Abstract:
A wireless communications device has a layer 2 interface that is designed as a finite state machine. The finite state machine includes a null state, a data transfer state, a reset pending state, a local suspend state and a reset/suspend state. In the null state, no communications channel is established. In all the other states, a communications channel is established with another communications device. In the data transfer state the communications channel is active. In the reset pending state communications is halted pending a reset acknowledge signal from the other device. In the local suspend state communications are temporarily suspended for all data after a predetermined event. The reset/suspend state explicitly supports the condition in which both rest pending and local suspend conditions are present, and enables the state machine to transition to a subsequent state without requiring knowledge of a previous state.

Description:
BACKGROUND OF INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a state model for a wireless communications device. In particular, the present invention discloses a finite state machine for the wireless device that includes a reset/suspend state.  
           [0003]    2. Description of the Prior Art  
           [0004]    Technological advances have moved hand in hand with more demanding consumer expectations. Devices that but ten years ago were considered cutting edge are today obsolete. These consumer demands in the marketplace spur companies towards innovation. The resulting technological advances, in turn, raise consumer expectations. Presently, portable wireless devices, such as cellular telephones, personal data assistants (PDAs), notebook computers, etc., are a high-growth market. However, the communications protocols used by these wireless devices are quite old. Consumers are demanding faster wireless access with greater throughput and flexibility. This has placed pressure upon industry to develop increasingly sophisticated communications standards. The 3 rd  Generation Partnership Project (3GPP™) is an example of such a new communications protocol.  
           [0005]    The 3GPP™ standard utilizes a three-layered approach to communications. Please refer to FIG. 1. FIG. 1 is a simplified block diagram of the prior art communications model. A prior art wireless system includes a first device  20  and a second device  30 , both of which are in wireless communications with each other. As an example, the first device  20  may be a mobile unit, such as a cellular telephone, and the second device  30  may be a base station. An application  24  on the first device  20  needs to send data  24   d  to an application  34  on the second device  30 . The application  24  connects with a layer  3  interface  23  (termed the radio resource control (RRC)), and passes the data  24   d  to the layer  3  interface  23 . The layer  3  interface  23  uses the data  24   d  to form a layer  3  protocol data unit (PDU)  23   p . The layer  3  PDU  23   p  includes a layer  3  header  23   h  and data  23   d , which is identical to the data  24   d . The layer  3  header  23   h  in the layer  3  PDU  23   p  contains information needed by the corresponding layer  3  interface  33  on the second device  30  to effect proper communications. The layer  3  interface  23  then passes the layer  3  PDU  23   p  to a layer  2  interface  22 . The layer  2  interface  22  (also termed the radio link control (RLC)) uses the layer  3  PDU  23   p  to build one or more layer  2  PDUs  22   p . Generally speaking, each layer  2  PDU  22   p  has the same fixed size. Consequently, if the layer  3  PDU  23   p  is quite large, the layer  3  PDU  23   p  will be broken into chunks by the layer  2  interface  22  to form the layer  2  PDUs  22   p , as is shown in FIG. 1. Each layer  2  PDU  22   p  contains a data region  22   d , and a layer  2  header  22   h . In FIG. 1, the data  23   d  has been broken into two layer  2  PDUs  22   p . Also note that the layer  3  header  23   h  is placed in the data region  22   d  of a layer  2  PDU  22   p . The layer  3  header  23   h  holds no significance for the layer  2  interface  22 , and is simply treated as data. The layer  2  interface  22  then passes the layer  2  PDUs  22   p  to a layer  1  interface  21 . The layer  1  interface  21  is the physical interface, and does all the actual transmitting and receiving of data. The layer  1  interface  21  accepts the layer  2  PDUs  22   p  and uses them to build layer  1  PDUs  21   p . As with the preceding layers, each layer  1  PDU  21   p  has a data region  21   d  and a layer  1  header  21   h . Note that the layer  3  header  23   h  and layer  2  headers  22   h  are no more important to the layer  1  interface  21  than the application data  24   d . The layer  1  interface  21  then transmits the layer  1  PDUs  21   p  to the second device  30 .  
           [0006]    A reverse process occurs on the second device  30 . After receiving layer  1  PDUs  31   p  from the first device  20 , a layer  1  interface  31  on the second device  30  removes the layer  1  headers  31   h  from each received layer  1  PDU  31   p . This leaves only the layer  1  data regions  31   d,  which are, in effect, layer  2  PDUs. These layer  1  data regions  31   d  are passed up to a layer  2  interface  32 . The layer  2  interface  32  accepts the layer  2  PDUs  32   p  and uses the layer  2  headers  32   h  to determine how to assemble the layer  2  PDUs  32   p  into appropriate layer  3  PDUs. In the example depicted in FIG. 1, the layer  2  headers  32   h  are stripped from the layer  2  PDUs  32   p , leaving only the data regions  32   d . The data regions  32   d  are appended to each other in the proper order, and then passed up to the layer  3  interface  33 . The layer  3  interface  33  accepts the layer  3  PDU  33   p  from the layer  2  interface  32 , strips the header  33   h  from the layer  3  PDU  33   p , and passes the data region  33   d  to the application  34 . The application  34  thus has data  34   d  that should be identical to the data  24   d  sent by the application  24  on the first device  20 .  
           [0007]    Please refer to FIG. 2 in conjunction with FIG. 1. FIG. 2 is simplified block diagram of a layer  2  PDU  40 . The layer  2  PDU  40  has a layer  2  header  41  and a data region  45 . As noted above, the data region  45  is used to carry layer  3  PDUs  23   p  received from the layer  3  interface  23 . The layer  2  header  41  includes a data/control indicator bit  42 , a sequence number field  43 , and additional fields  44 . The additional fields  44  are not of direct relevance to the present invention, and so will not be discussed. The data/control bit  42  is used to indicate if the layer  2  PDU  40  is a data PDU or a control PDU. Data PDUs are used to carry layer  3  data. Control PDUs are generated internally by the layer  2  interface  22 ,  32  and are used exclusively for signaling between the layer  2  interfaces  22  and  32 , such as the passing of reset and reset acknowledgment signals. Control PDUs are thus never passed up to the layer  3  interface  23 ,  33 . The sequence number field  43  contains a 12-bit or 7-bit value that is used to reassemble the layer  2  PDUs  40  into layer  3  PDUs  33   p . Each layer  2  PDU  22   p  is transmitted with a successively higher value in the sequence number field  43 , and in this manner the layer  2  interface  32  knows the correct ordering of received layer  2  PDUs  32   p.    
           [0008]    Please refer to FIGS. 3 and 4 in conjunction with FIGS. 1 and 2. FIGS. 3 and 4 are state model diagrams of a prior art layer  2  interface. The prior art layer  2  interface  22 ,  32  is designed as a finite state machine. FIG. 3 depicts the state model for the layer  2  interface  22 ,  32  when a reset command is performed. FIG. 4 depicts the state model when a local suspend command is performed. Transitions between states are noted by arrows in FIGS. 3 and 4. Received signals associated with a state transition are noted above a horizontal line, and signals sent in response to the state transition are noted below the horizontal line. The layer  2  interface  22 ,  32  includes a null state  50 , a data transfer ready state  52 , a reset pending state  54  and a local suspend state  56 . To explain these state models, the first device  20  will be used as an example. When the layer  2  interface  22  is in the null state  50 , the layer  2  interface  22  has no established wireless channel  11  with the second device  30 . The layer  2  interface  22  of the first device  20  thus cannot transmit any layer  2  PDUs  22   p  to the second device  30 . When the application  24  determines that it wishes to send the data  24   d  to the application  34 , the application  24  signals this intent to the layer  3  interface  23 . The layer  3  interface  23  then performs whatever functions are necessary to establish the channel  11  with the second device  30 . In particular, the layer  3  interface  23  sends an establish primitive to the layer  2  interface  22 . On reception of the establish primitive, the layer  2  interface  22  transitions from the null state  50  to the data transfer state  52 . In the process of doing so, the layer  2  interface  22  establishes the wireless channel  11  with the second device  30 . While in the data transfer ready state  52 , the first device  20  can freely transmit layer  2  PDUs  22   p  along the channel  11 . At any time when the layer  2  interface  22  is in the data transfer state  52  and receives a release primitive from the layer  3  interface  23 , the layer  2  interface  22  will transition back to the null state  50 . In the process of doing so, the layer  2  interface  22  will close down the channel  11 .  
           [0009]    From time to time, the layer  2  interface  22  may determine that communications along the channel  11  are malfunctioning. In this case, the layer  2  interface  22  will desire to reset the communications system. To ensure that the entire system is reset, both the first device  20  and the second device  30  must be reset. To reset the second device  30 , the layer  2  interface  22  generates a reset control PDU, and sends the reset control PDU along the channel  11  to the layer  2  interface  32  on the second device  30 . The layer  2  interface  22  on the first device  20  then transitions from the data transfer state  52  to the reset pending state  54 . While in the reset pending state  54 , the layer  2  interface  22  will transmit no PDUs  22   p  to the second device  30  along the channel  11 . This effectively halts communications along the channel  11 . The layer  2  interface  22  remains in the reset pending state  54  until reception of a reset acknowledgment control PDU from the layer  2  interface  32  on the second device  30 . This reset acknowledgment control PDU informs the layer  2  interface  22  that the layer  2  interface  32  received the reset control PDU and internally reset the layer  2  interface  32 . When the layer  2  interface  22  receives the reset acknowledgment control PDU, the layer  2  interface  22  transitions from the reset pending state  54  to the data transfer ready state  52 , and in the process of doing so resets the entire layer  2  state machine  22 , such as flushing transmission and reception buffers, setting control variables to default values, etc. Communications along channel  11  are in this way reset back to default conditions so as to reestablish normal communications between the first device  20  and the second device  30 . If at any time while the layer  2  interface  22  is in the reset pending state  54  and the layer  2  interface  22  receives a release primitive from the layer  3  interface  23 , the layer  2  interface will transition to the null state  50 . In the process of doing so, the layer  2  interface  22  will close down the channel  11 . Also note that the layer  2  interface  22  may receive a reset control PDU from the layer  2  interface  32  of the second station  30  while in the data transfer ready state  52 . Upon reception of such a layer  2  control PDU, the layer  2  interface  22  will internally reset the layer  2  interface state machine  22  for the channel  11 , and then transmit a reset acknowledgment control PDU to the layer  2  interface  32 . The layer  2  interface  22  remains, however, in the data transfer ready state  52  during this exchange.  
           [0010]    The local suspend state  56  is used to temporarily halt the transfer of layer  2  PDUs  22   p  along the channel  11 , and is initiated by a suspend-request primitive from the layer  3  interface  23 . The primary purpose of the local suspend state  56  is to ensure a proper ciphering configuration change between the first device  20  and the second device  30  along the channel  11 . At any time while in the data transfer ready state  52 , the layer  2  interface  22  may transition to the local suspend state  56  upon reception of the suspend-request primitive from the layer  3  interface  23 . The suspend-request primitive contains a variable N  56   n,  which indicates a sequence number value  43 . While in the local suspend state  56 , the layer  2  interface  22  may transmit along channel  11  layer  2  PDUs  22   p  with sequence number values  43  that are sequentially before a value indicated by N  56   n.  Any layer  2  PDU  22   p  having a sequence number value  43  that is sequentially after the value indicated by N  56   n  will not be transmitted by the layer  2  interface  22   p  along the channel  11 . Upon reception of a resume primitive from the layer  3  interface  23 , the layer  2  interface  22  will transition from the local suspend state  56  back to the data transfer ready state  52 .  
           [0011]    The prior art state models of FIGS. 3 and 4 cannot account for transitions between the local suspend state  56  and the reset pending state  54 , although such transitions are assumed possible. For example, it is not difficult to imagine a situation arising in which, while the layer  2  interface  22  is in the local suspend state  56 , the layer  2  interface  22  detects a communications error along the channel  11  and desires to initiate a reset procedure. Sending a reset control PDU to the second device  30  along the channel  11  would force the layer  2  interface  22  to transition into the reset pending state  54  to await the resulting reset acknowledgment control PDU from the layer  2  interface  32  of the second device  30 . According to the state model of FIG. 3, reception of the reset acknowledgment control PDU should cause the layer  2  interface  22  to transition into the data transfer ready state  52 . This would be incorrect in this situation, however, as the layer  2  interface should more properly return back to the local suspend state  56 . To properly implement the prior art state model, the reset pending state  54  and the local suspend state  56  cannot be “memoryless” states, but must remember from which state they transitioned so as to properly return to that state. Generally speaking, a proper state model should have no hysteresis, i.e., the reaction of a state to inputs should not depend upon past reactions but only upon the present inputs, as this leads to a simpler and more consistent implementation. Internal consistency is essential to avoid programming bugs arising from unexpected state interactions within the model.  
         SUMMARY OF INVENTION  
         [0012]    It is therefore a primary objective of this invention to provide a wireless communications device with a state model having a reset/suspend state to provide internal consistency to the state model, and to avoid previous state memory requirements of the state model.  
           [0013]    Briefly summarized, the preferred embodiment of the present invention discloses a wireless communications device that transacts muti-layered communications with a second wireless device. The wireless communications device has a processor, and a program in memory that is executed by the processor to effect a multi-layered communications protocol. The multi-layered communications protocol has a layer  3  interface in communications with a layer  2  interface. The layer  2  interface transmits and receives layer  2  communications data. The layer  2  interface utilizes a null state, a data transfer state, a reset pending state, a local suspend state and a reset/suspend state. While in the null state, the layer  2  interface has no established layer  2  wireless connection with the second wireless device. While in the data transfer state, the layer  2  interface is in wireless communications with a layer  2  interface on the second wireless device and transmits the layer  2  communications data to the layer  2  interface on the second wireless device. The processor switches from the null state to the data transfer state according to an establish primitive from the layer  3  interface, and switches from the data transfer state to the null state according to a release primitive from the layer  3  interface. While in the reset pending state, the layer  2  interface is in wireless communications with the layer  2  interface on the second wireless device and the transmission of the layer  2  communications data is halted. The processor switches from the data transfer state to the reset pending state when a protocol error is found by the layer  2  interface, switches from the reset pending state to the data transfer state according to a reset acknowledge signal received from the second wireless device, and switches from the reset pending state to the null state according to the release primitive from the layer  3  interface. While in the local suspend state, the layer  2  interface is in wireless communications with the layer  2  interface on the second wireless device and halts the transmission of the layer  2  communications data after a predetermined event indicated by the layer  3  interface. The processor switches from the data transfer state to the local suspend state according to a suspend primitive from the layer  3  interface, switches from the local suspend state to the data transfer state according to a resume primitive from the layer  3  interface, and switches from the local suspend state to the null state according to the release primitive from the layer  3  interface. Finally, while in the reset/suspend state, the layer  2  interface is in wireless communications with the layer  2  interface on the second wireless device and the transmission of the layer  2  communications data is halted. The processor switches from the reset/suspend state to the reset pending state according to the resume primitive from the layer  3  interface, switches from the reset pending state to the reset/suspend state according to the suspend primitive from the layer  3  interface, switches from the reset/suspend state to the local suspend state according to the reset acknowledge signal received from the second wireless device, switches from the local suspend state to the reset/suspend state when a protocol error is found by the layer  2  interface, and switches from the reset/suspend state to the null state according to the release primitive from the layer  3  interface.  
           [0014]    It is an advantage of the present invention that by providing the reset/suspend state, the state machine of the layer  2  interface requires no memory of previous states when transitioning to subsequent states. The state model is thus more internally consistent, and therefore easier to implement and less likely to be error-prone. 
       
    
    
       [0015]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.  
       BRIEF DESCRIPTION OF DRAWINGS  
       [0016]    [0016]FIG. 1 is a simplified block diagram of a prior art communications model.  
         [0017]    [0017]FIG. 2 is simplified block diagram of a layer  2  protocol data unit (PDU).  
         [0018]    [0018]FIG. 3 depicts a state model for a prior art layer  2  interface when a reset command is performed.  
         [0019]    [0019]FIG. 4 depicts a state model for a prior art layer  2  interface when a local suspend command is performed.  
         [0020]    [0020]FIG. 5 illustrates a state model according to the present invention.  
         [0021]    [0021]FIG. 6 presents a simplified block diagram a wireless communications device that implements the state model depicted in FIG. 5. 
     
    
     DETAILED DESCRIPTION  
       [0022]    In the following description, a wireless communications device may be a mobile telephone, a handheld transceiver, a base station, a personal data assistant (PDA), a computer, or any other device that requires a wireless exchange of data. It should be understood that many means may be used for the physical layer  1  to effect wireless transmissions, and that any such means may be used for the system hereinafter disclosed.  
         [0023]    Please refer to FIG. 5. FIG. 5 depicts a state model  60  for a layer  2  interface of wireless communications device according to the present invention. The state model  60  of the present invention provides a unique reset/suspend state  68  that enables the state model  60  to function based solely on inputs. The state model  60  with the reset/suspend state  68  thus does not require a wireless device to recall a previous state from which a transition occurred when transiting to a subsequent state. Internal consistency is thereby obtained in the present invention state model  60 , with a corresponding easing of program implementation and a reduction of potential errors. A further advantage of the state model  60  is that the state model  60  is fully compatible with the prior art state model and corresponding protocols.  
         [0024]    The state model  60  includes, in addition to the reset/suspend state  68 , a null state  61 , a data transfer state  62 , a reset pending state  64  and a local suspend state  66 . Please refer to FIG. 6 with reference to FIG. 5. FIG. 6 is a simplified block diagram of a wireless communications device  70  according to the present invention, which is capable of effecting multi-layered communications along one or more established channels  78  with a suitable second wireless device  200 . The wireless communications device  70  comprises a processor  74  electrically connected to a transceiver  72  and a memory  76 . The transceiver  72  is used to send and receive wireless signals, the operations of which are controlled by the processor  74 . To control the transceiver  72 , the processor  74  executes in the memory  76  a multi-layered protocol program  80 . The multi-layered protocol program  80  is software that is used to effect a three-tiered communications protocol, which includes a layer  3  interface  83 , a layer  2  interface  82  and a layer  1  interface  81 . Although not shown in FIG. 6, in some embodiments, the layer  1  interface  81 , or portions thereof, may be embedded within the transceiver  72 .  
         [0025]    Of particular concern to the present invention is the layer  2  interface  82 , the software implementation of which includes a finite state machine  90  that conforms to the state model  60 , and which is used for communications along a particular channel  78 . That is, each channel  78  has a corresponding finite state machine  90  within the layer  2  interface  82 . For purposes of simplicity in the following description, only one communications channel  78  is considered. During operations, the layer  2  interface  82  has layer  2  communications data  82   d . The communications data  82   d  may be layer  3  data that is being processed before being passed to the layer  1  interface  81  for transmission, or may be layer  1  data that is being reassembled before being passed up to the layer  3  interface  83 . The communications data  82   d  may also be layer  2  signaling data that is to be sent to, or is received from, a layer  2  interface  202  on the second wireless device  200 .  
         [0026]    The finite state machine  90  includes a plurality of state variables  92  that are required to properly implement the layer  2  interface  82  for the channel  78 . An example of such a state variable  92  is VT(S)  92   s , which holds the value of the sequence number (item  43  in FIG. 2) of a layer  2  protocol data unit  82   p  that is next to be transmitted. The layer  2  interface  82  also includes a reset procedure  100  that sets the state variables  92  to a default condition. For example, when the wireless communications device  70  is first turned on, the reset procedure  100  is executed to place the layer  2  interface  82  into a default condition, which includes placing a zero into VT(S)  92   s , as the first PDU  82   p  to be transmitted along a newly created communications channel  78  should normally have a sequence number  43  of zero.  
         [0027]    Initially, the finite state machine  90  is in the null state  61 . While in the null state  61 , the communications channel  78  is not established. This is in contrast to all the other states  62 ,  64 ,  66  and  68  in which the layer  2  interface  82  is in wireless communications with the layer  2  interface  202  of the second wireless device  200  along an established channel  78 . While in the null state  61 , there is thus no exchanging of layer  2  communications data  82   d  with the layer  2  interface  202 . As noted previously with regards to the prior art, the layer  3  interface  83  can send commands (termed primitives) to the layer  2  interface  82 . In particular, upon response to an establish primitive from the layer  3  interface  83 , the layer  2  interface  82  transitions from the null state  61  to the data transfer state  62 . That is, the finite state machine  90  goes from the null state  61  to the data transfer state  62 . In the process of doing so, the layer  2  interface  82  works with the layer  1  interface  81  to establish a communications channel  78  with the layer  2  interface  202  on the second wireless device  200 . The reset procedure  100  is also executed so as to place the state variables  92  for the new channel  78  into a default state. If at any time while in the data transfer state  62  the layer  2  interface  82  receives a release primitive from the layer  3  interface  83  for the channel  78 , the finite state machine  90  will transition from the data transfer state  62  back to the null state  61 . In the process of doing so, the finite state machine  90  shuts down the associated communications channel  78 .  
         [0028]    During communications with the second wireless device  200  and while the finite state machine  90  is in the data transfer state  62 , the layer  2  interface  82  may determine that communications along the channel  78  are disrupted and that the channel  78  needs to be reset. The layer  2  interface  82  composes a layer  2  reset control PDU  82   r,  which is a layer  2  signaling PDU exchanged between the layer  2  interfaces  82  and  202 , to reset the channel  78 . The finite state machine  90  causes the reset control PDU  82   r  to be sent to the layer  2  interface  202 , and then the finite state machine  90  transitions to the reset pending state  64 . While the finite state machine  90  is in the reset pending state  64 , the layer  2  interface  82  transmits no layer  2  communications data  82   d  along the channel  78 . Other channels may be established with the second wireless device  200  over which layer  2  communications data  82   d  may be sent, but no communications data  82   d  is sent along the channel  78  whose corresponding finite state machine  90  is in the reset pending state  64 . Upon reception of a reset acknowledge PDU  82   a  from the second wireless device  200 , the finite state machine  90  executes the reset procedure  100 , and then transitions from the reset pending state  64  back to the data transfer state  62 . Like the reset control PDU  82   r , the reset acknowledge PDU  82   a  is a type of layer  2  signaling PDU. It is also possible for the wireless communications device  70  to receive a reset control PDU  82   r  from the second wireless device  200 . If the finite state machine  90  is in the data transfer state  62 , upon reception of the reset control PDU  82   r  from the layer  2  interface  202 , the finite state machine  90  sends a reset acknowledge PDU  82   a  to the layer  2  interface  202 , and then executes the reset procedure  200  to reset the state variables  92  of the channel  78 . The finite state machine  90  remains, however, in the data transfer state  62 . Similarly, if the finite state machine  90  receives a reset control PDU  82   r  from the layer  2  interface  202  while in the reset pending state  64 , the finite state machine  90  will respond by sending a reset acknowledge PDU  82   a  to the layer  2  interface  202 . For the sake of consistency, the finite state machine  64  should also probably execute the reset procedure  100 , though this is not totally necessary as this will happen upon the transition back to the data transfer state  62 . In the meantime, the finite state machine remains in the reset pending state  64 . As with the data transfer state  62 , if the finite state machine  90  receives a release primitive from the layer  3  interface  83  while in the reset pending state  64 , the finite state machine  90  will transition to the null state  61 , and in the process of doing so shut down the corresponding communications channel  78 .  
         [0029]    It is also possible to temporarily halt layer  2  communications along the channel  78 . This is usually done when changing the ciphering configuration of the channel  78 . Ciphering is performed utilizing the sequence number  43  (of FIG. 2) of each individual layer  2  PDU  82   p . A new ciphering configuration is used for PDUs  82   x  that have sequence number values  43  that are sequentially after an activation value  83   a . To ensure proper communications along the channel  78 , it is necessary that both the wireless communications device  70  and the second wireless device  200  agree upon the new ciphering configuration. Communications along the channel  78  are thus suspended for all PDUs  82   x  whose sequence number values  43  exceed the activation value  83   a,  and remains suspended until the wireless communications device  70  is assured that proper ciphering synchronization exists with the second wireless device  200 . This is the primary purpose of the local suspend state  66 . Ciphering is controlled by the layer  3  interface  83 , and so it is the layer  3  interface  83  that sends a suspend primitive to the finite state machine  90 . The suspend primitive indicates the activation value  83   a  to the finite state machine  90 . Upon reception of the suspend primitive, the finite state machine  90  transitions from the data transfer state  62  to the local suspend state  66 , and responds to the suspend primitive by passing a suspend confirmation message to the layer  3  interface  83 . While in the local suspend state  66 , the finite state machine  90  transmits along channel  78  any layer  2  PDUs  82   p  that have sequence number values  43  that are sequentially before the activation value  83   a , using the old ciphering configuration. PDUs  82   x  having sequence number values  43  that are sequentially after the activation value  83   a  are not transmitted. Transmission along the channel  78  is thus suspended after an event indicated by the layer  3  interface  83 , i.e., the activation value  83   a . Upon reception of a resume primitive from the layer  3  interface  83 , the finite state machine  90  transitions back to the data transfer state  62  from the local suspend state  66 . As with both the reset pending state  64  and the data transfer state  62 , upon reception of the release primitive from the layer  3  interface  83 , the finite state machine  90  transitions into the null state  61  from the local suspend state  66 , terminating the associated channel  78  in the process.  
         [0030]    The reset/suspend state  68  exists for those rare situations in which the finite state machine  90  is both suspended, as per the local suspend state  66 , and awaiting a reset acknowledge PDU  82   a  along the associated channel  78  from the second wireless device  200 . This may occur when the finite state machine  90  determines that the communications channel  78  is to be reset while in the local suspend state  66 , or when the layer  3  interface  83  issues a suspend primitive while the finite state machine  90  is in the reset pending state  64 . The reset/suspend state  68  is similar to the reset pending state  64  in that no layer  2  communications data  82   d  is transmitted by the wireless communications device  70  along the channel  78  while the associated finite state machine  90  is in the reset/suspend state  68 . The finite state machine  90  will transition into the reset/suspend state  68  from the reset pending state  64  on reception of a suspend primitive from the layer  3  interface  83 . In this transition, the finite state machine  90  responds to the suspend primitive with a suspend confirmation message to the layer  3  interface  83 , analogous to state transitions between the data transfer state  62  and the local suspend state  66 . Alternatively, the finite state machine  90  will transition into the reset/suspend state  68  from the local suspend state  66  upon determination that the channel  78  needs to be reset because protocol errors are detected by the layer  2  interface  82  on the channel  78 . Under this transition, the finite state machine  90  sends a reset command PDU  82   r  to the second wireless device  200 , and then transitions into the reset/suspend state  68 . Transitioning out of the reset/suspend state  68  depends only upon the external inputs into the finite state machine  90 , i.e., primitives received from the layer  3  interface  83 , or layer  2  signaling PDUs from the layer  2  interface  202  of the second wireless device  200 . The finite state machine  90  is not required to recall a previous state in order to transition to a subsequent state. While in the reset/suspend state  68 , the finite state machine  90  will transition to the reset pending state  64  upon receiving a resume primitive from the layer  3  interface  83 . Or, the finite state machine  90  will transition from the reset/suspend state  68  to the local suspend state  66  upon reception of a reset acknowledge PDU  82   a  along the associated channel  78  from the second wireless device  200 , and consequently causing the reset procedure  100  to be executed to reset the channel  78 . As with all the other states in which an established channel  78  exists, the finite state machine  90  will transition into the null state  61  from the reset/suspend state  68  upon reception of a release primitive from the layer  3  interface  83 , terminating the associated channel  78  in the process.  
         [0031]    In contrast to the prior art, the present invention provides a wireless communications device with a finite state machine that has a unique reset/suspend state. The reset/suspend state is used to explicitly support those conditions in which both a channel reset and a channel suspend operation are being simultaneously performed. The reset/suspend state enables the finite state machine to operate in a “state memoryless” condition, in that the finite state machine is not required to recall a previous state in order to determine transitions to a next state from a current state. The reset/suspend state thus provides a more consistent state machine design, and is consequently less likely to suffer from errors in implementation.  
         [0032]    Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.