Patent Publication Number: US-2010110886-A1

Title: Automated local spectrum usage awareness

Description:
TECHNICAL FIELD 
     The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to wireless communication system that use uncoordinated spectrum deployments possibly in combination with flexible spectrum usage. 
     BACKGROUND 
     This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section. 
     The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows: 
     3GPP third generation partnership project
 
ADSL asymmetric digital subscriber line
 
AP access point (base station)
 
BS base station
 
BW bandwidth
 
DL downlink (AP towards UT)
 
eNB EUTRAN Node B (evolved Node B)
 
EPC evolved packet core
 
EUTRAN evolved UTRAN (LTE)
 
FSU flexible spectrum use
 
LTE long term evolution
 
MAC medium access control
 
MM/MME mobility management/mobility management entity
 
MS mobile station
 
OFDMA orthogonal frequency division multiple access
 
PDCP packet data convergence protocol
 
PDU protocol data unit
 
PHY physical
 
RLC radio link control
 
RRC radio resource control
 
SGW serving gateway
 
TDD time division duplex
 
UE user equipment
 
UT user terminal
 
UL uplink (UT towards AP)
 
UTRAN universal terrestrial radio access network
 
     The specification of a communication system known as evolved UTRAN (EUTRAN, also referred to as UTRAN LTE or as EUTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA (single carrier, frequency division multiple access). 
     One specification of interest in this regard is 3GPP TS 36.300, V8.5.0 (2008-05), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8), which is incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8, or simply as Rel-8. Note that this is a stage 2 specification, and may not exactly describe the system as it is currently expected to be implemented. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the entire Release 8 LTE system. 
     Of particular interest herein are the further releases of 3GPP LTE targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Of additional interest herein are local area (LA) deployment scenarios using a scalable bandwidth (of up to, for example, 100 MHz) with flexible spectrum use (FSU). This system concept may be referred to herein for convenience as LTE-A. 
     Reference can also be made to 3GPP TR 36.913, V8.0.0 (2008-06), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E-UTRA (LTE-Advanced) (Release 8), incorporated by reference herein in its entirety. 
     As cell sizes become smaller and data rates increase, the limited availability of spectrum drives wireless systems to use higher center frequencies. The use of smaller cells makes it more difficult to provide outdoor to indoor coverage transitions, and it also tends to increase the number of access points. It can be expected that a need will arise to handle deployments of a much larger number of access points, in particular in locations with restricted access (such as homes and offices). 
     This development has lead to a need to standardize small access points for cellular systems, sometimes referred to as “pico” or “femto” access points (e.g., having uncoordinated coverage distances measured in, for example, meters or tens of meters), in order to support high data rates in small areas. Such system architectures can be contrasted to current (coordinated deployment) cellular systems, and are typically based on privately owned and installed uncoordinated deployments. Such uncoordinated deployments are likely to consist of separate, overlapping networks, creating a demand for an approach that enables more than one network to co-exist in the same frequency band. 
     The use of FSU for future wireless systems is intended to provide spectrum sharing between the parties that participate actively in the communication process. A goal is to utilize the spectrum in an as optimal a manner as possible in order to achieve a high use flexibility of the radio resources. 
     In uncoordinated deployments there is no overall control over the placement of access points, nor is there any expectation of frequency planning or any other traditional network planning methods. As a result, the transmissions of neighboring access points may cause severe interference, even though there would be unused radio resources available. One result is a degradation of overall system capacity. 
     In LTE radio resource management is arranged within a single network and utilizes the X2 interface between base stations (eNBs). Reference in this regard may be made to  FIG. 1 , which reproduces  FIG. 4.1  of 3GPP TS 36.300, and shows the overall architecture of the EUTRAN (LTE) system. The EUTRAN system includes eNBs that provide the EUTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE. The eNBs are interconnected with each other by means of the above-mentioned X2 interface. The eNBs are also connected by means of an S1 interface to an EPC, more specifically to a MME (Mobility Management Entity) by means of a S1 MME interface and to a Serving Gateway (SGW) by means of a S1 interface. The S1 interface supports a many to many relationship between MMEs/Serving Gateways and eNBs. 
     However, the inter-access point interface does not exist when cells belong to different networks, or are based on an ADSL backbone (femto BS). 
     FSU utilizing over the air communication between BSs has been previously considered. For example, reference can be made to IST-4-027756 WINNER II, D6.13.14, version 1.1, WINNER II System Concept Description, G. Auer et al. Jan. 18, 2008. However, this approach presents at least one problem in that a communication channel between BSs does not necessarily exist, even though a neighboring BS may be interfering with terminals of the BS. 
     SUMMARY 
     The foregoing and other problems are overcome, and other advantages are realized, by the use of the exemplary embodiments of this invention. 
     A first aspect of the exemplary embodiments of this invention provides a method that comprises transmitting a beacon from a first access node for reception by a first user terminal that is associated with the first access node and also by a second user terminal that is associated with a second access node; and receiving feedback from the first user terminal that is associated with the first access node, the feedback comprising information obtained by the first user terminal from a beacon received from the second access node. 
     Another aspect of the exemplary embodiments of this invention provides a computer-readable memory medium that stores program instructions, the execution of which result in performing operations that comprise transmitting a beacon from a first access node for reception by a first user terminal that is associated with the first access node and also by a second user terminal that is associated with a second access node; and receiving feedback from the first user terminal that is associated with the first access node, the feedback comprising information obtained by the first user terminal from a beacon received from the second access node. 
     Another aspect of the exemplary embodiments of this invention provides an apparatus that comprises a controller configured to operate with a wireless transmitter and a wireless receiver to transmit a beacon for reception by a first user terminal that is associated with the apparatus and also by a second user terminal that is associated with a second apparatus. The controller is further configured to receive feedback from the first user terminal that is associated with the apparatus, the feedback comprising information obtained by the first user terminal from a beacon received from the second apparatus. 
     Yet another aspect of the exemplary embodiments of this invention provides a method that comprises receiving at a user terminal a first beacon from a first access node that is associated with the user terminal and a second beacon from a second access node that is not associated with the user terminal, where the first and second beacons each comprise information descriptive of radio resources that are used by the access node that transmits the beacon. The method further includes transmitting feedback from the user terminal to the first access node, the feedback comprising at least the information descriptive of the radio resources that are used by the second access node. 
     Yet another aspect of the exemplary embodiments of this invention provides an apparatus that comprises a controller embodied in a user terminal and configured to operate with a wireless transmitter and a wireless receiver to receive a first beacon from a first access node that is associated with the user terminal and a second beacon from a second access node that is not associated with the user terminal. The first and second beacons each comprise information descriptive of radio resources that are used by the access node that transmits the beacon. The controller is further configured to transmit feedback to the first access node, the feedback comprising at least the information descriptive of the radio resources that are used by the second access node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the attached Drawing Figures: 
         FIG. 1  reproduces  FIG. 4  of 3GPP TS 36.300, and shows the overall architecture of the EUTRAN system. 
         FIG. 2  shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention. 
         FIG. 3  is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, in accordance with the exemplary embodiments of this invention. 
         FIG. 4  is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, further in accordance with the exemplary embodiments of this invention. 
     
    
    
     DETAILED DESCRIPTION 
     Uncoordinated deployments would benefit significantly from the application of self-organizing flexible spectrum use, in practice providing some degree of automated network optimization for the system. 
     Reference can be made to  FIG. 2  which shows a plurality of APs  10  and UTs  20 . The APs  10 , each of which may also be referred to without a loss of generality as an access node (AN) or as a base station (BS), may be associated with different radio access networks, and may be considered as neighbors, enabling a single UT  20  to receive transmissions from its own AP  10  as well as from a neighboring AP  10 . The UTs  20  may also be referred to, without a loss of generality, as mobile nodes (MNs), or as UEs, or as MSs. The AP  10  will generally include at least one controller  10 A, such as at least one data processor, possibly a digital signal processor (DSP), at least one memory  10 B and at least one radio frequency or other type of wireless transceiver  10 C for connection with at least one antenna  10 D. The memory  10 B, which may be viewed as a computer-readable memory medium, stores in part computer program instructions that when executed enable the AP  10  to function in accordance with the exemplary embodiments of this invention. The UT  20  will also generally include at least one controller  20 A, such as at least one data processor, possibly a DSP, at least one memory  20 B and at least one radio frequency or other type of wireless transceiver  20 C for connection with at least one antenna  20 D. The memory  20 B, which may also be viewed as a computer-readable memory medium, stores in part computer program instructions that when executed enable the UT  20  to function in accordance with the exemplary embodiments of this invention. 
     In  FIG. 2  the AP  10  is assumed to be associated with a first network, while the AP  10 * (and UT  20 *) is assumed to be associated with a second, different network. Each AP  10  may be assumed to establish a cell that defines the communication coverage area associated with the AP  10 . The cells may be considered in some embodiments to be pico cells or femto cells, i.e., cells having smaller coverage areas than cells associated with conventional cellular communication systems (which may have dimensions measured in kilometers or tens of kilometers). 
     The exemplary embodiments of this invention utilize in-band broadcast control information that is used to locally monitor the spectrum usage situation. Broadcast messages, also referred to herein as beacons  30 , are received by UTs  20  of the same network, as well as by UTs  20  belonging to different, neighboring networks. Each UT  20  further makes and processes measurements to create an understanding of the current spectrum usage situation in the current location of the UT  20 . The UT  20  transmits feedback  40  to its own AP  10  in order to create awareness of the spectrum usage over the entire cell. 
     The transmission of the broadcast control information “in-band” implies that the broadcast control information, referred to herein for convenience as the beacon  30 , is transmitted in a same frequency band that is used for transmitting communication data from the access point  10  to the user terminals  20 . Note, however, that in other embodiments the beacon  30  could be transmitted out-of-band, i.e., in a frequency band not used for transmitting control data to the user terminals  20 . 
     The exemplary embodiments of this invention provide a method of creating an understanding of the local spectrum usage situation, and thus provide local awareness for the AP  10 . The mechanism for creating the local awareness is based on the broadcast control messages, i.e., the beacons  30 , which are transmitted by APs  10  and received by UTs  20 , and on the resulting feedback  40  from the UTs  20 . 
     The beacons  30  may be used to identify neighbor cells, and which radio resources the neighbor cells are using. The beacons  30  may also be used for estimating how much interference the neighbor cells are causing (how close they are). 
     As employed herein a radio resource can include, as non-limiting examples, one or more of frequency channels, time slots and/or spreading codes, as well as the use of some resource, such as a frequency channel, for some certain duration, depending on the specifics of the underlying radio access technology. 
     In order to achieve these goals, a particular beacon  30  includes at least an indication of the resources in use. Note that a particular beacon  30  may also include, as optional information, one or more of the cell identity (which could be received from another channel); and a reference signal for supporting measurements made by the UTs  20  (which may instead be sent via some other mechanism by the system). The reference signal is preferably a known (to the UT  20 ) type of signal transmitted by the AP  10  that can be used by the UT  20  for at least one of synchronization, detection and/or channel estimation purposes. 
     Optionally, a beacon  30  may also include information descriptive of bandwidth demand estimates (i.e., an estimated future bandwidth required by the cell (AP  10 ) to serve the current traffic load of the cell). The estimate may be in the form of more/none/less, as one non-limiting example. 
     Optionally, a beacon  30  may also include information descriptive of an UL/DL switching point. The use of a flexible UL/DL TDD switching point allows adjusting the balance between UL and DL resources (i.e., what portion of the frames are used for the UL and for the DL). This factor may impact the amount of interference if neighboring cells do not have synchronized and identical frame structures. 
     Optionally, a beacon  30  may also include information that is related to fairness of resource use amongst the APs  10 . The fairness of resource usage may be derived through various signaling mechanisms such as, but not limited to, trading negotiations, auctions and usage history. 
     Optionally, a beacon  30  may also include information descriptive of any neighbor APs detected by the AP  10 . This information refers to the possibility to forward information (related to one or more of the foregoing beacon  30  contents) that is received from neighboring APs  20 . This feature enables disseminating the system-related information even further than relying solely on the feedback  40  received from the UTs  20 . 
     A UT  20  receives beacons  30  from one or more neighboring cells (neighboring APs  10 ) and gathers the information specific to the physical location of the UT  20 . The UT  20  then transmits information to the AP  10  that the UT  20  is currently connected to. The beacons  30  received by a UT  20  connected to a particular AP  10 , and the resulting information sent as feedback  40  to the AP  10 , enable the AP  10  to achieve a collective understanding of the radio resource allocations made by itself for its associated cell, as well as radio resource allocations made by other neighboring APs that affect (or overlap) the cell of the AP  10 . The UT  20  feedback  40  reports may contain compressed information of the local situation, such as the available spectrum resources. 
     The AP  10  operates in part to estimate if the resources currently used by it are sufficient for operation. If the AP  10  finds that it has excess resources, i.e., more resources than are currently necessary to support communications with the UT or UTs  20  within its cell, the AP  10  may release some or all of the excess resources and modify its own beacon  30  accordingly (i.e., to announce that resource(s) released are now free for use by other APs  10 ). If the current resources of the AP  10  are sufficient, and there are no excess resources available, then no action need be taken. If there is a need for additional resources at the AP  10  then the AP  10  takes action to obtain additional resources. 
     If the local awareness (obtained from the feedback  40  from UTs  20 ) indicates that free resources are available, the AP  10  may reserve the resources by modifying resource reservation information in its transmitted beacon  30  to include the new resources. Note that this resource reservation information could be the same as the “resources in use” information discussed above or, alternatively, it could be additional (optional) beacon  30  information that indicates a future intention of the AP  10  with respect to these resources, in addition to the current reservation. Otherwise, the AP  10  waits until resources become available due to a resource release mechanism, or a conflict resolution mechanism may be used to obtain additional resources. 
     Based on the foregoing it should be appreciated that an aspect of these exemplary embodiments of the invention is providing a local awareness scheme that enables gaining knowledge of the spectrum situation in a local area (a neighborhood), in order to enable self-organizing flexible spectrum use. The local awareness defines which resources are clear to transmit for an AP  10  and which resources are clear for receiving for the AP  10 . In addition, the local awareness may contain information of neighboring APs  10  and their future intentions. 
     The beacons  30  are transmitted only by an AP  10 , and the beacon information is received by a UT  20 , which then processes and forwards the awareness information to the AP  10 . 
     In general, a beacon frame may be periodically transmitted by an AP  10 . Alternatively, the beacon  30  can be embedded into a frame or frames. Separate (possibly dedicated) interference-protected resources may be used for transmission of a beacon  30 . 
     A particular beacon  30  may, in a non-limiting embodiment, contain the cell identification (e.g., using 8 bits) and the resources in use (e.g., using 64 bits). History information may also be present, such as a priority index (e.g., using 6 bits). In addition, a beacon  30  may contain information concerning neighbor APs  10 , and possibly a reference signal for synchronization purposes. The AP  10  may also indicate its future intentions, such as by providing a traffic prediction and/or information regarding upcoming resource reservations. 
     Reference with regard to the priority index may be made to U.S. Provisional Patent Application No. 61/______, filed on even date with this patent application, and entitled “Priority Based Technique to Achieve Fairness for Radio Resource Sharing, Elena Virtej, Jari P. Lundén and Antti S. Sorri, incorporated by reference herein. 
     One result of using the beacons  30  is that local awareness is gained in the UT  20 . This local awareness may include, but is not limited to, neighbor AP  10  detection, occupied channels, interference levels on resources, future intent of neighbor APs  10  and their status and priorities, the TDD frame structure and the UL/DL switching point of neighbor APs  10  (if TDD is used as the radio access technology), as well as the signal strength and channel quality of the associated AP  10 . 
     What may be thus understood at the UT  20  can include, but is not limited to, which resource(s) are available, which resource(s) would be best to use, which resource(s) cannot be used, resource swapping opportunities and/or whether one or more neighbor APs  10  intends to change (reduce or increase) their resource allocations. 
     Local awareness at the AP  10  can include based on AP  10  measurements, what (UL) resource(s) the AP  10  sees interference on, and can further include the feedback  40  from the UTs  20 , own traffic load and where to transmit and schedule the UL. 
     There are a number of advantages and technical features made possible by the use of these exemplary embodiments. 
     For example, the use of FSU can greatly improve the spectral efficiency in those situations where deployments are uncoordinated, and traditional frequency planning is not possible or difficult to implement. FSU also enables the network to use higher peak data rates, since instantaneously the UT  20  can have access to a wider spectrum than in a conventional block division of spectrum. In order to make the use of FSU technically feasible, the exemplary embodiments of this invention provide awareness of the spectrum usage situation in a distributed, automated manner. 
     In general, the exemplary embodiments of this invention may be implemented at least in part by computer software executable by the controllers  10 A,  20 A, or by hardware, or by a combination of software and hardware (and firmware). The controllers  10 A,  20 A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi-core processor architecture, as non-limiting examples. The computer readable memories  10 B and  20 B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. 
     In general, the various embodiments of the UT  20  can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions. 
     The exemplary embodiments may include various integrated circuits and, in a most compact case, may all be embodied physically within a single chip. 
     Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a method, apparatus and computer program(s) to enhance local awareness of spectrum usage and other factors of a wireless communication system. 
       FIG. 3  is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, in accordance with the exemplary embodiments of this invention. In accordance with these exemplary embodiments a method performs, at Block  3 A, a step of transmitting a beacon from a first access node for reception by a first user terminal that is associated with the first access node and also by a second user terminal that is associated with a second access node. The method further performs, at Block  3 B, a step of receiving feedback from the first user terminal that is associated with the first access node, the feedback comprising information obtained by the first user terminal from a beacon received from the second access node. 
       FIG. 4  is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, further in accordance with the exemplary embodiments of this invention. In accordance with these exemplary embodiments a method performs, at Block  4 A, a step of receiving at a user terminal a first beacon from a first access node that is associated with the user terminal and a second beacon from a second access node that is not associated with the user terminal, where the first and second beacons each comprise information descriptive of radio resources that are used by the access node that transmits the beacon. The method further includes, at Block  4 B, a step of transmitting feedback from the user terminal to the first access node, the feedback comprising at least the information descriptive of the radio resources that are used by the second access node. 
     The various blocks shown in  FIGS. 3 and 4  may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). 
     In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. 
     It should thus be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention. 
     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, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention. 
     For example, while the exemplary embodiments have been described above at least partially in the context of the LTE-A system, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems. Further, it should be appreciated that the use of this invention may be made in both TDD and FDD type systems. 
     It should be noted that the terms “connected,” “coupled,” or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are “connected” or “coupled” together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be “connected” or “coupled” together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples. 
     Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.