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Fast Cell Switching

Fast Cell Switching. Motivation Simulation parameters Fast cell switching C/I improvements Fast cell switching throughput improvements Summary. Fast Cell Switching Dependencies. Feature is made possible by the use of the 1XRTT reverse link in 1XEV. Use R-DCCH with short frames (5 ms.).

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Fast Cell Switching

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  1. Fast Cell Switching • Motivation • Simulation parameters • Fast cell switching C/I improvements • Fast cell switching throughput improvements • Summary

  2. Fast Cell Switching Dependencies • Feature is made possible by the use of the 1XRTT reverse link in 1XEV. • Use R-DCCH with short frames (5 ms.). • Additional dependency on 1XEV Dual ARQ proposal. • Reduced RLP retransmission delays enables fast cell switching. • A BTS-centric RLP architecture is also an enabler. • Sequence number reported using R-DCCH or R-FCH for fast cell switching. • Allows successive forward link packets to be efficiently transmitted from different base stations. • Lower delays than BSC-centric s/w architectures results in shorter delays between packets transmitted from different base stations.

  3. Fast Cell Switching • Results in a more effective macro-diversity strategy • Allows enhanced throughput when channel conditions are worst=> users positioned near the cell edge. • The transmitting BTS is chosen by the mobile based on the most favorable FL channel in the active set. • Refinements of the 1XEV RL have been proposed for the RL messaging needed to support this.

  4. Fast Cell SwitchingSimulation Parameters • Tri-sectored Network of 19 cells • (1/d) path loss model, with path loss exponent of 3.5 • Log-Normal shadowing with standard deviation of 8dB and cell-to-cell correlation of 50% • One path Rayleigh fading per sector • 5 Hz Fading Doppler considered • Doppler uniformly distributed between 1 and 2 Hz considered • Uniform distribution of terminals in center sector • Uniformly distributed throughout entire sector considered • Uniformly distributed in outer 20% of sector also considered • 30 seconds call time per user location

  5. Fast Cell SwitchingSimulation Parameters: cont’d • Horizontal antenna pattern with 90º beam width and -20dB front to back loss • C/I ratio determined for every pilot transmission from every Rayleigh fading sector • Assuming perfect C/I estimates • Mapping of C/I ratio to data rate is based on; CDMA/HDR: A Bandwidth Efficient High Speed Wireless Data Service for Nomadic Users; Bender et al, QUALCOMM • Averaging of C/I of every sector done over 20ms or 100ms • Based on average, decision to switch to new sector made and executed immediately • further work will examine sensitivity to switching methodology

  6. Simulation Results: C/IUsers unif. distributed over entire cell. Mean C/I increase from 10 Hz to 50 Hz switching1-2 Hz Doppler: C/I = 1.2 dB5 Hz. Doppler: C/I =1. 5 dB

  7. Simulation Results: C/IUsers unif. distributed over outer 20% of cell area Mean C/I increase from 10 Hz to 50 Hz switching1-2 Hz Doppler: C/I = 1.6 dB5 Hz. Doppler: C/I = 2 dB

  8. Simulation Results: FL throughputUsers unif. distributed over entire cell. Mean increase in throughput from 10 Hz to 50 Hz switching1-2 Hz Doppler: % = 7.3%5 Hz. Doppler: % = 8.6%

  9. Simulation Results: C/IUsers unif. distributed over outer 20% of cell area Mean C/I increase from 10 Hz to 50 Hz switching1-2 Hz Doppler: % = 12%5 Hz. Doppler: % = 17%

  10. Fast Cell Switching Summary • Based on the assumptions simulated the overall increase in data rate throughput per sector is about: • 8-9% throughput gain with fast switching at 5Hz Doppler • 7-8% throughput gain with fast switching at 1-2Hz Doppler • Focusing on terminals around the soft handoff region, e.g. outer 20% area of the sector • 16-17% throughput gain with fast switching at 5Hz Doppler • 11-12% throughput gain with fast switching at 1-2Hz Doppler • The absolute throughput numbers are based on C/I to Data rate mapping provided by Qualcomm document

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