Transmission and reception of reference preamble signals in OFDMA or OFDM communication systems
AssigneeZTE (USA) Inc.
InventorsJason Hou, Jing Wang, Sean Cai, Dazi Feng, Yonggang Fang, Yunsong Yang
Life of this patent
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Abstract
Techniques for generating preamble sequences for OFDM and OFDMA communication systems based on CAZAC sequences with desired properties of constant amplitudes (CA) and zero autocorrelation (ZAC). Such preamble sequences may be used for synchronization and identification of individual transmitters. For example, the OFDMA symbol is constructed using a CAZAC sequence in the frequency-domain and the resulting time-domain waveform is a near-CAZAC sequence.
Claims20
A method for communications based on orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA), comprising:
- selecting an initial constant amplitude zero autocorrelation (CAZAC) sequence;
- producing a first sequence by setting one or more amplitudes of respective one or more frequency components in a portion of the initial CAZAC sequence to zero and adding a first phase shift factor for one or more frequency components in another portion of the initial CAZAC sequence,
- producing a second, different sequence by setting one or more amplitudes of respective one or more frequency components in a different portion of the initial CAZAC sequence to zero and adding a second phase shift factor for one or more frequency components in the another portion of the initial CAZAC sequence, where the second phase shift factor is the inverse of the first phase shift factor,
- joining the first sequence and the second sequence, such that they are connected, to generate a modified sequence;
- and using the modified sequence as part of a preamble of a downlink signal from a base station to a mobile station.
A method for communications based on orthogonal frequency division multiplexing (OFDM) or orthogonal frequency division multiple access (OFDMA), comprising:
- selecting a constant amplitude zero autocorrelation (CAZAC) sequence of a length L in frequency which includes spectral components in first, second and third sequential portions in frequency;
- modifying the CAZAC sequence to produce a first modified sequence by setting amplitudes of spectral components in the first portion of the CAZAC sequence to zeros and adding a first phase shift on spectral components of the second portion of the CAZAC sequence, without changing the third portion;
- modifying the CAZAC sequence to produce a second modified sequence by setting amplitudes of spectral components in the third portion of the CAZAC sequence to zeros and adding a second phase shift on spectral components of the second portion of the CAZAC sequence, without changing the first portion;
- combining the first and second modified sequences to form a combined sequence in frequency of a length 2L, wherein the first portion from the first modified sequence is positioned next to the third portion from the second modified sequence in the combined sequence;
- performing an inverse fast Fourier transform on the combined sequence to generate a first preamble sequence;
- and
- using the first preamble sequence in a communication device for OFDM or OFDMA communication.
Dependencies are inferred from the claim text.