ill (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. Adding Cells to a CDMA System Increasing Capacity This cost-saving opportunity may go away if the neighboring old cells no longer have adequate coverage of the new-cell area. This would happen if we downtilted the anten- nas on the old cells to restrict their interference with the new cells. In such a case, the decision not to employ redundant base stations for growth cells is a decision to risk loss of system coverage and not just higher blocking during a base station outage. The wireless service provider has to make a decision, one of those cost-versus- quality tradeoffs. The consequence of a growth-cell outage is a much higher blocking rate for a period of time. We have already made the decision in our design process what level of QoS we are willing to pay for in buying equipment and adding base sta- tions. We now have to decide what QoS is going to have the extra level of reliability that a more expensive, redundant base station provides. It is reasonable to decide that all the base stations should be fully redundant and re- liable. If we marketed the 3G CDMA product as being rugged, tough-as-nails depend- able, then an outage that causes poor service is not going to please subscribers who are paying a premium for our superior product. Or we may have large business contracts with service-level agreements (SLAs) that we can only meet when all the base stations have high reliability. It is also reasonable to decide that occasional periods of high blocking are acceptable. If we marketed our product to a casual voice call community on the basis of price, then it may be perfectly reasonable to have two or three days per year when it is very hard to make a call. The base station equipment cost saving can be passed on to the sub- scribers in the form of lower, more competitive rates. In any case, equipment failure in a base station should be a rare e