Effects of a Phase Rotation Scheme on the DTX Detection Performance for the E-UTRA Uplink ACK/NACK Signals

Seigo NAKAO  Tomohumi TAKATA  Daichi IMAMURA  Katsuhiko HIRAMATSU  

IEICE TRANSACTIONS on Communications   Vol.E94-B    No.1    pp.262-272
Publication Date: 2011/01/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E94.B.262
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Terrestrial Wireless Communication/Broadcasting Technologies
cyclic shift sequence,  CDMA,  inter-code interference,  phase rotation,  HARQ,  E-UTRA,  DTX detection,  uplink control channel,  

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Hybrid automatic repeat request (HARQ) is employed for the Evolved Universal Terrestrial Radio Access (E-UTRA) downlink. The base station not only decodes the ACK/NACK signals from the user equipment (UE), but also detects a termination of the transmission (DTX) of the ACK/NACK signals caused by the mis-detection of the downlink control information (DCI) at the UE side. Since ACK/NACK signals from UEs are multiplexed by CDMA, there are sometimes severe inter-code interference (ICI) effects, which significantly degrade the performance of ACK/NACK signals. In order to mitigate such ICI effects, in [1],[2], we proposed a novel phase rotation scheme on the constellations of the uplink ACK/NACK signals, and confirmed the effects on the ACK/NACK bit error rate performance; however, the previous paper did not analyze the effects of the phase rotation on the DTX detection performance. Hence, in this paper, we further analyze the effects of the phase rotation for the ACK/NACK signals in conjunction with a new DTX detection scheme which utilizes equalizer outputs, and investigate the performance of the proposed scheme by means of computer simulations.