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

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)

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

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

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

Candidate Frequency Search

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)

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

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

IF HHO Performance Example on RL

IF HHO Performance Example on RL