U.S. patent application number 10/064269 was filed with the patent office on 2004-01-01 for insertion of null packets to mitigate the effects of interference in wireless communications.
This patent application is currently assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Lyle, Ruthie D., Lynch, Jamel Pleasant JR., Udoh, Usen E., Vigilante, William JR..
Application Number | 20040001530 10/064269 |
Document ID | / |
Family ID | 29778403 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040001530 |
Kind Code |
A1 |
Lyle, Ruthie D. ; et
al. |
January 1, 2004 |
Insertion of null packets to mitigate the effects of interference
in wireless communications
Abstract
Mitigation of interference effects in certain wireless
communications is accomplished by the disclosed method. A wireless
communications device communicates utilizing a protocol which
requires hopping from channel to channel within a communications
frequency band while transmitting. Operating according to the
disclosed method, the device scans the available communications
channels and identifies channel(s) experiencing interference from
other transmitting devices. When hopping to such identified
channels, the device transmits only null packets, thus avoiding the
need to re-transmit packets due to interference and mitigating the
effects of such interference on the communications data rate.
Inventors: |
Lyle, Ruthie D.; (Durham,
NC) ; Lynch, Jamel Pleasant JR.; (Durham, NC)
; Udoh, Usen E.; (Raleigh, NC) ; Vigilante,
William JR.; (Raleigh, NC) |
Correspondence
Address: |
IBM CORPORATION
PO BOX 12195
DEPT 9CCA, BLDG 002
RESEARCH TRIANGLE PARK
NC
27709
US
|
Assignee: |
INTERNATIONAL BUSINESS MACHINES
CORPORATION
New orchard Road
Armonk
NY
10504
|
Family ID: |
29778403 |
Appl. No.: |
10/064269 |
Filed: |
June 27, 2002 |
Current U.S.
Class: |
375/132 ;
375/E1.036 |
Current CPC
Class: |
H04B 1/715 20130101 |
Class at
Publication: |
375/132 |
International
Class: |
H04B 001/713 |
Claims
1. in a wireless communications system providing for communication
over two or more channels utilizing a communications architecture
that calls for hopping from channel to channel during data
transmission, a method for mitigating the effects of interference,
the method comprising: scanning the channels for interference and
identifying channels experiencing interference; transmitting only
null packets when hopping to a channel identified as experiencing
interference; transmitting normal data when hopping to a channel
not identified as experiencing interference.
2. The method of claim 1 wherein the scanning step is performed
upon the commencement of data transmission.
3. The method of claim 1 wherein the scanning step is performed
upon each passage of a first time period.
4. The method of claim 2 wherein the scanning step is repeated
periodically during data transmission.
5. The method of claim 1 wherein the scanning step is performed
when a data throughput rate falls below a predefined value.
6. The method of claim 1 wherein the scanning step is performed
when requested by a user.
7. The method of claim 2 wherein the scanning step is repeated
whenever: a) a second time period has passed: b) a data throughput
rate falls below a predefined value; or c) requested by a user.
8. The method of claim 1 wherein the communication architecture is
the standard known as Bluetooth.
9. The method of claim 1 wherein the communication architecture is
the standard known as IEEE 802.15.1.
10. The method of claim 7 wherein the communication architecture is
the standard known as Bluetooth.
11. 1)The method of claim 7 wherein the communication architecture
is the standard known as IEEE 802.15.1.
12. In a wireless communications system providing for communication
in the ISM communications frequency band by a communications device
operating according to the Bluetooth standard, a method for
mitigating the effects of interference, the method comprising: upon
power up of the device, scanning the available channels for
interference and identifying channels experiencing interference;
transmitting only null packets when hopping to a channel identified
as experiencing interference; transmitting normal data when hopping
to a channel not identified as experiencing interference.
13. The method of claim 12 wherein the scanning step is repeated
periodically during data transmission.
14. The method of claim 12 wherein the scanning step is repeated
when a data throughput rate falls below a predefined value.
15. The method of claim 12 wherein the scanning step is repeated
when requested by a user.
16. The method of claim 12 wherein the scanning step is repeated
whenever: a) a third time period has passed; b) a data throughput
rate falls below a predefined value; or c) requested by a user.
17. In a wireless communications system providing for communication
in the ISM communications frequency band by a communications device
operating according to the IEEE 802.15.1 standard, a method for
mitigating the effects of interference, the method comprising: upon
power up of the device, scanning the available channels for
interference and identifying channels experiencing interference;
transmitting only null packets when hopping to a channel identified
as experiencing interference; transmitting normal data when hopping
to a channel not identified as experiencing interference.
18. The method of claim 17 wherein the scanning step is repeated
when a data throughput rate falls below a predefined value.
19. The method of claim 17 wherein the scanning step is repeated
when requested by a user.
20. The method of claim 17 wherein the scanning step is repeated
whenever: a) a fourth time period has passed; b) a data throughput
rate falls below a predefined value; or c) requested by a user.
Description
BACKGROUND OF THE INVENTION
[0001] Wireless communications is currently enjoying a period of
rapid technological advancement and tremendous growth in
popularity. In order to allow wireless communication to become
truly convenient and omnipresent, standards have been developed and
implemented so that the various wireless-enabled devices may
readily communicate with one another. One such standard has been
developed by Bluetooth SIG, Inc. (SIG="Special Interest Group"), a
consortium of companies interested in seeing the growth in wireless
networks continue. The standard developed by this group has become
known as Bluetooth and devices conforming to the standard are known
as Bluetooth devices or Bluetooth-enabled devices. The Bluetooth
standard is based on the IEEE ("Institute of Electrical and
Electronics Engineers") 802.11b standard and applies to a
short-range radio system designed to replace cables in a personal
area network (in the 10 m range). These devices operate in what is
known as the Industrial Science and Medicine ("ISM") communications
band around a frequency of 2.45 Ghz. The ISM band actually extends
from 2.4 Ghz to 2.480 Ghz and includes 79 communication channels or
sub-ranges of frequency, on which devices may communicate.
[0002] Many other types of devices operating according to
applicable standards also operate on the various channels within
the ISM band. For instance, Wireless Local Area Network ("WLAN")
devices (also based on the IEEE 802.11b standard) operate in the
ISM. Devices operating according to the WLAN standard are designed
to replace a wired LAN infrastructure. Other types of devices that
operate in the ISM band include microwaves, various types of
monitoring devices such as baby monitors, etc.
[0003] Very recently, the IEEE Standards Board adopted a new
communications standard, IEEE 802.15.1, known as "Wireless MAC and
PHY Specifications for Wireless Personal Area Networks
(WPANs.TM.)". This standard closely mirrors the Bluetooth standard.
Adoption of such a standard by the widely-recognized IEEE Standards
Board means that wireless devices designed to operate in wireless
personal area networks are even more likely to model their
operation on this standard. Unless otherwise noted, where specific
features or requirements of the Bluetooth standard and Bluetooth
devices are discussed below, those same features or requirements
are present in the IEEE 802.15.1 standard.
[0004] As enabling technologies advance and as standards are
developed and adopted, wireless networks and the communications and
other applications running thereon, are expected to become more and
more prevalent. This area of technology is expected to experience
explosive growth over the next several years. Even before the
recent standard adoption by the IEEE, it was forecast that by the
year 2004 there will be over 100 million Bluetooth devices in the
United States alone and over 400 million worldwide.
[0005] One problem associated with all types of wireless
communications is that signals being transmitted by different
devices at the same frequency can interfere with one another. This
can be referred to as co-channel interference when it occurs
between devices operating in the same ISM channel. Interference can
also occur between devices operating at frequencies which are not
the same but which are close to one another. For devices operating
in adjacent ISM channels, this can be referred to as adjacent
interference. Both types of interference can cause communication
packets to be lost, garbled or misinterpreted by the receiving
device, hindering the practical speed and accuracy of the wireless
communications.
[0006] In an attempt to minimize the incidence of serious
interference, the Bluetooth standard calls for Bluetooth devices to
"hop" on all 79 channels within the ISM band. That is, the devices
transmit only a certain amount of data on a channel before moving
to another channel to continue transmitting. The standard
establishes the criteria for hopping--how much data to transmit on
each channel, when to hop and the order in which to hop to each
channel. Devices following the standard understand these criteria
and are able to establish and maintain communications with one
another while hopping from channel to channel. Because of the
advantages of hopping from channel to channel while transmitting,
it is likely that other, non-Bluetooth devices will implement this
strategy for avoiding interference.
[0007] The Bluetooth standard calls for re-transmitting packets
when data is lost in transmission, typically due to interference.
The procedure for re-transmitting increases transmission time and
degrades the data rate. In many of the applications to which
Bluetooth devices are applied, such as voice transmissions over IP
(internet protocol), even the smallest degradation in the data rate
is unacceptable because the quality of the signal quickly degrades
to an unusable state.
[0008] Unlike Bluetooth devices, WLAN devices, and most other
devices operating in the ISM band, select one static channel and
transmit data only on that channel. Because they are designed to
operate over a greater distance than Bluetooth devices, WLAN
devices transmit much more powerful signals. Therefore, Bluetooth
device signals can experience serious interference problems when
hopping to a channel upon which a WLAN device is transmitting, or
to an adjacent channel. As Bluetooth and WLAN devices, and other
types of devices operating in the ISM band, become more and more
popular, the prevalence of this type of interference will increase.
The resulting degradation in performance will seriously hinder
customer acceptance of this emerging technology.
[0009] For these reasons, and others readily identified by those
skilled in the art, it would be desirable to develop communications
techniques applicable to the Bluetooth (and IEEE 802.15.1)
standard, and to the communication protocols of any other wireless
devices which hop from channel to channel while transmitting, which
will minimize the effects on performance of any interference due to
the transmission signals of other devices in the ISM band.
SUMMARY OF THE INVENTION
[0010] The present invention contemplates a method whereby a
wireless device communicating according to certain communications
standards may eliminate or mitigate the effects on the
communication rate of interference from other wireless
communications signals. The present invention is applicable to
wireless devices operating according to any communications standard
which requires that the device hop from communications channel to
communications channel within a defined communication frequency
band. This method does not require changes to the standards
definitions nor does it require any modifications to the receiving
device. In realizing these and other purposes of the present
invention, a communications method calls for a wireless device to
scan the channels of the applicable communications frequency band
and identify any channel where other device(s) are transmitting and
causing interference. When the wireless device hops to one of the
channels identified as experiencing interference, the device
transmits only null packet(s) on that channel instead of data
packet(s). Normal communications transmission is continued when the
device hops to a channel which has not been identified as
experiencing interference.
BRIEF DESCRIPTION OF DRAWINGS
[0011] Some of the purposes of the invention having been stated,
others will appear as the description proceeds, when taken in
conjunction with the accompanying drawing, in which:
[0012] FIG. 1 is a figurative illustration of the ISM
communications frequency band showing a WLAN device transmitting on
one channel.
[0013] FIG. 2 is a simple representation of a wireless
communications device according to the present invention, showing
one possible method of marking channels which are experiencing
interference.
[0014] FIG. 3 is a figurative illustration of a wireless
communications device according to the present invention
transmitting data.
[0015] FIG. 4a is a flow-chart of a first embodiment of the method
of the present invention.
[0016] FIG. 4b is a flow-chart of a second embodiment of the method
of the present invention.
[0017] FIG. 4c is a flow-chart of a third embodiment of the method
of the present invention.
[0018] FIG. 4d is a flow-chart of a fourth embodiment of the method
of the present invention.
DETAILED DESCRIPTION
[0019] While the present invention will be described more fully
hereinafter with reference to the accompanying drawings, in which a
preferred embodiment(s) of the present invention is shown, it is to
be understood at the outset of the description which follows that
persons of skill in the appropriate arts may modify the invention
here described while still achieving the favorable results of the
invention. Accordingly, the description which follows is to be
understood as being a broad, teaching disclosure directed to
persons of skill in the appropriate arts, and not as limiting upon
the present invention.
[0020] Devices capable of wireless communications according to the
Bluetooth, IEEE 802.15.1 and other standards and the various
methods and technologies employed by such devices to transmit and
receive data are well known to persons skilled in the relevant
arts. Such devices may be implemented in any of the many alternate
embodiments that are available without departing from the spirit of
the present invention. Detailed descriptions of such devices and
technologies are not required for an understanding of the present
invention. This invention relates only to an improvement to the
method of operation of such devices.
[0021] In accordance with this invention, a device capable of
wireless communication over one or more channels within a defined
frequency band, such as a Bluetooth device, for example, is
provided with the capability of scanning the available channels and
identifying any channels on which other devices are transmitting.
FIG. 1 illustrates the ISM communications band 100 with its various
communications channels 110. A WLAN device (not shown), for
example, transmitting communications packets 130 on one of the
channels, identified as channel 3 for purposes of illustration. In
this example, channel 3 would be identified as experiencing
interference.
[0022] A Bluetooth device practicing the communications method
according to the present invention includes the capability to
maintain a record of which channel(s) have been so identified at
least as long as the device is powered on and operating. With
reference to FIG. 2, this might be accomplished using a simple
array 160 stored in a local volatile or non-volatile memory module
170 of the communicating device 180. The array could include an
entry 190 for each available channel whose value (0 or 1, for
example) could indicate whether the associated channel was
currently identified as experiencing interference. The device could
alternatively maintain a record of channels identified as
experiencing interference in any one of the many other ways such
information is stored and accessed in electronic devices, as well
understood by those skilled in the relevant arts.
[0023] As discussed above, a communications device according to the
present invention hops from channel to channel while transmitting
data. When practicing the method of the present invention, the
device checks its record of channels experiencing interference each
time it hops. If it is hopping to a channel currently marked as
experiencing interference, only null packets, that is, packets
containing no data, are transmitted on such channel. If it is
hopping to a channel that is not currently marked as experiencing
interference, normal data packets are transmitted. In this way, the
device avoids the need to re-transmit packets which are lost or
garbled due to being transmitted on channels experiencing
interference. Since the device knows that only null packets were
transmitted on those channels, any packets lost or garbled on those
channels can simply be ignored.
[0024] Referring now to FIG. 3, a communicating device according to
the present invention is (not shown) transmitting data packets 200
on the various available communications channels 110 in the manner
called for by the Bluetooth and similar standards. As described in
the example above, channel 3 has been identified as experiencing
interference from a transmitting WLAN device. As such, when hopping
to channel 3, the device according to the present invention only
transmits a null packet(s) 210, and continues transmitting data
packets 200 when the transmission moves on to other channels.
[0025] In one embodiment of the present invention, a wireless
communications device practicing the method of the present
invention automatically scans the available communications channels
upon power up, marking those channels experiencing interference.
This embodiment of the present method is illustrated in FIG. 4a. In
another embodiment, a wireless communications device practicing the
method of the present invention would not automatically scan the
channels at power up. Instead, scanning would be initiated only if
the communications data rate dropped below a certain level. The
threshold data rate could be user-configurable or could be set at
manufacture. In any event, the threshold would be set at a point
where it is apparent that interference is seriously impacting the
effective data rate. This embodiment of the present method is
illustrated in FIG. 4b.
[0026] A third embodiment calls for a wireless communications
device practicing the method of the present invention to initiate a
scan of the channels for interference only when manually triggered
to do so by a user. This embodiment of the present method is
illustrated in FIG. 4c. Finally, a fourth embodiment requires that
the wireless communications device practicing the method of the
present invention perform the channel scan after the passage of a
certain time period. This embodiment of the present method is
illustrated in FIG. 4d. Again, the time period could be
user-configurable or could be set at manufacture. This would insure
that the channels marked as experiencing interference would remain
accurate and up-to-date.
[0027] These embodiments of the present method can also be used in
combination. A wireless communications device of the present
invention could scan for channels experiencing interference upon
power up. Then, if the wireless communications data rate were to
fall below a certain rate, the device could initiate a new scan to
determine if different or additional channels were experiencing
interference. Or, a new scan could be initiated after each passage
of a certain amount of time. This would avoid the situation where
the device continues sending null packets on a channel marked as
experiencing interference long after the marked channel ceased
experiencing interference. On top of all that, the device could
allow a user to initiate a new scan at any time through some type
of user input interface.
[0028] As readily recognized by those skilled in the art, the exact
order of the method steps illustrated and discussed herein may be
varied in any advantageous manner without deviating from the
present invention. Also, where appropriate, steps may be repeated,
skipped or combined to better operate in a given environment.
[0029] In the drawings and specification there has been set forth
preferred embodiments of the invention, and, although specific
terms are used, the description thus given uses terminology in a
generic and descriptive sense only and not for purposes of
limitation.
* * * * *