Optimizing Performance and Efficiency of PAs in Wireless Base Stations (Rev. A

1G Analog Cellular Recent years have seen tremendous growth in wireless subscribers. Moreover, new services like music downloads and Internet access on wireless cell phones have meant more and more data transmissions over wireless infrastructures. At the same time, however, the frequency spectrum allocated for wireless communications has been essentially constant. But with more users and more traffic, the wireless spectrum has become very crowded. This is analogous to a very crowded highway at rush hour. Think of the frequency spectrum as a highway and the data (voice call, music or Internet content) as cars. The highway width or number of lanes represents the fixed available wireless spectrum. Adding lanes to this wireless data highway is a tremendous undertaking, much like adding lanes to a real highway–land must be purchased, buildings torn down and more lanes constructed. On a vehicular highway, the cars are all going somewhere and their drivers want to arrive on time. Each car represents part of a voice call or a music download; many cars all arriving at the right time represent a completed download or call. As more subscribers use wireless devices to access digital content, more cars are added to the highway. When too many cars clog the freeway, everything slows down. The same thing happens on wireless networks. To solve this problem, wireless providers have switched to wireless standards that use the spectrum more efficiently. This is analogous to stacking multiple cars (with the same destination) on top of a truck and sending the truck down the highway. This allows more data to flow on the same highway without slowing down traffic. The wireless standards CDMA2000, W-CDMA, TD-SCDMA, MC-GSM, WiMAX and LTE were all deployed or defined to improve spectral efficiency. Figure 1 shows the wireless standards deployed or defined in recent years to improve spectral efficiency. David Brubaker Product Line Manager, Wireless Infrastructure Radio Products [email protected]