Asymmetrical forward/reverse transmission bandwidth
A wireless communications system employs code-division multiple access information transmission techniques where the uplink and downlink transmission bandwidths are unequal. The higher bandwidth is an integer multiple of the lower bandwidth. The present system requires a base station and a subscriber unit to have two pseudo-random code generators which can be clocked separately. Alignment of the uplink and downlink pseudo-random spreading codes is achieved by truncating the code sequence for the lower speed link at the conclusion of a complete code sequence for the higher speed link.
1. A communication method for use in a code division multiple access (CDMA) system, comprising:
combining a first pseudo-random code and a portion of a second pseudo-random code to generate an output code, the first pseudo-random code having a length equal to a first number of chips, the second pseudo-random code having a length equal to a second number of chips, the first number of chips being less than the second number of chips, and the output code having a length equal to a third number of chips, the third number of chips being less than a product of the first number of chips and the second number of chips; and
spreading a signal based on the output code, wherein the signal carries information.
2. A communication method in accordance with claim 1 , further comprising filtering the spread signal.
3. A communication apparatus for use in a code division multiple access (CDMA) system, the communication apparatus comprising:
a circuit configured to combine a first pseudo-random code and a portion of a second pseudo-random code to generate an output code, the first pseudo-random code having a length equal to a first number of chips, the second pseudo-random code having a length equal to a second number of chips, the first number of chips being less than the second number of chips, and the output code having a length equal to a third number of chips, the third number of chips being less than a product of the first number of chips and the second number of chips, and the circuit is configured to spread a signal based on the output code, wherein the signal carries information; and
an antenna coupled to the circuit, the antenna being configured to output the spread signal.
4. A communication apparatus in accordance with claim 3 , further comprising a filter.