MXPA96000130A - System to explore cana - Google Patents

Abstract

The present invention relates to a communication system for communicating a stream of data, said communication system comprising: a receiving device having a processing means and a receiving means, said receiving means having the ability to receive on a plurality of channels: a transmission device for transmitting a data stream containing messages that can be repeated, said receiving means receives said data stream and said processing means determines if: (i) the following message is a repetition of a message previous (ii) the previous message was received, and said receiving means examines a different channel to the channel on which said message was received if said next message is a repetition of a previous message and the previous message was received.

Description

SYSTEM FOR EXPLORING CHANNELS Field of the Invention The present invention relates generally to portable telephones, and more particularly to an improved portable telephone that operates in both cellular and wireless telephone systems. BACKGROUND OF THE INVENTION Typically, a wireless telephone system includes a wireless portable headset and a wireless base station connected to a phone system of a telephone company by means of wireline telephone lines. The wireless base station has a dedicated wireline telephone number that allows the user to place and receive calls using the wireless portable handset within a limited range of the wireless base station, such as at an address. However, due to its limited range, the portable wireless headset provides the user with relatively local radiotelephone communication. The user may also be provided with radiotelephone communication outside the range of the wireless telephone system through a cellular telephone system. Typically, a cellular telephone system includes cellular (mobile or portable) subscriber units and cellular base stations connected to the landline telephone system through one or more cellular switching networks. Each cellular subscriber unit has an assigned cellular telephone number that allows the user to place and receive calls within a wide range of cellular base stations, such as throughout an entire metropolitan area. However, the cost of using the cell phone service is much greater than the wireless telephone service. There is a problem for the user who frequently relocates between the wireless and cellular telephone systems. An incoming call directed to the system where the user is not located can be lost. In this way, there is a need for a system that re-directs a telephone call from the user to the system where the user is located. Additionally, a portable radiotelephone that transmits and receives calls on both cellular and wireless systems must have the ability to select the clearest channel available for use. An automatic channel selection must minimize the interference and eliminate the need for conventional frequency planning. There is a problem in selecting a clear channel without losing data or adding costs to either the wireless base station or the radiotelephone. Thus, there is a need for a system that can select a clear channel without losing data or adding costs to the wireless base station or the radiotelephone. Additionally, any portable radio device that uses batteries can take advantage of a system to increase the period of time between battery recharge times. The previous solutions in the cellular telephone system depend on the messages that are repeated for an error correction by majority vote. The radiotelephone turns off its receiver if it correctly decodes the first message or there are no errors in a majority of votes of the first three transmissions of the message. The receiver remains off for the remaining repetitions of the message. However, this solution requires the system to use error correction by a majority vote. In this way, there is a need for an energy saving system that does not depend on error correction by majority vote. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of an operating configuration for a portable radiotelephone in which various systems, including both a cellular and a wireless system, can be accessed by means of the same portable radiotelephone. Figure 2 is a block diagram of an authorization and call routing equipment (ACRE).

Figure 3 is a schematic map showing a typical installation of coverage areas for wireless systems, microcellular and cellular. Figure 4 is a block diagram of a wireless base station that can employ the present invention. Figure 5 is a block diagram of a portable radiotelephone that can employ the present invention. Figure 6 is a timeline of the system scanning process that can be employed in the portable radiotelephone of Figure 5. Figure 7 is a data format for a message stream. Fig. 8 is a flow chart describing a process for determining whether the radiotelephone of Fig. 5 can turn off its receiver. Fig. 9 is a flow chart describing the process for determining when to turn on the radiotelephone receiver. Figure 10 shows a message stream for a wireless channel. Figure 11 shows a message protocol. DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT A generalized block diagram of an application of the present invention is shown in Figure 1. A portable wireless cellular radiotelephone (PCC) 101 is shown having the ability to communicate with a conventional cellular radiotelephone system 103, which has a plurality of cellular base stations 105, 107 located in geographically separate locations but installed to provide radiotelephone coverage over a wide geographical area. The cellular base stations are coupled to a control terminal 109 which provides coordination between the plurality of cellular base stations, including the loose control of the user's mobile and cellular equipment, and provides call switching and interconnects to the telephone network public switched (identified hereinafter as "TELCO") lll. The PCC 101 also has the ability to communicate with a microcellular base station 113, which is a cellular attached cell that has limited capabilities and lower power but that provides public radiotelephone service to different areas such as shopping malls, airports, etc. The microcell base station 113 is coupled to the TELCO 111 wireline telephone system so that calls can be placed on the TELCO. The PCC 101 further has the ability to communicate with and output the radiotelephone calls via a wireless base station 115, which provides a private telephone line interconnection with the TELCO III for the PCC 101 user. The wireless communication system uses an authorization and call routing equipment (ACRE) 117 for providing call routing information to a telephone switching system. In this way, the switching system automatically directs telephone calls between the cellular, microcellular and wireless systems. The ACRE 117 also authorizes the wireless base station 115 to use the channels. The ACRE 117 can be part of the TELCO 111 or it can be an independent device. As noted previously, the wireless base station 115 and the PCC 101 collectively provide the limited range radio service conventionally known as wireless telephone service. Such a service has become saturated, conventionally using a few radio frequency channels in the radio bands of VHF (very high frequency) or UHF (ultra high frequency). The user of a radiotelephone must expect the radiotelephone service to be available wherever he / she travels in the United States and that this service is provided at the lowest cost. It should also be expected that the radiotelephone service will be provided in a portable unit that is as compact and inexpensive as possible. The PCC 101 is uniquely configured to fulfill this purpose. In addition, the wireless base station 115 is uniquely designed to provide interconnection of the telephone with the telephone line of the user's home when the user has the PCC 101 within the radio range of the station. wireless base 115. Figure 2 shows a block diagram of the ACRE 117. The ACRE 117 is connected to a TELCO 111 via an interface 202. The interface 202 controls and formats the messages between the TELCO 111 and a processor 204. The processor 204 in combination with a control software memory 206 is the intelligence of the ACRE 117 and performs the authorization and authentication tasks and provides the call routing information. A database of the subscriber 208 contains the data required by the processor 204 in order to carry out the tasks previously discussed. The ACRE 117 can be separated from the TELCO 111 as shown in Figure 2 or it can be part of the TELCO 111, usually part of the switching equipment. When the ACRE 117 is part of the TELCO 111, the ACRE 117 may not need the interface 202. Additionally, the functions of the ACRE can be carried out by the existing equipment in the TELCO.

Figure 3 shows a typical installation of coverage areas for wireless, microcellular and cellular systems. The coverage area of the wireless system is the smallest and resides within the microcellular system. The microcellular system has an intermediate coverage and resides within the cellular system. The coverage area of each system may depend on, but not limited to, the number of base stations in each system, the antenna height of each base station, and the energy level used by each system. The user of the portable radiotelephone can relocate between the various coverage areas. The portable radiotelephone can change between systems based on, but not limited to, the location of the portable radiotelephone, the availability of the system and the user's preference. The areas of coverage of the systems are not limited to the particular installation as shown in Figure 3. A coverage area may be independent of another coverage area or may partially overlap one or more different coverage areas. The wireless base station 115, conceptually, is a subminiature cellular system that provides a single signaling channel which transmits output data messages in a manner analogous to a conventional cellular output signaling channel and receives service demands from of a remote unit, such as a PCC 101. Appropriate service demands are granted with an allocation of a voice channel (done via the control channel) in the same or a second radio frequency in which the PCC 101 to tune in to your phone call. Figure 4 shows the basic implementation of a wireless base station. A conventional transmitter 301 and a conventional receiver 303 suitable for use in the frequency band 869 to 894 MHz and 824 to 849 MHz, respectively, which are used for conventional cellular services, are coupled to a common antenna 305 via a 307 duplexer The power output of the transmitter 301 is limited to approximately 6 milliwatts in order to minimize interference to other services and other wireless telephone stations. The selection of the channel frequency is implemented by a frequency synthesizer 309 controlled by a logic unit 311. Within the logic unit 311 is a microprocessor 313, such as a 68HC11 available from Motorola, Inc., or a similar microprocessor, which is coupled to the conventional memory devices 315 that store the microprocessor operating program, the base identification (BID) and the personality of the client, and other configurations. The transmitted and received data is encoded / decoded and coupled between the receiver 303, the transmitter 301, and the microprocessor 313 via the signaling interface hardware 317. The instructions of the microprocessor are communicated and implemented by the control hardware 319. The interface with the wireline telephone line of the user's home is conventionally carried out via an interface of the TELCO 321. The power is supplied from the main conventional AC lines and returned with a battery reserve (all represented as energy 323). The PCC 101 is a portable radiotelephone transceiver shown in block diagram form in Figure 5. A portable radio receiver 401, capable of receiving the frequency band between 869 and 894 MHz, and a portable transmitter 403, capable of transmitting with low energy (approximately 6 milliwatts in the preferred embodiment) over frequencies between 824 and 849 MHz, they are coupled to antenna 405 of PCC 101 by means of a duplexer 407. The particular radio frequency channel to be used by the transmitter 403 and receiver 401 are determined by microprocessor 409 and communicated to frequency synthesizer 411 via the interface circuit 413. The signals of the data received by the receiver 401 are decoded and coupled to the microprocessor 409 by the interface circuit 413 and the data signals to be transmitted by the transmitter 403 are generated by the microprocessor 409 and formatted by the interface 413 before to be transmitted by the transmitter 403. The operational status of the transmitter 403 and the receiver 401 is enabled or disabled by the interface 413. The interface also controls the diodes that emit light, 415 and 417, which are used to indicate to the user which system currently receives the PCC 101. The control of the user's audio, the microphone output and the horn input is controlled by the audio processing circuitry 419. In the preferred embodiment, the microprocessor 409 is a 68HC11 microprocessor, available from Motorola, Inc., and performs the necessary processing functions under the control of the programs stored in a conventional ROM 421. The characterization settings of the PCC 101 are stored in EEPROM 423 (which can also be stored in the microprocessor, EEPROM on board) and include the number assignment (NAM) required for operation in a conventional cellular system and the base identification (BID) required for operation with the base Wireless user's own. The transmitter 403 of the PCC 101 has the ability to transmit with the full range of output power that is required for operation in a conventional cellular system. This output energy range consists of six groups of output power magnitudes ranging from a high output power level of approximately 600 milliwatts to a low output power level of 6 milliwatts. This range of six power output groups is enabled when the PCC 101 is in the cellular system mode. In accordance with the preferred embodiment of the present invention, the same PCC 101 is compatible with both the cellular and wireless telephone systems 103. This is achieved by allowing the PCC 101 to operate on both cellular and wireless telephone systems 103 using only cellular telephone frequencies. . The installation of the radiotelephone has desirable advantages for the user. The PCC 101, in combination with the wireless base station 115, can automatically direct, via the ACRE 117, an incoming call to the telephone system in which the PCC 101 is located without causing inconvenience to the user. The TELCO 111, in combination with the ACRE 117, can automatically direct an incoming call to the PCC 101 without causing inconvenience to the user. The established priority for PCC 101 is that the wireless base station 115 is the first desired path for a user's telephone call and the conventional cellular (or microcellular system) is the second alternative, the implementation process of that priority is shown in FIG. Figure 6. The representation in Figure 6 is of the reception of receiver 401 of the PCC of the output signaling channel or of the group of signaling channels transmitted from the cellular system, the wireless base, and the microcellular system in relation to time. This diagram helps the understanding of the unique scanning priority configuration of the present invention. The PCC receiver 401 can monitor 431 the output message stream that is transmitted from the signaling channel of the cellular system (which was selected from among the plurality of cellular signaling channels in a conventional manner). At the appropriate time, the PCC receiver 401 is instructed by its microprocessor 409 to tune in to the frequency or one of the frequencies that is used by the wireless base station 115 as a signaling channel. The PCC receiver 401 scans the channel or output signaling channels of the wireless base 433 for a period of time t2. If the signaling data stream is not received with sufficient quality, the PCC receiver 401 is returned to the previously selected signaling channel of the cellular system 103. It remains tuned to this signaling channel 435 for a period of time, tl t before Try another exploration of a signaling channel of one of the alternative systems. The relation of y t2 is such that a cell page message (ie, a radiotelephone call or other transmitted requirement) that is repeated, conventionally, after a 5 second pause it will not be omitted because the PCC 401 receiver was scanning an alternate system during both cell page message transmission times. The time t must be greater than the sum of the pause between the two pages and the typical time to transmit two pages. The time t2 must be less than the time between the two pages. If the time pause is 5 seconds and the typical time to transmit a page is 185.2 milliseconds, t1 must be greater than 5.3704 seconds and t2 must be less than 5 seconds. After monitoring the signaling channel of the cellular system for a time t, the PCC 401 receiver can be instructed to tune to the signaling channel or to the signaling channels, sequentially, of the microcellular system, as shown at 437. If not a suitable microcellular signaling channel is found during scanning of the predetermined signaling channel frequencies, the PCC 401 receiver is tuned back to the signaling channel of the cellular system, as shown at 439. An exploration of the signaling channels , 441, of the wireless base station 115 that discovers a signaling data stream that meets the appropriate quality requirements results in the PCC receiver 401 continuing to monitor the wireless signaling channel. The PCC receiver 401 remains in the wireless signaling channel without re-scanning another system until the PCC 101 can not receive the transmitted signal from the wireless base for a period of time of 5 continuous seconds. The effect of this priority process is to give priority to the wireless base station 115 in the PCC 101. Once the signaling channel of the wireless base station 115 is discovered, the PCC 101 remains tuned to this channel. In this way, when the PCC 101 is initially tuned to the cellular system, it will automatically switch to the wireless base station when it is possible to access the wireless base station. Once the PCC receiver 401 has found the wireless base signaling channel, it remains tuned to that channel. When the PCC transceiver is first turned on, its first scan of the signaling channels is the restored signaling channel or channels of the wireless base station 115. Of course, the user can modify the hierarchy of the automatic priority scan by entering a modification code in the PCC 101. In this way, the user can only force the exploration of the signaling channels of the cellular system, only the signaling channels of the wireless base, only the signaling channels of the microcellular system, or combinations of the systems . The user can also carry out a call origin with changing once to the system of his choice. Once the signaling channel of a system has been monitored, a visual indication is given to the user of the PCC transceiver. In the preferred embodiment, this indicator is a set of light emitting diodes (LEDs) 415, 417, one of which is illuminated in a unique manner to indicate to which system the PCC transceiver is tuned. Other indicators may alternatively be used to communicate the same information. For example, an identifier system may appear in the numerical display of PCC 101, or a flashing symbol (having different flashing rates) may be used. However, this indication allows the user to determine which system he is in and decide if he wants to complete a radiotelephone call in the indicated system. PCC 101 is a battery-operated radiotelephone. All battery operated radio communication devices are interested in saving energy to lengthen the time between battery recharging. The PCC 101, like all cell phones and wireless, spend most of their time monitoring incoming calls. Many of the messages received by PCC 101 during this period are repetitive. If the PCC 101 could detect which messages are repetitions, it could choose not to receive those messages and turn off the receiver 401 and the frequency synthesizer 411 during the repeated message, thus saving the energy that would otherwise be spent to receive the repeated message. Figure 7 shows a simplified diagram of the message format used in the dual-use radiotelephone system. The message format has a repeat indication (R / I) 502, a message type (MSG TYPE) 504, followed by the message (MSG) 506. The repetition indication 502 and the message type 504 are sometimes grouped together as the repetition indication field 508. The sequence of the message type does not follow a default rotation so an "E" type message does not always follow a "A" type message. Figure 8 shows a process for determining whether a message is repeated from a previously received message. The process begins in block 510, and the repeat indication field is received in block 512. In block 514 it is determined whether repetition indication 502 indicates that the message will be a repetition. If the message is not a repetition in block 514, the message is received in block 516. In block 518 a counter is set to zero, which counts the number of messages that were not received because they were repetitions, and the process starts again. If in block 514 the message is a repetition, in block 520 it is determined whether the message has been previously received. One way to determine this is for PCC 101 to store a list of all types of messages that have been previously received. If the message type field 504 is matched to a message type in the list, the message has been previously received. If the message has not been previously received, the process continues in block 516. If the message was previously received in block 520, the counter in block 522 (counter_DRx) is examined to determine if it is greater than a maximum limit. If the limit has been exceeded then the process continues in block 516. If in block 522 the limit was not exceeded then the receiver is disabled for a portion of the message in block 524. The counter is incremented in block 526 and then the process is restarted for the next message. Fig. 9 shows a flowchart to control the time the receiver is turned off in block 524 of Fig. 8. The process begins in block 530, and the receiver is turned off in block 532. In block 534 it is reset a timer (time counter_DRx). Then the time counter is examined in block 536 until the time counter is greater than a predetermined value, waiting time. Once the waiting time has been exceeded, the receiver is turned on in block 568, which terminates the process in block 540. In order to select a channel to be used, the available channels must be examined. Sometimes this process is called "exploration". This examination determines if the channel is in use by another device and optionally determines the type of device that is using this channel. One way to determine if a channel is available for service is by measuring the resistance of the signal. An alternative method is by measuring the error rate in the bits. In order to build a low-cost wireless telephone system, this measurement is preferably made in both the PCC 101 and the wireless base station 115. Alternatively, this could be done exclusively in the PCC 101 of the wireless base station 115. A difficulty in using the PCC 101 to carry out this measurement is that it has a single receiver 401. When the PCC receiver 401 is examining the channels, it can not receive the information that is transmitted by the transmitter 301 of the wireless base station 115. Accordingly, the PCC 101 could lose important information that is being transmitted by the wireless base station 115. One solution to this problem is to add a second receiver to the PCC 101. However, this adds a considerable cost to the PCC 101. using the wireless base station 115 to carry out this measurement is that the transmitter 301 and the receiver 303 of the base station 115 in the preferred embodiment are designed such that the receiver 303 can only receive communication on the channel over which the wireless base station 115 transmits. This is because a single frequency synthesizer 309 is coupled to both the receiver 303 as to the transmitter 301. Consequently, in order for the wireless base station 115 to examine the channels, it must change the channel on which its transmitter 301 operates. This has the undesirable defect of causing the PCC 101 to think that it can not receive a signal transmitted by the base station wireless 115 This could cause PCC 101 to look for other services such as cellular or microcellular services. One solution to this problem is to implement the wireless base station 115 with two frequency synthesizers. One of the frequency synthesizers would be coupled to the transmitter 301 and the other frequency synthesizer would be coupled to the receiver 303. Both frequency synthesizers would be connected to the control means 319. The disadvantage of this approach is that the cost of the base station is increased wireless 115. Accordingly, there is a need for an improved channel examination mechanism. Figure 10 shows a chronogram of the information transmitted on the multiple channels. One of these channels 601 is used by the wireless base station 115 for the transmission of information to the PCC 101. Several other channels 603 are channels that can be examined for their potential use by the wireless system. The channel that is used by the wireless base station 115 for the transmission of information contains an information stream. Generally speaking, this stream contains a continuous stream of data that includes a repeating indication (R / I) field 605 followed by a message type field 607 followed by a message data 609. The stream continuously repeats this sequence. The R / I field 605 indicates whether the message data that follows is a repeated transmission or a new transmission. The message type field 607 indicates which message is being transmitted. The data field of the message 609 contains a particular message, for example, MSG-A. A PCC 101 that receives the data stream transmitted on the wireless channel first receives the repetition indication field 605 which indicates that the message is a new transmission. Since it is a new transmission it receives the message type field 607, which indicates that MSG-A is contained in the message data 609 that follows. The PCC receives the MSG-A 609 and remembers that it received this message. Then the PCC 101 receives the repeat indication field 611 which indicates that the data of the following message is a repetition. The message type field 613 is then received. This message type field indicates that the data in the subsequent message contains the MSG-A. At this point, PCC 101 determines that MSG-A 615 is a repeated transmission since it received the original transmission from MSG-A 609 and the repeat indication field 611 indicates that this instance of message A is a repetition. According to the above, the PCC does not need to receive the MSG-A 615 and can use the reception time of the MSG-A 615 for other purposes. In particular, PCC 101 can use the reception time to examine one or more different channels as shown in 617 and 619. One reason to examine other channels is to determine the best channel to be used in the communication. You could also examine other channels to find other types of services that may be available. Other possible services include, but are not limited to, cellular service, microcellular service, or data services such as a paging system. Additionally, the PCC 101 could search for another wireless base station 115. After scanning the desired channels, the PCC 101 returns to monitor the wireless channel. The PCC may return to the start of the next repeat indication field 621 or slightly before the start of the next repeat indication field 621 in order to allow time for the receiver to be established. Then the PCC 101 receives the repeat indication field 621. Now another time is shown where the scan may occur. The PCC 101 receives the message type 623 which contains a value indicating that the wireless base station will scan other channels during the time where the message data field would normally be located. The wireless base station 115 scans one or more channels as described at 625 and 627 and retransmits the repeat indication field 629 at a predetermined time. In the preferred mode, this would be the time required to send the message data since the communication system is preferably a synchronous transmission system. This invention could also be carried out in an asynchronous transmission system. The wireless base station 115 may enable its transmitter slightly before transmitting the next repeat indication field 629 to allow the PCC receiver time to be established. PCC 101 ignores the wireless channel during the time when transmission does not occur. The transmission stream then continues with the following repeat indication field 629, the message type field 631, and the data field of the next message 633, which contain the MSG-B. Instead of ignoring the wireless channel during the time where transmission does not occur, the PCC 101 may also examine one or more channels as described at 625 and 627. The PCC would return its receiver 303 to the wireless channel slightly before the next field of communication. repetition indication 629. As in the previous case, this examination of channels could be used to determine the best channel or channels for communication or it could be used to find services. The PCC 101 could use the data it finds when examining the channels to choose the best channel or could transmit this information to the wireless base station 115. Likewise, the wireless base station 115 could use the data it finds when examining the channels to choose the better channel or could transmit this information to PCC 101. Although these methods of channel examination are described for a wireless communication system, they could also be used in cellular communication systems or in other communication systems. The use of these channel examination messages in any system is considered within the scope of this invention. Figure 11 shows an image of the message stream in the preferred embodiment. This synchronous message transmission format contains a sync qualifier field 640 followed by a synchronization field 642 followed by a word 644. These three fields are repeated continuously. Synchronous field 642 is used by PCC 101 to synchronize its receiver. The preferred mode allows two different values for the synchronous field. These values are the inverse of each other. A value, 10110100110010011001, indicates that an identification word follows, the other value, 01001011001101100110, indicates that a call processing word follows. The synchronous qualifier field 640 indicates that the subsequent word contains a new transmission, that the subsequent word contains a repetition, or that the wireless base station 115 will scan during the time when the word data would normally be transmitted. If the synchronous qualifier field indicates that the word contains a repeated transmission, the value in the synchronous qualifier field also indicates which word is being repeated. In this way the synchronous qualifier field 640 is very similar to the combination of a message type 607 and a repetition indication 605 as shown in figure 10. In a synchronous transmission system a message is usually comprised of one or more words . In this way, the message fields 609, 615, and 633 of Figure 10 could also be called a word. Similarly, in Figure 7, messages 506 could also be called a word. For the purposes of the above described scanning methods and the energy saving receiver method described above, the terms word and message can be used interchangeably. A radiotelephone and a system have been described for allowing the radiotelephone to operate in cellular, microcellular or wireless communication systems. The PCC 101 receives a data stream from a wireless base station 115. The wireless base station 115 transmits an indication in the data stream that it is going to start scanning. While the wireless base station 115 is scanning, the PCC 101 conducts a scan on its own. The PCC 101 also performs a scan when it determines that a message is a repetition and has been previously received. For those skilled in the art, it is obvious that many modifications can be made to the invention without departing from the spirit of the invention. For example, ACRE 117 can be carried out by several pieces of equipment, which could be placed separately from each other. The equipment and the authorization function could be separated from the function and the call routing equipment. Any such modification is considered part of the exclusive rights of the inventor of this invention. For a full understanding of the scope of the invention reference should be made to the appended claims.

Claims (10)

1. Novelty of the Invention Having described the present invention is considered as a novelty and therefore claimed as property described in the following claims: 1. A communication system to communicate a stream of data, said communication system comprises: a device for reception having a processing means and a reception means, said reception means has the reception capacity over a plurality of channels; a transmission device for transmitting a stream of data containing messages that can be repeated; said receiving means receives said data stream and said processing means determines whether; (i) the following message is a repetition of a previous message (ii) the previous message was received, and said receiving means examines a different channel to the channel on which said previous message was received if said next message is a repetition of a previous message and the previous message was received. The communication system according to claim 1, characterized in that the receiving device receives the following message if it is not a repetition of a previous message. The communication system according to claim 1, characterized in that the receiving device receives the following message if said previous message has not been received. The communication system according to claim 1, characterized in that the data stream contains a repetition indication that uses the processing means to determine whether the next message is a repetition of a previous message. The communication system according to claim 4, characterized in that the repetition indication is a field in the data stream. The communication system according to claim 4, characterized in that the repetition indication is a position in the data stream. The communication system according to claim 5, characterized in that the repetition indication field further comprises a message type field and the processing means determines whether the previous message having the same type of message was received. The communication system according to claim 5, characterized in that the processing means counts the number of successive repetition indication fields that are true and if that count exceeds a predetermined number, it receives the message. 9. A communication system comprising: a base station including a processor and a receiver, said base station transmits a stream of data over a channel; said processor directs the base station for, - (i) transmitting a scan indicator (ii) terminating said data stream after transmitting the scan indicator (iii) examining a different channel to the data stream channel after finishing said data stream data stream (iv) summarizing said data stream in said channel of the data stream after a predetermined period of time. The communication system according to claim 9, further characterized in that it comprises a radiotelephone, said radiotelephone receives said data stream. SYSTEM FOR EXPLORING CHANNELS Summary of the Invention A communication system has a PCC 101 that receives a stream of data from a wireless base station 115. The wireless base station 115 transmits an indication in the data stream that a exploration. While the wireless base station 115 is scanning, the PCC 101 conducts a scan on its own. The PCC 101 also performs a scan when it determines that a message is a repetition and that it has been previously received.