th spread-spectrum systems can be applied to a network of many cells in a high-density area. 3.5.4 The Outbound Channel Up to now, the discussion of spread-spectrum CDMA focused on the recep- tion of mobile radio transmitters at the cell site. Normally, for large cells with large multipath delays, it may be difficult to time-synchronize mobile trans- mitters SO that their signals arrive at the cell site within a fraction of a chip time. Such synchronization in the inbound direction becomes even more dif- ficult as the data rate increases, and, in data networks, the data rate is usu- ally very high. Thus, the inbound channel may be characterized as asynchronous CDMA (A-CDMA), with mutual interference characterized by random delays and larger delay multipath components relative to the chip-time interval. Such A-CDMA channels are usually analyzed by mak- ing an equivalent noise model of the mutual interference. With S-CDMA channels with small, random time offsets, performance analysis is usually per- formed for specific codes. The outbound channel (cell site to mobile radios) performs very differ- ently from the inbound channel. Since transmitters for the outbound chan- nel are all located at the cell site, all radio signals to mobile radios can be easily synchronized. Each mobile radio then receives from the cell site the radio signals synchronized in time, or S-CDMA. Since the outbound chan- nel can be synchronized, orthogonal codewords are typically used for trans- missions from the cell site to mobile radios. Of course, multipath can result in interference in the mobile receivers. For large cells such as in the digital cellular IS-95 standard radios, the inbound channel is A-CDMA and the outbound channel is S-CDMA. Direct-Sequence Spread-Spectrum CDMA in High-Density Networks Consider the S-CDMA outbound channel in wireless LAN applications in which a wired LAN can be accessed by wireless laptop computers. On average, the amount of data outbound (LAN server to mobile laptop) is about 10 times as much as the data