JP3989748B2 - Wireless call system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication system, and in particular, one of a plurality of communication units that perform wireless communication with each other operates in a master mode, the other communication units operate in a slave mode, and each communication unit is battery-driven. The present invention relates to a wireless communication system suitable for the system.
[0002]
[Prior art]
In order to enable conversation between passengers on motorcycles, each person's helmet is equipped with a so-called intercom system consisting of speakers, microphones and communication units so that passengers can talk directly to each other. A wireless system is disclosed in Japanese Utility Model Publication No. 62-155535 as a telephone system. Japanese Laid-Open Patent Publication No. 2001-148657 discloses a technology that employs Bluetooth as an intercom wireless communication standard.
[0003]
[Problems to be solved by the invention]
When the wireless communication unit is mounted on each occupant's helmet, if the power is supplied from the vehicle side, wiring to connect the vehicle and the occupant's helmet is required. Can be considered. In this case, in order to enable long-time driving with a battery, a technique for reducing power consumption is important.
[0004]
In a general wireless communication system, when a period during which communication is not performed exceeds a predetermined time, each communication unit shifts to a power saving mode called a sleep mode or a standby mode.
[0005]
On the other hand, in Bluetooth, which is spreading as a short-range wireless communication system, one of a plurality of communication units functions as a master and the other functions as a slave, and forms a short-distance network called a piconet. This piconet also has a power saving mode called “Sniff Mode”.
In the normal mode other than the sniff mode, each slave needs to prepare for reception from the master in all time slots of the ACL (Asynchronous Connection-Less) link. However, in the sniff mode, as shown in FIG. 16, a time slot (sniff slot) defined for each predetermined period called a sniff period (Tsniff) is provided, and packet transmission / reception is limited to the sniff slot.
Each slave can maintain intra-piconet synchronization even in the sniff mode, and holds its own address information (BD_ADDR). When a packet is received in the sniff slot, AM_ADDR registered in the packet header is referred to, and reception is continued as long as the packet is addressed to itself. Prepare for. The sniff slot need not be a single time slot (625 μs), and may be a plurality of (Nsniffattempt) time slots, as shown in FIG.
[0006]
As described above, since the communication unit in the slave mode does not need to receive packets in all reception slots in the sniff mode, power consumption can be suppressed, but the master cannot transition to the sniff mode.
[0007]
For this reason, only the battery of the communication unit that operates as a master tends to be consumed earlier than the batteries of other communication units that operate as a slave. Then, when the master falls into an inoperable state due to a shortage of remaining battery capacity, there is a technical problem that other slaves also become unable to communicate even though the remaining battery capacity is sufficient.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems of the prior art and provide a radio communication system in which not only a communication unit that operates in a slave mode but also a communication unit that operates in a master mode can transition to an energy saving mode. There is.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention includes a plurality of communication units constituting a wireless network, and the plurality of communication units operate partly in a master mode and others operate in a slave mode. The wireless communication system that allows transition to the sleep state while operating in the slave mode is characterized in that the following measures are taken.
(1) The communication unit operating in the master mode pauses its transmission / reception operation in synchronization with the transition of the communication unit operating in the slave mode to the dormant state.
(2) The wireless network constitutes an intercom.
(3) The wireless network is a short-range network using Bluetooth.
(4) All of the plurality of communication units operating in the slave mode are substantially simultaneously changed to the sleep state.
(5) The sniff period of the plurality of communication units operating in the slave mode is substantially the same period and the same phase.
(6) The plurality of communication units operating in the slave mode have substantially the same period and different phases.
(7) A plurality of communication units operating in the slave mode have consecutive sniff cycles.
(8) It is characterized in that the roles of master / slave are interchanged so that the remaining battery capacity of each communication unit is equalized.
[0010]
According to the feature (1) described above, not only the communication unit that operates in the slave mode but also the communication unit that operates in the master mode can be shifted to the dormant state without impairing the convenience of the network.
According to the above feature (2), it is possible to prevent only the remaining battery capacity of the communication unit operating in the master mode from rapidly decreasing, and to extend the battery driving time of the entire intercom.
According to the above feature (3), in a highly versatile communication system, the battery drive time of each communication unit can be extended regardless of the operation mode.
According to the above feature (4), it is possible to prevent a part of the battery driving time among the plurality of slaves from being shortened.
According to the above feature (5), since the sniff slots of the slaves substantially coincide, the operation time of the master can be shortened.
According to the feature (6) described above, since the period during which the master communicates with one of the slaves can be a pause time of the other slaves, the total length of the sniff slot that is the slave operation time can be shortened. .
According to the above feature (7), since the number of times the master is activated from the hibernation state can be reduced, further power saving of the master is possible.
According to the feature (8) described above, since the operation mode of each communication unit can be changed every predetermined time, the time during which each communication unit operates as a master can be made equal. Therefore, it is possible to prevent an imbalance in which only the remaining battery power of some communication units is significantly reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a minimum configuration of a vehicle radio communication system to which the present invention is applied. Helmets 1a and 1b worn by a driver and a passenger are microphones 11a and 11b, speakers 12a, and 12a, respectively. 12b and wireless communication units 13a and 13b are provided.
[0012]
Each of the wireless communication units 13a and 13b conforms to the Bluetooth standard, and performs wireless communication with each other while operating in the master mode and the other in the slave mode on the piconet that uses them as accommodating terminals. When the communication units 13a and 13b operate in the slave mode, the communication units 13a and 13b can transition to a power saving mode called a sniff mode under a predetermined condition.
[0013]
FIG. 2 is a block diagram showing the configuration of the main part of the communication unit 13a. The same reference numerals as those described above represent the same or equivalent parts.
[0014]
The antenna 314 of the communication unit 13a is connected to the RFIC 316 via the band pass filter 315. The RFIC 316 has a reception side path and a transmission side path, and these are switched by the antenna switch SW316a. The reception side path is composed of a low noise amplifier LNA, a mixer IRM, an IF band pass filter IFBPF, a limit amplifier LIMAMP, a demodulator DEM, and a low pass filter LPF. On the other hand, the transmission side circuit is composed of a Gaussian filter, a switch SW, a PLL circuit, an LPF, voltage controlled oscillators VCO and SW, and a power amplifier PA.
[0015]
A baseband IC 317 that is a baseband signal processing device includes a baseband controller, a ROM, a RAM, a CPU, a PCM / CVSD transcoder, an external bus I / F, a device controller, and a power supply voltage, each connected to a bus. It comprises a voltage regulator that stabilizes the power supply and a power management unit PMU.
[0016]
The sound picked up by the microphone 11 a is amplified by the power amplifier 318 and connected to the input / output I / F 320. On the other hand, the received audio signal sent from the input / output I / F 320 is amplified by the power amplifier 319, reaches the speaker 12a, and is reproduced as audio. A main SW 322 is connected to the switch interface SWI / F 321. Note that the RFIC 316 and the baseband IC 317 are well-known circuits, and thus a detailed description of the operation is omitted.
[0017]
FIG. 3 is a diagram schematically showing another configuration example of the vehicle radio communication system to which the present invention is applied. The same reference numerals as those described above represent the same or equivalent parts.
[0018]
In the present embodiment, not only the communication units 13a and 13b attached to the helmets 1a and 1b of the driver and the passenger, but also mobile phones (mobile phones or PHS) 13c and 13d carried by the driver and the passenger are Bluetooth. A communication function conforming to the standard is provided. The communication units 13a and 13b and the mobile phones 13c and 13d constitute a piconet, and one performs wireless communication with each other while operating in the master mode and the other in the slave mode. Also in this embodiment, each communication unit (including a mobile phone, the same applies hereinafter) can transition to the sniff mode under predetermined conditions when operating in the slave mode.
[0019]
FIG. 4 is a flowchart showing an operation of the power saving mode request process in which the master requests each slave to transition to the sniff mode under a predetermined condition, and is repeatedly executed at a predetermined cycle in each communication unit. Here, in the communication mode (four communication units) described with reference to FIG. 3, it is assumed that the communication unit 13a operates in the master mode and the communication unit 13b and the mobile phones 13c and 13d operate in the slave mode. To do.
[0020]
In step S1, it is determined whether the current operation mode is the master or the slave. If the master mode is selected, the process proceeds to step S2, and if the slave mode is selected, the process is terminated. Therefore, if the communication unit 13b and the mobile telephones 13c and 13d are used, the processing ends.
[0021]
On the other hand, if the communication unit 13a is in the master mode, the process proceeds to step S2, and it is determined whether the transition condition to the sniff mode is satisfied. In this embodiment, if the state in which communication other than polling is not performed continues for a predetermined time or more, it is determined that the transition condition is satisfied.
[0022]
In step S3, it is determined whether or not there is a SCO ( Synchronous Connection-Oriented) link that transmits and receives data packets that require real-time performance such as voice one-to-one. When this SCO link is detected, an SOC link disconnection request (LMP_remove_soc_link_req) is transmitted in step S4 to disconnect the SOC link. In step S5, a process for transitioning each slave to the sniff mode is executed.
[0023]
FIG. 5 is a flowchart showing the operation of the sniff mode transition process executed in step S5.
[0024]
In step S51, the number of slaves Nslave that currently constitutes the piconet is substituted into a variable N. In the present embodiment, since the three communication units 13b, 13c, and 13d are operating in the slave mode, “3” is substituted into the variable N.
[0025]
In step S52, the number of sniff slots Nsniffattempt is set to 3 times the number of slaves Nslave (in this embodiment, “9”). This is because, for one slave, (1) the slot in which the master polls the slave, (2) the slot in which the slave sends a response in response to polling, and (3) data other than polling is sent from the master to the slave This is to secure three of the spare slots for the purpose.
[0026]
Further, even when a packet is not transmitted from the master, the slave number Nslave is additionally set as the number of slots that the slave continues to receive (the reception continuation slot number Nsnifftimeout). Furthermore, after performing the transmission / reception operation in the sniff slot, the transmission / reception is suspended, and 10 times the number of sniff slots Nsniffattempt is set as a period (sniff cycle Tsniff) for starting the transmission / reception operation again.
[0027]
In step S53, the sniff slot number Nsniffattempt, the reception continuation slot number Nsnifftimeout and the sniff period Tsniff are transferred to the first slave (N = 3) together with the sniff mode transition request packet (LMP_Sniff_req) as shown in FIG. In response to this, a control packet (LMP_accepted) is returned from the slave. In step S54, the variable N is decremented. In step S55, it is determined whether or not the variable N has reached zero, and the processes in steps S53 to S55 are repeated until it is determined that the variable N is zero. In this way, the transition to the snim mode is understood with all the slaves.
Returning to FIG. 4, when the sniff mode transition request for all the slaves is completed as described above, in step S6, based on the number of sniff slots Nsniffattempt, the number of reception continuation slots Nsnifftimeout notified by the master, and the sniff period Tsniff. Transition to the sleep mode at the same cycle as each slave. The normal return from the sniff mode can be requested from either the master or the slave according to the Bluetooth standard.
[0028]
FIG. 7 is a flowchart showing the operation in the sleep state of the master, and FIG. 8 is a timing chart thereof.
[0029]
When the sniff cycle is reached at time t1 in FIG. 8 and this is detected in step S61 in FIG. 7, the number of sniff slots Nsniffattempt (“9” in this embodiment) is added to the variable Na representing the number of unprocessed slots in step S62. ) Is substituted, and the number of slaves Nslave (in this embodiment, “3”) is substituted for the variable Nb representing the number of unprocessed slaves. In step S63, it is determined whether or not it is a sniff slot. Here, since it is determined that it is the first sniff slot, the process proceeds to step S64. In step S64, the variable Na (number of unprocessed slots) representing the number of unprocessed slots is decremented.
In step S65, it is determined whether or not the Nb-th slave has been polled. Here, since it is determined that polling has not been completed, the process proceeds to step S66. In step S66, the Nb-th slave (here, the communication unit 13b which is the third slave) is polled. In step S69, it is determined whether or not the variable Nb is equal to or less than zero. Here, since it is determined that it is not equal to or less than zero, the process returns to step S63.
[0030]
When the second sniff slot is detected at time t2 (step S63), it is determined in step S65 that polling has been completed, and the process proceeds to step S67 to receive a response signal transmitted from the current Nb-th or third slave. The In step S68, the variable Nb representing the number of unprocessed slaves is decremented. In step S69, it is determined whether or not the variable Nb is equal to or less than zero. Here, since it is determined that it is not less than zero, the process returns to step S63.
[0031]
Similarly, when the third sniff slot is detected at time t3 (step S63), in step S65, it is determined that the Nb-th (here, second) slave has not been polled, and the process proceeds to step S66. The second slave is polled. When the fourth sniff slot is detected at time t4 (step S63), in step S65, it is determined that the Nb-th slave has been polled, so the process proceeds to step S67 and a response signal transmitted from the second slave is received. Received. In step S68, the variable Nb is decremented. In step S69, it is determined whether or not the variable Nb is equal to or less than zero. Here, since it is determined that it is not less than zero, the process returns to step S63.
Further, when the fifth sniff slot is detected at time t5 (step S63), it is determined in step S65 that the Nb-th (here, the first) slave has not been polled, and the process proceeds to step S66. The Nbth slave is polled. When the sixth sniff slot is detected at time t6 (step S63), in step S65, it is determined that the Nb-th slave has been polled, and the process proceeds to step S67, and a response signal transmitted from the Nb-th slave is received. Is done. In step S68, the variable Nb is decremented. In step S69, since it is determined that the variable Nb is equal to or less than zero, the process proceeds to step S70.
[0032]
In step S70, it is determined whether or not the variable Na (number of unprocessed slots) is equal to or smaller than zero. Here, since it is larger than zero, the process proceeds to step S71. When the seventh sniff slot is detected at time t7 (step S71), the variable Na is decremented in step S72.
[0033]
Similarly, the variable Na is decremented in step S72 every time the eighth and ninth sniff slots are detected at times t8 and t9. Thereafter, in step S70, it is determined that the variable Na is equal to or less than zero, that is, when the current sniff slot is completed, the process returns to step S61, and the transmission / reception operation is stopped until the next sniff slot. That is, the master transitions to a dormant state until the next sniff cycle.
[0034]
According to this embodiment, not only the communication unit that operates in the slave mode but also the communication unit that operates in the master mode can transition to the dormant state. Therefore, in the wireless communication system in which each communication unit is battery-driven, it is possible to prevent only the remaining battery capacity of the communication unit operating in the master mode from rapidly decreasing, and the battery drive time of the entire communication system can be extended.
[0035]
FIG. 9 is a time chart showing the operation timing of the second embodiment of the present invention. In the first embodiment described above, each communication unit 13b, 13c, 13d operating in the slave mode has been described as transitioning to a dormant state with substantially the same period and the same phase. However, in this embodiment, the slave mode The communication units 13b, 13c, and 13d that operate in the above state shift to a dormant state with the same period but shifted by several slots. Furthermore, in this embodiment, the number of sniff slots Nsniffattempt is reduced to twice the number of slaves.
[0036]
According to the present embodiment, for example, if the period at which each slave shifts to the dormant state is different by two slots, the slave 13c can be put into the dormant state while the master polls the slave 13b and receives the response signal. The sleep time of each slave can be extended as compared with the first embodiment.
[0037]
According to each of the embodiments described above, although the battery drive time of the communication unit operating in the master mode can be significantly extended compared to the conventional case, the packet is compared with other communication units operating in the slave mode. As the number of times of transmission / reception is large, power consumption is relatively large. Therefore, in the third embodiment described below, each communication unit alternates its operation mode so that the remaining battery level of each communication unit is evenly reduced.
[0038]
FIG. 10 is a flowchart showing the operation of the operation mode change procedure (part 1), which is repeatedly executed at a predetermined cycle in each communication unit. Here, in the communication mode (two communication units) described with reference to FIG. 1, the description starts from a state in which the communication unit 13a operates in the master mode and the communication unit 13b operates in the slave mode.
[0039]
In step S11, it is determined whether its current operation mode is a master or a slave. If it is the master mode (that is, the communication unit 13a), the process proceeds to step S12, and if it is the slave mode (that is, the communication unit 13b), the process ends. In step S12, the communication unit 13a operating in the master mode obtains a duration Tmc_a from when the communication unit 13a starts operating in the current master mode.
[0040]
In step S13, the operation duration time Tmc_a as the master is compared with a predetermined replacement reference time Tmc_a_ref. If the duration time Tmc_a is shorter than the alternation reference time Tmc_a_ref, the processing is terminated and the operation in the master mode is continued. On the other hand, if the duration time Tmc_a is equal to or longer than the replacement reference time Tmc_a_ref, the process proceeds to step S14. In step S14, a master / slave switching request packet (LMP_switch_req) is transmitted to the communication unit 13b operating in the slave mode.
[0041]
FIG. 11 is a communication sequence showing a procedure in which the master and the slave switch their operation modes in response to the master / slave switching request packet (LMP_switch_req) transmitted from the master as described above.
Upon receiving the (LMP_switch_req) master / slave switch request packet, the slave mode communication unit 13b returns an LMP_accepted packet (acknowledgment of acceptance of the switch request) in response to this and further performs intra-piconet synchronization. An LMP_slot_offset (slot offset information) packet and an FHS (synchronization establishment by FHS packet) packet for establishment are transmitted. In response to this, the communication unit 13a in the master mode transmits its own ID packet for confirmation of reception. Thereafter, a POLL (polling) packet is newly transmitted from the communication unit 13b operating in the master mode, and a NULL packet is returned from the communication unit 13a newly operating in the slave mode.
[0042]
In the above-described embodiment, the communication unit 13a operating in the master mode has been described as counting the duration, but conversely, the communication unit 13b operating in the slave mode has the duration. The master / slave switching request packet (LMP_switch_req) may be transmitted to the communication unit operating in the master mode when the time is measured and the duration exceeds a predetermined time.
[0043]
FIG. 12 is a communication sequence showing a procedure in which the master and the slave switch their operation modes in response to the master / slave switching request (LMP_switch_req) transmitted from the slave.
[0044]
According to this embodiment, since the operation mode of each communication unit can be changed every predetermined time, it is possible to equalize the time during which each communication unit operates as a master. Therefore, it is possible to prevent an imbalance in which only one communication unit continues to operate as a master and only the remaining battery level is significantly reduced.
[0045]
FIG. 13 is a flowchart showing the operation of another operation mode change procedure (part 2), which is repeatedly executed at a predetermined cycle in each communication unit. Here, in the communication mode (four communication units) described with reference to FIG. 3, the communication unit 13a operates in the master mode, and the communication unit 13b and the mobile phones 13c and 13d operate in the slave mode. Begin.
[0046]
In step S21, each of the communication units 13a, 13b and the mobile phones 13c, 13d obtains their battery remaining capacity Q (Qa, Qb, Qc, Qd) based on the terminal voltage and charge / discharge history. If the battery is a lithium ion battery, the remaining battery capacity can be accurately obtained based on information from the power management means built in the lithium ion battery.
[0047]
In step S22, based on its own battery remaining capacity Q and its current operation mode, the time during which the current operation mode (master or slave) can be continued normally when the current operation mode (master or slave) is continued, that is, the operation is maintained. Calculate the estimated time. For example, in the case of the communication unit 13a operating in the master mode, the predicted operation maintenance time can be obtained by dividing its own battery remaining capacity Qa by the average power consumption when operating in the master mode.
[0048]
In step S23, it is determined whether the current operation mode is the master or the slave. If it is the master mode, the process proceeds to step S24, and if it is the slave mode, the process proceeds to step S28. Therefore, if it is the communication unit 13b and the mobile phones 13c and 13d, the process proceeds to step S28, and the predicted operation maintenance time T (Tb, Tc, Td) obtained in step S22 is transmitted to the communication unit 13a operating in the master mode. To do.
[0049]
On the other hand, if the communication unit 13a is in the master mode, the process proceeds to step S24, and the other operation unit (13b, 13c, 13d) operating in the slave mode in the piconet to which it belongs belongs to the predicted operation maintenance time T ( Tb, Tc, Td) are acquired.
[0050]
In step S25, from the predicted operation maintenance time Ta operating in the master mode and the predicted operation maintenance times Tb, Tc, Td acquired from the other communication units 13b, 13c, 13d operating in the slave mode. The longest one is selected and registered as the longest maintenance prediction time Tmax. In the present embodiment, the description is continued assuming that the operation maintenance predicted time Tb of the communication unit 13b is the longest.
In step S26, the difference between the longest maintenance predicted time Tmax (= Tb) and its own motion maintenance predicted time Ta is compared with a predetermined alternation determination time Tref.
[0051]
If the difference is smaller than the determination time Tref, the process is terminated as it is. If the difference is larger than the determination time Tref, the process proceeds to step S27. In step S27, in order to shift the communication unit (in this embodiment, the communication terminal 13b) having the longest operation maintenance prediction time T (Tmax) to the master mode, the communication unit itself shifts to the master mode. A master / slave switching request packet (LMP_switch_req) is transmitted to 13b.
[0052]
Thereafter, the communication sequence described with reference to FIG. 11 is executed, the communication unit 13a that has been operating in the master mode until then shifts to the slave mode, and the communication unit 13b that has been operated in the slave mode shifts to the master mode. To do.
[0053]
According to the present embodiment, the estimated operation maintenance time when the current operation mode is continued for each communication unit is measured, and the communication unit with the longest operation is operated in the master mode. Even when the power consumption of the modes is different, the master mode can be assigned to the optimum communication unit.
[0054]
In the above-described embodiment, the operation maintenance prediction time is obtained based on the battery remaining capacity Q, and the communication unit having the longest operation maintenance prediction time is operated as a master. However, the battery remaining capacity Q is the maximum. The communication unit may be operated as a master. At this time, if a lithium-ion battery is used as the battery, the remaining battery capacity can be accurately recognized based on information from the power management means built in the lithium-ion battery, so accurate determination can be made with a simple configuration. become.
[0055]
FIG. 14 is a flowchart showing the operation of another operation mode change procedure (part 3), which is repeatedly executed at a predetermined cycle in each communication unit. Here, in the communication mode (four communication units) described with reference to FIG. 3, the communication unit 13a operates in the master mode, and the communication unit 13b and the mobile phones 13c and 13d operate in the slave mode. Begin.
[0056]
In step S31, each of the communication units 13a and 13b and the mobile phones 13c and 13d obtains an accumulated time Ts (Ts_a, Ts_b, Ts_c, Ts_d) in which the communication units 13a and 13b and the mobile phones 13c and 13d operate in the power saving mode. In step S32, it is determined whether the current operation mode is the master or the slave. If it is the master mode, the process proceeds to step S34, and if it is the slave mode, the process proceeds to step S33. Therefore, if the communication unit 13b and the mobile phones 13c and 13d are used, the process proceeds to step S33, and the accumulated time Ts (Ts_b, Ts_c, Ts_d) obtained in step S31 is transmitted to the communication unit 13a operating in the master mode.
[0057]
On the other hand, if the communication unit 13a is in the master mode, the process proceeds to step S34, and the accumulated time Ts (Ts_b, T) from other communication units (13b, 13c, 13d) operating in the slave mode in the piconet to which the master mode belongs. Ts_c, Ts_d) are acquired.
[0058]
In step S35, the communication unit 13a operating in the master mode has its own accumulated time Ts_a and the accumulated time Ts_b, Ts_c, Ts_d acquired from the other communication units 13b, 13c, 13d operating in the slave mode. The longest one is selected and registered as the longest cumulative time Tmax. In the present embodiment, the description will be continued assuming that the accumulated time Ts_b of the communication unit 13b is the longest.
In step S36, it is determined whether or not the difference between the longest accumulated time Tmax (= Ts_b) and its own accumulated time Ts_a is equal to or longer than a predetermined alternation reference time Ts_ref.
[0059]
If the difference is smaller than the reference time Ts_ref, the process is terminated as it is. If the difference is equal to or greater than the reference time Tsref, the process proceeds to step S37. In step S37, the communication unit 13a performs communication in order to shift the communication unit (in this embodiment, the communication terminal 13b) having the longest accumulated time Ts (Tmin) to the master mode. A master / slave change request packet (LMP switch req) is transmitted to the unit 13b.
[0060]
Thereafter, the communication sequence described with reference to FIG. 11 is executed, the communication unit 13a that has been operating in the master mode until then shifts to the slave mode, and the communication unit 13b that has been operated in the slave mode shifts to the master mode. To do.
[0061]
According to the present embodiment, the accumulated time of operation in the power saving mode is obtained for each communication unit, and the master mode is assigned to the communication unit that is predicted to have the longest battery capacity, that is, the remaining battery level is maximum. It is possible to prevent an imbalance in which only the remaining battery power of the unit is significantly reduced.
[0062]
FIG. 15 is a flowchart showing the operation of another operation mode change procedure (part 4), which is repeatedly executed at a predetermined cycle in each communication unit. Here, in the communication mode (four communication units) described with reference to FIG. 3, the communication unit 13a operates in the master mode, and the communication unit 13b and the mobile phones 13c and 13d operate in the slave mode. Begin.
[0063]
In step S41, each of the communication units 13a and 13b and the mobile phones 13c and 13d obtains an accumulated time Tm (Tm_a, Tm_b, Tm_c, Tm_d) in which the communication unit 13a and 13b and the mobile phone 13c operate as a master. In step S42, it is determined whether the current operation mode is master or slave. If it is the master mode, the process proceeds to step S44, and if it is the slave mode, the process proceeds to step S43. Therefore, if the communication unit 13b and the mobile phones 13c and 13d are used, the process proceeds to step S43, and the accumulated time Tm (Tm_b, Tm_c, Tm_d) obtained in step S41 is transmitted to the communication unit 13a operating in the master mode.
[0064]
On the other hand, if the communication unit 13a is in the master mode, the process proceeds to step S44, and the accumulated time Tm (Tm_b, Tm_b, from other communication units (13b, 13c, 13d) operating in the slave mode in the piconet to which the master mode belongs. Tm_c, Tm_d) are acquired.
[0065]
In step S45, the communication unit 13a operating in the master mode has the accumulated time Tm_a and the accumulated times Tm_b, Tm_c, and Tm_d acquired from the other communication units 13b, 13c, and 13d operating in the slave mode. The shortest one is selected and registered as the shortest cumulative time Tmin. In the present embodiment, the description will be continued assuming that the accumulated time Tm_c of the communication unit 13c is the shortest.
In step S46, it is determined whether or not the difference between the shortest cumulative time Tmin (= Tm_c) and the own cumulative time Tm_a is equal to or longer than a predetermined replacement reference time Tm_ref.
[0066]
If the difference is smaller than the reference time Tm_ref, the process is terminated as it is, and if the difference is equal to or greater than the reference time Tmref, the process proceeds to step S47. In step S47, the communication unit 13a performs communication in order to shift the communication unit (in this embodiment, the communication terminal 13b) having the shortest (Tmin) cumulative time Tm to the master mode. A master / slave switch request packet (LMP switch req) is transmitted to the unit 13c.
[0067]
Thereafter, the communication sequence described with reference to FIG. 11 is executed, the communication unit 13a that has been operating in the master mode until then shifts to the slave mode, and the communication unit 13c that has been operated in the slave mode shifts to the master mode. To do.
[0068]
According to the present embodiment, the accumulated time of operating as a master for each communication unit is obtained, and this is assigned the master mode to the communication unit that is predicted to have the shortest, that is, the maximum remaining battery power. It is possible to prevent an imbalance in which only the remaining battery level is significantly reduced.
[0069]
【The invention's effect】
According to the present invention, the following effects are achieved.
(1) Not only a communication unit that operates in the slave mode but also a communication unit that operates in the master mode can transition to a dormant state. Therefore, in a wireless communication system in which each communication unit is battery-driven, it is possible to prevent only the remaining battery capacity of the communication unit operating in the master mode from rapidly decreasing, and the battery drive time of the entire communication system can be extended.
(2) Since the operation mode of each communication unit can be changed every predetermined time, the time during which each communication unit operates as a master can be made equal. Therefore, it is possible to prevent an imbalance in which only the remaining battery power of some communication units is significantly reduced.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a minimum configuration of a vehicle radio communication system to which the present invention is applied.
FIG. 2 is a block diagram showing a configuration of a main part of a communication unit.
FIG. 3 is a diagram schematically showing another configuration example of a vehicle radio communication system to which the present invention is applied.
FIG. 4 is a flowchart showing an operation of a power saving mode request process.
FIG. 5 is a flowchart showing an operation of a sniff mode transition process.
FIG. 6 is a diagram showing a communication protocol for a request to change to sniff mode and a response to the request.
FIG. 7 is a flowchart showing an operation in a sleep state of a master.
FIG. 8 is a time chart showing an operation in a sleep state of a master.
FIG. 9 is a time chart showing an operation in a dormant state in another embodiment of the master.
FIG. 10 is a flowchart of an operation mode change procedure (part 1);
FIG. 11 is a diagram showing an example of a communication sequence executed between communication units that alternate master / slave.
FIG. 12 is a diagram showing another example of a communication sequence executed between communication units that alternate master / slave.
FIG. 13 is a flowchart of an operation mode change procedure (part 2);
FIG. 14 is a flowchart of an operation mode change procedure (No. 3);
FIG. 15 is a flowchart of an operation mode change procedure (part 4);
FIG. 16 is an explanatory diagram of a Bluetooth sniff slot.
FIG. 17 is an explanatory diagram of a Bluetooth sniff slot.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a, 1b ... Helmet, 11a, 11b ... Microphone, 12a, 12b ... Speaker, 13a, 13b ... Wireless communication unit, 13c, 13d ... Mobile phone

Claims (14)

Including a plurality of communication units constituting a wireless network, a part of the plurality of communication units operating in the master mode, the other operating in the slave mode, and entering the sleep state while operating in the slave mode. In a wireless communication system that allows transition,
Each communication unit includes a battery as a drive power source,
The communication unit operating in the master mode is
Means for detecting the sniff period;
Means for communicating within a predetermined period with each communication unit operating in slave mode for each sniff period;
And a means for suspending its own transmission / reception operation until the next sniff cycle in synchronization with the transition of the communication unit operating in the slave mode to the suspend state.   The wireless communication system according to claim 1, wherein the wireless network constitutes an intercom.   2. The wireless communication system according to claim 1, wherein the wireless network is a short-distance network using Bluetooth.   The wireless communication system according to any one of claims 1 to 3, wherein all of the plurality of communication units operating in the slave mode transition to the dormant state substantially simultaneously.   4. The wireless communication system according to claim 1, wherein sniff periods of the plurality of communication units operating in the slave mode have substantially the same period and the same phase.   4. The wireless communication system according to claim 1, wherein the plurality of communication units operating in the slave mode have substantially the same period and different phases.   The wireless communication system according to claim 6, wherein sniff cycles of a plurality of communication units operating in the slave mode are continuous.   8. The wireless communication system according to claim 1, wherein the roles of the master / slave are interchanged so that the remaining battery capacity of each communication unit is equalized. Each communication unit
When operating in the master mode, equipped with a means for measuring the operation continuation time as the master this time,
9. The wireless communication system according to claim 8, wherein when the operation continuation time exceeds a predetermined reference time, the roles of the master / slave and the other terminals in the slave mode are interchanged. Each communication unit
Means for detecting the remaining battery level;
Means for exchanging the detected remaining battery capacity with other terminals,
9. The wireless communication system according to claim 8, wherein a master is assigned to a terminal having a relatively large remaining battery level. Each communication unit
Means for timing the operation duration prediction time in the current operation mode;
Means for exchanging the operation duration prediction time with other terminals,
9. The wireless communication system according to claim 8, wherein a master is assigned to a terminal having a relatively long estimated operation duration. Each communication unit
Comprising means for timing the cumulative time of operation in master mode;
Means for exchanging the accumulated time with other terminals,
9. The wireless communication system according to claim 8, wherein a master is assigned to a terminal having a relatively short cumulative time. Each communication unit
Means for timing the accumulated time operating in the power saving mode;
Means for exchanging the accumulated time with other terminals,
9. The wireless communication system according to claim 8, wherein a master is assigned to a terminal having a relatively long accumulated time.   14. The wireless communication system according to claim 8, wherein the battery is a lithium ion battery.

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