Patent Description:
The present application claims is related to PCT Patent Application entitled "UNLICENSED FREQUENCY BAND WITH LICENSED FREQUENCY BAND TIMING", Docket Number TUTL <NUM> PC, PCT Patent Application entitled "COMMUNICATION RESOURCE SCHEDULING FOR DEVICE-TO-DEVICE (D2D) COMMUNICATION IN AN UNLICENSED FREQUENCY BAND", Docket Number TUTL <NUM> PC, and PCT Patent Application entitled "PHYSICAL CHANNEL STRUCTURE FOR COMMUNICATION IN UNLICENSED FREQUENCY BAND", Docket Number TUTL <NUM> PC all assigned to the assignee hereof.

This invention generally relates to wireless communications and more particularly to assigning unused communication resources in an unlicensed frequency band equipment operating in a licensed frequency band.

The frequency spectrum used by a particular communication system may be licensed or unlicensed. Licensed frequency spectrum (frequency band) is licensed to a system operator by a government agency such as the Federal Communications Commission (FCC). An example of such licensed spectrum includes frequency bands used for cellular communication. An unlicensed frequency band is any portion of frequency spectrum that does not require a license from the government agency to communicate with the unlicensed frequency band. Equipment operating within the unlicensed band, however, typically must adhere to regulations and/or communication standards. An example of unlicensed frequency spectrum includes frequency bands used for Institute of Electrical and Electronics Engineers (IEEE) <NUM> communication.

<CIT> discloses a method of operating a first communications device comprising: establishing, during a first time interval, a communications link between said first communications device and a second communications device using a first frequency band; communicating data between said first communications device and said second communications device using a second frequency band in a second time interval following said first time interval, said first and second frequency bands being non-overlapping frequency bands; and communicating a control signal between said first communications device and said second communications device using said first frequency band during said second time interval.

<CIT> discloses a method comprising: collecting at a cellular network node information about at least interference in a plurality of channels in unlicensed spectrum; and using the collected information to update an allocation of the channels among at least two different access points.

<CIT> discloses a method for communication implementation for a user equipment, comprising: reporting, by a user equipment, to a network state information of other sub-devices except a sub-device adopting Long Term Evolution (LTE) technology; and performing, by the network, radio resource management according to the state information.

The present invention provides a method according to claim <NUM>, and a user equipment according to claim <NUM>. Further embodiments of the present invention are disclosed in the dependent claims.

Communication equipment communicating in a licensed frequency band identifies unused unlicensed communication resources within an unlicensed frequency band. The communication equipment uses the identified unlicensed communication resources to communicate within the unlicensed frequency band. In some circumstances, the unused unlicensed communication resources are identified based on resource information received from a base station where the resource information identifies unlicensed communication resources that will be used by the base station. In other circumstances, the unused unlicensed communication resources are identified based on frequency band measurements of the unlicensed frequency band over an observation time duration longer than a sensing time duration used by unlicensed equipment using the unlicensed frequency band.

<FIG> is a block diagram of a licensed communication system <NUM> having a licensed service area <NUM> where communication equipment <NUM>, <NUM>, <NUM>, <NUM> communicates using an unlicensed frequency band. The licensed communication system <NUM> may be any communication system that uses a portion of frequency spectrum (frequency band) that is licensed to the system operator by a government agency such as the Federal Communications Commission (FCC). For the examples discussed herein, the licensed communication system <NUM> is a cellular system that operates in accordance with at least one revision of The Third-Generation Partnership Project Long-Term Evolution (3GPP LTE) communication specification. Examples of licensed frequency bands include Advanced Wireless Service (AWS) <NUM> frequencies in the range of <NUM>,<NUM>-<NUM>,<NUM> and <NUM>,<NUM>-<NUM>,<NUM>. The unlicensed frequency band is any portion of frequency spectrum that does not require a license from the government agency to communicate with the unlicensed frequency band. Equipment operating within the unlicensed band, however, typically must adhere to regulations and/or communication standards. Examples of unlicensed bands include frequency bands used for IEEE <NUM> standards that comply with the FCC Rules and Regulations such as WiFi, Bluetooth, and Zigbee. For the example <FIG>, an eNB <NUM> provides wireless service to user equipment (UE) devices <NUM>, <NUM>, <NUM> within a geographical service area (licensed service area) <NUM> using one or more licensed frequency bands.

A cellular communication system is typically required to adhere to a communication standard or specification. The communication specification defines physical channel structure that at least includes a data channel and a control channel for uplink and downlink transmissions and specifies at least some timing and frequency parameters for physical downlink control channels from a base station to a wireless communication device. The Third-Generation Partnership Project Long-Term Evolution (3GPP LTE) communication specification is a specification for systems where communication stations (eNodeBs) provide service to wireless communication devices (UE devices) using orthogonal frequency-division multiple access (OFDMA) on the downlink and single-carrier frequency-division multiple access (SC-FDMA) on the uplink. Although the techniques described herein may be applied in other types of communication systems, the exemplary systems discussed herein operate in accordance with an FDD 3GPP LTE communication specification.

The eNB <NUM> can be any type of communication station or transceiver station or radio head and may be referred to as a base station, eNodeB, fixed station, access point, and other terms. The eNB <NUM> may be connected within a network of several other eNBs through a backhaul (not shown in <FIG>). The UE devices <NUM>, <NUM>, <NUM> are any type of user devices and are sometimes referred to by other terms such as, for example, handset, phone, smartphone, mobile device, portable device, and modems. Communication using the licensed band may include downlink transmissions from the eNB to UE devices, uplink communication from UE devices to the eNB, and device-to-device (D2D) communication between two or more UE devices. The bi-directional arrows between the UE devices and the eNB in <FIG> represent a connection and/or an association but do not necessarily indicate an ongoing communication session. For example, a UE device may be registered to the eNB and receiving control information but not exchanging data with the eNB.

The licensed communication equipment communicates in the licensed frequency band using a licensed physical channel structure. The physical channel structure for downlink communication may differ from the physical channel structure for uplink communication. The licensed physical channel structure partitions time and frequency to define a plurality of time-frequency resources (resource elements). Sets of resources are allocated for a particular type of communication. For example, different sets of time-frequency communication resources can be allocated for data, control, and reference signals. For the examples herein, the licensed physical channel structure adheres to at least one revision of the 3GPP LTE communication specification.

Other unlicensed devices <NUM>, <NUM>, <NUM>, <NUM> within the licensed service area <NUM> use an unlicensed frequency band for communication. The unlicensed devices <NUM>, <NUM>, <NUM>, <NUM> may include access points <NUM> providing service to mobile devices <NUM> and devices <NUM>, <NUM> operating in device-to-device communication scenarios. The unlicensed communications may be ad hoc communication scenarios and may be bidirectional or one way. Accordingly, the unlicensed devices <NUM>, <NUM>, <NUM>, <NUM> may include various types of devices and equipment. For the example of <FIG>, an access point <NUM> provides wireless service to mobile devices <NUM> within an unlicensed service area <NUM> and two other devices <NUM>, <NUM> communicate directly with each other using the unlicensed frequency band.

For the examples herein, the licensed equipment <NUM>, <NUM>, <NUM>, <NUM> uses an unlicensed physical channel structure for communication in the unlicensed frequency band where the unlicensed physical channel structure at least has the same time and frequency divisions as the licensed physical channel structure. Although the frequencies are different, each frequency division in the unlicensed structure corresponds to a frequency division in the licensed structure such that the communication resource elements in the unlicensed structure correlate to the communication resource elements in the licensed structure. A reference set of communication resource elements for transmission of reference signals have the same symbol times as a reference set of resource elements allocated in the licensed physical channel structure for reference signals. Other arrangements may be used in some circumstances. An example of physical channel structure related to licensed and unlicensed communication is discussed in patent application entitled "Physical Channel Structure For Communication In Unlicensed Frequency Band", Docket Number TUTL <NUM> PC.

For the examples herein, the licensed equipment <NUM>, <NUM>, <NUM>, <NUM> uses the unlicensed frequency band for communication at times determined to avoid interference or at least to result in a tolerable level of interface with communication between unlicensed devices and, in some situations, other licensed devices using the unlicensed frequency band. When it is determined that unlicensed equipment is operating nearby, the unlicensed frequency band is monitored prior to transmission to determine if the band is currently in use. If it is determined that the band is not in use, the licensed equipment transmits signals within the unlicensed frequency band. The monitoring procedure prior to transmission is the same, or at least similar to the sensing/back off procedures employed by conventional devices operating in the unlicensed frequency band. The techniques may be required by rules or standards governing operation in the unlicensed frequency band. For the example of <FIG>, dashed arrows indicate transmissions within the unlicensed band by the licensed system equipment. In some scenarios, UE devices <NUM>, <NUM> transmit signals <NUM>, <NUM> to the eNB <NUM> within the unlicensed frequency band. The signals <NUM>, <NUM> reach the unlicensed devices that are sufficiently close depending on the power level of the signal. For example, the signal <NUM> from one UE device <NUM> may reach the access point <NUM> and the unlicensed mobile device <NUM> and the signal <NUM> from second UE device <NUM> may reach the unlicensed mobile device <NUM>, <NUM>. In another scenario, the eNB <NUM> transmits a signal <NUM> within the unlicensed frequency band to one or more UE devices <NUM> and the signal <NUM> may reach the unlicensed mobile devices <NUM>, <NUM>. The unlicensed mobile device <NUM> may be outside of the licensed service area <NUM> in some situations. Since the unlicensed frequency band is monitored for energy prior to transmission by the UE device <NUM>, interference at the unlicensed devices is reduced. In addition, interference at the licensed devices due to transmission by the unlicensed devices is also reduced.

In one example, eNBs provide unlicensed resource information to other nearby eNBs where the unlicensed resource information identifies the unlicensed communication resources that are being, or will be, used for communication in the unlicensed frequency band. The eNBs receiving the resource information identify unused unlicensed resources based on the resource information and use unlicensed communication resources least likely to cause interference.

In other examples, as discussed in further detail below, on observation procedure is performed by one or more eNBs and/or one or more UE devices. Frequency band measurements are taken by one or more eNBs and/or one or more UE devices to determine if it is likely that the unlicensed frequency band is in used by other equipment sufficiently close to result in interference. The unlicensed frequency band is observed for a relatively long period of time as compared to conventional sensing techniques used prior to a transmission in the unlicensed frequency band. For example, the unlicensed frequency band may be monitored on the order of hours. The energy within the unlicensed frequency band is measured and compared to a threshold. If the energy level is below a threshold (e.g., no interference is detected), it is determined that no nearby equipment is using the unlicensed frequency band and the licensed equipment operates in a non-sensing mode where the sensing/monitoring of unlicensed frequency band before transmission is omitted or at least reduced. The non-sensing mode differs from a sensing mode where devices sense or monitor one or more channels before transmitting a signal in the unlicensed frequency band. The sensing mode, therefore, is employed when it is confirmed that other nearby devices are using the unlicensed frequency band for communication or when it cannot be determined that no devices are using the unlicensed frequency band.

For the examples herein, the frequency band measurements of the observation procedure also differ from conventional listen-before-talk sensing techniques in that the interference measurements are based on the entire, or nearly entire, unlicensed frequency band. Conventional sensing techniques sense particular channels within the unlicensed frequency band to detect potential signals. In contrast, for the examples herein, the unlicensed frequency band is observed to detect any energy anywhere in the band that may indicate the band is in use.

The eNB may execute the observation procedure by making the frequency band measurements and/or may instruct one or more UE devices to perform the observation procedure by taking frequency band measurements and reporting the results to the eNB. For the example discussed with reference to <FIG>, for example, the eNB observes the unlicensed frequency band for the observation period and if the energy level does not exceed a threshold during the observation period, instructs at least one UE device to perform the observation procedure. The UE device reports the results and, if the UE did not detect energy above a threshold, the eNB instructs the UE devices that it is serving to operate in a non-sensing mode.

<FIG> is a block diagram of an example of a UE device <NUM> suitable for use as one of the UE devices <NUM>, <NUM>, <NUM> in <FIG>. The UE device <NUM> includes a licensed band transceiver <NUM>, a controller <NUM>, as well as other components and circuitry (not shown) such as memory, for example. For the examples herein, each UE device also includes an unlicensed band transceiver <NUM> which includes an unlicensed band receiver <NUM> and an unlicensed band transmitter <NUM>. The unlicensed band transmitter <NUM> transmits signals over the unlicensed frequency band where, depending on the situation, the signals may provide uplink control information to the eNB, uplink data information to the eNB, D2D control information to another UE, and/or D2D data information to another UE device. The unlicensed band transmitter <NUM> may also be used in some situations to transmit a reserve signal in the unlicensed frequency band as discussed below in further detail. The unlicensed band transmitter <NUM> may be omitted from the UE device <NUM>. This may be the case where the UE device <NUM> is used to only monitor the unlicensed band and/or only to receive signals within the unlicensed band. The unlicensed band receiver <NUM> receives signals over the unlicensed frequency band where, depending on the situation, the signals may provide downlink control information from the eNB, downlink data information from the eNB, D2D control information from another UE, and/or D2D data information from another UE device.

The licensed band transceiver <NUM> includes a transmitter that transmits uplink wireless signals to eNBs and a receiver that receives downlink wireless signals from the eNBs within the licensed frequency band. The transceiver can also be configured to transmit and receive D2D signals using allocated licensed uplink communication resources. The controller <NUM> controls components of the UE device <NUM> to manage the functions of the device <NUM> described herein as well as to facilitate the overall functionality of the device <NUM>. The controller <NUM> is connected to the transceivers <NUM>, <NUM> and other components such as memory.

The unlicensed band receiver <NUM> may be used to sense/monitor the unlicensed frequency band before a transmission in the unlicensed frequency band when the UE device is operating in the sensing mode. In addition, the unlicensed band receiver <NUM> may be used to perform the observation procedure. For the examples, the controller and the unlicensed band receiver <NUM> measure one or parameters that indicate the energy level within the unlicensed frequency band. An example of a suitable technique includes determining the received signal strength indicator (RSSI) which is a measurement of the power present in the received radio signal. The RSSI is compared to a threshold.

As discussed below, the unlicensed band receiver <NUM> is also used to measure channel conditions of the unlicensed frequency band during the non-sensing mode. Using techniques at least similar (if not the same) as the techniques used in the licensed frequency band for radio resource management (RRM) measurements.

<FIG> is a block diagram of an example of an eNB <NUM> suitable for use as the eNB <NUM> in <FIG>. The eNB <NUM> includes a licensed band transceiver <NUM>, a controller <NUM>, as well as other components and circuitry (not shown) such as memory, for example. For the examples herein, the eNB also includes an unlicensed band transceiver <NUM> which includes an unlicensed band receiver <NUM> and an unlicensed band transmitter <NUM>. The unlicensed band transmitter <NUM> transmits signals over the unlicensed frequency band where, depending on the situation, the signals may provide downlink control information to the UE device and downlink data information to the UE device. The unlicensed band transmitter <NUM> may also be used in some situations to transmit a reserve signal in the unlicensed frequency band as discussed below in further detail. The unlicensed band transmitter <NUM> may be omitted from the eNB <NUM>. This may be the case where the eNB is used to only monitor the unlicensed band and/or only to receive signals within the unlicensed band. The licensed band transceiver <NUM> exchanges wireless signals with the UE devices <NUM>, <NUM>, <NUM>, <NUM> within the service area <NUM>. Transmissions within the licensed band from the eNB and from the UE devices are governed by a communication specification that defines signaling, protocols, and parameters of the transmission with the frequency band licensed to the operator of the licensed system <NUM>. The communication specification may provide strict rules for communication and may also provide general requirements where specific implementations may vary while still adhering to the communication specification. Although the discussion herein is directed to the 3GPP Long Term Evolution (LTE) communication specification, other communication specifications may be used in some circumstances. The communication specification defines at least a data channel and a control channel for uplink and downlink transmissions and specifies at least some timing and frequency parameters for physical channels. As discussed below in further detail, at least one of the timing parameters is applied to the unlicensed frequency band.

The licensed band transceiver <NUM>, therefore, includes at least a downlink transmitter for transmitting downlink signals and an uplink receiver for receiving uplink signals. In some situations, the licensed band transceiver also includes downlink receiver. As discussed below, eNBs may wirelessly transmit unlicensed frequency band communication resource information in a downlink broadcast message for receipt by other nearby eNBs. Accordingly, the downlink receiver in the eNB <NUM> receives downlink signals from other eNBs.

The unlicensed band receiver <NUM> may be used to sense/monitor the unlicensed frequency band before a transmission in the unlicensed frequency band when the eNB is operating in the sensing mode. In addition, the unlicensed band receiver <NUM> may be used to perform the observation procedure. For the examples, the controller and the unlicensed band receiver <NUM> measure one or parameters that indicate the energy level within the unlicensed frequency band. An example of a suitable technique includes determining the received signal strength indicator (RSSI) which is a measurement of the power present in the received radio signal. The RSSI is compared to a threshold. The threshold used by the eNB is typically the same as the threshold used by UE devices although in some circumstances the thresholds may be different.

For the example, the eNB <NUM> also includes a communication interface <NUM> for facilitating communication over the backhaul with other eNBs and network entities. Where X2 signaling is available, the communication interface <NUM> communicates over the backhaul using X2.

<FIG> is a block diagram of a first eNB <NUM> and a second eNB <NUM> of the licensed communication system <NUM> for an example where unlicensed frequency band resource information <NUM> is provided by the first eNB <NUM> to the second eNB <NUM>. The eNBs <NUM>, <NUM> are eNBs are examples of the eNBs <NUM>, <NUM> discussed above and provide wireless service within the licensed frequency band in accordance with communication specification such as LTE. For the example, the first eNB <NUM> communicates with one or more UE devices <NUM> over a wireless channel <NUM> in the unlicensed frequency band. Accordingly, the first eNB <NUM> uses unlicensed communication resources in the unlicensed frequency band. For the example, the first eNB <NUM> provides unlicensed frequency band resource information <NUM> to other nearby eNBs such as the second eNB <NUM>. The unlicensed frequency band resource information <NUM> is indicative of the unlicensed frequency band communication resources that are being used to communicate with the one or more UE devices <NUM> and/or that will be used to communicate with the one or more UE devices <NUM>. The unlicensed frequency band communication resource information <NUM> in the examples herein is a message or signal that specifies the time-frequency resources that are to be used by the eNB <NUM> for communication in the unlicensed frequency band. The specified time-frequency resources may be used for downlink communication and/or uplink communication.

In some situations, the first eNB <NUM> is connected to the second eNB through a backhaul <NUM>. The backhaul can utilize any combination of wired and wireless communication links to establish communication between the eNBs. The backhaul <NUM>, for example, may include radio frequency and point-to-point microwave links and transmission hardware such as transmitters, receivers, wires, coaxial cables, fiber optic cables, and other known devices and equipment. In some circumstance, the backhaul supports X2 signaling and/or packet data protocols such as those used with the Internet. Where a backhaul is available, the first eNB transmits the unlicensed frequency band resource information over the backhaul <NUM> by applying techniques in accordance with conventional signaling over a backhaul. An X2 message, for example, can be sent including the unlicensed frequency band communication resource information.

In situations where the eNBs are not connected through a backhaul, the first eNB <NUM> provides unlicensed frequency band communication resource information <NUM> to nearby eNBs (<NUM>) by broadcasting the unlicensed frequency band communication resource information over a wireless channel <NUM>. An example of a suitable technique of broadcasting the information <NUM> in an LTE system includes transmitting a System Information Blocks (SIB) message including the information <NUM>. Since SIBs are transmitted in the downlink channel, the nearby eNBs <NUM> receive the SIB signals using a downlink receiver.

In another example, the first eNB <NUM> broadcasts the unlicensed frequency band communication resource information in the uplink channel. An example of suitable technique for broadcasting the unlicensed frequency band communication resource information on the uplink channel includes using a D2D channel defined by some revisions of the LTE standard. For example a broadcasts message similar to a D2D discovery signal can be sent from the eNB <NUM>.

After receiving the unlicensed frequency band communication resource information <NUM>, the second eNB <NUM> identifies which communication resources within the unlicensed frequency band are not in use. These unused unlicensed frequency band resources can then be used by the second eNB <NUM> to communicate with one or more UE devices <NUM> over a wireless channel <NUM> in the unlicensed frequency band. Generally, the unlicensed frequency band resources identified in the unlicensed frequency band communication resource information are not used by the eNB <NUM>. Therefore, the first eNB <NUM> reserves unlicensed frequency band resources for communication minimizing interference in the unlicensed frequency band. In some situations, the second eNB <NUM> may respond to the first eNB <NUM> with an indication that identified resources should not be used by the first eNB <NUM>. Such a situation may occur where the second eNB <NUM> requires the resources for high priority communication such as E911. Although not shown in <FIG>, the second eNB <NUM> transmits its own unlicensed frequency band communication resource information to nearby eNBs (such as the first eNB <NUM>). In some situations there are more than two eNBs within proximity of each other and each eNB received multiple unlicensed frequency band communication resource information messages from multiple eNBs.

<FIG> is a block diagram of licensed equipment <NUM> performing an observation procedure of the unlicensed frequency band. The licensed equipment observing device is any device that operates in the licensed band. For the example of <FIG>, the licensed equipment observing device <NUM> can be either an eNB or a UE device where more specific examples of each are discussed below. The licensed equipment observing device <NUM> monitors the unlicensed frequency band for radio energy that may be caused by unlicensed equipment <NUM> or licensed equipment <NUM> using the unlicensed frequency band. Signals <NUM> transmitted by an eNB or UE device and signal <NUM> transmitted by access points (APs) and mobile devices are received by the licensed equipment observing device <NUM> and evaluated. The received RF energy level is periodically measured during the observation time and compared to a threshold. If during the observation time, the energy level exceeds the threshold, the licensed equipment observing device <NUM> determines that other equipment within the service area is using the unlicensed spectrum. Otherwise, it is determined that the unlicensed frequency band is not in use.

Although various measurement timings and techniques can be used, the timing should be selected such that the likelihood that a device is using the unlicensed frequency band but is not detected is minimized. For example, the time period between measurements should not have a length such that a device could transmit between measurements and not be detected. The time period between measurements can be dynamic and, in some situations, be varied depending on current circumstances. Unlike for the case of RSRP/RSRQ measurements for LTE in licensed bands, there are no specific reference signals that the device is measuring in predefined subframe locations. The eNB should specify the periodicity and time period of each RSSI measurement. The eNB may determine the current periodicity and time period of the RSSI measurements using observed traffic patterns from e.g., APs in the unlicensed band. Alternatively, the eNB may configure measurement gaps to the device to allow the UE device to perform RSSI measurements based on these measurement gaps. The UE device may also perform RSSI measurements using Autonomous Gaps. If autonomous gaps are used to perform measurements, the UE is allowed to temporarily abort communication with all serving cell(s), i.e., create autonomous gaps to perform the corresponding measurements within the limits specified in TS <NUM> [<NUM>]. In yet another mode of operation, the UE device with multiple receivers may continuously measure the RSSI signal for the entire duration of the measurement request from the eNB (e.g., <NUM> hour) in the specified frequency/band without any impact to its cellular reception. The UE may determine such measurement based on its reserved battery power remaining. Other signal measurements can also be used. Examples of other forms of measurements include BeaconRSSI, RCPI (Received channel power indicator) and RSNI (Received Signal to Noise Indicator) that are specific to WLAN in case the eNB is already aware of the type of interference expected in the region.

<FIG> is an illustration of a timing relationship <NUM> of the unlicensed frequency <NUM> of the observing procedure as compared to a sensing/back-off procedure. Typically, equipment operating in an unlicensed frequency band, such as an <NUM> band, must adhere to regulations and/or communication standards. These regulation or standards often utilize carrier sense multiple access (CSMA) where a transmitting device is required to "listen before talk". Unlicensed systems may also employ collision avoidance techniques. In some circumstances, licensed equipment operating in the unlicensed frequency band may also employ the channel access techniques required in the unlicensed frequency band.

For the example, channel access procedure used in the unlicensed frequency band is a sense and back-off procedure (sense/back-off procedure) where the unlicensed frequency band is monitored <NUM> for a sensing time duration <NUM> and, if no other devices are determined to be using the band, the eNB waits a back-off period <NUM> before transmitting. The back-off period <NUM> is dynamic and may be determined by a formula typically applied by unlicensed equipment in the unlicensed band. The sensing time duration <NUM> is typically on the order of tens of microseconds.

The licensed equipment observing device <NUM> performs an observation procedure <NUM> for an observation time duration <NUM>. As discussed above, the licensed equipment <NUM> continually (or periodically at a sufficient frequency) compares received signal energy in the unlicensed frequency band to a threshold. If the threshold is exceeded, it is determined that other equipment using the unlicensed frequency band is sufficiently close to create interference. As illustrated in <FIG>, the observing time duration <NUM> is relatively long and is significantly longer than the sending time duration <NUM>. The time duration <NUM> is selected such that it is sufficiently long to allow reliable determination that no other equipment is using the unlicensed frequency band. The observation time duration <NUM> is typically on the order of hours and may be several days. An example of a suitable observing time duration <NUM> is <NUM> hours. Other time durations can be used and may depend on the factors such as the expected radio traffic in the area, history of radio traffic in the area, and other factors. In some circumstances, the time duration <NUM> may be less than an hour.

<FIG> is an illustration of unlicensed equipment and licensed equipment for an example where the licensed equipment observing device <NUM> is a UE device <NUM>. The observing UE device <NUM> monitors the unlicensed frequency band for energy from signals transmitted within the unlicensed frequency band where the signals may include signals <NUM> transmitted by another UE device <NUM>, signals <NUM> transmitted by an eNB <NUM>, signals <NUM> transmitted by a mobile device <NUM>, and signals <NUM> transmitted by an access point (AP) <NUM>. The signals <NUM>, <NUM> result from communication <NUM> in the unlicensed frequency band between the eNB <NUM> and the UE device <NUM>. Therefore, the signal energy at the UE device <NUM> may be due to licensed equipment operating in the unlicensed frequency band. The signals <NUM>, <NUM> result from communication <NUM> in the unlicensed frequency band between the access point <NUM> and the mobile device <NUM>. The signal energy, therefore, at the UE device <NUM> may result from one more unlicensed devices operating in the unlicensed frequency band.

The UE device <NUM> observes the unlicensed frequency band by taking frequency band measurements and, if the detected energy is below the threshold for a sufficiently long time, determines that the unlicensed frequency band is not being used by any nearby equipment. For the examples herein, the UE device <NUM> reports the results in frequency band measurement information <NUM> to its serving eNB <NUM>. The eNB <NUM>, at least partially based on the frequency band measurement information <NUM>, determines whether communications <NUM> in the unlicensed frequency band should be modified. For example, the eNB <NUM> may determine that the eNB and UE device can operate in a non-sensing mode where the equipment does not employ a sense/back-off procedure before transmitting in the unlicensed frequency band. An example of suitable technique includes operating in the unlicensed frequency band with the same channel access protocol used in the licensed frequency band. The eNB <NUM> and the UE device <NUM>, therefore, operate in sensing mode when the unlicensed frequency band is being used by other nearby equipment and operate in a non-sensing mode when it is determined that the unlicensed frequency band is not being used by other equipment.

The frequency band measurement information <NUM> is indicative of the frequency band measurements taken by the UE device. In some situations, frequency band measurement information <NUM> is indicative of a comparison of one or more measured energy levels to the threshold. For example, the frequency band measurement information <NUM> may simply be a flag indicating that the energy level has exceeded the threshold within the observation time period. In other situations, the frequency band measurement information <NUM> may be measurements, values, or data based on measurement values which can be used by the eNB to make determinations regarding the use of the unlicensed frequency band by other devices.

<FIG> is an illustration of unlicensed equipment and licensed equipment for an example where the licensed equipment observing device <NUM> is an eNB <NUM>. The eNB <NUM> monitors the unlicensed frequency band for energy from signals transmitted within the unlicensed frequency band where the signals may include signals <NUM> transmitted by another UE device <NUM>, signals <NUM> transmitted by an eNB <NUM>, signals <NUM> transmitted by a mobile device <NUM>, and signals <NUM> transmitted by an access point (AP) <NUM>. The signals <NUM>, <NUM> result from communication <NUM> in the unlicensed frequency band between the eNB <NUM> and the UE device <NUM>. Therefore, the signal energy at the eNB <NUM> may be due to licensed equipment operating in the unlicensed frequency band. The signals <NUM>, <NUM> result from communication <NUM> in the unlicensed frequency band between the access point <NUM> and the mobile device <NUM>. The signal energy, therefore, at the eNB <NUM> may result from one or more unlicensed devices operating in the unlicensed frequency band.

The eNB <NUM> monitors the unlicensed frequency band and, if the detected energy is below the threshold for a sufficiently long time, determines that the unlicensed frequency band is not being used by any nearby equipment. The eNB <NUM>, at least partially based on the measurements of the unlicensed frequency band, determines whether communications in the unlicensed frequency band should be modified. For example, the eNB <NUM> may determine that the eNB and UE device can operate in the non-sensing mode where the equipment does not employ a sense/back-off procedure before transmitting in the unlicensed frequency band.

In many circumstances, the eNB <NUM> bases the determination on multiple interference measurement reports receives from multiple UE devices as well as on its own measurements of the unlicensed frequency band. The eNB <NUM> may approach the use of the non-sensing mode more conservatively. In case any UE device reports a measurement above the threshold the eNB <NUM> should not apply the non-sensing mode. Another technique includes having coordination among eNBs whereby the first eNB <NUM> informs the second eNB <NUM> in case eNB <NUM> detects interference in the unlicensed band but the second eNB <NUM> does not. This technique assumes that the two eNBs are in close proximity.

The eNB <NUM> and the UE device <NUM> continue to monitor the unlicensed frequency band when in the non-sensing mode. In one example, UE devices operating in the non-sensing mode perform Radio Resource Management (RRM) measurements of the unlicensed frequency band and report the RRM measurements to the eNB <NUM>. The eNB <NUM> configures one or more thresholds in the UE devices either by broadcast (SIB) or dedicated controls signals. The thresholds may include one or more of a radio signal strength indicator (RSSI), a received channel power indicator (RCPI), a received signal to noise indicator (RSNI), and an average noise plus interference (ANPI) indicator. The eNB compares the reported RRM measurements to thresholds and makes an assessment of the channel characteristics. In some situations, the channel characteristics may indicate a potential interferer which triggers the eNB to return to sensing mode, perform the frequency band observation procedure, and/or instruct one or more UE devices to perform the frequency band observation procedure.

<FIG> is a flow chart of a method performed at an eNB for an example of managing operation of a licensed communication system in an unlicensed frequency band in a sensing mode and a non-sensing mode.

At step <NUM>, the eNB performs a frequency band observation procedure on the unlicensed frequency band. The eNB periodically measures the energy level within the unlicensed frequency band for the observation time. As discussed above, an example of a suitable technique of observing the band includes measuring RSSI over for the entire band and comparing the level to a threshold.

At step <NUM>, if the energy level exceeds a threshold, the eNB determines that other devices are transmitting within the unlicensed frequency band. If other devices are using the unlicensed frequency band, the method continues at step <NUM>. Otherwise, the method continues at step <NUM>.

At step <NUM>, the system communicates in the unlicensed frequency band <NUM> in the sensing mode. Since other devices are using the unlicensed frequency band, the licensed equipment (eNB and UE devices) must sense the band before transmitting. The method returns to step <NUM> to perform the observation procedure. Although the eNB can immediately begin the procedure, it some circumstances the eNB can delay before beginning the procedure. The eNB could, for example, wait at least an hour before performing step <NUM>. Delaying is not critical for the eNB since the eNB is not power constrained. Therefore, even continuous measurement is not a significant consideration for the eNB in most circumstances. The length of the delay may be based on a fixed time or may be based on other factors. For example, when measured channel quality is above a threshold, the eNB may perform the observation procedure.

At step <NUM>, the eNB instructs one or more UE devices to perform a frequency band observation procedure. Although the eNB has not detected significant energy in the unlicensed frequency band, it is possible that other devices are operating in the unlicensed frequency band. Such a situation is often referred to as the "hidden node". The UE devices are more likely to detect the energy of these other devices in these cases. In some situations, the UE devices and the eNB may perform their observation procedures simultaneously or at least have overlapping observation times. In most situations, in order to avoid unnecessary power consumption by the UE devices, the eNB does not instruct the UE devices to perform the observation procedure until a relatively high confidence level that no other devices are present is achieved.

At step <NUM>, the eNB receives, from the one or more UE devices, the results of the observation procedures performed by the UE devices. For the example, the UE devices transmit frequency band measurement information indicative of the observation procedure measurements. The information includes measurements or information based on measurements. For example, the results may include information regarding whether the UE device has determined whether or not other devices are using the unlicensed frequency band. When performing the observation procedure for the examples herein, each UE device periodically measures the RSSI over an observation period, compares the RSSI levels to a threshold, and reports to the eNB the results. The observation times and the thresholds of the UE devices and the eNB may be the same or may be different, depending on the particular implementation. The UE devices, however may report the measurements or other information in some situations.

A step <NUM>, the eNB determines whether the unlicensed frequency band is in use by other devices. The eNB makes the determination at least partially based on the results received from one or more of the UE devices. Where the results indicate that an UE device has determined that the energy level has exceeded the threshold and other devices are using the unlicensed frequency band, the eNB determines that the band is in use. Where measurements or other less definitive information is provided by the UE devices, the eNB processes the information to determine whether the unlicensed frequency band is in use by other devices. The eNB may process the information from each UE device individually or may process the information from multiple UE devices collectively. In some situations, the eNB may include measurements taken at the eNB when evaluating the results provided by the UE devices and determining whether the unlicensed frequency band is in use by other devices. If it is determined that the unlicensed frequency band is in use by other devices, the method returns to step <NUM>. Otherwise, the method continues at step <NUM>.

At step <NUM>, the system operates in the unlicensed frequency band in the non-sensing mode. The eNB instructs the UE devices to operate in the non-sensing mode starting at a particular frame, subframe, or time. The eNB and the UE devices do not sense the unlicensed frequency band before transmissions as dictated by the rules or standards governing the unlicensed frequency band. Rather, the licensed equipment operates similarly to the operation in the licensed frequency band. For example, the techniques used in an LTE system operating in accordance with one or more revision of the 3GPP LTE standard are used to communicate in the unlicensed frequency band (at the different frequencies).

At step <NUM>, the eNB receives RRM measurements from the UE devices. For the examples, the eNB receives the RRM measurement while the system is communicating in the non-sensing mode (step <NUM>). For the example, the RRM measurements are the same RRM measurements taken and reported by the UE devices when operating in the licensed frequency band except that the measurements are taken at the different frequencies of the unlicensed frequency band.

At step <NUM>, the eNB determines whether the frequency band observation procedure should be performed by the eNB. The determination may be based on several factors or combination of factors including, but not limited to, RRM measurements, channel characteristics, elapsed time since the eNB has performed the observation procedure, and the elapsed time since an eNB as performed an observation procedure. If it is determined that the observation procedure should be performed, the method returns to step <NUM>. Otherwise, the method continues at step <NUM>. As discussed above, the observation procedure may be performed by the UE device and the eNB at the same time in some circumstances. Where the decision to perform the observation procedure is based on RRM measurements from the UE devices, the eNB may determine that the UE device should perform the observation procedure at step <NUM>.

At step <NUM>, the eNB determines whether the frequency band observation procedure should be performed at one or more UE devices. The determination may be based on several factors or combination of factors including, but not limited to, RRM measurements, channel characteristics, elapsed time since the eNB has performed the observation procedure, and the elapsed time since an eNB as performed an observation procedure. If it is determined that the observation procedure should be performed, the method returns to step <NUM>. Otherwise, the method returns to step <NUM>. As discussed above, the observation procedure may be performed by the UE device and the eNB and the same time in some circumstances. The eNB may determine that the eNB should also perform the observation procedure at step <NUM>.

<FIG> is a flow chart of a method performed at a UE device for an example of managing operation of a licensed communication system in an unlicensed frequency band in a sensing mode and a non-sensing mode.

At step <NUM>, the UE device operates in the sensing mode in the unlicensed frequency band. Accordingly, the UE device monitored the unlicensed frequency band before transmission in the unlicensed frequency band.

At step <NUM>, the UE device determines if an instruction has been received from the eNB to perform frequency band observation procedure. If an instruction has been received, the method continues at step <NUM>. Otherwise, the method returns to step <NUM>.

A step <NUM>, the UE device performs the frequency band observation procedure. As discussed above, the UE device measures the energy in the unlicensed frequency band for an observation time. The UE device may measure RSSI for the band, for example.

At step <NUM>, the UE device reports the results of the observation procedure. For the example, the results include a determination of whether the RSSI level exceeded a threshold. In some circumstances, however, results of the observation procedure may include the RSSI measurements and/or other information.

At step <NUM>, the UE device determines if an instruction to operate in the non-sensing mode has been received. If the eNB instructs the UE device to operate in the non-sensing mode, the UE device continues at step <NUM> where the device operates in the non-sending mode. Otherwise, the method returns to step <NUM>.

At step <NUM> and <NUM>, the UE device performs and reports RRM measurements to the eNB while operating in the sensing mode. As discussed above, the RRM measurement procedure is similar to the procedure followed in the licensed frequency band.

At step <NUM>, the UE device determines whether an instruction has been received to operate in the sensing mode. If an instruction has been received, the method returns to step <NUM>. Otherwise, the method continues at step <NUM>.

At step <NUM>, the eNB determines whether an instruction has been received to perform the observation procedure. If an instruction has been received, the method proceeds to step <NUM>. Otherwise, the method returns to step <NUM>.

At step <NUM>, the UE performs the observation procedure and reports the results at step <NUM>. In some situations, the eNB instructs the UE device to operate in the sensing mode when performing the observation procedure, and in other situations, the UE device continues operating in the non-sensing mode, reporting RRM measurements and performing the observation procedure.

Claim 1:
A method comprising:
transmitting, from a base station to a user equipment, UE, (<NUM>, <NUM>, <NUM>, <NUM>), mode information specifying either a sensing mode or a non-sensing mode;
in response to the UE receiving the mode information specifying the sensing mode, performing, at the UE, a first monitoring of an unlicensed frequency band to determine whether the unlicensed frequency band is in use; and
in response to the UE receiving the mode information specifying the non-sensing mode, performing, at the UE, a second monitoring of the unlicensed frequency band to determine whether the unlicensed frequency band is in use, the second monitoring being a reduced monitoring compared to the first monitoring.