Abstract:
A system and method for communicating real time information using a wide area network protocol and communications protocol that mitigates against potentially significant packet loss rates caused by events such as signal blockage occurring at the underlying wireless transmission (e.g., radio) links. In one implementation the method involves creating a first data packet having a first segment of information, and a first identification (ID) code. The first data packet is then transmitted. A second data packet is then created having information forming the first data packet and also a second segment of information identified by a second code. The second packet is then transmitted. Subsequently formed data packets may include all of the information from previously created data packets until a maximum packet depth is reached, and then each subsequently created new data packet drops off the oldest packet information from the previously created packet while including new information.

Description:
FIELD 
       [0001]    The present disclosure relates to systems and methods for wirelessly transmitting real time information, and more particularly to systems and methods for wirelessly transmitting real time multimedia (e.g., voice, video) information over a wide area network in environments where high signal intermittence is encountered, by mitigating the packet data loss often encountered in such environments. 
       BACKGROUND 
       [0002]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0003]    Interest in the use of multi-hop, voice over Internet protocol (VoIP) communications is gaining popularity as a means for conveying real time speech communications over the Internet between two or more users at geographically diverse locations. Although this description and disclosure explicitly references VoIP communications, it is equally applicable to other real time communication uses including video, chat, and alerts or alarms of various types. Many real time protocol systems (i.e., voice, video) regularly transmit chunks of encoded voice or video data at specific time intervals. This encoded data is physically conveyed across the network within network packets. This is traditionally accomplished by using a data communications protocol stack that uses the Internet Protocol (IP) at the network layer and the User Datagram Protocol (UDP) at the transport layer. Voice and video transmissions usually also use the Real Time Protocol (RTP) at the application layer. This combination of IP, UDP, and (optionally) RTP to convey human speech in a telephony-like manner is traditionally called VoIP. Current VoIP techniques require high availability network transports that ensure that the transmitted packets are reliably delivered to their destination(s). The latency and jitter-mitigation requirements of voice and video applications are achieved by implementing traditional quality of service (QoS) techniques. Networks supporting VoIP therefore either use wired media or else wireless media that have been carefully engineered to ensure high network availability (e.g., microwave). 
         [0004]    By contrast, high network availability may not exist in first responder (e.g., fire, ambulance, police) and tactical military environments (e.g., warfare environments). Reliable multi-hop VoIP traffic is often difficult to achieve in these environments because their communications rely upon highly dynamic, self-forming networks that are built upon radio systems (potentially including satellite) in order to support extensive mobility within arbitrarily difficult physical deployment environments and conditions. These environments cannot guarantee packet delivery. While the maturing mobile ad hoc network (MANET) protocol techniques address many mobility affects of tactical deployments, they cannot address the possibility of potentially significant wireless signal intermittence and loss between the networked radios and the corresponding packet loss that occurs during signal disruptions. Signal intermittence events are particularly prevalent for communications being transmitted or received while travelling in a mobile platform (including dismounted soldiers) or in actively hostile environments. 
         [0005]    Because current VoIP protocols and techniques don&#39;t consider the possibility of extensive packet loss within the communications path itself, these protocols do not currently have any mechanism to compensate or mitigate against the potentially significant packet loss that occurs during signal blockage events. VoIP protocols are therefore susceptible to unreliable operation in topologically challenging environments such as environments having significant foliage (e.g., forests that block radio signals), urban deployments (buildings that block signals) or significant landscape topographies (mountains or canyons that block signals). Signal blockage also can occur within environments having heavy particulate matter (e.g., dust storms) and whenever the pitch, roll, or yaw of a mobile vehicle (or dismounted soldier) blocks the signal reception or transmission capabilities of its antenna(s). Large transmission distances can also cause signal attenuation and loss. These environmental factors can be especially problematic in combat settings, and they may cause VoIP communications to fail outright in multi-hop network settings. Nevertheless, the U.S. military has firm requirements that necessitate that reliable multi-hop VoIP must occur. Reliable multi-hop VoIP would also be desirable in non-military applications such as first responders. 
         [0006]    Present day solutions to obtaining reliable multi-hop VoIP rely on Quality of Service (QoS) at the data link, network, and/or application layers. QoS techniques have been demonstrated to positively enhance the internal packet queuing and packet drop disciplines of IP devices and to ensure prioritized packet delivery. These techniques offer expedited packet flows. These enhancements are very effective when used in highly available wired network environments and therefore are a important contributing factor for all successful VoIP deployments. Successful VoIP implementations are therefore reliant upon effective QoS configurations. 
         [0007]    Unfortunately, the benefits obtained from QoS enhancements often pale in the face of packets lost due to signal intermittence and mobility affects that occur in tactical military (or other types of MANET networks) deployments, which may significantly diminish the value of these QoS enhancements to the user. Specifically, the gains accomplished by QoS within each forwarding hop (i.e., packet forwarding device) operate at millisecond granularities while signal intermittence events, which are due to signal blockages in the underlying wireless data transmission path, may range from truly transient intermittent events to indeterminately long outages (e.g., seconds, minutes, or even longer). A single signal loss event, therefore, can introduce unacceptably large data loss and jitter into the real time voice (or other real time media) session which QoS techniques cannot mitigate. Indeed, QoS is not designed to be able to compensate for wireless signal intermittence and loss, nor are the VoIP protocols themselves designed to withstand such packet losses. Furthermore, because the timeframes of signal disruptions may be arbitrarily large, and certainly could exceed the cumulative benefit of QoS queuing disciplines, the current VoIP approach of using telephony data conversion devices (i.e., CODECS) that regularly transmit small voice encodings is inherently vulnerable to signal disruptions in MANET environments. Indeed, there is not much that can be done at the subnetwork or IP layers to ensure that these regular transmissions are protected from signal loss within highly mobile environments or in topologically challenging environments. 
       SUMMARY 
       [0008]    The present disclosure relates a system and method for redundantly transmitting real time information within multiple data packets in order to minimize the affects caused by data packets becoming lost by events such as wireless signal intermittence. 
         [0009]    In one implementation a method is disclosed that involves creating a first data packet having a first segment of information, and a first identification (ID) code. The first data packet is transmitted. A second data packet is then created that includes information forming the first data packet and also a second segment of information identified by a second ID code. The second data packet is then transmitted. Thus, the second data packet also includes the information that formed the first data packet. Subsequently created data packets may include the information of previously created data packets until a predefined maximum packet depth, D, is reached, at which time each subsequently created data packet will have the oldest packet information from the previous data packet omitted, while including new information. 
         [0010]    In one implementation the wide area network protocol may comprise a voice over Internet protocol (VoIP). In various implementations the real time segments of information may comprise audio information, and in some implementations voice information. In other implementations the real time segments may comprise segments of real time video information. In yet other implementations it may comprise real time chat information and in another implementation it may comprise alarms or alerts or other real time data. 
         [0011]    Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
           [0013]      FIG. 1  is a high level block diagram of one embodiment of a system in accordance with the present disclosure; 
           [0014]      FIGS. 2 through 7  illustrate the contents of five sequentially created data packets (i.e., packets  1 - 5 ) created using the methodology of the present disclosure; and 
           [0015]      FIG. 8  is a high level flowchart summarizing a plurality of operations of the system of  FIG. 1  in creating the data packets shown in  FIGS. 2-7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
         [0017]    Overview 
         [0018]    The system and method of the present disclosure enables real time protocols to be able to specify how many packets will redundantly convey the same data segment content. By so doing it identifies the radio signal intermittence duration that will be mitigated against in that implementation. Since both voice and video real time transmissions usually occur at predefined time intervals, this approach ensures that signal intermittence events of up to R*(D−1) seconds will be transparent (i.e., mitigated) to the recipients, where R is the expected transmission rate (in seconds) of the digital multimedia encoding (e.g., the normal multimedia (e.g., VoIP, video) transmission rates for that media stream—this rate is itself usually a function of the specific CODEC being used to digitally encode that multimedia data) and “D” is the number of different successive packets that will redundantly convey that same data. The value of D also determines the number of distinct multimedia encodings (from that same multimedia data stream) that will be conveyed within a data packet. In order to satisfy the latency and jitter requirements of voice and/or video transmissions, the approach permits packets to carry less than D distinct multimedia encodings for cases in which the conveyed multimedia stream is beginning or ending. In this manner, multimedia data is being transmitted at the same data rates that would otherwise be supported for that same CODEC in traditional VoIP or other multimedia implementations. 
         [0019]    Because redundant multimedia segments are transmitted in multiple packets, the various embodiments of the present disclosure preferably also includes the requirement that each transmitted data segment instance within the packet must be associated with a unique identifier to assist the recipient to identify redundant data segments and discern the proper order in which they should be decoded or presented. This system and method of the present disclosure does not specify what type of identifier should be used, only that each identifier instance should be unique and unambiguous. The identifier can be a timestamp, a sequence number, or any other unique identifier system. 
         [0020]    The present disclosure also assumes that other information can also optionally accompany each data segment instance within the packet. For example, transmitting Cyclic Redundancy Check (CRC) information is optionally used in some multimedia streaming implementations (e.g., Microsoft&#39;s NetShow™) to ensure that received multimedia data that has become corrupted in transit can be identified and reconstituted to its original form by the receiver. 
         [0021]    Referring now to  FIG. 1 , there is shown a system  10  in accordance with an embodiment of the present disclosure. The system  10  may include a controller  12 , a transmitter  14  and an antenna  16 . Alternatively, if bidirectional communications are desired, a transceiver  18  may be substituted for the transmitter  14 . The controller may be in communication with a wide area network, for example the Internet. The controller  12  prepares data packets of information that are sent to the transmitter  14 , which are then transmitted in wireless form via the antenna  16  to remotely located receivers. As explained above, the remotely located receivers may be in topologically challenged locations where signal intermittence may be expected. The signal intermittence may cause an unacceptable loss of packet data to the remote receiver. The system  10  and method of the present disclosure, through its data packet forming methodology, ensures that a sufficient degree of data packet redundancy exists to overcome the signal intermittence problem. 
         [0022]    The data packets form real time segments of information that are transmitted in accordance with a wide area network communications protocol, for example a voice over Internet protocol (VoIP). Merely for convenience, the following discussion will center on the system and method of the present disclosure being implemented with a VoIP methodology. 
         [0023]    Referring to  FIG. 2 , the method of the present disclosure initially involves using the controller  12  to initially generate a first data packet  20  for a specific VoIP data stream. In this example the data packets shown in  FIGS. 2-6  have a maximum packet “depth” of five packets, meaning that each data packet may include a maximum of five separate segments of voice information. In  FIG. 2 , packet  20  is the first data packet created for that VoIP data stream and includes a first field  20   a  having an initial segment of a voice (i.e., speech) recording “Recording n”. Recording n has a first identification code “ID n” associated with it, and optionally contains a first cyclic redundancy check “CRC n” created as a check for bit errors to ensure the integrity of the information that forms both the first ID n and Recording n. The first packet  20  has room for four additional fields of information  20   b ,  20   c ,  20   d  and  20   e , but these fields are empty at this point. Once created, the first data packet  20  may be transmitted using the transmitter  14  and the antenna  16 . Including only the voice segment information pertaining to Recording n, ID n and CRC n in the first data packet  20  ensures that the delay to the recipient(s) is minimized. 
         [0024]    The next data packet  22  created is shown in  FIG. 3 . Data packet  22  includes the voice information from the first data packet  20  in field  22   a , and also includes new voice information in field  22   b  in the form of a new (i.e., subsequent) segment of the voice recording “Recording n+1”, a new ID code “ID n+1”, associated with Recording n+1, and optionally a new CRC number “CRC n+1”. New CRC number CRC n+1 is a check for bit errors to ensure the integrity of both the Recording n+1 and ID n+1 information. Fields  22   c ,  22   d  and  22   e  remain empty. The second data packet  22  may then be transmitted to the recipient (s). 
         [0025]    A third data packet  24  is subsequently created as shown in  FIG. 4 . The third data packet  24  includes the information from the first and second data packets  20  and  22  in fields  24   a  and  24   b , respectively, and also includes a new (i.e., subsequent) voice recording segment Recording n+2, new ID n+2, and optionally a new CRC n+2 associated with Recording n+2 and ID n+2 in field  24   c . The fields  26   d  and  26   e  remain unused at this point. The third data packet  24  is then transmitted to the recipient(s). 
         [0026]    Referring to  FIGS. 5 and 6 , fourth and fifth data packets  26  and  28  are created using new sequential segments of the voice recording. Packet  26  has one unused field (field  26   e ), while packet  28  is completely full (i.e., all of fields  28   a - 28   e  used). Again, it will be appreciated that a packet depth of five is illustrated merely as one example of how the present methodology may be implemented. Packet depths of greater or less than five may be implemented to suit specific applications or mission requirements. 
         [0027]    In  FIG. 7 , the next data packet  30  is created by dropping (i.e., omitting) the oldest data from previously constructed data packet  28 , which is the data that occupied field  28   a  in data packet  28 , and including a new (i.e., subsequent) voice recording segment in field  30   e  of packet  30 . Each subsequently created packet follows this pattern of dropping the oldest information from the previously transmitted packet to make room for the new voice recording segment and its associated ID code and CRC number. 
         [0028]    Referring to  FIG. 8 , a high level flowchart  100  is shown to further illustrate the methodology of the present application. At operation  102  a maximum packet depth is defined. This occurs when the real time application (e.g., VoIP) is initially configured, previous to initial usage. At operation  104  a first data packet is constructed containing only the information pertaining to a first segment of recorded speech, a first ID code and optionally a first CRC value. At operation  106 , the first data packet is transmitted. At operation  108  a subsequent data packet is constructed using the information from the first data packet and a subsequent (i.e., second) segment of recorded speech, an associated ID code and CRC number. The subsequent data packet is then transmitted at operation  110 . 
         [0029]    At operation  112 , a check is then made to determine if the entire voice segment has been transmitted. If this answer is “No”, then a check is made at operation  114  to determine if the maximum packet depth has been achieved. If the check at operation  114  is “No”, then all of the information from the previously created data packet is used together with new information to create the next new data packet, as indicated at operation  108 . If the check at operation  114  indicates a “Yes” answer, then the next new data packet is created by dropping the oldest voice recording segment and its associated data and obtaining the next segment of recorded speech, and its related ID code and CRC number, as indicated at operation  116 . A check is then made after operations  112  and  116  to determine if the entire voice recording has been converted and transmitted and, if so, the transmission is complete after the last data segment information has been redundantly transmitted the required number of times. If not, operations  108 ,  110  and  112  are repeated. 
         [0030]    The present system  10  and method minimizes latencies experienced by the recipient when receiving data VoIP transmitted packets, while ensuring that signal intermittence caused by topologic factors (buildings, mountains, etc.) does not adversely affect the reception of data packets using a VoIP communications scheme. A real time voice recording or real time video data may be encoded and transmitted using the system and methodology of the present disclosure. The recipient of real time data uses the ID information contained within each packet to identify redundant data and the proper ordering of the received data. In this way, the recipient ensures that redundant data transmissions are decoded or presented only once in the proper order. 
         [0031]    While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.