KR100664020B1 - Mac scheduling method for bluetooth - Google Patents

Abstract

The present invention relates to a MAC scheduling technique for improving performance in a Bluetooth system. The present invention checks the packet size of a plurality of queues allocated between a master and a plurality of slaves at any time in the scheduler, and thus has a master-slave having a queue close to the maximum payload according to a defined packet type between each master-slave. Comparing a first process of giving a higher transmission priority to the second process, comparing the maximum number of services received and the minimum number of packets transmitted from a plurality of queues, and the difference in the number of serviced times of the two packets to be compared is smaller than a preset threshold. The packet is serviced according to the transmission priority, and if the packet is larger than the threshold, the unserviced packet is serviced.

Description

How to schedule an MC in Bluetooth {MAC SCHEDULING METHOD FOR BLUETOOTH}

1 is an exemplary diagram of maximum payload according to each packet type.

Figure 2 is a signal flow diagram of the MC scheduling method according to the present invention.

*** Description of the symbols for the main parts of the drawings ***

S1-S7: steps 1-7

The present invention relates to MAC (MAC) scheduling technology for improving performance in a Bluetooth system, and in particular, MC scheduling of Bluetooth for sharing bandwidth and link utilization evenly when transferring data between master and slaves. It is about a method.

Recently, due to the advancement of home networking technology, research is being actively conducted to equip various home appliances with Bluetooth. Bluetooth aims to achieve a maximum data transfer rate of 1Mbps (actually up to 721kbps) and a maximum transmission distance of 10m. 1Mbps is the highest transfer rate that can be realized easily and at low cost by utilizing Industrial Scientific Medical (ISM) in the 2.4GHz band that users can use without a license. An optional amplifier, such as an output amplifier, can transmit up to 100m. That is, Bluetooth transceivers within 10m can be automatically connected and send and receive data without a separate cable.

Looking at the operation of Bluetooth briefly, Bluetooth devices are composed of a minimum unit called a piconet, and these piconets are gathered to form a higher unit called a scatternet. Devices in the same piconet will have the same frequency hopping pattern, and if they belong to different piconets even if they are in the same scatternet, they will follow different types of frequency hopping patterns. A piconet starts with two connected devices, such as a portable PC and a mobile phone, and can have up to eight devices in a single piconet.

In addition, these Blue Pitcher devices are divided into one master device and up to seven slave devices. Any device in a piconet can be a master device and a master device of one piconet can be a slave of another piconet at the same time. Bluetooth devices check for new messages every 1 second in standby mode when the communication is interrupted, the device requesting service becomes a master and starts the recognition of peripheral devices, and the other devices act as slaves to form a piconet. do.

To date, the round robin method is mainly used as a medium access control (MAC) technology, and a buffer according to each slave is allocated to execute a certain time called a quantum. However, the Bluetooth piconet situation is a situation in which multiple transport layer sessions share a radio link on a piconet when multiple slaves operate or a slave is in a multiple data connection state. In addition, round robin scheduling scheduled at the master can equally share bandwidth and link utilization when each master-slave connection has the same data flow. In most cases, however, each slave in the piconet has a varying input ratio. Thus, many baseband slots are wasted by polling resources that have a low input rate.

As described above, in the conventional MAC scheduling technique, in each case, each slave in the piconet has various input ratios, and thus, many baseband slots have a defect in wasted by polling resources having a small input ratio.

Accordingly, it is an object of the present invention to provide an MC scheduling method of Bluetooth that shares bandwidth and link utilization evenly when transmitting data between master and slaves.

According to the first aspect of the present invention, the master-slave having a queue closest to the maximum payload, rather than transmitting data uniformly according to a predetermined period between the master and the slave, is higher than the master-slave. The priority is to transfer data by assigning priority.

According to the second aspect of the present invention, in order to prevent the starvation phenomenon of the master-slave from occurring by preempting the master-slave with a small packet type continuously, the master-service already applied by applying the maximum-minimum algorithm- The slave increments the service count value, and transfers the service authority to Qmin when Qmax-Qmin exceeds the threshold according to the maximum payload rate.

In the MC scheduling method of Bluetooth according to the present invention, the scheduler checks the packet size of a plurality of queues allocated between a master and a plurality of slaves at an arbitrary time, and determines the maximum payload according to a packet type defined between each master-slave. Assigning higher transmission priority to a master-slave with adjacent queues, comparing the maximum number of services received and the minimum number of packets transmitted from the plurality of queues, and the number of serviced times of the two packets being compared. When the difference is smaller than a predetermined threshold, the packet is serviced according to the transmission priority, and when the difference is larger than the threshold, the unserviced packet is serviced. When described in detail with reference to as follows.

As shown in FIG. 1, if the input queue is in a first-in-first-out (FIFO) order, and the buffer of the other slave slave (Master-Slave Pair) is full when the packet in the header of the master queue is to be transmitted, HOL (HOL: Head) Of line) packet blocking occurs to transmit the packet to another slave.

In order to prevent such HOL blocking, there is a queue for each slave in each master.

Looking at the Bluetooth specification, you can see that it provides various packets for transmitting data. Typically, access control list (ACL) links use DH or DM packets, and the maximum payload (bytes) for data varies by packet type.

In the present invention, the scheduler checks the packet size of the queues at any time and gives higher priority to the master-slave having the queue closest to the maximum payload according to the defined packet type between each master-slave. Introduced the scheduling scheme to transmit to the network. Here, the consideration should be to fill the maximum payload according to the packet type of the selected master-slave queue as much as possible to increase the efficiency of the link.

However, when two queues, for example, a queue transmitting DH1 packets and a queue transmitting DH5 packets are contended (assuming that the maximum payload is DH1 <DH5), DH1 packets having a small maximum payload are preemptively. The case occurs. To prevent this from happening, a counter is assigned to each packet to count the number of times serviced, and a difference between the maximum serviced value (QMAX) and the minimum count value (QMIN) that is serviced is a preset threshold (eg, QMAX-QMIN). <12) was not exceeded. In other words, even packets with a relatively large maximum payload can be serviced at some point.

For reference, in the scheduler of FIG. 1, the maximum payload is 27 bytes for the DH1 packet, 183 bytes for the DH3 packet, and 339 bytes for the DH5 packet. The threshold is set according to the relative ratio of the maximum payload of DH5 to the maximum payload of DH3 and the maximum payload of DH1, and each packet type is calculated based on the smallest maximum payload on the master-slave. do.

For example, if the DH1 packet is serviced six times while the DH3 packet is not serviced, the service is unconditionally serviced. If the DH1 packet is serviced 12 times, the DH5 packet is serviced unconditionally. If the DH3 packet and the DH5 packet are competing, the threshold value is set to three. The threshold is limited at the ACL link based on the case where there is no FEC.

Meanwhile, the MAC scheduling process will be described with reference to FIG. 2.

A queue is created for each slave, and if there is data to be transmitted in the queue, the backlog on the packet is set to 1 (S1-S3).

Next, the packet type is checked, and the closest queue is found by comparing the size of the data remaining in the queue with the maximum payload of the preset packet type (S4).

After that, if the difference between the selected queue and the minimum serviced queue is compared with the preset threshold, and the difference is less than the threshold, the data close to the maximum payload is transmitted and its service count is " It resets to 0 "and if it is higher than the threshold, the queue which has not been serviced yet is transmitted first. (S5-S7)

As described in detail above, the present invention has an effect of improving transmission performance by scheduling the bandwidth and link utilization to be equally shared when transmitting data between master and slaves.

Claims (2)

Checking the packet sizes of the multiple queues allocated between the master and the multiple slaves, and assigning higher transmission priority to the master-slave having a queue closer to the maximum payload according to the defined packet type between each master-slave; MC scheduling method of Bluetooth characterized in that it comprises the step of transmitting the packet in the order of the high transmission priority. The method of claim 1, wherein the transmitting of the packet comprises And if the service recovery difference between the packet to be serviced and the unserviced packet is greater than a preset threshold, then performing the service of the unserviced packet to be serviced.

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