1. Copyright 2003, ZTE CORPORATION CDMA KEY TECHNOLOGY 2004.10.3

2. Copyright 2003, ZTE CORPORATION Objectives -- Power control in CDMA why power control how to realize -- Handoff in CDMA what is handoff CDMA’s soft handoff soft handoff procedure Upon completion of this lesson, the student will be able to master:

3. 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 Figure of Merit: E c /I o, E b /N o (energy per chip [bit] / interference [noise] spectral density ) CDMA: E c /I o -17 to -2 dB CDMA: E b /N o ~6to7 dB Figure of Merit: E c /I o, E b /N o (energy per chip [bit] / interference [noise] spectral density ) CDMA: E c /I o -17 to -2 dB CDMA: E b /N o ~6to7 dB

4. Copyright 2003, ZTE CORPORATION Reverse Open Loop Power Control 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 MobileBTS Reverse Open Loop Power Control

5. Copyright 2003, ZTE CORPORATION Estimated Reverse Open Loop Output Power mean output power (dBm) =- mean power input (dBm) + K + NOM_PWR - 16 x NOM_PWR_EXT + INIT_PWR Power output level for the initial probe during open loop probing on the Access Channel (with closed loop correction inactive): 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

6. Copyright 2003, ZTE CORPORATION Estimated Reverse Open Loop Output Power Power output level for the initial transmission on the Reverse Traffic 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)

7. Copyright 2003, ZTE CORPORATION Reverse Closed Loop Power Control 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 MobileBTS Signal Strength Measurement Setpoint or Reverse Closed Loop Power Control

8. Copyright 2003, ZTE CORPORATION Reverse Outer Loop Power Control 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 FER MobileBTS BSC Reverse Outer Loop Power Control Signal Strength Measurement Setpoint or Reverse Closed Loop Power Control

9. Copyright 2003, ZTE CORPORATION Forward Traffic Channel 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. FER MobileBTS BSC Adjust Fwd. power Forward Link Power Control

10. Copyright 2003, ZTE CORPORATION Summary of All Power Control Mechanisms 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. FER MobileBTS BSC Signal Strength Measurement Setpoint or Adjust Fwd. power Reverse Outer Loop Power Control Reverse Closed Loop Power Control Forward Link Power Control Reverse Open Loop Power Control

11. 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

12. Copyright 2003, ZTE CORPORATION 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) Cell Site B Cell Site A Cell Site A Cell Site B CDMA

13. Copyright 2003, ZTE CORPORATION CDMA Handoffs (cont.) During a Call Idle Handoff Soft Handoff Softer Handoff CDMA-to-CDMA Handoff Inter-System Soft Handoff CDMA-to-Analog Handoff While in the Idle State

14. Copyright 2003, ZTE CORPORATION Soft Handoff 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 Cell Site B Cell Site A PSTN MSC BSCBSC

15. Copyright 2003, ZTE CORPORATION Softer Handoff 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 alpha beta gamma

16. Copyright 2003, ZTE CORPORATION Inter-System Soft Handoffs (ISSHO) 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 MSC SVBS HIRS E1 Links MSC SVBS HIRS A f1 A f1 D f1 D f1 B f1 B f1 E f1 E f1 C f1 C f1 F f1 F f1 U f1 U f1 X f1 X f1 V f1 V f1 Y f1 Y f1 W f1 W f1 Z f1 Z f1 CDMA Soft Handoff ISSHO CDMA Hard Handoff E1 Links TIA/EIA-41D

17. Copyright 2003, ZTE CORPORATION CDMA-to-CDMA Hard Handoff Between cells operating on different frequencies Between cells that could be on the same frequency, but which are subordinated to different MSC A(ƒ1)A(ƒ1) PSTN MSC BSC B(ƒ2)B(ƒ2) A PSTN MSC BSC B MSC BSC T1 or E1 Links TIA/EIA-41D

18. Copyright 2003, ZTE CORPORATION What ’ s In a Handset? Receiver RF Section IF, Detector Transmitter RF Section Vocoder Digital Rake Receiver Traffic Correlator PN xxxWalsh xx Traffic Correlator PN xxxWalsh xx Traffic Correlator PN xxxWalsh xx Pilot Searcher PN xxxWalsh 0 Viterbi Decoder CPU Duplexer Transmitter Digital Section Long Code Gen. Open Loop Transmit Gain Adjust Messages Audio Bit Packets Symbols Chips RF AGC Bit Packets 

19. Copyright 2003, ZTE CORPORATION Soft Handoff Key: Ec/Io Short PN Code Offsets Neighbor Set Active Set Candidate Set Remaining Set  Rake Fingers 1 2 3  Understand the searcher’s effect in different state --- MS power up state --- MS idle and calling state

20. Copyright 2003, ZTE CORPORATION Pilot Sets 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 Pilot Sets 1. Active 2. Candidate 3. Neighbor 4. Remaining

21. Copyright 2003, ZTE CORPORATION Pilot Set Initialization (While in the Idle or in an Active Call) Candidate Remaining Active Neighbor Pilot whose Paging Channel is being monitored or associated with the assigned Forward Traffic Channel Pilots specified in the most recently received Extended Neighbor List Message (AGE set at NGHBR_MAX_AGE) Empty Any other possible pilot in the system

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

23. Copyright 2003, ZTE CORPORATION Pilot Strength Measurement Message (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. A B C Pilot Channel Timing Traffic Channels PSMM

24. Copyright 2003, ZTE CORPORATION Pilot Search Windows 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 Search Window for pilots in the Active and Candidate Set: Search Window for pilots in the Neighbor Set: Search Window for pilots in the Remaining Set: Earliest arriving usable multipath component of the pilot pilot PN offset SRCH_WIN_N SRCH_WIN_A SRCH_WIN_R

25. Copyright 2003, ZTE CORPORATION Pilot Strength Pilot Strength exceeds T_ADD EHOD message received, Pilot Dropped into Neighbor Set, EHOC message sent, NLU message received Time Pilot strength drops below T_DROP, Drop Timer started T_TDROP T_ADD T_DROP EHOD message received, Pilot Added to Active Set, EHOC message sent, NLU message received NCNA (1)(2)(3)(4)(5)(6)(7) Drop Timer expires PSMM sent (request to add), Pilot added to Candidate Set PSMM Sent (request to remove) Soft Handoff Signaling 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

26. Copyright 2003, ZTE CORPORATION System Parameters Message (PCH) MSG_TYPE (‘00000001’) PILOT_PN 8 9 CONFIG_MSG_SEQ 6 SID 15 NID16 REG_ZONE 12 TOTAL_ZONES3 ZONE_TIMER3 MULT_SIDS1 MULT_NIDS1 BASE_ID 16 BASE_CLASS 4 PAGE_CHAN 3 MAX_SLOT_CYCLE_INDEX3 HOME_REG FOR_SID_REG 1 1 FOR_NID_REG1 POWER_UP_REG1 POWER_DOWN_REG1 PARAMETER_REG1 REG_PRD7 BASE_LAT 22 BASE_LONG23 REG_DIST 11 SRCH_WIN_A 4 SRCH_WIN_N 4 SRCH_WIN_R4 NGHBR_MAX_AGE 4 PWR_REP_THRESH PWR_REP_FRAMES 5 4 PWR_THRESH_ENABLE1 PWR_PERIOD_ENABLE1 PWR_REP_DELAY5 RESCAN1 T_ADD6 T_DROP 6 T_COMP 4 T_TDROP4 EXT_SYS_PARAMETER1 EXT_NGHBR_LIST 1 GLOBAL_REDIRECT 1 RESERVED 1 Field Length (bits)

27. 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.

28. Copyright 2003, ZTE CORPORATION Soft Handoff New Parameter in 1X IS-2000princinple

29. Copyright 2003, ZTE CORPORATION Handoff Parameters T_ADD T_DROP T_TDROP T_COMP SOFT_SLOPE ADD_INTERCEPT DROP_INTERCEPT SRCH_WIN_A SRCH_WIN_N SRCH_WIN_R

30. Copyright 2003, ZTE CORPORATION Prefered Parameters Setting namerangePrefered range Qualcomm prefered T_ADD0~3124~2828 T_DROP0~3128~3232 T_TDROP0~152~43 T_COMP0~154~65 SRCH_WIN_A0~157~98 SRCH_WIN_N0~159~1110 SRCH_WIN_R0~159~1110 SOFT_SLOPE0~63 18 ADD_INTERCEPT 0~63 6 DROP_INTERCEP T 0~63 2~6

31. Copyright 2003, ZTE CORPORATION Search Window Setting SRCH_WIN_val 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Width, Chips 4 (±2) 6 (±3) 8 (±4) 10 (±5) 14 (±7) 20 (±10) 28 (±14) 40 (±20) 60 (±30) 80 (±40) 100 (±50) 130 (±65) 160 (±80) 226 (±113) 330 (±165) 452 (±226)

32. Copyright 2003, ZTE CORPORATION The End!