MXPA96005112A - System and method of cellular communication that provides better transfer capacity - Google Patents

Abstract

A system and method of cellular communication that provides improved transfer capacity which reduces mutation during transfers. During transfers, the system simultaneously monitors the signals received from both the cell site in service on a first channel and the target cell site on a second channel and outputs the received signal containing an information signal. Additionally, the system simultaneously transmits an information signal to a mobile unit through the cellular site in service on a first channel and through the target cell site on a second channel.

Description

SYSTEM AND METHOD OF CELLULAR COMMUNICATION THAT PROVIDES IMPROVED TRANSFER CAPACITY BACKGROUND OF THE INVENTION The present invention relates to cellular communication systems. More particularly, the present invention relates to a cellular communication system that provides improved transfers between cell sites. Conventional cellular telephone systems provide radio communications over a service area that uses an assigned frequency band divided into radio channels. The service area is divided geographically into cells. Each cell contains an associated cell site that provides radio communications for the cell. Cell sites include, inter alia, a radio transmitter and a radio receiver to establish radio communications with a mobile telephone. Each cell site is coupled to a system controller, such as a mobile phone transfer office (MTSO), either directly or through a base station controller (cell site). In conventional cellular telephone systems, transfers allow a call to continue as a mobile phone crosses the boundary between two cells. Figure 1 illustrates the sequence of a conventional transfer. For purposes of simplicity, it is assumed that cell sites connect directly to the MTSO. It is understood, however, that an analogous transfer sequence would be applied in systems employing base station controllers. Referring to Figure 1, a transfer from one cell site to another is initiated when the cellular site that handles the call (the serving cell site) determines that the signal strength received from the mobile phone falls below a value of default threshold. (Stage 105). An indication of low signal strength means that the mobile phone is close to the cell boundary. When the signal level falls below the predetermined threshold value, the cell site in service sends a transfer request to the MTSO. (Stage 110). In response, the MTSO sends "location measurement demands" (Step 115) to the cell site in service and its surrounding cell sites to determine which cell site receives the signal from the mobile phone with the best signal strength. In response, the surrounding cell sites employ scanning receivers to determine the strength of the signal from the mobile telephone over the specified channel. The surrounding cell sites, as well as the cell site in service, send "location measurement responses" to the MTSO. (Stage 120). If one of the surrounding cell sites reports a better signal level to the MTSO, a transfer to that cell site (the target cell site) will be attempted. To attempt a transfer, the MTSO sends a new channel establishment request to the target cell site. (Stage 125) In response, the target cell site confirms the demand for establishing a new channel by indicating that the new channel is ready to receive the mobile phone. (Stage 130). The MTSO then initiates the transfer by sending a transfer order to the cell site in service. (Stage 135) In response, the cell site in service sends a transfer order to the mobile phone ordering it to switch from the current channel to the new channel. (Stage 140). The mobile phone then sends a confirmation of transfer order to the cell site in service. (Stage 145). The cell site in service sends a confirmation to the MTSO (Step 150) and, after receiving the confirmation, the MTSO switches the call from the cell site in service to the target cell site and releases the old channel (Step 152). Meanwhile, after the mobile phone sends the transfer order confirmation (Step 145), it is switched to the second channel. After your arrival, the mobile phone sends a "mobile on-channel" signal to the target cell site (Stage 155), which in turn, sends a "mobile channel" signal to the MTSO (Stage 160). If the MTSO did not previously receive the transfer order confirmation (for example, due to fading or distortion), the MTSO switches the call from the cell site in service to the target cell site and releases the old channel (Step 152) after receiving the signal "mobile in channel". During the portions of the transfer sequence described in FIG. 1, system users experience periods of muting while their call is transferred from the cell site in service to the target cell site. As system operators reconfigure their systems to meet growing demand by contracting cells, instituting sectorization, and deploying microcells, the resulting frequency of transfers and muting increases, especially in densely populated areas. Communications can be significantly denigrated depending on the duration of the mute. For example, in communications involving data transfer, interruptions caused by mute can affect reliability, forcing some mobile users to use special modem equipment to ensure the integrity of the data. In addition, even in ordinary conversations, intervals of more than 250 milisengudos are generally notable for most subscribers. In a conventional transfer, the communication of the mobile telephone is muted from the moment when the mobile telephone receives a transfer order (Step 140) until the mobile telephone finishes transmitting a signal "mobile on channel" (Step 155). The duration of this muting varies from approximately 100 milliseconds in the Multiple Time Division Access (TDMA) systems to approximately 250 milliseconds in Advanced Mobile Telephony Systems (AMPS). Because this period is determined by the characteristics of the mobile phone itself (for example, the radio interface standard employed and the speed of the frequency synthesizer), little can be done to shorten this period without the use of special mobile equipment. On the switch side, the conversation is muted from the moment the mobile phone receives a transfer order (Step 140) until the mobile phone finishes transmitting a "mobile channel" signal (Step 155) or the path of the network is switched in response to a transfer order confirmation (Stage 150), whichever comes last. If the MTSO does not receive any transfer confirmation (for example, due to fading or distortion), the conversation is muted until the network path is switched in response to the "mobile on channel" signal or an indication from the old channel. that the mobile is no longer present, whatever happens to the last one. If the mobile arrives at the new channel before the network path is switched, the muting period imposed by the mobile phone itself may be extended by 150 milliseconds or more. U.S. Patent No. 5,101,501 to Gihousen et al., Assigned to Qualcomm Incorporated, discloses a Code Division Multiple Access (CDMA) cellular system capable of reducing certain muting during transfers by using a "soft transfer" technique. According to this technique, the cell sites in service and objectives monitor the same frame of the same channel and, on a framing-by-framing basis, a selector evaluates both frames and chooses the frame with the highest quality. This is possible in a CDMA system because adjacent cellular sites can use the same radio channel and thus simultaneously monitor the same transmission of a mobile telephone. Similarly, in the reverse direction, both serving cellular sites and targets simultaneously transmit to the mobile telephone. Although this soft transfer technique is effective in reducing certain mute during transfers, this depends on the infrastructure and coding of CDMA and is not feasible in existing AMPS and TDMA systems. U.S. Patents Nos. 5,327,577 and 5,109,528 of Uddenfelt, assigned to Telefonaktiebolaget L M Ericsson, are directed to transfer techniques that reduce the mute in cellular communication systems. However, the systems of these patents depend in large part on an adaptive channel allocation system where at least some radio channels are common to the surrounding cell sites. In this way, as in the CDMA system, these techniques are generally incompatible with the existing AMPS and TDMA systems. To reduce mutation problems, some existing AMPS systems use conference bridges that combine conversation through target cell sites and sources during transfers. Although it reduces the muting due to the loss of transfer confirmations, the action of switching the conference bridge in and out of the call, itself, breaks the network path due to a brief muting before and after the transfer. In addition, conference bridges are generally only suitable for AMPS systems since they do not support encrypted speech, such as Vector Sum Excited Linear Prediction (VSELP) coding used in TDMA systems. Conference bridges also represent a significant investment of specialized equipment and should be designed to withstand peak transfer activity without diminishing the degree of service to mobile subscribers. In accordance with the foregoing, there remains a need for a cellular communication system and method that provides an improved transfer capability which reduces mutation during transfers between cell sites and is compatible with existing cellular telephone standards and systems, without incur the disadvantages associated with conference bridges. SUMMARY OF THE INVENTION In accordance with the foregoing, the present invention is directed to a cellular communication system and method that provides improved transfer capability which substantially avoids one or more of the problems due to the limitations and disadvantages of the prior art. It is an object of the present invention to provide a system and method of cellular communication that reduces the mutation experienced by users during transfers between cell sites. It is a further object of the present invention to provide a cellular communication system and method that provides an enhanced transfer capability that is compatible with existing cellular telephone systems and standards, including AMPS and TDMA systems. It is also an object of the present invention to provide a cellular communication system and method that minimizes the breaks in the network trajectories during transfers between cell sites. It is another object of the present invention to provide a cellular communication system and method that reduces the need for special modem equipment for mobile data transmissions. It is still another object of the present invention to provide a cellular communication system and method that provides improved transfer capacity without incurring the costs and risks of the deployment of CDMA technology. The additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description or may be learned by practicing the invention. The objects and advantages of the invention will be realized and achieved by means of the elements, method steps, and combinations particularly pointed out in the appended claims. To achieve the objects and in accordance with the purpose of the invention, as incorporated herein and extensively described herein, the invention comprises a method for transferring communications between a mobile unit and another unit from a cellular site in service on a first channel to target cellular sites on a second channel in a cellular communication system where the mobile unit is communicating a first information signal to the other unit and the other unit is communicating a second information signal to the mobile unit. The method includes the step of simultaneously monitoring a first signal received from the cell site in service on the first channel and a second signal received from the target cell site on the second channel, and transmitting a selected signal to the other unit. The selected signal comprises either the first or the second received signal. The method further includes the steps of sending a transfer order to the mobile unit through the cellular site in service on the first channel to switch to the second channel, and receive a "mobile channel" signal from the mobile unit through the mobile unit. target cell site on the second channel. In response to the "mobile on channel" signal, the monitoring stage, the selection stage and the transmission stage of a selected signal are terminated, and the second received signal is transmitted to the other unit. Furthermore, as embodied and broadly described herein, the invention comprises a cellular communication system for communicating information signals between a mobile unit and another unit coupled to said system using an assigned frequency band divided into radio channels. The system includes a system controller, a plurality of cellular sites connected to said system controller, and means for transferring communications between the mobile unit and the other unit from cellular sites in service on first channels to target cellular sites on a few second channels. The transfer means includes means for simultaneously monitoring a first signal received from the cell site in service on the first channel and a second signal received from the target cell site on the second channel and means for transmitting a selected signal to the other unit . The selected signal comprises either the first or the second received signal.

Both the above general description and the following detailed description are only exemplary and explanatory and not restrictive of the invention, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one embodiment of the invention and together with the description serve to explain the principles of the invention. In the drawings: Figure 1 is a diagram illustrating the sequence of a conventional transfer; Figure 2 is a block diagram illustrating the communication system of the present invention; Figure 3 is a block diagram illustrating the selector of the communication system illustrated in Figure 2; Figure 4 is a flow diagram illustrating the transfer method of the present invention. Figure 5 illustrates the communication links established during the normal operation of the system 200 illustrated in Figure 2. Figure 6 illustrates the communication links established after step 445 of the transfer method illustrated in Figure 4.

Figure 7 illustrates the communication links established after the end of the transfer method illustrated in Figure 4. DESCRIPTION OF THE PREFERRED MODALITY Reference will now be made in detail to the current preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Whenever possible, the same reference numbers will be used throughout all the drawings to refer to similar or equal parts. The communication system of the present invention is shown in Figure 2 and is generally designated by the reference number 200. The communication system 200 provides radio communications over a service area using an assigned frequency band divided into radio channels . Preferably, the communication system 200 uses standards and conventions of a standard AMPS or TDMA cellular system. For example, under the AMPS standard, the 25 MHz bandwidth is divided into 832 frequency channels of 30 KHz bandwidth. Many of the details of communication system 200 are well known in the art and are not specifically pertinent to the present invention. Accordingly, some such detail has been omitted for purposes of clarity.

As embodied herein and referring to Figure 2, the communication system 200 includes a system controller 205 for connecting to a public switched telephone network (PSTN) 208. The communication system 200 also includes a plurality of cell sites 210 geographically separated. A set of frequency channels is assigned to each cell site 210. The channels are assigned to cellular sites 210 in such a way as to minimize the possibility of co-channel interference. In this way, a channel used in a cellular site 210 will typically not be used in the surrounding cell sites or any other cellular site with transmission characteristics that could create co-channel interference. In a typical application, system 200 would include a large number of cell sites 210. However, because the operation of the system is essentially the same with few or with many cell sites, this description refers to three cell sites 210. Each cellular site 210 includes radio transmission and reception equipment (not shown) for establishing radio communications with a mobile unit 220. Cell sites 210 are connected to system controller 205 through data transmission system 215 which may be , for example, a microwave link, optical fibers, or wires, as is known in the art. Similarly, the system controller 205 is connected to the PSTN 208 through the data transmission system 218. Co or shown in Figure 2, the system controller 205 connects directly to the cellular sites 210. In a way alternative, the system controller 205 connects to the cellular sites 210 through one or more controllers of the base station (not shown). The configuration is further described in the US patent application of Donald V. Hanley and Jerry J. Parker, entitled "System and Method for Providing Cellular Communication Services Using a Transcoder," filed on the same date as this, and the which is incorporated herein for reference. The system controller 205 is preferably an MTSO, a mobile telephone switching center (MTSC), or a mobile telephone exchange (MTX), as is known in the art. For example, the system controller 205 may comprise a DMS-MTX system controller, as commercially available from Northern Telecom, Ltd. The communication system 200 of the present invention also includes a selector 230. The selector 230 is coupled to the system controller 205 through a connection 235. The selector 230 is further illustrated in Figure 3. As shown in Figure 3, the selector 230 includes a detector 315 which controls the operation of a switch 320. A The output of the switch 325 is connected to a decoder 330 to convert a radio signal input through the switch output 325 into a pulse code modulation (PCM) signal that is output from the encoder 330 through a connection 335. For example, when the communication system 200 of the present invention employs an adaptive differential PCM (ADPCM), the decoder 330 converts an ADPCM signal into a to PCM signal. When the communication system 200 employs a TDMA standard, the decoder 330 converts the VSELP decoding to PCM. Alternatively, when the communication system 200 employs a standard that directly generates a PCM (e.g., conventional AMPS signaling), the selector 230 does not include a decoder. The detector 315 monitors two signals input to the selector 230 through the connections 305 (s) and 305 (t). For AMPS systems, the detector 315 is adapted to continuously select the signal with the highest level of acoustic energy used by the Voice Activity Detection (VAD) or any similar technique, as is known in the art. For TDMA systems, detector 315 selects, on a frame-by-frame basis, the best acoustic sample to be sent to decoder 330. Detector 315 controls switch 320 so that the selected channel is broadcast from the connection 335 through the switch output 325 and the decoder 330. Because the surrounding cell sites 210 of the present invention do not use common channels, and because the mobile unit 220 does not transmit simultaneously over multiple channels, the signals Acoustic signals will not normally occur on both 305 (s) and 305 (t) connections at the same time. Thus, in a typical operation, the detector 315 selects between a signal containing a conversation and a null signal or signal containing noise or distortion. The selector 230 further includes a connection 340 to the encoder 360 for converting a signal input through the connection 340 into the adopted standard for the communication system 200. The encoded signal is output to the switch input 363. For example, when the communication system 200 of the present invention employs an ADPCM standard, the encoder 360 converts a PCM signal into an ADPCM signal. When the communication system 200 employs a TDMA standard, the encoder 360 converts a PCM signal into a VSELP signal. Alternatively, when the communication system 200 employs a standard that directly uses a PCM (e.g., conventional AMPS signaling), no encoder is included in the selector 230. The selector 230 further includes a switch 363 for connecting the input. of switch 363 to one or both of connections 350 (s) and 350 (t). Alternatively, the switch 363 continuously connects the switch input 363 to both of the connections 350 (s) and 350 (t). The switch 363 is controlled by the system controller 205 through the connection 235. The connections 305 (s), 305 (t), 335, 340, 350 (s), and 350 (t) or the selector 230 are coupled to system controller 205 through connection 235. In normal operation of communication system 200 (i.e., when system 200 is not attempting a transfer), mobile unit 220 communicates information signals (i.e., signals that carry recognizable or useful information) with another unit 240 through one of the cell sites 210 designated as the cellular site 210 '. Cell site 210 'is known as the cell site in service. The other unit 240 can be a wireline user connected to the system 200 through the PSTN 208. Alternatively, the other unit 240 can be another mobile unit connected to the system 200 through one of the cell sites 210. communications between the mobile unit 220 and the other unit 240 occur with the mobile unit 220 using a first radio channel of the set allocated to the cellular site in service 210 '. The communications between the mobile unit 220 and the other unit 240 are bidirectional. In this way, the mobile unit 220 communicates a first information signal to the other unit 240 while the other unit 240 simultaneously communicates a second information signal to the mobile unit 220. However, sometimes one or both of the information signals , first and second, may contain silence or a null signal. The information signals, first and second, can comprise a conversation, information, or any type of data. The first information signal is transmitted by the mobile signal 220 on the first radio channel to the cellular site 210 'which transmits the first information signal to the system controller 205 through the data transmission system 215'. The system controller 205 connects the received signal from the serving cell site 210 '(the first received signal) to the connection 305 (s) of the selector 230. In normal operation of the system 200, the first received signal is the first signal of information. Further, in normal operation, the switch 320 is set to constantly connect the connector 305 (s) to the switch output 325 without taking the detector 315 into account. In this way, the decoder 330 decodes the first information signal and outputs it as a PCM signal on the connection 335. The connection 335 is coupled to the other unit 240 via the system controller 205 and the PSTN 208. The second information signal is transmitted from the other unit 240 to the controller. system 205 through the PSTN 208 and the transmission system 218. The system controller 205 connects the second information signal to the connection 340 of the selector 230. The encoder 360 encodes the second information signal and outputs it as a coded signal to the switch input 363. In normal operation of the system 200, the switch 345 is set in such a manner that the second information signal is constantly transmitted through the connection ion 350 (s), not through connection 350 (t). The connection 350 (s) is coupled to the cellular site 210 'through the system controller 205 and the data transmission system 215'. The cellular site 210 'transmits the second information signal on the first channel to the mobile unit 220. Figure 5 illustrates the communication links established during the normal operation of the system 200. A bidirectional communication link is established between the mobile unit 220 and the other unit 240 through the PSTN 208, the connection 218, the system controller 205, the connection 235, the selector 230, the data transmission system 215 ', and the cellular site in service 210' which uses the first channel. During normal operation, if the serving cell site 210 'determines that the signal strength received from the mobile unit 220 falls below a predetermined threshold value, a transfer is initiated and the normal operation described above of the system 200 is altered as follows . A flow diagram illustrating the transfer method of the present invention is shown in Figure 4. The preferred transfer method is generally designated as 400. In transfer method 400, system 200 starts in normal operation. (Stage 402). When the signal level received from the mobile unit 220 falls below the predetermined threshold value, the serving cell site 210 'sends a transfer request to the system controller 205. (Step 405). In response, the system controller 205 sends "location measurement demands" for the serving cell site 210 'and other cellular sites 210 surrounding the serving cell site 210' to determine which cellular site 210 receives the mobile unit signal with the best signal strength. (Stage 410). In response, the surrounding cell sites 210 employ scan receivers to determine the signal strength of the mobile unit 220 on the first channel. Surrounding cell sites 210, as well as serving cell sites 210 ', send "location measurement responses" to system controller 205. (Step 415). If one of the surrounding cell sites 210 reports a better signal level for the system controller 205, that cell site is chosen as the target cell site, designated as the 210"cell site, to which the transfer will be attempted. (Step 420) Then a second channel is chosen from the inactive channels of the set used by the target cell site 210. " (Stage 425). Once the cellular site 210"and the second channel are determined, the system controller 205 couples the signal received from the target cell site 210" on the second channel (the second received signal) to the connection 305 (t) of the selector 230. (Stage 430). The system controller 205 establishes the switch 320 in such a way that the detector 315 simultaneously monitors the received signals, first and second, (Step 435), and continuously selects the received signal containing an information signal, causing the selected signal to be connects to switch output 325 and is transmitted to the other unit 240 via connection 235, system controller 205, connection 218, and PSTN 208. (Step 440). The system controller 205 also sets the switch 345 in such a way that the second information signal is transmitted simultaneously through the connections 350 (s) and 350 (t). The connection 350 (t) is coupled to the target cell site 210"via the connection 235, the system controller 205, and the data transmission system 215". The cellular site 210 'transmits the second information signal on the second channel to the mobile unit 220. In this way, the second information signal is transmitted simultaneously through the cellular site in service 210' on the first channel and through the site. target cell 210"on the second channel (Step 445) Figure 6 illustrates the communication links established after step 445 of the transfer method 400. A bidirectional communication link is established between the mobile unit 200 and the other unit 240 through the PSTN 208, the connection 218, the system controller 205, the connection 235, the selector 230, the data transmission system 215 ', and the cellular site in service 210' using the first channel. a bidirectional communication link is established between the second channel and the other unit 240 through the PSTN 208, the connection 218, the system controller 205, the connection 235, the selector 23 0, the data transmission medium 215", and the target cell site 210". Because the mobile unit 220 does not simultaneously transmit signals over multiple channels and simultaneously receives signals over multiple channels, however, communications will not actually occur on both established links at the same time. Referring again to Figure 4, the system controller 205 then sends a transfer order to the serving cell site 210 'which, in turn, sends a transfer order to the mobile unit 220 on said first channel to switch to said cell. second channel. (Stage 450). In response, the mobile unit 220 sends a transfer confirmation on the first channel. (Stage 455). This confirmation is received by the system controller 205 through the cellular site in service 210 'on said first channel. The mobile unit 220 is then switched to the second channel (Step 458) and sends a "mobile channel" signal to the system controller 205 through the target cell site 210"on the second channel (Step 460). "mobile on channel" signal, the system controller 205 establishes that the switch 320 be connected to the connector 305 (t) to switch to the output 325 without taking the detector 315 into account, and establishes the switch 345 in such a way that the second information signal is issued through the connection 350 (s) In this way, the system controller 205 ends the monitoring of the received signals, first and second, (Stage 465), the selection between the received signals ends, first and second, (Step 470), and the transmission of a selected signal stage ends (Step 475) In addition, the system controller 205 terminates the simultaneous transmission of the second information signal through both the cellular site in service 210 '. on the first channel as the target cell site 210"on the second channel. (Stage 480). Figure 7 illustrates the communication links established after the termination of the transfer method 400. A bidirectional communication link is established between the mobile unit 220 and the other unit 240 through the PSTN 208, the connection 218, the system controller 205, connection 235, selector 230, data transmission system 215", and target cell site 210" using the second channel. Referring again to Figure 4, at this point, system 200 has completed the transfer and is operating again in a normal manner (Step 402). The only difference is that cell site 210"now acts as the cell site in service and connections 305 (s) and 305 (t) and connections 350 (s) and 350 (t) are reversed in their designation. to those skilled in the art that various modifications and variations may be made to the computerized system and method of the present invention without departing from the spirit or scope of the invention, In addition, other embodiments of the invention will be apparent to those skilled in the art from of the consideration of the specification and practice of the invention set forth herein The specification and examples are thus only exemplary, indicating the true scope and spirit of the invention by the following claims.

Claims (23)

1. NOVELTY OF THE INVENTION Having described the present invention, (Considers as novelty and therefore the property described in the following claims is claimed as a property: 1. In a cellular communication system comprising a system controller and a plurality of cellular sites coupled to said system controller, wherein a unit mobile and another unit communicate information signals through one in service of said cellular sites on a first channel, said mobile unit communicating a first information signal to said other unit and communicating said other unit a second information signal to said mobile unit , a method of transferring communications between said mobile unit and said other unit of said cellular site in service on said first channel towards an objective one of said cellular sites on a second channel comprising the steps of: simultaneously monitoring a first signal received from of said cell site in service on said first channel and a second signal l received from said target cell site on said second channel; transmitting a selected signal to said other unit comprising said selected signal one of the group of said received signals, first and second; sending a transfer order to said mobile unit through said cellular site in service on said first channel to switch to said second channel; receiving a "mobile channel" signal from said mobile unit through said target cell site on said second channel; and terminating said monitoring step, said selecting step, and said step of transmitting a selected signal, and transmitting said second received signal to said other unit, in response to said "mobile in channel" signal. The method according to claim 1, characterized in that it further comprises the steps of: simultaneously transmitting said second information signal through said cellular site in service on said first channel and through said target cellular site on said second channel before sending said transfer order; and terminating said simultaneous transmission stage and transmitting said second information signal through said target cell site on said second channel in response to said "mobile channel" signal. The method according to claim 1, characterized in that said selected signal comprises said first received signal if said first received signal is an information signal or said second received signal if said second received signal is an information signal. The method according to claim 2, characterized in that said selected signal comprises said first received signal if said first received signal is an information signal or said second received signal if said second received signal is an information signal. The method according to claim 1, characterized in that said selected signal comprises said first received signal if the acoustic energy level of said first received signal is greater than the acoustic energy level of said second received signal or said second received signal if the The acoustic energy level of said second received signal is greater than the acoustic energy level of said first received signal. The method according to claim 2, characterized in that said selected signal comprises said first received signal if the acoustic energy level of said first received signal is greater than the acoustic energy level of said second received signal or said second received signal if the The acoustic energy level of said second received signal is greater than the acoustic energy level of said first received signal. The method according to claim 4, characterized in that said second channel is different from said first channel. The method according to claim 7, characterized in that said method further comprises the steps of: receiving a transfer request from said cellular site in service communicating with said mobile telephone on said first channel; and selecting said target cell site from said plurality of cell sites in response to said transfer request, 9. The method according to claim 8, characterized in that said cellular communication system uses an AMPS communication standard. The method according to claim 9, characterized in that said information signals, first and second, comprise encrypted PCM conversation. The method according to claim 9, characterized in that said information signals, first and second, comprise data encoded by PCM. The method according to claim 8, characterized in that said cellular communication system uses a TDMA communication standard. The method according to claim 12, characterized in that said information signals, first and second, comprise speech coded by VSELP. The method according to claim 12, characterized in that said information signals, first and second, comprise data encoded by VSELP. 15. In an AMPS cellular communication system comprising a system controller and a plurality of cellular sites coupled to said system controller, wherein a mobile unit and another unit communicate acoustic signals encoded by PCM through one in service of said cellular sites on a first channel, said mobile unit communicating a first information signal to said other unit and said other unit communicating a second information signal to said mobile unit, a method of transferring communications between said mobile unit and said other unit of said cellular site in service on said first channel towards an objective of said cellular sites on a second channel different to said first channel comprising the steps of: receiving a transfer request from said cellular site in service communicating with said mobile unit on said first channel; selecting said target cell site from said plurality of cell sites in response to said transfer request; simultaneously transmitting said second information signal through said cellular site in service on said first channel and through said target cellular site on said second channel; simultaneously monitoring a first signal received from said cellular site in service on said first channel and a second signal received from said target cellular site on said second channel; transmitting a selected signal to said other unit comprising said selected signal said first received signal if the acoustic energy level of said first received signal is greater than the acoustic energy level of said second received signal or said second received signal if the acoustic energy level of said second received signal is greater than the acoustic energy level of said first received signal; sending a transfer order to said mobile unit through said cellular site in service on said first channel to switch to said second channel; receiving a "mobile channel" signal from said mobile unit through said target cell site on said second channel; and ending said simultaneous transmission stage, said monitoring step, said selecting step, and said step of transmitting a selected signal, transmitting said second information signal through said target cellular site on said second channel, and transmitting said second signal. received signal to said other unit, in response to said "mobile on channel" signal. 16. A cellular communication system for providing communication of information signals between a mobile unit and another unit coupled to said system using an assigned frequency band divided into radio channels, comprising: a system controller; a plurality of cellular sites connected to said system controller; and means for transferring communications between said mobile unit and said other unit from one in service of said cellular sites on a first said channel to a target of said cellular sites on a second of said channels.said means of transfer including means for simultaneously monitoring a first signal received from said cell site in service on said first channel and a second signal received from said target cell site on said second channel, and means for transmitting a selected signal to said other unit, said selected signal comprising one of the group of said received signals, first and second. The communication system according to claim 16, characterized in that said transfer means further include means for simultaneously transmitting a second information signal communicated from said other unit through said cellular site in service on said first channel and through said target cell site on said second channel. 18. The communication system according to claim 17, characterized in that said selected signal transmission means comprises means for transmitting said first received signal if said first received signal is an information signal or said second received signal if said second received signal is a signal of information. The communication system according to claim 17, characterized in that said selected signal transmission means comprise means for transmitting said first received signal if the acoustic energy level of said first received signal is greater than the acoustic energy level of said second signal. received or said second received signal if the acoustic energy level of said second received signal is greater than the acoustic energy level of said first received signal. The communication system according to claim 18, characterized in that said second channel is different from said first channel. 21. The communication system according to claim 20, characterized in that said system uses an AMPS communication standard. 22. The communication system according to claim 20, characterized in that said system uses a TDMA communication standard. 23. A cellular communication system comprising a system controller and a plurality of cellular sites coupled to said system controller, wherein a mobile unit and another unit communicate acoustic signals encoded by PCM through one in service of said cellular sites on a first channel, said mobile unit communicating a first information signal to said other unit and communicating said other unit a second information signal to said mobile unit, said system comprises: means for transferring communications between said mobile unit and said other unit starting from said cellular site in service on said first channel to an objective one of said cellular sites on a second channel different to said first channel, said transfer means include: means for transmitting said second information signal through said cellular site in service on said first channel and through said target cell site about said second channel; means for simultaneously monitoring a first signal received from said cellular site in service on said first channel and a second signal received from said target cellular site on said second channel; means for transmitting a selected signal to said other unit, said selected signal comprising said first received signal if the acoustic energy level of said first received signal is greater than the acoustic energy level of said second received signal or said second received signal if the level of acoustic energy of said second received signal is greater than the acoustic energy level of said first received signal.