tting node itself, as the name implies. Nevertheless, it is meant for the neighboring nodes, if it is detected. A new generation Wi-Fi node transmits a CTS-to-self frame immediately before transmitting. The duration field of the CTS-to-self packet contains the time of the following traffic frame, thereby providing more effective protection of the subsequent frame than relying on physi- cal medium sensing. IEEE 802.11 supports two network architecture types namely infrastructure and ad-hoc modes. The basic service set (BSS) is the basic building block of an IEEE 802.11 network. Direct association of stations in ad-hoc network forms an independent BSS or IBSS. The interconnection of a number of BSS through a distributed system creates an extended ser- vice set. IEEE 802.11 specifications define multiple physical layers and a common MAC layer for wireless local area networks (as shown in Fig. 8.6). Another important aspect of this family is that they use unlicensed spectrum in 2.4, 5, and 60 GHz for operation. The IEEE 802.11 family comprises many technologies that have evolved from direct sequence spread spectrum (DSSS) and complementary code keying (CCK) in the first gen- eration to OFDM waveforms combined with advanced coding and modulation techniques and spatial division multiplexing (SDM) multi-antenna schemes in the latest generations that, depending on channel conditions, can provide data rates in the excess of a few gigabits per second within short distances. Table 8.2 summarizes the key physical layer characteris- tics of IEEE 802.11 air-interface technologies. There are other IEEE 802.11 family mem- bers that each provides an extension to the baseline standard by adding new features such as handover and roaming, mesh networking, QoS, security, regulatory, and measurement for various regions of the world [30]. In IEEE 802.11, the stations and the access point are not synchronized except when they exchange data or control information in the downlink or uplink. An LBT method combined with CSMA/CA is used to g