Determining a location of a UE within a coverage area

A method and a device for performing massive multiple-input and multiple-output (“MIMO”) operations with a user equipment (UE). The method and device receive signals from a UE within a coverage area of the device, determine a location of the UE within the coverage area and assign an operating frequency band to the UE for communication with the device, wherein the coverage area includes a plurality of regions and the operating frequency band assigned to the UE is based on the one of the regions corresponding to the location and transmit the operating frequency band assignment to the UE.

BACKGROUND

In wireless communication networks, multiple-input and multiple-output (“MIMO”) operations are methods for multiplying the capacity of a radio link through the use of multiple transmit and receive antennas. MIMO technology has been incorporated into wireless broadband standards such as the third generation partnership project (“3GPP”) standards (e.g., 4G-Long Term Evolution (“LTE”) networks) and the Institute of Electrical and Electronics Engineers (“IEEE”) wireless technologies. By exploiting multipath propagation, MIMO communications utilizes more antennas per transmitter/receiver to allow for both a greater number of possible signal paths and improved performance in terms of data rate and link reliability. However, the downside of MIMO-based communications includes increased complexity of the hardware and the complexity as well as the energy consumption of the signal processing at both ends of a transmission.

Massive MIMO, or large-scale MIMO, refers to techniques using a very large number (e.g., hundreds or thousands) of transmit and receive antennas. Accordingly, massive MIMO makes improvements over current practice through the use of these numerous antennas that are operated coherently and adaptively. Extra antennas help by focusing the transmission and reception of signal energy into ever-smaller regions of space. This can bring significant improvements in throughput and reductions in required transmit power, particularly when combined with simultaneous scheduling of a large number of user terminals (e.g., tens or hundreds). Massive MIMO networks can also significantly increase the signal strength at a mobile device, or user equipment (“UE”), even if only the serving node, or enhanced Node B (“eNB”), has the large number of antennas. However, it is important to note that conventional usage of massive MIMO communications is based on single frequency networks. Furthermore, while massive MIMO reduces required transmit power, conventional MIMO (i.e., not massive MIMO) requires more energy consumed at the UE due to multiple radio frequency (“RF”) chains and complex signal processing.

While benefits of massive MIMO include the extensive use of inexpensive low-power components, reduced latency and simplification of the media access control (“MAC”) layer, there are limitations to the current operations. For instance, in conventional methods for managing interference between different cells in a network, the eNB coordinates the transmissions of UEs at the cell edge. These coordinated transmissions direct the UEs to use a specific part of the frequency spectrum band. However, these communications can necessitate a great deal of overhead and power consumption in order to distribute the management information throughout the network. Accordingly, a more efficient system and method are needed for interference management in massive MIMO communication systems.

SUMMARY

Described herein are systems and methods for interference management in a massive MIMO communication system. A method may comprise determining, by a base station, a user equipment (“UE”) location of a first UE, wherein the base station communicates with the first UE via massive multiple-input and multiple-output (“MIMO”) operations, assigning a frequency band to be used by the first UE based on the UE location, identifying a new UE location of the first UE, and adjusting the frequency band to be used by the first UE based on the new UE location.

Further described herein is a base station device having a plurality of antennas configured to perform massive multiple-input and multiple-output (“MIMO”) operations, receive circuitry configured to receive signals from a user equipment (UE) within a coverage area of the base station, a baseband processor configured to determine a location of the UE within the coverage area and assign an operating frequency band to the UE for communication with the base station, wherein the coverage area includes a plurality of regions and the operating frequency band assigned to the UE is based on the one of the regions corresponding to the location and transmit circuitry to transmit the operating frequency band assignment to the UE.

Further described herein is a method performed by a base station. The method includes communicating with a first user equipment (“UE”) and a second UE via massive multiple-input and multiple-output (“MIMO”) operations, determining that the first UE is located in a first geographical area relative to the base station, determining that the second UE is located in a second geographical area relative to the base station, assigning the first UE to a first frequency band including a first range of frequencies and assigning the second UE to a second frequency band including a second range of frequencies, wherein the second range of frequencies is a subset of the first range of frequencies.

DETAILED DESCRIPTION

The exemplary embodiments may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The exemplary embodiments describe an apparatus, system and method for allocating frequency bands to UEs within a coverage area of a base station operating as a massive MIMO base station. In the exemplary embodiments, the base station will be described as an evolved Node B (eNB) base station, which is generally known as being a base station associated with LTE networks. However, it will be understood by those skilled in the art that base stations operating in accordance with other network standards may also implement the exemplary embodiments in accordance with the functionalities and principles described herein, including further advancements in networking standards such as those commonly referred to as 5G systems and later.

Prior to describing the exemplary embodiments, several terms that will be used throughout this description will be described by example. A frequency spectrum for a radio access technology may be divided into different frequency bands. For example, LTE may be assigned a frequency spectrum. This frequency spectrum may be divided into a number N of discrete frequency bands. For example, in LTE, frequency band1may include the range of frequencies 1920-1980 MHz in the uplink (UL) and 2110-2170 MHz in the downlink (DL), frequency band2may include the range of frequencies 1850-1910 MHz in the UL and 1930-1990 MHz in the DL and frequency band3may include the range of frequencies 1710-1785 MHz in the UL and 1805-1880 MHz in the DL. LTE includes many more frequency bands, and these are provided only as an example.

Throughout this description, when it is referred to a UE being assigned a full frequency band, it means that the UE may use any of the frequencies within the assigned frequency band. For example, if a UE was assigned the full frequency band of LTE frequency band1, the UE may use any of the frequencies 1920-1980 MHz in the UL. In contrast, when the UE is assigned a partial frequency band, the UE may only use a portion of the frequencies within the assigned frequency band. For example, if a UE was assigned the partial frequency band of LTE frequency band1, the UE may use only a partial range of the frequencies 1920-1980 MHz in the UL, e.g., 1940-1960 MHz.

FIG. 1shows an exemplary massive MIMO communication system100according to various embodiments described herein. The exemplary system100may include a massive MIMO base station, such as an eNB110, in communication with a plurality of mobile devices, such as UEs120-140. Furthermore, the eNB110may include a control system111, a baseband processor112, transmit circuitry113, receive circuitry114, a network interface115, and a plurality of multiple antennas116. The receive circuitry114may receive radio frequency signals bearing information, such as location information, from one or more remote transmitters provided by UEs120-140.

The baseband processor112of the eNB110may process the digitized received signal to extract the information or data bits conveyed in the received signal. This processing may include, for example, demodulation, decoding, and error correction operations. Accordingly, the baseband processor112may be implemented in one or more digital signal processors (“DSPs”) or application-specific integrated circuits (“ASICs”). As described above, the information received from any one of the UEs120-140may be used to determine a location of the specific UE.

It should be noted that each of the components111-115of the eNB110may be implemented using a variety of electronic components including integrated circuits, ASICs, digital signal processors, etc. These components111-115may also execute software or firmware to perform the herein described functionalities. In addition, the eNB110may also include additional components that are not shown inFIG. 1.

Once the eNB110determines the current location of the UE, the eNB110may assign a frequency band for use by the UE. As described above, the frequency assigned to UE may include the full frequency band or a partial frequency band. The assignment by the eNB110of the full frequency band or partial frequency band may depend on the determined location of the UEs120-140. The relative location of the UEs120-140may include, for example, being on the edge of the eNB110cell coverage, close to the eNB110, etc. The assignment of the frequency band will be described in greater detail below. This assigned frequency band information may then be sent across a wireless network via the network interface115and may be transmitted back to UE.

In order to perform the transmission of the assignment information, the baseband processor112may receive digitized data, such as control information, from the network interface115under the control of control system111, and encode the data for transmission. The encoded data is output to the transmit circuitry113, where it is modulated by one or more carrier signals having a desired transmit frequency or frequencies. A power amplifier (not shown) may also be used to amplify the modulated carrier signals to a level appropriate for transmission, and deliver the modulated carrier signals to the antennas of the UEs120-140.

FIGS. 2A and 2Bshow frequency band usage throughout an exemplary massive MIMO cell according to an embodiment described herein.FIG. 2Aillustrates a cell layout map210of an exemplary eNB (e.g., eNB110) for managing the interference levels of a plurality of UEs in a massive MIMO network according to various embodiments described herein. As depicted inFIG. 2A, the frequency band assigned to the UE may be based on the cell in which the UE presently resides. More specifically, each of the cells in cell layout map210may represent a different frequency band. For example, in the cell layout map210, cell211is assigned frequency band221, cell212is assigned frequency band222, cell213is assigned frequency band223, cell214is assigned frequency band224, cell215is assigned frequency band225, cell216is assigned frequency band226and cell217is assigned frequency band227. It may be noted that frequency band assignments for each of the eNBs may be predetermined, and thus do not require any communication between the eNBs.

FIG. 2Billustrates the eNB assignment230of frequency band based on the proximity of the UEs to the eNB according to various embodiments described herein. For example,FIG. 2Bmay represent any of the individual cells211-217having the corresponding frequency bands221-227as shown inFIG. 2A, e.g., the eNB assignment230may represent the cell211having frequency band assignment221. As depicted inFIG. 2B, the eNB may adaptively adjust the frequency bands (e.g., full frequency band or partial frequency band) assigned to a UE as the location of the UE changes. Specifically, a UE traveling away from the eNB may transition from using the full frequency band231when in a region241closest to the eNB, to an adaptive usage232between full frequency band and partial frequency band when in a region242, and finally to a partial frequency band233when on the edge of the cell in the region243. During the adaptive usage232, the eNB may alternate between full frequency band and partial frequency band depending on the current location information received from the UE, such as, but not limited to path loss and interference measurements. The aggregated regions241-243is the coverage area of the cell. Those skilled in the art will understand that the coverage area of the cell may be more irregular than the hexagonal shape shown inFIG. 2Aand the circular shape shown inFIG. 2B.

According to the exemplary embodiments described herein, UEs that are in close proximity to the eNB (e.g., in region241) may be assigned the full frequency band for use. For UEs that are further from the eNB, on the edge of the cell (e.g., in region243), the eNB may assign only the partial frequency band. In order to minimize the potential for interference at the UE, the portion of the frequencies that correspond to a particular partial frequency band may be predetermined. Due to the fact that the eNB deploys a large number of antennas for massive MIMO communications with the UEs in the network, the eNB may compensate for the throughput loss of the UEs on the edge of the cell. It should be noted that the exact distances from the eNB that correspond to each of these regions241-243(e.g., full frequency band region241, adaptive region242, partial frequency band region243) may depend on any number of factors. For example, an eNB that is located in close proximity to a large number of other eNBs, may have an edge region (partial frequency band region243) that is larger than an eNB that is in proximity to a small number of other eNBs because there is a higher likelihood of interference between signals where there is a higher density of eNBs. Other factors such as physical obstructions may also be considered. In one exemplary embodiment, a frequency map may be created for each deployed eNB based on network planning factors. Thus, it is possible that each eNB may have a different frequency map (e.g., different regions241-243).

FIG. 3shows an exemplary method300for interference management by adapting a frequency band usage of a UE within a massive MIMO communication system according to various embodiments described herein. It is noted that the entirety of method300may be performed by a base station, or eNB, capable of utilizing a plurality of antennas for communicating with at least one UE using massive MIMO operations. The exemplary method will be described with reference to the eNB110and UEs120-140ofFIG. 1and the cell regions241-243ofFIG. 2B. However, as described above, the exemplary method may be implemented in other types of arrangements.

In310, the eNB110may receive information from the UE (e.g., UE120) indicating a location of the UE120and/or signal quality information for the UE120. For instance, the received information may include location information such as Global Positioning Satellite (“GPS”) information for the UE120or signal quality information such as a received signal strength indication (“RSSI”) for the UE120. One skilled in the art would understand that using GPS information is one exemplary method for determining a location of the UE, and the servicing eNB may use any number of alternative locating methods. For instance, other locating methods may include global navigation satellite systems (“GNSS”), visible WiFi access points, visible eNBs, etc. Furthermore, using the RSSI information is one exemplary method for determining signal quality, and the servicing eNB may use any number of alternative signal quality measuring methods. For instance, other measured signal quality metrics may include channel quality indicator (“CQI”), rank, signal to noise plus interference ratio (“SNIR”), etc.

In320, the eNB110may determine a location of the UE120based on the received information. For instance, the eNB110may identify the relative location of the UE120as one of close to the eNB, midway within the cell coverage radius, or on the edge of the cell coverage. As noted above, UEs that are located in each of these locations may receive different treatment from eNB110.

In330, the eNB110may assign a frequency band for use by the UE120based on the determined location of the UE120. For instance, any UEs that reside close to the eNB (e.g., in region241) may be assigned the full frequency band for use, and any UEs that reside on the cell edge (e.g., in region243) may be assigned a partial frequency band for use. In addition, UEs that are midway within the cell coverage radius (e.g., in region242) may be provided with an adaptive assignment as the UE transitions either away or towards the eNB.

It should be noted that it is described in320that the eNB110determines the location of the UE120based on the location information. The signal quality information may also be used to determine the location. For example, the regions241-243may be defined in terms of the signal quality information rather than a geographic region. To provide a specific example, it may be considered that those UEs having an RSSI above a first threshold (e.g., a relatively high RSSI) may be considered to be in the region241that is relatively close to the eNB110and therefore are assigned the full frequency band. In contrast, those UEs having an RSSI below a second threshold (e.g., a relatively low RSSI) may be considered to be in the region243that is relatively far from the eNB110and therefore are assigned the partial frequency band. The adaptive region242may be considered to be the RSSI between these two thresholds. Again, it should be noted that this is only one example of using the signal quality information to be a proxy for a location and there may be other manners of making this location determination.

It should also be noted that it is described in330that the eNB110assigns the frequency band based on the identified region. However, the signal quality information may also be used to assign the frequency band. For example, the eNB110may use the location information to determine which region (e.g., regions241-243) the eNB110is currently occupying. However, the eNB110may also use the signal quality information in making the assignment of the frequency band. For example, the eNB110may determine the UE is in region241using the location information. However, the signal quality information may indicate that there is a low signal quality between the UE120and the eNB110(e.g., a low RSSI). In such a situation, the eNB110may also consider the signal quality information when assigning the frequency band. For example, the combination of being in region241and a relatively low RSSI may lead the eNB110to assign the UE120to the adaptive band232, rather than the full frequency band231.

In340, the eNB110may receive further information indicating a change in the location of the UE120. As noted above, the information may include information related to location and/or signal quality information (e.g., GPS data and/or RSSI information) from the UE120. Accordingly, in350, the eNB110may determine a new location of the UE120based on the further location information.

In360, the eNB110may adjust the frequency band assignment for use by the UE120based on the new location information. As described above, the assignment of the frequency band may be adaptive to allow for a change in a UE's assignment as the UE120travels within the coverage area of the eNB110. Specifically, when the UE120travels to the cell edge (e.g., in region243), the eNB110may adjust the frequency band assignment from the full frequency band to the partial frequency band.

The exemplary method300provides a manner of determining which region (e.g., regions241-243) the UEs are currently occupying and which frequency band assignment (e.g., assignments231-233) the eNB is to assign to the UEs. If the UE120is assigned to the adaptive usage232, the eNB110may alternate between full frequency band and partial frequency band. For example, the UE120may remain within the same region242, but in some instances be assigned the full frequency band and in other instances be assigned the partial frequency band. The eNB110may determine this adaptive usage based on factors that are directly related to the UE120and/or factors that are not directly related to the UE120. In one example, the eNB110may make direct measurements from signals received from the UE120, such as, but not limited to path loss and interference measurements to determine whether to assign the full frequency band or the partial frequency band to the UE120(e.g., high path loss or interference indicates the eNB110should assign the partial frequency band to the UE120). These measurements relate directly to the operation of the UE120. In another example, the eNB110may make the determination based on information such as, but not limited to, cell loading or UE clustering information based on beam foaming required to be used by the cell (e.g., a high cell load or highly clustered UEs indicates the eNB110should assign the partial frequency band to the UE120). These measurements do not relate directly to the operation of the UE120, but rather relate to the operation or conditions within the cell.

By utilizing the frequency management embodiment described above in the method300ofFIG. 3, the eNB110may continue to manage the frequency band usage of the UE120, as well as any other UEs in the cell (e.g., UEs130and140), while minimizing the interference levels of the UEs.

FIG. 4shows an exemplary method400for managing interference levels for a plurality of UEs within a massive MIMO communication system according to various embodiments described herein. Again, this exemplary method400will be described with reference to the eNB110and UEs120-140ofFIG. 1and the cell regions241-243ofFIG. 2B.

In410, the exemplary eNB (e.g., eNB110), or base station, may communicate with a first UE (“UE1”) (e.g., UE130) and a second UE (“UE2”) (e.g., UE140) via massive MIMO operations. According to one embodiment of the method400, the UE1130may reside close to the eNB110and the UE2140may reside on the edge of the cell.

In420, the eNB110may determine that the UE1130is located in a first geographical area relative to the base station (e.g., region241). As noted above, the eNB110may utilize any number of locating techniques and signal quality measuring techniques, such as analysis of GPS data and/or RSSI data of the UE1130.

In430, the eNB110may determine that the UE2140is located in a second geographical area relative to the base station (e.g., region243), wherein the second geographical area is further from the base station than the first geographical area. More specifically, the eNB110may identify the UE2140as being located at the edge of the cell coverage.

In440, the eNB110may assign the full frequency band to the UE1130. Since the UE1130is in close proximity to the eNB110, the level of interference received at the UE1130may be minimal. Accordingly, the UE1130may be allocated the full frequency band231from the eNB110because the UE1130is unlikely to receive interference from signals from other eNBs. Those skilled in the art will understand that the use of the full frequency band231allows the UE to support a higher throughput.

In450, the eNB110may assign the partial frequency band233to the UE2140. Since the UE2140is further from the eNB110, the potential for interference from neighboring cells may be high. Accordingly, the UE2140may be allocated the partial frequency band by the eNB110. This partial frequency band may be predetermined by the eNB110as to minimize the level of interference received at the UE2140as it resides on the cell edge (e.g., region243). For example, the range of frequencies in the partial frequency band may be selected as mid-range frequencies within the frequency band because these are less likely to interfere with adjacent frequency bands. For example, in LTE frequency band1having the range of 1920-1980 MHz in the uplink (UL), the partial frequency band may be assigned as 1940-1960 MHz. In contrast to using the full frequency band, this usage of the partial frequency band results in a lower throughput. However, the use of the massive MIMO scheme may alleviate the throughput disadvantages caused by the partial frequency band usage.

FIG. 5shows an exemplary graph illustrating interference levels within a massive MIMO network according to various embodiments described herein. Specifically, the graph500shows the asymptotic results of interference measurements exhibiting high signal to noise ratios (“SNR”). As depicted in the graph500, the interference level of a UE increases as the UE moves away from the servicing eNB and toward the edge of the cell. With the increase in the interference level, the number of interferers can be reduced in order to maintain the same throughput. Accordingly, a smaller bandwidth may be used at the UE by the eNB assigning the partial frequency band to any UEs at the edge of the cell.

It may be noted that the exemplary embodiments are described with reference to the LTE-Advanced massive MIMO communication system. However, those skilled in the art will understand that the exemplary embodiments may be applied to managing the interference within any wireless communication schemes including those having different characteristics from the LTE-Advanced scheme.