Concatenated PCU frames for TD-SCDMA
Original Publication Date: 2001-Dec-01
Included in the Prior Art Database: 2003-Jul-23
Existing mobile networks are optimized for speech with a maximal data rate of 13.3kbps. Therefore one divides the standard PCM30 channels (64kbps) which are used for the terrestrial interfaces (e.g. between BSC and BTS) by 4 getting subchan- nels with a datarate of 16kbps each. Those subchannels are sufficient for the terrestrial transport of speech but there are strong market de- mands for mobile data communications with high datarates. With the (quasi standard) 16kbps subchan- nels of course only those packet data communications can be supported which need together with their in- band signalling less or equal 16kbps (GPRS: CS-1 with 9.05kbps, CS-2 with 13.4kbps; EGPRS: MCS-1 with 8.8kbps, MCS-2 with 11.2kbps, may be also MCS-3 with 13.6kbps or 14.8kbps).
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Concatenated PCU frames for TD-SCDMA
Idee: Arnulf Deinzer, München
Existing mobile networks are optimized for speechwith a maximal data rate of 13.3kbps.
Therefore one divides the standard PCM30 channels(64kbps) which are used for the terrestrial interfaces(e.g. between BSC and BTS) by 4 getting subchan-nels with a datarate of 16kbps each.
Those subchannels� are� sufficient� for� the� terrestrialtransport of speech but there are strong market de-mands� for� mobile� data� communications with highdatarates. With the (quasi standard) 16kbps subchan-nels of course only those packet data communicationscan be supported which need together with their in-band signalling less or equal 16kbps (GPRS: CS-1with 9.05kbps, CS-2 with 13.4kbps; EGPRS: MCS-1with 8.8kbps,� MCS-2� with� 11.2kbps,� may� be� alsoMCS-3 with 13.6kbps or 14.8kbps).
The solution for higher datarates (GPRS: CS-3 with15.6kbps, CS-4 with 21.4kbps, EGPRS: from MCS-4with 17.6kbps to MCS-9 to 59.2kbps) are so calledconcatenated PCU frames, described in GR 00E1752DE. The PCU frames described there are not suitedfor TD-SCDMA what will be outlined in the follow-ing.
For the TD-SCDMA realisation neither the'old'/standard PCU frames (described in FRS 0725)nor the new concatenated PCU frames (described inFRS 0431 'New EDGE/EGPRS/ GPRS PCU Frames(concatenated PCU� frames)'� –� these� are� the� PCUframes described in GR 00E1752 DE) can/shall beused:
•� � The 'old'/standard PCU frames had already to bechanged� to� support� the specific TD-SCDMAspecific needs� and are in no way future proof(i.e. expandable for higher CS or MCS or TD-SCDMA specific CS� with� datarates� not� fittinginto a single 16kbps subchannel – this the idea ofGR 00E1752 DE).
•� � The concatenated PCU frames as they are nowdefined� for� GSM/GPRS/EGPRS� are� in somekind on the one side
•� � overengineered from� the� TD-SCDMA� point� ofview (e.g. support of 'smart' antennas, IR) andbear on the other side
•� � restrictions due legacy� situation/need� of� back-ward compatibility (e.g. 2 starting octets insteadof only 1 because BBSIG44 in BTS1 need those2 octets for synchronization – see FRS 0431).
This overhead� leads to the situation, that those CS2realisations need 2 concatenated PCU frames.
This is not quite a problem for EGPRS/GPRS, be-cause there is a multiplexing of several mobiles onthe same GSM TS, hence Abis allocation is that ofthe maximum CS allocated on that TS. Simulationsshow that under rural and urban deployments in mosttimes at least MCS-5 could be used – so 2 16kbpssubchannels on Abis have to be allocated anyway.
On the other hand would a CS2 realisation with morethan one PCU frame cause a terrible waste of A bisresources for the TD-SCDMA services with higherdatarates (All those services are supported by a mul-titude of CS2 channels� with� 13.4� kbps� –� 'HSCSDapproach'. 384/13.4=28.7 so at least 29 CS2 channelsare needed to support 384kbps, with 2 PCU framesper CS2 realis...