A Method

Field of the Invention

The present invention relates to a method, an apparatus and to a computer program.

Description of related art

A communication device can be understood as a device provided with appropriate communication and control capabilities for enabling use thereof for communication with others parties. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. A communication device typically enables a user of the device to receive and transmit communication via a communication system and can thus be used for accessing various service applications.

A communication system is a facility which facilitates the communication between two or more entities such as the communication devices, network entities and other nodes. A communication system may be provided by one or more interconnected networks. One or more gateway nodes may be provided for interconnecting various networks of the system. For example, a gateway node is typically provided between an access network and other communication networks, for example a core network and/or a data network.

An appropriate access system allows the communication device to access to the wider communication system. An access to the wider communications system may be provided by means of a fixed line or wireless communication interface, or a combination of these. Communication systems providing wireless access typically enable at least some mobility for the users thereof. Examples of these include wireless communications systems where the access is provided by means of an arrangement of cellular access networks. Other examples of wireless access

technologies include different wireless local area networks (WLANs) and satellite based communication systems.

A wireless access system typically operates in accordance with a wireless standard and/or with a set of specifications which set out what the various elements of the system are permitted to do and how that should be achieved. For example, the standard or specification may define if the user, or more precisely user equipment, is provided with a circuit switched bearer or a packet switched bearer, or both. Communication protocols and/or parameters which should be used for the connection are also typically defined. For example, the manner in which communication should be implemented between the user equipment and the elements of the networks and their functions and responsibilities are typically defined by a predefined communication protocol.

In the cellular systems a network entity in the form of a base station provides a node for communication with mobile devices in one or more cells or sectors. It is noted that in certain systems a base station is called 'Node B'. Typically the operation of a base station apparatus and other apparatus of an access system required for the communication is controlled by a particular control entity. The control entity is typically interconnected with other control entities of the particular communication network. Examples of cellular access systems include Universal Terrestrial Radio Access Networks (UTRAN) and GSM (Global System for Mobile) EDGE (Enhanced Data for GSM Evolution) Radio Access Networks (GERAN).

A non-limiting example of another type of access architectures is a concept known as the Evolved Universal Terrestrial Radio Access (E-UTRA). This is also known as Long term Evolution UTRA or LTE. An Evolved Universal Terrestrial Radio Access Network (E-UTRAN) consists of E-UTRAN Node Bs (eNBs) which are configured to provide base station and control functionalities of the radio access network. The eNBs may provide E-UTRA features such as user plane radio link control/medium access control/physical layer protocol (RLC/MAC/PHY) and control plane radio resource control (RRC) protocoi terminations towards the mobile devices.

In systems providing packet switched connections the access networks are connected to a packet switched core network via appropriate gateways. For example, the eNBs are connected to a packet data core network via an E-UTRAN access gateway (aGW) - these gateways are also known as service gateways (sGW) or mobility management entities (MME),

Currently, in terms of concept creation in relation to the LTE 3GPP project, work is being done on release 8. Currently, this proposes a system bandwidth of a maximum of 20MHz. Work is currently being started on release 9 of the LTE 3GPP project. It is currently being proposed that the release 9 version contemplate supporting a wider bandwidth than the release 8 version.

Currently, with the release 8 proposals, 28 bits are used for indicating the actual resource allocation within the bandwidth.

Two proposals are suggested for implementing this. The first proposal is provided in the 3GPP TSG RAN WG1 MEETING #51 bis which took place in Seville, in January 2008. The document is numbered R1 -080030. This document proposes a slot-level user equipment specific resource re-mapping that provides intra-celi interference randomisation.

In that same meeting, document R1 -080452 was also discussed. This document considers the signalling for downlink resource block assignment.

The inventors have appreciated that the proposed methods for signalling resource allocation whilst being workable with the proposed release 8 bandwidth may not be feasible with the wider bandwidth proposed in release 9.

An additional problem that the inventors have noted is with compatibility with both release 8 and release 9, resulting from the differing bandwidths.

It is an aim of some embodiments of the present invention to address one or more of the above-mentioned problems.

Summary of Invention

According to one aspect of the present invention, there is provided a method comprising transmitting, in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at least one second control channel is arranged to provide resource allocation information with a second resolution different from said first resolution.

According to another aspect of the present invention, there is provided a method comprising receiving, in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at ieast one second control channel is arranged to provide resource allocation information with a second resolution different from said first resolution.

According to a further aspect of the present invention, there is an apparatus comprising means for defining in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at least one second control channel is arranged to provide resource allocation information with a second resolution different from said first resolution.

According to a further aspect of the present invention, there is provided an apparatus comprising means for processing in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at least one second control channel is arranged to provide resource allocation information with a second resolution different from said first resolution.

According to a further aspect of the present invention, there is provided a method comprising providing in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at

least one second control channel is arranged to provide resource ailocatioπ information with a second resolution different from said first resolution.

According to another aspect of the present invention, there is provided a method comprising processing in one mode, a plurality of control channels providing resource allocation information, wherein at least one first control channel is arranged to provide resource allocation information with a first resolution and at least one second control channel is arranged to provide resource allocation information with a second resolution different from said first resolution.

Brief Description of Figures

For a better understanding of the present invention and as to how the same may be carried into effect, reference will now be made by way of example only to the accompanying drawings in which:

Figure 1 shows schematically an LTE system;

Figure 2 shows schematically downlink physical resource block allocation signalling schemes for LTE release 8; Figure 3 shows the bandwidths in LTE release 8 and release 9;

Figure 4 shows the an LTE release 9 bandwidth divided into a plurality of bands;

Figure 5 shows a flow diagram illustrating a method performed by user equipment; and

Figure 6 shows a flow diagram illustrating a method performed by an eNode B.

Detailed Description of Preferred Embodiments of the Invention

Some embodiments of this invention are related to the long term evolution (LTE) of 3GPP. In the proposed LTE structure the Base Station is called eNode B. The Physical layer is based on SC FDMA (single carrier division multiple access) for the Uplink and OFDMA (orthogonal frequency division multiple access) for the Downlink.

Certain embodiments can be used, in a long term evolution (LTE) radio system. Therefore the non-limiting example of Figure 1 shows the concept of what is known as the long term evolution (LTE). This system provides an evolved radio access system that is connected to a packet data system. Such an access system may be provided, for example, based on architecture that is known from the Evolved Universal Terrestrial Radio Access (E-UTRA) and based on use of the Evolved Universal Terrestria! Radio Access Networks (E-UTRAN) Node Bs (eNBs). An Evolved Universal Terrestrial Radio Access Network (E-UTRAN) consists of E-UTRAN Node Bs (eNBs) which are configured to provide base station and control functionalities. For example, the eNBs nodes can provide independently radio access network features such as user plane radio link control/medium access control/physical fayer protocol (RLC/M AC/PHY) and control plane radio resource control (RRC) protocol terminations towards the user devices.

it is noted that Figure 1 shows this architecture only to give an example of a possible communication system where the embodiments described below may be provided and that other arrangements and architectures are also possible. For example, the user device may communicate with a different access system.

The eNodeB 1 1 has an antenna 10 for communicating with the user equipment via wireless link. The eNodeB has a data processing entity for carrying out various processes. Additionally a memory 13 is provided which stores information which is used by the eNode B.

The user device 1 can be used for various tasks such as making and receiving phone calls, for receiving and sending data from and to a data network and for experiencing, for example, multimedia or other content. For example, a user device may access data applications provided via a data network. For example, various applications may be offered in a data network that is based on the Internet Protocol (IP) or any other appropriate protocol. An appropriate user device may be provided by any device capable of sending and receiving radio signals. Non- limiting examples include a mobile station (MS), a portable computer provided with a wireless interface card or other wireless interface facility, personal data assistant

(PDA) provided with wireless communication capabilities, or any combinations of these or the like. The user device may be any suitable apparatus or comprise any suitable apparatus.

The mobile device may communicate via an appropriate radio interface arrangement of the mobile device. The interface arrangement may be provided for example by means of a radio part 7 and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the mobile device.

A mobile device is typically provided with at least one data processing entity 3 and at least one memory 4 for use in tasks it is designed to perform. The data processing and storage entities can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 6.

Figure 1 shows further a modulator component 9 connected to the other elements. It is noted that the modulator functions may be arranged to be provided by the data processing entity 3 instead of a separate component.

The user may control the operation of the mobile device by means of a suitable user interface such as key pad 2, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 5, a speaker and a microphone are also typically provided. Furthermore, a mobile device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto.

In the proposed LTE structure, the physical fayer details are as follows.

The physical channels defined in the downlink are the Physical Downlink Shared Channel (PDSCH) ₁ the Physical Downlink Control Channel (PDCCH) ₁ the PCFICH Physical control format indication channel and PHICH Physical H-ARQ (Hybrid Automatic Repeat Request) indication channel. The physical channels defined in the uplink are the Physical Uplink Shared Channel (PUSCH) and the Physical Uplink Control Channel (PUCCH).

In preferred embodiments of the present invention, compatibility between release 8 and release 9 of the LTE proposals will be described. However, it should be appreciated that this is by way of example only and embodiments of the present invention may be applied in any other suitable scenario. Embodiments of the present invention may for example be applied in a scenario where there is a first available bandwidth, in one mode and a second, large available bandwidth in a second mode. Embodiments of the invention are not limited to release 8 and 9 and can be any other two or more releases of the standard. It should be appreciated that embodiments of the invention may be applied to standards other than LTE. It should be appreciated that embodiments of the invention can be used with two or more different standards and not only different versions of the same standard.

Currently, with release 8 of LTE, the system bandwidth is proposed to be a maximum of 20 MHz. However, for future releases, including release 9, this is a parameter the increase of which is being considered. Increase of the bandwidth is able to provide higher-per-user peak data rate as well as increased local area coverage.

In embodiments of the present invention, a user device which is able to operate in accordance with the release 9 version of the standard is able to access a release 8 version of the radio access network and vice-versa.

In an embodiment of the invention, the downlink resource assignment is considered. The downlink is the transmission path from the eNode B to the user equipment. It should be appreciated that embodiments of the invention may be used for uplink resource assignment. The resource being assigned may be resource in one or more data channels or may be any other resource on any other channel. Some embodiments of the invention may be used where dynamic allocation of resources is provided.

Downlink resource allocation signaling on the PDCCH (Physical Downlink Control Channel) has been proposed by the release 8 proposals. The release 8 proposal currently defines a number of possible payload formats which are currently

indicated in the document 3GPP series 36.212. In one example, the number of information bits in each payload is expected to be in the region of 50-60 bits for fully flexible downlink allocations. Two formats have been proposed, format 1 for single code word operation and format 2 for dual code word MIMO (Multiple Input Multiple Output) operation. Flexible downlink allocation means that it is possible for eNode B to do frequency domain packet scheduling FDPS within the defined bandwidth.

Reference is now made to Figure 2 which shows an illustration of a downlink PRB allocation signaling scheme.

Consider the following example: in a 20 MHz system bandwidth sub-band, there will be a 100 physical resource blocks PRBs. If there is a resource block group RBG size of 4, 28 bits would be required for indicating the actual resource allocation within the 20MHz bandwidth. Figure 2 shows 25 resource block groups. Consider the approach 1 illustrated in Figure 2. A bit map would indicate the use or otherwise of each group of resource blocks. In this example, each resource block comprises two PRBs, corresponding to the 10 MHz configuration. Accordingly, each pair of PRBs is allocated a RBG number RBG n where n is an integer from 1 to 13 in the example shown in Figure 2. Thus, setting the bit RBG1 would indicate the use of PRB1 and PRB2.

Figure 2 also shows approach 2 where a subset of the resources are defined and the signaling indicates to which subset the bit map should be applied. In the example shown in Figure 2, two sub-sets are considered and the PDCCH header which would indicate which is selected. Thus, in the example shown in Figure 1, subset 1 comprises PRB 1 , 2, 5, 6, 9, 10 etc and the second subset comprises PRB 3, 4, 7, 8, etc. It should be appreciated that each resource block is consecutively numbered in each subset. Accordingly, in order to signal block PRB3 and PRB4 would require the header to indicate that subset 2 has been selected and that bits RB1 and RB2 have been set.

However, the release 8 proposal does not provide any possibilities to reference outside the defined system bandwidth.

In embodiments of the present invention, the user equipment is able to decode a predetermined set of the PDCCHs for each release 8 sub-band to provide maximum scheduling flexibility. However, in one embodiment of the present invention, the user equipment is arranged so that it does not decode all of the PDCCH channels when operating in a release 9 mode. Instead, the user equipment is allocated to a so-called PDCCH mother-band as will be discussed.

In one embodiment of the invention, there is a resource block sampling and grouping factor which would depend on the distance in frequency to the mother band frequency. This sampling and grouping factor is such that by default the resource assignment mechanism is retained in the mother band which is defined by the release 8 sub-band. When addressing outside the mother band, the resolution is decreased gradually in a way that will obtain a signaling load decrease relative to having full signalling flexibility over the entire bandwidth.. Thus, the PDCCH signaling overhead for the release 9 UE may be reduced, whilst increasing the bandwidth. This may facilitate a trade off between the signaling overhead as against the scheduling freedom over the complete release 9 bandwidth.

As can be seen from Figure 3, the bandwidth 100 for the release 8 mode is very much smaller than the bandwidth 102 for the release 9 mode. However, it should be appreciated that the release 8 bandwidth 100 is completely contained within the release 9 bandwidth 102. The release 8 bandwidth 100 is defined as the mother band.

In Figure 3, as shown by blocks 120 and 122, a similar approach to that described in relation to downlink resource allocation can be used for uplink data. The eNode B is in control of the uplink resource grants for the uplink data channels as represented by block 120. The uplink data channels are represented by block 122.

In one embodiment of the present invention, the user equipment is arranged to have information on the following: system bandwidth for the release 9 mode; start

and end frequency of the release 9 mode bandwidth; and the position of the mother band, defined by the release 8 mode.

This information may be stored in the memory 4 or any other suitable storage facility on the mobile device.

The mobile device may have that information pre-stored and/or may receive the device from for example the eNode B.

The user equipment will then start sampling the data channel immediately when the data transmission starts using the above information. There may be a decoding delay of the control channel PDCCH such that some data would typically have been transmitted/received when the UE knows its resource allocation.

The signaling reduction mechanism, as compared to the release 8 mode and used in the release 9 mode will now be described. This is referred to as the sampling and grouping factor.

Reference is made to Figure 2 where it can be seen that each PRB is represented by a bit. Each PRB covers twelve sub-carriers for a duration of a total of one TTI (Transmission Time Interval). This corresponds generally to one ms.

When in the release 9 mode and outside the mother band, there is an additional grouping factor which provides information on the number of PRBs which are put together into an extended PRB. This extended PRB can then be allocated/assigned using a normal resource allocation signaling mechanism. Thus, if there is a grouping factor of, for example 4, then there will be four PRBs in an extended PRB.

Additionally, in an embodiment of the present invention, the sampling/grouping factor is dependent on the distance to the mother band. This can be understood with reference to table 1 which is below.

Table 1

The table assumes that the release 9 mode has a maximum bandwidth of 100MHz and that the maximum 20MHz bandwidth is used for the release 8 mode.

Consider the case of an allocating release 8 band with index 2. This case corresponds to the case where the allocating release 8 carrier is located from 20- 40MHz of the full release 9 system bandwidth. In this, band 1 will be using an extended grouping factor of 2 which means that two adjacent PRBs will be grouped before being allocated/scheduled. This means that it is possible to use half of the signaling to address this frequency range from 0 to 20MHz, relative to the release 8 bandwidth. The mother band from 20 to 40MHz will use the usual resource allocation signaling as for the release 8 mode, that is with a group factor or 1 The band from 40 to 60 MHz will use a grouping factor of 2 similar to the 0 to 20MHz range. Finally, the range from 60 to 100MHz will use a grouping factor of 4. It should be noted that the range from 60 to 100MHz can be regarded as being two groups from 60 to 80MHz and from 80 to 100MHz, each having a grouping factor of 4. This is represented by the band of the allocating release 8 indicated by 2 in the above table.

In this regard, reference is made to Figure 4 which shows the five bands 100A-E corresponding to each of the release 8 mother bands. Band 1 is reference 100A ₁ band 2 is referenced 100B and so on. The five bands represent the release 9 bandwidth.

Other examples of these grouping are shown for each of the arrangements. Generally, the rules can be summarized as follows: for the band which

corresponds to the mother band of the release 8, a grouping of factor of 1 is used. For the band immediatety adjacent to the mother band, a grouping of 2 is used. Depending on the position of the mother band, there may be a group on either side of the mother band. For those groups which are not immediately adjacent the mother band, a grouping factor of 4 is used.

It should be appreciated that these grouping factors are by way of example only. In one alternative embodiment of the present invention, a first grouping number is used for the mother band. That grouping number may be 1 but in alternative embodiments of the present invention may be more than one. In an alternative embodiment of the present invention, all bands, except the mother band may have the same grouping factor which may be 2 or more.

In the example described, grouping factors of 1 2 and 4 have been described. However, alternative embodiments of the present invention may have any suitable value, including 3 and values above 4. It should be obvious to one skilled in the art that grouping factors including fractions, such as 1.5 can also be applicable.

In the embodiment described with reference to the table, the required additional signaling is as follows: using a 2x20MHz system bandwidth for a release 9 system will require a 50% larger resource allocation map. Using a 3x20MHz system bandwidth for a release 9 system will require a 100% larger resource allocation map and using a 5x20MHz system bandwidth for a release 9 system will require a

150% larger resource allocation compared to an allocation within the mother band using release 8 resource allocation signalling.

As can be appreciated, there will be a compression of the required signaling overhead. This does not scale linearly with the corresponding supported bandwidth allocation.

Consider the following example where allocation is to a maximum bandwidth that is allocation from a 20MHz system to a 100MHz release system. With the current assumption for the release 8 20MHz resource allocation signaling is that the total

PDCCH payload will be 60 to 70 bits whilst the resource allocation indication will take up to 37 bits.

Using the above suggested embodiment, the resource allocation map will be around 120 bits.

Reference is now made to Table 2 below.

Table 2

in this example, the allocation for the band corresponding to the mother band is 1. For band immediately adjacent the mother band, the allocation grouping is 2.

For the bands which are separated by the mother band by one intermediatary band, the grouping is 4. For any other band, the grouping factor is 8.

For comparison's sake, band 2 will be considered. The mother band, that is band 2 will have a grouping of 1. The first and third band will have a grouping factor of 2 whilst the fourth and fifth band will be a grouping factor of 4 and 8 respectively.

Reference is made to Figure 5 which describes a method embodiment the present invention.

In step S1 , the user equipment receives one or more of the following pieces of information: the system bandwidth for the release 9 mode; the start and end frequency of the release 9 system bandwidth; and the position of the mother band.

In other words, this will provide information as to whether the mother band is band 1 2 3 4 or 5 shown in Figure 4.

It should be appreciated that the information discussed in relation to step S1 can be provided together and/or separately. That information may be provided in conjunction with other information.

In step S2, the user equipment is provided with information as to whether or not the user equipment is to operate in a release 8 or a release 9 mode. This may be combined with the providing of one or more bits of information from the base station, and the signalling means for controlling this can be provided at any level or layer L. That is, L1 , L2 or even L3 signalling may be used. The 3GPP terms used for these signalling means are: physical, MAC (media access control) and RRC (radio resource control) signaling respectively. Thus in S2 the user equipment receives information to be configured to interpret PDCCH messages or physical layer control messages in the Release 8 or the Release 9 mode.

It should be appreciated that in an alternative embodiment of the present invention, the user equipment may be able to make a determination as to whether or not to operate in a release 8 or in a release 9 mode as a result of implicit signaling from the base station and/or as a result of a determination made by that user equipment in dependence on one or more factors.

The next step is step S3, if it is determined that the user equipment is to operate in the release 8 mode. In this mode, the user equipment will decode the PDCCHs for the mother band. In a preferred embodiment of the present invention, the user equipment will decode all of the PDCCH blocks.

If the UE is to operate in the Release 9 mode, the next step is S4 then the user equipment will use this information on the PDCCHs to identify the allocated resource blocks.

It should be appreciated that the eNode B will formulate the information provided on the PDCCH in order to indicate to the user equipment as to which resource block has been allocated in the data channel.

In this regard, reference is made to Figure 6 which shows a flow chart of the method steps carried out by the base station.

In step T1 , the base station makes a determination as to whether or not the release 8 or release 9 mode is to be used. This may be based on any suitable criteria. For example, the network may control which of the modes is to be used. Alternatively, the modes which are to be used may be dependent on the data to be transferred. For example, the volume and type of data may in fact make an impact as to whether or not the release 8 or release 9 mode is to be selected.

In step T2, the resources to be used in the data channel for a particular data transfer are ailocated. The resources are allocated in accordance with appropriate rules.

In step T3, the eNode B then signals the user equipment as to the allocated blocks by the PDCCH. This is done in accordance with the signaling described above,

it should be appreciated that embodiments of the present invention can be used in any system where there is two modes, the first mode having a smaller bandwidth and a second mode having a larger bandwidth. Embodiments of the present invention need not be applicable to the release 8 and release 9 versions of the LTE based 3GPP standard.

It should be appreciated that in preferred embodiments of the present invention, the so-called mother bandwidth has a first number of resource blocks which can be grouped. This first number can be one or more. The bandwidth adjacent to the mother channel will use a second number of resource blocks grouped together. That second number is generally two or more. It should be appreciated that one or more bandwidths adjacent the mother channel may be treated in the same way as the mother channel i.e. with the first number of resource block. The mother

bandwidth may have a first number of resource blocks allocated and outside the mother band, all of the other resource blocks may be all grouped with a second number, generally larger than the first number but possibly smaller than the first number.

Embodiments of the invention have described selecting the number of resource blocks to be grouped in dependence into which bandwidth the channel falls. It should be appreciated that alternative criteria may be used for deciding the number of resource blocks to be grouped. First criteria may be applied in the mother band and second different criteria outside the band. For example one or more of data quantity, quality of service, channel strength, channel allocation in one or more adjacent cells or the ϋke may be used to determine the number of resource blocks which are to be grouped. The number of resource blocks to be grouped may be determined on a channel by channel basis.

It should be appreciated that although the preferred embodiments of the invention have been described in the context of the LTE proposals, embodiments of the present invention may be used within the framework provided by any other standard whether it has proposed or has yet to be evolved. Embodiments of the invention may also be used in scenarios where there is no standardized framework. Accordingly references to an eNode B shouid be considered to be equally applicable to a base station or a control entity.

In the described embodiment, the sizes of the bandwidths are by way of example as are the relative sizes. The release 8 and 9 bandwidths can be replaced by any other suitable bandwidth sizes.

It is noted that whilst embodiments have been described in relation to mobile devices such as mobile terminals, embodiments of the present invention are applicable to any other suitable type of apparatus suitable for communication via access systems. A mobile device may be configured to enable use of different access technologies, for example, based on an appropriate multi-radio implementation.

The above described operations may require data processing in the various entities. The data processing may be provided by means of one or more data processors. Similarly various entities described in the above embodiments may be implemented within a single or a plurality of data processing entities and/or data processors. Appropriately adapted computer program code product may be used for implementing the embodiments, when loaded to a computer. The program code product for providing the operation may be stored on and provided by means of a carrier medium such as a carrier disc, card or tape. A possibility is to download the program code product via a data network. Implementation may be provided with appropriate software in a server.

For example the embodiments of the invention may be implemented as a chipset, in other words a series of integrated circuits communicating among each other. The chipset may comprise microprocessors arranged to run code, application specific integrated circuits (ASICs), or programmable digital signal processors for performing the operations described above.

In the above described embodiments various numbers have been given for various parameters and characteristics. However, these are by way of example and in different scenarios and/or as a result of the changes to standard specifications different values can be used.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized

electronic format (e.g., Opus, GDSIl, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication.

The foregoing description has provided by way of exemplary and non-iimiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims.

However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims.