Found 498 Articles for Computer Engineering

What is wireless broadband (WiBB)?

Updated on 09-Jan-2020 10:10:23
Wireless broadband (WiBB) a networking technology designed to impart highspeed Internet and data service through wireless networks. Wireless broadband may be delivered through wireless local area networks (WLANs) or wide area networks (WWANs).Similar to other wireless services, wireless broadband can be either fixed or mobile.Features of WiBBWiBB is similar to wired broadband service since they connect to an internet backbone, with the difference that they use radio waves instead of cables to connect to the last mile of the network.The range of most broadband wireless access (BWA) services varies around 50 km from the transmitting tower.Download speeds provided by some ... Read More

Advanced Encryption Standard (AES)

Updated on 09-Jan-2020 07:53:44
The Advanced Encryption Standard, or AES, is an encryption standard established in 2001 by the National Institute of Standards and Technology (NIST) of USA. It is implemented worldwide both in hardware and software to encrypt sensitive data. AES finds wide usage while transmitting data over computer networks, particularly in wireless networks.Features of AESAES is a subset of Rijndael block cipher.It is a successor of Data Encryption Standard (DES) and is stronger and faster than DES.It is a symmetric key symmetric block cipher.It operates on 128-bit (16 bytes) data.The cipher key may be of 128, 192 or 256 bits.All computations are ... Read More

Wired Equivalent Privacy (WEP)

Updated on 09-Jan-2020 07:50:51
Wired Equivalent Privacy (WEP) is a security standard for wireless networks or WiFi. It was a part of the original IEEE 802.11 protocol. As wireless networks transmit data over radio waves, eavesdropping on wireless data transmissions is relatively easier than in wired networks connected by cables. WEP aims to provide the same level of security and confidentiality in wireless networks as in wired counterparts.Features of WEPWEP was introduced as a part of IEEE 802.11 standard in 1997.It was available for 802.11a and 802.11b devices.WEP uses encryption of data to make it unrecognizable to eavesdroppers.It uses RC4, a stream cipher, for ... Read More

WiFi Protected Access (WPA) and WiFi Protected Access 2 (WPA2)

Updated on 09-Jan-2020 07:47:58
Wi-Fi Protected Access (WPA) and Wi-Fi Protected Access 2 (WPA2) are security standards to protect network stations connected to WiFi networks. They were developed by WiFi Alliance for delivering sophisticated data encryption technologies and improved user authentication than the pre-existing Wired Equivalent Privacy (WEP).WiFi Protected Access (WPA)Wi-Fi Protected Access (WPA) was supported in IEEE 802.11i wireless networks and was proposed in 2004. It was backward-compatible with the existing WEP that led to its rapid, hassle-free adoption.The encryption method adopted in WPA is the Temporal Key Integrity Protocol (TKIP). TKIP includes per-packet key, integrity check, re-keying mechanism. It dynamically generates an ... Read More

What are the IEEE 802.11 Wireless LAN Standards?

Updated on 09-Jan-2020 07:45:29
IEEE 802.11 standard, popularly known as WiFi, lays down the architecture and specifications of wireless LANs (WLANs). WiFi or WLAN uses high frequency radio waves for connecting the nodes.There are several standards of IEEE 802.11 WLANs. The prominent among them are 802.11, 802.11a, 802.11b, 802.11g, 802.11n and 802.11p. All the standards use carrier-sense multiple access with collision avoidance (CSMA/CA). Also, they have support for both centralised base station based as well as ad hoc networks.IEEE 802.11IEEE 802.11 was the original version released in 1997. It provided 1 Mbps or 2 Mbps data rate in the 2.4 GHz band and used ... Read More

The 802.11 Frame Structure

Updated on 09-Jan-2020 07:41:13
The IEEE 802.11 standard, lays down the architecture and specifications of wireless local area networks (WLANs). WLAN or WiFi uses high frequency radio waves instead of cables for connecting the devices in LAN. Users connected by WLANs can move around within the area of network coverage.The 802.11 MAC sublayer provides an abstraction of the physical layer to the logical link control sublayer and upper layers of the OSI network. It is responsible for encapsulating frames and describing frame formats.MAC Sublayer Frame Structure of IEEE 802.11The main fields of a frame in WLANs as laid down by IEEE 802.11 are as ... Read More

Inter – frame spaces (RIFS, SIFS, PIFS, DIFS, AIFS, EIFS)

Updated on 02-Dec-2019 10:19:09
Inter – frame SpacesInter − frame spaces (IFS) are waiting periods between transmission of frames operating in the medium access control (MAC) sublayer where carrier-sense multiple access with collision avoidance (CSMA/CA) is used. These are techniques used to prevent collisions as defined in IEEE 802.11-based WLAN standard (Wi-Fi).IFS is the time period between completion of the transmission of the last frame and starting transmission of the next frame apart from the variable back-off period.The diagram below shows the different types of inter − frame spacing starting from the shortest duration (highest priority) to the longest duration (lowest priority). Among these, ... Read More

Transmission opportunity (TXOP)

Updated on 02-Dec-2019 10:15:42
Transmit opportunity (TXOP) is a MAC layer feature used in IEEE 802.11-based wireless local area network (WLAN). TXOP defines the time duration for which a station can send frames after it has gained contention for the transmission medium. By providing this contention-free time period, TXOP aims to increase the throughput of high priority data, such as voice and video.TXOP is available in Quality of Service as part of Enhanced Distributed Channel Access (EDCA).Working PrincipleTXOP operates in the following sequence of steps −When a station in the WLAN has frames to send, it waits till it’s Network Allocation Vector (NAV) decrements ... Read More

Extended Inter-Frame Spacing (EIFS)

Updated on 02-Dec-2019 10:13:52
Extended inter-frame spacing (EIFS), is a waiting period used in MAC layer of IEEE 802.11-based wireless local area network standard (WLAN standard). It is an additional waiting period used in addition to the mandatory DISF technique in case of corrupted frames.DISF (Distributed coordination function inter-frame spacing) is inserted before sending frames to avoid collisions in areas where carrier-sense multiple access with collision avoidance (CSMA/CA) is used. EISF is used for erroneous frames.Functioning of EIFSIn normal delivery of frames, DISF waiting period is good enough. However, when a previously received frame is corrupted, the DISF waiting period proves to be insufficient. ... Read More

Rate Anomaly in CSMA/CA

Updated on 02-Dec-2019 10:07:18
Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) is a network protocol for carrier transmission that operates in the Medium Access Control (MAC) layer. CSMA/CA prevents collisions prior to their occurrence and is ideally used in wireless communications.Rate anomaly occurs when the performance of a high speed station is impaired due to a low speed station, thus reducing the average throughput of the entire wireless network.ExplanationThe CSMA/CA allows each station to send a single frame at a time. Before sending a frame, the station waits for a certain inter-frame spacing (IFS). Following the IFS, it sends the request to send ... Read More
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