Practical M-ary demodulator and method of operation for use in a CDMA wireless network base station

A code division multiple access (CDMA) wireless network comprising a plurality of base transceiver stations capable of communicating with access terminals located in a coverage area of said wireless network, wherein a first one of said plurality of base transceiver stations comprises:

• a demodulator for demodulating a set of S possible orthogonal modulation codes received serially as binary data, wherein each of said orthogonal modulation codes comprises M binary bits representing an N-bit data symbol and wherein M=2N, said demodulator comprising:
• a Logic 00 input detector capable of comparing sequential non-overlapping pairs of said M binary bits of said serially received orthogonal modulation codes to a Logic 00 value and outputting a [+1,+1] signal if a match occurs and outputting a [−1,−1] signal if a match does not occur;
• a summation circuit comprising S accumulators;
• a Logic 00 switch array comprising S switches, wherein a Kth one of said S switches in said Logic 00 switch array is capable of coupling an output of said Logic 00 input detector to a first input of a Kth one of said S accumulators;
• a storage array capable of storing S code masks associated with said S orthogonal modulation codes, wherein each of said S code masks comprises M/2 code mask bits and each of said M/2 code mask bits is associated with a corresponding one of said sequential non-overlapping pairs of said M binary bits in one of said orthogonal modulation codes;
• and
• control circuitry capable of synchronously applying the M/2 code mask bits in a Kth one of said S code masks in said storage array as a switch control signal to said Kth switch in said Logic 00 switch array such that a Logic 1 code mask bit in said Kth code mask closes said Kth switch in said Logic 00 switch array whenever said Logic 00 input detector is comparing a sequential non-overlapping pair of said M binary bits equal to 00, thereby connecting the [+1,+1] output signals of said Logic 00 input detector to said first input of said Kth accumulator.

For use in a base station of a wireless network capable of communicating with mobile stations located in a coverage area of the wireless network, a method of demodulating a set of S possible orthogonal modulation codes received serially as binary data, wherein each of the orthogonal modulation codes comprises M binary bits representing an N-bit data symbol and wherein M=2N, the method comprising the steps of:

• in a Logic 00 input detector, comparing sequential non-overlapping pairs of the M binary bits of the serially received orthogonal modulation codes to a Logic 00 value and outputting a [+1,+1] signal if a match occurs and outputting a [−1,−1] signal if a match does not occur;
• retrieving from a storage array a Kth one of S code masks associated with the S orthogonal modulation codes, wherein each of the S code masks comprises M/2 code mask bits and each of the M/2 code mask bits is associated with a corresponding one of the sequential non-overlapping pairs of the M binary bits in one of the orthogonal modulation codes;
• and
• synchronously applying the M/2 code mask bits of the Kth S code mask as a switch control signal to a Kth switch in a Logic 00 switch array comprising S switches, wherein the Kth switch in the Logic00 switch array is capable of coupling an output of the Logic00 input detector to a first input of a Kth one of S accumulators, and wherein a Logic 1 code mask bit in the Kth code mask closes the Kth switch in the Logic00 switch array whenever the Logic 00 input detector is comparing a sequential non-overlapping pair of the M binary bits equal to 00, thereby connecting the [+1,+1] output signals of the Logic 00 input detector to the first input of the Kth accumulator.