MXPA95004036A - Method and apparatus to provide a sincron communication environment - Google Patents

Abstract

An apparatus and method provides synchronous communication in a communication environment (102) where the multiple base stations are adapted to operate on the same frequencies. In particular, the base stations that operate within the range between them must be coordinated to minimize interference to other base stations that may otherwise operate independently. Each base station operates on one system, and another base station operating on the same frequencies is within of the range (310). One of the base stations will assume a role as a pattern and the remaining base station will then be synchronized with the standard base station (312). Preferred methods for synchronizing base stations include protocol signaling (702, 902) and collision avoidance techniques for multiple access digital communication systems.

Description

METHOD AND APPARATUS TO PROVIDE A SYNCHRONOUS COMMUNICATION ENVIRONMENT ASSIGNEE: MOTOROLA, INC. , SOCIEDAD DE NACIONALIDAD NORTEAMERICANA, WITH ADDRESS AT: 1303 EAST ALGONQUIN ROAD, SCHAUMBURG, ILLINOIS 60196 - E. U. A.

INVENTORS: DAVID L. WEIGAND, OF NACIONALIDAD NORTEAMERI CANA, WITH ADDRESS AT: 1035 ÁSTER AVENUE, # 3115, SUNNYVALE, CALIFORNIA 94086, E.U.A.

CHARLES J. MALEK, OF NACIONALIDADIDAD NORTEAMERI CANA, WITH ADDRESS AT: 915 CAMELOT DRIVE, CRYSTAL LAKE, ILLINOIS 60014, E.U.A.

SUMMARY OF THE INVENTION An apparatus and method provides synchronous communication in a communication environment (102) where the multiple base stations are adapted to operate on the same frequencies. In particular, base stations that operate within the range between them must be coordinated to minimize interference with other base stations that may otherwise operate independently. Each base station operating in a system will determine if another base station operating on the same frequencies is within the range (310). One of the base stations will assume a role as a pattern and the remaining base station will then be synchronized with the standard base station (312). Preferred methods for synchronizing base stations include protocol signaling (702, 902) and collision avoidance techniques for digital multiple access communication systems.

FIELD OF THE INVENTION This invention relates to radio frequency (RF) communication systems, and more particularly to a method and apparatus for providing a synchronous communication environment.

BACKGROUND OF THE INVENTION In wireless communication systems, efforts have been made to increase the use of the spectrum to allow a large number of users of a frequency band Dadaist. An example of a technique to increase spectrum efficiency is a frequency division multiple access (FDMA) technique. In a conventional FDMA system, a given frequency band is divided into a number of channels, where each channel is occupied by a user. An FDMA system can also be a time division duplex (TDD) system where a given RF channel is used for both directions, forward and inverse, of the communication that are separated in time.

Other techniques include digital multiple access communication systems. A conventional digital multiple access technique to increase the efficiency of the use of a spectrum is a time division multiple access (TDMA) technique. In a TDMA system, each channel for the transmission of signals is divided into a number of time segments. Each time segment can be assigned to a different call. A TDMA system can also use TDD techniques. Accordingly, a number of channels can be simultaneously transmitted in a single frequency channel.

Finally, the increased spectrum efficiency can be achieved by means of distribution spectrum techniques, in the form of both a low frequency reflected wave (Hopper) path system and a direct sequence CDMA system. In a low frequency Hopper system, the carrier frequency of the signal changes at a predetermined speed over a wide range of possible frequencies in a pseudo-random sequence that the receiver knows in advance. Generally, distribution spectrum techniques reduce the effects of both intentional and unintentional interference. CDMA direct sequence systems allow multiple users to share the same spectrum where each user is assigned to a unique pseudo-noise code sequence.

In digital multi-access communication systems that have multiple base stations, there must be some coordination between the base stations to ensure that the base stations are properly synchronized.

The synchronization of the base stations can be achieved if the base stations are part of a common system and are physically connected. Nevertheless, base stations that are not physically connected should be synchronized if they are part of a common system. Furthermore, if the base stations operate independently on common frequencies, the base stations must communicate that they are properly synchronized. Accordingly, there is a need for a method and apparatus for synchronizing the base stations operating in a digital multiple access communication system.

BRIEF DESCRIPTION OF THE DIAGRAMS Figure 1 is a plan view of a wireless communication system having multiple base stations connected to the telephone network of the public system.

Figure 2 is a block diagram of the circuits for a wireless base station or telephone.

Figure 3 is a flow diagram illustrating the preferred steps for determining the pattern and dependent designations for the base station and the formation of strings in the wireless communication system of System 1.

Figure 4 is a flow diagram showing the preferred steps for determining an index available in the low frequency Hopper system.

Figure 5 is a network topological diagram showing the coordination of base stations that overlap in wireless communication systems.

Figure 6 is a flow diagram showing the general steps for the coordination of the base stations during the chain inversion as shown in the Figure Figure 7 is a first configuration of an air interface protocol having multiple synchronization channels for coordinating the base stations.

Figure 8 is a detailed flow chart showing the coordination of base stations that have an air interface protocol shown in Figure 7.

Figure 9 is a second configuration of an air interface protocol having a simple synchronization channel and a blank channel for coordinating base stations and telephones.

Figure 10 is a detailed flow chart showing the coordination of base stations that have an air interface protocol shown in Figure 9.

Figure 11 is a flow chart showing a loop operation of the phase lock for a base with a synchronization source.

DESCRIPTION OF THE CONFIGURATIONS PREFERRED In a digital multi-access communication system, each base station operating within a range of another base station must be synchronized to prevent interference. The present invention provides synchronous communication in a communication environment in which multiple base stations are adapted to operate on the same frequencies. In particular, base stations such as, for example, resident base stations must be coordinated to minimize interference with the other base stations operating otherwise independently. In accordance with the present invention, each base station operates on a system that will determine if another base station operating on the same frequencies is within the range. One of the base stations will assume a role as a master and the rest of the base station will then be synchronized with the master base station. Preferred methods for synchronizing the base stations, including the signaling protocols, the formation of the synchronization chain and the techniques to avoid collision to form the synchronization chains, are also described.

Turning first to Figure 1, a wireless communication system 102 is shown. The wireless communication system has a number of base stations 104, each of which provides RF coverage in an area 108. Each base station can be connected to a telephone network of the public system 106. However, it should be understood that the circuit and method of the present invention could be implemented in a wireless communication system having base stations that are not connected to the telephone network of the public system. The base stations could be connected together in a separate network, or they could be single units operating in the same frequency bands. Each base station is also adapted to communicate with one or more telephones 110. Finally, each base station can communicate with another base station that is within range by means of RF signals.

Turning now to Figure 2, a block diagram shows a base or telephone circuit. In the preferred configuration, an ASIC (Specific Integrated Circuit and Application) 201, such as, for example, a CMOS ASIC in MDA08 or H4C technology also available by Motorola, inc. and a microprocessor 203, such as the 68HC11 microprocessor that is available from Motorola, Inc., are combined to generate the communication protocol shown in FIG.

Figures 7 and 9. The AF IC 201 preferably includes a separate search engine for detecting a second source of synchronization according to the present invention. The second search engine could be a digital phase lock loop (DPLL) or a cross correlator.

The loops of the digital phase lock are well known in the art. An example of a phase lock loop can be found in US Patent 3,983,498 entitled "Digital Phase Loop" which was granted on September 28, 1976 to Malek. The complete contents of US Patent 3,983,498 is incorporated for reference. An example of a crossover correlator can be found in U.S. Patent 5,117,441 entitled "Method and Apparatus for Real Time Demodulation of a GMSK Signal by A Non-Coherent Receiver" ("Method and Apparatus for Real-time Demodulation of a GMSK Signal by a Non-Coherent Receiver ") granted on May 26, 1992 to Weigand. The complete contents of U.S. Patent 5,117,441 are also incorporated herein for reference.

The microprocessor 203 uses RAM 205, EEPROM 207, and ROM 209, consolidated in a packet 211 in the preferred configuration, to execute the steps necessary to generate the protocol and perform other functions for the communication unit, such as writing on a screen 213, accepting keyboard information 215, and controlling a frequency synthesizer 225. The ASIC 201 processes the audio transformed by the audio circuits 219 from a microphone 217 and to a speaker 221.

Certain message fields are built by the ASIC 201 and are inhabited by the audio circuits 219, the microprocessor 203 and others are built by the ASIC 201, which generates the message structure and transfers it to the transmitter 223. The transmitter 223 transmits through an antenna 229 using carrier frequencies produced by the frequency synthesizer 225 in the Hopping manner chosen by the system and directed by the microprocessor 203. The information received by the antenna of the communication unit 229 enters the receiver 227 which demodulates the symbols comprising the message structure using the carrier frequencies of the frequency synthesizer 225, according to the Hopping mode chosen for the system. The ASIC 203 then analyzes the structure of the message received in its constituent parts. If the circuits of Figure 2 are incorporated into a resident base station, the audio circuits of the base station can be connected to the telecommunications network (telco) 233.

Turning now to Figure 3, a flow chart shows the preferred steps for determining whether the particular base station in the wireless communication system having a number of base stations operating within the range of another is a standard base station. The method of the present invention is preferably used in a personal cordless base station, such as a base station for office or residence, but could be employed in any system using wireless base stations. The base station is powered in step 302 and closed at the frequency fO in step 304. In step 306, the base station determines whether synchronization and cyclic redundancy control (CRC) signals are detected in step 306 If the signals are detected, the base station follows a Hop sequence in a step 308. Frequency Hopping systems are well known in the art and will not be described in detail in this application. The base station then determines whether a beacon signal is heard in step 310. This signal could be a beacon signal message generated by another source, or it could be a communication traffic generated by another source, such as a telephone or one base. If no beacon signal is detected in step 310, the base station assumes the role of the master base station in step 312 and assumes normal operation in step 314. As a standard base station, the base station will make Hop among the different frequencies, while the other base stations will maintain the synchronization with the base station pattern (for example, follow the same pattern Hopping frequency, but out of phase with the pattern, in a different Hop index).

However, if a beacon signal is detected by the base station in step 310, the base assumes a dependent role in step 316 and implements a digital phase lock (DPLL) loop. The base station assumes normal operation in a step 318, and determines whether the synchronization with the master station in step 320 has been lost. If the base station has lost synchronization, then it determines whether it is in a call in a step 322. If the base station is not on a call, it closes at the frequency fO at the weight 304. However, if the base station is on a call, it is aware of a possible master base station at a step 324. If the base station detect another pattern in a step 326, the base station assumes a dependent role in step 316. Preferred methods for detecting a base station will be described in detail with respect to Figures 7-10. If no pattern is detected, the base station assumes a master role in step 312.

Turning now to Figure 4, the preferred steps for following the Hop sequence in block 308 of Figure 3 are shown. In a step 402, the index (e.g., an outstanding voltage within a predetermined sequence of channels beginning with a first channel) are set equal to zero. In step 404, the base station investigates the near index (the same sequence of channels beginning the second channel in the sequence) and determines whether the receiver signal strength indicator (RSSI) of all the channels is less than the predetermined threshold in step 406. If the RSSI of all the channels is less than the predetermined threshold, the base station stores an indication that an index N has zero occupied channels in step 408. If the RSSI of all the channels is not less than the threshold in step 406, the base station indicates the number of channels occupied in a step 410.

In a step 412, the base station determines if three indexes are available that do not have channels occupied. If there are three available indices, the base station selects the first index in step 414, and assumes normal operation in a step 416. However, if all three indices are not available, the base station determines whether all indices have been tracked in a step 418. If all the indices have not been tracked, the base station investigates the next index in step 404. If all the indices have been tracked, the base station uses the best available index depending on the least number of occupied channels which have an RSSI value greater than the predetermined threshold. The three indexes are used to form a better next list. If the index is altered during a call, a request could be sent to change the index. The best upcoming list can be updated periodically according to radio resources and other limitations. While the RSSI determination was described above, an evaluation of channel quality by the RSSI is merely given as an example. Any other method for determining the quality of the signal could be used within the scope of the present invention.

Turning now to Figure 5, a time diagram shows the synchronization of base stations that are within a range between them according to the present invention. The original teachers Al and Bl, who are outside a range between them, are shown in TI time. Other base stations (A2 through A5) fall within the range of the original Al pattern and are synchronized to form a synchronization chain according to the steps described in Figure 6. Similarly, base stations B2 and B3 fall within the range of the original pattern Bl to form another synchronization chain.

As shown in Figure 6, the method that synchronizes the individual chains of the base stations is illustrated in a general manner. The growth of the chain can be both between the base stations (for example, each base station puts the other base station out of synchronization based on a beacon signal message (Figures 7 and 8)), or a more dynamic chain with base stations that detect a beacon signal message or telephone traffic associated with another base to form a chain (Figures 9 and 10). While the general concept of a chain formation described in Figure 6 applies to any method for forming a synchronous chain, the general implementation for each configuration will be described separately below for a better understanding.

In particular, the development of a synchronization string between the base stations begins at a step 602 in which a base station becomes synchronized after the ignition of an existing base station according to the steps described in Figure 3. A base station it can also be within the range of and detect two sources of synchronization. A base station determines whether a message a second beacon signal message from an unsynchronized base station is detected in step 604. If this beacon signal message is not detected, the base station continues to synchronize in the existing pattern in step 606. However, if a second beacon signal message from a base station is detected, the base station is synchronized with the unsynchronized base station detected in step 608. The base station migrates slowly towards the other base station to avoid any interruption in communication. The base station then determines whether the synchronization is completed in step 610. If the synchronization is not completed, the base station continues to migrate slowly towards the other base station in step 608. If the synchronization is complete, the base station will assume the operation normal in a step 612. The base station will then determine whether the same synchronization distribution is received in a step 614. If the same synchronization distribution is received, the base station will summon the normal operation in step 612. Otherwise, the The base station will control if there is a second beacon signal or an unsynchronized telephone traffic in step 604. A method for migrating to another base station is described below with respect to FIG. 11.

Using the string A1-A5 as an example, at a time TI, a base station Al exists as an original master base station.

A second base station A2 then turns on, detects Al and is synchronized according to Al. Then a third base station A3 is turned on. According to Figure 3 of the present invention, A3 detects a synchronization source (A2) and synchronizes according to the synchronization source. The chain continues forming as base stations that are synchronized to the chain. In summary, when a base station is added to either end of the chain (for example, it turns on and looks for a pattern), the base station will be synchronized to the chain.

At a time t2, the two synchronization chains can be found and will form a single chain of synchronized base stations C1-C9. The new base station bridging the two base station chains (designated as base station C4 and a time t2) will detect a first base station and synchronize to that base station. While C4 is within the range of and could detect both C3 and C5, any technique to avoid a collision could be used to determine which base station will be synchronized to which C3. As will be described in detail later, the base station could be synchronized by default to one or two base stations. The default method will depend on the synchronization protocol. Assuming, for example, that C4 first synchronizes with C5, C3 (which is synchronized with C2) then it will detect the second base station (C4) that is now out of synchronization and will be synchronized to the base station. C2 (which is synchronized with Cl) will then detect a second synchronization source that is out of synchronization? C3), and C2 will synchronize with C3. Finally, Cl will be out of sync with C2 and then synchronize with C2 to complete the reversal of the synchronization chain. In this way, Cl, abandons the pattern. Accordingly, the method of the present invention will allow synchronization chains to be formed, and particularly to allow unique synchronization chains to be formed when two synchronization chains collide.

Similarly, the development of a synchronization chain based on the detection of both beacon signals and telephone traffic is also described with respect to Figures 5 and 6. While a base station will transmit a beacon signal when power is applied to the base station, the term "turn on" will also refer to the transmission of telephone traffic when a base station is on a call. A base station determines whether a beacon signal or unsynchronized telephone traffic is detected in step 604. If neither a beacon signal nor an unsynchronized telephone traffic is detected, the base station remains in the loop in step 606. However , if a beacon signal or unsynchronized traffic is detected, the base station is synchronized with the base station detected in step 608. The base station would slowly look towards the detected base station to avoid any interruption in communication. The base station then determines whether the synchronization is completed in step 610. If the synchronization is not completed, the base station continues to migrate slowly to the other synchronization source in step 608. If the synchronization is completed, the base station will assume the normal operation in step 612. The base station will then determine whether the same synchronization distribution is received in step 614. If the same synchronization distribution is received, the base station will assume normal operation in step 612. Otherwise, the base station will control a second beacon signal or unsynchronized telephone traffic in step 604.

Using the Al-A5 chain once more as an example, Al as a base station exists in an original pattern. A base station A2 is switched on, detects a beacon signal from Al and is synchronized with Al. Another base station A3 is then turned on. In accordance with the operation of the present invention, if the base station A2 is in a call, A3 detects the telephone traffic A2 and synchronizes with A2. A3 transmits a beacon signal. The base station A4 then turns on and synchronizes with the base station A3. If another base station (A5) is turned on, it will be synchronized with the telephone traffic of the base station A4. In short, the base stations detect both a beacon signal or telephone traffic and are synchronized to the source of the beacon signal or telephone traffic to form the chains.

At a time t2, the two synchronization chains can be found and will form a single chain of synchronized devices C1-C9. The base station that bridges the two chains (designated as C4 in a type t2) will be synchronized with one of the two devices. While the base station C4 is within the range and can detect both C3 and C5, any collision avoidance technique can be used to determine which base station will synchronize with which C3. Taking as an example that the C4 telephone first synchronizes with C5, C3 will then detect both a beacon signal or telephone traffic from C4 that is out of synchronization and will be synchronized with C4. C2 will then detect a second source that is out of synchronization (C3), and C2 will synchronize with C3. Finally, Cl will be out of sync with C2 and then be synchronized with C2 to complete the inversion of the synchronization chain. Cl leaves the leadership in this way.

Considering now the protocol for synchronizing the communication devices, the preferred methods for synchronizing the communication devices in a chain will be described in detail with respect to Figures 7-10. Turning now to Figure 7, an air interface protocol for synchronizing base stations is shown.

Preferably, both the primary and redundant structures 702 and 704 are transmitted between the base stations as illustrated in Figure 7. A method and apparatus for maintaining frequency and bit synchronization having primary and redundant structures is described in Pickert et al. ., U.S. Patent 5,212,715 entitled "Digital Communication Signaling System" ("Digital Communication Signaling System"), granted on May 18, 1993. With respect now to the specific time segments, structure 702 includes a segment of 706 time for the synthesizer lock time. The next four time segments are to send the primary and redundant data fields and invert the primary and redundant data fields. In particular, the time segment 708 is for a first time data segment (base-with-telephone). Time segment 710 is a forward redundant data field. The time segment 712 is a reverse primary data field (telephone-with-base). The time segment 716 is a time segment of the synthesizer.

The following two time segments are beacon times segment, designated as beacon time segment A718 (time segment A) and beacon time segment B720 (time segment B). The beacon time segment is used to transmit a base synchronization field that is used to synchronize the base stations. A beacon signal message could comprise a number of beacon signals transmitted in the beacon time segment. The function of the beacon signal time segment A and the beacon signal time segment B will be described in detail with respect to FIG. 8.

As illustrated in Figure 7, the first forward time time segment 708 of the primary structure 702 is also transmitted in the redundant forward time segment 726 of the redundant structure 704. This is. , the redundant time segment contains the information that matches the previous primary time segment of structures. Similarly, the reverse primary time segment 712 of the primary structure 702 is transmitted in the redundant reverse time segment 730 of the redundant time structure 704. The transmission operation of the primary and redundant data fields is well known in the technique and will not be described in more detail. However, it should be understood that the system transmitting the redundant time segment need not be used in accordance with the present invention, and that a single structure could be transmitted.

Figure 7 further shows the preferred time segment structure for the data time segment in both the forward and reverse directions, or a primary time segment or a redundant time segment in any direction. Preferred fields for the Digital Control Time Segment Field (DCCH) 750 are illustrated. Each DCCH data time segment comprises a ramp / safety (R / G) field 754, a preamble field 756, a sync field 758 , a data field 760, a cyclic redundancy control (CRC) field 762, and an R / G field 764. A digital traffic field 752 is also shown. The preamble field represents a marker signal to identify the base station. In the reverse time segment, the marking signal would identify the telephone. The data time segment of the digital traffic time segment comprises an R / G field 766, a synchronization field 768, an associated slow control time segment (SACCH) 770, a CRC 772 field, a payload field of vocoder 774, and an R / G field 776. While the preferred data field protocol is described in Figure 7, few additional fields or fields may be transmitted within the scope of the present invention.

With respect now to Figure 8, the preferred steps for synchronizing base stations using the air protocol of Figure 7 are described. In particular, in step 804, the base station determines whether a beacon signal message is acquired in both channel A or B. If the beacon signal is not acquired in the A and B tie segments, the base station is transformed into a synchronization pattern and transmits a beacon signal message in the time segment A in step 806. The base station then monitors an out-of-phase synchronization source in step 808. If the out-of-phase synchronization source is detected, the base station continues to determine whether the message of the beacon signal is acquired in the time segment A or in the time segment B of step 804. If an out-of-phase synchronization source is detected in step 808, the base station is synchronized with the other base station as a dependent in step 810. The The base station then determines if the same synchronization distribution continues to be received in step 812 (for example, the same synchronization source previously detected is the only source of detected synchronization). If the same synchronization distribution continues to be received, the base station is synchronized with the other base station as a dependent in step 810.

However, if a new synchronization distribution is received in step 812, the base station determines whether synchronization is acquired in the time segment A or in the time segment B in step 804. If a synchronization is acquired in the time segment A, but not in the time segment B in step 814, the base station is synchronized in the time segment A as a dependent and retransmits a beacon signal message in the time segment B in step 816. If the original synchronization distribution continues to be received in step 818, the base station continues to synchronize with the time segment A as a dependent and retransmitting in the time segment B. However, if the synchronization distribution does not continue, the base station monitors an out-of-phase synchronization source in step 808.

If the base station detects a beacon signal in the time segment B, but not in the time segment A, in a step 820, the base station synchronizes with the time segment B as a dependent and retransmits a beacon signal in the time segment A in step 822. If the distribution continues to be received in a step 824, the base station continues to synchronize in time segment B as a dependent and retransmits in time segment A. However, if the The original timing distribution is not received, the base station monitors an out-of-phase synchronization source in step 808.

Finally, if a synchronization is acquired in both the time segment A and the time segment B in a step 825, the base station is synchronized with one of the time segments. By way of example, the base station could be synchronized with an omitted time segment (e.g., a time segment A) in step 826. Without the original synchronization distribution continuing to be received in step 828, the base station continues to synchronize to a segment of time A as a dependent. Otherwise, the base station monitors for an out-of-phase synchronization source in step 808.

In sum, the base station monitors two segments of beacon signal times to detect an unsynchronized source. If the beacon signal is detected in any beacon signal time segment, the base station functions as a standard base station. If the base station detects a beacon signal in one of the beacon signal time segments, the base stations are synchronized to the base station and retransmit a beacon signal in the beacon signal time segment to enable another base station to synchronize with her. If a certain base station detects a beacon signal in both time segments A and B simultaneously (eg, a beacon signal from two base stations), the base station will be synchronized with one of the base stations. The other of the two base stations will then detect that a certain base station is out of synchronization and will be synchronized to that base station. Accordingly, all base stations of the separate chains will be synchronized.

Turning now to Figure 9, an alternative configuration of an air interface protocol for synchronizing base stations in a chain is shown. As illustrated in Figure 9, a structure 902 includes a time slice 906 for the synthesizer lock time. The next four timeslots are for the redundant forward and primary forward data fields, and the reverse and primary redundant data fields. In particular, the time segment 908 is for a first data forward (base-with-telephone) time segment. Time segment 910 is a redundant forward data field. Time segment 912 is a first inverse data field (telephone-base). The time segment 910 is a forward redundant data field. The time segment 912 is a first inverse data field (telephone-with-base), while the time segment 914 is a reverse redundant data field. At least one blank time segment 916 is also included to allow detection of telephone traffic in an alternative configuration. The time segment 918 is a time segment of the synthesizer latch, followed by a simple time segment, designated as the beacon signal time segment 918. The function of the beacon signal time segment will be described in detail with respect to Figure 10. While the redundant and primary structures 902 and 904 are preferably transmitted between the base stations as illustrated in Figure 7, a single simple time structure could be transmitted. In addition, the DCCH and DTC data fields described in Figure 7 could be used in the alternative configuration.

Turning now to Figure 10, the preferred steps for the alternative configuration to synchronize base stations using the air protocol of Figure 9 having at least one blank time segment and one beacon signal time segment are described. simple. In a step 1004, if a beacon signal is not detected in the beacon signal time segment and no unsynchronized telephone traffic is detected in the blank time segment, the base station is transformed into a synchronization pattern and transmits a beacon message in the beacon signal time segment in step 1006. The base station then monitors an out-of-phase synchronization source in the blank time segment in a step 1008. If no synchronization source is out of phase it is detected, the base station continues to determine whether the beacon signal message is acquired in the beacon signal time segment or the unsynchronized telephone traffic in the blank time segment is detected in step 1004. If a telephone is out of phase is detected in step 1008, the base station slowly migrates to the other source and is synchronized with the telephone as a dependent in step 1010. The base station then determines whether the same synchronization distribution continues to be received in a step 1012. If the the same synchronization distribution continues to be received, the base station continues to synchronize with the other telephone as a dependent in step 1010.

However, if a new synchronization distribution is received in step 10102, the base station determines whether the message of the beacon signal is acquired in the beacon signal time segment or the telephone traffic in the time segment in blank in step 1004. If a beacon signal message is detected in the beacon signal time segment and an unsynchronized telephone traffic is detected in the blank time segment in a step 1014, the base station is synchronized in the beacon signal time segment as dependent in a step 1016. However, if the synchronization distribution does not continue, the base station monitors an out-of-phase synchronization source in step 1008.

If the base station detects unsynchronized telephone traffic in a blank time segment, but no beacon signal is detected in the time segment of the beacon signal in a step 1020, the base station is synchronized in the segment of blank time as a dependent in a step 1022. If the original synchronization distribution continues to be received in a step 1024, the base station continues to synchronize in the blank time segment as a dependent and retransmits in the time segment of the beacon signal . However, if the original synchronization distribution is not received, the base station monitors an out-of-phase synchronization source in step 1008.

Finally, if a beacon signal message is detected in the beacon signal time segment and an interference is detected in the telephone traffic in the blank time segment in step 1025, the base station is synchronized with the segment of beacon signal time and a dependent one in step 1026. If the original synchronization distribution continues to be received in step 1028, the base station continues to be synchronized in the time segment of the beacon signal as dependent. Otherwise, the base station monitors an out-of-phase synchronization source in step 1008.

In sum, an alternative configuration describes base stations that monitor a beacon signal in a time segment of beacon signal or telephone traffic in a blank time segment to detect an unsynchronized source. If no beacon signal is detected in the beacon signal time segment and no telephone traffic is detected in the blank time segment, the base station functions as a standard base station. If the base station detects a beacon signal in the beacon signal or telephone traffic time segments in the blank time segment, the base stations are synchronized with that base station. If the telephone traffic was detected, the base station also retransmits a beacon signal in the time segment of the beacon signal to allow another base station to synchronize with it. If a certain base station detects a beacon signal in the time segment of beacon signal and telephone traffic in the blank time segment, the base station will be synchronized to one of the base stations, preferably the base station detected in the segment of the base station. beacon signal time. The other of the two base stations will then detect that a certain base station is out of sync and will be synchronized with that base station. Accordingly, all base stations of separate chains will be synchronized.

Turning now to Figure 11, a preferred method for achieving or maintaining a synchronization using a DPLL is described. In particular, a time segment is established as a synchronization source in a step 1104.

Then, the base station will determine if a beacon signal is received in a step 1106. If a beacon signal is received, the base station will then determine whether the beacon signal is received early in a step 1108. If the beacon signal is receives early, the base station will transmit a structure that has a surveillance band that has Nl bits in a step 1110. If, however, the beacon signal is not received early, the base station will transmit a surveillance band that has N + l bit. While the method of Figure 11 is a method for maintaining synchronization, it should be understood that other methods known in the art could be used to maintain synchronization.

In sum, the present invention provides a synchronous communication in a communication environment where the multiple base stations are adapted to operate on the same frequencies. In particular, co base stations or for example residential base stations must be coordinated to minimize interference to other base stations that otherwise operate independently. In accordance with the present invention, each base station operating in a system will determine whether another base station operating on the same frequencies is within the range. One of the base stations will assume the role of principal and the remaining base station will then be synchronized with the main base station. Preferred methods for synchronizing base stations, including signaling protocols and collision avoidance techniques, are also described.

While the specific configurations are described by way of example in the foregoing description, the modifications and alternative configurations are within the range and scope of the present invention. The present invention should be limited only by the following claims.

Claims (10)

1. A digital radio frequency (RF) multiple access communication system adapted to operate within the range of other RF digital multiple access communication systems, the RF digital multiple access communication system is characterized P ° r: a base station (104 characterized by a transmitter for transmitting communication signals, said communication signals comprising a beacon signal; a receiver for receiving communication signals comprising a beacon signal transmitted by another base station operating within the range of said RF digital multiple access communication system; Y at least one portable device (110) adapted to communicate with said base station.

2. A digital radio frequency (RF) multiple access communication system having a number of independent base stations adapted to operate within the range between them, each base station is characterized by: a transmitter (223) for transmitting communication signals, said communication signals comprising a beacon signal; and a receiver (227) for receiving communication signals comprising a beacon signal transmitted by another base station operating within the range of the RF digital multiple access communication system.

3 A time division multiple access (TDMA) communication system adapted to operate within the range of another TDMA communication system operating in the same frequency bands with the same communication protocols, the TDMA communication system is characterized by : a personal cordless base station (104) is characterized by: a transmitter for transmitting communication signals, said communication signals comprising a base synchronization field; a receiver for receiving communication signals, said communication signals comprising a base synchronization field transmitted by a second base station without personal cable operating within the range of the TDMA communication system; and at least one portable device (110) adapted to communicate with said base station without personal cable.

4. A communication device for transmitting communication signals characterized by: circuits (201) for generating a message structure having a time segment structure characterized by: (i) time segments of the synthesizer lock (716); (ii) a number of time segments for data transmission (706-714); Y (iii) a beacon time segment (718) for synchronizing base stations in a communication system; a transmitter (223) for transmitting said message structure; Y a receiver (227) for receiving a message structure.

5. A method for establishing communication in a base station without wireless, said wireless base station is adapted to communicate with at least one remote device, said method is characterized by the steps of: listening (304) a beacon signal after the ignition of said wireless base station; Y setting (312) said base station as a synchronization pattern if a beacon signal is not received.

6. A method for establishing a synchronous communication in a first base station without personal cable, said first base station without cable is adapted to communicate with at least one remote device, said method is characterized by the following steps: listening (304) to a synchronization signal after the ignition of said base station without personal cable; setting (316) said first wireless base station as a synchronization dependent after receiving said synchronization signal generated by a second base station without personal cable; setting (312) said first base station without personal cable as a synchronization pattern if a synchronization signal is not received from a second base station without personal cable; Y transmitting (314) a synchronization signal of said first base station without personal cable.

7. A method for establishing synchronous communication in a system adapted to operate with a number of base stations within the range between them, said method characterized by the following steps: transmitting (302) a beacon signal from said base station; listening (304) a beacon signal from said base station; establishing (312) a first base station of said number of base stations as a standard base station if a beacon signal is not received; Y establishing (316) a second base station of said number of base stations as a dependent base station upon receipt of the beacon signal from said standard base station.

8. A method for providing synchronous communication in a communication system having a number of base stations adapted to operate within the range between them, said method is characterized by the following steps: detecting a beacon signal from a first base station and a second base station at a third base station; synchronizing said third base station with said first base station; detecting, in said second base station, a beacon signal from a third base station; Y synchronize said second base station to said third base station.

9. A method for providing synchronous communication in a communication system having a number of base stations adapted to operate within the range between them, said method is characterized by the following steps: detecting (804) a beacon signal from each of the first base station and second base station in a third base station; synchronizing (806) said third base station with said first base station; generating (806) a beacon signal in said third base station; detecting (808), in said second base station, said beacon signal generated in said third base station; Y synchronizing (810) said second base station with said third base station.

10. A method for providing synchronous communication in a communication system having a number of base stations adapted to operate within the range between them, said method is characterized by the following steps: detecting (1014) a beacon signal from each of the first and second base stations at a third base station; synchronizing (1016) said third base station with said first base station; detecting (1025) said telephone traffic from the second base station from a telephone adapted to communicate with said base station; Y synchronizing (1026) said second base station with said third base station in said telephone traffic.