Abstract:
Systems and techniques for negotiated control of multipoint coordination. A first device (such as a central entity or base station) signals a second device regarding its desire to assert control over, or readiness to accept control by, the second device, with respect to coordinated radio transmission. The negotiation may include, for example, acceptance of control, rejection of control, specification of resources subject to or exempt from control, and priority-based decisions to override or refrain from overriding rejections. Coordinated transmission is then conducted based on the outcome of the negotiation.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to wireless network communication. More particularly, the invention relates to improved systems and techniques for multi-cell coordinated scheduling. 
       BACKGROUND 
       [0002]    Efficiency in wireless network communication is an important objective, becoming more and more important as the number of users and their demands for service continue to increase. Network operators wish to minimize the infrastructure they must provide. In addition, the frequency bands dedicated to wireless network communication are a finite and valuable resource, and network operators are constantly working to use this resource efficiently in order to prevent the available frequencies from becoming oversaturated. If frequencies are oversaturated, network elements will interfere with one another. For example, transmission by one base station may interfere with transmission by an adjacent base station. In order to prevent interference. Network operators may take into account the presence of nearby transmitters in making scheduling decisions, and transmitters (such as base stations) may coordinate their transmissions so as to avoid interference with one another. 
       SUMMARY 
       [0003]    In one embodiment of the invention, an apparatus comprises at least one processor and memory storing a program of instructions. The memory storing the program of instructions is configured to, with the at least one processor, cause the apparatus to at least, in response to a control assertion request to allow a controlling entity to control coordinated radio transmission by the apparatus, respond with an acceptance or denial of the request and, if the response is an acceptance, perform coordinated transmission under control of the controlling entity. 
         [0004]    In another embodiment of the invention, a method comprises, in response to a control assertion request to allow a controlling entity to control coordinated radio transmission by a base station, responding with an acceptance or denial of the request and, if the response is an acceptance, performing coordinated transmission under control of the controlling entity. 
         [0005]    In another embodiment of the invention, a non-transitory computer readable medium stores a program of instructions. Execution of the program of instructions by at least one processor configures an apparatus to at least in response to a control assertion request to allow a controlling entity to control coordinated radio transmission by the apparatus, respond with an acceptance or denial of the request and, if the response is an acceptance, perform coordinated transmission under control of the controlling entity. 
         [0006]    In another embodiment of the invention, an apparatus comprises at least one processor and memory storing a program of instructions. The memory storing the program of instructions is configured to, with the at least one processor, cause the apparatus to at least send a control assertion request to a base station, requesting control of coordinated radio transmission by the base station and, in response to acceptance of the request by the base station, send one or more requests to the base station to mute transmission. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  illustrates a wireless network according to an embodiment of the present invention; 
           [0008]      FIGS. 2-6  illustrate signaling between and operations of elements carrying out embodiments of the present invention; 
           [0009]      FIG. 7  illustrates details of elements according to an embodiment of the present invention; and 
           [0010]      FIG. 8  illustrates a process according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of the present invention address improvements to coordinated multipoint communication—specifically, multi-cell coordinated scheduling. Various approaches to multi-cell coordinated scheduling are in development or in use in cellular communication systems. These include centralized and decentralized approaches. Base stations may coordinate transmission order to avoid interference with one another. One mechanism is to mute transmission requiring particular resources or at a particular time (with muting being defined as a zero-power transmission or interval), while another mechanism is to transmit at reduced power in particular resources or time periods. In a decentralized approach to coordinated scheduling, a cell, which may be represented by a base station, makes its own decision on muting (that is, refraining from transmitting or scheduling transmission from one or more of its user devices). In networks operating according to standards of the third generation partnership project (3GPP), 3GPP long term evolution (LTE) and 3GPP LTE-advanced (LTE-A), a base station may be implemented as an eNodeB (eNB), with an eNB serving user equipments (UEs) within its coverage area. 
         [0012]    In a network or portion of a network that follows a centralized approach, a central entity makes decisions about whether a particular base station should mute, and issues an appropriate request to the base station (such as an eNB). A base station may be designed for centralized control (such a base station may be referred to for convenience as a centrally controlled base station) or may be designed for decentralized operation (such a base station may be referred to as an autonomous base station —meaning that the base station&#39;s coordination decisions are autonomous). A centrally controlled base stations will perform coordination as directed by the central entity, and an autonomous base station will generally ignore requests by the central entity. In some cases, a base station may respond to requests from a central entity during most of its operation, but, under some circumstances, ignore requests and make its own decisions. Such circumstances may include, for example, handing of high priority traffic using specified resources. Such a base station may be referred to for convenience as a partially autonomous base station. The various elements participating in and controlling coordinated transmission may be referred to as nodes, and one or more of the nodes may conveniently be referred to as an independent node, which may control and direct other nodes, but which may not itself serve a user device. In one or more embodiments of the invention, the central entity may be an independent node. 
         [0013]    In an environment in which centrally controlled base and autonomous base stations are both present, such mixing may lead to conflicts, as a central entity sends requests to both autonomous base stations and centrally controlled base stations, and the two types of base stations conflict because the behavior of the autonomous base station is unpredictable. 
         [0014]    In one or more embodiments of the invention, therefore, a unified signaling procedure is employed that encompasses centrally controlled and autonomous coordination. Various embodiments of the unified signaling procedure prevent conflicts involving interaction between a central entity and an autonomous base station; interaction between a central entity and a centrally controlled base station; interaction between an autonomous base station and a centrally controlled base station; interaction between two autonomous base stations; and interaction between a central entity and a centrally controlled base station that behaves autonomously with respect to specified resources. 
         [0015]      FIG. 1  illustrates a network  100  according to an embodiment of the present invention. The network  100  comprises base stations implemented as eNBs  102 A and  102 B, defining cells  104 A and  104 B, respectively, and communicating with a central entity  106 . The eNBs  102 A and  102 B serve a plurality of UEs  108 A- 108 E, which may move between cells or be turned off or otherwise disconnected to the network. Other UEs may be introduced to the network as they are turned on or moved in from elsewhere. One or more network nodes, such as the eNBs  102 A and  102 B or the central entity  106 , may engage in coordinated scheduling in order to reduce interference. 
         [0016]    In one or more embodiments of the invention, network nodes involved in such coordination negotiate with one another. In one example, a requesting node (such as the central entity  106 ) needing to scheduling decisions for a responding node (such as one of the eNBs  102 A or  102 B) indicates to the second node that it needs to make such decisions and issue requests to the second node to take such action. The second node responds to the first node by indicating that it will or that it will not accept such requests. It will be noted that whether the responding node is to indicate acceptance or denial can be based on any criteria desired. For example, the responding node may indicate acceptance to a request from a first requesting node, or may indicate denial to a second responding node, or may generally accept requests but may deny requests and make decisions autonomously with respect to specific traffic categories or resources. For example, either the requesting or the responding node, or both, may assign specific physical resource blocks (PRBs) to a high priority or protected category, and the requesting node may decline to request, or the responding node may decline to accept, centrally controlled scheduling with respect to those blocks. 
         [0017]    If a response is a denial, various embodiments of the invention provide for mechanisms to specify which node&#39;s indications will take priority—that is, whether denials will be accepted. If the requesting node is given priority, the responding node will be forced to accept its requests, and if the responding node is given priority, its denials will be accepted. It will be recognized that assignment of priority can be based on any criteria desired, and can change. For example, nodes can be ranked, so that a first central entity (for example) may be able to override a denial by a specific responding node, while a second central entity may be unable to override a denial by the same responding node. Responding nodes may be similarly ranked. Alternative approaches may involve the assignments of weightings to nodes, so that a higher weighted node may be given priority over a lower weighted node. Priority decisions can be made per-transaction, or criteria may be defined so that nodes have higher priority with respect to particular resources or traffic categories than with other resources or traffic categories. For example, specific physical resource blocks (PRBs) may belong to a high priority or protected category, with higher weighting assigned to use of those blocks by the responding node. 
         [0018]    In one or more embodiments of the invention, various entities, such as the eNB  102 A, the eNB  102 B, and the central entity, communicate as governed by a specified signaling framework designed to provide for support of both centralized and distributed coordination. By pre-negotiation or operation and maintenance configuration, the decision maker for coordination interactions is specified. Selection of the decision maker can be accomplished according to any criteria desired—for example, identifying an entity as dominant, choosing a dominant entity based on conditions such as traffic levels, or specifying decision makers for each radio resource unit (for example, frequency domain resources such as physical resource blocks (PRBs) or resource block groups (RBGs), or time domain resources such as transmission time intervals (TTIs). As described in greater detail below, coordination may be managed in a hand-shaking coordination request (request and response). The decision maker may be the node making the request or the node receiving the request. 
         [0019]    For radio resource units (for example, individual PRBs or RBGs, or alternatively across the whole bandwidth), if the requesting entity is the decision maker, the receiving eNB must respond as requested. 
         [0020]    In cases in which the eNB receiving a request has the final authority, the receiving eNB may reject the request if needed: for example, making best efforts to fulfill a request but not guaranteeing that the request will be fulfilled. Such an approach is useful if a radio resource has been reserved for a specific purpose—for example, if an eNB has configured an SPS transmission on specified PRBs, or PRBs have been configured as a physical download control channel. In another typical case, the receiving eNB may have been designed for autonomous or decentralized operation, making its own determination of its coordination action (such as muting) so that it would not generally accept requests from another node. As discussed in greater detail below, relative priorities between nodes can be adjusted based on factors such as current load and traffic type. A network such as the network  100  can therefore exist as a hybrid between centralized and autonomous communication. 
         [0021]      FIG. 2  illustrates a diagram  200  presenting signaling and operations by and between a requesting node, taking the form of a central entity  202 , and a responding node, taking the form of an eNB  204 . The central entity  202  issues a control assertion message  206 , notifying the eNB  204  of its intention to make centrally-controlled scheduling requests—either in general, or on a more limited basis, such as per-PKB or per-RBG, or with most resources being subject to central control, but with specified resources being managed autonomously. The eNB  204  responds to the control assertion message  206  with a control acceptance message  208 , indicating its agreement to accept centrally controlled scheduling requests—again, either in general or on a more limited basis either general or on a more limited basis. The central entity may then make requests  210  to the eNB  204 , which may then respond with acknowledgements  212 . At an appropriate subsequent time, the eNB  204  may send a control acceptance update message  214  to the central entity  202 , indicating a modification of the requests to which it will respond. At further appropriate subsequent times, the central entity  202  may send a control assertion update message  216  to the eNB  204 , indicating a change in the nature of requests it will make (for example, changing the resources that may be subject to a request. The eNB  204  may respond with a modification acceptance message  218 . 
         [0022]      FIG. 3  illustrates a diagram  300 , showing interactions between and operations by the central entity  202  and the eNB  204 , with the eNB  204  initiating the negotiation. The eNB  204  sends a control acceptance readiness message  306  to the central entity  202 , indicating agreement to accept requests. The central entity  202  responds with a control assertion readiness message  308 . The central entity  202  then proceeds to make requests  310 , and the eNB  204  responds with acknowledgements  312 . As needed, the eNB  204  sends a control acceptance update message  314 , indicating a change to its agreement to accept requests, and the central entity  202  responds with an acknowledgement  316 . Similarly, as needed, the central entity  202  sends a control assertion update message  318 , and the eNB  204  responds with an acknowledgement  320 . 
         [0023]      FIG. 4  illustrates a diagram  400  presenting operations of and messages between a central entity  402  and an eNB  404 , designed for decentralized operation. The central entity  402  sends a control assertion message  406  to the eNB  404 , which responds to the control assertion message  406  with a control decline message  408 . The central entity  402  makes a determination  410  of its priority with respect to the eNB  404 , and if ( 412 ) the central entity  202  has a higher priority, it sends an override message  414  to the eNB  404 , which responds with an override acknowledgement  416 , and then sends requests  418  which are then responded to with acknowledgements  420 . If ( 422 ) the central entity  202  has a lower priority than does the eNB  204 , the central entity  402  makes no further decisions regarding actions to be performed by the eNB  204 . 
         [0024]      FIG. 5  illustrates a diagram  500  presenting operations of and messages between a first enB  502  and a second eNB  504 , with the first eNB  502  being designed for centralized operation and the second eNB  504  being designed for decentralized operation. The first eNB  504  sends a control acceptance message  506 , indicating a willingness to accept control, but the second eNB  506  responds with a control assertion decline message  508 , indicating an unwillingness to exercise control. The second eNB  504  makes ( 510 ) no attempt to exert control and the first eNB optionally seeks ( 512 ) another entity for centralized control. 
         [0025]      FIG. 6  illustrates a diagram  600  presenting operations of and messages between a first enB  602  and a second eNB  604 , with both of the eNBs  602  and  604  being designed for decentralized operation. The first eNB  604  sends a control assertion rejection message  606 , indicating an unwillingness to assert control, and the second eNB  606  responds with a control rejection message  608 , indicating an unwillingness to accept control. 
         [0026]    Reference is now made to  FIG. 7  for illustrating a simplified block diagram of a base station, such an eNB  700  and a user device, such as a UE  750 , suitable for use in practicing exemplary embodiments of this invention. In  FIG. 7  an apparatus, such as the eNB  700 , is adapted for communication with other apparatuses having wireless communication capability, such as the UE  750 . 
         [0027]    The eNB  700  includes processing means such as at least one data processor (DP)  1204 , storing means such as at least one computer-readable memory (MEM)  706  storing data  708  and at least one computer program (PROG)  710  or other set of executable instructions, communicating means such as a transmitter TX  712  and a receiver RX  714  for bidirectional wireless communications with the UE  750  via one or more antennas  716 . 
         [0028]    The UE  750  includes processing means such as at least one data processor (DP)  754 , storing means such as at least one computer-readable memory (MEM)  756  storing data  758  and at least one computer program (PROG)  760  or other set of executable instructions, communicating means such as a transmitter TX  762  and a receiver RX  764  for bidirectional wireless communications with the eNB  1200  via one or more antennas  766 . 
         [0029]    At least one of the PROGs  710  in the eNB  700  is assumed to include a set of program instructions that, when executed by the associated DP  704 , enable the device to operate in accordance with the exemplary embodiments of this invention, as detailed above. In these regards the exemplary embodiments of this invention may be implemented at least in part by computer software stored on the MEM  706 , which is executable by the DP  704  of the eNB  700 , or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Similarly, at least one of the PROGs  760  in the UE  750  is assumed to include a set of program instructions that, when executed by the associated DP  754 , enable the device to operate in accordance with the exemplary embodiments of this invention, as detailed above. Electronic devices implementing these aspects of the invention need not be the entire devices as depicted at  FIG. 1  or  FIG. 7  or may be one or more components of same such as the above described tangibly stored software, hardware, firmware and DP, or a system on a chip SOC or an application specific integrated circuit ASIC. 
         [0030]    In general, the various embodiments of the UE  750  can include, but are not limited to personal portable digital devices having wireless communication capabilities, including but not limited to cellular telephones, navigation devices, laptop/palmtop/tablet computers, digital cameras and music devices, and Internet appliances. 
         [0031]    Various embodiments of the computer readable MEM  706  and  756  include any data storage technology type which is suitable to the local technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DP  704  and  754  include but are not limited to general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and multi-core processors. 
         [0032]      FIG. 8  illustrates a process  800  according to an embodiment of the present invention. At block  802 , a first and a second device engage in negotiation to determine whether the first device will control, or will be controlled by, the second device with respect to coordinated transmission. The devices may be, for example, a central entity or a base station, and the negotiation may take the form of an assertion of control and an acceptance or denial, a notification that one device is ready to accept control and an acceptance or denial of assertion or control, or a notification that a device is not ready to accept control, and an acknowledgement. At block  804 , coordination proceeds according to the negotiation. 
         [0033]    While various exemplary embodiments have been described above it should be appreciated that the practice of the invention is not limited to the exemplary embodiments shown and discussed here. Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description. 
         [0034]    Further, some of the various features of the above non-limiting embodiments may be used to advantage without the corresponding use of other described features. 
         [0035]    The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.