JP2017228937A - System and method for fdma communication, base station device, and terminal station device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cause each terminal station to autonomously divide and occupy a frequency band according to each requested band, without centralized control, in an FDMA communication system including one base station and a plurality of terminal stations.SOLUTION: A terminal station includes means for detecting an unused frequency band out of all available frequency bands in an uplink to the base station, and for transmitting to the base station an allocation request signal through the unused frequency band. The base station includes means for notifying, through a control channel, the allocation permission of the unused frequency band through which the allocation request signal is received, and a maximum allocatable frequency band according to the number of the terminal stations which is communicating at the time point of the allocation request signal reception. The terminal station, having transmitted the allocation request signal, includes means for repeating processing to occupy the frequency band, of which allocation is permitted from the base station, and to increase and decrease the frequency band to be occupied in a range not exceeding a maximum allocatable frequency band.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an FDMA communication system, an FDMA communication method, a base station apparatus, and a terminal station apparatus that are configured by one base station and a plurality of terminal stations, and in which each terminal station occupies different frequency bands and performs communication.

  In radio communication, in order to efficiently allocate radio resources to a plurality of radio stations without interference, for example, an access control technique such as a frequency division multiple access (FDMA) system that divides a frequency band and allocates the radio resources to each radio station is used.

  Further, in the FDMA communication system, when the number of accommodated stations and traffic fluctuate according to time, as an access control technique with high frequency utilization efficiency, DAMA (assigning a necessary frequency channel according to a request of a wireless station performing communication) Demand Assign Multiple Access) is enabled. This is because the base station that controls the DAMA can sequentially manage the required bandwidth and line state of the terminal station and perform bandwidth allocation efficiently. However, the DAMA system requires a complicated centralized control mechanism for managing all terminal stations, and also increases the overhead required for control, reducing the connection delay until channel allocation and bandwidth utilization efficiency. There was a problem to do.

  Therefore, instead of DAMA, an access control technique that can effectively use a free bandwidth without performing centralized control has been studied. For example, CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) technology (Non-Patent Document 1) represented by random access and Aloha technology (Non-Patent Document 2). These are methods for efficiently utilizing available resources by autonomously sensing and performing segregation in the time direction.

  Patent Document 1 is a technique for switching the band occupation states of a plurality of terminal stations by frequency hopping. However, this technology requires a centralized control station that manages all terminal stations and calculates the allocated bandwidth according to the requested traffic volume.

Mattisson, Sven. "Frequency-hopping in a bandwidth-on-demand system." U.S. Patent No. 6,246,713. 12 Jun. 2001.

Ziouva, Eustathia, and Theodore Antonakopoulos. "CSMA / CA performance under high traffic conditions: throughput and delay analysis." Computer communications 25.3 (2002): 313-321. Abramson, Norman. "THE ALOHA SYSTEM: another alternative for computer communications." Proceedings of the November 17-19, 1970, fall joint computer conference. ACM, 1970.

  Since the CSMA / CA scheme that performs distributed control is a scheme in which time resources of the same frequency are shared while being divided among a plurality of radio stations, an FDMA communication system that continuously uses and occupies time resources of frequency resources allocated to each user. (For example, it cannot be applied to a satellite communication system).

  In addition, the CSMA / CA method needs to sense the communication status of other radio stations. However, in the case of a satellite communication system that is performed via a geostationary satellite at a distance of 36,000 km, a round trip delay of 0.25 sec. As a result, the back-off time for avoiding the collision becomes great. As a result, there is a problem that the line establishment time becomes long and the line utilization efficiency of the system decreases.

  In this way, for example, in order to support a plurality of applications having different bandwidths in a satellite communication system, the satellite transponder band is effectively used without requiring centralized control, and an important line such as a satellite telephone in a disaster is maintained. Uplink random access technology is required.

  The present invention provides an FDMA communication system composed of one base station and a plurality of terminal stations, wherein each terminal station autonomously divides the frequency band according to the respective required band without requiring centralized control, and the terminal It is an object of the present invention to provide an FDMA communication system, an FDMA communication method, a base station apparatus, and a terminal station apparatus that can maintain a predetermined line for each station.

  A first invention is an FDMA communication system that includes one base station and a plurality of terminal stations, and each terminal station performs communication while occupying different frequency bands. The terminal station is an uplink to the base station. A means for detecting an unused frequency band from all the usable frequency bands and transmitting an allocation request signal to the base station in the unused frequency band, and the base station receives an unused frequency at which the allocation request signal is received. The terminal station that transmitted the allocation request signal is permitted to be allocated by the base station, and includes means for notifying the allocation of the band and the maximum allocatable frequency band according to the number of terminal stations that are currently communicating through the control channel. Means for repeating the process of occupying the frequency band and increasing / decreasing the occupied frequency band in a range not exceeding the maximum allocatable frequency band is provided.

  In the FDMA communication system according to the first aspect, the base station receives an allocation request signal from a subordinate terminal station or detects that a change has occurred in the maximum allocatable frequency band because the terminal station in communication has stopped communicating. In this case, the control channel is used to notify all subordinate terminal stations of the change of the maximum allocatable frequency band, and the terminal station occupies the frequency band that the terminal station occupies within a range not exceeding the maximum allocatable frequency band. It is the structure which performs the process which increases / decreases.

  In the FDMA communication system of the first invention, the maximum allocatable frequency band is at least one unused frequency that is not occupied by each terminal station with respect to all frequency bands that can be used in the uplink from the terminal station to the base station. It is configured to provide a band, and the terminal station can transmit an allocation request signal in this unused frequency band.

  In the FDMA communication system of the first invention, when the terminal station increases or decreases the frequency band occupied by increasing or decreasing the maximum allocatable frequency band, the terminal station secures a predetermined frequency band and maintains communication using the frequency band. It is a configuration.

  A second aspect of the present invention is an FDMA communication method that includes one base station and a plurality of terminal stations, and each terminal station occupies different frequency bands and performs communication. The terminal station is an uplink to the base station. Detecting an unused frequency band from all usable frequency bands, and transmitting an allocation request signal to the base station in the unused frequency band, and the base station receives an unused The terminal station that transmitted the allocation request signal has the step of notifying the allocation of the frequency band and notifying the maximum allocatable frequency band according to the number of terminal stations currently in communication through the control channel. And a step of repeating the process of increasing / decreasing the occupied frequency band in a range not exceeding the maximum allocatable frequency band.

  In the FDMA communication method of the second invention, the maximum allocatable frequency band is at least one unused frequency that is not occupied by each terminal station with respect to all frequency bands that can be used in the uplink from the terminal station to the base station. The terminal station is set to provide a band, and the terminal station transmits an allocation request signal in this unused frequency band.

  According to a third aspect of the present invention, there is provided a base station apparatus of an FDMA communication system that includes one base station and a plurality of terminal stations, and each terminal station occupies different frequency bands and performs communication. When an unused frequency band is detected from all frequency bands available in the uplink and an allocation request signal transmitted in the unused frequency band is received, the allocation permission of the unused frequency band and the time point Means for notifying the maximum allocatable frequency band according to the number of terminal stations in communication using the control channel, and receiving the allocation request signal from the subordinate terminal station or stopping the communication at the communicating terminal station, Means for notifying all subordinate terminal stations of the change of the maximum allocatable frequency band using the control channel when it is detected that the band has changed.

  A fourth aspect of the present invention is a terminal station apparatus of an FDMA communication system that includes one base station and a plurality of terminal stations, and each terminal station occupies different frequency bands and performs communication. A means for detecting an unused frequency band from all usable frequency bands and transmitting an allocation request signal to the base station in the unused frequency band, and a base station receiving the allocation request signal in an unused frequency band. A range that occupies the allocated frequency band and does not exceed the maximum allocatable frequency band when the control channel is notified of the allocation permission and the maximum allocatable frequency band according to the number of terminal stations currently communicating. Means for repeating the process of increasing / decreasing the frequency band occupied by.

  The present invention provides a conventional FDMA communication system in which each terminal station occupies a different frequency band and communicates with each other, so that each terminal station can grasp the frequency band occupancy and autonomously increase or decrease the frequency bandwidth. A common frequency band can be autonomously and flexibly shared by a plurality of terminal stations autonomously in an FDMA system, which has been difficult to realize with technology, and an empty frequency band can be used efficiently.

  In the present invention, since each terminal station transmits an allocation request signal using a different frequency band, the backoff time can be designed on the assumption that the collision probability of the allocation request signal between the terminal stations is reduced. Therefore, line utilization efficiency can be improved.

  In the present invention, each terminal station autonomously selects an unused frequency band and increases or decreases the frequency bandwidth, thereby eliminating the need for an expensive line control system using a centralized control station.

  Further, as an accompanying effect, in the present invention, by adopting a method of gradually increasing the line speed, the collision probability can be reduced and the line utilization efficiency as the FDMA communication system can be further improved.

It is a figure which shows the structural example of the FDMA communication system of this invention. FIG. 2 is a diagram illustrating a configuration example of a base station 10 and a terminal station 20. 3 is a flowchart illustrating an example of a processing procedure in a base station 10 and a terminal station 20. It is a figure which shows the process example at the time of the communication start of the terminal station 20-1. It is a figure which shows the process example of the base station 10 at the time of the communication start of the terminal station 20-1. It is a figure which shows the process example in which the terminal station 20-1 occupies another frequency slot. It is a figure which shows the example of a process when the terminal station 20-1 occupies the maximum number of frequency slots which can be allocated, and the communication of the terminal station 20-2 is started. It is a figure which shows the process example in which the terminal station 20-1 open | releases a part of occupied frequency slot. It is a figure which shows the state in which the terminal stations 20-1 and 20-2 occupy the maximum number of frequency slots which can be allocated. It is a figure which shows the example of a process at the time of the communication start of the terminal station 20-3 before the terminal station 20-2 occupies the maximum number of frequency slots which can be allocated. It is a figure which shows the process example in which the terminal station 20-1 open | releases a part of occupied frequency slot. It is a figure which shows the state in which the terminal stations 20-1 to 20-3 occupy the maximum number of frequency slots that can be allocated. It is a figure which shows the process example (S8) of the base station 10 when the terminal station 20-1 stops communication. It is a figure which shows the state in which the terminal stations 20-2 and 20-3 occupy the maximum number of frequency slots that can be allocated. It is a figure which shows the example of the frequency slot to give priority. It is a figure which shows the TDMA control example of a downlink control channel.

(System configuration)
FIG. 1 shows a configuration example of an FDMA communication system according to the present invention.
In FIG. 1, the FDAM communication system is composed of one base station 10 and a plurality (three in this case) of terminal stations 20-1 to 20-3. The downlink indicates communication from the base station 10 to the terminal station 20, and the uplink indicates communication from the terminal station 20 to the base station 10. The frequency channel in this system configuration includes a downlink control channel and an uplink channel, and the uplink channel allocates frequency slots (f1 to f8) for each fixed frequency bandwidth, and the base station 10 and the terminal station 20 Both assume that the frequency slot position is known.

(Configuration example of base station and terminal station)
FIG. 2 shows a configuration example of the base station 10 and the terminal station 20.
2, the base station 10 includes an uplink signal receiving unit 11, a frequency slot occupation state detecting unit 12, an allocation request signal detecting unit 13, a connecting terminal storage unit 14, a maximum allocatable frequency slot number calculating unit 15, and a downlink signal transmitting unit. 16. The terminal station 20 includes a downlink signal reception unit 21, a frequency slot occupation state detection unit 22, an ACK signal detection unit 23, a maximum allocatable frequency slot number detection unit 24, a bandwidth increase / decrease control unit 25, and an uplink signal transmission unit 26. The

FIG. 3 shows a processing procedure example in the base station 10 and the terminal station 20.
2 and 3, the uplink signal transmission unit 26 of the terminal station 20 detects an unused frequency slot fi of the uplink channel by carrier sense (S1), and uses the uplink control signal (allocation request signal) in the frequency slot fi. ) Is transmitted to the base station 10 (S2). The allocation request signal has a synchronization preamble and a terminal number. When the occupation information of the frequency slot of the uplink channel is notified from the base station 10 through the downlink control channel, the terminal station 20 detects the unused frequency slot fi from the occupation information of the frequency slot of the uplink channel. May be.

  The uplink signal receiving unit 11 of the base station 10 determines whether or not the allocation request signal has been normally received (S3). When the allocation request signal is normally received and the allocation of the frequency slot fi is permitted, the uplink signal reception unit 11 A control signal (ACK signal) is generated and transmitted through the downlink control channel from the downlink signal transmission unit 16 (S4). The ACK signal includes ACK notification information, a terminal number that grants allocation permission to the allocation request signal, an allocation-permitted frequency slot number fi, and a maximum allocatable frequency slot number M.

Here, the frequency slot occupancy state detection unit 12 detects the frequency slot occupancy state of the uplink channel, and the allocation request signal detection unit 13 detects the frequency slot number fi and the terminal number that have received the allocation request signal, and connects them respectively. Notify the terminal storage unit 14. The maximum allocatable frequency slot number calculation unit 15 is based on the number m of terminal stations in communication ascertained in the connected terminal storage unit 14 and the frequency slot number s of uplink channels (s = 8 in the case of FIG. 1). Thus, the maximum assignable frequency slot number M in each terminal station is calculated by the following equation.
M = [(s−a) / m]
[X] is a maximum integer less than or equal to x, and a is an arbitrary number. For example, when a = 1, at least one frequency slot is vacant, and at least one terminal station transmits an allocation request signal. Transmission is possible.

  When the downlink signal receiving unit 21 and the ACK signal detecting unit 23 of the terminal station 20 detect the ACK signal in the downlink control channel, the downlink signal receiving unit 21 and the ACK signal detecting unit 23 start transmission of the data signal in the frequency slot fi permitted to be allocated by the uplink signal transmitting unit 26 ( S5). Further, the maximum allocatable frequency slot number detection unit 24 detects the maximum allocatable frequency slot number M not only for the ACK signal addressed to the own station but also for the ACK signal addressed to other stations, and the frequency slot occupation state detection unit 22 detects the number of occupied frequency slots U and notifies the bandwidth increase / decrease control unit 25 respectively. The bandwidth increase / decrease control unit 25 returns to step S1 and repeats the allocation request for the frequency slot to be added until the occupied frequency slot number U reaches the maximum allocatable frequency slot number M (S6, S7).

  On the other hand, when the base station 10 detects that the terminal station in communication has been stopped, the number m of terminal stations in communication decreases, so the maximum number of frequency slots M that can be allocated is recalculated, and the maximum allocation is possible. A change notification signal having the frequency slot number M is transmitted (S8). This M change notification signal has a configuration in which only the maximum assignable frequency slot number M is effective with respect to the frame configuration of the ACK signal shown in FIG.

  Here, the maximum allocatable frequency slot number M decreases when an allocation request signal is received from a terminal station, and increases when a terminal station in communication is stopped. The terminal station 20 compares the maximum allocatable frequency slot number M obtained by the ACK signal or the M change notification signal with the current occupied frequency slot number U (S9), and if M <U, the occupied frequency slot The number U is reduced to the maximum allocatable frequency slot number M (S10), and if M ≧ U, the process returns to step S6, and further to step S1 until the occupied frequency slot number reaches the maximum allocatable frequency slot number M. Returning, the frequency slot allocation request to be added is repeated (S6, S7).

Hereinafter, a specific description will be given with reference to FIGS.
FIG. 4 shows a processing example (S1, S2) at the start of communication of the terminal station 20-1. Here, it is assumed that all the terminal stations 20-1 to 20-3 are not communicating.

  In FIG. 4, the terminal station 20-1 detects an unused frequency slot f1 by carrier sense, and transmits an allocation request signal in the frequency slot f1. The allocation request signal is a burst signal to which a synchronization preamble is added, and facilitates establishment of reception synchronization at the base station by continuously transmitting, and an unused frequency slot when another station senses a carrier. Prevent misjudgment.

  For example, it is assumed that the terminal stations 20-1 and 20-2 perform carrier sense and simultaneously transmit the allocation request signal in the unused frequency slot f1. In this case, the allocation request signals collide with each other and are not normally received by the base station 10, and an ACK signal is not returned from the base station 10 to each terminal station. When the terminal stations 20-1 and 20-2 that have transmitted the allocation request signal do not receive ACK within a predetermined time, after performing carrier sense again and detecting an unused frequency slot at random, after each random time By transmitting the allocation request signal, a collision can be avoided. The same applies to the processing examples shown below.

FIG. 5 shows a processing example (S3, S4) of the base station 10 at the start of communication of the terminal station 20-1.
In FIG. 5, when the base station 10 receives the allocation request signal in the frequency slot f1, the base station 10 transmits an ACK signal to the terminal station 20-1 using the downlink control channel. ACK signal, terminal number (1), frequency slot number (f1), maximum number of frequency slots that can be allocated (M = [(8-1) / 1] = 7) are given to the ACK signal. Is done. This ACK signal is destined for the terminal 20-1, but the other terminal stations 20-2 and 20-3 can identify the maximum assignable frequency slot number (7).

FIG. 6 shows a processing example (S5, S6, S1, S2) in which the terminal station 20-1 occupies other frequency slots.
In FIG. 6, when the terminal station 20-1 receives the ACK signal, the terminal station 20-1 starts transmission of the data signal in the frequency slot f1 and M (= 7)> U (= 1). An unused frequency slot f3 is detected, and an allocation request signal is transmitted in the frequency slot f3. Similarly, the transmission of the data signal is started in the frequency slot f3, and the processes of S1 to S5 are repeated until the occupied frequency slot number U reaches the maximum allocatable frequency slot number M (= 7).

FIG. 7 shows a processing example (S7, S1, S2) when the terminal station 20-1 occupies the maximum allocatable frequency slot number and the terminal station 20-2 starts communication.
In FIG. 7, even if the occupied frequency slot number U of the terminal station 20-1 reaches the maximum assignable frequency slot number M (= 7), one unused frequency slot remains. The terminal station 20-2 detects an unused frequency slot f7 by carrier sense, and transmits an allocation request signal in the frequency slot f7.

FIG. 8 shows a processing example (S8, S9, S10) in which the terminal station 20-1 releases part of the occupied frequency slot.
In FIG. 8, when the base station 10 receives the allocation request signal in the frequency slot f7, the base station 10 transmits an ACK signal to the terminal station 20-2 using the downlink control channel. ACK signal, terminal number (2), frequency slot number (f7), maximum number of frequency slots that can be allocated (M = [(8-1) / 2] = 3) are given to the ACK signal. Is done. This ACK signal is destined for the terminal 20-2, but the other terminal stations 20-1 and 20-3 can identify the maximum assignable frequency slot number M (= 3).

  Thereby, in the terminal station 20-1, the occupied frequency slot number U (= 7) exceeds the maximum allocatable frequency slot number M (= 3), so that the occupied frequency slot U becomes the maximum allocatable frequency slot number M. Here, four frequency slots f4, f5, f6, and f8 are opened.

  On the other hand, when the terminal station 20-2 receives the ACK signal, the terminal station 20-2 starts transmission of the data signal in the frequency slot f7 and M (= 3)> U (= 1). Repeat until U reaches the maximum allocatable frequency slot number M (= 3).

FIG. 9 shows a state in which the terminal stations 20-1 and 20-2 occupy the maximum number of frequency slots that can be allocated.
In FIG. 9, when the terminal station 20-1 occupies the frequency slots f1, f2, and f3 and the terminal station 20-2 occupies the frequency slots f4, f6, and f7, two unused frequency slots f5 and f8 remain. It will be.

FIG. 10 shows a processing example (S1, S2) when the terminal station 20-3 starts communication before the terminal station 20-2 occupies the maximum allocatable frequency slot number.
10, when the terminal station 20-1 occupies three frequency slots f1, f2, and f3, and the terminal station 20-2 occupies one frequency slot f7 (the frequency slots f4 and f6 in FIG. Before the terminal station 20-3 occupies, the terminal station 20-3 detects an unused frequency slot f5 by carrier sense, and transmits an allocation request signal in the frequency slot f5.

FIG. 11 shows a processing example (S8, S9, S10) in which the terminal station 20-1 releases part of the occupied frequency slot.
In FIG. 11, when the base station 10 receives the allocation request signal in the frequency slot f5, the base station 10 transmits an ACK signal to the terminal station 20-3 using the downlink control channel. ACK signal, terminal number (3), frequency slot number (f5), maximum number of frequency slots that can be allocated (M = [(8-1) / 3] = 2) are given to the ACK signal. Is done. This ACK signal is destined for the terminal 20-3, but the other terminal stations 20-1 and 20-2 can identify the maximum assignable frequency slot number M (= 2).

  Thereby, in the terminal station 20-1, since the occupied frequency slot number U (= 3) exceeds the maximum allocatable frequency slot number M (= 2), the occupied frequency slot U becomes the maximum allocatable frequency slot number M. Here, one frequency slot f3 is opened.

  On the other hand, when the terminal station 20-3 receives the ACK signal, the terminal station 20-3 starts transmitting the data signal in the frequency slot f5, and M (= 2)> U (= 1). Repeat until U reaches the maximum allocatable frequency slot number M (= 2).

FIG. 12 shows a state in which the terminal stations 20-1 to 20-3 occupy the maximum number of frequency slots that can be allocated.
In FIG. 12, when the terminal station 20-1 occupies the frequency slots f1 and f2, the terminal station 20-2 occupies the frequency slots f6 and f7, and the terminal station 20-3 occupies the frequency slots f3 and f5, unused frequencies. Two slots f4 and f8 remain.

FIG. 13 shows a processing example (S8) of the base station 10 when the terminal station 20-1 stops communication.
In FIG. 13, when the base station 10 confirms that the terminal station 20-1 has not transmitted a signal for a predetermined time in the frequency slots f1 and f2 monitored by the frequency slot occupation state detection unit 12, the connected terminal storage unit 14 deletes the occupation information of the frequency slots f1 and f2. Here, since the number m of terminal stations in communication decreases from 3 to 2, the maximum allocatable frequency slot number calculating unit 15 calculates the maximum allocatable frequency slot number (M = [(8-1) / 2] = 3 ) And retransmit M change notification signals using the downlink control channel. The maximum number of allocatable frequency slots M of the M change notification signals can be identified by the terminal stations 20-1 to 20-3.

  Thus, the terminal stations 20-2 and 20-3 transmit the allocation request signal and occupy the frequency slots until the occupied frequency slot number U (= 1) reaches the maximum allocatable frequency slot number M (= 3). To repeat the process.

FIG. 14 shows a state where the terminal stations 20-2 and 20-3 occupy the maximum number of frequency slots that can be allocated.
In FIG. 14, when the terminal station 20-2 occupies the frequency slots f4, f6, f7 and the terminal station 20-3 occupies the frequency slots f2, f3, f5, two unused frequency slots f1, f8 remain. It will be.

  By the way, in each terminal station, it is conceivable that an instantaneous interruption occurs when adding or releasing occupied frequency slots as the maximum number of frequency slots M that can be allocated increases or decreases. For example, when OFDM is applied to this system, assuming that a frequency slot is a segment composed of frequency subcarriers or a plurality of subcarriers, the rate of occurrence of packet errors in the transient state when the number of occupied frequency slots is increased or decreased. It can be considered high. Since the packet error rate is improved in a steady state, no problem occurs in the case of communication that does not require real-time performance. However, when a real-time property is required such as a satellite phone and the line is an important line, this packet error becomes a big problem. Therefore, as in the subcarriers marked with * in FIG. 15, each terminal station distinguishes a path to be transmitted in a frequency slot established at the start of communication from a path to be communicated including a frequency slot to be added thereafter, and the frequency slot When the frequency slot is reduced, priority is given to the frequency slot added later, so that it is possible to guarantee the communication quality of the important line without affecting the path established at the start of communication.

  In the present invention, by performing access control for each frequency slot, the number of accesses per frequency slot can be distributed as compared with CSMA / CA and Reservation-ALOHA. In particular, the present invention can change the bandwidth while maintaining communication while reducing an increase in waiting time and an increase in collision probability caused by access control of a system with a large delay such as a satellite line.

  In addition, it is desirable that the downlink bandwidth from the base station to the terminal station is similarly changed according to the uplink occupied frequency band increased by the present technology. For example, as shown in FIG. 16, this scheme is used for the uplink, and since all terminal stations can receive signals at the same timing, a single carrier is used for the downlink and time division multiple access (TDMA) is adopted. In this case, it is possible to achieve the same bandwidth allocation on the uplink / downlink by allocating 1/3 of the time slot allocation at the same rate (1/3 here) as the uplink bandwidth allocation. is there. Also, in the case of the downlink, it is not necessary to consider the occurrence of a new terminal, so it is not necessary to provide a free band as in the uplink.

DESCRIPTION OF SYMBOLS 10 Base station 11 Uplink signal receiving part 12 4 wave number slot occupation state detection part 13 Assignment request signal detection part 14 Connection terminal memory | storage part 15 Maximum allocation frequency slot number calculation part 16 Downstream signal transmission part 20 Terminal station 21 Downstream signal reception part 22 Frequency slot occupation state detection unit 23 ACK signal detection unit 24 Maximum assignable frequency slot number detection unit 25 Bandwidth increase / decrease control unit 26 Uplink signal transmission unit

Claims (8)

In an FDMA communication system composed of one base station and a plurality of terminal stations, each terminal station occupying different frequency bands and performing communication,
The terminal station comprises means for detecting an unused frequency band from all frequency bands available in the uplink to the base station, and transmitting an allocation request signal to the base station in the unused frequency band,
The base station comprises means for notifying the allocation permission of the unused frequency band that has received the allocation request signal, and a maximum allocatable frequency band according to the number of terminal stations that are currently communicating on the control channel,
The terminal station that has transmitted the allocation request signal includes means for repeating the process of increasing / decreasing the frequency band occupied within a range not exceeding the maximum allocatable frequency band and occupying the frequency band permitted to be allocated by the base station. An FDMA communication system characterized by that. The FDMA communication system according to claim 1, wherein
The base station uses the control channel when it receives an allocation request signal from a terminal station under its control or detects that a change has occurred in the maximum allocatable frequency band because the terminal station in communication has stopped communicating. The terminal station is notified of the change of the maximum allocatable frequency band, and the terminal station increases or decreases the frequency band occupied by the terminal station within a range not exceeding the maximum allocatable frequency band. The FDMA communication system characterized by the above-mentioned. In the FDMA communication system according to claim 1 or 2,
The maximum allocatable frequency band is set to provide at least one unused frequency band that is not occupied by each terminal station with respect to all frequency bands that can be used in uplink from the terminal station to the base station. The FDMA communication system, wherein the terminal station transmits the allocation request signal in the unused frequency band. The FDMA communication system according to claim 1, wherein
The terminal station is configured to secure a predetermined frequency band and maintain communication using the frequency band when the occupied frequency band is increased or decreased by increasing or decreasing the maximum allocatable frequency band. FDMA communication system. In an FDMA communication method, which is composed of one base station and a plurality of terminal stations, each terminal station occupying a different frequency band and performing communication,
The terminal station has a step of detecting an unused frequency band from all frequency bands usable in the uplink to the base station, and transmitting an allocation request signal to the base station in the unused frequency band. ,
The base station has a step of notifying the allocation permission of the unused frequency band that has received the allocation request signal and a maximum allocatable frequency band according to the number of terminal stations that are currently communicating through a control channel. ,
The terminal station that has transmitted the allocation request signal has the steps of repeating the process of increasing and decreasing the frequency band occupied within a range not exceeding the maximum allocatable frequency band while occupying the frequency band permitted to be allocated by the base station. An FDMA communication method characterized by the above. The FDMA communication method according to claim 5, wherein
The maximum allocatable frequency band is set to provide at least one unused frequency band that is not occupied by each terminal station with respect to all frequency bands that can be used in uplink from the terminal station to the base station. The FDMA communication method, wherein the terminal station transmits the allocation request signal in the unused frequency band. In a base station apparatus of an FDMA communication system that is composed of one base station and a plurality of terminal stations, and each terminal station occupies a different frequency band and performs communication,
When the terminal station detects an unused frequency band from all the frequency bands that can be used in the uplink to the base station, and receives an allocation request signal transmitted in the unused frequency band, the terminal station A means for notifying frequency band allocation permission and a maximum allocatable frequency band according to the number of terminal stations in communication at that time, using a control channel;
When receiving an allocation request signal from a subordinate terminal station or detecting that a change has occurred in the maximum allocatable frequency band due to a communication stop of a terminal station in communication, all subordinates using the control channel are detected. Means for notifying the terminal station of a change in the maximum allocatable frequency band. In a terminal station apparatus of an FDMA communication system, which is composed of one base station and a plurality of terminal stations, and each terminal station occupies different frequency bands and performs communication,
Means for detecting an unused frequency band from all frequency bands available in the uplink to the base station, and transmitting an allocation request signal to the base station in the unused frequency band;
When the base station that has received the allocation request signal notifies the allocation permission of the unused frequency band and the maximum allocatable frequency band according to the number of terminal stations that are currently communicating through the control channel, the allocation permission And a means for repeating the process of increasing / decreasing the occupied frequency band within a range not exceeding the maximum allocatable frequency band.

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