Legacy Rate and Length HT Rate and Length in .NET Integrated QR in .NET Legacy Rate and Length HT Rate and Length

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Legacy Rate and Length HT Rate and Length using barcode generator for .net control to generate, create qr code image in .net applications. bar code L-TFs L-SIG HT-SIG HT-TFs Data ACK Duration in L-SIG = (Legacy L ength) /( Legacy Rate). Figure 1.8: Basic Concept of L-SIG Protection. To ensure the coexistence, it is required in 802.11n that GF mode operation must be protected when there are non-GF mode devices present nearby. It is also required that 40 MHz operation must be protected in the presence of non-HT devices.

. 1.2 IEEE 802.11k: Radio Resource Measurement Emerging technologies and wir eless applications (such as voice over IP, video over IP, location services, large scale WLAN deployment and management) impose many new requirements over the capabilities of WLANs. These advancements demand standardized facilities to acquire and exchange statistics and measurements to better deploy and manage the WLAN, to better utilize the wireless bandwidth, to automatically optimize network performance, and to improve the reliability of the WLAN. Such facilities are of key importance to the pre-eminence of 802.

11 wireless networks.. Emerging IEEE 802.11 Standards 802.11k Radio Resource Measur ement (RRM) specifies the facilities to meet the requirements of information about the radio environment. The specification defines Radio Resource Measurement enhancements by specifying a list of standardized measurements for radio resources and providing mechanisms to higher layers in the network stack for consistent radio and network measurement reports.

The mechanisms include measurement requests and reports as well as the MIB with an Object Identifier (OID) interface to upper layers. The provided radio measurements can be used for various benefits such as enabling simplified and automatic radio configuration, achieving better performance for the WLAN, optimizing the use of the client s radio resources, alerting a network administrator to issues, notifying end user radio status, etc. The 802.

11k RRM measurements are exchanged with measurement pairs of requests and reports. The measurements include: Beacons, Measurement Pilots, summary of received packets, Noise Histograms, STA Statistics, Location Configuration Information, Neighbor Report, Link Measurements, QoS, QBSS Loads, Access Delay, etc. 802.

11k adopts a layer management request/response model to collect statistics and perform measurements. In general, 802.11k only contains measurements that nearly all vendors can support via a driver or firmware upgrade without requiring hardware modifications.

. 1.3 802.11p: Wireless Access for the Vehicular Environment IEEE 802.11p defines enhancem ents to 802.11 required to support Intelligent Transportation Systems (ITS) applications, which includes data exchange between highspeed vehicles and between the vehicles and the roadside infrastructure in the licensed ITS band of 5.

9 GHz (5.85-5.925 GHz).

802.11p is also referred to as Wireless Access for the Vehicular Environment (WAVE). 802.

11p provides the lower layers of the Dedicated Short Range Communications (DSRC) solution and will be used as the groundwork for DSRC. DSRC is a U.S.

Department of Transportation project. It targets at vehicle-based communication networks, especially for applications such as vehicle safety services, toll collections, and commerce transactions via cars. Its ultimate vision is a nationwide network that enables communications between vehicles and other vehicles or roadside access points.

The higher layers of the DSRC solution are provided by standards outside of IEEE 802.11family, such as IEEE 1609, IEEE 1556 for beacon authentication, and NEMO for mobility. 802.

11p uses 5 and 10 MHz channels of 802.11 OFDM PHY at 5.9 GHz, with a spectral mask that cannot be easily met by 802.

11a devices. It also requires a substantially extended MAC and uses only very few 802.11 facilities such as a basic access mechanism of EDCA.

. Emerging IEEE 802.11 Standards 1.4 802.11r: Fast BSS-Transitions Prior to 802.11r, BSS transit Denso QR Bar Code for .NET ions are supported under 802.

11a/b/g, but only good enough for the best-effort data, not for QoS data. With the emergence of QoS applications, such as Voice over IP (VoIP), a satisfactory BSS transition solution for QoS data is required. VoIP mobile phones are designed to work with wireless Internet networks.

These VoIP devices must be able to disassociate from one access point and associate to another rapidly. The handoff delay typically cannot exceed a threshold of about 20 msec. There are several issues with the BSS transitions.

For one thing, the handover latency is too long (often average in the hundreds of milliseconds) to support QoS traffic. This excess delay can lead to loss of call connectivity or degradation of voice quality. Another problem is that a VoIP device cannot know if necessary QoS resources are available at a new access point until after a transition.

It is therefore impossible to know beforehand whether a transition will lead to satisfactory VoIP performance. In addition, it is also problematic for secure 802.11 connections using WPA2 or WPA.

802.11r defines enhancements to 802.11 required to provide a solution for fast BSS transition.

It provides a faster handoff solution to address the needs of security, a minimal latency, and QoS resource reservation, which is essential to widely deployed VoIP applications. 802.11r will permit connectivity aboard vehicles in motion, with fast handoffs from one access point to another seamlessly.

802.11r allows a wireless client to establish a security and QoS state at a new access point before making a transition, which leads to minimal connectivity loss and application disruption. The overall changes of the roaming process do not introduce any new security vulnerabilities.

This preserves the behavior of current stations and access points. 802.11r will govern the way roaming clients communicate with candidate APs for instance in establishing security associations and reserving QoS resources.

Under 802.11r, clients can use the current AP as a passage to other APs, allowing clients to minimize disruptions caused by the roaming transition..

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