By Matthew Gast
This can be a nice ebook for wireless method engineers to appreciate 802.11 a\b\g PHY and MAC. The ebook not just talks approximately theoretical stuff but in addition provides useful features of wireless networking.
Read or Download 802.11 Wireless Networks: The Definitive Guide (O'Reilly Networking) PDF
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It is a nice e-book for wireless method engineers to appreciate 802. eleven a\b\g PHY and MAC. The publication not just talks approximately theoretical stuff but additionally offers useful features of wireless networking.
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Additional resources for 802.11 Wireless Networks: The Definitive Guide (O'Reilly Networking)
As in Ethernet, the backoff time is selected from a larger range each time a transmission fails. Figure 3-7 illustrates the growth of the contention window as the number of transmissions increases, using the numbers from the direct-sequence spread-spectrum (DSSS) physical layer. Other physical layers use different sizes, but the principle is identical. , 31, 63, 127, 255). Each time the retry counter increases, the contention window moves to the next greatest power of two. The size of the contention window is limited by the physical layer.
Figure 3-18. 3 Power-Saving Sequences The most power-hungry components in RF systems are the amplifiers used to boost a signal immediately prior to transmission and to boost the received signal to an intelligible level immediately after its reception. 11 stations can maximize battery life by shutting down the radio transceiver and sleeping periodically. During sleeping periods, access points buffer any unicast frames for sleeping stations. These frames are announced by subsequent Beacon frames.
If the two match, there is a high probability that the frame was not damaged in transit. On Ethernets, frames with a bad FCS are simply discarded, and frames with a good FCS are passed up the protocol stack. 11 networks, frames that pass the integrity check may also require the receiver to send an acknowledgment. For example, data frames that are received correctly must be positively acknowledged, or they are retransmitted. 11 does not have a negative acknowledgment for frames that fail the FCS; stations must wait for the acknowledgment timeout before retransmitting.