KR20160140350A - Method and apparatus for beam scheduling - Google Patents

Abstract

The present disclosure relates to a fifth generation (5G) or pre-5G communication system that is to be provided to support higher data rates after a fourth generation (4G) communication system such as long term evolution (LTE). The method is to operate a base station in a wireless communication network allowing the base station to make communication with portable phones using directional beams. The method comprising: determining a set of beams for communicating with a plurality of portable terminals; determining a set of beam sequences, each beam sequence including a unique sequence of the beams within the set of beams; transmitting probe signals to the portable terminals in accordance with a respective beam sequence in the set of beam sequences; receiving an indicator having link quality from the portable terminals in response to the probe signals; selecting a beam sequence within the set of beam sequences based on the indicator having the received link quality; and communicating with the portable terminals according to the selected beam sequence. A corresponding method of operating the portable terminal is also disclosed.

Description

[0001] METHOD AND APPARATUS FOR BEAM SCHEDULING [0002]

The present invention relates to a beam scheduling method and apparatus.

Efforts are underway to develop an improved 5G or pre-5G communication system to meet the growing demand for wireless data traffic after commercialization of the 4G communication system. For this reason, a 5G communication system or a pre-5G communication system is called a system after a 4G network (Beyond 4G network) communication system or after a LTE system (Post LTE).

To achieve a high data rate, 5G communication systems are being considered for implementation in very high frequency (mmWave) bands (e.g., 60 gigahertz (60GHz) bands). In order to mitigate the path loss of the radio wave in the very high frequency band and to increase the propagation distance of the radio wave, in the 5G communication system, beamforming, massive MIMO, full-dimension MIMO (FD-MIMO ), Array antennas, analog beam-forming, and large scale antenna technologies are being discussed.

In order to improve the network of the system, the 5G communication system has developed an advanced small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, (D2D), a wireless backhaul, a moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation Have been developed.

In addition, in the 5G communication system, the Advanced Coding Modulation (ACM) scheme, Hybrid FSK and QAM Modulation, Sliding Window Superposition Coding (SWSC), Filter Bank Multi Carrier (FBMC) Non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA).

On the other hand, unauthorized spectrum can be used by operators for offloading traffic from unauthorized spectrum in the licensed spectrum, for example in the 2 to 5 GHz band, (Via LTE / Wi-Fi interworking), LTE over unlicensed (LTE-U), or license-assisted access (LAA) technology. However, the result of this use of unauthorized spectrum is that network operators can no longer have exclusive access to the spectrum band.

The present invention provides a method and apparatus for resolving at least some of the aforementioned problems associated with wireless communication in an unlicensed 60 GHz spectrum.

In particular, certain embodiments of the present invention provide methods and apparatus for spectrally efficient coexistence of a plurality of interfering base stations or other transmitters in the 60 GHz band.

According to a first aspect of the present invention there is provided a method of operating a base station in a wireless communication network in which a base station communicates with mobile terminals using directional beams, the method comprising determining a set of beams communicating with a plurality of mobile terminals ; Determining a set of beam sequences, each beam sequence comprising a unique sequence of beams in the set of beams; Transmitting probe signals to mobile terminals in accordance with a respective beam sequence in a set of beam sequences; Receiving indicators of link quality from portable terminals in response to probe signals; Selecting a beam sequence within the set of beam sequences based on indicators of received link quality; And communicating with the mobile terminals according to the selected beam sequence.

A directional beam can be defined as a beam that is transmitted within a relatively narrow beam width where most of the transmitted power is. This is in contrast to an isotropic beam whose power is transmitted approximately equally in all directions. This is done to maximize received power in a given direction (and to minimize received power in unintended directions). This serves to mitigate path loss and also allows for tighter frequency reuse distances. The directional beam can be defined by the beam width. The beam width is generally defined by the angular extent of the beam whose power is at or above the critical rate of power along the axis of the beam. The directional beams can also be defined by additional antenna gain (with reference to the omnidirectional antenna) required to achieve the desired link budget in a given deployment scenario.

The step of determining the set of beams may include determining a beam direction for each of the plurality of portable terminals that enables the base station to transmit data to and receive data from the portable terminal.

The plurality of portable terminals may include portable terminals located within a predetermined distance inside the edge of the cell in which the base station can communicate with the portable terminals.

The set of beam sequences may comprise all possible eigenbeam sequences in the set of beams or a subset of all possible eigenbeam sequences.

The step of selecting a beam sequence comprises: calculating a utility function for each beam sequence in the set of beam sequences based on indicators of received link quality; And selecting the beam sequence according to the calculated utility functions.

The step of selecting a beam sequence according to the calculated utility functions comprises the steps of: assigning a probability to each beam sequence according to the calculated utility functions; And stochastically selecting a beam sequence according to the assigned probabilities.

Assigning a probability to each beam sequence assigns a probability to each sequence in the set of beam sequences based on the utility function calculated for the previous sequence and the probability assigned to the previous sequence in the set of beam sequences step; Or allocating a maximum probability to a sequence in the set of beam sequences if the utility function calculated for the previous sequence is the largest computed utility function, and otherwise assigning a minimum probability.

The step of stochastically selecting a beam sequence comprises the steps of: determining a cumulative probability for each sequence in the set of beam sequences; Randomly selecting a number between a minimum probability and a maximum probability; And selecting a sequence that is less than the cumulative probability for that beam sequence, although the randomly selected number exceeds the cumulative probability for the previous beam sequence in the set of beam sequences.

The method may further comprise determining to return to transmitting the probe signals when a predetermined event occurs, wherein the predetermined event is a change in the detected link quality that is greater than a threshold value when communicating with the mobile stations, This includes expiration of the timer.

The method includes receiving additional indicators of link quality when communicating with mobile terminals in accordance with a selected beam sequence; And detecting a change in link quality based on an additional indicator of the received link quality.

The method may further include determining to return to the step of determining a set of beams in response to detecting a configuration change of the plurality of portable terminals.

According to a second aspect of the present invention there is provided a method of operating a mobile terminal in a wireless communication network in which a base station communicates with a mobile terminal using a directional beam, the method comprising the steps of: Receiving probe signals from a base station; Transmitting an indicator of link quality to a base station in connection with the received probe signal; And communicating with the base station in accordance with the beam sequence established by the base station based on the indicator of the transmitted link quality.

The step of communicating with the base station may further include transmitting an additional indicator of link quality to the base station upon receiving the data transmitted to the mobile terminal.

Communication between the base station and the mobile terminal may be based on directional beams in unlicensed frequency bands.

Unlicensed frequency bands may include 60 GHz bands.

According to a third aspect of the present invention, a base station is provided for performing the method.

According to a fourth aspect of the present invention, there is provided a portable terminal arranged to perform the method.

Another aspect of the present invention provides a computer program containing instructions to be executed when executed to implement a method and / or apparatus in accordance with any of the above aspects. Another aspect provides a machine-readable storage device for storing such a program.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will now be further described with reference to the accompanying drawings.
1 schematically shows an outline of an LTE mobile communication network.
Figure 2 schematically illustrates the integration of LTE macrocells with 60 GHz 5G miniature cells providing users with a high data rate.
Figure 3 schematically illustrates interference in a 60 GHz coexistence scenario resulting from improper beam selection.
Figure 4 schematically illustrates an optimal beam sequence selection such as may occur due to the application of the present invention in a 60 GHz coexistence scenario.
5 is a flow diagram illustrating a method of a base station or access point establishing a beam sequence in accordance with an embodiment of the present invention.
6 is a message flow diagram illustrating an embodiment of the present invention.
FIG. 7 schematically illustrates the structure of a 5G base station according to an embodiment of the present invention.
8 schematically shows the structure of a UE according to an embodiment of the present invention.
9 and 10 illustrate modeling results for spectral efficiency when two 5G base stations implement a beam sequence selection method in accordance with an embodiment of the present invention.

Embodiments of the present invention will now be described in the context of a 5G network implementation that is augmented by small cells operating in the 60 GHz band where LTE compliant wireless mobile communication networks are not authorized. However, it will be appreciated that this is only an example, and that other embodiments may include other wireless networks operating in accordance with other wireless access technologies. Although reference is made herein to a beam sequence selection method implemented by a 5G base station, the present invention is most generally applicable to any network element that transmits directional beams, in order to minimize interference and maximize spectral efficiency, As well as a method for adjusting the temperature of the water.

As described above, when communicating in the 60 GHz band, beamforming generally needs to avoid server path loss. For actual wireless communication systems of the type described in this document, beamforming must be considered essential. In essence, beamforming serves to reduce interference, but without optimal scheduling of the beams, interference can be significant due to the possibility of beam collisions. Various access networks operating at 60 GHz can use different resource allocation strategies for multi-user access. For example, 60 GHz cellular systems may use time-frequency resource blocks similar to LTE, where the available spectrum bandwidth is divided into a plurality of frequency and time slots and then users are served through scheduling of resource blocks. In addition, the beam direction can be considered as a feature that allows multiplexing in addition to the time frequency resource blocks used in LTE.

The present invention focuses on 5G radio access technologies, for example in unlicensed 60 GHz bands, which provide significantly higher peak data rates than LTE systems. However, one way that the 60 GHz spectrum can be utilized is through the deployment of 60 GHz small cells under the control of LTE macrocells using a core network that can be based on EPC (which can be referred to herein as a 5G base station Through the base station). As such, an overview of the LTE network is shown in FIG. 1, and the interrelationship between 60 GHz small cells and LTE macrocells will be described later in connection with FIG.

1, the LTE system includes three lower level components, namely at least one UE 102, E-UTRAN 104 and EPC 106. EPC 106 (core network) communicates with external servers or packet data networks (PDNs) 108. Interfaces between different parts of the LTE system are shown in FIG. The double-ended arrows indicate the air interface between the UE 102 and the E-UTRAN 104. For the remaining interfaces, the user data is represented by solid lines, and the signaling by dotted lines.

The E-UTRAN 104 (Radio Access Network (RAN)) is generally a plurality of eNBs arranged to process wireless communication between the UE 102 and the EPC 106 over the air interface, -UTRAN Node B). LTE is a cellular system in which e-NBs provide coverage across one or more cells.

The main components of the EPC 106 are shown in FIG. In an LTE network, it will be appreciated that there may be more than one of each component depending on the number of UEs 102, the geographic area of the network, and the amount of data to be transmitted over the network. data traffic is transferred between the eNB and each of the eNBs and the corresponding serving gateway (S-GW) 110 that transmits data between the eNB and the PDN gateway (P-GW) The P-GW 112 is responsible for connecting the UE to one or more external servers or PDNs 108. The Mobility Management Entity (MME) 114 controls the high-level operation of the UE 102 via signaling messages exchanged with the UE 102 via the E-UTRAN 104. [ The MME 114 exchanges signaling traffic with the S-GW 110 to support data traffic transmission. The MME 114 also communicates with a home subscriber server (HSS) 116 that stores information about users registered on the network.

The increase in consumer demand for wireless broadband data is evidenced by the rapid absorption of LTE around the world. In this regard, and in view of the high cost associated with increasing capacity of LTE networks, data service providers and operators are increasingly exploring ways to augment these networks. One such approach is to use unlicensed spectrum to supplement LTE broadband data services. The move to additional use of the unlicensed spectrum is partially driven by the desire to increase the data rate for consumers through the opening of new parts of the spectrum, Due to regulatory delays and significant investment required. In addition, much of the licensed spectrum around existing frequencies used by LTE is already in use. It is a challenge to find an authorized spectrum of sufficient bandwidth to support the proposed 5G networks.

Unauthorized spectrum may be used, for example, in Wi-Fi (LTE < RTI ID = 0.0 > / Wi-Fi interworking), LTE over unlicensed (LTE-U), or license-assisted access (LAA) technology. 3GPP Release 13 is expected to include support for LTE operations in the unlicensed 5 GHz band. The ongoing 3GPP study will be completed in June 2015 and will also cover mechanisms for coexistence in the 5 GHz band.

In the LAA, primary LTE cells operating in the licensed spectrum are aggregated with secondary cells operating in an unlicensed spectrum. That is, the LAA may allow for centralized scheduling to be performed by the eNB that also handles carrier selection for the UEs under its control. The LTE-U provides a broad networking solution to what is provided by the LAA technology, for example, by providing a stand-alone LTE-U solution in which only unlicensed frequencies are used in networks that otherwise operate in accordance with the typical configuration of LTE . ≪ / RTI > The licensed spectrum is used to ensure quality of service and to provide important information, but unlicensed spectrum can be utilized to increase the data rate if necessary.

Obviously, the result of this use of unauthorized spectrum is that network operators can no longer have exclusive access to the spectrum band. If there is exclusive access to the allocated band, the transmission can be coordinated over the network so that multiple base stations and mobile devices can coexist either through peer-to-peer signaling or through a centralized scheme of time frequency resources. This adjustment is not always possible in unlicensed spectrum because there is no requirement that network operators notify each other of their use of spectrum.

One option for ensuring fair access to unauthorized spectrum and minimizing interference is to use the listen-before-talk (LBT) procedure to facilitate effective sharing of unauthorized spectrum and to detect carriers before transmission to be. The LBT procedure is a contention-based protocol that can be described as a mechanism for applying an empty channel assessment (CCA) check before a device or component (e.g., UE or eNB) uses the channel. (Minimum) energy detection, the CCA allows the presence of other signals in the channel to be determined. As a result, therefore, it can be determined whether the channel is empty or occupied.

In the LBT, the eNB tries to access the channel only at a pre-allocated time instant indicated by the "transmission opportunity ". At the transmission opportunity, if data should be transmitted and not yet transmitted, detection based on energy detection in the channel for a predefined time interval is made. If the detected energy is below the threshold, the channel is considered usable and the transmission is made. If the detected energy is above the threshold, the channel is considered crowded and no transmission occurs. The coexistence gap provides opportunities for other networks operating in the same band using gaps in LTE transmissions. Coexistence gaps are silent gaps that can be considered LTE "OFF" periods. The eNB resumes transmission at the end of each coexistence gap without evaluating the availability of the channel. The LBT allows efficient data packet transmission between components sharing the transmission medium or network. However, if there are hidden nodes, problems may occur in these networks. In this case, the hidden node may be visible to a second node (e.g., UE), but may not be visible to a third node (e.g., eNB) communicating with the second node (e.g., (ENB or WLAN access point (AP) belonging to the eNB). This lack of visibility is hidden (or potentially vice versa) at the third node, or hidden at the third node, because the nodes may simply be out of range of each other. In order to provide an alternative, the hidden node may be caused to corner back from the directional beam transmission (i. E. The node is outside the path of the directional beam). The presence of hidden nodes can cause problems such as data packet collisions and corruption. The presence of hidden nodes can lead to interference that can not be mitigated by the use of the LBT procedure.

One option for meeting the ever-increasing demand for higher data rates and higher data amounts transmitted over wireless communication systems, as described above, is to use an extremely high frequency (EHF) frequency band from 30 GHz to 300 GHz, A much wider frequency band, such as that available in the band, or a much wider frequency band, for example, to include a spectrum around 28 GHz. Since radio waves in these bands range from 10 mm to 1 mm, the band is sometimes referred to as millimeter band or millimeter wave (mmW). In particular, unlicensed spectra around 60 GHz can be used to provide high data rate services in small cells, typically supplementing LTE macrocells. Approximately 8 GHz bandwidth is available in unlicensed bands of 60 GHz, which can be used in cellular systems: a concept that can be referred to as pre-5G (pending standardization of 5G technologies). The exact range of unlicensed 60 GHz spectrum differs between different regions. Referring to Table 1 below, this shows unlicensed 60 GHz spectral bands in seven different regions. In addition, Table 2 identifies the maximum equivalent isotropic radiated power (EIRP) in dBm (decibel-milliwatt) for each band with the maximum transmit power in the beam. For the purposes of the present invention, the exact unauthorized band under consideration is irrelevant, only the corresponding directional beams are used.

Radio waves in the 60 GHz band are limited in scope despite the benefit of smaller frequency reuse distance tolerance because they are subject to high atmospheric attenuation due to absorption by atmospheric gases. Also, EHF transmissions are generally line of sight, easily blocked by objects in their path, or reflected or diffracted by building edges.

These constraints on EHF transmission can be mitigated through the use of beam-forming, which can increase the effective transmission range. The beamforming can be classified into transmit beamforming and receive beamforming. The transmission beamforming uses a plurality of antennas (antenna arrays) to concentrate the arrival region of radio waves in a specific direction. The transmission range is increased in the intended direction and minimized in the other direction. The interference to other users in directions other than the intended direction is reduced. In receive beamforming, the receiver focuses on the reception of radio waves from the intended direction using the receive antenna array. The received signal strength from the intended direction is increased and the received signal strength from the other directions is minimized.

It will be appreciated that if an unauthorized 60 GHz band is used, it is also necessary to minimize interference from other users of the aforementioned spectrum in relation to the LAA that occurs. The 60 GHz band is already well suited for high-bandwidth communication links, especially point-to-point. The 60 GHz band is also used by WiGig (wireless gigabit alliance) to facilitate the use of the 60 GHz band for wireless networking in accordance with the Institute of Electrical and Electronics Engineers (IEEE) 802.11ad standard and to transmit high definition video content between consumer electronic devices For wireless HD (also known as Ultra Giga). However, this is a common case for EHF transmission, but the above-described LBT procedure is deemed ineffective if high-directional transmission is used. In contrast, the expected transmission scenarios for LAAs in the 2 to 5 GHz band are omnidirectional or sector-specific (i.e., the antenna radiation pattern of the transmit antenna has a wide beamwidth). For example, a 5G base station that points its receiver beam in a particular direction and implements an LBT can not "receive " transmissions by other nearby 5G base stations (e.g., WiGig APs). Thus, a 5G base station will initiate transmissions that may cause interference to the victim system (e.g., a WiGig AP or a 5G base station belonging to a different operator) because it assumes no channel. In addition, the LBT is spectrally inefficient, which first weakens a significant portion of the evidence supporting the shift to 60 GHz transmission.

Although WiGig is randomly assigned to one user at a given time, the entire channel is allocated to a single user, but users can use a hybrid TDMA-CSMA scheme based on IEEE 802.11 Enhanced Distributed Channel Access (EDCA) Method is used to solve the interference problem. WiGig supports up to four transmitter antennas, four receiver antennas, and 128 sectors. Beamforming is required for 802.11ad, and both transmitter side beamforming and receiver side beamforming are supported. The WiGig contention based approach also suffers from spectrum inefficiency.

Referring to Figure 2, this shows the integration of 60 GHz small cells into an LTE (or similar) 4G network. 2 shows an LTE eNB 200 broadcasting in an authorized LTE band in a macro cell 202 to a user 204 (herein assumed to be a UE). The LTE transmission may be limited to network signaling indicated by dashed line 206 only. Because of the reduced signal attenuation in the authorized frequency bands and its greater reliability due to the use of the exclusive spectrum, it is desirable that the signaling be transmitted over the LTE RAN. In addition, some user data may be transmitted between the UE 204 and the eNB 200, as indicated by solid lines 208. A plurality of high capacity 60 GHz wireless APs 210 serving small cells directly connected to the eNB 200 via wired or wireless links 212 are integrated with the LTE network. A 60 GHz AP may alternatively be referred to as a 5G base station in the current document to show that it acts as a base station in a 5G wireless communication network. The 60 GHz APs 210 are under the control of the eNB 200 and transmit user data to the UEs as indicated by the solid line 214 when the UE is within range of the 5G base station 210, And receives data. Although the communication is achieved using beamforming to generate a high directional transmission beam and a reception beam as described above, the range of the 60 GHz base station 210 is indicated by the ellipse 216. [ 5G base stations serve as hotspots that provide high user data rates and are deployed where such high data rates may be needed, such as in offices and busy public places.

In addition to the physical layer, medium access control (MAC) layer and network layer algorithms that are suited to the characteristics of unlicensed 60 GHz bands, to efficiently use unauthorized spectrum for 5G cellular systems, efficient interference mitigation and coexistence mechanisms Are needed. As discussed above, efficient interference mitigation and coexistence mechanisms may be used for systems using other standards (e.g., WiGig) that may also operate in the 60 GHz band as well as other 5G cellular systems operating in this band For example, systems belonging to different operators). Referring now to FIG. 3, this illustrates this deployment scenario.

3 shows a first 5G base station 300 and a second 5G base station 302 operated by different network operators (operator A and operator B, respectively). It is assumed that each operator does not recognize the presence of another operator or that they decide not to coordinate their transmission. Of course, if cooperation should be possible, beam sequences can be synchronized to maximize spectral efficiency, minimizing interference, in the same way that it can be performed where multiple 5G base stations are operated by a single operator. 3 also shows a WiGig AP 304 operated by an operator C. In multi-standard and multi-operator spectrum sharing scenarios, because cellular systems and, for example, WiGig use very different physical layers and MAC layers (such as different frame structures) to prevent direct signaling and synchronization between these networks, Cooperation is impossible or challenging. Each 5G base station 300, 3002 or AP 304 may be transmitted in the same portion of the 60 GHz band to one or more devices 306-314, such as UEs and other fixed or mobile electronic devices. Although only a 5G base station or AP suitable for communicating with the illustrated devices 306-314 is shown, each 5G base station or AP 300-310 can transmit data via a plurality of different beams.

In the example of FIG. 3, it can be seen that there is a possibility that some 5G base stations or APs can simultaneously transmit over a plurality of beams that are provided with a plurality of antenna arrays, but each 5G base station or AP has one beam Lt; RTI ID = 0.0 > data. ≪ / RTI > Specifically, the 5G base station 300 is shown as being able to transmit data to the device 306 using beam a1. The 5G base station 302 may transmit data to the device 308 using the beam b1 and may transmit data to the device 310 using the beam b2. WiGig AP 304 may transmit data to device 312 using beam c1 and transmit data to device 314 using beam c2. In Figure 3, these beams that are transmitting at a given instant are shown in solid lines and the rest are shown in dashed lines. If beams (a1, b1, c1) are being transmitted at a moment, there is a high likelihood that interference will cross these beams in the area of device 306, device 308 and device 312. Such interference scenarios with inadequate beam timing are likely to result in an increasing number of APs, beams, and devices.

Referring now to FIG. 4, an adaptive and distributed solution for beam sequence selection is provided that, according to one embodiment of the present invention, each 5G base station dynamically aligns the scheduling of beams to its users. It can be seen that for each 5G base station or WiGig AP, a beam sequence is defined, as shown in the upper left of the figure. For 5G base station 300, the beam sequence includes transmission using beam a1 at each instant when it is the only beam being used for communication with the UE. It can be seen that the beams being transmitted at each instant are vertically arranged in the beam sequences such that beams a1, b2 and c2 are transmitted at the first illustrated instant (identified by the box). The risk of interference due to collisions of the transmissions from the 5G base station 302 and the WiGig AP 304 is minimized by ensuring that the beam b1 and the beam c2 are not being transmitted simultaneously.

The adaptive scheduling resulting in optimal beam sequencing of FIG. 4 is described in greater detail below with reference to the flow diagram of FIG. Adaptive scheduling is based on each 5G base station (or, in the examples below, 5G base station making, but other APs) that independently probes the limited configuration space of its own beam sequences. The beam sequences may be tested to obtain feedback from the UEs served by the 5G base station and then apply a learning algorithm to select the optimal beam sequence. Embodiments of the present invention do not rely on intervention from a central controller or explicit cycling between base stations for each 5G base station to select a beam sequence that results in an overall system operating very close to maximum spectral efficiency. After adaptation, each base station / AP starts a new search phase where the beam sequences can be redefined after a certain period of time. For example, a new search phase may be triggered using a randomized timer, or by an event, for example, when a new UE enters or leaves the cell.

Referring now to FIG. 5, this is a flow chart illustrating a method for establishing beam sequences in a 5G base station (or any base station or AP operating using truly directional beams). The method of FIG. 5 will first be summarized first, and then each individual step will be illustrated in more detail.

인 빔 방향(B_i)들의 집합이 확립된다. i는 UE 및 그들의 관련 빔들에 대한 인덱스(i=1, M_j)이고, j는 기지국들에 대한 인덱스(j=1,N)이다.The method begins at step 500 where a beam discovery step is performed. The beam discovery step is a process of the base station that identifies each beam (i. E., Each beam direction) that needs to be transmitted to transmit user data to each UE that is communicating. For example, although each device may be associated with a plurality of beams, and one beam may be used to communicate with more than one device, the base station may establish a beam associated with each device with which it is communicating . The beam discovery step further comprises determining a set of possible beam sequences. Each sequence in the set represents one sequence in which beams can be formed to sequentially communicate with each UE. Those skilled in the art will understand that the invention is scalable to situations where more than one frequency is used with beamforming to minimize interference, but Figure 5 is based on the assumption that the 5G base station communicates with each UE at the same frequency . The beams can be optimized beams that communicate with each device through which one or more beams can transmit data to the device. Referring again to FIG. 4, for a 5G base station 302 operated by operator B, the set of beam directions includes {b ₁ , b ₂ }. More generally, for a set of M _j UEs that the base station needs to transmit data, i = 1, M _j :

A set of in-beam directions _Bi is established. i is the index (i = 1, M _j ) for the UE and their associated beams, and j is the index for the base stations (j = 1, N).

,

,...,

, 여기에서, 각각의 조합은 해당 집합 내의 빔들이 형성될 수 있는 순서를 나타내고, 5G 셀 내의 UE들과 통신하기 위해 기지국에 의해 사용될 수 있는 고유 빔 시퀀스이다. 빔 시퀀싱 조합들의 집합(C)이 빔 방향들의 집합의 모든 가능한 조합들을 포함할 수 있다는 것을 알 수 있을 것이다. 대안적으로, 도 5의 방법의 나머지 부분의 계산 복잡성을 줄이기 위해, 집합은 간섭받을 것이라고 알려진 시퀀스들을 제외하도록 제한될 수 있다. 예를 들어, 하나의 운영자가 그들의 전송을 조정하는 동일한 영역에 복수의 기지국을 갖는 이벤트에서, 알려진 간섭 조합들이 제외될 수 있다. 이것은 LTE eNB의 제어 하에서 LTE 제어 채널을 사용하여 달성될 수 있다. 기지국이 동시에 복수의 빔을 전송할 수 있는 경우, 시퀀스들은 상이한 UE들을 서빙하는 동시 빔들의 그룹 또는 쌍을 지정하기 위해 확장될 수 있다는 것을 또한 이해할 것이다. 또한, 시간 슬롯들이 기지국 사이에서 서로 다를 수 있고, 본 발명에 따른 기지국들 간의 시간 슬롯들의 동기화를 위한 요구 사항은 없지만, 각각의 기지국은 미리 정의된 시간 슬롯들에서 빔들을 전송할 수 있다. 시간 슬롯 동기화는 허가되지 않은 스펙트럼에 우선하는 것과 같이 다중 운영자 및 다중 무선 액세스 표준 환경에서 가능성이 없다.Next, at step 500, a set of m beam sequence combinations (C) is established as follows:

,

, ...,

, Where each combination represents a sequence in which the beams in the set can be formed and is a unique beam sequence that can be used by the base station to communicate with the UEs in the 5G cell. It will be appreciated that the set of beam sequencing combinations C may include all possible combinations of sets of beam directions. Alternatively, to reduce the computational complexity of the remainder of the method of FIG. 5, the aggregation may be limited to exclude sequences known to be interfered. For example, in an event where one operator has a plurality of base stations in the same area to coordinate their transmission, known interference combinations may be excluded. This can be accomplished using an LTE control channel under control of an LTE eNB. It will also be appreciated that, where a base station can transmit multiple beams simultaneously, the sequences may be extended to specify a group or pair of concurrent beams serving different UEs. Also, although the time slots may be different between base stations and there is no requirement for synchronization of time slots between base stations in accordance with the present invention, each base station may transmit the beams in predefined time slots. Time-slot synchronization is unlikely in multi-operator and multi-radio access standard environments, such as overriding unauthorized spectrum.

The remainder of the method of Figure 5 includes determining an optimal beam sequence from among a set of possible beam sequence combinations. In step 502, a search step is performed. For each of the sets of beam sequence combinations established in step 500, the base station forms the beams according to the sequence and transmits the probe signals to the corresponding UEs using the respective beams. Alternatively, only a subset of the beam sequences may be transmitted. For each transmitted sequence, the base station receives feedback, e.g., bit error rate (BER) or average reference signal reception quality (RSRQ), from the UEs. This feedback may be returned directly to the 5G base station via the directional beam transmitted by the UE, or alternatively such feedback may be transmitted via the LTE eNB. More generally, feedback provides a measure of link quality or link performance between each UE and the 5G base station for that beam sequence. Specifically, for a set of C _m beam sequences and k = 1, m random beam sequences (C _k ) are selected, and for i = 1, M _j beams are transmitted from the sequence (C _k ) And is formed in accordance with the received feedback. If all possible unique beam sequences are included in the set of C _m beam sequences, then m = M _j . If a set of reduced beam sequences (except for known interference sequences, for example, as described above) is used, m < M _j . This search process is then repeated for each beam sequence combination of the set. In one embodiment, the beam sequences of the set may be searched sequentially, or sequentially, starting from the first selected sequence at random. The UE then computes a system defined utility function for each tested beam sequence combination in accordance with the received UE feedback. The utility function U ( _Ck ) for the sequence ( _Ck ) is based on cumulative feedback from the UEs. As only three examples, U (C _k ) may include the sum of the average or minimum UE feedback. Additional examples of utility functions will be apparent to those skilled in the art in accordance with certain implementation scenarios.

에 따라 확률적으로 선택된다.The learning step is performed in step 504 while the base station selects one of the possible sets of beam sequence combinations (C _m ) based on the computed utility function U (C _k ) obtained in the search step (step 502). Specifically, a discrete probability function P (U (C _k )) is established for each beam sequence, and an optimal beam sequence (C _opt )

. &Lt; / RTI &gt;

In the execution phase, at step 506, the selected optimal beam sequence combination (C _opt ) is used to transmit data to the UEs during the communication session. Specifically, for i = 1, M _j beams are formed according to the sequence (C _opt ) to communicate with M _j UEs served by the corresponding base station. During the execution phase, data is sent to (and optionally received from) the corresponding UEs, and feedback can be collected and stored from the UEs. The formation of the feedback may be the same as that sent from the UEs during the search step 502 and may be transmitted in response to data being transmitted from the base station to the UE.

In step 508, it is determined in step 502 whether another search step is required. This is accomplished in a randomized timer expiration or execution step 506 where the base station needs to switch to the new optimal beam sequence serving the UE when significant changes are detected (e.g., a new UE enters the cell) (E.g., a significant increase in BER / RSRQ) to the detected link quality as a result of feedback at the base station. If a new search step is not required, the base station remains in the execute step at step 506. [ If a new discovery step is required, then in step 510 it is determined whether this is because the UE has joined or left the cell. If so, the base station first returns to the beam discovery step 500, else the method proceeds to the search step 502 using the previously calculated beam sequence combinations.

에 의해 (dB로) 주어진다, 여기에서 G_omni는 어떠한 빔 포밍도 적용되지 않을 때의 기존(전방향) 안테나 이득이고, G_BF는 빔 포밍 이득이다. 일 예로서, 아날로그 빔 포밍을 사용하여, 특정 UE에 대한 지향성 빔을 형성하기 위해 각각의 안테나에 대한 입력 신호의 크기 및 위상을 제어함으로써 빔 포밍 이득이 획득된다. 기지국은 기지국 주위의 방위각 방향들을 균일하게 커버하는 카디널리티 N (또는 코드북이 UE의 개수 변화를 기반으로 하여 다시 계산되는 경우 시간이 지남에 따라 카디널리티가 변경될 수 있는 이벤트에서의 N_t)을 갖는 미리 정의된 빔 코드북 내에서 또는 (상황에 따라) 동적으로 각각의 UE에 대해 최적의 빔 구성을 계산할 수 있다. 주어진 기지국(j)에서의 코드북은

차원의

개의 가중치 인자

에 의해 형성되고, 여기에서 N_BS는 기지국의 총 개수이다. 각각의 벡터는

로서 계산되고, 여기에서

는 i번째 송신 빔에 대한 방위각이고, jj는

를 의미한다. 각각의 UE에 대해, 최적의 빔 포밍을 결정하는 방법은 예를 들어, US-2014/0056256-A1에 개시된 것과 같은 또는 IEE 802.11ad 표준에서 사용된 것과 같은 기존의 방법일 수 있다.The beam discovery step 500 of FIG. 5 will now be described in more detail. Base station / AP antenna gain

(In dB), where G _omni is the conventional (omnidirectional) antenna gain when no beamforming is applied and G _BF is the beamforming gain. As an example, using the analog beamforming, a beamforming gain is obtained by controlling the magnitude and phase of the input signal for each antenna to form a directional beam for a particular UE. The base station may perform a pre-processing with a cardinality N that uniformly covers the azimuth directions around the base station (or N _t in event that the cardinality may change over time if the codebook is recalculated based on the number of UE changes) The optimal beam configuration can be calculated for each UE in the defined beam codebook or dynamically (depending on the situation). The codebook at a given base station (j)

Dimensional

Number of weighting factors

, Where N _BS is the total number of base stations. Each vector

Lt; RTI ID = 0.0 &gt;

Is the azimuth angle for the i &lt; th &gt; transmission beam, jj is

. For each UE, a method for determining optimal beamforming may be an existing method such as, for example, as disclosed in US-2014/0056256-A1 or as used in the IEE 802.11ad standard.

을 형성하기 위해 각각의 UE에 대해 최적의 송신 빔들을 결정하기 위해 확장될 수 있다는 것을 알 수 있을 것이다.US-2014/0056256-A1 discloses a method for forming and maintaining transmission and reception of beams between a transmitting station and a receiving station. The transmitter transmits a set of reference signals to the receiver using different beams. Based on these, the receiver transmits the desired beam information back to the transmitter. Using this information, the transmitter transmits the data to the receiver using the desired beam. If the above needs to be performed for all transmitter and receiver beam pairs, a similar procedure may be used to receive the beamforming. After the initial optimal beamforming, the beam changing procedure can be initiated by the receiver if necessary. When beam errors occur in the receiver (which may be detected from multiple indicators or one indicator), a beam change step is determined to be necessary and is performed upon receiving a beam change request from the receiver. In addition to the beam changing procedure that occurs upon request from the receiver, a full beam changing procedure is performed periodically. This procedure may be performed by a set of beams

Lt; RTI ID = 0.0 &gt; UE &lt; / RTI &gt; to form optimal transmission beams for each UE.

이 주어지면, 기지국이 차례로 각각의 UE에 빔들을 전송할 수 있는 순서에 대해 M_j개의 가능한 빔 스케줄링 시퀀스, 즉 M_j개의 가능한 조합(C)이 존재한다. 예를 들어, 시퀀스

,

, 또는

등. 탐사 절차에서, 각각의 기지국은 모든 가능한 빔 포밍 시퀀스 또는 빔 포밍 시퀀스들의 부분집합을 따르는 빔 방향들의 집합으로부터 해당 빔들을 사용하여 차례로 각각의 UE에 프로브 신호들을 전송한다. 각각의 빔 형성 시퀀스에 대해, 각각의 UE는 그의 RSRQ, BER, 또는 해당 특정 시퀀스에 대한 링크 품질의 다른 지시자를 측정하고, 각각의 UE는 5G 기지국에 이것을 다시 보고한다. 이러한 정보를 수집한 후에, 기지국은 해당 특정 빔 시퀀스(

)에 대응하는 유틸리티 함수를 계산한다. The exploration step 502 of FIG. 5 will now be described in more detail. For M _j UEs associated with a given base station (j) and base station (j), a set of beam directions

, There are M _j possible beam scheduling sequences, i.e. M _j possible combinations (C), for the order in which the base stations can in turn transmit beams to each UE. For example,

,

, or

Etc. In the probe procedure, each base station transmits probe signals to each UE in turn using the corresponding beams from a set of all possible beamforming sequences or beam directions that follow a subset of the beamforming sequences. For each beamforming sequence, each UE measures its RSRQ, BER, or other indicator of link quality for that particular sequence, and each UE reports this back to the 5G base station. After collecting such information, the base station transmits the specific beam sequence (

) &Lt; / RTI &gt;

Those skilled in the art should be familiar with utility functions. As an example, each base station may be associated with a non-cooperative utility function. The UE measurement RSRQ or BER values for a given beam sequence may be used. Alternatively, base stations belonging to the same operator may cooperate, using a cooperative utility function, using an LTE control channel that exchanges information to use a system level utility function. One example of such a utility function is the average obtained over the utility function of all base stations belonging to the same operator.

Because the number of possible configurations M _{j for a} base station can be very large, in certain embodiments, the base station can reduce the search time by considering only the beam sequences corresponding to UEs near the cell edge. At this time, the search step is performed only for M ' _j configurations, which is the number of UEs near the cell edge. The 5G base station can deduce which UEs are near the cell edge based on location information received from the UEs by using the information / control data received from the basic LTE network. As described above, the search space may be further reduced by excluding known beam sequences that are known to cause interference to other 5G base stations operating by the same operator or that are subject to interference from other 5G base stations. If beam sequencing and scheduling information is available through cooperation with other operators, including different radio access technologies, the same reduction in search space can also be achieved.

이 주어지면, 전술한 바와 같이 기지국 당 M_j개의 가능한 빔 시퀀스 조합(C)이 존재한다. 학습 단계(504)에서, 모두 합해서 1과 동일하고, 범위가 0부터 1까지인 M_j개의 확률의 합계가 존재하도록 확률(p)이 각각의 조합에 할당된다. 당업자들은 유틸리티 함수들을 기반으로 하여 확률들을 할당하는 기술에 대해 잘 알아야 한다. 두 개의 실시예가 단지 예시를 위해 제시된다.The learning step 504 of FIG. 5 will now be described in more detail. A set of beam directions, such as those obtained via the beam discovery step 502 for a given base station j and its associated M _j UEs,

, There are M _j possible beam sequence combinations C per base station as described above. In the learning step 504, a probability p is assigned to each combination such that there is a sum of M _j probabilities, all of which are equal to 1 and range 0 to 1. Those skilled in the art should be familiar with techniques for assigning probabilities based on utility functions. Two embodiments are presented for illustrative purposes only.

이고, 여기서

는 탐색 단계에서 측정되는 바와 같이, 구성(C_i)을 사용하여 획득되는 유틸리티 함수이고,

는 탐색 단계(t=1)에서의 유틸리티 함수들의 최대값이다. 마지막으로, b는 빔 시퀀스들이 각각의 탐색 단계 이후에 구성되는 속도를 조정하는 0과 1 사이의 매개변수이다. b=0이면, 어떠한 구성도 없다. k는 빔 시퀀스에 대한 인덱스이고, k=1, M_j이다.According to the first option, a learning update is applied in which the probability applied to each sequence is a function of the utility function of the previous sequence and the probability of being applied to the previous sequence. E.g,

, Where

Is a utility function obtained using configuration C _i , as measured in the search phase,

Is the maximum value of the utility functions at the search stage (t = 1). Finally, b is a parameter between 0 and 1 that adjusts the rate at which the beam sequences are constructed after each search phase. If b = 0, there is no configuration. k is the index for the beam sequence, k = 1, M _j .

이면

이 최대이고 그렇지 않으면 0이다. t는 탐색 단계에 대한 인덱스(t, t+1, t+2 등)이다. 본질적으로, 그리디 업데이트는 가장 높은 유틸리티 함수를 갖는 빔 시퀀스 조합을 식별하는 단계 및 아래에 명시되는 선택 절차에 따라 확률적으로 선택되기 때문에, 선택된 최적의 빔 시퀀스 조합(C_opt)에 더 빈번한 변화들을 초래할 가능성이 있음을 보장하는 단계를 포함한다. 학습 업데이트는 탐색 단계(502) 및 학습 단계(504)가 다른 빔 시퀀스 조합들에 대해 계산된 유틸리티 함수를 고려하여 수행될 때마다 항상 조합을 전환하도록 이러한 경향을 완화시킨다. 이것은 적절한 성능을 제공하는 조합에서 나쁜 조합으로의 전환의 위험을 감소시키는 데 유리할 수 있다. 또한, 그것은 시간이 흐름에 따라, 일반적으로 심각하게 특정 구성들에 영향을 미치는 간섭 소스가 존재하는 상황에서 유리할 수 있는 광범위한 범위의 구성들이 사용된다는 것을 확인하는 역할을 한다.According to the second option, a greedy update is applied, in which only the largest utility function is considered:

If

Is the maximum, and 0 otherwise. t is the index (t, t + 1, t + 2, etc.) for the search phase. In essence, since the greedy update is more probable that a more frequent change in the selected optimal beam sequence combination (C _opt ), since the greedy update is selected stochastically in accordance with the selection procedure specified below and identifying the beam sequence combination with the highest utility function &Lt; RTI ID = 0.0 &gt; and / or &lt; / RTI &gt; The learning update alleviates this tendency to always switch the combination whenever the search step 502 and the learning step 504 are performed taking into account the utility function calculated for different beam sequence combinations. This may be beneficial in reducing the risk of switching from a combination to a bad combination that provides adequate performance. It also serves to ensure that over time a wide range of configurations are used, which can be advantageous in situations where there is generally an interference source that seriously affects certain configurations.

을 가정하면, 시퀀스들 중 하나가 다음과 같이 랜덤으로 선택될 수 있다.Once all probabilities have been updated, the base station randomly selects one of the beam scheduling sequences according to the assigned probabilities. Those skilled in the art should be familiar with techniques for stochastic selection. As an example, for each of the M _j beam sequences a set of probabilities

, One of the sequences may be randomly selected as follows.

을 계산한다.1. Cumulative probability

.

2. Next, a random number (U) between [0, 1] is generated.

Finally,

이면, 시퀀스 1이 선택되고,a.

, The sequence 1 is selected,

이면, 시퀀스 2가 선택되고,b.

, The sequence 2 is selected,

이면, 시퀀스 3이 선택된다. 이것으로부터 그리디 업데이트를 적용하여, 가장 높은 유틸리티 함수를 갖는 빔 시퀀스 조합이 항상 선택될 것이라는 것을 알 수 있다.c.

, Sequence 3 is selected. Applying a greedy update from this, we can see that the beam sequence combination with the highest utility function will always be selected.

Referring now to FIG. 6, the exchange of messages between UEs in the cell and the 5G base station is shown. During the search phase 502 of FIG. 5 for each of the possible beam sequences or each subset of possible beam sequences, as described above, the 5G base station determines the beam (i. E. Beam direction) identified in the beam & (Three are shown in FIG. 6) using the probe signals 600. The probe signals 600 are then transmitted to the respective UEs (shown in FIG. Each UE receiving a probe signal, which may be addressed specifically to that UE, re-measures link quality 602, such as RSRQ or BER measurements. Figure 6 illustrates an example of a first configuration (C _j), the sequence is for a beam beams of transmitting the probe signal in 600 to the UE1, UE2 and UE3 in that order. Later, during execution step 506, the 5G base station transmits user data to each UE using the selected optimal configuration (C _opt ). In Fig. 6, an example is shown in which the best configuration includes transmitting user data 604 to UE1, UE3 and UE2 in that order.

FIG. 7 provides a schematic diagram of the structure of a 5G base station 700 that is arranged to operate in accordance with the above-described examples of the present invention. A 5G base station includes a transmitter 702 arranged to transmit user data 604 and probe signals 600 to UEs; A receiver 704 arranged to receive link quality feedback 604 from the UEs; And a controller 706, which is arranged to control the transmitter and the receiver and to perform processing such as in accordance with the method of Fig.

8 provides a schematic diagram of the structure of a UE 800 that is arranged to operate in accordance with the above-described examples of the present invention. A UE 802 is arranged to transmit link quality feedback 604 to a 5G base station; A receiver 804 arranged to receive user data 604 and probe signals 600 from a 5G base station; And a controller 806 that is arranged to control the transmitter and the receiver and perform processing.

Although the transmitter, the receiver, and the controller are shown as separate elements in Figs. 7 and 8, one element or a plurality of elements that provide equivalent functions may be used to implement the above-described examples of the present invention.

Advantageously, the present invention permits beam sequence selection at a 5G base station operating in the unlicensed 60 GHz band without requiring cooperation with other operators. This is achieved by utilizing the common beamforming function of any radio access technology operating in the 60 GHz band and therefore equally applicable to all suitable beamforming radio access technologies (at other frequencies, etc.). Thus, it works in multi-standard and multi-operator scenarios. Embodiments of the present invention can achieve high spectral efficiencies approaching the theoretical maximum spectral efficiency that can be achieved assuming total cooperation between operators, as evidenced by the modeling presented below. In addition, embodiments of the present invention do not suffer from the "hearing loss" problem of the listen before talk (LBK) method, which is a hearing loss inherent in directional transmission scenarios.

Modeling using the model of the present invention created using MATLAB® (available from www.mathworks.com, MathWorks®, Natick, Mass., USA) is now presented. In the model, 5G base stations in two 60 GHz bands serve multiple UEs within their service area, respectively. For each UE, analog beamforming is used to form an optimal beam serving that UE. Each base station has 16 antenna elements. Additional parameters used in the simulation are given in Table 2 below.

Given the set of base stations, the corresponding UEs, and the beams associated with each of the UEs, the potential interference levels for all possible scheduling configurations have been computed, and the optimal beam for each base station maximizing the overall system spectral efficiency A thorough centralized search was performed to determine the scheduling sequence. Although it is possible to search thoroughly for a few base stations, but it can not be calculated if the number of base stations is small, it is generally not possible to implement the system, It will be possible. From this thorough search, a beam scheduling sequence that minimizes overall system spectral efficiency has also been determined.

The results were then used to benchmark the performance of the beam scheduling methods according to embodiments of the present invention, where each base station autonomously adapts its beam scheduling sequence without signaling exchange with other base stations. The locations of the UEs associated with each base station have been randomly selected. In order to obtain statistically reliable results, a Monte Carlo implementation was performed in which the cumulative dispersion function (CDF) of the system spectral efficiency (according to the nominal scale) for each scenario was obtained.

Figures 9 and 10 illustrate the case of two 60 GHz 5G base stations, each serving five UEs at their respective cell edges, obtained for different point-to-point distances of 400 m and 300 m respectively between base stations These are the results. The bold black line corresponds to the maximum system spectral efficiency obtained from exhaustive search results (corresponding to the most optimal beam scheduling), and the thin black line corresponds to the worst possible beam scheduling to minimize system spectral efficiency. Results obtained using the two implementations of the proposed method are also shown using a greedy or a non-greedy learning step (indicated by a circle).

Embodiments of the present invention are such that this spectrally efficient coexistence does not depend on coordination or cooperation among a plurality of operators and is effective regardless of the radio access technology used by these operators.

It can be seen that the implementation of the two distributed scheduling methods performs close to the theoretical maximum obtained from the exhaustive search, using a Greedy algorithm that exhibits somewhat better performance. As described above, in certain implementation scenarios, the non-greedy learning step may be desirable to minimize the frequency of beam sequence changes.

Throughout the description and claims of this specification, the terms "comprise" and "contain" and variations thereof mean "including but not limited to" Or &lt; / RTI &gt; steps. Throughout the description and claims of this specification, the singular forms include the plural unless the context otherwise requires. In particular, where indefinite articles are used, the specification should be understood to include both singular and plural, unless the context requires otherwise.

It is to be understood that the features, integers, or characteristics described in connection with a particular aspect, example, or illustration of the present invention are applicable to the other aspects, embodiments, or illustrations described herein unless they are incompatible therewith do. All features disclosed in this specification (including any accompanying claims, abstract, and drawings) and / or all steps of a method or process disclosed thereby are to be interpreted as including all but one of the features and / Can be combined. The present invention is not limited to the details of the above-described embodiments. The invention is not limited to any novel one or any novel combination of features disclosed herein (including any accompanying claims, abstract, and drawings), or any novel one or any combination of the steps of the disclosed method or process And expands to any new combination.

The reader is interested in all papers and documents submitted herein prior to or concurrently with the present specification and which are accompanied by this specification, and the contents of all such papers and documents are incorporated herein by reference.

Various embodiments of the present invention may also be implemented via computer-executable instructions stored on a computer-readable storage medium, in order to cause the computer to operate in accordance with other previously described embodiments, when executed.

The above embodiments are to be understood as illustrative examples of the present invention. Further embodiments of the present invention are contemplated. Any feature described with respect to any one embodiment may be used alone or in combination with other features described and may be combined with any combination of any other embodiments or any other features &Lt; / RTI &gt; It is also to be understood that equivalents and modifications not described above may also be employed without departing from the scope of the invention as defined in the appended claims.

Claims (30)

A method of operating a base station in a wireless communication network in which a base station communicates with mobile terminals using directional beams,
Determining a set of beams for communicating with a plurality of portable terminals;
Determining a set of beam sequences, each beam sequence comprising a unique sequence of beams in the set of beams;
Transmitting a probe signal to the mobile terminals according to a respective beam sequence in the set of beam sequences;
Receiving indicators of link quality from the mobile terminals in response to a probe signal;
Selecting a beam sequence within the set of beam sequences based on indicators of received link quality; And
And communicating with the mobile terminals in accordance with the selected beam sequence. 2. The method of claim 1, wherein determining the set of beams comprises:
Determining a beam direction for each of the plurality of portable terminals, wherein the base station is capable of transmitting data to and receiving data from the portable terminal. 3. The method of claim 2, wherein the plurality of portable terminals comprise portable terminals located within a predetermined distance of a cell edge within which the base station can communicate with the portable terminals. 4. The method of claim 3, wherein the set of beam sequences comprises:
All possible unique beam sequences in the set of beams; or
&Lt; / RTI &gt; comprising a subset of all possible eigenbeam sequences. 5. The method of claim 4, wherein selecting a beam sequence comprises:
Calculating a utility function for each beam sequence in the set of beam sequences based on the received link quality indicators; And
And selecting a beam sequence according to the calculated utility functions. 6. The method of claim 5, wherein selecting a beam sequence according to the calculated utility functions comprises:
Assigning a probability to each beam sequence according to the calculated utility functions; And
And probabilistically selecting a beam sequence according to the assigned probabilities. 7. The method of claim 6, wherein assigning a probability to each beam sequence comprises:
Assigning a probability to each sequence in the set of beam sequences based on the utility function calculated for a previous sequence and a probability assigned to a previous sequence in the set of beam sequences; or
Assign a maximum probability to a sequence in the set of beam sequences if the utility function computed for the previous sequence is a computed maximum utility function; and if the utility function computed for the previous sequence is not a computed maximum utility function, And assigning a probability. 8. The method of claim 7, wherein stochastically selecting the beam sequence comprises:
Determining a cumulative probability for each sequence in the set of beam sequences;
Randomly selecting a number between a minimum probability and a maximum probability; And
Wherein the randomly selected number exceeds a cumulative probability for a previous beam sequence in the set of beam sequences and selects a sequence that is less than the cumulative probability for that beam sequence. 9. The method of claim 8, further comprising determining to return to transmitting probe signals when a predetermined event occurs,
Wherein the predetermined event comprises:
Timer expiration; or
A change in detected link quality that is greater than a threshold when communicating with mobile stations. 10. The method of claim 9,
Receiving additional indicators of link quality when communicating with the mobile terminals in accordance with the selected beam sequence; And
Further comprising detecting a change in link quality based on additional indicators of the received link quality. 11. The method according to any one of claims 1 to 10, further comprising determining to return to the step of determining a set of beams in response to detecting a configuration change of the plurality of portable terminals. A method of operating a mobile terminal in a wireless communication network in which a base station communicates with the mobile terminal using a directional beam,
Receiving probe signals from the base station in accordance with two or more beam sequences applied by the base station;
Transmitting link quality indicators to the base station for the received probe signal; And
And communicating with the base station in accordance with a beam sequence established by the base station based on the transmitted link quality indicators. 13. The method of claim 12, wherein communicating with the base station further comprises transmitting an additional indicator of link quality to the base station upon receipt of data to be transmitted to the mobile terminal. 14. The method of claim 13, wherein the communication between the base station and the portable terminal is based on directional beams in an unlicensed frequency band. 15. The method of claim 14, wherein the unlicensed frequency band comprises a 60 GHz band. An apparatus of a base station in a wireless communication network in which a base station communicates with mobile terminals using directional beams,
A controller for determining a set of beams for communicating with a plurality of portable terminals, each beam sequence determining a set of beam sequences including a unique order of the beams in the set of beams;
A transmitter for transmitting a probe signal to the mobile terminals according to a respective beam sequence in the set of beam sequences; And
And a receiver for receiving indicators of link quality from the mobile terminals in response to the probe signal,
Wherein the controller selects a beam sequence within the set of beam sequences based on indicators of received link quality and communicates with the mobile terminals according to the selected beam sequence. 17. The apparatus of claim 16, wherein, when determining the set of beams,
And determine a beam direction for each of the plurality of portable terminals. 18. The apparatus of claim 17, wherein the plurality of mobile terminals comprise mobile terminals located within a predetermined distance of a cell edge within which the base station can communicate with the mobile terminals. 19. The method of claim 18, wherein the set of beam sequences comprises:
All possible unique beam sequences in the set of beams; or
And a subset of all possible eigenbeam sequences. The apparatus of claim 19, wherein, when the beam sequence is selected,
Calculate a utility function for each beam sequence in the set of beam sequences based on the indicators of the received link quality, and select a beam sequence according to the calculated utility functions. 21. The apparatus of claim 20, wherein when the beam sequence is selected according to the calculated utility functions, the controller allocates a probability to each beam sequence according to the calculated utility functions, And to select a beam sequence stochastically. 22. The apparatus of claim 21, wherein the control unit is further configured to: when assigning a probability to each beam sequence, calculating, based on the utility function calculated for a previous sequence and the probability assigned to a previous sequence in the set of beam sequences, Assign a probability to each sequence in the set, or
Assign a maximum probability to a sequence in the set of beam sequences if the utility function computed for the previous sequence is a computed maximum utility function; and if the utility function computed for the previous sequence is not a computed maximum utility function, And to assign a probability. 23. The apparatus of claim 22, wherein, when the beam sequence is selected stochastically,
Determining a cumulative probability for each sequence in the set of beam sequences, randomly selecting a number between a minimum probability and a maximum probability, and comparing the randomly selected number to a cumulative value for a previous beam sequence in the set of beam sequences And to select a sequence that is greater than the cumulative probability for a corresponding beam sequence. 24. The apparatus of claim 23, wherein the controller is further configured to return to transmitting probe signals when a predetermined event occurs,
Wherein the predetermined event comprises:
Timer expiration; or
And a detected link quality change greater than a threshold when communicating with the mobile stations. 25. The method of claim 24,
Wherein the controller is further configured to receive additional indicators of link quality when communicating with the mobile terminals in accordance with the selected beam sequence and to detect a change in link quality based on additional indicators of the received link quality Device. 26. The apparatus of claim 25, wherein the control unit is configured to return to determining a set of beams in response to detecting a configuration change of the plurality of portable terminals. An apparatus of a mobile terminal in a wireless communication network in which a base station communicates with the mobile terminal using a directional beam,
A receiver for receiving probe signals from the base station in accordance with two or more beam sequences applied by the base station;
A transmitter for transmitting link quality indicators to the base station for the received probe signal; And
And a controller for communicating with the base station in accordance with the beam sequence established by the base station based on the transmitted link quality indicators. 28. The apparatus of claim 27, wherein the controller is further configured to, when communicating with the base station, transmit an additional indicator of link quality to the base station upon receipt of data to be transmitted to the mobile terminal. 29. The apparatus of claim 28, wherein communication between the base station and the portable terminal is based on directional beams in an unlicensed frequency band. 30. The apparatus of claim 29, wherein the unlicensed frequency band comprises a 60 GHz band.

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