WO2014032724A1

WO2014032724A1 - Scheduling wireless communications

Info

Publication number: WO2014032724A1
Application number: PCT/EP2012/066947
Authority: WO
Inventors: Timo Erkki Lunttila; Kari Juhani Hooli
Original assignee: Nokia Siemens Networks Oy
Priority date: 2012-08-31
Filing date: 2012-08-31
Publication date: 2014-03-06

Abstract

Methods and apparatuses for wireless communications are disclosed. First communications such as reference signals are scheduled based on a first timing scheme where data is carried in at least one predefined subframe resource. Information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications is signalled to modify timing of the second communications such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme. A device operated to communicate based on a first timing scheme receives the information, and in response thereto, modifies timing of the second communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme. An example is the delaying of or modifying the timing scheme of HARQ transmissions to fit the timing scheme of a new carrier type in order to achieve power saving both at user equipment and base station.

Description

SCHEDULING WIRELESS COMMUNICATIONS

This disclosure relates to scheduling of resources for wireless communications and more particularly but not explicitly to scheduling of resources for periodic uplink and/or downlink communications in a communication system.

A communication system can be seen as a facility that enables communication sessions between two or more nodes such as fixed or mobile devices, machine-type terminals, access nodes such as base stations, servers and so on. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define when and how devices shall communicate, how various aspects of communications shall be implemented and how devices for use in the system shall be configured. A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal.

Communications can be carried on wireless carriers. Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station of an access network and/or another user equipment. The two directions of communications between a base station and communication devices of users have been conventionally referred to as downlink and uplink. Downlink (DL) can be understood as the direction from the base station to the communication device and uplink (UL) the direction from the communication device to the base station. In wireless systems a device in communication with other devices needs to have its transmitter and receiver on, this consuming resources such as energy. In accordance with one scheme to save energy transmissions take place only in certain subframes of a radio frame while the other periods are left blank. The transmitter and/or receiver can be switched off for these periods, thus saving energy. Furthermore, interference to other devices in the vicinity as well as possibility of collisions can be reduced by this. The transmission timing scheme can be such that for example one or two subframes of each radio frame are designated for communications whilst the others are left blank.

A communication system typically operates various processes which are based on fixed timing relations between uplink and downlink transmissions. For example, an acknowledgement message of an error correction mechanism is typically sent after a pre-defined number of subframes back to the sending station. For example, a hybrid automatic repeat request (HARQ) acknowledgement message is sent after four subframes to the sending station. A problem in here may occur in that the timing scheme of such transmissions does not match a predefined timing scheme, such as one designed to conserve energy. In this occasion either data is lost or the transmitters and/or receivers are unnecessarily kept on when there might not be a need for it.

It is noted that the above discussed issues are not limited to any particular communication environment and station apparatus, but may occur in any appropriate station apparatus where internal communications are required.

Embodiments of the invention aim to address one or several of the above issues.

In accordance with an embodiment there is provided a method for wireless communications, comprising scheduling first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, and signalling information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications to modify timing of the second communications such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

According to another aspect, there is provided a method for wireless communications, comprising operating a device to communicate first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, receiving information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications, and in response to the information, modifying timing of the second communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

According to another aspect, there is provided an apparatus for a network node, configured to schedule first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, and cause signalling of information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications to modify timing of the second communications such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

An apparatus for a communication device may also be provided, the apparatus being configured to communicate first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, receive information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications, and in response to the information, modify timing of the second communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

According to a more detailed aspect, only predefined subframes of a radio frame are for carrying data in the first timing scheme while the other subframes of the radio frame are left empty. The first communications may comprise communication of common control information. The second communications may comprise communications of at least one of a downlink acknowledgement, an uplink acknowledgement, a downlink shared channel, and an uplink shared channel.

A receiver and/or a transmitter may be switched on and off according to the first timing scheme.

The second timing scheme may be changed by extending or delaying a default timing of the second communications to coincide with a next available subframe according to the first timing scheme. The information indicative of a change may comprise a timing offset.

Change of the second timing scheme may also comprise modifying the second timing scheme such that the predefined relationship between resources for related downlink and uplink communications and/or location of subframe resources of the second timing scheme corresponds to the periodicity and/or location of the subframe resources of the first timing scheme.

Change of the second timing scheme may also comprise changing from a first preconfigured uplink-downlink configuration for the second communications to a second preconfigured configuration for the second communications.

Information of the change may be included in downlink control information.

The number of subframes per radio frame available for the first and second communications may depend on the load.

In accordance with a particular embodiment the second communications comprises at least one of an enhanced Physical HARQ Indicator Channel (ePHICH), a Physical Uplink Control Channel, and a Physical Uplink Shared Channel.

A device such as a base station, a communication device of a user or a machine type terminal can be configured to operate in accordance with the various embodiments. A computer program comprising program code means adapted to perform the method may also be provided. The computer program may be stored and/or otherwise embodied by means of a carrier medium.

It should be appreciated that any feature of any aspect may be combined with any other feature of any other aspect.

Embodiments will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

Figure 1 shows a schematic diagram of a communication system comprising a base station and a plurality of communication devices;

Figure 2 shows a schematic diagram of a mobile communication device according to some embodiments;

Figure 3 shows a schematic diagram of a control apparatus according to some embodiments;

Figures 4, 5 and 6 illustrate principles of scheduling communications in a radio frame;

Figures 7 and 8 show flowcharts according to certain embodiments; Figures 9A to C, 10A and B, and 1 1 A and B show transmission timings in accordance with various embodiments.

In the following certain exemplifying embodiments are explained with reference to a wireless or mobile communication system for serving mobile communication devices. Before explaining in detail the exemplifying embodiments, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to Figures 1 to 3 to assist in understanding the technology underlying the described examples.

A device capable of wireless communications can communicate via at least one base station or similar wireless transmitter and/or receiver node. In figure 1 a base station 10 is shown to be serving various mobile devices 20 and a machine-like terminal 22. Base stations are typically controlled by at least one appropriate controller apparatus so as to enable operation thereof and management of mobile communication devices in communication with the base stations. The base station can be connected further to a broader communications system 12. It shall be understood that a number of neighbouring and/or overlapping access systems or radio service areas provided by a number of base stations may exist. A base station site can provide one or more cells or sectors, each sector providing a cell or a subarea of a cell. Each device and base station may have one or more radio channels open at the same time and may send signals to and/or receive signals from one or more sources. As a plurality of devices can use the same wireless resource, transmissions thereof need to be scheduled to avoid collisions and/or interference.

A possible mobile communication device for transmitting in uplink and receiving in downlink will now be described in more detail with reference to Figure 2 showing a schematic, partially sectioned view of a communication device 20. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate communication device may be provided by any device capable of sending radio signals to and/or receiving radio signals. Non-limiting examples include a mobile station (MS) such as a mobile phone or what is known as a 'smart phone', a portable computer provided with a wireless interface card or other wireless interface facility, personal data assistant (PDA) provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Non-limiting examples of content data include downloads, television and radio programs, videos, advertisements, various alerts and other information.

The device 20 is configured to receive signals in the downlink 29 over an air interface via appropriate apparatus for receiving and to transmit signals in the uplink 28 via appropriate apparatus for transmitting radio signals. In Figure 2 the transceiver apparatus is designated schematically by block 26. The transceiver apparatus 26 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile communication device is also provided with at least one data processing entity 21 , at least one memory 22 and other possible components 23 for use in software and hardware aided execution of tasks it is designed to perform, including various aspects of communications with base stations and/or other communication devices such as timing of reception and transmission. The data processing, storage and other relevant apparatus can be provided on an appropriate circuit board and/or in chipsets. This apparatus is denoted by reference 24.

The user may control the operation of the mobile device by means of a suitable user interface such as key pad 25, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 27, a speaker and a microphone can be also provided. Furthermore, a communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

Figure 3 shows an example of a control apparatus 30 for a communication system, for example to be coupled to and/or for controlling a base station. In some embodiments a base station may comprise an integrated control apparatus and some other embodiments the control apparatus can be provided by a separate network element. The control apparatus can be interconnected with other control entities. The control apparatus and functions may be distributed between a plurality of control units. In some embodiments each base station can comprise a control apparatus. In alternative embodiments, two or more base stations may share a control apparatus. The arrangement of the control depends on the standard, and for example in accordance with the current LTE specifications no separate radio network controller is provided. Regardless the location, the control apparatus 30 can be understood as providing control on communications in the service area of at least one base station. The control apparatus 30 can be configured to provide control functions in association with scheduling of uplink and/or downlink communications in accordance with embodiments described below. For this purpose the control apparatus can comprise at least one memory 31 , at least one data processing unit 32, 33 and an input/output interface 34. Via the interface the control apparatus can be coupled to a base station to cause operation of the base station in accordance with the below described embodiments. The control apparatus can be configured to execute an appropriate software code to provide the control functions.

A wireless communication device, such as a mobile device, machine-like terminal or a base station, can be provided with a Multiple Input / Multiple Output (Ml MO) antenna system. Ml MO arrangements as such are known. Ml MO systems use multiple antennas at the transmitter and receiver along with advanced digital signal processing to improve link quality and capacity. For example, the transceiver apparatus 26 of Figure 2 can provide a plurality of antenna ports. More data can be received and/or sent where there are more antennae elements.

An example of wireless communication systems are those based on architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The various development stages of the 3GPP LTE specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). In the 3GPP terminology base station nodes are often referred to as NodeBs (NB) and evolved NodeB (eNB) depending on the type thereof. Other examples of radio access system include those provided by base stations of systems that are based on technologies such as wireless local area network (WLAN) and/or WiMax (Worldwide Interoperability for Microwave Access).

Energy consumption is an important aspect of a communication system. Various ways have been proposed to save as much energy as possible, for example at bases stations, related controllers and mobile devices. One way to save energy is to minimise transmission and/or reception periods. For example, in the 3GPP a specific New Carrier Type (NCT) has been proposed for maximizing eNodeB energy efficiency in the downlink (DL) by scheduling transmissions in as few DL subframes as possible. This way the rest of the subframes can be kept completely empty ("blank") and the transmitter of the eNodeB can be shut down in those subframes to save energy. A proposal is that the new carrier type carries a reference signal (RS) port within a subframe with 5ms periodicity. The signalling port may consists e.g. of 3GPP Release 8 common reference signal (CRS) Port 0 reference elements (REs) per physical resource block (PRB) and a Release 8 sequence. These are referred herein as New Carrier Type - Common Reference Signals (NCT-CRS).

Common (cell specific) DL signals can thus only be transmitted when necessary, for example at the periodicity of 5 ms (i.e. in every 5^th subframe). For example, when the network traffic load is low, an eNodeB can switch to a mode where it starts scheduling DL signals firstly to subframes #0 and/or #5 in each radio frame consisting of ten subframes before scheduling any data in other subframes. These signals may include data on physical downlink shared channel (PDSCH) as well as control information (e.g. enhanced Physical Downlink Control Channel (ePDCCH), enhanced Physical Hybrid Automatic Repeat Request (HARQ) Indicator Channel (ePHICH), and so on. Thus all common signals can be concentrated into the same subframes.

An example of timing of NCT-CRS in downlink is illustrated in Fig. 4. In this example CRS is carried in predefined subframes #0, #5, #10, and #15.

Correspondingly, in the UL side the eNodeB can similarly concentrate UL transmissions to as few subframes as possible to allow for the eNodeB receiver to be turned off as often and for as long periods as possible. This can include both semi-statically scheduled transmissions (e.g. many of the Physical Uplink Control Channel (PUCCH) signals, Physical Random Access Channel (PRACH), semi-persistently scheduled data, periodic sounding reference signal (SRS) etc.) as well as dynamically scheduled transmissions. For example Physical Uplink Shared Channel (PUSCH), aperiodic channel state information / sounding reference signal (CSI/SRS) and so on.

A problem in here may be that there are processes where a different timing scheme is used in a predefined manner. For example, the current Hybrid Automatic Repeat Request (HARQ) timing definitions assume 8 ms round trip time for the data and related acknowledgement (positive or negative) with frequency division duplexing (FDD). This matches poorly with a different predefined NCT-CRS transmission cycle, for example the proposed 5 ms cycle.

To illustrate this further, the timing principle of physical uplink shared channel (PUSCH) scheduling and corresponding DL HARQ feedback is shown in Figure 5 for frequency division duplexing. As shown, an eNodeB can transmit in the DL an enhanced Physical Downlink Control Channel (ePDCCH) carrying an uplink (UL) grant in subframe #0. The mobile device (UE) can then transmit the corresponding PUSCH in the UL in subframe #4 and the eNodeB sends the HARQ-ACK (acknowledgement) corresponding to the PUSCH data using e.g. enhanced Physical HARQ Indicator Channel (ePHICH) in subframe #8. Thus, in addition to subframes #0 and #5, the eNodeB transmitter needs to be "on" also in the subframe #8 for the ePHICH transmission. Also, the eNodeB receiver needs to be "on" in subframe #4 for PUSCH reception or UL HARQ-ACK reception.

Assuming that there is at least one PUSCH scheduled in every NCT- CRS subframe, the eNodeB transmitter may need to be "on" 40 % of the time due to HARQ-ACK transmission which take place in the DL on (e)PHICH. This can significantly reduce the possibilities for energy savings.

Moreover, some eNodeB implementations might benefit in terms of energy savings also from the alignment of times when the transmitter (TX) and receiver (RX) are switched off. More particularly, they might benefit from being able to turn off TX and RX simultaneously. The current timing arrangements do not allow for this. If at least one PUSCH is scheduled in every 5^th subframe (i.e. NCT-CRS subframes) either RX or TX need to be active 60 % of the time. This scenario for the PDSCH transmission is illustrated in Figure 6. NCT-CRS subframes are at #0 and #5. Due to the fixed HARQ timing, the UE will transmit the UL HARQ-ACK in subframe # n+4 and hence the eNodeB receiver ON-time cannot be aligned with the transmission instances.

In the above it is assumed that ePHICH will send ACK to halt PUSCH HARQ re-transmissions, and that required re-transmissions are triggered with ePDCCH. If ePHICH were used to trigger a re-transmission then the re- transmission for the example discussed above would occur in subframe #12 and corresponding ePHICH would be transmitted in subframe #6. This would reduce the possibilities to save energy even further.

Figure 7 shows a flowchart for operation where aligning of the different timings is provided. More particularly, Figure 7 illustrates how a network node, for example an eNB, can ensure that all communications take place in predefined subframe resources to save energy when this is possible, e.g. when the load is determined as being low enough for enabling such an operation.

At to the network node can schedule at 40 first communications based on a first timing scheme. In the first timing scheme data is carried on at least one predefined subframe resource, for example in at least one subframe of a radio frame having a predefined location in time with respect to the radio frame and periodicity. In accordance with certain embodiments other subframes of the radio frame are left empty. Information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications is signalled at 42 to modify timing of the second communications by a communication device such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme. The information can be provided to modify timing of the second communications such that is corresponds to the timing of at least one subframe for carrying data according to the first timing scheme. For example, the periodicity and/or location of the subframe resources (e.g. in time and/or frequency) can be modified such that there is a correspondence between the first and second schemes. The network node can then configure itself so that the on-time of a transmitter and/or receiver thereof is optimised.

Figure 8 shows the operation at the device receiving the information, for example at a mobile device. The device can be operated at 44 to communicate first communications (either send or receive) based on the first timing scheme. The device can receive at 46 information indicative of a change of the second timing scheme defining a predefined relationship between resources for related downlink and uplink communications. In response to the information, the device can modify at 48 timing of the second communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

In the following more detailed examples are given for signalling solutions for maximizing eNodeB energy savings with carriers such as the above discussed 3GPP New Carrier Type (NCT). The described signalling arrangements may enable a network to better control the time instances for communications such as PUSCH and HARQ-ACK transmissions to optimise energy savings available based on use of the NCT. More particularly, in the below described signalling mechanisms the timing relationships between DL / UL data transmissions (e.g. PDSCH / PUSCH) and corresponding UL / DL HARQ signals (e.g. on PUCCH / ePHICH), respectively, can be modified. Also, the timing relations between UL scheduling information transmitted on DL (i.e. DCI UL grant) on ePDCCH and corresponding UL data transmission may be modified to allow for alignment with the transmission instances of NCT-CRS.

The signalling can provide an indication to the other party, for example a user equipment (UE) to modify timing for example such that a default timing is extended/delayed so that transmission occurs in next subframe containing NCT-CRS instead of a predefined subframe. In case of UL, the timing can be extended/delayed to next subframe linked to a DL subframe with NCT-CRS. The linkage can be predetermined. Alternatively, the linkage can be e.g. defined with a configurable offset. Information of the configurable offset can be signalled on a higher layer.

According to a possibility a default timing is modified. For example, a default timing scheme can be modified to follow 10 ms round trip time if 5ms cycles are used for the NCT. That is, n+5 timing is followed by a user equipment in response to a received indication that such timing shall be used. This option is perhaps best suited for use in connection frequency division duplexing (FDD). By means of this the HARQ round trip time can be redefined and fixed so that it is aligned with 5 ms NCT-CRS periodicity (e.g. HARQ- ACKs for PDSCH received in subframe # n would be transmitted in subframe # n+5).

It is also possible to change a default timing to follow timing of pre- configured, alternative UL-DL frame configuration. The user equipment can switch to the alternative configuration is response to a change indication from the network. This option is perhaps better suited for use for time division duplexing (TDD) with dynamic signalling of UL-DL configurations.

Signalling of the timing relationships can be dynamic and included into ePDCCH scheduling information. Alternatively, or in addition, a network may broadcast the indication of the modified HARQ timing using e.g. master information block (MIB) on (e)PBCH or some of the system information blocks (SIBs).

In the following more specific examples for different signals are presented with reference to Figures 9 to 1 1 to illustrate some detailed aspects further.

The first example relates to PHICH or ePHICH where HARQ-ACK signalling is provided for PUSCH data packets. As discussed above, a fixed default PHICH timing for HARQ-ACK for a PUSCH received in subframe #n is set such that the acknowledgement is transmitted on PHICH in subframe # n+4. This timing scheme is not in alignment with the transmissions instances of any other periodicity, for example NCT-CRS with 5ms cycle. This may not be an issue when the traffic load on the NCT is high as DL transmissions will anyway take place in most if not all of the subframes. However, during low network load energy resources may be unnecessarily consumed. Also, overhead and interference may be unnecessarily caused by non-aligned transmissions. To address this DL signalling can be provided for indicating to the mobile device that the transmission timing for the HARQ-ACK for PUSCH on (e)PHICH is to be modified.

Three different modification options discussed above and as applied to this scenario are shown in Figures 9A - 4C. More particularly, in the option shown in Figure 9A DL transmission of HARQ-ACK for PUSCH transmitted in subframe #4 is not transmitted in subframe #8 but is delayed until the next NCT-CRS subframe at subframe #10. Thus, instead of timing relationship of four subframes the acknowledgement is sent after six subframes, and the eNB does not need to switch its transmitter on at subframe #8.

In the option shown in Figure 9B signalling is provided so that the default timing of n+4 can be modified to follow n+5 timing scheme. In this embodiment the PUSCH is sent at subframe #5 and thus the eNB receiver can remain switched off during subframe #4. As above, the acknowledgement can be transmitted at subframe #10.

In the option shown in Figure 9C signalling is provide to change a default timing configuration (the upper configuration) to follow timing of a pre- configured, alternative UL-DL frame configuration (the lower configuration). In the energy saving configuration all downlink transmissions by the eNB are scheduled to take place at subframes #0 and #5, and uplink transmission by the mobile device are scheduled to take place at subframes #4 and #9.

Information of the timing modification can be signalled by indicating the change with downlink control information (DCI) format(s) that are used for scheduling UL PUSCH transmissions (i.e. in UL grants). The indication may be a separate bit added into a UL grant. According to a possibility, the indication may be done with existing bits in the UL grant by using some of the existing codepoints such as cyclic shift indicator field to provide an indication of the modification.

Figures 10A - 10B relate to a scenario where a HARQ-ACK is transmitted by a mobile device, or UE, in the uplink for PDSCH data packets. In here the timing of HARQ-ACK for PDSCH data packets is modified such that when the mobile device has received an indication of the modified HARQ- timing, it modifies the HARQ-ACK transmission timing thereof. An indication can be provided by the eNB with DL signalling what HARQ timing (default or modified) the device shall follow. Three timing modification options are considered with the principles shown in Figures 10A and 10B.

In accordance with a first option the transmission of the HARQ-ACK on PUCCH (or PUSCH) is delayed until the next NCT-CRS subframe. In Figure 10A this would be subframe #5. In accordance with another option a default timing of n+4 is modified to follow n+5 timing for HARQ-ACK on PUCCH (or PUSCH), again resulting transmission in subframe #5. In accordance with a third possible option for TDD and shown in Fig. 10B a default UL HARQ-ACK timing configuration is changed to follow timing of a pre-configured, alternative UL-DL (frame) configuration. Consider an example where a PDSCH is transmitted in SF#0. The arrangement allows sending of the related ACK on #SF4, and PDSCH retransmission can then occur in next SF#0. This option can be seen as a special way to implement the UL case where the timing can be extended / delayed to next subframe linked to a DL subframe with NCT-CRS for TDD.

The signalling may be e.g. provided as a dynamic signalling included in ePDCCH DCI scheduling of the PDSCH (i.e. in DL assignment). This indication may be a separate bit the DL assignment. According to a possibility the definition of an ACK NACK Resource Indicator (ARI) may be modified to include a possibility to indicate HARQ-ACK resources in different subframes by e,g. using transmit power control bits in the DL assignment, i.e. to delay the HARQ-ACK transmission, or to indicate modification in timing.

In addition to timing relation between UL and DL HARQ-ACK transmissions, a similar issue can occur for example with PUSCH scheduling as this follows the same timing as HARQ-ACK for PDSCH data. Therefore the same basic solutions can also be applied in this case as discussed above for scenario where HARQ-ACKs were transmitted for PDSCH data packets. Use of the second option is shown in Figures 1 1A and 1 1 B for two different load scenarios. The application of the modified scheduling of a default timing scheme allows for additional flexibility in eNB energy saving with respect to cell load as the transmission can be arranged not only in two subframes per radio frame, but also e.g. on four subframes per radio frames. This is shown in Figure 1 1 B.

In case of applying a modified, alternative UL-DL frame configuration instead of the default configuration, where the alternative (energy saving) UL- DL configuration is configuration 0, UL index field is not added to DCI signalling (unless the normal UL-DL configuration of cell is 0). Instead, a semi- static UL index field value can be defined to the device at the downlink either via higher layer signalling or via system information. This value is then used in the determination of PUSCH timing. Changes in system information broadcast on MIB or SIB or signalled as part of handover signalling may be provided for a better support of random access process in networks where energy savings are provided based on schemes such as the new carrier type. For example, Physical Random Access Channel (PRACH) Configuration field may need to be extended to cover also PRACH time-frequency configurations where PRACH occurs only in subframes on which eNodeB Rx is on, or only some of such subframes (e.g. on subframes #0 and #5). System information can include indication that the eNB is configured to use energy saving when possible. With this system information, the mobile device becomes aware of the correct form for DCI (i.e. presence of additional DCI field for timing modification indication or different interpretation of DCI content) already from the beginning when the device connects to the cell. Timing modification indication can be included as part of random access message 3 scheduling information in a random access response or message 2. In case of the third option discussed above, system information may contain sufficient configuration information for alternative UL- DL (frame) configuration.

Various advantages may be provided by the embodiments. For example, eNodeB energy efficiency may be improved by aligning the transmission instances with the common signals. Without a possibility for timing alignment large part of the energy saving potential of the 3GPP New Carrier Type or similar arrangement may be lost. Dynamic control of energy saving may be provided in certain embodiments. This can be of particular importance in small cells with rapidly varying cell load. Overall, flexibility with respect to changing load conditions may be improved.

It is noted that whilst embodiments have been described in relation to 3GPP based systems, similar principles can be applied to any other communication system or to further developments with 3GPP. Also, instead of scheduling that is provided by a control apparatus associated with a base station scheduling may be provided by any apparatus for scheduling transmissions in two directions between at least two devices. Thus, although the embodiments are described with references to uplink and downlink, this disclosure is not limited by these directions between a base station and a user terminal. Instead, the invention is applicable to any system where a control apparatus can schedule transmissions between two or more communicating entities, wherein the scheduling entity can be seen as being in the "higher" end of the link. For example, this may be the case in application where no fixed equipment provided but a communication system is provided by means of a plurality of user equipment, for example in adhoc networks. Therefore, although certain embodiments were described above by way of example with reference to certain exemplifying architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

The required data processing apparatus and functions of a base station apparatus, a communication device and any other appropriate apparatus may be provided by means of one or more data processors. The described functions at each end may be provided by separate processors or by an integrated processor. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi core processor architecture, as non- limiting examples. The data processing may be distributed across several data processing modules. A data processor may be provided by means of, for example, at least one chip. Appropriate memory capacity can also be provided in the relevant devices. The memory or memories may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD.

The foregoing description has provided by way of exemplary and non- limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed there is a further embodiment comprising a combination of one or more of any of the other embodiments previously discussed.

Claims

1. A method for wireless communications, comprising

scheduling first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, and

signalling information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications to modify timing of the second communications such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

2. A method for wireless communications, comprising

operating a device to communicate first communications based on a first timing scheme where data is carried in at least one predefined subframe resource,

receiving information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications, and

in response to the information, modifying timing of the second communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

3. A method according to claim 1 or 2, wherein in the first timing scheme only predefined subframes of a radio frame are for carrying data while the other subframes of the radio frame are left empty.

4. A method according to claim 3, where data is communicated only on every fifth subframe.

5. A method according to any preceding claim, wherein the first communications comprises communications on a New Carrier Type in accordance with specifications by the 3^rd Generation Partnership Project.

6. A method according to any preceding claim, wherein the first communications comprises communication of common control information.

7. A method according to claim 6, wherein the control information comprises common reference signals and/or synchronization signals.

8. A method according to any preceding claim, wherein the second communications comprises communications of at least one of a downlink acknowledgement, an uplink acknowledgement, a downlink shared channel, and an uplink shared channel.

9. A method according to any preceding claim, comprising switching a receiver and/or a transmitter on and off according to the first timing scheme.

10. A method according to any preceding claim, wherein the change of the second timing scheme comprises extending or delaying a default timing of the second communications to coincide with a next available subframe according to the first timing scheme.

1 1. A method according to claim 10, wherein the information indicative of a change comprises a timing offset.

12. A method according to any of claims 1 to 9, wherein the change of the second timing scheme comprises modifying the second timing scheme such that the predefined relationship between resources for related downlink and uplink communications and/or location of subframe resources of the second timing scheme corresponds to the periodicity and/or location of the subframe resources of the first timing scheme.

13. A method according to any of claims 1 to 9, wherein the change of the second timing scheme comprises changing from a first preconfigured uplink- downlink configuration for the second communications to a second preconfigured configuration for the second communications.

14. A method according to any preceding claim, wherein the information of the change is included in downlink control information.

15. A method according to any preceding claims, wherein the number of subframes per radio frame available for the first and second communications depends on the load.

16. A method according to any preceding claim, wherein the second communications comprises at least one of an enhanced Physical HARQ

Indicator Channel (ePHICH), a Physical Uplink Control Channel, and a Physical Uplink Shared Channel.

17. An apparatus for a network node, configure to

schedule first communications based on a first timing scheme where data is carried in at least one predefined subframe resource, and

cause signalling of information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications to modify timing of the second communications such that the subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

18. An apparatus for a communication device, configured to:

communicate first communications based on a first timing scheme where data is carried in at least one predefined subframe resource,

receive information indicative of a change of a second timing scheme defining a predefined relationship between resources for related downlink and uplink communications, and

in response to the information, modify timing of the second

communications such that subframe resources for carrying the second communications correspond to the at least one subframe resource of the first timing scheme.

19. An apparatus according to claim 17 or 18, wherein in the first timing scheme only predefined subframes of a radio frame are for carrying data while the other subframes of the radio frame are left empty.

20. An apparatus according to any of claims 17 to 19, wherein the first communications comprises communication of common control information and/or the second communications comprises communications of at least one of a downlink acknowledgement, an uplink acknowledgement, a downlink shared channel, and an uplink shared channel.

21. An apparatus according to any of claims 17 to 20, wherein the change of the second timing scheme comprises one of

extending or delaying a default timing of the second communications to coincide with a next available subframe according to the first timing scheme, modifying the second timing scheme such that the predefined relationship between resources for related downlink and uplink

communications and/or location of subframe resources of the second timing scheme corresponds to the periodicity and/or location of the subframe resources of the first timing scheme, and

changing from a first preconfigured uplink-downlink configuration for the second communications to a second preconfigured configuration for the second communications.

22. An apparatus according to any of claims 17 to 21 , wherein the number of subframes per radio frame available for the first and second

communications depends on the load.

23. A device for a communication system comprising the apparatus as claimed in any of claims 17 to 22.

24. A computer program comprising code means adapted to perform the steps of any of claims 1 to 16 when the program is run on a processor.