C30-20090330-051

Date: 30 March, 2009

Abstract: This contribution contains the active set management proposal for cdma2000 1x Rev E

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Active Set Management Modifications for 1x Rev EActive Set Management Modifications for 1x Rev E

Recommendation: Review and adopt

Source: Shu Wang and Tony Lee VIA Telecom

Contact: shuwang@via-telecom.com

C30-20090330-051

Active Set Management Modifications Active Set Management Modifications for 1x Rev. Efor 1x Rev. E

Source: Shu Wang and Tony Lee

VIA Telecom

OutlineOutline

• The dilemma in the existing active set management

• Suggested modifications Solution 1:

• Add some mechanisms for mobiles to configure/recommend the size of Forward Active Set.

Solution 2:• Mobiles dynamically send commands to temporally suspend

unnecessary forward link transmission from some base stations in the active set when doing soft handoff.

Active Set ManagementActive Set Management

• The existing Active Set management in C.S0005-E 3.6.6.2.4.1 Receiving During Soft Handoff

[ … ] Each base station in the Active Set shall demodulate the Reverse Traffic Channel. The base station should provide diversity combining of the demodulated signals obtained by each base station in the Active Set. [ … ]

3.6.6.2.4.2 Transmitting During Soft Handoff [ … ] The base station shall use the same long code mask on all

Forward Traffic Channels whose associated pilots are in the Active Set. [ … ]

• Proposed Modifications 3.6.6.2.4.1 Receiving During Soft Handoff

[ … ] Each base station in the Active Set shall demodulate the Reverse Traffic Channel. The base station should provide diversity combining of the demodulated signals obtained by each base stations. [ …]

3.6.6.2.4.2 Transmitting During Soft Handoff [ … ] The base station shall use the same long code mask on all

Forward Traffic Channels whose associated pilots are in the Active Set. [ … ]

The Dilemma in Active Set Management

• The Active Set Size should be large enough to maximize reverse link macro-diversity gain . This is well understood in the industry. And it is desired for both 1x and DO

reverse link design. “… For EV-DO Rev A, the voice capacity in a single 1.25 MHz carrier

increases from 41[1] to 66 per sector with 4-way RX diversity. In this case, the number of MAC indices is the limiting factor for voice capacity.” --- Source: Qualcomm Incorporated, VoIP white paper “VoIP Overview” [1] EVRC, RL 2-way diversity, no IC, no DTX/DRX, inter-base station distance of 2 km.

However, it is well-known that high order receiver diversity at BS is hard to achieved due to the limitation of antenna array design.

• The Active Set Size should be small enough to avoid unnecessary inter-cell interference in forward link. If the active set size is too large, there will be more users in soft

handoff and more interference to other users in the same or different base stations.

• Soft handoff incurs extra load on the system due to the increase in the number of channels occupied and reserved for macro-diversity.

– Too many SHO users may block the admission of new traffics and decrease the actual user capacity.

• With more users in SHO, both transmission power and interference increases.– More interference to the adjacent cells.

Active Set Size 2 or 3 can be the good number.

User Capacity Gain (1/2)

20 25 30 35 40 45 505

10

15

20

Active User per Base Station

Tran

smis

sion

Pow

er (w

)

FOR_ACTIVE_SET_SIZE = 2, SHOFOR_ACTIVE_SET_SIZE = 3, SHOFOR_ACTIVE_SET_SIZE = 4, SHOFOR_ACTIVE_SET_SIZE = 2, CSHOFOR_ACTIVE_SET_SIZE = 3, CSHOFOR_ACTIVE_SET_SIZE = 4, CSHO

VoIP User Capacity, Outage Based, T_ADD=-18dB, Channel B, RAKE finger number = 6

User Capacity Gain (2/2)

The Remedies

• Modification 1: Add some mechanisms for mobiles to configure/recommend

the size of Forward Active Set.• MSs send its recommendation or configuration for the size of

Forward Active Set.

• Modification 2: Cell Selection Handoff help the system to achieve the

optimal operation point between reliability and throughput as well as minimize inter-cell interference.

CSHO help achieve more spatial diversity gain in soft handoff in addition to the time diversity explored by the frame early termination with R-ACKCH.