Abstract:
A method and system thereof for maintaining and broadcasting frame numbers in a digital communication system. The system monitors a frame number controller through a central controlling unit. The frame number controller maintains the frame numbers required by the system, as well as broadcasts the frame number for the subsequent data frame to each frame number receiver in the operational components. Each frame number receiver generates a frame boundary signal when a complete frame number is received from the frame number controller, and notifies the corresponding operational component to start using the frame number just received. The operational component can also determine if unfinished work according to the frame boundary signal exists, and report the error to the system. The aim is to provide a simple mechanism to maintain the synchronization of the system, and utilizes the serial port to transmit information related to the new frame number.

Description:
BACKGROUND  
       [0001]     The present invention relates to a frame number broadcasting scheme, and more particularly, to a method and apparatus thereof to maintain and broadcast a frame number through central management.  
         [0002]     In a digital communication system, operational components often need to exchange real time information. The system usually appends a frame number to each data frame to maintain the synchronization between the operational components. Each operational component processes operations according to the frame number of the data frame to ensure that every operational component completes the expected operations within the transmission period of a data frame before passing the data frame to other operational components. In the digital communication system, some operational components are responsible for transmitting a data stream, while others are responsible for channel coding or decoding. The frame number currently used in every operational component of the system must be identical, and all the operational components must identify the beginning of a new data frame at the same time.  
         [0003]     Accordingly, the digital communication system requires a dynamic mechanism for maintaining and redefining the frame number used in the operational components of the system. The mechanism is responsible for notifying the operational components to update the frame number. Furthermore the mechanism must precisely notify all the operational components of when to use the new frame number, so that all operational components may be synchronized by always using the same frame number. The operational component may also generate an error message to notify the system when unfinished work to be completed in the previous data frame exists. The system ensures that the real time information is processed correctly in all of the operational components if the system does not receive any error messages.  
       SUMMARY  
       [0004]     A method for maintaining and-broadcasting frame numbers in an existing digital system is provided. The digital system monitors a frame number controller through a central controlling unit to broadcast a new frame number of a next data frame to operational components, wherein each of the operational components has a corresponding frame number receiver. The frame number controller obtains the new frame number during a transmission period of a current data frame, and then broadcasts information related to the new frame number to the frame number receivers. Each operational component generates a frame boundary signal when the corresponding frame number receiver receives the new frame number from the frame number controller. The operational components then use the new frame number to process following operations. The frame boundary signal generated by each frame number receiver directs the corresponding operational component to determine if any unfinished work exists from the previous frame, if so the operational component may report to the central controlling unit.  
         [0005]     The frame number controller determines the new frame number for the next data frame according to an update confirmation signal. The frame number controller receives the new frame number transmitted from the central controlling unit if the central controlling unit sends the update confirmation signal before a predetermined fixed period, otherwise the new frame number is acquired by increasing the frame number of the current data frame by one.  
         [0006]     The predetermined fixed period is agreed to by both the central controlling unit and the frame number controller. The digital system uses a clock signal for timing and, frequency reference, and the predetermined fixed period is usually a multiple of a clock cycle to simplify the calculations. The predetermined fixed period must be shorter than the transmission period of a data frame.  
         [0007]     Key features of the method and system for maintaining and broadcasting the frame number include transmitting the information related to the new frame number to each frame number receiver in serial. The frame number controller connects the frame number receiver using a serial port in practice. An advantage of using the serial port as an interface between the frame number controller and the frame number receivers is to reduce the number of cables, thus minimizing the hardware required. Additionally the serial port is much easy to arrange and implement.  
         [0008]     The frame number controller sends information related to the new frame number to each frame number receiver, wherein the information comprises a frame number reset signal, a frame number data signal, and a frame number synchronous signal. The frame number reset signal is a notification to the frame number receivers to prepare for reception of the new frame number. The frame number data signal carries the new frame number bit by bit. The frame number synchronous signal is a reference clock signal for the frame number data signal, thus the frame number receivers are able to determine the duration of one bit in the frame number data signal. The frequency of the frame number synchronous signal is lower than the clock signal in the system,-and the period of the frame number synchronous signal is an integral multiple of the period of the clock signal. Each bit of the new frame number is transmitted at a lower frequency via the serial port. The bandwidth needed by each of these signals is only one bit per unit time, thus three single-bit transmission lines in the serial port are enough for implementation.  
         [0009]     A system for maintaining and broadcasting frame numbers in an existing digital system is provided. The digital system monitors the frame number used in each operational component of the digital system through a central controlling unit. The system comprises a frame number controller connected to a plurality of frame number receivers in serial, wherein each frame number receiver is installed in a corresponding operational component. The frame number controller is controlled by the central controlling unit which determines a new frame number for a subsequent data frame, and broadcasts the information related to the new frame number to each of the operational components. The frame number controller obtains the new frame number by either receiving it from the central controlling unit or increasing the frame number of the current data frame during the transmission period of the current data frame. Each frame number receiver generates a frame boundary signal when receiving a complete new frame number and hence the corresponding operational component can start using the new frame number.  
         [0010]     Each operational component determines the frame boundaries by counting the number of bits received in the frame number data signal, and generates the frame boundary signal indicating use of the new frame number. Thus the frame number controller does not need to connect extra lines to signal all the operational components to start using the new frame number. Better synchronization can thus be achieved as the frame boundary is identified by each operational component individually, so the latency delay can be minimized.  
         [0011]     Another advantage is achieved by transmitting the new frame number to all operational components in the system by broadcasting. As a result, the central controlling unit only sends commands to the frame number controller, and is not requiring to perform any computation unless the frame number needs to be updated. The frame number controller has a counting mechanism which increases the current frame number by one if the central controlling unit does not send an update confirmation signal before a predetermined fixed period. The workload of the central controlling unit can be reduced, thus improving the performance of the system. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0012]     The invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
         [0013]      FIG. 1  is a simple block diagram showing an embodiment of the system for maintaining and broadcasting the frame number;  
         [0014]      FIG. 2   a ˜ FIG. 2   d  illustrate the status of various signals of the present embodiment when the frame number controller does not receive the command to update the frame number;  
         [0015]      FIG. 3   a ˜ FIG. 3   d  illustrate the status of various signals of the present embodiment when the frame number controller receives the command to update the frame number;  
         [0016]      FIG. 4  is a flowchart showing the process performed by the frame number controller in an embodiment;  
         [0017]      FIG. 5  is a flowchart showing the process performed by the frame number receiver in an embodiment. 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 1  is a simple block diagram illustrating an embodiment of a system for maintaining and broadcasting frame numbers. A frame number controller  102  receives an update confirmation signal  110  from a central controlling unit  100 , and the frame number controller  102  determines a new frame number for a subsequent data frame according to the update confirmation signal  110 . The frame number controller  102  receives a frame number  108  from the central controlling unit if the update confirmation signal  110  indicates “update valid”. The frame number controller  102  has a counting mechanism for the frame number, which adds one to the current frame number, producing a new frame number if the central controlling unit  100  has not performed the process of updating the frame number after a predetermined fixed number of clock signal periods, wherein the central controlling unit  100  performs the process of updating the frame number by sending an “update valid” command in the update confirmation signal  110  to the frame number controller  102 . The frame number controller  102  is then responsible for broadcasting the new frame number to all frame number receivers  106  to maintain the synchronization by ensuring the same frame number is always used in every operational component. Each frame number receiver  106  is installed in a corresponding operational component  104 .  
         [0019]     The frame number controller  102  may connect each of the frame number receivers  106  using three single-bit transmission lines through a serial port. The signals transmitted on the three transmission lines are frame number reset signal  114 , frame number synchronous signal  115 , and frame number data signal  116 . The frame number reset signal  114  indicates the beginning of the new frame number transmission. The frame number synchronous signal  115  has a lower frequency than the frequency of the clock signal  112 , which serves as the reference clock signal for the frame number data signal  116 . The frame number data signal  116  transmits the new frame number bit by bit. The frame number data signal  116  transmits one bit in every period of the frame number synchronous signal  115 . The frame number receivers  106  determine the boundaries of the bits transmitted in the frame number data signal  116  according to the rising or falling edges of the frame number synchronous signal  115 . The frame number receiver  106  can ignore the frame number synchronous signal  115  when receiving the frame number data if the timing of the receiver and the transmitter is already synchronized. The frame number synchronous signal  115  can be optionally used by the frame number receivers.  
         [0020]     In accordance with  FIG. 1 ,  FIG. 2   a ˜ FIG. 2   d  and  FIG. 3   a ˜ FIG. 3   d  illustrate two methods of obtaining the new frame number described in an embodiment.  FIG. 2   a ˜ FIG. 2   d  illustrate the status of various signals when the frame number controller  102  does not receive the command to update the frame number from the central controlling unit  100 . The diagram shows the last portion of the transmission period of a data frame  202 , wherein the system frame number (FN) of the data frame  202  is n (assumed the binary description is FNn). When an “update invalid” command is obtained from the signal status  212  of the update confirmation signal  110 , the frame number controller  102  updates the frame number of the subsequent data frame  204  to be n+1 (binary description is FNn+1) as an increment of the current frame number of the data frame  202 . In this case, the frame number controller  102  does not receive the new frame number  108  (signal status  210 ) from the central controlling unit  100 .  
         [0021]     The frame number controller  102  comprises a counter, and the signal status  208  of this counter counts the period of the clock signal  112  (signal status  206 ). The transmission period of a data frame is assumed to be S periods of the clock signal  112  in this example. The signal status  214  of the frame number reset signal  114  generates a reset signal at a predetermined fixed point  226  to notify the frame number receiver  106  to start receiving the new frame number. The fixed point  226  is defined as the signal status  208  of the counter is S−(P*M). It is assumed that each frame number is M bits, and the frame number data signal  116  (signal status  218 ) transmits one bit in every P clock signal periods. P is 2 in this example, representing the period of the frame number synchronous signal  115  (signal status  216 ) is equivalent to two periods of the clock signal  112  (signal status  206 ).  
         [0022]     The frame number controller  102  transmits one bit of the new frame number (FNn+1) in every period of the frame number synchronous signal  115  (signal status  216 ) after the fixed point  226 . Each frame number receiver  106  also comprises a counter for counting the number of bits received from the frame number controller  102 . At point  232 , the frame number receiver  106  generates a frame boundary signal (signal status  220 ) immediately after receiving the last bit of the new frame number. The frame boundary signal  220  indicates that a complete frame number has been received, as well as notifying the operational component  104  to update the frame number. The frame boundary signal  220  also provides reference timing for the operational component  104  if any operation is processed according to the timing of the new data frame.  
         [0023]     The broadcasting period of the new frame number (period  228 ) starts from the fixed point  226  when the frame number controller  102  transmits the reset signal, until the beginning of the subsequent frame (point  232 ). The operating period  230  of the frame number controller  102  and the frame number receivers  106  is the time period  228 , and further comprises a previous and a subsequent clock signal periods. The current frame number  222  of the frame number controller  102  is monitored by the central controlling unit  100 . The frame number  222  of the frame number controller  102  should always be identical to the frame number  224  of the frame number receivers  106 . Both the frame number controller  102  and the frame number receivers  106  should also update the new frame number at the same time (point  232  on the diagram) as the frame number receivers  106  generate the frame boundary signal (signal status  220 ).  
         [0024]      FIG. 3   a ˜ FIG. 3   d  are similar to  FIG. 2   a ˜ FIG. 2   d , the difference is that in this case the frame number controller  102  receives an “update valid” command in the update confirmation signal  110  (signal status  312 ) before the fixed point  326 . The central controlling unit  100  assigns the new frame number of the subsequent data frame to be k (binary description is FNk), so that the new frame number k is irrelevant to the current frame number n. The central controlling unit  100  sends this new frame number k to the frame number controller  102  before the fixed point  326 . The new frame number FNk is transmitted with the frame number data signal  116  (signal status  218 ) bit by bit, and the last bit is received by the frame number receivers  106  at point  332 . Since the new frame number FNk has been completely transmitted to the frame number receivers at point  332 , both the frame number controller and the frame number receivers update the frame number from FNn to FNk.  
         [0025]      FIG. 4  is a flowchart illustrating the operations performed by the frame number controller in an embodiment. The frame number controller maintains the frame number by incrementing the current frame number after the predetermined fixed point in time, thus there is still a new frame number for the subsequent data frame regardless of the update information from the central controlling unit. The frame number used in the frame number controller is reset to zero in step  400 , and the frame number controller is in the standby mode  402  until the counter is (S−1)-(P*M), which is a clock signal period before the predetermined fixed point  226  in  FIG. 2 . After satisfying the request in step  404 , the frame number controller determines if the “update valid” command has been sent from the central controlling unit. The frame number controller processes step  410  if it receives the “update valid” command, otherwise step  408  is processed. The new frame number is received from the central controlling unit in step  410 , and the new frame number is obtained by adding one to the current frame number as shown in step  408 . The frame number controller transmits the new frame number bit by bit according to the frequency of the frame number synchronous signal, and the frame number controller examines if the transmission operation has been complete in step  412  and step  414 . The frame number controller updates the current frame number to the new frame number immediately after the new frame number has been transmitted completely. The frame number controller then returns to the standby mode (step  402 ) and waits for the next frame number updating process.  
         [0026]      FIG. 5  is a flowchart illustrating the operations performed by the frame number receiver of an embodiment. The frame number of the frame number receiver is reset in step  500 . The frame number receiver is in the standby mode (step  502 ) before receiving a reset command with the frame number reset signal. The frame number receiver starts to receive the new frame number bit by bit after receiving the reset command in step  506 . The frame number receiver knows the total number of bits in the frame number, thus it detects if the new frame number has been received completely in step  508 . The frame number receiver sets the current frame number to the new frame number in step  510 , and immediately generates a frame boundary signal in step  512 . The frame number receiver then returns to standby mode in step  502  until the next reset command is sent with the frame number reset signal.  
         [0027]     Finally, while the invention has been described by way of example and in terms of the above, it is to be understood that the invention is not limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.