KR100599534B1 - Adaptive Grouping Method for Wireless MAC Protocol - Google Patents

Abstract

The present invention is applicable to a wireless MAC protocol, and relates to a method for quickly resolving a collision caused by simultaneous transmission of wireless terminals sharing a medium.

In the present invention, the base station informs the base station through the appropriate signaling procedure while maintaining the split state information of each terminal in order to determine its access position, or splits itself using the information received by the base station at the time of network registration It suggests how to maintain state information.

In addition, in the present invention, in order to operate the length of the contention period in accordance with the network situation, the conflict resolution algorithm repeatedly performs division and merging of the groups so as to generate an adaptive state change, depending on the traffic state of the contention period. It can operate adaptively and propose a method to calculate the length of the competition section based on this.

MAC, Wireless Media, Media Access Control, Splitting

Description

Adaptive Grouping Method for Wireless MAC Protocol

1 is a flowchart illustrating a contention access process performed by terminals of the present invention.

2 is a flowchart illustrating a method of operation at the base station side of the present invention.

3 is an explanatory diagram of a splitting method.

4 is a diagram illustrating an upstream configuration of a wireless MAC protocol.

Figure 5 shows the division and merging process of each group of the present invention.

The present invention is applicable to the wireless MAC protocol, and the collision occurs when the wireless terminals sharing the medium are simultaneously transmitted, and a method for solving this as soon as possible.

 The wireless MAC protocol stipulates that message delivery such as a registration procedure or a bandwidth request of a terminal occurs in a contention period. Using a competition-based protocol for this purpose is quite efficient, but appropriate countermeasures against collisions are needed. A collision is a phenomenon in which two or more network entities start transmitting at the same time, resulting in data loss. If a collision occurs, additional bandwidth is required to resolve it, which reduces throughput, and delays the time for registration or bandwidth allocation requests to be delivered. Therefore, conflict resolution schemes have a significant impact on throughput. Go crazy. Collision resolution methods include splitting and binary exponential back-off.

< Splitting method>

The basic idea of the splitting approach is to resolve the conflicting network entities into n subgroups. In general, n = 2 or n = 3, in which one group is selected from among the divided subgroups to resolve the conflict first, and the other subgroups wait for transmission during this period. This process can be thought of as an n-ary tree structure, a basic example of which is shown in FIG. 3.

In the splitting method, the message generated during the conflict resolution period is postponed, so that the splitting method can be divided into a tree method maintaining a tree structure and a stack method of solving a new message together.

< Truncated Binary Exponential Random Back-off (TBERB) Method>

The TBERB method is widely used for ALOHA series protocols and is a standard of IEEE 802.3 Ethernet LAN. The basic philosophy of this approach is to suppress the occurrence of continuous collisions by spreading messages retransmitted by collisions in time.

The conflict resolution procedure is as follows.

a) The network entity transmits using the first time slot accessible when a new packet occurs.

b) The network entity waits for a feedback message.

c) If n collisions occur, generate one random number in the range of 1 to 2n, wait for that number, and try to retransmit (generally n ≤ 10).

d) If retransmission is repeated for a certain number of times and the collision is not resolved, then the packet is discarded.

The TBERB method includes a p-persistence method considering the temporal fairness between collided packets and new-comers and a Pseudo-Bayesian method considering stability.

The two prior arts are used for collision resolution. In fact, the splitting scheme is known to have a lower delay time than the TBERB scheme.

In general, the collision resolution scheme under the wireless MAC protocol plays an important role in determining the position and length (number of time slots) of a contention section in the entire frame format. Therefore, in order to apply the splitting scheme to the wireless MAC, several factors need to be modified.

First, when a collision occurs and splits, each terminal must determine a location to be split. This means that the current split state information must be maintained at the base station or the terminal.

Second, there is a need for a method of adjusting the length of the competition section to match the network situation. In other words, if there is more access to the competition section, the competition section should be longer, and if it is slightly reduced, the length of the competition section should be shorter. However, this is an area that cannot be solved by the splitting method alone, so a separate method is required.

The present invention is to solve the problems of the prior art, an object of the present invention is to inform the base station through the appropriate signaling procedure while maintaining the state information of each terminal in order for the divided terminal to determine its access position, It is to provide a method for each terminal to maintain the split state information by using the information received at the base station registration network.

Another object of the present invention is to adjust the length of the competition section according to the network situation, the collision resolution method is adaptive (adaptive) state change to perform the division and merging of the group repeatedly according to the traffic conditions of the competition section It is possible to operate adaptively and to provide a method for calculating the length of the competition section based on this.

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

The present invention aims to propose a conflict resolution method for the wireless MAC protocol and to determine the length of the contention interval thereby.

4 is an upframe structure diagram of a wireless MAC assumed in the present invention.

Most demand-assignment wireless MAC protocols have a similar form.

In this environment, the present development technology will be described in detail with reference to FIG. 1, and the process of solving the problems of the conventional technology presented above is as follows.

1 is a flowchart illustrating a contention access process performed by terminals of the present invention.

In the present invention, the competition section access process performed by each terminal is as follows.

Generating data to be transmitted through the competition section (S10);

Receiving contention section access information from the base station (S12),

Determining a timeslot to which the user can access based on the received base station information (S14);

Receiving contention interval access result information from the base station (S16);

If there is a collision or transmission fails due to a channel error, the method returns to step S12 and retransmits (S18).

Looking at the contention interval access process of the terminal in the above process, it can be seen that two types of information should be received from the base station.

The first information is competition section access information, which is a time slot position of a competition section that each group can currently access. As mentioned above, the base station maintains state information of each divided group and allocates time slots of contention intervals to each group according to a policy. Each terminal does not need to know what group it belongs to. This is because it is only necessary to look at the information broadcast from the base station to determine the location of the timeslot to be accessed.

In addition, the second information that the terminal should receive from the base station is the competition section access result information. In the present invention, this is divided into two types: transmission success and transmission failure. Each terminal may determine whether to retransmit according to these two states, or to transition to waiting for the next higher layer data. Transmission failure is divided into failure due to collision and failure due to transmission medium characteristics. If the two can be distinguished by hardware functions, unnecessary partitioning process caused by transmission medium error can be eliminated.

2 is a flowchart of an operation performed at the base station side of the present invention.

Referring to FIG. 2, the process of managing the competition section performed by the base station in the present invention is as follows.

Grouping all terminals into one group (S102);

Allocating time slots of a contention period by the number of groups currently registered (S104);

Broadcasting the location and number of time slots and a list of terminals that can use the slots (S106);

Receiving a terminal access in the standby state (S108),

During the competition period of the uplink frame, determining whether the terminal accesses (S110),

If there is a slot of the contention in which the collision occurred, dividing the group using the slot (S112);

If there is a slot of a contention section in which transmission is successful, maintaining the group using the slot as it is (S114),

If there is an empty slot, merging with the group using the slot and the group with few members (S116),

And broadcasting whether the channel is used or not, and returning to step S104 (S118).

As described above, it can be seen that the base station delivers two types of information to the terminal. The important thing is that the number of groups currently registered changes variably. If there is a collision in the slot used by the group, the group is divided, and if no one has access to the competition section among the members, merging with other groups occurs. .

Using the present invention can solve two problems of the conventional splitting method.

That is, first, to determine its access position, the divided terminal can know only by listening to the message broadcast from the base station. For this purpose, it is not necessary to define a separate signaling message. In general, a slight modification of the message broadcasted by the base station for the medium access control in the wireless MAC is required.

Second, in order to operate the length of the contention period according to the network situation, it has already been mentioned that the collision resolution method must generate an adaptive state change. That is, a large number of contention interval time slots are allocated when there are many accesses to a contention interval, and a small number of time slots are allocated when there are few.

As described above, in the present invention, when there are many collisions due to a lot of access to the contention period, the number of divided groups increases and thus the number of time slots increases. This reduces the number of groups, which in turn reduces the number of time slots.

5 shows a process of splitting and merging of four terminals of the present invention. In FIG. 5, a small number of terminals are selected for example. The first group G ₁ can be seen that all four terminals are registered. In this case, one time slot is allocated to the contention period. However, if a collision occurs, G ₁ divides the terminal into two subgroups. In this case, therefore, two time slots are needed in the contention period. Similarly, when one of these two subgroups is divided, three time slots are allocated, and finally four time slots have to be used.

According to the present invention, it is possible to improve the overall performance of the protocol by suggesting a fast collision resolution method of the contention within the wireless MAC protocol, and to adaptively calculate the length of the contention within the entire uplink frame.

Claims (4)

In the conflict resolution method for a wireless MAC protocol, Repeatedly performing division and merging of groups by generating an adaptive state change within a contention period; Adaptively operating according to traffic conditions of a contention section; A collision resolution method for a wireless MAC protocol comprising calculating a length of a contention section based on this. In a collision resolution method for a wireless MAC protocol including a contention section access process and a contention section management process, The competition section access process performed by the terminals, Generating data to be transmitted through the competition section (S10); Receiving the corresponding information from the base station (S12), Determining a timeslot to which the user can access based on the received base station information (S14); Receiving contention interval access result information from the base station (S16); If there is a collision or a transmission fails due to a channel error, returning to step S12 and retransmitting (S18). The method according to claim 2, And the information received from the base station is contention section access information and contention section access result information. In a collision resolution method for a wireless MAC protocol including a contention section access process and a contention section management process, The competition section management process performed by the base station, Grouping all terminals into one group (S102); Allocating time slots of a contention period by the number of groups currently registered (S104); Broadcasting the location and number of time slots and a list of terminals capable of using the slots (S106); Receiving a terminal access in the standby state (S108), During the competition period of the uplink frame, determining whether the terminal accesses (S110), If there is a slot of the contention in which the collision occurred, dividing the group using the slot (S112); If there is a slot of a contention section in which transmission is successful, maintaining the group using the slot as it is (S114), If there is an empty slot, merging with the group using the slot and the group having few members (S116), Method for resolving a conflict for the wireless MAC protocol comprising the step (S118) of broadcasting whether the channel is used or not.

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