Abstract:
A dual mode decoder operable with external memory. At least some of the illustrative embodiments are integrated circuit products comprising a processor portion, a memory portion coupled to the processor portion, and a hardware demodulation portion coupled to the processor portion. The processor portion and hardware demodulation portion work together to demodulate a first digital transmission signal created utilizing a first modulation system, and the processor portion and hardware demodulation portion work together to decode a second digital transmission signal created using a second modulation system different than the first modulation system (the second digital signal having at least one time interleaved segment). The integrated circuit product couples to an external memory for purposes of time de-interleaving when an amount of memory of the memory portion is insufficient for time de-interleaving for a number of segments of the second digital transmission signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of Provisional Application Ser. No. 60/725,695 filed Oct. 12, 2005 entitled “External Memory for Time Interleaver of ISDB-T,” and the application is incorporated by reference herein as if reproduced in full below. 
     
    
     BACKGROUND  
       [0002]     With the advent of mobile devices capable of displaying video, several encoding standards have arisen to meet needs specific to broadcasting video, along with other non-video data, to the mobile devices. For example, the European Television Standards Institute (ETSI) has developed a Digital Video Broadcasting to Handheld terminals (DVB-H) standard. In order to address “bursty” errors in transmission, the DVB-H standard defines the use of forward error correction for multiprotocol encapsulated data (MPE-FEC).  
         [0003]     Another example of a broadcasting standard to meet needs specific to broadcasting video and other non-video data to mobile devices is the Terrestrial Integrated Services Digital Broadcasting (ISDB-T) standard in use in Japan. The ISDB-T standard defines thirteen segments within the transmission band, each segment being a band within which data may be modulated using orthogonal frequency division multiplexing. However, one need not modulate within all thirteen segments, with the standard defining use with less than all thirteen, including use of only a single segment. Rather than MPE-FEC to address bursty errors in the transmission medium, the ISDB-T standard defines the use of time interleaving to address bursty errors. The amount of memory needed to time de-interleave a received signal varies proportionally to the number of segments utilized.  
         [0004]     Having an application specific integrated circuit (ASIC) with sufficient memory to time de-interleave a thirteen segment ISDB-T transmission when fewer segments are actually used may make the ASIC cost and size prohibitive for most mobile devices. Moreover, having individual ASICs for each transmission standard limits flexibility and the potential markets for the ASICs.  
       SUMMARY  
       [0005]     The problems noted above are solved in large part by a dual mode decoder operable with external memory. At least some of the illustrative embodiments are integrated circuit products comprising a processor portion, a memory portion coupled to the processor portion, and a hardware decoder portion coupled to the processor portion. The processor portion and hardware decoder portion work together to decode a first digital transmission signal created utilizing a first encoding system, and the processor portion and hardware decoder portion work together to decode a second digital transmission signal created using a second encoding system different than the first encoding system (the second digital signal having at least one time interleaved segment). The integrated circuit product couples to an external memory for purposes of time de-interleaving when an amount of memory of the memory portion is insufficient for time de-interleaving for a number of segments of the second digital transmission signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     For a detailed description of exemplary embodiments, reference will now be made to the accompanying drawings in which:  
         [0007]      FIG. 1  shows a mobile electronic device in accordance with at least some embodiments; and  
         [0008]      FIG. 2  shows an ASIC in accordance with at least some embodiments. 
     
    
     NOTATION AND NOMENCLATURE  
       [0009]     Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function.  
         [0010]     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and connections.  
       DETAILED DESCRIPTION  
       [0011]     The following discussion is directed to various embodiments of the invention. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.  
         [0012]      FIG. 1  illustrates a mobile electronic device  100  in accordance with at least some embodiments. In particular, the mobile electronic device  100  comprises a processor  10  coupled to a memory  12  by way of a bus  14 . The processor  10  may be any currently available or after-developed processor suitable for operation in mobile devices. In some embodiments, memory  12  is dynamic random access memory (DRAM), or any of the variants of DRAM such as synchronous DRAM (SDRAM). In other embodiments, the memory  12  may be a non-volatile memory, such as an electrically erasable programmable read only memory (EEPROM) or non-volatile magnetic memory.  
         [0013]     In order to interface with a human operator, the mobile electronic device may further comprise a keyboard or key pad  16  that couples to the processor  10  by way of a keypad driver  18 . In embodiments where the mobile electronic device  101  is a mobile telephone, the keypad  16  is a twelve key numeric keypad. In embodiments where the mobile electronic device is a wireless messaging device, the key pad  16  is a reduced size alpha-numeric keypad. In embodiments were the mobile electronic device is a laptop or notebook computer, the keypad  16  is a full or reduced size alpha-numeric keyboard. In embodiments where the mobile electronic device is a personal portable media player (e.g., a MPEG, MC, AVC, H.264, Windows video or MP3 player), the keypad  16  may be circular user interface.  
         [0014]     The mobile electronic device  100  further comprises a display device  20  coupled to the processor  10  and memory  12  through a display driver  22 . Contents of the display may be modified by manipulating display memory in either the memory  12  and/or in memory of the display driver  22 . In cases where the mobile electronic device  100  is a mobile telephone, wireless messaging device or a personal music player, the display device  20  may be a relatively small (e.g., one to five inch diagonal) color liquid crystal display (LCD). In embodiments where the mobile electronic device is a laptop or notebook computer, the display device  20  may be a relatively large (e.g.,  15  inch diagonal) color liquid crystal display.  
         [0015]     In accordance with at least some embodiments, the mobile electronic device  100  may be used in geographic areas where video is broadcast, and in some cases the video may be specifically targeted to mobile electronic devices. Thus, mobile electronic device  100  may further comprise an antenna  24  coupled to a broadcast video receiver  26 . Video received by the antenna  24  and demodulated by the broadcast video receiver  26  may then couple to the processor  10 , the memory  12  and/or the display driver  22  for display on the display device  20 .  
         [0016]     In order to address concerns specific to receiving and displaying video on mobile electronic devices (in addition to non-video data transfer) several encoding standards have arisen. For example, the European Television Standards Institute (ETSI) has developed a Digital Video Broadcasting to Handheld terminals (DVB-H) standard ETSI EN 302 304. DVB-H uses forward error correction for multiprotocol encapsulated data (MPE-FEC) to address “bursty” errors in transmission, and thus need not implement time interleaving as part of the modulation process (although other interleaving (e.g., bit and symbol) may be used). Correspondingly, a demodulator under the DVB-H standard need not implement a time de-interleaver.  
         [0017]     Another example of a broadcasting standard to meet needs specific to broadcasting motion video to mobile devices is the Terrestrial Integrated Services Digital Broadcasting (ISDB-T) standard in use in Japan. Within the bandwidth of a channel, an ISDB-T compliant system may have up to thirteen individual segments within which orthogonal frequency division multiplexing (OFDM) may be used. Thus, some ISDB-T systems may utilize only one segment, other ISDB-T systems may utilize three segments, and yet still others may utilize anywhere from three to thirteen segments. Rather than using MPE-FEC to address bursty errors in the transmission medium, the ISDB-T standard defines the use of time interleaving. With respect to decoding ISDB-T compliant signals, the amount of memory needed to time de-interleave varies proportionally to the number of segments utilized.  
         [0018]     Returning to  FIG. 1 , in accordance with embodiments of the invention the broadcast video receiver  26  is designed and constructed to demodulate multiple signals from multiple encoding systems. For example, receiver  26  in accordance with some embodiments is configured to demodulate signals modulated using the DVB-H standard, and is also configured to demodulate signals using the ISDB-T standard. In this way a single broadcast video receiver design (e.g., in the form of an application specific integrated circuit (ASIC)) may find use in multiple types of mobile electronic devices  100 , including mobile electronic devices to be operated in geographic locations operating under different standards for the broadcast of video.  
         [0019]      FIG. 2  illustrates in greater detail the broadcast video receiver  26  in accordance with at least some embodiments. In particular, the receiver  26  comprises a processor portion  30 . The processor portion  30  may be a register- and/or stack-based processor that executes instructions. The instructions executed may be executed from the internal memory  32  coupled to the processor  30 . The receiver  26  may further comprise a hardware decoder portion  34  which couples at least to the processor portion  30 . Thus, the processor portion  30  (executing instructions from and operating on data structures in the internal memory  32 ) works together with the hardware decoder portion  34  to demodulate digital transmission signals modulated using various encoding schemes.  
         [0020]     In accordance with some embodiments, the processor portion  30  and hardware decoder  34  work together to demodulate digital transmission signals modulated using the DVB-H standard, and also work together to demodulate digital transmission signal modulated using the ISDB-T standard, though the decoding of the signals using different standards may not necessarily take place simultaneously. Whether the broadcast video receiver  26  attempts to demodulate signals as DVB-H signals or ISDB-T signals is dependent upon the geographic location of use of the mobile electronic device and/or how the receiver  26  is configured. Configuring receiver  26  to demodulate the illustrative DVB or ISDB signals may be accomplished by way of software routines (e.g., writing a particular value to a register of the processor or other location in the receiver  26 ), by hardware (e.g., hardware jumper settings), or a combination of both. It is noted that having a receiver  26  that demodulates either under the DVB-H standard or the ISDB-T standard is merely illustrative. The receiver  26  may be configured to demodulate signals modulated using any currently available or after-developed encoding standard.  
         [0021]     As mentioned above, the illustrative DVB-H standard uses MPE-FEC as the mechanism to combat bursty errors introduced in the transmission of digital video signals. The illustrative ISDB-T standard, by contrast, uses time interleaving as the mechanism to combat bursty errors introduced in the transmission of the digital video signals. Time interleaving as part of encoding dictates the use of time de-interleaving as part of decoding. Time de-interleaving is a memory intensive operation as all the parameters to de-interleave are held in a memory during the de-interleaving process. Thus, as the number of segments in the illustrative ISDB-T standard increases, the amount of memory needed to time de-interleave the signal likewise increases, with ISDB-T defining up to 13 segments. While it is possible to design a demodulator of a broadcast video receiver  26  with sufficient memory to demodulate a 13 segment ISDB-T signal, the physical size of such an ASIC limits its use. Moreover, an ASIC with sufficient internal memory to time de-interleave a 13 segment ISDB-T signal may be cost prohibitive in systems where fewer segments are used.  
         [0022]     In order to address such concerns, and in accordance with embodiments of the invention, the broadcast video receiver  26  internal memory  32  is sized to accommodate decoding the MPE-FEC signals of a DVB-H and to accommodate time de-interleaving of less than all 13 possible segments in an ISDB-T signal. Decoding MPE-FEC signals utilizes approximately 2 Mega-bits (Mbits) of internal memory space. Time de-interleaving of ISDB-T signals utilizes approximately 1.75 Mbits for each segment at 64 bit quadrature amplitude modulation (QAM), and uses approximately 1.167 Mbits for each segment at 16 bit QAM. Thus, in accordance with some embodiments, the receiver  26  implements internal memory on the order of approximately 2 Mbits, which enables the ASIC to demodulate DVB-H signals as well as one segment ISDB-T signals. In alternative embodiments, the receiver  26  implements approximately 5.25 Mbits, such that there is sufficient internal memory to demodulate the DVB-H signals as well as a three segment ISDB-T signal at 64 bit QAM or a four segment ISDB-T signal at 16 bit QAM.  
         [0023]     However, there may be situations where the broadcast video receiver  26  is used in systems where more than one or three segment ISDB-T is used. In such situations, an in accordance with embodiments of the invention, the receiver  26  is further configured to couple to external memory such that overall memory size is increased to accommodate more segments in the ISDB-T signal.  FIG. 2  illustrates an ability of the receiver  26  to couple to external memory by memory bus  36 . Memory bus  36  may comprise, in some embodiments, a 24 pin bus (8 data lines, 13 address lines, a clock line, an enable line and a read/write line); however, any currently available or after-developed bus system for communicating with a memory device may be equivalently used.  FIG. 1  illustrates an ability of the receiver  26  to couple to external memory by showing the receiver  26  coupled to external de-interleaver memory  38  (shown in dashed lines to highlight the optional use). Thus, in mobile electronic devices  100  where the amount of internal memory  32  is sufficient to time de-interleave a received digital signal, the receiver  26  may be implemented without the de-interleaver memory  38 . In mobile electronic devices  100  where the amount of internal memory  32  is insufficient to time de-interleave a received digital signal, the receiver  26  may couple to the additional de-interleaver memory  38 . When using the external de-interleaver memory  38 , the data may be split between the internal memory  32  ( FIG. 2 ) and the external memory  38  ( FIG. 1 ), or the data may reside solely within the external memory  38 . If the number of segments or other parameters change such that internal memory  32  is sufficient for time de-interleaving, the external memory  38 , though present, may be ignored.  
         [0024]     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. For example, while the various embodiments are described in terms of a mobile electronic device, the methods and systems are equally applicable to devices considered non-mobile, such as television sets that do not implement operation from battery power. Moreover, while some of the embodiments are discussed in terms of DVB-H and ISDB-T signals, these encoding schemes are merely illustrative, and other encoding schemes (e.g. DBH-T used in China) may be equivalently implemented. The internal/external memory dichotomy is applicable to any decoding system where time de-interleaving is used. It is intended that the following claims be interpreted to embrace all such variations and modifications.