Dynamic HARQ-id reservation
09853780 · 2017-12-26
Assignee
Inventors
Cpc classification
H04L1/1867
ELECTRICITY
International classification
Abstract
The method is used for detection and/or removal of errors in transmission systems which comprise a transmitter unit and at least one receiver unit. The transmitter unit transmits to the receiver unit on a semi-persistent transmission resource which provides an adjustable frequency range and an adjustable time period. Furthermore, the self-repeating, semi-persistent transmission resource repeating with the period T.sub.SPS is rigidly assigned to the receiver unit. Following this, at least one but not all of the HARQ process numbers available for the self-repeating, semi-persistent transmission resource are reserved for the latter.
Claims
1. A device for detection and/or removal of errors in transmission systems, said device comprising: a transmitter unit which transmits payload data to the at least one receiver unit on a semi-persistent transmission resource which provides an adjustable frequency range and an adjustable time period; a control unit which assigns a self-repeating, semi-persistent transmission resource repeating with the period semi-persistent scheduling is present in the transmitter unit; and reserves one but not all of the Hybrid Automatic Repeat Request (HARQ) process numbers available for the self-repeating, semi-persistent transmission resource, wherein the number of HARQ process numbers which are reserved for the semi-persistent transmission resource is varied dependent upon data volume on other transmission resources by the control unit, wherein the HARQ process number which is reserved is needed for at least one next semi-persistent transmission resource, a processing unit processing the payload data by means of turbo-coding, so that transmission errors are corrected in the receiver unit, wherein the device is associated with at least one of the following: the semi-persistent transmission resource relates to radio resources which are configured semi-persistently by the control unit by means of semi-persistent scheduling (SPS) and are assigned to the receiver unit for a relatively longer time period than one subframe; the transmitter unit is an LTE base-station, and the at least one receiver unit is an LTE receiver unit; the control unit dynamically varies the number of HARQ process numbers to be reserved; the control unit reduces the number in the case of a relatively higher data volume on the other transmission resources with reference to the semi-persistent transmission resource from the transmitter unit to the at least one receiver unit; the control unit increases the number in the case of a low data volume on the other transmission resources with reference to the semi-persistent transmission resource; fewer of the HARQ process numbers assigned for the semi-persistent transmission resource are reserved in the case of a relatively high quality of the transmission channel than in the case of a relatively poor quality of the transmission channel; and the payload data which are transmitted via the semi-persistent transmission resource are VoIP-data.
2. The device according to claim 1, wherein the control unit releases at least one HARQ process number which can be used for a transmission of the payload data on the self-repeating, semi-persistent transmission resource but which is not reserved for this transmission resource by the control unit for at least one further transmission process from the transmitter unit to the at least one receiver unit.
3. The device according to claim 1, wherein the control unit releases that HARQ process number for which a transmission of the payload data on one of the self-repeating, semi-persistent transmission resources has been successful, for at least one further transmission process which uses another transmission resource from the transmitter unit to the at least one receiver unit.
4. The device according to claim 1, wherein the control unit reserves the number of HARQ process numbers which are used for the semi-persistent transmission resource; wherein the number of HARQ process numbers to be reserved depends upon the period of the self-repeating, semi-persistent transmission resource.
5. The device according to claim 1, wherein the transmitter unit comprises: a medium access control (MAC) layer; and a physical layer for coding of HARQ processing.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Various exemplary embodiments of the invention are described by way of example below with reference to the drawings. Identical subject matters provide the same reference numbers. In detail, the corresponding figures of the drawings show:
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DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
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(12) For the payload data which are transmitted on the DLSCH (English: Downlink Shared Channel; German: gemeinsamer Abwäartskanal), a checksum is calculated in a first processing unit 4. In this context, CRC stands for Cyclic Redundancy Check (German: zyklische Redundanzprüfung). The checksums (CRC) calculated by the first processing unit allow the receiver unit 2 to identify errors.
(13) Following this, a coding and data matching is implemented within a second processing unit 5. In this context, the output of the first processing unit 4 is connected to the input of the second processing unit 5. The second processing unit 5 preferably contains an option for processing the payload data by means of turbo-coding, so that transmission errors can be corrected in the receiver unit 2. Rate matching is used not only for matching the number of bits to be transmitted to the number of transmission resources available on the DLSCH, but additionally for generating various redundant versions, as provided by the HARQ protocol.
(14) The second processing unit 5 is connected in turn to a third processing unit 6. Within the first processing unit 6, a digital modulation by means of QPSK (English: Quadrature Phase-Shift Keying; German: Quadraturphasenumtastung) or 16 QAM (English: Quadrature Amplitude Modulation; German: Quadraturamplitudenmodulation) 64 QAM is implemented.
(15) The third processing unit 6 is further connected to a fourth processing unit 7. The fourth processing unit 7 is responsible for the antenna assignment and supports various multi-antenna transmission schemes. These include diversity transmission, beam forming (German: Richtbildung) and spatial-multiplexing (German: räumliches Multiplexing).
(16) The output of the fourth processing unit 7 is connected to a fifth processing unit 8. Within the fifth processing unit 8, an assignment to the physical resources used within the DLSCH is implemented.
(17) The third processing unit 6, the fourth processing unit 7 and the fifth processing unit 8 are controlled by a central control unit 9. Another HARQ processing unit 10 is also connected to the central control unit 9. The HARQ processing unit 10 is also connected to the second processing unit 5. The HARQ processing unit 10 receives packets which specify whether a packet transmitted from the LTE transmitter unit 1 has been correctly received by the receiver unit 2. These specifications are ACK (English: positive acknowledgement; German: positive Rückmeldung) and NAK packets (English: negative acknowledgement; German: negative Rückmeldung), which are transmitted on the PHICH (English: physical hybrid ARQ indicator channel, German: physikalischer Hybrid-ARQ-Kanalindikator). Furthermore, the HARQ information is prepared and transmitted by the HARQ processing unit 10.
(18) The SPS control unit 11, which is referred to below as the control unit 11, is also disposed within the HARQ processing unit 10. As will be explained in due course, the control unit 11 is responsible for assigning the various HARQ processes to the transmission resources. As already explained, a fixed number of HARQ processes are assigned for the transmission resources configured in a semi-persistent manner, that is, the SPS-configured transmission resources.
(19) The fifth processing unit 8 in the exemplary embodiment from
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(21) For instance, within
(22) This overhead can be minimized with the use of SPS. It is clearly evident that, via the RRC layer, the control unit 11 is notified, within the MAC layer that a transmission resource 20 is to be configured in a semi-persistent manner. The control unit 11 is notified via the RRC layer that the transmission resource 20 is to be configured in a semi-persistent manner, that is, for SPS in subframe 8 in the first frame (Frame 0 ). It is also specified that the period T.sub.SPS with which the semi-persistent transmission resources 20 are repeated, TTI=4, should therefore be four subframes. For this purpose, the mobile-terminal device 2 is notified, on the PDDCH in subframe eight of the first frame (0), that the transmission resource 20 on the PDSCH is configured in a semi-persistent manner, that is, for SPS. Starting from this subframe, data can be transmitted from the transmitter unit 1 to the at least one receiver unit 2 on all of the subsequent subframes, which are distanced from one another by the previously determined period T.sub.SPS, without the need to communicate additional control information to the at least one receiver unit 2 on the PDCCH.
(23) Within
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(25) If four HARQ processes are to be used for the semi-persistent transmission resources 20, the lowest HARQ process numbers are automatically used. In this case, the HARQ process numbers zero to three are assigned to the semi-persistent transmission resources 20. If three HARQ process numbers can be used for the semi-persistent transmission resources 20,
HARQ process number=[floor(t/T.sub.SPS)] mod N.sub.SPS (1)
(26) The valid HARQ process number is calculated according to equation (1), whereas t=10*SFN+sf. Accordingly, t specifies the subframe, for which the HARQ process number should be determined. Selecting the value t=2 requests the HARQ process number of the subframe disposed in the second position. T.sub.SPS specifies the period with which the semi-persistently configured transmission resources 20 are repeated. In the example from
(27) The determination of the HARQ process numbers according to equation (1) is reproduced, for example, in the corresponding standardization document of the 3GPP under TS 36.321, which, like the standardization document TS 36.213, is included in full within the present document. The calculation of equation (1) can be implemented, for example, in the control unit 11.
(28) Furthermore, by means of equation (2), it is possible to request the subframe in which the next transmission of a semi-persistently configured transmission resource 20, that is, of an SPS transmission resource 20, takes place.
T.sub.SPS[n]=(10*SFN+sf) =[(10*SFN.sub.SPS,start+sf.sub.SPS,start)+n*T.sub.SPS] mod 10240 (2)
(29) In the exemplary embodiment from
(30) By calculating equation (1) and (2), the control unit 11 according to the invention can determine when a new transmission on a semi-persistently configured transmission resource 20 will take place and which HARQ processes must be used for this purpose with which process numbers.
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(33) According to the exemplary embodiment from
(34) Accordingly, the control unit 11 according to the invention reserves at least one but not all of the HARQ process numbers available for the self-repeating, semi-persistently configured transmission resources 20. By preference, the control unit 11 according to the invention reserves a number of HARQ process numbers which are used for the semi-persistently configured transmission resources 20, whereas the number of HARQ process numbers to be reserved depends upon the period T.sub.SPS of the self-repeating, semi-persistently configured transmission resources 20. In this context, that HARQ process number is reserved, which are needed for the at least one semi-persistently configured transmission resource 20.
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(36) Table (1) shows, for example, that not only the next HARQ process number is reserved by the control unit 11 according to the invention, but a different number of HARQ process numbers are reserved dependent upon the period T.sub.SPS.
(37) TABLE-US-00001 TABLE (1) T.sub.SPS N.sub.SPS-Temp sf .Math. 10 3 sf .Math. 20, sf .Math. 32 2 >sf .Math. 32 1
(38) If the period T.sub.SPS=10×sf, that is, one semi-persistently configured transmission resource 20 is repeated every ten subframes, it is proposed that the control unit 11 according to the invention reserves the next three HARQ process numbers. This is explained by the fact that N.sub.SPS-Temp=3. For example, if the period T.sub.SPS=20×sf or T.sub.SPS=32×sf, that is, if the semi-persistently configured transmission resources 20 are repeated every 20 subframes or every 32 subframes, it is proposed that the control unit 11 according to the invention reserves only the next two HARQ process numbers. The value for N.sub.SPS-Temp in this case is two, as shown in Table (1). If the period is T.sub.SPS>sf×32, that is, if the semi-persistently configured transmission resources 20 are repeated at an interval of more than 32 subframes, only the HARQ process number required as the next one is reserved by the control unit 11 according to the invention, as explained by N.sub.SPS-Temp=1.
(39) In
(40) As shown in
(41) The control unit 11 according to the invention releases a HARQ process number for the at least one other transmission resource 21 only if the following applies: N.sub.SPS-Temp<N.sub.SPS.
(42) In this case, the control unit 11 according to the invention releases the HARQ process number if a transmission of the payload data on one of the self-repeating, semi-persistently configured transmission resources 20 has been successful, because, in the case of an unsuccessful transmission, the HARQ process number must be used for the re-transmission of the same payload data. If the transmission of the payload data was successful, the HARQ process number can be used for at least one further transmission process from the transmitter unit 1 to the at least one receiver unit 2, whereas this transmission process uses another transmission resource 21. This other transmission resource 21 is preferably not a self-repeating, semi-persistently configured transmission resource 20.
(43) The number of HARQ process numbers to be reserved as suggested in Table (1) can also be varied dynamically during the operation of the transmitter unit 1 according to the invention by the control unit 11 according to the invention. In this manner, with a relatively high quality of the transmission channel, fewer of the HARQ process numbers assigned for the semi-persistent transmission resources 20 can be reserved than in the case of a relatively poor quality of the transmission channel, because the probability that payload data need to be transmitted more than twice before the transmission process is successful is very low. A relatively high quality and a relatively poor quality of the transmission channel are measured according to an adjustable threshold value. For example, the bit error rate can be specified. If this is undershot, a relatively high quality of the transmission channel is present. If it is overshot, a relatively poor quality of the transmission channel is present. The bit error rate can be adjusted arbitrarily or can be taken from the specifications for the corresponding standard.
(44) As already explained, the self-repeating, semi-persistently configured transmission resources 20 are preferably suitable for the transmission of VoIP data, because the codec which generates the VoIP data generates a new data packet only every 20 ms. However, this VoIP codec generates a new data packet regularly every 20 ms, so that a plurality of control data on the PDCCH can be saved by the semi-persistent transmission resources 20, especially since the VoIP data packets are relatively small. As a result, the overhead in the transmission of VoIP data falls significantly.
(45) The control unit 11 according to the invention can also reduce the value N.sub.SPS-Temp for the number of HARQ process numbers to be reserved if the data rate from the transmitter unit 1 according to the invention to the at least one mobile-terminal device 2 rises. Conversely, the control unit 11 according to the invention can increase the number of HARQ process numbers to be reserved if the data rate of the transmitter unit 1 according to the invention to the at least one mobile-terminal device 2 falls.
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(50) Within the scope of the invention, all of the features illustrated and/or described can be combined with one another as required. In particular, the dependent claims relating to the method can also be combined with the device claims relating to the device and vice versa.