FCC sends mixed messages on free broadband wireless service
So contend the Center for Democracy and Technology (CDT), People for the American Way, Adam Thierer of the Progress and Freedom Foundation, the Public Interest Spectrum Coalition, the American Booksellers Association, the Von Coalition, the Electronic Frontier Foundation, and fifteen other groups. It was inevitable that this shoe would drop on a scheme that is already taking heavy incoming fire from the wireless industry for its alleged technical shortcomings.
Free smutless broadband
In late June the FCC launched a proceeding on an idea long advocated by M2Z Networks: a free, national wireless broadband service. The proposed system would work its magic way up there in the Advanced Wireless Services area number three region of the spectrum (AWS-3, 2155-2180 MHz). Bidders would compete for the zone in a public auction, then commit to rolling the plan out to 95 percent of the United States over a ten year period at 768Kbps, the FCC's new minimum rate for "high speed" broadband. The provider would make money on the service via ad revenue, paying five percent of its gross annual income to Uncle Sam.
The CDT et al filing doesn't have any issues with this. It's the filtering part that's the big problem, the 22 groups say. The FCC's proposal makes it pretty clear how it is supposed to work. The auction winner must provide a feature that "filters or blocks images and text that constitute obscenity or pornography and, in context, as measured by contemporary community standards and existing law, any images or text that otherwise would be harmful to teens and adolescents." The outline defines teens and adolescents as "children 5 through 17 years of age."
The CDT filing warns that not only does this plan violate the First Amendment, it repeatedly crosses the Supreme Court's interpretation of the First Amendment in its important indecency rulings.
A new standard for censorship
The FCC's filtering plan "would censor content far beyond anything ever upheld by any court for any medium," warns the CDT group. Vague and over broad, the proposal's provision to block out anything that might be disturbing to five year olds could deny access to a wide variety of content, including conventional news reports. "This prohibition would plainly infringe on the rights of adults to access broad categories of lawful speech," they write.
The idea also runs afoul of several key Supreme Court cases, CDT warns, most notably the crucial Reno vs. ACLU ruling of 1997. That decision bumped off a big chunk of the Communications Decency Act's prohibition against the "knowing" transmission of indecent images over the Internet to minors. The high court insisted that in regulating indecent speech, the government must mandate "the least restrictive" way to protect children from smut: client-side filtering software being the best candidate, then and now.
Don't count on Pacifica And so the FCC can't rely on that old standby, Pacifica vs. FCC (1978), to justify this proposal, argues CDT, because unlike terrestrial radio, undesired content on the Internet can be filtered out at the user end. Nor could an "opt-in" filtering system get around the fact that the FCC's proposal effectively creates a filtering blacklist. "The FCC cannot constitutionally serve as a censorship board that selects which Internet websites should be available to all Americans," CDT says. In addition, the Commission's plan violates an often forgotten part of Pacifica, its prohibition on government censorship in advance.
"Given the insurmountable constitutional problems raised by the filtering mandate," the CDT group observes, it would serve as target practice for First Amendment lawyers if actually approved by the FCC. Their filing concludes by suggesting that the FCC go back to square one on the idea and try it again, sans filtering.
This proposal isn't just getting piledriven by civil liberties groups. It's also drawing fire from just about every big wireless company around, with T-Mobile leading the pack. Its latest statement—over 100 pages long—charges that the AWS-3 plan will mess with mobile receivers running on the nearby AWS-1 band. "For consumers, the interference will be extensive, widespread, and unpredictable," T-Mobile warns, "significantly degrading their service."
The company says it wants the FCC to extend this proceeding and submit its proposed AWS-3 specs to independent testing. But it's obvious that the commercial wireless community hates the basic idea on principle. "The Commission's free service proposal would be of little or no help to those it is designed to support, given that the 'free' aspect of the service would be vastly inferior to any commercial service on the market and will not even be available for years," T-Mobile concludes.
FCC Chair Martin has been enjoying a good run of late, with the Sirius/XM merger in cement and a net neutrality order on Comcast due this Friday. But his "family friendly" broadband plan could definitely use a friend or two about now.
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