KR100347731B1 - 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 that enables efficient resource utilization in multimedia traffic by using a combination of code division multiple access and packet reservation multiple access. Is divided into a reservation request section, a voice reservation section, and a round robin reservation / random access competition section, the reservation request section is divided into subslots, and the channel access of the data terminal calculated based on the channel access rate and the slot access function. Function to control the packet transmission of each data terminal in contention mode, and by selectively (or adaptively) using random access round robin or random access depending on the amount of input traffic for the data terminal, Multi-user by suppressing mutual interference that may occur between users of The efficiency of resource utilization in air traffic that will be realized.

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 time-division multiple access method and the code division multiple access method are mainly used as media access methods that are currently put into practice, and each of these methods has different advantages and disadvantages in satisfying various levels of service quality. Have

In this case, the time division multiple access scheme has a relatively low complexity and a relatively easy implementation of multimedia services by varying the number of slots to be allocated, but has a disadvantage in that many restrictions are placed on the number of acceptable users. The partitioned multiple access scheme has the disadvantage of being unsuitable for high-speed multimedia services because it can accommodate a large number of users and has a strong advantage against various types of interference, while increasing the complexity of the system in high-speed transmission.

Therefore, as one of the methods for solving the problems of the two methods described above, an algorithm combining the characteristics of the two methods has been introduced, one of which is a random access method. However, this approach has a problem of low overall link efficiency since the slot is accessed in the same manner as slotted Aloha (ALOHA).

In addition, a hybrid code division multiple access / packet reservation multiple access algorithm has been introduced as an advanced algorithm than the above-described random access scheme. In this advanced algorithm, a probability proportional to the number of terminals that reserved a slot access is provided. Control method. Thus, advanced algorithms perform better than the random approach described above.

However, the above-described advanced algorithm simply applies the packet reservation multiple access scheme to the code division multiple access scheme, and thus, there is a problem that an increase in the packet discard rate due to collision between packets lowers the efficiency of the link. It is a fundamental problem that efficient resource allocation is difficult because it is difficult to optimize the acceptance probability function. Therefore, the traffic control method according to the conventional method described above has a fundamental problem that it is not suitable for multimedia services.

Accordingly, the present invention is to solve the above problems of the prior art, by using a combination of code division multiple access and packet reservation multiple access traffic control in a wireless mobile terminal that can realize efficient resource utilization in multimedia traffic The purpose is to provide a method.

In order to achieve the above object, the present invention provides a method for controlling traffic for channel reservation 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. In the above, each frame in voice and / or data traffic is divided into a reservation request section, an N slot voice reservation section, an N slot round robin reservation / random access competition section, and the reservation request section is divided into a voice. The method is divided into a reservation request subslot for a terminal and a round robin reservation request subslot for a data terminal. The method includes packet transmission using a random access method and a round robin method according to the amount of input traffic for data traffic. Wireless traffic control characterized in that for adaptive A traffic control method in a mobile terminal is provided.

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;

2 is an exemplary diagram showing a state of a packet transmitted from each terminal to a base station as an example;

3 is a frame structure diagram adopted in accordance with a preferred embodiment of the present invention,

4 is a graph illustrating a relationship between a slot access function and a channel access ratio as an example;

FIG. 5 is a graph illustrating delay characteristics of a data packet according to a change in a channel access permission function (CPR), assuming 170 terminals share 20 codes.

6 is a structural diagram illustrating a round robin scheme selectively used according to the amount of input traffic in a data terminal according to the present invention;

7A, 7B, and 7C illustrate a process of a voice terminal requesting a reservation using a reservation request subslot, transmitting a voice packet through a slot allocated in a voice active period, and releasing the allocated slot in a voice idle period. Also illustrated as an example for the purpose of

8 is an example diagram illustrating a process of requesting a reservation by a data terminal in a round robin manner, transmitting a packet using an allocated slot, and releasing the allocated slot after packet transmission is completed;

9 is an experimental graph illustrating a process of changing a packet discard rate according to the number of voice terminals;

10 is a process for switching from random access to round robin according to the amount of input traffic, when N is 40 and the value of the interval T3 in the frame is 9 according to the present invention. Experimental graph shown to illustrate.

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

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 divide a frame structure into a reservation request section, a voice reservation section, and a round robin reservation / random access competition section, divide the reservation request section into subslots, and allow a channel access permission ratio (CPR: By using the channel access function of the data terminal calculated based on the Channel access Permission Ratio) and the slot access permission function, the packet transmission of each data terminal is controlled in the contention mode, and random access is made to the data terminal according to the amount of input traffic. By using a round robin or random approach selectively (or adaptive), it is possible through these technical means to easily achieve the objectives of the present invention.

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) and base station 104. 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, for example, IMT-2000, and the like. Transmits the packet to the base station 104 using an assigned code or a randomly selected code among available codes (ie, unreserved codes) in a given code.

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 services, slot allocation and release, etc.), and when a reservation packet is received from each wireless mobile terminal through a reserved access channel, that is, When the terminal succeeds in the reservation, the terminal transmits information about a code and a slot necessary for transmitting the information packet to the terminal that has successfully reserved.

In addition, the base station 104 calculates a channel access function of the data terminal based on a channel permission rate (CPR) and a slot access permission function in the contention mode of the data terminal, and calculates each of the calculated channel access functions. By transmitting to the terminals in a broadcast manner, packet transmission at each data terminal is controlled.

Moreover, the base station 104 selectively (or adaptively) uses a random access round robin scheme or a random access scheme according to the amount of input traffic in the round robin reserved mode for the data terminal to perform packet transmission at each data terminal. To control.

To this end, in the traffic control method according to the present invention, as shown in FIG. 3 as an example, a time frame is divided into slots having a predetermined size, and a plurality of slots are combined to form a frame, that is, a frame is reserved. The request section T1, the voice reservation section T2, and the round robin reservation / random access competition section T3 are divided, and the reservation request section T1 is also reserved for the voice request terminal slot slot t1 and data. A frame structure is divided into a round robin reservation request subslot period t2 for the terminal. Here, the time axis of slots for each section is divided into a plurality of slots having arbitrary codes.

Therefore, in the frame structure according to the present invention, several terminals transmit packets to the base station 104 using different codes (for example, A, B, C, D, E, etc.) during one slot. In addition, the present invention uses a shared code concept to prevent performance degradation due to mutual interference between packets generated when many terminals simultaneously send packets to one slot, and to efficiently use limited code resources.

That is, given a set of shared codes that can be used under a given environment, a terminal in a network may receive one of the shared codes from the base station 104 (reservation mode) or randomly select one code (competition mode) to generate a packet. Will be sent. Accordingly, the base station 104 informs all terminals of the available codes (ie, unreserved codes) among the given codes at the start of each slot.

At this time, if all the terminals select different codes and send packets to the base station, all the transmitted packets will be transmitted without any problem, that is, slots K + 1 and K + 3 shown in FIG. 2 as an example. If two or more terminals select the same code (that is, in the case of code C of slot K of FIG. 2), packets of the terminal using the same code are discarded by collision according to two situations.

More specifically, if the number of terminals transmitting a packet through the slot exceeds the maximum number of users per slot (i.e., the maximum number of users that can be transmitted simultaneously while guaranteeing the bit error rate as desired under a given environment) (e.g., In the case of slot K of FIG. 2, at least four or more persons), since packet collision in the slot also affects packets using other codes, all packets transmitted through the slot are discarded. On the contrary, when the number of terminals transmitting a packet through the corresponding slot is smaller than the maximum number of users per slot (for example, when the number of terminals using the B code in slot K of FIG. 2 is 2), the same code (for example, For example, only packets sent using slot B in slot K are discarded and packets sent using other codes (e.g., A code in slot K) are correctly delivered without being discarded.

On the other hand, for voice traffic, the frame rate is determined by the packet arrival rate. That is, if only one packet is sent per frame, the voice traffic can satisfy a given transmission rate. In this case, the number of slots per frame and the number of bits per slot can be obtained under a given environment. Accordingly, the present invention employs a frame structure as shown in FIG. 3 as an example.

Referring to FIG. 3, T1 indicates a reservation request interval. In general, since a control message such as a reservation request requires a smaller amount of information (smaller bit amount) than user's actual data, the slot is divided into several sub slots. Can be. At this time, the maximum number of sub-slots that can be divided can be obtained based on given parameter values. That is, as an example, the T1 section is divided into two sections t1 and t2, wherein the first section t1 is a reservation request subslot for the voice terminal and the second section t2 is a round robin reservation for the data terminal. Request subslot. In this case, in the case of voice traffic, a message for reserving one slot through a reservation request subslot may be transmitted at the time when the voice active interval starts.

In addition, T2 represents a voice reservation section, and assumes that a resource reserved by a reservation request of a voice terminal is allocated to this section and that no collision or interference occurs because the resource allocation in this section is controlled by the base station. Can be. Here, the reserved resources are allocated to be equally distributed to all slots in the interval T2. In this case, since the code usage situation of one slot is always monitored by the base station, the base station may request a power level corresponding to the situation of the slot from each terminal. Therefore, if a maximum user per slot rarely approaches a slot, the required power level of the terminal may be reduced.

Next, T3 represents a round robin reservation / arbitrary contention competition interval in which two types of access are allowed, i.e. resources from random access for data with small amounts of data and small access delays are allocated to this interval. The resource of the data terminal by the round robin reservation request is allocated to this interval. At this time, the terminal accessing by competition is determined whether to allow access in consideration of the current state of the slot, that is, the reservation status of the slot.

Meanwhile, the traffic control method according to the present invention has a reservation mode, a competition mode, and a round robin reservation mode.

In the reserved mode of the above modes, a voice terminal that successfully reserves one slot by using a reserved slot is assigned one slot from a base station, and is also given a code to be used at this time, and the corresponding terminal is voiced. The assigned code of a given slot is used exclusively during the active period. At the end of the voice active period, the reservation is released, and the released resource is allocated to another terminal.

Therefore, the voice terminal uses one bit of the transmitted packet as the reservation release identifier information to inform the base station of the release time of the reservation. For example, if the reservation release identifier information bit is "1", the reservation for the slot is continued. If it means "0", it means to reserve the slot. Accordingly, the base station performs slot control such as reservation maintenance or reservation cancellation of the corresponding slot based on the reservation release identifier information included in the received packet.

Next, in the contention mode, there are two types of contention for acquiring resources, that is, contention of voice terminals in a reserved slot, and contention mode in which a data terminal transmits a packet in a random approach.

First, when voice terminals are competing, given a certain amount of resources because the arrival rate of a reservation message of one terminal in one slot is very small, approximately 1 / (average voice active interval length + average voice idle interval length). A very small reserved sub packet discard rate can be maintained. Therefore, when the voice active period starts, the voice terminal randomly selects one of a plurality of sub slots, randomly selects one of the available codes (all codes can be used in the case of a reserved slot), and then uses the selected sub slot and code. Send a reservation message (reservation packet). At this time, if the reservation packet is discarded due to interference or collision, the terminal attempts to transmit again in the next frame.

In this case, since the voice packet has a delay sensitive characteristic, a packet delayed for a certain time is not useful and is discarded without being transmitted from each terminal. In the present invention, since the maximum allowable delay time is set to one frame time, one packet is discarded by discarding one reservation request message.

Secondly, when data terminals are competing when trying to transmit a packet by random access, the data terminal first selects one of the available codes first, and the number of codes already reserved in the corresponding slot, that is, from the base station. Based on the reservation code number information (ie, slot access function) transmitted by the broadcasting method, it is determined whether to transmit a packet to the corresponding slot. If a large number of codes are already reserved in the slot, the base station will transmit a channel access function with a small probability of transmission in order not to affect other reserved codes by interference or collision. If only a small number of codes are reserved (i.e., a large number of available codes), the base station will transmit a channel transmission function with a relatively high probability of transmission because of the relatively low probability of interference or collision. That is, the base station performs channel access control based on the number of users already reserved in each slot.

Accordingly, in view of the above, the base station calculates the channel access function, that is, calculates the channel access function based on the slot access allowance function and the channel access allowance ratio (CPR) for the current traffic situation. Broadcast a function to each terminal.

4 is a graph illustrating an example of a relationship between a slot access permission function and a channel access permission ratio (CPR).

Referring to FIG. 4, since a given function represents a general trend, the value of this function needs to change dynamically in order to meet a dynamically changing traffic situation. However, in view of the fact that it is practically impossible to obtain a function suitable for all traffic conditions, the present invention simplifies the calculation using a channel access permission function (CPR). Here, the channel access permission function (CPR) value is multiplied by the slot access permission function to generate an optimal channel access function for each traffic situation.

FIG. 5 is a graph illustrating delay characteristics of a data packet according to a change of a channel access permission function (CPR) as an example, when 170 terminals share 20 codes.

Referring to FIG. 5, since the channel access probability increases as the CPR increases, each terminal receives more opportunities to transmit data. However, when the channel access permission function (CPR) is above a certain value (for example, CPR = 0.17), it can be seen that the delay value of the packet transmission is suddenly increased. This is an increase in delay due to interference caused as a result of the transmission. Therefore, in the above traffic environment, the channel access permission function (CPR) has a value of 0.17.

On the other hand, the random access method in the data terminal, as is well known, shows a very good performance in a low traffic situation, but as the amount of traffic increases, a sharp performance decrease. This is a fundamental problem with random access, and it can never be the preferred access control in traffic situations that exceed a certain amount. Therefore, in the present invention, to improve this point, the round robin reservation service technique is adaptively (optionally) used with a random approach.

That is, the data terminals are allocated a round robin reservation request subcode (that is, a code assigned to the subslot of FIG. 3 called a subcode) resource required for a reservation request from a base station in a call setup process. Accordingly, as an example, as shown in FIG. 6, the number of frames per round robin period K is determined as in the following equation so that all terminals can make one or more reservation requests during one round robin period L. FIG. .

In Equation 1, reference numeral M denotes the number of round robin reservation request resources per frame, S denotes the total number of subcodes during one round robin period, and Md denotes the number of data terminals for which the call request was accepted. Indicates a number.

That is, the data terminal having the packet to be transmitted to the buffer requests reservation from the base station using the given sub code when its turn returns to the round robin reservation request slot, and the base station requests the resource in the interval T3 shown in FIG. Is allocated to the corresponding data terminal for which the reservation is requested. In this case, the allocated resource may be exclusively used by the corresponding data terminal every frame. Then, the allocated resources are released when there is no more data to send to the buffer.

Subsequently, when a new packet is generated in the corresponding data terminal, the above-described processes (that is, a reservation request process, a resource allocation process, a packet transmission process, etc.) are repeated to transmit the packets to the base station. In the above-described process, when the data terminal is allocated resources, one or more resources may be allocated according to the characteristics of the traffic. If the resources to be allocated are insufficient, the base station may allocate resources based on the characteristics of the traffic, that is, priority. By allocating, to satisfy the quality of service of each traffic. For example, when resources are allocated between voice and data when there is not enough allocated resources, priority is given to voice when allocating resources between data and constant data rate. When content is allocated between data, constant bit rate (CBR), Real-time variable bit rate (Rt-VBR), non-realtime variable bit rate (Nrt-VBR), available bit rate (ABR), unspecified bit rate Resources are allocated with priority in order of).

In more detail, a process in which a voice terminal is allocated a resource from a base station, transmits a packet to the base station using the allocated resource (slot), and releases the allocated resource.

First, when a voice active period starts, as shown in FIG. 7A, the voice terminal stores the generated bit stream in a buffer and attaches a header to the stored data for one frame time to generate a packet consisting of a header and a payload. do.

Then, the voice terminal requests a reservation by transmitting a message for reservation request to the base station by using the reservation request subslot shown in FIG. 3. That is, as an example, as shown in FIG. 7B, a reservation request is made using a second subslot and code A, and as a result of the request, a code C resource of slot 2 is allocated from the base station.

Subsequently, as shown in FIG. 7C, the voice terminal transmits the packet generated in the voice active period for K + 9 hours in the frame K to the base station through the allocated resource. Releases the resources allocated to the voice terminal.

Next, a process of transmitting data packets to the base station by allocating resources in a round robin manner and releasing the allocated resources will be described.

FIG. 8 is an exemplary diagram illustrating a process of requesting a reservation in a round robin manner, transmitting a packet using an allocated slot, and releasing the allocated slot after packet transmission is completed.

In FIG. 8, as an example, assuming that a reserved sub code of a data terminal is allocated to a K + 1th frame of a round robin period L, the first packet is generated during the third frame in the data traffic generation process illustrated in FIG. 7B. Although the data terminal cannot make a reservation request to the base station, the data terminal waits until the K-1 frame starts. At this time, the packet generated while waiting is stored in the buffer of the terminal.

Then, when a K + 1 frame starts, a reservation request is made to a base station using a reservation request sub code in a K + 1 frame, and one slot is allocated from the base station to the section T3 shown in FIG. The packet stored in the buffer is transmitted by using the slot of the base station. When the transmission of the packet is completed, the base station releases the allocated resource.

The inventors of the present invention conducted an experiment on the increase and decrease of the packet discard rate according to the increase and decrease of the voice terminal for the random access method and the joint cdma prma (packet reservation multiful access) (JCP) method, as shown in FIG. Got.

In the present experiment, the random access method is a case in which there is no restriction in channel access, and it is assumed that all terminals have different codes. As can be seen from the graph shown in FIG. Since there is no restriction, it can be seen that as the number of voice terminals increases, more interference occurs and the packet discard rate increases.

In addition, JCP is controlled by using a packet reservation multiple access method, which also assumes that all terminals have different codes. Channel access in the JCP is affected by the number of terminals already reserved in each slot. The traffic control method according to the present invention operates similarly to the method used in the JCP.

In this experiment, N = x is a case in which the number of codes is allocated to the number of terminals by 9, 29, 40, 80, and 200 so as to be shared. Therefore, as the number of codes increases, the number of codes that can be used in the reservation request subslot increases, so that the packet discard rate caused by the selection of the same code can be reduced, thereby improving performance of traffic control. At this time, as can be seen from Figure 9, if the number of terminals increases to some extent, the number of codes does not have a significant effect on the packet discard rate, which has a large effect on the traffic control performance, rather than the number of codes available reservation It means the amount of resources.

Accordingly, the present invention employs a technique of selectively using a random access method and a round robin method in accordance with the amount of input traffic for data traffic.

10 is a process for switching from random access to round robin according to the amount of input traffic, when N is 40 and the value of the interval T3 in the frame is 9 according to the present invention. As an experimental graph shown to illustrate, it can be seen that the method according to the present invention shows a performance almost close to the post prediction probability.

That is, in the case of the random access method, the transmission delay of the packet increases exponentially as the amount of traffic increases. Considering this, in the present invention, when the amount of traffic reaches a predetermined turning point, the random access terminals are selected. Switch to round robin.

Referring to FIG. 10, two approaches (an arbitrary approach and a round) where an experimental graph according to a random approach meets an experimental graph according to a round robin method (when N = 40 in FIG. 9 and the data terminal is about 180 or more) Robin method) is a tradeoff point (TP) to be switched. That is, according to the traffic control method according to the present invention, in a small traffic situation, a random approach is used, and when the amount of input traffic increases to reach the turning point TP, the traffic switching method is round robin. At this time, in the round robin method, since a resource for requesting a resource has been granted in advance, interference or collision occurring in a random access method does not occur.

Here, the switching point for switching from the random approach to the round robin method is a system parameter, which may be calculated in advance by designing a system using a traffic control method according to the present invention or by simulating a system upgrade. The calculated value can be set and used.

As described above, according to the present invention, the frame structure is divided into a reservation request section, a voice reservation section, and a round robin reservation / random access competition section, a reservation request section is divided into subslots, a channel access allowance rate and a slot access allowance. It controls the packet transmission of each data terminal in contention mode by using the channel access function of the data terminal calculated based on the function, and selects the random access round robin or random access method for the data terminal according to the amount of input traffic. By using (or adaptively), it is possible to suppress mutual interference that can occur between a large number of users, thereby realizing (maximizing) resource utilization in multimedia traffic.

Claims (8)

A method of controlling traffic for channel reservation 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 frame in voice and / or data traffic is divided into a reservation request section, an N slot voice reservation section, and an N slot round robin reservation / random access competition section, and the reservation request section is divided into two parts for a voice terminal. Split into a reservation request subslot and a round robin reservation request subslot for a data terminal, The method is a traffic control method for a wireless mobile terminal, characterized in that adaptively control the traffic for packet transmission by selectively using a random access method and a round robin method for the data traffic. The method of claim 1, wherein the base station calculates a channel access function based on the number of reserved codes, and then broadcasts the channel access function calculated for each terminal every one frame period, and each data terminal is based on a random access scheme. And determining packet transmission based on the channel access function received at the time of packet transmission. The wireless mobile terminal of claim 2, wherein the channel access function is calculated by multiplying the channel access permission ratio by a slot access permission function obtained based on a channel access permission ratio and the number of users reserved in the slot. Traffic control method. The method of claim 1, wherein the number of frames per one round robin period is determined by the length of a period during which all data terminals can make at least one reservation request during one round robin period. Way. 5. The method of claim 4, wherein the number of frames per one round robin period is determined by the following equation. In the above equation, reference numeral M denotes the number of round robin reservation request resources per frame, S denotes the total number of subcodes during one round robin period, and Md denotes the number of data terminals on which the call request was accepted. .) The method of claim 4, wherein if an unreserved resource that can be allocated at the time of resource allocation according to the round robin reservation request is not suitable for satisfying the quality of service, the resource is selectively allocated to the corresponding terminal based on the priority. Traffic control method in a wireless mobile terminal. 7. The method of claim 6, wherein the method assigns resource allocation priority to the voice terminal when the voice terminal and the data terminal contend for resource allocation. The wireless mobile terminal of claim 6, wherein the method assigns resource allocation priority in order of CBR, Rt-VBR, Nrt-VBR, ABR, and UBR when competing for resource allocation among data terminals. Traffic control method in.