WO2013026183A1

WO2013026183A1 - Method and apparatus to determine a timing advance for an extension carrier

Info

Publication number: WO2013026183A1
Application number: PCT/CN2011/001416
Authority: WO
Inventors: Wei Bai; Jing HAN; Haiming Wang
Original assignee: Renesas Mobile Corporation
Priority date: 2011-08-24
Filing date: 2011-08-24
Publication date: 2013-02-28

Abstract

Methods and apparatus are disclosed for calculating timing advance information for an extension earner, such as in an LTE/LTE-A system. In accordance with an embodiment of the invention, an apparatus determines if a timing advance is to be calculated for an extension carrier. The apparatus determines if physical random access channel (PRACH) resources are available on the extension carrier, and determines if a preamble transmission such as a random access channel (RACH) transmission is triggered on the extension carrier. In an instance in which RACH is triggered on the extension carrier, the apparatus causes the preamble to be transmitted on a respective PRACH resource. Furthermore, in an instance in which RACH is not triggered on the extension earner, the apparatus receives a scheduling grant for a physical uplink shared channel (PUSCH) on a respective PRACH resource.

Description

METHOD AND APPARATUS TO DETERMINE A TIMING ADVANCE FOR AN

EXTENSION CARRIER

TECHNOLOGICAL FIELD

Embodiments of the present invention relate generally to wireless communication technology and, more particularly, to a method and apparatus for determining a timing advance for an extension carrier, such as in a Long Term Evolution (LTE)/LTE-Advanced wireless communication system. BACKGROUND

In LTE/LTE-Advanced, a new carrier type has been proposed that includes extension carrier which can accommodate LTE mobile terminals as well as legacy terminals. One issue with this extension carrier is the provision of a timing advance (TA). In Release 10 of the LTE specification, 3GPP has stated that uplink intra-band carrier aggregation will include only one TA for all the uplink control channels. However, in Release 11 of the LTE specification and beyond, when taking inter-band carrier aggregation into consideration, as well as the Radio Remote Head (RRH) and repeater case, multiple TAs will be necessary. Therefore, it is unclear how TA will be handled for the extension carrier.

The extension carrier is a non-backward compatible carrier that does not include any control information, which avoids the overhead caused by control channel and system information. The extension carrier may not include synchronization signaling and may not support the radio access control channel (RACH). Therefore, it is also unclear how the TA will be provided for an extension carrier. Because the LTE-Advanced system utilizes orthogonal frequency division multiple access (OFDMA) as the access method, synchronization and timing advance information is important for coordinating uplink (UL) and downlink (DL) communication. Thus, a method and apparatus is needed for determining such timing advance information for an extension carrier, such as in an LTE/LTE-A environment.

BRIEF SUMMARY

Therefore, methods, apparatus and computer program products are provided for determining timing advance information, such as in a LTE/LTE-A environment. In one example embodiment, a method comprises determining physical random access channel (PRACH) resources available on an extension carrier; determining if a preamble transmission such as a random access channel (RACH) is triggered on the extension carrier; in an instance in which the preamble transmission is triggered on the extension carrier, causing the preamble to be transmitted on a respective PRACH resource; and in an instance in which the preamble transmission is not triggered on the extension carrier, receiving a scheduling grant for a physical uplink shared channel (PUSCH) on a respective PRACH resource. In an instance in which the timing advance is not calculated for the extension carrier, the method comprises applying the same timing advance for the extension carrier as the timing advance for a primary cell. The method may further determine if a timing advance is to be calculated for the extension carrier.

In this example embodiment, determining the PRACH resources may comprise establishing the same PRACH configuration for the extension carrier as a primary cell. The method causing the preamble to be transmitted may comprise causing a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field, or causing a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information.

In another example embodiment of the present invention, an apparatus comprises at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: determine configured PRACH resources available on the extension carrier; determine if a preamble transmission such as a RACH transmission is triggered on the extension carrier; in an instance in which RACH is triggered on the extension carrier, causing the preamble to be transmitted on a respective PRACH resource; and in an instance in which RACH is not triggered on the extension carrier, receiving a scheduling grant for a PUSCH on a respective PRACH resource. The computer program code may be further configured to, with the at least one processor, determine if a timing advance is to be calculated for the extension earner.

In this example embodiment, the apparatus may, in an instance in which the timing advance is not calculated for the extension carrier, apply the same timing advance for the extension carrier as the timing advance for a primary cell. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to establish the same PRACH configuration for the extension carrier as a primary cell, to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field, and to cause the apparatus to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information. The apparatus in this example embodiment may comprise a mobile terminal. The apparatus may further comprise a device interface configured to communicate with a base station in order to receive the scheduling grant for the PUSCH on the respective PRACH resource, and may be configured for use in a LTE system.

In yet another example embodiment of the present invention, computer program product comprises at least one non-transitory computer-readable storage medium having computer- readable program instructions stored therein, the computer-readable program instructions comprising program instructions configured to: determine PRACH resources available on an extension carrier; determine if a preamble transmission such as a RACH transmission is triggered on the extension carrier; in an instance in which the preamble transmission is triggered on the extension carrier, causing the preamble to be transmitted on a respective PRACH resource; and in an instance in which the preamble transmission is not triggered on the extension carrier, receiving a scheduling grant for a PUSCH on a respective PRACH resource. The program instructions may be further configured to determine if a timing advance is to be calculated for the extension carrier.

In this example embodiment, computer readable instructions may comprise program instructions further configured to, in an instance in which the timing advance is not calculated for the extension carrier, apply the same timing advance for the extension carrier as the timing advance for a primary cell. In another alternate embodiment of the invention, computer readable instructions may comprise program instructions configured to determine the timing advance for the primary cell in the event that the timing advance is not calculated. The program instructions may be configured to establish the same PRACH configuration for the extension carrier as a primary cell, to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field, and to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information. In this and other example embodiments, the computer program product may be stored within a memory within a mobile terminal, which may be configured for use in a LTE System. The mobile terminal or other apparatus in this example embodiment, may further comprise a device interface configured to communicate with a base station in order to receive the scheduling grant for the PUSCH on the respective PRACH resource.

In another example embodiment, an apparatus may comprise means for determining PRACH resources available on the extension carrier; means for determining if a preamble transmission such as a RACH transmission is triggered on the extension carrier; in an instance in which RACH is triggered on the extension carrier, the apparatus may comprise means for causing the preamble to be transmitted on a respective PRACH resource; and in an instance in which RACH is not triggered on the extension carrier, the apparatus may comprise means for receiving a scheduling grant for a PUSCH on a respective PRACH resource. In an instance in which the timing advance is not calculated for the extension carrier, the apparatus may comprise means for applying the same timing advance for the extension carrier as the timing advance for a primary cell. The apparatus may also comprise means for determining if a timing advance is to be calculated for the extension carrier.

In this example embodiment, means for determining the PRACH resources may comprise establishing the same PRACH configuration for the extension carrier as a primary cell. The means for causing the preamble to be transmitted may comprise means for causing a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field, or means for causing a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described example embodiments of the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

Figure 1 illustrates a system including a mobile terminal and a base station configured to support communications in accordance with one embodiment of the present invention.

Figure 2 is a block diagram of a mobile terminal in accordance with one embodiment of the present invention.

Figure 3 is a block diagram of a base station or other network element in accordance with one embodiment of the present invention.

Figure 4 is a flow diagram illustrating a PRACH determination process in accordance with one embodiment of the present invention.

Figure 5 is a flow diagram illustrating the operations performed in accordance with one embodiment of the present invention from the perspective of an apparatus such as a mobile terminal.

Figure 6 is a block diagram which illustrates another example embodiment of the present invention. DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.

This definition of 'circuitry' applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

As used in this application, a mobile terminal or device may include but is not limited to the following: (a) wired and wireless telephones (b) satellite telephones (c) personal communication devices; (d) electronic devices configured to share content in a local area network (LAN); (e) electronic gaming devices including, but not limited to, Nintendo^® Gameboy^® devices; (f) electronic music devices including, but not limited to, Apple^® iPod^® devices; (g) dual-mode cellular terminals which utilizes a cellular network and a non-cellular network; (h) any type of mobile terminal in a telecommunications network; or (i) any machines configured for wireless communications in various applications, including but not limited to, an automobile with wireless communication capabilities. A method, apparatus and computer program product are disclosed for measuring TA on an extension carrier. Although the method, apparatus and computer program product may be implemented in a variety of different systems, one example of such a system is shown in Figure 1, which includes a first communication device (e.g., mobile terminal 10) that is capable of communication with a network 12 (e.g., a core network) via an access point 14 (e.g., a Node B, an evolved Node B (eNB), a base station or the like). While the network may be configured in accordance with LTE or LTE-Advanced (LTE-A), other networks may support the method, apparatus and computer program product of embodiments of the present invention including those configured in accordance with wideband code division multiple access (W-CDMA), CDMA2000, global system for mobile communications (GSM), general packet radio service (GPRS) and/or the like.

The network 12 may include a collection of various different nodes, devices or functions that may be in communication with each other via corresponding wired and/or wireless interfaces. For example, the network may include one or more access points 14, each of which may serve a coverage area divided into one or more cells. The access points or other communication node could be, for example, part of one or more cellular or mobile networks or public land mobile networks (PLMNs). In turn, other devices such as processing devices (e.g., personal computers, server computers or the like) may be coupled to the mobile terminal and/or the second communication device via the network.

A communication device, such as the mobile terminal 10 (also known as user equipment

(UE)), may be in communication with other communication devices or other devices via the access point 14 and, in turn, the network 12. In some cases, the communication device may include an antenna for transmitting signals to and for receiving signals from an access point. In some example embodiments, the mobile terminal 10 may be a mobile communication device such as, for example, a mobile telephone, portable digital assistant (PDA), pager, laptop computer, or any of numerous other hand held or portable communication devices, computation devices, content generation devices, content consumption devices, or combinations thereof. As such, the mobile terminal may include one or more processors that may define processing circuitry either alone or in combination with one or more memories. The processing circuitry may utilize instructions stored in the memory to cause the mobile terminal to operate in a particular way or execute specific functionality when the instructions are executed by the one or more processors. The mobile terminal may also include communication circuitry and corresponding hardware/software to enable communication with other devices and/or the network 12.

In one embodiment, for example, the mobile terminal 10 may be embodied as or otherwise include an apparatus 20 as generically represented by the block diagram of Figure 2. While the apparatus may be employed, for example, by a mobile terminal, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

As shown in Figure 2, the apparatus 20 may include or otherwise be in communication with processing circuitry 22 that is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

In an example embodiment, the processing circuitry 22 may include a processor 24 and memory 26 that may be in communication with or otherwise control a device interface 28 and, in some cases, a user interface 29. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the mobile terminal 10, the processing circuitry may be embodied as a portion of a mobile computing device or other mobile terminal. The user interface 29 (if implemented) may be in communication with the processing circuitry 22 to receive an indication of a user input at the user interface and/or to provide an audible, visual, mechanical or other output to the user. As such, the user interface may include, for example, a keyboard, a mouse, a joystick, a display, a touch screen, a microphone, a speaker, and/or other input/output mechanisms.

The device interface 28 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the device interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 12 and/or any other device or module in communication with the processing circuitry 22. In this regard, the device interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

In an example embodiment, the memory 26 may include one or more non-transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 20 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 24. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

The processor 24 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor may be configured to execute instructions stored in the memory 26 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry 22) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

As noted above, an access point 14 or other network entity may be configured to communicate with the mobile terminal 10. In some cases, the access point may include an antenna or an array of antennas for transmitting signals to and for receiving signals from the mobile terminal. The access point may be embodied as a base station, e.g., a Node B, an evolved Node B (eNB) or the like, or may be communicably connected to a base station with the base station including one or more processors that may define processing circuitry either alone or in combination with one or more memories. The processing circuitry may utilize instructions stored in the memory to cause the base station to operate in a particular way or execute specific functionality when the instructions are executed by the one or more processors. The access point may also include communication circuitry and corresponding hardware/software to enable communication with the mobile terminal and/or the network 12,

In one embodiment in which the access point 14 is embodied as a base station, such as a Node B, an eNB or the like, the base station may be embodied as or otherwise include an apparatus 30 as generically represented by the block diagram of Figure 3. While the apparatus may be employed, for example, by a base station, it should be noted that the components, devices or elements described below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments may include further or different components, devices or elements beyond those shown and described herein.

As shown in Figure 3, the apparatus 30 may include or otherwise be in communication with processing circuitry 32 that is configurable to perform actions in accordance with example embodiments described herein. The processing circuitry may be configured to perform data processing, application execution and/or other processing and management services according to an example embodiment of the present invention. In some embodiments, the apparatus or the processing circuitry may be embodied as a chip or chip set. In other words, the apparatus or the processing circuitry may comprise one or more physical packages (e.g., chips) including materials, components and/or wires on a structural assembly (e.g., a baseboard). The structural assembly may provide physical strength, conservation of size, and/or limitation of electrical interaction for component circuitry included thereon. The apparatus or the processing circuitry may therefore, in some cases, be configured to implement an embodiment of the present invention on a single chip or as a single "system on a chip." As such, in some cases, a chip or chipset may constitute means for performing one or more operations for providing the functionalities described herein.

In an example embodiment, the processing circuitry 32 may include a processor 34 and memory 36 that may be in communication with or otherwise control a device interface 38. As such, the processing circuitry may be embodied as a circuit chip (e.g., an integrated circuit chip) configured (e.g., with hardware, software or a combination of hardware and software) to perform operations described herein. However, in some embodiments taken in the context of the base station, the processing circuitry may be embodied as a portion of a base station or other network entity.

The device interface 38 may include one or more interface mechanisms for enabling communication with other devices and/or networks. In some cases, the device interface may be any means such as a device or circuitry embodied in either hardware, or a combination of hardware and software that is configured to receive and/or transmit data from/to a network 12 and/or any other device or module in communication with the processing circuitry 32. In this regard, the device interface may include, for example, an antenna (or multiple antennas) and supporting hardware and/or software for enabling communications with a wireless communication network and/or a communication modem or other hardware/software for supporting communication via cable, digital subscriber line (DSL), universal serial bus (USB), Ethernet or other methods.

In an example embodiment, the memory 36 may include one or more non-transitory memory devices such as, for example, volatile and/or non-volatile memory that may be either fixed or removable. The memory may be configured to store information, data, applications, instructions or the like for enabling the apparatus 30 to carry out various functions in accordance with example embodiments of the present invention. For example, the memory could be configured to buffer input data for processing by the processor 34. Additionally or alternatively, the memory could be configured to store instructions for execution by the processor. As yet another alternative, the memory may include one of a plurality of databases that may store a variety of files, contents or data sets. Among the contents of the memory, applications may be stored for execution by the processor in order to carry out the functionality associated with each respective application. In some cases, the memory may be in communication with the processor via a bus for passing information among components of the apparatus.

The processor 34 may be embodied in a number of different ways. For example, the processor may be embodied as various processing means such as one or more of a microprocessor or other processing element, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), or the like. In an example embodiment, the processor 34 may be configured to execute instructions stored in the memory 36 or otherwise accessible to the processor. As such, whether configured by hardware or by a combination of hardware and software, the processor may represent an entity (e.g., physically embodied in circuitry - in the form of processing circuitry 32) capable of performing operations according to embodiments of the present invention while configured accordingly. Thus, for example, when the processor is embodied as an ASIC, FPGA or the like, the processor may be specifically configured hardware for conducting the operations described herein. Alternatively, as another example, when the processor is embodied as an executor of software instructions, the instructions may specifically configure the processor to perform the operations described herein.

Referring now to Figures 4-6, flowcharts illustrating the operations performed by a method, apparatus and computer program product, such as apparatus 20 of Figure 2 and apparatus 30 of Figure 3, in accordance with example embodiments of the present invention are illustrated. It will be understood that each block of the flowcharts, and combinations of blocks in the flowcharts, may be implemented by various means, such as hardware, firmware, processor, circuitry and/or other device associated with execution of software including one or more computer program instructions. For example, one or more of the procedures described above may be defined by computer program instructions. In this regard, the computer program instructions which embody the procedures described above may be stored by a memory device of an apparatus employing an embodiment of the present invention and executed by a processor in the apparatus.

As will be appreciated, any such computer program instructions may be loaded onto a computer or other programmable apparatus (e.g., hardware) to produce a machine, such that the resulting computer or other programmable apparatus provides for implementation of the functions specified in the flowcharts' block(s). These computer program instructions may also be stored in a non-transitory computer-readable storage memory that may direct a computer or other programmable apparatus to function in a particular manner, such that the instructions stored in the computer-readable storage memory produce an article of manufacture, the execution of which implements the function specified in the flowcharts' block(s). The computer program instructions may also be loaded onto a computer or other programmable apparatus to cause a series of operations to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide operations for implementing the functions specified in the flowcharts' block(s).

As such, the operations of Figures 4-6, when executed, convert a computer or processing circuitry into a particular machine configured to perform an example embodiment of the present invention. Accordingly, the operations of each of Figures 4-6 define an algorithm for configuring a computer or processing circuitry, e.g., processor 24, to perform an example embodiment. In some cases, a general purpose computer may be provided with an instance of the processor which performs the algorithm of a respective one of Figures 4-6 to transform the general purpose computer into a particular machine configured to perform an example embodiment,

Accordingly, blocks of the flowcharts support combinations of means for performing the specified functions and combinations of operations for performing the specified functions. It will also be understood that one or more blocks of the flowcharts, and combinations of blocks in the flowcharts, can be implemented by special purpose hardware-based computer systems which perform the specified functions, or combinations of special purpose hardware and computer instructions.

In various example embodiments of the present invention, apparatuses are provided to determine the timing advance for an extension carrier, such as an extension carrier in a LTE/LTE- Advanced system. In doing so, the apparatus is configured to avoid or limit interference that may otherwise occur from preamble transmissions which are autonomously generated by the mobile terminal. To avoid such interference, in accordance with one example embodiment, an apparatus executes a physical random access channel (PRACH) determination process as described in Figure 4. An apparatus 30, embodied, for example by an access point 14, may ascertain if PRACH is configured for a specific carrier. See block 42. If PRACH is not configured for the specific carrier, the apparatus 30 is configured to schedule the physical uplink shared channel (PUSCH) on the configured PRACH resource without concern for possible interference from the preamble transmission which is autonomously triggered by mobile terminal itself. See block 44. If PRACH is configured for a specific carrier, however, the apparatus 30 of this embodiment does not schedule the PUSCH on the PRACH resource so as to avoid interference and, instead, is configured to execute a preamble conversion process. See block 46. The preamble conversion process is described in greater detail in the discussion for Figure 5-6.

The PRACH determination process may be beneficial because one PRACH resource may occupy six physical resource blocks (PRBs). PRACH therefore represents a significant overhead in uplink (UL) transmissions, and configuring PRACH on the extension carrier could be a burden on system resources. By configuring PUSCH on the PRACH resource when available, this example embodiment provides a robust and efficient system for providing the PUSCH when appropriate, while obtaining timing advance information creating interference.

Once a random access channel (RACH) has been configured for a specific carrier, there may be either contention based RACH or non-contention based RACH. If the case of contention based RACH, an apparatus 30 embodied, for example, by an access point 14, without limitation, may allocate different preamble sets to a mobile terminal 10. The mobile terminal 10 may then select the preamble within the contention based set if the RACH is triggered by mobile terminal itself or triggered by the access point 14 in an instance in which the PRACH resource and preamble are not explicitly indicated to the mobile terminal. With a backward compatible carrier configured with RACH, a contention based preamble is needed for initial access, radio resource control (RRC) re-establishment, UL data arrival in an instance in which the UL is not synchronized, and dynamic source routing (D-SR) failure. Therefore, the access point 14 of one embodiment reserves all the configured PRACH resource, thereby not scheduling PUSCH on the configured PRACH resource, to avoid possible interference from the preamble transmission triggered by mobile terminal. If all the RACH is scheduled by the access point 14 with only contention free RACH being transmitted on a carrier, the PRACH resource could be shared with PUSCH as shown in block 44 of Figure 4, which results in a more efficient use of resources as the access point may schedule PUSCH or PRACH on the PRACH resource. Even in an instance in which the PRACH is scheduled, efficiency may not be comprised because the non-contention based preamble may be used for TA measurement.

By way of example for frequency division duplex (FDD), 10 PRACH resources may be reserved by the access point 10 in a radio frame, while up to 6 PRACH resources may be reserved by the access point in time division duplex (TDD). For a carrier with 20MHz bandwidth as example, if contention based RACH is allowed, the reserved resource could be 6% in FDD and at least 6% in TDD depending on the actual TDD configuration. The proportion of the reserved resource will increase if the bandwidth is smaller. Indeed, the maximum value could be even 100%, such as in the case that the bandwidth of the carrier is 1.4MHz, which has only 6 PRBs. But because the RACH is not expected to happen very frequently, if only contention free RACH is used, eNB could use the configured PRACH resource for UL transmission for most of the time, which leads to small overhead and no resource waste.

In the event that contention based RACH is allowed, at least four (4) preambles may be configured for contention based RACH. These preambles may include, without limitation:

preamblelnfo SEQmobile terminalNCE {

numberOfRA-Preambles ENUMERATED {

n4, n8, nl2, nl6 ,n20, n24, n28, n32, n36, n40, n44, n48, n52, n56, n60, n64} Thus, Figure 5 illustrates an example embodiment of the operations performed by an apparatus to restrict the mobile terminal triggered RACH, thereby improving the performance and reducing the configuration signaling overhead via a preamble conversion process. To restrict the mobile terminal triggered RACH, this example embodiment involves configuring an apparatus 20, such as may be embodied by a mobile terminal 10, without a contention based preamble. Without the contention based preamble, the mobile terminal may only be ordered by a non-contention based preamble transmission by an access point 14. For example and without limitation, one example of configuring a mobile terminal without a contention based preamble may comprise utilizing nO to replace n64 or any of the existing values, such as n4, n8, etc., in the

RACH configuration signaling from the access point to the mobile terminal via dedicated signaling, such as:

preamblelnfo SEQmobile terminalNCE {

numfaerOfRA-Preambles ENUMERATED {

nO, n4, n8, nl2, nl6 ,n20, n24, n28, n32, n36, n40, n44, n48, n52, n56, n60)

In another example embodiment, the access point 14 is configured to configure RACH on a backward compatible carrier with the mobile terminal 10 assuming the same PRACH configuration on the extension carrier as the primary cell. This process may be termed a mirror RACH process. In this embodiment, if the bandwidth of the corresponding secondary (SCell) cell is equal to, or greater than, the bandwidth of the primary cell (PCell), the mobile terminal 10 may apply the same primary cell configuration parameter, such as:

= ⁿpi_B,₀jjsei ■ However, if the bandwidth of the corresponding secondary cell is less than the bandwidth of the primary cell, the mobile terminal 10 of this embodiment is configured to define the PRACH resource configuration parameter in such a manner that the PRACH resource is in the secondary cell's bandwidth with a contiguous physical resource block (PRB). For example, the PRACH resource configuration parameter may be defined as follows: _nM _{= η} - (N^UL —N^UL \

With the mirror RACH process described above, the access point 14 may schedule a preamble transmission on the extension carrier along with a UL transmission. Further, the access point 14 may schedule a PUSCH transmission on the corresponding PRACH resource if no PRACH transmission is needed in the current subframe. The mirror RACH process is beneficial because different mobile terminals have different primary cells, and thus, the mirror RAHCJTI on the extension carrier for different mobile terminals could differ as well. As a result, for example, more than 10 PRACH in one radio frame (i.e. 10ms) may be available on the extension carrier for FDD and more than 6 PRACH in one radio frame (i.e. 10ms) may be available for TDD, thus providing more preamble scheduling flexibility.

In another embodiment of the present invention, the access point 14 may be configured to dynamically schedule a random access (RA) preamble using downlink control information (DCI) format 1A, with a re-assignment of un-used states in the resource block assignment field, and without the RACH resource configuration on the extension carrier. In one embodiment, the PRB number used for RA preamble may be fixed, such as to 6 PRBs. Un-used states in the resource block assignment field may be reused in this embodiment to indicate the allocated PRB location for the RA preamble in the corresponding transmission time interval (TTI), that is, the RA preamble resource is to start from which PRB. The RA preamble scheduled by this type of DCI format 1A may be fixed in the n+k+2; where n is the arrival time of PDCCH with the reconfigured DCI format 1A and k is the PUSCH timing for FDD or TDD, and k is defined in 36.312 table 8-2. In the DCI format 1A, some bits are used to describe resource allocation and one state (or one combination of the bits) stands for one state of the allocated resource. However, some un-used bit combinations result, wherein the state which the bits could combine is more than the states of the possible allocation results. If one state of the bits combination is not possible for resource allocation purposes, the state of the bits combination may be used for another purpose. For example, in 36.212, section 5.3.3.1.3, if the bits in the state of bits combination each comprise a "1", the state may comprise a RACH trigger. Therefore, this invention, we propose to use the other un-used state to indicate UE the resource which should be used to transmit preamble.

In an instance in which the carrier bandwidth equal 15 PRBs, there may not be enough un-used states in the resource block assignment. However, since the PRACH mask index may be not needed, a state in the RA could be served to indicate that the PRACH mask index will be used for allocation. The reused states in the resource block assignment field may be mapped to PRB location in a reverse order. For example, the last states may indicate the first PRB position, the penultimate states may indicate the second PRB position, and so on. The mobile terminal 10 may identify that DCI format 1A is a RACH order by checking re-explained states in the resource allocation assignment. The mobile terminal 10 of this embodiment may send a dedicated RA preamble in the PRB position that is indicated by the re-explained DCI format 1A that is described above. In another example embodiment of the present invention, the access point 14 may dynamically schedule the A preamble, such as by using a DCI format 1A, which utilizes reserved bits and a PRACH Mask Index field and sets a resource block assignment to a fixed state that is different than the legacy RACH order, and without the RACH resource configuration on extension carrier. The PRB number used for the RA preamble may be fixed, such as to 6 PRBs. The resource block assignment field may be set to a fixed state which is different than the states that are used for data scheduling as well as the states that are used for legacy RACH order. For example, the least significant bit (LSB) of this field may be set to "0" and all other bits may be set to "1". Other than the field of "flag for formatO/formatlA differentiation", "localized/distributed VRB assignment flag", "Resource block assignment" and "Preamble index", a "RA preamble ppsition" field, such as a field with 7 bits, could be configured to indicate the PRB positions of the RA preamble.

The scheduled RA preamble by this kind of DCI format 1 A will be fixed in the n+k+2; where n is the arrival time of PDCCH with the re-explained DCI format 1 A; and k is the PUSCH timing for FDD or TDD. Thus, the mobile terminal 10 of this embodiment may identify such a DCI format 1A by checking resource allocation assignment states and the "RA preamble position" field that is configured as described above. Then mobile terminal 10 may then send a dedicated RA preamble in the PRB position that indicated by the "RA preamble position" field.

Figure 5 further illustrates an example embodiment of the present invention. Once an apparatus 20 embodied, for example, by a mobile terminal 10 is configured with the extension carrier, the apparatus may include means, such as the processing circuitry 22, the processor 24 or the like, for determining if a separate TA value is needed for the extension carrier or not. See blocks 50 and 51. To make this determination, the apparatus 20, such as the processor 24, embodied by the mobile terminal 10 may determine if the configured extension carrier is in the same TA group with the PCell, and if so, the apparatus may apply the same TA value as the PCell, thereby not requiring a separate TA value for the extension carrier. If, however, the configured extension carrier does not belong to any of the existing TA group and a separate TA is needed on the extension carrier, the apparatus 20 embodied by the mobile terminal 10 may include means, such as the processing circuitry 22, the processor 24 or the like, for calculating the PRACH resource, such as described above. See block 52. Once the PRACH resource is determined, the apparatus 20 may include means, such as the processing circuitry 22, the processor 24, the device interface 28 or the like, for determining if the access point 14 has triggered RACH on the extension carrier. See block 52. If the access point 14 is determined to have triggered RACH on the extension carrier, the apparatus 20 may include means, such as the processing circuitry 22, the processor 24, the device interface 28 or the like, for causing the preamble to be transmitted on one of the PRACH resources as configured and in a manner that follows the RACH order. See block 55. Alternatively, if the access point is determined not to have triggered RACH on the extension carrier, the apparatus 20 may include means, such as the processing circuitry 22, the processor 24, the device interface 28 or the like, for determining if the access point 14 has provided a scheduling grant for PUSCH on the extension carrier. See block 54. If so, the apparatus 20 may include mans, such as the processing circuitry 22, the processor 24, the device interface 28 or the like, for causing the PUSCH to be transmitted on the corresponding PRACH resource according to the scheduling grant. See block 56 of Figure 5. The process then terminates at block 57.

As an example, a FDD system may comprise 20MHz bandwidth corresponding to 100 PRBs. Then, according to the resource block assignment, there may be [ bits which equal to 13 bits, i.e. 8192 states. The DCI format 1A for data scheduling may utilize states which equals to 5050 states. The DCI format 1A for legacy RACH scheduling may utilize 1 state, and therefore, exactly 8192-5050-1=3141 states may be un-used.

In accordance with an example embodiment of the present invention, the total PRBs that are needed is 100-6+1=95, and therefore, the total number of states that are needed in this embodiment is 95, which is much less than the un-used states number 3141. Thus, for 100 PRBs, that is, 20MHz bandwidth, the number of unused states is sufficient. For other bandwidths, the following table provides the un-used states number and needed states number for all possible bandwidths in an LTE system:

50 2048 1275 1 772 45

75 4096 2850 1 1245 70

100 8192 5050 1 3141 95

According to the table, when the bandwidth is 15 PRBs, the un-used states may not be sufficient. In this situation, the RA state of "1, 1,1,... ,0" may be reserved as a sign that the resource for preamble transmission will be indicated with PRACH mask index field.

Then, as illustrated in Figure 6, the apparatus such as the eNB may map reused states

(shown as States#l-#3) in resource block assignment 65 to PRB 60 in a reverse order. For example, if the access point 14 were to allocate PRBs for a RA preamble from PRB#3, then the access point would use the third state count from the last state. This process is illustrated in Figure 6, wherein PRB#3 is indicated by State#n-3, as shown. When the mobile terminal 10 receives this re-explained DCI format 1A from PDCCH in subframe n, the mobile terminal may prepare the RA preamble transmission in subframe n+k+2 where k is 4 for FDD. Thus, the mobile terminal of this embodiment may transmit the RA preamble in subframe n+6. This process also applies with RACH procedures.

Another example embodiment of the present invention provides an apparatus that includes means for configuring the fields in a DCI format for RACH order on an extension carrier to convert the preamble to a preferred preamble for determining timing advance information. Several adjustments may be applied to the RACH order on the extension carrier to provide DCI format 1A that is used for RACH order on extension carrier. These adjustments may comprise, without limitation, the following bit changes: 1) the 1 bit flag for formatO/formatlA differentiation may be set to "1"; 2) the 1 bit Localized/Distributed VRB assignment flag may be set to "0"; 3) the resource block assignment consisting of [ΙΟ₆₂ (Λ¾ ·(Λ¾ +Ι) / 2)] bits may have the LSB set to "0" and all other bits set to "1 "; 4) the Preamble

Index may have 6 bits; 5) the RA preamble position consisting of 7bits may indicate the PRB position on the extension carrier from which the RA preamble is to start; and/or all of the remaining bits in DCI format 1 A for compact scheduling assignment of one PDSCH codeword may be set to zero.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. A method comprising:

determining physical random access channel (PRACH) resources configured on an extension carrier;

determining if a preamble transmission is triggered on the extension carrier;

in an instance in which a preamble transmission is triggered on the extension carrier, causing the preamble to be transmitted on a respective PRACH resource; and

in an instance in which a preamble transmission is not triggered on the extension carrier, receiving a scheduling grant for a physical uplink shared channel (PUSCH) on a respective PRACH resource.

2. The method of Claim 1, further comprising, in an instance in which the timing advance is not calculated for the extension carrier, applying the same timing advance for the extension carrier as the timing advance for a primary cell.

3. The method of Claim 1, wherein determining the PRACH resources comprises establishing the same PRACH configuration for the extension carrier as a primary cell.

4. The method of Claim 1 , wherein causing the preamble to be transmitted comprises causing a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field.

5. The method of Claim 1, wherein causing the preamble to be transmitted comprises causing a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information.

6. The method of Claim 1 , wherein the preamble transmission comprises a random access channel (RACH) transmission.

7. The method of Claim 1, further comprising determining if a timing advance is to be calculated for the extension carrier.

8. An apparatus comprising:

at least one processor; and

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

determine physical random access channel (PRACH) resources available on an extension carrier;

determine if a preamble transmission is triggered on the extension carrier;

9. An apparatus according to Claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to in an instance in which the timing advance is not calculated for the extension carrier, apply the same timing advance for the extension carrier as the timing advance for a primary cell.

10. An apparatus according to Claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to establish the same PRACH configuration for the extension carrier as a primary cell.

11. An apparatus according to Claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field.

12. An apparatus according to Claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information.

13. An apparatus according to Claim 8, wherein the apparatus comprises a mobile terminal.

14. An apparatus according to Claim 8 further comprising a device interface configured to communicate with a base station in order to receive the scheduling grant for the PUSCH on the respective PRACH resource.

15. An apparatus according to Claim 8 wherein the mobile terminal is configured for use in a Long Term Evolution (LTE) system.

16. An apparatus according to Claim 8, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to determine if a timing advance is to be calculated for the extension carrier.

17. An apparatus according to Claim 8, wherein the preamble transmission comprises a random access channel (RACH) transmission.

18. A computer program product comprising at least one non-transitory computer-readable storage medium having computer-readable program instructions stored therein, the computer- readable program instructions comprising program instructions configured to:

determine physical random access channel (PRACH) resources available on the extension carrier;

determine if a random access channel (RACH) is triggered on an extension carrier;

in an instance in which RACH is triggered on the extension carrier, causing the preamble to be transmitted on a respective PRACH resource; and

in an instance in which RACH is not triggered on the extension carrier, receiving a scheduling grant for a physical uplink shared channel (PUSCH) on a respective PRACH resource.

19. The computer program product of Claim 18, wherein the computer readable instructions comprise program instructions further configured to, in an instance in which the timing advance is not calculated for the extension carrier, apply the same timing advance for the extension carrier as the timing advance for a primary cell.

20. The computer program product of Claim 18, wherein the computer readable instructions comprise program instructions further configured to establish the same PRACH configuration for the extension carrier as a primary cell.

21. The computer program product of Claim 18, wherein the computer readable instructions comprise program mstructions further configured to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a resource block assignment field.

22. The computer program product of Claim 18, wherein the computer readable instructions comprise program instructions further configured to cause a resource allocation preamble to be transmitted in a PRB position as indicated by a field within downlink control information.

23. The computer program product of Claim 18, wherein the computer program product is stored within a memory within a mobile terminal.

24. The computer program product according to Claim 18 further comprising a device interface configured to communicate with a base station in order to receive the scheduling grant for the PUSCH on the respective PRACH resource.

25. The computer program product according to Claim 18 wherein the mobile terminal is configured for use in a Long Term Evolution (LTE) system.

26. The computer program product according to Claim 18, wherein the computer readable instructions comprise program instructions further configured to determine if a timing advance is to be calculated for the extension carrier.