HK1149128B - Improved uplink scheduling in a cellular system - Google Patents

Description

Improved uplink scheduling in cellular systems

Technical Field

The present invention discloses a method and apparatus for use in a wireless cellular access system, wherein users in a cell in the system receive transmit power control commands on a control channel.

Background

In some cellular access systems, such as the LTE system (long term evolution), data in both the uplink and downlink (i.e., from and to a user, respectively) is transmitted between multiple users on a channel that is shared in both frequency and time. Examples of so-called physical channels shared in LTE systems are PDSCH and PUSCH, i.e. physical downlink shared channel and physical uplink shared channel.

Due to the principle of shared channels, control signaling is necessary at least in the downlink, i.e. for users in a cell of an LTE system.

One of the downlink control channels in the LTE system is a PDCCH channel (physical downlink control channel). The PDCCH is used for transmitting downlink control information DCI, such as, for example, scheduling decisions, transmit power control commands and other specific control signaling. In more detail, the downlink control information that may be transmitted on the PDCCH includes:

downlink scheduling assignment, including resource indication for PDSCH transport format, hybrid ARQ information, transport block size, MIMO related control information (if applicable), and PUCCH (physical uplink control channel) transmit power control commands.

Uplink scheduling grant including resource indication for PUSCH (physical uplink shared channel), transport format, hybrid ARQ related information, and PUSCH transmission power control command.

The transmission power control command of the user terminal group is complementary to the transmission power control command "piggybacked" together with the scheduling decision.

The PDCCH can use various formats for DCI. However, regardless of which DCI format is used, the PDCCH will include a so-called RNTI (radio network temporary identifier), which is the identity for the PDCCH and the user terminal to which the associated DCI is intended. To enable the use of RNTIs, each user terminal in a cell is assigned its own RNTI, a so-called C-RNTI, which may be used when making downlink transmissions to that user terminal.

In each so-called subframe, the user terminal monitors the PDCCH in the cell. When detecting its own identity, C-RNTI, in one of the PDCCHs, the user terminal declares that the PDCCH contents are valid and follows the contents of the PDCCH.

In the case where the PDCCH content is downlink scheduling, the user terminal attempts to decode the associated data transmission on the PDSCH resources indicated by the PDCCH. The result of the decoding attempt (i.e. positive acknowledgement ACK or negative acknowledgement NACK) is transmitted by the user terminal in the uplink.

Based on the ACK or NACK, a decision can be made as to whether to transmit new data (i.e. ACK received) or to retransmit the previous data (i.e. NACK received, indicating that the reception of the user terminal was erroneous). The ACK/NAK is typically transmitted on an uplink control channel called PUCCH (physical uplink control channel). Since the reception of ACK/NACK is important for the correct operation of the system, it is crucial to adjust the transmit output power of the PUCCH so that the received power is high enough to correctly receive the ACK/NACK, but not so high as to create unnecessary interference in the system.

In order to control the PUCCH output power of the user terminals in the cell, the PUCCH includes two bits representing the allowed transmit power of the PUCCH for the user terminals. The terminal increases or decreases the PUCCH transmission power using the information provided in the two bits. In this way, the network can ensure that the terminal uses an appropriate level of transmit power for the PUCCH.

As mentioned above, the C-RNTI is a unique identity of the terminal used for downlink addressing purposes. However, in addition to having a C-RNTI for the purpose of downlink "unicast" data, each terminal can also be allocated one or several so-called "group RNTIs". The group RNTI is an identity that is common to multiple terminals in a cell and is therefore used to convey downlink information related to more than one terminal.

One example of such information is system parameters that are necessary to enable all terminals in a cell to access the system. Obviously, this type of information should be transmitted using an RNTI known to all terminals in the cell. Another example of "multicast" information is paging using a paging channel PCH, wherein so-called paging groups are defined, each of which is assigned a common group paging RNTI.

A third example of downlink multicast information is the so-called random access response using random access RNTI. Also in this case, a plurality of terminals can be addressed by the group RNTI.

Thus, as explained above, the user terminal is required to be able to receive both unicast data addressed via the terminal-specific C-RNTI and common data, e.g. system information, addressed via different common (non-terminal-specific) RNTIs.

Obviously, when several terminals are addressed at the same time, they should not transmit any ACK/NACK on the PUCCH as a group, since the network may not be able to tell from which terminal each ACK/NACK originated. For this reason, in LTE systems, the current specifications specify that no ACK/NACK response should be sent in such cases. Since no ACK/NACK is transmitted, there is no need for the terminal to adjust the PUCCH transmission power in such cases.

Disclosure of Invention

The current LTE specifications specify that the terminal will always update its transmit power when receiving PDCCH orders. Thus, when multiple terminals are addressed using the group RNTI, according to the current solution all terminals in the group need to update their PUCCH transmit power according to power control commands in the PDCCH, which results in undesirable and inaccurate PUCCH power control results in the terminals in the group.

It is therefore an object of the present invention to mitigate or reduce the disadvantages of downlink group transmission, in particular with regard to the adjustment of uplink transmission power, and to provide an improved method and terminal for a wireless cellular access system.

This object is achieved by the present invention in that it discloses a method for use in a wireless cellular access system, according to which method users in a cell in the system receive transmit power control commands on a control channel.

According to the method, the transmit power control commands received by the users include identifiers for the intended user or users; the identifier is an identifier for a specific user or for a group of users and according to the method of the invention, a user disregards a transmission power control command if the identifier included in the transmission power control command is for the group of users in which the user is included.

Thus, the above-mentioned disadvantages can be reduced or even completely eliminated, because according to the invention a user will ignore a transmission power control command if it is addressed to more than one user by means of its identifier.

In one embodiment of the invention, the transmission power control command also includes format information, and the user will also ignore the transmission power control command if the format information in the transmission power control command is not one of a predefined set of at least one format.

The invention also discloses a transceiver for use as a user terminal in a system in which the invention is applied.

Drawings

The invention will be described in more detail below with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic sketch of a system in which the invention can be applied, an

FIGS. 2 and 3 show schematic flow diagrams of the method of the invention, and

fig. 4 shows a block diagram of a transceiver of the present invention.

Detailed Description

The invention will be described below using terminology from the LTE system (long term evolution). It should be noted, however, that this is done to facilitate the reader's understanding of the invention and is not intended to limit the scope of protection sought.

Fig. 1 shows a schematic diagram of a system 100 in which the present invention can be applied. In the system 100 there are a plurality of so-called cells 110, each cell being arranged to accommodate a plurality of user terminals "UE", one of which is shown as 120 by way of example. The cell 110 will also be associated with a control node 130, a so-called eNodeB. One of the functions an eNodeB has is to control traffic to and from UEs in a cell, and to issue certain control commands to UEs in a cell in order to coordinate their behavior.

The transmission from the UE to the eNodeB is known as uplink transmission UL, and the transmission from the eNodeB to the UE is known as downlink transmission DL.

As explained earlier herein, it is an object of the present invention to improve the way in which a terminal responds to transmit power control commands received from an eNodeB on a downlink control channel. The manner in which this is achieved will now be explained with reference to the method 200 shown in the flow charts of fig. 2 and 3. Optional or alternative steps are shown in fig. 2 and 3 by dashed lines.

Method 200 is for use in a wireless cellular access system, such as system 100 in fig. 1, and according to method 200, users, such as users 120 in cell 110 in the system, receive one or more transmit power control commands on a control channel, as shown in step 205 of fig. 2.

As shown in step 225 of fig. 2, the transmit power control command includes an identifier for the intended user or users, which can be an identifier for a particular user as shown in step 230 or an identifier for a group of users as shown in step 235.

According to the inventive method, a user disregards a transmission power control command if the identifier of the transmission power control command is for a user group in which said user is included, as shown in step 240.

As shown in step 215, in one embodiment, the transmit power control command includes format information, and the user also disregards the transmit power control command if the format information in the transmit power control command is not one of a predefined set of at least one format. This will be further elucidated together with an explanation of how the invention is applied in an LTE system.

As shown in step 220, in one embodiment, the method of the present invention can be applied to an LTE system. In such a case, i.e. an "LTE embodiment", then the control channel is suitably an LTE PDCCH (physical downlink control channel), as shown in step 245 in fig. 3, and the identifier for the intended user or users is an RNTI or C-RNTI, a (cell) radio network temporary identifier, as shown in step 250.

In LTE, PDCCH orders can be in a different format known as DCI (downlink control information format); examples of LTE DCI formats are those referred to as 1A, 1, 2, 3, or 3A, for example. As mentioned in connection with step 215, the user can also use the format to decide to ignore the transmit power control command (if the ID is also used for the user group). In the LTE application of the present invention, it is therefore the DCI format that is used for this purpose.

Some examples of this principle are as follows, the power control commands included in the PDCCH for the PUCCH shown as δ_PUCCH：

From Ocular with DCI Format 1A/1/2 and the associated RNTI is the group RNδ of PDCCH of TI_PUCCHAre ignored.

Another way to describe this in "pseudo code" is as follows:

omicron decodes PDCCH with DCI format 1A/1/2 and the corresponding detected RNTI is equal to the UE's C-RNTI, then the UE will use δ provided in that PDCCH_PUCCH，

else

Omicron decodes the PDCCH with DCI format 3/3a, then the UE will use δ provided in that PDCCH_PUCCH。

else

UE will set δ_PUCCH＝0dB。

As we have seen in the example, the transmit power control commands for a user are preferably for a certain uplink channel, which in this example is the so-called PUCCH (physical uplink control channel).

Fig. 4 shows a schematic block diagram of an inventive user terminal 400. As shown in fig. 4, user terminal 400 will include an antenna, shown as block 410, and will also include a receive part 420 and a transmit part 430. In addition, the user terminal 400 further includes a control section 440 such as a microprocessor and a memory 450.

Since these main functional blocks or components of the user terminal 400 are now already introduced by their reference numerals, they will now be referred to simply by their reference numerals, e.g. "component 410" instead of "antenna 410".

As has been shown from above, the user terminal 400 is intended for use in a wireless cellular access system and is equipped with means 410 and 420 for receiving transmit power control commands on a control channel and uses means 440 and 450 for detecting an identifier for the intended user or users in those transmit power control commands.

The identifier referred to here is an identifier for a specific user or for a specific group of users and if the identifier of the transmission power control command is for the group of users in which the user terminal itself is included, the user terminal 400 uses the components 440 and 450 to ignore the transmission power control command.

In one embodiment, the user terminal 400 further uses the means 440 and 450 to detect format information in the transmission power control command, and uses the means 440 and 450 to disregard the transmission power control command also when the transmission power control command is not one of a predefined set of at least one format.

In one embodiment, the user terminal 400 is a user terminal for an LTE system (long term evolution). In such embodiments, the control channel is an LTE PDCCH (physical downlink control channel) and the identifier can be an RNTI (radio network temporary identifier) or C-RNTI (cell radio network temporary identifier).

Furthermore, in one "LTE" embodiment of the user terminal 400, the identifiers are in DCI formats such that one DCI format is used to address individual users and another is used to address multiple users. In such a case, the format information can be LTE DCI (downlink control information).

The invention is not limited to the examples of embodiment described above and shown in the drawings, but may be varied freely within the scope of the appended claims.

Claims (14)

1. A method (200) for use in a wireless cellular access system (100), according to which method users (120) in a cell (110) in the system (100) receive transmission power control commands (205) on a control channel, the transmission power control commands comprising (225) an identifier for the intended user or users, the identifier being an identifier for a specific user (230) or for a group of users (235), the method being characterized in that a transmission power control command is disregarded (240) by a user if its identifier is for a group of users in which the user is included.

2. The method (200) of claim 1, according to which the transmission power control command comprises (215) format information, and if the format information in the transmission power control command is not one of a predefined set of at least one format, the user also disregards the transmission power control command.

3. The method (200) of claim 1 or 2, applied (220) to a long term evolution, LTE, system.

4. The method (200) of claim 3, according to which (245) the control channel is the LTE physical Downlink control channel, PDCCH.

5. The method (200) of claim 1 or 2, according to which (250) the identifier is a radio network temporary identifier, RNTI, or a cell radio network temporary identifier, C-RNTI.

6. The method (200) of claim 1 or 2, according to which (260) the identifiers are DCI formats, such that one DCI format is used to address individual users and another is used to address multiple users.

7. The method (200) of claim 2, wherein the format information is (255) LTE downlink control information, DCI.

8. A user terminal (400) for use in a wireless cellular access system (100), equipped with means (410, 420) for receiving transmission power control commands on a control channel and with means (440, 450) for detecting in said transmission power control commands an identifier for an intended user or users, said identifier being an identifier for a specific user or for a group of users, said user terminal being characterized in that it is also equipped with means (400, 450) for disregarding a transmission power control command if the identifier of the transmission power control command is for a group of users in which the user terminal itself is included.

9. The user terminal (400) of claim 8, being equipped with means (440, 450) for detecting format information in said transmission power control command and means (440, 450) for disregarding the transmission power control command also when the format information in the transmission power control command is not one of a predefined set of at least one format.

10. The user terminal (400) of claim 8 or 9, being a user terminal for a long term evolution, LTE, system.

11. The user terminal (400) according to claim 10, wherein the control channel is an LTE physical downlink control channel, PDCCH.

12. The user terminal (400) according to claim 8 or 9, wherein the identifier is a radio network temporary identifier, RNTI, or a cell radio network temporary identifier, C-RNTI.

13. The user terminal (400) of claim 8 or 9, in which the identifier is a DCI format, such that one DCI format is used to address individual users and another is used to address multiple users.

14. The user equipment according to claim 9, wherein said format information is LTE downlink control information, DCI.