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Hybrid Coordination Function
IEEE 802.11e-2005 or 802.11e is an approved amendment to the IEEE 802.11 standard that defines a set of quality of service (QoS) enhancements for wireless LAN applications through modifications to the media access control (MAC) layer.M. Benveniste, "WLAN QoS", Chapter 3 in ''Emerging Technologies in Wireless LANs: Theory, Design, and Deployment'', (B. Bing, ed.), Cambridge University Press, 2008, . The standard is considered of critical importance for delay-sensitive applications, such as Voice over Wireless LAN and streaming multimedia. The amendment has been incorporated into the published IEEE 802.11-2007 standard. Original 802.11 MAC Distributed Coordination Function (DCF) The basic 802.11 MAC layer uses the distributed coordination function (DCF) to share the medium between multiple stations. (DCF) relies on CSMA/CA and optional 802.11 RTS/CTS to share the medium between stations. This has several limitations: *if many stations attempt to communicate at the sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEEE 802
IEEE 802 is a family of Institute of Electrical and Electronics Engineers (IEEE) standards for local area networks (LAN), personal area network (PAN), and metropolitan area networks (MAN). The IEEE 802 LAN/MAN Standards Committee (LMSC) maintains these standards. The IEEE 802 family of standards has had twenty-four members, numbered 802.1 through 802.24, with a working group of the LMSC devoted to each. However, not all of these working groups are currently active. The IEEE 802 standards are restricted to computer networks carrying variable-size packets, unlike cell relay networks, for example, in which data is transmitted in short, uniformly sized units called cells. Isochronous signal networks, in which data is transmitted as a steady stream of octets, or groups of octets, at regular time intervals, are also outside the scope of the IEEE 802 standards. The number 802 has no significance: it was simply the next number in the sequence that the IEEE used for standards project ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Email
Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant only physical mail (hence '' e- + mail''). Email later became a ubiquitous (very widely used) communication medium, to the point that in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries. ''Email'' is the medium, and each message sent therewith is also called an ''email.'' The term is a mass noun. Email operates across computer networks, primarily the Internet, and also local area networks. Today's email systems are based on a store-and-forward model. Email servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TDLS
TDLS, shortened from Tunneled Direct Link Setup, is "a seamless way to stream media and other data faster between devices already on the same Wi-Fi network." Devices using it communicate directly with one another, without involving the wireless network's router. Wi-Fi Alliance added certification for TDLS in 2012. It describes this feature as technology that enables devices to link directly to one another when connected to a traditional Wi-Fi network. Wi-Fi CERTIFIED TDLS devices can set up secure links and transfer data directly between them. TDLS-linked devices benefit from an optimized connection to do things such as streaming video or synching content, without burdening the network as a whole. The IEEE has endorsed this as the IEEE 802.11z standard. Google's Cast protocol used by Chromecast utilizes TDLS to initiate screen mirroring. See also * Wi-Fi Direct Wi-Fi Direct (formerly Wi-Fi Peer-to-Peer) is a Wi-Fi standard for peer-to-peer wireless connections that allows t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basic Service Set
In IEEE 802.11 wireless local area networking standards (including Wi-Fi), a service set is a group of wireless network devices which share a ''service set identifier'' (''SSID'')—typically the natural language label that users see as a network name. (For example, all of the devices that together form and use a Wi‑Fi network called ''Foo'' are a service set.) A service set forms a logical network of nodes operating with shared link-layer networking parameters; they form one logical network segment. A service set is either a ''basic service set'' (''BSS'') or an ''extended service set'' (''ESS''). A ''basic service set'' is a subgroup, within a service set, of devices that share physical-layer medium access characteristics (e.g. radio frequency, modulation scheme, security settings) such that they are wirelessly networked. The basic service set is defined by a ''basic service set identifier'' (''BSSID'') shared by all devices within it. The BSSID is a 48-bit label that confor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VoIP Phones
A VoIP phone or IP phone uses voice over IP technologies for placing and transmitting telephone calls over an IP network, such as the Internet. This is in contrast to a standard phone which uses the traditional public switched telephone network (PSTN). Digital IP-based telephone service uses control protocols such as the Session Initiation Protocol (SIP), Skinny Client Control Protocol (SCCP) or various other proprietary protocols. Types VoIP phones can be simple software-based softphones or purpose-built hardware devices that appear much like an ordinary telephone or a cordless phone. Traditional PSTN phones can be used as VoIP phones with analog telephone adapters (ATA). A VoIP phone or application may have many features an analog phone doesn't support, such as e-mail-like IDs for contacts that may be easier to remember than names or phone numbers, or easy sharing of contact lists among multiple accounts. Generally the features of VoIP phones follow those of Skype and oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wi-Fi Multimedia
Wireless Multimedia Extensions (WME), also known as Wi-Fi Multimedia (WMM), is a Wi-Fi Alliance interoperability certification, based on the IEEE 802.11e standard. It provides basic Quality of service (QoS) features to IEEE 802.11 networks. WMM prioritizes traffic according to four Access Categories (AC): voice (AC_VO), video (AC_VI), best effort (AC_BE), and background (AC_BK). However, it does not provide guaranteed throughput. It is suitable for well-defined applications that require QoS, such as Voice over IP (VoIP) on Wi-Fi phones (VoWLAN). WMM replaces the Wi-Fi DCF distributed coordination function for CSMA/CA wireless frame transmission with Enhanced Distributed Coordination Function (EDCF). EDCF, according to version 1.1 of the WMM specifications by the Wi-Fi Alliance, defines Access Categories labels AC_VO, AC_VI, AC_BE, and AC_BK for the Enhanced Distributed Channel Access (EDCA) parameters that are used by a WMM-enabled station to control how long it sets its Tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IEEE P802
The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operations center in Piscataway, New Jersey. The mission of the IEEE is ''advancing technology for the benefit of humanity''. The IEEE was formed from the amalgamation of the American Institute of Electrical Engineers and the Institute of Radio Engineers in 1963. Due to its expansion of scope into so many related fields, it is simply referred to by the letters I-E-E-E (pronounced I-triple-E), except on legal business documents. , it is the world's largest association of technical professionals with more than 423,000 members in over 160 countries around the world. Its objectives are the educational and technical advancement of electrical and electronic engineering, telecommunications, computer engineering and similar disciplines. History Origi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MIMO
In radio, multiple-input and multiple-output, or MIMO (), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wireless communication standards including IEEE 802.11n (Wi-Fi 4), IEEE 802.11ac (Wi-Fi 5), HSPA+ (3G), WiMAX, and Long Term Evolution (LTE). More recently, MIMO has been applied to power-line communication for three-wire installations as part of the ITU G.hn standard and of the HomePlug AV2 specification. At one time, in wireless the term "MIMO" referred to the use of multiple antennas at the transmitter and the receiver. In modern usage, "MIMO" specifically refers to a class of techniques for sending and receiving more than one data signal simultaneously over the same radio channel by exploiting multipath propagation. Additionally, modern MIMO usage often refers to multiple data signals sent to different receivers (with one or more rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OFDM
In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G/ 5G mobile communications. OFDM is a frequency-division multiplexing (FDM) scheme that was introduced by Robert W. Chang of Bell Labs in 1966. In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel.webe.org - 2GHz BAS Relocation Tech-Fair, COFDM Technology Basics 2007-03-02 Demodu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MAC Service Data Unit
MAC service data unit (media access control service data unit, MSDU) is the service data unit that is received from the logical link control (LLC) sub-layer which lies above the media access control (MAC) sub-layer in a protocol stack. The LLC and MAC sub-layers are collectively referred to as the data link layer (DLL). See also * MAC protocol data unit * Packet segmentation * Packet aggregation {{Use mdy dates, date = March 2019 In a packet-based communications network, packet aggregation is the process of joining multiple packets together into a single transmission unit, in order to reduce the overhead associated with each transmissi ... External links 802.11 Wireless LAN IEEE standard Media access control {{telecomm-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Coordination Function
Distributed coordination function (DCF) is the fundamental medium access control (MAC) technique of the IEEE 802.11-based WLAN standard (including Wi-Fi). DCF employs a carrier-sense multiple access with collision avoidance (CSMA/CA) with the binary exponential backoff algorithm. DCF requires a station wishing to transmit to listen for the channel status for a DIFS interval. If the channel is found busy during the DIFS interval, the station defers its transmission. In a network where a number of stations contend for the wireless medium, if multiple stations sense the channel busy and defer their access, they will also virtually simultaneously find that the channel is released and then try to seize the channel. As a result, collisions may occur. In order to avoid such collisions, DCF also specifies random backoff, which forces a station to defer its access to the channel for an extra period. The length of the backoff period is determined by the following equation: \mathrm = \math ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arbitration Inter-frame Space
Arbitration inter-frame spacing (AIFS), in wireless LAN communications, is a method of prioritizing one Access Category (AC) over the other, such as giving voice or video priority over email. AIFS functions by shortening or expanding the period a wireless node has to wait before it is allowed to transmit its next frame. A shorter AIFS period means a message has a higher probability of being transmitted with low latency, which is particularly important for delay-critical data such as voice or streaming video. AIFS is a time interval between frames being transmitted under the IEEE 802.11e EDCA MAC. It depends on the Access Category and generally depends on the AIFSN, or AIFS-number. AIFS is defined by the formula AIFSN C* ST + SIFS, where the AIFSN depends on the Access Category. Slot time ST (also denoted by \sigma) is dependent on the physical layer. Short Interframe Space (SIFS) is the time between a DATA and ACK frame. AIFSN Cwill be set by the AP in the EDCA Parameter set ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
