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

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)

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

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

5. Inter-Frequency Hard Handoff
CFSRPM
(Report)
CRSCNM (Search Order)
F1 (serving)
F2 (candidate)
GHDM (HHO)
CRSRQM (Search Parameters)
CFSRSM
(Acceptance)

6. Candidate Frequency Search

7. Inter-freq. Handoff Failure Recovery
1. On Traffic Ch. on F 1
w/o Search Set ,
Reports on SS +
CFSReqM,
intended Active Set
CFSReqM, CF=F 2 ,
Search Set
CF=F 2 ,
Search
on F 2
= {P 1
,...,P n
}, start periodic
Set = {P 1
,...,P n }
EHDM to F 2
, periodic
Send s
Send s
off, HHO fails
CFSRspM
CFSRspM
2. On F 1
, Search Set on F 2
, no
periodic search
EHDM to F 2 ,
periodic on,
Reports on SS +
HHO fails
intended Active
CFSC
M, F 2 ,
CFSCM
, F 2 ,
Set on F
Reports on 2
periodic on
periodic off
SS + intended
Active Set
EHDM to F 2 ,
on F 2
periodic off,
HHO fails
3. Periodically searches for
Search Set on F 2
from F 1
Reports on
EHDM to F 2 ,
SS + intended
Active Set
periodic on,
on F
HHO fails 2
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
HHO Fig. 2 IS-95-B Inter-freq. Hard Handoff Example
(All hard handoffs fail)

8. 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 technology improves, performance increases

9. cdma2000 Forward Link HHO Searching
Method can be used when excursion is less than 10 ms
Forward Link Transmitted Power

10. IF HHO Performance Example on RL

11. IF HHO Performance Example on RL