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    • 专利摘要:
    PURPOSE: An apparatus for processing data is provided to multiplex data from multiple sources, encode, and transmit whilst preserving the relative propitiation of the data. CONSTITUTION: A method for preparing data forr transmission comprises the step of multiplexingdata from a plurality for sources(S1,..Si,..Sn) encoding data forr transmission. The multiplexing step comprises, forr at least one source (Si), classifying the data from the source (Si) into two or more classes (C1,... Cj,....Cm) according to the data 's priority, and mapping data from the sources into positions in a data structure (D) according both to the class (Cj) of thedata and to a further priority assigned to the source (Si) from which the data originated; and sub-dividing the data in the data structure (D) into framees whilst preserving the relative propitiation of the data. The encoding method forr transmitting data comprises the step of; preparing data from a plurality for sources; implementing forrward error correction (FEC) encoding the multiplexed data forr transmission whilst maintaining the data 's relative propitiation in data framees. The method forr decoding and demultiplexing encoded data according to encoding method comprises decoded data in the frame and data framees are again demultiplexed in forrmat of finally originated sources after reforrmed into data structure. The sources may be various multi-media sources.
    公开号:KR20000022381A
    申请号:KR1019980710812
    申请日:1998-04-30
    公开日:2000-04-25
    发明作者:조나단 얼래스테어 깁스；티모르 카디르
    申请人:에이치. 이보트슨；모토로라 리미티드；
    IPC主号:
    专利说明:

    Method and apparatus for processing data from multiple sources
    Examples of single media services are voice and data. For such a single media service, a forward error correction (hereinafter referred to as FEC) method is used, which is generated on a case-by-case basis. The FEC uses redundancy to enable the receiver of the corrupted digital signal to determine the actual signal transmitted. As such, FEC mitigates data corruption caused by error-prone transmission paths.
    In the case of voice, the development of the FEC method usually involves making a different method for each and every system, taking into account the different effects of bit error between transmissions on different parameters of the bit stream. This means that it is always necessary to redesign FEC to introduce new voice codecs into the system.
    In designing the FEC method for certain types of media transmissions, for example voice or video, some of the bits may not accommodate FEC protection at all, while allowing joint protection to provide good protection for more important segments of the data stream. It is desirable to use some type of channel or non-identical guard coding technique.
    The requirement that the FEC protection of any parameter or bit differ from each other is that it operates according to the well-known nature of the encoder of a low bit rate source for a single source, one particular type of media transmission. For example, an error in the motion vector in the context of video encoding causes a perceived degradation that is greater than an error in the discrete cosine transform (DCT) coefficients. This requirement means that FEC is applied with detailed knowledge of the source encoding algorithm.
    Current mobile system FEC methods for a single service, for example speech, are called Rate Compatible Punctured Convolutional (RCPC) to provide different error protection for different bits of the encoder bit stream. Coding is almost inevitable. For this, see the prior art publication "Rate-Compatible Punctured Convolutional Codes (RCPC codes) and their Applictions" published in IEEE Published Publication No. 36, April 1988. However, for this single service application, the number of protected bits is usually fixed as being the position in the FEC frame of the different parameter. Alternatively, for variable bit rate sources, encoding rules are selected from a limited number of possibilities.
    Considering mobile systems, the current approach to designing the FEC method for such a system is to develop the FEC method for a single service, ie voice. Although the performance of the FEC method is optimal for this single service, applying a similar approach to multimedia has the potential for mismatch in wasting channel resources and error performance of different services.
    In a multimedia environment, it is usually necessary to multiplex bit streams from multiple sources such as video, audio, data, etc. into a single bit stream. There are a number of standards that define how to achieve this, such as ITU-T Recommendation H.223 "Line Transmission of Non-Telephone Signals-Multiplexing Protocol for Low Bit Rate Multimedia Communication".
    Conventional designs for multimedia services use different FEC methods for each service being multiplexed. At this time, additional error protection is required to protect the multiplexed information. This is a complex and non-adaptive configuration. This design philosophy makes it very difficult for a service to have the same quality to channel bit error rate (BER) profile, especially when new service components are added, for example a new voice codec. Thus, the relative robustness of the multiple service components will lead to different degradation of the quality of the components occurring at different rates at different locations in the coverage area. In practice, a mobile user located in a regionally depressed area or at the edge of a coverage area may result in an excessive degradation of some of the multimedia services received before other users. This is not desirable if one component of a service component, which is more important, especially for a particular application such as text or picture, deteriorates faster than another service of less importance, such as sound.
    In the transmission of multimedia data for future mobile systems, service providers and network operators will want to introduce new services quickly and easily. In a multimedia context, this may include putting together different audio, voice, and video codecs to meet the specific market niche. This location will also require different requirements in view of the quality of the different components of the multimedia service.
    EP-A0171596 provides a signal concentrator configuration. Multiple user channels are concentrated on a common communication channel. To this end, information from each user channel is buffered, prioritized, and transferred to a common communication channel based on priority. The priority assigned to this information depends on its type, for example, data having a higher priority than voice packets. Some voice packets from certain sources may be given different priorities than other voice packets from other sources to maintain the area associated with normal voice.
    U. S. Patent No. 5,280, 479 shows a multiplexing device for inserting digital packets supplied by several different sources into the same transport channel. Each source generates an insertion priority for each packet as a function of the packet type. A particular source may have a different priority than other similar sources based on the number of packets that are storing idle transmissions.
    The present invention generally relates to multiplexing, encoding, and transmitting data. In particular, the present invention relates to the transmission of data originating from a plurality of sources.
    1 illustrates one embodiment of the present invention wherein data from multiple sources is multiplexed, prepared and encoded for TDMA transmission.
    2 illustrates selecting a bit from one of the sources, in which the same portion of each class of bit is taken.
    3A illustrates a method for mapping bits from two sources into a data structure in accordance with the present invention.
    3b illustrates another method for mapping bits from two sources into a data structure in accordance with the present invention.
    4 shows an example for adapting the FEC protection method to changes in data throughput.
    According to the present invention, a method for preparing data from multiple sources for transmission comprises the steps of multiplexing data from a plurality of sources, wherein the multiplexing step comprises at least one source, wherein Classifying the data from the source at the location of the data structure according to the rank of the data and the additional priority assigned to the source from which the data originated, classifying the data into two or more classes according to the ranking. Subdividing into frames while preserving relative priorities.
    If data from a second or additional source is classified into multiple grades, this grade does not necessarily need to be the same as that used for that source (ie the particular grade used is specific to the relevant source).
    Also provided is a method of encoding data for transmission in combination with a method for preparing data. A method of encoding data for transmission includes preparing data from a plurality of sources in connection with preparing the data, and performing forward error correction (FEC) encoding on a data frame while preserving the relative priority of the data. Steps.
    Partitioning data into rank and / or source priority is done according to the importance of the data and the importance of the source at the data receiver.
    Alternatively, partitioning the data into classes and / or sources of priority may be done according to the potential impact of transmission errors on the data.
    Also provided are methods for decoding and demultiplexing data.
    A method for decoding and demultiplexing data encoded according to the given encoding method includes data decoded first in a frame, and the data frame is reconstructed into a data structure and then demultiplexed back into a format of a finally sourced source. do.
    The invention also includes an apparatus adapted to perform any of the methods given above.
    The present invention facilitates data transfer to or from a multimedia terminal that can be moved. For this transmission, data processing involves multiplexing the data while considering the two priorities described above, dividing the created data structure into frames, and finally encoding the data using the RCPC forward error correction method.
    The present invention provides several advantages. In principle, the system can choose from a wide range of input sources and codecs without requiring major system redesign when new codecs are added or removed. As such, codecs can simply be treated as "modular" blocks.
    In order to encode pre-transmission data, a single FEC encoder and decoder design is used for all services and all logical channels, so it is necessary to redesign the FEC protection of either the new or existing codec to balance performance. It is simpler to add new codecs and new services without them.
    The present invention provides for each logical channel the flexibility to change the FEC rate, i.e. the source of the multimedia call (call), which allows FEC protection tradeoffs between different services of the multimedia transmission to be modified. This can happen even during a call. The relative priority of the sources and the different classes of data from a particular source are selectable at will.
    In its most general form, the present invention relates to preparations for transmitting data from several sources. Data from one source may be assigned to different priorities as the source itself. The data output by each source constitutes one " logical channel ", wherein the data of the logical channel must be multiplexed and divided in a frame in preparation for transmission.
    The preferred embodiment of the present invention shows a method and apparatus for preparing data as well as forward error correction of data and final transfer of data to a receiver according to the method described above. In its most complete form, the present invention takes data from multiple sources and optimizes the processing of the data for transmission. The data preparation and encoding included in the present invention is important for maximizing the usefulness of the data for the receiver, and the data preparation and encoding can be separated from the transmitting user by a transmission path that includes an error in the received data. The nature of the error and the frequency of occurrence of the error may change over time.
    The embodiment of the present invention shown in the figure receives data from multiple sources. The sources can have different data rates and formats, and each source can provide data of different importance to the sender. As an example, a source such as a video codec can generate more data frames than an audio codec but with fewer frames per second.
    1 shows the method of the present invention. Data sources can take various forms. Sources shown are video codec (VC), voice / audio codec (S / A C), and data source (DS1 ... DSn). There may be more or less video codecs than shown, and there are n data sources of generalized type of DS. These sources may be mobile multimedia terminals and may provide data for transmission to these terminals. This embodiment also includes a FEC framework for mobile multimedia systems. In this case, RCPC technology is shown. The present invention can be implemented as an extension of existing simple multiplexing methods such as Recommendation H.223.
    In view of the detail of FIG.
    (1) The top row of Fig. 1 shows the data sources VC, S / A C, DS1 .... DSn.
    (2) The second line shows the data from each source divided into classes. These classes represent examples of class N to class 1 for the video codec, with the CRC bit being a separate class.
    Prioritizing the bits from one source by class is known in the art for individual low bit rate voice codecs serving only one source. The bit streams of the individual channels are in most cases divided into units relating to some logical structure of the source encoding algorithm, such as speech frames or video frames. This applies to the configuration of the prior art for a single channel and the configuration for each channel of the present invention.
    (3) The third line shows a bold arrow indicating the steps for multiplexing the data into a single data structure, where data structure D consists of data of grades varying from P +, P, P-1 to 1 and shown in FIG. It is shown in the first line. An example of the relative priority of each source is shown superimposed in the drawing part, and the distance from the right edge of the drawing indicates the priority. For example, "Video Priority" is higher than "Data Source 1 Priority."
    The arrow just below the voice / audio codec shows that there is no limit on its width. This indicates that the voice / audio codec is a rate determination source. In practical terms, this is used for each data structure created by taking only parts of data from different sources. Only from the voice / audio codec is the entire unit of data generated by the source combined into one data structure, for example from the entire voice frame. The selection of the data portion from each source other than the rate determination source is shown in FIG. 2, which will be described in more detail with reference to the drawings. The rate determination source can be selected in various ways. For example, the rate determination source may be a source that supports a service where the inter-transmission delay is a maximum obstacle due to timing jitter.
    (4) The fourth line of the figure shows the data structure D as a result of the multiplexing step.
    (5) The fifth line of the figure shows the RCPC frame in which data from the data structure D is divided. This partitioning is to hold the relative priorities of the data in the data structure.
    (6) The sixth line of the figure shows the encoding and punctuation (segmentation) of the data from the RCPC frame and the interleaved final data into the slots for transmission, which are shown in the seventh and final lines of the figure. have.
    (7) The seventh line of the figure shows data in a slot for transmission, here a TDMA burst.
    Conventional FEC methods for multiple sources are designed to perform FEC encoding on each source before multiplexing. In the multiplexing phase, each service or logical channel has a fixed importance with respect to others. In contrast, embodiments of the present invention assign a relative priority to each logical channel (and thus related services) and perform pre-FEC multiplexing. Priority information must be included in the channel destination table and can be changed dynamically during a call.
    According to the invention, each logical channel has a finite number of priority classes, the priority classes have a known number of bits in each class, and each portion of the bit stream is aligned. The multiplexing layer selects a portion of the bits from each class in each logical channel. This selection will be described in more detail with reference to FIG. 2.
    In connection with the detailed description of FIG. 2,
    (1) In the upper part of the figure, a data frame from one of the sources is shown, and the data is divided into classes. Numbers 16, 16, 40, and 16 indicate the number of class bits of data immediately below each of these numbers.
    (2) The lower part of the figure shows the selection of bits taken to multiplex from the classes. In this example, the bit selection contains half of the bits as present in a single original data frame. The number of bits taken from each class of the original frame is shown as numbers 8, 8, 20, 8 under selection. The remaining data in the single frame shown in the upper part of the figure will be sequentially multiplexed into later data structures.
    According to the present invention, the number of bits selected from each class is limited to the size of the multiplexed output data unit. This size depends on the particular type and multiplexing implementation, but is constrained by logical channels and physical data rates where output frames cannot be divided across multiple output data units.
    In a conventional multiplexing method, bits are selected from input data units in a sequential manner. However, in the present invention, the bits for each class Cj are selected in the same way as in one data unit when there is the same portion of each class of bits, such as in an input data frame from a particular source (see Figure 2). ). Another way of describing this is to consider each class within a logical channel, such as a virtual subchannel, with its own data rate and protection.
    The final ranks from all logical channels are sorted in global priority order, thereby creating a data structure (D). This global priority is derived from the priority of the class and the relative priority of the logical channel within each channel. The data structure D is shown in FIG. 1 as the fourth line of the figure and consists of data classes P +, P, P-1, ....
    There are several ways to combine the priority of a channel with another channel and the priority of a particular class within the channel. Two methods for performing mapping of channel grades in full order are shown in FIGS. 3A and 3B.
    According to the configuration shown in FIG. 3A, a single number may be used to define the priority of each logical channel. Two channels, one video and audio channel and their data class, are shown in the upper row of the figure. The rating of each channel is shown again in the center of the figure, offset from the right edge of the figure as an amount according to the priority of the channel. The lower row of the figure shows the data structure D resulting from multiplexing the ratings from the two channels.
    In the illustrated case, the ordering within the data structure is simple shuffling of various classes. In this example, the CRC bit for each channel is added to the left edge of the highest rank data of that channel. Thus, the CRC bit of a video channel is added with the grade 3 bits of the channel. Except for the combination that includes the CRC bit, in the embodiment of FIG. 3A, the left edge of each class gets high priority among different channels. Outside of the embodiment of FIG. 3A, the CRC bit may be of greater or less importance than the source top grade of the data, depending on the included source.
    In the configuration of FIG. 3B, an alternative to FIG. 3A is shown. In this configuration, two identical channels having the same grade are shown at the top of the figure. Channel priority is defined by two numbers, namely maximum and minimum. This technique allows the grades in each channel to cross-disperse the global order between a given maximum and minimum priority. In the center of the figure again two channels are shown and offset from the right edge. This priority varies depending on the ratings in each channel, and the ratings are spread between "maximum priority" and "minimum priority" for each channel.
    This configuration is useful when the highest priority level of one channel is more important than that of the other channel and the lowest priority level is less important. The configuration of FIG. 3B actually divides the same class of data from the same channel as shown in FIG. 3A but results in a different data structure D.
    No alternative is shown in the figure, and the classes may have individual mappings of channel grades to global grades.
    Considering the data structure D as a result of the multiplexing, the data structure receives various classes mapped from different sources. 1 is shown as a line of grades P +, P, P-1, P-2 ..... 1. The data structure has a header that contains framing information and is placed within the top level. This grade is indicated as P + in FIG. 1. The header information is important and therefore importantly protected. If this header is damaged, the structure of the multiplexed data unit is unknown, which means that data is not available. The data structure as shown is in descending order of data from left to right.
    After mapping the data bits to data structure D, the bits from the global ordering are placed in the frame. This is a good FEC data frame for FEC encoding. The priority given to the data in the multiplexing phase must be maintained while this frame is created. FEC data frames support differential protection of different classes of bits. The RCPC technique is a clear candidate for this framing, although other techniques may be used.
    The relative priority of the data is preserved while parting the data from the data structure D into the FEC frame. The mapping of bits to FEC (RCPC) frames is done from the most significant bit to the least significant bit (class 1) in the global order (class P +), i.e. from left to right in FIG. Part) is filled first. This algorithm meets the requirement that the class P + bits be placed in the most protected portion of the first frame to minimize buffering requirements and delays. Some bits are left unprotected (classes 2 and 1 in FIG. 1). This bit can ultimately be an insensitive parameter of a bit or source coding method with an unbound delay requirement that uses the ARQ type of method to ensure accurate data transmission.
    The data frame is encoded for transmission. In a preferred embodiment, FEC coding is used. In the case of RCPC encoding, the data is verbalized (previously) while preserving the relative priority of the data. The data can then be transferred. Interleave is also applicable to improve performance on burst channels.
    The receiver of the data can convert the data back to the originally transmitted format. The data then regains its original format and meaning when generated by the incoming source source Si. Therefore, the present invention also extends to decoding and demultiplexing data methods.
    Decoding is the inverse of the encoding process. Knowledge of multiple framing, channel destinations, and details of the FEC method also exist in the encoder and decoder. Methods for decoding and demultiplexing data encoded according to the above methods include decoding the data into frames and demultiplexing the data back into a source format. Demultiplexing of data includes demultiplexing of multiplexed data as described above. In accordance with such demultiplexing, the inverse of the multiplexing step described above is performed, preferably on data received by the user after transmission and after inverse encoding. Demultiplexing converts the data back into the format of the source it originates from.
    Embodiment of the Adaptive FEC Rate Method
    To further enhance the basic invention, one has to adapt the used FEC protection method. This adaptation is done in response to a change in data throughput, a change in the quality of the radio channel used for transmission, or a change in the available channel bandwidth (eg, the number of TDMA slots).
    In the case of RCPC, the simplest approach is to apply verbalization (segmentation) between the output multiplexed data units, and the change of the verbal pattern is communicated to the receiver. To minimize the complexity of FEC decoding of an RCPC frame, multiple headers are encoded at the same rate, taking into account all circumstances at the beginning of the RCPC frame, and then a verbal pattern for bits outside the point within the RCPC frame (see Figure 4), normally Changes the 4-5 bond length of the parent convolution code.
    The method of the present invention can be clearly implemented using various circuits suitably applied to carry out the steps of the method described above. Although not limited to the above hardware, a circuit suitable for the performance of the present invention may be an integrated circuit of a particular application configured to perform the steps of the particular method.
    权利要求:
    Claims (7)
    [1" claim-type="Currently amended] As a way to prepare data for transfer,
    In the step of multiplexing data from a plurality of sources S1, ... Si, ... Sn, said multiplexing step includes for at least one source Si and the data from said source Si Are classified into two or more classes (C1, ... Cj, ... Cm) according to the priority of the data, so that the additional priority assigned to the source (Si) from which the data originates and the class (Cj) Thus mapping data from a plurality of sources at the location of the data structure D and subdividing the data of the data structure D into frames while preserving the relative priority of the data. How to prepare.
    [2" claim-type="Currently amended] As a method for encoding data for transmission,
    Preparing data from a plurality of sources (S1, ... Si, ... Sn) according to claim 1,
    Performing forward error correction (FEC) encoding on a data frame while preserving the relative priority of the data.
    [3" claim-type="Currently amended] The method of claim 1 or 2, wherein dividing the data into priorities of the grades (C1, ... Cj, ... Cm) and / or the sources (S1, ... Si, ... Sn) The method performed according to the importance of the data at the receiver and the importance of the source.
    [4" claim-type="Currently amended] The method of claim 1 or 2, wherein dividing the data into priorities of the grades (C1, ... Cj, ... Cm) and / or the sources (S1, ... Si, ... Sn) Method performed according to the potential effect of transmission error on the data.
    [5" claim-type="Currently amended] A method for decoding and demultiplexing data encoded according to any one of claims 2 to 4, wherein the data is first decoded into frames, and then the data frames are reconstructed into a data structure (D), and finally the data Is a method of decoding and demultiplexing data which is demultiplexed again in the format of the source (S1, ... Si, ... Sn) from which the data originates.
    [6" claim-type="Currently amended] Method as practically described so far with reference to any one of FIGS. 1,2, 3A, 3B or 4.
    [7" claim-type="Currently amended] Apparatus adapted to perform the method of any one of claims 1 to 6.
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    同族专利:
    公开号 | 公开日
    KR100763013B1|2008-01-18|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1997-05-02|Priority to GB9709100.3
    1998-04-30|Application filed by 에이치. 이보트슨, 모토로라 리미티드
    1998-04-30|Priority to KR1019980710812A
    2000-04-25|Publication of KR20000022381A
    2008-01-18|Application granted
    2008-01-18|Publication of KR100763013B1
    优先权:
    申请号 | 申请日 | 专利标题
    GB9709100.3|1997-05-02|
    KR1019980710812A|KR100763013B1|1997-05-02|1998-04-30|Method and apparatus for processing data from a plurality of sources|
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