Methods and apparatus for overlaying multi-carrier and direct sequence spread spectrum signals in a broadband wireless communication system
First Claim
1. In a broadband wireless communication system for a multi-user multi-cell environment, a system comprising:
- one of multiple transmitters configured to transmit overlaying Multi-Carrier (MC) and Direct Sequence Spread Spectrum (DSSS) signals, wherein;
the MC signal is modulated on subcarriers in the frequency domain;
the DSSS signal is modulated in either the time domain or the frequency domain;
the DSSS signal is aligned with a boundary of a MC slot or a MC symbol in the time domain when the DSSS and MC signals are synchronized, or the DSSS signal is arbitrarily placed in the time domain when the DSSS and MC signals are not synchronized; and
at least one subcarrier of the MC signal can be energized at a different power level, or not be energized at all, and the DSSS signal is transmitted at a power level significantly lower than that of the MC signal.
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Abstract
A broadband wireless communication system, wherein both Multi-Carrier (MC) and Direct Sequence Spread Spectrum (DSSS) signals are intentionally overlaid together, in both time and frequency domains. The overlaying mitigates the weaknesses of each technique. The MC signal carries the broadband data signal and takes advantage of its high spectral efficiency, while the DSSS signal is used for special purpose processing such as initial random access, channel probing, and short messaging, where properties such as signal simplicity, self synchronization, and performance under severe interference are desired. The methods and techniques ensure that the MC and the DSSS signals are both distinguishable and that the interference between the overlaid signals is minimized to have insignificant impact on the expected performance of either signal.
42 Citations
26 Claims
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1. In a broadband wireless communication system for a multi-user multi-cell environment, a system comprising:
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one of multiple transmitters configured to transmit overlaying Multi-Carrier (MC) and Direct Sequence Spread Spectrum (DSSS) signals, wherein; the MC signal is modulated on subcarriers in the frequency domain; the DSSS signal is modulated in either the time domain or the frequency domain; the DSSS signal is aligned with a boundary of a MC slot or a MC symbol in the time domain when the DSSS and MC signals are synchronized, or the DSSS signal is arbitrarily placed in the time domain when the DSSS and MC signals are not synchronized; and at least one subcarrier of the MC signal can be energized at a different power level, or not be energized at all, and the DSSS signal is transmitted at a power level significantly lower than that of the MC signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A communication system for a multi-user multi-cell environment, the system comprising:
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transmitter means for transmitting Multi-Carrier (MC) signals; transmitter means for transmitting Direct Sequence Spread Spectrum (DSSS) signals; wherein the MC signal carries broadband data and related control signals; wherein the DSSS signal performs initial random access, channel probing, or short messaging, or a combination thereof; wherein at least one transmitter means transmits overlaying DSSS and MC signals simultaneously, or wherein at least one transmitter means transmits only the DSSS signals and at least one transmitter means transmits only the MC signals and both DSSS and MC transmitted signals overlay on the same frequency channel, or wherein at least one transmitter means transmits overlaying DSSS and MC signals simultaneously and at least one transmitter means transmits only the DSSS signals and at least one transmitter means transmits only the MC signals and both DSSS and MC transmitted signals overlay on the same frequency channel. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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Specification