GB2432087A

GB2432087A - Dividing headers into data bursts

Info

Publication number: GB2432087A
Application number: GB0600482A
Authority: GB
Inventors: David Hole
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2005-11-02
Filing date: 2006-01-11
Publication date: 2007-05-09
Anticipated expiration: 2026-01-11
Also published as: GB0522322D0; GB2432087B; GB0600482D0

Abstract

Transmission data (16, 17) and header information is divided into four data bursts comprising two two-burst blocks (Fig. 2) such that the header information is interleaved across only the first bursts (8, 9) so that decoding attempts can be made before all bursts have arrived at a GSM/EDGE receiver (ie. after receiving a Minimum Burst Set, MBS). This speeds up the identification of the intended receiver, with header information and useful data segmented into earlier bursts and padding or redundant bits are sent in later bursts, with the uplink state flag (USF) interleaved as normal and decoded at the end of the fourth burst in order to allow backwards compatibility for old mobile devices. Using two bursts rather than four reduces latency by 10ms.

Description

A METHOD OF TRANSMITTING DATA

This invention relates to a method of transmitting data in a communication system, particularly for mobile communications.

In the 3rd generation partnership project (3GPP) global system for mobile communication (GSM)/enhanced data rates for GSM evolution (EDGE) radio access mobile network, user data is sent as a sequence of radio blocks, each block being encoded, split up and transmitted as four bursts.

Currently, a GSM/EDGE receiver must receive all four bursts before it can decode the radio block. This is because header information and, in some cases, data are interleaved across all four bursts. Under the current specification bursts are sent separated in time by a minimum of 4.62ms. This means that it takes a minimum of 14.4ms (= (3 x 4.62) + 0.577) before a receiver can decode the header and hence know whether the data, which in some cases may also not be decoded before this point, is intended for that receiver.

In accordance with the present invention, a method of transmitting data in a * * : communication system in groups of four bursts comprises taking data to be transmitted, together with the header information and dividing it into segments for transmission in between one and three data bursts; transmitting the data bursts followed by other bursts; and decoding data and header information from each of the data bursts following the * end of transmission of the last of the data bursts. *:::: The split of data and header information is rearranged, so that useful data and header information is sent in earlier bursts, whereas padding or redundant information is preferably sent in the later bursts. The uplink state flag (USF) is interleaved in the usual way, but the invention allows for both the data and the header information to be decoded sooner than in a conventional system. The scheme of the present invention encodes the data in a block so that in certain cases, specifically, when there is less than a complete block's worth of data to send, the data can be completely decoded after the reception of fewer than four bursts. The minimum set of bursts required to decode the user data is abbreviated to minimum burst set (MBS).

Backwards-compatibility for downlink (network to mobile) transmissions is a concern, since it is to be expected that only new mobile devices are designed to be able to decode data and header information transmitted according to the method of the present invention, so benefiting from the reduced delay. To enable existing devices to continue operating on receiving transmissions made according to the invention, they need to be able to read USF data, that is, the data which indicates which mobile has permission to transmit on the corresponding uplink timeslot.

Preferably, in uplink, uplink state flags are decoded at the end of the fourth burst.

The present invention addresses a specific problem in GSM/EDGE which up to now has not been dealt with within GSM/EDGE networks. It is specific to GSM/EDGE because of the constraints of the existing burst/block structure and backwards-compatibility concerns.

Preferably, each burst which is not a data burst contains redundant information for error correction. The redundant information may be provided by means of incremental redundancy or by providing a complete copy of the data in an earlier burst.

In one embodiment, the header information from non-data bursts is added to the last data burst expected to be necessary for decoding the data, and the earlier data bursts do not include header data. * * : Preferably, bits are provided in each burst as coding scheme indicators and optionally, as indicators of the total number of bursts required to decode all data.

In one embodiment, an attempt is made to decode the data at the end of each *.:.

burst, until it is correctly decoded. * **** It is desirable that the probability of a receiver decoding a block incorrectly *: ::.

using the new scheme, due to errors in reception, be no greater than the probability when using a conventional scheme.

Preferably, a coding scheme and a number of bursts comprising a minimum burst set (MBS) is fixed for a particular user data connection, or for all data connections to a particular mobile.

Preferably, the coding scheme and the number of bursts comprising the MBS is specified, or negotiated as part of a resource allocation procedure for that user data connection.

In one embodiment, all user data sent as part of a specific user data connection, which may be uni-directional or bi-directional, or all data sent to or from a particular mobile, is sent using a particular coding scheme, where the number of bursts in the MBS is fixed. This may be agreed between the mobile and the network during resource allocation, or re-allocation.

Typically, the communication system is a global system for mobile communication (GSM) system.

An example of a method of transmitting data in a communication system in groups of four bursts according to the present invention will now be described with reference to the accompanying drawings in which: Figure 1 illustrates arrangement of bits in a typical radio block for a conventional modulation coding scheme; Figure 2a illustrates a two burst radio block for the first and second bursts, using the method of the present invention; Figure 2b illustrates a two burst radio block for the third and fourth bursts, with backward compatible headers, using the method of the present invention; Figure 2c illustrates a two burst radio block for the third and fourth bursts, with increased data redundancy, using the method of the present invention; Figure 3 illustrates conventional uplink burst mapping for all four bursts; and s..

Figure 4 illustrates burst mapping for all four bursts using the method of the * * present invention.

Figure 1 shows uplink burst mapping in a block using existing modulation coding schemes (MCS) MCS-7, MCS-8, or MCS-9. The use of bits in a burst is the *.

same for all four bursts, so only the arrangement of bits for one burst is shown. The * radio block is divided into four parts, user data 1, 2, header information 3, 4, modulation and coding scheme indication bits, or stealing flags' 5 and for downlink blocks only, uplink scheduling information as uplink state flag (USF) 6, 7. In this example there are two sections 1, 2 of 153 bits for user data; two sections 3, 4 of 15 and 16 bits respectively for header information; two sections 6, 7 of 6 and 3 bits respectively for the USF and 2 bits for modulation and coding scheme indicators.

Encoding the user data such that it can be read using fewer bursts means that data can be passed through the network, to another protocol layer, for example, earlier than is currently possible. Using 2 bursts instead of 4 can reduce the latency by approximately 1 Oms, which is worthwhile given that typical end-to-end latency values for small amounts of data are around lOOms.

Adding redundant data to the remaining bursts means that, in the case that the receiver cannot decode the data using only the MBS, it is very likely that it will be able ) to do so by using the redundant data as well, without the need for requesting a retransmission of the data.

The header information includes addressing information, without which the data cannot be appropriately forwarded by the receiving device, or dropped, if the device is not the intended recipient. Thus, it must be possible to decode the header information in the same number of bursts as the data, so there are additional header bits 8, 9 in bursts 1 and 2, as shown in Fig. 2a, to ensure that all the header information is present, even if decoding takes place using only those first two bursts. The additional headers in this example have 16 and 15 bits respectively and there is a corresponding reduction in the number of data bits 10, 11 as a result.

Figures 2b and 2c illustrate further options. In option 1, Fig. 2b, the header is designed to be backwards compatible, so the header information is in its normal position. Allowing the header to be additionally decoded by existing devices may be of S...

benefit if there is information in the header that is of use to multiple receivers. The e contents of the third and fourth bursts, as shown in Fig. 2b, are based on the minimum * * requirements for backwards-compatibility with an option to allow existing mobiles to decode the header information. There are non-specified sections 12, 13 of 153 bits in: bursts 3 and 4.

Downlink messages contain scheduling information for the uplink timeslots, which, preferably, can be decoded by all mobiles in the cell. There is no advantage *: :: : from coding this so that fewer than four bursts are required to decode this information.

Therefore, this information is coded in a currently agreed fashion.

Fig. 2c has an option to include redundant' data information 14, 15 in bursts 3 and 4 which allows a receiver to attempt to decode the data using all four bursts, if it cannot do so using only two. A combination of the options of Fig. 2b and Fig. 2c is also possible.

Figure 3 shows the existing scheme for uplink burst mapping of burst I to 4 used for MCS-7', MCS-8' and MCS-9', whereby two separate blocks of data (RLC blocks') 16, 17 are interleaved in two bursts each, burst I and 2 for data 16 and burst 3 and 4 for data 17. The header 1-3, 1-4 to 4-3, 4-4 and USF 1-6, 1-7 to 4-6, 4-7 information are interleaved over all four bursts.

As shown by Fig. 3 for MCS7-9, two units of data (RLC blocks') are encoded in 4-bursts equal to I radio block. In MCS 7 and 8, data is interleaved over all four bursts. Fig. 3 shows the case specifically for MCS-9, where data for each RLC block is only interleaved across two bursts, but the (single) header is interleaved across all four bursts. Because of the way they are split up, although the data for each one uses only two bursts, having the header split over all four bursts and the fact that the data is useless without decoding the header, since the header includes the destination address, means that the data cannot be used by the receiver until all four bursts have been received and decoded.

In an example of how the present invention is used, in Fig. 4, it can be seen that data 1-10, 1-1 1, 2-10, 2-1 1 only appears in the first two bursts, Bi, B2 along with header information both in the burst 1-3, 1-4, 2-3, 2-4 and moved from burst 3 and 4, 3-8, 3-9, 4-8, 4-9 so the data and headers are decoded by the end of the second burst.

By contrast, a part of the USF 1-7, 1-6 to 4-6, 4-7 which is split among four bursts, not copied, is provided in each burst and only determined at the end of the fourth burst. V.,

For compatibility, headers 3-3, 3-4, 4-3, 4-4 in bursts B3 and B4 are left in their. .. V.-

conventional backwards compatible locations. * The figures described above are examples only, and relate to specific existing coding schemes (MCS-7' to MCS-9'), as used in the uplink (i.e. in the direction from the mobile to the network). The exact solutions are adapted for other existing coding schemes. p..,

The present invention has the advantages that unlike conventional methods, it is -: : not necessary to wait for all four bursts and store that data before it is decoded, but if the data can be decoded in one or two bursts, then there is less processing, no additional storage required and the USF can still be easily extracted from the data stream.

In the method of the present invention user data is encoded in a manner that allows a receiver to decode the user data having received only the MBS. Optionally, bursts not in the MBS can contain additional information that gives the receiver a second chance to decode the data, so that both the bursts in the MBS and the extra bursts are used together to decode the original data if there is a problem in decoding, due to, for example, errors caused by channel conditions. This may be in the form of the incremental redundancy scheme already used in some coding schemes. The header information is encoded in a manner that allows a receiver to decode the user data having received only the MBS. Optionally, the header data is encoded such that both a new' receiver and an old' receiver can decode the header.

The two additional optional features discussed above are not mutually exclusive. However the use of backward-compatible headers slightly reduces the amount of additional (or redundant) information that can be sent.

Uplink scheduling information is provided in downlink blocks only. The USF indicates which mobiles can transmit in which uplink timeslots. This information is desirably made available to all mobiles, not just those capable of decoding the new scheme. Furthermore, there is no benefit in a mobile being able to decode the USF information in fewer than four bursts. Hence, this information is encoded in the existing manner.

Stealing flags are currently used to indicate the coding scheme being used. This indication needs to be encoded such that the stealing flags included in the MBS are sufficiently different from currently defined values. In other words, it is not sufficient to use stealing flags that are not in the MBS to differentiate between this new scheme and existing schemes. S.. * wI.

Furthermore, the new stealing bit patterns can be designed in such a way that a new mobile (which understands the new scheme) would recognize the use of the new scheme, while an old legacy' mobile would attempt to correct' the unknown stealing flag pattern to one that it understands. This would allow a legacy mobile to decode the * : *.*.

header information, if the option to include the header information in its existing. * , locations is used. The existing patterns are very different from each other, but if the * new schemes are only slightly different from the existing patterns, the legacy mobile will just assume that the difference is due to channel conditions or other common faults, and correct it to an existing pattern.

Claims

CLAIMS

I. A method of transmitting data in a communication system in groups of four bursts, the method comprising taking data to be transmitted, together with the header information and dividing it into segments for transmission in between one and three data bursts; transmitting the data bursts followed by the other bursts; and decoding data and header information from each of the data bursts following the end of transmission of the last of the data burst.

2. A method according to claim 1, wherein in uplink, uplink state flags are decoded at the end of the fourth burst.

3 A method according to claim I or claim 2, wherein each burst which is not a data burst contains redundant information for error correction. a...

4. A method according to claim 3, wherein the redundant information is provided * by means of incremental redundancy, or by providing a complete copy of the data in an earlier burst. a... *a..

5. A method according to any preceding claim, wherein the header information.. aa** a...

from non-data bursts is added to the last data burst expected to be necessary for a decoding the data, and the earlier data bursts do not include header data.

6. A method according to any preceding claim, wherein bits are provided in each burst as coding scheme indicators and optionally, as indicators of the total number of bursts required to decode all data.

7. A method according to any preceding claim, wherein an attempt is made to decode the data at the end of each burst, until it is correctly decoded.

8. A method according to any preceding claim, wherein a coding scheme and a number of bursts comprising a minimum burst set (MBS) is fixed for a particular user data coimection, or for all data connections to a particular mobile.

9. A method according to claim 8, wherein the coding scheme and the number of bursts comprising the MBS is specified, or negotiated as part of a resource allocation procedure for that user data connection.

10. A method according to any preceding claim, wherein the communication system is a global system for mobile communication (GSM) system. * * ***. **** * S * * S *5IS

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