and 3G services are being deployed, the capacity of the air interface is in- creasing, and data in IP packets are being carried. In this environment, it is advanta- geous to turn the backhaul network into IP pipes rather than keep it as voice circuits. In some cases, the increased demand for capacity would require upgrading the capac- ity of the backhaul network. Prior to upgrade of the network to 3G, the backhaul was designed to meet the capacity requirements of the cdmaOne air interface. If the capac- ity of the air interface increases with the advent of 3G, then it may be necessary 5 Some dynamic allocation is already available through the use of multiplexed channels and sub- rates. However, VoIP will provide greater flexibiltiy and efficiency. 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. Hybrid Voice-Data Networks Hybrid Voice-Data Networks to modify the backhaul network. Otherwise, the backhaul network could become the bottleneck. If the backhaul network is not already using IP, then converting it to IP pipes will increase its capacity. The deployment of new radio air-interface technology at the base station requires vis- its to the base station now. It is most cost-effective to upgrade the base station's end of the backhaul network now. This is especially true in the case of cdma2000 1x, where the plan for later versions of cdma2000 is to install new cards that are software- upgradeable. If this plan succeeds, upgrade trips to base stations will be rarer in the future. It makes the most sense to get all the hardware changed out now. As a result, the cellular backhaul network is moving rapidly to IP pipes. The base stations are not the only locations in need of equipment changes in this process. Changes at the MSC are fairly simple because all the cards supporting the backhaul network are in one building. In addition, cellular provid