US20130039297A1

US20130039297A1 - Method for data transmission and base station and user equipment using the same

Info

Publication number: US20130039297A1
Application number: US13/570,260
Authority: US
Inventors: Chun-Yen Wang
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2011-08-10
Filing date: 2012-08-09
Publication date: 2013-02-14
Also published as: US20130039295A1; TW201308956A; US8873491B2; TWI472202B; TW201316732A; US20130039272A1; TW201320692A

Abstract

A method for data transmission, a base station using the same and a user equipment (UE) using the same are proposed. The present disclosure configures at a base station at least two user equipments into a UE group for aggregate transmission by sending a control message from the base station to the at least two user equipments. Next, the base station transmits aggregated data to the UE group containing a aggregated PDU format containing a unique group identifier. Next, the base station receives a response signal from the UE group based on whether the first transmission is received or not. The base station re-transmits the aggregated data to the UE group if the first transmission is not received. After all the aggregate transmission is complete, the base station de-configures the UE group from the aggregate transmission.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefits of U.S. provisional application Ser. No. 61/522,050, filed on Aug. 10, 2011. The entirety of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The present disclosure generally relates to a method for data transmission, a base station using the same and a user equipment (UE) using the same.

BACKGROUND

In current wireless broadband standards such as Third Generation Partnership Project Long Term Evolution (3GPP LTE), the control channel capacity usually is highly limited. Specifically, there may be about 10 Physical Downlink Control Channel (PDCCH) signaling which can be sent in one Transmission Time Interval (TTI) in a 10 MHz system bandwidth scenario, in which about at most 10 User Equipments (UEs) can be scheduled for either Downlink (DL) or Uplink (UL) data transmission. While dedicated UEs need to follow scheduling information carried by PDCCH, in fact a large proportion of Control Channel Elements (CCEs) has to be used for non-dedicated/common functions. For instance, about a total of 41 CCEs is available when 3 OFDM symbols are allocated for PDCCH, but out of the 41 available CCEs, up to 16 Control Channel Elements (CCEs) are commonly allocated for Common Search Space (CSS) including control functionalities such as System Information (SI), Paging, Random Access (RA), Transmission Power Control (TPC), and so like. This leaves only about 25 CCEs available for dedicated UE scheduling. For another example, in a scenario where 2 OFDM symbols are allocated for PDCCH, only about 10 CCEs out of a total of 25 CCEs are available for dedicated UE scheduling.
Moreover, the channel capacity is further limited under the circumstance of Carrier Aggregation (CA). In Carrier Aggregation (CA), cross-carrier scheduling may be used to schedule resources on another serving cell and therefore reduce inter-cell interference in Heterogeneous Networks. In addition, cross carrier scheduling may be used to schedule resources on non-backward compatible carriers. For instance, when a wireless communication system is operating with extension carriers, during a sub-frame in which the allocated frequency band for a first carrier (CC1) may contain data in the Physical Downlink Shared Channel (PDSCH) and a close by frequency band of a second carrier (CC2) may contain data in its PDSCH, the control region of a first carrier (CC1) may actually contain PDCCH for both CC1 and CC2 while no PDCCH would exist in the control region of CC2 in order to avoid interference to control region of other cells. For another example of non-backward compatible carriers, the control region for the single carrier may contain control signaling for both backward and non-backward compatible PDSCH regions, while the control region for a neighboring PDSCH is suppressed in order to avoid interference to control regions of other cells. This means that using carrier aggregation would further limit control channel capacity.
In a practical scenario, for example, the applications of instant communications (e.g. messages services and social networks) have long packet inter-arrival time while intermittent transmission of small amounts of data is used. In additional, the time of arrivals between packets may be large. If a scheme of periodic resource allocation is adopted, it would result in a waste of resource allocation if the scheduled period were short but would otherwise adversely affect interactivity if the period were long. For real time services such as gaming, video surveillance, remote control, and so like, tight delay and frequency transmissions of small amounts of data having variable sizes and arrival intervals may occur. Also for machine type of communication in general, such as machine-to-machine traffic, a large amount of small data traffic with variable sizes is required. Therefore, all that has been described necessitate a need for a mechanism to reduce the control signal (e.g. PDCCH) overhead.
Semi-Persistent Scheduling (SPS) could be used to reduce the control signal overhead. For services involving a semi-static packet rate such as VoIP, SPS can be configured to reduce the control signal overhead. For this kind of service to be implemented, the timing and the amount of radio resources require predictability. The SPS enables radio resources to be semi-statically configured and allocated to a UE for a longer time period than one sub-frame, and the SPS may avoid the need for transmitting specific downlink assignment messages or uplink grant messages over the PDCCH for each sub-frame. However, the SPS may not be suitable for other Internet applications such as social network applications since information on the social network website could not be easily predicted.

SUMMARY

Accordingly, the present disclosure is directed to a method for data transmission, a base station using the same and a user equipment (UE) using the same.
The present disclosure directs to a method which configures at a base station at least one user equipments into a UE group for aggregate transmission by configuring an aggregate transmission, transmitting a control signal to establish the aggregate transmission; and transmitting aggregate data after the aggregated transmission is established, wherein the aggregate data comprises data for the aggregate transmission.
The present disclosure directs to a base station which comprises a transceiver to transmit and receives wireless signal and a processor which configures at a base station at least one user equipments into a UE group for aggregate transmission by configuring an aggregate transmission, transmitting a control signal to establish the aggregate transmission; and transmitting aggregate data after the aggregated transmission is established, wherein the aggregate data comprises data for the aggregate transmission.
The present disclosure directs to a method of transmitting data adapted for an user equipment, the method contains the steps of receiving a control signal, being configured into an aggregate transmission according to the control signal, and receiving aggregate data after being configured for aggregate transmission, wherein the aggregate data comprises data for the user equipment and data not for the user equipment.
The present disclosure directs to an user equipment which comprises a transceiver to transmit and receive wireless signals and a processor which transmits and receives wireless information by receiving a control signal, being configured into an aggregate transmission according to the control signal, and receiving aggregate data after being configured for aggregate transmission, wherein the aggregate data comprises data for the user equipment and data not for the user equipment.
The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a wireless communication system including an eNB communicating with at least one UEs in accordance with an exemplary embodiment.

FIG. 2 is a flowchart illustrating a method of aggregating small data traffic for a plurality of UEs in a MAC PDU in accordance with an exemplary embodiment.

FIG. 3 illustrates a sequential flow of communication information between an eBN and a UE in accordance with an exemplary embodiment.

FIG. 4 illustrates a content of a RRC message which contains indicators in accordance with an exemplary embodiment.

FIG. 5A is a schematic diagram illustrating an UE acquiring its resource allocation assignment through extracting information in a control region by using a group identifier according to an exemplary embodiment.

FIG. 5B illustrates the UA MAC PDU format configured to send aggregated UE data in accordance with an exemplary embodiment.

FIG. 6 illustrates a MAC PDU format of the MAC Payload for a single UE within the UA MAC PDU in accordance with an exemplary embodiment.

FIG. 7 illustrates transmission of user aggregated data according to the first embodiment of the present disclosure.

FIG. 8 illustrates transmission of user aggregated data according to the second embodiment of the present disclosure.

FIG. 9 illustrates transmission of user aggregated data according to the third embodiment of the present disclosure.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

In this disclosure, we use 3GPP-like keywords or phrases are used merely as examples to present inventive concepts in accordance with the present disclosure; however, the same concept presented in the disclosure can be applied to any other systems such as IEEE 802.11, IEEE 802.16, WiMAX, and so like by persons of ordinarily skilled in the art.
Throughout the disclosure, the term PDCCH is used to represent the a control region or a downlink control channel to indicate downlink (DL)/uplink (UL) resource allocation assignment, the same concept by the present disclosure can also be applied to other downlink control channels including DL-MAP, UL-MAP, MBS-MAP, and so like through simple analogy.
The term “eNodeB” in this disclosure may be, for example, a base station (BS), a Node-B, an advanced base station (ABS), a base transceiver system (BTS), an access point, a home base station, a relay station, a scatterer, a repeater, an intermediate node, an intermediary, and/or satellite-based communication base stations, and so like.
The term “user equipment” (UE) in this disclosure may be, for example, a mobile station, an advanced mobile station (AMS), a server, a client, a desktop computer, a laptop computer, a network computer, a workstation, a personal digital assistant (PDA), a tablet personal computer (PC), a scanner, a telephone device, a pager, a camera, a television, a hand-held video game device, a musical device, a wireless sensor, and so like. In some applications, a UE may be a fixed computer device operating in a mobile environment, such as a bus, train, an airplane, a boat, a car, and so like.
Presently, with the applications using small data packets with diverse data sizes are on the rise, the control region in a sub-frame carrying control information may require more and more space in order to accommodate the increase of the control signaling space. However, since the PDCCH capacity in the control region is highly limited, there is a need to either reduce the PDCCH overhead or to increase the control region. In this present disclosure, a method for data transmission and a base station and a user equipment using the same method are proposed to enhance the data transmission by aggregating data traffic for a plurality of UEs.
FIG. 1 illustrates a wireless communication system according to an exemplary embodiment. The wireless communication system includes an eNodeB (101) in communication with at least one UEs (103, 105, . . . 10 x) in accordance with a wireless communication standard. Each UE may contain, for example, at least a transceiver circuit (111), an analog to digital/digital to analog converter (113), and a processing circuitry (115) or processor. The transceiver circuitry (111) is capable of transmitting uplink signal and/or receives downlink signal wirelessly. The transceiver circuitry (111) may also perform operations such as low noise amplifying, impedance matching, frequency mixing, up or down frequency conversion, filtering, amplifying, and so like. The transceiver circuitry (111) may also include an antenna unit (not shown in FIG. 1). The analog-to-digital (A/D)/digital-to-analog (D/C) converter (113) is configured to convert from analog signal format to digital signal format during downlink signal processing and digital signal to analog signal during uplink signal processing. The processing circuitry (115) is configured to process digital signal and to perform procedures of the proposed method for data transmission in accordance with exemplary embodiments of the present disclosure. Also, the processing circuitry (115) may include a memory unit (not shown in FIG. 1) to store data or record configurations assigned by the eNB 101. The eNB 101 contains similar elements which lead to the converted digital signal to be processed by its processing circuitry (117) or processor so as to implement the method for data transmission in accordance with exemplary embodiments of the present disclosure.
A method for data transmission is proposed to enhance data transmission for a wireless communication system. According to some embodiments of the disclosure, the concept of the method for data transmission is to aggregate small packet data traffic for different UEs in a UA (user aggregated) Medium Access Control Protocol Data Unit (MAC PDU) so that the small packet data traffic can be transmitted to UEs with less PDCCH signaling, thereby reducing the control signaling overhead even when the number of users (or UEs) served by a base station is huge. Conventionally, a Downlink Control Information (DCI) or a single PDCCH is assigned to each individual UE. However, this present disclosure proposes a method to transmit a group of UE signaling under the same PDCCH so as to reduce the overall control signal overhead during data transmission. Also in some circumstances, this present disclosure presents another method to omit the transmission of PDCCH entirely for the temporarily/dynamically configured group of UEs. Here the temporarily/dynamically configured group of UEs may be called a user aggregation (UA) group. Additionally, an eNB may assign one UE to more than one UA group(s) depending upon practical operation requirements.
FIG. 2 is a flow chart of a method for data transmission in accordance with an exemplary embodiment of the present disclosure. FIG. 3 illustrates a sequential flow of delivering communication information between an eNB (303) and a UE group (301) in accordance with an exemplary embodiment of the present disclosure. From an perspective, FIG. 3 may be seen the same as FIG. 2 except that FIG. 3 shows the relationship between an eNB (303) and a UE group (301). Referring to FIGS. 1, 2, and 3 together, in step S201 some individual UEs (103, 105, . . . 10 x) are configured or re-configured by an eNB (101 or 303) into at least one UE group (301) for aggregate transmission so that all UEs (301) belong to the same group may receive together as a group using the same PDCCH.
In step S203, after one or more UE groups are aggregated, the eNB (303) may send an aggregated data to a UE group (301). Here, the aggregated data may include data and/or control signaling of UL/DL resource allocation assignment to at least one UE in the UE group or to the UE group. Next, in step S205, the UE (301) group optionally send a response signal in the form of ACK/NACK feedback(s) back to the eNB (303) which acknowledges whether the transmission was received or not. Next in step S207, depending on the response of ACK/NACK, a re-transmission (S309) of the aggregated data from the eNB (S207) might be required. Afterwards, in step S209, a determination as to whether the process will continue may be made by the eNB (303). If the eNB (303) determines that the process continues, then the step S203 to the step S207 will be repeated. Otherwise, step S211 is performed to possibly de-configure the aggregate transmission. Here, the de-configuration of the aggregate transmission may include de-configure at least one UE from the previously assigned group of UEs (the UE group or the UA group). In FIG. 3, the steps S303, S305 and S307 are respectively similar to the steps S203, S205 and S207 in FIG. 2. Each of the steps of FIG. 2 will be illustrated in more details as follow.
In the step S201, the wireless network (e.g. through the eNB (303)) may send a RRC message such as a RRCconnectionReconfiguration message to aggregate multiple UEs together so as to achieve configuring or re-configuring UEs for subsequent aggregate transmission. In some embodiments, not all of UEs support the function of the aggregate transmission. Hence, UEs may provide its UE capability information to inform the network whether or not it can support the aggregate transmission, and the network may send the RRC message to configure UEs with the capability of the aggregate transmission into a UA group for the subsequent aggregate transmission. Here, the aggregated transmission is configured to deliver data and/or control signaling of UL/DL resource allocation assignment to at least one UE in the UE group or to the UE group(s). However, an eNB (303) may determine how to aggregate multiple UEs into a UE group (301). The user aggregation may be based on similar channel condition such as a possible criteria for the grouping of UEs. One of these following channel conditions may be used as the criteria: CQI, CSI, PMI, RI, PTI, bit error rate (BER), RSRP, RSRQ, and so forth. For example, the eNB may read the CQI reports from UEs so that UEs with similar CQI values or similar BER values can be assigned as a UE group, since the eNB can use the same Modulation Coding Scheme (MCS) for all these UEs. For example, currently, the CQI of an individual UE is represented by 4 bits which can be translated into a resolution of 16 possible levels. If supposedly two UEs have an identical CQI level, then the two UEs may be considered to be similar. Then, the eNB may group these two UEs into an identical UA group. For another example, the eNB may obtain RI reports from UEs. The RI of an individual UE may have 8 possible levels. If supposedly a plurality of UEs have an identical RI level, then the eNB may group these UEs with the same RI value into an identical UA group.
The UE aggregation can also be based on UEs having similar Quality of Service traffic parameter. For instance, UEs under VoIP application tend to have similar QoS traffic, or UEs operating under similar applications, such as gaming, may also have similar QoS so as to be aggregated into the same UE group. However, since a UE may experience different levels of traffic using different applications, a UE may belong or may be assigned to one or more UE aggregation group. In other words, a UE may be configured with more than one configuration for aggregate transmission.
Referring to FIG. 4 which illustrates the some content/some fields of a RRC message. The RRC message is transmitted from the eNB to individual UEs to aggregate the UEs into a group. The RRC message (400) transmitted from the eNB may include various parameters/fields. One of the RRC message parameter may contain a group identity information (e.g., a group-radio network temporary indicator (G-RNTI) or SPS cell-radio network temporary indicator (C-RNTI)) (401) which can be used to obtain the Downlink Control Information (DCI) by decoding the PDCCH. In other words, the RRC message may assign each UE group an identity, and this group identity information may be used in the PDCCH to indicate the DL/UL assignment information for the aggregate transmission. For example, parameters such as G-RNTI and/or SPS C-RNTI may be encoded and/or decoded with the cyclic redundant code (CRC) of the DCI in the PDCCH.
The RRC message also includes location information of UEs' data in the UA MAC PDU (403). For example, it may indicate which bit in the bitmap of the UA MAC header is used to indicate whether the data of a certain UE is present in the UA MAC PDU or not. Alternatively, it may contain information related to the data location in the UA MAC PDU by indicating the data location of each UE in the UA MAC PDU, or by indicating that the data of the UEs in the UA MAC PDU are arranged according to a predefined/pre-configured order. Under the presence of this parameter, the bitmap in the UA MAC header may be omitted so the bitmap is an optional field/element in the UA MAC header. Furthermore, the RRC message may contain numerous optional indicators which are described as follows.
The RRC message may contain a setup or release indicator (405) which is configured by the eNB to setup or release the aggregate transmission. For example, the eNB may add an UE into a UE group by setting the indicator to be “setup”, or eNB may de-configure or release an aggregated UE group (or a UA group) by setting the indicator to be “release”.
The RRC message may include a logical Channel Identity (LCID) indicator which may be used in the User Aggregation MAC (UA MAC) header to serve as an identification in order to indicate that the corresponding MAC PDU is a UA MAC PDU in accordance with the present disclosure rather than an ordinary or conventional PDU.
The RRC message may periodically include a sub-frame pattern configuration information such as semiPersistSchedInvervalDL (which may indicate Semi-Persistent Scheduling interval for downlink transmission) in order to indicate which sub-frame may be used for aggregate transmission. An eNB may not transfer data packet of the aggregation transmission in every single sub-frame of data transmission; therefore, a sub-frame pattern configuration information (e.g., a periodicity) may be configured to indicate which sub-frame may be used for aggregate transmission. The sub-frame configuration information may include an periodicity of data transmission in a manner similar to Semi-Persistent Scheduling (SPS).
The RRC message also may optionally include a ACK/NACK Resource parameter such as n1-PUCCH-AN-PERSISTLIST to indicate the resource for HARQ (hybrid automatic retransmission and request) ACK/NACK feedbacks. Also, the RRC message may include HARQ information indicators which may contain information for UE(s) to derive a HARQ process ID such as numberOfConfSPS-Processes (which may indicate the number of configured HARQ processes) and/or a maximum number of HARQ re-transmission. The purpose of the HARQ information indicators is configured for the UE to know the HARQ information associated with each aggregate transmission such as the timing as to when ACK/NACK should be transmitted or received and also how many times a HARQ re-transmission may be performed. An example of a HARQ indicator is shown in equation (1).
HARQ Process ID=[floor(CURRENT_TTI/semiPersistSchedIntervalDL)]modulo numberOFConfSPS-Processes equation (1).
In the equation (1), floor refers to a flooring function, a parameter “Current_TTI” refers to a current transmission time interval (TTI) or a current sub-frame identifier, a parameter “semiPersistSchedIntervalDL” refers to a scheduling interval for downlink transmission, modulo refers to a modulo function and a parameter “numberOfConfSPS-Processes” refers to a number of configured HARQ processes.
The RRC message may optionally include a MCS indicator to indicate the modulation and code rate used for aggregate transmission.
The RRC message may optionally include data size information to indicate the total data size of the UE group and/or indicate the data size of the specific UE in the UA MAC PDU in each aggregate transmission.
The RRC message may optionally include a parameter similar to the “SPS-Config” used in the Semi-Persistent Scheduling (SPS) configuration. The RRC message in the present disclosure may be regarded as a configuration message from another perspective.
After performing the step S201 of FIG. 2 in which the wireless network sends a RRC message to configure or re-configure multiple UEs for aggregate transmission, in the step S203 of FIG. 2 or equivalently in the step S305 of FIG. 3, the eNB (303) may transmit data by using an unconventional MAC PDU format specifically configured for multiple UE aggregation.
FIG. 5A is a schematic diagram illustrating an UE acquiring its resource allocation assignment through extracting information in a control region by using a group identifier according to an exemplary embodiment. Referring to FIG. 5A, within a pre-determined TTI, there may be allocated a sub-frame. For example, there may be 10 sub-frames in a frame of 10 ms. Each UE extract information from a sub-frame to obtain a control region and a data region. For example, an UE may obtain a control region 50 and a data region 51 in a sub-frame#1. The same operations may be applied to other sub-frames such as sub-frame#2 or sub-frame#8 to obtain their respective control region or data region. The control region 50 in the present embodiment may include PDCCH; the data region 51 in the present embodiment may be physical downlink shared channel (PDSCH), but the present disclosure is not limited thereto. UEs may blindly decode the control region 50 and obtain a plurality of DCIs with different identifiers such as C-RNTI, G-RNTI, P-RNTI, SI-RNTI, SPS C-RNTI, . . . . For example, a UE is previously assigned with a group identifier G-RNTI# in a previously transmitted RRC message, then the UE may decode a DCI by the G-RNTI# and the DCI may indicate that the UE's DL resource is allocated in a resource block#22 (RB#22) in the data region 52. Subsequently, the UE may decode the data in the resource block#22 to form a UA MAC PDU or a MAC PDU, where the UA MAC PDU will be further illustrated in more details.
FIG. 5B illustrates the format of an user aggregation MAC PDU (UA MAC PDU) (500) used to send aggregated UE data (S305) from an eNB (303) to a UE group (301). The user aggregate (UA) MAC PDU (500) may contain an user aggregate (UA) MAC header (503) or (user aggregate header in a plainer expression) and at least one of the MAC payloads (515, 517, 519) which sequentially follows the UA MAC PDU (500), for instance, MAC Payload for UE#1 (515), MAC Payload for UE#2 (517), and the i-th Payload for UE#i (519). Each MAC payload of a certain UE may contain the data traffic for the certain UE. In other words, user aggregate header may contain information regarding the location information for each division of the aggregate data.
The UA MAC header (503) may include an indicator to indicate that itself is a UA MAC PDU, rather than a conventional MAC PDU. In other words, the UA MAC header (503) may contain an aggregate transmission indicator. For example, the UA MAC header may use a logical channel ID (LCID) to indicate itself as a UA MAC PDU. The UA MAC header (503) may also include information related to the payload size or the size of the data for a certain UE (509, 511, 513) in this UA MAC PDU (500) as well as the information related to where the payload configured for a certain UE is located in the UA MAC PDU (500). However, if the data size information is present in the RRC message, the size parameter in the UA MAC header may be omitted. The UA MAC header (503) may also optionally contain a Bitmap (507) or a bit string with each bit dynamically set as 1 or 0 to indicate the presence or absence of communication data for a certain UE in the aggregate MAC payload.
As an example, FIG. 5 shows a possible format of the UA MAC header (503). The UA MAC header (503) may begin with a Bitmap (507) to be followed by data of MAC payload sizes for each of the UEs (509, 511, 513), for instance, size of MAC payload of UE#1 (509), size of MAC payload of UE#2 (511), and size of MAC payload of UE#i (513).
The Bitmap (507) located within the UA MAC header 503 may be a string of dynamically assigned bits with each bit corresponds to a different one of the UE in the UE group, and each bit is used to indicate whether the data for the corresponding UE is present in the UA MAC PDU (500) or not in the aggregate MAC payload. For example, in a scenario where a UE group contains 5 individual UEs, not all 5 UEs would be transmitted data in any given moment. Under the circumstance when an individual UE is not actively communicating with the eNB or has left the cell (or a radio service area of an eNB), a corresponding bit located within the Bitmap (507) would be set zero by the eNB, otherwise the bit is set to one if the UA MAC PDU includes MAC Payload for the individual UE. The Bitmap (507) may be configured to serve a useful purpose in a way that an individual UE of a UE group can be dynamically added or removed by setting their corresponding bit in the bitmap (507) to 1 or zero. Otherwise, the eNB may communicate to a UE group that one of its member has already left, and may constantly re-configure existing UE groups. Additionally, the aggregate MAC PDU in the aggregate MAC PDU may include MAC payload for UE#1 (515), MAC payload for UE#2 (517), . . . , MAC payload for UE#i (519) and an optional padding field.
FIG. 6 illustrates an example of a typical MAC PDU of an individual UE from a configured UE group (301). The MAC PDU for the i-th UE or UE#i (519) located within the UA MAC PDU (500) may contain a specific format. The specific format of the MAC Payload for UE#i as illustrated in FIG. 5 may be a conventional MAC PDU and therefore the technical content of the MAC PDU will not be explained in detail. In general, the MAC PDU may include MAC header 60, and the MAC payload for UE#i may include MAC control element 1 (60), MAC control element 2 (61), a plurality of MAC service data units (SDU) (62, 63, . . . , 69), and optional padding bits. The proposed UA MAC PDU (500) can aggregate small data packet data traffic for multiple users configured into the same UE group into an aggregated MAC PDU, and this aggregated data would then be transmitted from the eNB using the same control signalling (e.g., PDCCH) and therefore reduces the control signal overhead.
After UEs data traffic are aggregated to be sent from an eNB to a UE group, control signal overhead can also be saved based on how downlink assignments to an aggregated UE group are transmitted (S203) and re-transmitted (S207). In principle, during transmission and re-transmission, the group identity information such as G-RNTI or SPS C-RNIT is embedded within PDCCH to inform each aggregated UE group of its resource allocation. In accordance with the present disclosure, four different exemplary embodiments are proposed below in order to save control information overhead during data transmission and re-transmission.
The first embodiment uses PDCCH in downlink assignments during the first transmission and the subsequent re-transmissions to inform a UE group of its resource allocation based on the RNTI information. The first embodiment saves PDCCH overhead since a group of UEs are already aggregated in a MAC PDU and therefore, only one PDCCH is needed per UA group for its aggregated data transmission. In other words, an aggregate control signal which indicates the location of resource allocation could be used for the transmission and re-transmission. The second embodiment further saves PDCCH overhead in comparison with the first embodiment by only using PDCCH during the first transmission but not subsequent re-transmissions because by synchronizing HARQ in a periodic basis, G-RNTI information is then not needed for subsequent data re-transmissions. The third embodiment saves control signal overhead by using PDCCH only during data re-transmission, but the PDCCH is not used during the first transmission. This embodiment can be implemented similar to SPS. Since the period of transmission is already pre-configured, the information related to resource allocation is not required during the first transmission but otherwise required for subsequent data re-transmissions. The fourth embodiment uses PDCCH for neither the first transmission nor any subsequent re-transmissions. The fourth embodiment can be implemented in a scenario where flexibility for scheduling and resource allocation are not needed and therefore can be configured under a fixed periodic resource allocation without any G-RNTI information for transmission nor re-transmission. In other words, the aggregate data may optionally include the group identifier (e.g., G-RNTI). For each embodiment, more detailed information is provided as follows.

First Exemplary Embodiment

In the first embodiment, PDCCH is used for both the first transmission and the subsequent re-transmission of aggregated user data. For the first embodiment, FIG. 7 which illustrates transmission and re-transmission of user aggregated data will be referred. First in step S701, an eNB assigns a group identity such as G-RNTI to a UE group when the aggregation transmission is configured. The eNB can use the group identity in the control channel (e.g., PDCCH) to inform the UE group the location of its resource allocation assignment in the data region (e.g., PDCCH). Next, in step S703 the UE group may look for the downlink control information (DCI) with the associated G-RNTI by monitoring the control region (e.g., PDCCH) for each individual sub-frame or only for each configured sub-frame if the sub-frame pattern used for the aggregation transmission is pre-configured (e.g., when the aggregation transmission is configured). Then, in step S705, if the downlink control information is found by the UE in the PDCCH for the TTI, then the downlink assignment for the aggregate transmission can be determined by the UE. Further, in step S707, the UE looks/searches for another indicator, for example, the New Data Indicator (NDI) in the DCI information decoded from the PDCCH. In the present embodiment, the NDI is one of the parameters of the DCI information. If NDI from the received transmission is found by the UE to be 0, then the received information is considered to be the first transmission (S711). If the UE determines that the NDI in the received information is 1, then the received information is considered to be a re-transmission (S709).
In the first embodiment, the parameter included in the DCI may include parameters such as MCS, HARQ process ID, NDI, Redundancy Version, and transmission power control (TPC) command. According to another embodiment with most technical contents similar to the first embodiment, during a data re-transmission, UE-specific identifier or UE-specific RNTI such as C-RNTI can be used instead of the G-RNTI. The reason is that during data re-transmission, the data does not have to be transmitted to the entire group, and therefore a re-transmission can be made to a specific UE identified by an UE-specific RNTI such as C-RNTI. In this embodiment, the PDCCH may include the same HARQ process ID to indicate that this downlink assignment is used for re-transmission.

Second Exemplary Embodiment

For the second embodiment, PDCCH is used for the first transmission but not for any subsequent re-transmissions so as to save control signal overhead. Since PDCCH is also used for the first transmission of the first embodiment, the steps involved for the first transmission are identical with the first embodiment. Essentially, the network assigns a group identity such as G-RNTI to the aggregated UE group as the aggregate transmission is configured, and then for each sub-frame or for each configured sub-frame, the UE group monitors DCIs for the G-RNTI embedded in the PDCCH. In some embodiments, once the DCI embedded with the G-RNTI is detected, the transmission may be considered as a first transmission. In some other embodiments, once the DCI embedded with the G-RNTI is detected, the NDI information from the DCI is decoded by the UE. If the UE determines that the NDI indicator is 0, then the transmission is considered by the UE as a first transmission. Otherwise, if the NDI is found by the UE to be 1, then the transmission is considered a re-transmission.
However, under the second embodiment, the downlink assignment for re-transmission may be not indicated on the PDCCH because synchronous HARQ may be used for re-transmission which renders the sending of PDCCH entirely unnecessary.
As the synchronous HARQ is used in the second embodiment, any subsequent re-transmissions would occur at every fixed/pre-configured period; therefore, resource allocations of re-transmissions can be found by the UE in predictable locations of the transmitted sub-frames. An example of the method for data transmission according to the second embodiment is illustrated in FIG. 8. In step S801, a downlink assignment is received by the UE at sub-frame n. In other words, the eNB transmits a downlink assignment. In S805, the UE may receive and decode the first transmission received in the corresponding resource block(s) at sub-frame n. However, if the UE does not successfully receive or decode the transmission, the UE may assume that the next subsequent re-transmission would be found at sub-frame n+x where x may be 8 in a FDD system. In other words, the subsequent re-transmission may be found at the same resources as the first transmission but shifted by a predictable period. Then, the next re-transmission may be found by the UE after yet another same predictable period and so on and so forth. Therefore, PDCCH is not required in the second embodiment to be sent in a downlink assignment, and control signal overhead can be saved. Note that although the downlink assignment information for the re-transmission may be predicted by the UE, the eNB may still send the PDCCH for the re-transmission in order to, for example, re-schedule the downlink resource assignment.

Third Exemplary Embodiment

For the third embodiment, the PDCCH for the first transmission may normally be omitted but not for subsequent re-transmissions. PDCCH is not used for the first transmission according to the third embodiment except under some exceptions which will be discussed first. PDCCH would not normally be used for the third embodiment except when the base station wants to modify existing configurations or under the circumstance of initial configuration or de-configuration. For example, when the base station sends the RRC message to aggregate a group of UEs to configure the UA group for the first time, a group identity information such as G-RNTI or SPS C-RNTI which will be embedded within DCIs in the PDCCH is sent to a group of UEs. Likewise, after an aggregated UE group (or an UA group) has been configured, the base station may send release information in the PDCCH to release or de-configure the UE group, or the base station may decide to drop or add a member of the group.
FIG. 9 illustrates an overall process of a method for data transmission according to the third embodiment. First, in step S901, the aggregated transmission is configured by the eNB. Next in S903, for each sub-frame or for each configured sub-frame, the UE may monitor for the PDCCH. If the PDCCH embedded with the group identity (e.g., G-RNTI, SPS C-RNTI) is present, this means that either the upcoming transmission is a re-transmission or the base station wants to make modification to existing UE group configurations. Next, in step S905, one of the DCI parameters, NDI, is read by the UE. If the UE determines that NDI is 1, then the upcoming transmission is determined to be a re-transmission. In some other embodiments, the downlink assignment for the re-transmission may be indicated on the PDCCH by a UE-specific RNTI such as C-RNTI to signify that only certain UEs in the UA group need the re-transmission. Normally, the NDI indicator in PDCCH embedded with the group identity would be 1 and this would mean that the upcoming transmission is a re-transmission. However, if the NDI indicator in PDCCH embedded with the group identity is found by the UE to be 0 under this third embodiment, this means that the base station wants to make modifications to existing aggregated transmission configuration. Therefore, in steps S907-S917, the UE may store the new configuration as the new configuration will be implemented from this point on.
On the other hand, if NDI is determined by the UE to be 0, then in the step S907, the PDCCH content is read to see if the aggregated transmission is to be released or de-configured. If yes, then in the step S907, the configured aggregate transmission is to be cleared and the G-RNTI and SPS-C-RNTI indicator associated with the UA group may be released. If no, then in step S911, the downlink assignment may be stored by the UE as a new configuration which is initiated by the base station. The associated HARQ information as configured in the downlink assignment will also be stored by the UE. Next, in the step S913, in the current TTI, the configured downlink assignment is initialized if the aggregate transmission is not already active or re-initialized if already active. For example, the UE may assume that the downlink assignment recurs in each sub-frame for which (10*SFN+sub-frame)=[(10*SFNstart time+sub-framestart time)+N*semiPersistSchedIntervalDL] modulo 10240, for all N>0, where SFNstart time and sub-frame start time are the system frame number (SFN) and Sub-frame respectively, at the time the configured downlink assignment were initialized or re-initialized. Next, in step S915, the HARQ process ID is set to be the HARQ process ID associated with this TTI, or more specifically, according to following equation (2).
HARQ Process ID=[floor(Current_TTI/semiPersistSchedIntervalDL)]modulo numberOfConfSPS-Processes equation (2).
In the equation (2), floor refers to a flooring function, a parameter “Current_TTI” refers to a current transmission time interval (TTI) or a current sub-frame identifier, a parameter “semiPersistSchedIntervalDL” refers to a SPS scheduling interval for downlink transmission, modulo refers to a modulo function and a parameter “numberOfConfSPS-Processes” refers to a number of configured HARQ processes.
In step S917, the NDI bit is considered by the UE as zero which indicates first transmission. Furthermore, the presence of a configured downlink assignment is indicated and the stored HARQ information is delivered to the HARQ entity for this TTI.
Referring back to the step S903 of FIG. 9, if the UE determined that PDCCH is not present in the sub-frame during the current TTI, then downlink assignment for this TTI is presumed by the UE to be already configured. Next, in step S919, the HARQ process ID is set by the UE to the HARQ process ID associated with this TTI, and more specifically as following equation (3).
HARQ Process ID=[floor(CURRENT_TTI/semiPersistSchedIntervalDL)]modulo numberOFConfSPS-Processes. equation (3).
In the equation (3), floor refers to a flooring function, a parameter “Current_TTI” refers to a current transmission time interval (TTI) or a current sub-frame identifier, a parameter “semiPersistSchedIntervalDL” refers to a scheduling interval for downlink transmission, modulo refers to a modulo function and a parameter “numberOfConfSPS-Processes” refers to a number of configured HARQ processes.
Further, in step S921, the NDI bit is considered by the UE to the first transmission. Under the third embodiment, control signal overhead is saved as PDCCH is normally not present during the first transmission of data except in relatively rare circumstances as described previously.

Fourth Exemplary Embodiment

For the fourth embodiment, PDCCH may be not used in neither the first transmission nor subsequent re-transmissions. The lack of PDCCH for upcoming transmissions would be communicated to the UE in the initial RRC message as well as all information required for any first transmission and re-transmissions. In this fourth embodiment, the downlink resource for the aggregated transmission including the first and/or re-transmissions may appear or recur at a pre-configured resource location. For example, in some embodiments, the whole sub-frame in the pre-configured sub-frame can be used for the first transmission and/or re-transmission for the aggregated transmission. In some other embodiments, certain pre-defined resource blocks in the pre-configured sub-frame may be used for the aggregated transmission. For each configured sub-frame, the UE may set the HARQ Process ID to the HARQ Process ID associated with this TTI according to following equation (4).
HARQ Process ID=[floor(CURRENT_TTI/semiPersistSchedIntervalDL)]modulo numberOFConfSPS-Processes equation (4).
In the equation (4), In the equation (3), floor refers to a flooring function, a parameter “Current_TTI” refers to a current transmission time interval (TTI) or a current sub-frame identifier, a parameter “semiPersistSchedIntervalDL” refers to a SPS scheduling interval for downlink transmission, modulo refers to a modulo function and a parameter “numberOfConfSPS-Processes” refers to a number of configured HARQ processes.
In the fourth embodiment, control region (e.g., PDCCH) is not used for the first transmission or the subsequent re-transmission(s) as the UE directly looks for its resource allocation assignment in the data region by following pre-configured resource location of control signaling information delivered by the previous RRC message. As such, control signaling overhead is also reduced.
Referring back to FIG. 2, as the eNB sends an aggregated data transmission for the first time transmission or any subsequent re-transmissions, the UA group in the step S205 may respond with aggregated ACK/NACK feedbacks in order to indicate to the eNB whether the transmitted data has been successfully received and decoded. There may be two options for a UA group of UEs to accomplish aggregated ACK/NACK response. The first option is to use a shared ACK/NACK resource which is common for the entire UA group. The second option is to use a dedicated ACK/NACK response for each individual UE to respond to the eNB. In other words, the response is either an aggregate response or a dedicated response for an individual of the aggregate transmission.
For the first option, the UE group may be configured with the ACK/NACK resources which are shared by the UA group of UEs involved in the aggregate transmission. Under this first option, if the transmitted data in the soft buffer of the UE is not successfully decoded by the UA group, then the UA may send a NACK in the shared resource to the eNB in order for the eNB to re-transmit the data. If the UE has successfully received and decoded the transmission, then ACK may not be required to be sent from the UE. The resource to send ACK/NACK may be implicitly indicated by the downlink assignment such as the resource block index and/or demodulation reference signal (DMRS). Based on the detection of ACK feedback(s), the eNB may determine to re-transmit the aggregate data for the aggregate transmission.
For the second option, each of the UEs may be configured with dedicated ACK/NACK resources for the aggregate transmission. If the transmitted data in the soft buffer of the UE is successfully decoded, then each UE may send a ACK in the corresponding ACK/NACK resource to the eNB of the wireless communication network. Otherwise, if the data is not successfully decoded by the UE, each individual UE may send a NACK in the ACK/NACK resource to the eNB of the wireless communication network. Based on the detection of ACK/NACK feedback(s) from individual UE(s), the eNB may determine to re-transmit the aggregate data for the aggregate transmission, and/or the eNB may determine to re-transmit an individual data for the individual UE.
Referring back to FIG. 2, the process of the steps S201-S207 is repeated as there is more data to be transmitted. Otherwise, in the step S209, if there is no more data to be transmitted or if the base station decides that the aggregate transmission will not continue, in the step S211 the aggregate transmission will be de-configured. There may be two methods to de-configure the aggregate transmission. The first method is by explicit signaling, and the second method is by implicit.
For the first method of de-configuring the aggregate transmission, the wireless communication network may explicitly send a message by the eNB such as a release indicator in PDCCH or the same indicator in RRC message to release the aggregate transmission or to release a single UE from the UA group. (wherein the RRC message is a control message. In other words, since the RRC message is another control message, a release may be accomplished by sending another RRC message).
For the second method of de-configuring the aggregate transmission, the wireless communication network and/or UE may autonomously release the related configuration such as when the corresponding timer expires. In some embodiments, the network and/or UE may start or re-start a timer, for example, when the aggregation transmission is started or is configured. The length of the timer may be configured by the network by using the RRC message (400). Once the timer expires, the network and/or UE may autonomously release the configuration of the aggregate transmission. In some embodiments, when a timer such as a timea-lighmenttimer expires, the UE may notify RRC entity in the wireless communication network to release the configuration for the aggregate transmission and/or may clear the configured downlink assignments. The UE may notify the RRC entity to release the PUCCH resource for the ACK/NACK feedbacks and/or flush the corresponding HARQ buffers of its processing circuit.
In view of the aforementioned descriptions, the present disclosure is suitable for being used in a wireless communication system and is able to enhance data transmission by reducing the control signal overhead through user aggregation. Accordingly, overall control signaling space may be utilized in a more efficient manner to serve more user equipments, or overall system transmission efficiency as well as spectrum efficiency are improved.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.

Claims

1. A method of transmitting data, adapted for a base station, the method comprising:

configuring an aggregate transmission;

transmitting a control signal to establish the aggregate transmission; and

transmitting aggregate data after the aggregate transmission is established, wherein the aggregate data comprises data for the aggregate transmission.

2. The method of claim 1, wherein the step of transmitting aggregate data comprises:

transmitting the aggregate data comprising an aggregate header to be followed by payloads for the aggregate transmission.

3. The method of claim 1 further comprising:

receiving a response signal; and

re-transmitting the aggregate data according to the response signal.

4. The method of claim 1, further comprising:

de-configuring the aggregate transmission by sending another control message to an individual to de-configure the individual from the aggregate transmission.

5. The method of claim 1, further comprising:

starting a timer; and

de-configuring the aggregate transmission when the timer expires.

6. The method of claim 3, wherein the response is either an aggregate response or a dedicated response for an individual of the aggregate transmission.

7. The method of claim 1, wherein the control signal comprising a group identity information, location information for each division of the aggregate data, and an indicator to establish or de-configure the aggregate transmission.

8. The method of claim 2, wherein the aggregate header comprises:

an aggregate transmission indicator;

sizes of the payloads; and

a bitmap comprising indicating bits.

9. The method of claim 3, wherein the step of transmitting aggregate data comprises:

transmitting the aggregate data comprising an aggregate control signal which indicates the location of resource allocation used for the transmission; and

re-transmitting to the aggregate data comprising another aggregate control signal which indicates the location of resource allocation used for the re-transmission.

10. The method of claim 3, wherein the step of transmitting aggregate data comprises:

re-transmitting the aggregate data without a control signal overhead indicating the location of resource allocation used for the re-transmission.

11. The method of claim 3, wherein the step of transmitting aggregate data comprises:

transmitting the aggregate data without a control signal overhead indicating the location of resource allocation used for the transmission; and

re-transmitting the aggregate data comprising an aggregate control signal which indicates the location of resource allocation used for the re-transmission.

12. The method of claim 3, wherein the step of transmitting aggregate data comprises:

13. A method of transmitting data, adapted for a user equipment (UE), the method comprising:

receiving a control signal;

being configured into an aggregate transmission according to the control signal; and

receiving aggregate data after being configured for aggregate transmission, wherein the aggregate data comprises data for the user equipment and data not for the user equipment.

14. The method of claim 13, wherein the step of receiving aggregate data after being configured for aggregate transmission comprises:

receiving the aggregate data comprising an aggregate header to be followed by payloads for the aggregate transmission and optionally a group identifier.

15. The method of transmitting data of claim 13 further comprising:

transmitting a response signal; and

receiving re-transmitted aggregate data after sending the response signal.

16. The method of claim 13 further comprising:

de-configuring from the aggregate transmission by receiving another control message.

17. The method of claim 13 further comprising: starting a timer; and

de-configuring from the aggregate transmission when the timer expires.

18. The method of claim 15, wherein the response is either an aggregate response or an individual response.

19. The method of claim 13, wherein the control signal comprising a group identity information, location information for each division of the aggregate data, and an indicator to configure into or to de-configure from the aggregate transmission.

20. The method of claim 14, wherein the aggregate header comprises:

an aggregate transmission indicator;

sizes of the payloads; and

a bitmap comprising indicating bits.

21. The method of claim 15, wherein the step of receiving aggregate data comprises:

receiving the aggregate data comprising an aggregate control signal which indicates the location of resource allocation used for the transmission; and

receiving the re-transmitted aggregate data comprising another aggregate control signal which indicates the location of resource allocation used for the re-transmission.

22. The method of claim 15, wherein the step of receiving aggregate data comprises:

receiving the re-transmitted aggregate data without a control signal overhead indicating the location of resource allocation used for the re-transmission.

23. The method of claim 15, wherein the step of receiving aggregate data comprises:

receiving the aggregate data without a control signal overhead indicating the location of resource allocation used for the transmission; and

receiving the re-transmitted aggregate data comprising an aggregate control signal which indicates the location of resource allocation used for the re-transmission.

24. The method of claim 15, wherein the step of receiving aggregate data comprises:

25. The method of claim 2, wherein the aggregate data further comprising a group identifier.

26. A base station, comprising:

a transceiver, configured to transmit and receive wireless signals; and

a processor, connected to the transceiver, configured for:

configuring an aggregate transmission;

transmitting a control signal to establish the aggregate transmission; and

27. The base station of claim 26, wherein the processor is configured for transmitting the aggregate data comprises:

28. The base station of claim 26 wherein the processor is further configured for:

receiving a response signal; and

re-transmitting the aggregate data according to the response signal.

29. The base station of claim 26 further comprising:

de-configuring an individual from the aggregate transmission by sending another control message to the individual to de-configure the individual from the aggregate transmission.

30. The base station of claim 26 further comprising:

starting a timer; and

de-configuring the aggregate transmission when the timer expires.

31. The base station of claim 28, wherein the response is either an aggregate response or a dedicated response for an individual of the aggregate transmission.

32. The base station of claim 26, wherein the control signal comprising a group identity information, location information for each division of the aggregate data, and an indicator to setup or release the aggregate transmission.

33. The base station of claim 27, wherein the aggregate header comprises:

an aggregate transmission indicator;

sizes of the payloads; and

a bitmap comprising indicating bits.

34. The base station of claim 28, wherein the processor is configured for transmitting the aggregate data comprises:

re-transmitting the aggregate data comprising another aggregate control signal which indicates the location of resource allocation used for the re-transmission.

35. The base station of claim 28, wherein the processor is configured for transmitting the aggregate data comprises:

36. The base station of claim 28, wherein the processor is configured for transmitting the aggregate data comprises:

37. The base station of claim 28, wherein the processor is configured for transmitting the aggregate data comprises:

38. The base station of claim 27, wherein the aggregate data further comprising a group identifier.

39. A user equipment (UE) comprising:

a transceiver, configured to transmit and receive wireless signals; and

a processor, connected to the transceiver, configured for:

receiving a control signal;

40. The UE of claim 39, wherein the processor is configured for receiving the aggregate data comprises:

receiving the aggregate data comprising an aggregate header to be followed by payloads for the aggregate transmission.

41. The UE of claim 39 wherein the processor is further configured for:

transmitting a response signal; and

receiving re-transmitted aggregate data after sending the response signal.

42. The UE of claim 39 further comprising:

43. The UE of claim 39 further comprising:

starting a timer; and

de-configuring from the aggregate transmission when the timer expires.

44. The UE of claim 41, wherein the response is either an aggregate response or an individual response.

45. The UE of claim 39, wherein the control signal comprising a group identity information, location information for each division of the aggregate data, and an indicator to configure into or to de-configure from the aggregate transmission.

46. The UE of claim 40, wherein the aggregate header comprises:

an aggregate transmission indicator;

sizes of the payloads; and

a bitmap comprising indicating bits.

47. The UE of claim 41, wherein the processor is configured for receiving the aggregate data comprises:

48. The UE of claim 41, wherein the processor is configured for receiving the aggregate data comprises:

49. The UE of claim 41, wherein the processor is configured for receiving the aggregate data comprises:

50. The UE of claim 41, wherein the processor is configured for receiving the aggregate data comprises:

51. The UE of claim 40, wherein the aggregate data further comprising a group identifier.