System and method for performance optimization in and through a distributed antenna system

A method for operating a DAS includes providing a set of digital remote units (remotes) operable to send and receive wireless radio signals. Each of the set of remotes is associated with a geographic area. The method also includes providing a digital access unit (host) operable to communicate with the set of remotes, receiving uplink signals at one or more of the set of remotes, and monitoring train activity in the geographic areas. The method further includes increasing a gain coefficient associated with one of the set of remotes in response to determining an increase in monitored train activity, decreasing a gain coefficient associated with another of the set of remotes in response to determining a decrease in monitored train activity, and transmitting, to the host, scaled uplink signals associated with the one of the set of remotes and the another of the set of remotes.

SUMMARY OF THE INVENTION

Embodiments of the present invention relate to communication networks. More particularly, embodiment of the present invention provide methods and systems related to the provision and operation of distributed antenna systems (DAS). Merely by way of example, the present invention has been applied to distributed antenna systems. Another example of the present invention could include a system of distributed and configurable radios connected via a router to donors feeding a Base Station. The methods and systems described herein are applicable to a variety of communications systems including systems utilizing various communications standards.

According to an embodiment of the present invention, a method for operating a Distributed Antenna System (DAS) is provided. The method includes providing a set of Digital Remote Units (DRUs) operable to send and receive wireless radio signals. Each of the set of DRUs is associated with a geographic area. The method also includes providing a Digital Access Unit (DAU) operable to communicate with the set of DRUs via an optical signal. The DAU is coupled to at least sector of a base transceiver station (BTS). The method further includes receiving uplink signals at one or more of the set of DRUs and monitoring train activity in the geographic areas associated with the set of DRUs. The method includes increasing a gain coefficient associated with one of the set of DRUs in response to determining an increase in monitored train activity in the geographic area associated with the one of the set of DRUs, decreasing a gain coefficient associated with another of the set of DRUs in response to determining a decrease in monitored train activity in the geographic area associated with the another of the set of DRUs, and transmitting, to the DAU, scaled uplink signals associated with the one of the set of DRUs and the another of the set of DRUs.

According to another embodiment of the present invention, a system for operating a Distributed Antenna System (DAS) is provided. The system includes a plurality of Digital Remote Units (DRUs), each configured to receive wireless radio uplink signals and transmit wireless radio downlink signals and a plurality of inter-connected Digital Access Units (DAUs), each configured to communicate with at least one of the plurality of DRUs via optical signals and each being coupled to at least one sector of a base station. The system also includes a plurality of detectors, each configured to measure uplink power at one of the plurality of DRUs and a processor coupled to the plurality of detectors and configured to vary gain coefficients for each of the wireless radio uplink signals in response to the measured uplink power.

According to a specific embodiment of the present invention, a method for operating a Distributed Antenna System (DAS) is provided. The method includes providing a plurality of Digital Remote Units (DRUs), each configured to send and receive wireless radio signals and providing a plurality of inter-connected Digital Access Units (DAUs), each configured to communicate with at least one of the plurality of DRUs via optical signals and each being coupled to at least one sector of a base station. The method also includes providing a plurality of sensors operable to detect activity at each of the plurality of DRUs and turning off a DRU downlink signal at one of the plurality of DRUs in response to an output from one of the plurality of sensors. The method further includes turning on a DRU downlink signal at another of the plurality of DRUs in response to an output from another of the plurality of sensors.

Embodiments of the present invention relate to a dynamic configuration of the DAS network's digital remote units (DRUs) parameters, such that the DRU's parameters can be modified, despite a fixed physical architecture. An example of a digital remote units (DRU) is a configurable radio with integrated routing capability located at a remote location from the base station (BTS) or baseband units (BBU). An example of a digital access unit (DAU) is a configurable radio with integrated routing capability co-located with the base stations or Baseband Units. This objective may be accomplished, for example, by using a plurality of digital remote units (DRUs) based on a Distributed Antenna System (DAS). Each DAS may receive resources (e.g., RF carriers, Long Term Evolution Resource Blocks, Code Division Multiple Access codes or Time Division Multiple Access time slots) from a central base station including a plurality of sectors and distribute the resources to a plurality of digital remote units (DRUs). Each DRU can serve as an antenna, receiving and transmitting signals, and thereby providing network coverage to a local geographic area surrounding the physical DRU. The DAS may be physically coupled to the base station and to the plurality of DRUs, e.g., through an optical fiber link. Thus, resources provided by one base station may be distributed to a plurality of DRUs, thereby providing coverage over a larger geographical area.

A DAS may be coupled (e.g., through another optical fiber link) to one or more other BTSs. Therefore, the DAS may also: (1) allocate part of the resources associated with another base station (which may be referred to as a sector) to the DRUs physically coupled to the DAS; and/or (2) allocate resources from the sector physically coupled to the DAS to serve DRUs physically coupled to another DAS. This may allow a system to dynamically allocate resources from a plurality of sectors to a network of DRUs (e.g., responding to geographic and temporal patterns in device usage), thereby improving the efficiency of the system and meeting desired capacity and throughput objectives and/or wireless subscriber needs.

A DAS network performance can be optimized for environments that have intermittent activity, as example along a train track. Train activity at each DRU can be synchronized with the plurality of DRU parameters in order to improve performance and reduce operational expenses. Although some embodiments of the present invention are illustrated in the context of train applications, the present invention is not limited to this particular transportation system and other transportation systems, including highways, roads, rivers, and the like are included within the scope of the present invention. Therefore, although trains are one example of a system with which embodiments of the present invention can be utilized, other vehicles including cars, trucks, boats, planes, and the like can benefit from embodiments of the present invention. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

According to an embodiment of the present invention, a system for optimizing performance in a Distributed Antenna System is provided. The system includes a plurality of Digital Remote Units (DRUs) configured to send and receive wireless radio signals and a plurality of inter-connected Digital Access Units (DAUs), each configured to communicate with at least one of the plurality of DRUs via optical signals, and each being coupled to at least one sector. The system also includes a plurality of detectors to measure uplink power at each of the plurality of DRUs and an algorithm operable to turn off or on DRU uplink signals from one or more of the plurality of DRUs based on the uplink power detected by the plurality of detectors.

Each of the plurality of detectors can be implemented digitally using signal processing or as a discrete analog device. Each of the plurality of DAUs can be configured to communicate with the at least one of the DRUs by sending and receiving signals over at least one of an optical fiber, an Ethernet cable, microwave line of sight link, wireless link, or satellite link. The DRUs can be connected in a loop to a plurality of DAUs.

According to another embodiment of the present invention, a system for optimizing performance in a Distributed Antenna System is provided. The system includes a plurality of Digital Remote Units (DRUs) configured to send and receive wireless radio signals and a plurality of inter-connected Digital Access Units (DAUs), each configured to communicate with at least one of the DRUs via optical signals, and each being coupled to at least one sector. The system also includes a plurality of sensors operable to detect activity at each of the plurality of DRUs and an algorithm to turn off and on DRU downlink signals and DRU uplink signals associated with each of the plurality of DRUs based, at least in part, on outputs of the plurality of sensor.

In an embodiment, each of the plurality of DAUs is configured to communicate with the at least one of the DRUs by sending and receiving signals over at least one of an optical fiber, an Ethernet cable, microwave line of sight link, wireless link, or satellite link. Each of the DAUs can be co-located with the at least one sector. Each of the plurality of DAUs can be connected to a plurality of DRUs, for example, with at least some of the plurality of DRUs being connected in a daisy chain configuration or with the plurality of DRUs being connected to at least one of the plurality of DAUs in a star configuration.

According to a specific embodiment of the present invention, a non-transitory computer-readable storage medium comprising a plurality of computer-readable instructions tangibly embodied on the computer-readable storage medium, which, when executed by one or more data processors, provide routing of wireless network signals, is provided. The plurality of instructions include instructions that cause the data processor to decode a digital signal and instructions that cause the data processor to identify a Digital Remote Unit (DRU) based on the decoded signal. The plurality of instructions also include instructions that cause the data processor to convert the digital signal into a radio-frequency signal, instructions that cause the data processor to dynamically determine an assignment pairing the DRU with one or more Base Transceiver Station sectors, the assignment being at least partly determined by dynamic geographic discrepancies in network use, and instructions that cause the data processor to transmit the digital signal to the one or more assigned sectors.

Numerous benefits are achieved by way of the present invention over conventional techniques. For instance, embodiments of the present invention allow a network to effectively respond to a geographically changing mobile user base. For example, users concentrated in a train traverse the network of DRUs along the train track, some DRU resources may be allocated to serve this train only for time periods when the users actually are or are predicted to be at this location. Thus, a network operator need not either waste DRU resources to provide coverage in other sections of the track during these times, nor must it degrade system performance by adding noise from non-active DRUs. Rather, DRU resources may be flexibly managed and controlled, thereby improving a network's efficiency, usage, overall performance and economics. Further, due to this foreseeable efficiency, specialized applications and enhancements may be enabled, such as flexible simulcast, automatic traffic load-balancing, network and radio resource optimization, network calibration, autonomous/assisted commissioning, carrier pooling, automatic frequency selection, radio frequency carrier placement, traffic monitoring, traffic tagging, traffic shaping, traffic allocation, traffic management and the like. Embodiments may also be implemented to serve multiple operators, multiple standards, multi-mode radios (modulation-independent) and multiple frequency bands per operator to increase the efficiency and traffic capacity of the operators' wireless networks.

These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Wireless and mobile network operators face the continuing challenge of building networks that effectively manage high data-traffic growth rates and fluctuating traffic distribution. To ensure customer satisfaction, network operators attempt to provide networks that are available and functional in most locations where their clients will expect to be able to use their devices. This is a difficult task, as it is hard to determine how to geographically allocate resources, given the unpredictable nature of where and how users will wish to use their devices.

Allocating network resources is complicated by users' mobility and unpredictability. For example, configuring a network to effectively allocate wireless network resources to users on a train may present challenges (e.g., with regard to available wireless capacity and data throughput) as the train travels along the track.

Network operators are tasked with establishing wireless (e.g., cellular mobile communication systems) coverage across one or more large geographic areas. As described in greater detail below, dividing a geographic area into a plurality of cells allows a network operator to reuse resources (e.g., spectrum) across geographically separated cells.

FIG. 1is a diagram illustrating one wireless network system100that may provide coverage to a geographical area according to an embodiment of the present invention. The geographic area inFIG. 1is along train track120. Although embodiments have been described with reference to a train track example, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. System100may include a distributed antenna system (DAS), which may efficiently use base-station resources. One or more base stations105(also referred to as base transceiver stations (BTS)) may be located in a central location and/or at a base station hotel. One or more base stations105may include a plurality of independent outputs or radio resources, known as sectors110. Each sector110may be responsible for providing wireless resources (e.g., RF carrier signals, Long Term Evolution Resource Blocks, Code Division Multiple Access codes, Time Division Multiple Access time slots, etc.). The resources may include one or more resources that allow a wireless user mobile device to effectively and wirelessly send and receive communications over a network. Thus, the resources may include one or more resources, such as those listed above, that allow a signal to be encoded or decoded in a manner to prevent the signal from interfering with or being interfered with by other wireless signals.

Each sector may be coupled to a digital access unit (DAU)115, which may interface sector110(and thus base station105) with digital remote units (DRUs) installed along train track120. The coupling may represent a physical coupling. For example, DAU115may be connected to sector110and/or DRU1via a cable, a link, fiber, an RF cable, an optical fiber, an Ethernet cable, microwave link with or without line of sight, wireless link, satellite link, etc. In some instances, DAU115is connected to sector110via an RF cable. In some instances, DAU115is connected to one or more DRUs via an optical fiber or Ethernet cable. An associated sector110and DAU115may be located near each other or at a same location. DAU115may convert one or more signals, such as optical signals, RF signals, digital signals, etc. DAU115may include a multi-directional signal converter, such that, e.g., RF signals may be converted to optical signals and optical signals to RF signals, or to convert signals between a signal type associated with a sector and a signal type associated with a DRU. In one embodiment, DAU115converts a sector's downlink RF signals to optical signals, and/or converts a DRU's uplink optical signals to RF signals. DAU115may also or alternatively control routing of data and/or signals between sectors and DRUs, as explained in greater detail below. DAU115may generate, collect and/or store traffic statistics, such as a number of communications, calls, network-access and/or communication sessions, traffic volumes, quality of service data etc. between sector110and one or more DRUs.

Each DAU115may be coupled to a plurality of digital remote units (DRU). The plurality of DRUs may be coupled to the115through, e.g., a daisy-chain or loop (indirectly coupling a DAU with one or more DRUs) and/or star configuration (directly coupling a DAU to multiple DRUs).FIG. 1shows an example of daisy-chain configurations, wherein a DAU couples to a first DRU directly (e.g., direct connection from DAU1to DRU1), a second DRU indirectly (e.g., indirect connection from DAU1to DRU2through DRU1), a third DRU indirectly (e.g., indirect connection from DAU1to DRU3through DRUs1and2), etc.FIG. 1also shows an example of star configurations, wherein a DAU couples to multiple DRUs directly (e.g., direct connections from DAU1to DRU1and DRU15).

Each of the DRUs can provide coverage and capacity within a geographical area physically surrounding the DRU. DRUs may be strategically located to efficiently provide combined coverage across a larger geographical area. For example, DRUs1may be located e.g., along a train track, and/or coverage areas associated with adjacent DRUs may be barely overlapping. A network may include a plurality of independent cells that span a total coverage area.

As illustrated inFIG. 1, DRU8through DRU14are daisy chained to each other, with DRU8coupled, via an optical fiber, to DAU1(115). Because of the daisy chain architecture of this embodiment, as the train moves along the track from the cell associated with DRU14toward the cell associated with DRU8, the uplink signals communicated through DRU14are transported down the daisy chain toward DRU8. In some implementations, the noise associated with the uplink signals from each of the DRUs in the daisy chain is added as the uplink signals from the various DRUs are combined as the uplink signals move down the daisy chain toward DRU8. As a result, for an uplink signal received at DRU14, the noise from each of the intervening DRUs (DRU13through DRU8) is combined to the original signal, reducing the signal to noise ratio as the uplink signal moves down the daisy chain.

As described herein, in order to improve the signal to noise ratio of the uplink signals, the DRUs not in active communication with the train are deemphasized in various embodiments. As an example, the amplitude/power of signals and noise associated with DRUs not in active communication with the train can be decreased when the level of communication with the train is low and increased for the DRUs in the vicinity of the train. Additional description related to decreasing the noise signal through control of the uplink signals is provided, for example, in relation toFIG. 4below. In addition to control of the uplink signals, DRUs can be controlled to decrease the power associated with downlink signals broadcast by DRUs that are not in active communication with a train. Accordingly, power budgets and operational expenses can be reduced by control of the uplink and downlink traffic in areas where no train traffic is present. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

In conventional DAS networks, a first set of remote units in a first geographic area can be connected to a first BTS or a first sector of a BTS and a second set of remote units in a second geographic area can be connected to a second BTS or a second sector of the BTS. In an environment in which people are communicating while a train is moving, the calls for the users will be handed off from the first BTS to the second BTS as the train moves from the first geographic area to the second geographic area. If the volume of users is large, the heavy messaging traffic at the point of the hand offs can result in dropped calls, decreased data rates, and the like. Embodiments of the present invention provide methods and systems to ameliorate these problems associated with conventional systems.

Referring toFIG. 1, a benefit provided by the illustrated DAS network, with DRUs associated with a single sector of the BTS positioned along the track (e.g., DRU1through DRU7can be connected to Sector1(110)), is that as the train moves along the track from Cell1to Cell7, no handoffs are needed, reducing the number of dropped calls and interruptions in data service. The digital DAS system illustrated inFIG. 1provides DRUs positioned along the track in a generally linear manner in contrast with closed cell structures in which the cells are packed together in a hexagonal pattern covering a generally hexagonal/circular coverage area.

It should be noted that although a single train moving along the tracks is discussed in some embodiments, it will be appreciated that multiple trains can be traveling along the tracks concurrently and the discussions related to a single train can be extended to multiple trains as appropriate to the particular application.

Each cell may be assigned to a sector210.FIG. 2, for example, shows an embodiment in which Sector1provides resources to Cells15to21, Sector2to Cells1to7, and Sector3to Cells8to14. An associated sector may provide each DRU with resources, such as RF carriers, resource blocks, etc. In one embodiment, each of a plurality of sectors210is associated with a set of “channels” or frequency ranges. The set of channels associated with each sector210may be different from a set of channels associated with other sectors2and3in base station205. A network may be configured such that neighboring cells are associated with different channels (e.g., by being associated with different sectors210), as shown inFIG. 2. This may allow channels to be reused across multiple cells without the risk of creating interference.

In the embodiment shown inFIG. 1, each sector110is connected to an associated subset of all of the DRUs in the network. Thus, for example, Sector1's resources (e.g., assigned channels) cannot be used by a DRU located in Cell8without a physical alteration to the network hardware (e.g., by re-routing an optical fiber). This limitation is avoided by the embodiment shown inFIG. 2. Specifically, DRUs may be dynamically assigned to sectors210based on an interconnection between DAUs215. Thus, for example, DRUs8-14in Cell8to14may initially all be assigned to Sector3. (FIG. 2.) Subsequently, DRU7may be assigned to Sector3and DRU14may be assigned to Sector1. In such instances, signals to DRU7may pass from Sector2through DAU2and through DAU3. Similarly, signals may pass from DRU14through DAU3and DAU1to Sector1. In this manner, a sector may be indirectly connected with a larger subset of DRUs in a network or with all DRUs in a network. Communications between DAUs may be partly controlled by one or more servers225, as explained in greater detail below.

DAUs210may be physically and/or virtually connected. For example, in one embodiment, DAUs210are connected via a cable or fiber (e.g., an optical fiber, an Ethernet cable, microwave link with or without line of sight, wireless link, or satellite link). In one embodiment, a plurality of DAUs210are connected to a wireless network, which allows information to be transmitted from one DAU210to another DAU210and/or allows information to be transmitted from/to a plurality of DAUs210.

As shown inFIG. 3, a multi-operator system or a system with multiple base stations of one operator or a combination of both may include multiple base stations (or multiple base station hotels)305. A Neutral Host scenario is defined when multiple operators co-exist on the same infrastructure and a the system is hosted by either one of the operators or a 3rdparty. Different base stations305may be associated with the same, overlapping, non-overlapping or different frequency bands. Base stations305may be interconnected, e.g., to serve a geographic area. The interconnection may include a direct connection extending between the base stations (e.g., a cable) or an indirect connection (e.g., each base station connecting to a DAU, the DAUs being directly connected to each other). The greater number of base stations may increase the ability to add capacity for a given cell. Base stations305may represent independent wireless network operators and/or multiple standards (WCDMA, LTE, etc.), and/or they may represent provision of additional RF carriers as well as additional baseband capacity. In some embodiments, base station signals are combined before they are connected to a DAU, as may be the case for a Neutral Host application. In one instance, as shown inFIG. 3, sectors from BTS1are directly coupled to the same DAUs and/or DRUs that are directly coupled to sectors to BTS N. In some other instances, one or more sectors from different BTS may be directly coupled to DAUs not shared by sectors of one or more other DAUs.

FIG. 4is a diagram illustrating a distributed antenna system (DAS) that covers a portion of a train track according to an embodiment of the present invention. As illustrated inFIG. 4, this high level schematic diagram illustrates a wireless network system comprising daisy chained DRUs with the Up-Link signals from each DRU being scaled and summed, with the network providing coverage to a geographic area. In this example, DRU15to DRU21covering cells15to21are assigned to Sector1. Based on network hardware and architecture, signals from DRUs15-21are routed to DAU1. DAU1combines the uplink signals from DRU15-21or receives signals that are combined, in turn, at each of the DRUs. In this embodiment, DAU1associates gain coefficients {α, β, . . . δ} for each of the respective DRUs {15,16. . .21} assigned to DAU1. The gain coefficients are used to scale the uplink signals. The equation below demonstrates how the uplink signals from DRUs k through N (e.g.,15-21) are combined to provide scaled uplink signals that are transmitted to DAU1.

The gain coefficients are adjustable from zero to one, providing for individual control over the signals uplinked using each DRU. In some embodiments, the sum of the scaled uplink signals from the DRUs can be referred to as a scaled uplink signal, which is received at the DAU. In addition to uplink control, downlink control is provided in some embodiments. As an example, as a train moves from Cell15towards Cell21, initially Cell15is at full power (i.e., α=1) and Cell21is off (δ=0). Cells between Cell15and Cell21are at levels between zero and one. As the train moves towards Cell21, the gain coefficients are adjusted by decreasing a and increasing δ to match the gain associated with the DRUs to the position of the moving train.

A train contains a high density of mobile users. As this group of mobile users travel along the track different DRUs are active. However, the Up Link signal presented to BTS405comprises the addition of all the DRUs connected to DAU1. Even if a DRU experiences no activity it will contribute to the overall noise floor when all gain coefficients are set to unity. The DAS system inFIG. 4can alter the gain coefficients thereby turning the Uplink channels from the DRUs up or down (or on or off) depending on the train activity at their respective sites. DRUs with no activity can be switched off in order to reduce the noise contribution associated with those inactive DRUs. As discussed above, in addition to control of the uplink channels, control of downlink channels can be implemented to reduce the power consumption of DRUs that are not in active communication with the train and the resulting operating expenses.

FIG. 5is a simplified flowchart illustrating a method of controlling DRU uplink gain according to an embodiment of the present invention. In this embodiment, a performance optimization algorithm for the DAS network alongside of the train track is provided. In functional block505, the DRUs are assigned to various DAUs. As an example, DRUs connected to a DAU using an optical fiber can be assigned to the DAU to which they are connected. The DAUs are connected to sectors in the Base Transceiver Stations (BTSs). Functional block510assigns a subset of the DRUs to a section of the train track. This assignment relates the geographic location of the cells associated with the DRUs to their locations along the track. The network of DRUs, DAUs and BTSs are configured and the assignments are stored in memory (515).

The downlink signals from the BTS sectors are routed to the assigned DAUs and subsequently DRUs (520). The DRU uplink signals received at the DRUs are routed to the assigned DAU for the subset of DRUs assigned to the DAU. The uplink signals from the DRUs are scaled by a gain coefficient and then combined and fed to the sector for that specific BTS, in functional block525. As described above, inactive DRUs can contribute noise to the uplink signals thereby degrading the overall system performance. Functional block530monitors the train activity at each respective DRU, referred to as DRUk. Although embodiments have been described with reference to a train activity monitor example, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention.

The train activity monitor can be a sensor (e.g., an external monitor) that detects motion of the train along the track or it could be a measurement of the cellular signal strength or the cellular data activity in a geographic area. A monitor can be implemented using signal processing inside the DRU, for example, based on the uplink signal strength. An external monitor could be an optical detector, vibration detector, radar detector, etc. In some embodiments, train schedules are utilized to provide inputs to the system, effectively providing monitoring inputs. In other embodiments, communication from the train (e.g., a broadcasted GPS location) can be utilized as a monitor input, in place of or in conjunction with other monitors. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

The train activity monitor will become active when a train traverses a DRU cell that provides coverage to a geographical area. This will be an indication that the DRU will momentarily experience a large number of mobile users as the train enters the geographic area associated with the DRU. In some embodiments, a threshold will be set for the train activity monitor. Although embodiments have been described with reference to a threshold trigger example, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention.

If the train activity monitor indicates that the activity is increasing (or goes above a threshold setting), then the gain coefficient corresponding to that DRU will be transitioned toward unity (540). This will effectively connect the DRU with the given BTS sector, via the DAU. If the train activity monitor indicates that the activity is decreasing (or falls below the threshold) then the DRU uplink gain coefficient corresponding to that DRU will be transitioned toward zero (550). This will reduce the noise contribution from those DRUs that have no active mobile users passing through their cells.

A closed loop is demonstrated in the flowchart500, whereby the train activity monitors are continually or regularly analyzed or compared to the threshold and the gain coefficients are adjusted accordingly. In some embodiments, the closed loop returns to block530after decision point535and the gain adjustments in blocks540or550.

The train activity monitor/sensors are thus configured to provide data that is utilized by the system to control the operation of the DRUs as described herein. As illustrated by the operation discussed in relation toFIG. 5, some embodiments increase/decrease the gain coefficients in small steps or continuously to vary the gain between values of zero and one. As an example, as a train approaches a DRU, the gain can be turned up gradually, peaking at one when the train is adjacent to the DRU and then gradually turning the gain down as the train leaves the area of the DRU. Thus, some embodiments utilize a scale that increases/decreases the gain in response to increases/decreases in train activity. In other embodiments, the train activity is compared to a threshold. If the threshold is exceeded, the DRU uplink gain is set to unity. If the activity does not exceed the threshold, the DRU uplink gain is set to zero. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 6is a flowchart of one embodiment of the performance optimization algorithm for the DAS network alongside of the train track. Flowchart600has a similar functionality to flowchart500, with the exception that the DRU transmitters and or receivers will be controlled (e.g., turned off and on) depending on the train activity monitor. The primary objective of turning off the DRU transmitters and or receivers is to reduce the operational expenses and reduce the interference to Macro BTSs in neighboring cells. In some embodiments, the DRU downlink path is not turned off, but decreased in power as a function of the train activity that is monitored. In these embodiments, the train activity is monitored (630) on a periodic or other temporal basis. If the train activity is increasing, then the power associated with the downlink transmitter is increased toward a maximum power (similar to block640). If the train activity is decreasing, then the power associated with the downlink transmitter is decreased toward zero (similar to block650). Thus, blocks540and550illustrated inFIG. 5can be substituted for blocks640and650inFIG. 6. Likewise, blocks640and650illustrated inFIG. 6can be substituted for blocks540and550inFIG. 5as discussed above.

FIG. 7illustrates components of a DAU700according to an embodiment of the invention. DAU700may include a router (i.e., Local Router705). DAU700may include one or more ports715and720. Ports715and720may, e.g., enable DAU to connect to the Internet and/or a Host Unit or a server725. Server725may at least partly configure the DAU and/or control the routing of the signals between various Local Router ports. Server725may be, e.g., at least partly controlled by a remote operational control730(e.g., to set re-assignment conditions, identify assignments, store assignments, input network configurations, receive/collect/analyze network usage, etc.).

DAU700may include one or more physical nodes710, which may be coupled to Local Router705by one or more first-end ports735. Each physical node710may include one, two, or more ports, such as first-end ports, each of which may allow signals (e.g., RF signals and/or signals from/to a sector) to be received by or transmitted from DAU700. In some embodiments, a plurality of physical nodes710each includes a Downlink port712and an Uplink port713. In some embodiments, a physical node710may also include an additional Uplink port, e.g., to handle a diversity connection. Output ports (e.g., Downlink port712and Uplink port713) may be coupled to one or more ports (e.g., RF pots) of a base station. Thus, DAU700may be physically coupled to a base station.

Local Router705may include one or more second-end ports740, which may couple DAU700to one or more DRUs or DAUs e.g., via an optical fiber, Ethernet cable, line of sight or non-line of sight microwave connection, etc.). The second-end ports740may include LAN or PEER ports. Second-end ports740may be configured to send and/or receive signals, such as digital and/or optical signals. In one embodiment, at least one second-end port740couples DAU700to another DAU, and at least one second-end port740couples DAU700to a DRU. The local router also encodes the signals for transportation over the optical link as well as decodes the optical signals from the optical link. The Physical Nodes perform the function of translating the RF signals to baseband or translating the baseband signals to RF. The DAU can monitor the traffic on the various ports and either route this information to a server or store this information locally.

FIG. 8illustrates components of a DRU800according to an embodiment of the invention. DRU800may include a router (i.e., Remote Router805). DRU may include a network port810, which may allow DRU800to couple (via an Ethernet Switch815) to a (e.g., wireless) network. Through the network, DRU800may then be able to connect to a computer820. Thus, a remote connection may be established with DRU800.

Remote Router805may be configured by a server, such as server130, server725, a server connected to one or more DAUs, and/or any other server. Network port810may be used as a Wireless access point for connection to the Internet. The Internet connection may, e.g., established at the DAU and Internet traffic may be part of the data transport between the DRUs Physical Nodes and the DAU Physical Nodes.

DRU800may include one or more physical nodes825. Each physical node825may include one, two, or more ports, such as first-end ports830, each of which may allow for signals (e.g., RF signals and/or signals from mobile devices) to be received by or transmitted from DRU800. In some embodiments, a plurality of physical nodes825each include one or more ports configured to send/receive signals (e.g., RF signals) from/to DRU800. The ports may include, e.g., a Downlink port827and an Uplink port828. In some embodiments, an additional Uplink port exists for handling a diversity connection. Physical node ports (e.g., Downlink output port827and Uplink output port828) may be connected to one or more antennas (e.g., RF antennas), such that signals may be received from and/or transmitted to, e.g., mobile wireless devices.

Remote Router805may include one or more second-end ports835, which may couple DRU800to one or more DAUs or DRUs. Second-end ports835may include LAN or PEER ports, which may (e.g., physically) couple DRU800to one or more DAUs or DRUs via an optical fiber, Ethernet cable, line of sight or non-line of sight microwave connection.

Methods shown inFIGS. 5 and 6or elsewhere described may be performed by a variety of devices or components. For example, some processes may be performed solely or partly by one or more DAUs. Some processes may be performed solely or partly by a remote computer, e.g., coupled to one or more DAUs. Some processes may be performed by one or more DRUs. In some embodiments, shown or described process may be performed by multiple devices or components (e.g., by multiple DAUs, by one DAU and a remote server, by one or more DRUs and a DAU, etc.).

Above-described embodiments may be implemented with, e.g. distributed base stations, distributed antenna systems, distributed repeaters, remote radio units, mobile equipment and wireless terminals, portable wireless devices, and/or other wireless communication systems such as microwave and satellite communications. Many variations are possible. For example, embodiments including a single base station may be applied in systems including multiple, interconnected base stations. Embodiments may be modified to replace daisy-chain configurations with star configurations or the converse or extend daisy-chain configuration into loops. Embodiments showing a single server (e.g., connected to a plurality of DAUs) may be modified to include a plurality of servers (e.g., each connected to a different DAU or connected to all DAUs).

FIG. 9is a high level schematic diagram illustrating a computer system900including instructions to perform any one or more of the methodologies described herein. One or more of the above-described components (e.g., DAU115, DRU1, server130, server725, computer920, etc.) may include part or all of computer system900. System900may also perform all or part of one or more methods described herein.FIG. 9is meant only to provide a generalized illustration of various components, any or all of which may be utilized as appropriate.FIG. 9, therefore, broadly illustrates how individual system elements may be implemented in a relatively separated or relatively more integrated manner.

The computer system900is shown comprising hardware elements that can be electrically coupled via a bus905(or may otherwise be in communication, as appropriate). The hardware elements may include one or more processors910, including without limitation one or more general-purpose processors and/or one or more special-purpose processors (such as digital signal processing chips, graphics acceleration processors, and/or the like); one or more input devices915, which can include without limitation a mouse, a keyboard and/or the like; and one or more output devices920, which can include without limitation a display device, a printer and/or the like.

The computer system900might also include a communications subsystem930, which can include without limitation a modem, a network card (wireless or wired), an optical communication device, an infrared communication device, a wireless communication device and/or chipset (such as a Bluetooth device, a WiFi (802.11) device, a WiMax (802.16) device, a zigbee (802.15) device, cellular communication facilities, etc.), and/or the like. The communications subsystem930may permit data to be exchanged with a network (such as the network described below, to name one example), other computer systems, and/or any other devices described herein. In many embodiments, the computer system900will further comprise a working memory935, which can include a RAM or ROM device, as described above.

As mentioned above, in one aspect, some embodiments may employ a computer system (such as the computer system900) to perform methods in accordance with various embodiments of the invention. According to a set of embodiments, some or all of the procedures of such methods are performed by the computer system900in response to processor910executing one or more sequences of one or more instructions (which might be incorporated into the operating system940and/or other code, such as an application program945) contained in the working memory935. Such instructions may be read into the working memory935from another computer-readable medium, such as one or more of the storage device(s)925. Merely by way of example, execution of the sequences of instructions contained in the working memory935might cause the processor(s)910to perform one or more procedures of the methods described herein.

Cloud based computing is another example of an embodiment of the computer system900.

The embodiments described herein may be implemented in an operating environment comprising software installed on any programmable device, in hardware, or in a combination of software and hardware. Although embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.

Although embodiments of the present invention have been discussed in relation to digital DAS networks, the present invention is not limited to digital implementations and embodiments of the present invention are applicable to analog DAS networks. In these analog implementations, analog remotes are utilized that receive wireless signals in the uplink path and transmit analog signals to an analog host unit. In some analog embodiments, the analog remotes can be connected to the analog host unit using a star configuration in which the host unit is individually connected to each analog remote using a suitable connection, for example an analog over fiber connection. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.