Channel selection to reduce interference to a wireless local area network from a cellular network

Disclosed are systems and methods for selecting an operating channel for a cellular network to reduce interference to a wireless local area network (WLAN) operated by a small cell comprising a WLAN access point and a cellular network modem. The small cell performs a channel scan of available channels, determines whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and selects the clean channel as the operating channel for the cellular network based on the clean channel being available or turns off the cellular network based on no clean channel being available.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are widely deployed to provide various types of communication content, such as voice, data, and so on. Typical wireless communication systems are multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, etc.). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and others. These systems are often deployed in conformity with specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), evolution data optimized (EV-DO), etc.

In cellular networks, macro scale base stations (or macro NodeBs (MNBs)) provide connectivity and coverage to a large number of users over a certain geographical area. A macro network deployment is carefully planned, designed, and implemented to offer good coverage over the geographical region. Even such careful planning, however, cannot fully accommodate channel characteristics such as fading, multipath, shadowing, etc., especially in indoor environments. Indoor users therefore often face coverage issues (e.g., call outages and quality degradation) resulting in poor user experience.

To extend cellular coverage indoors, such as for residential homes and office buildings, additional small coverage, typically low power base stations have recently begun to be deployed to supplement conventional macro networks, providing more robust wireless coverage for mobile devices. These small coverage base stations are commonly referred to as Home NodeBs or Home eNBs (collectively, H(e)NBs), femto nodes, femtocells, femtocell base stations, pico nodes, micro nodes, etc., deployed for incremental capacity growth, richer user experience, in-building or other specific geographic coverage, and so on. Such small coverage base stations may be connected to the Internet and the mobile operator's network via a digital subscriber line (DSL) router or a cable modem, for example.

An unplanned deployment of large numbers of small coverage base stations, however, can be challenging in several respects.

SUMMARY

The disclosure is related to selecting an operating channel for a cellular network to reduce interference to a wireless local area network (WLAN) operated by a small cell. A method for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes performing, by the small cell, a channel scan of available channels, the small cell comprising a WLAN access point and a cellular network modem, determining whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and selecting the clean channel as the operating channel for the cellular network based on the clean channel being available or turning off the cellular network based on no clean channel being available.

Another method for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes performing, by a cellular network modem of the small cell, a first channel scan of available channels for operating the cellular network, performing, by a WLAN access point of the small cell, a second channel scan of the available channels for operating the cellular network, identifying, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, determining, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and selecting the clean channel as the operating channel for the cellular network based on the clean channel being available or turning off the cellular network based on no clean channel being available.

An apparatus for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes logic configured to perform, by the small cell, a channel scan of available channels, wherein the small cell comprises a WLAN access point and a cellular network modem, logic configured to determine whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and logic configured to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

Another apparatus for selecting an operating channel for a cellular network to reduce interference to a wireless local area network (WLAN) operated by a small cell includes logic configured to perform, by a cellular network modem of the small cell, a first channel scan of available channels for operating the cellular network, logic configured to perform, by a WLAN access point of the small cell, a second channel scan of the available channels for operating the cellular network, logic configured to identify, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, logic configured to determine, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and logic configured to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

A small cell base station capable of selecting an operating channel for a cellular network to reduce interference to a WLAN operated by the small cell base station includes a cellular network modem, an WLAN access point configured to perform an initial channel scan of available channels, and a processor configured to determine whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

A small cell base station capable of selecting an operating channel for a cellular network to reduce interference to a WLAN operated by the small cell base station includes a cellular network modem configured to perform a first channel scan of available channels for operating the cellular network, a WLAN access point configured to perform a second channel scan of the available channels for operating the cellular network, and a processor configured to identify, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, to determine, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

An apparatus for selecting an operating channel for a cellular network to reduce interference to a wireless local area network (WLAN) operated by a small cell includes means for performing, by the small cell, a channel scan of available channels, the small cell comprising a WLAN access point and a cellular network modem, means for determining whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and means for selecting the clean channel as the operating channel for the cellular network based on the clean channel being available or turning off the cellular network based on no clean channel being available.

An apparatus for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes means for performing, by a cellular network modem of the small cell, a first channel scan of available channels for operating the cellular network, means for performing, by a WLAN access point of the small cell, a second channel scan of the available channels for operating the cellular network, means for identifying, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, means for determining, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and means for selecting the clean channel as the operating channel for the cellular network based on the clean channel being available or turning off the cellular network based on no clean channel being available.

A non-transitory computer-readable medium for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes at least one instruction to perform, by the small cell, a channel scan of available channels, wherein the small cell comprises a WLAN access point and a cellular network modem, at least one instruction to determine whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and at least one instruction to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

A non-transitory computer-readable medium for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell includes at least one instruction to perform, by a cellular network modem of the small cell, a first channel scan of available channels for operating the cellular network, at least one instruction to perform, by a WLAN access point of the small cell, a second channel scan of the available channels for operating the cellular network, at least one instruction to identify, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, at least one instruction to determine, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, wherein a clean channel comprises a channel that interferes with the WLAN less than a WLAN interference threshold, and at least one instruction to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available.

DETAILED DESCRIPTION

The disclosure relates to channel selection to reduce interference to a wireless local area network (WLAN) from a cellular network. A small cell may establish a cellular network, such as a Long Term Evolution (LTE)/LTE Advanced network in unlicensed spectrum, in addition to a WLAN, provided there is a “clean” channel available on which to establish the cellular network. The small cell may determine whether or not a clean channel is available using measurements gathered by its co-located access point (AP), in addition to, or instead of, measurements that its co-located cellular modem, such as a femtocell station modem (FSM), would otherwise gather itself. The AP can provide these measurements to the cellular modem using the small cell's controller/processor and/or internal bus. The measurements may come from the network listen module (NLM) and/or attached user devices. By only establishing a cellular network on a clean channel, the cellular network's interference with the WLAN is mitigated.

The disclosure further relates to minimizing WLAN AP misdetection for channel selection for LTE/LTE Advanced in unlicensed spectrum in the presence of interference. To mitigate AP misdetection, the small cell can leverage its co-located NLM for LTE/LTE Advanced in unlicensed spectrum measurements and use it to appropriately filter WLAN AP scan reports. First, the small cell avoids channels with a strong presence in the LTE/LTE Advanced in unlicensed spectrum. Among the remaining weak channels in the LTE/LTE Advanced in unlicensed spectrum, assuming that at least one is available, the small cell uses a WLAN threshold to determine clean/unclean channels. If a subset of the channels has a strong presence in the LTE/LTE Advanced in unlicensed spectrum, the small cell “freezes” the channel database or uses Successive Interference Cancellation (SIC) to detect the beacons on those channels.

These and other aspects are described in the following description and related drawings. Alternate aspects may be devised without departing from the scope of the disclosure. Additionally, well-known elements of the disclosure will not be described in detail or will be omitted so as not to obscure the relevant details of the disclosure.

The techniques described herein may be employed in networks that include macro scale coverage (e.g., a large area cellular network such as 3G or 4G networks, typically referred to as a macro cell network) and smaller scale coverage (e.g., a residence-based or building-based network environment). As a user device moves through such networks, the user device may be served in certain locations by base stations that provide macro coverage and at other locations by base stations that provide smaller scale coverage. As discussed briefly in the background above, the smaller coverage base stations may be used to provide significant capacity growth, in-building coverage, and in some cases different services for a more robust user experience. In the discussion herein, a base station that provides coverage over a relatively large area is usually referred to as a macro base station, while a base station that provides coverage over a relatively small area (e.g., a residence) is usually referred to as a femto base station or a small cell. Intermediate base stations that provide coverage over an area that is smaller than a macro area but larger than a femto area are usually referred to as pico base stations (e.g., providing coverage within a commercial building). For convenience, however, the disclosure herein may describe various functionalities related to small coverage base stations in the context of a femto base station, with the understanding that a pico base station may provide the same or similar functionality for a larger coverage area. A cell associated with a macro base station, a femto base station, or a pico base station may be referred to as a macrocell, a femtocell, or a picocell, respectively. In some system implementations, each cell may be further associated with (e.g., divided into) one or more sectors.

In various applications, it will be appreciated that other terminology may be used to reference a macro base station, a femto base station, a pico base station, a user device, and other devices, and that the use of such terms is generally not intended to invoke or exclude a particular technology in relation to the aspects described or otherwise facilitated by the description herein. For example, a macro base station may be configured or alternatively referred to as a macro node, NodeB, evolved NodeB (eNodeB), macrocell, and so on. A femto base station may be configured or alternatively referred to as a femto node, Home NodeB, Home eNodeB, femtocell, a small cell, and so on. A user device may be configured or alternatively referred to as a device, user equipment (UE), subscriber unit, subscriber station, mobile station, mobile device, access terminal, and so on. For convenience, the disclosure herein will tend to describe various functionalities in the context of generic “base stations” and “user devices,” which, unless otherwise indicated by the particular context of the description, are intended to cover the corresponding technology and terminology in all wireless systems.

FIG. 1illustrates an example wireless communication network demonstrating the principles of multiple access communication. The illustrated wireless communication network100is configured to support communication between a number of users. As shown, the wireless communication network100may be divided into one or more cells102, such as the illustrated cells102A-102G. Communication coverage in cells102A-102G may be provided by one or more base stations104, such as the illustrated base stations104A-104G. In this way, each base station104may provide communication coverage to a corresponding cell102. The base station104may interact with a plurality of user devices106, such as the illustrated user devices106A-106L.

Each user device106may communicate with one or more of the base stations104on a downlink (DL) and/or an uplink (UL). In general, a DL is a communication link from a base station to a user device, while an UL is a communication link from a user device to a base station. The base stations104may be interconnected by appropriate wired or wireless interfaces allowing them to communicate with each other and/or other network equipment. Accordingly, each user device106may also communicate with another user device106through one or more of the base stations104. For example, the user device106J may communicate with the user device106H in the following manner: the user device106J may communicate with the base station104D, the base station104D may then communicate with the base station104B, and the base station104B may then communicate with the user device106H, allowing communication to be established between the user device106J and the user device106H.

The wireless communication network100may provide service over a large geographic region. For example, the cells102A-102G may cover a few blocks within a neighborhood or several square miles in a rural environment. As noted above, in some systems, each cell may be further divided into one or more sectors (not shown). In addition, the base stations104may provide the user devices106access within their respective coverage areas to other communication networks, such as the Internet or another cellular network. As further mentioned above, each user device106may be a wireless communication device (e.g., a mobile phone, router, personal computer, server, etc.) used by a user to send and receive voice or data over a communications network, and may be alternatively referred to as an access terminal (AT), a mobile station (MS), a user equipment (UE), etc. In the example shown inFIG. 1, the user devices106A,106H, and106J comprise routers, while the user devices106B-106G,1061,106K, and106L comprise mobile phones. Again, however, each of the user devices106A-106L may comprise any suitable communication device.

FIG. 2Aillustrates an example mixed communication network environment200in which small cells210and212are deployed in conjunction with macro cells. Here, a macro base station205may provide communication coverage to one or more user devices, such as the illustrated user devices220,221, and222, within a macro area230, while small cells210and212may provide their own communication coverage within respective areas215and217, with varying degrees of overlap among the different coverage areas. In this example, at least some user devices, such as the illustrated user device222, may be capable of operating both in macro environments (e.g., macro areas) and in smaller scale network environments (e.g., residential, femto areas, pico areas, etc.).

In the connections shown, the user device220may generate and transmit a message via a wireless link to the macro base station205, the message including information related to various types of communication (e.g., voice, data, multimedia services, etc.). The user device222may similarly communicate with the small cell210via a wireless link, and the user device221may similarly communicate with the small cell212via a wireless link. The macro base station205may also communicate with a corresponding wide area or external network240(e.g., the Internet), via a wired link or via a wireless link, while the small cell210and212may also similarly communicate with the network240, via their own wired or wireless links. For example, the small cell210and212may communicate with the network240by way of an Internet Protocol (IP) connection, such as via a digital subscriber line (DSL, e.g., including asymmetric DSL (ADSL), high data rate DSL (HDSL), very high speed DSL (VDSL), etc.), a TV cable carrying IP traffic, a broadband over power line (BPL) connection, an optical fiber (OF) link, or some other link.

The network240may comprise any type of electronically connected group of computers and/or devices, including, for example, the following networks: Internet, Intranet, Local Area Networks (LANs), or Wide Area Networks (WANs). In addition, the connectivity to the network may be, for example, by remote modem, Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), Fiber Distributed Datalink Interface (FDDI) Asynchronous Transfer Mode (ATM), Wireless Ethernet (IEEE 802.11), Bluetooth (IEEE 802.15.1), or some other connection. As used herein, the network240includes network variations such as the public Internet, a private network within the Internet, a secure network within the Internet, a private network, a public network, a value-added network, an intranet, and the like. In certain systems, the network240may also comprise a virtual private network (VPN).

Accordingly, it will be appreciated that the macro base station205and/or either or both of the small cells210and212may be connected to the network240using any of a multitude of devices or methods. These connections may be referred to as the “backbone” or the “backhaul” of the network. Devices such as a radio network controller (RNC), base station controller (BSC), or another device or system (not shown) may be used to manage communications between two or more macro base stations, pico base stations, and/or small cells. In this way, depending on the current location of the user device222, for example, the user device222may access the communication network240by the macro base station205or by the small cell210.

FIG. 2Billustrates an example of a small cell250according to one or more aspects of the disclosure. The small cell250may correspond to the small cell210and/or the small cell212illustrated inFIG. 2A. The small cell250may be able to provide a wireless local area network (WLAN) air interface (e.g., in accordance with an IEEE 802.11x protocol) as well as a cellular air interface (e.g., in accordance with an LTE protocol). As shown, in this regard the small cell250can include an 802.11x Access Point (AP)252co-located with a cellular modem254, such as a Femtocell Station Modem (FSM). The AP252and cellular modem254may perform monitoring of one or more channels (e.g., on a corresponding carrier frequency) to determine a corresponding channel quality (e.g., received signal strength) using corresponding network listen (NL) modules256and258, respectively, or other suitable component(s). Although illustrated as separate modules, the NL modules256and258may reside on a single NL module.

The small cell250may also include a host260, which may include one or more general purpose controllers or processors and memory configured to store related data or instructions. The host260may perform processing in accordance with the appropriate radio technology or technologies used for communication, as well as other functions for the small cell250.

The small cell250may communicate with one or more wireless devices via the AP252and the cellular modem254, illustrated as a station (STA)262and a UE264, respectively. WhileFIG. 2Billustrates a single STA262and a single UE264, it will be appreciated that the small cell250can communicate with multiple STAs and/or UEs. Additionally, whileFIG. 2Billustrates one type of wireless device communicating with the small cell250via the AP252(i.e., the STA262) and another type of wireless device communicating with the small cell250via the cellular modem254(i.e., the UE264), it will be appreciated that a single wireless device may be capable of communicating with the small cell250via both of the AP252and the cellular modem254, either simultaneously or at different times.

FIG. 3illustrates an example of a small cell301according to one or more aspects of the disclosure. The small cell301may correspond to any of small cells210,212, and/or250. While internal components of small cells can be embodied with different hardware configurations, a basic high-level configuration of internal hardware components is illustrated inFIG. 3. As shown, the small cell301includes a corresponding TX data processor310, symbol modulator320, transmitter unit (TMTR)330, antenna(s)340, receiver unit (RCVR)350, symbol demodulator360, RX data processor370, and configuration information processor380, performing various operations for communicating with one or more user devices302. The small cell301may also include one or more general purpose controllers or processors (illustrated in the singular as the controller/processor382) and memory384configured to store related data or instructions. Together, via a bus386, these units may perform processing in accordance with the appropriate radio technology or technologies used for communication, as well as other functions for the small cell301.

The small cell301may be able to provide a wireless local area network air interface (e.g., in accordance with an IEEE 802.11x protocol) as well as a cellular air interface (e.g., in accordance with an LTE protocol). As shown, in this regard the small cell301includes an 802.11x AP392co-located with a cellular modem394. The AP392and the cellular modem394may correspond to the AP252and the cellular modem254, respectively, illustrated inFIG. 2B. The AP392and the cellular modem394may perform monitoring of one or more channels (e.g., on a corresponding carrier frequency) to determine a corresponding channel quality (e.g., received signal strength) using a network listen module (NLM) or other suitable component (illustrated as NLM396and NLM398, respectively). It will be appreciated that, in some designs, the functionality of one or more of these components may be integrated directly into, or otherwise performed by, the general purpose controller/processor382of the small cell301, sometimes in conjunction with the memory384.

The small cell301may communicate with the user devices302via the AP392and/or the cellular modem394. It will be appreciated that a single user device302may be capable of communicating with the small cell301via both the AP392and the cellular modem394, either simultaneously or at different times. In this disclosure, where a user device302is referred to as making and/or providing WLAN-specific measurements or performing WLAN-specific functionality, that user device302is understood to be connected to the AP392. Likewise, where a user device302is referred to as making and/or providing cellular network-specific measurements or performing cellular network-specific functionality, that user device302is understood to be connected to the cellular modem394.

In general, the AP392may provide its air interface (e.g., in accordance with an IEEE 802.11x protocol) over an unlicensed portion of the wireless spectrum such as an industrial, scientific, and medical (ISM) radio band, whereas the cellular modem394may provide its air interface (e.g., in accordance with an LTE protocol) over a licensed portion of the wireless band reserved for cellular communications. However, the cellular modem394may also be configured to provide cellular (e.g., LTE) connectivity over an unlicensed portion of the wireless spectrum. This type of unlicensed cellular operation may include the use of an anchor licensed carrier operating in a licensed portion of the wireless spectrum (e.g., LTE Supplemental DownLink (SDL)) and an unlicensed portion of the wireless spectrum (e.g., LTE-Unlicensed), or may be a standalone configuration operating without the use of an anchor licensed carrier (e.g., LTE Standalone).

Accordingly, aspects of the disclosure can include a small cell (e.g., small cell301) including the ability to perform the functions described herein. As will be appreciated by those skilled in the art, the various logic elements can be embodied in discrete elements, software modules executed on a processor (e.g., controller/processor382), or any combination of software and/or hardware to achieve the functionality disclosed herein. For example, transmitter330, receiver350, processor/controller382, memory384, NLM396, AP392, NLM398, and cellular modem394may all be used cooperatively to load, store, and execute the various functions disclosed herein, and thus the logic to perform these functions may be distributed over various elements. Alternatively, the functionality could be incorporated into one discrete component. Therefore, the features of the small cell301are to be considered merely illustrative and the disclosure is not limited to the illustrated features or arrangement.

For example, the AP392and/or the NLM396may be configured to perform a channel scan of available channels, as described below with reference to410B ofFIG. 4B, for example. The processor382may be configured to determine whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan, as described below with reference to415B ofFIG. 4B, for example. The processor382may be further configured to select the clean channel as the operating channel for the cellular network based on the clean channel being available, as described below with reference to420B ofFIG. 4B, for example, or to turn off the cellular network based on no clean channel being available, as described below with reference to450B ofFIG. 4B, for example.

As another example, the cellular modem394and/or the NLM398may be configured to perform a first channel scan of available channels for operating the cellular network, as described below with reference to510ofFIG. 5, for example. The AP392and/or the NLM396may be configured to perform a second channel scan of the available channels for operating the cellular network, as described below with reference to410D ofFIG. 4D, for example. The processor382may be configured to identify, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, as described below with reference to520ofFIG. 5, for example. The processor382may be further configured to determine, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network, as described below with reference to415D ofFIG. 4D, for example. The processor382may be further configured to select the clean channel as the operating channel for the cellular network based on the clean channel being available or to turn off the cellular network based on no clean channel being available, as described below with reference to420D ofFIG. 4D, for example.

From time to time, the small cell301may perform various radio resource management decisions within the unlicensed spectrum that require or otherwise make use of various radio resource measurements from the one or more user devices302. The measurements may be performed by analyzing received radio signals (e.g. signal quality) and/or collecting traffic statistics (e.g. channel utilization). Conventionally, these measurements are carried over the WLAN link between the AP392and a given user device302. The IEEE 802.11k revision of the IEEE 802.11 specifications, for example, provides mechanisms for radio resource measurements in IEEE 802.11 systems enabling wireless stations of a WLAN to automatically adjust to their radio environment. A wireless station can make measurements locally as well as request measurements from other wireless stations with whom the wireless station has an association allowing direct radio communication. In this way, for example, the AP392can request radio resource measurements from another wireless station (e.g., one of the user devices302) within the same Basic Service Set (BSS) and vice versa. This signaling scheme requires, however, a standalone wireless station to be associated with the AP392in the small cell301, which is not guaranteed.

The small cell301may establish a cellular network, such as an LTE/LTE Advanced network in unlicensed spectrum, in addition to a WLAN, provided there is a “clean” channel available on which to establish the cellular network. The small cell301may determine whether or not a clean channel is available using measurements gathered by the AP392, in addition to, or instead of, measurements that the cellular modem394would otherwise gather itself. The AP392can provide these measurements to the cellular modem394using the controller/processor382and/or the bus386. The measurements may come from the NLM396and/or the user devices302. By only establishing a cellular network on a clean channel, the cellular network's interference with the WLAN is mitigated.

FIG. 4Aillustrates an exemplary flow for cellular network channel selection to reduce interference to a WLAN according to at least one aspect of the disclosure. The cellular network may be, for example, an LTE Advanced network in unlicensed spectrum. The flow illustrated inFIG. 4Amay be performed by the small cell301inFIG. 3. As used herein, a cellular network “channel” identifies a corresponding carrier frequency, or cellular network signal.

The flow begins at400A. At410A, the small cell301performs an initial channel scan of WLAN channels.

At415A, the small cell301determines whether or not there is a clean channel. If there are no clean channels, then the flow proceeds to450A, where the small cell301turns off, or does not establish, the cellular network. If, however, there are one or more clean channels, then at420A, the small cell301selects an operating channel for the cellular network from among the clean channels.

At425A, the small cell301performs a periodic channel scan. At430A, the small cell301updates a channel database of available channels.

At435A, the small cell301determines whether or not channel switching criteria have been met. If the channel switching criteria have not been met, then the flow returns to425A, where the small cell301continues performing periodic scans. If, however, the channel switching criteria have been met, then the flow proceeds to440A. At440A, the small cell301switches off the current carrier and selects the channel with the highest rank as the new operating channel for the cellular network.

At445A, the small cell301determines whether or not a clean channel was found. If a clean channel was found, then the small cell301switches to the new clean channel and the flow returns to425A, where the small cell301continues performing periodic scans, this time on the new clean channel. If a clean channel was not found, then at450A, the small cell301turns off the cellular network and provides only the WLAN. At455A, the small cell301performs some time hysteresis and the flow returns to400A.

FIG. 4Billustrates an exemplary flow for cellular network channel selection to reduce interference to a WLAN according to at least one aspect of the disclosure. The cellular network may be, for example, an LTE Advanced network in unlicensed spectrum. The flow illustrated inFIG. 4Bmay be performed by the small cell301inFIG. 3.

The flow begins at400B. At410B, the small cell301performs an initial channel scan of available channels. More specifically, the AP392, using the NLM396, may perform the initial channel scan. An available channel may be a channel on which the small cell301can establish the cellular network. However, the small cell301may also be capable of establishing a WLAN on such a channel. That is, the small cell301may be capable of establishing a WLAN or a cellular network on the same channel.

The NLM396receives as input, from the AP392, the channel numbers of all available channels and outputs, to the AP392, the received signal strength indicator (RSSI) of the channel beacon, the physical layer (PHY) mode (which may include the bandwidth and the primary and secondary channels), and the noise floor of each channel. A PHY module in the NLM396detects the WLAN beacon, the bandwidth of WLAN operation, and the location of the WLAN channel, if greater than a threshold (e.g., 20 MHz).

The AP392ignores all channels with a beacon RSSI greater than an RSSI threshold, as measured at the AP392. The RSSI threshold is an adjustable dBm level chosen such that if the interference from the cellular network is at that dBm level, the performance degradation to the WLAN is acceptable. If the RSSI threshold is increased, the interference and the performance degradation will be higher, but there may be more channels meeting that threshold. If the RSSI threshold is decreased, the interference and the performance degradation will be decreased, but there may be fewer channels meeting that threshold.

The small cell301then creates a channel database of the channels meeting the RSSI threshold using a utility function of the measured noise floor and the beacon RSSI of the channel. The utility function is a function that takes the beacon RSSI, which indicates the strength of the interference, and the noise floor already existing without interference and generates a utility value/metric that reflects the system performance for that channel. Thus, the channel with the maximum utility value is the channel with the maximum performance. Choosing the channel with a higher utility value means choosing the channel that decreases interference. As an example, the utility value could be the inverse of the absolute interference.

At415B, the AP392determines whether or not there is a clean channel. A clean channel is a channel with a maximum beacon RSSI, as measured at the AP392, less than the RSSI threshold. If there are no clean channels, then the flow proceeds to450B, where the small cell301turns off, or does not establish, the cellular network.

If, however, there are one or more clean channels, then at420B, the AP392selects as the operating channel for the cellular network the clean channel with the highest utility value, as determined by the utility function based on the measured noise floor and the beacon RSSI.

At425B, the AP392performs a periodic channel scan. The AP392can perform the scan every T seconds and/or upon some event trigger. A triggering event may be, for example, measuring a high interference to the current operating channel at the AP392or receiving an indication of a high interference from an STA report (received from a user device302connected to the AP392).

The periodic scan may detect whether or not new nearby AP(s) have started transmitting on the current operating channel. The AP392makes periodic measurements on the operating channel every T seconds. The choice of T impacts the latency to react to a new nearby AP and interruption to operation of both the cellular network and the WLAN in the small cell301. Lower duty cycle scans can be performed on the other channels.

More specifically, the AP392may perform two different scans according to two different duty cycles. The AP392may make intra-frequency measurements according to a first duty cycle (e.g., every T seconds, as described above), and inter-frequency measurements according to a second duty cycle. That is, the AP392can scan the operating channel according to the first duty cycle, and can scan all other channels according to the second duty cycle. Alternatively, the AP392may only scan the other clean channels. The second duty cycle may be less frequent than the first duty cycle. Both duty cycles may be relatively long, for example, measured in seconds or even minutes.

The channel scan can also be triggered if strong interference is detected, as discussed above. For example, the scan could be triggered based on uplink or downlink packet error rate (PER) metrics and/or channel quality indicator (CQI) reports from user devices302connected to the cellular network, which could be due to a new nearby WLAN AP. Performing a scan if strong interference is detected helps reduce latency to react to a new WLAN AP. The thresholds should be selected to reduce false alarms and minimize ongoing cellular network/WLAN traffic interruption.

The AP392may collect STA-assisted measurements, such as 802.11k measurements, from user devices302that are connected to the small cell301via the AP392. This can occur more frequently than collecting measurements from the NLM396. The STA-assisted measurements are used to update the utility value of the clean channel(s), and can trigger the AP392to perform a channel scan. To optimize the performance of the cellular network, the STA-assisted measurements can be complemented with cellular network measurements, such as radio resource measurements (RRM) and CQI reports, from user devices302.

At430B, the small cell301updates the channel database discussed above. The small cell301discards any channels with a beacon RSSI greater than the RSSI threshold. This can be based on only the WLAN AP scan. The STA reports play a role in determining the cleanest channel among this list of clean channels (i.e., channels with a beacon RSSI less than or equal to the RSSI threshold). The small cell301then calculates or updates the utility value (as calculated by the utility function discussed above) for the rest of the channels (i.e., the clean channels). The utility value takes into account the noise floor, the STA-assisted measurements, and/or any other cellular network interference. The small cell301then ranks the clean channels according to their utility values.

At435B, the small cell301determines whether or not channel switching criteria have been met. The channel switching criteria may include an indication of whether or not the beacon RSSI of a new beacon is greater than the RSSI threshold, as measured at the AP392, with some hysteresis and timing conditions. The criteria also include an indication of whether there is a new channel with a higher utility value than the current operating channel, again with some hysteresis and timing conditions.

The hysteresis and timing conditions are used to prevent the cellular modem394from bouncing between operating channels. For example, the small cell301may set a timer indicating how long the cellular modem394has been using the current operating channel. If the timer has not expired, the cellular modem394is not permitted to switch to the new operating channel. However, if the channel performance is especially poor, this timer can be ignored to allow the switching to happen faster.

If the channel switching criteria have not been met, then the flow returns to425B, where the AP392continues performing periodic scans. If, however, the channel switching criteria have been met, then the flow proceeds to440B. At440B, the small cell301switches off the carrier channel and selects the channel with the highest rank (i.e., the highest utility value).

At445B, the AP392determines whether or not a clean channel was found in440B. If a clean channel was found and the AP392switched to the new clean channel at440B, then the flow returns to425B, where the AP392continues performing periodic scans, this time on the new clean channel. If a clean channel was not found, however, then at450B, the small cell301turns off the cellular network and simply provides the WLAN.

Turning off the cellular network and switching to the WLAN is the fallback solution if there is no clean channel on which to establish the cellular network. For the baseline solution, the small cell301switches off the cellular network and the co-located AP392can start providing the WLAN on that channel instead. The user devices302can go to Radio Link Failure (RLF), meaning they will attempt connection re-establishment on another cellular network operating on a different frequency. Radio Resource Control (RRC) Connection Release can also be used to gracefully move out connected mode user devices in the system.

The small cell301can handoff active user devices to a neighboring cell before switching off the cellular network. Idle user devices simply perform cell selection when coming out of idle mode. Note that the channel utility function and channel selection are based on measurements from the AP392and/or the STA-assisted measurements. In contrast, turning off the cellular network is only based on the AP392measurements.

At455B, the small cell301performs some time hysteresis and the flow returns to400B. Specifically, since no clean channel was found and the cellular network was turned off, or not established, after some period of time, the flow then returns to400B to search again in an attempt to establish, or re-establish, the cellular network.

The following is a specific example of performing the initialization using the NLM396and the AP392. First, the AP392collects AP measurements on all channels from the NLM396. The AP392measures the beacon RSSI on different channels, for example, beacon_RSSIi,j, where i is the channel index and j is the beacon index. The AP392also measures the RSSI on different channels, taking into account all sources of interference including other cellular networks, for example, RSSIi, where i is the channel index.

Next, the AP392discards channel i with a maximumj(beacon_RSSIi,j) greater than the RSSI threshold. Discarded channels can be scanned again after some time hysteresis, as discussed above.

Next, the AP392computes an RSSI metric for the remaining clean channels, for example, Init_Metrici=α1RSSIi+α2Σj∈βbeacon_RSSIi,j. Among channels with a metric below Init_Metricthreshold, the AP392can randomly pick an operating channel for the cellular network. The AP392can bias this channel selection based on maximum transmission power requirements. This network listen can be repeated periodically or triggered by STA-assisted measurements.

Note, for a BSS with a bandwidth greater than 20 MHz (as indicated from High Throughput (HT) and Very High Throughput (VHT) Operation IE fields in the beacon), the AP392can apply the beacon RSSI to all secondary channels. The AP392can also add a back off amount to the beacon_RSSIi, when applied to secondary channels.

The STA reports (i.e., the STA-assisted measurements) discussed above can include a calculated channel penalty. The small cell301forms a database of STA beacon reports for each channel i. The small cell301can keep the newest Max_database reports and discards older reports to maintain a maximum database size. The small cell301can use, for example, the 802.11k beacon reports.

With each unique measurement, the small cell301can update each channel penalty metric Pifor channel i using all database entries k according to the formula Pi=Σkqi,k, where, if no beacon is detected, then qi,k=0, and if the beacon has an RSSI less than an RSSI_threshold, then qi,k=penalty_low, and if the beacon has an RSSI greater than the RSSI_threshold, then qi,k=penalty_high. This measures the percent coverage area with some desense due to AP interference. That is, the user devices302are in different locations in the coverage area and each sees some level of interference, indicated by qi,k. When the different q values of all user devices302on a given channel are summed, it indicates how good the coverage area for this channel is in terms of interference. For example, if the penalty is high, it means that in different places in the coverage area, there is high interference, and vice versa.

A unique measurement means a new data point significantly different from the earlier data point from that same user device302. For example, if there is at least X dBm RSSI difference between any beacon commonly reported in both reports, or if there is a new beacon with an RSSI above a threshold Y dBm, or if there is an old beacon with an RSSI above a threshold Z dBm that did not get detected, then the new data point may be considered to be significantly different from the earlier data point.

RRM measurements from user devices302can be taken into consideration to reduce inter-operator interference and pilot pollution. The channel penalty can also take into account these RRM measurements. The user devices302can report intra- and inter-frequency Reference Signal Received Power (RSRP) measurements of neighboring cells, which indicate how strong the desired signal is. These reports indicate whether the neighboring cell belongs to the same small cell operator or a different small cell operator in unlicensed spectrum (through Automatic Neighborhood Relations (ANR), which is a mechanism in LTE to discover neighbor cells and can be used for the same or different operators).

The channel penalty can be updated as described above. For each unique measurement, the small cell301can update each channel penalty metric Pifor channel i using all database entries k using the formula Pi=Σkwi,k. If no nearby small cell is detected, then wi,k=0. If the RSRP is less than an RSRP threshold, then wi,k=penalty_low_1/penalty_low_2 (for the same/different operator). If the RSRP is greater than the RSRP threshold, then wi,k=penalty_high_1/penalty_high_2 (for the same/different operator). Different operators (e.g., different operators in unlicensed spectrum) will have a higher penalty than the penalty that the operator of the small cell301will have.

The AP392can periodically update the channel penalty metric on all channels using the STA reports and network listen provided by the NLM396. If a channel is clean for more than some number of seconds, e.g., T, the channel is eligible to carry the cellular network.

Referring back to the channel switching criteria discussed above with reference to435B ofFIG. 4B, if a new beacon RSSI, as measured at the AP392, exceeds the RSSI threshold and some hysteresis for some timer period, then the AP392can switch to the next clean channel with the lowest penalty (highest utility). If there are a sufficient number of measurement reports available (e.g., a minimum database size), then the AP392can change the operating channel to j if Pj≠iis less than Piminus the hysteresis and the RSSIjmeasured at the AP392is below some threshold RSSI_UL. This condition should be met consistently for a certain duration of time or across a certain number of new measurement reports. If multiple channels satisfy this criterion, the AP392can use RSRP/RSRQ (Reference Signal Received Quality, which is an indicator of the Signal to Interference plus Noise Ratio (SINR) of the signal) related metrics to decide.

Referring back to the channel switching procedure discussed above with reference to440B ofFIG. 4B, the anchor carrier can de-activate user devices configured on the SDL. This stops the user devices from monitoring the Common Reference Signal (CRS), which is the pilot signal in LTE, on the SDL and sending CQI and RRM measurements. This can be accomplished through an RRC configuration message or Medium Access Control (MAC) control element.

Next, the small cell301can switch off the SDL and switch on a new SDL on a different channel, if a clean channel (i.e., a channel with a maximum beacon RSSI less than the RSSI threshold) for the cellular network is available. The user devices302can then be activated on the new channel via an RRC configuration message.

Note that in general, unlicensed Secondary Carrier Components (SCCs) should be barred so that user devices302do not camp on it.

The time scale for channel switching should be larger than the rate control and the other interference management (e.g., Fractional Frequency Reuse (FFR), which is an interference coordination mechanism between different small cells) of the other cellular network small cells on unlicensed carriers.

An issue with the flow illustrated inFIGS. 4B/4C is that small cells operating in the unlicensed band, such as small cell301, may not necessarily be synchronized to one another (especially if, for example, they belong to different operators). Even if small cells having the same operator are time synchronized, their actual AP scan times can still be offset from one another.

Since every small cell chooses a scan duration and periodicity for its AP scan and operates in an independent manner, there are situations where the small cell's co-located AP may perform an AP scan at the same time that other small cells are transmitting. This can cause undue interference at the co-located AP, thereby reducing its sensitivity to detect existing and new neighboring APs.

For example, small cell301may have previously received (and decoded) a neighboring AP signal at −80 dBm, after which a new small cell may begin transmitting on this channel. If the new small cell is sufficiently close and is received at above −80 dBm, for example, its AP beacon becomes un-decodable. This causes the small cell301's co-located AP392to think that this neighboring AP/WLAN is no longer present and that the channel has become cleaner, while in reality it has not. Further, the small cell301will not be able to discover new WLANs with similar signal strengths during the scan because of interference from other unlicensed cellular network air interfaces, such as LTE/LTE Advanced in unlicensed spectrum.

To mitigate this AP misdetection issue in the presence of interference from other small cells operating in LTE/LTE Advanced in unlicensed spectrum, small cell301can leverage its co-located NLM396/398for LTE/LTE Advanced in unlicensed spectrum measurements and use it to appropriately filter AP scan reports. First, the small cell301avoids channels with a strong presence in the LTE/LTE Advanced in unlicensed spectrum. Among the remaining weak channels in the LTE/LTE Advanced in unlicensed spectrum, assuming that at least one is available, the small cell301uses the WLAN threshold to determine clean/unclean channels. If a subset of the channels has a strong presence in the LTE/LTE Advanced in unlicensed spectrum, the small cell301“freezes” the channel database or uses Successive Interference Cancellation (SIC) to detect the beacons on those channels.

FIG. 4Cillustrates a high-level flow of an exemplary method for cellular network channel selection to reduce interference to a WLAN according to at least one aspect of the disclosure. The cellular network may be, for example, an LTE Advanced network in unlicensed spectrum. The flow illustrated inFIG. 4Cmay be performed by the small cell301inFIG. 3. As used herein, a cellular network “channel” identifies a corresponding carrier frequency, or cellular network signal.

The flow begins at400C. At405C, the small cell301, specifically both the AP392and the cellular modem394, performs an initial channel scan of available channels.

At415C, the small cell301determines whether or not there is a clean channel. If there are no clean channels, then the flow proceeds to450C, where the small cell301turns off, or does not establish, the cellular network. If, however, there are one or more clean channels, then at420C, the small cell301selects an operating channel for the cellular network from among the clean channels.

At425C, the small cell301, specifically both the AP392and the cellular modem394, performs a periodic channel scan. At427C, the small cell301determines whether or not there is at least one channel with weak or tolerable cellular interference based on the channel scan performed by the cellular modem394. If there is at least one channel with weak/tolerable cellular interference, then at430C, the small cell301updates a channel database of available channels as described above with reference to430B ofFIG. 4B. Otherwise, at433C, the small cell301updates a channel database of available channels as described below with reference to530-560ofFIG. 5 and 660B-675B and 645BofFIG. 6B.

At435C, the small cell301determines whether or not channel switching criteria have been met. If the channel switching criteria have not been met, then the flow returns to425C, where the small cell301continues performing periodic channel scans. If, however, the channel switching criteria have been met, then the flow proceeds to440C. At440C, the small cell301switches off the current carrier and selects the channel with the highest rank as the new operating channel for the cellular network.

At445C, the small cell301determines whether or not a clean channel was found. If a clean channel was found, then the small cell301switches to the new clean channel and the flow returns to425C, where the small cell301continues performing periodic scans, this time on the new clean channel. If a clean channel was not found, then at450C, the small cell301turns off the cellular network and provides only the WLAN. At455C, the small cell301performs some time hysteresis and the flow returns to400A.

FIG. 4Dillustrates the flow ofFIG. 4Cin greater detail. As withFIG. 4C, the flow illustrated inFIG. 4Dmay be performed by the small cell301inFIG. 3.

The flow begins at400D. At410D, the small cell301, specifically the cellular modem394using the NLM398, performs an initial channel scan of available channels (referred to inFIG. 4Das “Initial Channel Scan (NL)”), as discussed below with reference to510ofFIG. 5. The cellular modem394receives as input the channel numbers of all available channels and outputs the RSRP, PLMN ID, and noise floor of each channel. Channels with an RSRP less than a threshold at the cellular modem394are marked as available with weak/tolerable interference in the LTE Advanced in unlicensed spectrum. The small cell301creates a channel database with a utility function for each channel of the measured noise floor and the RSRP.

Also at410D, the small cell301, specifically the AP392, performs an initial channel scan. The AP392receives as input the channel numbers of all available channels and outputs the RSSI of the channel beacon, the PHY mode (which may include the bandwidth and the primary and secondary channels), and the noise floor of each channel. Channels with a beacon RSSI less than a threshold at the AP392are marked as clean. The small cell301creates a channel database with a utility function for each channel of the measured noise floor and the beacon RSSI, as described above with reference to410B ofFIG. 4B. Note that the channel database created at410D may be a different database than the database created at405D, or the information detected at410D may be added to the database created at405D.

At415D, the small cell301determines whether or not there is a clean channel. As discussed above with reference to415B ofFIG. 4B, a clean channel is a channel with a maximum beacon RSSI, as measured at the AP392, less than the RSSI threshold. If there are no clean channels, then the flow proceeds to450D, where the small cell301turns off, or does not establish, the cellular network.

If, however, there are one or more clean channels, then at420D, the AP392selects as the operating channel for the cellular network the clean channel with the highest utility value, as determined by the utility function based on the measured noise floor and the beacon RSSI.

At425D, the AP392and the cellular modem394perform periodic channel scans. The AP392and the cellular modem394can perform the scans every T seconds and/or upon some event trigger. A triggering event may be, for example, measuring a high interference to the current operating channel at the AP392or the cellular modem394or receiving an indication of a high interference from an STA or UE report (received from a user device302connected to the AP392and/or the cellular modem394).

At427D, the small cell301determines whether or not there is at least one channel with weak/tolerable cellular (e.g., LTE Advanced in unlicensed spectrum) interference based on the initial/periodic NL scan at410D and425D, as discussed below with reference to520ofFIG. 5. If at least one such channel is available, then at430D, the small cell301updates the channel database created during the AP scan at410D, as discussed above with reference to430B ofFIG. 4B. The small cell301marks channels as clean or unclean. If all available channels have strong (i.e., not weak/tolerable) interference in the LTE/LTE Advanced in unlicensed spectrum, the flow proceeds to433D, where the small cell301can perform the procedure in530-560ofFIG. 5 or 660B-675B and 645BofFIG. 6B, as discussed below. As part of the database updates, the small cell301calculates or updates the utility value (as calculated by the utility function discussed above) for the list of channels. The utility value takes into account the noise floor, the STA-assisted measurements, and/or any other cellular network interference. The small cell301then ranks the clean channels according to their utility values.

The flow then proceeds to435D,440D,445D,450D, and455D, which correspond to435B,440B,445B,450B, and455B ofFIG. 4B, respectively. For brevity, the discussion of these features is not repeated here.

FIG. 5illustrates an exemplary flow for minimizing WLAN AP misdetection for LTE/LTE Advanced in unlicensed spectrum channel selection in the presence of interference. The flow illustrated inFIG. 5may be performed by the small cell301inFIG. 3. The flow illustrated inFIG. 5may occur in conjunction with aspects of the flows illustrated inFIGS. 4B/4D.

Before performing WLAN measurements on all channels and choosing the cleanest channel, as in410B/410D and420B/420D ofFIGS. 4B/4D, at510, the small cell301(specifically the cellular modem394) can perform LTE/LTE Advanced in unlicensed spectrum channel scanning based on LTE/LTE Advanced in unlicensed spectrum network listen measurements from the NLM398, and then choose a set of channels with weak or tolerable interference in the LTE/LTE Advanced in unlicensed spectrum. The interference may be from other operators' small cells operating in the LTE/LTE Advanced in unlicensed spectrum. A “weak” or “tolerable” interference may be, for example, a Cell Edge RSRP equal to −120 dBm, or an RSSI (assuming full loading) equal to −120 plus 30, or −90 dBm. By choosing a set of channels with a weak or tolerable interference in the LTE/LTE Advanced in unlicensed spectrum, the small cell301/cellular modem394is avoiding channels with a strong presence in the LTE/LTE Advanced in unlicensed spectrum.

The small cell301(specifically the AP392) can then choose channels based on the received signal strength from the same or other operator small cells and the clean channel WLAN threshold, as discussed above with reference to410B/410D and420B/420D ofFIGS. 4B/4D. Specifically, the small cell301/AP392performs the scan illustrated in410B/410D of the channels with weak/tolerable cellular interference identified in510/520.

When choosing the channels, the small cell301can give different priorities to channels being used by the same operator (i.e., the operator of small cell301), different operators (i.e., operators different from the operator of small cell301), and WLAN. The small cell301can prioritize the same/different operators and WLAN channels using the channel penalty described above.

If, at520, a channel with weak or tolerable interference in the LTE/LTE Advanced in unlicensed spectrum is available, then there is no need to change the flow ofFIG. 4B/4D, since any WLAN AP beacons above the threshold can be decoded reliably. They can be decoded reliably because the NLM398identified that there is no interference in the LTE/LTE Advanced in unlicensed spectrum above this pre-defined signal level.

If, however, at520, such a “weak” or “tolerable” channel in the LTE/LTE Advanced in unlicensed spectrum is not available, the small cell301can leverage the presence of strong interference in the LTE/LTE Advanced in unlicensed spectrum to filter out unavailable channels. The channel scanning flow illustrated inFIG. 4Bhas a simple infinite impulse response (IIR) filter to average the beacon RSSI values obtained as a result of the WLAN AP scan. This simple filtering can be modified to account for detection in the presence of strong interference in the LTE/LTE Advanced in unlicensed spectrum.

Specifically, at530, during the duration of the periodic WLAN AP scan (425D ofFIG. 4D), the co-located cellular modem394can also perform a periodic network listen (425D ofFIG. 4D) to search for any strong LTE/LTE Advanced in unlicensed spectrum signals that overlap with the WLAN AP scan period. That way, a sudden beacon miss on a given channel in a given WLAN AP scan period (detected at540) can be correlated to the appearance of a strong LTE/LTE Advanced in unlicensed spectrum signal (from the NLM398) on that channel.

Given that a WLAN AP is usually static, a sudden beacon miss can be interpreted as a beacon that had been reported periodically during the “non-busy” hours but suddenly goes missing. If, at550, such an event occurs, then at560, the previous WLAN AP beacon RSSI value stored in the database for that channel is “frozen” until the strong LTE/LTE Advanced in unlicensed spectrum signal disappears. The small cell301then continues the periodic scanning of the remaining channels.

If, however, the miss is uncorrelated to any LTE/LTE Advanced in unlicensed spectrum signal presence, indicating that the WLAN AP on that channel is possibly shut OFF, then the beacon RSSI is aged as before, and the small cell301continues the periodic scanning of the remaining channels. The flow then proceeds to430B/430D ofFIG. 4B/4D and the database is updated with any new information discovered during the scanning. Note that whileFIGS. 4A-4Dillustrate the database update as being performed after the periodic channel scan, as is apparent, the database may be updated during the channel scan. That is, the entry for each channel may be updated (or not in the case of a “freeze”) based on the measurements of that channel made during the channel scan.

A more advanced LTE/LTE Advanced in unlicensed spectrum channel selection, for example, SIC, can actually use the co-located cellular modem394to store, decode, reconstruct, and cancel the LTE/LTE Advanced in unlicensed spectrum interference (e.g., primary synchronization signal (PSS), secondary synchronization signal (SSS), paging channel (PCH), Cell-specific Reference Signal (CRS), data channels, etc.) from the received waveform during the WLAN AP scan period and provide the “cleaned” residual waveform for WLAN detection to the co-located AP392at425B ofFIG. 4B. The small cell301can implement SIC using a shared memory, or the AP392can perform SIC.

The user device, such as user device302, could also use SIC when it collects 802.11k reports as part of the flow illustrated inFIG. 4B. The user device can cancel residual LTE/LTE Advanced in unlicensed spectrum interference and then perform WLAN detection to increase the probability of detecting an AP.

Finally, among small cells that belong to the same operator, the times of the periodic WLAN AP scans at425B ofFIG. 4Bcan be synchronized based on agreed upon times for performing the scans and/or signaling over the X2 or backhaul. At these synchronized measurement gaps, the small cells can mute together and allow their co-located WLAN APs to learn the WLAN environment around them. The pre-agreed times may be based on, for example, an absolute clock, such as a GPS or a network time protocol (NTP) clock.

FIG. 6Aillustrates an exemplary flow for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell, such as small cell301inFIG. 3. The cellular network may be an LTE network in unlicensed spectrum. The flow illustrated inFIG. 6Amay be performed by the small cell301inFIG. 3. As illustrated inFIG. 3, the small cell301may include a WLAN AP, such as AP392, and a cellular network modem, such as cellular modem394.

At610A, the small cell301performs a first channel scan of available channels for operating the cellular network, as at510ofFIG. 5. The cellular network channels may be LTE channels in unlicensed spectrum.

At620A, the small cell301performs a second channel scan of the available channels, as at410B/410D ofFIGS. 4B/4D. At630A, the small cell301identifies, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold, as at520ofFIG. 5. At640A, the small cell301determines, based on the second channel scan, whether or not a clean channel is available to be the operating channel for the cellular network, as at415B/415D ofFIGS. 4B/4D. As described above, a clean channel may be a channel that interferes with the WLAN less than a threshold.

At650A, the small cell301may select the clean channel as the operating channel for the cellular network, as at420B/420D ofFIGS. 4B/4D. Alternatively, at660A, the small cell301may turn off the cellular network based on a clean channel not being available, as at450B/450C ofFIGS. 4B/4C.

FIG. 6Billustrates an exemplary flow for selecting an operating channel for a cellular network to reduce interference to a WLAN operated by a small cell, such as small cell301inFIG. 3. The cellular network may be an LTE Advanced network in unlicensed spectrum. The flow illustrated inFIG. 6Bmay be performed by the small cell301inFIG. 3. As illustrated inFIG. 3, the small cell301may include a WLAN access point, such as AP392, and a cellular network modem, such as cellular modem394.

At605B, the small cell301, specifically the cellular modem394/NLM398, performs a channel scan of available cellular network channels, such as at410D ofFIG. 4D or 510ofFIG. 5. The cellular network channels may be LTE channels in unlicensed spectrum. This channel scan is performed primarily to avoid channels in the LTE/LTE Advanced in unlicensed spectrum being used by other operators. The order of priority in avoiding channels is: channels being used by other operators for LTE/LTE Advanced networks in unlicensed spectrum, channels being used for WLANs, channels being used by the same operator for LTE/LTE Advanced networks in unlicensed spectrum.

At610B, the small cell301, specifically the AP392/NLM394, performs an initial channel scan of available channels, such as at410B/410D ofFIGS. 4B/4D.

At615B, the small cell determines whether there are one or more cellular network channels with an interference level below a cellular network interference threshold available, such as at520ofFIG. 5. The cellular network channel(s) may be LTE Advanced channel(s) in unlicensed spectrum. The threshold may be an RSRP threshold, as described above.

At620B, the small cell301assigns a utility value to each available channel that has a maximum beacon RSSI less than the RSSI threshold, such as at410B/410D ofFIGS. 4B/4D. The utility value may be based on a noise floor and the maximum beacon RSSI. Note that although615B is illustrated as occurring before620B,620B may occur before615B.

At625B, the small cell301determines whether or not a clean channel is available to be the operating channel for the cellular network based on the initial channel scan, such as at415B/415D ofFIGS. 4B/4D. As described above, a clean channel may be a channel that interferes with the WLAN less than a threshold. A clean channel may be a channel with a maximum beacon RSSI less than an RSSI threshold.

At630B, the small cell301may select a clean channel as the operating channel for the cellular network based on a clean channel being available, such as at420B/420D ofFIGS. 4B/4D. The selected operating channel may be an available channel with the highest utility value. Alternatively, at635B, the small cell301may turn off the cellular network based on a clean channel not being available, such as at450B/450D ofFIGS. 4B/4D.

At640B, the small cell301performs a channel scan periodically or in response to an event, such as at425B/D ofFIGS. 4B/4D. As an example, the event may be the detection, by the WLAN AP or a user device connected to the WLAN AP, of interference on the operating channel higher than a threshold.

At645B, the small cell301updates a database of available channels, such as at430B/430D ofFIGS. 4B/4D.

At650B, the small cell301determines whether or not channel switching criteria for switching to a new operating channel based on the periodic channel scan have been met, such as at435B/435D ofFIGS. 4B/4D. As described above, the channel switching criteria may include an indication of whether or not a beacon RSSI of a new beacon is greater than the threshold and/or an indication of whether there is a new channel with a higher utility value than the operating channel.

At655B, the small cell switches to the new operating channel based on determining that the channel switching criteria have been met, such as at440B/440D ofFIGS. 4B/4D. Otherwise, if the channel switching criteria have not been met, the flow returns to640B.

Referring back to610B, if there are no cellular network channels with an interference level below the cellular network interference threshold, then at660B, the small cell301performs a network listen to search for any cellular network signals with an interference level above the cellular network interference threshold that overlap with a scan period of the WLAN AP, such as at530ofFIG. 5.

At665B, the small cell301detects an access point beacon miss in a given scan period of the WLAN AP, such as at540ofFIG. 5.

At670B, the small cell301determines whether the access point beacon miss is correlated to a presence of a cellular network signal, such as at550ofFIG. 5.

At675B, based on the access point beacon miss being correlated to a presence of a cellular network signal, the small cell301maintains, or “freezes,” a previous access point beacon RSSI for the cellular network channel corresponding to the cellular network signal until the interference level is not above the cellular network interference threshold, such as at560ofFIG. 5. Otherwise, if the miss is not correlated to a presence of a cellular network signal, the flow proceeds to645B.

Alternatively, rather than performing the flow of blocks660B-675B, the small cell301can perform successive interference cancellation (SIC) on a cellular network signal with an interference level above the cellular network interference threshold to generate a clean cellular network signal, as described above. The small cell3013can then provide the clean cellular network signal to the WLAN AP. The clean cellular network signal may be a waveform that does not include the cellular network signal with the interference level above the cellular network interference threshold and contains only residual WLAN AP signals for beacon detection. In an aspect, the SIC and the providing may be performed by a user device in communication with the small cell301, such as user device302. Alternatively, the SIC and the providing may be performed by the small cell301.

As another alternative, channel scans of available WLAN access point channels can be synchronized among a plurality of small cells, including small cell301, belonging to the same operator. In this case, the small cell301can be muted to permit the WLAN AP to determine a current wireless environment of the small cell.

FIG. 7illustrates a communication device700that includes logic configured to perform functionality. The communication device700can correspond to any of the above-noted communication devices, including but not limited to any component of the wireless communication network100, any component of the mixed communication network environment200, the small cell301, the user devices302, and so on.

Referring toFIG. 7, the communication device700includes logic configured to receive and/or transmit information705. In an example, if the communication device700corresponds to a wireless communications device (e.g., the small cell301or the user devices302), the logic configured to receive and/or transmit information705can include a wireless communications interface (e.g., Bluetooth, WiFi, 2G, CDMA, W-CDMA, 3G, 4G, LTE, etc.) such as a wireless transceiver and associated hardware (e.g., an RF antenna, a MODEM, a modulator and/or demodulator, etc.). In an aspect, if the communication device700corresponds to the small cell301inFIG. 3, the logic configured to receive and/or transmit information705can include, for example, antennas340, transmitter330, receiver350, NLM396, AP392, NLM398, and/or cellular modem394. In another example, the logic configured to receive and/or transmit information705can correspond to a wired communications interface (e.g., a serial connection, a USB or Firewire connection, an Ethernet connection through which the Internet can be accessed, etc.). Thus, if the communication device700corresponds to some type of network-based server (e.g., an application server), the logic configured to receive and/or transmit information705can correspond to an Ethernet card, in an example, that connects the network-based server to other communication entities via an Ethernet protocol. In a further example, the logic configured to receive and/or transmit information705can include sensory or measurement hardware by which the communication device700can monitor its local environment (e.g., an accelerometer, a temperature sensor, a light sensor, an antenna for monitoring local RF signals, etc.). The logic configured to receive and/or transmit information705can also include software that, when executed, permits the associated hardware of the logic configured to receive and/or transmit information705to perform its reception and/or transmission function(s). However, the logic configured to receive and/or transmit information705does not correspond to software alone, and the logic configured to receive and/or transmit information705relies at least in part upon hardware to achieve its functionality.

Referring toFIG. 7, the communication device700further includes logic configured to process information710. In an example, the logic configured to process information710can include at least a processor. Example implementations of the type of processing that can be performed by the logic configured to process information710includes but is not limited to performing determinations, establishing connections, making selections between different information options, performing evaluations related to data, interacting with sensors coupled to the communication device700to perform measurement operations, converting information from one format to another (e.g., between different protocols such as .wmv to .avi, etc.), and so on. For example, the processor included in the logic configured to process information710can correspond to a general purpose processor, a digital signal processor (DSP), an 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. In an aspect, if the communication device700corresponds to the small cell301inFIG. 3, the logic configured to process information710can include, for example, TX data processor310, RX data processor370, processor380, and/or controller/processor382. The logic configured to process information710can also include software that, when executed, permits the associated hardware of the logic configured to process information710to perform its processing function(s). However, the logic configured to process information710does not correspond to software alone, and the logic configured to process information710relies at least in part upon hardware to achieve its functionality.

Referring toFIG. 7, the communication device700further includes logic configured to store information715. In an example, the logic configured to store information715can include at least a non-transitory memory and associated hardware (e.g., a memory controller, etc.). For example, the non-transitory memory included in the logic configured to store information715can correspond to RAM, flash memory, ROM, erasable programmable ROM (EPROM), EEPROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. In an aspect, if the communication device700corresponds to the small cell301inFIG. 3, the logic configured to store information715can include, for example, memory384. The logic configured to store information715can also include software that, when executed, permits the associated hardware of the logic configured to store information715to perform its storage function(s). However, the logic configured to store information715does not correspond to software alone, and the logic configured to store information715relies at least in part upon hardware to achieve its functionality.

Referring toFIG. 7, the communication device700further optionally includes logic configured to present information720. In an example, the logic configured to present information720can include at least an output device and associated hardware. For example, the output device can include a video output device (e.g., a display screen, a port that can carry video information such as USB, HDMI, etc.), an audio output device (e.g., speakers, a port that can carry audio information such as a microphone jack, USB, HDMI, etc.), a vibration device and/or any other device by which information can be formatted for output or actually outputted by a user or operator of the communication device700. The logic configured to present information720can be omitted for certain communication devices, such as network communication devices that do not have a local user (e.g., network switches or routers, remote servers, etc.). The logic configured to present information720can also include software that, when executed, permits the associated hardware of the logic configured to present information720to perform its presentation function(s). However, the logic configured to present information720does not correspond to software alone, and the logic configured to present information720relies at least in part upon hardware to achieve its functionality.

Referring toFIG. 7, the communication device700further optionally includes logic configured to receive local user input725. In an example, the logic configured to receive local user input725can include at least a user input device and associated hardware. For example, the user input device can include buttons, a touchscreen display, a keyboard, a camera, an audio input device (e.g., a microphone or a port that can carry audio information such as a microphone jack, etc.), and/or any other device by which information can be received from a user or operator of the communication device700. The logic configured to receive local user input725can be omitted for certain communication devices, such as network communication devices that do not have a local user (e.g., network switches or routers, remote servers, etc.). The logic configured to receive local user input725can also include software that, when executed, permits the associated hardware of the logic configured to receive local user input725to perform its input reception function(s). However, the logic configured to receive local user input725does not correspond to software alone, and the logic configured to receive local user input725relies at least in part upon hardware to achieve its functionality.

Referring toFIG. 7, while the configured logics of705through725are shown as separate or distinct blocks inFIG. 7, it will be appreciated that the hardware and/or software by which the respective configured logic performs its functionality can overlap in part. For example, any software used to facilitate the functionality of the configured logics of705through725can be stored in the non-transitory memory associated with the logic configured to store information715, such that the configured logics of705through725each performs their functionality (i.e., in this case, software execution) based in part upon the operation of software stored by the logic configured to store information715. Likewise, hardware that is directly associated with one of the configured logics can be borrowed or used by other configured logics from time to time. For example, the processor of the logic configured to process information710can format data into an appropriate format before being transmitted by the logic configured to receive and/or transmit information705, such that the logic configured to receive and/or transmit information705performs its functionality (i.e., in this case, transmission of data) based in part upon the operation of hardware (i.e., the processor) associated with the logic configured to process information710.

Generally, unless stated otherwise explicitly, the phrase “logic configured to” as used throughout this disclosure is intended to invoke an aspect that is at least partially implemented with hardware, and is not intended to map to software-only implementations that are independent of hardware. Also, it will be appreciated that the configured logic or “logic configured to” in the various blocks are not limited to specific logic gates or elements, but generally refer to the ability to perform the functionality described herein (either via hardware or a combination of hardware and software). Thus, the configured logics or “logic configured to” as illustrated in the various blocks are not necessarily implemented as logic gates or logic elements despite sharing the word “logic.” Other interactions or cooperation between the logic in the various blocks will become clear to one of ordinary skill in the art from a review of the aspects described below in more detail.

FIG. 8illustrates several sample components (represented by corresponding blocks) that may be incorporated into an apparatus802, an apparatus804, and an apparatus806(corresponding to, for example, a user device, a small cell base station, and a network entity, respectively) to support the selection of an operating channel for a cellular network so as to reduce interference to a WLAN as taught herein. It will be appreciated that these components may be implemented in different types of apparatuses in different implementations (e.g., in an ASIC, in an SoC, etc.). The illustrated components may also be incorporated into other apparatuses in a communication system. For example, other apparatuses in a system may include components similar to those described to provide similar functionality. Also, a given apparatus may contain one or more of the components. For example, an apparatus may include multiple transceiver components that enable the apparatus to operate on multiple carriers and/or communicate via different technologies.

The apparatus802and the apparatus804each include at least one wireless communication device (represented by the communication devices808and814(and the communication device820if the apparatus804is a relay)) for communicating with other nodes via at least one designated RAT. Each communication device808includes at least one transmitter (represented by the transmitter810) for transmitting and encoding signals (e.g., messages, indications, information, and so on) and at least one receiver (represented by the receiver812) for receiving and decoding signals (e.g., messages, indications, information, pilots, and so on). Similarly, each communication device814includes at least one transmitter (represented by the transmitter816) for transmitting signals (e.g., messages, indications, information, pilots, and so on) and at least one receiver (represented by the receiver818) for receiving signals (e.g., messages, indications, information, and so on). If the apparatus804is a relay station, each communication device820may include at least one transmitter (represented by the transmitter822) for transmitting signals (e.g., messages, indications, information, pilots, and so on) and at least one receiver (represented by the receiver824) for receiving signals (e.g., messages, indications, information, and so on).

A transmitter and a receiver may comprise an integrated device (e.g., embodied as a transmitter circuit and a receiver circuit of a single communication device) in some implementations, may comprise a separate transmitter device and a separate receiver device in some implementations, or may be embodied in other ways in other implementations. A wireless communication device (e.g., one of multiple wireless communication devices) of the apparatus804may also comprise a Network Listen Module (NLM) or the like for performing various measurements.

The apparatus806(and the apparatus804if it is not a relay station) includes at least one communication device (represented by the communication device826and, optionally,820) for communicating with other nodes. For example, the communication device826may comprise a network interface that is configured to communicate with one or more network entities via a wire-based or wireless backhaul. In some aspects, the communication device826may be implemented as a transceiver configured to support wire-based or wireless signal communication. This communication may involve, for example, sending and receiving: messages, parameters, or other types of information. Accordingly, in the example ofFIG. 8, the communication device826is shown as comprising a transmitter828and a receiver830. Similarly, if the apparatus804is not a relay station, the communication device820may comprise a network interface that is configured to communicate with one or more network entities via a wire-based or wireless backhaul. As with the communication device826, the communication device820is shown as comprising a transmitter822and a receiver824.

The apparatuses802,804, and806also include other components that may be used in conjunction with the operations of selecting an operating channel for a cellular network so as to reduce interference to a WLAN as taught herein. The apparatus802includes a processing system832for providing functionality relating to, for example, STA and UE reports as taught herein and for providing other processing functionality. The apparatus804includes a processing system834for providing functionality relating to, for example, selecting an operating channel for a cellular network so as to reduce interference to a WLAN as taught herein and for providing other processing functionality. The apparatus806includes a processing system836for providing functionality relating to, for example, network operations to support the selection of an operating channel for a cellular network so as to reduce interference to a WLAN as taught herein and for providing other processing functionality. The apparatuses802,804, and806include memory components838,840, and842(e.g., each including a memory device), respectively, for maintaining information (e.g., information indicative of reserved resources, thresholds, parameters, and so on). In addition, the apparatuses802,804, and806include user interface devices844,846, and848, respectively, for providing indications (e.g., audible and/or visual indications) to a user and/or for receiving user input (e.g., upon user actuation of a sensing device such a keypad, a touch screen, a microphone, and so on).

For convenience, the apparatuses802,804, and/or806are shown inFIG. 8as including various components that may be configured according to the various examples described herein. It will be appreciated, however, that the illustrated blocks may have different functionality in different designs.

The components ofFIG. 8may be implemented in various ways. In some implementations, the components ofFIG. 8may be implemented in one or more circuits such as, for example, one or more processors and/or one or more ASICs (which may include one or more processors). Here, each circuit may use and/or incorporate at least one memory component for storing information or executable code used by the circuit to provide this functionality. For example, some or all of the functionality represented by blocks808,832,838, and844may be implemented by processor and memory component(s) of the apparatus802(e.g., by execution of appropriate code and/or by appropriate configuration of processor components). Similarly, some or all of the functionality represented by blocks814,820,834,840, and846may be implemented by processor and memory component(s) of the apparatus804(e.g., by execution of appropriate code and/or by appropriate configuration of processor components). Also, some or all of the functionality represented by blocks826,836,842, and848may be implemented by processor and memory component(s) of the apparatus806(e.g., by execution of appropriate code and/or by appropriate configuration of processor components).

FIG. 9illustrates an example base station apparatus900represented as a series of interrelated functional modules. A module for performing a channel scan of available channels902may correspond at least in some aspects to, for example, a WLAN access point and/or corresponding NLM, such as AP392and/or NLM396inFIG. 3, as discussed herein. A module for determining whether or not there is a clean channel to be the operating channel for the cellular network based on the channel scan904may correspond at least in some aspects to, for example, a processing system, such as processor382inFIG. 3, as discussed herein. A module for selecting the clean channel as the operating channel for the cellular network or turning off the cellular network based on no clean channel being available906may correspond at least in some aspects to, for example, a processing system, such as processor382inFIG. 3, as discussed herein.

FIG. 10illustrates an example user device apparatus1000represented as a series of interrelated functional modules. A module for performing a first channel scan of available channels for operating the cellular network1002may correspond at least in some aspects to, for example, a cellular modem and/or corresponding NLM, such as cellular modem394and/or NLM398inFIG. 3, as discussed herein. A module for performing a second channel scan of the available channels for operating the cellular network1004may correspond at least in some aspects to, for example, a WLAN access point and/or corresponding NLM, such as AP392and/or NLM396inFIG. 3, as discussed herein. A module for identifying, based on the first channel scan, one or more cellular network channels of the available channels that have an interference level below a cellular network interference threshold1006may correspond at least in some aspects to, for example, a processing system, such as processor382inFIG. 3, as discussed herein. A module for determining, based on the second channel scan, whether or not there is a clean channel in the identified one or more cellular network channels to be the operating channel for the cellular network1008may correspond at least in some aspects to, for example, a processing system, such as processor382inFIG. 3, as discussed herein. A module for selecting the clean channel as the operating channel for the cellular network based on the clean channel being available or turning off the cellular network based on no clean channel being available1010may correspond at least in some aspects to, for example, a processing system, such as processor382inFIG. 3, as discussed herein.

The functionality of the modules ofFIGS. 9-10may be implemented in various ways consistent with the teachings herein. In some designs, the functionality of these modules may be implemented as one or more electrical components. In some designs, the functionality of these blocks may be implemented as a processing system including one or more processor components. In some designs, the functionality of these modules may be implemented using, for example, at least a portion of one or more integrated circuits (e.g., an ASIC). As discussed herein, an integrated circuit may include a processor, software, other related components, or some combination thereof. Thus, the functionality of different modules may be implemented, for example, as different subsets of an integrated circuit, as different subsets of a set of software modules, or a combination thereof. Also, it will be appreciated that a given subset (e.g., of an integrated circuit and/or of a set of software modules) may provide at least a portion of the functionality for more than one module.

In addition, the components and functions represented byFIGS. 9-10, as well as other components and functions described herein, may be implemented using any suitable means. Such means also may be implemented, at least in part, using corresponding structure as taught herein. For example, the components described above in conjunction with the “module for” components ofFIGS. 9-10also may correspond to similarly designated “means for” functionality. Thus, in some aspects one or more of such means may be implemented using one or more of processor components, integrated circuits, or other suitable structure as taught herein.

Accordingly, an aspect of the disclosure can include a computer readable media embodying a method for channel selection to reduce interference to a wireless local area network from a cellular network. Accordingly, the disclosure is not limited to illustrated examples and any means for performing the functionality described herein are included in aspects of the disclosure.