Patent Publication Number: US-7724702-B2

Title: Multiple configuration communication apparatus

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to communication technology and more specifically to apparatus generally having a single instantiation of a radio device that is configurable to maintain multiple channels while switching between a plurality of communication configurations stored in the apparatus in order to transmit and receive information over the multiple channels at different times. 
     BACKGROUND OF THE INVENTION 
     As the number of communication units (e.g., laptops, Personal Digital Assistants (PDAs), cellular telephones, mobile and portable radios, etc.) in use continues to increase, this places a continued strain on already limited communication resources. To assist users of communication units in more effectively utilizing the limited communication resources, communication units have been designed to use multiple (i.e., two or more) communication protocols (e.g., 802.11, Bluetooth, various cellular protocols) and/or associated modulation techniques (e.g., CDMA (code-division multiple access), TDMA (time-division multiple access), OFDM (orthogonal frequency division multiplexing), etc.) to transmit information from and receive information to the communication unit. Such communication units are sometimes referred to as “multi-mode” or “multi-function” units and are typically implemented in one of two ways. 
     In the first implementation, the communication unit comprises multiple instantiations of radio apparatus, wherein each radio apparatus is configured to implement a different communication protocol and/or modulation technique. The unit can maintain multiple channels simultaneously. However, each radio in the unit is typically already pre-programmed for its intended use, so the number of physical radios that the unit contains limits the number of “modes” or “functions” that the radio may implement. In the second implementation, the communication unit comprises a single instantiation of radio apparatus which is configurable typically based on software stored in the radio. However, the radio apparatus can only maintain a single channel at any given time, wherein that channel corresponds to the mode in which the radio is currently configured. Therefore, if other functions are required, an application or user must decide whether to maintain any sessions or connections that are based on the current configuration, or to drop those sessions or connections and reconfigure the device to support others. 
     It would be advantageous for a communication unit to having a single instantiation of radio apparatus while being configurable for simultaneously maintaining and communicating over multiple channels. It would be further desirable that the limitations of the number of “modes” in which the radio can operate is limited primarily by the software stored on the unit for controlling its configuration into these various different modes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
         FIG. 1  illustrates multiple-configuration communication apparatus in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates a method performed in the apparatus of  FIG. 1 ; 
         FIG. 3  illustrates multiple-configuration communication apparatus in accordance with another embodiment of the present invention; 
         FIG. 4  illustrates a transmission flow for the apparatus of  FIG. 3 ; and 
         FIG. 5  illustrates a receive flow for the apparatus of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in combinations of method steps and apparatus components related to a method and apparatus for multiple-configuration communication apparatus. Accordingly, the apparatus components and method steps have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments. 
     It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions of the method and apparatus for multiple-configuration communication apparatus described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as steps of a method performed in the multiple-configuration communication apparatus described herein. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more Application Specific Integrated Circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation. 
     Generally speaking, pursuant to the various embodiments, the invention provides a method of supporting multiple applications with distinct requirements for a communications unit with a single hardware communication device, e.g., a radio. In accordance with embodiments described herein, multiple communication configurations are stored in a communication unit. Although only one configuration will typically be active at a particular time, the single hardware device can simultaneously maintain multiple connections or channels by using handshaking, sleep modes, error tolerance properties, or other features of selected protocols, and switch between configurations associated with the simultaneously maintained connections at a rate sufficient to keep all connections active. In this way, applications using the single hardware device may behave as though they have complete control of it—not only of information or paths, as is typical in modem operating systems, but over the configured properties of the device. A scheduling algorithm generally controls which of the configurations is active at a given time. 
     Moreover, current work in the area of software-defined radio (SDR) extends the value of the embodiments described herein even further, since an SDR is capable of supporting multiple systems and protocols depending on how it is configured. More particularly, the embodiments described herein enable a single SDR to support multiple systems simultaneously. As SDR becomes more prevalent in portable and computer devices, a single radio included in, for example, a PDA/cellular device can be designed to support a plurality of active networks such as, for instance, a WLAN (Wireless Local Area Network), a Bluetooth network, a cellular network, etc. and even provide bridging between these networks. 
     Those skilled in the art will realize that the above recognized advantages and other advantages described herein are merely exemplary and are not meant to be a complete rendering of all of the advantages of the various embodiments of the present invention. 
     Referring now to the drawings, and in particular  FIG. 1 , a multiple-configuration communication unit in accordance with an embodiment of the present invention is shown and indicated generally at  100 . Communication unit  100  may comprise, for example, a subscriber unit (such as a PDA, cellular telephone, portable device, mobile device, etc.) or a base station also known in the art as a base radio. Communication unit  100  contains a hardware peripheral  110  similar to a SDR, which is capable of supporting multiple communication configurations, wherein a communication configuration is characterized by software applications and data required to program peripheral  110  to communicate on a given network using a given communication protocol. In the particular embodiment illustrated, unit  100  supports three communication configurations for ease of illustration. However, those of ordinary skill in the art will realize that unit  100  can be configured to support any number of communication configurations as determined, for instance, by design and/or user specification. 
     Accordingly, peripheral  110  comprises a communication device  130  such as a radio. In this embodiment, device  130  comprises a suitable transceiver (e.g., comprising a transmitter and a receiver not shown) and an antenna  132  operatively coupled together. Since transceivers and antennas and their operation are generally known in the art, a detailed description of such will not be included here for the sake of brevity. Device  130  simultaneously maintains connections or channels  134 ,  136  and  138 , respectively, within networks  174 ,  176  and  178 , which may comprise any available networks including, but not limited to, one or more WLANs. Those of ordinary skill in the art will realize that a commercial embodiment of communication device  130  generally comprises other elements not shown such as various processors (e.g., a digital signal processor or DSP), clocks, memory, baseband logic, etc. A channel as used herein refers to an instance of medium use for the purpose of passing information over the channel. The channel may be a wireline or wireless channel, such as a radio frequency (RF) channel. In this illustration, channels  134 ,  136  and  138  are all wireless RF channels, wherein information is generally sent over the channels in packets in accordance with associated respective wireless protocols. 
     In order for communication device  130  to establish and simultaneously maintain channels  134 ,  136  and  138 , communication unit  100  has stored therein at least three communication configurations, with a different communication configuration supporting each of the three channels. In the illustrated embodiment, the three communication configurations comprise logical configuration blocks  114 ,  116  and  118  included in peripheral  110 . Each of the configuration blocks contains configuration data needed to program or configure communication device  130  to transmit and/or receive information over one of the channels (e.g.,  134 ,  136 ,  138 ) being maintained, using the associated protocol. The configuration data may comprise data related to, for example, modulation, rate, transmission power, channel, filter requirements, etc. 
     The three communication configurations further comprise (e.g., within peripheral  110 ) logical information or data paths  124 ,  126  and  128  coupled between communication device  130  and applications (e.g.,  144 ,  146 ,  148 ) stored in unit  100  and that support the various communication configurations, through which the data (e.g., audio, video, etc.) being communicated by unit  100  will pass as it is communicated over the respective channels (e.g.,  134 ,  136 ,  138 ). In one embodiment, for example, each data path and corresponding application is implemented as one or more layers of a protocol stack in accordance with the well known Open Systems Interconnect (OSI) model for processing the information transmitted from and received to communication unit  100 . In other embodiments each corresponding application and data path may comprise a medium access control (MAC) engine (for instance in accordance with the well known 802.11 WLAN protocol and as described in an embodiment in more detail below), a driver, a user application, or any other entity capable of utilizing the communication peripheral  110 . 
     The communication configurations including the data paths, configuration data and applications can be stored as data and/or software (as is required) in any suitable storage device or apparatus such as one or more read only memories, random access memories, etc. Unit  100  may comprise any suitable processor(s) (not shown) for implementing the various communication configurations stored therein. Depending on the device design requirements, applications  144 ,  146 ,  148  may interface to the peripheral  110  directly or they may be abstracted through, for instance, a driver or an application programming interface (API). 
     Peripheral  110  further comprises a configuration controller, which selects which communication configuration is active at any time and arbitrates the switching of hardware (any suitable hardware switching apparatus, e.g.,  150 ,  152 ) from one configuration to another as needed. The configuration controller in the embodiment illustrated comprises a hardware portion  120  referred to herein as the “controller” and a software portion  140  referred to herein as the “scheduler.” As mentioned above, data paths  124 ,  126 ,  128  are associated with configuration blocks  114 ,  116 ,  118  respectively. Controller  120  physically selects or switches to a given configuration block for configuring communication device  130  during a predetermined or prearranged time frame and further physically selects or switches to the corresponding data path associated with the selected configuration block. Thus, the communication device  130  may be configured using the data contained in the selected configuration block in order to communicate information via the associated selected data path. 
     Scheduler  140  programs controller  120  to select certain communication configurations and data paths at prearranged times. This arrangement allows the scheduler  140  to manage connections  134 ,  136 ,  138  to respective networks  174 ,  176 ,  178 , and enables these channels to be simultaneously maintained with device  130  being present on each channel for only a fraction of the time. Scheduler  140  can be said to comprise a single hardware abstraction layer (HAL) servicing multiple communication configurations by being an interface between applications  144 ,  146 ,  148  and communication device  130  so that applications  144 ,  146 ,  148  can perform their functions asynchronously while device  130  operates in real time to receive and transmit information over channels  134 ,  136 ,  138 . 
     To enable its functionality, scheduler  140  generally has some awareness of the protocols being used on networks  174 ,  176 ,  178  in order to arrange and interpret the times (e.g., time frames) that device  130 &#39;s presence on each channel is required or optional. Thus, scheduler  140  uses its knowledge of one or more parameters of the protocols associated with channels  134 ,  136 ,  138  (or more particularly associated with communicating information in networks  174 ,  176 ,  178  over the respective channels) to determine and program controller  120  with configuration scheduling for communication device  130 . The scheduling may be determined using any suitable scheduling algorithm stored on a storage device in unit  100 . The configuration scheduling determined by the scheduling algorithm may in general comprise: a first time frame during which controller  120  switches to configuration block  114  and associated data path  124  for controlling communication device  130  to reconfigure itself to communicate information over channel  134 ; a second and different time frame during which controller  120  switches to configuration block  116  and associated data path  126  for controlling communication device  130  to reconfigure itself to communicate information over channel  136 ; and yet a third and different time frame during which controller  120  switches to configuration block  118  and associated data path  128  for controlling communication device  130  to reconfigure itself to communicate information over channel  138 . 
     In one embodiment, this configuration scheduling is enabled by scheduler  140 &#39;s awareness of inactive modes utilized in the protocols associated with each channel. As used herein an inactive mode associated with a channel that is being maintained is characterized by a time frame during which a communication unit is not required by the protocol to be active on the channel. Depending on a given protocol, the inactive mode may be implementing, for example, using slot assignments, polled modes, time division multiplexing, or other scheduling mechanisms if the device is a server on the channel, or by scheduling sleep modes or requesting specific availability intervals if the device is a client, or may be implemented using various power saving mechanisms. The scheduler  140  then programs controller  120  to ensure that a particular configuration  114 ,  116 ,  118  is active at the times when its network  174 ,  176   178  requires its presence on the channel  134 ,  136 ,  138 . 
     Since scheduler  140  in effect serves as a HAL between applications  144 ,  146 ,  148  and device  130 , these applications can program configurations  114 ,  116 ,  118  and communicate through data paths  124 ,  126 ,  128  without specific knowledge of which of the configurations  114 ,  116 ,  118  is currently active. In this manner, applications  144 ,  146 ,  148  each have access to the configurations  114 ,  116 ,  118  and the data paths  124 ,  126 ,  128  at will, regardless of which of the configurations  114 ,  116 ,  118  is currently active and are, consequently therefore, relieved of real-time maintenance activities. This level of abstraction enables applications  144 ,  146 ,  148  to operate as though they had complete control of the communication device  130  even though in reality each application is sharing the device with other applications. 
     Turning now to  FIG. 2 , a method that may be performed in communication apparatus such as communication unit  100  is shown and generally indicated at  200 . In communication unit  100 , the method comprises the steps of: establishing and simultaneously maintaining ( 202 ) a first channel and at least a second channel using communication device  130 ; the scheduler  140  determining ( 204 ) a first time frame; during ( 206 ) the first time frame, the scheduler  140  selecting a first communication configuration of a plurality of communication configurations stored in the communication apparatus, the controller  120  controlling the communication device  130  to configure itself to the first communication configuration and the communication device  130  transmitting and/or receiving information over the first channel; the scheduler  140  determining ( 208 ) a second time frame that is different from the first time frame; and during ( 210 ) the second time frame, the scheduler  140  selecting a second communication configuration of the plurality of communication configurations, the controller  120  controlling the communication device  130  to configure itself to the second communication configuration and the communication device  130  transmitting and/or receiving information over the second channel. Those skilled in the art will realize that the unit  100 , while operational, will continue to determine additional time frames over which to switch between communication configurations to communicate over the multiple channels that it has maintained. 
     The remaining  FIGS. 3-5  illustrate a particular embodiment of the present invention including a specific implementation of apparatus  100  and method  200  in the context of 802.11 WLANs. Accordingly  FIG. 3  shows, by way of example and not limitation, software definable and multiple-configuration radio communication apparatus  300  in accordance with another embodiment of the present invention. Apparatus  300  corresponds to peripheral  110  of  FIG. 1  and comprises a radio  302  (corresponding to communication apparatus  130 ) and a configuration controller  310  that includes a master scheduler  312  (corresponding to scheduler  140 ) implemented in software and a slave scheduler  314  (corresponding to controller  120 ) implemented in hardware. Apparatus  300  further comprises a plurality of communication configurations stored therein and implemented as 802.11 MAC engines (three shown and denoted as  320 ,  330  and  330 ) operatively coupled to the slave scheduler  314  and the radio  302 . Only three MAC engines are shown for ease of illustration. However, skilled artisans will realize that any number of MAC engines may be implemented in apparatus  300  as a function, for instance, of user and/or design specifications. 
     MAC engines  320 ,  330 ,  340  and associated switching apparatus (illustrated generally by arrows between the controller  314  and the MAC engines) correspond, respectively, to data paths  124 ,  126 ,  128 . In general, each of the MAC engines is divided between hardware (e.g., denoted as Lower MAC ( 1 )  324 , Lower MAC (n−1)  334  and Lower MAC (n)  344 , where n=3 in this case) and software (denoted as Upper MAC ( 1 )  322 , Upper MAC (n−1)  332  and Upper MAC (n)  342 , where again n=3 in this case). Since software is inherently non-deterministic compared to hardware, operations requiring high-resolution timing are more appropriately handled in hardware. Accordingly, each software component handles complex but non real-time tasks (such as fragmentation and reassembly), while each hardware component handles simple but time-critical or real-time tasks (such as generation of an ACK frame, which must happen in short time). Each of the plurality of 802.11 MAC engines are operably connected to the single radio  302 , which can serve only a single 802.11 MAC engine at a time. 
     In accordance with this embodiment, usually each lower MAC engine comprises of two queues, a transmit queue (or TX queue) and a reception queue (or RX queue), also referred to herein as TXQ and RXQ respectively. The TXQ and RXQ for each MAC engine may be common and shared in one embodiment or, alternatively, separate in another embodiment. Each upper MAC receives data payload from the corresponding application (e.g.,  144 ,  146 ,  148  not shown in apparatus  300 ) for transmission over the wireless air interface (via the radio) and queues the data asynchronously to the TXQ in its corresponding lower MAC engine. Although all lower MAC engines can largely share the same lower MAC hardware, they usually have individual configurations and data paths, and appear to be multiple instantiations of identical lower MAC engines. For the purposes of this description, a lower MAC engine is described as being any of the multiple configurations and data paths associated with an upper MAC engine, regardless of the fact that they may share a large subset of the lower MAC hardware implementation. 
     To address the limitation that each MAC engine expects complete access to the radio, and being that the radio can only service a single MAC engine at a time, a fully asynchronous interface between the upper MACs and lower MACs (and/or) radio is desired to enable an effective separation between the time-critical and non-time critical tasks. Configuration controller  310  provides for this interface and as described above is, similarly to the MAC engines, partitioned into a software component  312  and a hardware component  314 . The complex scheduling algorithm is implemented in what is hereinafter referred to as “the scheduler” corresponding to scheduler  140  in  FIG. 1 , and the hard real-time switching of MAC engines to access the radio is controlled in the hardware component of the configuration controller, corresponding to controller  120  in  FIG. 1 . 
     The scheduler is aware of constraints placed upon the 802.11 MAC layer protocol such as (but not limited to) contention periods, contention free (polling) periods, and/or power saving protocols. The scheduler then determines and programs the controller with a schedule of when to switch access control to which lower MAC engine. As such, the scheduler abstracts from the software and hardware MAC engines the constraints imposed by the single radio. That is to say that each upper MAC engine behaves as if it has complete access to the radio, e.g., the upper MAC engines run all the time without knowledge of which lower MAC engine is selected by the controller. However, in reality the controller  314  is switching the lower MAC engine to other configurations at various times in a deterministic way. 
     To enable transmission of data frames or data packets by radio  302 , each upper MAC engine asynchronously queues data frames to its respective lower MAC engine (e.g., independent from the configuration scheduling determined by scheduler  312 ), and the lower MAC engine transmits the frames when the appropriate configuration is activated by the controller  314 . In one embodiment, the configuration is comprised of configuration registers programmed by the upper MAC to define the operation of the lower MAC as well as any state information in the lower MAC that needs to be retained from one active period to the next. 
       FIG. 4  illustrates a data frame transmission flow for apparatus  300  in accordance with an embodiment of the present invention. Illustrated in  FIG. 4 , are three upper MAC engines  402 ,  404 , 406  and a lower MAC engine  410 . It should be noted that since, as explained above, the three lower MAC engines corresponding to the three upper MAC engines largely share common hardware the lower MAC engine is represented as one hardware device. Also shown in  FIG. 4  is a TXQ  408  and a transmission frame description queue (denoted TXFDQ  412 ) included in the lower MAC engine, both of which are common to all three MAC engines. To aid in communication between the upper and lower MAC engines for purposes of distinguishing between which data frames are generated by which upper MAC engines, a descriptor may be generated and used by both the upper MAC engine the lower MAC engine for this purpose. 
     The frame descriptor can have any format but usually at a minimum identifies the particular upper MAC engine generating or passing the frames (e.g., through the use of a MAC engine identification or ID) and identifies the priority of the frames. In this embodiment, priority of the frames may correspond to the frames&#39; location in the TXQ  408 . To facilitate such an embodiment, the TXFQD may be implemented as a doubly linked list to the upper MAC engine and the TXQ, to enable the upper MAC engine to insert the frame descriptor in its proper place in the TXFDQ, for example, using a linear sort. 
     Accordingly for transmission of data frames, at a step  420  the upper MAC engine (e.g.,  402 ) receives data from upper layers (e.g., of the OSI model) for transmission by the radio. The upper MAC engine at a step  430  finds space in the TXQ  408  and inserts the frames therein. At a step  440 , the upper MAC engine creates a descriptor with its ID and inserts the descriptor into the TXFDQ  412  (denoted as location  414  in the TXFDQ) as an indication to the lower MAC engine of the priority of the identified frames. Upon the configuration controller selecting the MAC engine comprising upper MAC engine  402 , the lower MAC engine uses the descriptor  414  to locate the frames (at a step  450 ) in TXQ  408 , wherein the lower MAC transfers these frames to the radio (at a step  460 ) for transmission by the radio over the associated channel. 
     Reception of frames from radio  302  follows a similar model. When a lower MAC configuration is given access to radio  302  by controller  314 , it will spend part of its time “listening” instead of “talking.” When frames are received, they will be passed up to the upper MAC engine which will in turn pass the data to the application. Once again, the reader will appreciate the level of abstraction between the radio and MAC engines, in that neither the lower MAC engine, the upper MAC engine nor the application is aware of the single radio of which they all share access. 
       FIG. 5  illustrates a data frame reception flow for apparatus  300  in accordance with an embodiment of the present invention. Illustrated in  FIG. 5 , are the three upper MAC engines  402 ,  404 ,  406  and the lower MAC engine  410 . Also shown in  FIG. 5  is a MAC engine (ME) inbox sorter  504 , a RXQ  502  and a reception frame description queue (denoted RXFDQ  506 ) included in the lower MAC engine, all of which are common to all three MAC engines. Like the TXFDQ, the RXFDQ may be implemented as a doubly linked list. The ME inbox sorter  504  can be used to relieve each upper MAC engine of the responsibility for having to process reception or RX interrupts generated by the lower MAC engine and furthermore determine whether a given RX interrupt corresponds to frames that are available for processing by the upper MAC engine. The inbox sorter provides this functionality, thereby hiding such overhead from the upper MAC engines. 
     Accordingly for reception of data frames, the lower MAC engine receives frames from the radio at a step  510 , searches for a location in the RXQ and inserts the frames into the RXQ  502  at a step  520  and inserts an appropriate descriptor in the RXFDQ  506  (as denoted by a location  508 ). Similarly to the transmission model, the descriptor identifies an upper MAC engine ID and priority of received frames in the RXQ  502 . At a step  530 , the lower MAC engine generates a RX interrupts that it sends to the ME inbox sorter  504 , wherein the inbox sorter sends a notification to the appropriate upper MAC engine at a step  540 . The notification can have any suitable format and may comprise information such as, for instance, location and size of the received payload. Upon receipt of the notification, the upper MAC engine (e.g.,  402 ) retrieves (at a step  550 ) the descriptor (e.g.,  508 ) from RXFDQ  506  and retrieves (at a step  560 ) the corresponding frames from RXQ  502 , which it forwards up the layers to the application. 
     Returning again to  FIG. 3 , in order for radio  302  to transmit and receive data frames in accordance with the selected communication configuration (e.g., the selected MAC engine) radio  302  needs to be configured in accordance with the selected communication configuration, e.g., via reconfiguration or switching of its channel, modulation, etc. Generally, this will occur during the time frame that access is given to the appropriate lower MAC engine. In one embodiment, the lower MAC engine performs the reconfiguration of the radio to its own specification of parameters. Alternatively, the radio itself or some other entity in the peripheral (e.g., corresponding to configuration blocks  114 ,  116 ,  118 ) may store multiple configurations which are activated by the configuration controller in parallel with the selection of a lower MAC configuration. However, it is not limited to these methods, wherein in yet another embodiment the radio may be programmed by the controller  314  in a centralized (vs. distributed) manner. 
     In accordance with the 802.11 WLAN embodiment described above by reference to  FIG. 3 , four interfaces are defined: 1) the interface between the upper MAC engine (e.g.,  322 ) and the lower MAC engine (e.g.,  320 ); 2) the interface between the scheduler ( 312 ) and the controller ( 314 ); 3) the interface between the controller ( 314 ) and the lower MAC engines ( 324 ,  334 ,  344 ); and 4) the interface between the lower MAC engines and the single radio  302 . These interfaces are designed such that each of the plurality of MAC engines (comprised of their respective upper and lower instantiations in software and hardware, respectively) behave as though they have complete and unregulated access to the single radio such that no modification to the TX and RX state machines of said MAC engines is necessary for them to operate over a single radio. This level of abstraction is enabled by the configuration controller which removes the complexities of access from the MAC engines. This abstraction is also embodied within the interface between the upper MAC engine and lower MAC engine, where even though the lower MAC engine might not have access to the radio at a time T, the upper MAC engine is always able to queue frames to the lower MAC engine as though it does have such access. This combination of abstractions is an enabler of SDR. Each of these four interfaces is further described below. 
     The interface between the upper MAC engine and the lower MAC engine is fully asynchronous. Since the lower MAC engine only has access to the radio as per the scheduler, and since the controller operates in real time to meet the real times requirements of 802.11 and other protocols, it is not feasible that a software implementation of a MAC engine could keep synchronized with the hardware. That is to say that it is undesirable and impractical to attempt to start and pause the upper MAC engine in accord with the lower MAC engine&#39;s access to the radio. As such, each upper MAC engine may queue frames to its respective lower MAC engine without regard or care as to whether or not its respective lower MAC engine has or does not have access to the radio. 
     The interface between the scheduler and configuration controller is such that the scheduler contains all the intelligence about what MAC engines are running on the apparatus and what their unique air interface protocol requirements demand (e.g. beacons, polling, contention periods, etc.). The scheduler computes the most effective utilization of time sharing between the lower MAC engines and the radio and programs the controller with this optimized schedule. 
     The interface between the controller and lower MAC engines is controlled by the controller which functions as a master to the lower MAC engines, instructing the lower MAC engines when they have access to the radio and for how long based on its programming by the scheduler. The controller then in hardware real-time switches the MAC engines in and out of context. Thus, even though all lower MAC engines share the radio, they need not be aware of one another during their operation as their fair share to the radio is provided for by the configuration controller. 
     The interface between the lower MAC engines and the radio is many-to-one. Each lower MAC engine, when given access to the radio, may program the radio as per its own configuration (e.g. modulation, TX power, rate, channel, etc.). 
       FIG. 3  shows an embodiment of the present invention in accordance with the 802.11 wireless protocol. However, the present teachings can be readily applied to any protocols, modulations, configurations, etc. The scheduler in those embodiments would have the awareness of parameters associated with whatever configurations are programmed into a given communication unit in order to use those parameters to generate a configuration schedule for the communication unit in accordance with the teachings herein. 
     In yet another embodiment, some or all of the functionality of various elements described herein may be stored as processor readable code on a processor readable storage medium for programming a processor in the communication unit to perform steps in accordance with the teachings herein. For example, the processor readable code may program a processor to perform the steps implemented in the configuration controller of: determining a first time frame and during the first time frame, selecting a first communication configuration of a plurality of communication configurations stored in the communication apparatus and controlling the communication apparatus to configure itself to the first communication configuration to at least one of transmit and receive information over the first channel; determining a second time frame that is different from the first time frame and during the second time frame, selecting a second communication configuration of the plurality of communication configurations, and controlling the communication apparatus to configure itself to the second communication configuration to at least one of transmit and receive information over the second channel; and determining the first time frame based on at least a first parameter associated with the first channel, and determining the second time frame based on at least a second parameter associated with the second channel to enable the first and second channels to be simultaneously maintained. The processor readable storage medium may comprise any format including, but not limited to, read-only memory (ROM), random-access memory (RAM), a disk storage medium such as a CD-ROM, a magnetic tape, and an optical data storage device. 
     In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued. 
     Moreover, in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising, ” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.