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3G/UMTS |
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CPC (Continous Packet Connectivity)
Let's suppose a situation, say Web browsing for example. While you are reading a page, you are not downloading any data and there are no data communication between UE and the network. During this time, usually RRC state is put into Cell_FACH and Cell_PCH. When you finish reading the page and try to go next page, in this case the RRC state should change back into Cell_DCH.
Another way to improve the problem related to RRC State changes would be to increase the data rate at Cell_FACH. Theoretically you can transmit the data in Cell_FACH in previous technology and ideally the throughput is around 34 K. But if you really try it, you may notice the real throughput is much less than this. For HSPA+, the throuhgput for Cell_FACH has been much increased by Enhanced Cell_FACH.
To save battery consumption, UE can repeat very short cycles of 'sleeping mode' and 'wake up' mode when there is no data traffic and normally this repetition cycles is much shorter than DCH<--> FACH <--> PCH cycles. This kind of 'sleeping' and 'wake up' cycles are called DTX, DRX.
If you apply all these techniquest described above in wise combination, you would achieve such a status as i) Users feels like they are continuously connected to the network (User experience very short latency as if it is always connected). ii) Even with this kind of user experience, energy consumption (current consumption) on UE can be minimized
All the combination of this technique to achieve such a user experience is called "CPC". It means CPC is a collective terminoloty for a set of technologies, not any specific single technology. It implies that to understand CPC requires a lot of efforts -:)
Just in short, CPC is a combined technology of all of the following features.
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