Patent Publication Number: US-7590404-B1

Title: Surface wave communications between a remote antenna and a base station that is co-located with another base station

Description:
RELATED APPLICATIONS 
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     FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     MICROFICHE APPENDIX 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention is related to the field of communications, and in particular, to communications between antennas, base stations, and service nodes. 
     2. Description of the Prior Art 
       FIG. 1  illustrates communication system  100  in an example of the prior art. Communication system  100  includes antenna  103 , base station  104 , and service node  105 . Both antenna  103  and base station  104  are located at the same site  106 . In most cases, site  106  represents an elevated structure, such as a building or tower. 
     Antenna  103  exchanges user communications in a wireless communication format with wireless communication devices  101 - 102  over wireless communication links  111 - 112 . The wireless communication format could be Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), or some other wireless communication format. Thus, site  106  (antenna  103  and base station  104 ) provides wireless communication service to devices within an area defined by cell  107 . 
     Antenna  103  exchanges the user communications with base station  104  over communication link  113 . Communication link  113  is typically a relatively short metallic connection. Base station  104  exchanges the user communications with service node  105  over communication link  114 . Communication link  114  is typically a Time Division Multiplex (TDM) connection, such as a T1 or DS3. Service node  105  processes the user communications to provide a communication service, such as telephony or Internet access, to wireless communication devices  101 - 102 . 
     As the demand for wireless communications increases, antenna  103  and base station  104  eventually do not have the capacity to serve all potential users. To add capacity, cell  107  is split into two cells, where antenna  103  and base station  104  serve one split cell, and a new antenna and base station are installed at a new site to serve the other split cell.  FIG. 2  illustrates the resulting spilt-cell communication system. 
       FIG. 2  illustrates communication system  200  in an example of the prior art. Communication system  200  includes antennas  103  and  203 , base stations  104  and  204 , and service node  105 . Note that former cell  107  (See  FIG. 1 ) has been split into two cells  207  and  208 . Existing site  106  retains existing antenna  103  and existing base station  104  to serve new cell  207 . New site  206  includes new antenna  203  and new base station  204  to serve new cell  208 . In most cases, sites  106  and  206  represent elevated structures, such as buildings or towers. 
     Existing antenna  103  exchanges first user communications in a wireless communication format with wireless communication device  101  over wireless communication link  111 . Existing antenna  103  exchanges the first user communications with existing base station  104  over existing communication link  113 . Existing base station  104  exchanges the first user communications with existing service node  105  over existing communication link  114 . Existing service node  105  processes the first user communications to provide the communication service to wireless communication device  101 . 
     New antenna  203  exchanges second user communications in a wireless communication format with wireless communication device  102  over wireless communication link  211 . New antenna  203  exchanges the second user communications with new base station  204  over new communication link  213 . New base station  204  exchanges the second user communications with existing service node  105  over new communication link  214 . Existing service node  105  processes the user second communications to provide the communication service to wireless communication device  102 . 
     New cell  208  requires a new site  206  to house new antenna  203  and new base station  204 . Thus, new site  206  must have enough space to accommodate both new antenna  203  and new base station  204 . Since new site  206  is typically on an elevated structure, the elevated structure must have enough space to accommodate both new antenna  203  and new base station  204 . 
     Unfortunately, an elevated structure that is properly located to serve cell  208  and that has enough space for a new antenna and base station may be hard to find and may be very expensive. In addition, new communication link  214  is required from new site  206  to service node  105 , and new communication link  214  is typically an expensive TDM link. Thus, new site  206  may be very difficult or impossible to find, and new site  206  may become prohibitively expensive to implement. 
     Surface wave transmission systems have become available from suppliers, such as Coridor. Surface wave transmissions are guided microwave radio frequencies from approximately 800 MHz to 10 GHz whose properties enable their propagation as guided waves following a conductor path. In a surface wave transmission system, a first surface wave interface exchanges communication signals with a second surface wave interface over an electrical power line—possibly the power line neutral or a powered alternating current distribution line. The communication signals are transferred in the form of an electromagnetic wave that propagates externally to and around the surface of the power line as a guided Radio Frequency (RF) wave. In some cases, surface wave transceivers are doughnut-shaped around the power line, and they propagate doughnut-shaped electromagnetic waves around and along the external surface of the power line. Unfortunately, surface wave technology has not been effectively implemented to alleviate the split cell problem described above. 
     SUMMARY OF THE INVENTION 
     Examples of the invention include a communication system that comprises the following. A first antenna located at a first site is configured to exchange first user communications with first wireless communication devices in a wireless communication format and to exchange the first user communications over a first communication link. A first base station located at the first site is configured to exchange the first user communications with the first antenna over the first communication link and to exchange the first user communications over a second communication link. A service node is configured to exchange the first user communications with the first base station over the second communication link and to process the first user communications to provide a communication service to the first wireless communication devices. A second antenna is located at a second site and is configured to exchange second user communications with second wireless communication devices in the wireless communication format and to exchange the second user communications over a third communication link. A first surface wave communication interface is located at the second site and is configured to exchange the second user communications with the second antenna over the third communication link and to exchange the second user communications over a fourth communication link that comprises a surface wave communication link that transmits communication signals external to and around the surface of an electrical power line. A second surface wave communication interface is located at the first site and is configured to exchange the second user communications with the first surface wave interface over the surface wave communication link and to exchange the second user communications over a fifth communication link. A second base station is located at the first site and is configured to exchange the second user communications with the second surface wave communication interface over the fifth communication link and to exchange the second user communications over the second communication link or a sixth communication link. The service node is configured to exchange the second user communications with the second base station over the second communication link or the sixth communication link and to process the second user communications to provide the communication service to the second wireless communication devices. 
     In the context of the invention, the term “the second communication link or the sixth communication link” means one link or the other but not both, and both links do not need to exist. In the context of the invention, the terms “first” and “second” etc. distinguish different elements and do not indicate sequence. In the context of the invention, a “communication link” can be comprised of multiple communication links and other communication components. 
     In some examples of the invention, the communication system includes a cross connect device that forms a portion of the second communication link and that is configured to couple the second base station to the second communication link to aggregate the first user communications and the second user communications on the second communication link. 
     In some examples of the invention, the communication system includes a cross connect device that forms a portion of the second communication link and the sixth communication link and that is configured to couple the first base station to the sixth communication link to aggregate the first user communications and the second user communications on the sixth communication link. 
     In some examples of the invention, the communication system includes a cross connect device that forms a portion of the second communication link and the sixth communication link and that is configured to couple the first base station to the sixth communication link if the second communication link experiences a fault. 
     In some examples of the invention, the communication system includes a cross connect device that forms a portion of the second communication link and the sixth communication link and that is configured to couple the second base station to the second communication link if the sixth communication link experiences a fault. 
     In some examples of the invention, the power line is a neutral line or a powered alternating current distribution line. 
     In some examples of the invention, the service node comprises a mobile switching center. 
     In some examples of the invention, the first antenna serves a first cell including the first wireless devices and the second antenna serves a second cell including the second wireless devices. 
     In some examples of the invention, the first base station and the second base station share a same elevated structure. 
     In some examples of the invention, the second site does not include the first base station, does not include the second base station, and does not include other base stations. 
     Examples of the invention include a method of operating a communication system. The method comprises: exchanging first user communications in a wireless communication format between first wireless communication devices and a first antenna located at a first site; exchanging the first user communications between the first antenna and a first base station located at the first site; exchanging the first user communications between the first base station and a service node; processing the first user communications in the service node to provide a communication service to the first wireless communication devices; exchanging second user communications in the wireless communication format between second wireless communication devices and a second antenna located at a second site; exchanging the second user communications between the second antenna and a first surface wave communication interface located at the second site; exchanging the second user communications over a surface wave communication link between the first surface wave communication interface at the second site and a second surface wave communication interface located at the first site, wherein the surface wave communication link transports the second user communications in communication signals external to and along the surface of an electrical power line; exchanging the second user communications between the second surface wave communication interface at the first site and a second base station located at the first site; exchanging the second user communications between the second base station and the service node; and processing the second user communications in the service node to provide the communication service to the second wireless communication devices. 
     In some examples of the invention, the method includes, at the first site, aggregating the first user communications and the second user communications onto a same communication link between the first site and the service node. 
     In some examples of the invention, the method includes, at the first site, de-coupling the first base station from a faulty communication link to the service node and coupling the first base station to an operating communication link to the service node. 
     In some examples of the invention, the method includes, at the first site, de-coupling the second base station from a faulty communication link to the service node and coupling the second base station to an operating communication link to the service node. 
     In some examples of the invention, the method includes, at the first site, de-coupling one of the base stations from a faulty communication link to the service node and coupling the one base station to an operating communication link used by the other base station to communicate with the service node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The same reference number represents the same element on all drawings. 
         FIG. 1  illustrates communication system  100  in an example of the prior art. 
         FIG. 2  illustrates communication system  200  in an example of the prior art. 
         FIG. 3  illustrates communication system  300  in an example of the invention. 
         FIG. 4  illustrates communication system  400  in an example of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description and associated figures depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents. 
     Example #1 
       FIG. 3  illustrates communication system  300  in an example of the invention. Communication system  300  includes antennas  103  and  303 , base stations  104  and  304 , service node  105 , and surface wave interfaces  309 - 310 . Note that former cell  107  (See  FIG. 1 ) has been split into two cells  307  and  308 . Existing site  106  retains existing antenna  103  and existing base station  104  to serve new cell  307 . New site  306  includes new antenna  303  and new surface wave interface  309  to serve new cell  308 . 
     Note that new base station  304  and new surface wave interface  310  are located at existing site  106  and not at new site  306 . Thus, base stations  104  and  304  are co-located at site  106 . In some variations, sites  106  and  306  represent elevated structures, such as buildings or towers. In addition, sites  106  and  306  represent different locations that do not overlap. 
     At site  106 , antenna  103  exchanges first user communications in a wireless communication format with wireless communication device  101  over wireless communication link  111 . The wireless communication format could be CDMA, GSM, or some other wireless communication format. Antenna  103  exchanges the first user communications with base station  104  over communication link  113 . Communication link  113  is typically a relatively short metallic connection. Base station  104  exchanges the first user communications with service node  105  over communication link  114 . Communication link  114  is typically a TDM connection, such as a T1 or DS3. Service node  105  processes the first user communications to provide a communication service, such as telephony or Internet access, to wireless communication device  101 . In some variations, service node  105  comprises a mobile switching center. 
     At site  306 , antenna  303  exchanges second user communications in a wireless communication format with wireless communication device  102  over wireless communication link  311 . The wireless communication format could be CDMA, GSM, or some other wireless communication format. Antenna  303  exchanges the second user communications with surface wave interface  309  over communication link  312 . Communication link  312  is typically a relatively short metallic connection. 
     Surface wave interface  309  at site  306  exchanges the second user communications over communication link  313  with surface wave interface  310  at site  106 . Communication link  313  is a surface wave transmission link. In surface wave transmission, surface wave interfaces  309 - 310  exchange surface wave communication signals over an electrical power line—possibly the power line neutral or a powered alternating current distribution line. The communication signals transport the second user communications in the form of an electromagnetic wave that propagates externally to and around the surface of the power line as a guided RF wave. In some variations, surface wave transceivers are doughnut-shaped around the power line, and they propagate doughnut-shaped electromagnetic waves around and along the external surface of the power line. 
     At site  106 , surface wave interface  310  exchanges the second user communications with base station  304  over communication link  314 . Communication link  314  is typically a relatively short metallic connection. Base station  304  exchanges the second user communications with service node  105  over communication link  315 . Communication link  315  is typically a TDM connection, such as a T1 or DS3. Service node  105  processes the second user communications to provide the communication service to wireless communication device  102 . 
     Note that wireless communication devices in cell  307  are served by antenna  103  and base station  104  at site  106 . However, wireless communication devices in cell  308  are served by antenna  303  and surface wave interface  309  at site  306 , and by surface wave interface  310  and base station  304  at site  106 . Also note that communication system  300  is shown on  FIG. 3  as being adapted from communication system  100  in a split cell scenario, but communication system  300  could be implemented in other scenarios—including scenarios where no cell is split, and cells  307 - 308  are implemented as a part of a common design. 
     Example #4 
       FIG. 4  illustrates communication system  400  in an example of the invention. Communication system  400  is a variation of communication system  300  that includes service node  105  and sites  106  and  306 . Site  306  is configured and operates as described for site  306  in communication system  300 . Aside from communications with service node  105 , site  106  is configured and operates as described for site  106  in communication system  300 . Site  106  is depicted as an elevated structure in communication system  400  (although an elevated structure is not required in all examples). Note that base stations  104  and  304  are co-located the same elevated structure represented by site  106 . 
     Communication system  104  includes cross-connect device  401 . Cross-connect device  401  is coupled to communication link  411  that is coupled to base station  104 . Cross-connect device  401  is coupled to communication link  412  that is coupled to base station  304 . Cross-connect device  401  is coupled to communication links  413 - 415  that are coupled to service node  105 . Base station  104  exchanges the first user communications with communication link  411 , and base station  304  exchanges the second user communications with communication link  412 . Cross-connect  401  allows for multiple variations in the communications between service node  105  and co-located base stations  104  and  304 . 
     In one scenario, cross-connect device  401  couples both communication links  411 - 412  to communication link  413 . Base stations  104  and  304  communicate with service node  105  over the same communication link formed by links  411 - 413  and cross-connect device  401 . Thus, cross-connect device  401  effectively couples both base stations  104  and  304  to communication link  413  to aggregate the first and second user communications onto the same communication link for improved efficiency. In this scenario, communication link  414  could be omitted to save cost if desired. 
     In another scenario, cross-connect device  401  couples communication link  411  to communication link  413  and couples communication link  412  to communication link  414 . Base station  104  communicates with service node  105  over a communication link formed by cross-connect device  401  and links  411  and  413 . Base station  304  communicates with service node  105  over a communication link formed by cross-connect device  401  and links  412  and  414 . Thus, cross-connect device  401  effectively couples base stations  104  and  304  to separate communication links. 
     In the above scenario, one of the communication links  413 - 414  may experience a fault. If communication link  413  experiences the fault, then cross-connect device  401  de-couples link  411  from faulty link  413 , and couples link  411  to link  414 . Thus, cross-connect device  401  effectively couples both base stations  104  and  304  to communication link  414  to aggregate the first and second user communications onto the same communication link for improved fault tolerance. If communication link  414  experiences the fault, then cross-connect device  401  de-couples link  412  from faulty link  414 , and couples link  412  to link  413 . Thus, cross-connect device  401  effectively couples both base stations  104  and  304  to communication link  413  to aggregate the first and second user communications onto the same communication link for improved fault tolerance. 
     In the above scenario, one of the communication links  413 - 414  may experience a fault. If communication link  413  experiences the fault, then cross-connect device  401  de-couples link  411  from faulty link  413 , and couples link  411  to link  415 . If communication link  414  experiences the fault, then cross-connect device  401  de-couples link  412  from faulty link  414 , and couples link  412  to link  415 . Thus, cross-connect device  401  effectively couples both base stations  104  and  304  to communication link  415  in the event of a fault, so both base stations  104  and  304  may share a common back-up link. A shared back-up link is more efficient than dedicated back-up links, and typically provides acceptable fault tolerance. 
     ADVANTAGES 
     Referring to  FIG. 3 , site  306  does not include a base station. Surface wave interface  309  is typically much smaller than a base station, so site  306  can be much smaller than if a base station were present at site  306 . Since site  306  can be much smaller, it will be easier and cheaper to find a suitable site, especially on an elevated structure. In addition, base station  304  is located at existing site  106  to provide for more efficient use of that space. The co-location of the base stations and the cross-connect device allow for traffic aggregation to save cost. The co-location of the base stations and the cross-connect device also allow for link sharing to improve fault tolerance.