Method and apparatus to allow coexistence between wireless devices

The present invention relates generally to wireless transceivers, and more particularly but not exclusively to non 802.11 detection and avoidance methodologies for wireless devices including transceivers. In one or more implementations, a method for detecting non 802.11 operating in the unlicensed 5.25-5.35 and 5.47-10.725 GHz radio bands, using wireless devices, such as AP, are provided. An AP is used to automatically detect the presence of non 802.11 on all channels in these bands, alert all of its clients, and move to another channel that is known to be devoid of non 802.11 using one or more implementations.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is related to provisional patent application Ser. No. 61/104,693, filed Oct. 10, 2008, entitled “A Method and Apparatus to Allow Coexistence Between Wireless Devices,” and assigned to the assignee of the present application, and also to co-pending U.S. patent application Ser. No. 11/963,658, filed Dec. 21, 2007, entitled, “A Configurable Radar Detection and Avoidance System for Wireless OFDM Transceivers,” both of which are incorporated by reference in their entirety herein.

FIELD OF THE INVENTION

The present invention relates generally to wireless transceivers, and more particularly but not exclusively to non 802.11 detection and avoidance methodologies for wireless devices including transceivers.

BACKGROUND OF THE INVENTION

Presently, it is known that the ISM bands are becoming crowded, with many different types of wireless devices, among those being WiFi (802.11), BlueTooth (802.15.1), and Zigbee (802.15.4), cordless phones, and others. It is understood that when these devices operate in close proximity, interference between the devices may cause performance loss, or severe degradation for particular devices. In some cases, one particular device may be rendered inoperable, and lose wireless connectivity completely. There is a need in the industry for these devices to share the limited band so that all devices may function properly, and most desirably, with little or no performance degradation.

One particularly concerning interference problem is known to occur between existing non 802.11 devices such as Blue Tooth and Zigbee devices, and WiFi devices based on the upcoming 802.11n standard, which allows devices to operate at 40 MHz wide channels. A 40 MHz WiFi channel overlaps excessively with the Non 802.11 channel, and can interrupt Non 802.11 operation. Although the Non 802.11 is equipped with interference avoidance schemes like Adaptive Frequency Hopping (AFH), a wide bandwidth of 40 MHz WiFi channel will cause this mechanism to fail, and Non 802.11 performance to degrade. This occurs because the overlap with a 40 MHz WiFi channel can block out up to 75% of the Non 802.11 bandwidth. This particular problem is of great concern because of the deployment of WiFi and Non 802.11 devices is so widespread across the world.

A potential coexistence issue has been identified between Non 802.11 wireless devices (IEEE 802.15.1) and IEEE 802.11n in WiFi products, operating in the 2.4 GHz ISM band. An 802.11n STA operating with 40 MHz wide channels can degrade the performance of Non 802.11 headsets. One possible coexistence solution is for the 802.11n device to scan for the presence of non-802.11n devices, and switch to 20 MHz operation to avoid this conflict.

Industry standards often require interoperability, whenever possible, between different devices operating in the same frequency band. To avoid interference, devices will reduce transmit power levels, or move to a different channel in the band, or time-share the same channel. For the particular problem of WiFi/Non 802.11 interference, both devices have been shown to coexist, provided the WiFi device can properly detect the presence of a Non 802.11 device and appropriately limit operation to 20 MHz bandwidth. With the operation limited to 20 MHz, the Non 802.11 AFH feature enables the Non 802.11 device to operate in the remaining bandwidth, and avoid interference with the WiFi transmissions. This particular method of detecting the presence Non 802.11 devices, and backing off to 20 MHz operation to allow coexistence is recommended in the discussions at IEEE 802.11n standard (Draft 6.0).

Therefore, it is highly desired to be able to provide a solution which overcomes the shortcomings and limitations of the present art and more particularly provides a configurable non 802.11 detection and avoidance method and system for wireless devices.

The present invention in accordance with its various implementations herein, addresses such needs.

SUMMARY OF THE INVENTION

In various implementations of the present invention, a configurable non 802.11 detection and avoidance system is provided for wireless devices, thereby providing improved non 802.11 detection, timely transfers of communications to another channel as needed, and compliance with associated standards and specifications and coexistence between clients.

The present invention in various implementations provides for a configurable non 802.11 detection and avoidance system for wireless devices operating in the unlicensed band range.

In one aspect, one or more wireless devices, such as an AP, is used to automatically detect the presence of non 802.11 on each operable channel within the unlicensed band range, alert the clients in communication with the wireless device, and transfer the operation to another channel that is known to be devoid of non 802.11, or a channel that produces the least interference to allow for coexistence of such clients.

In another aspect, a configurable non 802.11 detection system comprising: one or more non 802.11 detector modules each module capable of detecting non 802.11 signals of non 802.11 types different from one another, a detection and analysis module to determine non 802.11 presence from one or more detected non 802.11 signals of one or more non 802.11 detector modules, an automatic gain controller for controlling one or more detection parameters of one or more non 802.11 detector modules, and, report signals for reporting detected the presence and type of non 802.11 signals, is provided.

In other aspects, using one or more wireless devices, a configurable non 802.11 detection and avoidance system is provided for detecting periodic (short pulse), non-periodic (long pulse) waveforms. In further aspects, a configurable non 802.11 detection and avoidance system is provided operable in high data traffic situations. This can be used to detect and characterize undesirable interference from non wireless systems, like microwave, hair dryer, etc. The details of this aspect are disclosed in “A Configurable Radar Detection and Avoidance System for Wireless OFDM Transceivers,” patent application Ser. No. 11/963,658, filed Dec. 21, 2007 and assigned to the assignee of the present invention, which is incorporated by reference in its entirety herein.

In another implementation, the present invention is a data system having computer-readable program code portions stored therein to.

DETAILED DESCRIPTION

The present invention relates generally to a system for non 802.11 detection and avoidance methodologies for wireless devices including transceivers.

As used herein, as will be appreciated, the invention and its agents, in one or more implementations, separately or jointly, may comprise any of software, firmware, program code, program products, custom coding, machine instructions, scripts, configuration, and applications with existing software, applications and data systems, and the like, without limitation.

U.S. patent application, Ser. No. 11/963,658, filed Dec. 21, 2007, entitled, “A Configurable Radar Detection and Avoidance System for Wireless OFDM Transceivers”, incorporated in its entirety herein, details technology that can be applied to the non 802.11 detection and avoidance problem, with special reference to periodic and non-periodic repeating waveforms (like DFS radar). It includes a configurable signal detection module, which can be programmed so that the detection sensitivity can be optimized for the signature of the non 802.11 signal.

A key feature of the present invention is that the detection of non 802.11 signals is performed during normal 802.11n WiFi operation. When non 802.11 signals are detected, the system then directs a basic service set (BSS) to switch channels to a non 802.11-free channel or choose an operating mode that results minimum interference. To maintain high throughput during the non 802.11 detection process, it is essential that the non 802.11 scanning occur simultaneously with normal network operation. The device details several mechanisms in the baseband, MAC and software layers to support this feature, and modified elements of this design are part of a system and method in accordance with the present invention.

FIG. 1depicts a diagram of a wireless local area network (WLAN) network having a WiFi phone device detection and avoidance system in accordance with one or more implementations.

InFIG. 1, a WLAN system100is depicted with components (i.e., client devices, devices or clients) of the WLAN that are in communication or capable of communication with the AP101and one another, as each is comprised of communication capability110and technology associated with WiFi-equipped devices111, for example. Client devices, such as 802.11n capable laptop computer102, a WiFi client103, or a WiFi (Skype) phone104, are examples of clients, but the present invention and its associated implementations are not so limited. By further example the AP, or base station,101is also in communication with an internet WAN or a local area network (LAN) at120.

FromFIG. 1, each device is capable of wireless transmission back to the base station, or AP, using a standard communication protocol and modulation scheme, such as but not limited to IEEE802.11n. Examples of types of applications and services supported by this type of network include Internet browsing on a laptop, photo sharing with a network enabled camera, phone call conversations via a “WiFi” phone, video viewing or sourcing with a high definition television (HDTV) or video server, or audio streaming of internet radio programs. Typically, the network will operate in the ISM (industrial, scientific, and medical) frequency bands (2.4-2.5 GHz, 5.725-5.875 GHz). In addition, operating in the same band may be other non-802.11 wireless devices, not complying with the 802.11 standard. In theFIG. 1, the 802.11n network devices are capable of operating using both 20 MHz and 40 MHz wide channels.

InFIG. 1, the AP101, while communicating with the clients, is also capable of detecting a non 802.11 source130on the communication channel via the non 802.11 detection system of the present invention140, in one or more implementations. If a transmitted non 802.11 signal135is detected by the AP161via the non 802.11 detection system140, the AP101will announce the presence of the non 802.11 detection by notifying the clients of a channel change, ceasing communication and changing all clients to a new channel that is known to be devoid of non 802.11 signals. If one of the clients (102,103or104) detects the presence of the non 802.11 signal via the detection system, then, they will communicate the details to the AP and the AP will suitably respond. The detailed procedure is explained below.

FIG. 2depicts a diagram200of the AP baseband (BB)211and medium access layer (MAC) processing220associated with non 802.11 detection, in accordance with one or more implementations.

FromFIG. 2, the AP210is equipped with the non 802.11 detection and avoidance system of the present invention, in one or more implementations. After the non 802.11 signal230enters (or is detected by) the receiver antenna235, the detected signal is converted to baseband by a converter240. A non 802.11 signal is output from the baseband non 802.11 filter block at246, and is further referenced inFIG. 3. Non 802.11 waveforms are detected by measuring energy, spectral bandwidth, periodicity, pulse width, chirp rate, tone frequency, and other signal features, and these “events” are logged in the baseband by the event logger250for future pattern recognition processing. It will be appreciated by those skilled in the art that the event logger retains event data which enhances the detection reliability and therefore will also lower false-alarm rates for the present invention. Preferably, the event logger also has preset thresholds for event parameters and number of logged events. Upon the event logger reaching predetermined or preset thresholds for periodicity and number of events, these logged events (i.e., event results) are passed from the baseband210to the medium access layer220. Preferably the MAC layer220is software-based and operates at a rate having a lower update requirement.

The logged events that are passed to the MAC along255are checked against known non 802.11 patterns, and optionally for self-consistency (e.g., persistence of a certain type of non 802.11), at the non 802.11 identification block260. Optionally, the MAC response processing265modifies the baseband non 802.11 thresholds via the threshold adjustment block270in order to improve reliability of the non 802.11 detection. In an alternate implementation, instead of adjusting the threshold via270, the MAC may declare the presence of a valid non 802.11 and initiate the appropriate response. Thereafter, a channel control message (CCM) or Management Action Frame (MAF) is prepared at275to be sent to the network clients. The CCM or MAF is optionally encoded at280, converted to radio frequency at285, and via the transmission from the AP at290, in which the CCM contains information requesting all associated clients to change to an operating channel clear of non 802.11 signals, as designated to enable coexistence with Blue tooth signals. It will be understood by those skilled in the art that “associated client(s)” includes those clients and devices in or capable of communication with the AP.

Network Wide Response

There are two cases in which a non 802.11 device can enter a 40 MHz WiFi BSS environment, operating in the 2.4 GHz band: at the AP, or at one of the clients. As shown inFIG. 1, the non 802.11 device could be interfering at either the client, or AP.

If the non 802.11 enters the BSS in close proximity to the AP, the non 802.11 signal will be detected, and the system will respond by alerting the clients that are associated with the BSS that the network will switch to 20 MHz operation. This is accomplished by transmitting a Management Action Frame (MAF), which is a network wide announcement. This system functionality is shown inFIG. 2, which will be discussed in detail hereinafter.

When the non 802.11 enters the WiFi network wireless area in close proximity to a remote station, or client, equipped with the functionality of the current invention, it will detect the non 802.11 signal, and send a message to the AP, alerting the network to the presence of a non 802.11 device. The AP then decodes this message, and sends out a MAF requesting a BSS operation switch to 20 MHz mode.

40 MHz Recovery Mode

After switching from 40 MHz to 20 MHz operation, the AP210and clients will operate in 20 Upper, or 20 Lower 40 MHz mode. This will allow the AP210and capable clients to continue to monitor the channel to detect whether the 40 MHz channel is free of interfering non 802.11 devices. After a period of time during which no non 802.11 devices are detected, the BSS can be safely moved back to 40 MHz operation, and thus improve network throughput

FIG. 3depicts a non 802.11 signal300at the output of the baseband non 802.11 filter block (as depicted inFIG. 2at246), in accordance with one or more implementations.FIG. 3ashows a possible AFH signal hopping in (upwards ramp) and out (flat section) of the bandwidth of the 802.11 device.FIG. 3bshows a pulsed interferer like a microwave that causes interference.

FIG. 4depicts the non 802.11 architecture400to detect various types of non 802.11 signatures, in accordance with one or more implementations;

FromFIG. 4, the non 802.11 architecture400, suitable for a system implementation, comprises a bank of detector modules410(e.g., 0-3, four shown) that can be individually tuned to handle different variety of non 802.11 types. The system architecture also provides for a Detection Log and Analysis module420, an automatic gain control (AGC) state indication430, the AGC Packet Detection function440, a MAC reporting block435, a threshold adjustment option at450and an analog to digital converter460.

The Detection Log and Analysis module420records possible non 802.11 pulse events and uses pattern recognition algorithms to determine the presence of non 802.11 with a high degree of probability, and a low false detection rate. The AGC state indication420enables/resets various elements of the non 802.11 module. The AGC Packet Detection function440also serves to qualify/disqualify non 802.11 detection events in the Detection Log420, where possible false non 802.11 “hits” are removed if energy bursts associated with data packets are determined.

FromFIG. 4, the MAC reporting block435provides a report signal to the MAC layer for additional non 802.11 detection decisions/screening. At the MAC layer various measures to increase the reliability of non 802.11 detection are performed. These may include controlling the loading of network data loading to ensure good observation periods, and dynamically changing the thresholds in the various modules to either increase or decrease the non 802.11 detection system sensitivity to a particular non 802.11 pattern.

InFIG. 4, the non 802.11 detector modules410are programmable to detect random (like AFH), long-pulse (like hair dryer, radar, etc) or periodic types (like microwave, radar, etc) of non 802.11. These non 802.11 modes are functionally similar in structure, with each assessing for rising and falling energy conditions, and computing desired parameters when the energy exceeds a certain threshold.

For event logging and analysis, the detected energy pulses are sent from the detector modules410. All of the occurrences of detected energy pulses are logged at420to determine the most likely non 802.11 pattern present. This is done by logging the time of arrival of the pulses, and any other associated non 802.11 parameter, such as tone frequency, tone energy, interference bandwidth, pulse width, chirp rate, etc. The periodicity will be determined by back-differencing the time-of-arrival values. To allow for missed non 802.11 pulses, both the fundamental non 802.11 period and integer multiples of the fundamental will be counted. When multiple occurrences of a particular period (or pulse width for long-pulse) are detected, the non 802.11 information will be passed to the MAC layer at435. The MAC layer will then preferably respond with the proper non 802.11 avoidance operations.

For MAC detection, the MAC responsibility in non 802.11 detection is to maintain proper adjustment of the detection parameters. The MAC, for example, can respond to high false-detection rate by raising energy thresholds for a particular detector module. Similarly, if a certain non 802.11 is found to be present consistently, more than one detector module can be optimized for this particular pattern, to cover a wide range of non 802.11 signal strengths.

Operationally, the AP must detect non 802.11 while data packets are being received from the client. During this operation, the non 802.11 and WiFi packet may overlap from time to time, and the WiFi energy may be as strong as the non 802.11 pulse. A result of this overlap situation is that a 0 dB detection problem arises, where the WiFi signal is an equal strength noise source.

This result is problematic for traditional methods of detection, partly due to the 0 dB issue and partly as the situation is further complicated as the non 802.11 signatures may vary greatly. Thus, it will be appreciated by those skilled in the art that a single filter module is unable to accurately account for all non 802.11 types by providing allow optimal detection performance.

FIG. 5depicts non 802.11 detection800of individual events which are uniquely determined by event parameters and time of arrival, in accordance with one or more implementations. FromFIG. 5, an arrangement of earlier described figures and processes is procedurally set forth. At810the non 802.11 data is received and cross-correlation and filtering at820. The output of the cross-correlation and filtering is input as one of the inputs for threshold checking interrupt software. The output of the threshold checking830is provided and recorded at845to the MAC layer at850, and prior data is available from the MAC layer for use in the respective process of cross-correlation820, threshold checking830and/or interrupt software840, along855,856and857respectively, as previously described.

In embodiment it is known that different signals, that are going to be encountered by the system, have various characteristics. For example:PacketHigh energyMinimal Cross-correlationWell defined start and endNoiseLow energyLong term average=0Non-802.11Low-to-high energyWell defined cross-correlation and/or event parameters

It is known that the deterministic preamble and random data have different statistical characteristics than non-802.11 signals. These characteristics are defined by the equation:

y=∑n=0N-1⁢x⁡[n]⁢x*⁡[n-Δ]where y is the input and x is the output.

When cross-correlation is utilized, random data is eliminated and Noise is averaged to 0. Carrier (of frequency ω and amplitude A) is equal to
N|A|2ejωΔ

Samples of noise and wide-band data that are farther away will be less correlated. RF and external environment will also affect the carrier signal which will limit the optimal value of delta (Δ). Δ is kept flexible in the current design. Because of deterministic preamble, some choices of Δ are detrimental. More averaging reduces the variance of noise. Time variations in non 802.11 signal will limit long term accumulation. Optimal choice of N is also kept flexible. Data systems typically have an Automatic Gain Control (AGC) to best utilize the A/D converters. The AGC will vary the amplitude A for the desired carrier radar on non-802.11 signal. Therefore the value of y can be renormalizing using the gain control values from the AGC and by local calculation of |x[n]| and |x[n−Δ]|.

The strength of the signal y can be used to measure A. Number of zero crossings of y can provide information about ω. Multiple measurements of these parameters can be averaged to get their nominal (noise-free) values.

In the presence of carrier radar or in-band AFH type non-802.11 signals a long term accumulation of y is a monotonically increasing sequence. Using a configurable threshold, the software (through an interrupt or control register) can be initiated, indicating a possible radar or non-802.11 signal is detected. A higher threshold will result in a longer time to generate interrupt, and a lower threshold will result in a shorter time to generate the interrupt. The software will obtain the parameters from the system and will perform a look-up-table validation of all the relevant parameters: frequency, strength, type, etc. The threshold can also be appropriately chosen to meet a “Channel Availability Check Time” requirement.

Advantages

Cross-correlation reduces the effect of random data. Averaging reduces the effect of noise and data. The output of the cross-correlation provides all the useful event parameters. Data path will determine the 20 MHz/40 MHz operation. A suitable choice of Δ and N will eliminate false triggers. Software interaction is reduced to setting the parameters and reacting to interrupts (which are almost guaranteed to be radar).

One of the numerous advantages over the prior methods is that in one or more implementations, non 802.11 detection is able to run in parallel with normal packet processing. The advantage is that high data throughput can be maintained while the AP actively seeks to detect the presence of non 802.11. Also, by filtering for specific non 802.11 patterns, the signal-to-noise ratio of the non 802.11 signal can be improved, particularly during WiFi operation. This enhances the detection rate, and lowers the probability of false alarms.

A further advantage in one or more implementations is that the back-difference buffer also enables the detection to occur reliably during WiFi operation by logging non 802.11 events between WiFi packets. By logging the non 802.11 pulse times and durations, the non 802.11 timeline can effectively be reconstructed and compared to known non 802.11 patterns. This enhances the reliability of detection compared to looking for a single set of contiguous non 802.11 pulse, by allowing for the non 802.11 pulse train to be interrupted by noise or WiFi packets.

As used herein, the term WiFi transceivers are widely used in wireless applications including ETSI DVB-T/H digital terrestrial television transmission and IEEE network standards such as 802.11 (“WiFi”), 802.16 (“WiMAX”), 802.20 (proposed PHY). Such transceivers have large arithmetic processing requirements which can become prohibitive if implemented in software on a DSP processor.

The present invention in one or more implementations may be implemented as part of a data system, an application operable with a data system, a remote software application for use with a data storage system or device, and in other arrangements.

Various implementations of a non 802.11 detection methodologies and systems have been described. Nevertheless, one of ordinary skill in the art will readily recognize that various modifications may be made to the implementations, and any variations would be within the spirit and scope of the present invention. For example, the above-described process flow is described with reference to a particular ordering of process actions. However, the ordering of many of the described process actions may be changed without affecting the scope or operation of the invention. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the following claims.