ically in Figure 5.1-11. antenna. Assume the receiving antenna has the same ef- fective area as an ideal isotropic receiver. Our allowed 5.1.3.4 802.11 Alphabet soup path loss-the link budget-is then (20 + 6 - (-80)) = 106 dB. Recalling that an isotropic antenna has an equiv- Products implementing the 802.11 classic standard were alent area of around 12 cm², this is equivalent to a free manufactured and sold in the late 1990s by vendors space path of 2000 m or 2 km! However, recall that such as Proxim, Breezecom (now part of Alvarion), Wireless local area networks CHAPTER 5.1 FREE SPACE free-space margin INDOORS no indoor margin excess noise thermal noise transmit antenna path loss antenna receive (S/N) output efficiency directivity efficiency signal requirement Figure 5.1-11 Link budget estimates for an 802. 11-compliant radio link. Lucent (under the WaveLAN brand), Raytheon, Symbol both client cards and access points fell even more rapidly Technologies, and Aironet (now part of Cisco). However, as numerous vendors entered the field. the maximum data rate of 2Mbps represented a signifi- The more audacious 802.1 la standard, which would cant obstacle to the intended target usage model of provide enhanced data rates of up to 54 Mbps, was seen by wirelessly extending Ethernet: even the slowest variant most industrial participants as a tool to hold in reserve for of Ethernet has a native bit rate of 10 Mbps and a true future use, but the start-up company Atheros proceeded throughput of around 8-9 Mbps. Work had started as to release chips implementing the 802.1 standard, with early as 1993 on improved physical layers, and by 1999 products available from Intel and Proxim in 2002. These two new higher performance PHY layers were released as products, although modestly successful at introduction, enhancements to the original 802.11 classic interfaces. clarified the desirability of combining the high data rates 802.1 was a fairly radical modification of the physical of the 802.11 standard with backward compatibility to 