Patent Application
20100173588
The present invention relates generally to the field of Bluetooth wireless communications, and more particularly to a method and apparatus for suppressing RF (radio frequency) interference that occurs when a Bluetooth wireless communications link is used in close proximity to a device which generates interfering RF noise.
The use of the Bluetooth wireless protocol has become extremely ubiquitous. One of the most common uses of Bluetooth is for providing wireless headset capability, such as, for example, those used to connect (wirelessly) to a mobile (cell) phone in order to provide the mobile phone user with fully hands-free operation. One of the common problems experienced with such uses however, is RF (radio frequency) interference that occurs whenever the headset and/or the mobile phone is used in close proximity to a device which generates such interfering RF noise. For example, when a mobile phone which uses a Bluetooth headset is physically located near a laptop or desktop computer, such RF interference is not uncommon. This causes noise to be introduced on the call which is disturbing to the other party (or parties) on the call, as well as to the user of the Bluetooth headset him- or herself. Similar interference problems may result from the use of a Bluetooth wireless device in close proximity to any other RF noise-generating apparatus, such as automobile engines, appliances, generators, etc.
Although there are noise cancellation schemes which cancel audio noise in the vicinity of the user, these schemes are of no help to the problem of electronic interference noise in the RF transmission path. Thus, unfortunately, the only solution currently available to a user of a Bluetooth headset and/or mobile phone in close proximity to a computer is to either stop using the headset or to move away from the computer. If the user is also making use of the computer, however, neither solution is acceptable (or at least desirable). Therefore, it would be highly beneficial if a method for suppressing RF (radio frequency) interference that occurs when a Bluetooth wireless communications link is used in close proximity to a device which generates interfering RF noise could be found.
We have recognized that RF (radio frequency) interference in a Bluetooth wireless communications link may be advantageously suppressed with use of an enhancement to the Bluetooth protocol which operates to eliminate noise that is not in the audio environment but that is induced on the RF path itself by external electronic interference. In particular, in accordance with an illustrative embodiment of the present invention, the sampling rate at a Bluetooth transmitter is doubled, and samples are transmitted alternately with and without the audio data (e.g., the microphone input data for a Bluetooth headset in transmit mode, or the speaker output data for a Bluetooth-enabled mobile phone in Bluetooth transmit mode) included therein. Then, at the Bluetooth receiver, the received samples which have been transmitted without the audio data therein are subtracted from (i.e., inverted and digitally added to) corresponding (i.e., adjacent) ones of the received samples which have been transmitted with the audio data, and the receiver then advantageously uses (only) the modified samples which result from this calculation as the actual audio data. This technique thereby advantageously removes the RF interference from the signal without reducing the effective sampling rate.
Note that since the sampling rate is high compared to the frequency of the first derivative of the noise (i.e., the change in the noise), the subtraction of these adjacent samples will advantageously result in an excellent representation of the pure audio signal with substantially reduced interference noise. That is, since a received sample which has been transmitted without the audio data included therein likely contains the same noise component as the corresponding (i.e., adjacent) received sample which has been transmitted with the audio data included therein, such a subtraction of these alternating samples (i.e., subtracting those without the audio data from those with the audio data) will advantageously result in an audio signal with reduced RF interference. In particular, this technique will thereby effectively remove any noise component with duration greater than twice the sampling frequency.
More specifically, in accordance with one illustrative embodiment of the present invention, a method and apparatus is provided for wirelessly transmitting audio data across a wireless link so as to enable a receiver to reduce Radio Frequency (RF) interference present in said wireless link, the wireless link being used to transmit a sequence of audio data samples each comprising a portion of said audio data, the method or apparatus comprising: transmitting a first sample comprising one of said audio data samples in said sequence; and transmitting a second sample, in close temporal proximity to said transmission of said first sample, wherein said second sample does not comprise any of said audio data.
In addition, in accordance with another illustrative embodiment of the present invention, a method and apparatus is provided for reducing Radio Frequency (RF) interference from audio data received at a wireless receiver from a wireless link, the wireless link being used to transmit a sequence of audio data samples each comprising a portion of said audio data, the method or apparatus comprising: receiving a first sample comprising one of said audio data samples in said sequence; receiving a second sample, in close temporal proximity to said receipt of said first sample, wherein said second sample does not comprise any of said audio data; and modifying said received first sample comprising said audio data sample based on said received second sample, such that a portion of said Radio Frequency (RF) interference is reduced.
As explained above, in accordance with an illustrative embodiment of the present invention, the sampling rate at a Bluetooth transmitter is advantageously doubled, and samples are advantageously transmitted alternately with and without the audio data (e.g., the microphone input data for a Bluetooth headset in transmit mode, or the speaker output data for a Bluetooth-enabled mobile phone in Bluetooth transmit mode) included therein. Then, at the Bluetooth receiver, the received samples which have been transmitted without the audio data therein are advantageously subtracted from (i.e., inverted and digitally added to) corresponding (i.e., adjacent) ones of the received samples which have been transmitted with the audio data, thereby removing the RF interference from the signal without reducing the effective sampling rate.
In accordance with one illustrative embodiment of the present invention, a flag is advantageously sent along with each sample to indicate whether the given sample comprises one which has been transmitted with the audio data included therein or one which has been transmitted without the audio data included therein. In this manner, the receiver can easily identify which samples have the audio data and which do not. In accordance with other illustrative embodiments of the present invention, other approaches, easily derived by those of ordinary skill in the art, may be employed to identify which samples have the audio data and which do not.
In accordance with one such illustrative embodiment of the present invention (which uses another approach to identify which samples have the audio data and which do not), for example, an initial flag indicating whether the first sample to be sent thereafter does or does not have the audio data, followed by a strict alternation of such samples, will enable the receiver to easily keep track of which samples are which. And, in accordance with yet another such illustrative embodiment of the present invention (which uses yet another approach to identify which samples have the audio data and which do not), no flags are transmitted along with the alternating samples (i.e., those with audio data and those without), and the receiver advantageously “assumes” that samples having a smaller magnitude (as compared with the preceding or following sample) are, in fact, samples without audio data included, whereas samples having a larger magnitude (as compared with the preceding or following sample) are, in fact, samples with audio data included.
Note that in accordance with various illustrative embodiments of the present invention, these processes may be performed in either one or in both directions of a Bluetooth wireless link. For example, in accordance with one illustrative embodiment of the present invention, the subtraction of alternative samples may be advantageously performed in a Bluetooth-enabled mobile phone but not in a Bluetooth headset (and, therefore, the transmission of alternating samples with and without the audio data included would be advantageously performed only in the headset and not in the mobile phone), since the smaller size and desired cost of the Bluetooth headset may make the inclusion of such functionality slightly more difficult or costly. It is preferable, however, to perform the illustrative processes of the present invention in both directions, in order to fully suppress the RF interference.
Specifically, in block 21 of the illustrative flowchart shown in
Specifically, in block 31 of the illustrative flowchart shown in
Next, in block 35, the sample (without audio data) received in block 34 is inverted and added to (i.e., subtracted from) the stored sample (i.e., the corresponding sample with the audio data) which was previously stored in accordance with block 33. The resultant value is then advantageously output in block 36. This output may, for example, comprise a modified (i.e., corrected) audio sample for use in an audio signal to be transmitted by a mobile phone to another party to the conversation. Finally, flow returns to block 31 to receive the next sample, which should be (again, based on the alternation of samples with and without audio data as transmitted by the illustrative flowchart of
It should be noted that all of the preceding discussion merely illustrates the general principles of the invention. It will be appreciated that those skilled in the art will be able to devise various other arrangements, which, although not explicitly described or shown herein, embody the principles of the invention, and are included within its spirit and scope. For example, although the above discussion has focused primarily on Bluetooth-enable mobile (e.g., cellular) phones and Bluetooth headsets, it will be obvious to those of ordinary skill in the art that the principles of the present invention may be equally advantageous and may be easily applied in numerous other contexts in which a wireless link of any type is subject to electronic (e.g., RF) interference from any source whatsoever.
In addition, although the above described embodiments have been limited to those which send (and receive) samples which strictly alternate between those that do have the audio data included therein and those that do not, it will be obvious to those skilled in the art that numerous other arrangements in which some samples are sent without the audio data may be used to accomplish the same result. That is, the fundamental principle of (a) transmitting samples which do not include the audio data, which are (in any way) interspersed with samples that do include the audio data, and (b) at the receiver, using the samples which do not include audio data as a basis with which to reduce or eliminate electronic interference present in the samples which do include the audio data, may be applied in a large variety of situations, and are all intended to be included within the scope of the instant claims herein.
In addition, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. It is also intended that such equivalents include both currently known equivalents as well as equivalents developed in the future—i.e., any elements developed that perform the same function, regardless of structure.
