JP4687915B2 - Wireless communication system, terminal station, wireless base station, and communication permission method - Google Patents

Description

  The present invention relates to a radio communication system, a terminal station, a radio base station, and a communication permission method.

  In general, in order to determine whether or not communication is possible between a radio base station and a terminal station, a technique called ranging is used. This ranging is a technique for adjusting the transmission power, transmission frequency, and transmission timing of a signal transmitted from a terminal station to a radio base station. If the uplink signal transmitted from the terminal station is received by the radio base station, the communication quality of the uplink signal is not ensured to a predetermined quality, and the radio base station rejects communication with the terminal station. The That is, communication between the radio base station and the terminal station is allowed only when the communication quality of the uplink signal is adjusted within a predetermined quality by ranging.

  In addition, systems called ARQ (Automatic Repeat Request) and HARQ (Hybrid Automatic Repeat Request) having a function of recovering an error by performing retransmission when a communication error occurs are also used. This is a notification from the reception side to the transmission source using an arrival confirmation signal called an ACK (Acknowledge) signal, whether or not the reception side of the signal has been correctly received.

When it is determined that the communication quality cannot be ensured or when an ACK signal is not notified, the communication quality is tried to be secured by transmitting (retransmitting) the signal again. Then, a technique for determining that communication between a radio base station and a terminal station is impossible when the number of retransmissions exceeds a predetermined number without ensuring communication quality is considered (for example, Patent Document 1). reference.).
JP-T-2007-504747

  However, in an asymmetric wireless communication system in which the transmission power of signals in the uplink and the transmission power of signals in the downlink are different, there are the following problems even when the above-described technique is used. . Here, the uplink is a line in the direction from the terminal station to the radio base station. The downlink is a line that is a direction from the radio base station to the terminal station.

  In an asymmetric wireless communication system in which transmission power differs between uplink (transmission power: small) and downlink (transmission power: high), downlink communication is possible when the uplink communication quality deteriorates. Nevertheless, there is a problem that communication is disabled and the line is disconnected. This is because, for example, the selection is performed by a ranging operation that accepts only a terminal station that has transmitted a signal having a predetermined communication quality received by a wireless base station as a communicable one. As described above, when there is a problem with the communication quality of transmission from the terminal station for some reason, the communication efficiency is lowered or communication is not possible. For example, it is not necessary to perform communication on the uplink, and if it is a use that only allows downlink communication, it is not necessary to determine whether communication is possible based on the communication quality of the uplink. In order to prevent this, it is only necessary to improve the transmission characteristics of the terminal stations. However, in a system on the assumption that various terminal stations exist, the characteristics of all the terminal stations cannot always be improved.

  In addition, although the signal can be received correctly at the receiving side and the ACK signal is transmitted from the receiving side to the transmission source, the ACK signal cannot be received at the transmission source due to low transmission power for transmitting the ACK signal. There is a problem. In addition, this causes a problem that retransmission is unnecessarily generated.

  The present invention has been made in view of the problems of the conventional techniques as described above, and is a wireless communication system capable of allowing communication between a terminal station and a wireless base station according to a communication form. An object of the present invention is to provide a terminal station, a radio base station, and a communication permission method.

In order to achieve the above object, the present invention provides:
In a radio communication system composed of a terminal station and a radio base station configured to be connectable to the terminal station,
Ranging to adjust the transmission timing of the uplink signal from the terminal station to the radio base station,
The terminal station transmits counts the number of failed the ranging, a ranging number of failures so far upon successful the ranging, and service information indicating the communication mode of the terminal station to the radio base station And
Whether the radio base station allows communication with the terminal station based on the service information, and allows communication with the terminal station based on the service information and the number of ranging failures It is characterized by updating the success range indicating the above.

  The radio base station may expand the success range when the number of ranging failures exceeds a threshold set based on the service information.

  Further, the threshold value is a number of times of ranging failure.

The radio base station may expand the success range when a ranging failure probability corresponding to the number of ranging failures exceeds a probability of ranging failure set as the threshold value .

In addition, the terminal station is configured to be connectable to a radio base station and performs ranging for adjusting the transmission timing of an uplink signal to the radio base station,
The number of times of ranging failure is counted, and when the ranging is successful, the number of ranging failures that have failed so far and service information indicating the communication form of the terminal station are transmitted to the radio base station.

A wireless base station configured to be connectable to a terminal station, wherein communication with the terminal station is permitted based on service information indicating a communication mode with the terminal station, and the terminal station Indicates whether or not to allow communication with the terminal station based on the service information and the number of ranging failures transmitted from the terminal station. Update success range .

  In addition, when the number of ranging failures exceeds a threshold set based on the service information, the success range is expanded.

Further, a communication permission method in a wireless communication system configured from a terminal station and a wireless base station configured to be connectable to the terminal station,
A process in which the terminal station transmits service information indicating a communication form of the terminal station to the radio base station;
A process for allowing the radio base station to communicate with the terminal station based on the service information ;
A process of counting the number of times the terminal station has failed ranging for adjusting the transmission timing of an uplink signal from the terminal station to the radio base station;
When the terminal station succeeds in the ranging, a process of transmitting the number of ranging failures that have failed so far to the radio base station;
The wireless base station has a process of updating a success range indicating whether or not to allow communication with the terminal station based on the service information and the number of ranging failures .

  The radio base station may further include a process of expanding the success range when the number of ranging failures exceeds a threshold set based on the service information.

  In the present invention configured as described above, service information indicating a communication form of the terminal station is transmitted from the terminal station to the radio base station configured to be connectable to the terminal station, and the service is performed at the radio base station. Communication with the terminal station is allowed based on the information.

  As a result, whether or not communication is possible is determined based on an acceptable standard according to various communication modes, and therefore communication is not rejected based on an unnecessary acceptable standard.

  As described above, in the present invention, service information indicating the communication mode of the terminal station is transmitted from the terminal station to the radio base station configured to be connectable to the terminal station, and the radio base station converts the service information to the service information. Based on this, since the communication with the terminal station is allowed, the communication between the terminal station and the radio base station can be allowed according to the communication form.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing an embodiment of a wireless communication system of the present invention.

  As shown in FIG. 1, this embodiment includes a radio base station 101 and a terminal station 102 connected to the radio base station 101. The uplink signal transmitted from the terminal station 102 is received by the radio base station 101. Further, the downlink signal transmitted from the radio base station 101 is received by the terminal station 102. In the form shown in FIG. 1, an example is shown in which the number of terminal stations connected to the radio base station 101 is one, but a plurality of terminal stations are connected to the radio base station 101. The number of units is not limited. Here, ranging is performed between the radio base station 101 and the terminal station 102 before starting communication.

  FIG. 2 is a diagram illustrating a configuration example of the radio base station 101 illustrated in FIG.

  As shown in FIG. 2, the radio base station 101 shown in FIG. 1 includes an antenna 110, a reception RF unit 111, a demodulation unit 112, a power calculation unit 113, a threshold setting unit 114, a modulation unit 115, A transmission RF unit 116 and a communication control unit 117 for controlling them are provided.

  The antenna 110 receives an uplink signal transmitted wirelessly from the terminal station 102. In addition, a downlink signal is transmitted to the terminal station 102 wirelessly.

  The reception RF unit 111 is an interface unit that converts an RF band uplink signal received by the antenna 110 into a signal inside the radio base station 101.

  The demodulation unit 112 demodulates the uplink signal converted by the reception RF unit 111. This demodulation method is the same as the conventional one. The demodulated uplink signal is output to the MAC (Media Access Control) layer and power calculator 113 as received data.

  The power calculator 113 calculates received power based on the received data output from the demodulator 112. This calculation method is the same as the conventional one.

  The threshold setting unit 114 sets a ranging failure probability threshold and the ranging success range for determining whether or not to update the ranging success range based on the number of ranging failures transmitted from the terminal station 102. If the ranging failure probability is within the ranging success range, communication between the terminal station and the radio base station is permitted.

  Modulator 115 modulates a downlink signal to be transmitted to terminal station 102. The downlink signal to be modulated here is transmission data output from the MAC layer. This modulation method is the same as the conventional method.

  The transmission RF unit 116 is an interface unit that converts a signal in the radio base station 101 into an RF band downlink signal transmitted from the antenna 110.

  FIG. 3 is a diagram illustrating a configuration example of the terminal station 102 illustrated in FIG.

  As shown in FIG. 3, the terminal station 102 shown in FIG. 1 includes an antenna 120, a reception RF unit 121, a demodulation unit 122, a power calculation unit 123, and a ranging (group) control unit 124 (hereinafter, ranging control). Unit 124), a modulation unit 125, a transmission RF unit 126, and a communication control unit 127 for controlling them.

  The antenna 120 receives a downlink signal transmitted wirelessly from the radio base station 101. In addition, an uplink signal is transmitted wirelessly to the wireless base station 101.

  The reception RF unit 121 is an interface unit that converts an RF band uplink signal received by the antenna 120 into a signal inside the terminal station 102.

  The demodulation unit 122 demodulates the uplink signal converted by the reception RF unit 121. This demodulation method is the same as the conventional one. The demodulated uplink signal is output to the MAC (Media Access Control) layer and power calculation unit 123 as received data.

  The power calculator 123 calculates received power based on the received data output from the demodulator 122. This calculation method is the same as the conventional one.

  The ranging control unit 124 generates a ranging code based on information on ranging transmitted from the radio base station 101.

  The modulation unit 125 modulates an uplink signal to be transmitted to the radio base station 101. The uplink signal to be modulated here is obtained by multiplexing transmission data output from the MAC layer and a ranging code. This modulation method is the same as the conventional method.

  The transmission RF unit 126 is an interface unit that converts a signal inside the terminal station 102 into an RF band downlink signal transmitted from the antenna 120.

  Below, the initial ranging procedure in the radio | wireless communications system shown in FIGS. 1-3 is demonstrated.

  FIG. 4 is a sequence diagram for explaining an initial ranging procedure in the wireless communication system shown in FIGS. This sequence diagram is an OFDMA (Orthogonal Frequency Division Multiplexing Amplification Procedure) for IEEEA (Orthogonal Frequency Division Multiplexing Amplification Procedure) defined in 802.16 defined by IEEE (The Institute of Electrical and Electronics Engineers, Inc.) 802.16. is there. In the IEEE 802.16 system, the terminal station 102 performs initial ranging before starting communication, and cannot perform communication unless ranging is successful.

  First, a UL-MAP signal necessary for a reception characteristic test is transmitted from the radio base station 101 to the terminal station 102 (step S1). This UL-MAP signal is a signal that defines uplink allocation. When the UL-MAP signal is periodically transmitted from the radio base station 101, it is notified at which timing the terminal station 102 should transmit the ranging code. Then, the terminal station 102 determines the timing for transmitting the ranging code based on the received UL-MAP signal, and the ranging code is transmitted to the radio base station 101 at the determined timing (step S2).

  When the ranging code transmitted from the terminal station 102 is received by the radio base station 101, whether the ranging is successful or unsuccessful is determined based on the ranging code received by the radio base station 101. Specifically, it is determined whether or not the received ranging code matches a ranging success condition preset in the radio base station 101.

  Then, the determination result is transmitted as a ranging response from the radio base station 101 to the terminal station 102 (step S3). At this time, if the determination result is “failure”, an adjustment value (information indicating how much the transmission power, frequency, and timing of the terminal station 102 should be shifted) necessary for the ranging to be successful is also included in the ranging. It is transmitted as a response.

  If the determination result is “success”, the ranging operation ends.

  On the other hand, if the determination result is “failure”, the ranging control unit 124 of the terminal station 102 performs processing based on the adjustment value transmitted from the radio base station 101, and the ranging code is determined based on the processing result. The data is transmitted from the terminal station 102 to the radio base station 101 (step S4).

  Then, a ranging response based on the ranging code transmitted from the terminal station 102 to the radio base station 101 in step S4 is transmitted from the radio base station 101 to the terminal station 102 (step S5).

  Until the determination result is “success”, the processes of step S4 and step S5 are repeated.

  At this time, if the communication quality of the uplink from the terminal station 102 to the radio base station 101 is degraded, the ranging may not be successful no matter how many times ranging is performed. However, since the terminal station 102 transmits the ranging code at the correct timing, it is considered that the UL-MAP transmitted from the radio base station 101 is correctly received by the terminal station 102.

  Therefore, when the terminal station 102 performs ranging and the probability that the radio base station 101 determines that the ranging has failed increases, the ranging success condition of the radio base station 101 is dynamically changed and relaxed. As a result, the terminal station 102 determined to have failed ranging even though the downlink can communicate correctly is rescued.

  Below, the communication permission method in the radio | wireless communications system shown in FIGS. 1-3 is demonstrated. First, processing in the terminal station 102 shown in FIGS. 1 and 3 will be described.

  FIG. 5 is a flowchart for explaining processing in the terminal station 102 in the communication permission method in the wireless communication system shown in FIGS.

  First, a ranging code is transmitted from the terminal station 102 to the radio base station 101 (step S11).

  Thereafter, the ranging control unit 124 determines whether or not the ranging is successful (step S12). This is determined based on the result indicated in the ranging response for the ranging code transmitted from the terminal station 102. As described above, the ranging response indicates whether ranging has succeeded or failed.

  If it is determined that ranging has failed, the ranging failure counter provided in the ranging control unit 124 is incremented (step S13). Then, processing is performed by the ranging control unit 124 of the terminal station 102 based on the adjustment value transmitted from the radio base station 101, and a ranging code is transmitted from the terminal station 102 to the radio base station 101 based on the processing result. The

  On the other hand, if it is determined that ranging has succeeded, the number of times that the terminal station 102 has failed before ranging is successful (hereinafter referred to as the number of ranging failures) is modulated by the modulation unit 125, and is transmitted via the transmission RF unit 126. Is transmitted from the antenna 120 to the radio base station 101 (step S14). Here, the number of times that the terminal station 102 has failed before the ranging is successful is the counter value of the ranging failure counter.

  Then, it is determined whether there is service information (step S15). The service information refers to the communication mode (use application) of the terminal station 102 set in the terminal station 102, for example, “terminal station A only needs to receive data broadcast to all terminals” or “terminal station B. Is mainly receiving data addressed to the own station, and there is almost no data transmission addressed to the wireless base station 101 (streaming).

  If it is determined that there is service information, the service information is modulated by the modulation unit 125 and transmitted from the antenna 120 to the radio base station 101 via the transmission RF unit 126 (step S16). The signal format of the service information to be transmitted is not particularly specified here.

  In addition to the above initial ranging, the terminal station 102 also has a periodic ranging function that is periodically performed during communication. In the present invention, a periodic ranging interval corresponding to service information and the number of ranging failures is stored in advance in the terminal station 102, and an appropriate periodic ranging interval is set according to the application of the terminal station 102 (step S17). .

  Next, processing in radio base station 101 shown in FIGS. 1 and 2 will be described. First, a method for processing service information transmitted from the terminal station 102 will be described.

  FIG. 6 is a flowchart for explaining a service information processing method in the radio base station 101 among the communication permission methods in the radio communication system shown in FIGS.

  First, it is determined whether or not service information is received from the terminal station 102 at the radio base station 101 (step S21). If it is determined that the service information has been received, it is determined whether the service information exists in a group table set in advance in the radio base station 101 (step S22).

  FIG. 7 is a diagram illustrating a configuration example of a group table set in advance in the radio base station 101 illustrated in FIGS. 1 and 2.

  In the radio base station 101 shown in FIG. 1 and FIG. 2, as shown in FIG. 7, service information indicating the communication mode of the terminal station, an interval, and a success range are associated with each other and set as a group table. For example, the period ranging period of a terminal station that has transmitted service information indicating that it is sufficient to receive data broadcast to all terminals is set to “a”, and the ranging success range is set to “α”. . Also, the period ranging period of the terminal station that has mainly received data addressed to itself and transmitted service information indicating that there is almost no data transmission addressed to the radio base station (streaming) is “b”, and the ranging was successful. The range is set to “β”. In addition, the period ranging period of the terminal station that has transmitted service information indicating that both uplink and downlink normally operate is “c”, and the ranging success range is “γ”.

  If it is determined that the corresponding service information is in the group table, the period and the success range associated with the service information are set (step S23). That is, the period and the success range used for ranging between the radio base station 101 and the terminal station 102 are set.

  On the other hand, when it is determined that the corresponding service information is not in the group table, the period and the success range used for ranging between the radio base station 101 and the terminal station 102 are set to default values (step S24). . This default value is an initial value of a preset period and a success range.

  Next, the ranging success range update processing in the radio base station 101 shown in FIGS. 1 and 2 will be described.

  FIG. 8 is a flowchart for explaining the ranging success range update processing in the radio base station 101 shown in FIGS. 1 and 2.

  Based on the number of ranging failures transmitted from the terminal station 102, the communication control unit 117 determines whether or not the number of ranging failures exceeds the threshold (step S31).

  When it is determined that the number of ranging failures exceeds the threshold value, it is determined whether the ranging success range is maximum (step S32). That is, it is determined whether the currently set ranging success range (for example, a threshold for determining success) is a preset maximum value.

  If it is determined that the ranging success range is not the maximum, the ranging success range is expanded (step S33). Specifically, the success range is set to a value wider than the currently set success range. At this time, the above-mentioned maximum value should not be exceeded. Thereby, a success condition can be eased. For example, a plurality of threshold values and success ranges can be set in advance, and the success range can be expanded step by step each time the threshold values are exceeded, that is, the success conditions can be relaxed. The relaxation of the ranging success condition increases the probability that the terminal station 102 whose uplink communication quality has deteriorated succeeds in ranging.

  On the other hand, if it is determined in step S31 that the number of ranging failures does not exceed the threshold, the ranging success range is returned to the default value in order to tighten the success conditions (step S34).

  Note that the threshold for determining whether or not to expand the success range may be the range failure probability, which is the probability of ranging failure, in addition to the number of ranging failures as described above.

  As described above, the present invention has three devised points.

  The first contrivance is to dynamically change and relax the ranging success condition.

  In general, a radio base station cannot recognize from which terminal station the ranging code is received. Whether or not the ranging success condition is relaxed is determined based on the ranging failure rate for all ranging codes received by the radio base station. By this relaxation, it becomes possible to relieve a terminal station with poor communication quality and perform communication. In addition, a plurality of threshold values for determining relaxation are prepared, and a plurality of degrees of relaxation are controlled. As a result, when many terminal stations cannot be accepted because many terminal stations belong to the wireless base station, it is possible to prevent a terminal station with poor communication quality from belonging unintentionally.

  The second contrivance is that the terminal station holds the number of ranging failures and notifies the number of failures after starting communication with the radio base station.

  According to this contrivance, it is possible to distinguish between a terminal station with good communication quality on the radio base station side and a terminal station that has deteriorated (unless normally, ranging is not successful).

  The third contrivance is that the concept of service group is introduced, and communication means can be selected according to the communication quality and usage of each terminal station.

  According to this device, for example, a terminal station that only needs to receive streaming data from a radio base station has a high uplink error rate due to asymmetric transmission power. If communication can be performed without any problem, a wireless base station can be set to provide only downlink communication. The concept of the service group is different from the concept of bandwidth guarantee such as QoS (Quality of Service).

  As described above, according to the present invention, when wireless communication is performed between a radio base station and a terminal station, communication in an uplink (communication from the terminal station to the radio base station) is performed because the system has an asymmetric transmission power. The communication condition setting of the radio base station is dynamically changed for a terminal station whose quality is deteriorated or cannot communicate. As a result, communication is resumed and maintained. In addition, a method for maintaining communication by classifying terminal stations into several service groups according to the communication quality and usage of the terminal stations and selecting a communication means corresponding to each service group is provided. With this method, it is possible to relieve a terminal station that cannot communicate because the communication quality has deteriorated for some reason.

  Further, as an embodiment similar to the present invention, there is a case where a retransmission function such as ARQ or HARQ is effective in an asymmetric wireless communication system in which transmission power is different between uplink and downlink. In this case, it is detected that the data successfully received despite the transmission of the ACK signal has been retransmitted (unnecessary retransmission), and the wireless base station is notified of the unnecessary retransmission. In addition, the terminal station communication mode (use application) set on the terminal station side, for example, “terminal station A only needs to be able to receive data broadcast to all terminals.”, “Terminal station B is addressed to itself. Is sent to the radio base station as a “group signal” such as “data transmission to the radio base station is rare (streaming)”. On the other hand, the radio base station implements a function of dynamically changing parameters (such as the number of retransmissions) related to retransmission based on unnecessary retransmission information notified from the terminal station. When receiving the group signal from the terminal station, the radio base station refers to a group table held in advance in the radio base station and performs an appropriate service group setting. If there is no corresponding service group or no group signal is transmitted from the terminal station, the default service group is set.

  The present invention is not limited to the above-described embodiments, and can be applied to all wireless communication systems in which transmission power is asymmetric between uplink and downlink.

It is a figure which shows one Embodiment of the radio | wireless communications system of this invention. FIG. 2 is a diagram illustrating a configuration example of a radio base station illustrated in FIG. 1. It is a figure which shows one structural example of the terminal station shown in FIG. It is a sequence diagram for demonstrating the initial ranging procedure in the radio | wireless communications system shown in FIGS. It is a flowchart for demonstrating the process in a terminal station among the communication permission methods in the radio | wireless communications system shown in FIGS. It is a flowchart for demonstrating the processing method of the service information in a wireless base station among the communication permission methods in the radio | wireless communications system shown in FIGS. FIG. 3 is a diagram illustrating a configuration example of a group table set in advance in the radio base station illustrated in FIGS. 1 and 2. FIG. 3 is a flowchart for explaining a ranging success range update process in the radio base station shown in FIGS. 1 and 2; FIG.

Explanation of symbols

101 radio base station 102 terminal station 110, 120 antenna 111, 121 reception RF unit 112, 122 demodulation unit 113, 123 power calculation unit 114 threshold setting unit 115, 125 modulation unit 116, 126 transmission RF unit 117, 127 communication control unit 124 Ranging (group) control unit

Claims (9)

In a radio communication system composed of a terminal station and a radio base station configured to be connectable to the terminal station,
Ranging to adjust the transmission timing of the uplink signal from the terminal station to the radio base station,
The terminal station transmits counts the number of failed the ranging, a ranging number of failures so far upon successful the ranging, and service information indicating the communication mode of the terminal station to the radio base station And
Whether the radio base station allows communication with the terminal station based on the service information, and allows communication with the terminal station based on the service information and the number of ranging failures A wireless communication system , wherein a success range indicating such is updated . The wireless communication system according to claim 1 , wherein
The wireless communication system, wherein the wireless base station expands the success range when the number of ranging failures exceeds a threshold set based on the service information. The wireless communication system according to claim 2 ,
The wireless communication system, wherein the threshold is the number of times of ranging failure. The wireless communication system according to claim 2 ,
The radio base station expands the success range when a ranging failure probability according to the number of ranging failures exceeds a probability of ranging failure set as the threshold . A terminal station that is configured to be connectable to a radio base station and performs ranging for adjusting the transmission timing of an uplink signal to the radio base station,
A terminal station that counts the number of times the ranging has failed and transmits the number of ranging failures that have failed so far when the ranging is successful and service information indicating a communication form of the terminal station to the radio base station. Transmission timing of an uplink signal that is configured to be connectable to a terminal station and that allows communication with the terminal station based on service information indicating a communication form with the terminal station and is transmitted from the terminal station A radio base station that performs ranging to adjust the frequency and updates a success range indicating whether to allow communication with the terminal station based on the service information and the number of ranging failures transmitted from the terminal station. The radio base station according to claim 6 ,
The radio base station, wherein the success range is expanded when the number of ranging failures exceeds a threshold set based on the service information. A communication permission method in a wireless communication system configured from a terminal station and a wireless base station configured to be connectable to the terminal station,
A process in which the terminal station transmits service information indicating a communication form of the terminal station to the radio base station;
A process for allowing the radio base station to communicate with the terminal station based on the service information ;
A process of counting the number of times the terminal station has failed ranging for adjusting the transmission timing of an uplink signal from the terminal station to the radio base station;
When the terminal station succeeds in the ranging, a process of transmitting the number of ranging failures that have failed so far to the radio base station;
The wireless base station includes a process of updating a success range indicating whether to allow communication with the terminal station based on the service information and the number of times of ranging failure . The communication permission method according to claim 8 , wherein
The wireless base station includes a process for expanding the success range when the number of ranging failures exceeds a threshold set based on the service information.

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