Patent Application
20070147409
The present application is generally directed towards the transmission of digital data. More specifically, the application includes features relating to the identification of unused portions of a time slice frame, and the re-use of those portions to transmit additional data. Some related features include methods and apparatuses for allocating that additional unused portion.
Mobile electronic devices are becoming more and more prevalent, with providers offering customers more and more features. One such feature is the transmission of digital video data, such as video mail, movies, television shows, video games, and the like. A prior standard for the transmission of digital video data, known as DVB-T (established by the European Telecommunication Standards Institute, or ETSI), had been established for the general transmission of video data in a digital network, but that standard had its drawbacks when applied in a mobile device. In particular, the DVB-T standard placed a greater power drain on the mobile device, shortening its battery life.
The reason for this power drain lay in the multiplexing of the data in the DVB-T standard. In that standard, data for multiple different elementary services (ES) were closely multiplexed together, thereby requiring receiving mobile devices to have their receiving circuitry turned on continuously during use. This continuous use of the circuitry drained battery power.
To address this, the ETSI has since developed a new standard, known as DVB-H, that overcomes this drawback by consolidating transmissions of ES streams into larger time slices, so that individual mobile devices can turn their reception circuitry on during a desired time slice, and off during other undesired time slices. The time slices are often used for the transmission of real-time data, and are periodic in nature (e.g., each slice may be a fixed period of time, such as 200 ms).
Due to the variable bandwidth nature of video (different amounts of bandwidth are needed at different points in the program), time slice periods are often defined with a worst-case scenario in mind—a period large enough to carry the maximum bit rate transmissions anticipated. At times when the video does not need the entire time slice period, the DVB-H standard contemplates filling the remainder of the time slice with NULL, or unused, packets that are essentially ignored by the receiver.
It would be an advance in the art to put these NULL portions of a time slice period to good use.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In some aspects, a method may include the allocation of first and second portions of a first time slice frame, where the first portion is allocated to a plurality of elementary services to be carried in said time slice frame, and the second portion is allocated to overhead data associated with the elementary services. Unused portions of these allocated portions may be identified, and used to carry additional data.
The unused portions may be aggregated, and then subdivided to form additional time slice frames using the unused portions. These additional time slice frames, formed from unused portions of the original frame, may carry non-real time data in portions of a frame allocated for the transmission of real-time data. These unused portion frames may be further divided into channels to carry data for different services, and the various channels may have static time intervals assigned to them, such that data for services supported by the channels appears at the same time in each received unused time slice frame.
In some aspects, these channels may include time slice interval data, which may be static, to identify the next time a receiver should tune in to receive data for a particular service supported by the aggregated, allocated, unused portion frames.
A receiver, such as a mobile terminal, may be configured to receive the time slice frame having this allocated data and the data in the aggregated, unused allocated portions of the time slice frame, and identify the data for the various services supported.
These and other aspects will be described in greater detail below.
A more complete understanding of the features described herein and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features, and wherein:
In the following description of the various embodiments, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration various embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope and spirit of the present invention.
Digital content may be created and/or provided by digital content sources 104 and may include video signals, audio signals, data, and so forth. Digital content sources 104 may provide content to digital broadcast transmitter 103 in the form of digital packets, e.g., Internet Protocol (IP) packets. A group of related IP packets sharing a certain unique IP address is sometimes described as an IP stream. Digital broadcast transmitter 103 may receive, process, and forward for transmission multiple IP streams from multiple digital content sources 104. The processed digital content may then be passed to digital broadcast tower 105 (or other physical transmission implements) for wireless transmission. Ultimately, mobile terminals 101 may selectively receive and consume digital content originating with digital content sources 104. It should be understood that mobile terminals 101 may be configured, through software, firmware and/or hardware circuitry, to receive, identify and extract the various portions of information addressed further below. This may be accomplished using any desired configuration, in accordance with the data format and structure described below.
The IP datagram demux block 202, 212 receives desired IP streams and divides those IP streams into elementary streams. Each elementary stream is written to a separate output. One elementary stream can contain one or more IP streams. The IP streams for each elementary stream are delivered to the Multi-Protocol Encapsulation-Forward Error Correction (MPE-FEC) encoding block 203, 213, where they are written into an application data table. Each elementary stream may be written into its own table. Once the application data table is full (or if an amount of time has passed such that another frame is needed, such as the delta-t period discussed below) the encoding block acts. If MPE-FEC is enabled, the block calculates Reed Solomon (RS) parity bytes and inserts them into an RS data table. Both data tables together, forming one MPE-FEC frame, are forwarded to the next functional block. If MPE-FEC is not enabled, then the block does not perform RS calculations, and merely buffers the IP streams for time-slice forming.
In DVB-H transmission systems, by sharing memory between the time slice buffer and the MPE-FEC RS code, a memory savings (up to 2048 kbits) may be achieved. Hence one Tisle, or time slice, burst is the same as one MPE-FEC frame. The word Tisle is intended to refer to time slicing of digital content as used, for example, by the DVB-H standard. A Tisle slot represents one time-sliced burst of digital content. A Tisle frame represents a collection of Tisle slots which repeat from frame to frame.
The MPE/MPE-FEC section encapsulation blocks 204, 214 encapsulate the payload from the previous block into a section and forms a section header. The payload is an IP datagram for a MPE section, and an RS column for a MPE-FEC section. All real-time parameters needed for each section, except for delta-t (explained below) and CRC-32, are inserted by block 204,214. Section header values, including address, table_boundary, and frame_boundary are inserted into the MPE and MPE-FEC sections. Additionally, MPE-FEC-specific header values are inserted into the section, including padding_columns, last_section_number, and section_number. The sections are then forwarded to the time slicing block 205, 215, where delta-t is calculated and inserted into section headers. Time slicing 205, 215 also calculates Cyclic Redundancy Check (CRC-32) values which are inserted into the sections as well.
Time slicing involves the transmitting of content in high-bandwidth bursts rather than in lower-bandwidth constant streams. As such, receivers of transmissions should be able to know when the next burst will be arriving, and hence delta-t is calculated to inform receivers when the following burst is to be expected. In this fashion, low power receivers are able to receive content in bursts and power down their radios in between transmissions. Differing content can be scheduled in interspersed intervals, allowing a receiver to turn on and off its radio only when content of interest is expected. A Tisle frame represents a series of time-sliced bursts sent in sequence. A Tisle slot is the spot that one burst takes within a Tisle frame. Content transmitted within a particular slot of a first frame will be broadcast in the same slot in a subsequent second frame.
The Transport Stream (TS) generation & multiplexing block 207 fragments incoming time-sliced sections into the payload of TS packet(s) and generates a header for each TS packet. The Moving Pictures Experts Group Transport Stream (MPEG TS) standard may be used to form the TS packets. The functional block also integrates sections from real-time services and non-real-time services. Finally, the time sliced sections and program specific information and signaling information (PSI/SI) from the PSI/SI generation block 206 are multiplexed into one output TS having a fixed data rate. Certain embodiments may incorporate the use of available burst size information from the TS generation & multiplexing block 207 into the MPE-FEC encoding process for non-real-time services.
An incoming signal is received by mobile terminal 101 and passed to receiver 301 as a transport stream (TS). The TS filtering block 302 receives the incoming TS in its entirety and, according to program identifiers (PIDs) assigned to TS packets, passes on only those TS packets belonging to desired content or elementary stream(s). Section parsing 303 decapsulates the payload of the TS packets and re-forms sections. The section decapsulation block 304 extracts real-time parameters and the payloads of each section. Based on the type of section (MPE/MPE-FEC or PSI/SI), it sends the section payloads and some real-time parameters to either the MPE/MPE-FEC decoding block 307 or PSI/SI table parsing block 305. The decapsulation block 304 may also send real-time parameters to the Tisle control and status block 306.
The Tisle control and status block 306 is responsible for switching off receiver 301 after a particular burst is fully received, and again switching the receiver back on before the next burst is about to be received. It also signals the MPE/MPE-FEC decoding block 307 when the time of maximum burst duration has elapsed. This signaling may be needed so that the decoding block knows to start decoding in the case where the tail end of a burst is lost.
MPE/MPE-FEC decoding block 307 writes section payloads into an MPE-FEC frame according to address information (as determined from the real-time parameters) and decodes the whole frame row by row. The decoder can be either an erasure or non-erasure decoder. Erasure info can be obtained from the section CRC-32 or, if the erroneous TS packets are passed forward, from the transport error indicator located in the header of the TS packet. If the MPE-FEC is not used, then this block may simply work as a time-slicing buffer storing one burst at a time.
IP parsing and filtering block 308 receives a whole MPE-FEC frame (or time-sliced burst). This filtering block goes through the corrected data areas in the frame to detect IP datagrams that were originally erroneous but were corrected by the decoder. It then only passes on IP datagrams having a desired IP address. PSI/SI table parsing 305 parses PSI/SI tables from among the sections and delivers signaling information to other portions of mobile terminal 101.
The data or bandwidth allocation within a Tisle 400 may include one portion 401 for PSI/SI information, or another type of overhead information associated with services carried in the Tisle 400. These types of overhead information may be viewed as being transmitted continuously, and may be used as a “roadmap” through the data stream. PSI tables may be generated according to the MPEG format, and may include a program association table (PAT—identifying services found in a transport stream); a program map table (PMT—identifying elementary streams located within a given service); a network information table (NIT—identifying information used for tuning to a particular stream); and a conditional access table (CAT—identifying conditional access systems applicable to one or more portions of the transport stream). SI tables may be generated according to the DVB standards, and may include a network information table (NIT—identifying tuning information for services); a bouquet association table (BAT—information linking multiple services on different transport streams together to allow the user to treat the services as if they were all part of a single transport stream); event information tables (EIT—listing schedules of events being transmitted); and other types of data.
The Tisle 400 may also include a portion 402 reserved for real-time burst service, which contains the actual data, such as video information, digital audio, etc., for a particular elementary stream ES, transport stream, and/or other service supported by the Tisle 400. The real-time burst portion may be divided into a number of data slots for different ES's, where each slot appears in each Tisle 400, and the delta-t value for the various slots indicates to the receivers when data for that slot's ES will be available.
Tisle 400 may also include a portion 403 reserved for the transmission of other data. This reserved portion allows the Tisle 400 to carry a guaranteed amount of real-time or non-real-time data used for a variety of purposes. The possible unused capacity from this reservation can also be used to carry other useful data, and the various portions of the tisle frames and unused portions may be independent from one another in terms of the data they carry and/or the services they support.
The allocations and reservations shown in
Aggregating all of this unused bandwidth shows, in
When the burst allocation is known, the transmitter 103 may then, in step 702, dynamically determine the amount of actual burst data that will be carried in a particular instance of the Tisle frame 400, and calculate the amount of unused transmission capability in the burst section. For example, the TS Generation and Multiplexing function 207 may compare the current ES bursts with the allocation given to the burst service in step 701. The unused amount is then identified (e.g., the times and bandwidth portions in the Tisle that have been allocated to the burst service data, but not currently used for the current Tisle), and the use of these unused portions is described further below.
In step 703, the overhead portion (PSI/SI 401) of the Tisle frame 400 is allocated. As noted above, this allocation may include the identification of separate divisions or slots corresponding to the different ES slots carried in the burst data 402. The allocation may also identify the locations (e.g., timing) of the individual contents of the PSI/SI information, such as individual tables.
Then, in step 704, the transmitter 103 may calculate the unused portion of the overhead portion 401, much in the same way as done with the burst portion. This calculation may involve consulting the unused bitrate of static reservations (e.g., for the PSI/SI channel). Similarly, in step 705, the transmitter 103 may allocate other data to portions of the frame, and in step 706, the transmitter may calculate the unused portion of those other portions of the frame.
In step 707, when the unused amounts (e.g., unused data slots) in the overhead portion 401, burst portion 402, and other portion 403 are known, the transmitter 103 may aggregate this unused transmission capability and allocate it to the transmission of additional data. Since the unused portions may come from a variety of locations within the Tisle 400 (e.g., some from an unused portion of a horizontally-divided ES 2 burst (shown in
As illustrated in
The individual unused timeslice frames 601 may be further divided into sub-channels, which can be used to support multiple distinct ES's, applications and devices. As shown in
Each burst 901 may be of a fixed period/duration, and may contain substantive data being transferred, such as portions of a file being transferred. The burst 901 may also include its own delta-t value (e.g., a delta-t time value that may indicate the next time a particular burst 901 is available), to allow receivers to know when to expect data for the particular burst 901. For example, the burst A(n) may contain information identifying the delta-t value for the time that will pass before the next burst A(n+1) is expected to be sent for the given channel. These delta-t values may, in some instances, be a static time slice interval where the values are identical in every burst, so that the bursts always appear at the same locations in the tisle.
With these divisions, the timing of the various service bursts 901 within the Tisle 400 may be reliably known to the receivers. Of course, the actual amount of data that can be transmitted in any given service burst 901 will vary depending on the amount of unused space in the various Tisles 400 (although the theoretical maximum will be the entire bandwidth of the allocated portion(s) in Tisle 400).
The processes described herein are conceptual in nature for ease of explanation, but need not be implemented in this same order described. Additionally, the various functions and process steps described above may be implemented by one or more processors (e.g., microprocessor in transmission station 103 or receiver), and stored on one or more computer-readable media in the form of computer-executable instructions.
The present application includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. While the features have been described with respect to specific examples, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. Thus, the spirit and scope of the application should be construed broadly as set forth in the appended claims.
