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Motorola Report on Power Balancing for WCDMA

IP.com Disclosure Number: IPCOM000007273D
Original Publication Date: 2002-Mar-08
Included in the Prior Art Database: 2002-Mar-08

Publishing Venue

Motorola

Related People

Robert Love: AUTHOR [+2]

Abstract

This document describes power-balancing function used in WCDMA and makes recommendations on algorithms and related parameters.

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TITLE:

                    Motorola Report on Power Balancing for WCDMA

DATE:

February 27, 2002

AUTHORS:

Robert Love, Jean-Aicard Fabien

Motorola, Inc.

Global Telecom Solutions Sector

ABSTRACT:

This document describes power-balancing function used in WCDMA and makes recommendations on algorithms and related parameters.

1          Overview


The purpose of power balancing is to reduce interference on the downlink from the base stations in the active set


Figure 1: Power Balancing Illustration

Figure 1 depicts the situation where the mobile is in soft handover with the two base stations in the active set. .  Typically because the error rate in the transmission of the transmit power control command is not the same for each base station, there is divergence between P1 and P2.  Note that in this document the terms node B and base station are used to have exactly the same meaning i.e. the base station node in the Radio Access Network (RAN) as defined in 3GPP UMTS specification.

1          Power Balancing Algorithm

 The purpose of power balancing to keep the output power of each base station (PWR_LVL 1 and 2 in Figure 1) in the active set the same within an error margin.   The power adjustment within a slot k for each base station is calculated as follows (see reference [1]):

                           (1)

PTPC (k)                                       Power control step depending on the receive TPC command in the uplink.  The TPC commands are derived in the UE based on measurement of the downlink DCH SIR and the SIR threshold.  The SIR threshold is based on the TFCI (frame format, link speed and coding) and the channel model.  The power adjustment from the uplink TPC command is also bounded by a power raise limit within a downlink power-averaging window.  The initial values used in the simulation will be 6 dB within 4 frames.  The power raise limit bound is optional. 

PBAL (k)                                       Correction factor is used to keep the output power of each base the same station within an error margin. 

To calculate PBALJ (2) each base station needs a reference value from the RNC.  The reference value should reflect the output power of each base station to provide a correction that makes P1 and P2 converge.

(2)

                           Convergence coefficient.  The initial value in the simulation is 0.98

                                                       The measured downlink power in the last slot of the adjustment period.  It is measured by each Node B and passed to the RNC via the following mechanism:

                            The downlink reference power is calculated by the RNC and derived from

                            The power control step may be 0.5, 1, 1.5 or 2 dB.  1 dB is mandatory.

                                  The adjustment period is 1 to 10 frames

2          Message flow for power balancing

There are two types of messages used for power balancing in the downlink:

-         Measurement messages

-         Power balancing commands

Measurement requests are sent from the RNC to each base station in the active set.  Each base station sends in reply measurement reports containing downlink power measurement for the specific radio link.  The RNC sends back the downlink power control command with a reference power that the base station uses with adjustment ratio coe...