Abstract:
A method for a requesting cell phone includes (1) generating a request to communicate with a base station, (2) transmitting the request to a repeater cell phone, and (3) upon receiving a response to the request, transmitting data to the repeater phone for relay to the base station. A method for the repeater phone includes (1) upon receiving the request, appending its identifier in a repeater phone list in the request, (2) transmitting the request to the base station or another repeater phone, (4) upon receiving the response to the request, relaying the response to the requesting phone, and (5) relaying data between the requesting phone and the base station. A method for the base station includes (1) upon receiving the request, transmitting the response through the last repeater phone in the list and (2) communicating with the requesting phone through the repeater phones in the list.

Description:
DESCRIPTION OF RELATED ART  
       [0001]     In a typical cell phone system in the United States, the cell phone carrier chops up a coverage area (e.g., a city) into cells. Each cell is typically sized at about 10 square miles. Cells are normally thought of as hexagons on a big hexagonal grid. Each cell has a base station that consists of a tower and a small building containing the radio equipment.  
         [0002]     Cell phones have low-power transmitters in them. The base station is also transmitting at low power. Low-power transmitters have two main advantages. First, the transmissions of a base station and the phones within its cell do not make it very far outside that cell. Therefore, the same frequencies can be reused extensively across the coverage area. Second, the power consumption of the cell phone, which is normally battery-operated, is relatively low. Low power means small batteries, which have made handheld cellular phones possible.  
         [0003]     The cellular approach requires a large number of base stations in a coverage area of any size. A typical large city can have hundreds of towers. Each carrier also runs one central office called the Mobile Telephone Switching Office (MTSO). This office handles all of the phone connections to the normal land-based phone system, and controls all of the base stations in the region.  
         [0004]     When a cell phone is first powered up, it listens for the control channel that cell phones and base stations use to talk to one another for call set-up and channel changing. If the phone cannot find any control channels to listen to, it knows it is out of range and displays a “no service” message.  
         [0005]     The cell phone may transmit a registration request to the cell phone system on the control channel, and the MTSO keeps track of the cell phone&#39;s location in a database. This way, the MTSO knows which cell the cell phone is in when it wants to ring the cell phone. When the MTSO gets a call for a cell phone, it looks in its database to see which cell the cell phone is in. The MTSO picks a channel pair that the cell phone will use in that cell to take the call. The MTSO communicates with the cell phone over the control channel to tell it which frequencies to use, and once the cell phone and the tower switch on those frequencies, the call is connected.  
         [0006]     As the cell phone moves toward the edge of a cell, the cell phone&#39;s base station notes that its signal strength is diminishing. Meanwhile, the base station in the cell that the cell phone is moving toward (which is listening and measuring signal strength on all frequencies) sees the cell phone&#39;s signal strength increasing. The two base stations coordinate with each other through the MTSO, and at some point, the cell phone gets a signal on the control channel telling it to change frequencies. This hand off switches the cell phone to the new cell.  
         [0007]     As described above, cell phone coverage is currently limited by the placement of base stations. Thus, what is needed is a method to increase coverage areas to allow for temporary networks in case of emergencies.  
       SUMMARY  
       [0008]     In one embodiment of the invention, a method for a requesting cell phone to communicate with a base station through repeater cell phones includes (1) generating a request to communicate with a base station, (2) transmitting the request to a repeater cell phone, and (3) upon receiving a response from the base station, transmitting data to the repeater cell phone for relay to the base station.  
         [0009]     In one embodiment of the invention, a method for a repeater cell phone to relay data between a requesting cell phone and a base station includes (1) upon receiving a request from the requesting cell phone to communicate with the base station, appending its identifier in a list of repeater cell phones in the request, (2) transmitting the request to the base station or another repeater cell phone, (3) upon receiving the response from the base station to the request, relaying the response to the requesting cell phone, and (5) relaying data between the requesting cell phone and the base station through repeater cell phones in the list.  
         [0010]     In one embodiment of the invention, a method for a base station to communicate with a requesting cell phone through repeater cell phones includes (1) upon receiving a request from the requesting cell phone to communicate, transmitting a response through the last repeater cell phone in a list of repeater cell phones in the request and (2) communicating with the requesting cell phone through the repeater cell phones in the list. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  illustrates a network of repeater cell phones establishing a communication link between a base station and a cell phone outside the coverage area of the base station in one embodiment of the invention.  
         [0012]      FIG. 2  illustrates another network of repeater cell phones establishing a communication link between a base station and a cell phone outside the coverage area of the base station in one embodiment of the invention.  
         [0013]      FIG. 3  illustrates another network of repeater cell phones establishing a communication link between a base station and a cell phone outside the coverage area of the base station in one embodiment of the invention.  
         [0014]      FIG. 4  is a flowchart of a method for a cell phone to communicate with a base station, which is located outside of the range of the cell phone, through repeater cell phones in one embodiment of the invention.  
         [0015]      FIGS. 5, 6 ,  7 , and  8  illustrate a request, a response, and messages between the cell phones and the base station in embodiments of the invention.  
         [0016]      FIG. 9  is a flowchart of a method for a repeater cell phone to relay data between a base station and a cell phone outside the coverage area of the base station in one embodiment of the invention.  
         [0017]      FIG. 10  is a flowchart of a method for a base station to communicate with a cell phone, which is located outside the coverage area of the base station, through repeater cell phones in one embodiment of the invention. 
     
    
       [0018]     Use of the same reference numbers in different figures indicates similar or identical elements.  
       DETAILED DESCRIPTION  
       [0019]      FIG. 1  illustrates a cell phone  102  that is outside the coverage area of a cell phone network  103 . Cell phone network  103  includes cells  104 ,  106 , and  108  having base stations  114 ,  116 , and  118 , respectively. For a number of reasons, such as a medical emergency in the wilderness, cell phone  102  needs to communicate with cell phone network  103 . In one embodiment of the invention, cell phones  122  and  124  are used to establish a communication link between cell phone  102  and cell phone network  103  (e.g., base station  118 ). Note that the communication range of each cell phone is indicated by a circular perimeter around the cell phone. Similar to  FIG. 1 ,  FIG. 2  illustrates a separate but longer communication link established by cell phones  132 ,  134 , and  136  between cell phone  102  and base station  118  in one embodiment of the invention.  FIGS. 1 and 2  illustrate one scenario where base station  118  can establish multiple communication links to cell phone  102  through multiple groups of repeater cell phones. In one embodiment, base station  102  uses the communication link that is the shortest (e.g., having the fewest repeater cell phones).  
         [0020]      FIG. 3  illustrates another communication link between cell phone  102  and cell phone network  103  in one embodiment of the invention. Instead of base station  118 , cell phone  102  is connected to base station  116  by cell phones  142 ,  144 ,  146 , and  148 .  FIGS. 1 and 3  illustrate one scenario where multiple base stations (e.g., base stations  118  and  116 ) can establish communication links to cell phone  102 . In one embodiment, each base station communicates to the Mobile Telephone Switching Office (MTSO) the number of cell phones in its communication link to cell phone  102 , and the MTSO selects the base station with the shortest communication link to communicate with cell phone  102 .  
         [0021]     Hereafter, a “requesting cell phone” refers to any cell phone located outside the coverage area of a cell phone network which it wishes to communicate with, and a “repeater cell phone” refers to any cell phone that relays data between the requesting cell phone and a base station in the cell phone network. Methods for implementing the above described communication links are described hereafter in reference to FIGS.  1  to  3 .  
         [0022]      FIG. 4  is a flowchart of a method  400  for a requesting cell phone (e.g., cell phone  102  in  FIGS. 1, 2 , and  3 ) outside of the coverage area of a cell phone network (e.g., cell phone network  103 ) to communicate with the cell phone network in one embodiment of the invention. Method  400  may be implemented in a cell phone with software, hardware, or a combination thereof.  
         [0023]     In step  402 , requesting cell phone  102  listens on the control channel for an available base station in cell phone network  103 . If requesting cell phone  102  finds a base station (e.g., base station  118  in  FIGS. 1, 2 , and  3 ), then step  402  is followed by step  404 . Otherwise step  402  is followed by step  406 .  
         [0024]     In step  404 , requesting cell phone  102  communicates conventionally with base station  118 . Step  404  is followed by step  414 , which ends method  400 .  
         [0025]     In step  406 , requesting cell phone  102  transmits a request  500  ( FIG. 5 ) to repeater cell phones in its vicinity to establish a communication link with cell phone network  103 . Request  500  includes a unique identifier  502  of requesting cell phone  102  in a repeater cell phone list  504 . Repeater cell phone list  504  tracks the unique identifiers of repeater cell phones that have relayed request  500  to another repeater cell phone or a base station. This list is a roadmap to the repeater cell phones that would make up the communication link between the requesting cell phone and the base station. In one embodiment, request  500  further includes a hop count or a latency timer  506 . The hop count tracks the number of repeater cell phones that have relayed request  500  to another repeater cell phone. Latency timer tracks the time that it has taken for request  500  to be relayed through the repeater cell phones. In one embodiment, requesting cell phone  102  transmits request  500  in the control channel that all cell phones monitor. Step  406  is followed by step  408 .  
         [0026]     In step  408 , requesting cell phone  102  listens for a response  600  ( FIG. 6 ) from a base station (e.g., base station  118 ) in cell phone network  103 . If requesting cell phone  102  does not receive response  600  before timing out, then step  408  is followed by step  410 . If requesting cell phone  102  receives response  600  before timing out, then step  408  is followed by step  412 .  
         [0027]     Response  600  would be relayed by a repeater cell phone over the control channel to requesting cell phone  102 . Response  600  includes a unique identifier  602  of base station  118  in a repeater cell phone list  604 . Repeater cell phone list  604  includes the unique identifiers of the repeater cell phones that form the communication link between base station  118  and requesting cell phone  102 .  
         [0028]     Response  600  further includes channel assignment list  606  for the cell phones in list  604 . Channel assignment can be performed by base station  118  or the MTSO. If the geographical location of each cell phone in list  604  is unknown, then the number of cell phones in the communication link between requesting cell phone  102  and base station  118  is limited. This is because the cell phone channels would not be reused in fear of interference with other cell phones in the vicinity. However, if the geographic location of each cell phone in list  604  is known through the use of GPS or signal strength triangulation built into the phone, then the cell phone channels can be reused to increase the number of cell phones that can be supported. In such an embodiment, each cell phone would append its geographic location in request  500 .  
         [0029]     In step  410 , requesting cell phone  102  indicates to the user that emergency cell phone service is not available and ends method  400 .  
         [0030]     In step  412 , requesting cell phone  102  communicates with base station  118  through the repeater cell phones in list  604  ( FIG. 6 ). Requesting cell phone  102  does this by transmitting a message  700  ( FIG. 7 ) to the first repeater cell phone in list  604 . Message  700  includes repeater cell phone list  604 , information  706  for registering with cell phone network  103 , a telephone number  708  to be dialed, and data  710  (e.g., voice to be communicated to the person at telephone number  708 ).  
         [0031]     After registering with cell phone network  103 , requesting cell phone  102  can transmit messages  700  with only repeater cell phone list  604  and data  710 . Requesting cell phone  102  also receives messages  800  ( FIG. 8 ) from base station  118 . Message  800  includes repeater cell phone list  604  and data  806  (e.g., voice data from the person at telephone number  708  to the user of requesting cell phone  102 ). Step  412  is followed by step  414 , which ends method  400 .  
         [0032]      FIG. 9  is a flowchart of a method  900  for a repeater cell phone (e.g., cell phone  122  in  FIG. 1 ) to establish a communication link between a requesting cell phone (e.g., cell phone  102 ) and a cell phone network (e.g., cell phone network  103 ) in one embodiment of the invention. Method  900  may be implemented in a cell phone with software, hardware, or a combination thereof.  
         [0033]     In step  902 , repeater cell phone  122  listens for request  500  ( FIG. 5 ) from cell phone  102  to communicate with cell phone network  103 . As described above, requesting cell phone  102  can transmits request  500  in the control channel that all cell phones monitor. If repeater cell phone  122  receives request  500 , then step  902  is followed by step  904 . Otherwise repeater cell phone  122  continues to listen for request  500 .  
         [0034]     In step  904 , repeater cell phone  122  determines if its own unique identifier is already in repeater cell phone list  504  ( FIG. 5 ) in request  500 . This occurs when repeater cell phone  122  has previously relayed request  500  and that request  500  has been unable to reach cell phone network  103  and has somehow been relayed back to repeater cell phone  122 . If so, step  904  is followed by step  926 , which ends method  900 . If repeater cell phone  122  does not find its own unique identifier in list  504 , then step  904  is followed by step  906 .  
         [0035]     In step  906 , repeater cell phone  122  determines if hop count/latency timer  506  ( FIG. 5 ) in request  500  is less than a minimum threshold (e.g., 0). As will be described later, hop count/latency timer  506  is decremented each time request  500  is relayed by a repeater cell phone. This ensures a good communication link can be established between requesting cell phone  102  and cell phone network  103  as long as hop count/latency timer  506  is greater than the minimum threshold. If hop count/latency timer  506  is less then the minimum threshold, then step  906  is followed by step  926 , which ends method  900 . Otherwise step  906  is followed by step  908 .  
         [0036]     In step  908 , repeater cell phone  122  determines if it has already overhead a response  600  ( FIG. 6 ) from a base station (e.g., base station  118 ) to requesting cell phone  102 . As all cell phones monitor the control channel, repeater cell phone  122  would know if base station  118  has already responded to request  500  ( FIG. 5 ) by transmitting response  600  over the control channel. If repeater cell phone  122  has already overheard response  600 , then step  908  is followed by step  926 , which ends method  900 . Otherwise step  908  is followed by step  910 .  
         [0037]     In step  910 , repeater cell phone  122  listens for an available base station in cell phone network  103 . If requesting cell phone  102  finds a base station (e.g., base station  118  in  FIG. 1 ), then step  910  is followed by step  912 . Otherwise step  910  is followed by step  914 .  
         [0038]     In step  912 , repeater cell phone  122  transmits request  500  ( FIG. 5 ) to base station  118 . In one embodiment, repeater cell phone  122  conventionally transmits request  500  to base station  118  over the control channel. Step  912  is followed by step  920 .  
         [0039]     In step  914 , repeater cell phone  122  appends its own unique identifier  508  ( FIG. 5 ) in repeater cell phone list  504 . Step  914  is followed by step  916 .  
         [0040]     In step  916 , repeater cell phone  122  decrements hop count/latency timer  506 . Step  916  is followed by step  918 .  
         [0041]     In step  918 , repeater cell phone  122  relays request  500  to another repeater cell phone, if any. Step  918  is followed by step  920 .  
         [0042]     In step  920 , repeater cell phone  122  listens for response  600  ( FIG. 6 ) from base station  118 . If repeater cell phone  122  receives response  600 , then step  920  is followed by step  922 . Otherwise repeater cell phone  122  continues to listen for response  600 .  
         [0043]     In step  922 , repeater cell phone  122  relays response  600  ( FIG. 6 ) to a preceding cell phone in repeater cell phone list  604 . The preceding cell phone could be another repeater cell phone or the requesting cell phone itself. Step  922  is followed by step  924 .  
         [0044]     In step  924 , repeater cell phone  122  relays messages between base station  118  and requesting cell phone  102 . Specifically, repeater cell phone  122  relays messages  700  ( FIG. 7 ) received from a preceding cell phone to a subsequent cell phone in list  604 , and messages  800  ( FIG. 8 ) received from the subsequent cell phone to the preceding cell phone in list  604 . As described before, repeater cell phones  122  would use the assigned channel specified in channel assignment  606  to communicate with the subsequent and preceding cell phones. Step  924  is followed by step  926 , which ends method  900 .  
         [0045]      FIG. 10  is a flowchart of a method  1000  for a base station (e.g., base station  118  in  FIGS. 1, 2 , and  3 ) to communicate with a requesting cell phone (e.g., cell phone  102 ) through a communication link established through repeater cell phones in one embodiment of the invention. Method  1000  may be implemented in base station radio equipment with software, hardware, or a combination thereof.  
         [0046]     In step  1002 , base station  118  listens for request  500  ( FIG. 5 ) from requesting cell phone  102 . As described above, a repeater cell phone can relay request  500  in the control channel that base station  118  monitors. If base station  118  receives request  500 , then step  1002  is followed by step  1004 . Otherwise base station  118  continues to listen for request  500 .  
         [0047]     In step  1004 , base station  118  determines if it has received multiple requests  500  ( FIG. 5 ) from requesting cell phone  102 . This can occur when request  500  gets relayed by different group of repeater cell phones to the same base station. For example,  FIG. 1  shows that repeater cell phones  122  and  124  establish one communication link while  FIG. 2  shows the repeater cell phones  132 ,  134 , and  136  establish another communication link. Thus, base station  118  can receive multiple requests  500  having different repeater cell phone lists  504 . If so, then step  1004  is followed by step  1006 . Otherwise step  1004  is followed by step  1008 .  
         [0048]     In step  1006 , base station  118  selects a request  500  ( FIG. 5 ) having the shortest repeater cell phone list  504 . This allows for the most efficient communication link between base station  118  and requesting cell phone  102 . Step  1006  is followed by step  1008 .  
         [0049]     In step  1008 , base station  118  communicates to the MTSO the shortest repeater cell phone list  504  ( FIG. 5 ) in order to determine it if has the shortest repeater cell phone list  504  among all the base stations that have received request  500 . This occurs when request  500  gets relayed by different groups of repeater cell phones to different base stations. For example,  FIG. 1  shows that repeater cell phones  122  and  124  establish one communication link between base station  118  and requesting cell phone  102  while  FIG. 3  shows the repeater cell phones  142 ,  144 ,  146 , and  148  establish another communication link between base station  116  and requesting cell phone  102 . Step  1008  is followed by step  1010 .  
         [0050]     In step  1010 , base station  118  determines if it has the shortest repeater cell phone list  504  ( FIG. 5 ) among all the base stations that have received request  500 . The MTSO can determine this by simply comparing all the lists  504  that it receives and informing the result to the base stations. If base station  118  has the shortest list  504 , then step  1010  is followed by step  1012 . Otherwise step  1010  is followed by step  1014 , which ends method  1000 .  
         [0051]     In step  1012 , base station  118  transmits response  600  ( FIG. 6 ) to the last repeater cell phone on list  604  in order to establish the communication link with requesting cell phone  102 . List  604  is the same as list  504  in request  500  once request  500  reaches base station  118 . Thereafter, base station  118  transmits messages  800  ( FIG. 8 ) to requesting cell phone  102  through the repeater cell phones on list  604 . Messages  800  includes repeater cell phone list  604  and data  806  (e.g., voice data to the user of requesting cell phone  102 ). Base station  118  also receives messages  700  ( FIG. 7 ) from requesting cell phone  102 .  
         [0052]     Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention. For example, messages  700  and  800  may not include repeater cell phone list  604  if each repeater cell phones remembers the assigned channels when it relays response  600  and continues to use the assigned channels until instructed otherwise by the base station. Numerous embodiments are encompassed by the following claims.