In brief, eNodeB select one MME based on IE:
Relative MME Capacity in S1 Setup Response,
S-GW and P-GW were selected by MME,
S-GW is selected based on TAI in S1AP message and P-GW is selected based on APN information
IPC
c LIBRARY
In telecommunications there may be different reasons why a handover might be conducted:
The most basic form of handover is when a phone call in progress is redirected from its current cell (called source) to a new cell (called target). In terrestrial networks the source and the target cells may be served from two different cell sites or from one and the same cell site (in the latter case the two cells are usually referred to as two sectors on that cell site). Such a handover, in which the source and the target are different cells (even if they are on the same cell site) is called inter-cell handover. The purpose of inter-cell handover is to maintain the call as the subscriber is moving out of the area covered by the source cell and entering the area of the target cell.
A special case is possible, in which the source and the target are one and the same cell and only the used channel is changed during the handover. Such a handover, in which the cell is not changed, is called intra-cell handover. The purpose of intra-cell handover is to change one channel, which may be interfered or fading with a new clearer or less fading channel.
219 327.012056000 192.168.0.241 192.168.0.16 S1AP 338 id-HandoverPreparation, HandoverRequired MasterInformationBlock SystemInformationBlock Type1SIB2
221 327.090744000 192.168.0.16 192.168.0.246 S1AP 394 id-HandoverResourceAllocation, HandoverRequest MasterInformationBlock SystemInformationBlock Type1SIB2
223 327.107316000 192.168.0.246 192.168.0.16 S1AP 250 SACK id-HandoverResourceAllocation, HandoverRequestAcknowledge RRCConnectionReconfiguration
225 327.130743000 192.168.0.16 192.168.0.241 S1AP 246 SACK id-HandoverPreparation, HandoverCommand RRCConnectionReconfiguration
226 327.136987000 192.168.0.241 192.168.0.16 S1AP 122 SACK id-eNBStatusTransfer
227 327.150732000 192.168.0.16 192.168.0.246 S1AP 122 SACK id-MMEStatusTransfer
229 327.188326000 192.168.0.246 192.168.0.16 S1AP 122 SACK id-HandoverNotification, HandoverNotify
SIG_DFL, SIG_IGN //sigaction - examine and change signal action
#define SIG_DFL /*implementation defined*/
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#define SIG_IGN /*implementation defined*/
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The SIG_DFL and SIG_IGN macros expand into integral expressions that are not equal to an address of any function. The macros define signal handling strategies for std::signal() function.
Constant | Explanation |
SIG_DFL |
default signal handling |
SIG_IGN |
signal is ignored |
S.N. | Macro & Description |
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1 | void va_start(va_list ap, last_arg) This macro initializes ap variable to be used with the va_arg and va_end macros. The last_arg is the last known fixed argument being passed to the function ie. the argument before the ellipsis. |
2 | type va_arg(va_list ap, type) This macro retrieves the next argument in the paramater list of the function with type type. |
3 | void va_end(va_list ap) This macro allows a function with variable arguments which used the va_start macro to return. If va_end is not called before returning from the function, the result is undefined. |