Abstract:
A distributed-antenna system is disclosed. The system has a least one leaky feeder, a plurality of RF signal sources, at least one data router providing IP addressing and data control to the RF signal sources (which may be data-controlled radios), and a plurality of RF filters connected between the respective RF signal sources and the leaky feeder and connecting the respective RF signal sources to the leaky feeder. The RF signal sources are distributed along the leaky feeder to optimize both spectrum use and coverage of predetermined areas in, for example, office or apartment buildings.

Description:
CLAIM FOR PRIORITY 
       [0001]    This application claims the priority of U.S. Provisional Patent Application, Ser. No. 62/142539, and filing date Apr. 3, 2015, which application is incorporated in its entirety by reference into the present application. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    This disclosure concerns the implementation of distributed-antenna systems providing multiple services, such as cellular telephone voice and data, Wi-Fi, broadband internet service, low-power TV and others. 
         [0004]    2. Background 
         [0005]    The wireless local area network (WLAN) market is rapidly growing, and the variety of hotspots targeted for implementation is considerable. A “hotspot” is a physical location that offers Internet access over a WLAN through the use of a router connected to a link to an Internet service provider. Hotspots typically use Wi-Fi technology. Many of the hotspots targeted are large and achieving good coverage may be challenging. The current standard for providing coverage is to distribute individual WLAN access points (APs) in the target area. The number of APs needed by using this method may become significant. For example, up to 5000 APs can be required to provide coverage in a facility such as an airport. Today, it is estimated that 80% percent of all mobile voice and data connections occur indoor, so the problem of providing connection to WLAN and other services is only growing. 
         [0006]    A distributed-antenna system (DAS) is the infrastructure used to distribute radio signals from one or more radio base stations and radio access points to any number of antennas located throughout the wanted coverage area. The coverage area may be covered by one or more cells, where each cell is typically served by any number of antennas multi-casting the same signal. 
         [0007]    The DAS is the most effective and most flexible method to provide coverage inside a building. A DAS allows better control of the service area borders of the in-building system. At the same time, it provides high-quality coverage and low interference compared with using base stations and access points with integrated antennas. In addition, the DAS provides better radio trunking efficiency by allowing larger portions of the building to be served by a single cell or access point. This makes the frequency planning easier since fewer channels are needed to support the in-building traffic, which results in higher capacity with less interference. 
         [0008]    An array of antennas distributed via a coaxial feeder network (passive DAS) is currently the most popular antenna configuration for cellular in-building solutions. The typical passive DAS comprises antennas, regenerators, power splitters and tappers, feeder cables, connectors and jumper cables. The disadvantage of a coaxial distributed-antenna network is that in a typical network, the coaxial cabling uses between 20 and 30 dB of the link budget. This results in the need of relatively high power at the base station antenna connector and the resulting high cost of the power amplifier. The possibly large cable loss puts also a limit to the WLAN deployment. 
         [0009]    Radiating cable is an alternative to distributed-antennas in many applications, such as large apartment or office buildings or tunnels. A radiating cable (also called “leaky cable,” or “leaky feeder” in this disclosure) is a modified coaxial cable with slots in the outer conductor, which allows a controlled part of the RF signal to leak out of the cable, and also allows external RF signals to be coupled into the cable. In this disclosure, the terms “radiating cable”, “leaky cable”, or “leaky feeder” can also refer to any RF transmission medium now known or hereafter developed that is capable of efficiently radiating and receiving RF radiation with a coupling loss less than about 80 dB. Thus, the cable works as a continuous antenna and can be placed everywhere coverage is needed. Current distributed-antenna systems, with or without radiating cable, do not satisfactorily address problems of multi-band operations (e.g., cellular voice and data, Wi-Fi, HD TV, low-power TV, and public safety radio, among others) on the same antenna, problems with optimizing signal power in different bands, difficulties with filtering, and implementation of data networks that could allow individual subscriber access to speed control. 
         [0010]    What is needed is a system that solves the problem of RF indoor coverage in a broad range of frequencies with the same distributed-antenna system. The solution should optimize both spectrum use and coverage of closed environments such as offices or apartment buildings. A desirable such system should comprise modules that can be pre-assembled and configured on-site to speed installation time and lower costs. The leaky cable of such a distributed-antenna system can be installed during new building construction, and data-controlled RF injection modules can be configured and installed as required, including accepting updates as new technologies offering new services evolve and thus “future proofed.” 
     
    
     
       DRAWINGS 
         [0011]    Non-limiting embodiments of the present disclosure are described by way of example in the accompanying drawings, which are schematic and are not intended to be drawn to scale. 
           [0012]      FIG. 1  is a schematic connection diagram showing basic elements contributing to an embodiment of the claimed distributed-antenna system 
           [0013]      FIG. 2  is a schematic connection diagram showing an example module of an embodiment of the claimed distributed-antenna system. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  shows a simplified connection schematic of an embodiment of the distributed-antenna system  100 . Firstly, an RF telecom signal source comprising a bi-directional amplifier (BDA)  110  is shown connected to an external antenna  115  to receive signals from remote cellular-radio transmissions. The output of the BDA  110  is coupled through appropriate RF filters  120  to the leaky cable  130  of the system, preferably at the head end  135  of the leaky cable  130 . The BDA  110  of course receives signals from the leaky cable  130  and re-transmits such signals to the external cellular-radio antenna  115 . In each case of a connection to the leaky cable  130 , such connection is made through a representative RF combiner  125 , as depicted in the figures. In the art, a BDA  110  may be referred to as a “repeater.” In practice, cellular telecom services in the range of 700 MHz to 2170 MHz could be injected by the BDA  110  into the leaky cable  130 , with the signal power levels of such signals adjusted to be radiated throughout the leaky cable  130  until its termination. 
         [0015]    The reader should understand that a BDA  110  may operate with signals in other bands than the cellular telecom region to connect those signals to the leaky feeder, and this disclosure is not limited to a BDA  110  operating in the cellular telecom region, but may include operation at frequencies between about 100 MHz and about 6 GHz, for example, US public-safety frequencies in the 700-800 MHz band. 
         [0016]    The presence or absence of such an RF telecom signal source (or other similar signal source) comprising a BDA  110  in the distributed-antenna system  100  is optional, depending on the needs of a particular installation, but the feature illustrates the flexibility of the claimed distributed-antenna system  100 . 
         [0017]      FIG. 1  also shows data-controlled radio modules  140  connected to the leaky cable  130 . (The details of the modules  140  are described further in the discussion below and in  FIG. 2 .) In this application, a “data-controlled radio” is a wireless radio, with features selectable by data inputs from an Ethernet connection. A data-controlled radio will have an Internet-Protocol (IP) address, and typically support power-over-Ethernet (POE). Thus data input to such a radio may modulate RF for further transmission, or demodulate RF for conversion to data signals, as well as provide control of the radio features and capabilities. A typical application would be transmitting and receiving RF using wireless protocols in the 2.4 GHz (Wi-Fi) and 5.8 GHz (wireless broadband) frequencies. 
         [0018]      FIG. 1  shows a data source  150  connected through data lines  175  to a core router  160 , which core router  160  is further connected through a data switch  170  and a POE injector  180 . Although shown as a separate POE injector  180  in  FIG. 1 , the POE capability may be provided by a POE-enabled data switch, such as the data switch  170 . 
         [0019]      FIG. 1  also shows an optional IP-addressed power rebooter device  185  connected to the core router  160 , which power rebooter device  185  has the capability to selectively re-boot AC power to any device connected to it as determined by data received at its IP address. 
         [0020]    The switched data flow is connected through the data line  175  to one or more modules  140 , which modules  140  may be daisy-chained together as shown, where a module  140  has an input  190  for data and POE, and an output  200  for data and POE. The data line  175  may be wire line or optical fiber, and preferably includes features supporting POE to power the daisy-chained modules  140 . Further, each module  140  has an RF output connection  210  to the leaky cable  130  of the distributed-antenna system  100 . Preferably, an uninterruptable power supply (UPS)  220  powers the data components. 
         [0021]    The data source  150  comprises both data for control of the operation of the modules  140 , as well as a data comprising digitized signals for conversion to RF and transmission on the leaky cable  130 . Non-limiting examples of services that may be so provided are described in the table below. RF signals are injected into the leaky cable  130  at pre-determined intervals from the modules  140  as shown in  FIG. 1 , and as discussed in more detail below with reference to  FIG. 2 . 
         [0022]      FIG. 2  illustrates a representative data-controlled radio module  140 . The module depicted has a data input  190 , a data output  200  (both input and output possibly being POE-enabled) connected to a module data switch  230 . ( FIG. 2  also shows how an optional second data switch  235  or switches may be further connected to the module data switch  230 , where hard-wired Ethernet connectivity is desired and available.) The module data switch  230  is connected to and controls one or more data-controlled radios  240 , shown in the figure, by example only, as operating at 2.4 GHz and 5.8 GHz. Each data-controlled radio  240  is further connected through RF filters  250  to a combiner  125 , and thereafter, through the module RF output  210  to the leaky cable  130  of the distributed-antenna system  100 .  FIG. 2  shows that one or more of the data-controlled radios  240  may have an optional auxiliary RF input  245 , from coaxial cable, for example. 
         [0023]    As shown in  FIG. 2  by example, 2.4 GHz Wi-Fi signals from the data-controlled radios  240  disposed in the modules  140  may be injected at approximately  100  meter intervals along the leaky cable  130  through RF filters  250  appropriate to the band of interest. The 2.4 GHz signal power levels should be set to radiate approximately 50 meters in both directions from each filtered data-controlled radio  240 . The 2.4 GHz channels  3  and  9  in this example are alternated along the leaky cable  130  to get maximum capacity and minimum interference between access points. Suitable signal sources and RF filters are available on the market and described in more detail below. 
         [0024]    In a further refinement, as shown in the description of the modules  140  and in  FIG. 2 , the RF signal sources  240  may also be 5.8 GHz broadband-internet data-controlled radios, having 20-40 MHz modulation, bandwidth-separated 10 MHz between adjacent 5.8 GHz access points. (In this disclosure, an “RF signal source” refers to a data-controlled radio, as described below, or a bi-directional amplifier, as the context requires). This embodiment demonstrates the spectrum efficiency and interference reduction benefit of distributed signal sources compared to amplifying and repeating the same signal from the head to the end of the leaky cable  130 , using, for example, regeneration of signals. 
         [0025]    The reader should note that the number of components of the claimed system is not limited to those shown in the drawings, and practical systems, may, for example, have more than one BDA  110 , or data source  150 , or, particularly, more than one module  140 . Further, each module  140  may have more than two data-controlled radios  240 , and this disclosure is not limited to the example shown in  FIG. 2 . 
         [0026]    A suitable BDA  110  for many embodiments would be the model CM 5000, manufactured by SureCall of Fremont, Calif. A suitable core router  160  would be the model RB2011UiAS, manufactured by MikroTik SIA of Riga, Latvia. A suitable data switch  230  would be the model ProCurve 2626, manufactured by Hewlett Packard of Palo Alto, Calif. In the data-controlled radio modules  140 , a suitable data-controlled radio  240  would be the model GrooveA 52HPn, manufactured by MikroTik SIA. Similar “small cell” data-controlled radios  240  offering IP data-to-RF translation include the model 3GE-16 manufactured by ip.access, Ltd. of Cambourne, Cambridge, United Kingdom and the model SCRN-310, manufactured by Spider Cloud Wireless of Milpitas, Calif. The reader should recognize that these particular enabling components are not necessarily required for implementation, and their mention here does not limit the scope of the claims. 
         [0027]    The BDA (if present) and the core router  160 , switch  170 , and data-related components just described may be conveniently located in a physical head-end rack (not shown) at the building or facility where the distributed-antenna system  100  is deployed. 
         [0028]    The following table lists examples of services that may be provided in the embodiments described in this disclosure; however, the list is not exhaustive, and provision of other services, now known or later developed, may be also be implemented through the same system, whereby the system may be said to be “future proofed”:
       Cellular 700 MHz long-term evolution (LTE) data, 800 MHz voice, 1900 MHz personal communication service (PCS), 2100 MHz AWS services.   HD TV, low-power TV, 600-700 MHz high definition digital television local low power TV services.   Wi-Fi 2.4 GHz Internet access hotspot services.   Broadband Internet 5.8 GHz high speed Internet services.   FM radio, translators 88-108 MHz services.   Voice-over-IP (VOIP) 2.4 GHz telephone access services.   Public Safety 150, 450, 800 MHz portable radio services.   Two-Way radio 150, 450, 800 MHz repeater services.   Enhanced-911 (E911) GPS 1100, 1500 MHz global positioning services.       
 
         [0038]    The reader should note that the above described embodiments do not rely on signal regeneration, or the provision of regenerators along a distributed-antenna system. Rather, the embodiments described in this application comprise local signal source insertion devices (e.g., the data-controlled radio modules  140 ). 
         [0039]    None of the description in this application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope; the scope of patented subject matter is defined only by the allowed claims. Moreover, none of these claims are intended to invoke paragraph six of 35 U.S.C. Section 112 unless the exact words “means for” are used, followed by a gerund. The claims as filed are intended to be as comprehensive as possible, and no subject matter is intentionally relinquished, dedicated, or abandoned.