2. 2
MSC Pool
Traffic Distribution
– BSC/RNC distributes subscribers roaming into the pool area among the MSCs.
– Subscribers remain registered in the same MSC until they roam out of the pool
area.
Service Area 1
MSCMSC
BSC/
RNC
BSC/
RNC
Service Area 2
MSCMSC
Service Area 3
MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
Pool Service Area
MSCMSC
BSC/
RNC
BSC/
RNC
MSCMSC MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
Traffic distribution
based on relative
MSC capacity
Reduced load, as
less Handover and
Location Update
traffic.
MSC MSC MSC
No impacts on
terminals.
3. 3
Relative Capacity
Factor (1-255),
defined in BSC
Resulting
Traffic
in %
MSC1 4 50%
MSC2 2 25%
MSC3 2 25%
Relative Capacity
Factor (1-255),
defined in BSC
Resulting
Traffic
in %
NRI (0-1023),
defined in MSC
and BSC
MSC1 4 50% 1, 2, 3, 4
MSC2 2 25% 5, 6
MSC3 2 25% 7, 8
MSC1MSC1
BSC/
RNC
BSC/
RNC
MSC2MSC2 MSC3MSC3
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
Pool Service Area
MSC Pool
Traffic Distribution, Example of Location Updating with IMSI
– BSC distributes subscribers roaming into the pool area among the MSCs.
– Subscribers remain registered in the same MSC until they roam out of the pool
area.
BSC selects one MSC,
according to the relative
MSC capacity factors.
BSC selects MSC1.
Location
Update
(IMSI)
Subscriber roams into
the pool.
MSC assigns a TMSI,
including a NRI. The
NRI identifies the MSC.
Temporary Mobile Subscriber Identity (TMSI)
TMSI
Generation
Network Resource
Identifier (NRI)
TMSI
Identification
TMSI Assignment
(TMSI incl. NRI=1)
4. 4
MSC1MSC1
BSC/
RNC
BSC/
RNC
MSC2MSC2 MSC3MSC3
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
Pool Service Area
MSC Pool
Traffic Distribution, Example of Call Setup
– BSC routes the traffic towards the MSC identified by the NRI
BSC routes the traffic
to the MSC identified
by the NRI. “Call Setup”
(TMSI incl.
NRI=1)Subscriber,
registered in the pool,
initiates now a call.
MSC verifies NRI and
handles call as normal.
Temporary Mobile Subscriber Identity (TMSI)
TMSI
Generation
Network Resource
Identifier (NRI)
TMSI
Identification
“Call Continue”
Relative Capacity
Factor (1-255),
defined in BSC
Resulting
Traffic
in %
NRI (0-1023),
defined in MSC
and BSC
MSC1 4 50% 1, 2, 3, 4
MSC2 2 25% 5, 6
MSC3 2 25% 7, 8
5. 5
MSC Pool
Load Distribution
Service Area 1
MSCMSC
BSC/
RNC
BSC/
RNC
Service Area 2
MSCMSC
Service Area 3
MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
Pool Service Area
MSCMSC
BSC/
RNC
BSC/
RNC
MSCMSC MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
– The load is distributed over the MSCs in the pool. No load peaks in individual MSCs.
– Pooling gives more capacity, as the existing capacity is utilized more efficiently.
MSC MSC MSC
MSC MSC MSCMSCMSC
MSCMSC MSCMSC MSCMSC
High Risk for
Congestion
No Risk for
Congestion
Simplified
dimensioning
and planning.
6. 6
MSC Pool
Scaleable Capacity
Pool Service Area
MSCMSC
BSC/
RNC
BSC/
RNC
MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
– Number of pool members can be increased over time to match the traffic growth
no complex BSC/RNC re-homing
Service Area 1
MSCMSC
BSC/
RNC
BSC/
RNC
Service Area 2
MSCMSC
BSCBSC BSCBSCBSC/
RNC
BSC/
RNC
BSCBSC
MSCMSC MSCMSC
MSCMSC MSCMSC
MSCMSCMSCMSC
MSCMSC MSCMSC
MSC
Service Area 2a Service Area 2b
MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
MSCMSCMSCMSCMSC MSCMSC
MSCMSCMSCMSC MSCMSCMSCMSC
Capacity
expansion by
service area split
(re-configuration
of radio network).
Simple capacity
expansion by
adding one MSC.
Independent RAN
and CN planning.
7. 7
MSC Pool
Redundancy
Service Area 1
MSCMSC
BSCBSC
Service Area 2
MSCMSC
Service Area 3
MSCMSC
BSCBSC BSCBSCBSCBSC BSCBSC
– When one MSC becomes unavailable (planned or unplanned) , the BSC/RNC
redistributes the mobiles when they access the network among the remaining MSCs.
Pool Service Area
MSCMSC
BSC/
RNC
BSC/
RNC
MSCMSC MSCMSC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
BSC/
RNC
MSCMSC
MSCMSC
MSC MSC
– Redistribution time of all mobiles is the ~same as the periodic registration time.
– Incoming calls can be received, when the mobile station has been redistributed.
– Benefit:
Increased MSC In-Service Performance. “Zero” Down Time on MSC layer.
An MSC can be taken out for service in controlled and graceful way for
planned maintenance or upgrade when using load re-distribution.
“Zero” Down
Time.
Increased ISP.
