# 809 Introduction to CDMA v2.0

CDMA KEY TECHNOLOGY 2004.10.3 Copyright 2003, ZTE CORPORATION Objectives Upon completion of this lesson, the student will be able to master: -- Power control in CDMA why power control how to realize -- Handoff in CDMA what is handoff CDMAs soft handoff soft handoff procedure Copyright 2003, ZTE CORPORATION Why Power Control? All CDMA users occupy the same frequency at the same time! Frequency and time are not used as discriminators. CDMA operates by using CODES to discriminate between users. CDMA interference comes mainly from nearby users

Each user is a small voice in a roaring crowd -- but with a uniquely recoverable code. Transmit power on all users must be tightly controlled so their signals reach the base station at the same signal level and at the absolute minimum power level necessary to ensure acceptable service quality Copyright 2003, ZTE CORPORATION Figure of Merit: Ec/Io, Eb/No (energy per chip [bit] / interference [noise] spectral density) CDMA: Ec/Io -17 to -2 dB CDMA: Eb/No ~6to7 dB Reverse Open Loop Power Control Reverse Open Loop Power Control Mobile BTS The mobile station makes a coarse initial estimation of the required transmit power, based upon the total received power. Problems with Reverse Open Loop Power Control: Assumes same exact path loss in both directions; therefore, cannot account for asymmetrical path loss

Estimates are based on total power received; therefore the power received from other cell sites by mobile station introduces inaccuracies Copyright 2003, ZTE CORPORATION Estimated Reverse Open Loop Output Power Power output level for the initial probe during open loop probing on the Access Channel (with closed loop correction inactive): mean output power (dBm) = - mean power input (dBm) +K + NOM_PWR - 16 x NOM_PWR_EXT + INIT_PWR Subsequent probes in the sequence are sent at increased power levels (each probe is incremented by a value equal to the parameter PWR_STEP) The turn around constant K is calculated assuming a nominal cell Effective Radiation Power (ERP) of 5 W and a nominal cell loading of 50%. Its value is -73 for cellular systems and -76 for PCS systems Copyright 2003, ZTE CORPORATION Estimated Reverse Open Loop Output Power Power Poweroutput outputlevel levelfor forthe theinitial initialtransmission transmissionon onthe theReverse ReverseTraffic TrafficChannel: Channel: mean output power (dBm) = - mean power input (dBm)

+K + NOM_PWR - 16 x NOM_PWR_EXT + INIT_PWR + the sum of all access probe corrections (dB) Copyright 2003, ZTE CORPORATION Reverse Closed Loop Power Control Mobile BTS Reverse Closed Loop Power Control or Signal Strength Measurement Setpoint Compensates for asymmetries between the forward and reverse paths Consists of power up (0) & power down (1) commands sent to the mobile stations, based upon their signal strength measured at the Base Station and compared to a specified threshold Each command requests a 1dB increase or decrease of the mobile station transmit power Transmitted 800 times per second, always at full power Allows to compensate for the effects of fast fading Copyright 2003, ZTE CORPORATION Reverse Outer Loop Power Control Mobile BTS

Reverse Closed Loop Power Control BSC or Signal Strength Measurement Setpoint Reverse Outer Loop Power Control FER Most gradual form of reverse link power control Setpoint is varied according to the FER on the Reverse Traffic Channel (determined at the Base Station Controller) Sampled at a rate of 50 frames per second (20 ms / frame) Setpoint adjusted every 1-2 seconds Copyright 2003, ZTE CORPORATION Forward Traffic Channel Power Control Mobile BTS BSC Adjust Fwd. power FER Forward Link Power Control

The base station slowly decreases power to each mobile station. As the FER (determined at the mobile station) increases, the mobile station requests a Forward Traffic Channel power increase. Copyright 2003, ZTE CORPORATION Summary of All Power Control Mechanisms Reverse Open Loop Power Control Mobile BTS Reverse Closed Loop Power Control FER BSC or Signal Strength Measurement Setpoint Adjust Fwd. power Reverse Outer Loop Power Control FER

Forward Link Power Control All types of power control work together to minimizes power consumption at the mobile stations, and increases the overall capacity of the system transmit power. Copyright 2003, ZTE CORPORATION Handoffs Handoff is the process by which a mobile station maintains communications with the Mobile Telephone Switching center(MSC), when traveling from the coverage area of one base station to that of another. Handoffs keep the call established during the following conditions: Subscriber crosses the boundaries of a cell Subscriber experiences noise or other interference above a specified threshold A base station component experiences an out-of-service condition during a call Copyright 2003, ZTE CORPORATION CDMA Handoffs CDMA Cell Site B Cell Site B Cell Site A Cell Site A CDMA Handoffs Make-before-break

Directed by the mobile not the base station Undetectable by user Improves call quality Handoffs consist of the following phases: Initiation (trigger), Target Selection, and Completion (execution) Copyright 2003, ZTE CORPORATION CDMA Handoffs (cont.) While in the Idle State Idle Handoff Soft Handoff Softer Handoff During a Call Inter-System Soft Handoff CDMA-to-CDMA Handoff CDMA-to-Analog Handoff Copyright 2003, ZTE CORPORATION Soft Handoff PSTN Cell Site A MSC Cell Site B B S C

Soft Handoff: the mobile station starts communications with a target base station without interrupting communications with the current serving base station. Can involve up to three cells simultaneously and use all signals Mobile station combines the frames from each cell Copyright 2003, ZTE CORPORATION Softer Handoff alpha beta gamma Copyright 2003, ZTE CORPORATION Handoff is between sectors of the same cell Communications are maintained across both sectors until the mobile station transition has completed May happen frequently MSC is aware but does not participate All activities are managed by

the cell site Signals received at both sectors can be combined for improved quality Inter-System Soft Handoffs (ISSHO) E1 Links TIA/EIA-41D MSC MSC SVBS SVBS E1 Links HIRS AA f1 f1 BB f1 f1 CC f1 f1 CDMA Soft Handoff DD

f1 f1 HIRS UU f1 f1 VV f1 f1 W W f1 f1 EE f1 f1 FF f1 f1 ISSHO XX f1 f1 YY f1 f1 ZZ f1 f1 CDMA Hard Handoff Mobile Station starts communications with a new cell controlled by a

different BSC while still communicating with the cell controlled by the source BSC Soft Handoffs over Hard Handoffs Fewer border cell Copyright 2003, ZTE CORPORATION CDMA-to-CDMA Hard Handoff PSTN PSTN MSC MSC BSC BSC A (1) B (2) A MSC T1 or E1 Links TIA/EIA-41D BSC

B Between cells operating on different frequencies Between cells that could be on the same frequency, but which are subordinated to different MSC Copyright 2003, ZTE CORPORATION Whats In a Handset? Digital Rake Receiver Symbols Chips Traffic Correlator PN xxx Receiver RF Section IF, Detector RF Transmitter RF Section Copyright 2003, ZTE CORPORATION PN xxx PN xxx Open Loop Duplexer Traffic Correlator Walsh xx Traffic Correlator

AGC RF Walsh xx Walsh xx Pilot Searcher PN xxx Walsh 0 Symbols Viterbi Decoder Messages Bit Packets Audio CPU Vocoder Transmit Gain Adjust Transmitter Digital Section Long Code Gen. Audio Messages Bit Packets Soft Handoff Key:

Understand the searchers effect in different state --- MS power up state --- MS idle and calling state Ec/Io Short PN Code Offsets Pilots Above Searched In This Order: Rake Fingers 1 2 3 Active Set Candidate Set Neighbor Set AAACNAAACNAAACNAAACNAAACNAAACNAAACN AAACNAAACNAAACNAAACNAAACNRAAACNAAAC NAAACNAAACNAAACNAAACNAAACNAAACNAAAC NAAACNAAACNAAACNRAAACNAAACNAAACNAAA CNAAACNAAACNAAACNAAACNAAACNAAACNAAA CNAAACNR Remaining Set Copyright 2003, ZTE CORPORATION Until all are scannedthen repeat Pilot Sets Pilot Sets 1. Active 2. Candidate 3. Neighbor

4. Remaining Pilot sets: Active Set: Pilots associated with the forward traffic channels assigned to the mobile station (max 6 pilots) Candidate Set: Pilots not currently in the Active Set, but received by the mobile with sufficient strength to indicate that the corresponding Traffic Channels can be successfully demodulated (max 5 pilots) Neighbor Set: Pilots not currently on the Active or Candidate Sets, that are likely handoff candidates (at least 20 pilots) Remaining Set: All other possible pilots in the current system on the current CDMA frequency assignment All pilots in a set have the same frequency assignment These sets can be updated during handoff by the base station Copyright 2003, ZTE CORPORATION Pilot Set Initialization (While in the Idle or in an Active Call) Active Pilot whose Paging Channel is being monitored or associated with the assigned Forward Traffic Channel Candidate Empty Neighbor

Pilots specified in the most recently received Extended Neighbor List Message Remaining Any other possible pilot in the system Copyright 2003, ZTE CORPORATION (AGE set at NGHBR_MAX_AGE) Pilot Set Maintenance (While in an Active Call) Active Pilots listed the most recently received Extended Handoff Direction Msg Candidate Pilots whose strength exceeds T_ADD Neighbor Remaining Copyright 2003, ZTE CORPORATION Pilots specified in the most recently received Neighbor List Update Message (or whose AGE is still less than NGHBR_MAX_AGE)

Any other possible pilot in the system Pilot Strength Measurement Message (PSMM) A B Timing C Pilot Channel nnels a h C c Traffi PSMM The Pilot Strength Measurement Message is used by the mobile station to direct the base station in the handoff process. Mobile station reports the strength of the pilots associated with forward traffic channels currently being demodulated (and whether it would like to continue to receive traffic from them), as well as pilots from the neighbor and remaining list which are being received with sufficient strength so that traffic could be demodulated from them successfully. Copyright 2003, ZTE CORPORATION Pilot Search Windows Search Window for pilots in the Active and Candidate Set: SRCH_WIN_A Earliest arriving usable multipath component of the pilot Search Window for pilots in the Neighbor Set:

SRCH_WIN_N pilot PN offset Search Window for pilots in the Remaining Set: SRCH_WIN_R pilot PN offset A search window is a range of PN offsets (in chips) where the mobile station searches for usable multipath components of the pilots in a set Usable means that multipath components can be used for demodulation of an associated traffic channel Copyright 2003, ZTE CORPORATION Soft Handoff Signaling PSMM sent (request to add) , Pilot added to Candidate Set Pilot Strength EHOD message received, Pilot Added to Active Set, EHOC message sent, NLU message received Pilot strength drops below T_DROP, Drop Timer started Pilot Strength exceeds T_ADD Drop Timer expires T_ADD PSMM Sent (request to remove) T_DROP EHOD message received, Pilot Dropped into Neighbor Set, EHOC message sent,

NLU message received T_TDROP Time (1)(2) N (3) C (4) (5)(6) (7) A N T_ADD: pilot detection threshold (Typically 26 = -13dB) T_DROP: pilot drop threshold (Typically 30 = -15 dB) T_TDROP: drop timer value (Typically 3 = 4 sec) Prevents unnecessary transmissions of PSMM when a mobile station experiences a fade Copyright 2003, ZTE CORPORATION System Parameters Message (PCH) Field Length

(bits) MSG_TYPE (00000001) 8 HOME_REG 1 PWR_REP_THRESH 5 PILOT_PN 9 FOR_SID_REG 1 PWR_REP_FRAMES 4 CONFIG_MSG_SEQ 6 FOR_NID_REG 1 PWR_THRESH_ENABLE 1

SID 15 POWER_UP_REG 1 PWR_PERIOD_ENABLE 1 NID 16 POWER_DOWN_REG 1 PWR_REP_DELAY 5 REG_ZONE 12 PARAMETER_REG 1 RESCAN 1 TOTAL_ZONES

3 REG_PRD 7 T_ADD 6 ZONE_TIMER 3 BASE_LAT 22 T_DROP 6 MULT_SIDS 1 BASE_LONG 23 T_COMP 4 MULT_NIDS 1

REG_DIST 11 T_TDROP 4 BASE_ID 16 SRCH_WIN_A 4 EXT_SYS_PARAMETER 1 BASE_CLASS 4 SRCH_WIN_N 4 EXT_NGHBR_LIST 1 PAGE_CHAN 3 SRCH_WIN_R

4 GLOBAL_REDIRECT 1 MAX_SLOT_CYCLE_INDEX 3 NGHBR_MAX_AGE 4 RESERVED 1 Copyright 2003, ZTE CORPORATION Power Control during Soft Handoff During soft handoff, the mobile station receives power control bits from multiple base stations. If two or more power control subchannels are identical, their power control bits are diversity combined into one per 1.25 ms time slot. If the mobile station receives different power control bits from different

power control subchannels, it decreases its mean power output level by 1 dB. Only if the power control bits from ALL power control subchannels request a power increase, the mobile station increases its mean power output level by 1 dB . Copyright 2003, ZTE CORPORATION Soft Handoff New Parameter in 1X 10log 10 Pilot Strength PS i A i IS-2000princinple IS-2000princinple P2 P1 T_ADD P2 T_DROP P1 Time (1) (2) (3)

Neighbor Candidate Set Set Copyright 2003, ZTE CORPORATION (4) (5) Active Set (6) (7) Candidate Set (8) Neighbor Set Handoff Parameters Copyright 2003, ZTE CORPORATION T_ADD T_DROP T_TDROP T_COMP

SOFT_SLOPE ADD_INTERCEPT DROP_INTERCEPT SRCH_WIN_A SRCH_WIN_N SRCH_WIN_R Prefered Parameters Setting name range Prefered range Qualcomm prefered T_ADD 0~31 24~28 28 T_DROP 0~31 28~32 32

T_TDROP 0~15 2~4 3 T_COMP 0~15 4~6 5 SRCH_WIN_A 0~15 7~9 8 SRCH_WIN_N 0~15 9~11 10 SRCH_WIN_R 0~15 9~11

10 SOFT_SLOPE 0~63 0~63 18 ADD_INTERCEPT 0~63 0~63 6 DROP_INTERCEP T 0~63 0~63 2~6 Copyright 2003, ZTE CORPORATION Search Window Setting Copyright 2003, ZTE CORPORATION SRCH_WIN_val Width, Chips 0

4 (2) 1 6 (3) 2 8 (4) 3 10 (5) 4 14 (7) 5 20 (10) 6 28 (14) 7 40 (20) 8 60 (30) 9 80 (40)

10 100 (50) 11 130 (65) 12 160 (80) 13 226 (113) 14 330 (165) 15 452 (226) The End! Copyright 2003, ZTE CORPORATION

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