Patent Publication Number: US-RE47466-E

Title: Systems and methods for IP communication over a distributed antenna system transport

Description:
CROSS-REFERENCE TO RELATED CASES 
     This Reissue Application is a reissue of application Ser. No. 13/529,607, filed Jun. 21, 2012, which issued as U.S. Pat. No. 8,958,410. This application is continuation of U.S. application Ser. No. 12/555,912 filed on Sep. 9, 2009 and entitled “SYSTEMS AND METHODS FOR IP COMMUNICATION OVER A DISTRIBUTED ANTENNA SYSTEM TRANSPORT,” which, in turn, claims the benefit of U.S. Provisional Application No. 61/144,255 filed on Jan. 13, 2009 both of which are incorporated herein by reference in their entirety. 
     This application is related to U.S. Provisional Application No. 61/144,257 filed on Jan. 13, 2009 entitled “SYSTEMS AND METHODS FOR MOBILE PHONE LOCATION WITH DIGITAL DISTRIBUTED ANTENNA SYSTEMS,” and which is incorporated herein by reference in its entirety. 
     This application is related to U.S. patent application Ser. No. 12/555,923 filed on Sep. 9, 2009 entitled “SYSTEMS AND METHODS FOR MOBILE PHONE LOCATION WITH DIGITAL DISTRIBUTED ANTENNA SYSTEMS,” and which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     A Distributed Antenna System, or DAS, is a network of spatially separated antenna nodes connected to a common node via a transport medium that provides wireless service within a geographic area or structure. Common wireless communication system configurations employ a host unit as the common node, which is located at a centralized location (for example, at a facility that is controlled by a wireless service provider). The antenna nodes and related broadcasting and receiving equipment, located at a location that is remote from the host unit (for example, at a facility or site that is not controlled by the wireless service provider), are also referred to as “remote units.” Radio frequency (RF) signals are communicated between the host unit and one or more remote units. In such a DAS, the host unit is typically communicatively coupled to one or more base stations (for example, via wired connection or via wireless connection) which allow bidirectional communications between wireless subscriber units within the DAS service area and communication networks such as, but not limited to, cellular phone networks, the public switch telephone network (PSTN) and the Internet. A DAS can thus provide, by its nature, an infrastructure within a community that can scatter remote units across a geographic area thus providing wireless services across that area. 
     For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for systems and methods for facilitation of supplemental data communication over a distributed antenna system transport. 
    
    
     
       DRAWINGS 
       Embodiments of the present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which: 
         FIG. 1  is a block diagram of a distributed antenna system (DAS) of one embodiment of the present invention; 
         FIG. 2  is a block diagram of a remote unit of one embodiment of the present invention; 
         FIG. 3  is a block diagram of a host unit of one embodiment of the present invention; 
         FIG. 4  illustrates a superframe structure of one embodiment of the present invention; and 
         FIG. 5  illustrates a method of one embodiment of the present invention. 
     
    
    
     In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present invention. Reference characters denote like elements throughout figures and text. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. 
     Embodiments of the present invention provide point-to-point Ethernet connections (100 Base-T, for example) between elements of a distributed antenna system by adapting the digital radio frequency (RF) transport medium to further carry internet protocol data traffic simultaneously with the RF traffic. Embodiments of the present invention enable installation of internet protocol devices at remote locations (for example, to extend a Local Area Network (LAN)/IP network into remote areas, or establish various services at remote locations that benefit from having IP network connectivity). Internet protocol devices may thus include networking devices such as switches, routers, and wireless access points (for WiFi, WiMAX, LTE, for example) or cameras, sensors, audio and/or video devices for security, distributing announcements, warnings or advertising. In one embodiment, the Internet Protocol device is a mobile phone locator such as described in the &#39;1075 Application herein incorporated by reference. One of ordinary skill in the art after reading this specification would thus realize that such internet connectivity allows utilization of the remote facilities of a distributed antenna system to provide functions beyond that related to the principal RF functions of the system. 
       FIG. 1  is a block diagram of a distributed antenna system (DAS)  100  of one embodiment of the present invention. DAS  100  includes a host unit  102  and a plurality of remote units  106 . At the physical layer, host units  102  and remote units  106  are interconnected via fiber optic cable as indicated in  FIG. 1  to form a bidirectional communication link network comprising a plurality of point-to-point communication links shown at  130 . Optionally, host units  102  and remote units  106  may be interconnected via coaxial cable, or a combination of both coaxial cable and fiber optic cable. Further, host units  102  and remote units  106  may be interconnected via wireless technology such as, but not limited to, microwave and e-band communication. 
     Remote units  106  each house electronic devices and systems used for wirelessly transmitting and receiving modulated radio frequency (RF) communications via antenna  107  with one or more mobile subscriber units  108 . Host unit  102  is coupled to at least one base transceiver station (BTS)  110  often referred to as a base station. BTS  110  communicates voice and other data signals between the respective host unit  102  and a larger communication network via a gateway  124  coupled to a telephone system network  122  (for example, the public switched telephone network and/or wireless service provider networks) and an internet protocol (IP) network  124 , such as the Internet. In one embodiment, DAS  100  comprises part of a cellular telephone network and subscriber units  108  are cellular telephones. 
     Downlink RF signals are received from the BTS  110  at the host unit  102 , which the host unit  102  uses to generate one or more downlink transport signals for transmitting to one or more of the remote units  106 . Each such remote unit  106  receives at least one downlink transport signal and reconstructs the downlink RF signals from the downlink transport signal and causes the reconstructed downlink RF signals to be radiated from a remote antenna  107  coupled to or included in that remote unit  106 . A similar process is performed in the uplink direction. Uplink RF signals received at one or more remote units  106  from subscriber  108  are used to generate respective uplink transport signals that are transmitted from the respective remote units  106  to the host unit  102 . The host unit  102  receives and combines the uplink transport signals transmitted from the multiple remote units  106 . The host unit  102  communicates the combined uplink RF signals to the BTS  110  over a broadband medium. 
     DAS  100  comprises a digital DAS transport meaning that the downlink and uplink transport signals transmitted between host unit  102  and remote units  106  over communication links  130  are generated by digitizing the downlink and uplink RF signals, respectively. In other words, the downlink and uplink transport signals are not analog RF signals but instead are digital data signals representing digital RF samples of a modulated RF signal. For example, if a particular communication signal destined for transmission to subscriber unit  108  is a modulated RF signal in the 900 MHz band, then host unit  102  will generate baseband digital samples of the modulated 900 MHz RF signal from BTS  110 , which are then distributed by host unit  102  to the remote units  106 . Alternatively, an all-digital BTS may generate baseband digital samples directly. At the remote units, the digital samples of the modulated RF signal are converted from digital into an analog RF signal to be wirelessly radiated from the antennas  107 . In the uplink analog RF signals received at remote unit  106  are sampled to generate RF data samples for the uplink transport signals. BTS  110 , host unit  102  and remote units  106  each accommodate processing communication signals for multiple bands and multiple modulate schemes simultaneously. In addition to communicating the downlink and uplink transport RF signals, the digital transport between host unit  102  and each remote units  106  includes sufficient bandwidth (that is, in excess of what is necessary to transport the digitized RF data samples) to implement an Ethernet pipe (100 Base-T) between each remote unit  106  and the host unit  102  for facilitating supplemental Internet Protocol formatted data communications. In one embodiment, the Ethernet pipe provides a bandwidth of at least 100M bits/sec. 
     It is understood in the art that RF signals are often transported at intermediate frequencies (IF) or baseband. Therefore, within the context of this application, the terms “digital RF”, “digitized RF data”, “digital RF signal”, “digital RF samples”, “digitized RF samples” and “digitized RF signals” are understood to include signals converted to IF and baseband frequencies. 
       FIG. 2  is a block diagram of a remote unit  200  of one embodiment of the present invention such as the remote units  106  discussed with respect to  FIG. 1 . Remote unit  200  includes a serial radio frequency (SeRF) module  220 , a digital to analog radio frequency transceiver (DART) module  208 , a remote DART interface board (RDI)  224 , a linear power amplifier  210 , antenna  212 , a duplexer  211 , a low noise amplifier  214  and an Internet Protocol device (IPD)  216 . In one embodiment, SeRF modules and DART modules and Internet Protocol (IP) devices described herein are realized using discrete RF components, FPGAs, ASICs, digital signal processing (DSP) boards, or similar devices. 
     DART module  208  provides bi-directional conversion between analog RF signals and digital sampled RF for the downlink and uplink transport signals transmitted between host unit  102  and remote units  106 . In the uplink, DART module  208  receives an incoming analog RF signal from subscriber unit  108  and samples the analog RF signal to generate a digital data signal for use by SeRF module  220 . Antenna  212  receives the wireless RF signal from subscriber  108  which passes the RF signal to DART module  208  via low noise amplifier  214 . In the downlink direction DART module  208  receives digital sampled RF data from SeRF module  220 , up converts the sampled RF data to a broadcast frequency, and converts the digital RF samples to analog RF for wireless transmission. After a signal is converted to an analog RF signal by DART module  208 , the analog RF signal is sent to linear power amplifier  210  for broadcast via antenna  212 . Linear power amplifier  210  amplifies the RF signal received from DART module  208  for output through duplexer  211  to antenna  212 . Duplexer  211  provides duplexing of the signal which is necessary to connect transmit and receive signals to a common antenna  212 . In one embodiment, low noise amplifier  214  is integrated into duplexer  211 . One of ordinary skill in the art upon reading this specification would appreciate that DART modules may function to optionally convert the digital RF samples into intermediate frequency (IF) samples instead of, or in addition to, baseband digital samples. 
     DART modules in a remote unit are specific for a particular frequency band. A single DART module operates over a defined band regardless of the modulation technology being used. Thus frequency band adjustments in a remote unit can be made by replacing a DART module covering one frequency band with a DART module covering a different frequency band. For example, in one implementation DART module  208  is designed to transmit 850 MHz cellular transmissions. As another example, in another implementation DART module  208  transmits 1900 MHz PCS signals. Some of the other options for a DART module  208  include, but are not limited to, Nextel 800 band, Nextel 900 band, PCS full band, PCS half band, BRS, WiMax, Long Term Evolution (LTE), and the European GSM 900, GSM 1800, and UMTS 2100. By allowing different varieties of DART modules  208  to be plugged into RDI  224 , remote unit  200  is configurable to any of the above frequency bands and technologies as well as any new technologies or frequency bands that are developed. Also, a single remote unit may be configured to operate over multiple bands by possessing multiple DART modules. The present discussion applies to such multiple band remote units, even though the present examples focuses on a the operation of a single DART module for simplicity. 
     SeRF module  220  is coupled to RDI  224 . RDI  224  has a plurality of connectors each of which is configured to receive a pluggable DART module  208  and connect DART module  208  to SeRF module  220 . RDI  224  is a common interface that is configured to allow communication between SeRF module  220  and different varieties of DART modules  208 . In this embodiment, RDI  204  is a passive host backplane to which SeRF module  220  also connects. In another embodiment, instead of being a host backplane, RDI  224  is integrated with SeRF module  220 . When a remote unit operates over multiple bands by possessing multiple DART modules, RDI  224  provides separate connection interfaces allowing each DART module to communicate RF data samples with SeRF module  220 . Although  FIG. 2  illustrates a single SeRF module connected to a single RDI, embodiments of the present invention are not limited to such. In alternate embodiments, a SeRF module may connect to multiple RDIs, each of which can connect to multiple DARTS. For example, in one embodiment, a SeRF module can connect to up to 3 RDIs, each of which can connect to up to 2 DARTs. SeRF module  220  provides bi-directional conversion between a serial stream of RF, IF or baseband data samples (a SeRF stream) and a high speed optical serial data stream. In the uplink direction, SeRF module  220  receives an incoming SeRF stream from DART modules  208  and sends a serial optical data stream over communication links  130  to host unit  102 . In the downlink direction, SeRF module  220  receives an optical serial data stream from host unit  102  and provides a SeRF stream to DART modules  208 . 
     Remote unit  200  further includes an internet protocol device (IPD)  216 . IPD  216  is coupled to SeRF module  220  via an interface  222  that provides bidirectional access to a point-to-point Ethernet pipe established between remote unit  200  and the host unit  102  over the serial optical data stream. In one embodiment, interface  222  is a receptacle for a standard 8 Position 8 Contact (8P8C) modular plug and category 5/5e cable. 
     IPD  216  may include any device designed to network using an Ethernet connection. For example, IPD  216  may comprise a networking devices such a switch, router, and/or wireless access point (for WiFi or WiMAX, for example). In another implementation, IPD  216  is a data collection device such as a weather station collecting weather related data such as, but not limited to, temperature, relative humidity, wind speed and direction, precipitation, and the like. In still other implementations, IPD  216  may include any number of other data collection devices such as a surveillance camera, a motion, heat or vibration sensor or a subscriber unit locator. IPD  216  formats data it collects for transmission over an internet protocol (IP) connection and then outputs the data to the SeRF module  220  via interface  222  which in turn routes data over the Ethernet pipe to the host unit  102 . In another implementation, IPD  216  is a data distribution device for distributing announcements, warnings or advertising. As such, IPD  216  may comprise a public announcement load speaker, sirens, or liquid crystal diode (LCD) display. Further IPD may support two way interactive messaging, chat, tele/video conferencing applications, and the like. 
     Although  FIG. 2  (discussed above) illustrates a single DART module coupled to a SeRF module, a single remote unit housing may operate over multiple bands and thus include multiple DART modules. In one such embodiment, the systems illustrated in  FIG. 2  would simply be replicated once for each band. In one alternate embodiment, a SeRF module also allows multiple DART modules to operate in parallel to communicate high speed optical serial data streams over a communication link with the host unit. In one such embodiment a SeRF module actively multiplexes the signals from multiple DART modules (each DART module processing a different RF band) such that they are sent simultaneously over a single transport communication link. In one embodiment a SeRF module presents a clock signal to each DART module to which it is coupled to ensure synchronization. 
       FIG. 3  is a block diagram illustrating a host unit (shown generally at  300 ) of one embodiment of the present invention such as the host unit  102  discussed with respect to  FIG. 1 . Multiple remote units  306  are coupled to host unit  300 , as described with respect to  FIG. 1 , to form a digital DAS. Host unit  300  includes a host unit digital to analog radio frequency transceiver (DART) module  308  and a host unit serial radio frequency (SeRF) module  320 . SeRF module  320  provides bi-directional conversion between a serial stream of RF data samples (a SeRF stream) and the multiple high speed optical serial data streams to and from the remote units  306 . Each serial optical data stream includes a digital transport for communicating downlink and uplink transport RF signals as well as an Ethernet pipe between each remote unit  306  and host unit  300 . In the uplink direction, SeRF module  320  receives incoming serial optical data streams from a plurality of remote units and converts each into a serial stream of digitized baseband RF data samples, which are summed into a broadband stream of RF data samples. DART module  308  provides a bi-directional interface between SeRF module  320  and one or more base stations, such as BTS  110 . As with the remote units, when host unit  320  operates over multiple bands with multiple base stations, a separate DART module  308  is provided for each frequency band. In one embodiment, host unit  300  also maintains an Ethernet pipe with at least one base station (such as BTS  110 ) which provides access to at least one Internet gateway. 
     Host unit  300  further includes an Ethernet port interface  324  for coupling an Internet Protocol Device (IPD)  330  to SeRF module  320  via an Ethernet link  325 . Ethernet link  325  may include a local area network (LAN), wide area network (WAN) having at least one network switch for routing data between interface  324  and IPD  330 . Alternatively, IPD  330  may be an internet switch, router, or any of the IP devices discussed above with respect to IPD  216 . Ethernet port interface  324  provides access to the Ethernet Pipes established between host unit  300  and one or more of the multiple remote units  306 . In one embodiment, a single 8 Position 8 Contact (8P8C) modular plug Ethernet port interface  324  provides access for communication via a virtual Ethernet connection with each multiple remote unit&#39;s Ethernet port interface (such as interface  222 ). In an alternate embodiment, Ethernet port interface  324  provides multiple 8 Position 8 Contact (8P8C) modular plug connection points which each form a point-to-point virtual Ethernet connection with a specific one of the multiple remote units  306 . 
     Referring back to  FIG. 2 , it can be seen that for upstream communications, IP data received via interface  222  and digitized RF data from DART module  208  are both pushed into SeRF  220  which produces the uplink transport signal that is communicated to the host unit  120  via communication links  130 . In doing so, SeRF  220  performs multiplexing in the time domain to route both the IP data and the RF data into time slots within frames communicated to host unit  120 . In downstream communications, SeRF  220  de-multiplexes IP data and RF data from within frames received from host unit  120 . RF data is routed to the DART module  208  while IP data is routed to Ethernet interface  222 . In the host unit  300  illustrated in  FIG. 3 , the host unit SeRF  320  similarly multiplexes and de-multiplexes IP data and RF data (via communication links  130 ) to route IP data to and from interface  324  and RF data to and from the host unit DART  308 . 
       FIG. 4  illustrates one embodiment of a superframe  400 , which may be used for either upstream or downstream communications between remote units  106  and host unit  102  via communication links  130 . The particular superframe  400  shown comprises  12  frames (shown at  420 - 1  to  420 - 12 ) with each frame divided into  16  timeslots (shown generally at  410 ). One of ordinary skill in the art upon reading this specification would appreciate that this particular configuration of 12 frames of 16 timeslots is for illustrative purposes only and that embodiments of the present invention may be practiced with superframes having different numbers of frames and timeslots. 
     In the particular embodiment shown in  FIG. 4 , each RF data sample carried over the digital transport of the DAS utilizes 15 of 16 available bits within a single timeslot (shown generally at  412 , for example). In one embodiment, the SeRF module  220  mulitplexes IP data into the remaining bits of each time slot. That is, for each timeslot carrying RF data, SeRF fills the 16 th  bit with IP data. The SeRF module assembling superframe  400  thus utilizes the remaining overhead in each time slot to transport the IP data along with the RF data sample. In other embodiments, the ratio and/or number of bits used to carry an RF data sample verses the total number of available bits per timeslot may vary. For example, in an alternate embodiment, an RF data sample may utilize 17 of 18 available bits in a timeslot. The SeRF may then fill the 18 th  bit with IP data. In another alternate embodiment, an RF data sample may utilize 15 of 18 available bits in a timeslot. The SeRF may then fill one or all of the 16 th , 17 th , and/or 18 th  bits with IP data. 
     At the receiving end of the communication link, the SeRF module receiving superframe  400  accordingly separates the IP data from each timeslot to reassemble standard IP data packets. It is not necessary that every timeslot of every frame will carry RF data. In other words, in some implementations, some timeslot of superframe  400  will not be utilized to carry RF data. This may occur where the bandwidth capacity of a particular communication link exceeds the bandwidth demand of a particular remote unit. In those cases, the SeRF module assembling superframe  400  may alternately multiplex IP data onto otherwise unutilized timeslots of superframe  400 . 
       FIG. 5  is a flow chart illustrating a method of one embodiment of the present invention. The method begins at  510  with receiving data from an internet protocol device, the data formatted for transport via an internet protocol network (IP data) at a remote unit of a distributed antenna system. The method proceeds to  520  with converting analog RF signals received at the remote unit into digitized RF samples. The method proceeds to  530  with multiplexing the IP data with the digitized RF samples into frames for transmission to a host unit of the distributed antenna system. In one embodiment, multiplexing the IP data with the digitized RF samples into frames is achieved by inserting digitized RF samples into timeslots and then multiplexing the IP data into remaining bits within each time slot. For example, where each RF data sample is 15 bits and each timeslot has a capacity of 16 bits, the method utilizes 15 of 16 available bits within a timeslot to carry the RF data sample and mulitplexes IP data into the remaining 16 th  bits of each timeslot. The method then proceeds to  540  with transmitting a superframe to the host unit, the superframe comprising timeslots carrying the IP data with the digitized RF samples. 
     Several means are available to implement the systems and methods of the current invention as discussed in this specification. In addition to any means discussed above, these means include, but are not limited to, digital computer systems, microprocessors, programmable controllers, field programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs). Therefore other embodiments of the present invention are program instructions resident on computer readable media which when implemented by such controllers, enable the controllers to implement embodiments of the present invention. Computer readable media include devices such as any physical form of computer memory, including but not limited to punch cards, magnetic disk or tape, any optical data storage system, flash read only memory (ROM), non-volatile ROM, programmable ROM (PROM), erasable-programmable ROM (E-PROM), random access memory (RAM), or any other form of permanent, semi-permanent, or temporary memory storage system or device. Program instructions include, but are not limited to computer-executable instructions executed by computer system processors and hardware description languages such as Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL). 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.