Patent ID: 12262367

BEST MODE FOR CARRYING OUT THE INVENTION

Overview

FIG.1schematically illustrates a mobile (cellular) telecommunication system1in which users of mobile telephones3-0,3-1, and3-2can communicate with other users (not shown) via a base station5and a telephone network7. In this exemplary embodiment, the base station5uses an orthogonal frequency division multiple access (OFDMA) technique in which the data to be transmitted to the mobile telephones3is modulated onto a plurality of sub-carriers. Different sub-carriers are allocated to each mobile telephone3depending on the amount of data to be sent to the mobile telephone3. In this exemplary embodiment the base station5also allocates the sub-carriers used to carry the data to the respective mobile telephones3in order to try to maintain a uniform distribution of the mobile telephones3operating across the base station's bandwidth. To achieve these goals, the base station5dynamically allocates sub-carriers for each mobile telephone3and signals the allocations for each time point (sub-frame) to each of the scheduled mobile telephones3.

In this exemplary embodiment, the base station5may dynamically allocate resources for downlink transmissions during transmission intervals in which the mobile telephone3is already scheduled to receive persistently scheduled data. In order to ensure that the mobile telephone3interprets the dynamic allocation of resources correctly, the base station5encodes appropriate data into the control channel used to carry the data defining the new allocation. It does this, in this exemplary embodiment, without changing the DL L1/L2 control channel structure used to signal the resource allocations.

Time/Frequency Resources

In this exemplary embodiment, the available transmission bandwidth is divided into a number of resource blocks, each of which comprises a number of contiguous sub-carriers (i.e. 12 subcarriers) arranged in contiguous blocks. Different mobile telephones3are allocated different resource block(s) (sub-carriers) for transmitting/receiving their data.FIG.2illustrates E-UTRA's latest definition of the transmission channel as comprising a sequence of 1 ms Transmission Time Intervals (TTIs)11-1,11-2, each of which consists of two 0.5 ms slots13-1and13-2. As shown, the available transmission bandwidth is divided into S resource blocks (RBs)15-1to15-sand each mobile telephone3is scheduled to transmit its uplink data and receive its downlink data in selected slots13and in selected resource block (RB)15. It is also possible each mobile telephone3to be assigned multiple resource blocks (RBS).

Base Station

FIG.3is a block diagram illustrating the main components of the base station5used in this exemplary embodiment. As shown, the base station5includes a transceiver circuit21which is operable to transmit signals to and to receive signals from the mobile telephones3via one or more antennae23(using the above described sub-carriers) and which is operable to transmit signals to and to receive signals from the telephone network7via a network interface25. The operation of the transceiver circuit21is controlled by a controller27in accordance with software stored in memory29. The software includes, among other things, an operating system31and a resource allocation module33. The resource allocation module33is operable for allocating the sub-carriers used by the transceiver circuit21in its communications with the mobile telephones3. As shown inFIG.3, the resource allocation module33includes control parameter generator module35for generating the required control parameters for defining the allocated resources.

Mobile Telephone

FIG.4schematically illustrates the main components of each of the mobile telephones3shown inFIG.1. As shown, the mobile telephones3include a transceiver circuit71which is operable to transmit signals to and to receive signals from the base station5via one or more antennae73. As shown, the mobile telephone3also includes a controller75which controls the operation of the mobile telephone3and which is connected to the transceiver circuit71and to a loudspeaker77, a microphone79, a display81, and a keypad83. The controller75operates in accordance with software instructions stored within memory85. As shown, these software instructions include, among other things, an operating system87and a communications module89. In this exemplary embodiment, the communications module89includes a control parameter interpreter module91for interpreting received control parameters that define a resource allocation.

In the above description, the base station5and the mobile telephones3are described for ease of understanding as having a number of discrete modules (such as the resource allocation module, control parameter generator module, communications module and control parameter interpreter module). Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities.

Operation

The current E-UTRAN (Evolved Universal Terrestrial Radio Access Network) specification states that in the downlink, resources (physical resource blocks (PRBs) and Modulation & coding scheme (MCS)) can be dynamically allocated to a mobile telephone3at each TTI via the C-RNTI on the L1/L2 control channel(s). A mobile telephone3always monitors the L1/L2 control channel(s) in order to find a possible allocation when its downlink reception is enabled (activity governed by DRX—discontinuous reception).

In addition, E-UTRAN can allocate predefined downlink resources for the first HARQ transmissions to mobile telephones3. When required, retransmissions ere explicitly signalled via the L1/L2 control channel(s). In the sub-frames where the mobile telephone3has been pre-assigned resources, if the mobile telephone3cannot find its C-RNTI on the L1/L2 control channel(s), a downlink transmission according to any pre-defined allocation that the mobile telephone3has been assigned in the TTI is assumed. As a result, the mobile telephone3performs blind decoding of the pre-defined resources (the subset of pre-defined resources shall be set in accordance with the mobile telephone's capability). Otherwise, in the sub-frames where the mobile telephone3has been pre-assigned resources, if the mobile telephone3finds its C-RNTI on the L1/L2 control channel(s), the L1/L2 control channel allocation overrides the pre-defined allocation for that TTI and the mobile telephone3does not perform blind decoding of the pre-defined resources.

Given this current proposal, if the base station5needs to dynamically allocate downlink resources in the same TTI where predefined downlink resources (persistently scheduled) for the first HARQ transmissions are scheduled for the mobile telephone3, a mechanism has to be provided which will enable the mobile telephone3to interpret the DL resource allocation differently without changing the DL control channel structure.

There are four possible allocations that can happen as shown in Table 1, Persistently scheduled allocations are not signalled in the DL L1/L2 control channel; as they are signalled from higher layers (i.e. L3).

TABLE 1Four Possible Allocations that can happenReallocation ofPersistently AllocatedNew dynamicResourcesallocated resourcesCommentsPersistently scheduledNot-allocated.There are no controlresources go as usual,channelsthere is no control channel.Reallocation overrides theNot-allocated.There is one controlpersistently scheduledchannelresources, there is controlchannel.Persistently scheduledAllocated, there isThere is one controlresources go as usual,control channel.channelthere is no control channel.Reallocation overrides theAllocated, there isThere are two controlpersistently scheduledcontrol channel.channelsresources, there is controlchannel.

As can be seen from Table 1, whenever a dynamic allocation is being made or whenever the persistently scheduled resources are to be reallocated, the base station5must generate and transmit control data over a control channel to the mobile telephone3to define the desired change. The last row of the table defines the situation where the base station5wishes to provide a dynamic allocation of the resources to be used in the current TTI and at the same time change the persistently allocated resources. This will require the use of two control channels within the same TTI to carry the appropriate control data to the mobile telephone3. Currently, the proposal is to have a maximum of one control channel within each TTI for each mobile telephone3. Therefore, the situation defined in the last row of Table 1 would not be supported by the current proposal. However, if the current proposal changes to allow the transmission of two control channels for a single mobile telephone3in the same TTI, then this situation would also be supported.

As will be apparent from the above discussion, the two cases that need to be distinguished by the mobile telephone3within the same TTI are:1) Reallocation of predefined (persistently scheduled) downlink resources; and2) New dynamic allocated resources.

The DL Control Channel Parameters that are generated by the base station5and transmitted to the mobile telephone3are shown in Table 2 below. The inventors believe that the required distinction can be achieved if the base station5sets the Transport Format or HARQ related information differently for the two cases and the mobile telephone3interprets the control data accordingly.

TABLE 2DL Control Channel ParametersControlsignalinginformationNumber of bitsCommentsMobile telephone1616-24 bit CRCIDResourceMaximum 18, 28,Location of the resource blocksassignment37 bits for 5,assigned to each mobile telephone10, 20 MHzin a TTI for DL transmission.Multi-antenna[2]Antenna informationinfoTransport[8]2 bits for modulation scheme, 6Format Info.bits for payload size.(Transport BlockSize + MCS)HARQ-related[5]3 bits for process number, 2 bitsinformationfor redundancy version and newdata indicator.

As shown in fable2, the DL Control Channel parameters that need to be set for the two cases are:Reallocation of Persistently Allocated Resources: Multi-antenna info/Transport Format/HARQ related Information can be set to specific pattern. Because, some of the information carried on the Multi-antenna info, Transport Format and HARQ related Information are not changed during reallocation of the persistently allocated resources, the pattern can be the two bits of the Multi-antenna info (for example bit pattern 11), and/or the last two bits of the Modulation scheme (for example bit pattern 11) in the Transport Format and/or the last three bits of the HARQ process number (for example bit pattern 111). Which part of the control parameters would be set in this pattern is, in this exemplary embodiment, determined in advance and known to the mobile telephone3and the base station5.New Resource allocation for Data/Signalling: All the control channel parameters would be set as usual for dynamically scheduled packet data.

Therefore, if the mobile telephone3receives DL control channel parameters in a current TTI in which it has persistently allocated resources, it first checks to see if the received parameters contain the predefined bit pattern in the appropriate location. If it finds the pattern, then it interprets the allocation as a reallocation of the persistently allocated resources; and if it does not find the pattern, then it treats the allocation as a new allocation for dynamically scheduled packet data. If it is a reallocation of the persistently allocated resources, the missing parameter information replaced by the bit pattern is taken from the control data that originally signalled the persistent allocation. For example if the bit pattern is included in the multi-antenna information field of the control data, then the mobile telephone3assumes that this information is not changed and uses the multi-antenna information that is stored for the persistently allocated resources (and which was signalled to the mobile telephone3at the time that the persistent allocation was originally signalled).

ACK/NACK Feedback

The proposed DL multiplexing deals only with a mixture of persistently scheduled and dynamically scheduled services. In this case, two HARQ processes are possible at maximum, resulting in two ACK/NACKs (2 bits) to be sent on the UL feedback (as opposed to one bit currently). This data can be sent using QPSK modulation and so, with this proposal, no modification is required for the UL control signalling either.

Conclusion

This patent application describes DL multiplexing for the case of simultaneous transmission of persistently scheduled and dynamically scheduled services. The advantages of doing so include:1) From a scheduling point of view, having both Persistent and Dynamic allocation within one sub frame would be very efficient.2) Resources for RRC/L2 signalling/Data could be dynamically allocated in the same sub frame in which VoIP packets are persistently scheduled.3) Increases DL capacity.4) Increased Battery life of the mobile telephone3as the “On-Duration” of the mobile telephone during DRX operation can be reduced.5) Different HARQ profile for VoIP (having persistently allocated resource) and Data (having dynamically allocated resource) is possible by having separate ACK/NACK for the different bearer types.

In addition, no modification is required to the current DL or UL L1/L2 control structure to accommodate the proposed multiplexing. The only requirement is the provision of a mechanism that will allow the mobile telephone3to distinguish between reallocation of Persistently Allocated Resources and the allocation of New Dynamic resources, such as by putting a predefined bit pattern in one or more of the DL Control Channel Parameters for the reallocation of the persistently allocated resources.

Modifications and Alternatives

A number of detailed exemplary embodiments have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above exemplary embodiments whilst still benefiting from the inventions embodied therein. By way of illustration only a number of these alternatives and modifications will now be described.

In the above exemplary embodiment, a mobile telephone based telecommunication system was described in which the above described signalling techniques were employed. As those skilled in the art will appreciate, the signalling of such resource allocation data can be employed in any communication system that uses a plurality of sub-carriers. In particular, the signalling techniques described above can be used in wire or wireless based communications either using electromagnetic signals or acoustic signals to carry the data. In the general case, the base station would be replaced by a communication node which communicates with a number of different user devices. User devices may include, for example, personal digital assistants, laptop computers, web browsers, etc.

In the above exemplary embodiments, a number of software modules were described. As those skilled will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the base station or to the mobile telephone as a signal over a computer network, or on a recording medium. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of base station5and the mobile telephones3in order to update their functionalities.

The following is a detailed description of the way in which the present inventions may be implemented in the currently proposed 3GPP LTE standard. Whilst various features are described as being essential or necessary, this may only be the case for the proposed 3GPP LTE standard, for example due to other requirements imposed by the standard. These statements not, therefore, be construed as limiting the present invention in any way.

Introduction

The current assumption in RAN 1 is that if the UE is having persistently allocated resources in a given TTI for example VoIP Service; no other resources could be allocated to the UE for data/signalling within the same TTI except with Dynamic Broadcasting Channel (DBCH). The restriction of having one transport block per TTI for the unicast transmissions comes from the fact that there will be only 1 HARQ process for non-A This issue was last discussed in RAN1 #46bis in Seoul, October 06 and since then there have not been any further discussion on this topic in subsequent meetings. In this contribution, we revisit the working assumption and discuss if the working assumption needs to be modified for simultaneous reception of persistently scheduled and dynamically scheduled services for one user in a TTI for DL transmissions.

Discussion

The main reason for agreeing this working assumption was that the DL control Channel structure and the resources needed for sending HARQ ACK/NACKS were not clear at that time. However, with progress on the DL Control channel structure: a) the proposal to separate out the ACK/NACK for persistently scheduled UE's and the dynamically scheduled UE's, b) the L1L2 signaling is basically not used to assign resources to the persistently scheduled UEs, we believe that these restrictions are no longer necessary. Further more, if multiple HARQ processes within one sub frame are allowed, UE could receive both a persistently scheduled (e.g. VOIP) packet and a dynamically scheduled (data) packet in the same sub-frame in the DL transmissions.

The possible benefits this could bring are:From scheduling point of view, having both Persistent and Dynamic allocation within one sub frame would be very efficient.Resources for RRC/L2 signalling/Data could be dynamically allocated in the same sub frame in which VoIP packets are persistently scheduled.Increases DL capacityIncreased Battery life of the UE as the “On-Duration” of UE during DRX operation can be reduced.Different HARQ profile for VoIP (having persistently allocated resource) and Data (having dynamically allocated resource) is possible by having separate ACK/NACK for different bearer type.

One could argue that this would increase UE complexity; however we believe that such functionality can be considered as a part of higher class/category UE. Early deployment UE may not implement such functionality. Mechanism for differentiating new dynamic allocation and persistent reallocation Stage 2 Technical Specification states that:

“In the downlink, E-UTRAN can dynamically allocate resources (PRBs and MCS) to UEs at each TTI via the C-RNTI on L1/L2 control channel(s). A UE always monitors the L1/L2 control channel(s) in order to find possible allocation when its downlink reception is enabled (activity governed by DRX).

In addition, E-UTRAN can allocate predefined downlink resources for the first HARQ transmissions to UEs. When required, retransmissions are explicitly signalled via the L1/L2 control channel(s). In the sub-frames where the UE has been pre-assigned resources, if the UE cannot find its C-RNTI on the L1/L2 control channel(s), a downlink transmission according to any pre-defined allocation that the UE has been assigned in the TTI is assumed. As a result, the UE performs blind decoding of the pre-defined resources (the subset of pre-defined resources shall be set in accordance to UE's capability). Otherwise, in the sub-frames where the UE has been pre-assigned resources, if the UE finds its C-RNTI on the L1/L2 control channel(s), the L1/L2 control channel allocation overrides the pre-defined allocation for that TTI and the UE does not perform blind decoding of the pre-defined resources”.

Given this, if we need to dynamically allocate downlink resources in the same TTI where the predefined downlink resources (persistently scheduled) for the first HARQ transmissions are scheduled for a UEs, we need to define a mechanism which will enable the UE to interpret DL grant differently without changing the DL control channel structure.

The two cases that need to be distinguished by the UE within the same TTI are:1) Reallocation of predefined (persistently scheduled) downlink resources2) New dynamic allocated resources.

There are four possible allocations that can happen as shown on Table 1. Persistently scheduled allocation does not use DL L1L2 control channel, but it is being signalled from higher layers (i.e., L3).

TABLE 1Four Possible Allocations that can happenReallocation ofPersistently AllocatedNew dynamicResourcesallocated resourcesCommentsPersistently scheduledNot-allocated.There are no controlresources go as usual,channelsthere is no control channel.Reallocation overrides theNot-allocated.There is one controlpersistently scheduledchannelresources, there is controlchannel.Persistently scheduledAllocated, there isThere is one controlresources go as usual,control channel.channelthere is no control channel.Reallocation overrides theAllocated, there isThere are two controlpersistently scheduledcontrol channel.channelsresources, there is controlchannel.

DL Control Channel Parameters are shown in Table 2 below. We believe that the distinction can be done if eNB sets the Transport Format and HARQ related information differently for the two cases and the UE interprets it accordingly.

As shown on table, DL Control Channel parameters that need to be set by for two cases are:Reallocation of Persistently Allocated Resources: Multi-antenna info/Transport Format/HARQ related Information can be set to specific pattern. Because, some of the information carried on the Multi-antenna info, Transport Format and HARQ related Information are not changed during reallocation of the persistently allocated resources. The pattern can be the last three bits of the Multi-antenna info (11), and or the last two bits of the Modulation scheme (11) in the Transport Format and or the last three bits of the HARQ process number (111).New Resource allocation of Data/Signalling: All the parameters would be set as usual for dynamically scheduled packet data.

TABLE 2DL Control Channel ParametersControlsignalinginformationNumber of bitsCommentsUE ID1616-24 bit CRCResourceMaximum 18, 28,Location of the resource blocksassignment37 bits for 5,assigned to each UE in a TTI for10, 20 MHzDL transmission.Multi-antenna[2]Antenna informationinfoTransport[8]2 bits for modulation scheme, 6Format Info.bits for payload size.(Transport BlockSize + MCS)HARQ-related[5]3 bits for process number, 2 bitsinformationfor redundancy version and newdata indicator.
ACK/NACK Feedback

The proposed DL multiplexing deals only a mixture of persistently scheduled and dynamic scheduled services. In this case, two HARQ processes are possible at maximum, resulting 2 ACK/NACKs (2 bits) to be sent on the UL feedback using QPSK modulation. So, with this proposal, no modification is required for the UL control signalling.

Conclusion

In this contribution, we have discussed and revisited the DL multiplexing for the case of simultaneous transmission of persistently scheduled and dynamic scheduled services. We highlighted the benefits of having such multiplexing for LTE downlink transmissions. In addition, no modification is required to the current DL/UL L1L2 control structure to accommodate the proposed multiplexing. It is only required to distinguish between reallocation of Persistently Allocated Resources and the allocation of New Dynamic resources by putting a unique pattern in some of the DL Control Channel Parameters for the reallocation of the Persistently Resources. So, we recommend RAN1/RAN2 to revisit the current working assumption and allow simultaneous reception of persistently scheduled and dynamically scheduled services for one user in a TTI for DL transmissions.

This application is based upon and claims the benefit of priority from United Kingdom Patent Application No. 0715822.3, filed on Aug. 14, 2007, the disclosure of which is incorporated herein in its entirety by reference.