Patent Application
20070002900
This invention relates to systems, methods, and network entities for data transmission and reception over a communication link.
Services used in mobile handheld terminals require relatively low bandwidth. The estimated maximum bitrate for streaming video using advanced compression like MPEG-4 is in the order of few hundred kilobits per second, one practical limit being 384 kbps coming from the 3G environment. Some other types of services, as file downloading, may require significantly higher bandwidth, though. Therefore we have requirement for flexibility.
Broadcast has an almost century long tradition in radio. Even with TV, the history goes back to 1930's. Broadcasting has been successful throughout the world in bringing both entertainment and information to mass audiences.
The latest step in broadcasting is the digitalization of both radio and TV. Digital radio has not gained much acceptance on the market. However, many hope that digital TV will bring new benefits and services to the consumer and, as a result, generate new revenue streams for the broadcasting industry. The basic concept of the TV service itself has, however, not changed much. Rather, the TV lives on as before even if it has become digital.
The data is formatted by using, for example, a multi-protocol encapsulator in accordance with Section 7 of European Standard EN 301 192 “Digital Video Broadcasting (DVB); DVB specification for data broadcasting.” Encapsulated data is sent by the multi-protocol encapsulator to a digital broadcast transmitter for broadcast to the digital broadcast receiver a signal.
It is noted that further information regarding DVB may be found, for example, in the following ETSI (European Telecommunications Standards Institute) document, each of which is incorporated herein by reference:
ETSI EN 300 468 “Digital Video Broadcasting (DVB); Specification for Service Information (SI) in DVB systems”
Latest appliances of broadcast have raised a need for power consumption consideration in the receiver, and some efforts for reducing power consumption in the receiver have been made. However, this has for one's part created new challenges for power conserving broadcast transmission/reception: the air interface. Because of the need for power conservation, which is particularly relevant for mobile environment, the air interface is more challenging than in traditional broadcasting.
One solution has been to introduce data error corrections to the reception. However, the mere correction of data is not enough, leaving too much responsibility for the mere correction, for the performance of the data correction method and for the performance of the receiver device. For example, a single bit error can drop out a lot of data from the reception, which leaves too much correction work for the data correction method of the receiver device.
In view of various inherent limitations of broadcasting, it would be desirable to avoid or mitigate these and other problems associated with prior art systems. Thus, there is a need for focusing the error correction for characterising portions of the mobile digital broadband transmission.
Now a method and arrangement have been invented to a header protection mechanism for mobile digital broadband transmission.
In accordance with an aspect of the invention there is provided a method for data transmission, comprising:
In accordance with a further aspect of the invention there is provided a method for data reception, comprising:
In accordance with yet further aspect of the invention, there is provided a system for data transfer comprising:
In accordance with yet further aspect of the invention, there is provided a receiver, comprising:
In some embodiments, there is provided a method and a system for transmission/reception, a transmitting node and a recipient node for a digital broadband transmission containing at least one data segment transmitted in a time division manner. A data protection encoding is provided for a header of a packet of said digital broadband transmission together with a higher level data protection encoding of several packets.
Embodiments of the invention are employed for digital broadband transmission based on bursts of data segments or packets for mobile environment.
Advantageously, the header can be protected separately, so that the header can be identified, analysed, and verified for data errors separately from another parts of the digital broadband transmission. The resources in respect to the higher level encoding for bigger data entities than those defined by the header is saved.
For better understanding of the present invention reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appending claims.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
Digital Video Broadcasting (DVB) offers a high bandwidth broadband transmission channel wherein delivery is typically broadcast, multicast or alternatively unicast. The high bandwidth transmission channel can offer a user of such system various services. Appropriate data corrected to correctly received is important for obtaining the various services. DVB offers applicable principles, and preferably, a Terrestrial Digital Video Broadcasting (DVB-T) is applied in the embodied invention. Alternatively, the DVB for mobile environment is in this description referred to as DVB-X. Thus, as used herein, transmission may refer to a broadcast, multicast, or unicast, and data can include but is not limited to, IP protocol-encoded data. Preferably, IP service data received over DVB-T is targeted for mobile reception.
Preferable embodiments of the invention provides a method, a system, a transmitter and a receiver defining a header protection mechanism for DVB MPE (Multi-Protocol Encapsulation) section protocol, which can be used in DVB-T mobile reception. MPE section in this case is referring to a proposal for using MPE section MAC (Media Access Control) bytes 1-5 to carry real time information related to time slice bursts. By using header protection mechanism together with high level FEC (Forward Error Correction), there is a way to enhance significantly mobile digital broadband data reception capabilities. Thus the header protection used together with the high level FEC in DVB, provides an advantageous solution for DVB mobile burst data reception. As the high level FEC e.g. the Reed Solomon encoding is used.
According to some preferable embodiments, all packets having an uncorrupted MPE section header may be put into an array for higher level error correction such as FEC. The array has addressable storage locations of mobile digital broadband data for correction of higher level data entity by FEC process.
At the receiver the packet is put into a buffer, a header is identified and checked against errors by using an error detection/correction code, such as e.g. CRC (Cyclic Redundancy Check) for the received header data. If the error detection/correction code (e.g. CRC) indicates substantially correct value or is OK, the address is extracted and the packet including the header is put into the array.
Advantageously, the need for buffering is very small as only the header data needs to be buffered before loading data into the array. The header may be as small as, for example, 12 bytes.
Preferably, by protecting, for example, 12 bytes in MPE section header with error detection/correction code (e.g. CRC), the overall performance of high level FEC is enhanced. One reason for this can be that corrupted packets can be placed into correct position inside a FEC frame. Moreover, the usage of memory on the receiver can be reduced. One reason for this can be that there is no need to buffer whole packet (for example, max. 4 kB) before the whole packet can be placed into the FEC frame.
Some embodiments of the invention apply time slice data transmission principle in DVB. The DVB transmission system usually provides bandwidth of 10 Mbps or even more. This provides a possibility to significantly reduce the average DVB receiver power consumption by introducing a schema based on time division multi-plexing (TDM). The introduced schema is called time slicing. The idea of time slicing is to send data in bursts using significantly higher bandwidth compared to the bandwidth required if the data was transmitted using static bandwidth. Within a burst, time to the beginning of the next burst (delta-t) is indicated. Between the bursts, data of the service is not transmitted, allowing other services to use the bandwidth otherwise allocated for the service. This enables a receiver to stay active only a fragment of the time, while receiving bursts of a requested service. In case a constant lower bitrate is required by the mobile handheld terminal, this may be provides by buffering the received bursts.
So data is transmitted in a burst, typically, short one, by using the great bandwidth of DVB. Some similarities to time division principle counts. The receiver may be shut down between the burst to conserver power. The data in the bursts is downloaded into a buffer and later applied for use. The bursts can be repeated at intervals wherein the time for next bursts is, thus, announced, for example, by the delta-t factor. The high level FEC is in the system to guarantee better uncorrupted packet feed through for the digital broadband system. Advantageously, by using the header protection mechanism in such a way that all packets having substantially correct header may be positioned into the array together with the higher level error correction coding for the array, any possibly corrupted packet can be placed into correct position into the array. Therefore the performance of the higher level error correction can be improved and also the performance of the entire mobile DVB reception/transmission.
Turning now to the structure of mobile digital broadband data transmission in some embodiments of the invention, MPE section is protected by CRC-32 code. The MPE section packet can be up to 4 kB long. The MPE section packet includes MPE section header and MPE section payload. The MPE section header contains 12 bytes. Assuming a single byte error to 4 kB MPE section packet, probability is only 0.3% (12/4096) that this error is in packet header. Vice versa, probability of having a single byte error inside MPE section payload is 99.7%. Therefore, it is very advantageous to focus on the header in the reception error correction. The additional benefit is also that based on the header identification, the address/location in the array can be obtained. Therefore, correct header data and the payload is easy to place into the array. No big stuffed data sections remain in the array, since the address of the header focuses the location in the array. This is beneficial because it relieves the work of the FEC process.
Some embodiments of the invention apply the array. A two-dimensional array of addressable storage locations is created and/or accessed by a transmission node. Packets corresponding to data to be transmitted by the node, typically in a particular burst, can be loaded into the two-dimensional array in a column-wise manner. Such packets can be, for example, IP packets. Accordingly, the contents of a loaded packet occupies one or more addressable storage locations of one or more columns. The high level FEC can be computed with respect to each row of the two-dimensional array. Accordingly, the recipient node, after perhaps having receiving indications of the array when receiving, for example, the mobile digital broadband transmission, can create and/or access the two dimensional array corresponding to the array created and/or accessed by the transmitting node.
In the following examples of loading, addressing, and sizing of the two-dimensional arrays is described in some further embodiments of the invention.
The two-dimensional array of the sort noted above could, in accordance with various embodiments of the present invention, be loaded in a number of ways. For example, in embodiments where loading is to be columnar-wise, implementation could be such that only one packet (e.g., IP packet) is loaded per column.
For such embodiments, array row and/or column size could be chosen such that a column would be capable of holding a maximally-sized packet. In the case where a packet or the like loaded into a column was of less than the maximal size, the remaining portion of the column might be filled with “stuff data”. As specific example, the remaining portion could be filled with zeros.
The exemplary packet can be maximally sized, so no stuff data is added to the column in which it resides. On the other hand, packet can be of less than the maximal size, and, accordingly, stuff data is added to its column such that the combination of packet and stuff data occupies the entire column. It is also possible that one or more entire columns contain only stuff data. Such columns may be placed before, between, or after the columns containing data, or a combination of these may be used.
As another example of loading in various embodiments where loading is to be columnar-wise, implementation could be such that in the case where a packet did not fully occupy the column into which it was loaded, loading of the column could continue with the next packet to be loaded into the array. Further, in the case where a packet being loaded into a column could not fully fit into that column, those portions which did not fit could be placed in one or more additional column.
Such functionality could be implemented, for example, in such a manner that where a particular packet did not fully fit inside a column, the column would be filled with contents of the packet up to the column's last addressable element (e.g., the element of the column having the highest row-wise address), and the remainder of the packet could be placed in the following column, starting with that columns first addressable element (e.g., the element of the column having the lowest row-wise address).
Turning to
In one embodiment of the invention, only MPE packet payloads are placed into the array according to the address in the MPE packet header and the packet headers are dropped out. This means that the FEC array comprises IP data packets and error detection/correction data bytes.
On the receiver node, there can be analysed correctness of each received MPE section (105) before the receiver node can place this packet into this 2 Mbit frame for FEC calculation. The reason for this can be that there should be a certain kind of firmness that received packet start address information has been correctly received. In case packet is placed into wrong position inside 2 Mbit FEC frame, it would mean that whole frame shall be corrupted, and after this data is not anymore useful for application.
Turning now to
Turning to
Some yet further embodiments of
In some further embodiments, after the end, there is started to process FEC over the array. When FEC process is ready and data is transferred away from the array, the process can also start over to receive data, process the error detection/correction code (e.g. CRC) over the header, and place packets into the FEC array.
In yet some further embodiments encapsulation takes place in the recipient node. Having received TS packets of the sort, the node could extract the DSM-CC sections carried by these packets. Next, the node could extract from those DSM-CC sections packets carrying data corresponding to header and originally-loaded packets.
Although DSM-CC MPE has been discussed here in the transmission and reception, it will be noted that other MPE techniques could be employed.
Some embodiments of the invention apply the system of
Still referring to the example of
Turning to the example of
Still referring to
Some preferable embodied ways for implementing the error detection/correction code (e.g. CRC) code in the header can be considered the hardware, for example shift register implementation. Also lookup table implementation for SW can be done. Implementation of CRC code is a straight forward process.
In yet some further embodiments, CRC-32 is applied for calculation for each MPE section packet but there is no need for buffering any more data of the MPE section payload. The data can be placed into memory after the MPE header is checked. In a rare case if all the MPE packets have to be CRC-32 corrected, then this means that whole 2 Mbit FEC frame is correct and there no need to perform the FEC algorithm at all.
It should be noted that the size of FEC frame of 2 Mbit, the size of the array, as well as the size of the 1024 MPE section packet and 12 bytes MPE section header are only examples defined in the standardization instance. However, the numerical presentation for those can vary within their respective operations and functions described.
The embodied inventions can save power in the receiver device, which contribute the mobility aspect of the DVB receiver. The performance of the embodiments boosts benefits of the invention such as economy. For example, DVB-T or DVB-X offers an effective and cheap way to distribute data.
Although the description above contains many specifics, these are merely provided to illustrate the invention and should not be constructed as limitations of the invention's scope. Thus it will be apparent for those skilled in the art that various modifications and variations can be made in the system, processed and entities of the present invention without departing from the characteristics or scope of the invention.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FI03/00208 | 3/18/2003 | WO | 8/25/2006 |
