KR100347733B1 - Method for controlling traffic of wireless mobile station - Google Patents

Abstract

The present invention relates to a traffic control technique in a wireless mobile terminal capable of improving network resources by adaptively allocating information slots based on a priority of a multimedia service delay and cell discard rate characteristics. The present invention controls the allocation of an information slot to a terminal requesting a service based on a priority according to the delay and cell discard rate characteristics of a multimedia service, and is a delay sensitive service (constant rate (CBR) service, real-time variable rate (Rt-)). VBR), which is a periodic reservation method, and congested for less delay-sensitive services (NRT-VBR service, Available Rate (ABR) service, and Undefined Rate (UBR) service). By controlling the traffic by applying the reservation method according to the, it is possible to suppress the mutual interference that can occur between multiple users Tea will be realized in the efficiency of resource utilization in the media traffic.

Description

Traffic control method in wireless mobile terminal {METHOD FOR CONTROLLING TRAFFIC OF WIRELESS MOBILE STATION}

The present invention relates to a method for controlling traffic in a wireless mobile terminal, and more particularly, to a traffic control method of a wireless mobile terminal suitable for efficiently using limited resources when providing a multimedia service in wireless or portable communication. It is about.

As is well known, the media access control for the multimedia environment is mainly a time division multiple access method, in which a packet is transmitted in a reservation mode for voice and a packet is transmitted in a collision mode for data. Representative examples include packet multiple reservation multiple access and dynamic slot allocation multiple access.

Here, the packet reservation multiple access method has a problem in that it is difficult to satisfy various levels of service quality because traffic is controlled based on probability information proportional to the number of terminals that reserve the reserved access of the slot.

On the other hand, the dynamic slot allocation multiple approach provides more granular quality of data, which may satisfy some of the quality of service, but the traffic control is complicated because at least two threshold variables are used to control the traffic. In addition, since there is no consideration of the available bit rate (ABR) suitable for Internet traffic, there is a fundamental problem that it is unsuitable for processing various multimedia services.

Accordingly, the present invention is to solve the above problems of the prior art, it is possible to improve the efficiency of network resources by adaptively allocating information slots based on the priority according to the characteristics of delay and cell discard rate of the multimedia service It is an object of the present invention to provide a traffic control method in a mobile terminal.

In order to achieve the above object, the present invention provides a method for controlling traffic in a wireless mobile terminal system having at least one base station providing communication service for a plurality of wireless mobile terminals belonging to a preset service area thereof. Each of the base station and the wireless mobile terminal has a threshold for defining a congestion state, and the method includes: whether there is a non-real time variable rate (Nrt-VBR) terminal in a frame received from the wireless mobile terminal. Checking and releasing a slot allocated to the traffic when there is a NRT-VBR terminal in a steady state; Checking whether there is an undefined rate (UBR) terminal in the frame, and releasing a slot allocated to traffic when there is an undefined rate (UBR) terminal as a result of the check; After checking whether there is a NRT-VBR terminal in the congested state in the frame, and assigning a slot to the traffic when there is a NRT-VBR terminal in the congested state Allocating an MCR to an available rate (ABR) terminal and allocating an MCR to the available rate (ABR) terminal when there is no NRT-VBR terminal in congestion; It is checked whether there is a constant rate (CBR) terminal or a real time variable rate (Rt-VBR) terminal in the frame, and as a result of the check, when there is a constant rate (CBR) terminal or a real time variable rate (Rt-VBR) terminal, Allocating slots; Checking whether the base station is in a normal state or the congestion state and assigning an additional slot to the available ABR terminal when the base station is in a normal state; Checking whether there are available free slots among network resources and ending traffic control when there are no free slots; When there is the empty slot, allocating a slot to the NRT-VBR terminal in the normal state and checking whether there is an available empty slot; And ending the traffic control when there is no empty slot, allocating a slot to the undefined transmission rate (UBR) terminal when there is an empty slot, and ending the traffic control. Provides a traffic control method.

1 is a schematic schematic diagram of an exemplary wireless mobile terminal system suitable for applying a method for controlling traffic of a wireless mobile terminal according to the present invention;

2A and 2B are structural diagrams of uplink and downlink frames;

3 is an exemplary diagram illustrating a priority given according to a congestion state when allocating a slot to a wireless mobile terminal;

4 is a flowchart illustrating a process of controlling traffic of a wireless mobile terminal according to a preferred embodiment of the present invention;

5 is a graph showing the relationship between the total load obtained through the experiment and the cell discard rate,

6 is a graph showing the relationship between total load and cell transmission delay obtained through experiments.

<Description of the code | symbol about the principal part of drawing>

102/1-102 / n: wireless mobile terminal 104: base station

106: network

The above and other objects and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, a key technical aspect of the present invention is to control allocation of an information slot to a terminal requesting a service on the basis of priority according to characteristics of delay and cell discard rate of a multimedia service, and a delay sensitive service (constant bit rate (CBR: constant bit)). rate reservation, real-time variable bit rate (Rt-VBR) service, and a periodic reservation method, and less delay-sensitive service (Nrt-VBR (non-realtime variable bit rate)) (B) applying a reservation method according to congestion for services, available bit rate (ABR) services, and unspcified bit rate (UBR) services). The bar can be easily achieved.

1 is a schematic schematic diagram of a typical wireless mobile terminal system suitable for applying a method for controlling traffic of a wireless mobile terminal in accordance with the present invention, wherein a typical wireless mobile terminal system comprises a plurality of wireless mobile terminals 102/1-102 /. n), base station 104 and network 106. In the figure, only one base station is shown for convenience of understanding, but in reality, there are a plurality of base stations belonging to one base station controller (not shown).

Referring to FIG. 1, each of the wireless mobile terminals 102/1-102 / n is a voice or data terminal that performs packet communication in a time division multiple access scheme such as, for example, IMT-2000. It provides traffic, sends a reservation message of an information slot to be used for a base station through a reserved slot of an uplink frame allocated through a reservation mode (cyclic reservation mode, a reservation mode according to congestion), and allocates an uplink allocated from the base station. The information packet is transmitted to the base station through the information slot of the link frame.

Next, the base station 104 establishes a communication service for wireless mobile terminals (voice terminals, data terminals) in its service area (eg, general call setup and release, mobile terminal location registration and release, Terminal status check, handoff processing, call setup and release for additional information service, slot allocation and release, etc.), and control traffic in the periodic reservation mode or the reservation mode according to the congestion state according to the quality of service. The allocation information of the information slot is broadcast to the terminal through the control slot of the downlink frame.

To this end, in the traffic control method according to the present invention, as shown in FIGS. 2A and 2B, an uplink frame is allocated to one reserved slot R and several information slots similarly to the conventional media access control scheme. (I), and a downlink frame is composed of a control slot (ACK) and a plurality of information slots (I) to be transmitted to the base station by the mobile station.

Referring back to FIG. 1, network 106 connects base station 104 and a base station controller or wireless switched network, not shown, as a wired asynchronous transmission mode network.

Next, a process of performing traffic control according to the present invention using the wireless mobile terminal system having the above-described configuration will be described.

As is well known in the art, traffic types defined in asynchronous transmission mode include constant rate (CBR), real-time variable rate (Rt-VBR), non-real time variable rate (Nrt-VBR), available rate (ABR), An Undefined Rate Rate (UBR) service.

Here, CBR is used for real-time applications that require strictly limited delays and delay deviations, such as voice and video, and Rt-VBR is used for real-time applications that require limited delays and delay deviations, such as CBR. The rate varies depending on the characteristics.

In addition, Nrt-VBR is used for non-real time applications with burst traffic characteristics, and the traffic characteristics are not sensitive to delay, and ABR is that the information transmission rate is adjusted at the terminal side based on the state information of the network. Cell rate and delay deviation are used for the upper limit of bandwidth, minimum cell rate is used for the lower limit of bandwidth, has the characteristics of burst traffic and is sensitive to cell loss rate.

Lastly, UBR supports applications that are not susceptible to delay variations and can withstand the application of bandwidth. This guarantees quality of service because bandwidth is not reserved.

On the other hand, since the traffic control method according to the present invention is based on a time division multiple access scheme, radio frames are composed of time slots. That is, as in the conventional medium access control scheme, the uplink frame is composed of one reserved slot (R) and several information slots (I), and the downlink frame is a control slot (ACK) to be transmitted by the mobile station to the base station. And several information slots (I). Therefore, the traffic control method according to the present invention groups the control messages and transmits only the control slots to the wireless mobile terminal by broadcasting, and transmits other information slots only to the corresponding wireless mobile terminal, thereby minimizing signal interference through power control. It can provide a network environment.

In this case, an M-ary Walsh code having an orthogonal property is used for a reserved slot of an uplink frame, and each terminal is assigned one single code from a base station. Here, the size of the reserved slot is determined by the available frequency band and transmission rate of the system. In addition, the base station transmits a confirmation message for transmission reservation to the wireless mobile terminals through the control slot of the downlink frame.

On the other hand, the traffic control method according to the present invention uses a congestion state to reflect the dynamic state of the wireless mobile terminal and the base station, where the congestion state is defined differently in the wireless mobile terminal and the base station.

That is, the wireless mobile terminal can be defined as having entered a congestion state when the size of the current buffer exceeds a certain threshold, which is set according to the type of service, that is, in the case of Nrt-VBR and ABR Should be set larger than other services (CBR, Rt-VBR, UBR).

In addition, the base station may be defined as a congestion state of the system when the number of reservation requests is greater than the number of control slots (ACKs) or when the information slot is above a certain limit. It is set differently accordingly. That is, in the traffic control method according to the present invention, as shown in FIG. 3 as an example, when allocating slots to a wireless mobile terminal, slots are assigned by setting priorities given according to congestion.

Next, in the traffic control method according to the present invention, traffic by service type will be described.

First, in case of CBR, the reservation request message is transmitted to the base station through an uplink control slot (R-Slot) immediately before the first message is transmitted after the call is set up, and the slot release is notified immediately before the last data message transmission. That is, bandwidth is allocated and released in units of calls. In the case of release, a method of notifying the base station by using a few bits at the end of the uplink information slot may be adopted. Once reserved, the CBR service is allocated to a certain slot of a frame to enable periodic data transmission, which continues until the allocated resources are released. Therefore, cell loss due to time delay may occur only until the first reservation. Here, the buffer size J of the CBR traffic may be calculated as in the following equation.

J = RP * MTD

In Equation 1, R _P denotes a maximum transfer rate, and a maximum transfer delay (MTD) denotes a cell transfer delay time.

In addition, in the case of the Rt-VBR service, the reservation operation is performed immediately before the burst start as in the above-described CBR, and the resource is released immediately before the burst end. The difference with CBR is that reservation and release operations are performed on a burst basis rather than on a call basis. In this case, the size J of the buffer may be calculated by Equation 1 as in the above-described CBR.

Next, in the case of Nrt-VBR service, the operation varies according to the congestion state of the terminal. When the buffer of the terminal is in a normal state, a data message can be transmitted through reservation every frame, and the buffer state of the terminal is congested. In the case of the state, the reservation operation is performed in the same manner as the Rt-VBR. That is, in the normal state of the terminal, when the base station is in a congested state, it protects the quality of the CBR or Rt-VBR service, provides better efficiency to the UBR, and after entering the congested state, even if the Nrt-VBR terminal is lost In order to prevent the error, the reservation operation is performed in the same manner as the Rt-VBR, thereby ensuring the quality of the Nrt-VBR. Herein, the size J of the buffer may be calculated as shown in Equation 2 using the equivalent bandwidth C according to the fluid flow method.

J = C * MTD

In Equation 2, MTD means maximum transmission delay.

Meanwhile, in the case of the ABR service, the minimum cell rate is periodically allocated as in the CBR. If the base station is in a normal state (that is, if the base station has a spare slot and there is an empty slot remaining in the information slot or more), the base station may additionally reserve the bandwidth to the minimum cell rate. In this case, the reservation scheme is performed every frame. When the base station is congested, allocation of the minimum cell rate is continued to ensure minimum quality.

In addition, in case of UBR service, reservation is allowed on a frame-by-frame basis only when the base station is in a normal state. When system resources are large, overhead of sending a reservation message every frame can be reduced.

Next, a process of controlling traffic using a periodic reservation method and a reservation method according to a congestion state according to the present invention will be described.

4 is a flowchart illustrating a process of controlling traffic of a wireless mobile terminal according to a preferred embodiment of the present invention.

Referring to FIG. 4, the base station 104 searches for whether there is a Nrt-VBR terminal in a normal state in a frame received from the wireless mobile terminal (step 402), where the Nrt- in normal state in the search result frame is found. If there is a VBR terminal, the allocated slot is released (step 404), and then the process proceeds to step 406 which will be described later. It proceeds immediately.

Next, in step 406, the UBR terminal is searched again in the frame. If the UBR terminal is found in the search result frame, the allocated slot is released (step 408). Proceeding to step 410, if there is no UBR terminal in the frame, processing proceeds directly to step 410, which will be described later.

Further, in step 410, whether the Nrt-VBR terminal is found in the frame is searched again. If there is an Nrt-VBR terminal in the search result frame, the slot is allocated to the traffic (step 412). In step 414, the MBR (minimum cell rate) is allocated to the ABR terminal. If there is no Nrt-VBR terminal in the frame, the process proceeds directly to step 414, and the MCR is allocated to the ABR terminal.

On the other hand, the base station 104 to search whether there is a CBR terminal or Rt-VBR terminal in the frame (step 416), if there is a CBR terminal or Rt-VBR terminal in the search result frame here slots in the traffic After the allocation (step 418), the process proceeds to step 420 described later, and if there is no CBR terminal or Rt-VBR terminal in the frame, the process proceeds directly to step 420 described later.

Next, in step 420, it is checked whether the current base station is in a normal state or a congested state. If it is determined that the base station is in a normal state, then an additional slot is allocated to the ABR terminal ( Step 422), the process proceeds to step 424, which will be described later. If the check result indicates that the base station is congested, the process proceeds directly to step 424, which will be described later.

In step 424, it is checked whether there are available free slots among the network resources, and if there is no free available slot as a result of the check here, traffic control is terminated.

Unlike the above, as a result of the check in step 424, if there are available empty slots, slots are allocated to the Nrt-VBR terminal in a normal state (step 426), and then it is checked whether there are available empty slots ( Step 428).

As a result of the check in step 428, if there is no available empty slot, the traffic control is terminated. If there is an available empty slot, the slot is allocated to the UBR terminal (step 430), and the traffic control is terminated.

On the other hand, the inventors of the present invention, in order to ensure the reliability of the traffic control method according to the present invention, when the number of cells in the buffer of the wireless mobile terminal exceeds the predetermined threshold value to set the congestion state to change the threshold value The change of the cell discard rate was tested, and the result is as shown in FIG. 5.

That is, referring to FIG. 5, as the threshold value of Nrt-VBR increases, Rt-VBR makes a slot reservation while securing more resources, thereby increasing the probability of success of the reservation, thereby reducing the cell discard rate. there was. On the contrary, Nrt-VBR has been found to increase the cell discard rate because it becomes more difficult to successfully reserve a cell.

In addition, the inventors of the present invention, in order to secure the reliability of the traffic control method according to the present invention, the change between the cell transmission delay according to the total load, the results are shown in FIG.

Referring to FIG. 6, since Rt-VBR is a delay sensitive traffic, it should always be transmitted within a given maximum allowable delay time. In the case of Rt-VBR, a cell transmission delay does not exceed the maximum allowable delay time regardless of a change in a limit value. It can be seen that the value close to. On the other hand, in the case of Nrt-VBR, the resource request is increased every frame as the limit increases. If the request is not allowed, the cell transmission delay increases because the request is waited until the next frame.

Next, in the case of ABR, the cell discard rate decreases as the minimum cell rate increases. In other words, in order to improve the performance of the ABR, the minimum cell rate must be increased. However, since the transmission efficiency is reduced, an appropriate value considering this is required. In addition, in case of UBR, slots are allocated when all slots remain after allocating other traffic. Therefore, it is understood that the change of the limit value of Nrt-VBR does not significantly change the cell transmission delay of UBR traffic. Could.

As described above, according to the present invention, the allocation of information slots to the terminal requesting the service is controlled based on the priority of the delay and the cell discard rate of the multimedia service, and the delay-sensitive constant rate (CBR) and the real-time variable rate ( Rt-VBR) is a periodic reservation method, and reservation method based on congestion for non-real-time variable rate (Nrt-VBR), available rate (ABR), and undefined rate (UBR) services By controlling the traffic in such a manner as to control the traffic, efficient interference (maximization) of resource utilization in multimedia traffic can be realized by suppressing mutual interference that can occur between a plurality of users.

Claims (13)

A method of controlling traffic in a wireless mobile terminal system having at least one base station providing communication service for a plurality of wireless mobile terminals belonging to a preset service area thereof, Each of the base station and the wireless mobile terminal has a threshold for defining a congestion state, respectively, The method controls the traffic in a periodic reservation manner for a relatively delay sensitive service among a plurality of services, and controls the traffic in a reservation manner according to a congestion state for a relatively less sensitive service. A method for controlling traffic in a wireless mobile terminal, comprising allocating information slots to traffic based on priorities according to delay and cell discard rate characteristics. The method of claim 1, wherein the wireless mobile terminal regards the congestion when the size of a buffer exceeds a preset limit. The method of claim 1, wherein the base station considers the congestion state when the number of reservation requests is larger than the number of control slots. The method of claim 1, wherein the base station considers the congestion when an available empty information slot exceeds a preset limit. The method according to any one of claims 1 to 4, wherein the method controls the constant rate (CBR) traffic and the real time variable rate (Rt-VBR) traffic by the periodic reservation method, and the non-real time variable rate (Nrt−). VBR) Traffic control method in the wireless mobile terminal, characterized in that the control of the congestion state, the available rate (ABR) traffic and undefined rate (UBR) traffic. [6] The wireless mobile terminal of claim 5, wherein the constant rate (CBR) traffic and the real time variable rate (Rt-VBR) traffic are set to a size of a buffer multiplied by a maximum rate and a cell transmission delay time. Traffic control method. 6. The method of claim 5, wherein the buffer of NRT-VBR traffic is set to a size multiplied by an equivalent bandwidth and a maximum transmission delay. A method of controlling traffic in a wireless mobile terminal system having at least one base station providing communication services for a plurality of wireless mobile terminals belonging to a preset service area thereof, Each of the base station and the wireless mobile terminal has a threshold for defining a congestion state, respectively, The method is: Checks whether there is a NRT-VBR terminal in a steady state in a frame received from the wireless mobile terminal, and assigns to traffic when there is a NRT-VBR terminal in a steady state as a result of the check. Releasing the reserved slots; Checking whether there is an undefined rate (UBR) terminal in the frame, and releasing a slot allocated to traffic when there is an undefined rate (UBR) terminal as a result of the check; After checking whether there is a NRT-VBR terminal in the congested state in the frame, and assigning a slot to the traffic when there is a NRT-VBR terminal in the congested state Allocating an MCR to an available rate (ABR) terminal and allocating an MCR to the available rate (ABR) terminal when there is no NRT-VBR terminal in congestion; It is checked whether there is a constant rate (CBR) terminal or a real time variable rate (Rt-VBR) terminal in the frame, and as a result of the check, when there is a constant rate (CBR) terminal or a real time variable rate (Rt-VBR) terminal, Allocating slots; Checking whether the base station is in a normal state or the congestion state and assigning an additional slot to the available ABR terminal when the base station is in a normal state; Checking whether there are available free slots among network resources and ending traffic control when there are no free slots; When there is the empty slot, allocating a slot to the NRT-VBR terminal in the normal state and checking whether there is an available empty slot; And As a result of the check, the traffic control is terminated when there is no empty slot, and when there is an empty slot, allocating a slot to the undefined transmission rate (UBR) terminal and ending the traffic control. Control method. 10. The method of claim 8, wherein the wireless mobile terminal regards the congestion when the size of a buffer exceeds a preset limit. The method of claim 8, wherein the base station considers the congestion when the number of reservation requests is relatively large compared to the number of control slots. The method of claim 8, wherein the base station considers the congestion when an available empty information slot exceeds a preset limit. The buffer of any one of claims 8 to 11, wherein the buffer of the constant rate (CBR) terminal and the real-time variable rate (Rt-VBR) terminal is set to a size of a product obtained by multiplying a maximum transmission rate and a cell transmission delay time. A traffic control method in a wireless mobile terminal. 12. The wireless mobile terminal of claim 8, wherein the buffer of the NRT-VBR terminal is set to a size multiplied by an equivalent bandwidth and a maximum transmission delay. Traffic control method.