Patent Description:
In wireless communications systems, such as long term evolution (LTE) systems, downlink and uplink transmissions may be organized into two duplex modes: frequency division duplex (FDD) mode and time division duplex (TDD) mode. The FDD mode uses a paired spectrum where the frequency domain is used to separate the uplink (UL) and downlink (DL) transmissions. <FIG> is a graphical illustration of an uplink and downlink sub-frame separated in the frequency domain for the FDD mode. In TDD systems, an unpaired spectrum may be used where both UL and DL are transmitted over the same carrier frequency. The UL and DL are separated in the time domain. <FIG> is a graphical illustration of UL and DL sub-frames sharing a carrier frequency in the TDD mode. In LTE-Advanced, carrier aggregation allows expansion of effective bandwidth delivered to a user terminal through concurrent utilization of radio resources across multiple carriers. Multiple component carriers are aggregated to form a larger overall transmission bandwidth. Carrier aggregation may be performed in LTE-Advanced TDD or LTE-Advanced FDD systems. The following terms and abbreviations may be used throughout this disclosure:.

3GPP TSG-RAN WG1 #<NUM> (ref. R1-<NUM>) discusses the impacts on PDSCH HARQ feedback due to the introduction of different UL/DL configuration PDSCH HARQ reference timings.

It should be understood at the outset that although illustrative implementations of one or more embodiments of the present disclosure are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described.

The present disclosure includes methods and systems for carrier aggregation between two cells of a different UL/DL configuration. According to certain illustrative examples, for each sub-frame that differs between the two cells, the HARQ-ACK scheme can be adjusted so that the same number of ACK/NACK bits is sent to both cells. This may be done so that standard mapping tables in existing specifications may be used. The following provides a more detailed explanation.

Certain aspects of the implementations include systems, methods, and user equipment (UE) for transmitting Acknowledgement/Negative Acknowledgement (ACK/NACK) bits for carrier aggregation between a first cell and a second cell in a User Equipment (UE). In certain aspects, the method may include, with the UE, for a sub-frame, comparing a first number of ACK/NACK bits for the first cell with a second number of ACK/NACK bits for the second cell. If a first number of ACK/NACK bits for the first cell is less than a second number of ACK/NACK bits for the second cell, an ACK/NACK bit position from the first cell can be used to transmit an ACK/NACK bit for the second cell.

Certain aspects of the implementations include determining that sub-frames that correspond to ACK/NACK bits for a first cell are of a different configuration than sub-frames that correspond to ACK/NACK bits for a second cell.

In certain implementations, the ACK/NACK bit positions for a cell are described in a table, the table associating combinations of ACK/NACK bits to ACK/NACK signals transmitted by the UE. If the number of ACK/NACK bits for the first cell is the same as the number of ACK/NACK bits for the second cell, all ACK/NACK bit positions from the first cell can be used to transmit only ACK/NACK bits for the first cell.

Certain aspects also include, for the sub-frame, determining that the first number of ACK/NACK bits for the first cell is zero. One or more resources (e.g., ACK/NACK resources) can be used to indicate with an ACK/NACK Resource Indicator (ARI) the number of resources being equal to the second number of ACK/NACK bits for the second cell.

In certain aspects of the implementations, the ACK/NACK bit for the second cell transmitted in the bit position for the first cell comprises one of: a DTX bit or an ACK bit.

Certain aspects of the implementations may also include reordering the ACK/NACK bit positions of at least one of: the bit positions for the first cell or the bit positions of the second cell.

In certain implementations, the reordering comprises transmitting a last ACK/NACK bit for the second cell using the position of one of: a last ACK/NACK bit or a next to last ACK/NACK bit for the first cell, wherein the last ACK/NACK bit corresponds to a sub-frame that is transmitted last to the UE, and the next to last ACK/NACK bit corresponds to a sub-frame that is transmitted immediately prior to a sub-frame that is transmitted last to the UE.

In certain aspects of the implementations, the first cell is a primary cell and the second cell is a secondary cell.

In some aspects of the implementations, the second cell is a primary cell and the first cell is a secondary cell.

Aspects of the implementations are directed to systems, methods, and UE for transmitting Acknowledgement/Negative Acknowledgement (ACK/NACK) bits for carrier aggregation between a first cell and a second cell in a User Equipment (UE). In the UE, for a sub-frame, it may be determined that a first number of ACK/NACK bits for the first cell is different than a second number of ACK/NACK bits for the second cell. It may also be determined that the sum of the first number and the second number is less than a predetermined number. The ACK/NACK bits of the first cell can be concatenated with the ACK/NACK bits of the second cell. A set of ACK/NACK bit positions corresponding to the predetermined number can be used to transmit the concatenated bits.

Certain aspects of the implementations may include, in the UE, determining that sub-frames that correspond to ACK/NACK bits for the first cell are of a different configuration than sub-frames that correspond to ACK/NACK bits for the second cell.

In certain aspects of the implementations, the first cell may be a primary cell and the second cell may be a secondary cell.

In certain implementations, the second cell may be a primary cell and the first cell may be a secondary cell.

Certain aspects of the implementations are directed to systems, methods, and UE for transmitting Acknowledgement/Negative Acknowledgement (ACK/NACK) bits for carrier aggregation between a first cell and a second cell in a User Equipment (UE). In the UE, for a sub-frame, it may be determined that a first number of ACK/NACK bits for the first cell is different than a second number of ACK/NACK bits for the second cell. An extra number of ACK/NACK bit positions may be added to a smaller of the first number and the second number of ACK/NACK bits.

Certain aspects of the implementations also may include, in the UE, determining that sub-frames that correspond to ACK/NACK bits for a first cell are of a different configuration than sub-frames that correspond to ACK/NACK bits for a second cell.

In certain implementations, the ACK/NACK bit positions for a cell are described in a table, the table associating combinations of ACK/NACK bits to ACK/NACK signals transmitted by the UE.

Certain aspects of the implementations may also include, for the sub-frame, determining that the first number of ACK/NACK bits for the first cell is zero. One or more resources (e.g., ACK/NACK resources) may indicate with an ACK/NACK Resource Indicator (ARI), the number of resources being equal to the second number of ACK/NACK bits for the second cell.

In certain aspects of the implementations, at least one bit transmitted in the extra bit positions comprises at least one bit corresponding to the cell with a larger of the first number and the second number of ACK/NACK bits.

In certain aspects of the implementations, the second cell may be a primary cell and the first cell may be a secondary cell.

<FIG> are diagrams showing the difference between FDD and TDD systems. The charts shown in <FIG> represent frequency with the y axis and time with the x axis. The FDD chart <NUM> of <FIG> illustrates the downlink sub-frame <NUM> on channel <NUM><NUM> and the uplink sub-frame <NUM> on channel <NUM><NUM>. Alternatively, the TDD chart <NUM> of <FIG> illustrates both the downlink sub-frames <NUM> and the uplink sub-frames <NUM> on the same channel <NUM>.

In the 3GPP LTE TDD system, a sub-frame of a radio frame can be a downlink, an uplink or a special sub-frame. The special sub-frame comprises downlink and uplink time regions separated by a guard period for downlink to uplink switching. The 3GPP specification standards define seven different UL/DL configuration schemes for LTE TDD operations. These schemes are listed in Table <NUM>. D represents downlink sub-frames, U represents uplink sub-frames and S represents the special sub-frame. The special sub-frame includes three parts, (<NUM>) the downlink pilot time slot (DwPTS), (<NUM>) the uplink pilot time slot (UpPTS) and (<NUM>) the guard period (GP). Downlink transmissions on the PDSCH may be made in DL sub-frames or in the DwPTS portion of a special sub-frame.

The table below illustrates LTE TDD uplink-downlink configurations.

As Table <NUM> shows, there are two switching point periodicities specified in the LTE standard; <NUM> and <NUM>. The <NUM> switching point periodicity is introduced to support the co-existence between LTE and low chip rate UTRA TDD systems and <NUM> switching point periodicity is for the coexistence between LTE and high chip rate UTRA TDD systems. The supported configurations cover a wide range of UL/DL allocations from a DL heavy <NUM>:<NUM> ratio to a UL heavy <NUM>:<NUM> ratio. The DL allocations in these ratios include both DL sub-frames and special sub-frames, which can also carry downlink transmissions in DwPTS. Therefore, compared to FDD systems, TDD systems have more flexibility in terms of the proportion of resources assignable to uplink and downlink communications within a given assignment of spectrum. Specifically, it is possible to distribute the radio resources unevenly between uplink and downlink. This will provide a way to utilize the radio resources more efficiently by selecting an appropriate UL/DL configuration based on interference situation and different traffic characteristics in DL and UL.

Because the UL and DL transmissions are not continuous (i.e. UL or DL transmissions do not necessarily occur in every sub-frame) in an LTE TDD system, the scheduling and HARQ timing relationships are separately defined in the specifications. Currently, the HARQ ACK/NACK timing relationship for the downlink is shown below in Table <NUM>. It associates an UL sub-frame n, which conveys ACK/NACK, with DL sub-frames n-ki, i=<NUM> to M-<NUM>. The set of DL sub-frames for which ACK/NACK is provided is referred to herein as the bundling window, and the number of sub-frames for which ACK/NACK is provided, M, is referred to as the bundling window size.

The uplink HARQ ACK/NACK timing linkage is shown in table <NUM> below. The table indicates that the PHICH ACK/NACK received in the DL sub-frame i is linked with the UL data transmission in the UL sub-frame i-k, k being given in Table <NUM>. In addition, for UL/DL configuration <NUM>, in sub-frames <NUM> and <NUM>, IPHICH=<NUM> and k=<NUM>. This is because there may be two ACK/NACKs for a UE transmitted on the PHICH in sub-frames <NUM> and <NUM>, one is represented by IPHICH=<NUM>, the other is IPHICH=<NUM>. IPHICH just serves as an index.

The UL grant, ACK/NACK and transmission/retransmission relationship is shown below in Table <NUM>. The UE shall upon detection of a PDCCH with DCI format <NUM> and/or a PHICH transmission in sub-frame n intended for the UE, adjust the corresponding PUSCH transmission in sub-frame n+k, with k given in Table <NUM>.

For TDD UL/DL configuration <NUM>, if the least significant bit (LSB) of the UL index in the DCI format <NUM> is set to <NUM> in sub-frame n or a PHICH is received in sub-frame n=<NUM> or <NUM> in the resource corresponding to IPHICH=<NUM>, or PHICH is received in sub-frame n=<NUM> or <NUM>, the UE shall adjust the corresponding PUSCH transmission in sub-frame n+<NUM>. If, for TDD UL/DL configuration <NUM>, both the most significant bit (MSB) and LSB of the UL index in the DCI format <NUM> are set in sub-frame n, the UE shall adjust the corresponding PUSCH transmission in both sub-frames n+ k and n+<NUM>, with k given in Table <NUM>.

As can be seen, both grant and HARQ timing linkage in TDD are much more complicated than the fixed time linkages used in an LTE FDD system. It usually requires more attention in design.

The physical uplink control channel (PUCCH) format 1a/1b is used to transmit the ACK/NACK signaling when ACK/NACK is not multiplexed into a PUSCH transmission. The slot structure of PUCCH formats 1a and 1b with normal cyclic prefix is shown in <FIG>. Each format 1a/1b PUCCH is in a sub-frame made up of two slots. The same modulation symbol is used in both slots. Formats 1a and 1b carry one and two ACK/NACK bits, respectively. These bits are encoded into the modulation symbol using either BPSK or QPSK modulation using a sequence modulator <NUM>, the modulation being based on the number of ACK/NACK bits. The symbol is multiplied by a cyclic-shifted sequence <NUM> with length-<NUM>. Then, the samples are mapped to the <NUM> subcarriers that the PUCCH is to occupy and then converted to the time domain via an IDFT <NUM>. The spread signal is then multiplied with an orthogonal cover sequence with length of <NUM>, w(m), where m ∈ {<NUM>,<NUM>,<NUM>,<NUM>} corresponds to each one of <NUM> data bearing symbols in the slot. There are three reference symbols <NUM> in each slot (located in the middle symbols of the slot) that allow channel estimation for coherent demodulation of formats 1a/1b.

When downlink carrier aggregation is used or when TDD has more downlink sub-frames than uplink sub-frames, more than the two ACK/NACK bits that can be supported on PUCCH format 1b may be required. When <NUM> or <NUM> ACK/NACK bits are needed, PUCCH format 1b may be used with channel selection.

A UE encodes information using channel selection by selecting a PUCCH resource on which to transmit. Channel selection may use <NUM> PUCCH resources to convey two extra bits. This can be described using a <NUM> bit ACK/NACK configuration for TDD, shown below in Table <NUM>:.

Each row of the table indicates a combination of ACK/NACK bits to be transmitted. The column headed by n(<NUM>)PUCCH indicates a PUCCH resource to transmit on (using format 1b), while the column headed by b(<NUM>), b(<NUM>) indicates the value of the QPSK modulation symbol to transmit on the PUCCH resource. For LTE Rel-<NUM>, values of b(<NUM>), b(<NUM>) map to QPSK modulation symbols as shown in Table <NUM> above. The UE transmits on ('selects') one of four PUCCH resources n(<NUM>)PUCCHi , which conveys two bits of information in addition to the two bits carried by the QPSK modulation. The PUCCH resource which a UE is to use may be signaled via either implicit or explicit signaling.

In LTE TDD operation, the number of ACK/NACK bits to be transmitted may be reduced by spatial bundling. In spatial bundling, two HARQ-ACK bits for two transport blocks transmitted on one PDSCH are logical AND'd together, resulting in one spatially bundled HARQ-ACK bit. In Rel-<NUM> TDD, spatial bundling is applied in subframes where the bundling window size is larger than <NUM>, and so in this case the number of HARQ-ACK bits is equal to the bundling window size. Also, because only one HARQ-ACK bit is needed when MIMO is not configured for a UE, the number of HARQ-ACK bits is equal to the bundling window size when MIMO is not configured.

In the case of implicit signaling for TDD, for a PDSCH transmission indicated by the detection of corresponding PDCCH or a PDCCH indicating downlink SPS release in sub-frame n-ki where ki is an element of K, ki ∈ K, defined in Table <NUM>, the PUCCH resource <MAT>, where c is selected from {<NUM>, <NUM>, <NUM>, <NUM>} such that Nc ≤ nCCE,i < Nc+<NUM>, where M is the number of elements in the set K defined in Table <NUM>. <MAT>, nCCE,i is the number of the first CCE used for transmission of the corresponding PDCCH in sub-frame n-ki, and <MAT> is configured by higher layers. In the case of explicit signaling, the PUCCH resource is indicated via the ACK/NACK resource indicator (ARI) bits and higher layer configuration. <FIG> illustrates the PUCCH resource mapping scheme.

In carrier aggregation (CA), PUCCH resources <NUM> are signaled implicitly using the location of the scheduling grant for the UE on the PDCCH of its primary cell (PCell), and PUCCH resources <NUM> may be indicated using the ARI bits contained in the grant for the UE on the PDCCH <NUM> of one of the UE's secondary cells (SCells). This means that, if the secondary cell ("SCell") is cross carrier scheduled by PDCCH <NUM> transmitted on the primary cell ("PCell"), then the PUCCH resource <NUM> is implicitly signaled by the first CCE index. If the SCell schedules a PDSCH using its own PDCCH <NUM>, the PUCCH resource index is determined by the ARI bits.

As in LTE FDD, the current Rel-<NUM> LTE specification defines carrier aggregation (CA) for TDD systems. However, it only supports CA for cells having the same UL/DL configuration on the aggregated carriers. Methods described herein enable support for CA with cells that have different TDD UL/DL configurations.

PDSCH HARQ timing of SCell may follow the reference configuration timing summarized in Table <NUM> at least for full duplex self-scheduling case.

It is noted that a component carrier ('CC') is also known as a serving cell or a cell. Furthermore, when multiple CCs are scheduled, for each UE, one of the CCs is designated as the primary carrier which is used for PUCCH transmission, semi-persistent scheduling, etc, while the remaining CCs are configured as secondary CCs. This primary carrier is also known as PCell (Primary cell), while the secondary CC is known as SCell (Secondary cell).

Because UEs receiving a PDSCH on a PCell use the PCell as the HARQ timing reference for the PDSCH, there are cases where the timing reference for the PDSCH on the SCell based on Table <NUM> may be different from that of the PCell. As a result, the downlink association sets of PCell and SCell may be different for a given UL sub-frame in Table <NUM>. The current specification (Rel-<NUM>) only specifies the method of transmitting PDSCH ACK/NACK bits using PUCCH format 1a/1b with channel selection in the scenario with the same downlink association set (therefore having the same bundling window size). This method needs to be changed to deal with the different bundling window sizes in inter-band CA with different UL/DL configurations.

In methods described herein, PUCCH may be transmitted only on PCell in the case of inter-band CA with different UL/DL configurations. Therefore, PDSCH HARQ ACK/NACK bits for both PCell and SCell have to be conveyed on PCell if PUCCH is used. For the same bundling window size on PCell and SCell, the scheme to use PUCCH format 1b with channel selection for ACK/NACK transmission has been defined in Release <NUM> specification 3GPP TS <NUM>. References to tables <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, or <NUM>. <NUM>-<NUM> are references to tables found in 3gPP TS <NUM>.

In inter-band CA with different UL/DL configurations, the bundling window size of different cells may be different. For example, as shown in <FIG>, the PCell with UL/DL configuration <NUM> is aggregated with the SCell of UL/DL configuration <NUM>. Based on the PDSCH HARQ timing agreement, the PCell follows its own UL/DL configuration <NUM> PDSCH HARQ timing. The SCell follows UL/DL configuration <NUM> timing reference, as indicated in Table <NUM>. The solid line <NUM> represents the PDSCH HARQ timing linkage of the PCell. The dotted line <NUM> represents the PDSCH HARQ timing of SCell. Herein we refer to the bundling window size for PCell using Mp, and the bundling window for SCell using Ms. On PCell sub-frame #<NUM> or #<NUM>, the bundling window size for the PCell is two (Mp=<NUM>), and for the SCell it is four (Ms=<NUM>). At sub-frame #<NUM> or #<NUM>, Mp=<NUM>, Ms=<NUM>. In this case the bundling window size matches the number of elements in the downlink association set in Table <NUM>. However, the bundling window sizes are different for the PCell and the SCell.

Another example where the PCell is configuration <NUM> and the SCell is configuration <NUM> is shown in <FIG>. From Table <NUM>, the PDSCH HARQ timing follows configuration <NUM> for both the PCell and the SCell. So, the downlink association set is the same for both cells if it is solely dependent on Table <NUM>. However, as we can see from <FIG>, because sub-frame #<NUM> and #<NUM> on the SCell are UL sub-frames, there will never be PDSCH on these two sub-frames. Again, the solid line <NUM> represents the PDSCH HARQ timing linkage of the PCell and the dotted line <NUM> represents the PDSCH HARQ timing of SCell. The bundling window size for the PCell is four (Mp=<NUM>), and for the SCell is three (Ms=<NUM>). They are different as well even though the downlink association set is same based on the reference UL/DL configuration. Therefore, new schemes have to be proposed to deal with the different bundling window sizes in inter-band CA with different UL/DL configurations.

Through methods described herein, the existing ACK/NACK codebook for a one serving cell mapping table and a two cell mapping table (see appendices for example tables) can be directly used without any modification. At a sub-frame where all ACK/NACKs are for one cell, a one serving cell mapping table is used to avoid using unnecessary DTX bits. If the number of ACK/NACK bits for the first cell and second cell are different, but non-zero, then the ACK/NACK bits can be reordered or adjusted to minimize the number of ACK/NACK bits required. This can be done without the need for modified codebooks.

Table lists possible combinations of bundling window size for PCell and SCell, (Mp, Ms). Note that this is only intended for PUCCH format 1b with channel selection. Any CA case involving UL/DL configuration <NUM> or referring it as reference timing may use PUCCH format <NUM> due to the large number of ACK/NACK bits. The CA with the same UL/DL configuration on both PCell and SCell is not listed in the table either because it has already been covered in the current specification.

With the methods described herein, the existing ACK/NACK codebook for one serving cell Table <NUM>. <NUM>-<NUM>/<NUM>/<NUM> and two cells Table <NUM>. <NUM>-<NUM>/<NUM>/<NUM>/<NUM>/<NUM> defined in 3GPP TS <NUM> can be directly used without any modification.

An example of a mapping table is shown below:.

An example of a two cell mapping is shown below:.

<FIG> is a diagram showing an illustrative communication system <NUM> in which carrier aggregation may be used. According to certain illustrative examples, the system <NUM> includes a primary cell <NUM>, a secondary cell <NUM>, and a UE <NUM>. Both cells <NUM>, <NUM> include a processor <NUM>, a computer readable medium <NUM>, and a communication interface <NUM>. The processor <NUM> is used to process a set of computer readable instructions which may be stored on the computer readable medium <NUM>. The computer readable instructions, when executed by the processor <NUM>, cause the cell to perform a variety of tasks related to routing, switching, and other tasks for management of wireless voice and data traffic between the cells and a number of UEs <NUM>.

<FIG> is a schematic block diagram of the UE <NUM>. The UE <NUM> includes a digital signal processor (DSP) <NUM> and a memory <NUM>. As shown, the UE <NUM> may further include an antenna and front end unit <NUM>, a radio frequency (RF) transceiver <NUM>, an analog baseband processing unit <NUM>, a microphone <NUM>, an earpiece speaker <NUM>, a headset port <NUM>, an input/output interface <NUM>, a removable memory card <NUM>, a universal serial bus (USB) port <NUM>, a short range wireless communication sub-system <NUM>, an alert <NUM>, a keypad <NUM>, a liquid crystal display (LCD), which may include a touch sensitive surface <NUM>, an LCD controller <NUM>, a charge-coupled device (CCD) camera <NUM>, a camera controller <NUM>, and a global positioning system (GPS) sensor <NUM>.

The DSP <NUM> or some other form of controller or central processing unit operates to control the various components of the UE <NUM> in accordance with embedded software or firmware stored in memory <NUM>. In addition to the embedded software or firmware, the DSP <NUM> may execute other applications stored in the memory <NUM> or made available via information carrier media such as portable data storage media like the removable memory card <NUM> or via wired or wireless network communications. The application software may comprise a compiled set of machine-readable instructions that configure the DSP <NUM> to provide the desired functionality, or the application software may be high-level software instructions to be processed by an interpreter or compiler to indirectly configure the DSP <NUM>.

The antenna and front end unit <NUM> may be provided to convert between wireless signals and electrical signals, enabling the UE <NUM> to send and receive information from a cellular network or some other available wireless communications network. The RF transceiver <NUM> provides frequency shifting, converting received RF signals to baseband and converting baseband transmit signals to RF. The analog baseband processing unit <NUM> may provide channel equalization and signal demodulation to extract information from received signals, may modulate information to create transmit signals, and may provide analog filtering for audio signals. To that end, the analog baseband processing unit <NUM> may have ports for connecting to the built-in microphone <NUM> and the earpiece speaker <NUM> that enable the UE <NUM> to be used as a cell phone. The analog baseband processing unit <NUM> may further include a port for connecting to a headset or other hands-free microphone and speaker configuration.

The DSP <NUM> may send and receive digital communications with a wireless network via the analog baseband processing unit <NUM>. In some embodiments, these digital communications may provide Internet connectivity, enabling a user to gain access to content on the Internet and to send and receive e-mail or text messages. The input/output interface <NUM> interconnects the DSP <NUM> and various memories and interfaces. The memory <NUM> and the removable memory card <NUM> may provide software and data to configure the operation of the DSP <NUM>. Among the interfaces may be the USB interface <NUM> and the short range wireless communication sub-system <NUM>. The USB interface <NUM> may be used to charge the UE <NUM> and may also enable the UE <NUM> to function as a peripheral device to exchange information with a personal computer or other computer system. The short range wireless communication sub-system <NUM> may include an infrared port, a Bluetooth interface, an IEEE <NUM> compliant wireless interface, or any other short range wireless communication sub-system, which may enable the UE <NUM> to communicate wirelessly with other nearby mobile devices and/or wireless base stations.

The input/output interface <NUM> may further connect the DSP <NUM> to the alert <NUM> that, when triggered, causes the UE <NUM> to provide a notice to the user, for example, by ringing, playing a melody, or vibrating. The alert <NUM> may serve as a mechanism for alerting the user to any of various events such as an incoming call, a new text message, and an appointment reminder by silently vibrating, or by playing a specific preassigned melody for a particular caller.

The keypad <NUM> couples to the DSP <NUM> via the interface <NUM> to provide one mechanism for the user to make selections, enter information, and otherwise provide input to the UE <NUM>. The keyboard <NUM> may be a full or reduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY and sequential types, or a traditional numeric keypad with alphabet letters associated with a telephone keypad. The input keys may include a trackwheel, an exit or escape key, a trackball, and other navigational or functional keys, which may be inwardly depressed to provide further input function. Another input mechanism may be the LCD <NUM>, which may include touch screen capability and also display text and/or graphics to the user. The LCD controller <NUM> couples the DSP <NUM> to the LCD <NUM>.

The CCD camera <NUM>, if equipped, enables the UE <NUM> to take digital pictures. The DSP <NUM> communicates with the CCD camera <NUM> via the camera controller <NUM>. The GPS sensor <NUM> is coupled to the DSP <NUM> to decode global positioning system signals, thereby enabling the UE <NUM> to determine its position. Various other peripherals may also be included to provide additional functions, e.g., radio and television reception.

<FIG> is a flowchart showing an illustrative method <NUM> for adjusting the number and/or order of ACK/NACK bits. In this illustrative method, Mp is equal to the number of ACK/NACK bits for the primary cell, and Ms is equal to the number of ACK/NACK bits for the SCell. According to certain illustrative examples, for a particular sub-frame, it is determined <NUM> whether the bundling window size for a primary cell (Mp) is equal to the bundling window size for a secondary cell (Ms). If it is determined (<NUM>, YES) that Mp = Ms, then the method proceeds <NUM> according to normal operations. This involves using a standard mapping table for the appropriate bundling window size.

If it is determined (<NUM>, NO) that Mp does not equal Ms, then the method proceeds. It is next determined <NUM> whether or not both Mp and Ms are non-zero. If it is determined that either Mp or Ms is zero (<NUM>, NO), then a one serving cell mapping table is used <NUM>. The number of ACK/NACK bit positions for the mapping table will be equal to the non-zero number of either Mp or Ms. In some examples, a resource allocation method may then be used <NUM>. This resource allocation method will be discussed in more detail below.

If it is determined (<NUM>, YES) that both Mp and Ms are non-zero, then a two serving cell mapping table is used. The M value to be used in the table will be <NUM> the greater of Mp or Ms. The remaining bits from the smaller of Mp or Ms may then be filled in <NUM> with extra bits. These extra bits may be, e.g., DTX bits or ACK bits.

An example of this method may also be described as follows:.

Alternatively, UE may set ACK instead of DTX for {HARQ-ACK(min{Mp, Ms}),. , HARQ-ACK(M-<NUM>)} bits if there is a performance advantage to do so. Other alternatives, such as using (M, min{Mp, Ms}) block code, are also possible.

It is noted that using the Rel-<NUM> mapping for one serving cell (that is, one of tables <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, or <NUM>. <NUM>-<NUM>)) requires the use of a one serving cell resource allocation method. The Rel-<NUM> implicit one serving cell resource allocation is used in our method if the PCell is not DTX. However, when the PCell is DTX, up to <NUM> PUCCH resources will be needed from the SCell. In Rel-<NUM>, ART is used to allocate up to <NUM> PUCCH resources when a PDCCH is detected on SCell. Therefore, in our method, when a one serving cell mapping table is used and a PDCCH is detected on SCell, ARI (using the two power control bits in the SCell's PDCCHs) will indicate <NUM>, <NUM>, or, <NUM> PUCCH resources for sub-frames with Ms=<NUM>, <NUM>, or <NUM>, respectively. This has an advantage when one of the Mp and Ms equals to zero. For example, when PCell is UL/DL configuration <NUM> and SCell configuration <NUM>, at sub-frame #<NUM>, Mp=<NUM>, Ms=<NUM>.

<FIG> is a flowchart showing an embodiment method <NUM> for adjusting the number and/or order of ACK/NACK bits. In this illustrative method, Mp is equal to the number of ACK/NACK bits for the primary cell, and Ms is equal to the number of ACK/NACK bits for the SCell. According to certain illustrative examples, assuming that HARQ-ACK<NUM>(i) is an ACK/NACK bit for the serving cell with the larger bundling window size, and HARQ-ACK<NUM>(i) is an ACK/NACK bit for the smaller bundling window size, and that both Mp and Ms are not equal and both non-zero, the method starts by setting <NUM> equal to (Mp + Ms)/<NUM> while rounding up if necessary. It is then determined <NUM> whether the larger of Mp or Ms (Mmax) minus the smaller of Mp or Ms (Mmin) is greater than one. If it is determined (<NUM>, NO) that Mmax - Mmin is equal to one, then an extra bit position is appended <NUM> to ACK/NACK bit set with length of Mmin. If, however, it is determined (<NUM>, YES) that Mmax - Mmin is greater than one, the method proceeds. The ACK/NACK bits are then set <NUM> for both cells as follows:.

It is then determined <NUM> whether the number of elements in {HARQ-ACK<NUM>(<NUM>),. , HARQ-ACK<NUM>(Mmin-<NUM>), HARQ-ACK<NUM>(M),. , HARQ-ACK<NUM>(Mmax-<NUM>)} (illustrated as "X" in the flowchart) is less than M. If so (<NUM>, YES), then a bit is appended <NUM> to it as follows:.

Otherwise (<NUM>, NO), the method proceeds as follows to use <NUM> the two serving cell mapping table:.

With methods described herein, reordering the ACK/NACK bits instead of filling up with DTX bits before using the existing ACK/NACK codebooks may be done. Assume that HARQ-ACK<NUM>(i) is the ACK/NACK bit for the serving cell with the larger bundling window size, and HARQ-ACK<NUM>(i) for the smaller bundling window size. Mmax = max {Mp, Ms}, Mmin = min{Mp, Ms}. This approach may also be described as follows, additionally comprising PUCCH resource allocation:.

<FIG> is a flowchart showing an illustrative method <NUM> for adjusting ACK/NACK bits. According to certain illustrative examples, the contents of HARQ-ACK<NUM>(i) and HARQ-ACK<NUM>(i) are determined as follows when Mp and Ms are not equal, and one of Mp and Ms is not zero. This approach strives to keep the maximum number of PCell bits in HARQ-ACK<NUM>(i) and the maximum number of SCell bits in HARQ-ACK<NUM>(i). Also, the HARQ-ACK bits with highest DAI index are bundled across cells.

It is first determined <NUM> if Mmax - Mmin = <NUM>. If it is determined (<NUM>, YES) that Mmax-Mmin = <NUM>, then the bits are set as follows:.

If it is determined (<NUM>, NO) that Mmax - Mmin is not equal to <NUM>, then the method proceeds. It is then determined <NUM> whether Mmax - Mmin = <NUM>. If it is determined (<NUM>, YES) that Mmax - Mmin = <NUM>, then the ACK/NACK bits are set as follows:.

If it is determined (<NUM>, NO) that Mmax - Mmin is not equal to <NUM>, then the method proceeds. It is then determined <NUM> whether Mmax - Mmin = <NUM>. If it is determined (<NUM>, YES) that Mmax - Mmin = <NUM>, then a DTX bit is appended to the cell with the smaller number of ACK/NACK bits and the bits are set as follows:.

In some examples, the UE can append an ACK bit instead of a DTX bit to make two HARQ-ACK sets with the same length.

If Mmax - Mmin does not equal <NUM>, and if Mmax = Mmin, then the process can end (<NUM>).

This method also uses fewer ACK/NACK bits. Therefore it has good resource utilization and performance. For example, when the PCell is UL/DL configuration <NUM> and SCell configuration <NUM>, at sub-frame #<NUM>, where Mp=<NUM>, Ms=<NUM>, the number of ACK/NACK bits will be M = ceil{(Mp+Ms)/<NUM>}=<NUM>, which means that the mapping table uses a total of six bits over both PCell and SCell.

<FIG> is a flowchart showing an illustrative method <NUM> for reducing the number of ACK/NACK bits. In this illustrative method, Mp is equal to the number of ACK/NACK bits for the primary cell, and Ms is equal to the number of ACK/NACK bits for the SCell. According to certain illustrative examples, it is determined <NUM> if Mp + Ms is less than a predetermined number ("X"), e.g., MP + MS < <NUM>. For example, the number of ACK/NACK bits can be further reduced if they are arranged to use one serving cell codebook (one of tables <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, or <NUM>. <NUM>-<NUM>) when Mp + Ms is less than five.

If it is determined that Mp + Ms is not less than the predetermined number, then another method may be used <NUM>. If, however, it is determined that Mp + Ms is indeed less than the predetermined number, then the ACK/NACK bits from the PCell and the SCell can be concatenated <NUM>. The two serving cell mapping table with a bundling window of M = the value of the predetermined number can then be used <NUM>; as is discussed in more detail below.

Alternatively, ACK/NACK Tables (one of tables <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, <NUM>. <NUM>-<NUM>, or <NUM>. <NUM>-<NUM>) and the associated resource allocation may be used when Mp + Ms < <NUM> and the greater of Mp or Ms < <NUM>. Through use of methods and systems described herein, ACK/BACK bit positions may be used more efficiently without requiring modification of standard codebook mapping tables.

Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations.

The features described above may give rise to one or more advantages. For example, methods described herein enable support for carrier aggregation of cells that have different TDD UL/DL configurations while allowing for better performing transmission of ACK/NACK bits.

Claim 1:
A method for transmitting Acknowledgement/Negative Acknowledgement, ACK/NACK, bits for Long Term Evolution, LTE, or Long Term Evolution-Advanced, LTE-A, carrier aggregation between a first cell (<NUM>, <NUM>) and a second cell (<NUM>, <NUM>) by a User Equipment, UE, (<NUM>), wherein the first cell and the second cell are of a different uplink-downlink, UL-DL, configuration, the method comprising:
for a sub-frame, comparing a first number of ACK/NACK bits for the first cell with a second number of ACK/NACK bits for the second cell, wherein the second number is greater than the first number; and
setting (<NUM>) an average number being an average of the first number of ACK/NACK bits for the first cell and the second number of ACK/NACK bits for the second cell, while rounding up if necessary,
if the second number minus the first number is equal to one, append (<NUM>) an extra bit position to the ACK/NACK bits of the first cell,
if the second number minus the first number is greater than one, adjusting (<NUM>) the ACK/NACK bits between the first cell and the second cell, whereby after adjusting:
the number of ACK/NACK bits for the second cell is equal to the average number,
the number of ACK/NACK bits for the first cell is the first number plus an extra number of ACK/NACK bits, wherein the extra number is equal to the second number minus the average number,
if the number of the adjusted ACK/NACK bits for the first cell is smaller than the average number, append (<NUM>) a DTX bit to the adjusted ACK/NACK bits for the first cell,
transmitting one or more ACK/NACK bits for the second cell using the extra number of an ACK/NACK bit position from the first cell, in the same order as they were ordered in the second number of ACK/NACK bits for the second cell, the one or more bits starting immediately after the first number of the ACK/NACK bits from the first cell.