# Patent

## Title
Method and system for message transmission and reception

## Abstract

Wireless devices may contain multiple radio transceivers, each conforming to different communication protocols. A first transceiver conforming to a first communication protocol in a first wireless device may be able to receive, detect, and/or decode messages transmitted by a second transceiver in a second wireless device conforming to a second communication protocol. The first transceiver may communicate received, detected, and/or decoded information to a different transceiver in the same first wireless device, thus enabling the collocated transceivers to work in concert efficiently. A wideband transceiver using a set of multiple sub-channels in parallel may receive, detect, and/or decode messages transmitted by a narrowband transceiver using a set of multiple channels serially, thereby reducing scan time and power consumption.

## Background
RELATED APPLICATIONS
This application claims priority of U.S. Provisional Patent Application 61/049,282, entitled “WLAN Assisted Bluetooth Inquiry And Paging” filed Apr. 30, 2008.


BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the present invention generally relate to wireless communication systems, and more particularly to wireless personal area networking and wireless local area networking.
2. Description of the Related Art
Wireless communication systems transfer data from a transmitting station to one or more receiving stations using modulated radio frequency (RF) signals. BluetoothTM systems are wireless communication systems governed, in part, by the BluetoothTM Special Interest Group (SIG) which publishes specifications and compliance standards. Current BluetoothTM devices that follow the BluetoothTM standards, up to version 2.1, use an inquiry scan procedure to discover new devices and a page scan procedure to connect to connectable devices. The inquiry scan and page scan procedures may take many seconds to complete because a BluetoothTM transceiver listens for the inquiry and page messages across a series of relatively narrow radio frequency channels, while a BluetoothTM transceiver transmits on a potentially different series of narrow radio frequency channels. Wireless local area networking (WLAN) devices are generally governed by the specifications and rules specified by the IEEE 802.11 working group. The IEEE 802.11b, 802.11g and 802.11n wireless local area networking standards provide exemplary wider bandwidth transmission methods that may use the same radio frequency band as BluetoothTM standards. Portable electronic devices such as laptop computers, personal digital assistants and cellular telephones may incorporate hardware to support multiple wireless standards in the same device.
Both the BluetoothTM and IEEE 802.11b/g/n wireless standards may use the unlicensed industrial scientific medical (ISM) frequency band from about 2.4 GHz to 2.5 GHz including guard bands at the upper and lower boundaries. BluetoothTM physical layer radio channels may frequency hop among a set of 79 different 1 MHz wide radio frequency channels, while an IEEE 802.11 physical layer radio channel may occupy a 20 MHz or 40 MHz contiguous frequency band. As BluetoothTM devices may be designed for low power consumption, reducing the time required to complete an inquiry or page procedure may reduce power consumed also.
Thus, there exists a need for a wireless radio reception method that uses a wider bandwidth transceiver in combination with a wide or narrow bandwidth transceiver to shorten the discovery and connect procedures thereby conserving energy within a wireless communication system.
SUMMARY OF THE INVENTION
Wireless devices may contain multiple radio transceivers, each conforming to different communication protocols. A first transceiver conforming to a first communication protocol in a first wireless device may be able to receive, detect, and/or decode messages transmitted by a second transceiver in a second wireless device conforming to a second communication protocol. The first transceiver may communicate received, detected, and/or decoded information to a different transceiver in the same first wireless device, thus enabling the collocated transceivers to work in concert efficiently. A wideband transceiver using a set of multiple sub-channels in parallel may receive, detect, and/or decode messages transmitted by a narrowband transceiver using a set of multiple channels serially, thereby reducing scan time and power consumption.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a prior art dual radio communication device operating on two wireless networks.
FIG. 2 illustrates a dual wireless radio device receiving signals from a BluetoothTM device through an IEEE 802.11 RF interface.
FIG. 3 illustrates a set of time slots for inquiry messaging in a BluetoothTM piconet.
FIG. 4 illustrates a flowchart for receiving a BluetoothTM inquiry message through an IEEE 802.11 RF interface and responding through a BluetoothTM RF interface.
FIG. 5 illustrates signal processing blocks in a dual wireless radio device receiving signals for a BluetoothTM device through an IEEE 802.11 RF interface and a BluetoothTM interface.
FIG. 6 illustrates signal processing blocks in a dual wireless radio device receiving signal through an IEEE 802.11 RF interface and processing multiple BluetoothTM correlations in the time domain.
FIG. 7 illustrates signal processing blocks in a dual wireless radio device receiving signals through an IEEE 802.11 RF interface and processing multiple correlations in the frequency domain.
FIG. 8 illustrates signal processing blocks in a dual wireless radio device transmitting BluetoothTM signals on multiple sub-carriers through a modified IEEE 802.11 RF interface.



DETAILED DESCRIPTION
Electronic devices may include both a BluetoothTM transceiver and an IEEE 802.11 transceiver. A wider bandwidth transceiver, such as an IEEE 802.11 transceiver, may listen for BluetoothTM transmissions across a range of frequencies simultaneously and may shorten inquiry and page scan procedures that establish and maintain connections in a BluetoothTM network. An IEEE 802.11 radio transceiver may listen to many BluetoothTM 1 MHz wide radio frequency channels simultaneously, thus increasing the probability of detecting an inquiry or page message successfully in a shorter time than a BluetoothTM radio transceiver that listens to only a single 1 MHz wide radio frequency channel at a time.
A BluetoothTM piconet may consist of a master device and multiple slave devices. Although master and slave roles may not be defined prior to the establishment of a connection in the BluetoothTM piconet, an inquiring device may be referred to as the master device, while an inquiry scanning device may be referred to as the slave device. The BluetoothTM master device may periodically transmit inquiry messages containing a general or dedicated inquiry access code by modulating a series of 32 carrier frequencies distributed over a set of 79 possible carrier frequencies spaced 1 MHz apart in the ISM band. For inquiry scan, the set of 32 frequencies and their frequency hopping sequence may be selected based on a calculation using a general inquiry access code (GIAC). Each inquiry message may consist of 68 bits transmitted at a rate of 1 Mbit per second within a single 1 MHz frequency channel and may occupy 68 micro-seconds of a 312.5 micro-second transmit interval, i.e. half of a 625 micro-second time slot. The inquiry message may be repeated within a second, different 1 MHz frequency channel in a succeeding 312.5 micro-second transmit interval. An inquiry frequency hopping sequence may determine the succession of frequencies on which the master device may transmit the inquiry messages. BluetoothTM systems may use a time division duplex transmission method alternating between transmit time slots used for master to slave communication and receive time slots used for slave to master communication. The inquiry message may be sent repeatedly on a sequential train of 16 different frequencies during a series of transmit timeslots, cycling through the set of 16 frequencies 256 times for a total duration of 1.28 seconds. The BluetoothTM master device may then send the inquiry message on a different train of 16 frequencies chosen from the set of 32 possible frequencies during each subsequent 1.28 second interval.
A BluetoothTM slave device may listen (scan) for an inquiry message transmitted within a single 1 MHz frequency channel during an inquiry scan window of 11.25 msec out of an inquiry scan interval of 1.28 seconds. During the 18 consecutive 625 micro-second time slots spanning the inquiry scan window of 11.25 msec, the BluetoothTM master may transmit within up to 16 different frequencies channels; however, the BluetoothTM slave may listen on one of the 16 frequencies not transmitted out of the 32 possible frequencies. During each succeeding inquiry scan window, the BluetoothTM slave may listen on a different 1 MHz frequency channel following an inquiry scan frequency hopping sequence. Eventually, the BluetoothTM slave may listen to one of the frequency channels when the BluetoothTM master may transmit an inquiry message on the same frequency channel; however, multiple successive inquiry scan intervals may occur thereby extending the time for the scan procedure to complete. A benefit of the invention is to reduce the time for the scan procedure by using a transceiver that listens to multiple 1 MHz frequency channels simultaneously increasing the likelihood of observing the BluetoothTM master device's transmitted inquiry message.
FIG. 1 illustrates a wireless communication system including three wireless devices, a first device including two wireless transceivers using two communication protocols, a second wireless device including a wireless transceiver using one of the two communication protocols and a third wireless device including a wireless transceiver using the other of the two communication protocols. More specifically, FIG. 1 provides an exemplary architecture for a dual radio communication device 100 including a BluetoothTM transceiver (blocks 101, 103, 105) and an IEEE 802.11 transceiver (blocks 102, 104, 106). The blocks 101-106 may represent the functions associated with the layers in the standard OSI seven layer communications protocol stack. Communication between blocks vertically, i.e. between a given layer and the next higher or lower layer, while not indicated explicitly in FIG. 1, may exist for the communication protocol stack to function. The dual radio device 100 may include an IEEE 802.11 WLAN radio frequency (RF) block 106 and a BluetoothTM RF block 105 that transmit and receive separate signals from an IEEE 802.11 device 120 and a BluetoothTM device 110 respectively. The dual radio device 100 may communicate on two parallel communication networks, a BluetoothTM personal area network (PAN) 130 and an IEEE 802.11 wireless local area network (WLAN) 140. Limited communication between the BluetoothTM and IEEE 802.11 transceivers within the dual radio communication device 100 may seek to minimize interference between transmissions on the BluetoothTM PAN 130 and transmissions on the IEEE 802.11 WLAN 140. For example, the BluetoothTM higher layer 101 and the IEEE 802.11 higher layer 102 in the dual radio communication device 100 may communicate with each other to coordinate transmissions on the BluetoothTM PAN 130 and the IEEE 802.11 WLAN 140 to minimize overlapping frequencies or to share by time division a set of overlapping frequencies. Alternatively, without communication between them, the BluetoothTM and 802.11 transceivers may each examine one or more frequency bands prior to transmitting to avoid frequencies used by the other system's transceiver. For any of these techniques, one transceiver may treat the transmissions of the other transceiver as “noise” to ignore rather than as an information carrying “signal” to decode. The present invention recognizes that an IEEE 802.11 transceiver may be able to detect and decode a BluetoothTM inquiry or page message quicker than a BluetoothTM transceiver, and a dual radio device may benefit as a result.
FIG. 2 illustrates a wireless communication system in which a dual radio communication device 200 may communicate with the BluetoothTM device 110 through a BluetoothTM RF block 205 and through an IEEE 802.11 RF block 206. Information received from or transmitted to the BluetoothTM device 110 by the IEEE 802.11 RF block 206 may be communicated within the dual radio device 200 between the higher layer blocks 201 and 202 and/or between the middle layer blocks 203 and 204. Examples of information communicated between the transceivers are detailed later. Note that the functional blocks of the dual radio communication device 200 may be realized using a number of different architectures. Some processing blocks in both the BluetoothTM transceiver and the IEEE 802.11 transceiver may be realized in common processing units or alternatively in separately dedicated processing units. Some embodiments of the dual radio communication device 200 may use a common antenna and/or a common analog front end to realize the BluetoothTM RF 205 and IEEE 802.11 RF 206 blocks for example. The BluetoothTM higher layers block 201 and the IEEE 802.11 higher layers block 202 may also be realized in a common processing core. Any variant architecture that includes both a BluetoothTM transceiver and an IEEE 802.11 transceiver may benefit from the invention disclosed herein.
As illustrated in FIG. 2, the dual radio communication device 200 may include an IEEE 802.11 wireless local area networking (WLAN) baseband processing block 204 containing one or more fast Fourier transform (FFT) processing blocks that may listen to one or more 20 MHz wide contiguous bands of radio frequencies in the ISM band. (Depending on the sampling rate into and processing rate of the FFT block, a sub-band of or the entire ISM band may be monitored.) The BluetoothTM device 110 may transmit, at least in part, within a portion of the band of radio frequencies on which the IEEE 802.11 transceiver may listen. During communication on an IEEE 802.11 WLAN, e.g. from the IEEE 802.11 device 120 through the IEEE 802.11 RF block 206 via the path 209, the IEEE 802.11 WLAN baseband processing block 204 may compute a set of receive symbols transmitted using an orthogonal frequency division multiplexing (OFDM) method. In the absence of an IEEE 802.11 transmission via the path 209, the IEEE 802.11 WLAN baseband processing block 204 may compute the presence of other signals within the same set of frequencies normally occupied by a set of OFDM symbols, e.g. transmissions from the BluetoothTM device 110 through the IEEE 802.11 RF transceiver 206 via the path 207.
Two different reception embodiments may be considered for a dual radio communication device 200 that includes both an IEEE 802.11 transceiver and a BluetoothTM transceiver. In a first reception embodiment, the IEEE 802.11 baseband processing block 204 may detect the presence of a Bluetooth inquiry message transmitted by the BluetoothTM device 110 through path 207 and may alert the BluetoothTM transceiver on which frequencies to decode the BluetoothTM inquiry message. The IEEE 802.11 baseband processing block 204 may alert the BluetoothTM transceiver by communicating directly with the BluetoothTM baseband/link layer block 203 or may communicate through the IEEE 802.11 higher layers block 202 and the BluetoothTM higher layers block 201. In a second reception embodiment, the IEEE 802.11 baseband processing block 204 may both detect and decode a BluetoothTM inquiry message and then may communicate to the BluetoothTM transceiver the received inquiry message. In either embodiment, the BluetoothTM transceiver within the dual radio communication device 200 may respond to the inquiry message by transmitting to the BluetoothTM device 110 through path 208. Details of the embodiments are described below.
In the first reception embodiment, the output of an FFT processing block in the IEEE 802.11 baseband/MAC layer block 204 may consist of a set of complex values, each complex value associated with a different radio frequency sub-channel spread across a bandwidth of 20 MHz in the ISM band. The number of different frequency sub-channels may depend on the size of the FFT; e.g. an IEEE 802.11 baseband processor may calculate a set of complex values for 64 frequency sub-channels spaced 312.5 kHz apart based on a set of time samples received during a 4 micro-second interval. As a BluetoothTM inquiry or page message extends for 68 micro-seconds on a single carrier frequency, the IEEE 802.11 baseband/MAC layer block 204 may have sufficient time to detect the presence of the BluetoothTM inquiry or page message by processing one or more sets of time samples received during one or more 4 micro-second intervals.
Note that BluetoothTM carrier frequencies may be spaced 1 MHz apart, so a BluetoothTM transceiver's single frequency energy in one 1 MHz frequency channel may appear in more than one of the IEEE 802.11 baseband/MAC layer block's frequency sub-channels spaced 312.5 kHz apart output by the FFT processing block. In some embodiments, the processing rate and size of an FFT processing block may be flexible, enabling values to be set to match those of Bluetooth transceivers. For example, using a 128 point FFT with an input sample rate of 128 MHz may result in a set of 128 complex values every 1 μsec, i.e. at 1 MHz, matching the symbol rate of a BluetoothTM transceiver. In this case, a BluetoothTM transceiver's single frequency energy in one 1 MHz frequency channel may appear primarily in one of the frequency sub-channels spaced 1 MHz apart output by an FFT processing block.
Additionally, BluetoothTM transceivers may use Gaussian Frequency Shift Keying (GFSK) modulation in which the BluetoothTM carrier frequency may be shifted by at least +115 kHz from a nominal frequency for a binary one and by at least −115 kHz from the nominal frequency for a binary zero at a rate of 1 Mhz, i.e. every one micro-second a new bit may be transmitted. Using an energy threshold detector that estimates the presence or absence of a signal on the set of frequencies output from the FFT processing block, an 802.11 baseband/MAC layer block 204 may determine on which frequency the BluetoothTM device 110 may be transmitting an inquiry message, distinguishing the BluetoothTM signal from background noise. With additional processing as described below, an output from an FFT processing block may also be used to estimate the bit pattern of an inquiry message sent by the BluetoothTM device 110.
As illustrated in FIG. 3, a BluetoothTM system may divide transmissions into a series of transmit (TX) master-to-slave time slots and receive (RX) slave-to-master time slots each time slot extending 625 micro-seconds. Note that the timeslots in FIG. 3 are labeled TX or RX from the point of view of the master (inquiring) device. During a first time slot 301, an inquiring (master) device may send an inquiry message consisting of a 68 bit inquiry access code at a rate of 1 Mbit/sec for a first 68 micro-second interval 310 on a first frequency f1 during a first portion of the first time slot 301 and then may repeat the inquiry message for a second 68 micro-second interval 311 on a second frequency f2 during a second portion of the first time slot 301. During a second time slot 302 immediately following the first time slot 301, an inquiry scanning (slave) device may respond to the inquiry message by sending an inquiry response message during a 68 micro-second interval 312 on a first response frequency f′1 or during a second interval 313 on a second response frequency f′2. If the inquiring (master) device does not receive an inquiry response message during the second time slot 302, then the inquiring (master) device may repeat the same inquiry message during a third time slot 303 modulating a third frequency f3 and a fourth frequency f4. If the inquiry scanning (slave) device responds during a fourth time slot 304, then the inquiry scanning (slave) device may send an inquiry response message modulating a third response frequency f′3 or a fourth response frequency f′4.
The inquiry and inquiry response frequency hopping sequences used by the inquiring (master) device and the inquiry scanning (slave) device respectively may be in part determined by a general inquiry access code (GIAC) transmitted in the inquiry message. As such, the inquiry scanning (slave) device may need to decode the inquiry message before responding to the inquiring (master) device, as the inquiry scanning (slave) device may not know a priori the inquiry response frequency hopping sequence. Knowing which frequency on which the inquiring (master) device transmitted an inquiry message alone may be insufficient to determine the inquiry response frequency hopping sequence. The inquiring (master) device may also transmit a dedicated inquiry access code (DIAC), rather than a GIAC, to which only certain slave devices may respond. The inquiry scanning (slave) device may detect which frequency on which the inquiring (master) device transmitted an inquiry message, but the inquiry scanning (slave) device may not know whether to respond without decoding the inquiry message.
To conserve power consumption, e.g. in a battery operated version of the dual radio device 200, a BluetoothTM transceiver may be in “sleep mode” awaiting the presence of an inquiry message. In order to “waken” the BluetoothTM transceiver to capture and decode the inquiry message, the IEEE 802.11 baseband processor 204 may detect the inquiry message during the first few micro-seconds of receiving the inquiry message, e.g. based on energy received from the first few bits of the 68 bit long inquiry message in a number of receive frequencies output by the FFT processing block. The IEEE 802.11 transceiver may alert the BluetoothTM transceiver on which frequency to begin receiving the inquiry message by communicating between the middle layer blocks 204 and 203 or between the higher layer blocks 202 and 201. As the BluetoothTM transceiver may “sleep” during a number of micro-seconds of the inquiry message, the IEEE 802.11 baseband processor 104 may provide a set of time domain samples that include at least a period from the beginning of the inquiry message to a point when the BluetoothTM transceiver begins receiving and sampling the inquiry message through its BluetoothTM RF block 205. Preferably the set of time domain samples may be formatted to minimize calculations required by the BluetoothTM transceiver to decode the inquiry message. Thus a first portion of a BluetoothTM inquiry message may be received from the BluetoothTM device 110 through the IEEE 802.11 RF block 206 via path 207 and a second portion of the same BluetoothTM inquiry message may be received through the BluetoothTM RF block 205 via path 208.
In the second reception embodiment of the invention, the IEEE 802.11 baseband processing block 204 may calculate an FFT sufficiently quickly that each one micro-second long bit of a 68 micro-second inquiry message may be detected and decoded as a “one” or a “zero” individually. The FFT processing block in the IEEE 802.11 baseband processing block 204 may output a set of complex values every one micro-second rather than every four micro-seconds. With such a quick FFT, the IEEE 802.11 baseband processing block 204 may determine both a carrier frequency used by the BluetoothTM device 110 for transmitting the inquiry message and the inquiry access code, i.e. the actual 68 bit transmitted sequence. The IEEE 802.11 baseband processing block 204 may then transmit the received inquiry message and the determined carrier frequency to the BluetoothTM transceiver. The BluetoothTM transceiver may respond to the inquiry message in a subsequent receive scan time slot on an appropriate carrier frequency based on the information provided by the IEEE 802.11 baseband processing block 204. For example a BluetoothTM inquiry scanning device may respond on carrier frequency f′1 in time slot 302 after receiving a decoded inquiry access code from the IEEE 802.11 baseband processing block 204 during time slot 301. Alternatively a BluetoothTM inquiry scanning device may confirm a decoded inquiry access code provided by the IEEE 802.11 baseband processing block 204 during a first portion of time slot 301 by listening to receive the same inquiry access code on frequency f2 during a second portion of time slot 301 before responding to the inquiry message in time slot 302 on either frequency f′1 or frequency f′2.
FIG. 4 illustrates a flowchart of several exemplary method steps of the invention indicating the operations and interactions of the computational blocks of the devices in FIG. 2 following a portion of the inquiry messaging sequence of FIG. 3. Starting at the top of the flowchart in step 401, the BluetoothTM device 110 may transmit an inquiry message 310 on carrier frequency f1 in time slot 301. The IEEE 802.11 RF interface 206 in the dual radio BluetoothTM/IEEE 802.11 device 200 may receive at least a portion of the inquiry message 310 in step 402. The IEEE 802.11 Baseband/MAC layer 204 may detect the inquiry message 310 and may identify the carrier frequency f1 on which the message was transmitted in step 403. Following step 403 in FIG. 4, the method may proceed along one of three different branches as outlined by the dashed boxes 420 (left column), 430 (center column) and 440 (right column). Each branch of the method may advantageously allow portions of the dual radio communication device 200 configured to process WLAN signals to assist in the processing of BluetoothTM signals.
In the left column 420 starting in step 404, the IEEE 802.11 Baseband/MAC layer 204 may identify the carrier frequency f1 to the BluetoothTM Baseband/Link layer 203, either directly or through the higher layers 202 and 201. The BluetoothTM RF block 205 may awaken and may listen for a subsequent inquiry message on carrier frequency f1, receiving an inquiry message 314 in time slot 305. Note that the BluetoothTM RF block 205 after waking up may have missed a first portion of the inquiry message 310 in time slot 301, thus the BluetoothTM RF block 205 may wait for the next inquiry message 314 transmitted on the carrier frequency f1 which may occur in time slot 305 (step 405). The BluetoothTM Baseband/Link Layer 203 may decode the received inquiry message 314 (step 406) and may respond by transmitting an inquiry response message 316 by modulating carrier frequency f′1 in time slot 306 (step 407). Similarly, the BluetoothTM RF block 205 after waking up may have missed a first portion of the inquiry message 311 in time slot 301, thus the BluetoothTM RF block 205 may wait for the next inquiry message 315 transmitted on the carrier frequency f2 which may occur in time slot 305. The BluetoothTM Baseband/Link Layer 203 may decode the received inquiry message 315 and may respond by transmitting an inquiry response message 317 by modulating carrier frequency f′2 in time slot 306.
FIG. 5 illustrates an exemplary embodiment of select processing blocks in a dual radio device that may implement the method illustrated in the left column 420 of FIG. 4. Inside the IEEE 802.11 RF block 206, an IEEE 802.11 analog front end 501 may receive from an antenna BluetoothTM signals that may be sampled by an A/D converter 502 before being transformed by an FFT block 503 in the IEEE 802.11 baseband/MAC layer block 204. The output of the FFT block 503 may provide a set of complex values for a set of frequencies to an energy detection block 504, which may determine if a BluetoothTM inquiry message has been received on a particular frequency. The frequency detected may then be communicated to a BluetoothTM analog front end 505 within the BluetoothTM RF block 205 indicating on which frequency channel the BluetoothTM transceiver may receive a message. A received digital signal output from an Analog to Digital converter 506 in the BluetoothTM RF block 205 may be processed by a finite impulse response (FIR) filter 508 and then by a correlation block 509 in the BluetoothTM baseband/MAC layer block 203 to detect a BluetoothTM inquiry message. Note that while FIG. 5 illustrates an IEEE 802.11 analog front end 501 that may use 20 or 40 MHz of bandwidth, the same device may use a modified analog front end with wider analog filters and higher A/D sampling to cover a wider bandwidth, for example 128 MHz that may span the entire ISM band. The energy detection block 504 may also determine if one or more BluetoothTM inquiry message have been received on one or more frequencies rather than just the one frequency described in FIG. 4 and shown in FIG. 5. Multiple frequencies may be communicated by the energy detection block 504 to the BluetoothTM baseband/link layer block 203 so that the BluetoothTM transceiver may look for inquiry messages on one or more frequencies.
A second method may follow the center column 430 of FIG. 4. Starting in step 408, the IEEE 802.11 Baseband/MAC layer 204 may store a set of time domain samples received by the IEEE 802.11 RF block 206 that may include a first part of the received inquiry message 310. The IEEE 802.11 Baseband/MAC layer 204 may identify the detected carrier frequency f1 and may communicate the saved time domain samples to the BluetoothTM Baseband/Link Layer block 203 (step 409). The BluetoothTM RF block 205 may awaken and receive a second part of the inquiry message 310 on carrier frequency f1 in time slot 301 (step 410). The BluetoothTM Baseband/Link Layer block 203 may decode the inquiry message 310 by combining the first part of the received inquiry message 310 based on the saved time domain samples received through the IEEE 802.11 RF block 206 and the second part of the received inquiry message 310 received through the BluetoothTM RF block 205 (step 411). The BluetoothTM Baseband/Link Layer 203 may respond to the inquiry message 310 by transmitting an inquiry response message 312 on carrier frequency f′1 in time slot 302 (step 412).
FIG. 6 illustrates an exemplary embodiment of select processing blocks in a dual radio device that may implement the method illustrated in the center column 430 of FIG. 4. As in FIG. 5, the IEEE 802.11 analog front end 501 in the IEEE 802.11 RF block 206 may receive a BluetoothTM signal from an antenna, and a digitally sampled version of the BluetoothTM signal may be input to the FFT block 503 in the IEEE 802.11 Baseband/MAC layer block 204. As the FFT block 503 may transform a set of samples in parallel, a buffer 601 may store a set of inputs before the FFT processing, and a subset of these stored inputs may also be transmitted to the BluetoothTM baseband/link layer block 203 and combined with a digital frequency signal therein. A frequency generator block 507 in the BluetoothTM baseband/link layer block 203 may generate the digital frequency signal based on information communicated from the energy detection block 504 in the IEEE 802.11 baseband/MAC layer block 204. Note that multiple frequencies may be detected by the energy detection block 504, and multiple BluetoothTM frequencies may be filtered and correlated in parallel in the BluetoothTM baseband/link layer block 203 using a bank of FIR filters 508 and correlation blocks 509. In this manner, the BluetoothTM transceiver in a dual radio device 200 may detect inquiry messages simultaneously from multiple BluetoothTM devices that each may transmit on different frequency channels. This parallel processing may speed the completion of an inquiry procedure between a BluetoothTM master (inquiring) device and multiple BluetoothTM slave (inquiry scanning) devices.
A third method may follow the right column 440 of FIG. 4. Starting in step 413, the IEEE 802.11 Baseband/MAC layer 204 may decode the received inquiry message 310. The IEEE 802.11 Baseband/MAC layer 204 may identify the detected carrier frequency f1 and may communicate the received decoded inquiry message 310 to the BluetoothTM Baseband/Link Layer block 203 (step 414). The BluetoothTM Baseband/Link Layer 203 may respond to the inquiry message 310 by transmitting an inquiry response message 312 by modulating the carrier frequency f′1 in time slot 302 (step 415).
FIG. 7 illustrates an exemplary embodiment of select processing blocks in a dual radio device that may implement the method illustrated in the right column 440 of FIG. 4. In this embodiment, BluetoothTM messages may be detected and decoded on one or more frequency sub-channels using blocks in the IEEE 802.11 Baseband/MAC layer 204. Each BluetoothTM symbol may occupy a time span of one μsec, and a 128 point FFT transforming a set of samples from a 128 MHz sampling Analog to Digital converter may result in one complex value per frequency sub-channel spaced 1 MHz apart across a 128 MHz bandwidth. Other A-to-D sampling rates and FFT sizes may also be used that result in frequency sub-channels spaced 1 MHz apart, for example a 64 point FFT transforming a set of samples from a 64 MHz sampling A-to-D converter. While these frequency domain samples may provide enough information for energy detection, as described for FIGS. 5 and 6, additionally calculating the actual positive or negative frequency shift of the BluetoothTM frequency carrier to determine the bit value may require additional processing. An FFT frame of 128 samples input to a 128 point FFT may not align with a transmitted BluetoothTM symbol boundary, and thus an FFT block 701 may transform together part of one transmitted BluetoothTM symbol and part of a subsequently transmitted BluetoothTM symbol.
In an embodiment of the invention, the FFT block 701 may operate at least at twice the processing rate compared with the sample rate of the Analog to Digital converter 502, computing at least two FFT transforms for each BluetoothTM symbol (bit) period of one μsec. One FFT transform may be shifted by one half of a BluetoothTM symbol period with respect to the other FFT transform. For example the FFT block 701 may transform a set of samples {x[0], x[1], . . . , x[127]} followed by a set of samples {x[64], x[65], . . . , x[191]} followed by a set of samples {x[128], x[129], . . . , x[255]}, etc. thereby using each sample from the Analog to Digital converter 502 twice. One of the transforms may contain at least 3⁄4 of one BluetoothTM symbol together with at most 1⁄4 of a second BluetoothTM symbol, which may provide sufficient information to decode which bit was transmitted. The GFSK modulation method used by the BluetoothTM standard may encode a “one” as a positive shift in frequency and a “zero” as a negative shift in frequency. As the FFT block 701 may integrate the frequency change over time in its FFT transform, a “one” bit value may still result in a positive phase shift on the associated frequency sub-channel output from the FFT block 701, while a “zero” may still result in a negative phase shift, even if the next BluetoothTM symbol, of which part may be transformed together with the current BluetoothTM symbol, may encode a different bit value. Operating the FFT block 701 at twice the Analog to Digital converter 502 sampling rate provides sufficient information to decode the GFSK modulated BluetoothTM symbols; higher rates such as three or four times the sampling rate or more may also be used.
A set of samples output from the FFT block 701 may be processed by an energy detection and frequency calculation block 702. Of the 128 frequency sub-channels spaced 1 MHz apart, up to 79 frequency sub-channels may contain information from a BluetoothTM message in general, but up to only 32 frequency sub-channels may contain information for BluetoothTM inquiry (or page) messages. The energy detection and frequency calculation block 702 may process only a subset of all of the FFT block 701 outputs to minimize computations. For each frequency sub-channel on which energy may be detected, the quantity sign(x[n]·conj(x[n−2]) may be computed by the energy detection and frequency calculation block 701 to determine the frequency and thereby the bit received on that frequency sub-channel. The calculation may be performed twice, once for each FFT “phase”, and the best result may be used. A set of resulting demodulated bits may be transferred through a frequency selection block 703 that may route the results to a bank of correlation blocks 509. Each correlation block 509 may determine whether a particular bit pattern may be received on a particular frequency sub-channel. The frequency sub-channel associated with each correlation block 509 may be changed based on which frequency sub-channels are detected in the energy detection and frequency calculation block 702. A BluetoothTM message detected by a correlation block 509 may be transmitted, along with the associated frequency sub-channel, to the BluetoothTM baseband/link layer 203 as indicated in step 414 of FIG. 4.
Each of the three methods illustrated in FIG. 4 may offer varying options to balance processing capabilities in the BluetoothTM and IEEE 802.11 blocks of the dual radio BluetoothTM/IEEE 802.11 device 200. The left column 420 method may require minimal computations by the IEEE 802.11 Baseband/MAC layer block 204 but may take longer for the BluetoothTM Baseband/Link layer block 203 to respond to the inquiry message 310. This delay may be due to waiting to receive the second inquiry message 314 before responding. The center column 430 method may require some additional computations for the BluetoothTM Baseband/Link layer block 203 to combine time samples from the IEEE 802.11 RF block 206 and the BluetoothTM RF block 205 to receive the inquiry message 310; however, the BluetoothTM Baseband/Link layer block 203 may respond more quickly than using the left column 420 method. The right column 440 method may require more computations by the IEEE 802.11 Baseband/MAC layer block 204 to decode the inquiry message 310, but the BluetoothTM Baseband/Link Layer block 203 may respond quickly to the inquiry message 310 with minimal computations. Other variant embodiments of the invention may be possible in addition to those illustrated in FIG. 4.
As described above for inquiry messages, the invention may apply also to detecting and decoding page messages transmitted by a BluetoothTM paging (master) device and responded to by a BluetoothTM page scanning (slave) device. Page messages may consist of a 68 bit sequence transmitted using a page frequency hopping sequence in the same time slotted format as indicated for inquiry messages in FIG. 3. An IEEE 802.11 baseband processing block 204 in a dual radio IEEE 802.11/BluetoothTM device 200 may listen for BluetoothTM page messages, may detect carrier frequencies on which such page messages are transmitted and may decode such page messages as described above for inquiry messages. BluetoothTM page messages may differ from BluetoothTM inquiry messages by their specific bit sequence and by the frequency hopping sequence used.
As described above for receiving BluetoothTM messages on multiple frequency sub-channels, dual radio devices 200 that include both a BluetoothTM transceiver and an IEEE 802.11 transceiver may also transmit on multiple frequency sub-channels. A wider bandwidth transceiver, such as an IEEE 802.11 transceiver, may transmit BluetoothTM messages across a range of frequencies simultaneously and may shorten inquiry and page scan procedures that establish and maintain connections in a BluetoothTM network. An IEEE 802.11 radio transceiver in the dual radio device 200 may transmit the same BluetoothTM message on multiple BluetoothTM 1 MHz wide radio frequency channels simultaneously, thus increasing the probability that the BluetoothTM transceiver 110 that may listen on only a single 1 MHz wide radio frequency channel at a time may detect an inquiry or page message successfully in a shorter time.
FIG. 8 illustrates an example of how a BluetoothTM message may be replicated across multiple frequency channels using the IFFT of a modified IEEE 802.11 transceiver. A BluetoothTM message generator 801 may output a bit value at a 1 MHz rate to a Gaussian Frequency Shift Key (GFSK) modulation block 802 that may produce a BluetoothTM bit pulse each 1 μsec. The power spectrum of that bit pulse may be illustrated by the graph 805. A frequency vector generator 803 may input a vector of 128 ones and zeroes to a 128 point inverse Fast Fourier Transform (IFFT) block 804 that may produce a transformed set of outputs every 1 μsec. The block 804 may output a set of sinusoids (sub-carriers) at different frequencies, where frequency sub-carriers with a “one” input may contain a non-zero energy sinusoid, while frequency sub-carriers with a “zero” input may contain no energy. The power spectrum of the output of the IFFT 804 may be a series of impulses spaced 1 MHz apart as indicated in graph 806. Combining the output of the IFFT 804 with the output of the GFSK modulation block 802 using a mixer 809 may result in a signal with a power spectrum that replicates the BluetoothTM bit pulse on each of the different frequency sub-carriers as shown in graph 807. The combined signal may then be processed through a wideband analog front end, such as a modified 802.11 IEEE analog block 808, for transmission through an antenna to multiple BluetoothTM devices (not shown) simultaneously.
Although illustrative embodiments of the invention have been described in detail herein with reference to the accompanying figures, it is to be understood that the invention is not limited to those precise embodiments. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. As such, many modifications and variations will be apparent. Accordingly, it is intended that the scope of the invention be defined by the following Claims and their equivalents.

## Claims

1. A wireless communication method comprising:
receiving a communication message by a first wireless transceiver in a dual radio device, wherein the first wireless transceiver conforms to a first communication protocol that uses a plurality of frequency sub-channels in parallel from a set of frequency sub-channels, and wherein the communication message was transmitted using a second communication protocol that uses a subset of frequency channels from a set of frequency channels, wherein the second communication protocol uses the subset of frequency channels serially;
detecting, by the first wireless transceiver, the communication message on one or more frequency sub-channels in the plurality of frequency sub-channels;
identifying, by the first wireless transceiver to a second wireless transceiver in the dual radio device, a frequency channel on which the communication message was transmitted, wherein the second wireless transceiver conforms to the second communication protocol,
based on the identifying, the second wireless transceiver receiving at least part of the communication message on the frequency channel using one or more time slots.

2. The method of claim 1, further including
communicating, by the first wireless transceiver to the second wireless transceiver, a first portion of the communication message.

3. The method of claim 2, further including
receiving, by the second wireless transceiver, a second portion of the communication message on the frequency channel, and
decoding, by the second wireless transceiver, the communication message.

4. The method of claim 3, further including
wakening the second wireless transceiver from a reduced power state before receiving the second portion of the communication message on the frequency channel.

5. The method of claim 1, further including
decoding, by the first wireless transceiver, the communication message;
communicating, by the first wireless transceiver to the second wireless transceiver, the communication message.

6. The method of claim 1, wherein detecting the communication message includes measuring a received energy in one or more of the plurality of frequency sub-channels in the set of frequency sub-channels.

7. The method of claim 1, wherein the first communication protocol is an orthogonal frequency division multiplexing protocol and the second communication protocol is a frequency hopping spread spectrum protocol.

8. The method of claim 1, wherein the first communication protocol is an IEEE 802.11 wireless protocol and the second communication protocol is a BluetoothTM protocol.

9. The method of claim 8, wherein the communication message is an inquiry message.

10. The method of claim 8, wherein the communication message is a page message.

11. The method of claim 5, wherein the first communication protocol is an IEEE 802.11 wireless protocol and the second communication protocol is a BluetoothTM protocol.

12. The method of claim 11, wherein the communication message is an inquiry message.

13. The method of claim 11, wherein the communication message is a page message.

14. A wireless communication method comprising:
receiving a communication message by a first wireless transceiver in a dual radio device, wherein the first wireless transceiver conforms to a first communication protocol that uses a plurality of frequency sub-channels in parallel from a set of frequency sub-channels, wherein the communication message was transmitted using a second communication protocol that uses a subset of frequency channels from a set of frequency channels, and wherein the second communication protocol uses the subset of frequency channels serially;
detecting, by the first wireless transceiver, the communication message on one or more frequency sub-channels in the plurality of frequency sub-channels; and
identifying, by the first wireless transceiver to a second wireless transceiver in the dual radio device, a frequency channel on which the communication message was transmitted, wherein the second wireless transceiver conforms to the second communication protocol.