Method for minimizing time critical transmit processing for a personal computer implementation of a wireless local area network adapter

Abstract

A personal computer's (PC) microprocessor is used to provide both the physical layer (PHY) and media access control (MAC) processing functions required to implement a wireless local area network (WLAN) adapter. This technique uses the microprocessor within the personal computer to pre-compute the time critical PHY waveforms required to respond to received packets. For instance, the acknowledge (ACK) waveform required to respond to a received WLAN packet is pre-computed and stored in the PC memory. Upon receipt of a valid packet, the samples of the ACK waveform are transferred from the PC memory to a digital to analog converter (DAC). The DAC generates the transmit waveform required for the radio modulator. By pre-computing the transmit waveform samples, the required loading on the PC microprocessor is reduced during time critical periods.

1. A method for the reduction of transmit processing in response to a received packet in a communications system comprising:
 generating a plurality of transmit control frames for responding to received packets;
 generating transmit waveform samples from the generated plurality of transmit control frames; 
 storing the transmit waveform samples in buffer memory; 
 receiving a packet; 
 determining a transmit waveform sample associated with the received packet; and 
 transmitting the determined transmit waveform sample. 
 
 
     
     
       2. A method as in  claim 1 , wherein the generating transmit control frames contain data which are learned over time from the communications system. 
     
     
       3. A method as in  claim 1 , wherein the generating transmit control frames contain a duration field. 
     
     
       4. A method as in  claim 3 , wherein the duration field is set to a maximum length packet exchange for a specific data rate. 
     
     
       5. A method as in  claim 1 , wherein the generated transmit control frames contain power management mode information. 
     
     
       6. A method as in  claim 1 , wherein the generation of the transmit waveform samples varies by data rate. 
     
     
       7. A method as in  claim 2 , wherein the learned data are transmit addresses of received packets. 
     
     
       8. A method as in  claim 1 , in which the communications system is wireless. 
     
     
       9. A method as in  claim 1 , in which the communications system is IEEE 802.11. 
     
     
       10. A method as in  claim 1 , in which the communications system is Bluetooth. 
     
     
       11. A method as in  claim 1 , in which the communications system is IEEE 802.15. 
     
     
       12. A method for the reduction of transmit processing in response to a received packet in a communications system comprising the steps of:
 maintaining in memory a plurality of transmit waveform samples; 
 generating new transmit waveform samples in response to detection of new transmit addresses in the system; 
 saving the new transmit waveform samples to the memory; 
 indexing the memory based on receiving a specific transmit address in a received packet; 
 determining an appropriate transmit waveform sample from the indexed memory; and 
 transmitting the appropriate transmit waveform sample. 
 
     
     
       13. A method as in  claim 12 , wherein the transmit waveform samples vary by data rate. 
     
     
       14. A method as in  claim 12 , wherein the indexing of memory varies by data rate. 
     
     
       15. A method as in  claim 12 , in which the communications system is wireless. 
     
     
       16. A method as in  claim 12 , in which the communications system is IEEE 802.11. 
     
     
       17. A method as in  claim 12 , in which the communications system is IEEE 802.15. 
     
     
       18. A host computer comprising:
 means for pre-computing a transmit waveform; and   means for transmitting, the pre-computed transmit waveform in response to receiving a packet, wherein the means for pre-computing the transmit waveform comprise means for generating a transmit waveform for each control frame in the set of control frames, the means comprising:   means for generating a first set of frames comprising a request to send (RTS) control frame, a clear to send (CTS) control frame, an acknowledge (ACK) control frame, a PS-Poll control frame, and a CF-End control frame, wherein a receive address for each frame in the first set of frames comprises a transmitter address of a received packet;   for each frame in the first set of frames, means for generating a second set of frames comprising a frame with a power management bit set to a 1 and a frame with the power management bit set to a 0; and   for each frame in the second set of frames, means for generating a third set of frames comprising a frame for each of one or more data rates.   
     
     
       19. A host computer comprising:
 a memory; and   a central processing unit (CPU) configured to:
 make a determination that the transmitter address of a received packet is not in an index of known addresses; 
 in response to making the determination, generate a set of control frames for the transmitter address; 
 generate a transmit waveform for each control frame in the set of control frames; and 
 store the generated transmit waveforms in the memory. 
   
     
     
       20. The host computer of claim 19, wherein the CPU configured to generate the set of control frames comprises the CPU configured to:
 generate a first set of frames comprising a request to send (RTS) control frame, a clear to send (CTS) control frame, an acknowledge (ACK) control frame, a PS-Poll control frame, and a CF-End control frame, wherein a receive address for each frame in the first set of frames comprises the transmitter address of the received packet;   for each frame in the first set of frames, generate a second set of frames comprising a frame with a power management bit set to a 1 and a frame with the power management bit set to a 0; and   for each frame in the second set of frames, generate a third set of frames comprising a frame for each of one or more data rates.