Optimum Power Ratio between Pilot and Information Bits if User Specific Beamforming is used in UMTS FDD

part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher. Notwithstanding, instructors are permitted to photocopy isolated articles for noncommercial classroom use without fee. —Mobiles operating in a UMTS network that uses user specific beamforming have to use the so called dedicated pilot bits for channel estimation that are time multiplexed with the user data. The reason therefore is that the Common Pilot Channel that is broadcast into the entire cell and typically used for channel estimation experiences a different radio channel than the user data sent on the user specific beam. In this paper, we determine the optimum power ratio between the dedicated pilot bits and the information bits for the 144kbit/s reference channel specified for terminal conformance tests in the UMTS specification. For the ITU-Vehicular A channel with 3km/h mobile speed, we find the optimum power ratio between dedicated pilot bits and information bits at 4 to 7dB. This optimum power ratio gives a ! # " reduction of more than 1.5dB for a target block error rate of 1% compared to a system with equal power for all bits.