WO2016138664A1

WO2016138664A1 - Coordination between macro cell and small cell to handle interference for flexible duplex system

Info

Publication number: WO2016138664A1
Application number: PCT/CN2015/073694
Authority: WO
Inventors: Peng Cheng; Yin Huang; Neng Wang; Chao Wei
Original assignee: Qualcomm Incorporated
Priority date: 2015-03-05
Filing date: 2015-03-05
Publication date: 2016-09-09

Abstract

Systems, methods, and apparatuses for managing interference between macro cell base station and small cell base station are disclosed. In accordance with the present disclosure, a macro cell base station may generate a timing pattern (e.g., "ON-OFF" period) to schedule communication with at least one or more UEs within its coverage area. In some examples, the timing pattern may comprise a first time period (e.g., "ON" time period) for scheduling uplink transmission from the one or more UEs. Additionally or alternatively, the timing pattern may include a second time period (e.g., "OFF" time period) for suspending communication with the UE and allowing a small cell base station to reconfigure a frequency division duplexing (FDD) uplink band for time division duplexing (TDD) transmission. In some aspects of the present disclosure, the macro cell base station may signal the timing pattern to a small cell base station to coordinate interference management.

Description

COORDINATION BETWEEN MACRO CELL AND SMALL CELL TO HANDLE INTERFERENCE FOR FLEXIBLE DUPLEX SYSTEM

BACKGROUND

Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power) . Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems, (e.g., an LTE system) .

By way of example, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UEs) , mobile devices or stations (STAs) . A base station may communicate with the communication devices on downlink channels (e.g., for transmissions from a base station to a UE) and uplink channels (e.g., for transmissions from a UE to a base station) .

As cellular networks have become more congested, operators are beginning to look at ways to maximize the use of available network resources. One approach may include utilizing spare resources (e.g., available spectrum) to schedule downlink traffic from the base station to one or more communication devices. However, in some cases, when spare resources are used, interference may be caused between uplink (UL) and downlink (DL) communications (e.g., interference between UL and DL communication from different base stations, interference between UL and DL communications from base stations and UEs, etc. ) . Where different base stations (e.g., macro cell base station and small cell base station) serve different UEs within overlapping coverage areas according to different UL-DL configurations, a UE attempting to receive and decode a DL transmission from a serving base station may experience interference from UL transmissions from other, proximately located UEs.

SUMMARY

Systems, methods, and apparatuses for managing interference between macro cell base station and small cell base station are disclosed. In accordance with the present disclosure, a macro cell base station may generate a timing pattern (e.g., “ON-OFF” period) to schedule communication with at least one or more UEs within its coverage area. In some examples, the timing pattern may comprise a first time period (e.g., “ON” time period) for scheduling uplink transmission from the one or more UEs. Additionally or alternatively, the timing pattern may include a second time period (e.g., “OFF” time period) for suspending communication with the UE and allowing a small cell base station to reconfigure a frequency division duplexing (FDD) uplink band for time division duplexing (TDD) transmission. In some aspects of the present disclosure, the macro cell base station may signal the timing pattern to a small cell base station to coordinate interference management. Accordingly, in some aspects, the small cell base station may utilize the knowledge of the macro cell base station’s timing pattern to dynamically adjust its uplink and downlink configuration to maximize resource efficiency, and scheduling flexibility.

According to a first set of illustrative embodiments, a method for mitigating inter-cell interference is described. The method may include identifying a traffic load at a first base station and determining a timing pattern for the first base station based on the traffic load. In some examples, the timing pattern may include a first time period for scheduling data communication with a UE and a second time period for suspending data communication with the UE and allowing a second base station to reconfigure a FDD uplink band for TDD transmissions. In some aspects, the method may further include transmitting the timing pattern to the second base stations. In some examples, a computer readable medium may be configured to execute the method steps identified above in accordance with the first set of embodiments.

According to a second set of illustrative embodiments, an apparatus for mitigating inter-cell interference is described. The apparatus may comprise means for identifying a traffic load at a first base station and means for determining a timing pattern for the first base station based on the traffic load. The timing pattern may include a first time period for scheduling data communication with a UE and a second time period for suspending data communication with the UE and allowing a second base station to reconfigure an FDD uplink band for TDD transmission. The apparatus may further include means for transmitting the timing pattern to a second base station.

According to a third set of illustrative embodiments, another method for mitigating inter-cell interference is described. The method may include receiving, at a first base station, a timing pattern associated with a second base station and communicating with a UE using FDD during a first time period based on the timing pattern associated with the second base station. Additionally or alternatively, the method may further reconfigure the first base station to use TDD for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the second base station. In some examples, a computer readable medium may be configured to execute the method steps identified above in accordance with the second set of embodiments.

According to a fourth set of illustrative embodiments, another apparatus for mitigating inter-cell interference is described. The apparatus may comprise means for receiving, at a first base station, a timing pattern associated with a second base station and means for communicating with a UE using FDD during a first time period based on the timing pattern associated with the second base station. In some examples, the apparatus may further include means for reconfiguring the first base station to use TDD for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the second base station.

The foregoing has outlined rather broadly the features and technical advantages of examples according to the disclosure in order that the detailed description that follows may be better understood. Additional features and advantages will be described hereinafter. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, both their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and not as a definition of the limits of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects of the present disclosure will hereinafter be described in conjunction with the appended drawings, provided to illustrate and not to limit the disclosed aspects, wherein like designations denote like elements, where a dashed line may indicate an optional component, and in which:

FIG. 1 illustrates an example of a wireless communications system for managing interference between macro base station and small cell base station in accordance with various aspects of the present disclosure；

FIG. 2 illustrates another example of a wireless communications system in accordance with various aspects of the present disclosure；

FIG. 3 illustrates an example of a flexible duplex configuration for managing interference between macro base station and small cell base station in accordance with various aspects of the present disclosure；

FIG. 4 illustrates an example of a radio subframe in accordance with aspects of the present disclosure；

FIG. 5 illustrates an example of a timing diagram that shows aspects for managing interference between macro base station and small cell base station in accordance with various aspects of the present disclosure；

FIG. 6 illustrates an example of a schematic diagram of a communication network including aspects of small cell and macro cell base stations in accordance with various aspects of the present disclosure；

FIG. 7 is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system；

FIG. 8 illustrates an example of a flowchart that shows aspects for managing interference between macro base station and small cell base station in accordance with various aspects of the present disclosure； and

FIG. 9 illustrates an example of a flowchart that shows aspects for managing interference between macro base station and small cell base station in accordance with various aspects of the present disclosure.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In the following description, for purposes of explanation, numerous specific details are set forth to provide a thorough understanding of one or more aspects. It should be understood, however, that such aspect (s) may be practiced without these specific details.

Multiple access technologies may use Frequency Division Duplexing (FDD) or Time Division Duplexing (TDD) to provide uplink and downlink communications over one or more carriers. Each multiplexing scheme may offer certain benefits over other schemes with respect to latency, efficiency, and scheduling flexibility. TDD operation, for example, may provide relatively flexible deployments without requiring paired spectrum resources. TDD formats include transmission of frames of data, each including a number of different subframes in which different subframes may be uplink or downlink subframes. In systems that operate using TDD, different formats may be used in which uplink and downlink communications may be asymmetric. FDD operation utilizes different carriers for concurrent uplink and downlink communications.

Flexible duplexing can be implemented in FDD to allow, for example, the uplink frequency band in the FDD operation to include both uplink and downlink subframes for communication using TDD. This allows for providing more downlink bandwidth at the base station to better match the traffic pattern at the base station. It is to be appreciated, however, that flexible duplexing may also include allowing the downlink frequency band in the FDD operation to include both downlink and uplink subframes for communication using TDD (e.g., where more uplink bandwidth is needed at the base station) , though it is described more in terms of splitting the uplink frequency band herein. Allocating the uplink frequency band in this regard, however, may impact certain uplink transmissions in certain radio access technologies, such as third generation partnership project (3GPP) long term evolution (LTE) .

According to the particular benefits of each multiplexing scheme, one type of multiplexing may be more suitable for a certain type of transmission than another. Thus, a physical layer signaling mechanism may allow a base station (e.g., macro cell base station or small cell base station) to flexibly and dynamically choose one of the multiplexing modes, depending, for example, on the status of the base station. In some aspects, a base station may switch between different modes of operation (e.g., TDD or FDD) in order to maximize existing resources (e.g., utilizing spare uplink resources to schedule downlink transmission) . For example, a base station may use the FDD downlink frequency band and spare uplink resources available by configuring TDD communications in the FDD uplink frequency band to provide greater downlink capabilities than those available to the FDD downlink frequency band alone.

However, as discussed above, interference may be caused between uplink and downlink communications where different base stations (e.g., macro cell base station and small cell base station) serve different UEs within overlapping coverage areas according to different UL-DL configurations. In some examples, different UL-DL configuration may be associated with scheduling downlink transmissions on an uplink band. Thus, the use of uplink band to schedule downlink traffic may cause inter-cell interference to cells using the uplink FDD band for uplink traffic. Accordingly, aspects of the present disclosure mitigate such interference by coordinating scheduling timing patterns between the macro cell base station and the small cell base station.

FIG. 1 illustrates an example of a wireless communications system for coordinating interference management in accordance with various aspects of the present disclosure. The system 100 includes base stations 105, access points (AP) 120, mobile devices 115, and a core network 130. ) . In some aspects of the present disclosure, the base station 105 may be referred to as a macro cell base station, and AP 120 may be referred to as small cell base station. The core network 130 may provide user authentication, access authorization, tracking, internet protocol (IP) connectivity, and other access, routing, or mobility functions. The base stations 105 interface with the core network 130 through backhaul links 132 (e.g., S1, etc. ) . The base stations 105 and AP 120 may perform radio configuration and scheduling for communication with the mobile devices 115, or may operate under the control of a base station controller (not shown) . In various examples, the base station 105 and AP 120 may communicate, either directly or indirectly (e.g., through core network 130) , with each other over backhaul links 134 (e.g., X2, Over-the-air (OTA) etc. ) , which may be wired or wireless communication links. In some aspects of the present disclosure, the base station 105 and AP 120 may share their respective timing parameters associated with communication scheduling. For example, the base station 105 may share its ON-OFF pattern with the AP 120 using the backhaul links 134.

The base station 105 and AP 120 may wirelessly communicate with the mobile device 115 via one or more antennas. Each of the base station 105 and AP 120 may provide communication coverage for a respective geographic coverage area 110. In some examples, base station 105 may be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNodeB (eNB) , Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area 110-a for a base station 105 and coverage area 110-b for AP 120 may be divided into sectors making up only a portion of the coverage area (not shown) . The wireless communications system 100 may include base station 105 and AP 120 of different types (e.g., macro or small cell base stations) . There may be overlapping geographic coverage areas 110 for different technologies.

While the mobile devices 115 may communicate with each other through the base station 105 and AP 120 using communication links 125, each mobile device 115 may also communicate directly with one or more other mobile devices 115 via a direct wireless link 135. Two or more mobile devices 115 may communicate via a direct wireless link 135 when both mobile devices 115 are in the geographic coverage area 110 or when one or neither mobile device 115 is within the AP geographic coverage area 110. Examples of direct wireless links 135 may include Wi-Fi Direct connections, connections established using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections. In other implementations, other peer-to-peer connections or ad hoc networks may be implemented within the system 100.

In some examples, the wireless communications system 100 includes a wireless wide area network (WWAN) such as an LTE/LTE-Advanced (LTE-A) network. In LTE/LTE-A networks, the term evolved node B (eNB) may be generally used to describe the base stations 105, while the term user equipment (UEs) may be generally used to describe the mobile devices 115. The wireless communications system 100 may include a heterogeneous LTE/LTE-A network in which different types of eNBs provide coverage for various geographical regions. The wireless communications system 100 may, in some examples, also support a wireless local area network (WLAN) . A WLAN may be a network employing techniques based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards (“Wi-Fi” ) . In some examples, each eNB or base station 105 and AP 120 may provide communication coverage for a macro cell, a small cell, or other types of cell. The term “cell” is a 3GPP term that can be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc. ) of a carrier or base station, depending on context.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by mobile device 115 with service subscriptions with the network provider. A small cell is a lower-powered base station, as compared with a macro cell, that may operate in the same or different (e.g., licensed, unlicensed, etc. ) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by mobile device 115 with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by mobile device 115 having an association with the femto cell (e.g., mobile device 115 in a closed subscriber group (CSG) , mobile device 115 for users in the home, and the like) . An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells (e.g., component carriers) . In some aspects of the present disclosure, the base station 105 may be referred to as a macro cell base station, and AP 120 may be referred to as small cell base station.

The wireless communications system 100 may support synchronous or asynchronous operation. For synchronous operation, the base stations 105 may have similar frame timing, and transmissions from different base stations 105 may be approximately aligned in time. For asynchronous operation, the base stations 105 may have different frame timing, and transmissions from different base stations 105 may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

The communication networks that may accommodate some of the various disclosed examples may be packet-based networks that operate according to a layered protocol stack. In the user plane, communications at the bearer or packet data convergence protocol (PDCP) layer may be IP-based. A radio link control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A medium access control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the radio resource control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a mobile device 115 and the base stations 105. The RRC protocol layer may also be used for core network 130 support of radio bearers for the user plane data. At the physical (PHY) layer, the transport channels may be mapped to physical channels.

The mobile devices 115 may be dispersed throughout the wireless communications system 100, and each mobile device 115 may be stationary or mobile. A mobile device 115 may also include or be referred to by those skilled in the art as a user equipment (UE) , mobile station, a subscriber station, STA, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A mobile device 115 may be a cellular phone, a personal digital assistant (PDA) , a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a wireless local loop (WLL) station, or the like. A mobile device may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, relay base stations, and the like. The mobile devices 115 may be multi-radio devices employing adaptive scanning techniques. For example, a mobile device 115 may dynamically adapt scanning operations of one of its radios based on a signal quality of another of its radios. In some examples, a dual-radio UE 115-a, may include a WLAN radio (not shown) and a WWAN radio (not shown) that may be configured to concurrently communicate with base station 105 (using the WWAN radio) and with AP 120 (using the WLAN radio) .

The communication links 125 shown in wireless communications system 100 may include uplink (UL) transmissions from a mobile device 115 to a base station 105 or AP 120, or downlink (DL) transmissions, from a base station 105 or AP 120 to a mobile device 115. The downlink transmissions may also be called forward link transmissions while the uplink transmissions may also be called reverse link transmissions. Each communication link 125 may include one or more carriers, where each carrier may be a signal made up of multiple sub-carriers (e.g., waveform signals of different frequencies) modulated according to the various radio technologies described above. Each modulated signal may be sent on a different sub-carrier and may carry control information (e.g., reference signals, control channels, etc. ) , overhead information, user data, etc. The communication links 125 may transmit bidirectional communications using frequency division duplex (FDD) (e.g., using paired spectrum resources) or time division duplex (TDD) operation (e.g., using unpaired spectrum resources) . Frame structures may be defined for FDD (e.g., frame structure type 1) and TDD(e.g., frame structure type 2) .

The communication links 125 may utilize resources of licensed spectrum or unlicensed spectrum, or both. Broadly speaking, the unlicensed spectrum in some jurisdictions may range from 600 Megahertz (MHz) to 6 Gigahertz (GHz) , but need not be limited to that range. As used herein, the term “unlicensed spectrum” or “shared spectrum” may thus refer to industrial, scientific and medical (ISM) radio bands, irrespective of the frequency of those bands. An “unlicensed spectrum” or “shared spectrum” may refer to a spectrum used in a contention-based communications system. In some examples, unlicensed spectrum is the U-NII radio band, which may also be referred to as the 5GHz or 5G band. By contrast, the term “licensed spectrum” or “cellular spectrum” may be used herein to refer to wireless spectrum utilized by wireless network operators under administrative license from a governing agency.

Wireless communications system 100 may support operation on multiple cells or carriers, a feature which may be referred to as carrier aggregation (CA) or multi-carrier operation. A carrier may also be referred to as a component carrier (CC) , a layer, a channel, etc. The terms “carrier, ” “component carrier, ” “cell, ” and “channel” may be used interchangeably herein. A mobile device 115 may be configured with multiple downlink CCs and one or more uplink CCs for carrier aggregation. Carrier aggregation may be used with both FDD and TDD component carriers.

Data in wireless communications system 100 may be divided into logical channels, transport channels, and physical layer channels. Channels may also be classified into Control Channels and Traffic Channels. Logical control channels may include paging control channel (PCCH) for paging information, broadcast control channel (BCCH) for broadcast system control information, multicast control channel (MCCH) for transmitting multimedia broadcast multicast service (MBMS) scheduling and control information, dedicated control channel (DCCH) for transmitting dedicated control information, common control channel (CCCH) for random access information, DTCH for dedicated UE data, and multicast traffic channel (MTCH) , for multicast data. DL transport channels may include broadcast channel (BCH) for broadcast information, a DL shared channel (DL-SCH) for data transfer, paging channel (PCH) for paging information, and multicast channel (MCH) for multicast transmissions.

FIG. 2 illustrates a system 200 in which a base station 105 and AP 120 may coordinate interference management by sharing timing patterns (e.g., ON-OFF periods) for scheduling communication. System 200 may illustrate, for example, aspects of wireless communication system 100 illustrated in FIG. 1. In the example of FIG. 2, a base station 105-a may communicate with one or more UEs 115-c within a coverage area 110-a of the base station 105-a. Additionally or alternatively, a small cell AP 120 may communicate with one or more UEs 115-b within the coverage area 205 of the AP 120. Thus, the coverage area 205 of the AP 120 may overlap with the coverage area 110-a of the base station 105.

In some examples, system 200 may support bidirectional communications using FDD (e.g., using paired spectrum resources) or TDD operation (e.g., using unpaired spectrum resources) . Different carriers, or cells, may be configured with different frame structures (e.g., FDD or TDD) , and each base station may utilize one of several different multiplexing configurations. For TDD frame structures, each subframe may carry uplink or downlink traffic, and special subframes may be used to switch between uplink and downlink transmission. Allocation of uplink and downlink subframes within radio frames may be symmetric or asymmetric and may be statically determined or may be reconfigured semi-statically. Special subframes may carry downlink or uplink traffic and may include a Guard Period (GP) between downlink and uplink traffic.

In some examples, flexible duplexing can be implemented in FDD to allow, for example, the uplink frequency band to include both uplink and downlink subframes in TDD. This may allow more downlink bandwidth at the base station (base station 105 and/or AP 120) to better match the traffic pattern at the base station. Accordingly, use of TDD may offer flexible deployments without requiring paired UL-DL spectrum resources. However, in some aspects, downlink transmissions on the uplink band may cause inter-cell interference to cells using the uplink FDD band for uplink traffic. For example, inter-cell interference may be base station 105 and AP 120, if, for example, the base station 105 schedules uplink traffic with UE 115-c on an uplink FDD band concurrently with AP 120 utilizing the uplink FDD band to schedule downlink traffic with UE 115-b. Thus, where different base stations (e.g., base station 105 and AP 120) serve different UEs 115 within overlapping coverage areas according to different UL-DL configurations, downlink transmissions on the uplink band may cause inter-cell interference to cells using the uplink FDD band for uplink traffic. Accordingly, aspects of the present disclosure mitigate such interference by sharing scheduling timing patterns between base station 105 and AP 120.

In some aspects of the present disclosure, a base station 105 may identify a traffic load (e.g., uplink and downlink traffic) at the base station 105. The traffic load may identify number of UEs 115 supported by the base station 105 or amount/type of traffic scheduled for transmission or reception. Based on the traffic load, the base station 105 may determine a timing pattern that includes a first time period (e.g., ON time period) for scheduling uplink communication with UE 115-c and second time period (e.g., OFF time period) for suspending communication on at least one uplink channel with the UE 115-c and allowing the AP 120 to reconfigure a frequency division duplexing (FDD) uplink band for time division duplexing (TDD) transmission with UE 115-b. In some examples, the base station 105 may transmit the timing pattern to the AP 120 over backhaul link 134 (e.g., X2, Over-the-air (OTA) etc. ) , which may be wired or wireless communication link.

The AP 120, upon receiving the timing pattern (or some indication of the timing pattern) from the base station 105, may synchronize its uplink and downlink communications based in part on the timing pattern of the base station 105. For example, the AP 120 may identify the first and second time periods respectively based on the timing pattern of the base station 105 to schedule the uplink and downlink communication between the AP 120 and the UE 115-b within coverage area 205. In one example, the AP 120 may schedule uplink traffic during the first time period and dynamically reconfigure the AP 120 to use TDD for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the base station 105. Additionally or alternatively, the AP 120 may flexibly and dynamically choose multiplexing modes (e.g., TDD or FDD) for each uplink or downlink communication according to traffic load and type of traffic scheduled for transmission.

FIG. 3 shows a block diagram 300 conceptually illustrating example of a flexible duplex configuration for managing interference between base station 105 and AP 120. The diagram 300 may include radio frames 305 transmitted or received by the base station 105 in communication with one or more UEs 115 in its coverage area (e.g., coverage area 110-a in FIGs. 1-2) . Additionally or alternatively, the diagram 300 may include radio frames 310 transmitted or received by the AP 120 in communication with one or more UEs 115 in the AP coverage area (e.g., coverage area 205 in FIG. 2) . In some examples, the AP 120 may be initialized to operate in FDD multiplexing mode.

In accordance with the present disclosure, the base station 105 may determine a timing pattern for the base station 105. In some examples, the timing pattern may include a first time period 320 for scheduling data communication with a UE 115. Additionally or alternatively, the timing pattern may include a second time period 325 for suspending data communication with the UE 115 and allowing an AP 120 to reconfigure FDD uplink band for TDD transmissions (e.g., downlink transmissions to UE associated with AP 120) . In some examples, the base station 105 may transmit the timing pattern to the AP 120 over a backhaul link (e.g., X2 interface and/or OTA interface) . Accordingly, during the first time period 320, the base station 105 and AP 120 may be configured to schedule uplink traffic 335 with one or more UEs 115 over FDD uplink band.

However, during the second time period 325, the base station 105 may suspend data communication with the UE 115. In one or more examples, suspending data communication with the UE during the second time period may comprise muting a physical uplink shared channel (PUSCH) associated with base station 105 and communicating control signals on a physical uplink control channel (PUCCH) . Accordingly, the AP 120, during the second time period may reconfigure FDD uplink band for TDD transmissions (e.g., downlink frames 345, special frames 350, and/or uplink frames 355 to UE) .

At the conclusion of the second time period 325, the base station 105 and AP 120 may return to normal operations. In some examples, normal operation may comprise scheduling uplink transmissions over FDD uplink band. Thus, in accordance with the present disclosure, the AP 120 may off-load one or more traffic without causing inter-cell interference between the base station 105 and the AP 120.

With reference now to FIG. 4 a block diagram 400 conceptually illustrates an example of a radio subframe transmitted by AP 120 during the second time period described with reference to FIG. 3. The radio subframe structure illustrated in block diagram 400 may be an example of

frame

345, 350, and 355 described with reference to FIG. 3. In some examples, the radio subframe structure of FIG. 4 may be transmitted using portions of the wireless communications system 100 described with reference to FIG. 1 between one or more APs 120 and one or more UEs 115, for example.

In some examples, a radio subframe may include a subframe structure that comprises 14 OFDM symbols within each 1 millisecond (ms) subframe 405. Each subframe 405 may include physical uplink control channel (PUCCH) regions 410, guard band regions 415 and data communication regions 425. In some examples, the PUCCH region 410 may be reserved for control signals during the second time period when the base station 105 suspends communication. Guard band regions 415 may be needed to protect the PUCCH for the base station 105 during the second time period. In some examples, the configuration of the guard band (e.g., location, size, etc. ) may be pre-determined for both the macro cell base station 105 and/or the small cell AP 120. Alternatively, in some aspects, the guard band configuration may be dynamically or semi-statically adaptable and signaled between the AP 120 and the base station 105 through backhaul link (e.g., X2 interface and/or OTA interface) . Additionally or alternatively, data communication regions 425 may be utilized by the AP 120 for data communications. The data communication regions 425 may be utilized to transmit downlink, uplink and/or special subframes.

FIG. 5 is a flowchart conceptually illustrating an example of a method 500 of wireless communication, in accordance with aspects of the present disclosure. For clarity, the method 500 is described below with reference to ones of the access points 120, eNBs 105 and/or UEs 115, described with reference to FIGs. 1-3.

In some examples, a base station 105 (e.g., macro cell base station) , at block 505, may configure timing parameters associated with the base station 105. Configuring timing pattern may include identifying a traffic load (e.g., uplink traffic and/or downlink traffic) at the base station 105. The base station 105, based on the traffic load, may determine a timing pattern for the base station 105. In some examples, the timing pattern may include a first time period configured for scheduling data communication with a UE 115-b. Additionally or alternatively, the timing pattern may include a second time period for suspending data communication with UE 115-b and allowing an AP 120 to reconfigure FDD uplink band for TDD transmissions (e.g., downlink transmissions) with UE 115-a.

At block 510, the base station 105 may transmit the timing information to the AP 120. The timing information may include the timing pattern determined by the base station 105. In some examples, the timing information (e.g., timing pattern) may be transmitted to the AP 120 over an X2 interface or an over-the-air (OTA) interface. At block 515, the AP 120, upon receiving the timing pattern, may identify a first time period and the second time period associated with the timing pattern. As discussed above, a first time period may be configured for scheduling data communication between base station 105 and UE 115-b, while the second time period may be configured for suspending data communication between base station 105 and the UE 115-b and allowing an AP 120 to reconfigure FDD uplink band for TDD transmissions (e.g., downlink transmissions) with UE 115-a.

At block 520, the base station 105 may enter the first time period (ON time period) . During the first time period, the base station 105 may schedule uplink transmission (s) 530, 540 with the UE 115-b. Concurrently, during the first time period, the AP 120 may also schedule

uplink transmissions

525, 535 with UE 115-b. In some examples, communicating with UE 115-a during the first time period may comprise communicating with the UE 115-a using FDD operations. At block 545, the base station 105 may transition to the second time period and enter OFF time period. During the second time period, the base station 105, at block 550, may suspend data communication with UE 115-b. Suspending data communication with the UE 115-b during the second time period may comprise muting a physical uplink shared channel (PUSCH) associated with the base station 105 and transmitting control signals on a physical uplink control channel (PUCCH) with the UE 115-b.

In some aspects, during the second time period, the AP 120, at block 555, may reconfigure the AP 120 to use TDD for downlink transmission with UE 115-a on an FDD uplink band. Accordingly, at block 560, the AP 120 may schedule downlink traffic with UE 115-a using TDD on an FDD uplink band. At block 565, the base station 105 may exit the OFF time period (i.e., second time period) and return to normal operations.

Referring now to FIG. 6, in an aspect, a wireless communication system 600 includes at least one base station 105 in communication with an AP 120. In some examples, the base station 105 may be an example of base station 105 described with reference to FIGS. 1-3. Additionally, the AP 120 may be an example of AP 120 described with reference to FIGS. 1-3. The base station 105 may communicate using a communications link 602 with an AP 120 over backhaul links 134 (e.g., X2, Over-the-air(OTA) etc. ) described in FIGS. 1 and 2, which may be wired or wireless communication links. In some aspects of the present disclosure, the base station 105 and AP 120 may share their respective timing parameters associated with traffic scheduling. For example, the base station 105 may share its ON-OFF pattern with the AP 120 using the backhaul links 134.

In some examples, the base station 105 may include a macro cell management module 605 configured to perform the functions, methodologies (e.g., methodology 500 of FIG. 5 and methodology 800 of FIG. 8) , or methods presented in the present disclosure. The macro cell management module 605 may include a traffic load identification module for identifying a traffic load (e.g., uplink traffic and downlink traffic) at the base station 105. In some examples, the traffic load identification module 605 may monitor the downlink traffic load at the base station 105 and determine whether the traffic load has satisfied a threshold. If, the traffic load identification module 605 determines that the downlink traffic has exceeded the threshold, the traffic load identification module 605 may trigger an alert to signal high traffic load. In some examples, the traffic load identification module 605 may additionally signal updated traffic load signals based on the active monitoring.

Based on the traffic load signaling from the traffic load identification module 605, the timing pattern configuration module 620 may determine a timing pattern for the base station 105. In some examples, the timing pattern may include a first time period configured by ON period module 625 for scheduling data communication with a UE 115. In one or more examples, the ON period module 625 may schedule an uplink transmission with the UE during the first time period based on the timing pattern. Additionally or alternatively, the timing pattern may include a second time period configured by OFF period module 630 for suspending data communication with the UE 115 and allowing an AP 120 to reconfigure FDD uplink band for TDD transmissions (e.g., downlink transmissions to UE associated with AP 120) . In one or more examples, suspending data communication with the UE during the second time period may comprise muting a physical uplink shared channel (PUSCH) associated with base station 105 and communicating control signals on a physical uplink control channel (PUCCH) . In some aspects, the timing pattern configuration module 620 may adapt the timing pattern based on updated signals from the traffic load identification module 615. In some aspects, dynamically adjusting the timing pattern may include increasing or reducing the first or second time period to satisfy the traffic load at the base station 105.

Additionally or alternatively, the macro cell management module 605 may further include backhaul signaling module 635. The backhaul signaling module 635 may transmit the timing pattern to the AP 120 over an X2 interface or an over-the-air (OTA) interface.

In some aspects, an AP 120 may include a small cell management module 610 configured to perform the functions, methodologies (e.g., methodology 500 of FIG. 5 and methodology 900 of FIG. 9) , or methods presented in the present disclosure. As discussed above, the macro cell management module 605 may transmit the timing pattern associated with the base station 105 to the AP 120. Thus, in some examples, the small cell management module 610 may include a timing coordination module 640 configured to receive andprocess the timing pattern associated with the base station 105.

In further examples, the small cell management module 610 may also include a flexible duplexing module 645 for communicating with a UE using FDD and/or TDD. For example, in some aspects, a frequency divisional duplexing module 650 may be configured to communicate with the UE using FDD. Additionally or alternatively, a time division duplexing module 655 may be configured to communicate with the UE using TDD. Thus, in some examples, the flexible duplexing module 645 may communicate with a UE using FDD during a first time period based on the timing pattern associated with the second base station. In some examples, the AP 120 may be configured and/or reconfigured by the reconfiguration module 660 to use TDD for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the second base station.

In some examples, the reconfiguration module 660 may disable reconfiguration capabilities of the AP 120 during the first time period (e.g., ON time period) and enable reconfiguration capability of the AP 120 during the second time period (e.g., OFF time period) . In yet further examples, the small cell management module 610 may also include power management module 665. In some aspects, an AP 120 may experience different level of interference during the first time period and the second time period. For example, during first time period, the AP 120 may experience interference from UEs 115 of other cells, while during the second time period, the AP 120 may experience interference from UEs 115 and other small cell APs 120. In some aspects, the interference during the second time period (i.e., AP-to-AP interference) may be stronger than the first time period (i.e., UE-to-AP interference) . Thus, in order to mitigate different level of interference, the power management module 665 may use different power control parameters during the first time period and the second time period. In some instances, the power management module 665 may communicate with the UE 115 during the first time period using a first power control parameter. Additionally or alternatively, the power management module 665 may communicate with the UE 115 during the second time period using the second power control parameter. In one example, the first and the second power control parameters may be signaled semi-statically via radio resource control (RRC) signaling.

FIG. 7 is a conceptual diagram illustrating an example of a hardware implementation for an apparatus 700 employing a processing system 714. In some examples, the processing system 714 may be an example of base station 105 or AP 120 described with reference to FIGs. 1-3 and/or FIG. 5. In this example, the processing system 714 may be implemented with a bus architecture, represented generally by the bus 702. The bus 702 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 714 and the overall design constraints. The bus 702 links together various circuits including one or more processors, represented generally by the processor 704, computer-readable media, represented generally by the computer-readable medium 706, a macro cell management module 605 (see FIG. 6) and small cell management module 610 (see FIG. 6) , which may be configured to carry out one or more methods or procedures described herein. In some instances, a macro cell management module 605 may be implemented when processing system 714 is used in a base station 105. Conversely, a small cell management module 610 may be implemented when the processing system 714 is used in an AP 120. In an aspect, small cell management module 605, macro cell management module 610 and the components therein may comprise hardware, software, or a combination of hardware and software that may be configured to perform the functions, methodologies (e.g., methodology 500 of FIG. 5) , or methods presented in the present disclosure.

The bus 702 may also link various other circuits such as timing sources, peripherals, voltage regulators and power management circuits, which are well known in the art, and therefore, will not be described any further. A bus interface 708 provides an interface between the bus 702 and a transceiver 710. The transceiver 710 provides a means for communicating with various other apparatus over a transmission medium. Depending upon the nature of the apparatus, a user interface 712 (e.g., keypad, display, speaker, microphone, joystick) may also be provided.

The processor 704 is responsible for managing the bus 702 and general processing, including the execution of software stored on the computer-readable medium 706. The software, when executed by the processor 704, causes the processing system 714 to perform the various functions described infra for any particular apparatus. The computer-readable medium 706 may also be used for storing data that is manipulated by the processor 704 when executing software. In some aspects, at least a portion of the functions, methodologies, or methods associated with the communication management module 705 may be performed or implemented by the processor 504 and/or the computer-readable medium 706.

FIG. 8 is a flowchart conceptually illustrating an example of a method 800 of wireless communication, in accordance with aspects of the present disclosure. For clarity, the method 800 is described below with reference to base station 105, described with reference to FIGS. 1-3.

At block 805, the method 800 may identify a traffic load at a first base station. The first base station may be a macro cell base station 105 described with reference to FIGS. 1-3. In some examples, identifying a traffic load may include monitoring the downlink traffic load at the base station 105 and determining whether the traffic load has satisfied a threshold. If the downlink traffic load at the base station 105 exceeds the threshold, the method 800 may include triggering an alert to signal high traffic load. In some examples, the method may include periodically signaling updated traffic load alerts based on the active monitoring. Aspects of block 805 may be performed by traffic identification module 615 described with reference to FIG. 6.

At block 810, the method 800 may determine a timing pattern for the first base station 105 based on the traffic load. The timing pattern may include a first time period for scheduling data communication with a UE 115 and a second time period for suspending data communication with the UE 115 and allowing a second base station 120 to reconfigure a frequency division duplexing (FDD) uplink band for time division duplexing (TDD) transmission. Aspects of block 810 may be performed by timing pattern configuration module 620 described with reference to FIG. 6

At block 815, the method 800 may transmit the timing pattern to a second base station 120. Aspects of block 815 may be performed by the backhaul signaling module 635 that may transmit the timing pattern to the AP 120 over an X2 interface or an over-the-air (OTA) interface.

Optionally, the method 800, at block 820, may schedule an uplink transmission with the UE during the first time period based on the timing pattern. Aspects of block 820 may be performed by ON period module 625 described with reference to FIG. 6.

At block 825, the method 800 may further include suspending data communication with the UE during the second time period. Aspects of block 825 may be performed by the OFF period module 830 described with reference to FIG. 6.

FIG. 9 is a flowchart conceptually illustrating an example of a method 900 of wireless communication, in accordance with aspects of the present disclosure. For clarity, the method 900 is described below with reference to AP 120, described with reference to FIGS. 1-3.

At block 905, the method 900 may include receiving, at a first base station 120, a timing pattern associated with a second base station 105. The first base station 120 may receive the timing pattern over an X2 interface or an over-the-air (OTA) interface. Aspects of block 905 may be performed by timing coordination module 640 described with reference to FIG. 6.

At block 910, the method 900 may include communicating with a UE using FDD during a first time period based on the timing pattern associated with the second base station 105. Aspects of block 910 may be performed by flexible duplexing module 645 described with reference to FIG. 6

At block 915, the method 900 may further include reconfiguring the first base station 120 to use TDD for downlink transmission with the UE on the FDD uplink band during a second time period based on the timing pattern associated with the second base station. Aspects of block 915 may be performed by reconfiguration module 660 described with reference to FIG. 6.

The detailed description set forth above in connection with the appended drawings describes example embodiments and does not represent all the embodiments that may be implemented or that are within the scope of the claims. The term “exemplary, ” as used in this description, means “serving as an example, instance, or illustration, ” and not “preferred” or “advantageous over other embodiments. ” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described embodiments.

Information and signals may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP) , an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration) .

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described above can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, “or “as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of” or “one or more of” ) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC(i.e., Aand B and C) .

Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, computer-readable media can comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM) , compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) , or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD) , floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

The previous description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA) , time division multiple access (TDMA) , frequency division multiple access (FDMA) , orthogonal frequency division multiple access (OFDMA) , single carrier frequency division multiple access (SC-FDMA) , and other systems. The terms “system” and “network” are often used interchangeably. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA) , etc. CDMA2000 covers IS-2000, IS-95, and IS-856 standards. IS-2000 Releases 0 and A are commonly referred to as CDMA2000 1X, 1X, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 1xEV-DO, High Rate Packet Data (HRPD) , etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM) . An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB) , Evolved UTRA (E-UTRA) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are new releases of Universal Mobile Telecommunications System (UMTS) that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and Global System for Mobile Communications (GSM) are described in documents from an organization named “3rd Generation Partnership Project” (3GPP) . CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2) . The techniques described herein may be used for the systems and radio technologies mentioned above as well as other systems and radio technologies. The description above, however, describes an LTE system for purposes of example, and LTE terminology is used in much of the description above, although the techniques are applicable beyond LTE applications.

Claims

A method for mitigating inter-cell interference, comprising:

identifying a traffic load at a first base station；

determining a timing pattern for the first base station based on the traffic load, wherein the timing pattern includes a first time period for scheduling data communication with a user equipment (UE) and a second time period for suspending data communication with the UE and allowing a second base station to reconfigure a frequency division duplexing (FDD) uplink band for time division duplexing (TDD) transmission； and

transmitting the timing pattern to a second base station.
The method of claim 1, further comprising:

scheduling an uplink transmission with the UE during the first time period based on the timing pattern； and

suspending data communication with the UE during the second time period.
The method of claim 2, wherein suspending data communication with the UE during the second time period comprises:

muting a physical uplink shared channel (PUSCH) associated with the first base station； and

communicating control signals on a physical uplink control channel (PUCCH) .
The method of claim 1, further comprising:

determining an updated traffic load at the first base station； and

adapting the timing pattern based on the updated traffic load.
The method of claim 1, wherein transmitting the timing pattern to the second base station comprises transmitting the timing pattern over an X2 interface or an over-the-air (OTA) interface.
The method of claim 1, wherein the first base station is a macro base station and a second base station is a small cell base station.
A computer-readable medium storing code for mitigating inter-cell interference, the code comprising instructions executable to:

identify a traffic load at a first base station；

determine a timing pattern for the first base station based on the traffic load, wherein the timing pattern includes a first time period for scheduling data communication with a user equipment (UE) and a second time period for suspending data communication with the UE and allowing a second base station to reconfigure a frequency division duplexing (FDD) uplinkband for time division duplexing (TDD) transmission； and

transmit the timing pattern to a second base station.
The computer-readable medium of claim 7, wherein the code comprises instructions executable to perform one or more of the methods in claims 2-6.
A method for mitigating inter-cell interference, comprising:

receiving, at a first base station, atiming pattern associated with a second base station；

communicating with a user equipment (UE) using frequency division duplexing (FDD) during a first time period based on the timing pattern associated with the second base station； and

reconfiguring the first base station to use time division duplexing (TDD) for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the secondbase station.
The method of claim 9, further comprising:

disabling reconfiguration capability for the first base station during the first time period.
The method of claim 9, wherein reconfiguring the first base station to communicate with the UE using TDD during the second time period comprises:

identifying a downlink and uplink traffic load at the first base station； and

determining whether to reconfigure to TDD during the second time period based on the downlink and uplink traffic load.
The method of claim 9, wherein reconfiguring the first base station to communicate with the UE using TDD during the second time period comprises:

utilizing a portion of the FDD uplink band for guard band to reduce interference to physical uplink control channel (PUCCH) of the second base station.
The method of claim 12, further comprising:

signaling, from the first base station, aguard band configuration to the second base station over an X2 interface or an over-the-air (OTA) interface, wherein the guard band configuration is dynamically adaptable.
The method of claim 9, wherein communicating with the UE during the first time period comprises using a first power control parameter； and

wherein communicating with the UE during the second time period comprises using a second power control parameter.
The method of claim 14, wherein the first power control parameter and the second power control parameter are signaled semi-statically via radio resource control (RRC) signaling.
The method of claim 9, wherein the timing pattern associated with the second base station identifies the first time period during which the secondbase station is communicating on an uplink channel and the second time period during which the second base station suspends data communication.
The method of claim 9, wherein receiving the timing pattern associated with the second base station comprises receiving the timing pattern over an X2 interface or an over-the-air (OTA) interface.
The method ofclaim 9, wherein the first base station is a small cell base station and a second base station is a macro base station.
A computer-readable medium storing code for mitigating inter-cell interference, the code comprising instructions executable to:

receive, at a first base station, atiming pattern associated with a secondbase station；

communicate with a user equipment (UE) using frequency division duplexing (FDD) during a first time period based on the timing pattern associated with the secondbase station； and

reconfigure the first base station to use time division duplexing (TDD) for downlink transmission with the UE on an FDD uplink band during a second time period based on the timing pattern associated with the secondbase station.
The computer-readable medium ofclaim 19, wherein the code comprises instructions executable to perform one or more ofthe methods in claims 10-18.