Università degli studi di Roma “ “Tor Vergata” ” Corso di Laurea Magistrale in Internet Engineering Handover and Call Control Application Presentation Application Session Transport Transport Network Internet Data Link Network Interface Physical Layer Physical
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Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Handover and Call ControlApplication
Presentation Application
Session
Transport Transport
Network Internet
Data Link Network Interface
Physical Layer Physical
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Handover generalities• In the case of relative motion between satellites and users the
link geometry variation imposes the dynamic modification of active connections, i.e. handover.
• Different types of handover:– Handover between satellites– Handover between on-board spots– Handover between GESs– Handover between segments (chapter 17)
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21485Globalstar
10278Iridium
Minimum (s)Mean (s)
Time between handoversHandover between satellites
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/3
MAHO
Handover Procedure Schemes
Backward Handover
Forward Handover
Signalling Diversity
Hard Handover
Soft Handover
NAHO
MCHO
NCHO
Execution Phase
Decision Phase
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/4
HANDOVER STRATEGIES
Handover strategies
Controlling schemes
NCHO NAHO MCHO MAHO
Connection establishment
scheme
BWHO FWHO
Connection transference
scheme
SWHO
SWHO CBHO
HDHO DVHO
SWHO: SWITCHED HOCBHO: COMBINED HO
SWHO: SOFT HOHDHO: HARD HODVHO: DIVERSITY HO
BWHO: BACKWARD HOFWHO: FORWARD HOMAHO: MOBILE ASSISTED HO
MCHO: MOBILE CONTROLLED HONAHO: NETWORK ASSISTED HONCHO: NETWORK CONTROLLED HO
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Characteristics of handover controlling schemes
MCHO NCHO MAHO NAHOHandover process Centralized Centralized Decentralized DecentralizedTerminal complexity High Low Moderate HighSpeed of handover Fast Slow SlowSignaling load Low Low High HighReliability Moderate Moderate High High
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Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/6
Hard handover
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
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Soft Handover- Switched diversity HO
Before handover
Tr ansition stage – preparation of target links
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/8
Soft Handover- combined diversity HO
Before handoverTransition stage – preparation of target links
After handover
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/9
Signalling Diversity
Before Handover
traffik link signaling link
transition stage – preparation of target links
traffic link signaling link
After Handover
traffic link signaling link
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
HO and constellationsGEO HEO MEO LEO
User Typology Mobile Fixed Mobile Fixed Mobile Fixed Mobile Fixed
Satellite HO Not critical - Not critical Not critical Critical Critical Very critical Critical
Spot HO Not critical - Not critical - Critical Critical Very critical Very critical
Gateway HO Not critical - - - Not critical Not critical Critical -
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Low altitudes and/or high number of spots:
Moving and multiple spots ⇒ All types of handoverFixed or single spot ⇒ No spot handover
Handover and types of local area coverage
• increased probability of spot handover• reduced available time to end the procedure
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Call Control and Handoff Control procedures for UMTS satellite access link
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Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Scenario
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ISDN PSTN IP LAN
NetworkGW Terminal
Characteristicsü LEO satellite constellation
ü CDMA access system
ü Satellite diversity
ü GW controlled system
MT
Sat#1Sat#2
Sat#3
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Forward Link
• DPDCH (Dedicated Physical Data Channel) carries the following logical channels:
– DTCH (Dedicated traffic Channel) supports user traffic.
– DCCH (Dedicated Control Channel) supports in band signalling for control procedures.
• CCPCH (Common Control Physical Channel) carries the following logical channel:
– FACH (Forward Access Channel) supports out of band signalling for control procedures.
• DPDCH (Dedicated Physical Data Channel) carries the following logicalchannels:
– DTCH (Dedicated traffic Channel) supports user traffic.
– DCCH (Dedicated Control Channel) supports in band signalling for control procedures.
• Il PRACH (Physical Random Access Channel) carries the following logicalchannel:
– RACH (Random Access Channel) supports out of band signalling for control procedures.
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MT GWDPDCH
CCPCH
MTGW
DPDCH
PRACH
Return Link
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering