Handover and Call Control
Transcript of Handover and Call Control
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)
Internet via Satellite (AA2017/18) P8/2
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
Internet via Satellite (AA2017/18) P8/5
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
Internet via Satellite (AA2017/18) P8/7
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 -
Internet via Satellite (AA2017/18) P8/10
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
Internet via Satellite (AA2017/18) P8/11
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Scenario
Internet via Satellite (AA2017/18) P8/12
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.
Internet via Satellite (AA2017/18) P8/13
MT GWDPDCH
CCPCH
MTGW
DPDCH
PRACH
Return Link
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Logical channels over dedicated physical channel
Internet via Satellite (AA2017/18) P8/14
Slot #1 Slot #2 SSlloott ## ii Slot #Ns
PilotNpilot bits
TPCNtpc bits
RINri bits
DataNdata Bits
DDPPCCCCHH DDPPDDCCHH
TTff ==1100 mmss ((TTBBCC))
Frame #1 Frame #2 FFrraammee ## ii Frame #Nf
TTssuuppeerr == 772200 mmss
TTss== 00..662255mmss ((TTBBCC)),, 2200**22 bbiittss ((kk==00 ......66))kk
DPDCH = Dedicated Phisical Data Channel = DCCH + DTCHDCCH = Dedicated Control ChannelDTCH = Dedicated Traffic Channel
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Call Control Procedures • Include all the functionality to set up, maintain and tear down the dedicated
physical channel necessary to transfer both user traffic and in band signalling(Dedicated Physical Data Channel)
Internet via Satellite (AA2017/18) P8/15
Ø Registration Ø Handoff Control
• Involves MT and GW; initiated by MT• Allows GW to know of the presence of
MT in its coverage area• Such info is used by GW for paging
function in case of Call Setup initiatedby remote users (or by GW)
• Localization imposed by:Ø Terminal mobilityØ Satellite mobility (LEO, MEO)
• Control messages are exchanged usingRACH and FACH channels for out of band signalling (dedicated channelDCCH is not available)
• Both on MT and GW side• It can be initiated by both MT and GW• Allows, on demand, to set up a DTCH
for user traffic between MT and terrestrial network and viceversa
• If initiated by GW, it is based on pagingfunction
• The channels utilized to exchangecontrol messages are:Ø RACH and FACH for out of band
signalling,Ø DCCH, when DPDCH is available
• Call Setup procedure ends whenDPDCH is succesfully set up or not
Registration Call SetupØ Call Setup Ø Call Teardown
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Handover
• Involves both MT and GW• Initiated by GW on the basis of
measurements performed by MT (MAHO) (design option)
• Due to– Terminal mobility– Satellite mobility (LEO)
• Diversity is supported• Soft handover• Control messages are
exchanged through DCCH• Handover procedure ends on
demand (Teardown) or in case of loss of coverage
• Both on MT and on GW side, can be initiated both by MT and by GW
• Can be initiated both explicitly by the terminal and by HO procedure
• DPDCH is released• Control messages are
exchanged through DCCH• Ends always successfully
Internet via Satellite (AA2017/18) P8/16
Teardown
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Inter-satellite and inter-beam handovers
Internet via Satellite (AA2017/18) P8/17
Sat#2Sat#1
MT
MT
GW
Sat
GW
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
State transition diagram (MT)
Internet via Satellite (AA2017/18) P8/18
REGISTRATION HANDOVER
MT_CALLSETUP MT_TEARDOWN
GW_TEARDOWNGW_CALLSETUP
end
end
end
end (positive outcome)
end (negative outcome)
Callteardown requestfrom remote system
(GW)
callteardown request
from local user
Callsetup requestfrom remote system
(GW)
Callsetup requestfrom local user
Sistem start
Mobile Terminal:
end (negative outcome)
end (positive outcome)
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Interfaces - control plane
Internet via Satellite (AA2017/18) P8/19
MT-CCU
MT-PIU
MT-UI
MT
GW-CCU
GW-PIU
GW-UI
GW
DCCH
RACHDCCH
FACH
user interface
call control unit
physical layercontrol interface unit
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Registration
Internet via Satellite (AA2017/18) P8/20
Gateway:
Mobile Terminal:
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/21
MT_NFSE(MTCCU)
GW_NFSE(GWCCU)
MT.REG.REQ
GW.REG.ACK
PIUMT
PIUGW
MT.COV.REQMT.COV.RESP
MT.REG.REQ
MT.COV.REQMT.COV.RESP
GW.REG.ACK
RACH
FACH
RACH
FACH
ETH ETHHW-SAT.SIM
START START
WAIT REGIST
STAND-BY STAND-BY
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Call Setup initiated by MT
Internet via Satellite (AA2017/18) P8/22
Gateway:
Mobile Terminal:
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/23
MT.CODE.ACK
GW.CODE.SETFACH
RACH
MT.CODE.SET.REQMT.CODE.SET.RESP
MT.FL.ACKRACH
GW.CODE.SET.REQGW.CODE.SET.RESP
GW.FL.DUMMY
FL-DPDCH
MT.RL.DUMMY
RL-DPDCH
GW.RL.ACKFL-DPDCH
.
.
.
.
MT_NFSE
(MTCCU)
GW_NFSE(GWCCU)
MT_PIU GW_PIUETH ETHHW-SAT.SIM
MT.CALL.REQRACH
MT.COV.REQMT.COV.RESP
START STAND-BY
WAIT CALLPROC
WAIT
SYNC
CALL
SETUP
SYNC
CALL
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Call Setup initiated by GW
Internet via Satellite (AA2017/18) P8/24
Gateway:
Mobile Terminal:
STAND-BY CALL PROC SETUPWAIT
GW.CALL.REQ MT.CALL.ACK
ERROR
GW.CODE.SETUP
TEAR DOWN
ERRORSYNC
MT.CODE.ACK
TIME-OUT
CALL
ERROR SYNC.ACK
START WAIT CALL ACK
WAIT CODE ACK
CODE DEF
GW.CALL.REQ MT.CALL.ACK
TIME-OUT
GW.CODE.SETUP
TEAR DOWN
TIME-OUTSYNC
MT.CODE.ACK
ERROR
CALL
ERROR SYNC.ACK
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/25
MT.CODE.ACK
GW.CODE.SETFACH
RACH
MT.CODE.SET.REQMT.CODE.SET.RESP
MT.FL.ACKRACH
GW.CODE.SET.REQGW.CODE.SET.RESP
GW.FL.DUMMY
FL-DPDCH
MT.RL.DUMMY
RL-DPDCH
GW.RL.ACKFL-DPDCH
.
.
.
.
MT_NFSE
(MTCCU)
GW_NFSE(GWCCU)
MT_PIU GW_PIUETH ETHHW-SAT.SIM
MT.CALL.ACKRACH
MT.COV.REQMT.COV.RESP
GW.CALL.REQFACH
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Handover
Internet via Satellite (AA2017/18) P8/26
Gateway:
Mobile Terminal:
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/27
MT_NFSE(MTCCU)
GW_NFSE(GWCCU)
MT.COV.REFR
GW.COV.ACK
MT_PIU GW_PIU
MT.COV.REQMT.COV.RESP
RL-DPDCH
FL-DPDCH
HW-SAT.SIM.
ETHETH
MT.COV.REQMT.COV.RESP
MT.COV.REFR
GW.COV.ACKRL-DPDCH
FL-DPDCH
.
.
.
.
.
Università degli studi di Roma ““Tor Vergata””Corso di Laurea Magistrale in Internet Engineering
Internet via Satellite (AA2017/18) P8/28
MT_NFSE(MTCCU) GW_NFSE
(GWCCU)MT_PIU GW_PIU
GW.CODE.ADD.REQ
GW.CODE.ADD.RESP
MT.COV.REQMT.COV.RESP
MT.CODE.ADD.REQMT.CODE.ADD.RESP
MT.ADD.ACK
GW.SYNC.REQ
MT.CODE.SYNC.REQMT.CODE.SYNC.RESP
RL-DPDCH
FL-DPDCH
HW-SAT.SIM.
ETHETH
MT.DROP.ACKRL-DPDCH
MT.CODE.DROP.REQMT.CODE.DROP.RESP
REQ
DROP
ADD
MT.CODE.DROP.REQMT.CODE.DROP.RESP
MT.COV.REFR
GW.HO.REQ
RL-DPDCH
FL-DPDCH