WO2013104118A1

WO2013104118A1 - Rach enhancement to support ues with different bandwidth requirements

Info

Publication number: WO2013104118A1
Application number: PCT/CN2012/070232
Authority: WO
Inventors: Chunyan Gao; Na WEI; Jing HAN; Shuang TAN; Haiming Wang; Wei Bai
Original assignee: Renesas Mobile Corporation
Priority date: 2012-01-11
Filing date: 2012-01-11
Publication date: 2013-07-18

Abstract

Embodiments provide a mapping between access resources and downlink control resources. Hence, an apparatus such as a user equipment may select an access resource of a plurality of access resources available for access to a network control element based on this mapping, and send an access request on the selected access resource.

Description

RACH ENHANCEMENT TO SUPPORT UES WITH DIFFERENT BANDWIDTH REQUIREMENTS Field of the invention

The present invention relates to methods, devices and computer program products by which a RACH enhancement can be achieved in order to support UEs with different bandwidth requirements, for example UEs with narrow bandwidth such as low cost MTC UEs.

Background

The following meanings for the abbreviations used in this specification apply:

3GPP 3rd Generation Partnership Project

eNB Enhanced Node B. Name for Node B in LTE

DL Downlink

E-PDCCH Enhanced Physical Downlink Control Channel

GRPS Genera] Packet Radio Service

GSM Global System for Mobile Communications

LTE Long Term Evolution

LTE-A Long Term Evolution Advanced

MTC Machine Type Communication

PDCCH Physical Downlink Control Channel

PDSCH Physical Downlink Shared Channel

PRACH Physical Random Access Channel

PRB Physical Resource Block

RACH Random Access Channel

RAN Radio Access Network

RAT Radio Access Technology

RRC Radio Resource Control UE User Equipment

UL Uplink

Some embodiments of the present invention relate to LTE and LTE-A, although not limiting thereon. As LTE deployments evolve, operators would like to reduce the cost of overall network maintenance by minimizing the number of RATs. Machine-Type Communications (MTC) is a market that is likely to continue expanding in the future. Many MTC devices are at targeting low-end (low cost, low data rate) applications that can be handled adequately by GSM/GPRS. Owing to the low cost of these devices and good coverage of GSM/GPRS, there is very little motivation for MTC device suppliers to use modules supporting the LTE radio interface. As more and more MTC devices are deployed in the field, this naturally increases the reliance on GSM/GPRS networks. This will cost operators not only in terms of maintaining multiple RATs, but also prevent operators to reap the maximum benefit out of their spectrum (given the non-optimal spectrum efficiency of GSM/GPRS).

Given the likely high number of MTC devices, the overall resource they will need for service provision may be correspondingly significant, and inefficiently assigned. Therefore, it is necessary to find a solution to ensure that there is a clear business benefit to MTC device vendors and operators for migrating low-end MTC devices from GSM/GPRS to LTE networks.

In the following, it is referred to the following references:

[1] : Rl-113158 ("On standards aspects with significant UE cost impact". Nokia, Nokia Siemens Networks. RANl#66bis, Zhuhai, China, 10-14 October 2011)

[2] : Rl-113180 ("Standards aspects of low-cost MTC LTE UEs". Renesas Mobile Europe Ltd. RANl#66bis, Zhuhai, China, 10-14 October 2011) [3] : Rl-112912 ("Overview on low-cost MTC UEs based on LTE". Huawe^'i, HiSilicon, CMCC. RANl#66bis, Zhuhai, China, 10-14 October 2011) [4] : Rl-113659 ("Considerations on the bandwidth reduction for low cost MTC UE", HuaWei)

In [1], it is suggested that solutions using, or evolved from LTE RAN specifications up to and including Rel-10 shall be investigated and evaluated to clearly understand the feasibility of creating a type of terminal that would permit the cost of terminals tailored for the low-end of the MTC market to be competitive with that of GSM/GPRS terminals targeting the same low-end MTC market. This is agreed to be new study item in 3GPP RANI.

Narrow bandwidth is considered to be a property for low cost MTC UEs due to low traffic needs. However, there are many problems to be solved to enable a narrow band UE operating in a wide band system. For example, in such a case the detection of conventional PDCCH which spreads over the whole bandwidth becomes a problem [1-2]. E-PDCCH had been proposed in current 3GPP discussion to enhance the PDCCH capacity and it is assumed to be sent in the PDSCH region. Such a design can be used to convey DL control in a narrow band to low cost MTC UEs. Another problem is the RACH transmission from low cost MTC UEs. It is proposed in [3] that the bandwidth reduction for DL and UL could be considered separately and the bandwidth reduction in DL provides more reduction than bandwidth reduction in UL. Then, the RACH transmission may be possible to share same resources with normal cellular UEs.

However, as indicated in [4], the RAR (Random Access Response) is scheduled by PDCCH. Therefore, if the RAR is scheduled in normal

PDCCH, the low cost MTC UEs with narrow band can not detect it. Then the eNB should know whether the RACH preamble is transmitted by a low cost UE or a normal UE to help decide where to send the grant for RAR. Two solutions are proposed in [4] as following:

Dedicated preambles for low cost UE

Dedicated PRACH resource for low cost UE The disadvantages of these solutions are that allocating dedicated preambles for the low cost UEs will increase the collision probability for both low cost MTC and non-MTC UEs, while dedicated PRACH resource will lead to more resource consumption on the uplink.

Summary

The present invention addresses such situations and deals in exemplary embodiments to overcome the above-described disadvantages and to support radio access also for low cost user entities (such as MTC UEs) with narrow bandwidth.

Various aspects of examples of the invention are set out in the claims.

According to an exemplary aspect of the present invention, there is provided an apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform: selecting an access resource of a plurality of access resources available for access to a network control element based on a mapping between the access resources and downlink control resources, and sending an access request on the selected access resource via the interface.

According to an exemplary aspect of the present invention, there is provided an apparatus comprising at least one processor, at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus, the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform : receiving an access request on an access resource of a plurality of access resources via the interface, selecting a downlink control resource for sending an access response based on a mapping between the access resources and downlink control resources, and sending the access response on the selected downlink control resource via the interface.

According to an exemplary aspect of the present invention, there is provided a method comprising selecting an access resource of a plurality of access resources available for access to a network control element based on a mapping between the access resources and downlink control resources, and sending an access request on the selected access resource.

According to an exemplary aspect of the present invention, there is provided a method comprising receiving an access request on an access resource of a plurality of access resources, selecting a downlink control resource for sending an access response based on a mapping between the access resources and downlink control resources, and sending the access response on the selected downlink control resource. According to an exemplary aspect of the present invention, there is provided a computer program product comprising computer-executable computer program code which, when the program is run on a computer (e.g. a computer of an apparatus according to any one of the aforementioned apparatus-related exemplary aspects of the present invention), is configured to cause the computer to carry out the method according to any one of the aforementioned method-related exemplary aspects of the present invention.

Such computer program product may comprise or be embodied as a (tangible) computer-readable (storage) medium or the like on which the computer-executable computer program code is stored, and/or the program may be directly loadable into an internal memory of the computer or a processor thereof. Advantageous further developments or modifications of the aforementioned exemplary aspects of the present invention are set out in the following. Thus, according to exemplary embodiments of the present invention, a mapping between access resources and downlink control resources is provided. In this way, a UE will know which downlink control resource it has to monitor for a response to an access request sent on a particular access resource. Therefore, also UEs with a narrow bandwidth are able to receive a response by selecting an appropriate access resource. Hence, UEs with different bandwidth requirements can be supported.

Brief description of drawings

For a more complete understanding of example embodiments of the present invention, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: Fig. 1 schematically illustrates a UE according to an embodiment of the present invention,

Fig. 2 schematically illustrates an eNB according to an embodiment of the present invention,

Fig. 3 shows a flow chart of a process performed by the eNB according to an embodiment of the present invention, and

Fig. 4A and 4B illustrate examples for RACH resource to PDCCH region mappings according to embodiments of the present invention.

Description of exemplary embodiments Exemplary aspects of the invention wiil be described herein below.

It is to be noted that the following exemplary description refers to an environment of the LTE system (long term evolution) and/or local area networks thereof. However, it is to be understood that this serves for explanatory purposes only. Other systems differing from the LTE system can be adopted. Fig. 1 illustrates a simplified block diagram of a user equipment (UE) 1 according to an embodiment of the present invention. It is noted that the UE, and the corresponding apparatus according to the embodiment may consist only of parts of the UE, so that the apparatus may be installed in an UE, for example. Moreover, also the UE is only an example and may be replaced by another suitable network element.

The UE 1 according to this embodiment comprises at least one processor 11, at least one memory 12 including computer program code and at least one interface 13 configured for communication with at least another apparatus. The processor 11 is configured to select an access resource of a plurality of access resources available for access to a network control element based on a mapping between the access resources and downlink control resources, and to send an access request on the selected access resource via the interface 13.

That is, the UE may use a mapping between the access resources (e.g., access resources on an access channel such as a random access channel (RACH) or a physical random access channel (PRACH)) and the downlink control resources (e.g., downlink control channel regions such as regions on a physical downlink control channel (PDCCH)), so that, when a certain access resource is selected, also the downlink control resource is known to the UE. Hence, the UE does not have to monitor all downlink control resources (or the whole downlink control channel) for a response to its access request from a network control element (e.g., an eNB), but only has to monitor the downlink control resource which corresponds (according to the mapping) to the selected access resource. Hence, the UE may operate with a narrow bandwidth. That is, also UEs with a narrow bandwidth are able to receive a response by selecting an appropriate access resource. Thus, UEs with different bandwidth requirements can be supported.

In addition, the processor 11, the memory 12 and the interface 13 may be inter-connected by a suitable connection 14, e.g., a bus or the like. Furthermore, it is noted that the apparatus may comprise more than one processor, more than one memory and/or more than one interface, if this Is suitable for a particular structure. Fig. 2 shows an eNB 2 according to an embodiment of the present invention. It is noted that the eNB, and the corresponding apparatus according to the embodiment may consist only of parts of the eNB, so that the apparatus may be installed in an eNB, for example. Moreover, also the eNB is only an example and may be replaced by another suitable network control element.

The eNB 2 according to this embodiment comprises at least one processor 21, at least one memory 22 including computer program code and at least one interface 23 configured for communication with at least another apparatus. The processor 21 is configured to receive an access request on an access resource of a plurality of access resources via the interface 23, to select an a downlink control resource for sending an access response based on a mapping between the access resources and downlink control resources, and to send the access response on the selected downlink control resource via the interface 23.

Moreover, similar as in case of the UE 1 shown in Fig. 1, the processor 21, the memory 22 and the interface 23 may be inter-connected by a suitable connection 24, e.g., a bus or the like. In addition, it is noted that the apparatus may comprise more than one processor, more than one memory and/or more than one interface, if this is suitable for a particular structure.

Fig. 3 shows a flow chart for describing the basic operations according to the embodiment described above.

In SI, a UE (e.g. UE 1 shown in Fig. 1) selects a RACH resource (as an example for the access resource as mentioned above) according to the mapping described above. In S2, the UE sends a preamble (as an example for an access request) on the selected RACH resource to an eNB (e.g. eNB 2 shown in Fig. 2). It is noted that, depending on the configuration of the mapping, the RACH resource may be a RACH preamble, so that in SI a RACH preamble is selected and in S2, the selected preamble is sent to the eNB.

In S3, the eNB determines a PDCCH region (as an example for a downlink control resource as mentioned above) for a RAR (as an example for an access request) based on the mapping. In S4, the eNB transmits the RAR to the UE on the selected PDCCH region.

After this, the normal access procedure can continue, for example by exchanging RRC signaling (indicated in S5 and S6).

Information regarding the mapping between the access resources and the downlink control resources may be provided for example by network configuration, and/or may be broadcasted by the eNB, for example. The processes according to the embodiments described above are described in the following in more detail by referring to specific examples. As mentioned above, embodiments of the present invention provide an enhancement for RACH in LTE, In order to support low cost MTC UEs with narrow bandwidth, wherein this enhancement enables the low cost MTC UEs to detect the corresponding RAR and enables PRACH resource sharing with normal UEs, and impact to legacy UEs can be avoided.

In the present description, legacy UEs stands for those UEs which do not support E-PDCCH; and new UE stands for those UEs which support E- PDCCH.

In detail, according to certain embodiments, the following is proposed:

A mapping is defined between the RACH resource (preamble or T-F resource) and the PDCCH region for RAR grant.

The mapping is implicitly predefined or explicitly signaled by higher layer signaling.

Based on configured PDCCH/E-PDCCH region to detect, UEs select the RACH resource/preamble to use.

Some UEs can be configured to detect common search space in multiple control regions. Legacy UEs are configured RACH resource which maps to RAR grant in normal PDCCH.

In the following, an implementation of the embodiment is described in more detail by referring to Figs. 4A and 4B which illustrates examples for a RACH resource to PDCCH region mappings.

According to Figs. 4A and 4B, the RACH resources are divided into some subsets (as examples for groups of access resources), and each subset maps to different PDCCH regions for RAR scheduling detection. The RACH resource can be divided in preamble, in subframe, in frequency, or divided using a combination of these solutions. Fig. 4A shows one example of RACH resource division based on preambles, while Fig. 4B shows one example of division based on subframe. In fact, there can be a combination, e.g., RACH resource in some subframe is divided into subsets, or, RACH resource in some PRBs is divided into subsets.

Such RACH resource division can be made transparent to legacy UEs by configuring different RACH resources to them. For example, according to Fig. 4B, the legacy UEs can be configured with the RACH resource in subframes indicated by horizontal hatching. That is, the legacy UEs will select to send RACH in subframes which map to RAR in legacy PDCCH region in a later subframe. For some new UEs, they can be configured to monitor common search space in both normal PDCCH and E-PDCCH and this provide more flexibility for the RACH resource selection. Low cost MTC UEs know which is the RACH resource whose RAR will be sent in the detectable control region, then can choose the RACH resource properly.

It is noted that the low cost MTC is not the only use case for this proposal, rather, this proposal also helps to handle the RAR for legacy and new release UEs. In this proposal, there is no dedicated RACH resource for legacy or low cost MTC UEs, and the RACH resource can be shared by UEs configured with multiple control regions.

Hence, according to embodiments described above, the problem of RAR detection for different UEs, e.g., UEs not capable to detect some control region, is solved. Moreover, a shared RACH resource is provided for UEs which reduce the collision possibility via control region configuration. Furthermore, there is no impact to legacy UEs. It is noted that the invention is not limited to the specific embodiments as described above.

In particular, although the embodiments were described by referring to LTE, the invention is not limited to this. That is, the solution as described according to embodiments may be applied to any case in which an access request is sent on a certain access resource, and an access response is sent on a downlink control resource, so that a mapping therebetween can be established.

Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware generally, but not exclusively, may reside on the devices' modem module. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "computer- readable medium" may be any media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer or smart phone, or user equipment.

The present invention relates in particular but without limitation to mobile communications, for example to environments under LTE, WCDMA, WIMAX and WLAN and can advantageously be implemented in user equipments or smart phones, or personal computers connectable to such networks. That is, it can be implemented as/in chipsets to connected devices, and/or modems or other modules thereof. If desired, at least some of different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. It is to be understood that any of the above modifications can be applied singly or in combination to the respective aspects and/or embodiments to which they refer, unless they are explicitly stated as excluding alternatives.

Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

According to a further exemplary embodiment of the present invention, an apparatus is provided which comprises means for selecting an access resource of a plurality of access resources available for access to a network control element based on a mapping between the access resources and downlink control resources, and means for sending an access request on the selected access resource. According to a another exemplary embodiment of the present invention, an apparatus is provided which comprises means for receiving an access request on an access resource of a plurality of access resources, means for selecting a downlink control resource for sending an access response based on a mapping between the access resources and downlink control resources, and means for sending the access response on the selected downlink control resource.

It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising

at least one processor,

at least one memory including computer program code, and at least one interface configured for communication with at least another apparatus,

the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform:

selecting an access resource of a plurality of access resources available for access to a network control element based on a mapping between the access resources and downlink control resources, and

sending an access request on the selected access resource via the interface.

2. The apparatus according to claim 1, wherein the access resources are on an access channel.

3. The apparatus according to claim 1 or 2, wherein the access resource is a resource block defined in time and/or frequency.

4. The apparatus according to any one of the claims 1 to 3, wherein downlink control resources are downlink control channel regions.

5. The apparatus according to any one of the claims 1 to 4, wherein the at least one processor, with the at least one memory and the computer program code, is configured to cause the apparatus to perform: selecting the access resource based on a downlink control resource which is detectable for the apparatus.

6. The apparatus according to any one of the claims 1 to 5, wherein the plurality of access resources is divided in groups each comprising at least one access resource, and in the mapping, each group of the plurality of access resources is mapped to a downlink control resource.

7. The apparatus according to claim 6, wherein the division of the plurality of access resources in groups is based on preambles to be used for access, and/or subframes and/or frequency.

8. The apparatus according to any one of the claims 1 to 7, wherein the at least one processor, with the at least one memory and the computer program code, is configured to cause the apparatus to perform: receiving an access response in the downlink control resource region to which the selected access resource Is mapped.

9. An apparatus comprising

at least one processor,

the at least one processor, with the at least one memory and the computer program code, being configured to cause the apparatus to perform :

receiving an access request on an access resource of a plurality of access resources via the interface,

selecting a downlink control resource for sending an access response based on a mapping between the access resources and downlink control resources, and

sending the access response on the selected downlink control resource via the interface.

10. The apparatus according to claim 9, wherein the plurality of access resources are on an access channel.

11. The apparatus according to claim 9 or 10, wherein the access resource is a resource block defined in time and/or frequency.

12. The apparatus according to any one of the claims 9 to 11, wherein downlink control resources are downlink control channel regions.

13. The apparatus according to any one of the claims 9 to 12, wherein the plurality of access resources is divided in groups each comprising at least one access resource, and in the mapping, each group of the plurality of access resources is mapped to a downlink control resource.

14. The apparatus according to claim 13, wherein the division of the plurality of access resources in groups is based on preambles to be used for access, and/or subframes and/or frequency.

15. The apparatus according to any one of the claims 9 to 14, wherein the at least one processor, with the at least one memory and the computer program code, is configured to cause the apparatus to perform: broadcasting information regarding the mapping.

16. A method comprising

sending an access request on the selected access resource.

17. The method according to claim 16, wherein the access resources are on an access channel.

18. The method according to claim 16 or 17, wherein the access resource is a resource block defined in time and/or frequency.

19. The method according to any one of the claims 16 to 18, wherein downlink control resources are downlink control channel regions.

20. The method according to any one of the claims 16 to 19, further comprising :

selecting the access resource based on a downlink control resource which is detectable for an apparatus carrying out the method.

21. The method according to any one of the claims 16 to 20, wherein the plurality of access resources is divided in groups each comprising at least one access resource, and in the mapping, each group of the plurality of access resources is mapped to a downlink control resource region.

22. The method according to claim 21, wherein the division of the plurality of access resources in groups is based on preambles to be used for access, and/or subframes and/or frequency.

23. The method according to any one of the claims 16 to 22, further comprising:

receiving an access response in the downlink control resource region to which the selected access resource is mapped.

24. A method comprising

receiving an access request on an access resource of a plurality of access resources,

sending the access response on the selected downlink control resource.

25. The method according to claim 24, wherein the plurality of access resources are on an access channel.

26. The method according to claim 24 or 25, wherein the access resource is a resource block defined in time and/or frequency.

27. The method according to any one of the claims 24 to 26, wherein downlink control resources are downlink control channel regions.

28. The method according to any one of the claims 24 to 27, wherein the plurality of access resources is divided in groups each comprising at least one access resource, and in the mapping, each group of the plurality of access resources is mapped to a downlink control resource region.

29. The method according to claim 28, wherein the division of the plurality of access resources in groups is based on preambles to be used for access, and/or subframes and/or frequency.

30. The method according to any one of the claims 24 to 29, further comprising:

broadcasting information regarding the mapping.

31. A computer program product comprising computer-executable computer program code which, when executed on a computer, is configured to carry out the method as defined in any one of the claims 16 to 23 or 24 to 30.

32. The computer program product according to claim 31, embodied as a computer readable storage medium.