GB2490661A

GB2490661A - Calculating User Equipment (UE) measurement gap requirement in a carrier aggregation system

Info

Publication number: GB2490661A
Application number: GB1107421.8A
Authority: GB
Inventors: Albert Mraz; Zoltan Nameth; Gabor Jeney
Original assignee: Sharp Corp
Current assignee: Sharp Corp
Priority date: 2011-05-04
Filing date: 2011-05-04
Publication date: 2012-11-14
Also published as: GB201107421D0

Abstract

A telecommunications system comprising a network node and a User Equipment (UE). The UE comprises a plurality of receivers, receiver 1, receiver 2, which may each support a plurality of carrier bands, band A, band B, band C etc. The system functions using carrier aggregation, whereby multiple carrier frequencies from one or more carrier bands may be used in a wireless communication session, wherein, the network node is operable to inform the UE of which carrier bands are to be used in a given wireless session, and in response to said information, said UE is operable to ascertain which bands comprise the carrier aggregation. In the system described the UE dynamically calculates on which bands said UE requires measurement gaps such that the number of said gaps is minimized (i.e. bandwidth is maximized), and it informs the network node accordingly. In a further embodiment the UE is operable to dynamically select which receivers of the plurality of receivers operate on which carrier bands to minimize the requirement for measurement gaps. In this arrangement the UE may use an algorithm to exhaustively search combinations of receiver capability and current carrier aggregation configuration.

Description

User Equipment and System using same The present invention relates generally to user equipment, such as mobile radio receivers and more specifically to user equipments applicable to Long Term Evolution (LTE)-Advanced system.

Description of related art

The first release of the LTE was referred to as release-8, and provided a peak rate of 300 Mbps, a radio network delay of less than 5ms, an increase in spectrum efficiency and new architecture to reduce cost and simplify operation.

LTE-A or LTE Advanced is currently being standardized by the 3GPP as an enhancement of LTE. LTE mobile communication systems are expected to be deployed from 2010 onwards as a natural evolution of GSM and UMTS. Further information on the 3GPP may be found at www.3gpp.org.

Being defined as 3.9G (3G+) technology, LTE does not meet the requirements for 4G, also called IMT Advanced, that has requirements such as peak data rates up to 1 Gbps.

In April 2008, the 3GPP agreed the plans for future work on Long Term Evolution (LTE). A first set of 3GPP requirements on LTE Advanced was approved in June 2008. The standard calls for a peak data rate of 1 Gbps.

To meet the proposed L.TE-Advanced requirements, support of wider transmission bandwidths is required than the 20 MHz bandwidth specified in 3CPP Release 8/9. To create greater bandwidths, carder a.ggrega.tlOn was proposed. Carrier aggregation allows expansion of effective bandwidth delivered to a user equipment (the term user equipment is used. to cover all types of user terminals, including mobile telephones) through concurrent utilization of radio resources across multiple carriers. Multiple component carriers are aggregated to form. a larger overall transr ission bandwidth, The 3GPP specifies carrier aggregation in LTE-A as including: *Re].-8/9 backward compa.tbie. carriers are to be. supported; Rei-i0 signalling to support aggregation of up to five downiink component carriers and five uplink component carriers, irrespective of intra-or inter-band Carrier Aggregation; Rel-I U to support both i n.tra-band and inter-band aggregation for both downiink & upii.nk in EDO; Ret-i 0 to support inter-hand aggregation with different signal reception timings across of component carriers of different bands for FDD downiinic; * UE*specific asymmetric number of component carriers in downiink and uplink; *Component carriers to have any Rel-8 bandwiths; and *Two or more component carriers can be aggregated to support wider transmission bandwidths up to 100 MHz. Spectrum deployment can be either contiguous or non-contiguous (ie the component carriers may have contiguous bandwidths, or may be separated within the frequency spectrum).

Support for carrier aggregation feature requires enhancement to the 3GPP LTE Release 8 & 9 physical, MAC, and RRC protocol layers. To an LTE Rel-8 terminal, each component carrier will appear as an LTE carrier, while an LTE-Advanced terminal can use the total aggregated bandwidth.

In cunent wireless communication systems, user equipments (UEs) may support different operating bands. Therefore, if a UE is required to change the operating frequency, such as during handover between cells, the UE will be required to measure the other frequencies belonging to the other cells in the downlink direction while operating on one or more frequencies with one or more serving cells.

Typically, due to the way individual receiver is designed, the UE may not be able to simultaneously operate on a first frequency and perform measurements on a second frequency.

To allow the UE to perform measurements of inter-frequency or inter-RAT neighbouring cells, the lIE requires gaps in the transmission to and reception from serving cells. These gaps, often allocated by the network, are referred to as measurement gaps.

However, measurement gaps can have an adverse effect on a wireless communication system, in that they can reduce the overall throughput by reducing the available opportunities for transmission and reception. Inefficient use of system resources may occur.

The current method under Rel-8!9 for indicating the need for measurement gaps is shown in figure 2. This method has the adverse effects that it may not efficiently use the available radio resource, because some of the gaps may be redundant, and achievable system throughput would be reduced. Initially a UE sends the indication information as shown in figure 3 as a static information in UE Capability signalling. Based on this information, a base station (eNodeB) or other node (such as a relay) configures the measurement gaps for each UE through a RRCConnectionReconfiguration signal to the UE. This signal specifies the measurement gap pattem and controls setup! release of measurement gaps. Figure 2 illustrates the procedures of measurement gap indication and measurement gap configuration for a UE under 3GGP release 8!9.

It should be noted that if the UE needs measurement gaps for inter-frequency measurements, but enough gaps are not configured by the system, then inter-frequency measurement requirements would not be satisfied. This may result in poor system performance, including delay in handovers, dropped calls, and so on.

To aid understanding of the present invention, further discussion of lIE hardware will now be made. A lIE will typically comprise one or more receivers. Each receiver may operate on one or more different carrier bands.

UE receivers may have different architectures, and depending on measurement requirements and receiver configuration, need differing measurement gaps to perform measurements on particular bands/frequencies. However, as the wireless communications network has to configure measurement gaps for each LIE, the network requires input from each of the LIEs about what combinations of frequencies/bands require measurement gaps. It is not desirable for the network to have to make decisions based on individual receiver design: it should be blind to the receiver details, and only depend on the inputs from the UEs. This means the effectiveness and efficiency of measurement gaps depends on the effectiveness of the method by which UEs inform the network about their need for having measurement gaps in different operating conditions, ie., when operating on certain bands.

To aid further understanding of the present invention, three different UE receiver designs are shown in figures la, lb and Ic.

The receiver design in figure 1 a shows two receivers. Each receiver can only support one band and each band can only work on one receiver.

The receiver design in figure lb shows two receivers, whereby each receiver is operable to support two component carrier bands. Thus each receiver can support multiple bands separately (not simultaneously), but each band can work on only one receiver (ie receiver 1 is operable to support band A and band B, whilst receiver 2 is operable to support band C and band D).

Some receivers can support multiple bands separately (not simultaneously) and some bands can work on more than one receiver. This arrangement is shown in figure ic. Here, a UE may have multiple receiver banks, in which a receiver bank may support multiple bands.

Some bands may be supported by multiple receiver banks. Measurement gaps are needed when, for a given measured band, the same receiver bank is used as for the serving band.

For 3GPP Rel-10, with a maximum 18 component carrier bands for frequency division duplex, depending on the maximum number of bands supported by a UE and with different UE receiver architecture, with more carriers considered for catTier aggregation, the amount of potentially measurement gaps increases.

On a related topic, research articles R2-106284, R2-1 10295, R2-1 10325, R2-l 10200, R2- 110429 expound the need for indicating measurement gaps to the network. These references may be found at www.3gpp.org As at the date of filing, the documents may be specifically found at www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSGR2_72/Docs/ and www.3gpp.org/ftp/tsg_ran/WG2_RL2/TSG R2_72bis/Docs.

Disclosure of the Invention

The effectiveness and efficiency of measurement gaps depends on the effectiveness of the method by which UEs inform the network about their requirement for having measurement gaps in different operating conditions, ie., when operating on certain bands, If the measurement gaps can be minimized, the system can make more efficient use of available resources.

Case A: It is desirable for the UE to find out quickly, depending on the current canier aggregation configuration, which bands will need measurement gaps and indicate the need for measurement gaps to the network, depending on which bands are present in each receiver.

Case B: If the receiver architecture is more flexible, the UE may be able to assign the bands to receivers dynamically, according to the current carrier aggregation configuration. In this case, it is desirable for the UE to assign the bands to receivers such that the need for measurement gaps can be minimized.

According to the present invention there is provided a telecommunications system comprising a network node and a user equipment (UE), wherein, said UE comprises a plurality of receivers; said system being operable to function using carrier aggregation whereby multiple carrier frequencies from one or more calTier bands may be used in a wireless communication session, wherein, said network node is operable to inform the UE of which carrier bands are to be used in a given wireless session, in response to said information, said UE is operable to ascertain which bands comprise the carrier aggregation, and dynamically calculate on which bands said UE requires measurement gaps such that the number of said gaps is minimized, and inform the network node accordingly.

Preferably the system is an LTE-advanced network.

It is particularly preferred that each receiver is operable to operate on a one or more carrier bands. Generally, most modern UE will comprise multiple receivers that are capable of functioning on multiple bands It is equally preferred that the carrier aggregation is contiguous or non-contiguous.

In a preferred arrangement, the UE is operable to dynamically select which receivers operate on which bands to minimize the requirement for measurement gaps.

Preferably the UE is operable to map a set of data comprising the current system carrier aggregation based on the number of bands assigned for wireless communication with a set of data comprising the number of carrier bands supported by a given receiver.

It is preferred that the UE is programmed to use the equation: [AJJ\[QAI uB i C to determine which carrier bands require measurement gaps in a given receiver configuration, where A represents the set of carrier bands supported by a given receiver and B represents the current carrier aggregation configuration. A full description, and derivation of the above equation is provided below.

Preferably the IJE uses an algorithm to exhaustively search combinations of receiver capability and current carrier aggregation configuration, it is also particularly preferred that the UE is operable to discard any combinations of receiver capability and current carrier aggregation configuration that are unachievable.

According to a second aspect of the present invention there is provided a user equipment comprising a plurality of receivers, wherein each receiver is operable to wirelessly communicate with a base station using one or more carrier frequencies in one or more component carrier bands in carrier aggregation, wherein said user equipment is operable, on receipt of a notice from the base station informing which carrier bands are to be used, to calculate which of its supported component carrier bands require measurements gaps. and transmit same to the base station.

Preferably the UE is operable to dynamically update its measurement gap requirements with the base station each time the carrier aggregation bands are altered.

It is also preferred that the IJE is operable to dynamically assign component carrier bands to specific receivers based on the carrier aggregation configuration.

Preferably the UE runs an algorithm to ascertain the optimum receiver configuration to minimize the number of required measurement gaps.

According to a third aspect of the present invention there is provided a wireless telecommunication system comprising: a network node; a UE operable to wireless communicate with the network node using a plurality of carrier bands; wherein the network node is operable to inform the FE which carrier band is to be used during wireless communication, in response to the network node's information, the UE is operable to dynamically calculate on which bands measurement gaps are required, and inform the network node.

Whilst it is envisaged that the present arrangement will efficiently allow UEs using carrier aggregation to determine which carrier bands need measurement gaps provided, it should be realised that this is not an essential aspect of the present invention.

According to a further aspect of the present invention there is provided a method of determining measurement gap requirements in a telecommunications system, comprising providing a FE with a set of receivers, each receiver being operable to function on one or more carrier bands, and a network including a network node, said UE operable to wireless communicate with the network node, wherein said network providing to the UE an indication of which carrier bands are to be used in wireless communication, the UE is operable to calculate, based on its receiver configuration and the indication from the network which carrier bands require measurement gaps.

Preferably the UE dynamically assigns receivers to use particular carrier bands to minimize the required number of measurement gaps.

As will be appreciated, the present invention also applies to a UE operable to perform the above calculations, and also to a telecommunications network including such UEs.

Description of the drawings

In order that the present invention be more readily understood, specific embodiments thereof will now be described with reference to the accompanying drawings.

Figure la shows an example of a UE receiver configuration; Figure lb shows an example of a further UE receiver configuration; Figure ic shows an example of another IJE receiver configuration; Figure 2 shows a table illustrating a known method for a UE to indicate the need for measurement gaps to a wireless telecommunications network; Figure 3 shows the signalling between a UE and a network node; arid Figure 4 shows a flow diagram illustrating a preferred method ascertaining which carrier bands require measurement gaps.

Description of Preferred Embodiments

A first aspect of the present invention relates to how to discover which component carrier bands require measurement gaps, based on a given configuration of UE receivers. The present description refers to set theory. A generalized theory is provided initially.

The present embodiments are described assuming that the telecommunications system is capable of using carrier aggregation (CA). This may be either contiguous CA or non-contiguous CA.

For the present example, assume that a UE comprises of a set of N receivers, each of which support particular component carrier (CC) bands. The CC bands are denoted as C. Accordingly the i th receiver can be described with the set of supported CC bands (A1) which is given as: A1 ={Cll,C/z,...CIA}, where C11,C12,. ..C1IAI denote the supported CC bands.

Two or more receivers might support the same band (from figure ic. it can be seen that both receivers support band A). Put another way, the arrangement: C,, = Ckl E (A, n Ak is possible.

Assume also that the current carrier aggregation configuration is described by B then is may be supposed that M CC bands are currently assigned for communication, B can be written as B = {C1, C2,.. .CM where C1, C2,. . . CM are the component carrier bands which are currently assigned for communication in the UE.

The UE maps the B set on A1 sets that all CC bands are served by a receiver. It is assumed that the mapping is possible (in the present arrangement, the network does not drive the LIE to make an impossible assignment). The mapping yields C = {m1, in2,.. .nzM I indices such that: C1 Am n B C2 E A nB CM E A nB The set of CC bands which are supported by the receivers that are currently used for communications is given as: UAm (1) nteC Note that B must be a subset of this set (B c U A, ). me C

The bands, which can be measured without requiring measurement gaps are given as a set of component carrier bands of the remaining (not used) receivers: UA1. (2) i=1,iC Thus, the bands which need measurement gaps can be derived by subtracting the union of B and (2) from (1). Bands in set B do not require any measurement gaps, since they can be measured during communication. So, the remaining set identifies the set of component carrier bands where measurement gaps are needed. It can be calculated as: [UAm9\ UA1UB, (3) meC tl i C where \ denotes the subtraction of sets. If a set element on the right side of \ is not available on the left, it should be neglected. Since extending the left side of \ with the right side does not have any effect on the result, equation 3 can be also rewritten as: [DA19\[DAiUBI. (4) iE C Note that the left side of \ is the capability of a UE, represented by all the CC bands which are supported by said UE. Thus, UE capability is independent of C, and it is constant (it should not be recomputed, if CC band reconfiguration occurs). However, the right side of \ changes, if system configuration changes, and so equation (4) must be recomputed if the configuration of the IJE changes.

The equations above describe the system perfectly. However, to aid practical implementation two models, which are more straightforward from the programming point of view, will now be described.

The following provides practical interpretation of equation (4) and its possible implementation. Firstly, an integer implementation of the method is provided, and secondly a binary solution is shown. Both solutions can be used to evaluate (4), although the latter one allows for quicker computation.

To understand the present aspect of the present embodiment, consider a capability matrix A, with binary elements. Matrix A contains N columns and K rows: N denotes the number of receivers in a UE, and K refers to the total number of component carrier bands. Matrix A describes the capabilities of IJE in binary form: the i th row and j th column component A tells whether the j th receiver supports the I th CC band. =1 states that it is supported, A11 =0 states that it is not supported. To ascertain how many receivers support a given component carrier band, a column vector can be computed as y=A1', where 1N is a column vector full of ones with length N. Vector y is an integer vector with K elements: y tells that how many receiver supports the i th CC band. If y1 = 0, no receiver in the UE is able to receive that CC band (matrix A contains full zeros in the i th row). Note the similarity between matrix A and the series of sets A1,A2,. . .AN: = 1, if C A1 and =0, otherwise.

It is known that there are UE receivers assigned for reception with indices in the set C = {in1, in2,. . . m}. Now defined is a new vector c with length N which contains ones in the indices set of C and zeros otherwise. That is, Cm = Cm = ... = Cm = 1 and c1 = 0, if i C. Also defined is vector b which contains non-zero elements where the set B is not empty: =1, if C1 B, b1 = 0, otherwise.

If matrix A is multiplied with vector i" -c from the right, the result is: x=A(1''c) (5) Vector x stores the bands which can be measured by the unused receivers without a measurement gap. Also the number at row j shows how many inactivated receivers can measure the j th CC band. Zeros in vector x tell that the corresponding component carrier bands cannot be measured if the receivers of C are active. Either measurement gaps are needed, or the UE does not support that CC band at all (if the corresponding row of matrix A contains only zeros).

The component carrier bands, where measurement gaps are required is computed as follows: sgn{y} -sgn{x+b} = sgn{A1'} _sgn{A(1"' -c) +b}, (6) where [1 ifz>0 sgnz= 0 ifz=0, [-i ifz<0, The last equality is never used, since the system only functions with natural numbers. Thus, sgn z produces the same dimensional vector as z and it must be computed component by component. Note that (6) states the same as (4), however here integer numbers can be used for evaluation.

Taking a working example, starling with the matrix A: 0111 3 1111 4 1010 2 A= 0 0 0 0 y= 0 1000 1 1100 2 1 and also with the computed vector y = Ai'.

Matrix A contains N =4 columns which tells us that four receivers exist in the UE, and K =7 rows, which tells us that seven separate CC bands could he used in the system. From the matrix it can be seen that both receivers 1 and 2 support four different CC bands, while receiver 3 and 4 support three and two, respectively (ie the first column contains four "1 s" and three "Os, whilst the fourth column contains two "is" and five "Os").

Vector y shows how many receivers supports the component carrier bands: e.g. band 1 is supported by three receivers, however, none of the receiver supports band 4.

In the present example, assume that receiver 2 and 4 are used (C = {2, 4J) and that they use bands 6 and 2 (B = (2, 6}), respectively. With the above described methodology vector c contains ones at position 2 and 4 (because receivers 2 and 4 are used), and zeros otherwise (c = (010 1)T) Matrix A must be multiplied by the inverse of this vector from the right, which yields: 0111 1 1111 2

I

1010 2 x=A(1'e)= 0 0 0 0 1 = 0 1000 i lioo i 0 The resultant vector x shows that, with this setup, all component carrier bands, except band 4 and band 7 can be measured without measurement gaps. Band 4 cannot be measured by the UE based on its capabilities because it does not comprise a receiver operable to receiver band 4 (the 4th row in matrix A contains zeros). From matrix A it will be noted that while band 7 can he measured by receiver 2, measurement gaps on band 6 are needed to measure band 7.

Using equation (6) it is also possible to ascertain that a measurement gap is required to make measurements on band 7.

3 1 1 1 t 4 3 1 1 0 2 2 1 1 0 sgn{y}-sgn{x+b}=sgn 0 -sgn 0 = 0 -0 = 0 Recall that sgn z equals 1 if z is greater than zero, and sgn z equals 0 if z equals zero.

The above shows that the derivation of the component carrier bands, where measurement gaps are required is possible to implement.

It is also derivable that the number of binary (elementary) operations (OR, XOR) equals K(N -M +1), where K is the number of CC bands, N is the total number of receivers, and M is the actually assigned receivers (or in other words, the number of component carrier bands currently used). With typical values (K =4, N = 4, M = 2) the number of binary operations is a relatively low number (only 12 binary operations are needed).

Based on the forgoing, it will be understood that the system provides for a method that allows a UE to easily and efficiently determine which carrier bands require measurement gaps, based on a configuration of bands per receiver.

S The present embodiment thus provides for a wireless telecommunication system comprising a network node, such as an eNodeB or a relay node. A UE operable to wireless communicate with the network node using a plurality of carrier bands. The system is configured such that the network node is operable to inform the UE which carrier band is to be used during wireless communication, and, in response to the network node's information, the FE is operable to dynamically calculate on which bands measurement gaps are required, and inform the network node.

Considered another way, the present embodiment thus provides a method of determining measurement gap requirements in a telecommunications system. A FE with a set of receivers, each receiver being operable to function on one or more carrier bands, and a network including a network node, is provided. The UE being operable to wireless communicate with the network node, wherein the network providing to the FE an indication of which carrier bands are to he used in wireless communication, and the UE is operable to calculate, based on its receiver configuration and the indication from the network which carrier bands require measurement gaps.

As stated earlier, typically the present arrangement will be used in a network, and on a FE, that supports carrier aggregation. Here, there will generally be provided a user equipment comprising a plurality of receivers, wherein each receiver is operable to wireles sly communicate with a base station using one or more carrier frequencies in one or more component carrier bands in carrier aggregation. Within this set up the user equipment is operable, on receipt of a notice from the base station informing which carrier bands are to be used, to calculate which of its supported component carrier hands require measurements gaps, and transmit same to the base station.

A second aspect of the present invention relates to an arrangement of how to minimize the need for measurement gaps by dynamically assigning hands within UE receivers. The present aspect has particular merit when the network uses canier aggregation to enhance bandwidth.

Thus, the UB is operable to dynamically select which receivers of the plurality of receivers operate on which bands to minimize the requirement for measurement gaps.

In this arrangement, the UE is operable to dynamically update its measurement gap requirements with the base station each time the carrier aggregation bands are altered.

Furthermore, the UE is operable to run an algorithm to ascertain the optimum receiver configuration to minimize the number of required measurement gaps.

Using the notations used above, the following describes an exhaustive search based assigning algorithm. That is, this algorithm assigns c (or C) based on the UE capability (A) and the order of the network (B). The algorithm is based on exhaustive search and uses an integer model. Furthermore, and importantly, the algorithm also takes into consideration that only valid combinations can work (if a combination of receivers cannot serve the required CC bands, it is neglected).

The algorithm should find a vector c, so that the number of needed measurement gaps determined by (iN)T (sgn {y} -sgn {x}) will be minimized, with the following conditions: * pre-defined matrix A (or equivalently set A) and * set B={L'l,C2,...,CM} with M«=N, and C1 refers to one of the K CC bands (C1e{1,2,...,K}).

It is assumed that the network takes into account the UE capability (set A, or matrix A) when assigning set B. That is, the network does not force the UE into an unachievable setup (unachievable refers to a situation which cannot be solved with the receivers of the UE).

Two key factors are that, on the one hand, each active receiver is able to handle a single CC: M CC bands must be served by M receivers. On the other hand, only M pieces of K CC bands can be active in a given transmission interval. Thus, the maximum number of CC bands, where measurement gaps are needed is limited by K -M Provided that only one receiver can handle only one CC band at once, if M CC bands are allocated for communication, M receivers must be active in the UE. That is, the number of ones' in vector c should be equal to M. The total possible combination for choosing M (N pieces of N receivers, equals NI The total number of possible c vectors equals the total possible combinations.

The UE performs a specific algorithm to assign component carriers to receivers. Details of the algorithm are set out below. However, prior to execution of the algorithm, a twofold initial check is performed with respect to set B to ensure that the UE is operable to run said algorithm. The details are: a. All of the selected CC hands should be supported by at least one receiver.

Namely, if matrix A has a row without 1' entries, and set B has an entry for this row (representing a component carrier band), the algorithm will generate an error message. Since the required CC band is not supported by any of the UE' s receivers. The algorithm will terminated with an error message regarding to B. b. M CC bands should be supported by at least M pieces of receivers. In other words, at least M pieces of rows of matrix A should contain at least one *1? entry at the selected positions of CC bands, defined by B. In the opposite case, the receiver (defined by this column) will not be able to support any CC band.

The following is an algorithmic description to aid understanding of the above: * Remove the rows of A, which are not selected by B. Let denote the rcsulted matrix with P. * Let calculate (1M).D, where (1M) denotes a column vector, containing full of ones with length of M (number of the rows of U).

* If there exists any 0' entry in (1M) .D, the algorithm will be terminated with error message respect to B. The steps of the algorithm are as follows: (N 1. Define an N x sized matrix C with binary entries on N bits, which M) contains all of the possibilities in its rows for the combination defined above.

Each row of matrix C represents a possible vector eT. The allocation possibilities are reduced (by clearing irrelevant rows of C) according to the following steps.

2. Selecting situations, in which certain needed CC bands are supported by a single receiver: Analyze the elements along set B. If y = 1, (for any j =1, ., M), that is the j -th CC band is supported by one sole receiver, if there is no such CC band, skip to Step 3.

Consideration is required for cases in which multiple 1 entries are present in vector y at the positions, which are determined by B. If these 1 entries determine such rows within matrix A, which are equal (the sole 1' entries within the rows are located in the same column), the algorithm will generate an error message and will stop, since the corresponding (multiple) CC bands cannot be supported by the same receiver. In this case, the given set B will not be

supportable.

According to the description above, a vector 1 with N entries can be defined, in which l contains the number of the identical rows within matrix A (selected by the entries of B), which are containing sole 1' values at column n. We can step forward to 2(a) only in that case, if each element of vector 1 is equal to zero. Note, that l!= 1 at any cases.

a. Find the column i in the row C. of matrix A, where the value one is situated.

(it requires maximum N steps). Parameter i identifies the receiver which must be switched on: this is the only receiver which supports the C1 band (since y3 =1).

b. Delete the rows of matrix C, which do not contain F at column i: we are not interested in the configurations where the i th receiver is not switched on. As we stated earlier, it must be switched on, so all other configurations should he dropped. The corresponding matrix is denoted by C'. After the removal of S rows, for all j, c. =1 certainly.

c. Find other receivers which must be switched on. In this arrangement, the column i of matrix A, is not considered, and the values of this column are set to zero. This modified matrix is hereinafter referred to as A'. With this modification it is possible to remove the effect of the i th receiver (which has already been identified as a required resource hence consideration is turned to the other receivers). Vector y' = AI1N is recalculated to get a new vector y' and repeat the tasks beginning from Step 2. In a prefened anangement, instead of multiplying A' by 1N, it is possible to substract the i th column of of A from y: y' = y -at. Processing operations can be avoided using this modification. Subtraction needs only K operations.

There is a limited number of combinations in matrix C. And it is known that all combinations are valid (there could not be combinations which cannot serve the assigned CC bands).

3. With the remaining rows of matrix C, we identify the needed gaps based on equation: yED(xub)=AolNe(Aocub) (7) where $ is the binary XOR operation, i.e., the binary subtraction, thus y $ (x ub) = sgn{Al"j -sgn{A(r -c) +b} The total number of gaps required is the sum of the vector elements: (1N)T(sgn{y}_sgn{x}).

4. The preferred solution is the row of matrix C where the total number of required gaps yields the lowest number.

A flow chart is shown in figure 4 that illustrates the above mechanism.

A working example of the above aspect is now provided. The same matrix A as used above is now used here for familiarity. Again, it should be noted that matrix A represents four receivers (the four columns) and seven bands (the seven rows).

A= 0 0 0 0 Set B relates to the number of bands currently in use in the system. in this arrangement let B = {2, 5,61 (or equivalently b = (010011 0)T). Thus, in this example, component carrier bands 2, 5 and 6 are used currently. From the previous examples it is known that: y=0.

Vector y represents the total number of receivers that are operable to support a given band. (4

Firstly, a Matrix C is generated with size of = 4x4, C= lOll Since set B contains a component carrier band, band 5, which is supported by a single receiver (see y5 = 1, while y2 = 4 and y6 = 2), it means that the corresponding receiver (namely the first one, see =1, while for all i!= 1, = 0) should be kept during the assignment. In this situation, all rows, where receiver 1 is not selected may be deleted from matrix C. In the present example, only the last row is be deleted, since it contains 0' at the position of the first receiver. The updated matrix is thus: C'= 1 1 0 1 Receiver 1 has thus been defined as a required resource. Accordingly, matrix A is updated so that the first column (represent receiver 1) is filled with zeros. The updated matrix A is represented thus: A'= 0 0 0 0 It is also necessary to re-calculate vector y' either by multiplication or by subtraction.

Updated vector y is shown below: )T'= 0 Since set B contains a component carrier band, band 6, which is supported by a single receiver (see y =1, while y, = 3 and v = 0), it means that the corresponding receiver (namely the second one, see = 1, while all other A. =0) should be kept during the assignment. In this situation, all rows from matrix C', where receiver 2 is not selected may be eliminated. In this example, only the last row {101 l} must be deleted, since it contains 0' at the position of the second receiver. The further updated matrix is thus: 1 1 0 l 1 0 1 Receiver 2 has been identified as a required resource, and original matrix A is updated with zeros in the second column of matrix A': K= 0 0 0 0 and recalculate vector y y"= 0 Set B does not contain any further component carrier band which is supported by a sole receiver (y2 = 2, while y5 = 0 and y5 = 0). This means that there is no possibility to further reduce matrix C. The next requirement is to calculate the needed measurement gaps for each row of C. According to (1N)T(sgn{y} -sgn{x} + b), the total number of the CC bands, where measurement gaps are needed is provided. In this situation there are two possible options: the first row of matrix C and 1 for the second row of C. The second row yields the lowest number of measurement gaps, the optimal assignment is the following: = (LL0,1)' With this setup, one sole CC band will require measurement gaps.

It will thus be appreciated that a UE uses an algorithm to exhaustively search combinations of receiver capability and current carrier aggregation configuration. Furthermore, more intelligence is provided as the UE is operable to discard any combinations of receiver capability and current carrier aggregation configuration that are unachievable.

Binary operations may also be used, which has two advantages compared to the integer S operations: * working with bits instead of integers requires less resources (both in terms of CPU load and memory), * binary implementation could be directly programmed without excessive work.

Starting from the same capability matrix A, which has binary elements. As before, matrix A describes the capabilities of UE in binary form: the i th row and / th column component A, tells whether the j th receiver supports the i th CC band. To read which CC bands are supported by the receiver, a binary column vector can he computed as y = A o lN, where o is a binary multiplication operation: vT a w computes u1 (v1 n we). Thus, vector Y becomes a binary vector with K elements: y1 tells whether the i th CC band is supported by any of the receivers. If y1 = 0, no receiver is able to receive that CC band (matrix A contains zeros in the ithrow). Note that Aol" =sgn{Al"}.

As before, vector c is defined with length N with ones in the indices set of C and zeros otherwise. That is, Cm = =... = Cm =1 and c = 0, if i E C. If matrix A is binary scalar multiplied with vector (the inverse of c) from the right, the result is: x=Ao (8) Vector x stores the bands which can be measured by the remaining set of receivers without a measurement gap. Here we lose the information about the number of receivers that can measure the bands. However, all zeros in vector x tells that the corresponding CC band cannot be measured if all the receivers of C are active. As before, either measurement gaps are needed, or the UE does not support that CC band (if the corresponding row of matrix A contains only zeros). Note that Aoc = sgn{A(1N -c)}.

Vector b is also used, which contains non-zero elements where the set B is not empty: =1, if C1 G B, b3 =0, otherwise.

The CC bands, where measurement gaps are needed is computed as follows: y$(xub)=AO1NED(Aocub) (9) where $ is the binary XOR operation, i.e., the binary subtraction, thus y $(x ub) = sgn{A1N} _sgn{A(P -c)+b} The description with bits is complete, and generally straightforward. Following (9), as A o is constant, only the right side, A ocub must be recomputed when a reconfiguration occurs.

Depending on M and N this yields N -M binary OR operations per CC band. The $ requires one additional operation, thus the total number of binary operations equals K(N-M+l).

Based on the foregoing binary embodiment, the example considered earlier will now be used further. Start with matrix A: 0111 1 1111 1 1010 1 A= 0 0 0 0 y=0.

1000 1 1100 1 1 and where vector y = A al" is calculated.

Matrix A contains N =4 columns which provides that four receivers exist in the liE, and K =7 rows, which tells provides that seven separate CC bands could he used in the system.

Both receivers 1 and 2 support four different CC bands, while receiver 3 and 4 support three and two, respectively. Vector y shows how many receiver supports the CC bands: e.g. band 1 is supported by three receivers, however, none of the receiver supports band 4.

Now assume that receiver 2 and 4 are used (C = {2,4}) and that they use bands 6 and 2 (B = {2, 6}), respectively, b = (010001 ofT With the above described methodology vector c contains ones at position 2 and 4, and zeros otherwise (c = (010 1ff) Matrix A must be multiplied by the inverse of this vector from the right, which yields 0111 1 1111 1 1010 1 x=Aoë= 0 0 0 0 0 = 0 1000 1 1100 1 0 That is, with this setup, all CC bands, except band 4 and band 7 can be measured without measurement gaps. Band 4 cannot he measured by the UE based on its capabilities (the 4th row in matrix A contains zeros), while band 7 can be measured by receiver 2: we need measurement gaps on band 6 to measure band 7. We also get band 7 from equation (9): 1 1 0 1 1 0 1 1 0 yEB(xub)= 0 $ 0 = 0 1 1 0 1 1 0 1 0 1 Although (for the sake of clarity) all the steps are shown in the present embodiment, it should be noted that the number of binary operations needed to get this figure equals 3x7 = 21.

Twenty one binary operations is readily achievable by the user equipment.

The present embodiment allows for a UE to dynamically adapt its use of its receivers. For example, using figure lc as an example, if the UE is using band A in receiver 1 to communicate with a network node (such as an eNodeB or relay), and there becomes a need for the UE to make measurements using band B, it is possible for the UE to re-assign its communication on band A to receiver 2, and use receiver 1 to communicate on band B. As will be appreciated, this dynamic assignment of canier bands within a UE' s receiver array allows for the reduction of measurement gaps.

Thus there is disclosed a telecommunications system comprising a network node -such as an eNodeB or a relay -and a UE. The UE comprises a plurality of receivers. The system is operable to function using carrier aggregation whereby multiple carrier frequencies from one or more carrier bands may be used in a wireless communication session. The network node is operable to inform the UE of which carrier bands are to be used in a given wireless session, and in response to said information, said UE is operable to ascertain which bands comprise the carrier aggregation, and dynamically calculate on which bands said UE requires measurement gaps such that the number of said gaps is minimized, and inform the network node accordingly.

All of the above embodiments are particularly applicable to LTE-A networks, but are not limited thereto.

Thus, based on the forgoing description, it will be appreciated that the UE is operable to map a set of data comprising the current system carrier aggregation based on the number of bands assigned for wireless communication with a set of data comprising the number of carrier bands supported by a given receiver.

It is to be appreciated that the present embodiments have been described for ease of understanding only, and that many modifications and variations are possible within the scope of the attached claims.

Claims

CLAIMS.1. A telecommunications system comprising a network node and a user equipment (UE), wherein, said UE comprises a plurality of receivers; said system being operable to function using carrier aggregation whereby multiple carrier frequencies from one or more carrier bands may be used in a wireless communication session, wherein, said network node is operable to inform said UE of which carrier bands are to be used in a given wireless session, in response to said information informed from the network node, said UE is operable to ascertain which carrier bands comprise the carrier aggregation, and dynamically calculate on which bands said UE requires measurement gaps such that the number of said measurement gaps is minimized, and inform said network node accordingly.
2 A telecommunications system according to claim 1, wherein the system is a Long Term Evolution (LTE) network.
3 A telecommunications system according to claim 1 or claim 2, wherein each receiver of the plurality of receivers is operable to operate on one or more carrier bands
4. A telecommunications system according to any of claims 1 to 3, wherein the carrier aggregation is contiguous.
5. A telecommunications system according to any of claim 1 to 3, wherein the carrier aggregation is non-contiguous.
6. A telecommunications system according to any preceding claim, whereby said UE is operable to dynamically select which receivers of the plurality of receivers operate on which carrier bands to minimize the requirement for measurement gaps.
7. A telecommunications system according to any preceding claim, whereby the IJE is operable to map a set of data comprising the current system carrier aggregation based on the number of carrier bands assigned for wireless communication with a set of data comprising the number of carrier bands supported by a given receiver.
8. A telecommunications system according to claim 5, wherein the UE is operable to use the equation: [ÜAJJ\[OA UBIICto determine which carrier bands require measurement gaps in a given receiver configuration, where A represents the set of carrier bands supported by a given receiver and B represents the current carrier aggregation configuration.
9. A telecommunications system according to claim 6, wherein UE uses an algorithm to exhaustively search combinations of receiver capability and current carrier aggregation configuration.
10. A telecommunications system according to claim 9, wherein the UE is operable to discard any combinations of receiver capability and current carrier aggregation configuration that are unachievable.
11. A user equipment (UE) comprising a plurality of receivers, wherein each receiver is operable to wirelessly communicate with a base station using one or more carrier frequencies in one or more component carrier bands in carrier aggregation, wherein said UE is operable, on receipt of a notice from the base station informing which carrier bands are to be used, to calculate which of its supported component carrier bands require measurements gaps, and transmit same to the base station.
12. A user equipment according to claim 11 whereby the UE is operable to dynamically update its measurement gap requirements with the base station each time the carrier aggregation bands are altered.
13. A user equipment according to claim 11 or claim 12, wherein the UE is operable to dynamically assign component carrier bands to specific receivers of the plurality of receivers based on the carrier aggregation configuration.
14. A user equipment according to claim 13, wherein the UE runs an algorithm to ascertain the optimum receiver configuration to minimize the number of required measurement gaps.
15. A wireless telecommunication system comprising: a network node; a user equipment (IJE) operable to wireless communicate with the network node using a plurality of carrier bands; wherein the network node is operable to inform the UE which carrier band is to be used during wireless communication, and S in response to the information informed from the network node, the UE is operable to dynamically calculate on which carrier bands measurement gaps are required, and inform the network node.16 A method of determining measurement gap requirements in a telecommunications system, comprising providing a user equipment (UE) with a set of receivers, each receiver being operable to function on one or more carrier bands, and a network including a network node, said UE operable to wireless communicate with the network node, wherein said network providing to the UE an indication of which carrier bands are to be used in wireless communication, the UE is operable to calculate, based on its receiver configuration and the indication from the network which carrier bands require measurement gaps.17. A method according to claim 16, wherein the UE dynamically assigns receivers to use particular carrier bands to minimize the required number of measurement gaps.18. A user equipment operable to perform the method according to claims 16 or 17.