WO2016074192A1

WO2016074192A1 - Using mbsfn for opportunistic detection of priority communications in multi-tiered access to licensed and unlicensed shared spectrum

Info

Publication number: WO2016074192A1
Application number: PCT/CN2014/090994
Authority: WO
Inventors: Ahmed Kamel Sadek; Yin Huang
Original assignee: Qualcomm Incorporated
Priority date: 2014-11-13
Filing date: 2014-11-13
Publication date: 2016-05-19

Abstract

Multicast-broadcast single frequency network (MBSFN) is disclosed for use in opportunistic detection of priority communications in multi-tiered access to licensed and unlicensed shared spectrum. In various aspects a base station may determine an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system. The base station mutes a transmit chain for one or more symbols within each of a plurality of MBSFN subframes of a transmission frame of the base station, The base station's receive chain may then monitor, during the muted transmit chain symbols, for transmissions from the priority communication system.

Description

USING MBSFN FOR OPPORTUNISTIC DETECTION OF PRIORITY COMMUNICATIONS IN MULTI-TIERED ACCESS TO LICENSED AND UNLICENSED SHARED SPECTRUM

BACKGROUND Field

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to using multicast-broadcast single frequency network (MBSFN) for opportunistic detection of priority communications in multi-tiered access to licensed and unlicensed shared spectrum.

Background

Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, and the like. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Such networks, which are usually multiple access networks, support communications for multiple users by sharing the available network resources. One example of such a network is the Universal Terrestrial Radio Access Network (UTRAN) . The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS) , a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP) . Examples of multiple-access network formats include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks. An OFDMA network may implement a radio technology, such as Evolved UTRA (E-UTRA) , Ultra Mobile Broadband (UMB) , IEEE 802.11 (Wi-Fi) , IEEE 802.16 (WiMAX) , IEEE 802.20, Flash-OFDMA, and the like. The UTRA and E-UTRA technologies are part of Universal Mobile Telecommunication System (UMTS) . 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newer releases of the UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization called the “3rd Generation Partnership Project” (3GPP) .

A wireless communication network may include a number of base stations or node Bs that can support communication for a number of user equipments (UEs) . A UE may communicate with a base station via downlink and uplink. The downlink (or forward link) refers to the communication link from the base station to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the base station.

A base station may transmit data and control information on the downlink to a UE and/or may receive data and control information on the uplink from the UE. On the downlink, a transmission from the base station may encounter interference due to transmissions from neighbor base stations or from other wireless radio frequency (RF) transmitters. On the uplink, a transmission from the UE may encounter interference from uplink transmissions of other UEs communicating with the neighbor base stations or from other wireless RF transmitters. This interference may degrade performance on both the downlink and uplink.

As the demand for mobile broadband access continues to increase, the possibilities of interference and congested networks grows with more UEs accessing the long-range wireless communication networks and more short-range wireless systems being deployed in communities. Research and development continue to advance the UMTS technologies not only to meet the growing demand for mobile broadband access, but to advance and enhance the user experience with mobile communications.

SUMMARY

In one aspect of the disclosure, a method of wireless communication includes determining, by a base station, an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system, muting, by the base station, a transmit chain of the base station for one or more symbols within each of a plurality of multicast-broadcast single frequency network (MBSFN) subframes of a transmission frame of the base station, and monitoring, by a receive chain of the base station during the one or more symbols, for transmissions from the priority communication system.

In an additional of the disclosure, an apparatus configured for wireless communication includes means for determining, by a base station, an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system, means for muting, by the base station, a transmit chain of the base station for one or more symbols within each of a plurality of MBSFN subframes of a transmission frame of the base station, and means for monitoring, by a receive chain of the base station during the one or more symbols, for transmissions from the priority communication system.

In an additional aspect of the disclosure, a computer-readable medium having program code recorded thereon. This program code includes code to determine, by a base station, an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system, code to mute, by the base station, a transmit chain of the base station for one or more symbols within each of a plurality of MBSFN subframes of a transmission frame of the base station, and code to monitor, by a receive chain of the base station during the one or more symbols, for transmissions from the priority communication system.

In an additional aspect of the disclosure, an apparatus includes at least one processor and a memory coupled to the processor. The processor is configured to determine, by a base station, an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system, to mute, by the base station, a transmit chain of the base station for one or more symbols within each of a plurality of MBSFN subframes of a transmission frame of the base station, and to monitor, by a receive chain of the base station during the one or more symbols, for transmissions from the priority communication system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram that illustrates an example of a wireless communications system according to various embodiments.

FIG. 2A shows a diagram that illustrates examples of deployment scenarios for using LTE in an unlicensed spectrum according to various embodiments.

FIG. 2B shows a diagram that illustrates another example of a deployment scenario for using LTE in an unlicensed spectrum according to various embodiments.

FIG. 3 shows a diagram that illustrates an example of carrier aggregation when using LTE concurrently in licensed and unlicensed spectrum according to various embodiments.

FIG. 4 is a block diagram conceptually illustrating a design of a base station/eNB and a UE configured according to one aspect of the present disclosure.

FIG. 5 is a block diagram illustrating multiple wireless networks deployed and coexisting with a priority communications system.

FIGs. 6A and 6B are block diagrams illustrating a UE in LTE/LTE-A networks with unlicensed spectrum in an SDL mode.

FIG. 7 is a block diagram illustrating an MBSFN subframe.

FIG. 8 is a block diagram illustrating example blocks executed to implement one aspect of the present disclosure.

FIGs. 9A and 9B are block diagrams illustrating a base station configured according to aspects of the present disclosure.

FIG. 10 is a block diagram illustrating a base station configured according to one aspect of the present disclosure.

DETAILED DESCRIPTION

The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to limit the scope of the disclosure. Rather, the detailed description includes specific details for the purpose of providing a thorough understanding of the inventive subject matter. It will be apparent to those skilled in the art that these specific details are not required in every case and that, in some instances, well-known structures and components are shown in block diagram form for clarity of presentation.

Operators have so far looked at WiFi as the primary mechanism to use unlicensed spectrum to relieve ever increasing levels of congestion in cellular networks. However, a new carrier type (NCT) based on LTE/LTE-A including an unlicensed spectrum may be compatible with carrier-grade WiFi, making LTE/LTE-A with unlicensed spectrum an alternative to WiFi. LTE/LTE-A with unlicensed spectrum may leverage LTE concepts and may introduce some modifications to physical layer (PHY) and media access control (MAC) aspects of the network or network devices to provide efficient operation in the unlicensed spectrum and to meet regulatory requirements. The unlicensed spectrum may range from 600 Megahertz (MHz) to 6 Gigahertz (GHz) , for example. In some scenarios, LTE/LTE-A with unlicensed spectrum may perform significantly better than WiFi. For example, an all LTE/LTE-A with unlicensed spectrum deployment (for single or multiple operators) compared to an all WiFi deployment, or when there are dense small cell deployments, LTE/LTE-A with unlicensed spectrum may perform significantly better than WiFi. LTE/LTE-A with unlicensed spectrum may perform better than WiFi in other scenarios such as when LTE/LTE-A with unlicensed spectrum is mixed with WiFi (for single or multiple operators) .

For a single service provider (SP) , an LTE/LTE-A network with unlicensed spectrum may be configured to be synchronous with a LTE network on the licensed spectrum. However, LTE/LTE-A networks with unlicensed spectrum deployed on a given channel by multiple SPs may be configured to be synchronous across the multiple SPs. One approach to incorporate both the above features may involve using a constant timing offset between LTE/LTE-A networks without unlicensed spectrum and LTE/LTE-A networks with unlicensed spectrum for a given SP. An LTE/LTE-A network with unlicensed spectrum may provide unicast and/or multicast services according to the needs of the SP. Moreover, an LTE/LTE-A network with unlicensed spectrum may operate in a bootstrapped mode in which LTE cells act as anchor and provide relevant cell information (e.g., radio frame timing, common channel configuration, system frame number or SFN, etc. ) for LTE/LTE-A cells with unlicensed spectrum. In this mode, there may be close interworking between LTE/LTE-A without unlicensed spectrum and LTE/LTE-A with unlicensed spectrum. For example, the bootstrapped mode may support the supplemental downlink and the carrier aggregation modes described above. The PHY-MAC layers of the LTE/LTE-A network with unlicensed spectrum may operate in a standalone mode in which the LTE/LTE-A network with unlicensed spectrum operates independently from an LTE network without unlicensed spectrum. In this case, there may be a loose interworking between LTE without unlicensed spectrum and LTE/LTE-A with unlicensed spectrum based on RLC-level aggregation with co-located LTE/LTE-A with/without unlicensed spectrum cells, or multiflow across multiple cells and/or base stations, for example.

The techniques described herein are not limited to LTE, and may also be used for various wireless communications systems such as CDMA, TDMA, FDMA, OFDMA, 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 Telecommunication System (UMTS) . LTE and LTE-Advanced (LTE-A) are new releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, and 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 below, however, describes an LTE system for purposes of example, and LTE terminology is used in much of the description below, although the techniques are applicable beyond LTE applications.

Thus, the following description provides examples, and is not limiting of the scope, applicability, or configuration set forth in the claims. Changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure. Various embodiments may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to certain embodiments may be combined in other embodiments.

Referring first to FIG. 1, a diagram illustrates an example of a wireless communications system or network 100. The system 100 includes base stations (or cells) 105, communication devices 115, and a core network 130. The base stations 105 may communicate with the communication devices 115 under the control of a base station controller (not shown) , which may be part of the core network 130 or the base stations 105 in various embodiments. Base stations 105 may communicate control information and/or user data with the core network 130 through backhaul links 132. In embodiments, the base stations 105 may communicate, either directly or indirectly, with each other over backhaul links 134, which may be wired or wireless communication links. The system 100 may support operation on multiple carriers (waveform signals of different frequencies) . Multi-carrier transmitters can transmit modulated signals simultaneously on the multiple carriers. For example, each communication link 125 may be a multi-carrier signal modulated according to the various radio technologies described above. Each modulated signal may be sent on a different carrier and may carry control information (e.g., reference signals, control channels, etc. ) , overhead information, data, etc.

The base stations 105 may wirelessly communicate with the devices 115 via one or more base station antennas. Each of the base station 105 sites may provide communication coverage for a respective geographic area 110. In some embodiments, base stations 105 may be referred to as a base transceiver station, a radio base station, an access point, a radio transceiver, a basic service set (BSS) , an extended service set (ESS) , a NodeB, eNodeB (eNB) , Home NodeB, a Home eNodeB, or some other suitable terminology. The coverage area 110 for a base station may be divided into sectors making up only a portion of the coverage area (not shown) . The system 100 may include base stations 105 of different types (e.g., macro, micro, and/or pico base stations) . There may be overlapping coverage areas for different technologies.

In some embodiments, the system 100 is an LTE/LTE-A network that supports one or more unlicensed spectrum modes of operation or deployment scenarios. In other embodiments, the system 100 may support wireless communications using an unlicensed spectrum and an access technology different from LTE/LTE-A with unlicensed spectrum, or a licensed spectrum and an access technology different from LTE/LTE-A. The terms evolved Node B (eNB) and user equipment (UE) may be generally used to describe the base stations 105 and devices 115, respectively. The system 100 may be a Heterogeneous LTE/LTE-A network with or without unlicensed spectrum in which different types of eNBs provide coverage for various geographical regions. For example, each eNB 105 may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cell. Small cells such as pico cells, femto cells, and/or other types of cells may include low power nodes or LPNs. A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A pico cell would generally cover a relatively smaller geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell would also generally cover a relatively small geographic area (e.g., a home) and, in addition to unrestricted access, may also provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG) , UEs 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 pico cell may be referred to as a pico eNB. And, an eNB for a femto cell may be referred to as a femto eNB or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells.

The core network 130 may communicate with the eNBs 105 via a backhaul 132 (e.g., S1, etc. ) . The eNBs 105 may also communicate with one another, e.g., directly or indirectly via backhaul links 134 (e.g., X2, etc. ) and/or via backhaul links 132 (e.g., through core network 130) . The system 100 may support synchronous or asynchronous operation. For synchronous operation, the eNBs may have similar frame and/or gating timing, and transmissions from different eNBs may be approximately aligned in time. For asynchronous operation, the eNBs may have different frame and/or gating timing, and transmissions from different eNBs may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

The UEs 115 are dispersed throughout the system 100, and each UE may be stationary or mobile. A UE 115 may also be referred to by those skilled in the art as a mobile station, a subscriber station, 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 UE 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 UE may be able to communicate with macro eNBs, pico eNBs, femto eNBs, relays, and the like.

The communications links 125 shown in system 100 may include uplink (UL) transmissions from a mobile device 115 to a base station 105, and/or downlink (DL) transmissions, from a base station 105 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. The downlink transmissions may be made using a licensed spectrum (e.g., LTE) , an unlicensed spectrum (e.g., LTE/LTE-A with unlicensed spectrum) , or both (LTE/LTE-A with/without unlicensed spectrum) . Similarly, the uplink transmissions may be made using a licensed spectrum (e.g., LTE) , an unlicensed spectrum (e.g., LTE/LTE-A with unlicensed spectrum) , or both (LTE/LTE-A with/without unlicensed spectrum) .

In some embodiments of the system 100, various deployment scenarios for LTE/LTE-A with unlicensed spectrum may be supported including a supplemental downlink (SDL) mode in which LTE downlink capacity in a licensed spectrum may be offloaded to an unlicensed spectrum, a carrier aggregation mode in which both LTE downlink and uplink capacity may be offloaded from a licensed spectrum to an unlicensed spectrum, and a standalone mode in which LTE downlink and uplink communications between a base station (e.g., eNB) and a UE may take place in an unlicensed spectrum. Base stations 105 as well as UEs 115 may support one or more of these or similar modes of operation. OFDMA communications signals may be used in the communications links 125 for LTE downlink transmissions in an unlicensed spectrum, while SC-FDMA communications signals may be used in the communications links 125 for LTE uplink transmissions in an unlicensed spectrum. Additional details regarding the implementation of LTE/LTE-A with unlicensed spectrum deployment scenarios or modes of operation in a system such as the system 100, as well as other features and functions related to the operation of LTE/LTE-A with unlicensed spectrum, are provided below with reference to FIGS. 2A–10.

Turning next to FIG. 2A, a diagram 200 shows examples of a supplemental downlink mode and of a carrier aggregation mode for an LTE network that supports LTE/LTE-A with unlicensed spectrum. The diagram 200 may be an example of portions of the system 100 of FIG. 1. Moreover, the base station 105-a may be an example of the base stations 105 of FIG. 1, while the UEs 115-a may be examples of the UEs 115 of FIG. 1.

In the example of a supplemental downlink mode in diagram 200, the base station 105-a may transmit OFDMA communications signals to a UE 115-a using a downlink 205. The downlink 205 is associated with a frequency F1 in an unlicensed spectrum. The base station 105-a may transmit OFDMA communications signals to the same UE 115-a using a bidirectional link 210 and may receive SC-FDMA communications signals from that UE 115-a using the bidirectional link 210. The bidirectional link 210 is associated with a frequency F4 in a licensed spectrum. The downlink 205 in the unlicensed spectrum and the bidirectional link 210 in the licensed spectrum may operate concurrently. The downlink 205 may provide a downlink capacity offload for the base station 105-a. In some embodiments, the downlink 205 may be used for unicast services (e.g., addressed to one UE) services or for multicast services (e.g., addressed to several UEs) . This scenario may occur with any service provider (e.g., traditional mobile network operator or MNO) that uses a licensed spectrum and needs to relieve some of the traffic and/or signaling congestion.

In one example of a carrier aggregation mode in diagram 200, the base station 105-a may transmit OFDMA communications signals to a UE 115-a using a bidirectional link 215 and may receive SC-FDMA communications signals from the same UE 115-a using the bidirectional link 215. The bidirectional link 215 is associated with the frequency F1 in the unlicensed spectrum. The base station 105-a may also transmit OFDMA communications signals to the same UE 115-a using a bidirectional link 220 and may receive SC-FDMA communications signals from the same UE 115-a using the bidirectional link 220. The bidirectional link 220 is associated with a frequency F2 in a licensed spectrum. The bidirectional link 215 may provide a downlink and uplink capacity offload for the base station 105-a. Like the supplemental downlink described above, this scenario may occur with any service provider (e.g., MNO) that uses a licensed spectrum and needs to relieve some of the traffic and/or signaling congestion.

In another example of a carrier aggregation mode in diagram 200, the base station 105-a may transmit OFDMA communications signals to a UE 115-a using a bidirectional link 225 and may receive SC-FDMA communications signals from the same UE 115-a using the bidirectional link 225. The bidirectional link 225 is associated with the frequency F3 in an unlicensed spectrum. The base station 105-a may also transmit OFDMA communications signals to the same UE 115-a using a bidirectional link 230 and may receive SC-FDMA communications signals from the same UE 115-a using the bidirectional link 230. The bidirectional link 230 is associated with the frequency F2 in the licensed spectrum. The bidirectional link 225 may provide a downlink and uplink capacity offload for the base station 105-a. This example and those provided above are presented for illustrative purposes and there may be other similar modes of operation or deployment scenarios that combine LTE/LTE-A with or without unlicensed spectrum for capacity offload.

As described above, the typical service provider that may benefit from the capacity offload offered by using LTE/LTE-A with unlicensed spectrum is a traditional MNO with LTE spectrum. For these service providers, an operational configuration may include a bootstrapped mode (e.g., supplemental downlink, carrier aggregation) that uses the LTE primary component carrier (PCC) on the licensed spectrum and the LTE secondary component carrier (SCC) on the unlicensed spectrum.

In the supplemental downlink mode, control for LTE/LTE-A with unlicensed spectrum may be transported over the LTE uplink (e.g., uplink portion of the bidirectional link 210) . One of the reasons to provide downlink capacity offload is because data demand is largely driven by downlink consumption. Moreover, in this mode, there may not be a regulatory impact since the UE is not transmitting in the unlicensed spectrum. There is no need to implement listen-before-talk (LBT) or carrier sense multiple access (CSMA) requirements on the UE. However, LBT may be implemented on the base station (e.g., eNB) by, for example, using a periodic (e.g., every 10 milliseconds) clear channel assessment (CCA) and/or a grab-and-relinquish mechanism aligned to a radio frame boundary.

In the carrier aggregation mode, data and control may be communicated in LTE (e.g.,

bidirectional links

210, 220, and 230) while data may be communicated in LTE/LTE-A with unlicensed spectrum (e.g., bidirectional links 215 and 225) . The carrier aggregation mechanisms supported when using LTE/LTE-A with unlicensed spectrum may fall under a hybrid frequency division duplexing-time division duplexing (FDD-TDD) carrier aggregation or a TDD-TDD carrier aggregation with different symmetry across component carriers.

FIG. 2B shows a diagram 200-a that illustrates an example of a standalone mode for LTE/LTE-A with unlicensed spectrum. The diagram 200-a may be an example of portions of the system 100 of FIG. 1. Moreover, the base station 105-b may be an example of the base stations 105 of FIG. 1 and the base station 105-a of FIG. 2A, while the UE 115-b may be an example of the UEs 115 of FIG. 1 and the UEs 115-a of FIG. 2A.

In the example of a standalone mode in diagram 200-a, the base station 105-b may transmit OFDMA communications signals to the UE 115-b using a bidirectional link 240 and may receive SC-FDMA communications signals from the UE 115-b using the bidirectional link 240. The bidirectional link 240 is associated with the frequency F3 in an unlicensed spectrum described above with reference to FIG. 2A. The standalone mode may be used in non-traditional wireless access scenarios, such as in-stadium access (e.g., unicast, multicast) . The typical service provider for this mode of operation may be a stadium owner, cable company, event hosts, hotels, enterprises, and large corporations that do not have licensed spectrum. For these service providers, an operational configuration for the standalone mode may use the PCC on the unlicensed spectrum. Moreover, LBT may be implemented on both the base station and the UE.

Turning next to FIG. 3, a diagram 300 illustrates an example of carrier aggregation when using LTE concurrently in licensed and unlicensed spectrum according to various embodiments. The carrier aggregation scheme in diagram 300 may correspond to the hybrid FDD-TDD carrier aggregation described above with reference to FIG. 2A. This type of carrier aggregation may be used in at least portions of the system 100 of FIG. 1. Moreover, this type of carrier aggregation may be used in the base stations 105 and 105-a of FIG. 1 and FIG. 2A, respectively, and/or in the UEs 115 and 115-a of FIG. 1 and FIG. 2A, respectively.

In this example, an FDD (FDD-LTE) may be performed in connection with LTE in the downlink, a first TDD (TDD1) may be performed in connection with LTE/LTE-A with unlicensed spectrum, a second TDD (TDD2) may be performed in connection with LTE with licensed spectrum, and another FDD (FDD-LTE) may be performed in connection with LTE in the uplink with licensed spectrum. TDD1 results in a DL:UL ratio of 6:4, while the ratio for TDD2 is 7:3. On the time scale, the different effective DL:UL ratios are 3:1, 1:3, 2:2, 3:1, 2:2, and 3:1. This example is presented for illustrative purposes and there may be other carrier aggregation schemes that combine the operations of LTE/LTE-A with or without unlicensed spectrum.

FIG. 4 shows a block diagram of a design of a base station/eNB 105 and a UE 115, which may be one of the base stations/eNBs and one of the UEs in FIG. 1. The eNB 105 may be equipped with antennas 434a through 434t, and the UE 115 may be equipped with antennas 452a through 452r. At the eNB 105, a transmit processor 420 may receive data from a data source 412 and control information from a controller/processor 440. The control information may be for the physical broadcast channel (PBCH) , physical control format indicator channel (PCFICH) , physical hybrid automatic repeat request indicator channel (PHICH) , physical downlink control channel (PDCCH) , etc. The data may be for the physical downlink shared channel (PDSCH) , etc. The transmit processor 420 may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 420 may also generate reference symbols, e.g., for the primary synchronization signal (PSS) , secondary synchronization signal (SSS) , and cell-specific reference signal. A transmit (TX) multiple-input multiple-output (MIMO) processor 430 may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to the modulators (MODs) 432a through 432t. Each modulator 432 may process a respective output symbol stream (e.g., for OFDM, etc. ) to obtain an output sample stream. Each modulator 432 may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulators 432a through 432t may be transmitted via the antennas 434a through 434t, respectively.

At the UE 115, the antennas 452a through 452r may receive the downlink signals from the eNB 105 and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively. Each demodulator 454 may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator 454 may further process the input samples (e.g., for OFDM, etc. ) to obtain received symbols. A MIMO detector 456 may obtain received symbols from all the demodulators 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 458 may process (e.g., demodulate, deinterleave, and decode) the detected symbols, provide decoded data for the UE 115 to a data sink 460, and provide decoded control information to a controller/processor 480.

On the uplink, at the UE 115, a transmit processor 464 may receive and process data (e.g., for the physical uplink shared channel (PUSCH) ) from a data source 462 and control information (e.g., for the physical uplink control channel (PUCCH) ) from the controller/processor 480. The transmit processor 464 may also generate reference symbols for a reference signal. The symbols from the transmit processor 464 may be precoded by a TX MIMO processor 466 if applicable, further processed by the demodulators 454a through 454r (e.g., for SC-FDM, etc. ) , and transmitted to the eNB 105. At the eNB 105, the uplink signals from the UE 115 may be received by the antennas 434, processed by the modulators 432, detected by a MIMO detector 436 if applicable, and further processed by a receive processor 438 to obtain decoded data and control information sent by the UE 115. The processor 438 may provide the decoded data to a data sink 439 and the decoded control information to the controller/processor 440.

The controllers/

processors

440 and 480 may direct the operation at the eNB 105 and the UE 115, respectively. The controller/processor 440 and/or other processors and modules at the eNB 105 may perform or direct the execution of various processes for the techniques described herein. The controllers/processor 480 and/or other processors and modules at the UE 115 may also perform or direct the execution of the functional blocks illustrated in FIG. 8, and/or other processes for the techniques described herein. The

memories

442 and 482 may store data and program codes for the eNB 105 and the UE 115, respectively. A scheduler 444 may schedule UEs for data transmission on the downlink and/or uplink.

The advance of the 802.11 wireless and the push to open up spectrum for unlicensed use prompted the creation of dynamic frequency selection (DFS) . DFS is a mechanism that allows unlicensed devices to use the 5 GHz frequency bands, which are already allocated to priority communications systems, such as radar systems, without causing interference to those priority systems. The coexistence of wireless systems with radars is illustrated in FIG. 5.

FIG. 5 is a block diagram illustrating multiple wireless networks deployed and coexisting with a radar system 500. Radar system 500 operates by sending radar pulses over the 5 GHz frequency band. Radar system 500 has priority access to the 5 GHz band and either core network 501 or core network 507 will perform DFS procedures in order to avoid interfering with the radar signals from radar system 500. Core network 501 includes an access point 502 which provides wireless communication in a coverage area 503. Coverage area 503 overlaps with coverage area 508, provided by access point 509 of core network 507. Access point 502 provides wireless communication through core network 501 to terminals 504-506, while access point 509 provides wireless communication through core network 507 to terminals 510-512. When any of

access points

502 and 509, and terminals 504-506 and 510-512 begin preparing to transmit over portions of the 5 GHz frequency band, they perform DFS in order to detect whether there are any existing radar pulses on the frequency they intend to transmit on, and, if so, to dynamically change the intended transmission frequency.

It should be noted that core network 501 and core network 507 may operate using any number of radio access technologies (RATs) . In one example of operation, core network 501 may operate WIFI communications, while core network 507 may operate LTE/LTE-A communications with unlicensed spectrum. In another example, core network 501 may operate GSM wireless communication with unlicensed spectrum, while core network 507 operates LTE/LTE-A communications with unlicensed spectrum. Any combination of RATs that allows communications over the unlicensed spectrum may be utilized in the representative aspects.

In the U.S., Europe, Japan, and China, any wireless systems deployed within a portion of the 5 GHz band (e.g., between 5170 MHz and 5835 MHz) will use DFS in order to avoid collisions or interference with priority communications systems, such as radar system 500. For example, in the U.S., DFS may be required for use by wireless systems operating between approximately 5240 MHz and 5750 MHz. Other frequencies within the 5 GHz band do not require such use in the U.S. Thus, when access points 502 and 509, and terminals 504-506 and 510-512 intend to transmit over a 5 GHz band frequency where DFS is not required, then these entities will transmit without first performing the DFS procedures.

The concept behind DFS is to have the unlicensed devices detect the presence of a radar system on the channel they are using. If the level of any detected radar signal is above a certain threshold, the unlicensed device will vacate that channel and select an alternate channel for transmission. An additional function of DFS is to detect and identify any potential communications from priority communications systems that the electronic device operating DFS intercepts.

In addition to the deployment of wireless systems and devices operating under current wireless standards, such as IEEE 802.11 devices, in the 5 GHz unlicensed band, LTE/LTE-A with unlicensed spectrum may also use unlicensed access to the 5 GHz band in order to increase unlicensed spectrum benefits for improved user experience and network coverage by building on the LTE scale and ecosystem. As previously indicated, one deployment mode for LTE/LTE-A with unlicensed spectrum is supplemental downlink (SDL) . In SDL mode, LTE downlink capacity in the licensed spectrum may be opportunistically offloaded to an unlicensed spectrum, while any feedback or other uplink communications are transmitted in license band.

FIGs. 6A and 6B are block diagrams illustrating UE 600 in LTE/LTE-A networks with unlicensed spectrum in an SDL mode. FIG. 6A depicts UE 600 operating in LTE/LTE-A network with unlicensed spectrum. In SDL mode, the primary component carrier (PCC) is carried in licensed frequency division duplex (FDD) carriers for uplink and downlink communications. The secondary component carrier (SCC) operates over an unlicensed carrier band, without any signaling, any feedback, or any uplink communications. FIG. 6B depicts UE 600 in another SDL mode network in which the PCC is carried in a licensed time division duplex (TDD) carrier with the SCC again carried over the unlicensed frequency band.

Transmitters operating in an LTE/LTE-A network with unlicensed spectrum when used in an SDL mode provide a challenge when deployed in DFS band, as there is no corresponding receive chain from which to detect communications from priority communications systems. The transmitters in SDL mode would only have transmit chains operational for the secondary unlicensed carriers carrying the supplemental downlink data. Moreover, the LTE waveform is a continuous waveform, thus, there would be no opportunity for the transmitter to detect such priority communications. The issue arises of how such transmitters operating in SDL mode would create a DFS opportunity that guarantees reliable identification of the priority communications while minimizing the impact to unicast services.

MBSFN (Multicast/Broadcast over Single Frequency Network) is introduced in LTE downlink for enhanced Multimedia Broadcast Multicast Service (eMBMS) . eMBMS can be combined with unicast transmissions by time division multiplexing MBSFN subframes with PDSCH subframes. Table 1 shows a subframe configuration for SDL deployment.

Table 1

Where, ‘D’ represents downlink data subframes for PDSCH and ‘M’ represents the MBSFN subframes. MBSFN subframes are prohibited to transmit in

subframe

0, 4, 5 and 9.

FIG. 7 is a block diagram illustrating an MBSFN subframe 70. An MBSFN subframe, such as MBSFN subframe 70, includes a non-MBSFN region 700 in the first two OFDM symbols, which supports normal and extended cyclic prefix (CP) . The non-MBSFN region 700 may also use both cell-specific and/or UE-specific reference signals, and may be used for unicast control channels (e.g., physical control format indicator channel (PCFICH) , physical downlink control channel (PDCCH) , etc. ) . An MBSFN subframe, such as MBSFN subframe 70, also includes an MBSFN region 701 in 10 OFDM symbols within an extended CP. MBSFN region 701 would include the physical multicast channel (PMCH) and a reference signal at antenna port 4. MBSFN region 701 is transmitted in subframes when PMCH is also transmitted.

Various aspects of the present disclosure configure MBSFN subframes with muted OFDM symbols in order to create opportunities for an SDL mode base station or transmitter to perform DFS for priority communications, such as radar. Aspects of the present disclosure would provide for the transmit chain of a base station or transmitter to be fully off during these muted OFDM symbols of the MBSFN subframes to enable detection of priority communications using the receive chain of the base station, such as through radar pulse detection.

In one example of a priority communications system, radar waveforms of a radar system are generally bursty and may contain multiple radar pulses. Thus, DFS would suggest a reliable detection of radar bursts based on multiple pulse observations. Federal Communication Commission (FCC) guidelines for simulated radar waveforms identify six different radar signal types. Table 2 identifies FCC radar types 1-4, which are short pulse radars.

Table 2

Where the pulse width represents the length of the radar pulse, PRI represents the pulse repetition interval, pulses per burst represents the number of radar pulses transmitted per radar burst, and minimum Pd represents the minimum acceptable probability of detection.

Table 3

Table 3 identifies FCC type 5 radar, the long pulse radar type, in which pulse widths range from 50-100 μsec. Table 4 below identifies FCC type 6 radar, which is a frequency hopping radar that also includes a hopping rate that represents the rate at which the radar bursts hop frequencies.

Table 4

In order to effectively ensure detection of priority transmissions, such as radar, a detection method would need to meet a certain threshold probability of detection, Pd. In order to meet such a threshold, a sufficient number of observation opportunities should be created. In the best case, all symbols in an MBSFN subframe may be muted, thus, allowing the receive chain an entire subframe to listen for priority transmissions. In the worst case, only the symbols in the MBSFN region of an MBSFN subframe are muted, which allows a much shorter amount of time for the receive chain to listen for the priority transmissions. Aspects of the present disclosure provide direction for determining the number of MBSFN subframes in a frame that should be configured to create observation opportunities and how many OFDM symbols in each such MBSFN subframe should be muted in order to guarantee the radar burst detection.

For single pulse detection probability, radar pulses can be detected during the MBSFN region with a certain pulse detection probability. The reliability of pulse detection probability directly impacts the burst detection performance. Simulations of such pulse detection processes conducted over each of the six FCC radar waveform types indicate that each MBSFN subframe should include muted symbols in order to create enough observation opportunities to guarantee minimum burst detection probability for each kind of six FCC radar waveforms. Providing for muted symbols in each MBSFN subframe provides observation opportunities for DFS in six of the ten subframes in a given transmission frame. Aspects of the present disclosure provide for each of the symbols in the MBSFN region of the MBSFN subframes to be muted. The non-MBSFN region of MBSFN subframes includes both CRS and PDCCH symbols. The CRS and PDCCH symbols may either be on or off, depending on the presence of unicast data transmitted in the non-MBSFN subframes, the priority communication type, and whether or not a minimum threshold probability of detection, Pd, may be achieved. For example, when there is no unicast data in the MBSFN subframe, the eNB may mute both the CRS and PDCCH symbols in the non-MBSFN subframes. When there is unicast data, the eNB will mute the PDCCH symbols but keep the CRS symbol on. In additional aspects, when the PDCCH symbol is muted, the eNB may allocate some of the unallocated RBs of the CRS symbol to PDCCH.

FIG. 8 is a block diagram illustrating example blocks executed to implement one aspect of the present disclosure. At block 800, a base station determines that its operational frequency lies within an unlicensed spectrum shared with a priority communication system. For example, the base station may operate within an LTE/LTE-A network with unlicensed spectrum. The base station provides transmission in an SDL mode over the unlicensed spectrum that is shared with a higher-priority communication system, such as a radar system.

At block 801, the base station mutes a transmit chain for one or more symbols within each MBSFN subframe of its transmission frame. The base station mutes its transmit chain during all of the symbols in the MBSFN region of the MBSFN subframe. The transmit chain includes the transmission components of the base station, such as each of the transmitters, antennas, transmit processors, modulators, and the like, which provide the transmitting functionality of the base station. Depending on whether downlink/unicast data is to be transmitted in the non-MBSFN subframes by the base station, it may also mute either the PDCCH symbols of the non-MBSFN region in the MBSFN subframe when there is downlink/unicast data for transmission or both the PDCCH symbols and CRS symbols in the non-MBSFN region when there is no downlink/unicast data for transmission.

At block 802, the base station uses its receive chain to monitor for transmissions from the priority communication system during the muted symbols. The receive chain includes the receiving components of the base station, such as each of the receivers, antennas, receive processors, demodulators, and the like, which provide the signal receiving functionality of the base station. The monitoring for priority transmission may include performing DFS for radar transmissions or other such higher-priority transmissions.

FIG. 9A is a block diagram illustrating a base station 900 configured according to one aspect of the present disclosure. Base station 900 operates to transmit an SCC over an unlicensed frequency band in an SDL mode of an LTE/LTE-A network. For transmitting over the unlicensed frequency band, base station 900 configures MBSFN subframe 900 to mute each of the symbols in MBSFN region 902 and mutes the PDCCH symbols in non-MBSFN region 903. Thus, base station 900 transmits CRS0 in non-MBSFN region 903 of MBSFN subframe 901. In the remaining symbols of MBSFN subframe 901, transmissions are muted, thus, the transmit chain of base station 900 is shut down. During this muted period, base station 900 activates its receive chain to monitor for priority communications, such as radar transmissions.

FIG. 9B is a block diagram illustrating base station 900 configured according to another aspect of the present disclosure. As in FIG. 9A, base station 900 transmits an SCC over an unlicensed frequency band in an SDL mode. However, according to the example illustrated in FIG. 9B, base station 900 detects that no unicast data is to be transmitted over the non-MBSFN subframes of a give transmission frame. Accordingly, base station 900 configures MBSFN subframe 901 to mute transmissions across the entire subframe in MBSFN region 902 and non-MBSFN region 903. During each of such MBSFN subframes, such as MBSFN subframe 901, base station 900 shuts down its transmit chain, and performs DFS for priority transmission using its receive chains.

As illustrated in Table 1,

subframes

0, 4, 5, and 9 may not be configured as an MBSFN subframe. When data is available for transmission,

subframes

0, 4, 5 and 9 may be used for downlink unicast transmission. If CRS are not transmitted because the base station has turned off the transmit chain in the

MBSFN subframes

1, 2, 3, 6, 7, and 8, UE channel estimation will not occur until CRS transmissions are resumed. This delay may cause a phase incontinuity for unicast channel estimation which impacts

subframes

4 and 9. Additional aspects of the present disclosure provide for opportunistically turning on the transmit chain for CRS symbols in

MBSFN subframes

3 and 8 as a “warm up period” for UE channel estimation prior to the

unicast subframes

4 and 9. By activating the transmit chain for CRS in

subframes

3 and 8, the probability of detection may be marginally reduced while UE channel estimation is protected. The marginal reduction may only fall below the minimum probability of detection, Pd, for certain priority transmission waveform types, such as certain FCC radar waveform types.

FIG. 10 is a block diagram illustrating a base station 1000 configured according to one aspect of the present disclosure. Base station 1000 transmits in SDL mode in an LTE/LTE-A network with unlicensed spectrum. The unlicensed spectrum is shared with priority communication system 1002. In transmitting SCC over the unlicensed spectrum, base station 1000 configures its transmission frame 1001 to create observation opportunities, such as by performing DFS, during the MBSFN subframes,

subframes

1, 2, 3, 6, 7, and 8. During

subframes

1, 2, 6, and 7, base station 1000 turns off transmit chain 1000-TX completely, while in

subframes

3 and 8, transmit chain 1000-TX is turned off only for the PDCCH symbols in

subframes

3 and 8. During the MBSFN subframes, base station 1000 activates receive chain 1000-RX in order to listen or perform DFS to detect transmissions by priority communication system 1002.

Base station 1000 further includes data for unicast transmission that is scheduled for transmission in

subframes

0, 4, 5, and 9. As noted above, if base station 1000 completely turns off transmit chain 1000-TX in

subframes

3 and 8, a UE scheduled to receive the unicast data would not be able to perform channel estimation on CRS prior to

subframes

4 and 9. However, as configured according to one aspect of the present disclosure, base station 1000 continues to transmit CRS in the symbols of the non-MBSFN region of

subframes

3 and 8. Thus, the UE may perform channel estimation based on the CRS in order to more accurately decode the unicast data transmitted by base station 1000 in

subframes

4 and 9.

Those of skill in the art would understand that 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 functional blocks and modules in FIG. 8 may comprise processors, electronics devices, hardware devices, electronics components, logical circuits, memories, software codes, firmware codes, etc., or any combination thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure. Skilled artisans will also readily recognize that the order or combination of components, methods, or interactions that are described herein are merely examples and that the components, methods, or interactions of the various aspects of the present disclosure may be combined or performed in ways other than those illustrated and described herein.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a field programmable gate array (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. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. 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. Computer-readable storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, 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, a connection may be 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, or digital subscriber line (DSL) , then the coaxial cable, fiber optic cable, twisted pair, or DSL, are included in the definition of medium. Disk and disc, as used herein, includes compact disc (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 should also be included within the scope of computer-readable media.

As used herein, including in the claims, the term “and/or, ” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone； B alone； C alone； A and B in combination； A and C in combination； B and C in combination； or A, B, and C in combination. 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 a disjunctive 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., A and B and C) .

The previous description of the disclosure is provided to enable any 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 spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

WHAT IS CLAIMED IS:

Claims

A method of wireless communication， comprising：

determining， by a base station， an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system；

muting， by the base station， atransmit chain of the base station for one or more symbols within each of a plurality of multicast-broadcast single frequency network (MBSFN) subframes of a transmission frame of the base station； and

monitoring， by a receive chain of the base station during the one or more symbols， for transmissions from the priority communication system.
The method of claim 1， wherein the muting includes：

muting each symbol in an MBSFN region of the MBSFN subframes； and

muting at least one symbol in a non-MBSFN region of the MBSFN subframes.
The method of claim 2， wherein the muting the at least one symbol in the non-MBSFN region includes one of：

muting a downlink control channel in the non-MBSFN region； or

muting the downlink control channel and a common reference signal in the non-MBSFN region when a minimum probability determination fails to meet a predefined threshold with muting only the downlink control channel.
The method of claim 2， further including：

determining， by the base station， unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the muting the at least one symbol in the non-MBSFN region includes：

muting a downlink control channel in the non-MBSFN region； and

muting a common reference signal in the non-MBSFN region of each of the MBSFN subframes located two or more subframes before the one or more non-MBSFN subframes with unicast data.
The method of claim 1， further including：

determining， by the base station， no unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the muting includes：

muting for all symbols in each of the plurality of non-MBSFN subframes of the transmission frame.
The method of any combination of claims 1-5.
An apparatus configured for wireless communication， comprising：

means for determining， by a base station， an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system；

means for muting， by the base station， atransmit chain of the base station for one or more symbols within each of a plurality of multicast-broadcast single frequency network (MBSFN) subframes of a transmission frame of the base station； and

means for monitoring， by a receive chain of the base station during the one or more symbols， for transmissions from the priority communication system.
The apparatus of claim 7， wherein the means for muting includes：

means for muting each symbol in an MBSFN region of the MBSFN subframes； and

means for muting at least one symbol in a non-MBSFN region of the MBSFN subframes.
The apparatus of claim 8， wherein the means for muting the at least one symbol in the non-MBSFN region includes one of：

means for muting a downlink control channel in the non-MBSFN region； or

means for muting the downlink control channel and a common reference signal in the non-MBSFN region when a minimum probability determination fails to meet a predefined threshold with muting only the downlink control channel.
The apparatus of claim 8， further including：

means for determining， by the base station， unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the means for muting the at least one symbol in the non-MBSFN region includes：

means for muting a downlink control channel in the non-MBSFN region； and

means for muting a common reference signal in the non-MBSFN region of each of the MBSFN subframes located two or more subframes before the one or more non-MBSFN subframes with unicast data.
The apparatus of claim 7， further including：

means for determining， by the base station， no unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the means for muting includes：

means for muting for all symbols in each of the plurality ofnon-MBSFN subframes of the transmission frame.
The apparatus of any combination of claims 7-11.
A non-transitory computer-readable medium having program code recorded thereon， the program code including：

program code for causing a computer to determine， by a base station， an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system；

program code for causing the computer to mute， by the base station， atransmit chain of the base station for one or more symbols within each of a plurality of multicast-broadcast single frequency network (MBSFN) subframes of a transmission frame of the base station； and

program code for causing the computer to monitor， by a receive chain of the base station during the one or more symbols， for transmissions from the priority communication system.
The non-transitory computer-readable medium of claim 13， wherein the program code for causing the computer to mute includes：

program code for causing the computer to mute each symbol in an MBSFN region of the MBSFN subframes； and

program code for causing the computer to mute at least one symbol in a non-MBSFN region of the MBSFN subframes.
The non-transitory computer-readable medium of claim 14， wherein the program code for causing the computer to mute the at least one symbol in the non-MBSFN region includes one of：

program code for causing the computer to mute a downlink control channel in the non-MBSFN region； or

program code for causing the computer to mute the downlink control channel and a common reference signal in the non-MBSFN region when a minimum probability determination fails to meet a predefined threshold with muting only the downlink control channel.
The non-transitory computer-readable medium of claim 14， further including：

program code for causing the computer to determine， by the base station， unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the program code for causing the computer to mute the at least one symbol in the non-MBSFN region includes：

program code for causing the computer to mute a downlink control channel in the non-MBSFN region； and

program code for causing the computer to mute a common reference signal in the non-MBSFN region of each of the MBSFN subframes located two or more subframes before the one or more non-MBSFN subframes with unicast data.
The non-transitory computer-readable medium of claim 13， further including：

program code for causing the computer to determine， by the base station， no unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the program code for causing the computer to mute includes：

program code for causing the computer to mute for all symbols in each of the plurality of non-MBSFN subframes of the transmission frame.
The non-transitory computer-readable medium of any combination of claims 13-17.
An apparatus configured for wireless communication， the apparatus comprising：

at least one processor； and

a memory coupled to the at least one processor，

wherein the at least one processor is configured：

to determine， by a base station， an operational frequency band of the base station is within an unlicensed spectrum shared with a priority communication system；

to mute， by the base station， atransmit chain of the base station for one or more symbols within each of a plurality of multicast-broadcast single frequency network (MBSFN) subframes of a transmission frame of the base station； and

to monitor， by a receive chain of the base station during the one or more symbols， for transmissions from the priority communication system.
The apparatus of claim 19， wherein the configuration of the at least one processor to mute includes configuration of the at least one processor：

to mute each symbol in an MBSFN region of the MBSFN subframes； and

to mute at least one symbol in a non-MBSFN region of the MBSFN subframes.
The apparatus of claim 20， wherein the configuration of the at least one processor to mute the at least one symbol in the non-MBSFN region includes configuration of the at least one processor to one of：

mute a downlink control channel in the non-MBSFN region； or

mute the downlink control channel and a common reference signal in the non-MBSFN region when a minimum probability determination fails to meet a predefined threshold with muting only the downlink control channel.
The apparatus of claim 20， further including configuration of the at least one processor to determine， by the base station， unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the configuration of the at least one processor to mute the at least one symbol in the non-MBSFN region includes configuration：

to mute a downlink control channel in the non-MBSFN region； and

to mute a common reference signal in the non-MBSFN region of each of the MBSFN subframes located two or more subframes before the one or more non-MBSFN subframes with unicast data.
The apparatus of claim 19， further including configuration of the at least one processor to determine， by the base station， no unicast data for downlink transmission in one or more non-MBSFN subframes of the transmission frame， wherein the configuration of the at least one processor to mute includes configuration to mute for all symbols in each of the plurality of non-MBSFN subframes of the transmission frame.
The apparatus of any combination of claims 19-23.