l (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Source: CDMA CAPACITY AND QUALITY OPTIMIZATION Chapter Capacity Issues Specific to CDMA Code division multiple access (CDMA), with its N = 1 reuse pattern, has fundamen- tally different design and capacity issues than conventional reuse systems have. While both types of systems have sectors, handoff, and problems with multipath, the reasons for these features and the nature of the problems are very different on CDMA systems. In this chapter we explore the functions of various CDMA components and their con- tribution to capacity management. We close the chapter with a section in which we pre- sent capacity estimates based on the CDMA equations and resolve them for each of the four standards (cdmaOne, cdma2000, W-CDMA, and TD-SCDMA) in both directions. These applications of the equations are approximations based on the best available fig- ures and do not provide guaranteed results. Our purpose in presenting them is not guarantee a certain capacity level but to present the methods available for applying the CDMA equations to the standards. This last section, "CDMA Radio Capacity Estima- tion," provides a jumping-off point for the practical guides to capacity planning and in- creasing capacity in Parts 6 and 7. 30.1 Sectorized Cells Sectors in CDMA are used for increased radio capacity. If we had a perfect base station antenna with 120 degrees of full gain and total attenuation in its backlobe, then a three-sector CDMA cell would have triple the capacity of an omnidirectional antenna. If our perfect antenna had 60 degrees and a perfect backlobe, then a six-sector CDMA cell would have six times the capacity. More realistic antenna patterns have significant sector-to-sector overflow, as shown in Fig. 1.7 in Sec. 1.8. This means that there is a significant amount of user terminal traffic with nearly equal signal paths to two sectors. The CDMA equations in 