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US 7,068,617 B1Granted
Low complexity CDMA receiver
AssigneeTexas Instruments Incorporated
InventorsShivaling S. Mahant-Shetti, Kiasaleh Kamran
Life of this patent
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Abstract
A CDMA receiver is provided which is operable to receive a CDMA encoded signal and decode the information therein utilizing a selected code. The systems utilizes a plurality of multiply-accumulation blocks (40) which are operable to receive the signal and compare the received signal with a Walsh-Hadamard code. The comparison and the accumulation is made only in the middle of a chip clock with the edges thereof blanked. This information in the middle of the chip clock is accumulated in an accumulator, the MAC (40), for a symbol period. This is then compared with a look up table and then a decision made as to the logic value thereof.
Claims21
A CDMA decoder for decoding a CDMA encoded signal from a desired CDMA channel, comprising:
- a receive input for receiving a CDMA encoded signal;
- a code generator for generating a predetermined CDMA code for a predetermined CDMA channel that corresponds to an encoded signal encoded with a corresponding CDMA code transmitted over the predetermined CDMA channel;
- a multiply or accumulate device including a multiplication device for multiplying said received signal received on said receive input by said predetermined CDMA code word and operating in the analog domain, said multiply or accumulate device also including an accumulator operable to accumulate the results of the multiplication operation over a symbol period to provide an analog result;
- a data conversion device for determining if the analog result corresponds to a predetermined digital state and, if so, generating a digital output corresponding to said predetermined digital state;
- and
- a summation device for subtracting the output of said multiplication device from said analog result of said multiply or accumulate device prior to input to said data conversion device associated with said multiply or accumulate device.
3 more elements
A CDMA decoder for decoding a CDMA encoded signal from a desired CDMA channel, comprising
- a receiving input for receiving a CDMA encoded signal;
- a code generator for generating a predetermined CDMA code for a predetermined CDMA channel that corresponds to an encoded signal encoded with a corresponding CDMA code transmitted over the predetermined CDMA channel, said code generator operable to generate a plurality of CDMA codes, each associated with one of a plurality of CDMA channels such that said received input can receive a plurality of CDMA encoded signals each on a different channel;
- a data conversion device for determining if the analog result corresponds to a predetermined digital state and, if so, generating a digital output corresponding to said predetermined digital state;
- a plurality of multiply or accumulate devices, one for each channel and for each code word generated by said code generator and wherein said data conversion device is operable to determine for each of the multiply or accumulate devices if the associated analog result corresponds to said predetermined digital state and if so, generating a digital output corresponding to the associated multiply/accumulation device such that a digital output is provided for each of said multiply or accumulate devices;
- further comprising a subtraction device for subtracting from the analog result output from each of said multiply or accumulate devices contributions from signals on selective ones of the other channels encoded with their associated CDMA codes.
2 more elements
The CDMA decoder for decoding a CDMA encoded signal from a desired CDMA channel, comprising:
- a receive input for receiving a CDMA encoded signal;
- a code generator for generating a predetermined CDMA code for a predetermined CDMA channel that corresponds to an encoded signal encoded with a corresponding CDMA code transmitted over the predetermined CDMA channel;
- a multiply or accumulate device for multiplying said received signal received on said receive input by said predetermined CDMA code and operating in the analog domain, said multiply or accumulate device operable to accumulate the results of the multiplication operation over a symbol period to provide an analog result;
- and
- a data conversion device for determining if the analog result corresponds to a predetermined digital state and, is so, generating a digital output corresponding to said predetermined digital state;
- wherein said multiply or accumulate device comprises:
- at least one series leg including first and second series connected transistors disposed between a first node and a second reference voltage, said first transistor having the gate thereof connected to the received signal on said receive input and the gate of said second transistor connected to receive said code;
- a storage device connected to said first node;
- a precharge device for enabling said first node to be precharged to a defined level prior to the initiation of the accumulation operation at the beginning of a symbol period;
- and
- wherein said first and second transistors provide a multiplication operation or said code word and the received signal and said storage device is operable to accumulate the results of the multiplication operation over a symbol period.
8 more elements
A method for decoding a CDMA encoded signal from a desired CDMA channel, comprising the steps of:
- receiving the CDMA encoded signal on a receive input;
- generating a predetermined CDMA code for a predetermined CDMA channel that corresponds to an encoded signal encoded with a corresponding CDMA code transmitted over the predetermined CDMA channel;
- providing a multiply/accumulate device including a data conversion device and a multiplication device multiplying the received signal received on the receive input by the predetermined CDMA code in the analog domain and accumulating the result of the multiplying over a symbol period to provide an analog result;
- determining if the analog result corresponds to a predetermined digital state;
- and
- providing a summation device for subtracting the output of said multiplication devices from said analog result of said multiply or accumulate device prior to input to said data conversion device associated with said multiply/accumulate device.
3 more elements
A method for decoding a CDMA encoded signal from a desired CDMA channel, comprising the steps of:
- receiving the CDMA encoded signal on a receive input;
- generating a predetermined CDMA code for a predetermined CDMA channel that corresponds to an encoded signal encoded with a corresponding CDMA code transmitted over the predetermined CDMA channel;
- multiplying in a multiplication operation the received signal received on the receive input by the predetermined CDMA code in the analog domain and accumulating the result of the multiplication operation over a symbol period to provide an analog result;
- determining if the analog result corresponds to a predetermined digital sate and, if so, generating a digital output corresponding to the predetermined digital state;
- wherein the step of generating the predetermined CDMA code is operable to generate a plurality of CDMA codes, each associated with one of a plurality of CDMA channels such that the receive input can receive a plurality of CDMA encoded signals, each signal on a different channel and further comprising the step of providing a plurality of multiply or accumulate devices, each for carrying out the multiplying and accumulation steps for a given one of the CDMA channels and wherein the step of determining for each of the multiply or accumulate devices is operable to determine if the associated analog result corresponds to the predetermined digital state and, if so, generating a digital output corresponding to the associated multiply or accumulate device such that a digital output is provided for each of the multiply or accumulate devices;
- further comprising the step of subtracting from the analog result output from each of the multiply or accumulate devices contributions from signals on selective ones of the other channels encoded with their associated CDMA codes.
3 more elements
Dependencies are inferred from the claim text.