JP4905334B2 - Communication apparatus and adaptive modulation method - Google Patents

Description

  The present invention relates to a communication device and an adaptive modulation method.

  In wireless communication, when radio wave quality is good, a high-speed modulation method is applied to maintain a high data rate, and when radio wave quality is poor, a low-speed modulation method is applied to avoid disconnection of the communication line. It is done. That is, the communication device is set so that a plurality of coded modulation schemes can be used, and the actual reception sensitivity value (radio wave condition) is compared with a preset threshold value for reception sensitivity. A modulation method is selected based on the comparison result (see, for example, Non-Patent Document 1).

In recent years, mobile WiMAX has attracted attention as a broadband wireless access system compliant with IEEE 802.16e.
Since WiMAX is a broadband wireless access system in which the Internet or the like is used as a host network, there are various types of application data (traffic type; also referred to as service class) to be communicated. In other words, applications assumed in WiMAX range from simple data communication to VoIP (Voice over IP).

Takeshi Hattori, Masanobu Fujioka, “Revised Wireless Broadband Textbook High-Speed IP Wireless”, First Edition, Impress R & D Inc., June 21, 2006, p. 48-50

  When communication data is required to be real-time like VoIP or video, it is better that data errors and delays are as small as possible. That is, when real-time performance is required as in VoIP and video, data errors and delays cause abnormalities such as breaks in audio and video and reduce the feeling of use.

  In a conventional communication apparatus, a comparison is made with a threshold for reception sensitivity such as CINR, and adaptive modulation is performed based on this comparison. However, when communication data is required to be real-time like VoIP or video, even if adaptive modulation is performed based on the threshold value for reception sensitivity, packet loss and packet errors frequently occur depending on the situation, and audio and video are interrupted. Etc. may occur. Moreover, how much real-time performance is required varies depending on the traffic type. Therefore, in the conventional adaptive modulation method, a feeling of use may be reduced in an environment where various traffic types exist, such as WiMAX.

  Therefore, an object of the present invention is to provide a communication apparatus and an adaptive modulation method that can appropriately perform adaptive modulation even when there are various types of traffic types.

  The present invention is a communication apparatus that performs adaptive modulation, and performs determination for changing a modulation method, and identifies a modulation method changing unit that changes the modulation method and a traffic type of communication data based on the determination result And a control unit that changes a packet loss rate threshold and / or a packet error rate threshold according to the traffic type identified by the identification unit, and the modulation scheme changing unit includes a packet loss rate. And / or it is comprised so that the determination for changing a modulation system may be performed according to whether the packet error rate has exceeded the threshold value changed by the said control part.

In addition, the present invention is an adaptive modulation method in which a communication apparatus performs a determination for changing a modulation method and performs adaptive modulation based on the determination result, and identifies and identifies a traffic type of communication data Change the packet loss rate threshold and / or packet error rate threshold according to the traffic type, and change the modulation method depending on whether the packet loss rate and / or packet error rate exceeds the changed threshold. To make a decision.
According to this communication apparatus and adaptive modulation method, the traffic type of communication data is identified, and the threshold value of the packet loss rate and / or the packet error rate is changed according to the identified traffic type. For this reason, since the modulation scheme can be changed depending on whether the packet loss rate and / or the packet error rate exceeds the threshold value changed according to the traffic type, there are various types of traffic types. Even if it exists, adaptive modulation can be appropriately performed based on a threshold value corresponding to the traffic type. The change of the modulation scheme includes a case where the coding rate is changed.

Further, in the communication apparatus, the control unit uses a determination factor used for the determination according to a traffic type identified by the identification unit from among a plurality of determination factor information including a packet loss rate and / or a packet error rate. While selecting information, it is preferable to determine the threshold value of the selected determination factor information according to the traffic type identified by the identification unit.
According to this, even if there are various types of traffic types, the determination factor information used for the determination is selected according to the traffic type, and the threshold value of the selected determination factor information is determined. Based on the determination factor information corresponding to the traffic type and its threshold value, adaptive modulation can be appropriately performed.

In this case, when the traffic type identified by the identification unit is a traffic type corresponding to at least VoIP, the control unit determines a packet loss rate and / or a packet from a plurality of pieces of determination factor information. It is preferable to select an error rate.
According to this, in the case of a traffic type corresponding to VoIP, since the modulation scheme is changed depending on whether the packet loss rate and / or the packet error rate exceeds a threshold, packet loss and / or packet error Generation is restricted, and interruption of sound can be prevented.

  According to the present invention, since the modulation scheme can be changed depending on whether the packet loss rate and / or the packet error rate exceeds the threshold value changed according to the traffic type, there are various types of traffic types. However, adaptive modulation can be appropriately performed based on a threshold value corresponding to the traffic type. As a result, it is possible to obtain a good feeling of use even in an environment where various traffic types exist.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the overall configuration of a communication system in mobile WiMAX. This communication system includes a terminal (MS; Mobile Station) 1 such as a mobile terminal, a plurality of base stations (BS; Base Station) 2 with which the terminal 1 communicates, and an ASN-GW (Access Service Network Gateway) 3 and HA (Home Agent) 4. Usually, a plurality (several thousand) of base stations 2 are connected to an ASN-GW (Access Service Network Gateway) 3. The ASN-GW 3 is connected to an upper network such as the Internet and other networks via an HA (Home Agent) 4.

Therefore, a packet (downlink data) transmitted from a higher network such as the Internet to the terminal 1 is transmitted from the base station 2 to the terminal 1 via the HA 4 and the ASN-GW 3.
The ASN-GW 3 has a function for controlling the base station 2. The terminal 1 is capable of VoIP (Voice over IP), streaming music or video, data communication, and web browsing.

FIG. 2 shows the configuration of the control device 5 on the base station 2 and ASN-GW 3 side. In this embodiment, the base station 2 will be described as having a control device 5.
The control device 5 includes: a modulation scheme changing unit 31 that changes a modulation scheme (speed) based on a threshold set in determination factor information described later; and traffic of packets (downlink packets) transmitted to the terminal 1 An identification unit 32 for identifying a type, a control unit 30 for changing the determination factor information and the threshold for the determination factor information, and a storage unit 34 for storing various types of information are provided.

  As described above, the modulation scheme changing unit 31 is configured to be able to change the modulation scheme based on the threshold set in the predetermined determination factor information. It is a determinator used by the changing unit 31 for determining a change in modulation scheme (whether to change the modulation scheme). For example, a packet loss rate, a packet error rate, and a CINR (Carrier to Interference plus Noise Ratio) There is. A predetermined threshold is set for each piece of determination factor information. In other words, the modulation scheme changing unit 31 changes the modulation scheme based on a threshold for at least one of a plurality of pieces of determination factor information such as a packet loss rate, a packet error rate, and CINR. Specifically, the modulation scheme changing unit 31 performs determination for changing the modulation scheme depending on whether or not the packet loss rate and / or the packet error rate exceeds a threshold, and performs modulation based on the determination result. Change the method.

The identification unit 32 performs identification by DSCP (Diff Service Code Point) in order to identify the traffic type of a packet (downlink packet) transmitted to the terminal 1. The identification unit 32 identifies the traffic type based on the combination information (FIG. 3) stored in the storage unit 34.
In Mobile WiMAX, a plurality of classes are defined as traffic types (also referred to as “QoS (Quality of Service) class” in WiMAX). For example, (1) classes applied to real-time applications such as VoIP (Voice over IP), (2) classes applied to applications such as music or video streaming, and (3) data communication and web browsing There are classes that apply.

Specifically, the identification of the traffic type by the identification unit 32 will be described. When the target packet is an IPv4 packet, the identification unit 32 determines the DSCP field (8 bits) included in the TOS (Type Of Service) field (8 bits) of the header. 6 bit), the traffic type can be identified.
For example, referring to the DSCP field (6 bits) in FIG. 3, when the value of the upper 3 bits is 7 or 6, the identification unit 32 determines that the traffic type is VoIP, and the value is 5 or If it is 4, it is determined that the traffic type is video, and if the value is 3 or 0, it is determined that the traffic type is data (for data communication and web browsing). When the value is 2 or 1, the control device 5 performs communication by fixing to the lowest speed modulation method without performing adaptive modulation.

  When the target packet is IPv6, the traffic type can be identified by referring to the DSCP field (6 bits) included in the Traffic class field (8 bits) of the header.

By defining the traffic type in this way (as shown in FIG. 3), the identification unit 32 can determine which traffic type the packet belongs to by referring to the DSCP field of the packet.
When the identification unit 32 outputs information on the traffic type as the identification result, the control unit 30 receives information on the traffic type identified by the identification unit 32. Thereby, the control unit 30 (determination factor information changing unit 35) changes the determination factor information used for determining the change of the modulation scheme in accordance with the identified traffic type (whether or not to change the determination factor information). Process). At the same time, the control unit 30 (threshold changing unit 33) performs processing for changing the threshold value of the determination factor information (whether or not to change the threshold value).

  That is, the control unit 30 is used for determination for changing the modulation scheme according to the traffic type identified by the identification unit 32 from among a plurality of determination factor information including the packet loss rate and / or the packet error rate. The determination factor information is selected, and the threshold value of the selected determination factor information is determined according to the traffic type identified by the identification unit 32.

  More specifically, when the information about the traffic type received by the control unit 30 is data, the control unit 30 uses the CINR as determination factor information according to the traffic type based on the combination information of FIG. And determine a threshold C for this CINR (depending on its traffic type). The threshold value C is a preset value and is stored in the storage unit 34 as combination information. Then, the control unit 30 outputs to the modulation method changing unit 31 that CINR has been selected as the determination factor information and information on the threshold C for the CINR.

When the modulation scheme changing unit 31 receives information about the CINR being selected as the determination factor information and the threshold C for the CINR, the modulation scheme changing unit 31 selects the modulation scheme based on the threshold C for the CINR. Perform the change process. The modulation scheme change based on the CINR threshold C is performed by the first changing section 31 a included in the modulation scheme changing section 31.
The first changing unit 31a acquires a probability distribution of CINR (hereinafter referred to as “received CINR”) within a predetermined time at the terminal 1 as a parameter at the terminal 1. That is, a probability distribution of received CINR for a plurality of frames (for example, 5 to 10 frames) is acquired. The 1st change part 31a can acquire the information about this reception CINR in the terminal 1 by an uplink. The first changing unit 31a obtains a change CINR for changing the modulation scheme based on the probability distribution.

  The first changing unit 31a obtains, for example, an average value of received CINRs (hereinafter referred to as an average CINR) as the changing CINR. If the values of the plurality of received CINRs acquired within the predetermined time are X1, X2, X3... And the number of occurrences of these values is Y1, Y2, Y3..., The average CINR is calculated {(X1 × Y1 + X2 × Y2 + X3 × Y3 +... + Xn × Yn) / (Y1 + Y2 + Y3 +... + Yn)}. Note that n is the number of received CINRs acquired within a predetermined time. In this process, when the number of occurrences is a predetermined value or less (for example, 2 times or less), the received CINR may not be included for calculating the average CINR. Further, the change CINR acquisition means may be other than this.

  The reason for obtaining the change CINR based on the probability distribution of the received CINR within a predetermined time is that, in the case of WiMAX, the received CINR constantly varies greatly and randomly, and the value of the received CINR is obtained. This is because it is complicated and unsuitable to change the modulation system based on this every time.

  When the first changing unit 31a obtains the changing CINR (average CINR), the first changing unit 31a changes the modulation scheme based on this value and the first information about the modulation scheme correspondence shown in FIG. be able to. The first information is set in advance and is stored in the storage unit 34. The change of the modulation scheme performed by the first changing unit 31 includes a change of the coding rate. The communication speed varies depending on the combination of the modulation scheme and the coding rate, and the first information includes a plurality of modulation schemes (including the coding rate) at different speeds and the corresponding CINR threshold value for change. It is information about the relationship with C (range of change CINR).

For example, when the acquired value of CINR for change (average CINR) is equal to or less than the threshold 20 and exceeds the threshold 15, the first changing unit 31a sets the modulation scheme to 16QAM 3/4. When the value of the change CINR within the next predetermined time is equal to or less than the threshold 15 and exceeds the threshold 10, the first changing unit 31a changes the modulation method to 16QAM 1/2. Furthermore, when the value of the change CINR within the next predetermined time exceeds the threshold 20, the first changing unit 31a changes the modulation method to 64QAM 1/2.
Then, the first changing unit 31 a transmits information indicating that the modulation scheme is changed to the terminal 1.

  Further, when the information about the traffic type received by the control unit 30 from the identification unit 32 is VoIP in FIG. 3, the control unit 30 responds to the traffic type based on the combination information of FIG. At least one of the packet loss rate and the packet error rate is selected as the determination factor information, and the threshold A (Ad and Au) and / or the packet error rate of the selected packet loss rate (according to the traffic type) is selected. Threshold A (Ad and Au) is determined. Then, the control unit 30 outputs to the modulation scheme changing unit 31 information on the packet loss rate (packet error rate) selected as the determination factor information and the threshold value A.

  When the modulation scheme changing unit 31 receives information about the packet loss rate (packet error rate) being selected as the determination factor information and the threshold value, the modulation scheme changing unit 31 receives the packet loss rate (packet error rate). ) Can be changed based on the threshold A. The modulation method change based on the threshold A of the packet loss rate (packet error rate) is performed by the second changing unit 31b included in the modulation method changing unit 31.

  If the information about the traffic type received by the control unit 30 from the identification unit 32 is video in FIG. 3, the control unit 30 uses the packet loss as determination factor information based on the combination information of FIG. A threshold B (Bd and Bu) for the selected packet loss rate and / or packet error rate (different from the threshold A for VoIP). decide. Then, the control unit 30 outputs to the modulation method changing unit 31 information on the packet loss rate (packet error rate) selected as the determination factor information and the threshold value B.

  When receiving the information about the packet loss rate (packet error rate) being selected as the determination factor information and the threshold value B, the modulation method changing unit 31 receives the packet loss rate (packet error rate). The modulation scheme can be changed based on the threshold B of the rate. The modulation method change based on the threshold B of the packet loss rate (packet error rate) is performed by the second changing unit 31b included in the modulation method changing unit 31.

FIG. 5 is a flowchart of an operation in which the second changing unit 31b changes the modulation method. Hereinafter, a case where the traffic type is VoIP, the packet loss rate (and / or packet error rate) is selected as the determination factor information, and the threshold value A (Ad and Au) is determined will be described.
The second changing unit 31b acquires the packet loss rate (and / or the packet error rate) as a parameter in the terminal 1 (step S1). This packet loss rate (packet error rate) can be obtained from the number of transmitted / received packets between the base station 2 and the terminal 1, and the number of received packets at the terminal 1 is acquired by the second changing unit 31b through the uplink. be able to. The packet loss rate can be obtained from the number of transmitted / received packets within a predetermined time, and can be obtained, for example, from the number of transmitted / received packets for a plurality of frames (for example, 5 to 10 frames).

  Then, the second changing unit 31b compares the acquired packet loss rate with the first threshold value Ad in the current modulation method (large / small determination) (step S2). The first threshold value Ad and a second threshold value Au, which will be described later, are set in advance in the second information (see FIG. 6) regarding the modulation system correspondence, and the second information is stored in the storage unit 34. . The first threshold value Ad (Ad1 to Ad7) is a threshold value for determining whether to lower the modulation method (communication speed). Note that all of the first threshold values Ad (Ad1 to Ad7) may be the same in a plurality of modulation schemes, but some or all of them may be different.

  Further, the second changing unit 31b makes the above determination and determines whether or not the current modulation method is the minimum speed in the second information (step S3 in FIG. 2). . That is, in FIG. 6, it is determined whether or not the current modulation method is QPSK 1/2. Furthermore, the second changing unit 31b also has a function of determining whether or not the current modulation method is the maximum speed (step S13 in FIG. 5 described later). That is, in FIG. 6, it is determined whether or not the current modulation scheme is 64QAM 5/6.

  Further, the second changing unit 31b has a function of selecting the changing means (change method) when it is determined that the modulation method needs to be changed in the direction of decreasing the speed from the current modulation method. (Step S4). The second changing unit 31b also has a function of selecting the changing means when it is determined that the modulation method needs to be changed in the direction of increasing the speed from the current modulation method (a diagram to be described later). 5 step S14). The selection of the changing means will be described later.

  In step S2 of FIG. 5, when the second change unit 31b determines that the packet loss rate acquired as a parameter is larger than the first threshold value Ad of the current modulation scheme (Yes in step S2), When the speed of the current modulation method is not the minimum speed (No in step S3), the second changing unit 31b selects changing means for reducing the speed (step S4), and decreases the communication speed. The modulation method is changed (step S5).

  In step S3, when the speed of the current modulation method is the minimum speed (Yes in step S3), the modulation method cannot be changed in the direction of decreasing the speed, so the second changing unit 31b The process returns to step S1 without changing the modulation method.

  For the selection of the changing means for reducing the speed (step S4) by the second changing unit 31b, for example, a plurality of types of changing means are prepared in advance, and the second changing unit 31b uses the acquired parameters (packet loss rate, etc.). This is done by selecting one of the plurality based on this. As the changing means, for example, a means for lowering the modulation system one by one (one step at a time) in FIG. 6 or a process for raising the modulation system after lowering to the slowest modulation system (means after step S12 described later) ) Is then performed. These changing means are stored as programs in the storage unit 34, and the second changing unit 31b selects and executes one of them.

Further, when the second changing unit 31b determines that the acquired packet loss rate is equal to or less than the first threshold value Ad of the current modulation method in Step S2 (No in Step S2), the second changing unit 31b Then, the packet loss rate is compared with the second threshold value Au of the current modulation method (decision of magnitude) (step S12).
In step S12, when the packet loss rate is equal to or greater than the second threshold value Au in the current modulation method (No in step S12), the second changing unit 31b returns to step S1 without changing the modulation method. The second threshold value Au is a threshold value for determining whether to increase the modulation method (communication speed). The second threshold values Au (Au1 to Au7 in FIG. 6) may all be the same, but some or all of them may be different.

  Also, as shown in FIG. 6, in the second information about a plurality of modulation schemes arranged in order from high speed to low speed, from a certain (current) modulation scheme (for example, 16QAM 3/4) to the next modulation scheme A first threshold value Ad (for example, Ad4) for reducing the one-step speed to (16QAM 1/2) and a one-step speed from the next modulation method (16QAM 1/2) to the certain modulation method (16QAM 3/4) The second threshold value Au (for example, Au5) for increasing the value may be the same or different. When making these threshold values different, it is preferable to make the first threshold value Ad (Ad4) smaller than the second threshold value Au (Au5).

Also, in step S12, when the acquired packet loss rate is smaller than the second threshold value Au, the second changing unit 31b determines (in the case of Yes in step S12), and the speed of the current modulation scheme is the maximum. If it is not the speed (No in step S13), the second changing unit 31b selects the changing means for increasing the speed (step S14), and changes the modulation method in the direction of decreasing the communication speed (step S15). ).
Then, the second changing unit 31b transmits information indicating that the modulation scheme is changed to the terminal 1.

  In step S13, if the current modulation method is the maximum speed (Yes in step S13), the modulation method cannot be changed in the direction of increasing the communication speed. The process returns to step S1 without changing the modulation method.

  The selection of the changing unit for increasing the speed by the second changing unit 31b is the same as the selection of the changing unit for decreasing the speed. For example, a plurality of types of changing units are prepared in advance, and the second changing unit 31b This is done by selecting one of the plurality based on the acquired parameters (packet loss rate, etc.). As the changing means, for example, there are means for increasing the modulation method one by one (step by step) in FIG. 6, and processing for lowering the modulation method after increasing to the fastest modulation method (means after step S2). There are means to be performed thereafter. These changing means are stored as programs in the storage unit 34, and the second changing unit 31b selects one of them and executes it.

  The above adaptive modulation method will be specifically described. In FIG. 6, when the current modulation scheme is 64QAM 1/2, the second changing unit 31b uses the first threshold Ad3 and the packet loss rate acquired as a parameter. If the packet loss rate is determined to be greater than the first threshold value Ad3, the modulation method (rate) is changed to the lower one (16QAM 3/4). By changing the modulation method in this way, the packet loss rate can be reduced. Note that this is a case where the changing means for lowering the modulation method one by one (one step at a time) is selected.

In addition, when the current modulation scheme is 16QAM 3/4, the second changing unit 31b determines that the acquired packet loss rate is equal to or less than the first threshold Ad4, and the second threshold Au4 and the acquisition The packet loss rate is compared, and if it is determined that the packet loss rate is smaller than the second threshold value Au4, the modulation method is changed to a higher one for speed (64QAM 1/2). This is a case where the changing means for increasing the modulation method one by one (one step at a time) is selected.
In one modulation scheme (for example, 16QAM 3/4), the first threshold value Ad (Ad4) is set to a value larger than the second threshold value Au (Au4).

As described above, the adaptive modulation method performed by the control device (communication device) 5 is set to determination factor information (for example, packet loss rate, packet error rate, CINR, etc.) for changing the modulation method. The control device 5 identifies the traffic type of the communication data, and the determination factor information used for determining the change of the modulation method according to the identified traffic type. The threshold value is changed, and the modulation scheme is changed based on the changed threshold value.
Specifically, the control device (communication device) 5 performs a determination for changing the modulation method and, based on the determination result, an adaptive modulation method that performs adaptive modulation, and identifies the traffic type of communication data Depending on the identified traffic type, the packet loss rate threshold and / or the packet error rate threshold is changed, and whether the packet loss rate and / or the packet error rate exceeds the changed threshold, The determination for changing the modulation method is performed, and adaptive modulation is performed based on the determination result.

And since WiMAX which is this embodiment is a broadband wireless access system in which the Internet or the like is used as an upper network, there are various types of traffic to be communicated.
Therefore, according to the communication apparatus and the adaptive modulation method of the present invention, determination factor information (packet loss rate and / or packet error rate) used for determination of modulation scheme change according to the traffic type to be communicated and its threshold value Is changed, and the modulation scheme is changed based on the changed determination factor information and the threshold value. Therefore, even if there are various types of traffic types, the determination factor information corresponding to the traffic type and the threshold value are used. Adaptive modulation can be performed.

  Specifically, the control unit 30 provided in the control device 5 includes a traffic type identified by the identification unit among a plurality of traffic types to be communicated, and a traffic type with a relatively small allowable data error. In the case of (a traffic type that requires real-time property (requires real-time property)), that is, when the traffic type corresponds to at least VoIP, the packet loss rate and / or the determination factor information The packet error rate is changed to be used, and the threshold for determining the packet loss rate and / or the packet error rate is also changed. Further, the control unit 30 uses CINR (reception quality; reception) as determination factor information for a traffic type with a relatively large allowable data error (a traffic type that does not require real-time performance) among a plurality of traffic types to be communicated. (Sensitivity) is used, and the threshold for determining this CINR is also changed. Although the CINR is used as the determination factor information when the traffic type to be communicated has a relatively large allowable data error, reception quality other than this may be used. This reception quality is a signal-to-noise ratio, and specifically, there is CNR in addition to CINR.

  As a result, when the traffic type to be communicated is such that the allowable data error is relatively small, that is, VoIP or video that requires real-time characteristics, the packet loss rate and / or the packet error rate Based on the threshold value A or the threshold value B (see FIG. 3), the modulation method changing unit 31 can change the modulation method. For this reason, it is possible to limit the occurrence of packet loss and / or packet error. As a result, delay and data error can be suppressed, communication quality can be ensured, and sound and video can be prevented from being disturbed or interrupted. .

On the other hand, if the traffic type to be communicated is a data error that is relatively large, that is, data that does not require much real-time performance (for data communication and web browsing), the CINR Based on the threshold value C (see FIG. 3), the modulation method changing unit 31 can change the modulation method. For this reason, data errors can be prevented.
In addition, when the traffic type is data and TCP transmission is used, even if a certain amount of packet loss or packet error occurs, real-time performance does not matter so much, and information may be retransmitted.

In addition, the communication device of the present invention is not limited to the illustrated form, and may be of another form within the scope of the present invention. For example, in the above-described embodiment, the communication device (control device 5) that performs adaptive modulation has been described as the base station 2. However, the identification unit 32, the threshold value changing unit 33, the modulation method changing unit 31, and the storage provided in the control device 5 At least one or all of the units 34 may be provided in the ASN-GW 3.
Further, the determination factor information used for determining the change of the modulation scheme preferably includes a packet loss rate and / or a packet error rate. However, other information can be included, for example, the number of packet retransmissions, RSSI ( Receive Signal Strength Indication).

  Moreover, although the said embodiment demonstrated as the case where the adaptive modulation for downlink was performed, also when performing the adaptive modulation for uplink, the adaptive modulation method similar to the said embodiment is employable. In this case, processing is performed using parameters in the base station 2 (received CINR and number of transmitted / received packets in the base station 2).

1 shows an overall configuration of a communication system in mobile WiMAX. It is a block diagram of a control apparatus. It is explanatory drawing of combination information. It is explanatory drawing of the 1st information about a modulation system correspondence. It is a flowchart of operation in which the 2nd change part changes a modulation system. It is explanatory drawing of the 2nd information about a modulation system correspondence.

Explanation of symbols

1 terminal 2 base station 3 ASN-GW
5 Control Device 30 Control Unit 31 Modulation Method Change Unit 32 Identification Unit

Claims (4)

A communication device that performs adaptive modulation,
A determination for changing the modulation method is performed, and a modulation method changing unit for changing the modulation method based on the determination result;
An identification part for identifying a traffic type of communication data;
A control unit that changes a packet loss rate threshold and / or a packet error rate threshold according to the traffic type identified by the identification unit;
With
The modulation scheme changing unit is configured to make a determination for changing the modulation scheme depending on whether a packet loss rate and / or a packet error rate exceeds a threshold value changed by the control unit. A communication device characterized by the above. The controller is
From among a plurality of determination factor information including a packet loss rate and / or a packet error rate, selecting the determination factor information used for the determination according to the traffic type identified by the identification unit,
The communication apparatus according to claim 1, wherein a threshold value of the selected determination factor information is determined according to a traffic type identified by the identification unit.   The control unit selects a packet loss rate and / or a packet error rate from a plurality of determination factor information when the traffic type identified by the identification unit is a traffic type corresponding to at least VoIP. The communication device according to claim 2. A communication device performs a determination for changing a modulation scheme, and is an adaptive modulation method for performing adaptive modulation based on the determination result,
The traffic type of the communication data is identified, the threshold of the packet loss rate and / or the packet error rate is changed according to the identified traffic type, and the packet loss rate and / or the packet error rate is changed to the changed threshold value. An adaptive modulation method, characterized in that a determination for changing a modulation method is performed depending on whether or not the frequency exceeds the limit.

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