HK1190841B

HK1190841B - A method and an arrangement in a telecommunication system

Info

Publication number: HK1190841B
Application number: HK14103858.9A
Authority: HK
Inventors: Michael Meyer; Henning Wiemann; Johan Torsner
Original assignee: Optis Cellular Technology, Llc
Priority date: 2008-02-08
Filing date: 2014-04-23
Publication date: 2018-06-22

Description

Method and arrangement in a telecommunication system

The filing date of the present divisional application is 2008, 9 and 18, and the application number is 200880126681.9, entitled "method and apparatus in a telecommunication system".

Technical Field

The present invention relates generally to the field of data unit communication, including methods and arrangements in a sending node and methods and arrangements in a receiving node. In particular, it relates to handling status information of data units transmitted from a transmitting node to a receiving node over a radio link.

Background

In today's data unit communication, the data volume is divided into units and the units are transmitted to the intended recipient over an appropriate communication path. This form of data communication is well known and widely used. The sending node may be, for example, a radio base station and the receiving node may be a user equipment such as a mobile phone, a portable computer, a Personal Digital Assistant (PDA) or vice versa. Most of these systems use two-way radio communication, where both nodes transmit and receive data units simultaneously or alternately.

Such data units carry a wide variety of names in the context of different communication systems and communication protocols, such as packets, frames, segments, protocol data units, and so forth. The term "data unit" as used in this specification and claims generally refers to any such division of data volume.

To ensure a complete and correct transmission of data units from a transmission to a receiving protocol peer, a mechanism called ARQ (automatic repeat request) is often used. The ARQ mechanism is typically part of a link layer protocol such as the Medium Access Control (MAC) protocol or the Radio Link Control (RLC) protocol specified for the Universal Mobile Telecommunications System (UMTS) terrestrial radio access network (UTRAN) and for the evolved UTRAN. When using the ARQ mechanism, the receiver of the data unit sends a feedback message to the sender, so that the sender can determine whether the sent data was received correctly or not, and when not, performs retransmission of the data unit appropriately.

The feedback message is a control data unit that is typically sent from a receiving entity of the ARQ protocol to a transmitting peer.

Feedback messages are often referred to as status messages, status reports, status, and the like. They may have different formats depending on the protocol specification. Known implementations of such status messages include one or more references to protocol data units, or portions thereof, received or expected by a receiving protocol entity. These references are generally denoted as positive and/or negative acknowledgements, also referred to as ACKs or NACKs. The acknowledgement provides the transfer protocol entity with information about the successful or unsuccessful reception of one or more data units at the receiving protocol entity. Many known ARQ protocols assign a so-called Sequence Number (SN) to each data unit and use this sequence number as a reference in the status message. Thus, a positive acknowledgement for a data unit with a given sequence number may be referred to as ACK _ SN, while a negative acknowledgement may be denoted as NACK _ SN. Known protocols make extensive use of lists and/or bitmaps in status messages. The acknowledgement may be explicit, i.e. representing the state of a particular data unit, or it may be cumulative, i.e. providing information about the state of a batch of data units.

The radio link control protocol specified for E-UTRAN uses a combination of the two. In the protocol, positive acknowledgements are cumulative, i.e. it positively acknowledges all data units with sequence numbers up to but not including ACK _ SN that are not explicitly negatively acknowledged. In the status message of the protocol, a negative acknowledgement is transmitted by means of the NACK _ SN field for each data unit not received up to below the ACK _ SN.

The control data unit and the data unit, e.g. a status message, may comprise a payload part containing the actual information to be exchanged between peer protocol entities and a header part carrying the information needed for correct decoding of the information. The header portion of the data unit may include, for example, an associated sequence number.

One example of a status message is the LTE RLC status PDU in E-UTRAN disclosed in FIG. 1. In the example of fig. 1, each row includes eight bits, i.e., one octet (octet 1, octet 2, etc.). The data unit includes a payload portion and a header portion. The header portion includes data/control (D/C) and Control PDU Type (CPT) fields. The D/C field indicates whether the data unit is an RLC data PDU or an RLC control PDU, i.e. a status message, carrying valid data from higher layers. The CPT field indicates the type of RLC control PDU. The payload portion following the header portion includes an ACK _ SN field and an extension flag E1. The former carries the sequence number following the highest received data unit sequence number and it accumulatesAll data units in the remainder of the status message up to but not including the sequence number that are not negatively acknowledged are product acknowledged. The E1 flag indicates whether a set of NACK _ SN, E1, and E2 follows. The NACK _ SN field includes the sequence number of the data unit that has been detected by the receiving protocol entity as missing (i.e., negative acknowledgement). The E2 field indicates whether a set of SOstart and SOend follows. The Sostart field indicates, together with the SOend field, the part of the data unit with SN NACK _ SN (Sostart related NACK _ SN) that has been detected as missing at the receiving protocol entity. In this example, the ACK _ SN field and all NACK _ SN fields include 10 bits, and thus can process 2¹⁰1024 serial numbers. To be able to transmit more data units, a wrap-around mechanism may be used to enable reuse of the sequence number space.

According to a conventional description of ARQ mechanisms, the transmitting side of an LTE RLC Acknowledged Mode (AM) RLC entity interprets received status PDUs so that all AMD PDUs up to but not including an Acknowledged Mode Data (AMD) PDU with SN ACK _ SN have been received by its peer AM RLC entity, does not include those AMD PDUs indicated in the status PDU with NACK _ SN, and does not include the part of the status PDU with NACK _ SN, SOstart and SOend indicating an AMD PDU.

Generally, and also in the specific example of LTE RLC, the status message provides complete status information to the ARQ sender, i.e. the status message comprises information about the complete receive window. Thus, the size of the status message increases with the number of negative acknowledgements to be reported by the receiving protocol entity. Due to varying radio channel quality or improper resource assignment, the available radio resources may not be sufficient to transmit a complete status message.

Examples of solutions to this problem are prioritizing status messages to ensure that sufficient resources are available, which means that other transmissions are delayed, or deferring the transmission of status messages until sufficient resources are available, which would result in window stalls or increased transmission delays, which are also disadvantageous. These solutions may lead to situations where the receiving party does not allow any status messages to be sent due to insufficient radio resources.

Disclosure of Invention

It is an object of the present invention to provide a mechanism for improving the handling of status messages transmitted from a data unit receiving node to a data unit sending node.

According to a first aspect of the present invention, the object is achieved by a method in a receiving node for handling status information of data units transmitted from a sending node to the receiving node over a radio link. The receiving node establishes that the plurality of data units transmitted by the sending node are missing. The receiving node sends the reduced status message to the transmitting node over the radio link. The message is reduced such that it comprises negative acknowledgements for a first part of the missing data units and omits negative acknowledgements for the remaining part of the missing data units. The omitted negative acknowledgement for the rest of the missing data units will not be erroneously interpreted by the sending node as correctly received data units.

According to a second aspect of the present invention, the object is achieved by a method in a sending node for handling status information of data transmitted from the sending node to a receiving node over a radio link. The sending node transmits a stream of data units over a radio link to the receiving node. The receiving node correctly receives some of the transmitted data units but misses a number of the transmitted data units. The transmitting node receives a reduced status message from the receiving node over the radio link. The message is reduced such that it comprises negative acknowledgements for a first part of the missing data units and omits negative acknowledgements for the remaining part of the missing data units. The omitted negative acknowledgement for the rest of the missing data units will not be erroneously interpreted by the sending node as correctly received data units.

According to a third aspect of the present invention, the object is achieved by an arrangement in a receiving node for handling status information of data units transmitted from a sending node to the receiving node over a radio link. The receiving node arrangement comprises an establishing unit configured to establish that a plurality of data units transmitted by the sending node are missing and a sending unit configured to send a reduced status message to the sending node over the radio link. The message is reduced such that it comprises negative acknowledgements for a first part of the missing data units and omits negative acknowledgements for the remaining part of the missing data units. The omitted negative acknowledgement for the rest of the missing data units will not be erroneously interpreted by the sending node as correctly received data units.

According to a fourth aspect of the present invention, the object is achieved by an arrangement in a sending node for handling status information of data units transmitted from the sending node to a receiving node over a radio link. The sending node arrangement comprises a sending unit configured to transmit a stream of data units over a radio link to a receiving node. The receiving node correctly receives some of the transmitted data units but misses a number of the transmitted data units. The sending node arrangement further comprises a receiving unit configured to receive the reduced status message from the receiving node over the radio link. The message is reduced such that it comprises negative acknowledgements for a first part of the missing data units and omits negative acknowledgements for the remaining part of the missing data units. The omitted negative acknowledgement for the rest of the missing data units will not be erroneously interpreted by the sending node as correctly received data units.

Since the use of a reduced status report only comprises negative acknowledgements for the first part of the sequence numbers of the missing data units, but omits negative acknowledgements for the sequence numbers of the remaining missing data units, less resources are required for the transmission, which in turn means that the handling of the status report transmitted from the sending node to the receiving node is improved.

Advantages of the invention include that the receiving node interprets the reduced status report correctly and does not move its transmission window forward beyond any unsuccessfully transmitted data units.

Drawings

The invention is described in more detail with reference to the accompanying drawings, which show exemplary embodiments of the invention, and in which:

fig. 1 is a schematic block diagram illustrating a status message according to the prior art.

Fig. 2 is a schematic block diagram illustrating a wireless communication system.

Fig. 3 is a schematic block diagram illustrating an embodiment of a method in a wireless telecommunication system.

Fig. 4 is a flow chart illustrating an embodiment of a method in a receiving node.

Fig. 5 is a schematic block diagram illustrating an embodiment of a receiving node apparatus.

Fig. 6 is a flow chart illustrating an embodiment of a method in a sending node.

Fig. 7 is a schematic block diagram illustrating an embodiment of a sending node apparatus.

Detailed Description

The present invention is defined as a method and apparatus that may be put into practice in the embodiments described below.

Fig. 2 shows a wireless telecommunication system 100 such as E-UTRAN, LTE, WCDMA, EDGE and WLAN. The wireless telecommunications system includes a transmitting node 110 and a receiving node 120. The transmitting node 110 is adapted to transmit data units, such as PDUs, over the radio link 130 to the receiving node 120. The transmitting node 110 may be a base station such as a NodeB, eNodeB or any other network element capable of transmitting data units over a radio link 130 to the receiving node 120. The receiving node 120 may be a wireless terminal such as a mobile phone, a Personal Digital Assistant (PDA), a User Equipment (UE) or any other network node capable of receiving data units from a sending node over a radio link 130. This may also be reversed such that the transmitting node 110 is a wireless terminal and the receiving node 120 is a base station.

To improve throughput, the transmitting node 110 and the receiving node 120 may use a window-based automatic repeat request (ARQ) mechanism. In this case, the sending node 110 includes a transmit window and the receiving node 120 includes a receive window. The window mechanism allows the sending node 110 to continuously send data units while waiting for an acknowledgement. The window can be considered as a buffer.

The sending node 110 may receive a notification about the size of the receive window of the receiving node 120 to enable the sending node 110 to avoid sending more data units than the receiving node 120 can currently handle. To do so, the sending node 110 may maintain a lower window edge that retains the sequence number of the oldest outstanding data unit for which a positive acknowledgement has not been received and an upper window edge that retains the sequence number of the next data unit to be transmitted. It also ensures that the distance between the lower and upper window edges does not exceed the size of the window for the recipient. With this prerequisite, the sending node 110 is able to send data units of the entire sender window before acknowledgement of the first data in the receive window, while still ensuring lossless operation and continuous data transfer. Upon receiving the acknowledgement, the lower edge of the sender window is moved forward so that the first data unit in the window is again the earliest transmitted but not yet acknowledged data unit.

Similarly, the receiving node 120 may maintain a lower window edge that retains the sequence number of the oldest outstanding (i.e., the next expected) data unit and a higher window edge that retains the sequence number following the highest received data unit sequence number. When the data unit with the corresponding sequence number has been received, both the lower and upper window edges are moved forward. If the lower window edge is equal to the upper window edge, there are no data units to be resolved. Otherwise, the data units may have been lost or at least reordered at a lower layer, and the receiving node may send a status message to the sending node 110. Such status messages include a list of sequence numbers of expected but not yet received data units (at least lower window edges and possibly more) and the sequence number of the highest received sequence number (higher window edge) or the following sequence number (depending on the protocol specification).

The following describes some non-limiting and non-exclusive examples of how to process the state information of a data unit transmitted from a sending node 110 to a receiving node 120.

Referring to fig. 3, a transmitting node 110 transmits data units (also referred to as protocol data units, PDUs, or packets) to a receiving node 120. Each unit of the data units to be transmitted is associated with a sequence number 301 before transmission, allowing the receiving node 120 to detect reordering, re-establish the original order of the data units, detect loss of data units, and act as a reference to be used in a status message sent from the receiving node 120 to the sending node 110.

The transmitting node 110 then transmits (302) the stream of data units over the radio link 130 to the receiving node 120. In the example of fig. 3, data units with sequence numbers 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 are transmitted to the receiving node 120. The data units are represented by squares containing associated sequence numbers. In the example of fig. 3, the receiving node 120 correctly receives data units with sequence numbers 1, 5, 9 and 10 as indicated by the straight arrows. As indicated by the curved arrows, the receiving node 120 does not receive or does not correctly receive the data units with sequence numbers 2, 3, 4, 6, 7 and 8.

If the channel resources allow, the receiving node 120 will send a complete status message (not shown in FIG. 3) to the sending node 110. This complete status message may comprise a negative acknowledgement for each of the respective data units with sequence numbers 2, 3, 4, 6, 7 and 8, i.e. it contains, for example, a NACK _ SN field for each missing data unit. The complete status message may also include cumulative negative acknowledgements for sequence numbers 1, 5, 9, and 10, e.g., ACK _ SN field set to 11, indicating that this is the next expected sequence number outside the receive window.

When, for example, the channel quality is too poor for sending a complete status message, as assumed in this example shown in fig. 3, the receiving node 120 may send (304) a reduced status message to the sending node 110(305, 306) to adapt the transmission to the available channel resources on the radio link 130. According to one example, due to limited resources, receiving node 120 includes an appropriate number of negative acknowledgements in the reduced status message, while omitting other negative acknowledgements. In this example, the reduced status message contains only three negative acknowledgements, e.g. represented by three NACK _ SNs set to sequence numbers 2, 3 and 4.

According to state of the art protocols, a cumulative positive acknowledgement (e.g., ACK _ SN) will indicate successful receipt of all data units having sequence numbers up to, but not including, 11, and not including those data units for which an explicit negative acknowledgement is included. A state-of-the-art sending node will thus interpret the reduced status message as if the data units with sequence numbers 6, 7 and 8 were successfully received. Thus, it will not perform a retransmission of those data units, and may even discard the data from its transmission window so that a retransmission cannot be performed later.

To overcome this misinterpretation problem, cumulative positive acknowledgements (e.g., ACK _ SN) may be set differently for reduced status messages than for full status messages. According to a first embodiment, a positive acknowledgement (e.g. ACK _ SN) in the reduced status message is set such that it does not acknowledge any data unit with a sequence number equal to or greater than the sequence number of the omitted data unit in the reduced status message. That is, the reduced status message only includes a positive acknowledgement for data units having sequence numbers equal to or less than the lowest omitted sequence number in the reduced status message.

In this way, the sending node 110 will not erroneously interpret as correctly received data units missing in the window of the receiving node but not reported in the reduced status message. In this example, this means that the reduced status message 305 will only acknowledge data units 1 and 5 positively, but not data units 9 and 10 positively. According to one embodiment of this example, the method sets the ACK _ SN field in the reduced status message to 6, thereby indicating to the sending node 110 successful receipt of all data units up to but not including sequence number 6 and explicitly not including sequence numbers 2, 3 and 4. This means that the sending node 110 receiving (306) the reduced status message treats it as if it were any complete status message and makes the correct status interpretation, i.e. considers that the data units with sequence numbers 1 and 5 were received correctly and retransmits the data units with sequence numbers 2, 3 and 4. The sending node 110 need not be aware that the status message is a reduced status message. However, it is contemplated that the further status message provides information on other data units to be resolved having sequence numbers 6, 7, 8, 9 and 10. One benefit of this embodiment is that it does not require any indicator to indicate that the status message is a reduced status message, i.e. to indicate that it does not contain a negative acknowledgement (e.g. NACK _ SN) for all missing (not received) data units or segments thereof, but only for subsets.

In this embodiment, it may be preferable not to send another status message until receiving node 120 is confident that the status message has been received (e.g., after receiving the expected retransmission). To avoid sending another status message, a status prohibit timer may be applied, which may be started at the time of data transfer and which, when running, prevents the receiving node from sending a status message.

According to a second embodiment, a special identifier included in the status message is used to indicate that this is a reduced status message and not a complete status message. For example, the reduced status message may negatively acknowledge the data unit (e.g., by means of one or more NACK _ SN fields), thereby triggering a retransmission from the sending node 110 to the receiving node 120. However, the identifier may prevent the sending node 110 from interpreting any data units that are not explicitly negatively acknowledged as successful acknowledgements. This means, inter alia, that the sending node 110 is not allowed to advance the lower edge of its receive window and to discard any associated data units. In the above example (not shown), the first reduced status message may contain negative acknowledgements for data units 6, 7 and 8, but is not to be interpreted as positive (cumulative) acknowledgements for data units having sequence numbers 1, 2, 3, 4, 5, 9 and 10.

The appropriate field indicating the special format may be, for example, a CPT field in a currently defined status format according to E-UTRAN. A special code point (code point) may be defined to indicate such a special NACK message.

If the sending node 110 operates according to this embodiment, several reduced status messages can be sent without any harm to the delivery window status, even if the status messages are reordered or lost.

If it is known that the field of acknowledgements should not be interpreted at the sending node 110 (e.g. ACK _ SN), this field may even be omitted, i.e. some special status message format is used for this purpose, which optimizes the size of the status message and will allow the transmission of further negative acknowledgements in a given radio resource.

Alternatively, in this particular example, the cumulative positive acknowledgement may be set to the higher edge of the receive window (ACK _ SN ═ 11 in this example), indicating to the sending node that at least (the segment of) the data unit with sequence number 10 has been received.

The transmitting node 110 often uses a polling flag included in the data unit to request a status message. This is typically done to advance the sender window. In this case, a status message according to the second embodiment that only includes a negative acknowledgement but prevents the sending node 110 from advancing its transmit window is not helpful.

According to a third embodiment, a special identifier included in the status message is used to indicate that this is a reduced status message and not a complete status message. Upon receiving this status message, the sending node 110 may advance the lower edge of the transmission window until the lowest negative acknowledgment data unit. However, it may not advance it beyond the sequence number of the highest negative acknowledgement unless it receives another status message that allows it to do so.

Special means in the receiving node 120, such as a status prohibit timer, must ensure that the receiving node 120 only sends one reduced status message comprising only a subset of negative acknowledgements.

In the above example (not shown in the figure), the reduced status message will contain, in addition to the special identifier, negative acknowledgements for data units with sequence numbers 2, 3 and 4. The sending node 110 can move the lower edge of the window up to sequence number 2, i.e. delete the data unit with sequence number 1 from the transfer window.

According to a fourth embodiment, if several reduced status messages are required to report all missing data units, one special status message type may be defined for a first reduced status message comprising negative acknowledgements closest to the lower window edge, and a second special status message type may be defined for a following reduced status message comprising any other negative acknowledgements.

Only the reduced status message of the first special status message format allows the sending node 110 to advance the lower window edge up to the sequence number of the first negative acknowledgement, whereas the reduced status message of the second special status message format must not be used to advance the transmission window.

In this embodiment, the cumulative positive acknowledgement field is not required and may be deleted from the special status message format in order to save transmission resources.

In the above example (not shown in the figure) the first reduced status message will comprise negative acknowledgements for data units having sequence numbers 2, 3 and 4. The reduced status message of the second special status message format comprises negative acknowledgements for data units having sequence numbers 6, 7 and 8.

Method steps in the receiving node 120 for handling status information of data unit segments "data units" or data units transmitted from the sending node 110 to the receiving node 120 over the radio link 130 according to some embodiments will now be described with reference to the flow chart shown in fig. 4. The method comprises the following steps:

401. the receiving node establishes that a number of data units 2, 3, 4, 6, 7, 8 transmitted by the sending node 110 are missing,

402. the receiving node 120 sends the reduced status message to the sending node 110 over the radio link. The message is reduced such that it comprises negative acknowledgements for the first part 2, 3, 4 of missing data units and omits negative acknowledgements for the remaining parts 6, 7, 8 of missing data units. The omitted negative acknowledgement for the remaining part 6, 7, 8 of the missing data unit will not be erroneously interpreted by the sending node 110 as a correctly received data unit.

In some embodiments, due to limited resources, the negative acknowledgements for the first part 2, 3, 4 of missing data units included in the reduced status message are represented by as many negative acknowledgements as fit into the reduced status message.

The receiving node 120 may use a receive window. In some embodiments, the negative acknowledgement for the first part 2, 3, 4 of missing data units is the missing data unit closest to the lower edge of the receive window.

In some embodiments, the reduced status message positively acknowledges certain data units up to but not including the first missing data unit for which a negative acknowledgement was omitted from the reduced status message.

In one embodiment, the positive acknowledgement is performed by setting the ACK _ SN field to the first missing data unit in the reduced status message for which a negative acknowledgement was omitted to indicate that data units having sequence numbers up to but not including the first missing data unit for which a negative acknowledgement was omitted were acknowledged.

In some embodiments, the reduced status message includes an indication of: correctly received data units 1, 5, 9, 10 will not be acknowledged in the reduced status message, so that only negatively acknowledged data units will be triggered to be retransmitted by the sending node 110. A particular format of the reduced status message may be an indication that the correctly received data unit 1, 5, 9, 10 will not acknowledge in the reduced status message. In some embodiments, the fields acknowledged in the reduced status message are not used for acknowledgement, but instead for additional negative acknowledgements.

403. This is an optional step. In some embodiments, the first special status message type is for a reduced status message comprising a negative acknowledgement for the first part 2, 3, 4 of missing data units closest to the lower edge of the reception window. In this step, the receiving node 120 may send a second reduced-status message to the sending node 110 over the radio link 130 using a second special status message type. The second reduced status message comprises at least one of the omitted negative acknowledgements for the remaining part 6, 7, 8 of the missing data unit.

In order to perform the above-described method for handling status information of data unit segments "data units" or data units transmitted from a sending node 110 to a receiving node 120 over a radio link 130, the receiving node 120 comprises the apparatus 500 shown in fig. 5.

The receiving node arrangement 500 comprises an establishing unit 510 configured to establish that a plurality of data units 2, 3, 4, 6, 7, 8 transmitted by the sending node 110 are missing.

The receiving node arrangement 500 further comprises a sending unit 520 configured to send the reduced status message over the radio link to the sending node 110. The message is reduced such that it comprises negative acknowledgements for the first part 2, 3, 4 of missing data units and omits negative acknowledgements for the remaining parts 6, 7, 8 of missing data units. The omitted negative acknowledgement for the remaining part 6, 7, 8 of the missing data unit will not be erroneously interpreted by the sending node 110 as a correctly received data unit.

Due to limited resources, negative acknowledgements for the first part 2, 3, 4 of missing data units included in the reduced status message may be indicated by as many negative acknowledgements as fit into the reduced status message.

The receiving node 120 may use the receive window and in some embodiments the negative acknowledgement for the first portion 2, 3, 4 of missing data units is the missing data unit closest to the lower edge of the receive window.

The first special status message type may be arranged for a reduced status message comprising negative acknowledgements for the first part 2, 3, 4 of missing data units closest to the lower edge of the reception window. The sending unit 520 may further be configured to send the second reduced-status message to the sending node 110 over the radio link 130 using the second special status message type. The second reduced status message is arranged to comprise at least one of the omitted negative acknowledgements for the remaining part (6, 7, 8) of the missing data unit.

In some embodiments, the reduced status message is arranged to positively acknowledge certain data units up to but not including the first missing data unit for which a negative acknowledgement was omitted from the reduced status message.

In one embodiment, the positive acknowledgement is arranged to be performed by setting the ACK SN field to the first missing data unit in the reduced status message for which a negative acknowledgement was omitted to indicate that data units having sequence numbers up to but not including the first missing data unit for which a negative acknowledgement was omitted were acknowledged.

In some embodiments, the reduced status message is arranged to include an indication that a correctly received data unit 1, 5, 9, 10 will not be acknowledged in the reduced status message, such that a retransmission by the sending node 110 of only negatively acknowledged data units will be triggered. A particular format of the reduced status message may be an indication that the correctly received data unit 1, 5, 9, 10 will not acknowledge in the reduced status message.

In some embodiments, the fields acknowledged in the reduced status message are not used for acknowledgement, but are instead arranged for further negative acknowledgement.

Method steps in the sending node 110 for handling status information of data unit segments "data units" or data units transmitted from the sending node 110 to the receiving node 120 over the radio link 130 according to some embodiments will now be described with reference to the flow chart shown in fig. 6. The method comprises the following steps:

601. the transmitting node 110 transmits the stream of data units or data unit segments 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 to the receiving node 120 over a radio link 130. The receiving unit 120 correctly receives some transmitted data units 1, 5, 9, 10 but misses a number of transmitted data units 2, 3, 4, 6, 7, 8.

602. The sending node 110 then receives the reduced status message from the receiving node 120 over the radio link 130. The message is reduced such that it comprises negative acknowledgements for the first part 2, 3, 4 of missing data units and omits negative acknowledgements for the remaining parts 6, 7, 8 of missing data units. The omitted negative acknowledgement for the remaining part 6, 7, 8 of the missing data unit will not be erroneously interpreted by the sending node 110 as a correctly received data unit.

In some embodiments, the negative acknowledgement for the first part 2, 3, 4 of missing data units is the missing data unit closest to the lower edge of the receiving window in the receiving node 120.

In some embodiments, the reduced status message positively acknowledges certain data units up to but not including the data unit for which the negative acknowledgement was omitted from the reduced status message.

In one embodiment, the positive acknowledgement is performed by setting the ACK SN field to the first missing data unit in the reduced status message for which the negative acknowledgement is omitted. This means that data units having sequence numbers up to but not including the first missing data unit for which a negative acknowledgement is omitted are acknowledged.

The reduced status message may comprise an indication that the correctly received data unit 1, 5, 9, 10 will not be acknowledged in the reduced status message, such that only negatively acknowledged data units will be triggered to be retransmitted. A particular format of the reduced status message may be an indication that the correctly received data unit 1, 5, 9, 10 will not acknowledge in the reduced status message.

In some embodiments, the fields acknowledged in the reduced status message are not used for acknowledgement, but instead for additional negative acknowledgements.

603. This is an optional step. In some embodiments, the transmitting node 110 uses a transmission window. In this step, the sending node 110 moves the lower edge of the transmission window up to the lowest negatively acknowledged data unit.

604. This is also an optional step. In some embodiments, the first special status message type is for a reduced status message comprising a negative acknowledgement for the first part 2, 3, 4 of missing data units closest to the lower edge of the receive window of the receiving node 120. In this step the sending node receives a second reduced status message from the receiving node 120 over the radio link 130, wherein a second special status message type is used. The second reduced status message comprises at least one of the omitted negative acknowledgements for the remaining part 6, 7, 8 of the missing data unit.

In some embodiments, receipt of a reduced status message of a first special status message type allows the sending node 110 to advance lower transmission window edges up to the sequence number of the first negative acknowledgement, whereas a reduced status message of a second special status message type does not allow the transmission window to be advanced.

In order to perform the above-described method for handling status information of data unit segments "data units" or data units transmitted from a sending node 110 to a receiving node 120 over a radio link 130, the sending node 110 comprises the device 700 shown in fig. 7.

The sending node arrangement 700 comprises a sending unit 710 configured to transmit a stream of data units 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 over the radio link 130 to the receiving node 120. The receiving unit 120 correctly receives some transmitted data units 1, 5, 9, 10 but misses a number of transmitted data units 2, 3, 4, 6, 7, 8.

The sending node arrangement 700 further comprises a receiving unit 720 configured to receive the reduced status message from the receiving node 120 over the radio link 130. The message is reduced such that it comprises negative acknowledgements for the first part 2, 3, 4 of missing data units and omits negative acknowledgements for the remaining parts 6, 7, 8 of missing data units. The omitted negative acknowledgement for the remaining part 6, 7, 8 of the missing data unit will not be erroneously interpreted by the sending node 110 as a correctly received data unit.

In some embodiments, due to limited resources, the negative acknowledgements for the first part 2, 3, 4 of missing data units included in the reduced status message are represented by as many negative acknowledgements as fit into the reduced status message. The negative acknowledgement for the first part 2, 3, 4 of missing data units may be the missing data unit closest to the lower edge of the receiving window in the receiving node 120. Note that the sequence number may wrap around at some point in time such that "lower" is no longer relevant. In this document, "lowest sequence number" refers to the sequence number closest to the lower window edge. Furthermore, all comparisons may be performed modulo some reference number.

According to some embodiments, the first special status message type is for a reduced status message comprising a negative acknowledgement for the first part 2, 3, 4 of missing data units closest to the lower edge of the reception window.

The receiving unit 720 may further be configured to receive a second reduced status message from the receiving node 120 over the radio link, wherein a second special status message type is used and the second reduced status message comprises at least one of the omitted negative acknowledgements for the remaining part 6, 7, 8 of the missing data unit.

In some embodiments, receipt of a reduced status message of a first special status message type allows the sending node 110 to advance the lower window edge up to the sequence number of the first negative acknowledgement, whereas a reduced status message of a second special status message type does not allow the forward transmission window.

The reduced status message may comprise an indication that the correctly received data unit 1, 5, 9, 10 will not be acknowledged in the reduced status message, such that only negatively acknowledged data units will be triggered to be retransmitted.

A particular format of the reduced status message may be an indication that the correctly received data unit 1, 5, 9, 10 will not acknowledge in the reduced status message.

The transmitting node 110 may use the transmission window. In some embodiments, the sending node arrangement 700 further comprises a window management unit 730 configured to move the lower edge of the transmission window up to the lowest negatively acknowledged data unit.

The inventive mechanism for handling status information of data units transmitted from a sending node 110 to a receiving node 120 over a radio link 130 may be implemented by one or more processors, such as the processor 530 in the receiving node arrangement 500 shown in fig. 5 or the processor 740 in the sending node arrangement 700 shown in fig. 7, together with computer program code for performing the functions of the present solution. The program code mentioned above may also be provided as a computer program product (for instance in the form of a data carrier carrying computer program code for performing the present solution when being loaded into the sending node 110 or the receiving node 120). One such carrier may be in the form of a CD ROM disc. However, other data carriers, such as memory sticks, are feasible. Furthermore, the computer program code can be provided as pure program code on a server and downloaded to the sending node 110 or the receiving node 120 remotely.

Some examples of the method may be described as a method in a sending node 110 for handling status information of data units transmitted by the sending node 110 to a receiving node 120 over a radio link 130.

The method comprises the step of transmitting a stream of data unit segments or data units, each data unit being associated with a sequence number, over a radio link to the receiving node 120. The method further comprises the step of receiving a reduced status message from the receiving node 120. The reduced status message includes information and an indication that the reduced status message is reduced and therefore will not be interpreted as a complete status message.

In some examples, the reduced status message further includes an indication of how to interpret fields in the reduced status message that includes the information.

The information is incomplete, which relates to which data units of the transport stream of data units and their respective sequence numbers have been received, i.e. acknowledged by the receiving node, and which have not been received, i.e. not acknowledged by the receiving node.

Some further examples of the method may be described as a method in a receiving node 120 for handling status information of data units transmitted by a sending node 110 to the receiving node 120 over a radio link 130.

The method comprises the step of receiving a data unit segment or a stream of data units from a transmitting node over a radio link, each data unit being associated with a sequence number. The method further comprises the step of sending the reduced status message to the sending node. In the reduced status message the acknowledgement of the sequence number associated with the data unit (e.g. ACK _ SN) is set such that it does not acknowledge any data unit with a corresponding no acknowledgement (e.g. NACK _ SN) of the associated sequence number equal to or greater than the sequence number associated with the data unit omitted in the reduced status message.

When the word "comprising" or "including … …" is used, it is to be construed as non-limiting, i.e., meaning "consisting of at least …".

The invention is not limited to the preferred embodiments described above. Various alternatives, modifications, and equivalents may be used. Accordingly, the above-described embodiments should not be taken as limiting the scope of the invention, which is defined by the appended claims.

Claims

1. A method in a receiving node (120) for processing status information of data units transmitted from a sending node (110) to the receiving node (120) over a radio link (130), the method comprising the steps of:

establishing (401) that a number of data units (2, 3, 4, 6, 7, 8) transmitted by the sending node (110) are missing,

sending (402) a reduced status message to the sending node (110) over the radio link, such that the reduced status message comprises a negative acknowledgement for a first part (2, 3, 4) of missing data units and omits negative acknowledgements for the remaining part (6, 7, 8) of the missing data units,

wherein the reduced status message positively acknowledges data units (1, 5) up to but not including a first missing data unit for which a negative acknowledgement is omitted in the reduced status message such that the omitted negative acknowledgements for the remaining part (6, 7, 8) of the missing data units will not be erroneously interpreted by the sending node (110) as correctly received data units,

wherein the positive acknowledgement is performed by setting the ACK _ SN field to the first missing data unit for which the negative acknowledgement was omitted in the reduced status message such that data units having sequence numbers up to but not including the first missing data unit for which the negative acknowledgement was omitted are acknowledged, and

wherein the ACK SN field is part of the reduced status message.

2. The method according to claim 1, wherein a negative acknowledgement for the first part (2, 3, 4) of missing data units comprised in the reduced status message is represented by up to a negative acknowledgement fitting into the reduced status message due to limited resources.

3. The method according to any of claims 1-2, wherein the receiving node uses a receiving window, and wherein the first part (2, 3, 4) of the missing data units is the missing data unit closest to the lower edge of the receiving window.

4. A method according to claim 3, wherein a first special status message type is used for a reduced status message comprising a negative acknowledgement for the first part (2, 3, 4) of missing data units closest to a lower edge of the reception window, the method comprising the further steps of:

sending (403) a second reduced status message to the sending node (110) over the radio link (130) using a second special status message type, the second reduced status message comprising at least one of the omitted negative acknowledgements for the remaining part (6, 7, 8) of the missing data unit.

5. The method according to claim 1, wherein the reduced status message comprises an indication that a correctly received data unit (1, 5, 9, 10) will not be acknowledged in the reduced status message, such that a retransmission by the sending node (110) of only negatively acknowledged data units will be triggered.

6. The method according to claim 5, wherein a certain special format of the reduced status message is the indication that a correctly received data unit (1, 5, 9, 10) will not be acknowledged in the reduced status message.

7. The method of claim 6, wherein the fields acknowledged in the reduced status message are not used for acknowledgement, but instead are used for additional negative acknowledgements.

8. A method in a sending node (110) for handling status information of data units transmitted from the sending node (110) to a receiving node (120) over a radio link (130), the method comprising the steps of:

transmitting (601) a stream of data units (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) over the radio link (130) to the receiving node (120), wherein the receiving node (120) correctly receives some (1, 5, 9, 10) of the transmitted data units but misses a number (2, 3, 4, 6, 7, 8) of the transmitted data units, and

receiving (602) a reduced status message from the receiving node (120) over the radio link (130), the message being reduced such that it comprises a negative acknowledgement for a first part (2, 3, 4) of missing data units and omits negative acknowledgements for the remaining part (6, 7, 8) of the missing data units,

wherein the ACK SN field is part of the reduced status message.

9. The method according to claim 8, wherein a negative acknowledgement for the first part (2, 3, 4) of missing data units comprised in the reduced status message is represented by up to a negative acknowledgement fitting into the reduced status message due to limited resources.

10. The method according to any of claims 8-9, wherein the receiving node uses a receiving window and wherein the first part (2, 3, 4) of the missing data units is the missing data unit closest to the lower edge of the receiving window.

11. Method according to claim 10, wherein a first special status message type is used for a reduced status message comprising a negative acknowledgement for the first part (2, 3, 4) of missing data units closest to a lower edge of the reception window, the method comprising the further steps of:

receiving (604) a second reduced status message from the receiving node (120) over the radio link, wherein a second special status message type is used, the second reduced status message comprising at least one of the omitted negative acknowledgements for the remaining part (6, 7, 8) of the missing data unit.

12. The method of claim 11, wherein the reception of the reduced status message of the first special status message type allows the sending node (110) to advance a lower transmission window edge up to a sequence number of a first negative acknowledgement, while the reduced status message of the second special status message type does not allow the advance of the transmission window.

13. The method of claim 8, wherein the reduced status message comprises an indication that a correctly received data unit (1, 5, 9, 10) will not be acknowledged in the reduced status message, such that only negatively acknowledged data units will be triggered to be retransmitted.

14. The method according to claim 13, wherein a certain special format of the reduced status message is the indication that a correctly received data unit (1, 5, 9, 10) will not be acknowledged in the reduced status message.

15. The method of claim 14, wherein the fields acknowledged in the reduced status message are not used for acknowledgement, but instead are used for additional negative acknowledgements.

16. The method of claim 8, wherein the sending node (110) uses a transmission window, comprising the further steps of:

moving the lower edge of the transmission window up to the lowest negatively acknowledged data unit.

17. An arrangement (500) in a receiving node (120) for handling status information of data units transmitted from a sending node (110) to the receiving node (120) over a radio link (130), the arrangement (500) comprising:

an establishing unit (510) configured to establish that a plurality of data units (2, 3, 4, 6, 7, 8) transmitted by the sending node (110) are missing, and

a sending unit (520) configured to send a reduced status message to the sending node (110) over the radio link such that the reduced status message comprises a negative acknowledgement for a first part (2, 3, 4) of missing data units and omits a negative acknowledgement for the remaining part (6, 7, 8) of the missing data units,

wherein the ACK SN field is part of the reduced status message.

18. An arrangement (700) in a sending node (110) for handling status information of data units transmitted from the sending node (110) over a radio link (130) to a receiving node (120), the arrangement (700) comprising:

a sending unit (710) configured to transmit a stream of data units (1, 2, 3, 4, 5, 6, 7, 8, 9, 10) over the radio link (130) to the receiving node (120), wherein the receiving node (120) correctly receives some (1, 5, 9, 10) of the transmitted data units but misses a number (2, 3, 4, 6, 7, 8) of the transmitted data units, and

a receiving unit (720) configured to receive a reduced status message from the receiving node (120) over the radio link (130) such that the reduced status message comprises a negative acknowledgement for a first part (2, 3, 4) of missing data units and omits negative acknowledgements for the remaining part (6, 7, 8) of the missing data units,

wherein the ACK SN field is part of the reduced status message.