engineer,
<< I think it means that you keep the GSM switch and network and you connect via the IS-41 MAP interface and use CDMA handsets and basestations over the top of it. If so, this means that they will use the standard Q handset chips and basestation chipsets. the only peice used will be the old GSM switches they already paid for. >>
I do not think that this is exactly the case. I agree with the first sentence in a general sense, but not the second, in its entirety. I am capable of (or should I say, willing to be) being enlightened, however. <g>
The overlay of a CDMA radio interface would, I would think, be accomplished along the lines of the 1997 Vodafone/Qualcomm Newbury trials, (although the Newbury trials obviously did not take this as far as needed to test intersystem operation or intersystem handover), which integrated the GSM Mobile services Switching Center (MSC), and the CDMA Base Station Subsystem (BSS) which communicated with each other over the GSM A-interface (aka Um interface) or radio link, and used the traditional GSM SIM for authentication.
3gpp2.org
As a practical matter, any existing GSM carrier who opts to overlay a GSM network with a CDMA air interface, would need to achieve interoperability with his own and other GSM networks. If that GSM operator (I'm thinking of Unicom or potentially Vodafone) also builds out a cdma2000 network that operator would need to achieve handoff to his GSM network. Obviously a SIM would be required (and shipping 2G Qualcomm chipsets have a SIM/R-UIM interface), but I think there is more.
I do not think that "standard Q handset chips and basestation chipsets" as they are shipping today will suffice.
I think some modification of the signaling protocol stack will be necessary. When 3GPP2 completed initial cross modal specifications this spring, this would have been taken into account.
The shipping 2nd generation (6th gen Qualcomm) MSM3100 evidently facilitates operation of a dual-mode GSM/CDMA handset on a CDMA network and allows that handset to authenticate to and communicate with a GSM network.
I am not sure that the same chipset can be used to satisfy the requirements of a GSM operator overlaying a GSM air interface on a GSM network. I am sure that future Qualcomm chipsets will.
Back to your original statement, I agree that probably most if not all of the network subsystem could stay intact, and the basestation subsystem would be replaced. Wouldn't some sort of new IP backbone need to be implemented however, in order to take advantage of the data capabilities of 1xMC and in the future 1xEV. I really don't think that many GSM opreators will hqve any motivation to do a cdmaOne overlay of their GSM network, so we are really looking at MSM5105 or MSM5100 chipsets or beyond to facilitate such an overlay.
I am obviously overstepping my own knowledge base here, and stepping into your area of considerable expertise, so if you would care to comment back on this, I think my thread mates would be interested. I cetainly would be.
- Eric - |
