WO2012040877A1 - Reference signals in a communication system - Google Patents

Abstract

Methods and apparatus for controlling reference signalling are disclosed. A signalling pattern that is associated with at least one radio service area is generated, the pattern comprising locations for indicating resources for reference signalling in a first radio service area. The pattern and clustering information are signalled in the radio service area. The clustering information comprises information of muting ports and/or frequency reuse to enable communication devices in the radio service area to determine a muting con¬ figuration. Resources indicated by one or more of the loca- tions in the muting cluster are used for reference signalling in a first radio service area while resources indicated by other locations in the muting cluster are muted.

Description

Reference signals in a communication system

This disclosure relates to reference signalling, and more particularly, but not exclusively, to signalling of resource patterns. The patterns can be used in communications systems by devices such as base stations and mobile communication devices for communication of information associated with signalling resources.

A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers and/or other communication nodes. 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 the manner how communication devices can access the communication system and how various aspects of communication shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of the communication between at least two stations occurs over a wireless link.

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 ( LAN) . A wireless system can be divided into cells, and hence these are often referred to as cellular systems. A cell is provided by a base station. Cells can have different shapes and sizes. A cell can also be divided into sectors. Regardless of the shape and size of the cell providing access for a u access is provided via a sector of a c< area can be called radio service are Neighbouring radio service areas typical! a communication in an area can listen tc station .

A user can access the communication syste propriate communication device. A commun user is often referred to as user equipme A communication device is provided with a receiving and transmitting arrangement f_' cations with other parties. Typically a is used for enabling receiving and transit tions such as speech and data. In wirel nication device provides a transceiver s municate with another communication de base station of an access network and/or ment. The communication device may acces by a station, for example a base station, receive communications on the carrier.

An example of communication systems atten increased demands for capacity is an arc ing standardized by the 3rd Generation

Various signalling information is sent be and mobile devices. For example, refers sent from a base station to mobile devi Information about the resources to be use nailing may need to be communicated to < signalling in a service area. For exampl system, a channel state information refer is proposed to implement downlink channel a CSI-RS pattern has been proposed for < formation associated with the reference prove channel estimation accuracy, Physd Channel (PDSCH) resource element (RE) mu to avoid interference to the channel stat ence signals (CSI-RS) by neighbouring se cells and/or sectors. The muting is a the neighbour areas (sectors or cells) a the muting for a sector or cell means source elements of the neighbours. That i transmitted, the resource elements to ot sponding to the serving area's CSI-RS s] sidering the mutual muting behaviour, u: serving area should know the current nur it can avoid neighbour area's CSI-RS. Ά ing of resources of neighbouring service

It is noted that the above discusses on. issues are not limited to any particula: tern, standard, specification and so fort any communication system where informat signalling resources may need to be commu ity services areas.

Embodiments of the invention aim to addre the above issues.

In accordance with an embodiment there : of controlling reference signalling, comp a signalling pattern associated with at 1 vice area, the pattern comprising locat resources for reference signalling in a area; signalling the pattern; signalling tion, the clustering information comprisi least one of muting ports and frequency munication devices in the first radio se mine a muting configuration based on th and said clustering information; and u, cated by one or more of the locations i: for reference signalling in the first ra muting resources indicated by other loci cluster.

based on the received signalling pattern information; and determining, based on tl tion, how muting of resources for referen ranged in the first radio service area.

In accordance with an embodiment there is tus comprising at least one processor, ai ory including computer program code, w one memory and the computer program code the at least one processor, to: generate associated with at least one radio servii comprising locations for indicating resc signalling in a first radio service area of the pattern and of clustering informa information comprising information of at ports and frequency reuse to enable comm the first radio service area to determine tion based on the pattern and said clu and use resources indicated by one or m< in the muting cluster for reference sigi radio service area and to mute resource; locations in the muting cluster.

In accordance with an embodiment there is tus comprising at least one processor, a

information; and determine, based on th tion, how muting of resources for referen ranged in the first radio service area.

In accordance with a more specific embod muting ports comprises the number of mut information of frequency reuse comprise number. The reference signalling may comp channel state information reference signa

In accordance with a more specific embodi clustered locations of the pattern can 1 for reference signalling. It can be det frequency reuse parameter, that at leas not belong to a full cluster, and in res dicator of an odd group can be sent or re cations of a port number can be mapped t of another port number.

A communication device and/or base stati trol apparatus configured to provide at bodiments can also be provided. The comir comprise a user equipment, for example a

A computer program comprising program o oerform the herein described methods may The invention will now be described in fu of example only, with reference to the fo accompanying drawings, in which:

Figure 1 shows an example of a coramunic; below described examples of the invention Figure 2 shows an example of a communicat Figure 3 shows an example of controller < station;

Figure 4 is flowchart illustrating an emb Figures 5A to 5C and 6A to 6C show exaim terns ;

Figure 7 shows two examples for grouping Figure 8 shows two examples for grouping accordance with a further embodiment;

Figure 9 shows an example of scenario wl different numbers of ports; and

Figures 10 and 11 show embodiments where clustering information is provided.

In the following certain exemplifying plained with reference to a wireless or system serving mobile communication devi ing in detail the exemplifying embodimei

eas 36, 37 and 38 are shown being provic 20. However, it is noted that instead o terns, any number of access systems may b< munication system. An access system may b of a cellular system or another system e tion device to access a communication sys site 20 can provide one or more cells, also provide a plurality of sectors, for sectors, each sector providing a cell or All sectors within a cell can be served b tion. A radio link within a sector can single logical identification belonging ^' a base station can provide one or more Each mobile communication device 21 and have one or more radio channels open at t send signals to and/or receive signals source .

A base station 20 is typically controllec propriate controller so as to enable o{ management of mobile communication devic tion with the base station. The control terconnected with other control entities troller apparatus is shown to be providec station control apparatus is typically ;

shown, the radio service areas can ov> transmitted in an area can interfere wit another area.

The communication devices 21 can acces system based on various access techniques sion multiple access (CDMA) , or wideband examples include time division multiple quency division multiple access (FDMA) thereof such as the interleaved frequenc access (IFDMA), single carrier frequenc access (SC-FDMA) and orthogonal frequenc access (OFDMA) , space division multiple on .

A non-limiting example of the recent deve cation systems is the long-term evolutic versal Mobile Telecommunications System standardized by the 3rd Generation (3GPP) . As explained above, further devel referred to as LTE-Advanced . Non-limitin priate access nodes are a base station o for example what is known as NodeB (NB) the 3GPP specifications. The LTE employ: ture known as the Evolved Universal Terr

(WLAN) and/or WiMax (Worldwide Interopera Access) .

In Figure 1 example the base stations oi are connected to a wider communications troller may be provided for coordinating access systems. Although not shown, a ς also be provided to connect to -another r work 35. The other network may be any ap wider communication system may thus be more interconnect networks and the eleme: or more gateways may be provided for int networks .

Figure 2 shows a schematic, partially communication device 21 that a user car tion. Such a communication device is o user equipment (UE) or terminal. An apprc nication device may be provided by an; sending and receiving radio signals. N include a mobile station (MS) such as a is known as a 'smart phone', a portab] with a wireless interface card or othe: facility, personal data assistant (PDA) less communication capabilities, or any c

data. Non-limiting examples of the conten television and radio programs, videos, a< ous alerts and other information. The m receive signals over an air interface 28 paratus for receiving and may transmit s: ate apparatus for transmitting radio si transceiver apparatus is designated sch 27. The transceiver may be provided for e radio part and associated antenna arran arrangement may be arranged internally c mobile device.

A wireless communication device can be pr pie Input / Multiple Output (MIMO) anter rangements as such are known. MIMO syste tennas at the transmitter and receiver digital signal processing to improve lin ity. Although not shown in Figures 1 and can be provided, for example at base stat tions, and the transceiver apparatus 27 < vide a plurality of antenna ports. More and/or sent where there are more antennae may comprise an array of multiple antenna ling and muting patterns can be associe numbers or port numbers of MIMO arrangeme

noted by reference 26. Possible control : configuring the mobile communication devi processing of information in associatio patterns and for muting signals by means ing facility in accordance with certain present invention will be described lat tion .

The user may control the operation of t means of a suitable user interface such . commands, touch sensitive screen or pad, or the like. A display 25, a speaker a also typically provided. Furthermore, a device may comprise appropriate connectc wireless) to other devices and/or for cor cessories, for example hands-free equipme

Figure 3 shows an example of a control communication system, for example to be c controlling a station of an access syste ratus 30 can be arranged to provide conti by mobile communication devices that are of the system. The control apparatus 30 provide control functions in association communication of transmission patterns a

The required data processing apparatus base station apparatus, a communication c appropriate station may be provided by m data processors. The described functions provided by separate processors or by ar sor. The data processors may be of any t local technical environment, and may inc general purpose computers, special purpo: processors, digital signal processors specific integrated circuits (ASIC) , gat< processors based on multi core processor limiting examples. The data processing across several data processing modules. Ί be provided by means of, for example, at propriate memory capacity can also be pi vant devices. The memory or memories may able to the local technical environment mented using any suitable data storage semiconductor based memory devices, magi and systems, optical memory devices and s and removable memory.

Various information can be signalled in base station to mobile communication devi

Clustering information is signalled at 56 time with step 54 or at a different time formation comprises information of at J ports and frequency reuse to enable the c in the at least one radio service area t< configuration based on the signalling pal tering information.

A communication device within the at lea: area receives the signalling pattern at ing information at 60. The communication termine at 62 a muting configuration ba signalling pattern and the clustering in indicated by one or more of the locations ter are used for a first radio service sources indicated by other locations in for at least one second radio service are

In accordance with a more detailed examp system, channel state information refer* is provided to save reference signal (RS) plement downlink channel estimation. Use has been proposed for communication of ir with the reference signalling. Examples 2, 4 and 8 CSI-RS ports are shown in

- _^ tion reference signals (CSI-RS) by neighl sectors. PDSCH RE muting can be applied ; locations that are intended for neighbo^' tors. Various parameters may need to be < ing is applied. For example, information quency reuse (FR) factor, number of CSI-R ences in the ports between neighbouring i may need to be provided and/or conside: vices. For example, in the LTE, eNB indii locations for the serving cell/sector. P cell can indicate its CSI-RS to the ui serving. The user equipment in a cell or ceive the CSI-RS location of its own eel not required that a user equipment knows or sector's CSI-RS location.

Information such as a "muting TX number" use (FR) number can be signalled to a us user equipment in relevant radio service that a muting TX number can be different number of the serving cell/sector. The si vided, for example, by signalling such as trol (RRC) signalling. For example, info FR number and/or muting Tx number can be cell-specific RRC signaling. Such signali

The following presents certain examples f dexes and patterns. This can be provided with different frequency reuse factors figurations. In some of the embodiments a transmitter (Tx) ports number configurati can be provided to address, for example, neighbouring sector has a different Tx m ing sector. In accordance with an embot pattern are cyclically reused.

In accordance with an embodiment at lea pattern can be grouped to provide an ir

The intra subframe index can then be us device, for example a user equipment list to select the muting cluster that is b this the receiving device can determine the pattern it shall use for reference si location of the serving access system c plicitly for the at least one user equ the user equipment can determine based clusters which locations are to be muted can assume that at least some resource el the PDSCH by the base station. The mut< can be decided based on information of and more particularly based on informs

as an example in- accordance with an emboc ures 5A - 5C. Figures 6A - 6C illustra CSI-RS location indexing scheme. It is r these are only examples that are given principle, and that any other appropriate dexing can also be used. In these Figure bers are using different indexing. In twenty CSI-RS resource element (RE) loca Downlink Shared Channel (PDSCH) are indi bers 0 to 19 in a two port pattern, in F. locations have indexes 0 to 9 in a four Figures 5C and 6C five CSI-RS resource el on a Physical Downlink Shared Channel (] by index numbers 0 to 4 in an eight pc group of indexes can be determined based the frequency reuse (FR) number.

All CSI-RS indexes can be categorized ii clusters. By grouping the indexes relate between a serving cell's / sector's CSI-F pattern. For example, a user equipment CSI-RS locations in the patterns in the c ing cell's / sector's CSI-RS index is ii CSI-RS indexes 1, 2, and 3 form a group, cell's / sector's CSI-RS index is 1, the

frequency reuse number may allow compatil: future systems and standards, such as c point transmission and reception (CoMP flexibility, the herein described group use of different muting FR numbers and Ί FR number can be different from 3, for ex

Considering a CSI-RS pattern, a CSI-RS po the maximum CSI-RS index. For example, i: 8Tx, the number of possible CSI-RS index if the port number is 4Tx, N = 10 (Fig. . number is 2Tx, N = 20 (Fig. 5A) . A user e aware of the Tx number, for example by b RS Tx number of the serving cell / sectc ment can then determine the number of CSI the Tx number.

This grouping arrangement can be describe Group_n = {m \ n * FR≤ m < (n + \) * FR - \, m < FR

m is an integer,

Group_n is the index set of grou] N is the number of CSI-RS ind

resources elements in group n are muted e source element of the user equipment

According to the above scheme, there can dexes not belonging to any group if N mod lustrated by Figure 7. For example, if FR case shown in the upper example CSI-RS within one group. However, ports 3, 4 d group (5 mod 3 = 2). Similarly, in the lo case where FR=3, CSI-RS ports 0, 1, 2 ai 3, 4, 5 are in another group, and port third group. However, port 9 des not be^] mod 3 = 1).

CSI-RS indexes not belonging to any group

N

FR ≤m < N

This scenario can be handled in various rr such CSI-RS indexes are prohibited in net for example if the Co P is deployed. Thi to implement, but may not always fully CSI-RS indexes.

An indication, for example a bit or anotl to indicate an "odd group" (cyclic tail o the indication is possible to reuse all C frequency reuse (FR) number. To provide 1 muting configuration signalling can be j that a special group (odd group) is usee single bit indicators may be used only inside a special muting group. For examp. cycle can be indicated by a single bit muting pattern is [0,1,2] or [3,4,0] for

By grouping all CSI-RS indexes, a muting ciated with a particular CSI-RS index. T can be associated with FR number and ser index .

PDSCH RE muting aims to avoid interferen RS patterns. When determining the muting ber of neighbour radio service area cai count. However, neighbouring cells or s ferent Tx numbers. Figure 9 illustrates E RS in a subframe where different sector

In accordance with an embodiment a scena cells or sectors have a different Tx num appropriate conversions between the diffe: For example, it is possible to convert fi example, with a nested structure, a serv index can be converted to a correspondin number. Thus, when the muting TX numbei serving sector's CSI-RS, the CSI-RS index a corresponding muting Tx number, and t take place based on a pre-defined index Tx number. To illustrate this, if a serv; and the CSI-RS index is 15 but muting T CSI-RS index 15 in 2Tx corresponds to CS case. The processor of the user equipment on this that the muting pattern is CSI-RS FR=3.

In case where multiple sectors within a different Tx numbers, the muting patten maximum Tx number. To provide this, an ac ample an eNB, informs all user equipment number (this can be same or different f] tor's CSI-RS Tx number) and muting FR nui means of RRC signalling. A user equipmer formation can then map serving sector' s C

^XN2 ^{= X}N\ ^m°d N2 , where

Nl is the CSI-RS location number ac rent Tx number, and N2 is the CSI-RS cording the muting Tx number.

Muting grouping can then be done using N input. The muting pattern is then decide

In accordance with an embodiment CSI-RS i formed in accordance with a rule betwee numbers. Based on a nested structure of < ports / 4 ports / 2 ports, this can be us tify a user equipment in a cooperative se tion or locations in the pattern should b

Via cyclic shift, when the number of CSI patterns cannot be fully divided by the f more possibilities of CSI-RS muting patte In the embodiments described above signa include the following information and b: tion assumes that the serving sector' s C already signalled to the user equipment): Pattern signalling Estimated Bits The above assumes that the Tx and FR pai separately. In accordance with a possibi] ing Tx parameter a jointly encoded. In tl a jointly encoded information is a parame ing cluster size". The muting cluster si an integer of 2Tx CSI-RS locations. For e

'The muting cluster size' = 'muting muting size'

In this equation the basic muting size c< Tx number (1 for 2Tx, 2 for 4Tx, 4 for 8T

The eNB can broadcast only this muting cell-specific parameter.

One example of this is as follows: 2 bits indication of the "muting cluster size" muting, 3, 6, 12 ] . Considering figu line indicates a muting group, this wouL cluster size = 6, then for cell with 4Tx 3 muting, and for cell with 2Tx this woi ing . Another possible signaling method is to j

In accordance with an example a muting pa ated with CSI-RS location, if muting FR=i tor is 8 Tx, then muting pattern can be tions [0-4] in figure 5C. In this case shall be configured with muting 8 Tx numb ing, the muting Tx number should be equa the CSI-RS Tx number of the serving cell/ an assumption that the serving cell/sect the muting group.

If a serving sector is 4 Tx, then there a ing patterns. In a case where neighbour number equals 4, the maximum pattern shal muting 4 Tx number. If it is supposed tha CSI-RS is located among positions [0-4] muting pattern would be [0-4]. In a cas cell maximum Tx number equals 8, the maxi configured with muting 8 Tx number. If the serving sector CSI-RS is located amon [5-9] in figure 5B, then muting pattern ¾

If the serving sector is 2 Tx, then three possible. In a case where neighbouring ce equals 2, the maximum pattern can be conf Tx number. If it is supposed that the s

[5-9] or [10-14] or [15-19] in figure 5A, would be [0-19] .

For the 4Tx CSI pattern shown in figure 5 be set as a multiple of 5, such as 5 or : pattern shown in figure 5A, FR number c, multiple as 5, such as 5, 10, 15 or 20. pattern sets include 5N pattern indexes. If the number of ports in a serving sect 2Tx, but a neighbour sector is 4Tx, and CSI-RS index is 15, then in 4Tx case the would be 15 mod 10 = 5. This belongs to muting REs are CSI-RS index [6-9] in the 5B.

It is noted that each cell CSI-RS inde differently. All possible CSI-RS REs can clusters according to pre-defined rules. which includes the cell's / sector's own the final muting pattern.

Another example will now be described muting FR=3 and the total CSI RS pattern of 5. A solution is to limit usage of the

then choose corresponding muting pattern tern sets in accordance with the serving index . Suppose serving sector is 2Tx, and it's and the muting TX number is 4. In this c< tor's CSI-RS index can be mapped from 21 on 15 mod 10 = 5. Thus the muting patte. based Index = 5 under 4Tx case. Since ir group consisting of indexes [3, 4, 5], tl RS indexing [3,4] in 4Tx case of Figure 5

In accordance with a yet further example additional information can be used to set. For example, for 8 TX pattern in fi sets can be defined, [0 1 2], [3 4 0]. ! can be found from two pattern sets. One b included e.g. in a broadcasting channel muting group this sector belongs to. Simi tern sets [0 1 2 ] [5 6 7] [3 4 8] [9 ( One bit signalling can be used to indi 0,1. For 2 Tx case, pattern sets [0 1 [10,11,12] [15,16,17] [9 13 14] [18 19 formation can be utilized to indicate inc

cord medium. A possibility is to downlo product via a data network. In general, ments may be implemented in hardware or cuits, software, logic or any combinatic ments of the inventions may thus be pract ponents such as integrated circuit modu. integrated circuits is by and large a hi ess. Complex and powerful software tool converting a logic level design into a s design ready to be etched and formed on strate .

The above described embodiments may pre tages. For example, all of the CSI-RS in Flexibly configurable frequency reuse nun In principle any number of muting frequer ployed. Different Tx configurations can Muting configuration does not cause unne head .

It is noted that whilst embodiments ha\ relation to communications system such a LTE and 3GPP based systems, similar princ to any other communication system where 2 used. Thus, instead of communications 1

fore, although certain embodiments were way of example with reference to certain tectures for wireless networks, technolc embodiments may be applied to any othe. communication systems than those illust herein .

It is also noted herein that while the plifying embodiments of the invention variations and modifications which may closed solution without departing from of the present invention.

Claims

Claims

1. A method of controlling reference sigi generating a signalling pattern assoc one radio service area, the pattern comp indicating resources for reference signa] dio service area;

signalling the pattern;

signalling clustering information, tt mation comprising information of at least and frequency reuse to enable communica first radio service area to determine a based on the signalling pattern and said tion; and

using resources indicated by one or m in the muting cluster for reference sigr radio service area and muting resources locations in the muting cluster. 2. A method of controlling reference sig receiving by a communication device a the pattern comprising locations for indi reference signalling in a first radio ser receiving by the communication device tion, the clustering information comprisi

and the information of frequency reuse c reuse number. . A method in accordance with any prec< the reference signalling comprises sign₍ state information reference signal.

5. A method in accordance with any prece ing cyclically reusing the clustered loca for reference signalling.

6. A method in accordance with any prece ing :

determining, based on a frequency re at least one location does not belong to sending or receiving an indicator of

7. A method in accordance with claim 6, mining comprises determining that the nu the pattern for indicating resources for is not a multiple of a relevant frequency

8. A method in accordance with any prec the clustering is determined based on:

N

Group_n ={m\n* FR≤m<(n + \)* FR-\,m< FR

Fl

9. A method in accordance with any prece the muting configuration is determined where x is the resource location index service area.

10. A method in accordance with any prece ing mapping of resource locations of a source locations of another port number.

11. A method in accordance with claim 10, the resource locations based on the numb< tions associated with the port number of vice area and the number of resource loc. ciated with a muting port number.

12. A method in accordance with claim 11, determining the muting cluster base number and a frequency reuse number, and determining the muting configuratior and number of resource locations associa port number.

13. A method in accordance with any prece ing separately encoding the information of frequency reuse.

16. A method in accordance with claim 14 joint encoding further comprises encoding indicator .

17. A method in accordance with any of t wherein the first radio service area comf cell or a cell. 18. An apparatus comprising at least on< least one memory including computer pro the at least one memory and the compute configured, with the at least one process to generate a signalling pattern asso one radio service area, the pattern comp indicating resources for reference signa.^" dio service area;

to cause signalling of the pattern ai formation, the clustering information co of at least one of muting ports and frequ communication devices in the first radio termine a muting configuration based on clustering information; and

to use resources indicated by one o tions in the muting cluster for referent first radio service area and to mute re to process a received signalling p; comprising locations for indicating reso signalling in a first radio service area; to process received clustering inforn ing information comprising information muting ports and frequency reuse;

to determine a muting configuration b< signalling pattern and the clustering inf to determine, based on the muting con ing of resources for reference signalling first radio service area.

20. An apparatus in accordance with clai the information of muting ports comprise ports and the information of frequency r< quency reuse number.

21. An apparatus in accordance with any wherein the reference signalling compri channel state information reference sigi source comprises a channel state informat resource element.

22. An apparatus in accordance with any configured to cyclically reuse the cluste oattern for reference signalling. dicating resources for reference signalli of a relevant frequency reuse number.

25. An apparatus in accordance with any configured to map resource locations of i. source locations of another port number.

26. An apparatus in accordance with clai map the resource locations based on basi resource locations associated with the first radio service area and the number o that is associated with a muting port num

27. An apparatus in accordance with clai determine the muting cluster based on a and a frequency reuse number, wherein tl tion is determined based on an index anc locations associated with the muting port

28. An apparatus in accordance with any wherein the first radio service area com; cell or a cell.

29. A communication device comprising an dance with any of claims 18 to 28.

32. A communication system comprising an nication device and/or a base station in of claims 18 to 31.

33. A computer program comprising prograi to perform the steps of any of claims 1 gram is run on a data processing apparatu