f the trans- mitting radio. Synchronization is one of the most problematical operations in frequency-hopping radios. 3.2.3.2 Cost of Development and Products The cost of development and the cost of the final product are important con- siderations in selecting a spread-spectrum technique. For most commercial applications, a fast frequency-hopping radio is not cost-effective. In fact, hop- ping rates of commercial radios are generally very slow compared to the data rates, typically having several hundreds of bits or more transmitted during a hop duration. Similarly, direct-sequence implementations for commercial applications with large processing gain require costly high-speed circuits which are generally impractical. Thus, the processing gain for commercial direct-sequence radios is usually limited to less than 20 dB to avoid having to use high-speed circuits. With lower processing gain (fewer chips per bit), direct-sequence radios for commercial applications can use digital matched fibers instead of ser- ial correlators. Matched filters have the advantage of being able to achieve faster acquisition times than serial correlators or frequency-hopping radios. In general, however, direct-sequence radios with matched filters demand a greater development effort than other types of spread-spectrum radios. The final cost of direct-sequence spread-spectrum radios with digital matched filters, however, is no greater than that for serial correlator type direct- sequence or frequency-hopping radios. In fact, as shown in the currently marketed cordless telephones, this type of direct-sequence spread-spectrum radio with digital matched filters can yield low-cost consumer electronics products. 3.2.3.3 Performance Without interference from other radios and in free space, both direct- sequence and frequency-hopping spread-spectrum radios would give the same performance-in theory. In practice, however, the performance depends on the design of the radio and propagation conditions, and the real- ized performance varies greatly. With