Although IEEE 802.11g is the fastest IEEE wireless network standard at present, it is frequently referred to as the slowest wireless network standard at many retail stores. This is because most vendors have created various extensions to the IEEE 802.11g standard in a drive to improve network performance and to sell more expensive network adapters, APs, and so forth. Proprietary extensions fall into the following categories:
Two major technologies are designed to improve IEEE 802.11g transfer rates: Atheros Super G and Broadcom Afterburner. Atheros and Broadcom are chipset vendors, not network adapter vendors. However, between them, almost all wireless network vendors offer one or the other speedup technologies as part of their product lines. Table 21.2 compares the major features of these technologies.
Although the real-world throughput of these products is considerably lower than the stated speeds, both types of products do provide about a 30%35% boost in real-world throughput over standard 802.11g hardware. For best results, products from the same vendor, or at least using the same chipset, should be used on a single network. The second type of improvement over standard IEEE 802.11g hardware involves improvements in range, often combined with speed improvements based on the technologies listed in Table 21.2. Table 21.3 compares range-improvement technologies used by major wireless network vendors. Most use some form of multiple in, multiple out (MIMO), which uses multiple antennas in various ways.
Note Airgo claims that the definition of MIMO involves techniques such as beam forming, receive combining, and multiplexing along with multiple antennas. Other vendors, such as Atheros and Video54, use MIMO to refer to other methods of using multiple antennas. At this point, there is no legal definition of MIMO, so different vendors are free (for now) to use (and argue over) the meaning of MIMO. Because these methods have been developed by chipset and technology vendors rather than by network adapter manufacturers themselves, you might see other vendors adopt various combinations of these technologies in the future. |