HK1224444B - A method of communicating in a distributed antenna system - Google Patents

Description

Method for communicating in a distributed antenna system

This patent application is a divisional application of a patent application with an international application date of August 16, 2011, a national application number of 201180050066.6, and an invention name of “Daisy Chain Ring for Remote Units of a Distributed Antenna System”.

This application claims the benefit of U.S. Patent Application Serial No. 61/439,940, filed February 7, 2011, entitled “DAISY CHAINED RING OF REMOTE UNITS FOR A DISTRIBUTED ANTENNA SYSTEM,” which is hereby incorporated by reference for all purposes.

Technical Field

The present invention generally relates to wireless communication systems that employ a distributed antenna system (DAS) as part of a distributed wireless network. More particularly, the present invention relates to a DAS that utilizes one or more remotely monitored and controlled digital access units configured to distribute specific packet transmissions to selected remote units among a plurality of remote units, wherein the remote units, in some embodiments, may be configured in a daisy-chained ring.

Background Art

Wireless and mobile network operators face the ongoing challenge of building networks that effectively manage high data traffic growth rates. The increasing level of mobility and multimedia content for end users requires end-to-end network adaptation to support both new services and the increasing demand for broadband and flat-rate Internet access. One of the greatest challenges facing network operators is maximizing the capacity of their DAS networks while ensuring cost-effective DAS deployments and at the same time providing a very high degree of DAS remote unit availability.

To provide DAS network capacity large enough to meet the short-term needs of network users at a specific location while avoiding the costly and inefficient deployment of radio resources, DAS network planners prefer to employ DAS architectures and solutions that offer a high degree of dynamic flexibility. Therefore, wireless network operators can benefit from employing DAS solutions that offer high flexibility and can be dynamically reconfigured based on changing network conditions and user needs. Furthermore, the more future-proof a DAS deployment is, the lower its lifecycle cost will generally be.

To help ensure that a specific DAS deployment is as cost-effective as possible, DAS network planners and system integrators employ many innovative approaches. The types of costs considered by network planners and integrators include DAS deployment costs, or DAS installation costs, as well as operational costs, including maintenance costs, emergency repair costs, and network re-provisioning costs. Re-provisioning costs are particularly significant for indoor DAS applications due to fluctuating facility requirements and frequent changes in building usage. Therefore, it would be advantageous to employ a DAS system and method that relies on minimal DAS transmission infrastructure to minimize installation and/or rental costs and that incorporates self-healing capabilities to avoid the need for expensive emergency repair services.

To achieve high DAS remote unit availability, two key conditions must be met. First, the DAS remote unit itself must be inherently reliable. Second, the transmission medium, such as optical fiber, must be highly reliable. It is well known that electrical and/or optical connections themselves are a significant source of failure or reduced availability in DAS networks. Companies maintaining outdoor DAS networks report that outside plant fiber optic infrastructure failures are not as uncommon as might be expected. Therefore, it would be advantageous to employ systems and methods that provide greater redundancy and/or self-healing properties in the event of transmission media connection failures.

Summary of the Invention

The present invention substantially achieves the aforementioned advantages and benefits and overcomes the limitations of the prior art discussed above by providing a distributed antenna system responsive to one or more base stations and having at least one, but in some embodiments, multiple, digital access units ("DAUs"), each of which operates to control packet traffic for an associated plurality of digital remote units ("DRUs"). In embodiments employing multiple DAUs, the DAUs may be arranged in a daisy-chained linear configuration or in a ring configuration. Similarly, the DRUs associated with a given DAU may be arranged in either a linear or ring daisy-chain configuration, depending on the implementation.

Data received from the base station is down-converted, digitized, and converted to baseband by the DAU. The data streams are then I/Q mapped, framed, and independently serialized so that multiple data streams can be obtained from the DAU in parallel. In at least some embodiments, the DAU communicates with the associated DRU via an optical transport arrangement. It will be understood by those skilled in the art that using the present invention, a distributed antenna system with n base stations can be configured, each base station providing m RF outputs transmitted by one or more associated DAUs to o DRUs, where the only limitations are imposed by the technical performance specifications of the particular DAS, such as latency.

By connecting using a ring configuration, in at least some embodiments, fault tolerance for DRUs and/or DAUs is built into the system, resulting in a highly available system. In a single DAU embodiment, each DRU can be accessed via two paths, thereby remaining available even in the event of a line outage. In a multi-DAU embodiment, where the DAUs are linearly daisy-chained, each DRU can be accessed from multiple DRUs, so that even if a DAU fails, the system will not be blocked. In embodiments that utilize a DAU ring connection, multiple paths exist for each DAU, thereby providing an additional level of fault tolerance as well as dynamic load balancing and resource management as discussed in more detail below.

Thus, the configuration of the advanced system architecture of the present invention provides a high degree of flexibility to manage, control, enhance, and improve the radio resource efficiency, usage, availability, and overall performance of distributed wireless networks. The present invention enables specialized applications and enhancements, including: flexible simulcasting, automatic traffic load balancing, network and radio resource optimization, network calibration, autonomous/assisted commissioning, carrier polling, automatic frequency selection, frequency carrier positioning, traffic monitoring, traffic tagging, and indoor location determination using pseudo pilots (Pilot Beacons). The present invention can also serve multiple operators, multi-mode radios (modulation independent), and multiple frequency bands per operator to improve the efficiency and traffic capacity of the operator's wireless network.

The present invention also provides a high degree of dynamic flexibility, supports dynamic relocation, and provides low life cycle costs. This advanced system architecture enables the deployment of DAS networks using fewer DAS transmission facilities to reduce costs while providing self-healing features. The present invention also provides redundancy and enhanced system availability.

The present invention is directed to providing flexible simulcast capabilities as disclosed in U.S. Provisional Application No. 61/382,836, filed September 14, 2010, entitled “Remotely Reconfigurable Distributed Antenna System and Methods,” incorporated herein by reference and attached hereto as Appendix A, in a high-availability ring configuration using, for example, fiber optic transport. As described above, because downlink and uplink signals can be rerouted to the various DRUs around a cable break, the ring configuration ensures that a break in any fiber optic cable will not shut down the daisy-chained network.

Another object of the present invention is to balance the bidirectional data rates on the optical fiber to increase the maximum achievable data rate of the ring network of DRUs during operation.

Another object of the present invention is to provide higher transmission network capacity when data transmission is asymmetric between downlink and uplink, which is typically the case in mobile broadband networks.

It is another object of the present invention to provide adaptive and automatic control for optimizing the transmission medium capacity on the ring.

Another object of the present invention is to provide a method for summing uplink signals of co-channel users in a DRU daisy chain.

The present invention is suitable for use with distributed base stations, distributed antenna systems, distributed repeaters, mobile devices and wireless terminals, portable wireless devices, and other wireless communication systems such as microwave communications and satellite communications. The present invention is also field upgradeable through a link such as an Ethernet connection to a remote computing center.

Another object of the present invention is to provide a method for communicating in a distributed antenna system, the method comprising: providing a plurality of digital remote units; providing at least one digital access unit configured to communicate with the plurality of digital remote units, the at least one digital access unit being configured to receive a plurality of downlink channels from at least one base station and to send the plurality of downlink channels to the plurality of digital remote units; sending a first part of the plurality of downlink channels from the at least one digital access unit to a first digital remote unit among the plurality of digital remote units; and sending a second part of the plurality of downlink channels from the at least one digital access unit to a second digital remote unit among the plurality of digital remote units, wherein at least some of the channels in the first part of the plurality of downlink channels are different from the channels in the second part of the plurality of downlink channels.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention may be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a basic structure and example of unidirectional channelized downlink transmission based on a ring scenario with 1 DAU and 4 DRUs according to an embodiment of the present invention.

2 is a block diagram illustrating a basic structure and example of unidirectional channelized uplink transmission as a ring scenario based on 1 DAU and 4 DRUs according to an embodiment of the present invention.

3 is a block diagram illustrating a basic structure and example of unidirectional channelized uplink transmission as a two-ring scenario based on 1 DAU and 8 DRUs according to an embodiment of the present invention.

Figure 4 is a block diagram illustrating a basic structure and example of unidirectional channelized uplink or downlink transmission according to an embodiment of the present invention.The example of the 5-ring scenario includes 2 DAUs and 20 DRUs.

FIG5 shows an embodiment of a cellular network system using multiple DRUs according to the present invention.

FIG. 6 illustrates an embodiment of a multi-band system employing six different services operating in different frequency channels with multiple DRUs according to the present invention.

FIG7 shows the interaction between the DAU embedded software control module and the DRU embedded software control module in the form of a block diagram.

FIG8 illustrates, in block diagram form, an embodiment of a DAS including daisy-chained DAUs according to an aspect of the present invention.

DETAILED DESCRIPTION

The present invention is a novel reconfigurable distributed antenna system that provides a high degree of flexibility to manage, control, reconfigure, enhance, and improve the efficiency, use, and overall performance of radio resources in distributed wireless networks. FIG1 illustrates an embodiment of a distributed antenna system 100 according to the present invention. The system utilizes a digital access unit function 105 (hereinafter referred to as a "DAU"). The DAU 105 serves as an interface between associated base stations (BTSs) 110A-B and multiple digital remote units (DRUs) 125A-n (although only four DRUs are shown in FIG1 ). While those skilled in the art will recognize that DRUs communicate with DAUs and RRUs communicate with base stations, due to the similarity of the functions discussed herein, "DRU" and remote radio head unit, or "RRU," may be used interchangeably in this specification. Furthermore, those skilled in the art will recognize that, as indicated by bidirectional link 115 in FIG1 , the DAU is monitored and controlled by a remote network operations center ("NOC"). Such a link is typically an Ethernet connection or an external modem, but can be any form of link suitable for remote monitoring and control. The NOC has the ability to remotely configure the DAU parameter settings, which in turn configure the DRU parameter settings. The NOC can request information from the DAU. The DAU can then request information from the DRU. The requested information includes, but is not limited to, uplink power, downlink power, optical error rate, gain settings, active carriers, etc.

For the downlink (DL) path, RF input signals 120A to 120n are received at the DAU 105 from one or more base station units (BTSs), designated 110A to 110p. These RF input signals are down-converted, digitized, and converted to baseband by the DAU (using a digital down-converter). The data streams are then I/Q mapped and framed again by the DAU 105, and the individual parallel data streams are then independently serialized and translated into optical signals using pluggable SFP modules. The independently serialized parallel data streams are then typically delivered to different DRUs 125A to 125k over optical cables arranged (in at least some embodiments, arranged in a ring configuration as designated by the connection pairs 140A to 145A, or in other embodiments, in a daisy-chain configuration) (in at least some embodiments, arranged in a ring configuration as designated by the connection pairs 140A to 145A, or in other embodiments, in a daisy-chain configuration). In addition, each DAU can support multiple rings with associated DRUs, with additional rings indicated by fiber pairings 140° through 145°. Those skilled in the art will appreciate that the number of RF inputs, DAUs, DRUs, and rings is limited only by network performance factors such as latency. Furthermore, as discussed herein in conjunction with FIG4 , the DAS can be further expanded by using rings or daisy chains of DAUs, each supporting the DRU and ring arrangement shown in FIG1 .

One function of the DAU 105 is to determine the direction in which the downlink channels propagate around the ring. While it should be understood that the number of channels propagating in each direction need not be equal, nor contiguous, or consecutive, as an example only, the embodiment shown in FIG1 is configured so that downlink channels A, B, C, and D propagate in a first direction, e.g., clockwise, and channels E, F, G, and H propagate in the opposite direction. Similarly, the number of channels received at each DRU is specified by the DAU and need not be equal, contiguous, or consecutive, but rather will generally be any configuration that optimizes network utilization.

Next, referring to Figure 2, one embodiment of the uplink (UL) path according to the present invention can be better understood. Each DRU 125A to 125k converts the channel associated with each DRU received at the antenna into an optical signal. The optical signal received from the DRU is serialized and deframed by the DAU 105 and is also digitally up-converted using a digital-to-digital converter implemented within the DAU 105. In the illustrated embodiment, each data stream is then independently converted to the analog domain and up-converted to the appropriate RF frequency band within the DAU 105, although this function can be separate. The RF signal is then passed to an appropriate one of the multiple BTSs 110A to 110p. As with the arrangement shown in Figure 1, the propagation direction of each channel is controlled by the DAU, with some channels propagating in a clockwise direction and others propagating in a counterclockwise direction. Moreover, as discussed in conjunction with Figure 1, although adjacent channels are shown in Figure 2 as propagating in the same direction, this is not required and any channel can be selected to propagate in any direction.

Referring again to Figure 1, those skilled in the art will appreciate that in some implementations of the DAS, there may be more than one carrier on each channel, whereby a DRU may receive a channel that includes signals comprising two or more carriers, or a wireless operator may have more than one RF carrier on each channel assigned to a single base station. This is referred to as a "composite signal." The manner in which the present invention manages composite downlink signals may be better understood with reference to Figure 1. In such a case, a DAU may receive a composite downlink input signal 130 from, for example, a first base station 110A belonging to a wireless operator, which enters the DAU 105 at RF input port 120A. Composite signal 130 includes carriers A through D. A second composite downlink input signal from, for example, a p-th base station 110p belonging to the same wireless operator enters the DAU1 at DAU1 RF input port 120n. Composite signal 135 includes carriers E through H. The functions of the DAU 105 and DRUs 125A through 125K, respectively, are explained in detail in U.S. Provisional Application No. 61/374,593, filed on August 17, 2010, entitled “Neutral Host Architecture for a Distributed Antenna System,” which is incorporated by reference into this application and attached hereto as Appendix B.

One optical output of DAU 105 is fed to DRU 125A via bidirectional optical cable 140A. A second optical output of DAU 105 is fed to DRU 3 via bidirectional optical cable 145A. Similarly, bidirectional optical cables 150, 155, and 160 connect DRUs 125A to 125n in a ring configuration, such that DRU 125A is connected to DRU 125B via optical cable 150A, DRU 125B is connected to DRU 125n via optical cable 150B, and DRU 125k is connected to DRU 125C or the k-1th DRU via optical cable 150m. This connection facilitates networking of DAUs 105, meaning that all carriers A to H can be used within DAU 105 to transmit data to DRUs 125A to 125k, depending on the software settings within the networked DAU system. Depending on the embodiment, software settings within DRU 125A are configured manually or automatically so that carriers A through H are present in downlink output signal 155A at the antenna port of DRU 125A. The presence of all eight carriers means that DRU 125A can potentially access the full capacity of the two base stations feeding DAU 105. One possible application for DRU 125A is in a cafeteria within a corporate building where a large number of wireless users gather during lunch hours.

DRU 125B is fed by DRU 125A's second optical port via bidirectional fiber optic cable 150A. Fiber optic cable 150A daisy-chains DRU 125A and DRU 125B. As with DRU 125A, software settings within DRU 125B are manually or automatically configured so that carriers A, C, D, and F are present in the downlink output signal 155B at DRU 125B's antenna port. DRU 125B's capacity is set significantly lower than that of DRU 125A through its specific channel settings, controlled by DAU 105. A single digital remote unit integrates frequency-selective DUCs and DDCs with per-carrier gain control. The DAU can remotely turn individual carriers on or off via gain control parameters.

In a manner similar to that described above for DRU 125A, software settings within DRU 125C are manually or automatically configured so that carriers B and F are present in the downlink output signal 155C at the antenna port of DRU 125C. Compared to the downlink signal 155B at the antenna port of DRU 125B, the capacity of DRU 125C, also configured via its software settings, is much smaller than the capacity of DRU 125B. DRU 125n is fed by optical cable 150m connected to the second optical port of the (n-1)th DRU (denoted as DRU 125C in FIG1 for simplicity). Software settings within DRU 125n are manually or automatically configured so that carriers A, D, E, and H are present in the downlink output signal 155D at the antenna port of DRU 125n. Typically, the capacity of DRU 125n is set to a value significantly smaller than that of DRU 125A. However, the relative capacity settings of each of DRUs 125A through 125n can be dynamically adjusted to meet capacity requirements within the coverage area determined by the physical location of the antennas connected to those DRUs. As mentioned above, a ring connection is achieved by interconnecting DRU 125B and DRU 125n via fiber optic cable 150B. The ring configuration ensures that any fiber optic cable break will not shut down the daisy-chain network. Downlink and uplink signals will be rerouted to their respective DRUs around the cable break.

The present invention facilitates the conversion and transmission of a number of discrete, relatively narrow RF bandwidths. This approach enables the conversion of only those specific, relatively narrow bandwidths that carry useful or specific information. This approach also enables neutral host applications to more efficiently use available fiber transmission bandwidth and enables the transmission of more frequency bands from various operators on the fiber. As disclosed in U.S. Provisional Application No. 61/374,593, filed on August 17, 2010, entitled "Neutral Host Architecture for a Distributed Antenna System," and U.S. Provisional Application No. 61/382,836, filed on September 14, 2010, entitled "Remotely Reconfigurable Distributed Antenna System and Methods" (both applications are assigned to the assignee of the present invention), and with reference also to FIG. 1 of the present patent application, as a result of a command from the NOC, a digital upconverter located within a DRU can be dynamically reconfigured to transmit any specific one or more narrow frequency bands, RF carriers, or RF channels available at the respective RF input ports of any DAU from the DAU input to any specific DRU output. Figure 1 illustrates this capability, where only specific frequency bands or RF carriers appear at the output of a given DRU. More specifically, via instructions received from the NOC, the FPGA within the DAU and one or more associated DRUs can be reprogrammed or reconfigured to convert or transmit only the desired narrow bandwidth.

A related capability of the present invention is that not only can the digital up-converter within each DRU be configured to pass any specific narrowband from the DAU input to any specific DRU output, but the digital up-converter within each DRU can also be configured to pass any specific time slot or timeslots of each carrier from the DAU input to any specific DRU output. The carriers and timeslots are monitored by the DAU by filtering the signal and performing power detection on each timeslot (information that can be transmitted to the NOC as desired). The DAU or the field programmable gate array (FPGA) within the DAU can then be dynamically reconfigured in a manner similar to software programmability by commands received from the NOC. The DAU detects which carriers and corresponding timeslots are active. This information is relayed to each DRU via the management control and monitoring protocol software. The DRU then uses this information to turn off and on each carrier and their corresponding timeslots as appropriate.

Data transfer between base stations and users is typically asymmetric, whereby the downlink data rate is higher than the uplink rate.A ring network configuration of daisy-chained DRUs can exploit this data rate asymmetry to maximize data transfer over optical fibers 150A to 150m.

The present invention balances bidirectional data rates on optical fibers to increase the maximum achievable data rate on the DRU ring network. Each downlink channel is transmitted unidirectionally along the ring network. Referring to Figure 1, downlink channels A, B, C, and D are transmitted in a clockwise direction around the ring of DRUs 125A to 125K. On the other hand, downlink channels E, F, G, and H are transmitted in a counterclockwise direction around the DRU ring. Referring to Figure 2, uplink channels J, K, L, and M are transmitted in a counterclockwise direction around the DRU ring, while the uplink channels are transmitted in a clockwise direction. If the downlink and uplink data rates were the same, there would be no advantage in this transmission mechanism. However, if data transmission is asymmetric between the downlink and uplink data rates, significant advantages can be achieved. For example, a two-fold difference between the downlink and uplink data rates can achieve a 4/3-fold increase in data transmission. The greater the asymmetry between the downlink and uplink data rates, the greater the increase in data transmission when using a unidirectional channel transmission mechanism around the ring.

Referring again to FIG. 1 , another embodiment according to another aspect of the present invention may be better understood. If there is a significant variation in the asymmetry between the downlink data rate and the uplink data rate and/or if there is a variation in the channel complement at the BTS, a management control module typically included within each DAU (discussed herein in conjunction with FIG. 7 ) can automatically and adaptively reallocate data transmission resources in a clockwise direction of the ring and in a counterclockwise direction of the ring to maximize overall transmission capacity. As previously discussed, the greater the asymmetry between the uplink data rate and the downlink data rate of a particular DAU, the greater the increase in data transmission when using a unidirectional channel transmission mechanism around the ring. If there is more than one DAU, in one embodiment, the NOC designates one DAU as the master DAU, and the management control module located within the master DAU makes the decision to optimize overall transmission capacity. If the master DAU fails, the NOC may designate another DAU as the master DAU. Alternatively, any suitable fault recovery algorithm may be implemented.

An alternative embodiment of the present invention can be better understood with reference to FIG3 , in which a single DAU controls multiple rings, each ring comprising multiple daisy-chained DRUs. In FIG3 , two daisy-chained rings, designated 300 and 305, are shown, although the number of rings may be larger and is primarily determined by design preferences up to the limits imposed by network performance. The two rings each link multiple DRUs 310A to 310n and DRUs 315A to 315m to a single DAU 320. The directional flow of data transmission is shown as dashed lines 325 and dotted lines 330. The downlink channels available from the multiple DRUs are divided into two subsets that flow in opposite directions around the two daisy-chained rings. The uplink channels are transmitted in a similar manner. The channels are grouped into two subsets to maximize data transmission to and from the DRUs. The DAUs communicate with one or more BTSs in turn via RF ports 335A to 335p.

A heuristic algorithm can be used to allocate RF channel data in a dual-ring DAS. Referring to Figure 3, there are two fiber rings R1 and R2 (clockwise and counterclockwise) and a set T (including uplink and downlink) of n≥2 independent RF channels Ki (1≤i≤n). Channel Ki requires bandwidth b(Ki) to transmit on the fiber ring. There are finite-time algorithms for obtaining a schedule with optimal bandwidth allocation (i.e., the maximum cumulative bandwidth of each ring is as small as possible). A large number of advanced heuristic algorithms have been developed to solve such scheduling optimization problems. Some examples include genetic algorithms, evolutionary algorithms, greedy search, tabu search, harmony search, simulated annealing, and ant colony optimization. Although the number of rings is not limited to two, for simplicity and clarity, this article describes a simple heuristic algorithm for two rings.

The algorithm starts by sorting the channels Ki in descending order of bandwidth b(Ki). Then, the channels are scheduled in such a way that each channel is assigned to the ring with the smallest cumulative bandwidth. The formal description of the algorithm is as follows.

Input: T = a set of n independent channels Ki with required bandwidth b(Ki), where 1≤i≤n.

Output: L ₁ , L ₂ and D ₁ , D ₂ . Lj is the set of channel schedules on the ring Rj, and _Dj is the maximum cumulative bandwidth of the ring Rj, Dj = (∑b(J), b(Ki), 1≤j≤2.

Algorithm (T, L, D)

Step 1 (initialize Ki and D ₁ , D ₂ ) Sort Ki so that b(Ki)≤b(Ki ₊₁ ), 1≤i≤n-1. _{D 1} ←0, D ₂ ←0.

Step 2 (Scheduling Channel)

For i=1 to n, step 1 do

If D ₁ ≤ _{D 2} , then [assign Ki to L ₁ , D ₁ ← D ₁ + b(Ki)].

else [assign Ki to L ₂ , D ₂ ←D ₂ +b(Ki)].

Referring next to FIG4 , yet another alternative embodiment of the present invention can be understood. The arrangement shown in FIG1 includes downlink signals from two separate base stations belonging to the same wireless carrier entering DAU 105 at input ports 110A and 110p, respectively. In the embodiment of FIG4 , a first composite signal enters first DAU 400 at its RF input port from base station 405, and a second composite downlink input signal, for example from a second base station 410 belonging to a different wireless carrier, enters second DAU 415 at its RF input port. DAU 400 directly supports two rings 420 and 425, DAU 415 directly supports two rings 430 and 435, and ring 440 is shared between DAU 400 and DAU 405. As discussed in conjunction with FIG1 , each of the aforementioned rings includes daisy-chained DRUs, generally designated 445, connected via, for example, fiber optic links. It should be noted that channel A is transmitted in the opposite direction to channel B. The downlink channels in subset A are transmitted in a counterclockwise direction around each ring, while the channels in subset B are transmitted in a clockwise direction around each ring. In this embodiment, because DAU 400 and DAU 405 are daisy-chained via fiber optic cable 440, signals belonging to both the first operator and the second operator are converted and transmitted to DRU 445 on ring 440. This embodiment provides an example of a neutral host wireless system in which multiple wireless operators share a common infrastructure including DAU 400, DAU 415, and DRU 445. All of the features and advantages mentioned above benefit each of the two wireless operators. It should also be understood that although Figure 4 shows only two DAUs connected in a daisy-chain fashion, more DAUs can be daisy-chained and the daisy-chained DAUs can be configured in a ring configuration in a manner similar to how the DRUs are connected. This arrangement is illustrated below in Figure 8.

As disclosed in U.S. Provisional Application No. 61/374,593, filed on August 17, 2010, entitled "Neutral Host Architecture for a Distributed Antenna System," and again with reference to FIG. 1 of the present patent application, the digital upconverters present in the DRUs of the present invention can be programmed to handle a variety of signal formats and modulation types, including FDMA, CDMA, TDMA, and OFDMA. Furthermore, the digital upconverters present in the respective DRUs can be programmed to operate on signals to be transmitted within various frequency bands subject to the capabilities and limitations of the system architecture disclosed in the aforementioned U.S. Provisional Application No. 61/374,593. In one embodiment of the present invention, where a wideband CDMA signal is present within a bandwidth corresponding to, for example, a first carrier at the input port to DAU 105, the signal transmitted at the antenna ports of DRUs 125A, 125B, and DRU k will be a wideband CDMA signal that is substantially identical to the signal present within the bandwidth corresponding to the first carrier at the input port to DAU 105.

As disclosed in U.S. Provisional Application No. 61/374,593, referenced again above, and also with reference to FIG. 1 of the present patent application, it will be understood that the digital upconverters present in the respective DRUs can be programmed to transmit any desired composite signal format to each respective DRU antenna port. For example, the digital upconverters present in DRU 125A and DRU 125B can be dynamically software reconfigured as previously described so that the signal presented at the antenna port of DRU 125A can correspond to the spectrum distribution shown at 155A in FIG. 1 and the signal presented at the antenna port of DRU 125B can correspond to the spectrum distribution shown at 155B in FIG. 1. An application for such dynamic rearrangement of DRU capacity can be, for example, if a company meeting is unexpectedly convened within the area of the enterprise corresponding to the coverage area of DRU 125B.

Referring again to FIG. 2 , another embodiment of the distributed antenna system of the present invention can be better understood. As disclosed in the aforementioned U.S. Provisional Application No. 61/374,593 and also shown in FIG. 2 , an optical ring transmission mechanism can be implemented for uplink signals. As previously discussed with respect to downlink signals and with reference to FIG. 1 , the uplink system shown in FIG. 2 primarily includes a DAU 105 and DRUs 125A through 125K. The operation of the uplink system shown in FIG. 2 can be understood as follows, similar to the downlink operation explained with reference to FIG. 1 .

As previously described, the digital down converters present in each of the DRUs 125A to 125k can be dynamically software reconfigured to select an uplink signal of the appropriate desired signal format presented at the receive antenna port of the respective DRU 125A-125k based on the desired uplink frequency band, so that the uplink signal is processed and filtered, converted, and transmitted to the appropriate uplink output port of the DAU 105. The DAU and DRU use the Common Public Interface standard (CPRI) to frame each data packet corresponding to their respective radio signatures. Other interface standards are applicable as long as they uniquely identify the data packet by the respective DRU. Header information is transmitted along with the data packet identifying the DRU and DAU corresponding to each data packet.

In one example embodiment shown in FIG2 , DRUs 125A and 125C are both configured to receive uplink signals within the channel K bandwidth, while DRUs 125B and 125n are both configured to reject uplink signals within the channel K bandwidth. When DRU 125C receives a sufficiently strong signal within the channel K bandwidth at its receive antenna port to be properly filtered and processed, the digital down-converter within DRU 125C facilitates processing and conversion. Similarly, when DRU 125A receives a sufficiently strong signal within the channel K bandwidth at its receive antenna port to be properly filtered and processed, the digital down-converter within DRU 125A facilitates processing and conversion. The signal from DRU 125A and the signal from DRU 125C are combined based on an active signal combining algorithm, and the combined signal is fed to a base station connected to the uplink output port of DAU 105. The term "simulcast" is often used to describe the operation of DRU 125A and DRU 125C for uplink and downlink signals within the bandwidth of channel K. The term "flexible simulcast" refers to the fact that the present invention supports dynamic and/or manual rearrangement of the specific DRUs involved in the signal combining process for each channel bandwidth.

Still referring to Figure 2, the digital down-converter present in DRU 125A is configured to receive and process signals within the bandwidths of channels J to Q. The digital down-converter present in DRU 125B is configured to receive and process signals within the bandwidths of channels J, L, M, and O. The digital down-converter present in DRU 125C is configured to receive and process signals within the bandwidths of channels K and O. The digital down-converter present in DRU 125n is configured to receive and process signals within the bandwidths of channels J, M, N, and Q. The individual high-speed digital signals resulting from the processing performed in each of the four DRUs are routed to the DAUs. As previously described, the uplink signals from the four DRUs are combined in the respective DAUs corresponding to each base station.

In summary, the reconfigurable distributed antenna system of the present invention described herein effectively saves resources and reduces costs. Because the algorithm can be adjusted at any time like software in a digital processor, the reconfigurable system is adaptive or manually programmable in the field.

Next, with reference to Figure 5, an alternative embodiment of the present invention may be better understood. Each DRU has a coverage radius that can be adjusted based on the power transmission from a particular remote unit. The DAU controls the transmission power of the various DRUs and can optimize the overall coverage area. In the illustrated embodiment, a DAU 502 is associated with a base station 501 and in turn interfaces with three DRUs 503, 504, and 505, again under the control of a NOC (not shown). Relatively uniform coverage is provided for a user 506 with a mobile device throughout the area covered by the three DRUs.

Referring next to Figure 6, yet another alternative embodiment may be better understood. Input frequency bands 605 to 630 (here represented as six frequency bands at 700, 800, 850, 1900, 2100, and 2600 MHz) are input from a BTS (not shown) to a DAU 600. In addition to the other functions discussed herein, the DAU includes a radio frequency IN section for each frequency band, and a digital distribution matrix for allocating the frequency bands to a plurality of DRUs daisy-chained along three independent rings 635, 640, and 645, designated DRU1 to DRU60, for achieving the desired coverage. The frequency bands are delivered to all or a subset of the DRUs. The specific number of frequency bands, DAUs, DRUs, and rings is merely exemplary and may in practice be any number suitable for the performance capabilities and requirements of the network.

Referring next to Figure 7, the software embedded in the DAU and DRU that controls the operation of the key functions of these devices can be better understood. Specifically, the DAU embedded software control module 700 includes a DAU management control module 705 and a DAU monitoring module 710. The DAU management control module 705 communicates with the NOC 715 and also communicates with the DAU monitoring module 710. One such key function is to determine and/or set the appropriate amount of radio resources (such as RF carriers, CDMA codes, or TDMA time slots) allocated to a particular DRU or group of DRUs to meet the desired capacity and throughput targets. As previously mentioned, in at least some embodiments, the NOC 715 monitors the operation of the DAS and sends instructions to the DAU for configuring various functions of the DRU and DAU.

Among other functions, the DAU monitoring module detects which carriers and corresponding time slots are active for each DRU. The DAU management control module communicates with the DRU embedded software control module 720 via a control protocol over the fiber link control channel. In one embodiment, the control protocol includes a header as well as a data packet so that both control information and data are transmitted together as a message to the DRU. The DRU functions or features that the header can control in the DRU are generally implementation specific and may include, among other things, measuring uplink and downlink power, measuring uplink and downlink gain, and monitoring alarms in the DRU.

In turn, the DRU management control module 725 within the DRU embedded software control module sets various parameters of all DRU digital up-converters 730 to enable or disable transmission of specific radio resources by a specific DRU or DRU group, and also sets various parameters of all DRU digital down-converters 735 to enable or disable transmission of specific radio resources by a specific DRU or DRU group. In addition, the DRU embedded software control module includes a DRU pseudo-pilot control module 740 that communicates with the DRU pseudo-pilot 745.

Next, referring to FIG8 , an embodiment of a daisy-chain configuration of DAUs is shown along with a daisy-chain configuration of DRUs. In one embodiment, each of a plurality of base stations 800A to 800n is associated with each of DAUs 805A to 805n. The DAUs are daisy-chained, and each DAU communicates with one or more daisy chains 810A to 810m of DRUs that may or may not be arranged in a ring configuration. It should be understood that the DAUs can also be configured in a ring configuration as described above.

An algorithm operating within the DAU monitoring module that detects which carriers and corresponding time slots for each carrier are active for each DRU provides information to the DAU management control module to help identify, for example, when a particular downlink carrier is loaded at a percentage above a predetermined threshold (the value of which is communicated to the DAU management control module via the DAU's remote monitoring and control function 715). If this occurs, the DAU management control module can adaptively modify the system configuration to begin (usually but not necessarily slowly) deploying additional radio resources (such as RF carriers, CDMA codes, or TDMA time slots) for use by specific DRUs within its coverage area that require those additional radio resources. At the same time, the DAU management control module typically adaptively modifies the system configuration to begin (usually still slowly) removing specific radio resources (such as RF carriers, CDMA codes, or TDMA time slots) for use by specific DRUs within its coverage area that no longer require those specific radio resources.

Although the present invention has been described with reference to preferred embodiments, it should be understood that the invention is not limited to the details described herein. Various substitutions and modifications have been suggested in the foregoing description, and other substitutions and modifications are also conceivable to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be included within the scope of the present invention as defined by the appended claims.

Inventive concept

The present invention provides the following inventive concepts:

A method for routing and switching carrier RF signals, comprising:

providing one or more remote radio units, each remote radio unit being configured to receive one or more downlink radio frequencies and to transmit one or more uplink radio frequencies,

providing at least one digital access unit configured to communicate with at least some of the remote radio units,

linking the one or more remote radio units and the at least one digital access unit in a ring configuration whereby each remote radio unit can be accessed in either direction around the ring, and

Packetized signals are routed and switched between the one or more radio units and the at least one digital access unit.

Claims (7)

1. A method for communication in a distributed antenna system, the method comprising: Provides multiple digital remote units; Provide at least one digital access unit configured to communicate with the plurality of digital remote units, the at least one digital access unit being configured to send a plurality of downlink channels to the plurality of digital remote units; Transmitting a first portion of the plurality of downlink channels from the at least one digital access unit to a first digital remote unit among the plurality of digital remote units; and The second portion of the plurality of downlink channels is transmitted from the at least one digital access unit to the second digital remote unit among the plurality of digital remote units, wherein at least some of the channels in the first portion of the plurality of downlink channels are different from the channels in the second portion of the plurality of downlink channels. 2. The method of claim 1, wherein the first digital remote unit is configured to transmit a first portion of the plurality of downlink channels received from the at least one digital access unit and a corresponding first portion of the uplink channels. 3. The method of claim 1, wherein the plurality of digital remote units and the at least one digital access unit are arranged in a daisy chain such that each digital remote unit is linked to the next digital remote unit or the at least one digital access unit via a single bidirectional optical fiber, and each digital remote unit can be accessed by the at least one digital access unit in any direction around the ring. 4. The method of claim 1, wherein the at least one digital access unit comprises a plurality of digital access units, each interconnected with at least one of the plurality of digital access units. 5. The method of claim 1, wherein the number of the first portions of the plurality of downlink channels is less than the number of the plurality of downlink channels. 6. The method of claim 1, wherein at least some of the channels in the first portion of the plurality of downlink channels are the same as the channels in the second portion of the plurality of downlink channels. 7. The method of claim 1, wherein the at least one digital access unit is configured to receive the plurality of downlink channels from at least one base station.