Abstract:
An over-the-air optical data communications system includes a plurality of transmission units that are mounted at separate locations in a geographical area to establish a mesh network that includes a plurality of line-of-sight optical communications links. A network controller is electronically connected with each communications link to monitor transmission quality on the link, and to selectively aim each transmission unit in the mesh network to an alternate transmission unit as required to maintain the mesh network. Additionally, a backbone network holds the mesh network together by interconnecting various communications stations that are each connected with at least one transmission unit in each of the communications links.

Description:
[0001]    This application claims priority of Provisional Application Serial No. 60/236,540, filed Sep. 29, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention pertains generally to systems and methods for implementing optical communications networks. More particularly, the present invention pertains to optical communications systems which incorporate controls for converting the system whenever an optical communication link in the system becomes unusable. The present invention is particularly, but not exclusively, useful as a two-tiered system which includes a secondary communications system that provides an underpinning for supplementary control and selective conversion of the optical communications links in the optical communications links of a primary system.  
         BACKGROUND OF THE INVENTION  
         [0003]    Optical systems for establishing line-of-sight communications links between two end-point communications terminals have been successfully employed in several configurations. More particularly, such optical links have become more commonly used in urban environments over the so-called “last mile” of a communications network. An example of such an optical link is disclosed and claimed in U.S. Pat. No. 5,777,768, which issued to Korevaar on Jul 7, 1998, for an invention entitled “Multiple Transmitter Laser Link” and which is assigned to the assignee of the present invention.  
           [0004]    In addition to their use as a point-to-point communications link, optical systems have also been employed in various network schemes. Additionally, they have been used in conjunction with other types of communications equipment. For example, U.S. Pat. No. 6,049,593, which issued to Acampora on Apr. 11, 2000, for an invention entitled “Hybrid Universal Broadband Telecommunications Using Small Radio Cells interconnected by Free-Space Optical Links,” discloses a multi-tier communications system that incorporates both radio and optical telecommunications equipment.  
           [0005]    It is well known that whenever a wireless optical telecommunications link is used in a communications system, it is vulnerable to difficulties that are associated with the variable attenuation of the media (air, free space). More specifically, randomly occurring phenomena such as fog, smoke, and precipitation can attenuate an optical link to the point where it is effectively inoperative. This factor is somewhat aggravated by the fact that, unless turning mirrors are used, optical systems which transmit light beams through free space are effectively limited to a line-of-sight link. Heretofore, the solution for overcoming an unwanted obstruction that has been introduced into an optical communications system has been to reroute communications from the affected link onto other preexisting links. The effectiveness and flexibility of this tactic, however, depends on the existence of preexisting links.  
           [0006]    In light of the above, it is an object of the present invention to provide a reconfigurable, over-the-air optical data communications system which incorporates optical transmission units that can be selectively aimed to establish alternate optical links, and to thereby convert a mesh network of optical links into an alternate mesh network which includes the alternate optical link(s). Another object of the present invention is to provide a reconfigurable over-the-air optical data communications system that incorporates a backbone network of landlines, or wireless or optical connections which will supplement a mesh network of optical communications links. Yet another object of the present invention is to provide a reconfigurable, over-the-air optical data communications system that coordinates the location of optical transmission units, together with the direction of respective optical beam paths from these transmission units in both elevation and azimuth, to selectively establish optical communications links in a mesh network. Still another object of the present invention is to provide a reconfigurable, over-the-air optical data communications system that is relatively easy to install, is simple to use, and is comparatively cost effective.  
         SUMMARY OF THE PREFERRED EMBODIMENTS  
         [0007]    An over-the-air optical data communications system in accordance with the present invention includes a plurality of transmission units that are mounted at separate locations throughout a regional area (e.g. an urban environment). More specifically, a number of such transmission units will be located at each of several separate transmission terminals. For example, in an urban environment the transmission terminals may be buildings or towers. Further, for the present invention there will be at least one, but probably two or more, transmission unit(s) at each transmission terminal. As envisioned for the present invention, a transmission unit at one terminal and a transmission unit at another terminal will be aimed toward each other to establish a line-of-sight optical data communications link therebetween. Several such line-of-sight optical communications links will thus establish a mesh network of communications links.  
           [0008]    The system of the present invention also includes a backbone network which provides an underpinning for control and conversion of the mesh network. More specifically, this backbone network includes a plurality of separate communications stations which are positioned at selected transmission terminals in the mesh network. Also, each of these communications stations is interconnected with at least two other communications stations and, preferably, they are all interconnected into a closed loop. Importantly, in addition to the transmission units that are used for the mesh network, each communications station in the backbone network may have an excess of pre-positioned transmission units that can be employed, as necessary, to replace outages of communications links in the mesh network. For purposes of the present invention, the communications links between communications stations in the backbone network can be either landline, wireless, or optical connections.  
           [0009]    Operation of the mesh network, as well as its interaction with the backbone network of the present invention, is accomplished by a network controller. As the operational nerve-center for the optical communications system of the present invention, this network controller is electronically connected with each of the communications links in the mesh network. Through these connections, the network controller performs several important functions. For one, it monitors the transmission quality on each of the communications links. Then, in response to the level of a predetermined transmission quality factor, the network controller provides commands for aiming appropriate transmission units toward each other. This action then converts the mesh network into an alternate mesh network in the event the transmission quality factor indicates a particular communications link, or links, has (have) become operationally ineffective.  
           [0010]    For its operation, the network controller is provided with information concerning the exact location of each transmission unit in the mesh network. Specifically, this information will include the coordinates and the height of each transmission unit relative to a predetermined datum. Using this information, the network controller is then capable of selectively aiming each transmission unit, in both elevation and azimuth, from its known location toward another transmission unit in the mesh network. Also, based on experience or actual measurements, line-of-sight blockages (e.g. mountains, buildings, walls and towers), can be preprogrammed into the network controller to more accurately define the operational envelope for each transmission unit. Accordingly, initial line-of-sight optical communications links can be established for the mesh network. Subsequently, this same information can be used to establish alternate line-of-sight optical communications links for an alternate mesh network in the event an unforeseen blockage is experienced (e.g. fog, smoke, or precipitation) of optical communications links.  
           [0011]    As a back-up for the network controller, local controllers can be installed at selected transmission terminals. Similar to the network controller, these local controllers will be provided with information concerning the exact location of transmission units at their respective transmission terminal, as well as information about transmission units at other terminals with which they can establish optical line-of-sight communications links. As before, this information will include the coordinates and the height of each transmission unit relative to the predetermined datum. In normal operation, the local controller will be used to interconnect the mesh network with the network controller. Alternatively, in the event there is an outage of the network controller, the local controller can be used to aim transmission units under its control to maintain or reconfigure the mesh network. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0013]    [0013]FIG. 1 is a perspective view of an urban environment which incorporates a reconfigurable over-the-air optical data communications system in accordance with the present invention;  
         [0014]    [0014]FIG. 2 is a schematic view of a mesh network in the optical communications system of the present invention, as shown in FIG. 1, superposed on a backbone network of the system for concerted operation therewith;  
         [0015]    [0015]FIG. 3 is a schematic view of a communications terminal in the optical communications system of the present invention; and  
         [0016]    [0016]FIG. 4 is a flow chart of actions and decisions that are to be taken to set-up or reconfigure the optical data communications system in accordance with the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0017]    Referring initially to FIG. 1 a reconfigurable optical communications system in accordance with the present invention is shown and generally designated  10 . As shown, the system  10  includes a mesh network  12  (dashed lines) and a backbone network  14  (double lines). As also shown in FIG. 1, both the mesh network  12  and the backbone network  14  interconnect various transmission terminals  16  (e.g. buildings) which are located in a same regional area (e.g. urban environment).  
         [0018]    To consider the interaction of the mesh network  12  with the backbone network  14 , in detail, it will be seen that the mesh network  12  includes a plurality of interconnected transmission modules  18 . More specifically, these transmission modules  18  are mounted on respective buildings  16  that are to be connected into the mesh network  12 . For example, the module  18   a  is shown mounted or positioned on the building  16   a  and, likewise, the modules  18   b  and  18   c  are shown positioned on respective buildings  16   b  and  16   c . As also shown, additional modules  18  are similarly mounted on other respective buildings  16 . On the other hand, the backbone network  14  is mounted on selected buildings  16  in the regional area covered by the system  10  of the present invention. More specifically, the backbone network  14  includes a plurality of communication stations  20 , of which the communications stations  20   a - d  shown in FIG. 2 are only exemplary.  
         [0019]    As best seen in FIG. 2, where the schematics of mesh network  12  and backbone network  14  are superposed on each other, it is possible for a transmission module  18  and a communications station  20  to be co-located at the same building  16 . For instance, by cross referencing FIG. 1 and FIG. 2 it will be appreciated that the transmission module  18   a  and the communications station  20   a  are co-located at the transmission terminal (building)  16   a . As intended for the present invention, the communications stations  20  of the backbone network  14  can be interconnected with each other in any of several ways known in the pertinent art, such as by landlines, wireless or optical communications links. Preferably, the backbone network  14  is configured as a closed loop wherein each transmission terminal (building)  16  in the loop is connected with at least two other communications stations  20  (e.g. buildings  16   a - 16   d - 16   e - 16   f - 16   g ). Unlike the backbone network  14 , however, the mesh network  12  for system  10  is specifically dedicated to optical communications links.  
         [0020]    Referring now to FIG. 3 it will be seen that the present invention contemplates the use of a plurality of transmission units  22  in each transmission module  18 . For example, the transmission module  18   a  is shown in FIG. 3 to include the transmission units  22   a ,  22   b , and  22   c . Although the transmission module  18   a  shown in FIG. 3 is indicated to be on the top of the transmission terminal  16   a  (i.e. roof of the building  16   a ), it is to be appreciated that the transmission units  22   a - c , or additional transmission units  22 , can be positioned on the side of the terminal  16   a  or at any convenient location which will ensure the establishment of a line-of-sight optical communications link  26 . Regardless where they are located, each transmission unit  22   a - c  is capable of generating a respective light beam  24   a - c  which is useful for optical communications. For this purpose it is necessary to consider the alignment of transmission units  22  at respective transmission terminals  16 .  
         [0021]    In FIG. 1, and with reference to FIG. 3, the transmission module  18   a  is used as an exemplary consideration. More specifically, consider the transmission unit  22   a . As intended for the present invention, the transmission unit  22   a  must be capable of being aimed to establish an optical communications link  26 . For example, as shown in FIG. 1, the transmission unit  22   a  in module  18   a  at building  16   a  must be aimed to establish the optical communications link  26   a  with a transmission unit  22  in the module  18   b  on building  16   b . This aiming, of course, requires that the transmission unit  22   a  be capable of traversing angles in both elevation and azimuth.  
         [0022]    Still referring to FIG. 1, an elevation angle, β, can be measured from a vertical axis  28  at the transmission module  18   a , and an azimuth angle, α, can likewise be measured from a horizontal axis  30 . The range of the respective angles α and β will depend on obstructions. In the case shown in FIG. 1 the elevation angle, β, is restricted by the building  16   a  while the azimuth angle, α, is primarily restricted by the building  16   g . In any event, by knowing the coordinates of the transmission unit  22   a  (e.g. longitude and latitude), and its elevation (e.g. above mean sea level), the aiming angles α and β can be appropriately selected to establish an end point for the optical communications link  26   a . Similar measurements for a transmission unit  22  in the module  18   b  on building  16   b , with reciprocal aiming angles for α and β, will then complete the optical communications link  26   a . With the above in mind, it is an important aspect of the present invention that the system  10  have accurate information as to the coordinates (e.g. longitude and latitude) and elevation (e.g. above mean sea level) of each individual transmission unit  22  in the mesh network  12 . Alternately, the relative aiming angles α and β for all possible links  26  in the system  10  can be known. With such information, the establishment of various optical communications links  26  between any two transmission units  22  in the mesh network  12  is simply a matter of orienting the different transmission units  26  with appropriate aiming angles α and β.  
         [0023]    [0023]FIG. 3 indicates that overall control of the system  10  is provided by a network controller  32  which can be selectively located anywhere in the regional area that is being serviced by the system  10 . Further, FIG. 3 indicates that a local controller  34  may be located at a transmission terminal (e.g. building  16   a ) as desired. The purpose of the local controller  34  is to serve as a back-up for the network controller  32  in the event the latter becomes inoperative for some reason. In either case, the network controller  32  will have the position information disclosed above for all transmission units  22  in the mesh network  12 . On the other hand, local controllers  34 , if used, need have position information on only those transmission units  22  with which the transmission module  18  at its particular terminal (building)  16  can communicate.  
         [0024]    Using the transmission terminal (building)  16   a  as an example (see FIG. 3), it will be seen that a network element  36  is connected directly with the transmission units  22   a - c . With these connections, wireless optical communications can be conducted on the respective light beams  24   a - c  and, consequently, over respective optical communications links  26 . Various communications devices  38  (the devices  38   a - d  are only exemplary) can then be connected onto the mesh network  12  through the network element  36 .  
         [0025]    In the operation of the system  10  of the present invention, the transmission units  22  in various modules  18  are initially aimed to establish communications links  26  for the mesh network  12 . Also, the backbone network  14  is established. Again, the particular mesh network  12  and backbone network  14  shown in FIGS. 1 and 2 are only exemplary. The importance of the system  10  is to then reconfigure the mesh network  12  in the event there is a system outage.  
         [0026]    Returning for the moment to FIG. 2, consider the possibility that fog, smoke, rain or some other attenuating phenomenon obscures optical communications with the transmission module  18   a  on building  16   a . If this happens, the wireless optical communications link  26   a  (between terminals  18   a  and  18   b ) and the link  26   b  (between terminals  18   a  and  18   c ) may become ineffective. Under such a scenario, the network controller  32  performs a logic routine that is intended to reconfigure the mesh network  12  into a viable alternate mesh network  12 ′ that will restore effective communications. Such a logic routine is shown in FIG. 4.  
         [0027]    In FIG. 4, block  40  indicates that the network controller  32  (possibly local controller  34 , if used) maintains the operational parameters for the system  10 . As implied above, these operational parameters will include the position information on transmission units  22  in the system  10 . Additionally, these operational parameters can include pertinent system reports and graphic user interface information for the operator of the network controller  32 . In an on-going operation, as indicated by inquiry block  42  in FIG. 4, the network controller  32  monitors the network elements  36  and, thus, the transmission units  22  that are initially connected into the mesh network  12 . If, as in the scenario presented above, the transmission terminal  16   a  becomes somehow disconnected, inquiry block  42  directs action to block  44  and a search for free transmission units  22 . Simultaneously, as indicated by block  46 , a search is made for free transmission units  22  at other locations (i.e. terminals  18 ). An attempt is then made to establish the affected communications link  26  (see block  48 ), and if successful (block  50 ) the mesh network  12  is reestablished (block  52 ).  
         [0028]    It may happen that a particular communications link  26  in the mesh network  12  may not be completely inoperative, but it begins to deteriorate. As indicated by the inquiry block  54 , if this happens an attempt is made as disclosed above (blocks  44 ,  46 ,  48 ,  50  and  52 ) to reestablish the link  26 . On the other hand, it can happen that the link has gone beyond deterioration, at this point inquiry block  56  questions whether there is a command for a new link. In this context, consider the scenario presented above.  
         [0029]    For situations, such as where optical communications have been disrupted with a transmission terminal  16  (e.g. terminal  16   a ) a new link command can be given. In this case, it can happen that the communications link  26   a  shown in FIG. 2 becomes unusable. The network controller  32  may then command a transmission unit  22  of the module  18   b  at transmission terminal  16   b  to establish an alternate optical communications link  26 ′ with the transmission module  18   g  at transmission terminal  16   g  (indicated by the dot-dash line in FIG. 2). Alternatively, the network controller  32  may have commanded the transmission unit  22  of the module  18   b  to establish an optical communications link  26  with the transmission module  18   d  at transmission terminal  16   d , if possible. The consequence in either case is an alternate mesh network  12 ′ that can be used until such time as the initial mesh network  12  can be reconstituted.  
         [0030]    In all of the possible situations discussed above, the block  58  in FIG. 4 indicates that the network controller  32  will make reports on outages for future use in reconfigurations of the mesh network  12 . Importantly, as envisioned for the present invention, the mesh network  12  can be reconfigured to maintain or restore communications by reconfiguring the network  12  with new optical communications links  26 . As disclosed above, this is accomplished by creating new optical communications links  26 , as required. More specifically, these new communications links are established when selected transmission units  22 , at selected transmission terminals  16  are caused to be aimed at each other to create the particular link  26 .  
         [0031]    While the particular Reconfigurable Over-the-Air Optical Data Transmission System as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.