WO2016188221A1

WO2016188221A1 - Methods and apparatus for performing jointly synchronized single-cell point to multipoint (sc-ptm) transmissions

Info

Publication number: WO2016188221A1
Application number: PCT/CN2016/077676
Authority: WO
Inventors: Xiaoxia Zhang; Xipeng Zhu; Jun Wang
Original assignee: Qualcomm Incorporated
Priority date: 2015-05-28
Filing date: 2016-03-29
Publication date: 2016-12-01
Also published as: WO2016187890A1

Abstract

Certain aspects of the present disclosure relate to methods and apparatus for performing jointly synchronized single-cell point to multipoint (SC-PTM) transmissions. A network entity identifies two or more base stations to participate in jointly synchronized SC-PTM transmissions and provides configuration information to synchronize SC-PTM transmissions by the identified two or more base stations. A base station receives the configuration information for synchronizing SC-PTM transmissions from the base station with SC-PTM transmissions from one or more other base stations and participates in joint SC-PTM transmissions with the one or more other base stations according to the configuration information. A User Equipment receives scheduling information for SC-PTM transmissions jointly transmitted from a plurality of base stations and receives SC-PTM transmissions from at least one base station according to the scheduling information.

Description

METHODS AND APPARATUS FOR PERFORMING JOINTLY SYNCHRONIZED SINGLE-CELL POINT TO MULTIPOINT (SC-PTM) TRANSMISSIONS

Claim of Priority

This application claims benefit of International Patent Application Serial No. PCT/CN2015/080131, filed May 28, 2015, which is herein incorporated by reference in its entirety.

BACKGROUND Field

The present disclosure relates generally to communication systems, and more particularly, to methods and apparatus for performing jointly synchronized single-cell point to multipoint (SC-PTM) transmissions.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE/LTE-Advanced is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL) , SC-FDMA on the uplink (UL) , and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.

SUMMARY

Certain aspects of the present disclosure provide a method for wireless communications by a base station. The method generally includes receiving configuration information for synchronizing single cell point to multipoint (SC-PTM) transmissions with SC-PTM transmissions from one or more other base stations. The method further includes the base station participating in joint SC-PTM transmissions with the one or more other base station according to the configuration information.

Certain aspects of the present disclosure provide a method for wireless communications by a User Equipment (UE) . The method generally includes receiving scheduling information for single cell point to multipoint (SC-PTM) transmissions jointly transmitted from a plurality of base stations. The method further includes the UE receiving SC-PTM transmissions from at least one base station of the plurality of base stations according to the scheduling information.

Certain aspects of the present disclosure provide a method for wireless communications by a network entity. The method generally includes identifying two or more base stations to participate in jointly synchronized single cell point to multipoint (SC-PTM) transmissions. The method further includes the network entity providing configuration information to synchronize SC-PTM transmissions by the identified two or more base stations.

Certain aspects of the present disclosure provide an apparatus for wireless communications by a base station. The apparatus generally includes means for receiving configuration information for synchronizing single cell point to multipoint (SC-PTM) transmissions from the base station with SC-PTM transmissions from one or more other base stations. The apparatus further includes means for participating in joint SC-PTM transmissions with the one or more other base station according to the configuration information.

Aspects generally include methods, apparatus, systems, computer program products, and processing systems, as substantially described herein with reference to and as illustrated by the accompanying drawings. “LTE” refers generally to LTE, LTE-Advanced (LTE-A) , LTE in an unlicensed spectrum (LTE-whitespace) , etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a network architecture, in accordance with certain aspects of the present disclosure.

FIG. 2 is a diagram illustrating an example of an access network, in accordance with certain aspects of the present disclosure.

FIG. 3 is a diagram illustrating an example of a DL frame structure in LTE, in accordance with certain aspects of the present disclosure.

FIG. 4 is a diagram illustrating an example of an UL frame structure in LTE, in accordance with certain aspects of the present disclosure.

FIG. 5 is a diagram illustrating an example of a radio protocol architecture for the user and control plane, in accordance with certain aspects of the present disclosure.

FIG. 6 is a diagram illustrating an example of an evolved Node B and user equipment in an access network, in accordance with certain aspects of the disclosure.

FIG. 7 is a diagram illustrating a topology of a Multicast Broadcast Multimedia Service (MBMS) service area, in accordance with certain aspects of the present disclosure.

FIG. 8 illustrates example MBMS architecture, in accordance with certain aspects of the present disclosure.

FIG. 9 illustrates example operations that may be performed by a network entity, such as an MCE or a controller eNB for joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates example operations performed by a base station for joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure

FIG. 11 illustrates example operations performed by a UE during joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure.

FIG. 12 illustrates an example multi-cell joint SC-PTM architecture utilizing a portion of MBMS system architecture, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

Multimedia Broadcast Multicast Service (MBMS) systems were originally designed for the provision of media content in a large pre-planned area (e.g., MBSFN area) for e.g. mobile TV. An MBSFN area is rather static (e.g. configured by O&M) and cannot be dynamically adjusted according to the user distribution. Further, MBMS transmission occupies the entire system bandwidth, and multiplexing with unicast in the same subframe is not allowed even though not all the radio resources in frequency domain are utilized. MBSFN subframe configuration is also rather static (e.g. configured by O&M) , which cannot be dynamically adjusted according to the number of active groups and the traffic load of active groups. In addition, radio resources configured for MBMS might be unnecessarily wasted when provisioning services for critical communications. MBMS also does not allow retransmission based on HARQ feedback.

Certain aspects of the present disclosure provide techniques to jointly transmit content to multiple users in several cells using the existing MBMS (or eMBMS) architecture while overcome some of the limitations of the MBMS systems noted above. For example, aspects of the present disclosure provide techniques for jointly synchronized single-cell point to multipoint (SC-PTM) transmissions while improving radio efficiency by providing more flexibility in terms of resource allocation and better resource utilization.

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using hardware, software/firmware, or combinations thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs) , field programmable gate arrays (FPGAs) , programmable logic devices (PLDs) , state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software/firmware, middleware, microcode, hardware description language, or otherwise.

Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software/firmware, or combinations thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD) , laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

FIG. 1 is a diagram illustrating an LTE network architecture 100 in which aspects of the present disclosure may be practiced. eNB 106 may receive configuration information for synchronizing SC-PTM transmissions of the eNB 106 with SC-PTM transmissions from one or more other eNBs 108. The eNB 106 may participate in joint transmissions with the one or more other eNBs 108 according to the received configuration information. Further, UE 102 may receive scheduling information for SC-PTM transmissions jointly transmitted from a plurality of eNBs (e.g., eNBs 106 and 108) . The UE 102 may receive SC-PTM transmissions from at least one eNB (e.g., eNBs 106 or 108) according to the received scheduling information.

The LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS 100 may include one or more user equipment (UE) 102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS) 120, and an Operator’s IP Services 122. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. Exemplary other access networks may include an IP Multimedia Subsystem (IMS) PDN, Internet PDN, Administrative PDN (e.g., Provisioning PDN) , carrier-specific PDN, operator-specific PDN, and/or GPS PDN. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.

The E-UTRAN includes the evolved Node B (eNB) 106 and other eNBs 108. The eNB 106 provides user and control plane protocol terminations toward the UE 102. The eNB 106 may be connected to the other eNBs 108 via an X2 interface (e.g., backhaul) . The eNB 106 may 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 eNB 106 provides an access point to the EPC 110 for a UE 102. Examples of UEs 102 include 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, a tablet, a netbook, a smart book, or any other similar functioning device. The UE 102 may 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 eNB 106 is connected by an S1 interface to the EPC 110. The EPC 110 includes a Mobility Management Entity (MME) 112, other MMEs 114, a Serving Gateway 116, and a Packet Data Network (PDN) Gateway 118. The MME 112 is the control node that processes the signaling between the UE 102 and the EPC 110. Generally, the MME 112 provides bearer and connection management. All user IP packets are transferred through the Serving Gateway 116, which itself is connected to the PDN Gateway 118. The PDN Gateway 118 provides UE IP address allocation as well as other functions. The PDN Gateway 118 is connected to the Operator’s IP Services 122. The Operator’s IP Services 122 may include, for example, the Internet, the Intranet, an IP Multimedia Subsystem (IMS) , and a PS Streaming Service (PSS) . In this manner, the UE102 may be coupled to the PDN through the LTE network.

FIG. 2 is a diagram illustrating an example of an access network 200 in an LTE network architecture in which aspects of the present disclosure may be practiced. eNB 204 may receive configuration information for synchronizing SC-PTM transmissions of the eNB 204 with SC-PTM transmissions from one or more other eNBs 204 in other cells. The eNB 204 may participate in joint transmissions with the one or more other eNBs 204 according to the received configuration information. Further, a UE 206 may receive scheduling information for SC-PTM transmissions jointly transmitted from a plurality of eNBs 204. The UE 206 may receive SC-PTM transmissions from at least one eNB 204 of the plurality of eNBs 204 according to the received scheduling information.

In this example, the access network 200 is divided into a number of cellular regions (cells) 202. One or more lower power class eNBs 208 may have cellular regions 210 that overlap with one or more of the cells 202. A lower power class eNB 208 may be referred to as a remote radio head (RRH) . The lower power class eNB 208 may be a femto cell (e.g., home eNB (HeNB) ) , pico cell, or micro cell. The macro eNBs 204 are each assigned to a respective cell 202 and are configured to provide an access point to the EPC 110 for all the UEs 206 in the cells 202. There is no centralized controller in this example of an access network 200, but a centralized controller may be used in alternative configurations. The eNBs 204 are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to the serving gateway 116.

The modulation and multiple access scheme employed by the access network 200 may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support both frequency division duplexing (FDD) and time division duplexing (TDD) . As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB) . EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA； Global System for Mobile Communications (GSM) employing TDMA； and Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.

The eNBs 204 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables the eNBs 204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data streams may be transmitted to a single UE 206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (e.g., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the DL. The spatially precoded data streams arrive at the UE (s) 206 with different spatial signatures, which enables each of the UE (s) 206 to recover the one or more data streams destined for that UE 206. On the UL, each UE 206 transmits a spatially precoded data stream, which enables the eNB 204 to identify the source of each spatially precoded data stream.

Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.

In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The UL may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR) .

FIG. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames with indices of 0 through 9. Each sub-frame may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated as

R

302, 304, include DL reference signals (DL-RS) . The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS) 302 and UE-specific RS (UE-RS) 304. UE-RS 304 are transmitted only on the resource blocks upon which the corresponding physical DL shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.

In LTE, an eNB may send a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) for each cell in the eNB. The primary and secondary synchronization signals may be sent in

symbol periods

6 and 5, respectively, in each of

subframes

0 and 5 of each radio frame with the normal cyclic prefix (CP) . The synchronization signals may be used by UEs for cell detection and acquisition. The eNB may send a Physical Broadcast Channel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. The PBCH may carry certain system information.

The eNB may send a Physical Control Format Indicator Channel (PCFICH) in the first symbol period of each subframe. The PCFICH may convey the number of symbol periods (M) used for control channels, where M may be equal to 1, 2 or 3 and may change from subframe to subframe. M may also be equal to 4 for a small system bandwidth, e.g., with less than 10 resource blocks. The eNB may send a Physical HARQ Indicator Channel (PHICH) and a Physical Downlink Control Channel (PDCCH) in the first M symbol periods of each subframe. The PHICH may carry information to support hybrid automatic repeat request (HARQ) . The PDCCH may carry information on resource allocation for UEs and control information for downlink channels. The eNB may send a Physical Downlink Shared Channel (PDSCH) in the remaining symbol periods of each subframe. The PDSCH may carry data for UEs scheduled for data transmission on the downlink.

The eNB may send the PSS, SSS, and PBCH in the center 1.08 MHz of the system bandwidth used by the eNB. The eNB may send the PCFICH and PHICH across the entire system bandwidth in each symbol period in which these channels are sent. The eNB may send the PDCCH to groups of UEs in certain portions of the system bandwidth. The eNB may send the PDSCH to specific UEs in specific portions of the system bandwidth. The eNB may send the PSS, SSS, PBCH, PCFICH, and PHICH in a broadcast manner to all UEs, may send the PDCCH in a unicast manner to specific UEs, and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period. Each resource element (RE) may cover one subcarrier in one symbol period and may be used to send one modulation symbol, which may be a real or complex value. Resource elements not used for a reference signal in each symbol period may be arranged into resource element groups (REGs) . Each REG may include four resource elements in one symbol period. The PCFICH may occupy four REGs, which may be spaced approximately equally across frequency, in symbol period 0. The PHICH may occupy three REGs, which may be spread across frequency, in one or more configurable symbol periods. For example, the three REGs for the PHICH may all belong in symbol period 0 or may be spread in

symbol periods

0, 1, and 2. The PDCCH may occupy 9, 18, 36, or 72 REGs, which may be selected from the available REGs, in the first M symbol periods, for example. Only certain combinations of REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. The UE may search different combinations of REGs for the PDCCH. The number of combinations to search is typically less than the number of allowed combinations for the PDCCH. An eNB may send the PDCCH to the UE in any of the combinations that the UE will search.

An enhanced PDCCH (ePDCCH) may also be defined, for example, in non-legacy systems (e.g., Rel-12 and beyond) which may complement or replace the legacy PDCCH. Unlike the legacy PDCCH which occupies the control region of the subframe in which it is transmitted, the ePDCCH generally occupies the data region of the subframe, similar to the legacy PDSCH. In other words, an ePDCCH region may be defined that occupies the conventional/legacy PDSCH region. The ePDCCH region may consist of multiple contiguous or non-contiguous Resource Blocks (RBs) and may occupy a subset of OFDM symbols within those RBs.

The ePDCCH may have several advantages over the legacy PDCCH. For example, the ePDCCH may help increase control channel capacity (e.g., and may add to the capacity of the legacy PDCCH) , support frequency-domain Inter-Cell Interference Cancellation (ICIC) , achieve improved spatial reuse of control channel resource, support beamforming and/or diversity, operate on a New Carrier Type (NCT) and in Multicast-Broadcast Single Frequency Network (MBSFN) subframes, and/or coexist on a same carrier as legacy UEs.

FIG. 4 is a diagram 400 illustrating an example of an UL frame structure in LTE. The available resource blocks for the UL 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 UL 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 blocks

410a, 410b in the control section to transmit control information to an eNB. The UE may also be assigned

resource blocks

420a, 420b in the data section to transmit data to the eNB. The UE may transmit control information in a physical UL 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 UL shared channel (PUSCH) on the assigned resource blocks in the data section. A UL transmission may span both slots of a subframe and may hop across frequency.

A set of resource blocks may be used to perform initial system access and achieve UL synchronization in a physical random access channel (PRACH) 430. The PRACH 430 carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (10 ms) .

FIG. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNB is shown with three layers: Layer 1, Layer 2, and Layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer 506. Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a media access control (MAC) sublayer 510, a radio link control (RLC) sublayer 512, and a packet data convergence protocol (PDCP) 514 sublayer, which are terminated at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer 508 including a network layer (e.g., IP layer) that is terminated at the PDN gateway 118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc. ) .

The PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNBs. The RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ) . The MAC sublayer 510 provides multiplexing between logical and transport channels. The MAC sublayer 510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 506 and the L2 layer 508 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC) sublayer 516 in Layer 3 (L3 layer) . The RRC sublayer 516 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNB and the UE.

FIG. 6 is a block diagram of an eNB 610 in communication with a UE 650 in an access network in which aspects of the present disclosure may be practiced. eNB 610 may receive configuration information for synchronizing SC-PTM transmissions of the eNB 610 with SC-PTM transmissions from one or more other eNBs (not shown) . The eNB 610 may participate in joint transmissions with the one or more other eNBs according to the received configuration information. Further, UE 650 may receive scheduling information for SC-PTM transmissions jointly transmitted from a plurality of eNBs (e.g., eNB 610 and the other eNBs) . The UE 650 may receive SC-PTM transmissions from at least one eNB 610 according to the received scheduling information.

In the DL, upper layer packets from the core network are provided to a controller/processor 675. The controller/processor 675 implements the functionality of the L2 layer. In the DL, the controller/processor 675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to the UE 650 based on various priority metrics. The controller/processor 675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 650.

The TX processor 616 implements various signal processing functions for the L1 layer (i.e., physical layer) . The signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at the UE 650 and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK) , quadrature phase-shift keying (QPSK) , M-phase-shift keying (M-PSK) , M-quadrature amplitude modulation (M-QAM) ) . The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from a channel estimator 674 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by the UE 650. Each spatial stream is then provided to a different antenna 620 via a separate transmitter 618TX. Each transmitter 618TX modulates an RF carrier with a respective spatial stream for transmission.

At the UE 650, each receiver 654RX receives a signal through its respective antenna 652. Each receiver 654RX recovers information modulated onto an RF carrier and provides the information to the receiver (RX) processor 656. The RX processor 656 implements various signal processing functions of the L1 layer. The RX processor 656 performs spatial processing on the information to recover any spatial streams destined for the UE 650. If multiple spatial streams are destined for the UE 650, they may be combined by the RX processor 656 into a single OFDM symbol stream. The RX processor 656 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT) . The frequency domain signal includes a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 610. These soft decisions may be based on channel estimates computed by the channel estimator 658. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB 610 on the physical channel. The data and control signals are then provided to the controller/processor 659.

The controller/processor 659 implements the L2 layer. The controller/processor can be associated with a memory 660 that stores program codes and data. The memory 660 may be referred to as a computer-readable medium. In the UL, the control/processor 659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink 662, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink 662 for L3 processing. The controller/processor 659 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets to the controller/processor 659. The data source 667 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission by the eNB 610, the controller/processor 659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by the eNB 610. The controller/processor 659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 610.

Channel estimates derived by a channel estimator 658 from a reference signal or feedback transmitted by the eNB 610 may be used by the TX processor 668 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by the TX processor 668 are provided to different antenna 652 via separate transmitters 654TX. Each transmitter 654TX modulates an RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the eNB 610 in a manner similar to that described in connection with the receiver function at the UE 650. Each receiver 618RX receives a signal through its respective antenna 620. Each receiver 618RX recovers information modulated onto an RF carrier and provides the information to a RX processor 670. The RX processor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. The controller/processor 675 can be associated with a memory 676 that stores program codes and data. The memory 676 may be referred to as a computer-readable medium. In the UL, the control/processor 675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 650. Upper layer packets from the controller/processor 675 may be provided to the core network. The controller/processor 675 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations. The controllers/

processors

675, 659 may direct the operation at the eNB 610 and the UE 650, respectively.

The controller/processor 675 and/or other processors, modules or components at the eNB 610 may perform or direct operations for example operations 1000 in FIG. 10, and/or other processes for the techniques described herein. For example, the controller/processor 675 in combination with RX processor 670 at the eNB 610 may be configured to cause the receiver RX of the transceiver 618 to receive configuration information for synchronizing SC-PTM transmissions with SC-PTM transmissions from one or more other eNBs. The controller/processor 675 may further configure the eNB 610 to participate in joint SC-PTM transmissions with the one or more other eNBs according to the received configuration information.

The controller/processor 659 and/or other processors, modules or components at the UE 650 may perform or direct operations for example operations 1100 in FIG. 11, and/or other processes for the techniques described herein. For example, controller/processor 659 and the RX processor 656 may be configured to cause the receiver RX of the transceiver 654 to receive scheduling information for SC-PTM transmissions jointly transmitted from a plurality of eNBs, and receive SC-PTM transmissions from at least one eNB of the plurality of eNBs according to the scheduling information. In certain aspects, one or more of any of the components shown in FIG. 6 may be employed to perform

example operations

1000 and 1100 and/or other processes for the techniques described herein. The

memories

660 and 676 may store data and program codes for the UE 650 and eNB 610, respectively, accessible and executable by one or more other components of the UE 650 and the eNB 610.

In certain aspects, Multicast Broadcast Multimedia Service (MBMS) or evolved MBMS (eMBMS) offers LTE service providers an effective way to lower cost per bit when delivering the same content simultaneously to multiple users. eMBMS allows multimedia content to be sent once and received by many end users and can be a valuable alternative to unicast when a large number of users are interested in the same content. The most common uses for eMBMS include distributing video, music, software, news, weather, advertisements and other data meant for mass audience.

FIG. 7 illustrates a topology of a Multicast Broadcast Multimedia Service (MBMS) service area 750 for providing MBMS (or eMBMS) , in accordance with certain aspects of the present disclosure. An MBMS service area 750 is generally an area supporting MBMS and may be divided into one or more Multi-Media Broadcast Single Frequency Network (MBSFN) areas. Each MBSFN area is an area of eNBs which may synchronously transmit the same MBMS control information and data. For example, the eNBs 752 in cells 752'may form a first MBSFN area and the eNBs 754 in cells 754'may form a second MBSFN area. The

eNBs

752, 754 may be associated with other MBSFN areas, for example, up to a total of eight MBSFN areas. A cell within an MBSFN area may be designated a reserved cell. Reserved cells do not provide multicast/broadcast content, but are time-synchronized to the cells 752', 754'and have restricted power on MBSFN resources in order to limit interference to the MBSFN areas.

Each area may support broadcast, multicast, and unicast services. A unicast service is a service intended for a specific user, e.g., a voice call. A multicast service is a service that may be received by a group of users, e.g., a subscription video service. A broadcast service is a service that may be received by all users, e.g., a news broadcast. For example, referring to FIG. 7, the first MBSFN area may support a first MBMS broadcast service, such as by providing a particular news broadcast to UEs in its service area (e.g., UE 770) . The second MBSFN area may support a second MBMS broadcast service, such as by providing a different news broadcast to UEs in its service area (e.g., UE 760) . Further, an MBSFN area may be used to broadcast venue, regional and/or national content. The size of an MBSFN area may be as small as one cell, for example, in case of an in-venue broadcast. Each MBSFN area supports a plurality of physical multicast channels (PMCH) (e.g., 15 PMCHs) . Each PMCH corresponds to a multicast channel (MCH) . Each MCH can multiplex a plurality (e.g., 29) of multicast logical channels. Each MBSFN area may have one multicast control channel (MCCH) . As such, one MCH may multiplex one MCCH and a plurality of multicast traffic channels (MTCHs) and the remaining MCHs may multiplex a plurality of MTCHs.

FIG. 8 illustrates example MBMS architecture 800, in accordance with certain aspects of the present disclosure. eNBs 820 may be part of an MBSFN capable of synchronously transmitting one or more MBMS services. Broadcast multicast service center (BMSC) 804 is generally located at the core of the network and manages the interface with content providers 802 including billing and the content to be transmitted over the wireless network. The MBMS gateway (MBMS GW) 806 is a logical element that uses IP multicast for point to multipoint delivery of MBMS traffic to eNBs 820 using the M1 interface. Multi-cell/multicast coordination entity (MCE) 810 is responsible for admission control and allocation of resources used by all eNBs (e.g., eNBs 820) in an MBSFN area for multi-cell MBMS transmissions. MCE generally conveys radio configuration information to the eNBs 820 via the M2 interface. Mobility Management Entity (MME) 808 generally performs the MBMS session control signaling including session start, update, and stop, as well as delivering additional MBMS information to the MCE 810 including information regarding Quality of Service (QoS) and MBMS service area. As shown in FIG. 8, the MME 808 may convey the session control information to the MCE via the M3 interface. The MBMS architecture of FIG. 8 is a centralized MCE architecture. The MCE 810 is a logical entity which means it can be deployed as a stand-alone physical entity or collocated in another physical entity e.g., eNB 820. In both cases the M2 interface is kept between the MCE 810 and all eNB (s) 820 belonging to the corresponding MBSFN area.

In an aspect, a distributed MCE architecture may be supported where the MCE 810 is part of the eNB (s) 820 and the M2 interface is kept between the MCE and the corresponding eNB 820. In an aspect, a SYNC protocol is defined as a protocol to carry additional information that enables eNBs 820 to identify the timing for radio frame transmission and detect packet loss. In an aspect, every MBMS service uses its own SYNC entity. The SYNC protocol is applicable to downlink (DL) and is terminated in the BMSC 804.

EXAMPLE METHODS AND APPARATUS FOR PERFORMING JOINTLY SYNCHRONIZED SINGLE-CELL POINT TO MULTIPOINT (SC-PTM) TRANSMISSIONS

MBMS was originally designed for the provision of media content in a large pre-planned area (e.g., MBSFN area) for e.g. mobile TV. An MBSFN area is rather static (e.g. configured by O&M) and cannot be dynamically adjusted according to the user distribution. Further, MBMS transmission occupies the entire system bandwidth, and multiplexing with unicast in the same subframe is not allowed even though not all the radio resources in frequency domain are utilized. MBSFN subframe configuration is also rather static (e.g. configured by O&M) , which cannot be dynamically adjusted according to the number of active groups and the traffic load of active groups. In addition, radio resources configured for MBMS might be unnecessarily wasted when provisioning services for critical communications. MBMS also does not allow retransmission based on HARQ feedback.

Certain aspects of the present disclosure provide techniques to jointly transmit content to multiple users in several cells using the existing MBMS (or eMBMS) architecture while overcoming some of the limitations of the MBMS systems noted above. For example, aspects of the present disclosure provide techniques for jointly synchronized single-cell point to multipoint (SC-PTM) transmissions while improving radio efficiency by providing more flexibility in terms of resource allocation and better resource utilization. In certain aspects, the joint SC-PTM transmissions reuse the existing MBMS (or eMBMS) system architecture, but focus on radio efficiency improvement. In certain aspects, these techniques include downlink multicast over PDSCH (instead of PMCH used in MBMS) of content that is intended for a group of users, for example, users that have common interest on a particular service/content. In an aspect, the techniques discussed herein may allow retransmissions based on HARQ feedback. Further, simultaneous unicast and one or more SC-PTM transmissions in one subframe may be supported allowing relatively more efficient resource usage than MBMS systems.

In an aspect, SC-PTM transmissions generally include point to multipoint transmissions from a single cell. Since SC-PTM uses a single cell configuration, it may use unicast structure. Further, since SC-PTM uses a single cell for downlink transmissions, relatively more optimization (e.g., resource optimization) as compared to MBMS is possible. For example, SC-PTM may be used for a relatively smaller area and the subframe resources used for SC-PTM transmissions may be adjusted based on the number of active groups of users and the traffic load of the active groups. Also, since SC-PTM transmits traffic using PDSCH, SC-PTM PDSCH may be multiplexed with unicast PDSCH in a same subframe, allowing relatively more efficient resource usage than MBMS systems.

Aspects of the present disclosure discuss techniques for extending SC-PTM by utilizing existing MBMS system architecture, by allowing multiple cells to jointly perform the same SC-PTM transmission (s) over PDSCH in a synchronous manner. In a way joint SC-PTM may be looked at as single cell MBMS. In an aspect, by utilizing the existing MBMS architecture, SC-PTM may reuse, at least in part, MBMS infrastructure and mechanisms. For example, if multiple neighboring cells are transmitting SC-PTM independently of each other, then each cell may use different scrambling and may cause interference to one another. However, mechanisms to synchronize simultaneous transmissions from multiple cells already exist in MBMS (e.g., SYNC protocol) . Thus, using MBMS architecture will ensure that there is little or no interference among cells jointly transmitting SC-PTM content. Further, allowing joint SC-PTM transmission across multiple cells may be beneficial in that UEs may benefit from MBSFN gain with joint SC-PTM and better link efficiency may be expected. Moreover, operators may still benefit from the flexibility provided by SC-PTM noted above, for example, due to its single cell configuration..

For example, referring back to FIG.. 8, BMSC 804 manages the interface with content providers (e.g., content providers 802) including the SC-PTM content to be transmitted over the wireless network. The MBMS gateway (MBMS GW) 806 performs point to multipoint delivery of SC-PTM traffic to eNBs participating in the joint SC-PTM transmission. MCE 810 is responsible for providing configuration information to the participating eNBs, for example, including information regarding allocation of resources used by the eNBs within an area of the joint SC-PTM transmissions.

As noted above, by using MBMS system architecture, when multiple cells are synchronized and transmit same SC-PTM service (s) , the content of transmission may be synchronized using the SYNC protocol defined in MBMS. However content synchronization may not guarantee joint transmission. For example, unlike MBMS where the scheduling is common among the eNBs transmitting MBMS content, in SC-PTM each eNB generally schedules for its cell independently. But for synchronous joint transmission from multiple cells, scheduling must be synchronized, for example, including same MCS, and same RB allocation in a subframe. Further, since SC-PTM is generally based on a single cell, CRS based transmission may be performed within the single cell. However, for joint transmission from multiple eNBs, CRS based transmission may not work. Aspects of the present disclosure discuss techniques for joint scheduling of multiple eNBs for joint transmission of SC-PTM content.

In certain aspects, the MCE 810 may provide configuration information for each of a plurality of eNBs participating in the joint SC-PTM transmission, and each participating eNB may schedule SC-PTM transmissions based on the MCE configuration. In an aspect, since it may not be feasible for the MCE to perform dynamic scheduling, a distributed RB allocation is configured. For example, each participating eNB transmits control information regarding the SC-PTM content to the UEs (e.g., UEs served by the eNB) via the PDCCH (or ePDCCH) , as opposed to the MCCH used by the MBMS systems. The control information may include at least some of the parameters configured by the MCE. Further as noted above, each participating eNBs may transmit SC-PTM data using the PDSCH.

FIG. 9 illustrates example operations 900 performed by a network entity (e.g., MCE or a controller eNB, e.g., eNB 610 of FIG. 6) for joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure. Operations 900 begin, at 902, by identifying two or more base stations to participate in jointly synchronized SC-PTM transmissions. At 904, the network entity provides configuration information to synchronize SC-PTM transmissions by the identified two or more base stations. In certain aspects, when the operations 900 are performed by a controller eNB (e.g., eNB 610 of FIG. 6) , the identifying step of process block 902 may be performed by Controller/Processor 675 of eNB 610 as shown in FIG. 6. Further, the step of providing configuration information of process block 904 may be performed by transmitter 618 as shown in FIG. 6.

In an aspect, the jointly synchronized SC-PTM transmissions utilize MBMS system architecture. In an aspect, the network entity (or controller eNB) allocates resources used by the two or more base stations participating in the jointly synchronized SC-PTM transmissions. In an aspect, the network entity includes an MCE. In an aspect, the network entity includes or resides within a base station of the two or more base stations participating in the jointly synchronized SC-PTM transmissions.

In an aspect, the configuration information includes at least one or an SC-PTM scheduling period, an RB assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a TTI length. In an aspect, the type of reference signal is a DM-RS signal, and the virtual cell ID is used to scramble the DM-RS when participating in the joint SC-PTM transmissions.

In an aspect, the two or more base stations includes a controller base station, and wherein the network entity provides the configuration information to the controller base station, the controller base station providing scheduling information to other base stations of the two or more base stations for the jointly synchronized SC-PTM transmissions.

FIG. 10 illustrates example operations 1000 performed by a base station (e.g., eNB 610 of FIG. 6) for joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure. Operations 1000 begin, at 1002, by receiving configuration information for synchronizing SC-PTM transmissions from the base station with SC-PTM transmissions from one or more other base stations. For example, the receiving may be performed by received 618 of eNB 610 as shown in FIG. 6. At 1004, the base station participates in joint SC-PTM transmissions with the one or more other base stations according to the received configuration information. For example, this step may be performed by Controller/Processor 675 of eNB 610 as shown in FIG. 6, based on the configuration information received by receiver 618.

In an aspect, the participating in the joint SC-PTM transmissions utilizes MBMS architecture. In an aspect, the configuration information is received from a network entity that allocates resources used by the base station participating in the joint SC-PTM transmissions. In an aspect, operations 1000 further include determining scheduling information for the one or more other base stations, and providing the determined scheduling information to the one or more other base stations for participating in the joint SC-PTM transmissions. In an aspect, operations 1000 further include receiving HARQ feedback from at least one UE served by the base station, forwarding the received HARQ feedback to a controller base station, and receiving scheduling information from the controller base station for retransmission of one or more packets to the at least one UE, based on the HARQ feedback.

In an aspect, operations 1000 further include receiving HARQ feedback from the one or more other base stations corresponding to at least one UE served by at least one of the one or more other base stations, and providing scheduling information to the at least one other base station for retransmission of one or more packets to the at least one UE, in response to the HARQ feedback.

In an aspect, the configuration information includes at least one of an SC-PTM scheduling period, an RB assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a TTI length. In an aspect, the type of reference signal is a DM-RS signal, and the virtual cell ID is used to scramble the DM-RS when participating in the joint SC-PTM transmissions.

In an aspect, the configuration information includes at least one feedback configuration for one or more SC-PTM bearers. In an aspect, participating in the joint SC-PTM transmissions includes transmitting scheduling information to one or more UEs using at least one of a type of PDCCH, ePDCCH, or a PDSCH. In an aspect, participating in the joint SC-PTM transmissions includes transmitting content to one or more UEs using a PDSCH. In an aspect, operations 1000 furhter include multiplexing unicast data with SC-PTM data within a same subframe.

FIG. 11 illustrates example operations 1100 performed by a UE (e.g., UE 650 of FIG. 6) during joint SC-PTM transmissions, in accordance with certain aspects of the present disclosure. Operations 1100 begin, at 1102, by receiving scheduling information for SC-PTM transmissions jointly transmitted from a plurality of base stations. At 1104, the UE receives SC-PTM transmissions from at least one base station of the plurality of base stations according to the scheduling information. For example, the receiving steps of process blocks 1102 and 1104 may be performed by receiver 654 of UE 650 as shown in FIG. 6.

In an aspect, the scheduling information includes at least one of an SC-PTM scheduling period, an RB assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a TTI length. In an aspect, the type of reference signal is a DM-RS signal, and the virtual cell ID is used to scramble the DM-RS by base stations participating in the joint SC-PTM transmissions.

In an aspect, the scheduling information includes at least one feedback configuration for one or more SC-PTM bearers. In an aspect, the scheduling information is received via a type of PDCCH or ePDCCH. In an aspect, operations 1100 further include receiving scheduling information via a type of SC-PTM control channel, and comparing the scheduling information received via the PDCCH with the scheduling information received via the SC-PTM control channel for verification.

In an aspect, the scheduling information is received via a PDSCH. In an aspect, operations 1100 further include receiving unicast data multiplexed with SC-PTM data within a same subframe. In an aspect, the UE receives the SC-PTM transmissions from the at least one base station while in an idle mode.

FIG. 12 illustrates an example multi-cell joint SC-PTM architecture 1200 utilizing a portion of MBMS system architecture, in accordance with certain aspects of the present disclosure. As noted above, BM-SC 804, MBMS-GW 806, and MCE 810 belong to the MBMS architecture. In certain aspects, an SC-PTM cell group 1210 including multiple eNBs 1212a-c may be identified for joint transmission of SC-PTM content from the eNBs 1212. In an aspect, the eNBs (e.g., eNBs 1212) for the SC-PTM cell group 1210 may be identified based on the area served by each of the eNBs, target audience, type of content, etc. eNBs 1212a-c may be configured to jointly transmit synchronized SC-PTM content within a virtual cell area 1250 including cell areas 1222a-c corresponding to eNBs 1212a-c respectively.

BMSC 804 manages the interface with content providers (e.g., content providers 802 of FIG. 8) including the SC-PTM content to be transmitted over the wireless network. The MBMS gateway (MBMS GW) 806 performs point to multipoint delivery of SC-PTM traffic to eNBs 1212a-c. Multi-cell/multicast coordination entity (MCE) 810 is responsible for providing configuration information to the eNBs 1212a-c, for example, including information regarding allocation of resources used by the eNBs 1212 within the virtual cell area 1250 for SC-PTM transmissions. As in the MBMS case, the MCE 810 may be deployed as a stand-alone physical entity or collocated in another physical entity e.g., eNB 1212.

In certain aspects, the MCE 810 may provide configuration information for each eNB 1212 in the SC-PTM cell group 1210, and each eNB 1212 may schedule SC-PTM transmissions based on the MCE configuration. In an aspect, the MCE 810 configuration information includes information relating to one or more of an SC-PTM scheduling period, MCS, RB assignment, transmission mode, virtual cell ID, TTI length, and subframes to be assigned to each SC-PTM service. In an aspect, control information and SC-PTM data packets are scheduled in each SC-PTM scheduling period. Unlike MBMS where RB assignment is dictated by the bandwidth used, RBs for SC-PTM transmissions have to be explicitly configured by the MCE 810. In an aspect, since it may not be feasible for the MCE to perform dynamic scheduling, a distributed RB allocation is configured. As shown in FIG. 12, eNBs 1212 may transmit control information regarding the SC-PTM content to the UEs (e.g., in cell areas 1222) via the PDCCH (or ePDCCH) , as opposed to the MCCH used by the MBMS systems. The control information may include at least some of the parameters configured by the MCE. Further as noted above, the eNBs 1212 may transmit SC-PTM data using the PDSCH.

In certain aspects, an eNB 1212 may schedule data packets received from the MBMS-GW 806 in the first SC-PTM scheduling period following the time point indicated by the time stamp (e.g., defined by the SYNC protocol) to ensure the synchronization of scheduling with other eNBs participating in the joint SC-PTM transmission.. In case the SYNC protocol delivers more data than the air interface can transport in the scheduling period, the eNB may drop some of the received data in accordance with a dropping rule. For example, if four subframes 0-3 are configured for each scheduling period, eNB starts scheduling data with subframe 0 (e.g., after the time stamp) . If the eNB may not fit all the data meant for the scheduling period in the four subframes, it may drop the remaining data that it was unable to fit in the scheduling period. For example, if the eNB was able to fit only 3 subframes in a scheduling period, it drops remaining data after subframe 3 is fully scheduled. On the other hand, if some of the subframe resources remain free after scheduling SC-PTM data, the eNB may schedule other unicast data in the remaining subframe resources. As noted above, SC-PTM data may be multiplexed with unicast data in the same subframe.

In an aspect, since CRS based transmission may not be used for SC-PTM transmissions from multiple cells, eNBs use DMRS based transmission for SC-PTM where the data and DMRS are scrambled by a virtual cell ID of the virtual cell 1250. Two transmission modes may be defined for SC-PTM, CRS based transmission mode and DMRS based transmission mode. In an aspect, the CRS based transmission mode is used for SC-PTM transmissions from a single cell. The virtual cell ID may not be configured in the CRS based transmission mode since the cell ID of the cell may be used for decoding the transmissions. However, if a virtual cell (e.g., virtual cell 1250) is configured including multiple cells (e.g., cells 1222) , the DMRS based transmission mode may be used where the DMRS is scrambled using the virtual cell ID of the virtual cell. In an aspect, when the virtual cell ID is different from a serving cell ID, a UE assumes that timing for receiving SC-PTM content is based on embedded DM-RS rather than serving cell.

In certain aspects, as a result of utilizing the MBMS architecture, each eNB 1212, by default, may transmit configuration information received from the MCE 810, for example, using an SC-PTM control channel, similar to the MCCH used by the MBMS architecture. In an aspect, while the MCE configuration is needed for the eNB for synchronous scheduling of the eNBs 1212, not all of the configuration information is required by the UEs for receiving SC-PTM content as all the required scheduling information will be carried by the PDCCH (or ePDCCH) . Thus, there may be redundancy of control information between the PDCCH and the SC-PTM control channel. In an aspect, a UE may compare the scheduling information received via the PDCCH with configuration information received via the SC-PTM control channel for verification. In certain aspects, the eNB may transmit scheduling information to the UEs via the PDSCH, e.g. group PDSCH meant for a group of UEs, to indicate which subframes are scheduled for the SC-PTM transmissions. For example, a first subframe in an SC-PTM scheduling period carries the scheduling information. In an aspect, the MCS for conveying the scheduling information is different from the MCS used for SC-PTM traffic, and is signaled in System Information Block (SIB) or the SC-PTM control channel.

In certain aspects, the MCE 810 may obtain a cell list from the BM-SC 804, including a list of cells that may transmit same SC-PTM services at the same time. The MCE 810 may configure one or more SC-PTM cell groups (e.g., SC-PTM cell group 1210) for joint transmission of SC-PTM content by selecting cells from the received cell list. In certain aspects, the MCE may configure different MCS and/or different number of subframes for different cell groups. In an aspect, the network obtains a different MCS setting depending on the number of cells as well as the actual cells participating in joint SC-PTM. For example, the MCE assigns a different MCS to one or more cells that are in the immediate neighborhood of a cell that is participating in the joint transmission, in order to avoid or reduce interference from the neighbor cell.

In certain aspects, the MCE, when utilized for MBMS transmissions, generally is unable to dynamically adapt MCS, subframe allocation and retransmission to CSI and ACK/NACK feedback. However, the MCE, when used for SC-PTM transmissions according to the methods discussed herein, may at least adjust MCS, TTI length, and subframe allocation semi-statically by updating the configuration. In an aspect, this may be sufficient especially when there is no individual ACK/NACK feedback or HARQ retransmission.

In certain aspects, the MCE may configure a controller eNB for an SC-PTM cell group (e.g., SC-PTM cell group 1210) , which may or may not be one of the cells of the configured SC-PTM cell group. The controller eNB may determine scheduling information for each of the cells in the cell group based on configuration received from the MCE, and may provide the determined scheduling information to the cells for participating in joint SC-PTM transmissions. The MCE configuration information, generally common to a cell group may include information regarding one or more of SC-PTM control channel configuration, TMGI/G-RNTI mapping for each SC-PTM bearer, transmission mode for each SC-PTM bearer, subframes where each SC-PTM bearer may be potentially scheduled, or CSI/HARQ feedback configuration for each SC-PTM bearer. The MCE configuration information may further include information regarding cell group common CSI-RS, virtual cell ID. In an aspect, the MCE acts as the controller eNB and performs the functions of the controller eNB.

In an aspect, the SC-PTM architecture allows CSI feedback for adjusting scheduling for joint SC-PTM transmissions. The CSI feedback from one or more UEs in a cell group may be received by a serving eNB and may be forwarded to the controller eNB. In an aspect, the controller eNB may be responsible to adjust scheduling (e.g., MCS, subframe assignment etc. ) based on the received feedback. In an aspect, the controller eNB forwards the received CSI feedback to the MCE, which may adjust the configuration information and convey the adjusted configuration to the controller eNB for scheduling.

In certain aspects, the controller eNB may make scheduling decisions every SC-PTM scheduling period (e.g., including MCS, RB assignment, subframes) based CSI feedbacks and/or received data. The controller eNB may send the scheduling decision to the member cells/eNBs of a cell group. Each member cell may send the scheduling information to one or more of its served UEs via PDCCH (or ePDCCH) . Alternatively, the scheduling information may be conveyed by the member cells over PDSCH in MAC control elements. In an aspect, the MCS used for transmitting scheduling information may be different from the one used for SC-PTM traffic, and may be signaled in SIB or the SC-PTM control channel. In certain aspects, if an ideal backhaul is available between the controller eNB and the member eNBs, scheduling information may be sent to the member cells much faster, e.g., per subframe or per TTI.

In certain aspects, unlike MBMS architecture, the SC-PTM architecture may allow HARQ feedback and retransmission of packets. In an aspect, a group ACK/NACK mechanism may be supported. For example, UEs that failed to decode one or more packets may send NACK on shared resources to the serving member eNB of an SC-PTM cell group. Each member eNB of the cell group may receive NACK feedbacks from one or more UEs served by the member eNB and forward information regarding the received NACK feedback to the controller eNB. The controller eNB may determine whether or not and how the retransmissions of one or more packets may be performed based on the HARQ feedback. For example the retransmissions may be performed in either the next SC-PTM scheduling period or a current scheduling period. In an aspect, the retransmission may be either back-to-back retransmission or HARQ retransmission. The controller eNB may provide scheduling information to the eNB for retransmission of the one or more packets to the one or more UEs in response to the HARQ feedback.

Alternatively, in certain aspects, the CSI/HARQ feedback may be received by the controller eNB via UL cooperative multipoint (CoMP) transmission.

In certain aspects, the UE may receive SC-PTM transmissions while in RRC_IDLE state. For example, if one or more of the block error rate (BLER) , reference signal received quality (RSRQ) or the reference signal received power (RSRP) is in acceptable range, and the UE may receive normally, the UE may receive the SC-PTM broadcast without sending CSI/HARQ feedback. Otherwise, the UE may enter the RRC_CONNECTED state.

It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an example, “at least one of: a, b, or c” is intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” Unless specifically stated otherwise, the term “some” refers to one or more. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

WHAT IS CLAIMED IS:

Claims

A method of wireless communications by a base station, comprising:

receiving configuration information for synchronizing single cell point to multipoint (SC-PTM) transmissions from the base station with SC-PTM transmissions from one or more other base stations； and

participating in joint SC-PTM transmissions with the one or more other base stations according to the configuration information.
The method of claim 1, wherein participating in joint SC-PTM transmissions utilizes multimedia broadcast multicast service (MBMS) system architecture.
The method of claim 1, wherein the configuration information is received from a network entity that allocates resources used by the base station participating in the joint SC-PTM transmissions.
The method of claim 1, further comprising:

determining scheduling information for the one or more other base stations； and

providing the determined scheduling information to the one or more other base stations for participating in the joint SC-PTM transmissions.
The method of claim 1, further comprising:

receiving Hybrid Automatic Repeat Request (HARQ) feedback from at least one user equipment (UE) served by the base station；

forwarding the received HARQ feedback to a controller base station； and

receiving scheduling information from the controller base station for retransmission of one or more packets to the at least one UE, based on the HARQ feedback.
The method of claim 1, further comprising:

receiving HARQ feedback from the one or more other base stations corresponding to at least one UE served by at least one of the one or more other base stations；

providing scheduling information to the at least one other base station for retransmission of one or more packets to the at least one UE, in response to the HARQ feedback.
The method of claim 1, wherein the configuration information comprises at least one of an SC-PTM scheduling period, a resource block (RB) assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a transmission time interval (TTI) length.
The method of claim 7, wherein:

the type of reference signal is a demodulation reference signal (DM-RS) ； and

the virtual cell ID is used to scramble the DM-RS when participating in the joint SC-PTM transmissions.
The method of claim 1, wherein the configuration information comprises at least one feedback configuration for one or more SC-PTM bearers.
The method of claim 1, wherein participating in joint SC-PTM transmissions comprises transmitting scheduling information to one or more user equipments (UEs) using at least one of a type of physical downlink control channel (PDCCH) , enhanced PDCCH (ePDCCH) or a Physical Downlink Shared Channel (PDSCH) .
The method of claim 1, wherein participating in joint SC-PTM transmissions comprises transmitting content to one or more user equipments (UEs) using a physical downlink shared channel (PDSCH) .
The method of claim 1, further comprising multiplexing unicast data with SC-PTM data within a same subframe.
A method of wireless communications by a user equipment, comprising:

receiving scheduling information for single cell point to multipoint (SC-PTM) transmissions jointly transmitted from a plurality of base stations； and

receiving SC-PTM transmissions from at least one base station of the plurality of base stations according to the scheduling information.
The method of claim 13, wherein the scheduling information comprises at least one of an SC-PTM scheduling period, a resource block (RB) assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a transmission time interval (TTI) length.
The method of claim 14, wherein:

the type of reference signal is a demodulation reference signal (DM-RS) ； and

the virtual cell ID is used to scramble the DM-RS by base stations participating in the joint SC-PTM transmissions.
The method of claim 13, wherein the scheduling information comprises at least one feedback configuration for one or more SC-PTM bearers.
The method of claim 13, wherein the scheduling information is received via a type of physical downlink control channel (PDCCH) or enhanced PDCCH (ePDCCH) .
The method of claim 17, further comprising:

receiving scheduling information via a type of SC-PTM control channel； and

comparing the scheduling information received via the PDCCH with the scheduling information received via the SC-PTM control channel for verification.
The method of claim 13, wherein the scheduling information is received via a physical downlink shared channel (PDSCH) .
The method of claim 13, further comprising receiving unicast data multiplexed with SC-PTM data within a same subframe.
The method of claim 13, wherein the UE receives the SC-PTM transmissions from the at least one base station while in an idle mode.
A method of wireless communications by a network entity, comprising:

identifying two or more base stations to participate in jointly synchronized single cell point to multipoint (SC-PTM) transmissions； and

providing configuration information to synchronize SC-PTM transmissions by the identified two or more base stations.
The method of claim 22, wherein the jointly synchronized SC-PTM transmissions utilize multimedia broadcast multicast service (MBMS) system architecture.
The method of claim 22, wherein the network entity allocates resources used by the two or more base stations participating in the jointly synchronized SC-PTM transmissions.
The method of claim 24, wherein the network entity comprises a multi-cell/multicast Coordination Entity (MCE) .
The method of claim 24, wherein the network entity comprises or resides within a base station of the two or more base stations participating in the jointly synchronized SC-PTM transmissions.
The method of claim 22, wherein the configuration information comprises at least one of an SC-PTM scheduling period, a resource block (RB) assignment, a transmission mode indicating a type of reference signal, a virtual cell ID, or a transmission time interval (TTI) length.
The method of claim 27, wherein:

the type of reference signal is a demodulation reference signal (DM-RS) ； and

the virtual cell ID is used to scramble the DM-RS when participating in the joint SC-PTM transmissions.
The method of claim 22, wherein the two or more base stations comprises a controller base station, and wherein the network entity provides the configuration information to the controller base station, the controller base station providing scheduling information to other base stations of the two or more base stations for the jointly synchronized SC-PTM transmissions.
An apparatus for wireless communications by a base station, comprising:

means for receiving configuration information for synchronizing single cell point to multipoint (SC-PTM) transmissions from the base station with SC-PTM transmissions from one or more other base stations； and

means for participating in joint SC-PTM transmissions with the one or more other base stations according to the configuration information.