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802.11 Frame Types
In the IEEE 802.11 wireless LAN protocols (such as Wi-Fi), a MAC frame is constructed of common fields (which are present in all types of frames) and specific fields (present in certain cases, depending on the type and subtype specified in the first octet of the frame). The very first two octets transmitted by a station are the Frame Control. The first three subfields within the frame control and the last field ( FCS) are always present in all types of 802.11 frames. These three subfields consist of two bits Protocol Version subfield, two bits Type subfield, and four bits Subtype subfield. Frame Control The first three fields (Protocol Version, Type and Subtype) in the Frame Control field are always present. The fields, in their order of appearance in transmission, are: # Protocol Version # Type #Subtype # To-DS # From-DS # More-Fragments # Retry # Power Management # More Data # Protected Frame # +HTC/Order Protocol Version Subfield The 2-bits Protocol Version subfie ... [...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 projects. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
WiGig
WiGig, alternatively known as 60 GHz Wi-Fi, refers to a set of 60 GHz wireless network protocols. It includes the current IEEE 802.11ad standard and also the IEEE 802.11ay standard. The WiGig specification allows devices to communicate without wires at multi-gigabit speeds. It enables high performance wireless data, display and audio applications that supplement the capabilities of previous wireless LAN devices. WiGig tri-band-enabled devices, which operate in the 2.4, 5 and 60 GHz bands, deliver data transfer rates up to 7 Gbit/s (for 11ad), about as fast as an 8-band 802.11ac transmission, and more than eleven times as fast than the highest 802.11n rate, while maintaining compatibility with existing Wi-Fi devices. The 60 GHz millimeter wave signal cannot typically penetrate walls but can propagate by reflection from walls, ceilings, floors and objects using beamforming built into the WiGig system. When roaming away from the main room, the protocol can switch to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quality Of Service
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput, transmission delay, availability, jitter, etc. In the field of computer networking and other packet-switched telecommunication networks, quality of service refers to traffic prioritization and resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priorities to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow. Quality of service is particularly important for the transport of traffic with special requirements. In particular, developers have introduced Voice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Acknowledgement (data Networks)
In data networking, telecommunications, and computer buses, an acknowledgment (ACK) is a signal that is passed between communicating processes, computers, or devices to signify acknowledgment, or receipt of message, as part of a communications protocol. The negative-acknowledgement (NAK or NACK) is a signal that is sent to reject a previously received message or to indicate some kind of error. Acknowledgments and negative acknowledgments inform a sender of the receiver's state so that it can adjust its own state accordingly. Many protocols contain checksums to verify the integrity of the payload and header. Checksums are used to detect data corruption. If a message is received with an invalid checksum (that is, the data received would have a different checksum than the message had), the receiver can know that some information was corrupted. Most often, when checksums are employed, a corrupted message received will either not be served an ACK signal, or will be served a NAK sig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Acknowledgement
Block acknowledgement (BA) was initially defined in IEEE 802.11e as an optional scheme to improve the MAC efficiency. 802.11n amendment ratified in 2009 enhances this BA mechanism then made it as mandatory to support by all 802.11n-capable devices (formally known as HT - High Throughput devices). Instead of transmitting an individual ACK for every MPDU (i.e., frame A frame is often a structural system that supports other components of a physical construction and/or steel frame that limits the construction's extent. Frame and FRAME may also refer to: Physical objects In building construction *Framing (con ...), multiple MPDUs can be acknowledged together using a single BA frame. Block Ack (BA) contains bitmap size of 64*16 bits. These 16 bits accounts the fragment number of the MPDUs to be acknowledged. Each bit of this bitmap represent the status (success/failure) of a MPDU. Block acknowledgement consist of a setup and tear-down of the session phases. In the setup phase, c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beamforming
Beamforming or spatial filtering is a signal processing technique used in sensor arrays for directional signal transmission or reception. This is achieved by combining elements in an antenna array in such a way that signals at particular angles experience constructive interference while others experience destructive interference. Beamforming can be used at both the transmitting and receiving ends in order to achieve spatial selectivity. The improvement compared with omnidirectional reception/transmission is known as the directivity of the array. Beamforming can be used for radio or sound waves. It has found numerous applications in radar, sonar, seismology, wireless communications, radio astronomy, acoustics and biomedicine. Adaptive beamforming is used to detect and estimate the signal of interest at the output of a sensor array by means of optimal (e.g. least-squares) spatial filtering and interference rejection. Techniques To change the directionality of the array when transm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Announcement Traffic Indication Message , a communication via news media
{{Disambiguation ...
Announcement may refer to: * "Announcement" (song), a 2008 song by Common * Announcement (computing), a message about a new software version * Campaign announcement, a type of political speech * Public service announcement, a media message in the public interest * Press release A press release is an official statement delivered to members of the news media for the purpose of providing information, creating an official statement, or making an announcement directed for public release. Press releases are also considere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beacon Frame
Beacon frame is one of the management frames in IEEE 802.11 based WLANs. It contains all the information about the network. Beacon frames are transmitted periodically, they serve to announce the presence of a wireless LAN and to synchronise the members of the service set. Beacon frames are transmitted by the access point (AP) in an infrastructure basic service set (BSS). In IBSS network beacon generation is distributed among the stations. For the 2.4 GHz spectrum, when having more than 15 SSIDs on non-overlapping channels (or more than 45 in total), beacon frames start to consume significant amount of air time and degrade performance even when most of the networks are idle. Components Beacon frames consist of an 802.11 MAC header, body and FCS. Some of the fields in the body are listed below. * * * * SSID * Supported rates * Frequency-hopping (FH) Parameter Set * Direct-Sequence (DS) Parameter Set * Contention-Free (CF) Parameter Set * IBSS Parameter Set * Traffic indi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retry
Retry may refer to: * Retrial, in which a person is retried in court for various reasons * Retry, another term for a single play-turn in a video game * ''Retry'' (video game), a former 2014 video game developed by Rovio * Part of the DOS error message, Abort, Retry, Fail? "Abort, Retry, Fail?" (or "Abort, Retry, Ignore?") is an error message found in DOS operating systems, which prompts the end-user for a course of action to follow. Although welcomed by some, the message also has been cited as an example of poo ... See also * * Try (other) {{Disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wireless LAN
A wireless LAN (WLAN) is a wireless computer network A wireless network is a computer network that uses wireless data connections between network nodes. Wireless networking is a method by which homes, telecommunications networks and business installations avoid the costly process of introducing c ... that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building. This gives users the ability to move around within the area and remain connected to the network. Through a Gateway (telecommunications), gateway, a WLAN can also provide a connection to the wider Internet. Wireless LANs based on the IEEE 802.11 standards are the most widely used computer networks in the world. These are commonly called Wi-Fi, which is a trademark belonging to the Wi-Fi Alliance. They are used for home and small office networks that link together laptop computers, printer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ToDS And FromDS
Tod's S.p.A., also known as Tod's Group, is an Italian company which produces luxury shoes and other leather goods. The company is majority controlled by the founding family Della Valle Family and is listed on the Italy's Milan Stock Exchange being part of the FTSE Italia Mid Cap index. It is presided over by businessman Diego Della Valle. History Filippo Della Valle started the shoemaking business out of a basement in the late 1920s. Diego Della Valle, the elder son of Dorino Della Valle and a grandson of Filippo Della Valle, expanded the workshop and turned it into a factory that started manufacturing shoes for American department stores in the 1970s. Mr. Della Valle says he became interested in the retailer on his first visit to the United States as a youth, when he stopped in at a Saks Fifth Avenue store, to which his father used to sell shoes. Diego brought in innovative marketing strategies in the early 1980s, kept the handmade manufacturing process and went on to create br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
