MXPA96000131A - Energy saving system for a radio mo - Google Patents

Abstract

The present invention relates to a method for reducing the energy consumed by a receiving device used in a data communication system having at least one message transmitted a plurality of times, having the associated message and an associated repetition indication, in where the message type and the repetition indication are transmitted before the message and the repetition indication is true when the message is a repetition transmission, the repeating device having a receiver capable of receiving the transmitted message type, the indication of repetition and the message, the method comprising the steps of: receiving the transmitted repetition indication, determining whether the received repetition indication is true, initiating a count when the received repetition indication is not true, determining whether the transmitted message was previously received when the indication of repetition received is true a, so that the type of message transmitted is received, determine if the type of message received is related to a previously received message type, start the count when the transmitted message has not been previously received, determine if the count is greater than a limit when the transmitted message has been previously received, start the count when the count is greater than the limit, increase the count by one when the count is less than or equal to the limit, so the number of messages not received is counted because were received, to be turned off at least for a predetermined period of time, the receiver, when the indication of repetition received is true and the transmitted message has been previously received, so that the energy consumed by the receiving device is reduced

Description

ENERGY SAVING SYSTEM FOR A MOBILE RADIO 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 A wireless telephone system typically includes a portable wireless headset and a wireless base station connected to a telephone system of a telephone company using landline telephone lines. The wireless base station has an assigned landline telephone number that allows the user to make and receive calls using the wireless portable headset within a limited range of the wireless base station, such as in a home. However, due to its limited range, the portable wireless headset provides the user with relatively local radiotelephone communication. The radiotelephone communication outside the range of the wireless telephone system can also be provided to the user via a cell phone system. Typically, a cellular telephone system includes cellular subscriber units (mobile or portable) and base cellular stations connected to the terrestrial telephone system via one or more cellular switching networks. Each subscriber's cellular unit has an assigned cellular telephone number that allows the user to make and receive calls within an extended range of base cellular 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 cellular and wireless telephone systems. An incoming call that goes to the system where the user is not located can be lost. Thus there is a need for a system that redirects the user's telephone calls to the system where the user is located. Additionally, any portable radio device that uses batteries may benefit from a system to increase the period of time between the battery surcharge times. The previous solutions in the cell phone system depend on the messages being repeated for a majority vote error correction. The radiotelephone turns off its receiver if it correctly decodes the first message or there is no error in a majority of votes of the first three transmissions of the message. The receiver remains off by the remaining repetitions of the message. However, this solution requires the system to use the majority vote error correction. Thus, there is a need for an energy saving system which does not depend on the majority vote error correction.

Brief Description of the Drawings Figure 1 is a block diagram of an operating configuration for a portable radiotelephone i ') - "in which several systems, including both a cellular system and a wireless system, can be accessed by the same portable radiotelephone Figure 2 is a block diagram of an authorization and call routing equipment (ACRE) 15 Figure 3 is a schematic map showing a typical installation of the coverage areas for wireless, microcellular and cellular systems. Figure 4 is a block diagram of a wireless base station which 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 chronogram of the process scanning of the system that can be employed in the portable radiotelephone of Figure 5. Figure 7 is a data format for a current of m Figure 8 is a flowchart describing a process for determining whether the radiotelephone of Figure 5 can turn off its receiver. Fig. 9 is a flow chart describing the process for determining when to turn on the radiotelephone receiver. id 'Figure 10 shows a message stream for a wireless channel. Figure 11 shows a message protocol. Detailed Description of a Preferred Modality Figure 1 shows a block diagram generalized of an application of the present invention.

A portable cellular wireless radiotelephone is shown (PCC) 101 having the ability to communicate with a conventional cellular radiotelephone system 103, which has a plurality of cellular base stations 105, 107 0 located in geographically separate locations but arranged to provide radiotelephone coverage over a broad geographic area. The cellular base stations are coupled to a control terminal 109 which provides coordination among the plurality of base stations 5, including the hands-free cellular and mobile handset of the user, and provides call switching and interconnects to the switched telephone network public (hereinafter referred to as "TELCO") 111. 5 PCC 101 also has the ability to communicate with a microcellular base station 113, which is an attached cell cell that has lower power and limited capabilities but that provides service public radiotelephone to different areas such as (* commercial galleries, airports, etc. The microcellular base station 113 is coupled to the terrestrial telephone system of the TELCO 111 so that calls can be made in the TELCO.The PCC 101 also has the capacity to communicate 5 and make radiotelephone calls via a wireless base station 115, which provides an inte connection to the private telephone line with the TELCO 111 for the user of the PCC 101. The wireless communication system uses a call routing and authorization equipment (ACRE) 117 to provide 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 5 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 meet "this end. In addition, the wireless base station 115 is uniquely designed to provide telephone interconnection to the telephone line of the user's home when the user has the PCC 101 within the radio range of the wireless base station 115. Figure 2 shows a block diagram of the ACRE 117. The ACRE 117 is connected to a TELCO lll 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 memory of Control Software 206 is the intelligence of the ACRE 117 and performs the authorization and authentication tasks and provides the call routing information. 5 A subscriber database 208 contains the data required by the processor 204 in order to carry out the tasks discussed above. 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 can In addition, the functions of the ACRE can be carried out using 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 area of The coverage 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 5 different 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 a remote unit, such as a PCC 101. Appropriate service demands are granted with an allocation of a voice channel (done via the ... control honeycomb) on the same or a second radio frequency for which the PCC 101 is instructed to tune in to its telephone 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 conventional memory devices 315 that store the microprocessor operating program, base identification (BID) and customer personality, 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 interface hardware of the signaling 317. The instructions of the microprocessor are transmitted and implemented by the control hardware 319. The interface with the landline 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 line and is protected with a battery backup (represented all 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 407 duplexer. The particular radio frequency channel to be used by the transmitter 403 and the receiver 401 are "determined by the microprocessor 409 and transmitted to the frequency synthesizer 411 via the interface circuit 413. The data signals received by the receiver 401 are decoded and coupled to the microprocessor 409 by the circuit interface 413 and the data signals to be transmitted by transmitter 403 are generated by microprocessor 409 and are formatted by interface 413 before transmitting is transmitted by transmitter 403. The operational status of transmitter 403 and receiver 401 is enabled or disabled by interface 413. The interface also controls diodes that emit light, 415 and 417, which are used to indicate to the user which system of the PCC 101 is currently receiving. 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"s 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 the EEPROM 423 (which can also be stored in the microprocessor, EEPROM on board) and include the number assignment (NAM) required for the operation in a conventional cellular system and the "base identification (BID) required for the operation with the user's own wireless base. 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 range of output energy consists of six groups of output energy magnitudes that vary , -from a high output energy level of approximately 600 milliwatts to a low output power level of 6 milliwatts. This range of six groups of output power is enabled when the PCC 101 is in cellular system mode. According to 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 14, in combination with the ACRE 117, can automatically direct an incoming call to the PCC 101 without inconvenience to the user.The priority established for the PCC 101 is that the wireless base station 115 is the first desired path for a user telephone call and the conventional cellular (or microcellular system) is the second alternative, the process of implementing that priority , is shown in figure 6. The representation in the figure 6 is the reception of the PCC receiver 401 of the output signaling channel or the group of channels of signaling 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 cellular system signaling gateway (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 receiver of the PCC 401 scans 433 the channel or signaling channels l < f '• output from the wireless base 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, ti, before attempting another scan of a channel .-signaling of one of the alternative systems. The relation of ti and t2 is such that a cell page message (ie, a radiotelephone call or other transmitted request or 0) that is repeated, conventionally, after a 5 second pause will not be omitted because the PCC 401 receiver was scanning an alternate system during both message transmission times. cell page The time ti must be greater than the sum 5 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, you must be greater than 5.3704 seconds 5 and t2 must be less than 5 seconds. After monitoring the signaling channel of the cellular system for a time ti, the PCC receiver 401 can be instructed to tune to the signaling channel or to the signaling channels, sequentially, of the microcellular system, as shown in 437. If a suitable microcellular signaling channel is not found during scanning of the predetermined signaling channel frequencies, the PCC 401 receiver returns to the signaling channel of the cellular system, as shown in FIG. 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 0 the PCC 401 receiver 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 5 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 receiver of the PCC 401 has l < found the wireless base signaling channel, remains tuned to that channel. When the PCC transceiver is turned on first, its first scan of the signaling channels is the channel or signaling channels reset from the wireless base station 115. Of course, the user can cancel the hierarchy of the automatic priority scan by entering a cancellation code in PCC 101. In this way, the user can force only the scanning of the signaling channels of the cellular system, only the channels of 0 signaling 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 canceling the system of his choice once. 5 Once the signaling channel of a system has been monitored, a visual indication is given to the PCC transceiver's socket. 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 transmit the same information. For example, an identification system may appear on the numerical screen of PCC 101, or it may K / use a flashing symbol (having different flashing speeds). 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. 15 PCC 101 is a battery-operated radiotelephone. All radio communication devices -JPperated with battery are connected to a power saver to prolong the time between battery surcharges. PCC 101 like all cordless phones and cell phones consume most of this time detecting incoming calls. Many of the messages received by PCC 101 during this period are repetitive. If the PCC 101 could detect which messages are repetitive, it could choose not to receive those messages and turn off the receiver 5 401 and the frequency synthesizer 411 during the repeated message, thus saving the energy that could otherwise be consumed to receive the repeated message . A simplified diagram of the message format used in the dual-use radiotelephone system is shown in Figure 7. The message format has a repetition 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 indication field Repeat K / ~ 508. The message-type sequence does not follow a predetermined rotation so that an "E" type message does not always follow a "A" type message. A process for determining whether a message is a repeated one of a previously received message is shown in Figure 8. The process starts in block 510 and the repetition indication field is received in the block -512. In block 514 it is determined whether repetition indication 502 indicates that the message will be one repeated. If the message is not one repeated, block 514, the message is receives in block 516. A counter that counts the number of messages that have not been received because they were repeated is set to zero, in block 518 and the process begins again. If the message is one repeated in block 514, 5 it is determined if the message has been previously received, in block 520. One way to determine this is by the iOl PCC to store a list of all types of messages that have been previously received. If the message type field 504 compares a message type in the list of messages that have been previously received. If the message has not been previously received the procedure continues in block 516. If the message was previously received in block 520 the counter (DR_count) is examined in block 522, to determine if it is greater than a maximum limit. If the limit has been exceeded, then the procedure continues in block 516. If the limit was not exceeded in block 522 then the receiver is disabled for a portion of the message in block 524. The counter is incremented in block 526 and then the procedure starts again for the next message. Figure 9 shows a flowchart to control the time the receiver shuts off block 524 of figure 8. The process starts block 530 and the receiver shuts off in block 532. A stopwatch (chronometer_DRx) is reset in block 534. Then the timer is examined in block 536 until the timer exceeds a predetermined value of temporary suspension. Once the temporary suspension has been exceeded, the receiver is turned on in block 538, which ends the process in block 540. In order to select a channel to be used, the available channels must be examined. This process is sometimes 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 signal strength. An alternative method is by measuring the degree of bit error. In order to make a low-cost wireless telephone system, this measurement is preferably made in both the PCC 101 and the wireless base station 115. Alternatively it can be done exclusively in the PCC 101 or in the wireless base station 115. A difficulty when using PCC 101 to -To effect this measurement is that it has a single receiver 401.

When the receiver 401 of the PCC is scanning the channels, it can not receive information which is being transmitted by the transmitter 301 of the wireless base station 115. Consequently, 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 considerable cost to the PCC 101.

One difficulty in using the wireless base station 115 to perform this measurement is that the transmitter 301 and the receiver 303 of the wireless base station 115 in the preferred embodiment is designed such that the receiver 303 can only receive communication on the channel in which the wireless base station 115 is transmitting. This is because a single frequency synthesizer 309 is coupled to both the receiver 303 and the transmitter 301. Consequently, in order for the wireless base station 115 to examine the channels it must change the channel in which its transmitter 301 is operating. This has the undesirable effect of causing the PCC 101 to think that it can not receive a signal transmitted by the wireless base station 115.

This could cause PCC 101 to look for other services such as cellular or microcellular services. A solution to ..- this problem is to implement the wireless base station 115 with two frequency synthesizers. One of the frequency synthesizers could be coupled to the transmitter 301 and the other frequency synthesizer could be coupled to the receiver 303. Both frequency synthesizers could be connected to the control means 319. The disadvantage for this approach is that it increases the cost of the wireless base station 115. 5 According to the above, there is a need for an improved channel scanning mechanism. * 'Figure 10 shows a chronogram of the information transmitted in multiple channels. One of these channels 601 is used by the wireless base station 5 115 for the transmission of information to the PCC 101. Several other channels 603 are channels that can be examined for potential use by the wireless system. The channels that are used by the wireless base station 115 for the transmission of information l 'contain a stream of information. Generally speaking, this stream contains a continuous stream of data that includes a repeating indication field (R / I) 605 followed by a message type field 607 followed by a message data 609. The stream continuously repeat 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 message data field 609 contains a particular message, for example MSG- 0 A. A PCC 101 receiving 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 this is a new transmission this receives the message type field 617 which indicates that MSG-A is contained in the message data r > 09 that follow. The PCC receives MSG-A 609 and remembers receiving this message. Then the PCC 101 receives the repeat indication field 611 which indicates that the following message data is a repetition. The message type field 613 is then received. This message type field indicates that the subsequent message data contains MSG-A. At this point the PCC 101 determines that MSG-A 615 is a repeated transmission since it received the original transmission of MSG-A 609 and the repeated indication field 611 indicates that this message case A is a repetition. According to the above, the PCC does not need to receive MSG-A 615 and can use the reception time for MSG-A 615 for other purposes. 15 In particular, PCC 101 can use the reception time to examine one or the other channel as It shows in 617 and 619. One reason to examine other channels is to determine the best channel to be used in communication. Other channels 0 could also be examined to find other types of services which may be available. Other possible services include but are not limited to cellular services, microcellular services, or data services such as a page system. Additionally, PCC 101 could scan 5 other wireless base stations 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 to allow time to set the receiver. The PCC then receives the repeat indication field 621. Another time is now shown in which the scan may occur. The PCC 101 receives message type 623 which contains a value indicating that the wireless base station is scanning other channels during the time when the message data field could be located normally. The wireless base station 115 scans one or more channels as described at 625 and 627 and returns to transmit the repeat indication field 629 at a predetermined time.In the preferred embodiment this could be the time in which it is required to send the message data from the communication system preferably a synchronous transmission system. The invention could also be performed in an asynchronous transmission system. The wireless base station 115 can enable its transmitter to transmit slightly before the next repetition indication field 629 to allow the PCC to set the reception time. PCC 101 ignores the wireless channel during the time when transmission does not occur. Then the transmission stream continues with the following repeat indication field 629, the message type field 631, and the next message data field 633, which contains MSG-B. Instead of ignoring the wireless channel during the time when transmission does not occur, the PCC 101 may also examine one or more channels as described in 625 and 627. The PCC could return its receiver 303 to the wireless channel slightly before the next field of communication. repetition indication 629. As in the previous case, this channel examination could be used to determine the best channel or channels for communication or it could be used to find services. The PCC 101 can use the data it finds, - ^ 1 examine channels to choose the best channel or can transmit this information to the wireless base station 115. Also, the wireless base station 115 can use the data it found based on the test of channels to choose the best channel or can transmit this information to PCC 101. Although these methods of examining the channels are described for a wireless communication system, they could also be used in cellular communication systems or in other communication systems. The use of those messages that examine channels in any system is considered within the scope of this invention. Figure 11 shows a description of the message stream in the preferred embodiment. This synchronous message transmission format contains a synchronization qualifier field 640 followed by a synchronization field 642 followed by a word 644. lf) These three fields are repeated continuously. The synchronization field is used by PCC 101 to synchronize its receiver. The preferred mode allows two different values for the synchronization 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 follows - ** that processes words. The synchronization 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 that word data could be transmitted normally. If the synchronization qualifier field indicates that the word contains a repeated transmission, the value in the synchronization qualifier field 5 also indicates that the word is being repeated. In this way the qualifier field synchronization 640 is very similar to the combination of a message type 607 and a repetition indication 605 as shown in FIG. 10. In a synchronous transmission system a message is usually compressed into one or more words. Thus the message fields 609, 615 and 633 of Figure 10 can also be called a word. In the same way in figure 7, messages 506 can also be called a word. For purposes of the above-described scanning methods and the energy-saving receiving 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 3.01 is a device Battery operated and like all battery-operated radio devices that conserve energy it is important to extend the time between the battery surcharge. The PCC 101 samples a stream of data to determine whether a repetition indication is indicative of a repeated message. If the message is a repeated message, PCC 101 determines if it has already received the message. If the message has already been received, the receiver 401 is switched off during transmission of the message. When turning off the receiver, energy is saved and the life of the battery charge is extended. It is obvious to those skilled in the art 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 located separately from one another. 0 the authorization function and the equipment could be separated from the function and the call routing equipment. Any modification is considered part of the exclusive rights of the inventor in 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, it is considered as a novelty and therefore the property described in the following claims is claimed as property. 1. A communication system for communicating a data stream, said communication system comprising: a receiving device (101) having a receiving means (401) and a processing means (409); a transmitting device (115) for transmitting a data stream, said data stream comprising a repeating indication field (508) and a message field (506); and said receiving means (401) receiving said data stream and said processing means (409) determine if; (i) said indication of repetition is true; (ii) the message was previously received, and (iii) turn off the power for at least the receiving media - (401) for a predetermined period of time if said repetition indication is true and the message was previously received. The communication system according to claim 1, characterized in that the receiving device (101) receives the data stream if the repetition indication message is false. 3. The communication system according to claim 1, characterized in that the receiving device (101) receives the data stream if the message has been previously received. The communication system according to claim 1, characterized in that the repetition indication field (508) further includes a message type field (504) and the processing means (409) determine whether the previous message having the same type Message was received. The communication system according to claim 1, characterized in that the processing means (409) count the number of successive repetition indication fields (508) that are true and, if that count exceeds a predetermined number, receives the message. 6. The communication system according to claim 1, characterized in that the period of time -default is a slightly less time than the time until the next repetition indication field (508) is received. 7. A method to save energy in a data communication system that has a receiving device (101) and a transmitting device (115), said receiving device (101) has a receiving means (401), the method comprises the steps of: receiving a data stream comprising a repeating indication field (508) and a message field (506); determining whether a field 4e repetition indication (508) is true; determine, when the indication of repetition is true, if the message has been previously received; and shutting down at least said receiving means (401) for a predetermined period of time if said message is a repetition and if the message has been previously received. The method according to claim 7, characterized in that it also includes the step of receiving the message if the indication of repetition is not true. The method according to claim 7, characterized in that the predetermined period of time is slightly less than the previous time when the next repetition indication field is received. The method according to claim 7, characterized in that at least said receiving means - (401) does not turn off for a predetermined period of time if the repetition indication field (508) has been true for a predetermined number of cycles. ENERGY SAVING SYSTEM FOR A MOBILE RADIO - alarm of the invention A communication system having a cellular wireless hand-held radiotelephone 101 (PCC) which receives a stream of data from a wireless base station (115) when the PCC (101) He is not busy in a phone call. The data stream has a repeating indication field (508) and a message field (506) that the PCC (101) uses to determine if the message has already been received. If the PCC (101) determines that the message has already been received, the PCC (101) turns off its receiver (401) for a duration of time slightly less than the time of the message field. This results in an energy saving for the PCC (101)