Wi-Fi (IPA: /ˈwaɪfaɪ/) is a trademark of the Wi-Fi Alliance, founded in 1999 as Wireless Internet Compatibility Alliance (WICA), comprising more than 300 companies, whose products are certified by the Wi-Fi Alliance, based on the IEEE 802.11 standards (also called Wireless LAN (WLAN) and Wi-Fi). This certification warrants interoperability between different wireless devices.
The alliance was founded because many products did not correctly implement IEEE 802.11 and some included proprietary extensions. This led to incompatibilities between products from different manufacturers.
The Wi-Fi Alliance tests the wireless components to their own terms of reference. Products that pass become Wi-Fi certified and may carry the Wi-Fi logo. Only products of Wi-Fi Members are tested, because they pay membership and per-item fees. Absence of the Wi-Fi logo does not necessarily mean non-compliance with the standard.
In France, Poland, the United States, and some other countries, the term Wi-Fi often is used by the public as a synonym for wireless Internet (WLAN); but not every wireless Internet product has a Wi-Fi certification, which may be because of certification costs that must be paid for each certified device type.
Wi-Fi certification is provided for technology used in home networks, mobile phones, video games, and other devices that require wireless networking. It covers IEEE 802.11 standards, including 802.11a, 802.11b, 802.11g, and 802.11n.
Wi-Fi is supported by most personal computer operating systems, many game consoles, laptops, smartphones, printers, and other peripherals.
19 Maret 2009
WiMAX
WiMAX, meaning Worldwide Inter-operability for Microwave Access, is a telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point-to-multipoint links to portable and fully mobile internet access. The technology provides up to 72 Mbit/s symmetric broadband speed without the need for cables. The technology is based on the IEEE 802.16 standard (also called Broadband Wireless Access). The name "WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to promote conformity and interoperability of the standard. The forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".
Definitions
The terms "fixed WiMAX", "mobile WiMAX", "802.16d" and "802.16e" are frequently used incorrectly. Correct definitions are the following:
* 802.16-2004 is often called 802.16d, since that was the working party that developed the standard. It is also frequently referred to as "fixed WiMAX" since it has no support for mobility.
* 802.16e-2005 is an amendment to 802.16-2004 and is often referred to in shortened form as 802.16e. It introduced support for mobility, amongst other things and is therefore also known as "mobile WiMAX".
Definitions
The terms "fixed WiMAX", "mobile WiMAX", "802.16d" and "802.16e" are frequently used incorrectly. Correct definitions are the following:
* 802.16-2004 is often called 802.16d, since that was the working party that developed the standard. It is also frequently referred to as "fixed WiMAX" since it has no support for mobility.
* 802.16e-2005 is an amendment to 802.16-2004 and is often referred to in shortened form as 802.16e. It introduced support for mobility, amongst other things and is therefore also known as "mobile WiMAX".
18 Maret 2009
Signal
Some definitions
Definitions specific to subfields are common. For example, in information theory, a signal is a codified message, that is, the sequence of states in a communication channel that encodes a message.
In the context of signal processing, arbitrary binary data streams are not considered as signals, but only analog and digital signals that are representations of analog physical quantities.
In a communication system, a transmitter encodes a message into a signal, which is carried to a receiver by the communications channel. For example, the words "Mary had a little lamb" might be the message spoken into a telephone. The telephone transmitter converts the sounds into an electrical voltage signal. The signal is transmitted to the receiving telephone by wires; and at the receiver it is reconverted into sounds.
In telephone networks, signalling, for example common channel signalling, refers to phone number and other digital control information rather than the actual voice signal.
Signals can be categorized in various ways. The most common distinction is between discrete and continuous spaces that the functions are defined over, for example discrete and continuous time domains. Discrete-time signals are often referred to as time series in other fields. Continuous-time signals are often referred to as continuous signals even when the signal functions are not continuous; an example is a square-wave signal.
A second important distinction is between discrete-valued and continuous-valued. Digital signals are sometimes defined as discrete-valued sequencies of quantified values, that may or may not be derived from an underlying continuous-valued physical process. In other contexts, digital signals are defined as the continuous-time waveform signals in a digital system, representing a bit-stream. In the first case, a signal that is generated by means of a digital modulation method is considered as converted to an analog signal, while it is considered as a digital signal in the second case.
Definitions specific to subfields are common. For example, in information theory, a signal is a codified message, that is, the sequence of states in a communication channel that encodes a message.
In the context of signal processing, arbitrary binary data streams are not considered as signals, but only analog and digital signals that are representations of analog physical quantities.
In a communication system, a transmitter encodes a message into a signal, which is carried to a receiver by the communications channel. For example, the words "Mary had a little lamb" might be the message spoken into a telephone. The telephone transmitter converts the sounds into an electrical voltage signal. The signal is transmitted to the receiving telephone by wires; and at the receiver it is reconverted into sounds.
In telephone networks, signalling, for example common channel signalling, refers to phone number and other digital control information rather than the actual voice signal.
Signals can be categorized in various ways. The most common distinction is between discrete and continuous spaces that the functions are defined over, for example discrete and continuous time domains. Discrete-time signals are often referred to as time series in other fields. Continuous-time signals are often referred to as continuous signals even when the signal functions are not continuous; an example is a square-wave signal.
A second important distinction is between discrete-valued and continuous-valued. Digital signals are sometimes defined as discrete-valued sequencies of quantified values, that may or may not be derived from an underlying continuous-valued physical process. In other contexts, digital signals are defined as the continuous-time waveform signals in a digital system, representing a bit-stream. In the first case, a signal that is generated by means of a digital modulation method is considered as converted to an analog signal, while it is considered as a digital signal in the second case.
12 Maret 2009
10 Reasons to Smile
1. Smiling Makes Us Attractive
2. Smiling Changes Our Mood
3. Smiling Is Contagious
4. Smiling Relieves Stress
5. Smiling Boosts Your Immune System
6. Smiling Lowers Your Blood Pressure
7. Smiling Releases Endorphins, Natural Pain Killers and Serotonin
8. Smiling Lifts the Face and Makes You Look Younger
9. Smiling Makes You Seem Successful
10. Smiling Helps You Stay Positive
http://longevity.about.com/od/lifelongbeauty/tp/smiling.htm
2. Smiling Changes Our Mood
3. Smiling Is Contagious
4. Smiling Relieves Stress
5. Smiling Boosts Your Immune System
6. Smiling Lowers Your Blood Pressure
7. Smiling Releases Endorphins, Natural Pain Killers and Serotonin
8. Smiling Lifts the Face and Makes You Look Younger
9. Smiling Makes You Seem Successful
10. Smiling Helps You Stay Positive
http://longevity.about.com/od/lifelongbeauty/tp/smiling.htm
Wise Meaning
(v.) Dictated or guided by wisdom; containing or exhibiting wisdom; well adapted to produce good effects; judicious; discreet; as, a wise saying; a wise scheme or plan; wise conduct or management; a wise determination.
(v.) Having knowledge; knowing; enlightened; of extensive information; erudite; learned.
(v.) Versed in art or science; skillful; dexterous; specifically, skilled in divination.
(v.) Hence, prudent; calculating; shrewd; wary; subtle; crafty.
(v.) Hence, especially, making due use of knowledge; discerning and judging soundly concerning what is true or false, proper or improper; choosing the best ends and the best means for accomplishing them; sagacious.
(v.) Way of being or acting; manner; mode; fashion.
(v.) Having knowledge; knowing; enlightened; of extensive information; erudite; learned.
(v.) Versed in art or science; skillful; dexterous; specifically, skilled in divination.
(v.) Hence, prudent; calculating; shrewd; wary; subtle; crafty.
(v.) Hence, especially, making due use of knowledge; discerning and judging soundly concerning what is true or false, proper or improper; choosing the best ends and the best means for accomplishing them; sagacious.
(v.) Way of being or acting; manner; mode; fashion.
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