Post on 08-Nov-2014
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Section 3:cdma2000 Handoff
1
Soft Handoff
• Soft handoff for MC 1X and DS works as in IS-95-B
• Soft handoff for MC 3X is a straightforward extension of that in MC 1X
– Ec/I0 used is the sum of the Ec/I0 on all three carriers
Section 3:cdma2000 Handoff
2
Inter-Frequency Hard Handoff
• Inter-Frequency Hard Handoff (HHO) required in following situations– Handoff between operators in different bands
– Handoff between different CDMA RF carriers for congestion control
– Handoff from a (private) micro-cell to a macro-cell
– Handoff between different radio technologies (CDMA to AMPS, GSM, …, OHG DS)
Section 3:cdma2000 Handoff
3
Messages for HHO
• CFSRQM (Candidate Frequency Search Request Message)
– BS informs MS about» Candidate Freq. Neighbor List (CFNL)
» Candidate Freq Search Set (CFSS), a subset of CFNL
» Freq. band and channel number
» Search Period (for Periodic Search)
» Thresholds (MS Rx power and total pilot Ec/I0, etc.)
» Can specify a search for AMPS (other formats can be added) -MS support is optional
» Optionally, can synchronize timing between MS and BS
– Can also start search
• CFSRSM (Candidate Frequency Search Response Message)
– MS replies to CFSRQM» Dead time to search entire CFSS (fwd and rev)
» Dead time per visit to candidate frequency (fwd and rev)• Dead time can be specified in frames or in 1.25 ms slots
Section 3:cdma2000 Handoff
4
Messages for HHO (cont.)
• CFSCNM (Candidate Frequency Search Control Message)
– To start and stop searches (periodic or single)
• GHDM (General Handoff Direction Msg)
– Contains flags to specify» Use of this procedure upon HHO failure
• CFRSPM (Candidate Frequency Search Report Message):
– MS reports to BS on the serving freq» MS rx power on candidate freq.
» Pilots above T_ADD
» Sent in periodic search only if total Ec/I0 of Candidate Freq. Search Set is above threshold
» All pilot measurements have to be made within 0.8 sec. of the report
Section 3:cdma2000 Handoff
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Inter-Frequency Hard Handoff
CFSRPM(Report)
CRSCNM(Search Order)
F1 (serving)
F2 (candidate)
GHDM(HHO)
CRSRQM(Search Parameters)
CFSRSM(Acceptance)
Section 3:cdma2000 Handoff
6
Candidate Frequency Search
CFSCM, F2,
periodic off
Searches &reports F2
Reports on F2
Total Ec/Io of pilots in SSabove CF_T_Add
exceeds Threshold from CFNLM
3. Periodically searches forSearch Set on F2 from F1
2. On F1, Search Set on F2, no
periodic search
CFSCM, F2,
periodic on
HHO Fig. 1 IS-95B Inter-freq. Hard Handoff Mobile Example(All handoffs successful)
EHDM to F3,
periodic off
EHDM to F2,
periodic on/off
4. On F2, Search Set on F2, no
periodic search
EHDM to F2,
periodic on/off
Notes: -CF: Candidate Freq. -SS: Search Set -CFSReqM: CF Search Request Msg -CFSRspM: CF Search Response Msg -SS update by CFSRegM not shown -Hard handoff failure not shown -Not all EHDM shown -Handoff Completion Msg omitted
CFSReqM, CF=F2,
Search Set ={P1,...,Pn}
SendsCFSRspM
6. Periodically searches forSearch Set on F2 from F3
5. On F3, Search Set on F2, no
periodic search
EHDM, to F3,
periodic on
EHDM, to F3,
periodic off
EHDM to F3,
periodic on
CFSCM, F2,
periodic off
1. On Traffic Ch. on F1,
w/o Search Set
CFSReqM, CF=F2,
Search Set = {P1,...,Pn},
Start Periodic
SendsCFSRspM
Section 3:cdma2000 Handoff
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Inter-freq. Handoff Failure Recovery
3. Periodically searches forSearch Set on F 2 from F1
2. On F1, Search Set on F 2, no
periodic search
CFSCM, F2,
periodic on
HHO Fig. 2 IS-95-B Inter-freq. Hard Handoff Example(All hard handoffs fail)
EHDM to F2,
periodic off,HHO fails
EHDM to F2,
periodic on,HHO fails
Notes: -CF: Candidate Freq. -SS: Search Set -CFSReqM: CF Search Request Msg -CFSRspM: CF Search Response Msg -SS update by CFSReqM not shown -Not all EHDM shown
Reports on SS +intended Active
Set on F2CFSCM, F2,
periodic off
Reports on SS +intended Active Set
on F2
EHDM to F2, periodic
off, HHO failsSendsCFSRspM
CFSReqM,CF=F2, Search
Set = {P1,...,Pn}
1. On Traffic Ch. on F1,w/o Search Set
EHDM to F2,
periodic on, HHO fails
Reports onSS + intended
Active Set on F2
Reports onSS + intended
Active Set on F2
SendsCFSRspM
CFSReqM, CF=F2, Search Set
= {P1,...,Pn}, start periodic
Section 3:cdma2000 Handoff
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cdma2000 Inter-Frequency HHO Improvements
• To minimize interruptions during search excursions:– MS can store pilot samples while on target frequency and process
them offline (when returning to originating frequency)
– Forward link target Eb/Nt theshold is increased before search excursion; Viterbi decoder uses additional symbol energy to decode frame successfully
– Reverse link traffic to pilot ratio for code channel increased
If synthesizer can be tuned fast enough, no frames are lost
– No complex BS-MS coordination required for search
– As RF phone technologyimproves, performance increases
Section 3:cdma2000 Handoff
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cdma2000 Forward Link HHO Searching
• Method can be used when excursion is less than 10 ms
tsearchN PCG
regular power controlMS sends up
commands to ramp uppower before search
PC is random
regular powercontrol resumes
MS tunes toanother
frequency
MS returnsfrom search
Fra
me
Bou
ndar
y
Fra
me
Bou
ndar
y
MS increasestarget Eb/No by
target
MS decreasestarget Eb/No by
target
Forward Link Transmitted Power
Section 3:cdma2000 Handoff
10
IF HHO Performance Example on RL
9600, 5ms, Pilot Ec/Io = 3ms
0.00001
0.0001
0.001
0.01
0.1
1
3 3.5 4 4.5 5 5.5 6 6.5
Traffic/Pilot Ratio in dB
FE
R
120kph
30kph
5kph
awgn
Section 3:cdma2000 Handoff
11
IF HHO Performance Example on RL
9600, 5ms, Pilot Ec/Io = -23.75dB
0.000001
0.00001
0.0001
0.001
0.01
0.1
1
3 3.5 4 4.5 5 5.5 6 6.5 7
Traffic/Pilot Ratio in dB
FE
R
120kph
30kph
5kph
awgn