ion will be needed further down the road in the CDMA planning process. 31.3 Estimating Demand for Other Services There are other 3G CDMA services. We do not yet know which of these will be popular and which will fall by the wayside. But any of these could be popular features in the brave new world of 3G. One service that may become popular is sending images using multimedia service (MMS), as described in Sec. 20.5. This is a visual extension of short message service (SMS). The subscriber might be able to point a cellular phone, press a button, take a digital photo, and send the picture to another subscriber. As we said in the same Sec. 20.5, videotelephony was tried 40 years ago in the form of PicturePhone. It was terribly expensive, and it was tied to a home telephone. Per- haps in today's more mobile and more visual environment, real-time videotelephony will catch on. Bit rates tend to be high for video, and delay requirements are very low, so a video call demands a lot of CDMA capacity. In estimating our total demand, we must develop a picture of the future that includes these services that go beyond voice telephony and data services. We need a picture of the subscriber base that will be using video phones and sending MMS images. There are other services not on the beaten path that may become popular in the 3G environment. The 3G CDMA planners should do the best job they can of predicting what these services are. Downloaded from Digital Engineering Library @ McGraw-Hill (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. Estimating Wireless Telephone Demand Planning for CDMA Capacity For each of these services, we need a prediction of how many subscribers will be us- ing the service and its busy-hour erlang count e. As hard as it is to predict data service subscriber counts, these other services will be harder to forecast. After all, we have some idea of what a realistic data service is and who migh