e, as in the Qualcomm system. To achieve the rapid acquisition needed for TDD sys- items, each receiver should use matched filters rather than the serial corre- lators typically used with longer PN sequences. Soft handoff can be achieved by using a RAKE receiver processor as in the IS-95 system. Another alternative is to allow the receiver to track more Spread-Spectrum CDMA for PCS and PCN than one signal with different codewords. With programmable matched fil- ters, this can be done in practice with very few additional gates in a custom chip design. 3.6.3.4 Comparison with DECT For PCS applications, the current DECT system, using TDMA, serves as a baseline for comparison with the S-CDMA system described here. DECT has been under development in Europe for several years and represents the state of the art for PCS using conventional TDMA radios. These PCS sys- items, which involve users carrying portable or mobile handsets while roam- ing in an area covered by many microcells, are designed for microcells of up to approximately 200 m in diameter. The most important criterion for com- parison is capacity, as measured by the total number of simultaneous voice users in a given high-density area (1 km², for example), in which the num- ber of microcell sites and the total bandwidth within each area are constant. The comparison should also assume that overall complexity and cost are roughly equivalent, although these can be difficult to measure. As pointed out earlier, the design philosophy regarding spread-spectrum radios is different: Now interference is tolerated, and the primary issue is to design to a tolerable level of interference. This new design criterion for a net- work of microcells adds another design dimension that does not apply with conventional narrowband radios and places a much stronger emphasis on the quality of radios developed and the overall system design and signal coordination. Radios that tolerate greater interference afford more flexibility in designing a network of microcells, which is especiall