KR20060014900A - Intermediation Method of Transmission of Beacons - Google Patents

Abstract

The present invention relates to a method for inter-transmission arbitration of beacons, and more particularly, to a method for mediating transmission between beacons in which all beacons get a fair transmission opportunity and improve channel utilization when inter-transmission beacons collide. will be.

The inter-transmission arbitration method of the beacons of the present invention comprises the steps of: setting the priority bit of the beacon to the dominant or recessive bit level, and detecting the channel level; Transmitting SOF bits of dominant bit level by the channel level; Detecting the channel level and comparing the channel level with a transmission level; Transmitting a next arbitration bit and detecting a channel level; Detecting the channel level and comparing the channel level with the transmission level; Determining whether transmission of the arbitration bit is completed; Transmitting an ultrasonic pulse and the remaining frame; Assigning a low priority to the beacon after the transmission is completed; And determining whether transmission of all data frames has been completed.

Accordingly, the inter-transmission arbitration method of the beacons of the present invention resolves collisions that may occur between transmissions of beacons, thereby guaranteeing a fair transmission opportunity for all beacons, thereby avoiding transmission failures of beacons and improving channel utilization to update position of the positioning system It has the advantage of increasing the rate or information update rate, and beacons that transmit successfully give low priority, and beacons that give up transmission during the arbitration process give high priority, thus ensuring equal transmission opportunities for all beacons. have.

Beacon, Collision, Send, Mediation, Priority

Description

Method for arbitrating transmissions between beacon}             

1 is a block diagram illustrating a data frame of an RF signal according to the present invention.

2 is a flowchart illustrating a method for arbitration between transmissions of beacons according to the present invention.

    <Explanation of symbols for the main parts of the drawings>

     100. SOF Field 110. Arbitration Department

     120. Message section 130. EOF field

     140. IFS Field 150. Priority Bits

     160. ID field

The present invention relates to a method for inter-transmission arbitration of beacons, and more particularly, to a method for mediating transmission between beacons in which all beacons get a fair transmission opportunity and improve channel utilization when inter-transmission beacons collide. will be.

In the ubiquitous environment, context-aware application services will be widely deployed in which the behavior of the user device and the user interface are adaptively changed according to the properties and conditions of the physical environment presently located. The user's location information is very important and essential for situational awareness.

In the outdoor, user's location information can be obtained through GPS (Global Positioning System), but proper positioning technology is needed for indoor ubiquitous environment where computing resources are concentrated. In addition, research is being conducted on positioning technology using RFID (Radio Frequency Identification) to replace GPS outdoors.

Conventional indoor positioning technologies include the RADAR (1999) and Easy Living (2001) systems at Microsoft Labs, the Active BAT system at AT & T Labs (1999), the Smart Floor (2000) at Georgia Institute of Technology, and SpotON (University of Washington). 2000). However, this technique has a problem in protecting privacy for a user's location as a location tracking system rather than location recognition.

In order to have a privacy-protected structure, the positioning system for ubiquitous computing should have a structure in which a beacon for positioning transmits and a user device receives the position recognition. It should also be a distributed structure without any kind of centralized control between the beacons to facilitate extended deployment of the positioning system. Therefore, each beacon should try to transmit asynchronously and irregularly, and take distributed contention based transmission.

Indoor positioning systems for ubiquitous computing include cricket systems (2000) developed by MIT University in the United States, ISP systems (2002) at Bristol University in the UK, and DOLPHIN systems (2003) at Cambridge University. It has the best technology and structure to apply to the environment.

The cricket system consists of a plurality of beacons mounted on the ceiling and a listener attached to a mobile computing device. At least four distances from the beacon are needed to calculate the position of one listener. In order to measure the distance from the listener to the beacon, each beacon simultaneously transmits ultrasonic pulses (sound speed) and RF carriers (light beam) with different propagation speeds. The listener calculates the distance to the beacon by measuring the difference in arrival time between the received RF carrier and the ultrasonic pulse. In this case, the distance between the beacons and the listeners is increased so that the time difference between the two signals increases.

In order to distinguish between the RF carrier and the ultrasonic pulse pair of each beacon in a situation in which a plurality of beacons transmit the ultrasonic pulse and the RF carrier so that ultrasonic waves transmitted from different beacons may be mixed, first, each beacon is radiated ultrasonic waves. By continuing to transmit the RF carrier until the pulse reaches the listener, the listener always receives the ultrasonic pulse while receiving the RF carrier. Beacons also attempt to transmit signals at random time intervals and detect RF carriers before transmitting their signals to avoid collisions with potential transmissions of other beacons.

Various transmission methods can be used for the transmission of the RF carrier in the beacon, but since there is not much data to transmit in the beacon and the price is the biggest problem when installed in a large area, the actual RF carrier transmission in the beacon is simple OOK (On- Off Keying) method. However, when the OOK transmission method is used, the collision detection between the beacons cannot be completely avoided by the carrier detection method, thereby reducing the location update rate of the listener.

The prior art bus arbitration method of Korean Patent No. 10-263791 is to arbitrate the work of a low priority requester delayed by a fixed priority method by a fairer rule. However, the prior art has a problem that a level having a priority does not give a low priority after completing a transmission.

Accordingly, the present invention is to solve the above-mentioned disadvantages and problems of the prior art, when a collision occurs between the transmission of beacons, even if two or more beacons transmit at the same time by decomposing the collision itself is the priority of transmission To ensure that only one of the beacons that attempted transmission at the same time continues to transmit, beacons that have successfully transmitted once have a lower priority, and beacons that give up transmissions in the arbitration process have higher priority to all beacons. It is an object of the present invention to provide a method for inter-transmission arbitration of beacons to ensure a fair transmission opportunity.

The object of the present invention is to set a priority bit of a beacon to a dominant or recessive bit level and to sense a channel level; Transmitting SOF bits of dominant bit level by the channel level; Detecting the channel level and comparing the channel level with a transmission level; Transmitting a next arbitration bit and detecting a channel level; Detecting the channel level and comparing the channel level with the transmission level; Determining whether transmission of the arbitration bit is completed; Transmitting an ultrasonic pulse and the remaining frame; Assigning a low priority to the beacon after the transmission is completed; And determining whether transmission of all data frames is completed.

Details of the above object and technical configuration of the present invention and the effects thereof according to the present invention will be more clearly understood by the following detailed description with reference to the drawings showing preferred embodiments of the present invention.

The RF carrier transmitted by the beacon is sufficient to use the OOK transmission method. The OOK transmission method transmits a logic-1 and a logic-0 value by transmitting or blocking a carrier. In this case, the carrier is transmitted when the logic-1 bit is transmitted and the carrier is blocked when the logic-0 bit is transmitted. Of course, the opposite does not change much. If any beacon transmits a logic-1 bit, the channel will be sensed at a bit level of logic-1 (carrier transmission), and the channel will be logical only if the beacons are all transmitting logic-0 bits or not all. The bit level is -0 (carrier blocking). Therefore, the logic-1 bit level is called the dominant bit level, and the logic-0 bit level is called the recessive bit level. In addition, an idle channel that is not transmitting all beacons is in a recessive bit level state.

1 is a block diagram illustrating a data frame of an RF signal according to the present invention. As shown in FIG. 1, the structure of a frame includes a start-of-frame (SOF) field 100, an arbitration unit 110, a message unit 120, an end-of-frame (EOF) field 130, and IFS (Interframe space) field 140, and the like.

The SOF field 100 indicates the start of data frame transmission and is one logic, that is, one bit. Beacons attempt arbitration for transmission only when the bus is idle. The end of the current frame transmission is indicated by the EOF 130.

The arbitration unit 110 is a part transmitted to arbitrate only beacons having a higher priority when two or more beacons attempt to transmit simultaneously. The arbitration unit 110 includes a priority bit 150 and an ID field 160. . The ID field 160 is a unique ID assigned to each beacon and may be expressed as a (x, y, z) coordinate value of the beacon. Each coordinate value consists of n bits, and especially the z coordinate can be omitted if all beacons are installed at the same height.

The message unit 120 is a part including data to be transmitted through an RF carrier and may be defined and used in an appropriate format. It can also be omitted if there is no data to transmit. However, in order to distinguish the EOF field 130 composed of consecutive n logical-0 bits, a logical 0 bit of at least 1 bit is configured.

The EOF field 130 is composed of consecutive n logical-0 bits as a part for indicating the end of a frame, and a channel between the frame and the frame has an IFS field 140 having a b bit recessive bit level of at least 1 bit. .

In the embodiment of the present invention, when the IFS field 140 is configured with a b bit recessive bit string, a bit string of consecutive n + b recessive bit levels of the EOF field 130 and the IFS field 140 in the channel is generated. After being in the channel, the channel is idle.

2 is a flowchart illustrating a method for arbitration between transmissions of beacons according to the present invention. Referring to FIG. 2, the beacon sets a priority bit to a logic-1 or logic-0 bit level (S100), and waits until a time point to transmit a data frame (S110).

The time point at which the beacon transmits a data frame may be determined due to an irregular time interval or may be set to always transmit. When all beacons are set to transmit at all times, the step S110 may be omitted, and even if set to transmit all beacons in the system at all times in the present invention, all beacons have a fair transmission opportunity.

When it is time for the beacon to transmit, it detects the channel state to detect the continuous recessed bit level of at least n + b bits, and waits until the channel is in the idle state (S120). If the beacon, which was in charge of the previous data frame, attempted the next transmission, I sent the EOF field, so the SOF is sent immediately after the IFS field of the continuous logical-0 bit sequence of b bits and immediately participates in the arbitration process. .

If a contiguous Logic-0 bit of at least n + b bits including an EOF field and an IFS field is detected on the channel, the channel can be considered idle. The idle state may transmit any beacons in which transmission preparation is completed. The beacon which confirms that the channel is in an idle state and initiates transmission informs the start of data frame transmission by first transmitting the SOF bit of the dominant bit level (S130). Therefore, the data frame waiting for the transmission of the previous data frame starts the transmission from the next bit of the IFS field.

Thereafter, an arbitration process is performed while transmitting an arbitration unit consisting of a priority bit and an ID field. During the arbitration process, all transmission beacons detect a channel state immediately after transmitting one bit and compare it with the transmitted bit level. That is, the channel level is first detected after the priority bit is transmitted (S140).

The transmission level of the priority bits is compared with the sensed channel level (S150). If the transmission level and the channel level are the same, the next arbitration bit is transmitted (S160).

However, when the transmission level and the channel level are different, two cases occur. When the dominant bit level is transmitted, an error state is generated (S200), and when the dominant bit level is not transmitted, a data frame is received (S190). . That is, although the dominant bit level indicating a high priority is transmitted (S180), when the recessive bit level is detected in the channel, an error state is entered (S200), but the recessive bit level indicating a low priority is transmitted. In operation S180, when the dominant bit level is sensed in the channel, because the case is lost to another beacon in the arbitration process, the transmission is abandoned and the device enters a mode for receiving a data frame transmitted by the other beacon (S190). And waits until the channel is available (S120) and attempts to retransmit.

The transmission level and the channel level are the same, and the next arbitration bit is transmitted, the channel level is sensed (S160), and the transmitted bit level and the channel level are compared (S170). If the transmission level and the channel level are the same, the arbitration bits are transmitted until the transmission of the ID field is completed (S230).

However, if the transmission level and the channel level are different, two cases occur. First, the dominant bit level indicating a high priority is transmitted (S210), but when the recessive bit level is detected in the channel, an error state is entered (S200). Second, the recessive bit level indicating a low priority is entered. Although the transmission (S210), if the dominant bit level is detected in the channel because it is lost to other beacons in the mediation process, the transmission is abandoned and waits for the next mediation process.

In this case, a high priority is set to secure a high priority in the next arbitration process (S220). The reason for this is that when a low priority beacon loses its right to transmit in the arbitration process, it will also fail in arbitration if a collision with the same beacon occurs in the subsequent arbitration process.

Therefore, once successful in the arbitration process, it has a low priority (S250), and if it fails, it has a high priority (S220), so that it has a fair transmission opportunity. After entering the mode to receive a frame transmitted by another beacon (S190), and waits until the channel is useful (S120) attempts to retransmit.

When the transmission of the arbitration bits is not completed in step S230, the process is performed again from step S160. When the transmission of the arbitration bits is completed, transmission of the message unit such as an ultrasonic pulse and the EOF field is completed (S240).

Only one beacon has a chance to transmit the ultrasonic pulse and the rest of the message at the completion of the arbitration. If the transmission is successfully completed, it is set to have a low priority in order to yield a transmission opportunity to other beacons having a high priority in the next arbitration process (S250), and confirms whether transmission of all data frames is completed. (S260).

If the transmission of all data frames is not completed, the operation is repeated until the next data frame is transmitted (S110), and if the transmission of all the arbitration bits is completed, the operation ends.

Although the present invention has been shown and described with reference to the preferred embodiments as described above, it is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

Accordingly, the inter-transmission arbitration method of the beacons of the present invention resolves collisions that may occur between transmissions of beacons, thereby guaranteeing a fair transmission opportunity for all beacons, thereby avoiding transmission failures of beacons and improving channel utilization to update position of the positioning system It has the advantage of increasing the rate or information update rate, and beacons that transmit successfully give low priority, and beacons that give up transmission during the arbitration process give high priority, thus ensuring equal transmission opportunities for all beacons. have.

Claims (11)

In the inter-transmission arbitration method, (a) setting the priority bit of the beacon to the dominant or recessive bit level and detecting the channel level; (b) transmitting the SOF bits of the dominant bit level by the channel level; (c) detecting the channel level and comparing it with a transmission level; (d) sending the next arbitration bit and sensing channel level; (e) detecting the channel level and comparing it with the transmission level; And (f) determining whether transmission of the arbitration bit is completed; Method for mediating transmission between beacons, characterized in that comprises a. The method of claim 1, (g) transmitting ultrasonic pulses and the remaining frames; (h) giving the transmission beacons a low priority; And (i) determining whether all data frames have been transmitted; Method for mediating transmission between beacons, characterized in that further comprises. The method of claim 1, The step (a) further comprises the step of waiting until the time to transmit the data frame inter-transmission arbitration method of the beacons. The method of claim 1, The step (a) is to detect the channel level when the transmission mode of the beacons, characterized in that the transmission of the data frame in the idle state. The method of claim 1, Step (c) goes to step (d) when the transmission level and the channel level are the same, and when the dominant bit level is transmitted among the transmission level and the channel level are different, an error state occurs and the dominant bit level is not transmitted. And in case of receiving a data frame. The method of claim 5, And after receiving the data frame, wait until the channel is available and attempt to retransmit. The method of claim 1, Step (e) goes to step (f) when the transmission level and the channel level are the same, and when the dominant bit level is transmitted among the transmission level and the channel level are different, an error state occurs and the dominant bit level is not transmitted. If not, a high priority is set in the next arbitration process. The method of claim 7, wherein And after setting the high priority, waits until the channel is available through the receive mode and attempts to retransmit. The method according to claim 1 or 2, Step (f) goes to step (g) if the transmission of the arbitration bits is completed, and if the transmission of the arbitration bits is not completed, the step (f) is performed again from step (d). Arbitration Method. The method of claim 2, Step (h) is a method for arbitration between transmissions of beacons, characterized in that to give a high priority to the beacons for giving up transmission. The method of claim 2, The step (i) is terminated when the transmission is completed, and if the transmission is not completed, waiting until the data frame transmission time to repeat the operations of (a) to (i) of the beacons Intertransmission Arbitration Method.

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