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Unbalanced AltBOC: a Compass B1 candidate with generalized MPOCET technique

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Abstract

With the proposed new GNSS signals, enhanced navigation performance is expected in both civil and military applications. However, these new signals introduce the difficulty of combining multiple signal components into a constant-envelope signal. For the Compass B1 band, the problem is to multiplex a QPSK(2) signal and a new multiplexed binary offset carrier (MBOC) signal with a center frequency difference of 14.322 MHz. One approach for multiplexing spreading codes is the phase-optimized constant-envelope transmission (POCET) method proposed for the GPS L1 band. However, only binary spreading codes are considered in POCET. We first generalize the POCET method as a multilevel POCET (MPOCET) algorithm for multilevel coded signals. A new implementation of the alternative binary offset carrier (AltBOC) generator is derived from MPOCET. Secondly, the multiplexing problem for Compass is modeled by MPOCET. Multilevel subcarriers of AltBOC are adopted in the model. As a result, an 8-PSK unbalanced AltBOC (UAltBOC) modulation, which has a QPSK(2) signal at the lower sideband and a TMBOC signal at the upper sideband, is obtained. Simulations for signal model validation and power spectrum analysis are conducted. Numerical results indicate that UAltBOC successfully combines the QPSK and TMBOC signals with only 0.16-dB additional combining loss compared to AltBOC. The proposed MPOCET technique is demonstrated as a unified multiplexing method for navigation signals.

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Abbreviations

AltBOC:

Alternative binary offset carrier

BOC:

Binary offset carrier

CASM:

Coherent adaptive subcarrier modulation

CBOC:

Composite binary offset carrier

HPA:

High-power amplifiers

ICD:

Interface control document

MBOC:

Multiplexed binary offset carrier

MCS:

Multilevel coded symbol

MPOCET:

Multilevel phase-optimized constant-envelope transmission

MV:

Majority vote

POCET:

Phase-optimized constant-envelope transmission

PRN:

Pseudorandom noise

PRS:

Public regulated service

PSD:

Power spectrum density

SLV:

Symbol level vector

TMBOC:

Time-multiplexed binary offset carrier

UAltBOC:

Unbalanced alternative binary offset carrier

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Acknowledgments

This work was supported by the Best Paper Award of the 2nd China Satellite Navigation Conference (No. CSNC2011-QY-06). We thank the anonymous reviewers for helpful review comments that substantially improved this manuscript.

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Authors and Affiliations

  1. School of Electronic Science and Engineering, National University of Defense Technology, Changsha, 410073, China

    Kai Zhang & Feixue Wang

  2. Beijing Institute of Tracking and Telecommunication Technology, Beijing, 100094, China

    Hongwei Zhou

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  1. Kai Zhang
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  2. Hongwei Zhou
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  3. Feixue Wang
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Correspondence to Kai Zhang.

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Zhang, K., Zhou, H. & Wang, F. Unbalanced AltBOC: a Compass B1 candidate with generalized MPOCET technique. GPS Solut 17, 153–164 (2013). https://doi.org/10.1007/s10291-012-0268-6

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