Quantum leap in test difficulty

04 Nov 2006

In future updates to cdma2000 networks, test difficulties won't just increase linearly with increasing data rates. Quantum jumps in test difficulty will occur because of the addition of new technologies as EV-DO moves from Release 0 to Revision B

Planners have worked hard to minimize the impact to network operators as they move along the cdma2000 evolutionary path. cdma2000 1x is backward and forward compatible with 2G IS-95. However, the jump to cdma2000 1x EV-DO Release 0 isn't quite as painless. To take full advantage of an all-IP network and have an air interface that has been optimized for data, the Rel 0 specifications do require multi-mode devices to be fully backward compatible. The tradeoff, however, is that a large amount of infrastructure can be reused. Plus, once the network operator has migrated to Rel 0, then future revisions will be fully backward and forward compatible.

The planners have also worked hard to minimize the impact on the operators' radio access networks. They claim that the migration from 2G to 1x and through all the EV-DO revisions is almost as simple as inserting a new channel card.

A third constraint that planners have imposed on themselves is to stick with a 1.25-MHz radio carrier in the same spectrum bands through all the EV-DO revisions.

Yet with these constraints in place, look at the 'headline' specifications for the steps along the evolutionary path. Peak data rate for the forward link jumps 15 fold from 0.153 Mbps to 2.4 Mbps when moving from 1x to EV-DO Rel 0. The jump from Rel 0 to Rev A isn't as eye-popping - 2.4 Mbps to 3.1 Mbps - but the jump from Rev A to Rev B certainly is. By allocating multiple RF carriers across wider frequency blocks, the headline specification jumps from 3.1 Mbps to 46.5 Mbps"&brkbar; or to 73.5 Mbps with 64-QAM modulation.

The peak data rate for the reverse link when moving from 1x to Rel 0 stays the same - 153 kbps - with all the development effort going into improving the forward link speeds. But in the step from Rel 0 to Rev A, the jump is 11 fold to 1.8 Mbps. Then a 15-fold jump from 1.8 Mbps to 27 Mbps when stepping from Rev A to Rev B.

Though the headline specification for EV-DO Rel 0 is 2.4 Mbps, real-world results indicate that users are seeing 400-kbps to 700-kbps data rates with some seeing 1.0-Mbps to 1.5-Mbps rates. So for users, the headline specifications are just that: specifications that catch the user's eye. However, for the test community, the headline specifications are very real. Test equipment suppliers and test engineering must test networks and their components to these eye-catching specifications.

Quantum jumps in difficulties
Simultaneously, test difficulties won't just increase linearly as headline data rates increase with the addition of each revision to the network. Testing will experience quantum jumps in difficulty as the underlying technologies to make these speed gains possible are added.

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