WO2012000183A1

WO2012000183A1 - Method and apparatus for coordinated un sub-frame configuration for lte-a relay

Info

Publication number: WO2012000183A1
Application number: PCT/CN2010/074809
Authority: WO
Inventors: Haiming Wang; Jing HAN
Original assignee: Nokia Corporation
Priority date: 2010-06-30
Filing date: 2010-06-30
Publication date: 2012-01-05

Abstract

In accordance with an example embodiment of the present invention, methods and apparatus, including computer program products, are provided. In one aspect there is provided a method. The method may include receiving at a relay node an relay sub-frame update value. Increase or decrease the relay sub-frame allocation at the relay node based on the update value. In another aspect there is provided an apparatus. The apparatus is configured to receive at a relay node a relay sub-frame update value. Increase or decrease the Un sub-frame allocation at the relay node based on the sub-frame update values received from DeNB.. Related apparatus, systems, methods, and articles are also described.

Description

METHOD AND APPARATUS FOR COORDINATED UN SUB-FRAME

CONFIGURATION FOR LTE-A RELAY

TECHNICAL FIELD

[0001] The present application relates generally to wireless communications.

BACKGROUND

[0002] Long term evolution-advanced, LTE-A, aims to provide enhanced services by means of higher data rate and lower latency with reduced cost. Relay is one of the approaches proposed by LTE-A to enlarge the coverage, to improve the capacity and to improve the cell edge performance. In the initial LTE network development phase, building cost- effective coverage with relay is an attractive proposition for network operators. Relays may also be deployed in connection with other wireless technologies than LTE-A.

[0003] FIG, 1 depicts an example of relay with self-backhauling. In this example, the relay node, RN, is a small enhanced Node B, eNB, supporting one or more cells of its own. The RN is accessible to third generation partnership project, 3GPP, LTE Release-8 user equipments, UEs, for example, and provides its own downlink common and shared control signalling to allow UEs to access the relay cell, as would be the case for a traditional eNB cell. The main difference to a normal eNB cell is that the relay is wirelessly connected to rest of radio access network via a "donor" cell 110, which may provide larger coverage. This may be referred to as se!f-backhauling, where the SI and X2 interfaces 115 may use wireless in-band or out-band resources. SUMMARY

[0004] Various aspects of examples of the invention are set out in the claims.

[0005] According to a first aspect of the present invention, there is provided a method. The method may include receiving at a relay node a relay sub-frame update value. Increase or decrease the Un sub-frame allocation at the relay node based on the sub- frame update values received from DeNB.

[0006] According to a second aspect of the present invention, there is provided an apparatus. The apparatus is configured to receive at a relay node a relay sub-frame update value. Increase or decrease the relay sub-frame allocation at the relay node based on the sub-frame update values received from DeNB.

[0007] The above-noted aspects and features may be implemented in systems, apparatus, methods, and/or articles depending on the desired configuration. The details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF THE DRAWINGS

[0008] 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:

[0009] FIG. 1 depicts an example of relay with self-backhauling in accordance with an example embodiment of the invention; [0010] FIG. 2 depicts an example of separation of access and relay link in TDM (FDD mode) in accordance with an example embodiment of the invention;

[0011] FIG. 3 depicts an example of relay node-to-relay node interference for bit-map based methods in accordance with an example embodiment of the invention;

[00 2] FIG. 4 depicts an initial Un sub-frame configuration for RN1 and

RN2in accordance with an example embodiment of the invention;

[0013] FIG. 5 depicts an example of increasing Un sub-frame through coordinated method in accordance with an example embodiment of the invention;

[0014] FIG. 6 depicts an example of decreasing Un sub-frame through coordinated method in accordance with an example embodiment of the invention;

[00 5] FIG. 7 depicts an initial Un sub-frame configuration for RN1 and

RN2 based on 40ms periodicity in accordance with an example embodiment of the invention;

[0016] FIG. 8 depicts an example of increasing Un sub-frame configuration for R l and RN2 based on 40ms periodicity in accordance with an example embodiment of the invention;

[0017] FIG. 9 depicts an apparatus configurable to operate as a type 1 relay node in accordance with an example embodiment of the invention; and

[0018] FIG. 10 is a flow diagram showing operations for a relay node to update the sub-frame configuration in accordance with an example embodiment of the invention.

[0019] Like labels are used to refer to same or similar items in the drawings. DETAILED DESCRIPTION

[0020] The subject matter described herein relates to relay. Relay is one of the approaches to extend cell coverage and enhance cell capacity for wireless systems, for example LTE-A and/or worldwide interoperability for microwave access, WiMAX, systems. There are many kinds of relays, which might be applicable to different scenarios. Type 1 relay is an in-band relay, which uses the same frequency band for relay link and access link, and which is in control of cells of its own, and a unique physical-layer cell identity is provided for each of the cells. A relay link connects a RN to the eNB, whereas an access link is used to connect the RN to terminals. The same radio resource management mechanisms and protocol stacks that are available to eNBs may be available also to type 1 relays. From the UE perspective there may be no difference in the cells controlled by a relay and cells controlled by a "normal" eNB. Additionally, the cells controlled by the relays should support also LTE Rel-8 UEs if a mandatory backward compatibility is required. For type 1 relay, access link and relay link transmissions are time multiplexed, which means relay could not communicate with relay attached UEs, which may be known as RN-UEs, and eNB simultaneously.

[0021] An example embodiment of the present invention and its potential advantages are understood by referring to FIG. 2 through 10 of the drawings.

[0022] Frequency division duplex, FDD, mode is a transmission method that uses separate channel frequencies for uplink and downlink. Time division multiplexing, TDM, may be used between the relay link and the access link both in downlink and uplink. In an example embodiment, for an FDD system, eNB to RN transmissions are done in the downlink frequency band sharing the resource with RN to RN-UE transmissions. In the same example embodiment, RN to eNB transmissions is done in the uplink frequency band sharing the resource with RN-UE to RN transmissions. FIG. 2 depicts an example of separation of access link and relay link in TDM in accordance with an example embodiment of the invention. The relay link 205 in the figure also called "Un interface", and access link 210 in the figure called "Uu interface". In the example illustrated, the sub-frames used for Un interface are determined and allocated by donor eNB, DeNB, via signaling. One possible way to allocate and configure the sub-frame number and location for Un interface is to use a bit-map based signaling.

[0023] In this bit-map based method, several bits are mapped to the sub- frame location in the radio frame, and values "1" and "0" are used to represent if the sub-frame is allocated or not. However, an optimal Un sub-frame number that may be allocated to a RN may change over time, since an optimal Un sub-frame number may be impacted by several factors such as, for example, relay-attached user bearer number, required bit rate of relay bearer, relay number in the cell and Uu/Un link quality. Thus, DeNB may need an adjustment procedure to update an Un sub-frame configuration based on time-varying factors. When using a bit-map based method, if there is no restriction for sub-frame allocation and no coordination among neighboring DeNBs, the Un sub-frame could be allocated in different location by the neighboring DeNBs. This may cause relay node-to-relay node interference if the sub-frame used for Un interface by one relay is used for Uu interface by another relay.

[0024] FIG. 3 depicts a relay node-to-relay node interference examp a bit-map based method in accordance with an example embodiment of the invention. In this example, relay node RN1 is connected to the DeNB in the figure and relay node RN2 is connected to a neighboring DeNB, not shown in the figure. RN1 is assigned by the DeNB sub- frames #2 and #6 as the relay link while RN2 is assigned by a separate neighboring DeNB sub- frame #2 and #6 as the access link. RN2 is interfered by RN1 as when the RN2 is receiving from the RN-UE at sub-frame #2 and #6, R 1 is also transmitting data to eNB at the same sub- frames. Relay node-to-relay node interference is caused by the relay link from RN1 to eNB that interferes with the access link from UE to RN2. Thus an interference avoidance procedure is needed, which may increase the system complexity and cause all Un sub-frame configurations in neighboring cells to be reconfigured. Note that the interference from access link to relay link is not a problem causing relay node-to-relay node interference, since the relay link may be a much better link, for example due to a higher relay antenna, a better relay antenna gain, a better penetration loss and possible site planning gain. Aiming to at least partly address at least some of these example problems, another Un sub-frame configuration method called "coordinated Un sub-frame configuration" method is proposed. In relay systems, it may be the case that relay link to access link interference is more problematic than relay link to relay link interference. Relay link to relay link interference also exists, but is similar to UE to UE interference in a normal cellular system.

[0025J Currently FDD systems do not require synchronization among eNBs, in other words so there may exist different frame timing offsets among eNBs in FDD systems. Due to this un-synchronization feature of FDD mode, there is the possibility that the radio frame timing is not synchronized between different eNBs, If the timing offset is not coordinated between eNBs then at least some relay node-to-relay node interference may remain despite a coordination of the Un sub-frame. After the timing offset is synchronized among eNBs and the initial Un sub-frame configuration of DeNB is coordinated with the neighboring eNBs, this coordinated Un sub-frame configuration method could be utilized in DeNB to reconfigure Un sub-frame. An advantage may be that interference among neighboring eNB can be reduced without constant information exchanges between the eNBs.

[0026] FIG. 4 depicts an example of utilizing the coordinated Un sub- frame configuration method in accordance with an example embodiment of the invention. Initial Un sub-frame configuration has been done with both RN1 and RN2 configured with sub- frame #2 405 for Un transmission. In the example illustrated, RN1 is attached to donor eNB DeNBl and RN2 is attached to donor eNB DeNB2.

[0027J When DeNB I and DeNB2 decide to increase the Un sub-frame number for RN1 and RN2, a sub-fame update value will be indicated to RN1 and RN2 that an update value of sub-frame number is/are to be added. FIG. 5 depicts an example of increasing Un sub-frame utilizing this coordinated Un sub-frame configuration method. For example, the sub-frame update value could be +2 ms, and this value indicates an increase of two sub-frames. In the illustrated example, the granularity of the sub-frame update value is one sub-frame, i.e. lms based value. For example, the sub-frame update value could be one sub-frame, two sub- frames etc, The updated Un sub-frame location could be predefined in the specification or could be configured via RRC signaling. For example, an added Un sub-frame location could be in/after the end of already allocated Un sub-frames or in/before the head of existing Un sub- frames.

[0028] In the example depicted by FIG. 4, we assume the sub-frame update value equals to +2ms and the increase of Un sub-frames is effected from the end of an existing Un sub-frame, then after the sub-frame update value +2ms is indicated to R 1 and RN2 by DeNBl and DeNB2, RNl and RN2 will increase their Un sub-frame allocation in sub- frame #3 505 and #6 510. Based on LTE Release 8 standards, downlink sub-frames #0, #4, #5, #9 are reserved for control signaling and cannot be used as multimedia broadcast multicast service single frequency network, MBSFN, sub-frames. For backward compatibility, these same sub-frames could not be configured as downlink Un or Uu sub-frame either. Sub-frames #3 and #6 are two sub-frames available from the end of existing Un sub-frame #2. In FDD systems, type 1 relay, relay links and access links may be multiplexed in time to avoid interference. Sub-frames #2, #3, and #6 are use for relay link and sub-frames #1, #7, and #8 may be used for access link. In other words, the relay nodes may share a determination algorithm to determine which sub-frames to allocate responsive to the sub-frame update value. Thus, when more than one relay node receives the same sub-frame update value, the more than one relay nodes may responsively allocate the same sub-frame or sub-frames. Embodiments of this invention are also applicable to time division duplex, TDD, systems, since the interference problem in TDD systems is the same as in FDD systems. To accommodate a TDD system, one modification relative to FDD systems is that the granularity of the update value is not based on ms but based on uplink sub-frame number.

[0029] In some embodiments of the invention, if DeNB I and DeNB2 decide to decrease the Un sub-frame number for RNl and RN2, an sub-frame update value is indicated to RNl and RN2 that an update value of Un sub-frame number is/are to be reduced. FIG. 6 depicts an example of decreasing Un Sub-frame allocation through coordinated method in accordance with an example embodiment of the invention. If update value equals to -1ms is indicated and the decreased Un sub-frames is from the head of existing Un sub-frame, then the decreased Un sub-frame for R l and RN2 is sub-frame #2, 605 (assuming sub-frame #0, #4, #5, #9 are reserved for control signaling and could not be configured as Un sub-frame in FDD mode).

[0030] The previous examples are based on one radio frame 10ms periodicity allocation. For an FDD mode, it is also possible that the Un sub-frame allocation is based on four radio frames 40ms periodicity, for example. FIG. 7 depicts an example of an initial Un sub-frame configuration for RNl and RN2 based on 40ms periodicity in accordance with an example embodiment of the invention. In FIG. 7, sub-frames { 1 , 3, 7, 2} in radio frame {n, n+1, n+2, n+3} are allocated to RNl and RN2. This notation means that in radio frame n sub-frame 1 is allocated to RNl and RN2, and in radio frame n+1 sub-frame 3 is allocated to RNl and RN2, and in radio frame n+2 sub-frame 7 is allocated to RNl and RN2, and in radio frame n+3 sub-frame 2 is allocated to RNl and RNl for their respective relay links. Four bits signaling, radio frame update value, may be needed, in addition to the sub-frame update value, to indicate the radio frames of the updated Un sub-frames. For example, "0" stands for no updated Un sub-frames in corresponding radio frame and "1" stands for an updated Un sub- frames in corresponding radio frame. Therefore "0101" stands for no updated Un sub-frames in radio frames n and n+2 and updated backhaul sub-frames in radio frames n+1 and n+3.

[0031] FIG. 8 depicts an example of an updated Un sub-frame configuration for RNl and RN2 based on about 40ms periodicity in accordance with an example embodiment of the invention. If a radio frame update value bit string "0101" and a sub-frame update value "+lms" are applied and the increased Un sub-frame is from the end of an existing Un sub-frame, then the updated Un sub-frame configuration from the initial FIG, 7 configuration is represented in FIG. 8. In frame n+1, sub-frame 4 is occupied, therefore the RN will interpret the command as a command to select sub-frame 6 which is the next available sub- frame starting from sub-frame 3. DeNB may be configured to disallow the added Un sub-frame from falling into next radio frame. For example in FIG. 8, in radio frame n+1, if the initial Un sub-frame is in sub-frame 8, then DeNB will not increase Un sub-frame after sub-frame 8 in this radio frame, since the added Un sub-frame will fall into the radio frame n+2, or the RN will interpret the command in another way, for example, allocate sub-frame #1 in this radio frame.

[0032] Based on a DeNB decision about an Un sub-frame update, for example an update to allocate an Un sub-frame number or to deallocate an Un sub-frame number, DeNB may be configured to indicate to at least one relay a sub-frame update value to increase or decrease the Un sub-frame allocation. Signaling carrying a sub-frame update value could be based on R C signaling, medium access control, MAC, control element, or physical layer signaling. With the coordinated Un sub-frame configuration solutions, DeNB could adjust Un sub-frame allocations gradually with different configured granularities. As long as initial Un configurations for different relays are coordinated, the Un sub-frame for neighbor cells are always synchronized without the need for separate coordination procedure.

[0033] FIG. 9 depicts an example implementation of a type 1 relay node

900 in accordance with an example embodiment of the invention. The relay node may include an antenna 910 configured to transmit via a downlink and configured to receive via uplinks. The relay node 105 further may include a radio interface 920 coupled to the antenna 910, a processor 930 configured to control the relay node and for accessing and executing program code stored in memory 940. The radio interface 920 may further comprise other components, such as filters, converters such as, for example, digital-to-analog converters and the like, mappers, a fast fourier transform , FFT, module, and the like, to generate symbols for a transmission via one or more downlinks and to receive symbols via an uplink, for example. The processor 930 may receive information regarding the sub-frame configuration of the backhaul uplinks and or downlinks, as described herein. Memory 940 may be partially or completely comprised in processor 930, or alternatively memory 940 may be external to processor 930. Processor 930 may comprise a transceiver, not illustrated, configured to cause information to be transmitted to the radio interface 920 and configured to receive information from radio interface 920, If memory 940 is at least partially external to processor 930, then the transceiver comprised in processor 930 may also be configured to communicate with memory 940. Processor 930 may also comprise circuitry configured, with software stored in memory 940, to cause methods according to embodiments of the present invention to be performed. [0034] FIG. 10 depicts a process 1000 used by a relay node for sub-frame configuration in accordance with an example embodiment of the invention. At 1010, an Un sub-frame update value is received. The value may provide an indication to a relay node regarding the increase or decrease of the Un sub-frame. At 1020, the update command and update location are determined by the relay node based on the configuration from the DeNB. The configuration may be caused using one or more of the implementations described herein, such as radio resource signaling, MAC control element, or physical layer signaling. At 1030, the relay node may thus configure the Un sub-frame based on the update command and the update location.

[0035] 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 may reside on RN. If desired, part of the software, application logic and/or hardware may reside on DeNB, and part of the software, application logic and/or hardware may reside on RN. The subject matter described herein may be embodied in systems, apparatus, methods, and/or articles depending on the desired configuration. For example, the relay nodes and user equipments (or one or more components therein) and/or the processes described herein can be implemented using one or more of the following: a processor executing program code, an application-specific integrated circuit, ASIC, a digital signal processor, DSP, an embedded processor, a field programmable gate array, FPGA, and/or combinations thereof. These various implementations may include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. [0036] 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, with one example of a computer described and depicted in FIG 9. A computer-readable medium may comprise a computer-readable non-transitory storage medium that may be any media or means that can contain or store the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

[0037] If desired, the 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.

[0038] 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.

[0039] 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. A method comprising:

receiving, at a relay node, a relay sub-frame update value;

updating the relay sub-frame allocation based at least in part on said sub-frame update value;

wherein the updating comprises increasing the relay sub-frame allocation if said sub- frame update value indicates to increase the relay sub-frame allocation, and wherein the updating comprises decreasing the relay sub-frame allocation if said sub-frame update value indicates to reduce the relay sub-frame allocation.

2. The method of claim 1, wherein the sub-frame update value is in the unit of at least one sub-frame.

3. The method of claim 1, wherein the sub-frame update value is configured by at least one of the RRC signaling, MAC control element, and physical layer signaling.

4. The method of claim 1, wherein the increasing further comprises:

increasing said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location to increase relay sub-frame allocation is at least one of from before the head of existing relay sub-frames and after the end of existing relay sub-frames.

5. The method of claim 1, wherein the decreasing further comprises:

decreasing said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location to decrease relay sub-frame allocation is at least one of from the head of existing relay sub-frames and from the end of existing relay sub-frames.

6. The method of claim 1, wherein the receiving further comprises: receiving, at a relay node, a radio frame update value to indicate the radio frames to be updated when sub-frame allocation is based on more than one radio frame.

7. The method of claim 6, wherein the radio frame update value is a bit string with each bit mapping to a radio frame to indicate whether the sub-frames in the radio frame is to be updated.

8. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

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

receive, at a processor, a relay sub-frame update value;

update the relay sub-frame number based at least in part on said sub-frame update value; wherein the processor being configured to update said relay sub-frame allocation is further configured to increase the relay sub-frame allocation if said sub-frame update value indicates to increase the relay sub-frame allocation;

and wherein the processor being configured to update said relay sub-frame allocation is further configured to decrease the relay sub-frame allocation if said sub-frame update value indicates to reduce the relay sub-frame allocation.

9. The apparatus of claim 8, wherein the sub-frame update value is in the unit of at least one sub-frame.

10. The apparatus of claim 8, wherein the sub-frame update value is configured by at least one of the RRC signaling, MAC control element, and physical layer signaling.

1 1. The apparatus of claim 8, wherein the processor being configured to increase said relay sub-frame allocation is further configured to: increase said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location to increase relay sub-frame allocation is at least one of from before the head of existing relay sub-frames and after the end of existing relay sub-frames.

12. The apparatus of claim 8, wherein the processor being configured to decrease said relay sub-frame number is further configured to:

decrease said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location to increase relay sub-frame allocation is at least one of from the head of existing relay sub-frames and from the end of existing relay sub-frames.

13. The apparatus of claim 8, wherein the processor being configured to receive a sub-frame update value is further configured to:

receive, at a relay node, a radio frame update value to indicate the radio frames to be updated when sub-frame allocation is based on more than one radio frame.

14. The apparatus of claim 13, wherein the updated frame value is a bit string with each bit mapping to a radio frame to indicate whether the sub-frames in the radio frame is to be updated.

15. A computer program product comprising a computer-readable medium bearing computer program code embodied therein for use with a computer, the computer program code comprising:

a first program code configured to receive, at a relay node, a relay sub-frame update value;

a second program code configured to update the relay sub-frame allocation based at least in part on said sub-frame update value,

said second program code increases the relay sub-frame allocation if said sub-frame update value indicates to increase the relay sub-frame number and decreases the relay sub- frame allocation number if said sub-frame update value indicates to reduce the relay sub-frame number.

16. The computer-readable storage medium of claim 15, wherein the received sub- frame update value includes being configured in the unit of at least one sub-frame,

17. The computer-readable storage medium of claim 15, wherein the sub-frame update value includes being configured by at least one of the RRC signaling, MAC control element, and physical layer signaling.

18. The computer-readable storage medium of claim 15, wherein the second program code includes being configured to:

increase said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location includes being configured to be at least one of from the head of existing relay sub-frames and from the end of existing relay sub-frames.

19. The computer-readable storage medium of claim 15, wherein the second program code includes being configured to:

decrease said relay sub-frame allocation based on at least one of a predefined and a configured location wherein the location includes being configured to be at least one of from the head of existing relay sub-frames and from the end of existing relay sub-frames.

20. The computer-readable storage medium of claim 15, wherein the first program code includes being configured to:

receive, at a relay node, an radio frame update value to indicate the radio frames to be updated when sub-frame allocation is based on more than one radio frame.

21. A method comprising:

initializing, in a base station, the same relay sub-frame allocation with at least one neighboring base station; deciding with the at least one neighboring base station a relay sub-frame update value; transmitting said update value to at least one relay node coupled to the base station; wherein said update value is configured to cause the same relay sub-frames to be allocated in all relay nodes receiving said update value.

22. An apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

initialize the same relay sub-frame allocation with at least one neighboring base station; decide with the at least one neighboring base stations a relay sub-frame update value; transmit said update value to at least one relay node coupled to the base stations;

wherein said update value is configured to cause the same relay sub-frames to be allocated in all relay nodes receiving said update value.