Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/24—Radio transmission systems, i.e. using radiation field for communication between two or more posts
  • H04B7/26—Radio transmission systems, i.e. using radiation field for communication between two or more posts at least one of which is mobile
  • H04B7/2662—Arrangements for Wireless System Synchronisation
  • H04B7/2671—Arrangements for Wireless Time-Division Multiple Access [TDMA] System Synchronisation
  • H04B7/2678—Time synchronisation
  • H04B7/2687—Inter base stations synchronisation
  • H04B7/269—Master/slave synchronisation
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
  • H04B1/69—Spread spectrum techniques
  • H04B1/713—Spread spectrum techniques using frequency hopping
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/001—Synchronization between nodes
  • H04W56/002—Mutual synchronization
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W56/00—Synchronisation arrangements
  • H04W56/0035—Synchronisation arrangements detecting errors in frequency or phase
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W92/00—Interfaces specially adapted for wireless communication networks
  • H04W92/16—Interfaces between hierarchically similar devices
  • H04W92/18—Interfaces between hierarchically similar devices between terminal devices

Definitions

• This invention relates to wireless communication protocols, and more particularly to transmission synchronization among multiple wireless transceivers.
• Wireless transceivers such as mobile communication devices, sometimes use a half duplex mode of communication. Using the half duplex mode, a wireless transceiver can transmit and receive, but cannot simultaneously do both. When multiple wireless transceivers are communicating in a group environment, one or more wireless transceivers can receive a signal transmitted by another wireless transceiver. It is desirable, however, that only one transceiver transmit at any given time to avoid transmission collisions. Transmission collisions can disrupt communications. In a communication system that has a central controller, such as a base radio station, the central controller typically provides a timing signal to keep the transceivers synchronized, thereby preventing transmission collisions from occurring.
• a central controller such as a base radio station
• a systemless call environment that is a call environment that does not have a central controller such as a basestation
• the wireless transceivers typically are required to synchronize with each other at the start of each transmission. This synchronization process consumes time and power, thus reducing battery life.
• group calls there remains an issue of which member in the group is granted the group channel for transmission.
• wireless transceivers participating in a group call transmit at random. Thus, transmission collisions sometimes occur and multiple synchronization signals are sometimes generated.
• some members participating in a group may synchronize with a particular transceiver, while others may synchronize with another transceiver.
• the group can be divided into multiple subgroups with each subgroup having its own synchronization. Thus, no effective and efficient method appears to exist for providing synchronization between wireless transceivers participating in a group call when a central controller is not available.
• An embodiment in accordance with the present invention relates to a method of communicating with a transceiver.
• the method of communicating with a transceiver is performed in a systemless group environment.
• Synchronization information can be received from a mobile transceiver and used to synchronize to the mobile transceiver.
• the synchronization information can include a timing offset and a frequency offset. Synchronization can be maintained until a predetermined condition is met, for example, a predetermined amount of group inactivity.
• the method also can include the step of transmitting a transmission request.
• the transmission request can include a preamble being transmitted in a time slot synchronized with the mobile transceiver.
• the transmission request also can include synchronization information.
• a synchronized time slot can be randomly selected for transmitting the transmission request.
• the method also can include the steps of transmitting synchronization information to at least one transceiver and maintaining synchronization with the transceiver until a predetermined condition is met, such as a predetermined amount of group inactivity.
• the synchronization information can include a timing offset and a frequency offset.
• a transmission request comprising a preamble can be received from the transceiver.
• the transmission request can be received in a synchronous time slot.
• the method also can include the step of transmitting synchronization information to a second transceiver, the synchronization information establishing group synchronization with the second transceiver.
• the synchronization information can be transmitted to the second transceiver after the step of transmitting synchronization information to the at least one transceiver.
• the second transceiver can be a transceiver not already synchronized to the group.
• FIG. 1 is an exemplary schematic diagram of a wireless call group in accordance with the inventive arrangements disclosed herein.
• FIG. 2 is an exemplary frame sequence representing an exchange between a transmitting wireless transceiver and a receiving wireless transceiver in accordance with the inventive arrangements disclosed herein.
• FIG. 3 is a flow chart illustrating a method of providing group call management through receive/transmit synchronization in accordance with the inventive arrangements disclosed herein.
• FIG. 4 is an exemplary transmit timing diagram in accordance with the inventive arrangements disclosed herein.
• An embodiment in accordance with the present invention relates to a method and an apparatus that facilitates synchronization between wireless transceivers in, for example, a systemless group call environment.
• a first transceiver can transmit synchronization information in one or more frames to other members of a group.
• the synchronization information can specify a time offset and a frequency hopping seed that can be used by the other members of the group to remain synchronized to the first transceiver.
• the transceivers can remain synchronized in this manner until a predetermined condition is met.
• synchronization can be maintained until no group activity has been detected for a predetermined amount of hang time.
• hang time is the period of time that a group maintains synchronization during group inactivity, i.e. no further group activity is detected.
• the hang time can be a time period of six seconds following the termination of a transmission within the group.
• the group can maintain the established synchronization until another period of group inactivity is detected which exceeds the hang time. It is understood, however, that group inactivity for a predetermined amount of time is not the only predetermined condition for maintaining synchronization.
• the group 100 can comprise any plurality of transceivers.
• the group 100 can include a first transceiver 110, a second transceiver 120, a third transceiver 130 and a fourth transceiver 140.
• the transceivers 110, 120, 130, 140 can be transceivers which transmit and receive RF communication data.
• the transceivers 110, 120, 130, 140 can be mobile transceivers, such as mobile radios, cellular telephones or any other mobile communication device.
• the transceivers can support full duplex or half duplex communications services.
• the transceivers 110, 120, 130, 140 can be in a scan mode wherein the transceivers 110, 120, 130, 140 scan for preambles transmitted by another transceiver.
• the first transceiver 110 can transmit a transmission request comprising a preamble and synchronization information 150.
• the transceivers 120, 130, 140 can detect the preamble and use the synchronization information to synchronize to the first transceiver 110.
• a frame sequence 200 is shown which represents frames exchanged between the transceiver 110 (transmitter), and transceivers 120, 130, 140 (receivers) when a call is established.
• the transmitter can begin the sequence by transmitting preambles 210.
• the preambles 210 can be tones transmitted at specific RF frequencies which can be detected by the receivers.
• the preambles 210 can be used to synchronize the transmission timing between the transmitter and the receivers. For example, in the case that the transceivers operate using a FH-SS protocol, the preambles 210 can be used to determine a frequency hopping set.
• a plurality of preambles 210 can be transmitted, each at a different predetermined frequency. In the present example three preambles 210 can be transmitted.
• a receiver can continue to scan the predetermined frequencies for the preambles 210 until one of the preambles 210 is detected. For example, if the frequencies at which a first and a second preamble are transmitted are in use, a receiver may not detect the first and second preambles. However, the receiver may detect a third preamble if the frequency at which the third preamble is being transmitted is not in use by another transmitting device.
• the receiver can scan for an associated synchronization frame 220 generated by the transmitter.
• the synchronization frame 220 can be used by the receiver to synchronize timing and frequency with the transmitter.
• a receiver may not detect the first and second synchronization frames.
• the receiver may detect a third synchronization frame if the frequency at which the third synchronization frame is being transmitted is not in use by another transmitting device.
• the synchronization frames 220 can comprise a private identification, a group identification, and other information.
• the synchronization frames can contain a time offset and a frequency hopping seed.
• the frequency hopping seed can be an initial value which is used in a random number generator to generate new communication frequencies which can be used by the transmitter and receiver to communicate. To insure the transmitter and receiver remained synchronized, the transmitter and receiver can use the same random number generating algorithm.
• the time offset can identify time slots when transceivers within the group which are attempting to establish a call can transmit preambles and synchronization frames.
• the receiver After receiving a synchronization frame, the receiver can transmit an acknowledgement (ACK) frame 230 to the transmitter, which signals the transmitter that the receiver is ready to receive data.
• ACK acknowledgement
• the transmitter After receiving the ACK frame 230, the transmitter can transmit identification frames 240 and voice/data frames 250.
• the identification frames 240 can contain caller identification information.
• the voice/data frames 250 can contain voice and/or data.
• FIG. 3 An exemplary flow chart 300 illustrating a method of providing group call management through receive/transmit synchronization is shown in FIG. 3.
• a transceiver in a call group can monitor for a preamble.
• the transceiver can receive and decode a synchronization frame associated with the preamble.
• a group identification identifies with which group the transmitting device is associated.
• the transceiver can continue monitoring for preambles.
• the transceiver can synchronize to the transmitting device, as shown in step 325, and send an acknowledgement (ACK) transmission, as shown in step 330.
• the transceiver then can begin receive processing, as shown in step 335. Proceeding to step 365 and decision box 370, the transceiver can maintain synchronization until there has been no group activity detected for a predetermined amount of hang time. Once the hang time expires and there has been no group activity for the predetermined amount of time, the transceiver can again begin monitoring for preambles, as shown in step 305.
• the transceiver can transmit a transmission request comprising a preamble and a synchronization frame.
• the synchronization frame can contain synchronization information which can be used to establish group synchronization. This can be the case if the call group hang time has expired or the transceiver is joining the group after the initial synchronization. In the case that the transceiver is joining the group after the initial synchronization, the other members can re-synchronize to the new transceiver, so long as another transceiver within the call group is not currently transmitting.
• the synchronization information can be commensurate with the synchronization pattern already established for the group.
• the preamble and synchronization frame can be transmitted in time slots which are synchronous with the group.
• the exact synchronous time slots that are used to transmit the preambles and synchronization frames can be randomly selected. For example, if two members of a group simultaneously depress a PTT button on respective transceivers, each transceiver can randomly select synchronous time slots in which to transmit. Such random time slot selection significantly reduces the risk of two transceivers transmitting preambles/synchronization frames in the same time slot, which is commonly known as a transmission collision.
• the synchronization information can be used by transceivers attempting to join and synchronize to the group. For example, if a group call is in progress, and a new transceiver having the same group identification is switched on or enters the broadcast range of a transmitting transceiver within the group, the new transceiver can detect the preamble and synchronization frame being transmitted by a transmitting transceiver. The preamble and synchronization frame can be used by the new transceiver to synchronize to the group.
• the transceiver can begin its transmission sequence, as shown in step 355. Proceeding to steps 360 and 365, the transceiver can stop transmitting when the transmission sequence is complete and maintain synchronization with the group. Referring to decision box 370, once there has been no group activity for the predetermined amount of time, the transceiver can again begin monitoring for preambles, as shown in step 305.
• FIG. 4 an exemplary timing diagram 400 is shown which illustrates random time slot selection for preamble and synchronization frame transmissions.
• the first, second, third and fourth transceivers are synchronized, the hang time has not expired, and a PTT button is simultaneously depressed on the first, third and fourth transceivers.
• Each of the three transceivers then can transmit a preamble and synchronization frame in random synchronous time slots, as noted.
• the first transceiver has randomly selected the first and sixth time slots
• the third transceiver has selected the fourth and ninth time slots
• the fourth transceiver has selected the third and eighth time slots.
• the second transceiver If the second transceiver detects the first transceiver's preamble and synchronization frame which are transmitted in the first time slot, the second transceiver can send an ACK to the first transceiver and begin receiving transmissions. Since the second transceiver has already responded to the first transceiver, the second transceiver can ignore the third and fourth transceivers. Accordingly, the third and fourth transceivers will not receive an ACK. After a predetermined number of preamble/synchronization frames have been transmitted and no ACK has been received, the third and fourth transceivers can switch to a scan mode to begin monitoring for a preamble transmitted by another device, such as the first transceiver.
• the third and fourth transceivers Upon receiving the preamble/synchronization frames from the first transceiver, the third and fourth transceivers then can send an ACK and begin receiving transmissions from the first transceiver. Again, synchronization can be maintained until there has been no group activity for the predetermined period of time.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Mobile Radio Communication Systems (AREA)
• Time-Division Multiplex Systems (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (1)

Families Citing this family (28)

Citations (3)

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• 2003
  • 2003-10-09 US US10/682,772 patent/US7366532B2/en active Active
• 2004
  • 2004-10-07 EP EP20040794381 patent/EP1673894A4/en not_active Withdrawn
  • 2004-10-07 WO PCT/US2004/033008 patent/WO2005036801A2/en not_active Ceased
  • 2004-10-07 AU AU2004306745A patent/AU2004306745B2/en not_active Ceased
  • 2004-10-07 KR KR1020067006819A patent/KR100886098B1/ko not_active Expired - Fee Related
  • 2004-10-07 CN CN200480029619XA patent/CN101313499B/zh not_active Expired - Fee Related
  • 2004-10-07 JP JP2006534311A patent/JP4637109B2/ja not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (1)

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