Abstract:
A method and system for wireless communication is provided and may include, scanning by a wireless communication device, a plurality of radio frequencies for beacon messages from a plurality of master communication devices, in order to identify whether establishment of communication with at least one of said plurality of time-synchronous RF networks is possible. Each of the plurality of master communication devices may be associated with one of a plurality of time-synchronous RF networks. A network associated with one of the beacon messages may be selected based on predefined criteria. The selected network may be one of the plurality of time-synchronous RF networks. Communication may be established with said selected network by the wireless communication device. The plurality of time-synchronous RF networks may comprise a Bluetooth network and/or IEEE 802.11 Wireless Local Area (WLAN) network.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/214,620, filed Jun. 28, 2000 and U.S. Provisional Application No. 60/238,833, filed Oct. 6, 2000. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates generally to data communications and, more particularly, to systems and methods for controlling and managing network access in wireless communication systems.  
       BACKGROUND OF THE INVENTION  
       [0003]     Demand for wireless information services had led to the development of an ever increasing number of wireless network standards. For example, cellular and PCS networks, to name just two, provide wide area wireless telephone and data services. As the demand for these services increases, portable communication devices such as personal digital assistants (PDAs) are evolving to support integrated voice, data, and streaming media while providing seamless network coverage from personal area networks (PAN) to wide area networks (WAN). On the wireless WAN side, the prevailing standards are 2G+, 3G and 4G, among others. On the wireless PAN and local area networks (LAN) side, Bluetooth, HomeRF, and IEEE 802.11b standards are emerging as important standards. A Bluetooth network may provide data connectivity between devices such as personal computer and personal digital assistants (PDAs) that are in relatively close proximity to one another. A HomeRF network may provide wireless services at relatively high data rates over a small area of coverage such as a person&#39;s home.  
         [0004]     Boundaries between wireless WANs (including cellular networks) and LANs (e.g., home wireless LANs and other small pockets of wireless networks) are essentially disappearing as customers demand seamless continuation of service for their mobile communication device as they travel from their PAN to home network and further into the WANs.  
         [0005]     However, in general, devices that are compatible with one wireless network are incompatible with other wireless networks. This is due, in part, to each network&#39;s use of its own unique set of protocols for facilitating communication between compatible devices.  
         [0006]     Moreover, each network typically provides a unique set of services. Networks may provide different data transmission rates, for example, a GSM cellular telephone network typically supports data transfer rates of 64 kilobits per second (kbit/s) while a HomeRF network may support data transfer rates of 2-10 megabits per second. Networks also may provide service having different areas of coverage. For example, cellular networks provide coverage on a continental scale while Bluetooth networks typically provide coverage over the range of approximately 10 meters. Networks also may provide different information content to a user of the network. Legacy cellular telephone networks simply provided voice services. Newer networks such as PCS networks may support voice, data and other information services.  
         [0007]     In effect, these disparate networks have created a series of islands of wireless service throughout the geographical landscape, each with its own unique set of protocol standards, data rates, areas of coverage and services. Yet there are no single wireless technologies or standards that effectively satisfy the requirements of desired coverage area (from PAN to WAN) and quality of service (high bandwidth data, voice, and streaming media) for mobile multimedia devices.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention is directed to systems and methods for enabling a wireless communication device to communicate with a variety of wireless networks. In particular, a portable communication device constructed according to the invention can communicate with different networks as the device is moved through the areas of coverage supported by the different networks. To this end the invention provides techniques for controlling and managing network access to several networks. As a result, a device constructed according to the invention can take advantage of services provides by a particular network when the device is within the area of coverage provided by that network. For example, when the device is within the area of coverage of a network that provides high speed Internet access, the device may switch from the network with which it was connected to the network with the high speed Internet access. Similarly, the device may, for example, connect to networks that provide different quality of service, low cost service and/or different services (e.g., voice, data, multimedia, etc.).  
         [0009]     In one embodiment, the invention relates to systems and methods for implementing multi-mode wireless communication devices such as PDAs or multi-function (e.g. data, voice, and multimedia) mobile phones that best take advantage of the wireless networks in their proximity. That is, in the case where a nearby wireless network (WAN, LAN, or PAN) happens to provide more data bandwidth and/or better quality of service (QoS), a multi-mode wireless device may switch to that particular wireless network to access these services. Several network coverage scenarios include, for example: 
        (1) a PDA or a multi-function mobile phone connected to a low bandwidth internet service while located within a WAN could take advantage of a broadband internet service while located at home through a wireless LAN;     (2) a cellular phone could switch to a cordless telephone mode when at home to make calls over the wired infrastructure to avoid air-time charges;     (3) a PDA or a multi-function cell phone traveling through a WAN may encounter an island of high bandwidth wireless coverage (Bluetooth, HomeRF, 802.11b, etc.) in which case it could switch to a Bluetooth, HomeRF, or 802.11b mode to access the provided services;     (4) A Bluetooth enabled mobile WAN device may recognize and establish connection with a nearby HomeRF network; and     (5) A Bluetooth enabled mobile WAN device WAN device may recognize and establish connection with a nearby IEEE 802.11b network.        
 
         [0015]     One embodiment of a system constructed according to the invention consists of a multi-mode controller that, in effect, simultaneously processes communication signals for several wireless networks. The multi-mode controller processes signals to detect the presence of network services and, in the event services are detected, selectively establishes communications between the device and the network.  
         [0016]     One embodiment of a system constructed according to the invention consists of a dual-mode Bluetooth and HomeRF controller. The dual-mode controller, in effect, simultaneously generates polling signals and scans for polling signals to detect the presence of Bluetooth and HomeRF network services. In the event such services are detected, the device selectively establishes communications between the device and one of the two networks.  
         [0017]     One embodiment of a system constructed according to the invention consists of a dual-mode Bluetooth and IEEE 802.11b controller. The dual-mode controller, in effect, simultaneously generates polling signals and scans for polling signals to detect the presence of Bluetooth and IEEE 802.11b network services. In the event such services are detected, the device selectively establishes communications between the device and one of the two networks.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]     These and other features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed description, appended claims and accompanying drawings, wherein:  
         [0019]      FIG. 1  is a graphical representation of one embodiment of wireless communication networks defining different areas of coverage wherein a device constructed according to the invention may establish communication with one or more of the wireless communication networks;  
         [0020]      FIG. 2  is a block diagram of one embodiment of a multi-mode radio transmitter/receiver constructed in accordance with the invention;  
         [0021]      FIG. 3  is a block diagram of one embodiment of a multi-mode radio transmitter/receiver constructed in accordance with the invention;  
         [0022]      FIG. 4  is a block diagram of one embodiment of a multi-mode controller and user interface in accordance with the invention;  
         [0023]      FIG. 5  is a graphical representation of one embodiment of a communications system including Bluetooth and HomeRF networks wherein a device constructed according to the invention may establish communication with the Bluetooth and HomeRF networks;  
         [0024]      FIG. 6  is a block diagram of one embodiment of a dual mode Bluetooth and HomeRF radio transmitter/receiver constructed in accordance with the invention;  
         [0025]      FIG. 7  is a graphical representation of a Bluetooth network access procedure;  
         [0026]      FIG. 8  is a graphical representation of a HomeRF network access procedure;  
         [0027]      FIG. 9  is a graphical representation of one embodiment of a dual-mode Bluetooth and HomeRF network access procedure in accordance with the invention;  
         [0028]      FIG. 10  is a flowchart representative of one embodiment of a Bluetooth and HomeRF dual-mode controller state transition diagram in accordance with the invention;  
         [0029]      FIG. 11  is a block diagram of one embodiment of a dual mode Bluetooth and IEEE 802.11b radio transmitter/receiver constructed in accordance with the invention;  
         [0030]      FIG. 12  is a graphical representation of a IEEE 802.11b network access procedure;  
         [0031]      FIG. 13  is a graphical representation of one embodiment of a dual-mode Bluetooth and IEEE 802.11b network access procedure in accordance with the invention; and  
         [0032]      FIG. 14  is a flowchart representative of one embodiment of a Bluetooth and IEEE 802.11b dual-mode controller state transition diagram in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0033]     The invention is described below, with reference to detailed illustrative embodiments. It will be apparent that the invention can be embodied in a wide variety of forms, some of which may be quite different from those of the disclosed embodiments. Consequently, the specific structural and functional details disclosed herein are merely representative and do not limit the scope of the invention.  
         [0034]      FIG. 1  is a simplified graphical representation of a communications system S defined by several wireless networks. Dashed lines  20 ,  22  and  24  represent hypothetical areas of coverage for a few representative wireless networks. In this embodiment, wireless communication device  26  is associated with one network (designated network  1 ) and its associated area of coverage  20 . Similarly, wireless communication devices  28  and  32  are associated with another type of network (designated network  2 ) where each wireless communication device  28  and  32  is associated with a distinct area of coverage  22  and  24 , respectively.  
         [0035]     In accordance with one embodiment of the invention, multi-mode communication devices  30  and  34  may communicate with one or more of the wireless communication devices  26 ,  28  and  32 . Essentially, each multi-mode communication device  30  or  34  determines whether it is within the area of coverage of a type of network that is supported by the multi-mode communication device. For example, as multi-mode communication device  30  moves from a location outside of area  22  to a location within area  22 , the device  30  may selectively establish communications with a device in the wireless network represent by area  22  (e.g., device  28 ).  
         [0036]     Depending on the location of a multi-mode communication device  30  or  34 , the device  30  or  34  may be in an area of coverage for zero, one, two or more networks. Hence, in some situations the device  30  or  34  may need to select a network to which it will connect. As will be discussed in detail below, the decision to connect to a network may be based on different factors including, for example, the data transfer rates provided by the networks.  
         [0037]     Typically, the devices depicted in  FIG. 1  and discussions in the sections that follow are portable devices. However, it should be understood that the teachings of the invention may be applied to stationary devices in some applications.  
         [0038]      FIG. 2  is a simplified block diagram illustrating certain components of a multi-mode communication device that may operate with two or more wireless networks. A multi-mode controller  40  controls and manages network access to the wireless networks for the communication device. Processing elements  42  and  44  perform the signal processing associated with a given network. As represented by ellipses  52 , any number of processing elements for any number of networks may be supported, consistent with the teachings of the invention. Thus, the designation “N” for processing element  44  may represent the Nth network supported by the communication device.  
         [0039]     The multi-mode controller  40  and the processing elements  42  and  44  communicate with the network via a radio interface  46 . The radio interface transmits and receives signals (e.g., radio frequency signals such as microwave signals and those in the cellular and PCS bands) to other devices in a network via an antenna  48 .  
         [0040]     A user interface  50  enables a user (not shown) to transmit and receive information to and from a selected network via the corresponding processing elements  42  or  44  and the radio interface  46 .  
         [0041]      FIG. 3  is a block diagram that represents network selection operations that may be performed in accordance with the invention. In some instances, a multi-mode communication device will select one of two or more available networks. To this end, the device may selectively route information to/from a user interface  66  from/to another device in the selected network. Thus, information will be routed to/from an appropriate network processor element  60  or  62 . This selection may be based on many factors. The device may select a network with, for example, 1) a higher bandwidth; 2) a broader area of coverage; 3) less expensive connection costs; 4) different QoS; or 5) better services (e.g., Internet access, multi-media access, etc.).  
         [0042]     In one embodiment, a network selector  64  may consist of a hard switch (e.g., a multiplexor) that routes signals from one component to another. In another embodiment the functions of the network selector  64  may be accomplished using routing software that routes the information to an appropriate hardware component or a software subroutine. In the latter case, the network processing operations may take the form of software routines, whereby the multi-mode controller may control execution of the appropriate routine for the selected network. In this case, the information would then be routed to the enabled routine. Such an embodiment typically would be used in an implementation where the multi-mode controller and network processing functionality is performed by a common processing element such as a digital signal processor.  
         [0043]      FIG. 3  also illustrates that in some embodiments different radio interfaces  68  and  70  may be use for interfacing with different networks. Also, several antennae may be used in some applications.  
         [0044]      FIG. 4  further illustrates operations related to selecting a network. A multi-mode controller  80  receives network information  88  indicative of whether the device is within range of a supported network. An active network detector  92  processes the received network information to determine whether the device is within range of a supported network. In some embodiments, network detection involves sequentially sending and/or scanning for network polling information associated with each network.  
         [0045]     A network selector  94  may be used to determine whether to connect to a detected network. In some instances the device may be configured to only connect to certain types of networks. In other instances the device may be configured to choose between two or more detected networks.  
         [0046]     In practice, the decision to select a particular network may be based on a variety of factors. A given network may provide better quality of service than another network. One network may provide faster rates of data transfer. One network may provide less congestion. A network may be less expensive to use. A network may provide content (e.g., Internet access) that another network does not provide. One network may provide information services (e.g., voice, data, multimedia) that are not provided by another network.  
         [0047]     Many different schemes may be used to connect to a given network. For example, a device constructed according to the invention may query the user so that the user can decide whether to connect to a particular network. For example, the multi-mode controller may send a message that is displayed on a display  98  in the user interface  82 . The user may then use an input device  100  to send instructions to the multi-mode controller  80  regarding the user&#39;s selection.  
         [0048]     Alternatively, a device constructed according to the invention may automatically connect to a network. In the embodiment of  FIG. 4 , a data memory  84  may include information  96  that indicates, for example, that the device should: 1) never connect to a particular network; 2) always connect to a particular network if that network is detected; 3) prompt the user of the device for input as to whether the user wishes to connect to the network; and/or 4) connect to the network depending on other options. Examples of options in the last category (number four) include a switch on the device indicative of the user&#39;s preference under certain conditions or comparison of the service (e.g., available bandwidth, quality of service, networks costs) available from each network.  
         [0049]     Once a network has been selected, a connection manager  102  establishes communication with the network by, for example, causing the appropriate network processor  60  or  62  ( FIG. 3 ) to send the necessary signals to another device in the network (as represented by block  90 ).  
         [0050]     One embodiment of the invention relates to a method for a multi-mode wireless communication device to access and take advantage of the proximity wireless network that best satisfies its service needs. In particular, this embodiment includes a dual-mode wireless network chip set architecture that combines wireless PAN and LAN functions. The dual-mode operation is achieved by a device called a dual-mode controller (DMC) which controls and manages network access to a nearby PAN or a LAN.  
         [0051]      FIG. 5  depicts one embodiment of the invention that enables a device to utilize Bluetooth and HomeRF networks. Central to this embodiment is a Bluetooth and HomeRF dual mode controller as discussed in more below.  
         [0052]     A Bluetooth network is categorized as a personal area network (PAN). PANs such as Bluetooth typically have a range on the order of ten meters. Conventionally, Bluetooth devices support data transfer rates in the range of 1 Mbit/s. Current Bluetooth specifications include Bluetooth versions 1.0 and 1.1.  
         [0053]     In some instances, Bluetooth networks may be used in ad hoc peer-to-peer communications. Examples of communications over a Bluetooth network may include data transfers between a PDA and a nearby laptop computer or between a digital camera and a personal computer. In addition, an MP3 player may communicate with a computer or “juke box” over a Bluetooth network.  
         [0054]     A HomeRF network is categorized as a local area network (LAN) and, as such, typically supports communications over a area of coverage of approximately 100 meters. Conventional HomeRF devices support data transfer rates on the order of two to ten Mbit/s. Current HomeRF specifications include the Shared Wireless Access Protocol Specification, versions 1.3 and 2.0.  
         [0055]     Typically, a wireless PAN connects to a backbone that provides data connectivity to other networks. For example, a wireless PAN interface may connect to a T1 line to provide Internet connectivity. Alternatively a cable modem may include a wireless PAN interface that provides LAN connectivity to wireless devices that are within close proximity to the cable modem.  
         [0056]     Significantly, both Bluetooth and HomeRF incorporate frequency hopping. Thus, in this embodiment of the invention a portion of the RF front end may be effectively shared by the two networks. That is, some of the same circuits in the RF front end are used when the device is communicating with other Bluetooth devices or with other HomeRF devices.  
         [0057]     Referring now to  FIG. 5 , for purposes of explanation, an embodiment of a dual-mode mobile communication device  110  capable of accessing either Bluetooth network devices  112  or HomeRF network devices  116  will be described in the context of a residential gateway (e.g. a cable modem with a HomeRF wireless LAN interface  120 ). The residential gateway may provide a multi-user broadband internet access service and multi-channel cordless telephony via HomeRF interface. A PDA or a mobile phone with a dual-mode Bluetooth-HomeRF capability could switch to a HomeRF mode upon entering a home to take advantage of the broadband internet access service, or multi-channel cordless telephony service to avoid airtime charges while making a call.  
         [0058]     In  FIG. 6 , a chip architecture that provides this dual-mode functionality is illustrated. A dual-mode radio front-end  132  can be shared with different frequency hopping and modulation rate parameters between Bluetooth and HomeRF modes of operation. To achieve a dual-mode operation, a new timing mechanism (and respective state machines) is used since both Bluetooth and HomeRF are time-synchronous networks. A dual-mode controller  130  implements this timing mechanism and the state machines to achieve the dual-mode operation.  
         [0059]     The dual-mode controller  130  has the following operational modes: 
        Bluetooth-only mode     HomeRF-only mode     Dual Bluetooth-HomeRF mode        
 
         [0063]     In this embodiment, all three modes are set by an external user command. In the Bluetooth-only or HomeRF-only mode, the device operates in the native Bluetooth or HomeRF mode, respectively, i.e., whichever mode the device is in the other mode would be turned off. In the dual Bluetooth-HomeRF mode, Bluetooth and HomeRF baseband processors  134  and  136 , respectively, time-share the dual-mode radio front-end  132  under the time-synchronous management of the dual-mode controller  130 .  
         [0064]     The role of the dual-mode controller  130  may be better understood by first explaining the native Bluetooth and HomeRF network access mechanisms.  FIG. 7  illustrates what is called “inquiry scan procedure” used by new Bluetooth devices to access a nearby Bluetooth network. A Bluetooth master device (by default the first device that formed a Bluetooth network) sends a train of special inquiry sequences to probe if there are any new Bluetooth devices in the vicinity. The special inquiry sequences denoted by “A” and “B” each contain 8 frames where each frame is of time duration 1.25 ms and consists of a master-to-slave transmission slot (0.625 msec) and a slave-to-master transmission slot (0.625 msec). In every master-to-slave transmission slot, the master sends an inquiry access code on two consecutive hopping frequencies, thereby, covering 16 hopping frequencies for every 8 frames that make up the inquiry sequence “A.” As shown in  FIG. 7 , the inquiry sequence “A” is repeated 256 times. There are a total of 32 predetermined hopping frequencies allocated to the inquiry procedure. In the event that no inquiry response is received by the master during the first 2.56 sec interval, the remaining set of 16 hopping frequencies are used in transmitting another train of inquiry sequences denoted by “B” as shown in  FIG. 7 .  
         [0065]     New devices entering a Bluetooth network scan for inquiry sequences transmitted by a master device. The inquiry scan mechanism is also shown in  FIG. 7 . A new device scans the RF spectrum at a single hopping frequency for 11.25 ms in every 2.56 seconds interval. For each new scanning window, a new hopping frequency is selected based on a predetermined frequency hopping sequence. Upon receiving a valid inquiry code sequence, the new unit picks a random number N&lt;64 and continues to search for inquiry messages on the same hopping frequency. The unit then transmits an inquiry response message (containing the unit&#39;s access ID and other parameters) in the Nth slave-to-master slot corresponding to the master-to-slave slot that carried a valid inquiry code. Sending an inquiry response message at a randomly chosen slave-to-master slot reduces the probability of collision for transmissions by multiple new units responding to the same inquiry access code. The bound on the random number N is chosen such that the inquiry response message is sent to the master unit within the same train of inquiry code sequences “A” or “B”. Once the master unit receives an inquiry response message, the actual connection set up procedure is performed.  
         [0066]      FIG. 8  describes the HomeRF network scan procedure for a new isochronous device (called I-node) to join a HomeRF network managed by a Control Point (CP). In this case, the CP transmits a distinctive TDMA beacon every 20 msec at the beginning of each superframe. The superframe duration (20 msec) is based on the frequency hopping rate (50 hops/sec), i.e., each superframe is sent at a different hopping frequency. The beacon contains specific information about joining the HomeRF network. A new I-node performs a network scan procedure to search for a CP beacon on one of the three predetermined network scan frequencies for 1.52 seconds.  
         [0067]     Unless a beacon is received, all three scan frequencies are tried (each for 1.52 sec) in search of a CP beacon. If a TDMA beacon is received within the scanning window, the new I-node then extracts the network identity information and the timing information from the beacon to join the HomeRF network.  
         [0068]     HomeRF network access mechanism for a new device is somewhat similar to the Bluetooth network access mechanism. In both cases, the new device seeking admission into the network starts a network scan procedure searching for a special message from a master unit (for a HomeRF network, the master is the CP). This similarity establishes the basis for the operation of the dual-mode controller device. For a dual-mode Bluetooth-HomeRF communication device, the dual-mode controller manages the network access mechanism for both Bluetooth and HomeRF networks in a synchronous manner. A general illustration of the time interleaved access procedure is shown in  FIG. 9 .  
         [0069]     The dual-mode controller (DMC) device includes a new synchronous state machine that combines the standby, inquiry scan, network scan, and connection procedures carried out by Bluetooth and HomeRF devices. The dual-mode Bluetooth-HomeRF devices interoperate with standards based on Bluetooth-only or HomeRF-only devices. Network scan and connection setup procedures for a dual-mode device should follow the same rules as specified in the Bluetooth or HomeRF standards. In other words, dual-mode operation of the described embodiment should not alter the synchronous time flow of interdependent states (idle, network scan, scan response, etc.) that accomplish the respective network access procedures for Bluetooth or HomeRF networks. The exemplary dual-mode controller is configured such that Bluetooth and HomeRF network access state machines are combined without individually altering their functionalities. Detailed description of the dual-mode controller state machine is illustrated in  FIG. 10 .  
         [0070]     The default state for the dual-mode controller is the standby mode. In the absence of any network connection, the dual-mode controller initiates a new network scan request every 10.24 seconds. The very first network scan performed by the dual-mode controller searches for a HomeRF network. In this state, a new device performs a network scan procedure on one of the three HomeRF network scan frequencies for 1.52 sec searching for a CP beacon. Unless a beacon is received, all three scan frequencies are tried (each for 1.52 sec) in search of a CP beacon as shown in  FIG. 9 . Total duration of the HomeRF network scan procedure is 10.24 seconds. If a TDMA beacon is received within the scanning window, the new unit extracts the network identity information and the timing information from the beacon to join the HomeRF network. However, before the new device attempts to join the HomeRF network based on the beacon information, the user is informed via a display message etc. about the existence of a HomeRF network and the types of services that are available. Accordingly, the user may either approve or disapprove joining the HomeRF network for the specified services. If the user directs the dual-mode controller to establish a connection with the HomeRF network, the dual-mode device then joins the HomeRF network and maintains connection until the device transitions into an idle mode or until the CP beacon is no longer received by the unit. In both cases, the dual mode device goes into the dual-mode standby mode. If the user does not approve connecting to a HomeRF network, the dual-mode controller automatically starts an inquiry scan procedure to search for the existence of a Bluetooth network  188 . As illustrated in  FIG. 10 , the dual-mode controller jumps to the same state, that is, starting a Bluetooth inquiry scan if the initial HomeRF network scan fails to find a CP beacon. In this case, the Bluetooth inquiry scan procedure is also run for 10.24 seconds. This time duration is divided into four inquiry scan periods of each 2.56 seconds. As shown in  FIG. 9 , the inquiry scan procedure involves searching for a valid inquiry code for 11.25 msec (covering 16 inquiry frequencies) in a 2.56 second interval at a single hop frequency. The same procedure is repeated at different hop frequencies until an inquiry code is received, but no more than 3 times. If a valid Bluetooth inquiry code is not received within the 10.24 second interval, the dual-mode device goes back to the dual-mode standby mode  170 . In case the unit receives a valid inquiry code  190 , it goes into an inquiry-response mode  192  followed by the connection set up procedure  194  with the master as described earlier in the text. Finally, if there is no more data to be sent, the Bluetooth connection is terminated  196 , and the dual-mode device goes back into the dual-mode standby mode  170 .  
         [0071]     The embodiment described above typically would be implemented in one or more integrated circuits. For example the section including the baseband processors,  134  and  136 , the central processing unit  142  and the host interfaces  138  and  140  may be implemented in a single CMOS integrated circuit and the RF section may be implemented in a single integrated circuit. It should be appreciated, however, that the teachings of the invention may be implemented using a wide variety of electronic components and, typically, software programs.  
         [0072]     As in the embodiments of  FIGS. 2-5 , the operations of the dual mode controller may be implemented using various combinations of hardware and software. Hence, operations of the state machine of  FIG. 10  may be implemented using software code running on a processor or as hardware-based logic. For example, a network scanner component or routing may be used for the network scan operations. A connection manager component or routine may be used for the connection procedure. Note that these two operations may correspond with the network detector  92  and the connection manager  102  of  FIG. 4 .  
         [0073]     In addition, a dual-mode communication device incorporating this embodiment may include various optional user interfaces such as an audio interface and a visual interface for textual, graphical and video presentations. The device also includes an interface for user input (e.g., a keypad). The host interface may interface to a broadband backbone including, for example, an ethernet connection, satellite connection, wireless broadband, cable or the public switched telephone network (PSTN). Typical implementations of such a device may include, for example, PDAs, cellular telephones, MP3 players, still and video cameras and video recorders.  
         [0074]      FIG. 11  depicts one embodiment of the invention consisting of a dual-mode mobile communication device that is capable of accessing either a Bluetooth or a Point-Controller (PC) controlled IEEE 802.11b network. 802.11b networks fall under the category of a local area network (LAN). Conventional 802.11b devices support data transfer rates on the order of 5.5 Mbits/s and 11 Mbit/s.  
         [0075]     This embodiment is described in the context of a residential gateway (e.g. a cable modem with an 802.11b wireless LAN interface) providing a multi-user broadband internet access service and multi-channel cordless telephony via an 802.11b interface. A PDA or a mobile phone with a dual-mode Bluetooth-802.11b capability could switch to an 802.11b mode upon entering a home to take advantage of the broadband internet access service, or multi-channel cordless telephony service to avoid air-time charges while making a call.  
         [0076]     In  FIG. 11 , a chip architecture that provides this dual-mode functionality is illustrated. A dual-mode radio front-end  202  can be shared with different RF front-end and modulation rate parameters between Bluetooth and 802.11b modes of operation. To achieve a dual-mode operation, a new timing mechanism (and respective state machines) is required since both Bluetooth and 802.11bsystems are time-synchronous networks. A dual-mode controller  200  as shown in  FIG. 11  implements this timing mechanism and the state machines to achieve the dual-mode operation.  
         [0077]     The dual-mode controller  200  has the following operational modes: 
        Bluetooth-only mode     802.11b-only mode     Dual Bluetooth-802.11b mode        
 
         [0081]     In this embodiment, all three modes are set by an external user command. In the Bluetooth-only or 802.11b-only mode, the device operates in the native Bluetooth or 802.11b mode, respectively, i.e., whichever mode the device is in the other mode would be turned off. In the dual Bluetooth-802.11b mode, Bluetooth and 802.11b baseband processors  204  and  206 , respectively, time-share the dual-mode radio front-end  202  under the time-synchronous management of the dual-mode controller  200 .  
         [0082]      FIG. 12  describes the 802.11b network scan procedure for a new device to join an 802.11b network managed by a Point Controller (PC) device. In this case, the PC transmits a distinctive “beacon” every “CFP(Contention Free Period)RepetitionInterval” that is bounded by “CFPMaximumDuration” parameter per IEEE 802.11b MAC specification. Unlike in an HomeRF network, 802.11b transmissions take place at the same fixed carrier frequency, i.e., no frequency hopping is allowed. The beacon contains specific information about the existing 802.11b network.  
         [0083]     A new device with an intention to join the 802.11b network performs a network scan procedure to search for a PC beacon. Search for the PC beacon is repeated every “CFPMaximumDuration” interval per IEEE 820.11 MAC specification at the same carrier frequency. If a PC beacon is received within the scanning window, the new device then extracts the network identity information and the timing information from the beacon to join the 802.11b network.  
         [0084]     For a dual-mode Bluetooth-802.11b communication device, the dual-mode controller  200  manages the network access mechanism for both Bluetooth and 802.11b networks in a synchronous manner. A general illustration of the time interleaved access procedure is shown in  FIG. 13 .  
         [0085]     The dual-mode controller  200  includes a synchronous state machine that combines the standby, inquiry scan, network scan, and connection procedures carried out by Bluetooth and 802.11bdevices. It is important that dual-mode Bluetooth-802.11b devices interoperate with standards based Bluetooth-only or 802.11b-only devices. Network scan and connection setup procedures for a dual-mode device should follow the same rules as specified in the Bluetooth or 802.11b standards. In other words, dual-mode operation should not alter the synchronous time flow of interdependent states (idle, network scan, scan response, etc.) that accomplish the respective network access procedures for Bluetooth or 802.11b networks. Consequently, the objective of this invention disclosure is to devise a dual-mode controller such that Bluetooth and 802.11b network access state machines are combined without individually altering their functionalities. A description of one of the embodiments of the dual-mode controller state machine is illustrated in  FIG. 14 .  
         [0086]     The default state for the dual-mode controller is the standby mode  230 . In the absence of any network connection, the dual-mode controller initiates a new network scan request  232  every “CFPMaximumDuration” per 802.11b MAC specification. The very first network scan performed by the dual-mode controller searches for an 802.11b network. In this state, a new device performs a network scan procedure  236  searching for a 802.11b PC beacon. Total duration of the HomeRF network scan procedure is “CFPMaximumDuration”. If a TDMA beacon is received within the scanning window (block  238 ), the new unit extracts the network identity information and the timing information from the beacon to join the 802.11b network. However, before the new device attempts to join the 802.11b network based on the beacon information, the user is informed via a display message etc. about the existence of the 802.11b network and the types of services that are available. Accordingly, the user may either approve or disapprove joining the 802.11b network for the specified services (block  240 ). If the user directs the dual-mode controller to establish a connection with the 802.11b network, the dual-mode device then joins the 802.11b network and maintains connection until the device transitions into an idle mode  244  or until the PC beacon is no longer received by the unit  242 . In both cases, the dual mode device goes into the dual-mode standby mode. If the user does not approve connecting to the 802.11b network, the dual-mode controller automatically starts an inquiry scan procedure to search for the existence of a Bluetooth network  248 . As illustrated in  FIG. 14 , the dual-mode controller jumps to the same state, that is, starting a Bluetooth inquiry scan if the initial 802.11b network scan fails to find a PC beacon. In this case, the Bluetooth inquiry scan procedure is run for 10.24 seconds. This time duration is divided into four inquiry scan periods of each 2.56 seconds. As shown in  FIG. 13 , the inquiry scan procedure involves searching for a valid inquiry code for 11.25 msec (covering 16 inquiry frequencies) in a 2.56 second interval at a single hop frequency. Same procedure is repeated at different hop frequencies until an inquiry code is received but no more than 3 times. If a valid Bluetooth inquiry code is not received within the 10.24 second interval, the dual-mode device goes back to the dual-mode standby mode. In case the unit receives a valid inquiry code  250 , it goes into an inquiry-response mode  252  followed by the connection set up procedure  254  with the master as described earlier in the text. Finally, if there is no more data to be sent, the Bluetooth connection is terminated  256 , and the dual-mode device goes back into the dual-mode standby mode.  
         [0087]     While the embodiments described above generally have described portable devices, the invention may be incorporated in non-portable devices. For example, a multi-mode controller may be implemented in a stationary device in an area where the wireless services may change over time. Typical scenarios may include where the quality of service or effective data rate of a given wireless service varies over time. In general, in many applications wireless networking may be used in place of non-wireless connections. Hence, it should be understood that the teachings of the invention may be applied to virtually any connectivity application where there is a need to selectively utilize the services of more than one wireless network.  
         [0088]     In summary, the invention described herein teaches improved techniques for managing and controlling network connectivity in wireless systems. While certain exemplary embodiments have been described in detail and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive of the broad invention. It will thus be recognized that various modifications may be made to the illustrated and other embodiments of the invention described above, without departing from the broad inventive scope thereof. In view of the above it will be understood that the invention is not limited to the particular embodiments or arrangements disclosed, but is rather intended to cover any changes, adaptations or modifications which are within the scope and spirit of the invention as defined by the appended claims.