Coordination of duplex directions in NR TDD systems

Abstract

The present application relates to coordination of duplex directions in a NR TDD system. According to one embodiment, a method is provided for execution in a system including a joint traffic direction scheduler. The joint traffic direction scheduler is configured to coordinate time division duplex (TDD) transmissions for a plurality of cells. The method includes obtaining TDD operation information from each of the cells. The method also includes determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs). The method also includes indicating the determined transmission direction to the cell.

Description

[0001] This application is a divisional application of Chinese patent application 201880006173.0. The international filing date of the original application is January 9, 2018, and the name of the invention is “Coordination of duplex directions in NR TDD system”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 444,271, filed January 9, 2017, the subject matter of which is hereby incorporated herein by reference. Technical Field

[0004] The disclosed subject matter relates generally to telecommunications. Certain embodiments more particularly relate to coordination of duplex directions in New Radio (NR) Time Division Duplex (TDD) systems. Background Art

[0005] Within the Third Generation Partnership Project (3GPP), there are ongoing research projects investigating a new radio interface for fifth-generation telecommunications systems (5G). The terminology used to represent this new, next-generation technology has not yet been agreed upon, so the terms NR and 5G may be used interchangeably. Furthermore, a base station may be referred to as a gNB instead of an eNB. Alternatively, the term transmission reception point (TRP) may be used. Furthermore, the term access point (AP) may be used in place of TRP / eNB / gNB.

[0006] Conventional LTE technology only supports static or semi-static TDD, where time domain resources are divided between downlink and uplink based on a long-term configuration or only once every "N" subframes. This is very inefficient (especially when there is only one direction of traffic) because the other dedicated time resources for the other direction are wasted. NR can define dynamic time division duplexing (TDD) to maximize the use of given radio resources for both traffic directions in the most efficient way. Summary of the Invention

[0007] In certain embodiments of the disclosed subject matter, coordination is implemented between different cells (including co-located cells) to avoid cross-link interference. Certain embodiments include adaptive mode switching between static and dynamic TDD based on explicit signaling and information exchange between co-located cells (e.g., sector cells in the same macro site) to handle very strong cross-link interference from co-located cells. Certain embodiments also include methods for fast coordination between co-located or non-co-located cells.

[0008] Certain embodiments of the disclosed subject matter are proposed in recognition of the shortcomings associated with conventional methods and techniques, such as the examples below. Although dynamic TDD brings significant performance gains in the low to medium load range, as the traffic load increases, the performance benefits become smaller due to cross-link interference. In particular, if the cross-link interference comes from co-located cells, its impact on performance is very severe. For example, in Figure 1 In the second time slot, if macro cell 1 is in the uplink, it will experience very strong interference from macro cells 2 and 3 in the downlink, because all macro cells are co-located. Figure 2 This is demonstrated by the system-level evaluation shown in , where dynamic TDD performs much worse than static TDD in the medium to high load range.

[0009] Compared to conventional methods and techniques, certain embodiments of the disclosed embodiments may provide potential benefits (such as the examples below). In NR TDD operation, certain embodiments may reduce cross-link interference between non-co-located cells that may cause severe interference to each other, or reduce cross-link interference between co-located cells by adaptively switching the TDD mode between dynamic TDD mode and static TDD mode, so that erroneous transmissions may be avoided without wasting resources on the air interface. In addition, in NR TDD operation, certain embodiments may significantly enhance downlink and uplink performance. In addition, in NR operation, certain embodiments may ensure relatively fast coordination between cells.

[0010] In some embodiments of the disclosed subject matter, a method performed in a system including a joint traffic direction scheduler configured to coordinate time division duplex (TDD) transmissions for a plurality of cells comprises: obtaining TDD operation information from each of the cells; determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs); and indicating the determined transmission direction to the cells.

[0011] In certain related embodiments, indicating the determined transmission direction includes: signaling that one or more of the plurality of cells will use or will not use one or more predetermined TDD modes. The one or more predetermined TDD modes may indicate, for example, a predetermined ratio of downlink to uplink (DL:UL) transmission to be used by the one or more of the plurality of cells. The one or more predetermined TDD modes may include, for example, a fully dynamic TDD mode, or a hybrid dynamic TDD mode that imposes scheduling restrictions within a portion of the dynamic TDD duration. In addition, the method may further include signaling the duration of the one or more predetermined TDD modes.

[0012] In some related embodiments, indicating the determined transmission direction includes signaling that a predetermined TDD mode is to start or stop. In some such embodiments, the method may further include configuring the predetermined TDD mode independently of signaling that the predetermined TDD mode is to start or stop.

[0013] In certain related embodiments, indicating the determined transmission direction includes transmitting a bitmap for a set of upcoming TTIs, the bitmap indicating, for each TTI, a transmission direction to be used by each of the cells.

[0014] In certain related embodiments, the method further comprises one or more of the cells determining scheduling details for its own operation during the one or more TTIs, wherein the scheduling details include one or more user equipments (UEs) to be scheduled and a modulation and coding scheme to be used.

[0015] In certain related embodiments, determining the transmission direction to be used by each of the cells during the one or more TTIs comprises one or more of: (a) detecting a change in a buffer status of one or more of the cells; (b) detecting a buffer status of one or more of the cells; (c) detecting a change in a ratio of downlink to uplink (DL:UL) traffic in one or more buffers; and detecting a change in a quality of service (QoS) type to be applied to traffic associated with one or more of the cells. In some such embodiments, determining the transmission direction comprises detecting the buffer status change, and detecting the buffer status change comprises: receiving a periodic or event-based report; and determining whether one or more of the cells has upcoming traffic for both the uplink (UL) and downlink (DL) directions. In certain alternative embodiments, determining the transmission direction comprises detecting a change in a ratio of downlink to uplink traffic, and the method further comprises switching one or more TDD modes in response to the ratio crossing a threshold.

[0016] In certain related embodiments, the method further includes: when all of the cells will transmit data in the same TDD service direction during the one or more TTIs, sending a first mode selection signal to the cell to trigger the use of the dynamic TDD mode; otherwise, when not all of the cells will transmit data in the same TDD service direction during the one or more TTIs, sending a second mode selection signal to the cell to trigger the use of the static TDD mode.

[0017] In certain related embodiments, the method further includes: one or more of the cells switching from a current time division duplex (TDD) mode to a new TDD mode based on the indication.

[0018] In certain related embodiments, the method further includes controlling the plurality of cells to switch between a dynamic time division duplex (TDD) mode and a static TDD mode, comprising: (a) determining a direction of traffic to be scheduled for each of the plurality of cells during one or more TTIs; (b) in response to determining that the direction of the traffic is the same for each of the plurality of cells during the one or more TTIs, controlling the plurality of cells to operate according to the dynamic TDD mode; and (c) in response to determining that the direction of the traffic is different for each of the plurality of cells during the one or more TTIs, controlling the plurality of cells to operate according to the static TDD mode. In some such embodiments, the method further includes configuring the static TDD mode for each of the plurality of cells according to a fixed downlink to uplink (DL:UL) ratio. In some such embodiments, the method further includes adjusting the DL:UL ratio according to long-term traffic characteristics of the wireless communication network. Additionally, in some such embodiments, the plurality of cells may be co-located. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings illustrate selected embodiments of the disclosed subject matter. In the accompanying drawings, like reference numerals represent like features.

[0020] Figure 1 Illustrating the cross-link interference problem in co-located macro sites.

[0021] Figure 2 The performance loss of dynamic TDD due to intra-site cross-link interference under medium to high load is shown (average downlink data rate is shown relative to the traffic served by the site for the case of 7 macro sites with 3 sectors per site).

[0022] Figure 3 A communication system according to an embodiment of the disclosed subject matter is shown.

[0023] Figure 4A A wireless communication device in accordance with an embodiment of the disclosed subject matter is shown.

[0024] Figure 4B A wireless communication device according to another embodiment of the disclosed subject matter is shown.

[0025] Figure 5A A radio access node according to an embodiment of the disclosed subject matter is shown.

[0026] Figure 5BA radio access node according to another embodiment of the disclosed subject matter is shown.

[0027] Figure 6 A radio access node according to a further embodiment of the disclosed subject matter is shown.

[0028] Figure 7 A method according to an embodiment of the disclosed subject matter is shown. DETAILED DESCRIPTION

[0029] The following description presents various embodiments of the disclosed subject matter. These embodiments are presented as teaching examples and should not be interpreted as limiting the scope of the disclosed subject matter. For example, certain details of the described embodiments may be modified, omitted, or expanded without departing from the scope of the disclosed subject matter.

[0030] In the following description, the terms user equipment (UE), terminal, and handset are used interchangeably to refer to devices that communicate with the infrastructure. Generally speaking, these terms should not be construed as limiting to any particular type of device, and the described embodiments are applicable to any device capable of implementing the described functionality. The term base station is intended to refer to a node in the infrastructure that communicates with the UE.

[0031] Different names may apply, and the functionality of a base station may be distributed in various ways. For example, there may be a radio head that terminates some of the multiple radio protocols and a centralized unit that terminates other parts of the multiple radio protocols. We will not distinguish between such implementations here, but the term base station will refer to all alternative architectures for various embodiments.

[0032] Certain embodiments relate to dynamic TDD operation, in which time domain resources are dynamically allocated to DL or UL traffic. Compared to traditional static TDD in LTE, this can bring significant performance gains under low to medium loads because dynamic TDD does not have any restrictions on the use of time domain resources in a certain time period. U.S. patent application No. 62 / 421,740 considers fully distributed interference management in the absence of inter-cell signaling to adopt dynamic mode switching between static TDD and dynamic TDD. Compared to this approach, certain embodiments as described herein consider coordination based on explicit signaling between cells co-located at the same site (e.g., macro sector cells), and also add some additional embodiments for coordination between different cells that may not be co-located.

[0033] Certain embodiments as described herein provide intra-site cross-link interference management based on an adaptive mode switching scheme between static TDD and dynamic TDD to manage cross-link interference between cells at the same site (e.g., in a multi-sector site corresponding to an eNB). In addition, certain embodiments provide signaling types, timing, and triggering methods for TDD mode switching.

[0034] Example 1: Centralized Adaptive TDD Mode Switching

[0035] The first embodiment provides centralized TDD mode switching between dynamic TDD and predetermined static TDD. To coordinate a group of cells, a logical central entity can be introduced that employs a joint traffic direction scheduler for all cells in the coordination group. The logical central entity can be, for example, an additional inter-cell scheduling function on top of the existing cell-level scheduler. For example, it can be implemented in the baseband processor covering multiple remote radio units.

[0036] The transceivers for a group of cells may be located at the same site. The joint direction scheduler collects information from each cell and indicates the transmission direction to be used for all cells in the group for a transmission time interval (TTI) during a certain time period. Indicating the transmission direction for a TTI may be done by indicating the TDD mode.

[0037] Based on the indicated transmission direction, each cell determines other scheduling details for each TTI, including the UE to be scheduled, the modulation and coding scheme to be used, etc. Different types of indication signals can be considered for these transmission directions. As an example, a signal can be sent to the relevant cell to inform that a predetermined TDD mode is 'needed' or 'not needed'. When a specific TDD mode is required, the signal can further specify which of the predetermined TDD modes is required. Once each cell receives the signal, each cell switches to the indicated mode. Different predetermined modes can be, for example:

[0038] Different DL to UL ratios in configurations for static TDD

[0039] Fully dynamic TDD without any scheduling constraints

[0040] Hybrid dynamic TDD with scheduling restrictions. Scheduling restrictions can include static TDD in a certain portion of the entire dynamic TDD duration. This solution can be useful for reserving resources during dynamic TDD mode to protect QoS service types (such as voice or critical control signaling for video).

[0041] One way to reduce the signalling overhead may be to send only 'start' and 'stop' signalling of one predetermined TDD mode, instead of signalling the selected mode.The predetermined TDD mode may be updated separately from the 'start' and 'stop' signalling.

[0042] The indication signal may also include the duration of a selected TDD mode. For example, the signal may include a starting subframe index "N" and a duration "Delta" indicating the start and end timing of a TDD mode. In addition to the indicated duration, other alternative modes may be used.

[0043] When a specific TDD mode is not required, the signaling from the joint direction scheduler may include a bitmap for a set of upcoming TTIs that indicates the transmission direction to be used for each TTI. For example, a 0 in the bit corresponding to a TTI may indicate that the TTI will be used for downlink traffic, while a 1 in the bit may indicate that the TTI should be used for uplink traffic. In another embodiment, three-value signaling may be employed: a 0 in the signal corresponding to a TTI may indicate that the TTI will be used for downlink traffic, a 1 in the signal may indicate that the TTI should be used for uplink traffic, and a 2 in the signal may indicate that the TTI may be freely assigned to downlink or uplink traffic by each individual serving cell.

[0044] Example 2: Trigger for Transmission Direction Adaptation

[0045] This embodiment provides a trigger mechanism for switching or turning on / off the TDD mode for the cells in the coordination group. As a non-limiting example, this can be done based on a change in the buffer status of any of the cells in the group. The buffer status in each cell can be reported to the central entity periodically or in an event-based manner. For example, if any neighboring cell in the coordination group has traffic in both DL and UL directions, or any neighboring cell has traffic in a direction different from the most recently scheduled direction, the central entity sends a mode selection signal to all cells to ensure that a predetermined static TDD mode is used that avoids intra-site cross-link interference. In addition, when all neighboring cells have data only in the same traffic direction, it can send another signal to turn off the static TDD mode so as not to waste unused resources in one scheduling direction.

[0046] Another variation of this embodiment is to also consider the ratio between the DL and UL buffer sizes in a cell, rather than just the presence of traffic, in order to trade off the DL and UL performance of the co-located cells. For example, if any of the co-located cells has non-zero buffers in both directions, then mode switching is triggered only if the traffic ratio is above a certain threshold and the number of macro cells exceeding the threshold is greater than N (<= the total number of macro cells in a given coordination group). This triggering rule can be used to trade off DL and UL performance.

[0047] If the multi-directional traffic in the buffer is not large enough or does not exist in many cells in the coordination group, the joint directional scheduler can use the bitmap indicated in the previous embodiment to specify the transmission direction for a certain number of upcoming subframes. The duration of the bitmap is also signaled.

[0048] As a non-limiting example, mode switching can also be triggered based on a change in the QoS service type or a change in the ratio between the buffer sizes of different types of traffic, so as to further optimize the TDD mode selection by taking QoS into consideration. If there are more high QoS services in one cell, the central entity can be more conservative in ensuring a static TDD mode, even though it causes a waste of air resources in other co-located cells that do not have QoS services.

[0049] Example 3: Timing aspects of transmission direction signaling

[0050] Another embodiment provides for timing aspects of signaling for the transmission direction. Signaling can be used on a very fast time scale (e.g., TTI level) (which is feasible if all cells are physically connected in close proximity using a dedicated backhaul), or signaling can be used on a relatively long time scale (such as file arrival). This different time scale can be applied to trigger information updates to the central entity and transmission direction signaling from the central entity. In other words, trigger information updates to the central entity can be performed more frequently, but transmission direction signaling (e.g., in the form of the TDD mode to be used) can be done on a slower time scale.

[0051] In a variation of this embodiment, when the TDD mode is signaled, the TTI boundaries for the DL:UL ratio alignment are also explicitly or implicitly signaled. Thus, consider a TDD mode operating with 4 DL TTIs and one UL TTI. The central entity can then explicitly or implicitly signal that the 4:1 DL:UL ratio is aligned starting from TTIs {0, 5, ...}. The alignment information can also be part of the TDD mode definition.

[0052] In another variation of this embodiment, assuming that TDD mode is already in use, when the use of TDD mode is signaled, TDD mode can be immediately applied to the next TTI. To illustrate this, in the above example with a DL:UL ratio of 4:1, if the central entity signals the use of 4:1 TDD mode and this signaling is received in TTI 2, then even if there is some UL traffic to be scheduled, the cell only performs DL transmission in TTI 3 and waits until TTI 4 to transmit UL traffic, because if it has already started from TTI 0, this is consistent with the 4:1 TDD mode.

[0053] Example 4: Distributed Coordination

[0054] As long as the relevant trigger information is exchanged between cells without being reported to the central entity, TDD mode switching can be performed without explicit commands from the central entity. This solution can avoid TDD mode switching signaling overhead because all scheduling decisions will be made based on the exchanged trigger information, which will be common to all relevant cells in the same coordination group. When distributed coordination is used, an explicit TTI index can be used as part of the signaling to indicate the transmission direction to accommodate different signaling delays between different nodes.

[0055] The described embodiments may be implemented in any suitable type of communication system supporting any suitable communication standard and using any suitable components. As an example, the described embodiments may be implemented in a communication system such as Figure 3 Certain embodiments are implemented in a communication system such as that shown in . Although certain embodiments are described with respect to 3GPP systems and related terminology, the disclosed concepts are not limited to LTE or 3GPP systems. Additionally, although reference may be made to the term "cell," the concepts described may also be applied in other contexts, such as beamforming used in 5G.

[0056] refer to Figure 3 , the communication system 300 includes a plurality of wireless communication devices 305 (e.g., UEs, machine type communication [MTC] / machine to machine [M2M] UEs) and a plurality of radio access nodes 310 (e.g., eNodeBs or other base stations). The communication system 100 is structured into a plurality of cells 315, which are connected to a core network 320 via corresponding radio access nodes 310. The radio access nodes 310 are capable of communicating with the wireless communication devices 305 and any additional elements suitable for supporting communication between wireless communication devices or between a wireless communication device and another communication device (such as a landline phone).

[0057] Although wireless communication devices 305 may represent communication devices comprising any suitable combination of hardware and / or software, in some embodiments, these wireless communication devices may represent devices such as Figure 4A and 4B Similarly, although the radio access nodes shown may represent network nodes comprising any suitable combination of hardware and / or software, in certain embodiments these nodes may represent devices such as Figure 5A 、 5B and devices such as those shown in greater detail in 6 .

[0058] refer to Figure 4A , the wireless communication device 400A includes a processor 405 (e.g., a central processing unit [CPU], an application specific integrated circuit [ASIC], a field programmable gate array [FPGA], and / or the like), a memory 410, a transceiver 415, and an antenna 420. In certain embodiments, some or all of the functionality described as being provided by a UE, an MTC or M2M device, and / or any other type of wireless communication device may be provided by a device processor executing instructions stored on a computer-readable medium such as the memory 410. Alternative embodiments may include, in addition to Figure 4A Additional components beyond those shown in , which may be responsible for providing certain aspects of the functionality of the device, including any of the functionalities described herein.

[0059] refer to Figure 4B , the wireless communication device 400B includes at least one module 425 configured to perform one or more corresponding functions. Examples of such functions include various method steps or combinations of method steps as described herein with reference to the wireless communication device. In general, a module may include any suitable combination of software and / or hardware configured to perform a corresponding function. For example, in some embodiments, a module includes a module configured to, when on an associated platform such as Figure 4A Software that performs corresponding functions when executed on a platform (as shown in ).

[0060] refer to Figure 5AThe radio access node 500A includes a control system 520, which includes a node processor 505 (e.g., a central processing unit (CPU), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and / or the like), memory 510, and a network interface 515. Furthermore, the radio access node 500A includes at least one radio unit 525, which includes at least one transmitter 535 and at least one receiver coupled to at least one antenna 530. In some embodiments, the radio unit 525 is external to the control system 520 and is connected to the control system 520 via, for example, a wired connection (e.g., a fiber optic cable). However, in some other embodiments, the radio unit 525 and potentially the antenna 530 are integrated with the control system 520. The node processor 505 operates to provide at least one functionality 545 of the radio access node 500A as described herein. In some embodiments, the functionality is implemented in software, which is stored, for example, in the memory 510 and executed by the node processor 505.

[0061] In certain embodiments, some or all of the functionality described as being provided by a base station, Node B, eNode B, and / or any other type of network node may be provided by a node processor 505 executing code stored on a computer-readable medium such as a computer program. Figure 5A Alternative embodiments of the radio access node 500 may include additional components to provide additional functionality, such as the functionality described herein and / or related supporting functionality.

[0062] refer to Figure 5B , the radio access node 500B includes at least one module 550 configured to perform one or more corresponding functions. Examples of such functions include various method steps or combinations of method steps as described herein with reference to the radio access node. In general, a module may include any suitable combination of software and / or hardware configured to perform a corresponding function. For example, in some embodiments, a module includes a module configured to, when on an associated platform such as Figure 5A Software that performs corresponding functions when executed on a platform (as shown in ).

[0063] Figure 6 is a block diagram illustrating a virtualized radio access node 600 according to an embodiment of the disclosed subject matter. Figure 6 The concepts described can be similarly applied to other types of network nodes. Furthermore, other types of network nodes can have similar virtualized architectures. As used herein, the term "virtualized radio access node" refers to an implementation of a radio access node in which at least a portion of the functionality of the radio access node is implemented as a virtual component (e.g., via a virtual machine executing on a physical processing node in the network).

[0064] refer to Figure 6 , the radio access node 600 comprises Figure 5A Control system 520 is described.

[0065] Control system 520 is connected via network interface 515 to one or more processing nodes 620, which are coupled to or included as part of a network 625. Each processing node 620 includes one or more processors 605 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 610, and a network interface 615.

[0066] In this example, the functionality 545 of the radio access node 500A described herein is implemented at one or more processing nodes 620, or distributed across the control system 520 and one or more processing nodes 620 in any desired manner. In some embodiments, some or all of the functionality 545 of the radio access node 500A described herein is implemented as virtual components executed by one or more virtual machines implemented in a virtual environment hosted by the processing node 620. As will be understood by one of ordinary skill in the art, additional signaling or communication between the processing node 620 and the control system 320 is used in order to perform at least some of the desired functionality 545. As indicated by the dashed line, in some embodiments, the control system 520 may be omitted, in which case the radio unit 525 communicates directly with the processing node 620 via an appropriate network interface.

[0067] In some embodiments, the computer program includes instructions that, when executed by at least one processor, cause the at least one processor to perform the functions of a radio access node (e.g., radio access node 310 or 500A) or another node (e.g., processing node 620), the other node implementing one or more of the functions of a radio access node in a virtual environment according to any of the embodiments described herein.

[0068] Figure 7 is a flow chart illustrating a method according to an embodiment of the disclosed subject matter. The method may be performed by, for example, an apparatus comprising processing circuitry, a memory, and at least one transceiver configured to perform the relevant operations. The method is typically performed in a system comprising a joint traffic direction scheduler for a plurality of cells (e.g., a coordination group), and such a system may take any of a variety of alternative forms, such as in, for example, Figure 3 In such a system, the network shown in FIG. 1 can be configured in any suitable device (such as in, for example, Figures 3 to 6 ) to implement the specific steps of the method.

[0069] refer to Figure 7 The method includes collecting (or acquiring, identifying, obtaining, etc.) information for each cell (S705), determining a transmission direction to be used by the cell during at least one transmission time interval (TTI) based on the collected information (S710), and indicating the determined transmission direction to the cell (S715). The collected information typically includes TDD operation information, which is information associated with TDD operation performed by a wireless communication device or radio access node.

[0070] In certain related embodiments, indicating the determined transmission direction includes signaling that one or more of the multiple cells will use or will not use one or more predetermined TDD modes. The one or more predetermined TDD modes may indicate, for example, a predetermined ratio of downlink to uplink (DL:UL) transmission to be used by one or more of the multiple cells. The one or more predetermined TDD modes may include, for example, a full dynamic TDD mode, or a hybrid dynamic TDD mode that imposes scheduling restrictions within a portion of the dynamic TDD duration. In addition, the method may further include signaling the duration of the one or more predetermined TDD modes.

[0071] In certain related embodiments, indicating the determined transmission direction includes signaling that the predetermined TDD mode is to start or stop. In some such embodiments, the method may further include configuring the predetermined TDD mode independently of signaling that the predetermined TDD mode is to start or stop.

[0072] In certain related embodiments, indicating the determined transmission direction includes transmitting a bitmap for a set of upcoming TTIs that indicates, for each TTI, a transmission direction to be used by each of the cells.

[0073] In certain related embodiments, the method further includes one or more of the cells determining scheduling details for its own operation during one or more TTIs, wherein the scheduling details include one or more user equipments (UEs) to be scheduled and a modulation and coding scheme to be used.

[0074] In certain related embodiments, determining the transmission direction to be used by each of the cells during one or more TTIs comprises one or more of: (a) detecting a change in a buffer status of one or more of the cells, (b) detecting a buffer status of one or more of the cells, (c) detecting a change in a ratio of downlink to uplink (DL:UL) traffic in one or more of the buffers, and detecting a change in a quality of service (QoS) type to be applied to traffic associated with one or more of the cells. In some such embodiments, determining the transmission direction comprises detecting a buffer status change, and detecting the buffer status change comprises receiving periodic or event-based reports and determining whether one or more of the cells has upcoming traffic for both the uplink (UL) and downlink (DL) directions. In certain alternative embodiments, determining the transmission direction comprises detecting a change in a ratio of downlink to uplink traffic, and the method further comprises switching one or more TDD modes in response to the ratio crossing a threshold.

[0075] In certain related embodiments, the method further includes sending a first mode selection signal to the cell to trigger the use of the dynamic TDD mode when all cells will transmit data in the same TDD service direction during one or more TTIs; otherwise, when not all cells will transmit data in the same TDD service direction during one or more TTIs, sending a second mode selection signal to the cell to trigger the use of the static TDD mode.

[0076] In certain related embodiments, the method further includes one or more of the cells switching from a current time division duplex (TDD) mode to a new TDD mode based on the indication.

[0077] In certain related embodiments, the method further includes controlling the plurality of cells to switch between a dynamic time division duplex (TDD) mode and a static TDD mode, comprising: (a) determining a direction of traffic to be scheduled for each of the plurality of cells during one or more TTIs, (b) in response to determining that the direction of traffic for each of the plurality of cells during the one or more TTIs is the same, controlling the plurality of cells to operate according to the dynamic TDD mode, and (c) in response to determining that the direction of traffic for each of the plurality of cells during the one or more TTIs is different, controlling the plurality of cells to operate according to the static TDD mode. In some such embodiments, the method further includes configuring the static TDD mode for each of the plurality of cells according to a fixed downlink to uplink (DL:UL) ratio. In some such embodiments, the method further includes adjusting the DL:UL ratio according to long-term traffic characteristics of the wireless communication network. Additionally, in some such embodiments, the plurality of cells may be co-located.

[0078] While the disclosed subject matter has been presented above with reference to various embodiments, it will be understood that various changes in form and details may be made to the described embodiments without departing from the overall scope of the disclosed subject matter.

Claims

1. A method performed in a system including a joint traffic direction scheduler configured to coordinate time division duplex (TDD) transmission for a plurality of cells, the method comprising: Obtaining TDD operation information from each of the cells (S705); determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs) (S710); as well as indicating the determined transmission direction to the cell (S715); The method further includes controlling the plurality of cells to switch between a dynamic time division duplex (TDD) mode and a static TDD mode, which includes: determining a direction of traffic to be scheduled for each of the plurality of cells during one or more TTIs; In response to determining that the direction of the traffic is the same for each of the plurality of cells during the one or more TTIs, controlling the plurality of cells to operate according to a dynamic TDD mode; and In response to determining that the direction of the traffic is different for each of the plurality of cells during the one or more TTIs, the plurality of cells are controlled to operate according to a static TDD mode.

2. The method of claim 1 , wherein indicating the determined transmission direction comprises: One or more of the plurality of cells is signaled to use or not use one or more predetermined TDD modes.

3. The method of claim 2, wherein the one or more predetermined TDD modes indicate a predetermined ratio of downlink to uplink (DL:UL) transmission to be used by the one or more of the plurality of cells. The method of claim 2 , wherein the one or more predetermined TDD modes include a full dynamic TDD mode.

5. The method of claim 2, wherein the one or more predetermined TDD modes include: A hybrid dynamic TDD mode that imposes scheduling restrictions during a portion of the dynamic TDD duration.

6. The method of claim 2, further comprising: A duration of the one or more predetermined TDD modes is signaled.

7. The method of claim 1 , wherein indicating the determined transmission direction comprises: Signals that a predetermined TDD mode is to start or stop.

8. The method of claim 7, further comprising: The predetermined TDD mode is configured independently of signaling that the predetermined TDD mode is to be started or stopped.

9. The method of claim 1 , wherein indicating the determined transmission direction comprises: A bitmap for a set of upcoming TTIs is transmitted, the bitmap indicating, for each TTI, the transmission direction to be used by each of the cells.

10. The method of claim 1, further comprising: One or more of the cells determines scheduling details for its own operation during the one or more TTIs, wherein the scheduling details include one or more user equipments (UEs) to be scheduled and a modulation and coding scheme to be used.

11. The method of claim 1 , wherein determining the transmission direction to be used by each of the cells during the one or more TTIs comprises one or more of: detecting a buffer status change in one or more of the cells; detecting a buffer status of one or more of the cells; detecting a change in a ratio of downlink to uplink (DL:UL) traffic in one or more buffers; and A change in a type of quality of service (QoS) to be applied to traffic associated with one or more of the cells is detected.

12. The method of claim 11 , wherein determining the transmission direction comprises detecting the buffer status change, and detecting the buffer status change comprises: Receive periodic or event-based reports; as well as It is determined for both uplink (UL) and downlink (DL) directions whether one or more of the cells has upcoming traffic.

13. The method of claim 11, wherein determining the transmission direction comprises detecting a change in a ratio of downlink to uplink traffic, and the method further comprises switching one or more TDD modes in response to the ratio crossing a threshold.

14. The method of claim 1, further comprising: When all of the cells will transmit data in the same TDD service direction during the one or more TTIs, a first mode selection signal is sent to the cell to trigger the use of the dynamic TDD mode; otherwise, when not all of the cells will transmit data in the same TDD service direction during the one or more TTIs, a second mode selection signal is sent to the cell to trigger the use of the static TDD mode.

15. The method of claim 1, further comprising: One or more of the cells switches from a current time division duplex (TDD) mode to a new TDD mode based on the indication.

16. The method of claim 1, further comprising: A static TDD mode is configured for each of the plurality of cells according to a fixed downlink to uplink (DL:UL) ratio.

17. The method of claim 16, further comprising: The DL:UL ratio is adjusted according to long-term traffic characteristics of the wireless communication network.

18. The method of claim 1, wherein the plurality of cells are co-located.

19. An apparatus comprising a joint traffic direction scheduler configured to coordinate time division duplex (TDD) transmission for a plurality of cells, the apparatus comprising: processing circuitry, memory, and at least one transceiver, the processing circuitry, memory, and at least one transceiver being collectively configured to: Obtaining TDD operation information from each of the cells (S705); determining, based on the obtained TDD operation information, a transmission direction to be used by each of the cells during one or more transmission time intervals (TTIs) (S710); as well as indicating the determined transmission direction to the cell (S715); The processing circuit, the memory and the at least one transceiver are further configured to control the plurality of cells to switch between a dynamic time division duplex (TDD) mode and a static TDD mode, comprising: determining a direction of traffic to be scheduled for each of the plurality of cells during one or more TTIs; In response to determining that the direction of the traffic is the same for each of the plurality of cells during the one or more TTIs, controlling the plurality of cells to operate according to a dynamic TDD mode; and In response to determining that the direction of the traffic is different for each of the plurality of cells during the one or more TTIs, the plurality of cells are controlled to operate according to a static TDD mode.

20. The apparatus of claim 19, wherein indicating the determined transmission direction comprises: One or more of the plurality of cells is signaled to use or not use one or more predetermined TDD modes.

21. The apparatus of claim 20, wherein the one or more predetermined TDD modes indicate a predetermined ratio of downlink to uplink (DL:UL) transmission to be used by the one or more of the plurality of cells.

22. The apparatus of claim 20, wherein the one or more predetermined TDD modes include a full dynamic TDD mode.

23. The apparatus of claim 20, wherein the one or more predetermined TDD modes include: A hybrid dynamic TDD mode that imposes scheduling restrictions during a portion of the dynamic TDD duration.

24. The apparatus of claim 20, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to signal a duration of the one or more predetermined TDD modes.

25. The apparatus of claim 19, wherein indicating the determined transmission direction comprises: Signals that a predetermined TDD mode is to start or stop.

26. The apparatus of claim 25, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to configure the predetermined TDD mode independently of signaling that the predetermined TDD mode is to start or stop.

27. The apparatus of claim 19, wherein indicating the determined transmission direction comprises: A bitmap for a set of upcoming TTIs is transmitted, the bitmap indicating, for each TTI, the transmission direction to be used by each of the cells.

28. The apparatus of claim 19, wherein determining a transmission direction to be used by each of the cells during the one or more TTIs comprises one or more of: detecting a buffer status change in one or more of the cells; detecting a buffer status of one or more of the cells; detecting a change in a ratio of downlink to uplink (DL:UL) traffic in one or more buffers; and A change in a type of quality of service (QoS) to be applied to traffic associated with one or more of the cells is detected.

29. The apparatus of claim 28, wherein determining the transmission direction comprises detecting the buffer status change, and detecting the buffer status change comprises: Receive periodic or event-based reports; as well as It is determined for both uplink (UL) and downlink (DL) directions whether one or more of the cells has upcoming traffic.

30. The apparatus of claim 28, wherein determining the transmission direction comprises detecting a change in a ratio of downlink to uplink traffic, and wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to switch one or more TDD modes in response to the ratio crossing a threshold.

31. An apparatus as claimed in claim 19, wherein the processing circuit, memory and at least one transceiver are also jointly configured to send a first mode selection signal to the cell to trigger the use of the dynamic TDD mode when all of the cells will transmit data in the same TDD service direction during the one or more TTIs, otherwise, when not all of the cells will transmit data in the same TDD service direction during the one or more TTIs, send a second mode selection signal to the cell to trigger the use of the static TDD mode.

32. The apparatus of claim 19, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to configure a static TDD mode for each of the plurality of cells according to a fixed downlink to uplink (DL:UL) ratio.

33. The apparatus of claim 32, wherein the processing circuitry, memory, and at least one transceiver are further collectively configured to adjust the DL:UL ratio based on long-term traffic characteristics of a wireless communication network.

34. The apparatus of claim 19, wherein the plurality of cells are co-located.

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