Gaston Caswell


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On the other hand fragmentation ensures greater reliability of transmission. By that emits online tamil radio fewer data frames, it is more likely that data will be properly received. This feature is very useful in environments where it is not established a reliable connection and can be a loss, because the likelihood of success of the transfer of large data framework would be very small. 802. 11n had to make a compromise between reliability and high throughput. The proposed fragmentation/ aggregation scheme It combines a very efficient use of the range of aggregation with robust against false Transmission [2] [9].
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3.6 grade blue. A disadvantage is however that if the first fragment of the MSDU corrupt, as in the case of a control framework BAR (request to block confirmation) at A-MPDU, the entire A-MPDU to the receiving side online tamil radio dropped. However, the probability that this occurs is minimal, especially when one considers the size of BAR. Fragmentation MSDU at 802. 11 leads at high speeds for rapid debating. In high transmission speeds is significantly increasing overheads and thus reduces the throughput at the MAC layer. By reducing this overhead, we will achieve greater performance.
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In environments where there are original equipment (called greenfield) Backward compatibility is not required. By that we exclude the condition for providing feedback Compatibility with the preamble of a greenfield format shortened to 12 microseconds compared Mixed format. This difference is very online tamil radio noticeable, and it is increasingly enforced shorter packet length, as is necessary in the case of VoIP. To increase throughput on MAC layer uses 802. 11n fact that the head The MAC frame contains information that individual fragments of the MSDU same. Therefore, the header will only add to the first fragment achieve this by significantly reduce overhead. The fields that are common to all fragments of the same, are shown in Fig.
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To ensure backward compatibility between the 20 MHz band and 40 MHz bands is preamble for 40 MHz equal to 20 MHz is just repeated for two adjacent 20 MHz channels and informs that form a channel 40 MHz. This allows equipment operating with a bandwidth of 20 MHz on both adjacent channels decode control field and postpone the transfer. Preamble with 802 tamil web fm 11a has a length of 20 microseconds. Mixed format for 802. 11n will then have all the control and training field length of 36 microseconds for one surround channels and 48 microseconds for the four spatial channels. Unfortunately MIMO training and backward compatibility increases the overhead, which reduces efficiency transmission.
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11a, devices operating with OFDM and 802. 11g. Preamble with 802. 11n mixed format begins with a preamble as 802. 11a/ g. The includes short training field (short training field), long training field online tamil radio (long training field), and a control field (field signal). This allows the device 802. 11a/ g to detect 802. 11n packets mixed format and can then detect the control field. Although devices 802. 11a/ g will not be able to decode the rest of the packet broadcast standard 802. 11n will be able to properly defer its transmission according to the length specified in control field. The remainder consists of cells in mixed formats other short training field (Second short training field), additional long training fields (additional long training Fields), and additional control box (additional signal fields), then follow the data. These new fields are required for MIMO training and management of many tamil web fm new modes and operations.