Estimating the Block Error Rate at the Output of the Frame Selector in the UMTS System

D. Avidor (USA), C. Hartmann (Germany), and S. Mukherjee (USA)


Block Error Rate, Convolutional Codes, UMTS PowerControl.


The Block Error Rate (BLER) at the output of the Frame Selector (FS) is the usual measure of Quality of Service (QoS) in UMTS. For low specified BLER (e.g., 0.1%), the method of counting Cyclic Redundancy Code (CRC) errors requires an impractically large number of data blocks for an accurate estimate of BLER. We focus on the uplink and propose to estimate the BLER at the FS output based on the estimates of BLER performed by the individual base stations (BSs) supporting the mobile. We derive the joint probability density function of the Signal to Interference (+Noise) Ratios (SIRs) at the BSs for the general case of n BSs supporting a mobile in soft handoff, each using max imal ratio combining with m-fold diversity. We then cal culate the correlations between the SIRs for some example cases and show how the initial setting of the target SIR in the Outer Loop Power Control (OLPC) can be selected so as to expedite BLER convergence to the desired setting.

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