Resource mapping for ePDCCH in LTE

A method of wireless communication includes resource mapping for an enhanced physical downlink control channel (ePDCCH) or a physical downlink shared channel (PDSCH). A set of non-colliding resources and a set of colliding resources are determined. Code symbols are mapped for a channel first to the set of non-colliding resources and then to the set of colliding resources.

BACKGROUND

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly to resource mapping, for example for an enhanced physical downlink control channel (ePDCCH).

SUMMARY

In one aspect, a method of wireless communication is disclosed. The method includes determining a set of non-colliding resources and a set of colliding resources. The method also includes mapping code symbols for a channel first to the set of non-colliding resources and then to the set of colliding resources.

Another aspect discloses wireless communication having a memory and at least one processor coupled to the memory. The processor(s) is configured to determine a set of non-colliding resources and a set of colliding resources. The processor(s) is also configured to map code symbols for a channel first to the set of non-colliding resources and then to the set of colliding resources.

Another aspect discloses a computer program product for wireless communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of determining a set of non-colliding resources and a set of colliding resources. The program code also causes the processor(s) to map code symbols for a channel first to the set of non-colliding resources and then to the set of colliding resources.

Another aspect discloses an apparatus including means for determining a set of non-colliding resources and a set of colliding resources. Also disclosed is a means for mapping code symbols for a channel first to the set of non-colliding resources and then to the set of colliding resources.

In another aspect, a method of wireless communications is disclosed and includes generating a first mapping of a first set of resource elements to a first channel. The first channel comprises an enhanced physical downlink control channel (ePDCCH) or a physical downlink shared channel (PDSCH). The method also includes generating a second mapping of a second set of resource elements to the first channel and transmitting the first channel in accordance with one of the mappings.

Another aspect discloses wireless communication having a memory and at least one processor coupled to the memory. The processor(s) is configured to generate a first mapping of a first set of resource elements to a first channel. The first channel comprises an enhanced physical downlink control channel (ePDCCH) or a physical downlink shared channel (PDSCH). The processor is also configured to generate a second mapping of a second set of resource elements to the first channel and to transmit the first channel in accordance with one of the mappings.

Another aspect discloses a computer program product for wireless communications in a wireless network having a non-transitory computer-readable medium. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of generating a first mapping of a first set of resource elements to a first channel. The first channel comprises an enhanced physical downlink control channel (ePDCCH) or a physical downlink shared channel (PDSCH). The program code also causes the processor(s) to generate a second mapping of a second set of resource elements to the first channel and to transmit the first channel in accordance with one of the mappings.

Another aspect discloses an apparatus including means for generating a first mapping of a first set of resource elements to a first channel. The first channel comprises an enhanced physical downlink control channel (ePDCCH) or a physical downlink shared channel (PDSCH). The method also includes means for generating a second mapping of a second set of resource elements to the first channel and means for transmitting the first channel in accordance with one of the mappings.

DETAILED DESCRIPTION

The E-UTRAN includes the evolved Node B (eNodeB)106and other eNodeBs108. The eNodeB106provides user and control plane protocol terminations toward the UE102. The eNodeB106may be connected to the other eNodeBs108via an X2 interface (e.g., backhaul). The eNodeB106may also be referred to as a base station, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The eNodeB106provides an access point to the EPC110for a UE102. Examples of UEs102include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. The UE102may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.

The eNodeB106is connected by an S1 interface to the EPC110. The EPC110includes a Mobility Management Entity (MME)112, other MMEs114, a Serving Gateway116, and a Packet Data Network (PDN) Gateway118. The MME112is the control node that processes the signaling between the UE102and the EPC110. Generally, the MME112provides bearer and connection management. All user IP packets are transferred through the Serving Gateway116, which itself is connected to the PDN Gateway118. The PDN Gateway118provides UE IP address allocation as well as other functions. The PDN Gateway118is connected to the Operator's IP Services122. The Operator's IP Services122may include the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS Streaming Service (PSS).

FIG. 2is a diagram illustrating an example of an access network200in an LTE network architecture. In this example, the access network200is divided into a number of cellular regions (cells)202. One or more lower power class eNodeBs208may have cellular regions210that overlap with one or more of the cells202. A lower power class eNodeB208may be referred to as a remote radio head (RRH). The lower power class eNodeB208may be a femto cell (e.g., home eNodeB (HeNodeB)), pico cell, or micro cell. The macro eNodeBs204are each assigned to a respective cell202and are configured to provide an access point to the EPC110for all the UEs206in the cells202. There is no centralized controller in this example of an access network200, but a centralized controller may be used in alternative configurations. The eNodeBs204are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway116.

FIG. 4is a diagram400illustrating an example of an uplink frame structure in LTE. The available resource blocks for the uplink may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The uplink frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.

A UE may be assigned resource blocks410a,410bin the control section to transmit control information to an eNodeB. The UE may also be assigned resource blocks420a,420bin the data section to transmit data to the eNodeB. The UE may transmit control information in a physical uplink control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical uplink shared channel (PUSCH) on the assigned resource blocks in the data section. An uplink transmission may span both slots of a subframe and may hop across frequency.

FIG. 6is a block diagram of an eNodeB610in communication with a UE650in an access network. In the downlink, upper layer packets from the core network are provided to a controller/processor675. The controller/processor675implements the functionality of the L2 layer. In the downlink, the controller/processor675provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE650based on various priority metrics. The controller/processor675is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE650.

Resource Mapping for ePDDCH in LTE

In LTE Releases 8/9/10, the physical downlink control channel (PDCCH) is located within the first several symbols (e.g., one, two, three or four) in a subframe and fully distributed across the entire system bandwidth. Additionally, the PDCCH is time domain multiplexed (TDM'ed) with the physical downlink shared channel (PDSCH), which effectively divides a subframe into a control region and a data region.

Release-11 includes other channels, such as an enhanced PDCCH (ePDCCH), enhanced PCFICH (ePCFICH) and an enhanced PHICH (ePHICH). Unlike the legacy PDCCH, which occupies the first several control symbols in a subframe, the ePDCCH occupies the data region, similar to the PDSCH. The ePDCCH aids in increasing control channel capacity, supporting frequency-domain inter-cell interference coordination (ICIC), improving spatial reuse of control channel resources, supporting beamforming and/or diversity, operating on the new carrier type and in MBSFN subframes and in coexisting on the same carrier as legacy UEs.

FIG. 7illustrates various ePDCCH structures. For example, the ePDCCH structure may be the same as the relay physical downlink control channel (R-PDCCH) structure. Alternately, the ePDCCH may be FDM'ed with the data region. Optionally, in an alternate structure, the ePDCCH structure is TDM'ed with the data region. Alternately, the ePDCCH is similar, but not the same as R-PDCCH. In another alternate structure, the ePDCCH may combine TDM and FDM aspects.

Design alternatives to address the resource mapping of ePDCCH in the presence of other signals are described. Other signals may potentially include: common reference signals (CRSs), a legacy control region, primary/secondary synchronization signals (PSS/SSS), physical broadcast channels (PBCHs), PRSs (positioning reference signals), channel state information reference signals (CSI-RSs) and demodulation reference signals (DM-RSs).

One design alternative for ePDDCH resource element mapping includes puncturing the resource elements (REs) having coded symbols. The enhanced resource element group/enhanced control channel element ((e)REG)/(e)CCE) includes the resource elements (REs) possibly used by other signals. Each (e)REG/CCE contains a set of resource elements (REs) and is the construction unit for the ePDCCH. The coded symbols of the ePDCCH are mapped to all resource elements in the (e)REG/(e)CCE irrespective of other signals. Other signals may also be transmitted using some resource elements from the (e)REG/(e)CCE, and if so, these resource elements are “punctured” from the ePDCCH perspective (e.g., not used for ePDCCH but instead used for the other signals).

This design alternative makes it possible to use the ePDDCH for a standalone carrier. That is, the UE can possibly decode the ePDCCH (with some performance penalty) without the knowledge of other signals. However, this design impacts ePDCCH performance especially when the coding rate for the ePDCCH is high and when the number of punctured resource elements is large.

In another design for ePDDCH resource element mapping, the resource elements from the (e)REG/(e)CCE are punctured with rate matching in the coding chain. These (e)REGs/(e)CCEs include the resource elements possibly used by other signals, but the coded symbols of the ePDCCH are only mapped to the resource elements not used by other signals (i.e., rate matching is employed).

This design alternative cannot operate with a standalone carrier, but provides a simple definition of the (e)REG/(e)CCE and improved ePDCCH performance. In particular, the definition of the (e)REG/(e)CCE does not vary based on other signals.

To achieve comparable performance to the legacy PDCCH (with 4 possible aggregation levels 1, 2, 4, and 8, where each CCE has a fixed (e.g., 36) available REs), larger aggregation levels for ePDCCH may be involved because the available resource elements in an (e)REG/(e)CCE depend on the presence of other signals. Hence, the (e)REG/(e)CCE size is not fixed. The larger aggregation levels may complicate management of ePDCCH resources. Additionally, the aggregation levels may be subframe dependent, because the presence of other signals may be subframe dependent.

A third design for ePDDCH resource element mapping includes rate matching for the coding chain together with mapping the “(e)REG/(e)CCE” around the other signals. Here, the (e)REG/(e)CCE excludes the resource elements used by other signals, and the coded symbols are only mapped to the resource elements not used by other signals (rate matching).

This design cannot be operated with a standalone carrier, but provides a simple definition of aggregation levels for the ePDCCH and better ePDCCH performance. The number of (e)REGs/(e)CCEs for each physical resource block (PRB) pair may be variable, depending on the presence of other signals.

One aspect of the present disclosure is directed to a resource element mapping for the ePDDCH that may work with a standalone carrier, provide ePDDCH performance and have little impact on the existing LTE standard. In particular, one aspect is directed to re-ordered rate matching. Regardless of whether the (e)REG/(e)CCE definition includes or excludes the resource elements possibly used by other signals, the mapping of coded symbols for the ePDCCH begins with the resource elements not possibly colliding with other signals. The mapping continues with the resource elements possibly colliding with other signals.

In one illustrative example, the ePDCCH uses two eCCEs, where each CCE contains two sets of resource elements. For this example, the first set of resource elements is free of possible collision with other signals (S1_no_collision and S2_no_collision), while the second set may possibly collide with other signals (S1_collision and S2_collision). The two eCCEs may be classified as follows:

In one aspect, the mapping follows the following order: S1_no_collision, S2_no_collision, S1_collision, S2_collision. With this mapping, the ePDCCH may possibly be decoded by UEs who are not completely aware of the presence of other signals. In this example, each eCCE may have a time span of one subframe. The two eCCEs may have different sets of resource elements.

Another aspect of the present disclosure is directed to a decoding candidate dependent scheme. This aspect does not ensure all ePDCCH decoding candidates are possibly decoded by a UE without complete knowledge of other signals for standalone carrier operation. Rather, this aspect includes a subset of ePDCCH decoding candidates that can possibly be decoded by a UE without complete knowledge of other signals. The remaining ePDCCH decoding candidates are configured to target better ePDCCH performance, such as rate matching based ePDCCH resource element mapping.

In one configuration, the ePDCCH decoding candidates can be classified into two categories: standalone possible and standalone impossible. The classification may be based on: search space (e.g., common search space standalone possible; UE-specific search space not possible); aggregation level (e.g., large aggregation levels standalone possible, low aggregation levels not standalone possible); transmission type (e.g., distributed ePDCCH transmissions are standalone possible; localized ePDCCH not standalone possible); starting (e)CCE indices (e.g., even starting indices standalone possible; odd starting indices not standalone possible); subframe type (e.g., some subframes standalone possible; other subframes not standalone possible); and/or any combination thereof.

Additionally or separately, when a UE is not aware of other signals (e.g., initial access of the system), a puncturing operation is performed. If a UE is already aware of other signals (e.g., via an indication through RRC signaling), a rate matching operation is performed. Different UEs may employ different mapping schemes in a subframe. As an example, one UE may use puncturing based mapping while another UE uses rate-matching based mapping.

Additionally or separately, depending on whether puncturing or rate-matching based resource mapping scheme is used for the ePDCCH, a different interleaving scheme may be utilized for the ePDCCH. For example, for a rate-matching based ePDCCH, the same interleaving scheme as used with a legacy PDCCH can be applied. For a puncturing based ePDCCH, a different interleaving scheme can be applied in order to reduce or minimize the performance impact of puncturing.

For standalone possible ePDCCH decoding candidates, the resource mapping can include allowing successful ePDCCH decoding without the complete knowledge of other signals. For non-standalone possible ePDCCH decoding candidates, the resource mapping can target better ePDCCH performance.

One aspect includes the same definition of the (e)REG/(e)CCE for the two mapping schemes for the two types of ePDCCH decoding candidates. Another aspect includes standalone control channels and also standalone PDSCH channels (at least for some types of PDSCHs). The resource element mapping for the PDSCH can be performed by puncturing (by other signals) based resource mapping and/or by rate matching (around other signals) based resource mapping. For rate matching based resource mapping, the resource mapping for the PDSCH can be performed free of other signals following a specific order (e.g., time first, frequency second). Alternately, the resource mapping may be performed by resource mapping to the resources free of other signals first, followed by mapping to the resources that may potentially carry other signals, as described above with respect to ePDCCH.

For a standalone PDSCH, the resource element mapping may be performed via a puncturing based method or a rate matching based method. Whether PDSCH is standalone or not can be classified by: a radio network temporary identifier (RNTI), (e.g., broadcast RNTIs (SI/P/RA-RNTI standalone possible); unicast/groupcast not possible); transmission type (e.g., distributed PDSCH transmissions are standalone possible; localized PDSCH are not standalone); subframe type (e.g., some subframes standalone possible; other subframes are not); the type of ePDCCH (e.g., if ePDCCH is standalone, PDSCH is also standalone; if the ePDCCH is not standalone, then the PDSCH is not standalone); dynamically indicated via the ePDCCH (e.g., a bit to indicate whether a puncturing or rate-matching based solution is used for the scheduled PDSCH), or any combination thereof.

Additionally or separately, an ePDCCH may indicate whether some other signals are present for the corresponding PDSCH to facilitate the resource mapping operation for the corresponding PDSCH. Additionally or separately, depending on the mapping scheme used for the PDSCH, different coding schemes may be applied. As an example, for a puncturing based PDSCH, convolutional coding can be used. For a rate-matching based PDSCH, turbo coding can be used.

Additionally or separately, depending on the mapping scheme used for PDSCH, different transport block size determination schemes may be utilized. As an example, for rate-matching based PDSCH, the transport block size determination may be based on a modulation and coding scheme (MCS) index and a resource allocation size as part of a control channel assignment. For puncturing based PDSCH, the transport block size determination scheme may be based on an MCS and a resource allocation size as part a control channel assignment, and further based on a scaling factor, which can be predetermined or signaled to a UE.

Additionally or separately, the transport block size determination can be subframe-dependent, in light of possible subframe-dependent presence of other signals. As an example, a scaling factor of different values can be used for different subframes. The set of values can be indicated to the UE via radio resource control (RRC) signaling. In a subframe, different UEs may employ different mapping schemes. As an example, one UE may use puncturing based mapping while another UE uses rate-matching based mapping.

The presence of other signals may be subframe dependent. For example, in a new carrier type, the common reference signal (CRS) may be present only in some subframes (e.g., 1 every 5 subframes). In another example, the channel state information reference signal (CSI-RS) may be present only in some subframes. Additionally, the PSS/SSS may be present in only 1 of every 5 subframes.

Other signals may not be present in the entire bandwidth. For example, the positioning reference signal (PRS) may only be present in a fraction of the bandwidth. Further, the presence of other signals may be cell-specific or UE-specific. For example, CSI-RS may be configured on a per UE basis. Additionally, in another aspect, the amount of resource elements occupied by other signals may be subframe dependent. For example the size of the legacy control region can be subframe dependent.

In the puncturing/rate matching discussion above, the potential presence of other signals may consider a worst case for other signals, an actual presence of other signals, or a combination thereof. For example, a full bandwidth for a positioning reference signal (PRS) may be considered (i.e., worst case) and/or the actual presence of other signals (e.g., PSS/SSS) (i.e., actual presence) may be considered. Some signals may assume the worst case, while some assume the actual presence. As an example, rate matching may be performed for some signals, while puncturing may be performed for some other signals.

Those skilled in the art will understand that although the preceding description was primarily with respect to ePDCCH and PDSCH, the principles apply to other signals, for example ePHICH and ePCFICH.

FIGS. 8A-8Billustrate methods of resource mapping for the ePDCCH in LTE. InFIG. 8A, in block810, a set of non-colliding resources and a set of colliding resources are determined by a base station. Next, in block812, the base station maps code symbols for the ePDCCH to the non-colliding resources and then to the colliding resources.

InFIG. 8B, in block820, a base station generates a first mapping of a first set of resource elements to a first channel. The first channel can be the ePDCCH or the PDSCH. In block822, the base station generates a second mapping of a second set of resource elements to the first channel. Next, in block822, the base station transmits a first channel in accordance with one of the mappings.

In one configuration, the eNodeB610is configured for wireless communication including means for determining. In one aspect, the determining means may be the controller processor675and/or memory646configured to perform the functions recited by the determining means. The eNodeB610is also configured to include a means for mapping. In one aspect, the mapping means may be the controller processor674and/or memory646configured to perform the functions recited by the mapping means. In another aspect, the aforementioned means may be any module or any apparatus configured to perform the functions recited by the aforementioned means.

In another configuration, the eNodeB610is configured for wireless communication including means for generating. In one aspect, the generating means may be the controller processor675and/or memory646configured to perform the functions recited by the generating means. The eNodeB610is also configured to include a means for transmitting. In one aspect, the transmitting means may be the transmit processor616,618transceiver, antenna620, controller processor675and/or memory676configured to perform the functions recited by the transmitting means. In another aspect, the aforementioned means may be any module or any apparatus configured to perform the functions recited by the aforementioned means.

FIG. 9is a diagram illustrating an example of a hardware implementation for an apparatus900employing a processing system914. The processing system914may be implemented with a bus architecture, represented generally by the bus924. The bus924may include any number of interconnecting buses and bridges depending on the specific application of the processing system914and the overall design constraints. The bus924links together various circuits including one or more processors and/or hardware modules, represented by the processor922and the computer-readable medium926. The hardware modules may also include one or more of modules902,904,906and/or908. The bus924may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The apparatus includes a processing system914coupled to a transceiver930. The transceiver930is coupled to one or more antennas920. The transceiver930enables communicating with various other apparatus over a transmission medium. The processing system914includes a processor922coupled to a computer-readable medium926. The processor922is responsible for general processing, including the execution of software stored on the computer-readable medium926. The software, when executed by the processor922, causes the processing system914to perform the various functions described for any particular apparatus. The computer-readable medium926may also be used for storing data that is manipulated by the processor922when executing software.

In one aspect, the processing system includes a determining module902and a mapping module904. The determining module902can determine a set of non-colliding resources and a set of colliding resources. The mapping module904can map code symbols for a channel. Alternately, in another aspect, the processing system includes a generating module906and a transmitting module908. The generating module906can generate a first mapping of a first set of resource elements to a first channel and a second mapping of a second set of resource elements to the first channel. The transmitting module908can transmit the first channel in accordance with the mappings.

The modules may be software modules running in the processor922, resident/stored in the computer readable medium926, one or more hardware modules coupled to the processor922, or some combination thereof. The processing system914may be a component of the eNodeB610and may include the memory676, the transmit processor616, the transceiver618, the antenna620, and/or the controller/processor675.