Abstract:
The present invention is a system of at least one cordless telephone, a home base station and at least one non-home base station. A roaming cordless telephone out of range of its home base station will use a non-home base station to direct digital mode signals to its home base station. The home base station will convert the digital mode signals to analog signals and communicate them with the telephone network. Only a single direct line connection is needed for the home base station, as the digital mode signals and the analog signals communications do not interfere with each other. The user may potentially avoid long distance charges by using the non-home base station as a conduit while using the home base station as the telephone network site for long distance charge accrual. Further, the necessity for using a cellular telephone with the consequent charges is avoided.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to cordless telephones operating from base stations which are connected to conventional telephone systems. More particularly, the present invention relates to the field of cordless telephones that may operate with an effective, connection to a conventional telephone system when the cordless telephone is out of range of its base station. 
     There is an ongoing need for a communication system in which out of range operation for a cordless telephone can be achieved to thus eliminate the necessity for employing a cellular telephone (with the consequent cost) or the use of the telephone connection of another party. 
     SUMMARY OF THE INVENTION 
     The present invention is a cordless telephone that can place, receive or continue processing of telephone calls, whether or not the cordless telephone is in range of its home base station. When out of range of its home base station, the cordless telephone of the subject invention transmits or receives digital mode signals with a non-home base station. Those transmitted or received digital mode signals are routed in one of several possible methods between the cordless telephone and its home base station, wirelessly or by wired connection. 
     The home base station receives the transmitted digital mode signals from a non-home base station, translates them to analog or other digital (i.e, such as ISDN) or data signals and transmits them to a home telephone line. The home base station may also receive analog or other digital (i.e, such as ISDN) or data signals from the telephone line, translate them to digital mode signals and transmit them to the non-home base station for retransmission to the cordless telephone. 
     A non-home base station can wirelessly route digital mode signals to the home base station, or vice versa. The wireless routing can be direct or indirect. 
     Direct wireless routing has a non-home base station in wireless range of a home base station. The digital mode signals are directly exchanged between those two base stations. This means that the cordless phone is out of range of its home base station but in range of the non-home base station. 
     Indirect wireless routing uses additional, intervening non-home base stations. A first non-home base station is out of range of the home base station but in range of a second non-home base station. The second station is either in range of the home base station or in range of a third non-home station. If in range of the home base station, the second station acts as a wireless link from the first non-home base station to the home base station. Other intervening non-home base stations can act as additional wireless links to span the distance between the first non-home base station and the home base station. 
     As long as one or more non-home base stations have overlapping wireless communication ranges between the cordless phone and the home base station, the user can move freely out of range of the home base station without service interruption. More importantly, the user can conceivably avoid cellular or telephone network charges for wireless communication from the cordless phone to the home base station. The invention wireless routing can be made without devoting new wireless bandwidth to its operation. Most locations in the world have cordless phone bandwidth already segregated for that purpose apart from cellular or other uses. 
     For effective wireless routing, the user can strategically locate his own non-home base stations within wireless range of each other over a desired area. Or the user can depend on non-home base stations located in and operating as parts of the base stations of other invention cordless phones. A new user gets their own uniquely addressed cordless phone and home base station and installs the home base station at a desired location. That new base station has means for acting as a non-home base station for another cordless phone uniquely addressed to a different home base station. Each new home base station installation at the desired location of a new user becomes an extension of the effective wireless operating range of the invention system. 
     Such call processing of the invention cordless telephone through a non-home base station does not substantially affect call processing of a second telephone that can use the non-home base station as the second telephone&#39;s home base station. 
     Digital mode, as used herein, describes a digital transmission and reception technology signal, i.e., TDMA, E-TDMA, narrow band CDMA, and broadband CDMA, spread spectrum, or other appropriate mode that may be transmitted on a channel. In an optional mode, the cordless telephone may employ a direct wire connection with a non-home base station for processing. The subject system allows the cordless telephone user to roam away from his home base station to the range of another base station and transmit and receive in digital mode to the other base station without interfering with the local analog operation of the other base station. This aspect of non-interference or line sharing is entirely novel to the art. 
     For the out of range or roaming cordless telephone, digital mode signals are exchanged by a roaming cordless telephone at a signal-separable frequency than that of the one or more cordless telephone handsets for the other base station so the signals do not interfere with each other. In one of several methods of routing transmission from a roaming cordless telephone, a received signal from the out of range cordless telephone is received by the other base station and transmitted from the other base station to the home base station for translation to analog or other appropriate signals (such as for data communications). 
     The digital mode signals sent by the other base station are of course transmitted on the same conventional telephone network connection (land line, wireless or other means, referred to hereafter just as “land line ”) used by the other station for its own analog or other communications with a telephone network. The concurrent operation of the subject system and the normal operation of the other base station takes place so that the integrity of the normal operation of the other base station is at least its substantially maintained. Although complete absence of interference by line sharing would be preferable, the owner of the other base station may well accept a reduced performance of normal operation if in exchange for being part of the invention system and to share in its benefits. 
     In further explanation of the subject system, digital mode transmissions (and received signals as well) enter the land lines of the other base station from the other base station for handling in one of several modes of routing to the home base station. The digital mode transmissions may be received by the telephone network with unique identifier(s) indicating that the signals or packets must be directed to the home base station. 
     In an alternate embodiment, the other base station and its associated telephone account may be equipped with broad band communications technology, such as for DSL communications, permitting co-transmission of the digital mode signals with the normal operation of the other base station telephone line, although using some of the bandwidth of the telephone account for the other base station. In another alternate embodiment, the digital mode signals may be transmitted directly to the home base station without requiring processing by the telephone network. In one or more of these transmission (and/or receiving) methods for digital mode signals from the other base station to the home base station, the digital mode signals are delivered to the home base station. 
     The home base station incorporates apparatus for receiving these transmissions. in a manner such that it does not substantially impair the normal land line operation. The normal land line operation may include exchange of signals in analog or other digital (i.e., such as ISDN and the like) and data signals. Analog signals are needed for phone speaker and microphone operation. The home base station, upon receiving a digital mode signal from the roaming cordless telephone (for example, the first number of a desired telephone number that the user wants to call) moves the home base station to an off-hook state and transmits the transformed digital mode signal (now in analog or other digital (i.e, such as ISDN) form) to the telephone network for appropriate processing. Each subsequent number received from the roaming cordless telephone causes the telephone network to respond as if the cordless telephone were within its home base station range. When a dial up attempt is completed, the roaming cordless telephone receives communications signals in the reverse order, i.e., the home base station receives an analog signal from a telephone network source, the analog signal is,translated to a digital mode signal, the digital mode signal is transmitted to the other base station, the other base station transmits the non-analog signal to the roaming cordless telephone, and the roaming cordless telephone transforms the non-analog signal to an analog signal that may result in an audible or data output usable by the roaming cordless telephone holder. 
     These simple concepts eliminate the need for an out of range base station with a land line committed only to reception and transmission of signals from the roaming cordless handset. The prior art contains many examples of cordless telephones that switch to a cellular network when out of range of home base station. The present invention system is not one of that category. 
     The present invention may incorporate a feature for timing out in a standby mode for a period of time if the roaming cordless telephone moves out of range of any receptive base station, so that the user traveling in a car or other transport may not lose communication contact with the connected telephone number during a call. The out of range base station can. be a telephone with similar capabilities as that of the home base station, providing inducement for many user&#39;s in a locality (corporate building or campus small community or other relatively compact geographical area) to install the subject cordless telephone so that they may have the benefit of out of range operation without the need to pay for a cellular network call. 
     It is well known that cellular network calls are many times more expensive than those from a single land line telephone. The subject system having at least one cordless telephone and two or more. base stations permits the user to place and receive calls from out of range locations where the only charges that will accrue to the user will be those that would have accrued had the user been within range of the home base station. 
     The frequencies for a roaming cordless telephone and that set aside for the local cordless telephone preferably operate within the broad ranges set aside for the spread spectrum technology of the 900 MHz and 2.4 GHz cordless telephones. It is well known from the cellular telephone art and the cellular—cordless telephone art that one of several frequencies may be programmably selected by the invention cordless telephone so that its communication frequency does not interfere with the communications of a local. base station as opposed to the home base station of the roaming cordless telephone. It is also well known in the cellular telephone art and the cellular—cordless telephone art that base station range sensing expedients and range to range “hand-off” expedients presently exist for relatively simple incorporation into the subject system so a roaming cordless telephone can move out of range of one of the other base stations and automatically transfer all communication exchanges with a nearby or adjacent-range base station. Optionally, the user can be given a visual or audible signal that the roaming cordless telephone is moving out of and/or into range of another base station. Such signal will alert the user that their call may be terminated if another base station range is not at least nearby. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a block diagram of a cordless telephone C 1  within operating range. of its home base station CB 1 , showing other base stations and cordless telephones according to the invention connected by land lines to a telephone network. 
     FIG. 2 is a block diagram of a cordless telephone C 1  outside of operating range of its home base station CB 1 , showing other base stations and cordless telephones connected by land lines to a telephone network. 
     FIG. 3 is a flow chart of functions for the subject cordless telephone system. 
     FIG. 4 is a diagram of two cordless telephones and their respective base stations showing wireless connection of one cordless telephone to a non-home base station in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The subject system incorporates at least one cordless telephone and two or more base stations. The functions of an exemplary cordless telephone and the base stations are now discussed in more detail. 
     A cordless telephone in accordance with preferred embodiments of the present invention will have a transmit/receive circuit (with antenna(s)) operationally connected with programmable circuitry to select a transmit/receive frequency according the objects of the invention. The programmable circuitry may include a central processing unit connected to one or more forms of memory for directing and controlling the cordless telephone functions as required herein. As controlled by the programmable circuitry, a modem circuit can demodulate received radio signals into a continuous signal stream, which will be able to be decoded by the coder/decoder (CODEC) into an audio signal which is controllably amplified by an interface controller and output through a telephone speaker. Likewise, a reverse path is followed through the cordless telephone as the telephone microphone detects user speech. A keypad and a display provide conventional user input and output. Or more simply, as shown in cordless telephones C 1  and C 100  of FIG. 4, respective input/output circuitry  201  and  204  includes wireless transmission and reception apparatus in connection with logic  205  and  208  as well-as analog user interface  209  and  212 . 
     Each cordless telephone is identified to a base station by a unique identifier. As in FIG. 4, the base stations CB 1  and CB 100  respectively include input/output coupling circuitry  202  or  203  for connection by direct land line with the public telephone network or other telephone network. Base stations CB 1  and CB 100  also respectively incorporate logic  206  and  207  and analog user interfaces  210  and  211 . 
     The ability to switch between invention base stations may be accomplished with known range sensing and hand-off technology which use an over-air protocol as with a mobile telephone system, such as a Personal Communication System (PCS) with hand-held telephones in a cellular communication system or any cellular or mobile telephone system. The protocol defines a method in which user stations, such as cellular or mobile telephone handsets, communicate with one. or more base stations to place and receive telephone calls. The protocol provides air-channel agility between base stations and user stations. Each base station may simultaneously maintain communication with as many user stations as there are air channels in its polling loop. The ability of a user station to communicate on any unoccupied air channel makes the protocol air-channel agile. Each base station continually transmits on each one of its air channels in a predetermined sequence. 
     The ability and technology of a single circuit to conduct multiple simultaneous conversations through identical and closely coupled media without substantial interference are well known in the art. The present invention uses such technology for transmission, along the same land lines, the digital mode signals of the roaming cordless telephone and the analog signals from the cordless or other telephone of the local base station. 
     FIG. 1 shows a set of base stations C 1  to C 100  according to the invention connected by land line L 1 . Those base stations are connected without an intervening first switching telephone network TN 1 . Similarly, a set of the subject base stations C 101  to C 200  are connected by land line Ln. Those base stations are connected without an intervening first switching telephone network TNn. The set of telephone networks TN 1  to TNn represent a worldwide communication telephone network in which base stations according to the invention are capable of land line connection thereto for analog or other communication with any other effectively connected user of the worldwide communication telephone network. FIG. 1 shows only invention base stations in the worldwide communication telephone network. 
     The subject base stations each have unique station identifiers matching those programmed into programmable circuitry in the cordless telephones associated with them as in FIG. 1, i.e., cordless telephone C 1 . transmits in an analog or data mode directly with base station CB 1  when it is within its range. For a typical cordless telephone-operating at 900 MHz or 2.4 GHz, that range may be anywhere from a 10-20 feet to hundreds of feet. It is within skill in the art with this disclosure to provide greater operating range of one or more of the subject base stations as desired and/or as permitted by regulation. No other base station will receive analog or data communication from cordless telephone C 1  other than base station CB 1 , for example. 
     FIG. 2 shows cordless telephone C 1  out of range of its home base station, base station CB 1 , but within range of a non-home base station, base station CB 100 . Non-home base station CB 100  optionally has uniquely addressed to it a cordless telephone C 100 . A non-home base station CB 100  routing digital mode signals wirelessly on path  215  doesn&#39;t need a telephone network connection path  216  for the invention system to work. Path  216  may exist in that circumstance so that station CB 100  can act as a base station for cordless phone C 100 . A line is shown connecting cordless telephone C 1  with base station CB 100 , which has a different station identifier than that of telephone C 1 . Base station CB 100  cannot accept analog or data signals communicated by telephone C 1 . The base station incorporates standard cordless telephone circuitry with an additional transmit/receive circuit operatively connected with programmable circuitry which is turn is operatively connected with the land line connection of the base station to accomplish the objects of the invention. 
     The transmit/receive circuitry and programmable circuitry are adapted to permit transmit/receive functions of the subject system for more than one roaming cordless telephone. Where more than one cordless telephone is within range of a non-home base station, the programmable circuitry of the roaming cordless telephones and the non-home base station will operate to transmit/receive at separate frequencies for the roaming cordless telephones and operate on the digital mode signals of the multiple roaming cordless telephones as if they were different subscriber lines. Non-home base stations (as to telephone C 1 ) in the positions of base stations CB 2  to CB 100  may be capable of the transmit/receive functions for digital mode signals of the roaming cordless telephone to the home base station directly without intervening routing through the telephone network, as a portion of public telephone network TN 1 . More specifically, for a set of entirely local direct connection base stations as in base stations CB 1  to CB 100  (or the separate set of base stations CB 101  to CB 200 ), the several cordless telephones identified to their home base stations may roam from the range of their home base stations to the ranges of the local set of non-home base stations and be operatively connected with the home base station without intervening routing to the local telephone network. 
     The invention is now discussed with reference to the flow chart of FIG.  3 . Step  151  shows a first cordless telephone in a standby mode, thereafter performing step  152  of sensing for the range of a base station. If a base station is not sensed, the standby mode is maintained for a desired period of time. If a base station is sensed, step  153  is performed with communication established between the first cordless telephone and the base station to determine if the base station is the home base station of the first cordless telephone. 
     If a home base station is sensed in step  153 , the first cordless telephone is thereafter in a state to place, receive or continue a call as in step  154 . If a call is not placed, received or continued, the first cordless telephone is placed in a standby mode for a period of time. If a call is placed, received or continued, the first cordless telephone processes the call directly through its home base station as in step  155 . If the first cordless telephone moves out of range of its home base station, it is returned to the state of step  152  to sense for a base station, otherwise the call processing is completed as in Step  157  and the first cordless telephone is returned to a standby mode in Step  151 . 
     If at step  153  the first cordless telephone did not sense the home base station, it detects the non-home base station and its address in step  158 . The first cordless telephone is moved to a state to place, receive or continue calls in step  159 . If a call is not placed, received. or continued, the first cordless telephone is placed in the standby mode of step  151 . If a call is placed, received or continued, the first cordless telephone will transmit and receive digital signals as in step  160  to a non-home base station. This routing between the non-home and home base stations can be wireless or by wired connection. Digital mode signals are routed directly or indirectly to the home base station uniquely addressed to the roaming cordless telephone. The routing may use one or more intervening non-home base stations to connect the cordless phone with the home base station. 
     As a graphic example of the forms of routing, FIG. 4 shows wireless routing along path  215  between a non-home base station at CB 100  and a home base station at CB 1 . FIG. 4 also shows wired routing along path  216  between the non-home base station at CB 100  and a. home base station at CB 1 , with an optional routing through network TN 1  and path  219 . 
     In a wireless routing operation as shown in FIG. 4, non-home base station CB 100  has means for sensing if it is in wireless range of another base station and determining whether that other base station is the home base station of phone C 1  or if it is in wireless range of a non-home base station as to phone C 1 . Routing along path  215  is wirelessly established if non-home base station CB 100  senses home base station CB 1  for phone C 1 . If non-home base station CB 100  senses only one or more non-home base stations, non-home base station CB 100  directs a control signal to those other non-home base stations to sense as it has just done for wireless range to home base station CB 1  or to yet another non-home base station. Thus, an intervening non-home base station has means for receiving such a control signal, acting upon it to sense wireless range to other base stations and routing digital mode signals as an intervening link when the connection is ultimately made between non-home base station CB 100  and CB 1 . 
     If the first cordless telephone moves out of range of the non-home base station with which it exchanges digital signals, as in step  161 , the telephone is returned to the base station sensing step  152  for appropriate connection with a home base station or non-home base station. If in step  161  the first cordless telephone remains within the range of the non-home base station; the call processing is completed as in step  162 , and thereafter the first cordless telephone is returned to the standby state. 
     It is important that the present invention not be perceived as being especially limited to the routing process of digital signals between a home base station and a non-home base station exchanging digital signals with a cordless telephone addressed to that home base station. Such digital signals may be routed directly by wire or wireless connection, through a local telephone network, through a public telephone network, through one or more of a sequence or network of non-home base stations, or other such configuration. 
     The above options will sometimes present the skilled artisan with considerable and wide ranges from which to choose appropriate apparatus and method modifications for the above examples. However, the objects of the present invention will still be obtained by that skilled artisan applying such options in an appropriate manner.