Abstract:
A multi-dimensional Burst Link Access Streaming Transmission (BLAST) architecture, which provides flexible physical apparatus for balanced performance of data throughput, latency, and reliability of transmission (e.g. graceful degradation). A schedule is sent from a master node to alert targeted nodes regarding messages to be sent. The master node uses a P-Band transmission link operating a regular intervals to synchronize the system in preparation for receipt of a message over a synchronous link. Each node has the capability of sending and receiving synchronous and asynchronous messages.

Description:
[0001]     This application is a Non-Provisional of U.S. patent application which claims the benefit of U.S. Provisional Application No. 60/772,667 and filing date of Feb. 13, 2006, which is incorporated by reference as if fully set forth. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to transmission systems and to digital transceivers for use in broadband communication systems, and more particularly, to provide Multi-Dimensional Burst Link Access Streaming Transmission (BLAST) algorithms which can, in the time and the frequency domain, dynamically adaptively adjust transmission of data over a wide transmission rate range while maintaining low network latency.  
       BACKGROUND  
       [0003]     In burst digital communications the data is typically packed into a sequence of transmission packets. Those data packets can be transmitted via various transmissions schemes. In order to have reliable high data rate transmission via various cable channel environments, two basic transmission schemes have been used: single-carrier Quadrature Amplitude Modulation (QAM) technology and multi-carrier Orthogonal Frequency Division Modulation (OFDM) technology. These technologies provide relatively high bandwidth efficiency. QAM technology is relatively less complex than OFDM technology, and has been used in many major commercial products (for example: DOCSIS based cable modems). On the other hand, with the inherent frequency shaping flexibility and relative insensitivity to channel in-band distortion, OFDM has been increasingly adopted in industrial standards, for example, the DVB-T Euro. HDTVstandard.  
         [0004]     In some particular applications, such as military, automobile, industrial auto-control systems, the need for high data rate, and low latency, as well as graceful transmission degradation control, become equally critical. In such applications, neither QAM based architecture nor OFDM based architecture will provide satisfactory or equivalent performance.  
         [0005]     The present invention is characterized by comprising a multi-dimensional Burst Link Access Streaming Transmission (BLAST) architecture, which provides flexible physical means for balanced performance of data throughput, latency, and reliability of transmission (e.g. graceful degradation).  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention consists of two inter-related key technologies:  
         [0007]     1. Combination of Synchronized/Asynchronized Multi-channel architecture with:  
         [0008]     Wide-band: synchronized half-duplex transmission band (OFDM based).  
         [0009]     Narrow-band: asynchronized half-duplex transmission band (QAM based).  
         [0010]     Pilot band: asynchronized simplex transmission band (QAM based).  
         [0011]     2. Three-dimensional dynamic data transmission: Data transmission from one node to the other can be done via three (3) physical means: physical channel selection (Wide-band and Narrow-band), sub-frequency channel selection (Bin-locations in Wide-band), and time-slot selection in Wide-band. Those physical means are independent variables in Network Resource Allocation (NRA) space. In the present invention, data transmission is characterized in 3D-NRA space of (physical channel, sub-frequency, time-slot). For example, based on transmission condition (SNR, BER, Network node traffic condition, etc.), a network master alters data transmission from one channel to the other, and/or alter the time-slot(s) to dynamically allocate the network resource to maintain a balanced Network transmission level in terms of network throughput, latency, and reliability of the transmission. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0012]      FIG. 1  is a block diagram of a transmission network embodying the principles of the present invention.  
         [0013]      FIG. 2  is a diagram showing the modulation schemes which may be employed in the present invention.  
         [0014]      FIGS. 3A and 3B  are block diagrams showing one embodiment for transmitting and receiving data and control at two typical nodes in the system and  FIG. 3  shows the manner of arrangement of  FIGS. 3A and 3B . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     The Overview BLAST architecture  10 , is shown in  FIG. 1  and comprises:  
         [0016]     Blast Architecture, which Comprises Two Layer Processing:  
         [0017]     (1) A Scheduling and Resource Dynamic Allocation Module (SRDAM).  
         [0018]     In this module, multi-channel utilization is provided to leverage the strength of each band and transmission technology accordingly, via the establishment of three (3) interdependent links.  
         [0019]     In setting up a network of devices utilizing this technology it is envisioned that one of the nodes  100  is designated as the network controller. See  FIGS. 1 and 3 . This node has the role of generating the scheduling for the network, which is established based upon node and network requirements (bandwidth, update rate, etc.). Determination of the network requirements can either be explicit for a closed network, or dynamic via a login phase. Once the network controller  100  establishes a schedule, it is provided to all of the nodes, such as node  200 , via a broadcast over the Narrow-band link. This schedule defines time slice allotments of the Wide-band link for each node. Upon obtaining this schedule, each node locally manages its schedule and utilizes the Pilot-band for synchronization with the network clock, as will be described in detail below. Since all nodes locally maintain their own copy of the schedule, and use the same Pilot-band time base, it is possible to provide synchronized utilization of the asynchronous Wide-band link.  
         [0020]     Dynamic network changes are accommodated via periodic reassessment of the schedule by the network controller or in response to network changes (i.e., lost or added nodes, changes in bus stability, etc.). Establishment of a new network schedule by the network controller results in an update broadcast over the Narrow-band link, initiating the use of the new schedule. The schedule is preferably sent on a regular basis, such as one-second intervals. When there are no changes in the schedule, the latest update is resent.  
         [0021]     (2) Physical Layer (PHY) Multi-Band Module  
         [0022]     In this module, the data to be transmitted is modulated based on defined modulation schemes (OFDM or QAM), band location (wide-band or narrow-band, or pilot band), and the transmission time slot(s). The transmission parameters are determined by the SRDAM  102  shown in  FIG. 1 .  
         [0023]     The data received from the user interface (not shown for purposes of simplicity) is converted to a digital format and sent to SRDAM  102 , which creates the schedule, to be described below.  
         [0024]      FIGS. 3A and 3B , taken together in the manner shown in  FIG. 3 , show a block diagram of the transmitters/receivers of the physical (PHY) links  110  of first node  100 , which serves as the network controller, and the physical (PHY) transmitter/receiver links  210  of another node  200  communicating with the network controller node  100 . Only two (2) nodes have been shown for purposes of simplicity, it being understood that the number of nodes may be  100  or more. Making reference to  FIGS. 1 and 2 , the SRDAM  102  is coupled to the transmitters and receivers of node  100  by way of digital interface  104 . SRDA  102  schedules the data according to certain criteria, as will be described in detail below.  
         [0025]     The narrow band (N-band) link  160 , whose principal characteristics are shown in  FIG. 2 , comprises narrow band (N-Band) quadrature amplitude modulation (QAM) transmitter  162  which performs QAM on the bit stream derived from SRDAM  102 . The output of transmitter  162  is applied to an 8-bit digital-to-analog converter (DAC)  164 . The output of DAC  164  is coupled to an analog front end (AFE)  166  which, as is conventional, performs filtering, amplification and shaping of the signals applied to the radio frequency (RF) interface which may be any media such as a cable bus such as a MIL-STD 1553 bus, a twisted pair cable, a wireless channel, or the like.  
         [0026]     The output of AFE  166  is sent through the radio frequency (RF) interface  300  and is received by the AFE  266  of receiving link  260  of PHY link  220 , comprised of AFE  266 , analog to digital converter (ADC)  264 , comprising an 8-bit ADC and N-Band receiver (Rx)  262 , which applies the bit stream to a digital interface  202  forming part of SRDAM  202 . AFE  266  amplifies and conditions the received signals, as is conventional. The SRDAM  202  manages reception and transmission at node  200 .  
         [0027]     The digital interface  202  at node  200  is coupled to a host interface, such as a peripheral component interface (PCI), a host computer or control device (not shown for purposes of simplicity).  
         [0028]     The host interface comprises the SRDAM  102  which identifies the time slice allotments of the wide-band (W-band) link for node  200 . SRDAM  102  is coupled to the PHY links  110  by digital interface  104 , and controls the wide-band (W-band) transmitter (Tx)  142 , forming part of the transmission link  140  for selecting the time slot perimeters.  
         [0029]     W-band Tx  142  employs sub frequency division multiplexing upon the bit stream derived from digital interface  104 . W-band transmitter (Tx)  142  is controlled by a local clock  130  which also provides timing for the P-Band transmitter (Tx)  122 , DAC  124 , W-Band Tx  142  and DAC  144 . The bit stream, modulated at  142  and converted into analog form by D/A converter  144 , is applied to AFE  146  which conditions the modulated signals preparatory to entering the RF interface  300 .  
         [0030]     AFE  242  of receiving PHY link  240  receives the analog modulated bit stream which is applied to  16 -bit analog to digital converter (ADC)  244 .  
         [0031]     The modulated digital signal undergoes W-Band digital processing at  246  which includes base-band signal processing (SP), filtering, equalization, Fast Fourier Transform (FFT), decoding by forward error correction (FEC), descrambling, de-interleaving and channel estimation, providing a bit stream, at base-band, of the output of the W-band digital processor  246 , for application to digital interface  202  and then to the host interface through digital interface  202 .  
         [0032]     Synchronization of the W-band receiver link  240  at node  200  is obtained by way of the pilot-band (P-band) quadrature phase shift keying (QPSK) transmitter (Tx)  122  whose operating frequency is controlled by clock  130 , as was described above. The bit stream entering P-band Tx  122 , is applied to 8-bit digital to analog converter (DAC)  124 , operating at the clock frequency of  124  MHz. The modulated analog signals applied through AFE  126  of PHY link  120 , enter interface  300 . AFE  222  of P-band link  220  applies the received, modulated signal to 8-bit analog to digital converter (ADC)  224 . The output of ADC  224  is coupled to the P-Band digital processor  226  and undergoes digital processing at processor  226  for purposes of timing recovery, processor  226  comprising demodulator  227 , timing recovery circuit  228  and baseband QPSK signal processor (SP)  229 . The bit stream derived from processor  226  is also utilized to pass the schedule to the SRDAM forming part of digital interface  202  and thereby prepare node  200  for receipt of a high priority message, for example.  
         [0033]     The output of timing recovery circuit  228  is applied to a local clock source  232 , also operating at  124  MHz and having its timing corrected by frequency synthesizer  230 , the local clock source  232  providing clock timing for ADC  224 , QPSK SP  229 , W-band digital processor  246  and ADC  244 .  
         [0034]     The transmission of synchronized bit streams from node  200  to node  100  is provided by link  270  whose W-band Tx  272 , 16 bit digital to analog converter (DAC)  274  and AFE  276  are substantially identical in design and function to Tx  142 , DAC  144  and AFE  146 , described above.  
         [0035]     The output of AFE  276  is transmitted to AFE  172  of link  174  through RF interface  300  (described above) and received by AFE  172 , converted at 16-bit ADC  174  and a W-band digital processor  176  substantially identical in design and function to the AFE  242 , ADC  244  and W-band digital processor  246  respectively, which comprise receiver link  240  for node  200 .  
         [0036]     Transmission from node  200  to node  100  is either from the PHY W-band link  270  or the N-band PHY link  280 . As a result of the reception of the transmission from node  200  by node  100 , the host may alter the schedule.  
         [0037]     Explanation of Procedure for the Embodiment Shown in  FIGS. 1-3   
         [0038]     The transmission techniques of  FIG. 2  provide the advantages of each of the PHY links relative to one another. As one example, when a burst of data delivered to SRDAM  102  has a high priority and/or requires that the burst be sent at a high level of accuracy, SRDAM  102  determines that this burst be sent by the W-band transmitter. This requires that a schedule be sent to the recipient node (node  200 , for example) before the burst is sent. The schedule is preferably handled by the P-band transmitter, although the N-band transmission link  160  may be employed as an alternative.  
         [0039]     Node  100  preferably uses the P-Band link for sending the schedule and preferably sends the schedule at regular intervals. In one embodiment, the schedule is sent at one (1) second intervals, although a greater or lesser interval may be adopted dependent, among other things, schedule length and number of nodes in the system. The P-band transmission link  120  and its clock source  130  provide synchronization for the system and all of its nodes. It should be understood that node  100  may; transmit simultaneously over its transmission links; transmit and receive simultaneously and simultaneously receive messages over the W-Band and N-Band receiver links. The other nodes in the network have like capabilities (except they are normally not equipped with a P-Band transmitter—however, one or more nodes may be designated as standby master nodes and be provided with P-Band transmission links).  
         [0040]     The schedule prompts the targeted node(s) to prepare for receipt of high priority data. In one preferred embodiment, assuming the system comprises 100 nodes, a different time slot is assigned to each node, the time slots each being an interval of one millisecond (1 msec.). The binary state of one bit position in the time slot notifies the node of a data burst intended for that node when in one binary state (i.e., binary “1”), and no high priority data is intended for that node when that bit position is in an opposite binary state (i.e., binary “0”). Alternatively, bit positions in one common time slot may be assigned to each of the nodes.  
         [0041]     SRDAM  102  then controls transmission of the high priority data burst via W-Band transmission link  140 . The portion of the schedule intended for node  200  adjusts the clock  232  at node  200 , thereby synchronizing the W-Band receiving link  240 . Employing OFDM, the wide band may be divided into a large plurality of sub frequency ranges depending upon the needs of the network. As one example, the W-Band may be divided into  128  sub frequency bands and different messages may be sent over each one of the  128  sub frequency bands, each band being assigned to a given node, for example, (thus, the system may comprise  128  nodes). A greater or lesser number of sub frequency ranges may be provided according to the needs of the network.  
         [0042]     Although the schedule may be sent by the N-Band transmission link at node  100 , the P-band is nevertheless used for synchronization when high priority data is sent by the W-Band link  140 .  
         [0043]     In the event that node  200  wishes to send high priority data to node  100 , SRDAM  202  controls the N-Band transmission link  280  to notify node  100 . The high priority data burst is then sent over the W-Band transmission link  270 . The high priority data burst, in one embodiment, is sent in time slots reserved for use by node  200 .