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10 Designing for Next Gen Wi-Fi Applications and increased spectral efficiency. Table 2 lists the different modulations supported by 11a and their respective theoretical data rate. 802.11g Standard 802.11g became available in the summer of 2003. It uses the same OFDM technology introduced with 802.11a. Like 802.11a, it supports a maximum theoretical rate of 54 Mbps. But like 802.11b, it operates in the crowded 2.4GHz and hence is susceptible to interference issues. 802.11g is backward compatible with 802.11b (i.e., 802.11b devices can connect to an 802.11g access point). 802.11g was able to handle dual-band or dual-mode access points using 802.11a and 802.11b/g. 802.11n Standard With 802.11n, Wi-Fi became even faster and more reliable. This is achieved by adding multiple-input and multiple- output (MIMO) and 40MHz channels to the physical layer (PHY) and frame aggregation to the media access control (MAC) layer. MIMO is a method for multiplying the capacity of a radio link using multiple transmit and receive antennas to exploit multipath propagation. These antennas need to be spatially separated so that the signal from each transmit antenna to each receive antenna has a different spatial signature, so that on the receiver, it can separate these 802.11a products were not widely accepted initially because of cost, low range, and incompatibility with 802.11b. Of the 52 OFDM subcarriers, 48 are for data and 4 are pilot subcarriers with a carrier separation of 312.5kHz. Each of these subcarriers can be BPSK, QPSK, 16QAM or 64QAM. The bandwidth of channel is 20MHz with occupied bandwidth of 16.6MHz. Symbol duration is 4µsec that includes a guard interval of 0.8µsec. OFDM advantages include reduced multipath effects in reception Table 2 802.11a modulation rates and data rates for 20 MHz channel spacing