bsc6900 gsm signal flow

5 Signal Flow

About This Chapter

The BSC6900 signal flow consists of the user-plane signal flow, control-plane signal flow, andOM signal flow.

Definitionsl User plane

User plane refers to the set of logical functions of the BSC6900 that process the servicedata, including the speech data and packet data.

l Control planeControl plane refers to the set of logical functions of the BSC6900 that process the controlsignaling, including the call control signaling and the connection control signaling.

5.1 User-Plane Signal FlowThe user plane of the BSC6900 processes the user-plane messages on each interface.

5.2 Control-Plane Signal FlowThe control plane of the BSC6900 processes the control-plane messages on each interface.

5.3 OM Signal FlowOM signal flow refers to the messages transmitted between the BSC6900 and the LMT/M2000.The LMT or M2000 maintains and monitors the BSC6900 in real time through the OM signalflow.

BSC6900 GSMTechnical Description 5 Signal Flow

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5.1 User-Plane Signal FlowThe user plane of the BSC6900 processes the user-plane messages on each interface.

5.1.1 CBC Signal FlowThe data from the CBC-BSC interface to the Abis interface refers to the Cell Broadcast Center(CBC) signal flow.

5.1.2 GSM CS Signal FlowAfter a CS call is established in the GSM network, the MS and the network communicate witheach other through the CS signal flow. The method of processing the GSM CS signal flow variesaccording to the transmission mode adopted on the Abis and A interfaces and the configurationmode of the BSC6900 subracks.

5.1.3 GSM PS Signal FlowAfter a PS connection is established in the GSM network, the MS and the network communicatewith each other through the PS signal flow. The GSM PS signal flow varies according to thetransmission mode adopted on the Abis interface.

5.1.1 CBC Signal FlowThe data from the CBC-BSC interface to the Abis interface refers to the Cell Broadcast Center(CBC) signal flow.

Figure 5-1 shows the signal flow from the CBC-BSC interface to the Abis interface.

Figure 5-1 Signal flow from CBC-BSC to Abis

NOTE

l The INT in the figure stands for the interface board. You can use different interface boards as required.

l The boards shown in Figure 5-1 are only examples.

The signal flow is as follows:

1. The CBC sends the broadcast data to the XPUa board of the BSC6900 over the CBC-BSCinterface. The XPUa board processes the data according to the related protocols and thensends it to the Abis interface board.

5 Signal FlowBSC6900 GSM

Technical Description

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NOTE

If the XPUa board in a subrack cannot process the data, the data is switched by the MPS to the XPUaboard in another subrack.

2. The Abis interface board processes the data and then sends it to the BTS.3. The BTS broadcasts the data to the MSs in the cells served by the base station.

5.1.2 GSM CS Signal FlowAfter a CS call is established in the GSM network, the MS and the network communicate witheach other through the CS signal flow. The method of processing the GSM CS signal flow variesaccording to the transmission mode adopted on the Abis and A interfaces and the configurationmode of the BSC6900 subracks.

Abis over TDM and A over TDMFigure 5-2 shows the CS signal flow in Abis over TDM, Ater over TDM, A over TDM, andBM/TC separated mode.

NOTE

l The Abis, Ater, and A interface boards can be the EIUa/OIUa/POUc board. The boards shown in Figure5-2, Figure 5-3, and Figure 5-4 are only examples.


Figure 5-2 GSM CS signal flow (1)

As shown in Figure 5-2, the CS signal flow on the uplink is as follows:

1. The uplink CS signals are sent from the BTS to the Abis interface board in the MPS/EPS.2. The CS signals are demultiplexed in the Abis interface board. Each CS signal uses a 64

kbit/s timeslot and is transmitted to the Ater interface board through the TNUa board.3. The CS signals are multiplexed in the Ater interface board. Each full-rate CS signal uses a

16 kbit/s sub-timeslot, and each half-rate CS signal uses an 8 kbit/s sub-timeslot. The CSsignals are then transmitted to the Ater interface board in the TCS over the Ater interface.

4. The CS signals are demultiplexed in the Ater interface board of the TCS. Each CS signaluses a 64 kbit/s timeslot and is transmitted to the DPUc board through the TNUa board.

5. The DPUc board performs speech codec and rate adaptation on the CS signals, which areconverted into 64 kbit/s PCM signals. The 64 kbit/s PCM signals are transmitted to the Ainterface board through the TNUa board and then to the MSC over the A interface.



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The downlink flow is the reverse of the uplink flow.

Figure 5-3 shows the CS signal flow in Abis over TDM, Ater over IP, A over TDM, and BM/TC separated mode.




kbit/s timeslot and is transmitted to the Ater interface board through the TNUa board, DPUcboard, and SCUa board in sequence.

3. The CS signals are multiplexed in the Ater interface board. Each full-rate CS signal uses a16 kbit/s sub-timeslot, and each half-rate CS signal uses an 8 kbit/s sub-timeslot. The CSsignals are then transmitted to the Ater interface board in the TCS over the Ater interface.




In the case of BM/TC combined mode, the Ater interface does not exist. Figure 5-4 shows theCS signal flow in Abis over TDM and A over TDM mode.





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kbit/s timeslot and is transmitted to the DPUc board through the TNUa board.3. The DPUc board performs speech codec and rate adaptation on the CS signals, which are

converted into 64 kbit/s PCM signals. The 64 kbit/s PCM signals are transmitted to the Ainterface board through the TNUa board and then to the MSC over the A interface.


Abis over IP and A over TDMFigure 5-5 shows the CS signal flow in Abis over IP, Ater over TDM, A over TDM, and BM/TC separated mode.

NOTE

l The Abis interface board can be the PEUa/FG2a/GOUa/POUc/FG2c/GOUc board, and the Ater and Ainterface boards can be the EIUa/OIUa/POUc board. The boards shown in Figure 5-5, Figure 5-6, andFigure 5-7 are only examples.




1. The uplink CS signals are sent from the BTS to the Abis interface board in the MPS/EPS.2. The CS signals are transmitted from the Abis interface board to the DPUc board through

the SCUa board.3. The DPUc board reorders PTRAU frames, eliminates jitter, and converts PTRAU frames

into TRAU frames. Then, the TRAU frames are transmitted to the Ater interface boardthrough the TNUa board.

4. The CS signals are multiplexed in the Ater interface board in the MPS/EPS, and then aretransmitted to the Ater interface board in the TCS.





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Figure 5-6 shows the CS signal flow in Abis over IP, Ater over IP, A over TDM, and BM/TCseparated mode.




kbit/s timeslot and is transmitted to the Ater interface board through the SCUa board.3. The CS signals are multiplexed in the Ater interface board. Each full-rate CS signal uses a

16 kbit/s sub-timeslot, and each half-rate CS signal uses an 8 kbit/s sub-timeslot. The CSsignals are then transmitted to the Ater interface board in the TCS over the Ater interface.

4. The CS signals are demultiplexed in the Ater interface board of the TCS. Each CS signaluses a 64 kbit/s timeslot and is transmitted to the DPUc board through the SCUa board.



In the case of BM/TC combined mode, the Ater interface does not exist. Figure 5-7 shows theCS signal flow in Abis over IP and A over TDM mode.






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1. The uplink CS signals are sent from the BTS to the Abis interface board in the MPS/EPS.

2. The CS signals are transmitted to the DPUc board through the SCUa board.

3. The DPUc board reorders PTRAU frames, eliminates jitter, and performs speech codec andrate adaptation on the PTRAU frames, which are converted into 64 kbit/s PCM frames.

4. The PCM frames are transmitted to the A interface board through the TNUa board, andthen are transmitted to the MSC over the A interface.


Abis over TDM and A over IP

In the case of A over IP, the Ater interface does not exist. Figure 5-8 shows the CS signal flowin Abis over TDM and A over IP transmission mode.

NOTE

l The Abis interface board can be the EIUa/OIUa/POUc board, and the A interface board can be the FG2a/GOUa/FG2c/GOUc/POUc board. The boards shown in Figure 5-8 are only examples.




1. The uplink CS signals are sent from the BTS to the Abis interface board in the MPS/EPS.

2. The CS signals are demultiplexed in the Abis interface board. Each CS signal uses a 64kbit/s timeslot and is transmitted to the DPUc board through the TNUa board.

3. The DPUc board converts PTRAU frames into RTP frames, reorders RTP frames, andeliminates jitter.

4. The SCUa board transmits the CS signals to the A interface board, which then transmitsthe signals to the MGW over the A interface.


Abis over IP and A over IP

In the case of A over IP, the Ater interface does not exist. Figure 5-9 shows the CS signal flowin Abis over IP and A over IP transmission mode.



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NOTE

l The Abis interface board can be the PEUa/FG2a/GOUa/POUc/FG2c/GOUc board, and the A interface boardcan be the FG2a/GOUa/PEUa/FG2c/GOUc/POUc board. The boards shown in Figure 5-9 are onlyexamples.




1. The uplink CS signals are sent from the BTS to the Abis interface board in the MPS/EPS.2. The Abis interface board encapsulates the CS signals in PTRAU frames, which are then

transmitted to the DPUc board through the SCUa board.3. The DPUc board converts PTRAU frames into RTP frames, reorders RTP frames, and

eliminates jitter.4. The SCUa board transmits the CS signals to the A interface board, and then the A interface

board transmits the signals to the MGW over the A interface.


5.1.3 GSM PS Signal FlowAfter a PS connection is established in the GSM network, the MS and the network communicatewith each other through the PS signal flow. The GSM PS signal flow varies according to thetransmission mode adopted on the Abis interface.

Abis over TDMFigure 5-10 shows the PS signal flow in Abis over TDM transmission mode.

NOTE

l The Abis interface board can be the EIUa/OIUa/POUc board, and the Gb interface board can be the PEUa/FG2a/POUc/FG2c/GOUc board. The boards shown in Figure 5-10 are only examples.





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Figure 5-10 GSM PS signal flow (1)

As shown in Figure 5-10, the PS signal flow on the uplink is as follows:

1. The packet data is sent from the BTS to the Abis interface board in the MPS/EPS. The datauses one to four 16 kbit/s sub-timeslots on the Abis interface, depending on the modulationand coding scheme, for example, CS1-CS4 or MCS1-MCS9.

2. The Abis interface board transmits the packet data to the TNUa board, which then transmitsthe data to the DPUd board.

3. The DPUd board converts the frame format and then transmits the data to the Gb interfaceboard through the SCUa board.

4. The Gb interface board processes the packet data according to the IP or FR protocol andthen transmits it to the SGSN over the Gb interface.


Abis over IPFigure 5-11 shows the PS signal flow in Abis over IP transmission mode.

NOTE

l The Abis interface board can be the PEUa/FG2a/GOUa/POUc/FG2c/GOUc board, and the Gb interfaceboard can be the PEUa/FG2a/POUc/FG2c/GOUc board. The boards shown in Figure 5-11 are onlyexamples.


Figure 5-11 GSM PS signal flow (2)



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As shown in Figure 5-11, the PS signal flow on the uplink is as follows:

1. The packet data is sent from the BTS to the Abis interface board in the MPS/EPS.

2. The SCUa board transmits the packet data to the DPUd board.

3. The DPUd board converts the frame format and then transmits the data to the Gb interfaceboard through the SCUa board.

4. The Gb interface board processes the packet data according to the IP or FR protocol andthen transmits it to the SGSN over the Gb interface.


5.2 Control-Plane Signal FlowThe control plane of the BSC6900 processes the control-plane messages on each interface.

5.2.1 Signaling Flow on the A InterfaceThe signaling flow on the A interface refers to the signaling messages transmitted between theBSC6900 and the MGW/MSC. The signaling flow varies according to the transmission modeadopted on the A interface.

5.2.2 Signaling Flow on the Abis InterfaceThe signaling flow on the Abis interface refers to the signaling messages transmitted betweenthe BSC6900 and the base station. The signaling flow varies according to the transmission modeadopted on the Abis interface.

5.2.3 Signaling Flow on the Gb InterfaceThe signaling flow on the Gb interface refers to the signaling messages transmitted between theBSC6900 and the SGSN.

5.2.4 Signaling Flow on the Pb InterfaceThe signaling flow on the Pb interface refers to the signaling messages transmitted between theBSC6900 and the external PCU.

5.2.1 Signaling Flow on the A InterfaceThe signaling flow on the A interface refers to the signaling messages transmitted between theBSC6900 and the MGW/MSC. The signaling flow varies according to the transmission modeadopted on the A interface.

A over TDM

In A over TDM mode, the signaling flow on the A interface varies according to the configurationmode of BSC6900 subracks.

l Figure 5-12 shows the signaling flow on the A interface in BM/TC separated mode.

l Figure 5-13 shows the signaling flow on the A interface in BM/TC combined mode.

NOTE

l The A interface board can be the EIUa/OIUa/POUc board, and the XPUa/XPUb board processes signaling.The boards shown in Figure 5-12 and Figure 5-13 are only examples.





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Figure 5-12 Signaling flow on the A interface in A over TDM mode (BM/TC separated)

As shown in Figure 5-12, the uplink signaling flow on the A interface is as follows:

1. In the MPS/EPS, the XPUa board processes the signaling according to the MTP3, SCCP,and BSSAP protocols. Then, the signaling is transmitted to the Ater interface board throughthe SCUa board.

2. The Ater interface board processes the signaling according to the MTP2 protocol. Then,the signaling is transmitted to the Ater interface board in the TCS.

3. In the TCS, the Ater interface board transparently transmits the signaling to the TNUa boardand then to the A interface board. Then, the signaling is transmitted to the MSC over theA interface.


Figure 5-13 Signaling flow on the A interface in A over TDM mode (BM/TC combined)


1. In the MPS/EPS, the XPUa board processes the signaling according to the MTP3, SCCP,and BSSAP protocols. Then, the signaling is transmitted to the A interface board throughthe SCUa board.

2. The A interface board processes the signaling according to the MTP2 protocol. Then, thesignaling is transmitted to the MSC over the A interface.


A over IPFigure 5-14 shows the signaling flow on the A interface in A over IP mode.



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NOTE

l The A interface board can be the FG2a/GOUa/FG2c/GOUc/POUc board, and the XPUa/XPUb boardprocesses signaling. The boards shown in Figure 5-14 are only examples.


Figure 5-14 Signaling flow on the A interface in A over IP mode


1. In the MPS/EPS, the XPUa board processes the signaling according to the BSSAP, SCCP,SCTP, and M3UA protocols. Then, the signaling is transmitted to the A interface boardthrough the SCUa board.

2. The A interface board processes the signaling according to the IP protocol. Then, thesignaling is transmitted to the MSC server through the MGW.


5.2.2 Signaling Flow on the Abis InterfaceThe signaling flow on the Abis interface refers to the signaling messages transmitted betweenthe BSC6900 and the base station. The signaling flow varies according to the transmission modeadopted on the Abis interface.

Abis over TDMFigure 5-16 shows the signaling flow on the Abis interface in Abis over TDM mode.

NOTE

l The Abis interface board can be the EIUa/OIUa/POUc board, and the XPUa/XPUb board performs signalingprocessing. The boards shown in Figure 5-15 are only examples.





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Figure 5-15 Signaling flow on the Abis interface in Abis over TDM mode

As shown in Figure 5-15, the uplink signaling flow on the Abis interface is as follows:

1. The signaling from the BTS is transmitted to the Abis interface board in the MPS/EPS overthe Abis interface and is then transmitted to the SCUa board.

2. The SCUa board transmits the signaling to the signaling processing board.


Abis over IPFigure 5-16 shows the signaling flow on the Abis interface in Abis over IP mode.

NOTE

l The Abis interface board can be the FG2a/GOUa/PEUa/FG2c/GOUc/POUc board, and the XPUa/XPUbboard performs signaling processing. The boards shown in Figure 5-16 are only examples.


Figure 5-16 Signaling flow on the Abis interface in Abis over IP mode

As shown in Figure 5-16, the uplink signaling flow on the Abis interface is as follows:

1. The signaling from the BTS is transmitted to the Abis interface board in the MPS/EPS overthe Abis interface.

2. The Abis interface board processes the signaling according to the MAC, IP, and UDPprotocols. Then, the signaling is transmitted to the signaling processing board through theSCUa board.




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5.2.3 Signaling Flow on the Gb InterfaceThe signaling flow on the Gb interface refers to the signaling messages transmitted between theBSC6900 and the SGSN.

Figure 5-17 shows the signaling flow on the Gb interface.

NOTE

l The Gb interface board can be the PEUa/FG2a/POUc/FG2c board, and the XPUa/XPUb board performssignaling processing. The boards shown in Figure 5-17 are only examples.


Figure 5-17 Signaling flow on the Gb interface

As shown in Figure 5-17, the uplink signaling flow on the Gb interface is as follows:

1. In the MPS/EPS, the signaling processing board processes the signaling according to theNS and BSSGP protocols. Then, the signaling is transmitted to the Gb interface boardthrough the SCUa board.

2. The Gb interface board processes the signaling according to the IP or FR protocol. Then,the signaling is transmitted to the SGSN over the Gb interface.


5.2.4 Signaling Flow on the Pb InterfaceThe signaling flow on the Pb interface refers to the signaling messages transmitted between theBSC6900 and the external PCU.

Figure 5-18 shows the signaling flow on the Pb interface.

NOTE

l The Pb interface board can be the EIUa/OIUa/POUc board, and the XPUa board performs signalingprocessing. The boards shown in Figure 5-18 are only examples.





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Figure 5-18 Signaling flow on the Pb interface

As shown in Figure 5-18, the uplink signaling flow on the Pb interface is as follows:

1. In the MPS/EPS, the signaling processing board processes the signaling according to theIP and RR protocols. Then, the signaling is transmitted to the Pb interface board throughthe SCUa board.

2. The Pb interface board processes the signaling according to the LAPD protocol. Then, thesignaling is transmitted to the PCU over the Pb interface.


5.3 OM Signal FlowOM signal flow refers to the messages transmitted between the BSC6900 and the LMT/M2000.The LMT or M2000 maintains and monitors the BSC6900 in real time through the OM signalflow.

NOTE

The physical entity of the OMU can be the OMUa board, OMUb board, or GBAM. The following takes theOMUa board as example to describe environment monitoring.

The OM signal flow varies according to the configuration mode of subracks.

Scenario 1: BM/TC SeparatedFigure 5-19 shows the OM signal flow in the BSC6900 in BM/TC separated mode.



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Figure 5-19 OM signal flow (BM/TC separated)

As shown in Figure 5-19, the OM signal flow in the BSC6900 is as follows:

l OM signal flow in the MPS

1. The OM signal is transmitted from the LMT or M2000 to the OMUa board in theMPS.

2. After the OM signal is processed by the OMUa board, it is transmitted to the SCUaboard through the backplane of the MPS.

3. The SCUa board then transmits the OM signal to the service boards to be maintained.l OM signal flow in the EPS


2. After the OM signal is processed by the OMUa board, it is transmitted to the SCUaboard through the backplane of the MPS.

3. The SCUa board in the MPS transmits the OM signal to the SCUa board in the EPSthrough the Ethernet cable between the SCUa boards.

4. In the EPS, the SCUa board transmits the OM signal to the service boards to bemaintained.

l OM signal flow in the TCS


2. After being processed by the OMUa board, the OM signal is transmitted to the SCUaand Ater interface boards through the backplane of the MPS.

3. The OM signal is transmitted from the Ater interface board in the MPS to the Aterinterface board in the main TCS through the E1/T1 or optical cable between the Aterinterface boards. In the main TCS, the OM signal is transmitted from the Ater interfaceboard to the SCUa board through the backplane.




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4. In the main TCS, the backplane switches the signal from the SCUa board to the serviceboards to be maintained. The OM signal is transmitted from the SCUa board in themain TCS to the SCUa board in the extension TCS through the Ethernet cable betweenthe SCUa boards. In the extension TCS, the backplane switches the signal from theSCUa board to the service boards to be maintained.

Scenario 2: BM/TC Combined

In BM/TC combined mode, no TCS is configured. Figure 5-20 shows the OM signal flow.

Figure 5-20 OM signal flow (BM/TC combined)

As shown in Figure 5-20, the OM signal flow in the BSC6900 is as follows:

l OM signal flow in the MPS


2. After the OM signal is processed by the OMUa board, it is transmitted to the SCUaboard in the MPS through the backplane of the MPS.

3. The SCUa board then transmits the OM signal to the service boards to be maintained.

l OM signal flow in the EPS


2. After the OM signal is processed by the OMUa board, it is transmitted to the SCUaboard in the MPS through the backplane of the MPS.

3. The SCUa board in the MPS transmits the OM signal to the SCUa board in the EPSthrough the Ethernet cable between the SCUa boards.

4. In the EPS, the SCUa board transmits the OM signal to the service boards to bemaintained.

Scenario 3: A over IP

In BM/TC combined mode, no TCS is configured, and the TC function is performed by themedia gateway (MGW). The OM signal flow in A over IP mode is the same as that in BM/TCcombined mode.



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bsc6900 gsm signal flow

Documents

cell broadcast center

transmission mode adopted

ip transmission mode

dpud board converts

bm tc separated mode

bm tc combined mode

reorders rtp frames

ps signal flow