Method and apparatus for time aligning signals for reception in a code-division multiple access communication system
First Claim
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1. A method of time aligning signals for reception in a code-division multiple access (CDMA) communication system, the method comprising the steps of:
- receiving, at a base-station, signals transmitted by a plurality of subscriber units;
determining a time position of each signal received based on estimates of the power of a plurality of delayed rays representative of each signal; and
transmitting, from the base-station, an alignment signal, based on the step of determining, to each of the plurality of subscriber units such that subsequent signals transmitted by the plurality of subscriber units are received by the base-station substantially in time alignment.
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Abstract
A coherent reverse channel, a per-chip spreading function, orthogonal spreading functions and a time alignment of all traffic channels are implemented such that the main signal of each channel arrives at a base-station within a fraction of a chip of one another in accordance with the invention. With this, the orthogonality among all channels is maintained, and, when demodulated, all channels except the channel of interest provides a cross-correlation of substantially zero with respect to the remaining signals.
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Citations
18 Claims
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1. A method of time aligning signals for reception in a code-division multiple access (CDMA) communication system, the method comprising the steps of:
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receiving, at a base-station, signals transmitted by a plurality of subscriber units; determining a time position of each signal received based on estimates of the power of a plurality of delayed rays representative of each signal; and transmitting, from the base-station, an alignment signal, based on the step of determining, to each of the plurality of subscriber units such that subsequent signals transmitted by the plurality of subscriber units are received by the base-station substantially in time alignment. - View Dependent Claims (2, 3, 4, 5)
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6. A method of time aligning signals for reception in a code-division multiple access (CDMA) communication system, the method comprising the steps of:
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receiving, at a base-station, signals transmitted from a plurality of subscriber units, each signal modulated with a per symbol spreading function orthogonal to one another; determining a time position of each signal received based on estimates of the power of a plurality of delayed rays representative of each signal; and transmitting, from the base-station, an alignment signal, based on the step of determining, to each of the plurality of subscriber units such that subsequent signals transmitted by the plurality of subscriber units are received by the base-station substantially within a fraction of a chip of one another. - View Dependent Claims (7, 8)
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9. A base-station for time aligning signals for reception in a code-division multiple access (CDMA) communication system, the base-station comprising:
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means for receiving signals transmitted by a plurality of subscriber units; means, coupled to the means for receiving, for determining a time position of each signal received based on estimates of the power of a plurality of delayed rays representative of each signal; and means, coupled to the means for determining, for transmitting an alignment signal to each of the plurality of subscriber units such that subsequent signals transmitted by the plurality of subscriber units are received by the base-station substantially in time alignment. - View Dependent Claims (10, 11, 12)
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13. A base-station for time aligning signals for reception in a code-division multiple access (CDMA) communication system, the base-station comprising:
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a receiver for receiving signals transmitted by a plurality of subscriber units; a comparator, coupled to the receiver, for determining a time position of each signal received based on estimates of the power of a plurality of delayed rays representative of each signal; and a transmitter, coupled to the means for determining, for transmitting an alignment signal to each of the plurality of subscriber units such that subsequent signals transmitted by the plurality of subscriber units are received by the base-station substantially in time alignment. - View Dependent Claims (14, 15)
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16. A method of time aligning signals for reception in a microcellular code-division multiple access (CDMA) communication system, the method comprising the steps of:
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receiving, at base-stations within first and second microcells, signals transmitted by first and second groups of subscriber units; determining, for each group of signals, a time position of the signals within the group received relative to one another; comparing the time position for each group; and transmitting, from either the first or second base-station, an alignment signal, based on the step of comparing, to the corresponding first or second group of subscriber units such that subsequent signals transmitted by the group of subscriber units are received by the base-station within the first or second microcell substantially in time alignment with signals received by the basestation within the other microcell. - View Dependent Claims (17, 18)
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Specification