JPH03171931A - Mobile communication system - Google Patents

Abstract

PURPOSE:To prevent the collision of an idle/busy signal by sending out a data signal in which a preamble signal is introduced only when no transmission inhibiting signal is incorporated in a read signal. CONSTITUTION:A communication equipment 25 and plural base stations 1-3 are connected by a transmission line 7, plural base stations 1-3 and plural mobile stations 4, 5 are connected by a bidirectional radio channel, respectively, and communication is executed between the communication equipment 25 and plural mobile stations 4, 5 by the bidirectional radio channel through the base stations 1-3. Also, plural mobile stations 4, 5 are provided with a means for transmissing a transmission requesting signal to the base stations 1-3, respectively, and plural base stations 1-3 transmit a transmission permitting signal until a transmission requesting signal is received, respectively. Moreover, when the transmission requesting signal is received, a transmission inhibiting signal for inhibiting the transmission of other mobile stations 5 (4) than the mobile stations 4 (5) corresponding to this transmission requesting signal is transmitted only during the time allocated to its own station in time zones brought to multiplex time division of plural base stations 1-3, respectively. In such a manner, even if the base stations 1-3 generate different busy/idle signals, the collision of the busy/idle signal can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a mobile communication system, and particularly to a wireless network system for local mobile communication in a small zone.

(Prior Art) Recently, as a mobile communication system applied to a premises wireless network system, a local area network (L
ocsl Atet Network, hereinafter referred to as rLANJ
A method (internal wireless network) of wirelessly connecting a mobile station connected to a mobile station (hereinafter abbreviated as ) or a mobile station distributed processing computer wirelessly connected to a distributed processing computer is being considered.

Conventionally, for such in-premises wireless networks, one base station and multiple mobile stations have BWS for one frequency.
7 Tome Mwlliple Acctss (
Hereinafter, it is considered that communication is performed by multiple access using "BTMAJ" (abbreviated as BTMAJ).

However, when multiple access communication using BTMA is used in a campus wireless network office, etc., the propagation environment of wireless communication fluctuates due to the movement of lockers, desks, people, etc., and the communication circuit between the LAN and mobile station is physically There was an inconvenience in that the transmission of information was interrupted due to a disconnection.

(Problems to be Solved by the Invention) In order to eliminate such inconveniences, a plan has been proposed in the past to configure a local wireless network as shown in FIG. That is, a plurality of base stations 1 to 3 are connected to a common transmission path 6 in order to receive transmissions from a terminal (mobile station) 4,
Each base station 1, 2.3 uses a single frequency,
The configuration is such that it supports one channel as a whole.

With this configuration, even if the propagation environment changes and wireless transmission between a mobile station and one base station is cut off, it is possible to communicate using another base station. This is how it was done.

Access control between base stations and terminals (mobile stations) is the so-called B
Performed by TMA, each base station broadcasts a RID 1 eJ signal to permit transmission when there is no transmission from the mobile station, and the mobile station is configured to start access only when it receives the RIDLEJ signal from the base station. do. In addition, the base station that received the riddleJ signal from the mobile station
Change the signal to a "busyJ" signal, which prohibits transmission, and prohibits access from other mobile stations.

It has been known that there are two methods for implementing BTMA. The first method (a) is to modulate the RIDLEJ information and RBUSYJ information at each base station, and the mobile station demodulates the broadcast idie/busy signal to determine whether it is a RIDLEJ signal or not.
This is a method of determining whether it is a yJ signal.

(b) The second method is to emit a carrier wave from the base station as an rbusyJ signal and do not emit any radio waves as a riddleJ signal, or conversely, to emit a carrier wave as a riddleJ signal and not emit a carrier wave as an rbusyJ signal. It is. Then, the mobile station senses whether a carrier wave exists or not and determines whether it is rtdleJ or "busyJ".

If we consider the case where the first method is adopted in a system with the configuration shown in Figure 1, in this case, signals modulated by multiple base stations are simultaneously transmitted using a single frequency, so the carrier waves overlap. As a result, the mobile station is unable to demodulate the modulated signal, making it difficult to implement BTMA.

In addition, in the second method, the mobile station does not need to demodulate the IDLE/BUSY signal sent from the base station, and only needs to determine whether radio waves are being emitted from the base station. Okay, so the difficulty in the first method is eliminated. However, if the mobile station is unable to communicate with any base station because the transmission path is cut off due to an obstacle, etc., the user may have to ask whether all the base stations are LdleJ and the carrier wave is not detected, or if there is a mobile failure. Therefore, it is difficult to determine whether the carrier wave is not detected or whether communication with all base stations is impossible.

The present invention was made in view of the above-mentioned circumstances in conventional mobile communication systems, and even if a signal modulated by multiple base stations is transmitted using a single frequency, it can be demodulated by a mobile station. Furthermore, the present invention aims to provide a mobile communication system that allows communication between a mobile station and a base station even if the transmission path between the mobile station and the base station is cut off due to an obstacle or the like. .

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned problems, one claim (1) of the mobile communication system according to the present invention provides a mobile communication system in which a communication device and a plurality of base stations transmit data. The plurality of base stations and the plurality of mobile stations are each connected by a two-way radio line, and the communication device and the plurality of mobile stations are connected via the two-way radio line via the base station. In the communication mobile system, each of the plurality of mobile stations includes means for transmitting a transmission request signal to the base station, and each of the plurality of base stations transmits a transmission permission signal until it receives the transmission request signal. When the transmission request signal is received, a transmission prohibition signal is sent to the own station within the multiplexed time-division time period of each of the plurality of base stations. It is designed to transmit only during the allotted time.

Furthermore, another mobile communication system according to the present invention (
Claim <<2>>) provides that each of the plurality of mobile stations of the mobile communication system (described in claim (1)) transmits the transmission permission signal while receiving the transmission permission signal corresponding to its own station. The mobile station receiving the information is configured to communicate with the communication device.

(Function) As described above, a communication device and a plurality of base stations are connected by a transmission path, and each of these plurality of base stations and a plurality of mobile stations is connected by a bidirectional radio line, and a communication device is connected to a plurality of base stations via a base station. Since the system configuration is such that communication is performed between the communication device and a plurality of mobile stations using the two-way radio link, a situation may arise in which the two-way radio link between one mobile station and a base station is cut off. However, it is possible to communicate with communication devices via other base stations.

Further, each of the plurality of mobile stations includes means for transmitting a transmission request signal to the base station, and each of the plurality of base stations transmits a transmission permission signal until receiving the transmission request signal, and transmits the transmission request signal to the base station. When a transmission request signal is received, a transmission prohibition signal is transmitted to prohibit transmission by mobile stations other than the mobile station corresponding to this transmission request signal. Because it is configured to transmit only during certain times, different base stations may be busy.
Busy /id even if /idle signal is issued
Collision of Ie signals can be prevented.

Further, in the mobile communication system of claim (2), when each of the plurality of mobile stations receives a transmission permission signal corresponding to the mobile station, the transmission permission signal is transmitted between the mobile station that received the transmission permission signal and the communication device. Since the mobile station is configured to communicate with each other, it is possible to prevent a situation in which communication between each mobile station and the communication device becomes impossible.

(Example) Next, a typical example of the mobile communication system of the present invention will be described according to the drawings.

FIG. 1 shows an LA connected to a communication device 25 via a node 6.
The communication device 8 is connected to the transmission line of N7, and the schematic configuration of the mobile communication system within the premises is shown.
A signal is sent to the mobile station 4.5 using the down channel, and data is transmitted to the communication device 8 via the base station using the up channel.

The downlink channel used by base station 1.2.3 uses a single frequency, and the uplink channel used by mobile station 4.5 also uses a single frequency.

Each base station 1.2.3 indicates whether the current channel is available or unavailable to all mobile stations, i.e. id 1 e /
As shown in FIG. 1(b), in order to notify the base station, the idle/bu
sy Pre-Assign/Time that sends the y signal
])i▼isioa 111allipICAcc
ss (PA/TDMA) and this idle/
Busy signals (hereinafter referred to as "I/B") use the same frequency at each base station, so each terminal (mobile station)
Then, it is received as shown in FIG. 2(b).

Also, as shown in Fig. 2(b), all base stations are Ld1 e
One cycle is defined as the time required to complete transmitting the /busy signal, that is, three slots. Further, the signal sent by the mobile station is sent in a desired format with the prefix shown in FIG. 11.

Next, a method of controlling the base station will be explained.

As shown in FIG. 3(a), after the mobile communication system starts operating, the base station monitors whether there is an access from a mobile station (step 101).

When no preamble is detected, the transmission request signal rid is sent within the time slot assigned to the base station.
The leJ signal is sent (steps 102, 103).

If a preamble is detected, the base station transmits a "busyJ" signal within the time slot assigned to the base station (steps 104, 105), and receives data sent from the mobile station.

The procedure "determining allocated time slot" in step 104 is performed by the process shown in FIG. 3(b). This means that i d within the time slot assigned to the base station.
1 The means for transmitting the e/busy signal determines in step 201 whether the current time slot is the time slot assigned to the own base station, and if it is assigned, terminates the procedure; otherwise, For example, variable n
is incremented by 1 (step 202), waits for one time slot (step 203), and returns to step 201.

Through the above operations, the timing of time slots in which each base station issues an idle/busy signal is shown in FIG. 2(a). Since these are all on the same frequency, the IDIe/busy signal received by the mobile station becomes 1/D in FIG. 2(b).

Next, a method of controlling the mobile station will be explained with reference to FIG. 4(a). When a message to be transmitted is generated, the mobile station looks at the i d 1 e / Busy signal for a time interval of one period or more (step 301), and if the i d 1
If no e/busy signal is included, the mobile station determines that it is unable to communicate with the base station, and displays "Unable to communicate" on the display to notify the user.
Display (steps 302, 306). Step 302
If an idle/busy signal is detected in step 303, the process advances to step 303. If there is no slot that is "busyJ", start transmission (step 303.
304) "If one or more busyJ signals are detected, delay the appropriate time (step 305) or return to step 201.
This is the BTMA algorithm. Also Nonpersj
Instead of stentBTMA, it is possible to use the p-persistentBTMA algorithm shown in FIG. 4(b). Instead of step 3050 in FIG.
1) A random number from 0 to 1 is generated, and if it is equal to or greater than a predetermined value (0 x P≦1), data transmission is started (step 402). If P is larger than the random number, an appropriate time delay is performed (step 403), and then the process returns to step 404.

As a first case, a case will be explained in which all terminals and all base stations are in line-of-sight relationship with each other as shown in FIG. 1(a).

If no mobile station is currently communicating with the base station, each base station sends an IDEL signal between each allocated time slot, as shown in part 401 in Figure 1(b). There is. Assume that data is generated at the terminal 4 in FIG. 1 and it becomes necessary to acquire an uplink channel. Then, Figure 1 (a
) monitors the idle/busy signal for one period or more, and if all the base stations are rldleJ, the mobile station 4 in FIG. b) 402 part). Each base station that receives the preamble from the mobile station 4 changes the riddleJ signal to the busyJ signal according to the algorithm shown in Figure 3 (section 403 in Figure 1(b)). In other words, if the mobile station 5 tries to start access at part 403 in FIG. try.

As a second case, suppose that the communication paths between the mobile station 16 and the base station 14, 15, and between the mobile station 17 and the base station 13 are physically cut off by an obstacle such as a locker, as shown in FIG. When the mobile station 16 accesses
The /i d 1 e signal is monitored for one period or more, but in this case, the mobile station 16 receives only the bus y / L d 1 e signal from the base station 13, as shown in FIG. Then, if the busy signal is not included, the mobile station 16 starts accessing. Similarly, the mobile station 17 uses id 1 e / bus y for one period or more.
As shown in FIG. 8, only the base stations 14 and 15 actually receive the signal. and “b u s
If the yJ signal is not included, access is started.

In this way, the signals of the two mobile stations 16 and 17 do not interfere with each other, so that the mobile station 16 can communicate with the base station 13, and at the same time, the mobile station 17 can communicate with the base station 14.15. become. In other words, even though a single frequency is used, the same effect as using two channels can be obtained.

In a third case, as shown in FIG. 5, the communication path between mobile station 11 and base stations 9 and 10 is physically cut off by an obstacle such as a locker, and mobile station 12 has no line-of-sight relationship with all base stations. Consider the case in which If all base stations are now sending out idle signals, the mobile station 11 receives b
The usy/idle signal is as shown in part 501 in FIG. One cycle or more i d 1 e / bu
Suppose that the mobile station 11 accesses the s y signal because it does not contain the busyJ signal.Then, the mobile station 12 receives the b
u s y / id]e signal changes from “idleJ to rb u s yJ. In this case, the mobile station 12
The busy/idle signal received by the mobile station 12 becomes as shown in FIG. 6, and access by the mobile station 12 is prohibited.

In the fourth case, as shown in FIG. 9, when the mobile station 21 has communication paths with all base stations cut off by an obstacle, the mobile station 21 goes idle/bus as shown in FIG.
I can't read the y signal at all. Therefore, the mobile station indicates to the user on the display that communication is not possible according to the algorithms shown in FIGS. 3(a) and 3(b).

[Effects of the Invention] As is clear from the above description, the mobile communication system of the present invention includes a plurality of base stations and a plurality of mobile stations connected by a common two-way wireless communication line that transmits information signals. , until the mobile station detects a preamble signal, it leaves a permission signal that allows the mobile station to transmit, and when a preamble signal is detected, it broadcasts a prohibition signal that prohibits other mobile stations from transmitting, and the mobile station stops moving. In a mobile communication system that receives station signals, each base station transmits the transmission permission signal and transmission prohibition signal, respectively, only during the time allotted to the base station, and each mobile station A configuration that reads the transmission permission signal and the transmission prohibition signal at least once, and transmits the data signal prefixed with the preamble signal only when the read signal does not include any of the transmission prohibition signals. Therefore, when multiple base stations cover an area using one channel, each base station may be different depending on the situation within the premises.
Collision of idle/busy signals can be prevented even if a case occurs in which the u sy / i d 1 e signals are sent.

Furthermore, if it is determined that all base stations and mobile stations are unable to communicate, the system is configured to notify the user of the inability to communicate, as claimed in claim (3), so that the user can move the mobile station to a location where communication is possible. You can move around and use the mobile station.

[Brief explanation of the drawing]

FIG. 1(a) is an explanatory diagram showing the situation of environment 1 in which the mobile communication system of the present invention is implemented, and FIG.
An explanatory diagram showing the mode of the idle/busy signal received by the mobile station in the environment of a), Fig. 2 shows the i
The timing of the d1e/busy signal and the state diagram of the idle/busy signal, FIGS. Slot determination flowchart, Figure 4 (a
) and FIG. 4(b) are flowcharts of the control of the mobile station shown in the embodiment, FIG. 5 is an explanatory diagram showing other environmental conditions in which the mobile communication system of the present invention is summarized, and FIG. ID L e/busy received by the mobile station in the environment shown in Figure (a)
An explanatory diagram of signals; FIG. 7 is an explanatory diagram showing other environmental conditions of the mobile communication system of the present invention; and FIG. 8 is an explanatory diagram of other environmental conditions of the mobile communication system of the present invention. An explanatory diagram, FIG. 9 is an explanatory diagram of another environmental situation in which the mobile communication system of the present invention is summarized, and FIG. 10 is an ID 1 e/busy signal received by a mobile station in the environment of FIG. 9. FIG. 11 is an explanatory diagram of the data structure transmitted by the mobile station. 1, 2, 3, 8, 9, 10, 13.14.15, 18,
19.20... Base station 4, 5, 11, 12.16.17, 21.22... Mobile station

Claims (2)

[Claims] (1) A communication device and a plurality of base stations are connected by a transmission path, and the plurality of base stations and a plurality of mobile stations are each connected by a bidirectional radio line, and the two-way In a mobile system in which the communication device and a plurality of mobile stations communicate via a wireless link, each of the plurality of mobile stations includes means for transmitting a transmission request signal to the base station, and each of the plurality of base stations transmits a transmission request signal to the base station. The transmission permission signal is not sent until the transmission request signal is received.
When the transmission request signal is received, a transmission prohibition signal is sent to the own station within the multiplexed time-division time period of each of the plurality of base stations. A mobile communication system characterized by transmitting only during a time allotted to. (2) While each of the plurality of mobile stations is receiving the transmission permission signal corresponding to its own station, the mobile station that has received the transmission permission signal and the communication device communicate with each other. The mobile communication system according to claim (1).