Modifying system clocks based on particular WLAN channel that is selected to improve RF sensitivity of a radio module
Techniques are provided for selecting one of a plurality of clock signals used to drive a bus of a WLAN-enabled device having a WLAN radio module coupled to the bus and designed to operate over a plurality of WLAN channels. A network infrastructure device, such as an access point or port, is provided that comprises a WLAN radio module, a PCI bus coupled to the WLAN radio module, a look up table (LUT) and a processor. The WLAN radio module designed to operate over a plurality of WLAN channels in a first frequency band. The LUT comprises a plurality of entries. Each entry comprises: a particular one of the WLAN channels and a corresponding one of a first clock signal having a first clock frequency and a second clock signal having a second clock frequency that is to be selected. The first clock signal causes interference at the WLAN radio module when operating over a first subset of the WLAN channels, and the second clock signal causes interference at the WLAN radio module when operating over a second subset of the WLAN channels. The processor selects, from the LUT based on the one of the WLAN channels that has been selected for the WLAN radio module to communicate over, either the first clock signal or the second clock signal that is to be used to drive the bus.
1. A method for selecting one of a plurality of clock signals used to drive a bus of a radio device comprising a radio module coupled to the bus and designed to operate over a plurality of radio channels in a first frequency band, the method comprising:
storing a look up table (LUT) comprising a plurality of entries, wherein each entry comprises: a particular one of the radio channels and a corresponding one of a first clock signal having a first clock frequency and a second clock signal having a second clock frequency that is to be selected;
selecting, at a particular time, one of the radio channels that the radio module is to communicate over;
determining from the LUT, based on the one of the radio channels that has been selected for the radio module to communicate over, that either the first clock signal or the second clock signal is to be used to drive the bus;
sending a command indicating a selected clock signal from the determining step to a logic device;
selecting, at the logic device based on the command, either the first clock signal or the second clock signal to drive the bus; and
driving the bus with either the first clock signal or the second clock signal.
2. A method according to claim 1 , when the radio device is operating using the first clock signal and, further comprising:
receiving the command at the logic device that indicates that the logic device is to select the second clock signal as the clock signal that is provided to the bus; and
transparently transitioning from the first clock signal to the second clock signal as the particular clock signal that is used to drive the bus.
3. A method according to claim 2 , wherein the step of transparently transitioning from the first clock signal to the second clock signal as the particular clock signal that is used to drive the bus, comprises the steps of:
receiving the command;
waiting for a falling edge of the first clock signal to happen, stopping the first clock signal and holding the first clock signal low; and
waiting for a next rising edge of the second clock signal and resuming operation at the next rising edge of the second clock signal with the second clock signal driving the bus.
4. A method according to claim 1 , when the radio device is operating using the second clock signal and, further comprising:
receiving the command at the logic device that indicates that the logic device is to select the first clock signal as the clock signal that is provided to the bus; and
transparently transitioning from the second clock signal to the first clock signal as the particular clock signal that is used to drive the bus.
5. A method according to claim 4 , wherein the step of transparently transitioning from the second clock signal to the first clock signal as the particular clock signal that is used to drive the bus, comprises the steps of:
receiving the command;
waiting for a falling edge of the second clock signal to happen, stopping the second clock signal and holding the second clock signal low; and
waiting for a next rising edge of the first clock signal and resuming operation at the next rising edge of the first clock signal with the first clock signal driving the bus.
6. A method according to claim 1 , wherein the first clock signal causes interference at the radio module when the radio module is operating over a first subset of the radio channels, and wherein the second clock signal, causes interference at the radio module when the radio module is operating over a second subset of the radio channels.
7. A method according to claim 6 , wherein the first clock frequency is approximately 64.000 MHz, wherein the second clock frequency is approximately 66.667 MHz, and wherein the first frequency band is the 2.4 GHz frequency band.
8. A method according to claim 1 , wherein the radio device is an access point and the radio channels are wireless local area network (WLAN) channels, wherein the radio module is a WLAN radio module, wherein the bus is a Peripheral Component Interconnect (PCI) bus and wherein the processor is an embedded network processor.
9. A radio frequency (RF) device, comprising:
a bus;
a first clock source that generates a first clock signal having a first clock frequency, and a second clock source that generates a second clock signal having a second clock frequency;
a wireless local area network (WLAN) radio module coupled to the bus, and being designed to communicate over a plurality of WLAN channels in a first frequency band, and being configured at a particular time to operate over one of the WLAN channels;
a look up table (LUT) comprising a plurality of entries, wherein each entry comprises: a particular one of the WLAN channels and a corresponding one of the first clock signal or the second clock signal that is to be used to drive the bus;
a processor coupled to the bus and the WLAN radio module, wherein the processor is designed to determine from the LUT, based on a particular WLAN channel that has been selected for the WLAN radio module to communicate over, that either the first clock signal or the second clock signal is to be used to drive the bus, wherein the processor is further designed to generate and send a command to select either the first clock signal or the second clock signal as the particular clock signal that is to be used to drive the bus; and
a logic device, coupled to the processor, the WLAN radio module, the first clock source, the second clock source, wherein the logic device is designed to receive the command indicating the selected clock signal from the processor, and drive the bus with either the first clock signal or the second clock signal specified by the command.
10. A RF device according to claim 9 , when the first clock signal is driving the bus and the WLAN radio module prepares to change WLAN channels causing the logic device to receive the command to select the second clock signal as the particular clock signal that drives the bus, wherein the logic device is designed to transparently transition from the first clock signal to the second clock signal as the particular clock signal that drives the bus.
11. A RF device according to claim 10 , when the second clock signal is driving the bus and the WLAN radio module prepares to change WLAN channels causing the logic device to receive the command to select the first clock signal as the particular clock signal that drives the bus, wherein the logic device is designed to transparently transition from the second clock signal to the first clock signal as the particular clock signal that drives the bus.
12. A RF device according to claim 9 , wherein the first clock signal causes interference at the WLAN radio module when the WLAN radio module is operating over a first subset of the WLAN channels, and wherein the second clock signal, causes interference at the WLAN radio module when the WLAN radio module is operating over a second subset of the WLAN channels.
13. A RF device according to claim 12 , wherein the first clock frequency is approximately 64.000 MHz, wherein the second clock frequency is approximately 66.667 MHz, and wherein the first frequency band is the 2.4 GHz frequency band.
14. A RF device according to claim 9 , wherein the WLAN-enabled device is an access point, wherein the bus is a Peripheral Component Interconnect (PCI) bus and wherein the processor is an embedded network processor.
15. A network infrastructure device, comprising:
a WLAN radio module designed to operate over a plurality of WLAN channels in a first frequency band;
a Peripheral Component Interconnect (PCI) bus coupled to the WLAN radio module;
a look up table (LUT) comprising a plurality of entries, wherein each entry comprises: a particular one of the WLAN channels and a corresponding one of a first clock signal having a first clock frequency and a second clock signal having a second clock frequency that is to be selected, wherein the first clock signal causes interference at the WLAN radio module when operating over a first subset of the WLAN channels, and wherein the second clock signal causes interference at the WLAN radio module when operating over a second subset of the WLAN channels;
a processor designed to select from the LUT, based on a particular one of the WLAN channels that has been selected for the WLAN radio module to communicate over, either the first clock signal or the second clock signal that is to be used to drive the bus; and
a device designed to receive the first clock signal, the second clock signal and a command indicating a selected clock signal from the processor, and drive the bus, in response to the command, with either the first clock signal or the second clock signal that is selected by the processor.
16. A network infrastructure device according to claim 15 , wherein the first clock frequency is approximately 64.000 MHz, wherein the second clock frequency is approximately 66.667 MHz, and wherein the first frequency band is the 2.4 GHz frequency band.