GB2416963A - A telecommunication method for controlling a data uplink channel - Google Patents

Abstract

A telecommunications method for controlling a data uplink channel from a terminal in a mobile telecommunications system, comprising sending a single RRC message indicating that the terminal should add an additional radio link, and also that the terminal should change a parameter (e.g. TTI length) of the data uplink channel at a predetermined activation time. This may correspond to the soft handover time. In other embodiments the message may be an RRC message specifying an additional radio link, and a layer 1 or layer 2 message specifying that the parameter should be changed.

Description

Telecommunications Methods and Apparatus This invention relates to methods

and apparatus for controlling the uplink in a mobile telecommunications system, such as a UMTS system currently being developed by the 3GPP group. Such a system is described in 3GPP TS 25.401 v 5.7.0 (Dee 2003) (Technical Specification Group Radio Access Network UTRAN overall description (release 5)), available from the Third Generation Partnership Project (3GPP_), at 650 Route des Lucioles, Sophia Antipolis, Valbonne, France, or their website at www.3gpp.org (as are the other 3GPP documents referred to herein).

Data communications are often asymmetrical, requiring greater bandwidth on the downlink, so that the uplink bandwidth is often smaller than the downlink. There is currently an uplink data channel (DCH). It is currently proposed to add an enhanced uplink, to make it easier to play video games, for example. This is known as the EUDCH (Enhanced Uplink Data Channel) or E-DCH (Enhanced Data Channel). It is discussed in 3GPP TR 25.896 v 2.0.0 (Mar 2004), available from the Third Generation Partnership Project (3GPP_) 650 Route des Lucioles, Sophia Antipolis, Valbonne, France, or their website at www.3gpp.org A parameter of the EUDCH is the TTI (Transmission Time Interval).

This is the size of the interval allowed to each User Equipment (UK) - in other words, user terminal such as a mobile terminal (mobile phone or PDA) - to transmit data in a repeating cycle the length of which depends on the number of such channels. The TTI considerations for the EUDCH are discussed in 3GPP TR 25.896 v 2.0.0 (Mar 2004) Section 8.2.

There is a strong desire to re-use the TTI length of 10mS currently used for the DCH on the EUDCH. This is also long enough to allow data to be interleaved over the interval, giving greater error protection. The coding and repeat request (Hybrid ARQ or HARQ) handling of data on the EUDCH is generally described in 3GPP TR 25.088 v 0.0.3 (July 2004). On the other hand, it would be desirable to use a shorter TTI length to reduce transmission delays, so a period of 2mS has also been proposed.

Some or all UEs may therefore support both TTIs (as described in 3GPP TS 25.309 v 2.0, June 2006). Where UEs support both, it may be desirable to use the shorter TTI during communications except during soft handover, at which time the radio links to each cell may be less than optimal and so it may be preferable to use the longer interleaving period which is possible through using the longer TTI period. However, this issue has not been discussed in the open literature.

An objective of the present invention is to provide telecommunications methods and apparatus for a system in which the TTI and/or other uplink data channel parameters can be changed during a session. Particularly, but not exclusively, an object is to provide a means of changing TTI during soft handover (i.e. the period during handover whilst the HE is in communication with two radio stations, and therefore adds a further RL (Radio Link).

In RRC, RL reconfigurations are performed by one of the defined RRC reconfiguration procedures. These procedures can be used e.g. update the physical channel, transport channel or Radio Bearer configuration of the current radio connection.

The straightforward way of changing the TTI and/or other uplink data channel parameters would be to use and extend the current RRC (Radio Resource Control) signalling, as shown in Figure 2. Under this method, a new RL is first set up by signalling an ACTIVE SET UPDATE message to the UE to start using the new channel. An acknowledgement is sent back from the UK. A reconfiguration message is then sent to the UE to reconfigure the TTI time, specifying the future time point at which the UE and system will start to use the new TTI. In principle, of course, it would also be possible to perform these steps in reverse but this is less desirable since it would add a delay before communications on the new RL could start. The same two-stage signalling procedure is applied at the network end, between the control station (RNC) currently controlling a cell and auxiliary RNCs (DRNCs) and radio stations (Node-Be or base stations). In Figure 2, "XXX" is used to denote the different possible reconfiguration messages, e.g. "RADIO BEARER RECONFIGURATION" or "PHYSICAL CHANNEL RECONFIGURATION". The activation time for the reconfiguration procedure is denoted as "CFNy" because in RRC signalling normally time instances are indicated by referring to a so called "Connection Frame Number".

The present invention in various aspects is defined in the claims.

Other objects, aspects, and embodiments will be apparent from the description and drawings hereafter.

Embodiments of the invention will now be illustrated, by way of 5example only, with reference to the accompanying drawings in which: Figure 1 shows the structure of a known third generation mobile telecommunications network to which the invention is applicable; Figure 2 is a signal flow diagram indicating the most straightforward method of changing enhanced data channel parameters at soft handover; 10Figure 3a is a flow diagram showing the process formed within the network in a first embodiment to the invention to change enhanced data channel parameters at the soft handover times; Figure 3b is a corresponding flow diagram showing the operation of the embodiment of the user equipment; 15Figure 4 is a signal flow diagram illustrating the processes performed in the first embodiment and corresponding to Figure 1; Figures is a signal flow diagram corresponding to Figured and illustrating the processes performed in a second embodiment to the invention; Figured is a signal flow diagram corresponding to Figure 3 and 20illustrating the processes performed in a third embodiment to the invention; and Figure 7 (comprising figures 7a and 7b) corresponds to figure 3 and describes the processes performed during the third embodiment; Figure 8 is a signal flow diagram illustrating the signalling within the network in the first embodiment; Figure 9 is a signal flow diagram corresponding to figure 7 and illustrating the signalling within the network in a seventh embodiment; Figure 10 is a signal flow diagram corresponding to figured and illustrating the signalling within the network in a eighth embodiment.

First Embodiment Referring to Figure 2, a communication system such as a mobile telephony system comprises a plurality of user equipment (UK) such as mobile terminals 300a, 300b, in radio communication with a base station 100 referred to hereafter as a Node-B, provided within a cell.

Figure 1 is a diagram schematically illustrating a structure of a conventional Wideband Code Division Multiple Access (WCDMA) communication system. The WCDMA communication system comprises a core network (CN) 100, a plurality of radio network subsystems (RNSs) 110 and 120, and a user equipment (UK) 130. Each of the RNSs 110 and 120 comprise a radio network controller (RNC) and a plurality of Node-Bs (each handling a cell). More specifically, the RNS 1 10 comprises an RNC 111 and a plurality of NodeBs 113 and 115, and the RNS 120 comprises an RNC 112 and a plurality of Node-Bs 114 and 116. The RNCs are classified as either a Serving RNC (SRNC), a Drift RNC (DRNC), or a Controlling RNC (CRNC), according to their functions. The SRNC and the DRNC are classified according to their functions for each UK. An RNC that manages information on a UE and controls data exchange with a core network is an SRNC, and when data of a UE is transmitted to the SRNC, not directly but via a specific RNC, the specific RNC is called a DRNC of the UK.

The CRNC represents an RNC controlling each of Node-Bs. For example, in FIG. 1, if the RNC 111 manages information on the UE 130, it serves as an SRNC of the UE 130, and if data of the UE 130 is transmitted via the RNC 112, due to movement of the UE 130, the RNC 112 becomes a DRNC of the UE 130. The RNC 111 controlling the Node-B 113 becomes a CRNC of the Node-B 1 13.

The core network includes, for example, an Internet Protocol (IP) backbone network or other packet network, and/or a circuit switched (standard telephony) network. It will not further be discussed since it is of conventional type.

Each Node-B comprises a radio transmitter apparatus and a radio receiver apparatus, operating under the control of a control system comprising one or more programmable computers, so that it can send data to and receive data from the UEs on the data downlink and data uplink respectively, and to and from the RNC. It can also control some aspects of the communications links within its cell, and to this end it can send signalling data to and receive signalling data from the UEs on the signal downlink and signal uplink respectively.

Each UE comprises a radio transmitter apparatus and a radio receiver apparatus, operating under the control of a control circuit, together with a battery and/or other power supply, a user interface including input and output devices, and an output port for connection to other devices (such as a computer).

As these aspects of the equipment are conventional, well known to the reader, and unnecessary for an understanding of the present invention, further details are omitted herein. In the following embodiment, the programs operating the UK, RNC and Node-B are novel, but in other respects, the embodiments utilise conventional hardware meeting the abovedescribed

3GPP specifications.

Operation of the First Embodiment In this embodiment, referring to Figures 3 and 4, in step 1002, when the UE moves into a transition area within the coverage of two cells, the network decides to initiate a soft handover procedure, and therefore to allocate an additional radio link to the active set currently used by the UK. In step 104, a signal is sent from the Node-B to the UK. The signal is a modified version of the ACTIVE SET UPDATE REQUEST (ASU) message currently

defined in 3G network specifications.

The modified ASU message includes an IE "Activation time", indicating the time at which a new RL (Radio Link) is added or removed. It also includes an identification of the new RL. In this embodiment, it further includes an instruction to modify the EUDCH configuration. Specifically, in this embodiment, the instruction includes a portion specifying a switch (from a 2mS TTI normally used) to a 1 OmS TTI.

The UE 130 receives the message (step 1012). It then signals acceptance back with an ACTIVE SET UPDATE COMPLETE message (step 1016). If the network does not timely receive this reply message (step 1006), the procedure is aborted (and this is signalled to the UK).

At the occurrence of the appointed time (steps 1008, 1018), the UE adds the new radio link to the active set (step 1019) and both the UE (step 1020) and the Node-B (step 1010) switch to a lOmS TTI frame for the EUDCH, and communicate thereafter using that parameter.

Thus, in this embodiment, in the case when the UE moves in soft handover, the UE is communicating with several cells and the radio conditions to the different cells might not be optimal (since the UE is typically at the edges of cells), the UE can benefit from the greater error correction capacity available due to the larger interleaving period, and can benefit also from the reduced control signalling overhead. Handover can then take place if necessary.

Second Embodiment The above first embodiment might be considered more appropriate in case the EUDCH parameters that need to be updated only concern a few, mainly physical layer, parameters (such as just the TTI).

This second embodiment could be considered more appropriate when the number of EUDCH parameters that needs to be updated is larger. The system in this embodiment pre-defines 2 or more complete EUDCH configurations, which are stored at the UE and the Node-B, and then switches between the already configured configurations with the ASU message, as shown in Figure 5. In steps 1010 and 1020, the UE and Node-B therefore change multiple parameters at once. In other respects, Figure 3 remains applicable to the operation of this embodiment. This enables more efficient/faster RRC signalling.

In addition, this approach could enable a change in higher layer (e.g. transport channel level) configuration without explicitly having to include transport channel level information in the ASU message.

Third Embodiment The use in the above embodiments of the "Activation time" with another value than "now" will delay the RL addition since the activation time has to be set to a safe value so that UE and involved Node-B's are all aware of it. Using an activation time other than "now" is delay-costly in the sense that the activation time has to be set sufficiently in the future, so that the network knows for sure that the UE has received the ACTIVE SET UPDATE REQUEST message before the UE activation time will take place. Since a first transmission of the ACTIVE SET UPDATE message might be lost and lower layers have to retransmit the same message again after some time, the setting of the IE "Activation time" has to be set sufficiently in the future to take into account these retransmissions.

This problem can be overcome, as in this embodiment, by including a separate activation time in the ACTIVE SET UPDATE for executing the EUDCH related changes (e.g. "EUDCH modification time"). With this approach, the UE can still add the RL as soon as possible ("now"), and switch to the new EUDCH configuration at the separately indicated activation time.

An example sequence is shown Figure 6. Referring to Figures 7a and 7b, by comparison with Figures 3a and 3b (in which similarly numbered steps are the same and will not be further discussed), it is seen that after step 1012, the UE immediately adds the new RL in step 1014, rather than adding it at a later time in step 1019 as in the first and second embodiments. Naturally, in this embodiment, the EUDCH parameter could be other than the TTI, and (as in the second embodiment) the message could include an instruction to switch to a new predetermined parameter set rather than to change one parameter value.

Thus, this embodiment allows faster handover and more reliable communications by allowing immediate use of the new radio link.

Fourth Embodiment In this embodiment, the same process as the third embodiment is performed, except that instead of using a message with an explicitly signalled "EUDCH modification time", the Node-B and UE both store a predetermined rule which enables the UE to derive an activation time for the EUDCH modifications. As an example rule, this could be indicated as "the next CFN after the receipt of the ASU message for which CFNmod(x) = 0". Choosing "x" large enough guarantees that the UE will receive the ASU before the activation time of the EUDCH modification. Thus, in this embodiment the length of the message can be reduced, by use of an implicit activation time.

This embodiment therefore allows quick RL addition, but still provides efficient RRC handling with I procedure.

Processes performed in the Network In the above embodiments, the decision to initiate a change in EUDCH parameters is taken in the network, and may typically be taken at the RNC and signalled to the Node-B and the UK. In this case, some signalling on the lute and lur interfaces is required. Figure 8 illustrates the process. The Serving RNC (the SRNC) makes the decision, and signals to the Drift RNC (DRNC), if any, on the lur interface and to its Node-Bs on the lute interface.

The DRNC then sends an equivalent message on to the Node-B, which then performs as in the above-described embodiments.

The message from the SRNC corresponds to one which is conventionally used for extending the active set by changing the Radio Links (RL SETUP, RL ADDITION or RL DELETION), but extended with the option of changing the EUDCH configuration. In Figure 8, a separate activation time for executing the change of the EUDCH configuration is shown, as in the third embodiment above, but the same principles are applicable to all the earlier embodiments.

Basis of RNC decision to change EUDCH parameters The decision to be made by the RNC will typically be based on signal quality parameters, and these may be assessed by: The RNC, if data is forwarded to it; The Node-B; or The UK.

Fifth Embodiment In this embodiment, data is sent to the RNC so that it is made sufficiently aware of the performance achieved over the EUDCH that it can detect when performance is suboptimal and EUDCH configuration changes are needed. The Node-B accordingly periodically sends, for each EUDCH, a signal to the RNC indicating how many Hybrid ARQ (HARQ) retransmissions were required per PDU (Protocol Data Unit), as a measure of channel quality. The RNC then instructs a change in channel parameters (e.g. to a longer TTI if the quality falls below a predetermined threshold.

Sixth Embodiment In this embodiment, the Node-B receives messages from the UE which include data on the signal quality measured at the UK, and then forwards this information to the RNC as disclosed above. The UE may be able to better measure signal quality than the Node-B station under some circumstances.

This embodiment may, of course, be combined with the features of the previous embodiment.

Seventh Embodiment In this embodiment, rather than providing the RNC with detailed information so that it can decide by itself what EUDCH configuration parameters shoud be updated, the Node-B tests the signal quality (for example based on the ARQ statistics as in the above embodiments) and when a predetermined test is met, it sends the RNC a message which recommends it to update one or more EUDCH configuration parameters. It is still up to the RNC to decide whether or not to take the recommendation into account (for example, traffic considerations may rule it out or cause it to be deferred). An example signalling flow is shown in Figure 9. The Node-B sends an update message to the RNC, and (if the RNC decides to accept the suggestion) the RNC signals back a reconfiguration request to the Node-B, which the latter acknowledges. The RNC then sends a message through the Node-B to the UK, which replies with a RECONFIGURATION COMPLETE message, and the UE and Node-B change their parameter set together.

Multiple Node-Bs might be involved in EUDCH reception of the EUDCH from the UE in the uplink. It would be possible to allow all these Node-Bs to advise the RNC about EUDCH configuration changes, but it is preferable to introduce a restriction that only the Node-B currently contributing the most to the EUDCH reception quality, or a Node-B appointed by the UE or UTRAN (sometimes referred to as "the primary Node-B") should be allowed to advise the RNC. This reduces the lub/Iur signalling load from the other Node-B's, and ensures that the EUDCH configuration is tuned to the Node-B contributing most to the EUDCH reception.

Eighth Embodiment Instead of the Node-B providing a recommendation to the RNC, it might be more appropriate in some circumstances if the UE provides the recommendation to the RNC.

In the sixth embodiment, the RNC is triggered to execute a change of EUDCH setting by information provided by the UE e.g. through measurement reports. In this embodiment, instead of the UE providing certain information to the RNC on which the RNC could base a decision which parameters to change, the UE directly advises the RNC to update certain EUDCH parameters. An example signalling flow is shown in Figure 10. Initially, when it detects a need to change a parameter, the UE sends the EUDCH parameter update message through the Node-B to the RNC, in place of the message from the Node-B shown in figure 9. In other respects, the process is described as above in relation to figure 9.

The fifth to eighth embodiments have various benefits; the seventh and eighth embodiments grant more power to the UE and node-B, which are the points most intimately connected with the EUDCH channel, and may therefore give a decision which gives a result more finely tuned to each particular channel, whereas the fifth and sixth embodiments grant more power to the RNC, which is able to take into account conditions on other channels and the other cells. It will be realised that the embodiments may be combined, to make a decision based on some or all of the messages described above.

On the other hand, the fifth through eighth embodiments all require the RNC to make a decision, which delays the implementation of the configuration change due to several factors, namely; the time taken to detect the need for parameter reconfiguration, the time taken to signal on the internal interfaces (lub/lur) or to send an RMC signal from the UE to the RRC signal, and the time taken to send an RRC signal to the UE and to issue signals on the lub/lur interfaces to the node-B to execute the change.

The following embodiments alleviate these delays by direct signalling between the UE and the node-B.

Ninth Embodiment Instead of using RRC signalling for signalling the update of EUDCH parameters (such as a 2ms <-> 10ms EUDCH TTI change) as in the above embodiments, in this embodiment the signalling is by lower layer signalling such as Layer I or L1 (e.g. by adding special bits on physical layer) or Layer 2/L2 (e.g. by adding special MAC PDU contents).

If the update of the EUDCH configuration setting is required due to an ACTIVE SET UPDATE, RRC would only need to execute the active set update procedure. Then at some later stage, the UE takes the initiative to change to a 10ms TTI (assuming going into soft handover) and signals this to the involved Node-Bs by L1 or L2 signalling. A common timing reference (referred to as "EUDCH modification time") for the EUDCH TTI transition is agreed between UE and UTRAN based on direct signalling between the UE and the Node-B.

In the RRC ACTIVE SET UPDATE message, or RRC XXX_RECONFIGURATION_REQ message, no EUDCH related parameters have to be included since the complete updated EUDCH configuration can be signalled on L1 or L2 later.

Also in this embodiment, either the UK, or the Node-B, or both could be allowed to initiate the EUCH configuration setting update with the following procedures: - If the UE decides on an EUDCH configuration setting update, it can directly inform all involved Node-Bs.

- If one of the involved Node-Bs decides on an EUDCH configuration setting update, it needs to inform the UE which again needs to inform all the other Node-Bs.

An example of L1 signalling in combination with an active set update procedure is shown in Figure 11. In this example signalling flow, the RNC first adds a new RL using a RRC message to the UK. The UE replies to concerns adding the new RL. Then, the UE initiates the direct UE-to-NodeB signalling by using a L1 or L2 message exchange, specifying the new configuration (e.g. 10mS TTI), and the Node-B replies to confirm to the UK.

The UE and Node-B then both switch to the new parameter values at the specified time.

Having a L1/L2 procedure for changing (parts) of the EUDCH configuration has the additional benefit that it might enable changes to the EUDCH configuration not directly related to active set update signalling, i.e. at any other point in time at which UE or Node-B considers it useful to change the EUDCH configuration. The benefit of this solution is that it is very flexible. The UE or Node-B can take the decision to change EUDCH TTI whenever it considers suitable. Although it consists of two signalling exchanges, unlike the first embodiments, the second exchange takes place between the UE and Node-B and therefore does not incur the delay in going to and from the RNC, so it is still reasonably fast.

Tenth Embodiment In the preceding embodiment, in the RRC ACTIVE SET UPDATE message, or RRC XXX_RECONFIGURATION _REQ message, no EUDCH related parameters have to be included since all changes are completely signalled on L1 or L2 in a subsequent signalling exchange.

In this embodiment, however, some or all of the EUDCH parameters are still signalled in RRC (as in the first embodiments), and L1/L2 signalling is only reponsible for executing a synchronised activation at both the UE and the Node-B.

This could be implemented based on an approach where RRC signalling is used to configure 2 or more EUDCH configurations (as in the second embodiment), and Ll/2 signalling is used to get the UE and Node-B to agree when to switch to one of the EUDCH configurations which was configured by RRC signalling.

Communication with the RNC In any event, where the UE and the Node-B have the freedom to agree on EUDCH configuration changes, it may be important for the RNC to be aware of these changes e.g. in order to be able to interprete the data it is receiving from the Node-B.

Therefore the Node-B should inform the RNC about relevant EUDCH configuration updates over the Iub/Iur interfaces. Either control-plane or user plane signalling could be used.

Other Embodiments and Variations It is to be understood that the embodiments described above are preferred embodiments only. Various features may be omitted, modified or substituted by equivalents without departing from the scope of the present invention. The present invention may, for example, be used in other suitable telecommunications systems than 3G networks as presently contemplated.

The present invention extends to any and all such variants, and to any novel subject matter or combination thereof disclosed in the foregoing.

Claims (20)

1. Claims 1. A telecommunications method for controlling a data uplink

   channel from a terminal in a mobile telecommunications system, comprising: sending a single message indicating that the terminal should add an additional radio link, and also that the terminal should change a parameter of the data uplink channel at a predetermined activation time.
2. 2. A method according to claim 1, in which the parameter is the length of the time interval over which the terminal can transmit on the data uplink channel.
3. 3. A method according to claim 1 or claim 2, in which the message specifies one or more new parameter values.
4. 4. A method according to claim 1 or claim 2, in which the message specifies a predetermined channel configuration comprising a set of new parameter values.
5. 5. A method according to any preceding claim, in which the message specifies a separate activation time for the parameter, other than that for the new radio link.
6. 6. A method according to any preceding claim, in which the message indicates that the additional radio link should be used with immediate effect.
7. 7. A method according to any preceding claim, in which the message does not include an explicit parameter activation time, and the UP and the network store a predetermined rule and each calculate the parameter activation time from the time of the message, in accordance with the predetermined rule.
8. 8. A telecommunications method for controlling a data uplink channel from a terminal in a mobile telecommunications system, comprising: sending at least one layer 1 or layer 2 message between the base station and the terminal indicating that the terminal should change a parameter of the data uplink channel at a predetermined activation time.
9. 9. A method according to claim 8, further comprising: sending a radio resource control message from a network control station through a base station to a terminal, indicating that the terminal should add an additional radio link.
10. 10. A method according to claim 8 or claim 9, in which the radio resource control message specifies the parameter change, and the layer 1 or layer 2 message specifies the time of the change.
11. 11. A telecommunications method for controlling a data uplink channel from a terminal in a mobile telecommunications system, comprising: signalling data to a network control station to enable the network control station to decide when to change parameters of the data uplink channel.
12. 12. A method according to claim 11, in which a radio base station signals said data.
13. 13. A method according to claim 11, in which said terminal signals said data.
14. 14. A method according to any of claims 11 to 13, in which said data comprises measurement data and said network control station determines when to change parameters of the data uplink channel based on said measurement data.
15. 15. A method according to any of claims 11 to 13, in which said data comprises a signal recommending a change of said parameters.
16. 16. A telecommunications method for controlling a data uplink channel from a terminal in a mobile telecommunications system, comprising providing first and second transmit period lengths and switching said data uplink channel to the longer of said lengths on transition to a soft handover state.
17. 17. Apparatus comprising a programmable control circuit programmed for performing the method of any preceding claim.
18. 18. User terminal apparatus according to claim 17.
19. 19. Base station apparatus according to claim 17.
20. 20. Network control station apparatus according to claim 17.