COMMUNICATION SYSTEM

TECHNICAL FIELD

The present invention generally relates to a communication system, particularly to a method and apparatus for interference control in a wireless communication system.

DESCRIPTION OF THE RELATED ART

In wireless communications, multiuser multiple-input multiple-output (MIMO) transmission technologies have received considerable attention in recent years, due to their ability for providing significantly enhanced spectral efficiency and link reliability compared with conventional single antenna systems. It becomes a key technology used in the Third Generation Partnership Project (3GPP) Standard for Long Term Evolution (LTE) /LTE-Advanced (LTE-A) Long Term Evolution.

Coordinated MIMO processing technologies based on coordination of multiple base stations are proposed to cancel inter-cell interference and increase signal-to-interference plus noise ratio (SINR) . Coordinated base stations exchanges channel state information (CSI) and transmission data so as to perform MIMO processing coordinately.

To increase capacity of the network and reducing sever inter-cell interference between macro base stations in higher node deployment density, a network that consists of a mix of macro-cells and low-power and low-cost nodes or wireless assess points has emerged, which is called heterogeneous network. There are many deployment scenarios for a HetNet. For example, for a indoor scenario, femtocells can be used with transmission power lower than lOOmW and connected with macro cells via digital subscriber lines (DSLs) ; indoor relays can be used with transmission lower than lOOmW; indoor remote radio head (RRH) /Hotzone such as indoor picos are used with transmission power lower than lOOmW and connected with macro cells via high speed backhaul such as optical fiber. In a outdoor scenario, outdoor relays can be sued with 250mW-2W transmission power; outdoor RRH/Hotzone such outdoor pico can be used with 250mW-2W transmission power and connected with macro cells via high-speed backhaul such as optical fiber. In general, such small, low-power base stations can be called low-power base stations, which are in contrast to macro base stations in a HetNet.

In a HetNet, a macro base station and low-power base station (s) deployed in the edge of the macro base station's coverage can operate coordinately to act as an equivalent virtual MI O system. It is desired to provide a solution for interference control in a wireless communication system, which is adaptive to the scenarios of a HetNet.

SUMMARY OF THE INVENTION

To solve the problems in the prior art, one or more method and apparatus embodiments according to the present invention aim to provide an improved solution for interference control in a wireless communication system.

According to an aspect of the present invention, an embodiment of the present invention provides a method for operating a base station. The method comprises: receiving, from each of a first group of user equipments served by a first base station, first feedback information, the first feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix; exchanging feedback information with a second base station, wherein the second base station receives from each of a second group of user equipments served by the second base station second feedback information, the second feedback information including at least information indicative of a first precoding matrix and information indicative of a cluster that includes a second precoding matrix different from the first precoding matrix; coordinately scheduling, at least based on the first feedback information and the second feedback information, the first group of user equipments and the second group of user equipments. According to another aspect of the present invention, an embodiment of the present invention provides a base station. The base station comprises: receiving unit configured to receive, from each of a first group of user equipments served by the base station, first feedback information, the feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix; exchanging unit configured to exchange feedback information with a further base station, wherein the further base station receives from each of a second group of user equipments served by the further base station second feedback information, the second feedback information including at least information indicative of a first precoding matrix and information indicative of a cluster that includes a second precoding matrix different from the first precoding matrix; scheduling unit configured to schedule coordinately, at least based on the first feedback information and the second feedback information, the first group of user equipments and the second group of user equipments.

According to further aspect of the present invention, an embodiment of the present invention provides an apparatus for operating a base station. The apparatus comprises: means for receiving, from each of a first group of user equipments served by a first base station, first feedback information, the first feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix; means for exchanging feedback information with a second base station, wherein the second base station receives from each of a second group of user equipments served by the second base station second feedback information, the second feedback information including at least information indicative of a first precoding matrix and information indicative of a cluster that includes a second precoding matrix different from the first precoding matrix; means for scheduling coordinately, at least based on the first feedback information and the second feedback information, the first group of user equipments and the second group of user equipments .

According to further aspect of the present invention, an embodiment of the present invention provides a method for operating a user equipment, comprising: reporting to a base station which serves the user equipment feedback information, wherein the feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix.

According to further aspect of the present invention, an embodiment of the present invention provides a user equipment. The user equipment comprises: reporting unit configured to reporting to a base station which serves the user equipment feedback information, wherein the feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix.

According to further aspect of the present invention, an embodiment of the present invention provides an apparatus for operating a user equipment. The apparatus comprises: means for reporting to a base station which serves the user equipment feedback information, wherein the feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

Inventive features regarded as the characteristics of the present invention are set forth in the appended claims. However, the present invention, its implementation mode, other objectives, features and advantages will be better understood through reading the following detailed description on the exemplary embodiments with reference to the accompanying drawings, where in the drawings:

Fig. 1 schematically illustrates an example of a wireless communication system in which embodiments according to an embodiment of the present invention can be implemented;

Fig.2 schematically shows a flow chart of a method for operating a user equipment in a wireless communication system according to an embodiment of the present invention;

Fig.3 schematically illustrates beamforming patterns of an oversampled Discrete Fourier Transform (DFT) -based codebook;

Fig. 4 schematically illustrates a flow chart of a method for operating a base station in a wireless communication system according to an embodiment of the present invention; Fig.5 schematically shows a block diagram of a user equipment according to an embodiment of the present invention;

Fig.6 schematically shows a block diagram of a base station according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, many specific details are illustrated so as to understand the present invention more comprehensively. However, it is apparent to the skilled in the art that implementation of the present invention may not have these details . Additionally, it should be understood that the present invention is not limited to the particular embodiments as introduced here. On the contrary, any arbitrary combination of the following features and elements may be considered to implement and practice the present invention, regardless of whether they involve different embodiments. Thus, the following aspects, features, embodiments and advantages are only for illustrative purposes, and should not be understood as elements or limitations of the appended claims, unless otherwise explicitly specified in the claims.

Fig.1 schematically illustrates an example of a wireless communication system in which embodiments according to an embodiment of the present invention can be implemented.

Referring to Fig.l, a HetNet 100 as shown consists of a macro base station 110 and at least one low-power base station, for example, a RRH node 120. The macro base station 110 and the RRH node 120 can serve their own user equipments respectively. The RRH node 120 is connected with the macro base station 110 via backhaul, for example optical fiber. It should be noted that although taking the RRH node as an example of low-power base stations, the low-power base station according to one or more embodiments of the present invention is not limited to RRH nodes, but includes any suitable low-power base stations such as femto base stations, relay stations, pico base stations, etc.

A scenario is considered without loss any generality where the macro base station 110 and the RRH node 120 serve their own user equipments over the same radio spectrum resource, for example, occupying the same transmission bandwidth or sub-band. Assume that the macro base station 110 is equipped with N _m antennas, the RRH node 120 with antenna, while each user equipment is equipped with a single antenna. The macro base station 110 and the RRH node 120 have their own codebooks, which are denoted as d and C ₂ respectively. Both C ₁ and C ₂ are known to the macro base station 110 and the RRH node 120 as well as all user equipment in the HetNet 100.

A group of user equipments served by the macro base station 110 can denoted by I = {l,2,... ,i,...,K _x } , and a group of user equipments served by the RRH node 120 can be denoted by J = {l,2,.. ,,j,...,K ₂ } . A user equipment in the HetNet 100 can be assigned to one of the macro-user group and the RRH-user group based on a predefined rule. For example, such assignation can be based on the maximum reference signal received power (RSRP) A user equipment k receives reference signals from the macro base station 110 and the RRH node 120 respectively. The received power of the reference signal from the macro base station 110 is P^ _{o k} and from the RRH node 120 P*^ . If P _m ,k ^> P _{KRH IC >} k = l,.. . ,K is satisfied, then the user equipment k is assigned to the macro-user group; if Pj^ _k > P^^, k = l,...,K is satisfied, then the user k is assigned to the RRH-user group; and if i- ^s satisfied, then the user equipment can be assigned randomly to any one of the two group.

When the type of a user equipment (i.e., which group the user equipment belongs to) is determined, the user equipment calculates its feedback information and sends it to its serving base station for further handling.

According to one or more embodiments of the present invention, additional feedback information are introduced and beam and user equipment selection for macro base station such as the macro base station 110 and low-power base station such as the RRH node 120 can be performed j ointly and simultaneously to improve interference control. Furthermore, various embodiments of the present invention enable more balanced performances for both user equipments served by macro base stations and user equipments served by low-power base stations .

With reference to Figs. 2-6, various embodiments of the present invention will be described in details.

Fig.2 schematically shows a flow chart of a method 200 for operating a user equipment in a wireless communication system according to an embodiment of the present invention.

Referring to Fig, 2, in step S210, feedback information as calculated is reported from a user terminal to its serving base station.

According to one or more embodiments of the present invention, the feedback information includes at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix.

In one embodiment of the present invention, the first precoding matrix is a precoding matrix which enables a highest received power at the user equipment and the second precoding matrix is a companion precoding matrix which enables a least interference with said first precoding matrix.

In one embodiment of the present invention, precoding matrixes are grouped into different clusters according to a criterion that is to maximize mutual correlation within the same cluster and minimize cross correlation between different clusters .

Taking the oversampled DFT codebook with the oversampled facor 4 for instance, it can be grouped into 4 clusters according to the above criterion. Fig.3 schematically illustrates beamforming patterns of an oversampled Discrete Fourier Transform ( DFT) -based codebook. The cluster index (CI) is 0, 1, 2, 3 and the clusters can be denoted as below:

C ⁽⁰ > = {w _1} w ₂ ...w ₄ }

C ⁽¹⁾ = {w ₅ ,w ₆ ...w ₈ } ^ C ⁽²⁾ = {w ₉ , ₁₀ ... ₁₂ }

C ⁽³⁾ = {w ₁₃ ,w ₁₄ ...w ₁₆ } where precoding matrix (vector) k in the codebook is denoted

In the condition that the macro-user group / utilizes Μχ-clusters grouping scheme to the codebook Ci, each cluster has the number T _{l m} = 4(m = 0,1,... ,M _l - 1) of precoding vector w _n , where n εΩ„ = {Z _/m _, +1,..., Z^+T^} , Z _Jfi =0 and Z _n (i = 1,...,M) . As to low-power node, the low-power node user group J utilizes M ₂ -clusters grouping scheme to the codebook (¾, each cluster C ₂ ^m) has the number T _Jm =4

(m = Q,l,...,M ₂ -Y) of precoding vector w _fc , where ίεΩ _;κ =

Z _>0 =0and =∑^Γ^ U= - -, ₂ ) . For a macro user equipment z, the first precoding matrix indicator (PMI) is denoted as PMI^ and the second PMI is denoted as ΡΜΙ _ί2 and CI _M , CI _;2 denotes their corresponding CIs.

As such, according to one or more embodiments of the present invention, the feedback information of the macro user equipment ί can be obtained as (PMI _J CI _i2 ) , where

PMI^arg max (|h _li( w„| ² )

PMI., =arg min (|h, ,wj ) 3) ' ^{•2 to} -.z,.„,] ^v l ^2,1 *' where _{PMIj |} e C{ ^{a,,, }} and Wp^^ e C ¹ '' ²¹ ; C{ ^CIf,l) denotes the cluster containing the first precoding matrix w _PM] selected from the macro base station codebook Cj by the rule of maximizing the received signal power, and C ₂ ^CI,,l) is the cluster containing the second precoding matrix w _{PMI; 2} selected from the macro base station codebook Ci by the rule of minimizing interference; I · I is the magnitude of a scalar.

For a low-power node user equipment j _? the first precoding matrix indicator (PMI) is denoted as PMI _y . , and the second P I is denoted as PMI ₂ and CI _{y ]} , CI _{; 2} denotes their corresponding

CIs. As such, according to one or more embodiments of the present invention, the feedback information of the low-power node user equipment j can be obtained as (PMI _] ,CI _{j 2} ) , where

PMI , , ^■ are max (|h, , w _t I ) where w _{PM] (} e C ₂ ^{CI ,l)} and w _{PMI; !} e Cj ^{CI ,2)} ; c ¹ ' ^' ^ denotes the cluster containing the first precoding matrix w _{PMIj ]} selected from the macro base station codebook C¾ by the rule of maximizing the

(CI )

received signal power, and C, ^U1 is the cluster containing the second precoding matrix w _{PMI 2} selected from the macro base station codebook ₂ by the rule of minimizing interference; I · I is the magnitude of a scalar.

In one or more embodiments of the present invention, the feedback information further includes information indicative of SINK of the user equipment. In an implementation of the present invention, the SINR of the macro user equipment will be fed back to the macro base station: the SINR of the low-power node user equipment j will be fed back to the low-power base station: where p _m>n (m e {1,2},n e I J) represents the large-scale fading related to the distance between m ^th base station and n ^th user equipment; Pi and P2 represent the transmit power of macro base station and low-power base station satisfying Ρχ>Ρ ₂ h _u ,h _{1 ;} - eD ^N * are the channel vectors from the macro base station to the macro user equipment i and the low-power node user equipment j, while h _{2 (} .,h ₂ e□ ^[xNrk " represent the channel vectors from the low-power base station to the macro user equipment i and the low-power node user equipment j; | ·| is the magnitude of a scalar.

Fig. 4 schematically illustrates a flow chart of a method 400 for operating a base station in a wireless communication system according to an embodiment of the present invention.

Referring to Fig. 4, in step S410, first feedback information is received from each of a first group of user equipments served by a first base station. The first feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from said first precoding matrix.

In one embodiment of the present invention, the first precoding matrix is a precoding matrix which enables a highest received power at the user equipment and the second precoding matrix is a companion precoding matrix which enables a least interference with said first precoding matrix.

In one embodiment of the present invention, precoding matrixes are grouped into different clusters according to a criterion that is to maximize mutual correlation within the same cluster and minimize cross correlation between different clusters .

In an embodiment of the present invention, in the condition that the first base station is a macro base station, the first feedback information of a macro user equipment i can be obtained as (ΡΜΙ^,ΟΙ,.^) , as discussed above. In the condition that the first base station is a low-power base station, the first feedback information of a low-power node user equipment j can be obtained as (PMT.^CI · _ι2 ) , as discussed above .

In one or more embodiments of the present invention, the feedback information further includes information indicative of SINR of the respective user equipments.

In an implementation of the present invention, the SINR of the macro user equipment / can be expressed as equation 6) ; while the SINR of the low-power node user equipment j can be expressed as equation 7) .

In step S420, the first base station exchanges the feedback information with a second base station.

Similarly, the second base station receives from each of a second group of user equipments served by the second base station second feedback information. Like the first feedback information, the second feedback information includes at least information indicative of a first precoding matrix and information indicative of a cluster that includes a second precoding matrix different from the first precoding matrix.

According to an embodiment of the present invention, the first base station sends the first feedback information to the second base station and receives the second feedback information from the second base station. The exchanging procedure can be performed via backhaul between the first base station and the second base station. Then, the first base station (such as one selected from a set of a macro base station and a low-power base station) and the second base station (such as the other of said set) can share their user equipments' information between each other.

In step S430, at least based on the first feedback information and the second feedback information, the first group of user equipments and the second group of user equipments are scheduled coordinately .

According to one or more embodiments of the present invention, a first user equipment selected from said first group and a second user equipment selected from said second group are paired in responsive of determination that:

1) the second cluster of the first terminal is equal to the first cluster of the second user equipment; and

2) the first cluster of the first terminal is equal to the second cluster of said second user equipment.

Specifically, after exchanging procedure, both the first base station (such as one selected from a set of a macro base station and a low-power base station) and the second base station (such as the other of said set) maintain all feedback information from the first group of user equipments and the second user equipments. In an example, according to the exchanged feedback information (P I. _{jl }} CI _fj2 ) and (PMI _l ,CI _{y 2} ) , the macro base station and the low-power base station can obtain (CI,. , ,CI, ₂ ) and (CI . ,,CI _{y 2} ) . If CI _M = CI, ₂ and CI _{i 2} = CI _{y [} , then a user equipment pair is determined by both the macro base station and the low-power base station and denoted as Q ^{m) . Consequently, a set of all user equipment pairs as determined can be denoted as Q = {Q ^m ,...Q ^{m ...Q ^(M } , where M represents the largest number of user equipment pairs.

According to one or more embodiments of the present invention, a pair of a first user equipment and a second user equipment is selected by both the first base station and the second base station for coordinated scheduling.

Based on a same predetermined algorithm, the first base station and the second base station can determine a user equipment pair from the set of all user equipment pairs and then coordinately schedule the determined user equipment pair for transmission and allocate corresponding resource, modulation and coding scheme, etc.

As an example, the Proportional Fairness Scheduling algorithm can be used to determine the user equipment pair (/*,/*) for coordinated scheduling. For each (m=l,..,M), a fairness scaling factor can be calculated.

According to the proportional fairness scheduling algorithm, the current transmission rate R^t) of macro-user equipment / at time slot t can be calculated according to the SI R,. reported in the feedback information as below: R,.( = log ₂ (l + SINR _; ) 8) Then, the past average transmission rate R^t + l) of macro-user equipment i is calculated at time slot (t +l) :

where T _c is the time window size.

The fairness scaling factor for macro-user equipment can be expressed as i? ₍ .(0/R,(0 ·

Similarly, the fairness scaling factor for low-power noi user equipment j can be expressed as R _j (t) / R _j (t) , wherein

R,.(0 = k>g ₂ (l + SINR _y )

10)

where SINR _y . is reported in the feedback information of low-power node user equipment j ; and T _c is the time window size .

In an implementation of the present invention, a sum of the fairness scaling factors of the two user equipments in

Q ^{m) is used to determine the user equipment pair

In another implementation of the present invention considering the total transmission rates and total averag transmission rates of macro-user equipment and low-power node user equipment, the user equipment pair can be determined as below:

According to the above one or mo embodiments of the present invention, the fairness between two different kinds of user equipments such as macro-user equipments and low-power node user equipments are considered and thus relatively balanced performances can be achieved in a HetNet . In addition, as high-speed and reliable connection such as the backhaul, DSL, etc, is established between the first base station and the second base station in one or more embodiments, the increase of exchanged information between the first and second base stations (such as a macro base station and a RRH node) will not cause significant performance degradation.

The processing according to one or more embodiments of the present invention has been depicted in detail with reference to Figs. 2 and 4.

It should be noted that the above depiction is only exemplary, not intended for limiting the present invention. In other embodiments of the present invention, this method may have more, or less, or different steps, and numbering the steps is only for making the depiction more concise and much clearer, but not for stringently limiting the sequence between each steps; while the sequence of steps may be different from the depiction. For example, in some embodiments, the above one or more optional steps may be omitted. Specific embodiment of each step may be different from the depiction. All these variations fall within the spirit and scope of the present invention . Fig. 5 schematically shows a simplified block diagram of a user equipment according to an embodiment of the present invention .

In general, the various embodiments of the UE 500 can include, but are not limited to, cellular phones, PDAs having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, as well as portable units or terminals that incorporate combinations of such functions.

The UE 500 is adapted for communication with one or more base stations in the wireless communication system via its antenna array 550. The UE 500 includes a data processor (DP) 510, a memory

(MEM) 520 coupled to/embedded in the DP 510, and suitable RF transmitter TX/receiver RX module 540 coupling the antenna array 550 to the DP 510. The RF TX/RX module 540 is for bidirectional wireless communications with at least one base station. The MEM 520 stores a program (PROG) 530.

The PROG 530 is assumed to include program instructions that, when executed by the DP 510, enable the UE 500 to operate in accordance with the exemplary embodiments of this invention, as discussed herein with the method 200, as shown in Fig.3. The MEM 520 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one MEM is shown in the UE 500, there may be several physically distinct memory units in the UE 500.

The DP 510 performs any required calculation as described with reference to Figs 1 and 2. The DP 510 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, DSPs and processors based on multi-core processor architecture, as non-limiting examples.

The user equipment 500 comprises a reporting unit (not shown in Fig. 5) . The report unit is configured to report to a base station which serves said user equipment feedback information, wherein the feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from said first precoding matrix. It can be appreciated that the functionalities of the reporting unit can be implemented by one or more suitable modules of the user equipment 500 as described above.

Fig.6 schematically shows a simplified block diagram of a base station according to an embodiment of the present invention .

The base station 600 is adapted for communication with a group of UEs in the wireless communication system. As discussed previously, the base station 600 can be a macro base station (e.g., macro eNB) or a low-power base station (e.g., RRH node, pico base station, relay station, femto base station, etc . )

The base station 600 includes a data processor (DP) 610, a memory (MEM) 620 coupled to/embedded in the DP 610, and suitable RF transmitter TX/receiver RX module 640 coupling antenna array 650 to the DP 610. The RF TX/RX module 640 is for bidirectional wireless communications with at least one UE. The MEM 620 stores a program (PROG) 630.

The PROG 630 is assumed to include program instructions that, when executed by the DP 610, enable the base station 600 to operate in accordance with the exemplary embodiments of this invention, as discussed herein with the method 400, as shown in Fig.4 .

The MEM 620 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one MEM is shown in the base station 600, there may be several physically distinct memory units in the base station 600.

The DP 610 performs any required calculation as described with reference to Fig.4 . The DP 610 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, DSPs and processors based on multi-core processor architecture, as non-limiting examples.

The base station 600 comprises a receiving unit, an exchanging unit and a scheduling unit (not shown in Fig.6) . The receiving unit is configured to receive, from each of a first group of user equipments served by the base station 600, first feedback information, the first feedback information including at least information indicative of a first precoding matrix included in a first cluster and information indicative of a second cluster that includes a second precoding matrix different from the first precoding matrix . The exchanging unit is configured to exchange feedback information with a further base station, wherein the further base station receives from each of a second group of user equipments served by the further base station second feedback information, the second feedback information including at least information indicative of a first precoding matrix and information indicative of a cluster that includes a second precoding matrix different from the first precoding matrix. The scheduling unit is configured to schedule coordinately, at least based on the first feedback information and the second feedback information, the first group of user equipments and the second group of user equipments. It can be appreciated that the functionalities of the receiving unit, the exchanging unit and the scheduling unit can be implemented by one or more suitable modules of the base station 600 as described above. In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block and signaling diagrams, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof .

As such, it should be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules. As well known in the art, the design of integrated circuits is by and large a highly automated process .

The present invention may also be embodied in the computer program product which comprises all features capable of implementing the method as depicted herein and may implement the method when loaded to the computer system.

The present invention has been specifically illustrated and explained with reference to the preferred embodiments. The skilled in the art should understand various changes thereto in form and details may be made without departing from the spirit and scope of the present invention.