DE102008034271A1 - Method for controlling wireless communication between mobile subscribers over radio transmission medium, involves assigning configuration of radio transmission medium by subscriber depending on direction of motion in which subscriber moves - Google Patents

Abstract

The method involves assigning a configuration of a radio transmission medium by a subscriber depending on direction of motion in which the subscriber moves. The time slot is assigned for the utilization for the transmission of a communication data packet by an individual subscriber depending upon direction of motion of the respective subscriber during an assignment of the configuration of the radio transmission medium and the transmission of the communication data packet of the subscribers in a successive time slot of communication interval. An independent claim is also included for a subscriber radio transmission device comprising a radio communication unit.

Description

The The invention relates to a method for controlling wireless communication between mobile participants via one of participants in common used radio transmission medium.

The The invention further relates to a subscriber radio transmission device with a wireless communication unit for wireless communication between mobile subscribers via a subscriber's Radio transmission medium and with a communication control unit. Radio-based communication systems need protocols, the access to the common radio transmission medium governed by the transmission frequencies or transmission channels is fixed. A common set of logs looks a so-called negotiation phase (contention-phase) before the actual Data transfer before. The negotiation phase is in time slots divided up. Every participant wishing to send selects one certain scheme one of the time slots and catches to send on this. It can happen that two Participants select the same slot and thus radio collisions comes in the negotiation phase. These collisions lead to increase the latency and to reduce the Net data rate during radio transmission. The used Protocols differ essentially by how with these Collisions is handled. Unlike wired transmission networks is a simultaneous one with wireless radio transmission systems Sending and receiving a subscriber is not possible, among other things because when sending the much larger signal strength makes the simultaneous reception of signals impossible. Therefore, a participant can not determine during transmission if another participant is also sending at the moment. Collisions can therefore not like z. B. in the Ethernet protocol of sending participants be determined and resolved. Instead, it is added Protocols, such as carrier-sense-multiple-access / collision-avoidance (CSMA / CA) or the Self-Organized Time Divisons Multiple Access (SOTDMA) tries to avoid collisions by allowing participants to send, if the protocol determines that the radio transmission medium free is.

The CSMA / CA protocol allows participants to send immediately, if the radio transmission medium is currently free and before a certain amount of time was left free. If the radio transmission medium however, is currently being used by other participants, a participant may not yet immediately after the radio transmission medium again becomes free, send. Instead, a negotiation phase begins so-called "contention phase", the similarities with the collision resolution at the of the Ethernet protocol has her known methods. In the "contention phase" becomes the transmission time available there in several Split slots. Each participant chooses z. For example, randomly select one of the slots by starting the subscriber wants to send, if until then the radio transmission medium is still free. If, coincidentally, two participants the same slot, it can still lead to a collision.

Collisions can also result from the problem of invisible subscribers (hidden terminals). If z. B. two participants A and B independently of each other want to send a third party C a packet while the sending second party B is just outside the range of the first transmitting party A, the two sending participants A and B can not determine whether one of the two sending subscriber A or B already transmits data. When the time slot selected by the subscriber B starts, the first transmitting subscriber A is invisible to the second transmitting subscriber B. As a result, the second sending subscriber B would accordingly start to send himself to the third party C while disturbing the connection of the first sending party A and the third receiving party C. In order to prevent this, the known protocols provide that the transmitting subscriber A does not yet send his actual data packet at the beginning of the time slot assigned to him, but only sends a short request to the third subscriber C (request to send, RTS)). Only when the first subscriber A has received from the third subscriber C in response to the clear to send (CTS), the first transmitting subscriber A may start to send. However, this transmission acknowledgment signal CTS of the third receiving subscriber C can also be received by the second transmitting subscriber B and therefore knows that he is not yet allowed to transmit. Since the send request and send acknowledge signals RTS and CTS also contain the information as to how long the first sending party A wants or is allowed to send, the second sending party B also knows how long the radio transmission medium is being used by the first sending party A. Because the second sending subscriber B has information about the occupancy of the radio transmission medium in this way, without having to listen to the radio transmission medium, this principle is also called virtual carrier sense. Since the transmission request signals are only short, there is the positive side effect that possible collisions are relatively short in the event that several participants have selected the same time slot. The send request send acknowledgment data exchange is based on the so-called MACH protocol, which e.g. B. part of the radio used in the package AX.25 protocol is. The MACH protocol is for example in P. Karn: "MACH - A new channel access method for packet radio, ARRL / CRRL, Amateur Radio 9th Computer Networking Conference, 1990, pages 134-140 , described.

The Procedure does not require centralized control, so it virtually all relevant ad-hoc networks.

at The SOTDMA protocol becomes available time in time slots divided up. The participants continuously observe the radio transmission medium and remember the time slots as free, those of other participants not reserved. When the participants send messages want, the negotiation phase, in which a participant starts a free Timeslot uses and at the same time the next time slot reserved, which he wants to use. Again, collisions can through the problem of the invisible participant. All participants have regardless of the priority of the data the same Probability that their data will collide.

The SOTDMA protocol is defined in ITU standard ITU-R M. I 371-1 and is also referred to as a self-organizing TDMA protocol.

One Problem of the known methods, such as CSMA / CA or SOTDMA is that through the many waiting times, especially through the negotiation phase and the possible collisions still available Bandwidth of the radio transmission medium used only partially can be. In addition, a send-willing chooses Subscriber in the CSMA / CA procedure the next time slot to be used in the negotiation phase usually random. The kind The use of ad hoc communication can have a significant impact have it on whether the timeslot selection is cheap or unfavorable is.

The Ad-hoc communication via radio transmission media used for traffic control, for example. there can z. B. vehicles in traffic mutually over radio about your position and direction of movement to inform. Even a train-train communication is beneficial to to increase safety in rail traffic. Also one inter-network radio communication between vehicles may be useful. The wireless communication methods However, the fastest and most robust communication possible allow for collisions between vehicles to prevent. It is unfavorable if the radio communications oncoming vehicles delayed by data collisions or even prevented, as with random selection of timeslots equally distributed over the number of available Timeslots occurs.

EP 1 744 585 A2 discloses a method for ensuring access to a radio transmission medium in which time slots are selected during a controlled negotiation phase depending on the data transmission quality so that the time slot reduces the risk of collision and increases throughput. The transmission quality parameters considered for time slot selection do not include a direction of movement. The procedure is based on a non-existent central coordinator in ad-hoc networks.

NM Rabadi, SM Mahmud, "Priority-based MAC Protocol For Vehicle Collision Avoidance System Via Inter-Vehicle Communication Networks", in: PROC. of the 5th Annual Intelligent Vehicle Systems Symposium of National Defense Industries Association (NDIA), National Automotive Center and Vectronics Technology, June 13-16, 2005, Michigan, pp. 205-212 discloses an ad hoc communication method in which time slots are assigned priority-dependent and the priority assignment of the time slots is selected as a function of the vehicle speed.

outgoing It is the object of the present invention to provide a method for controlling wireless communication between mobile subscribers via a radio network shared by subscribers to improve so that as fast as possible, early and secure data communication through improved allocation is ensured by time slots.

The Task is characterized by the method of the type mentioned by solved that occupancy of the radio transmission medium by a participant depending on the direction of movement, in which the respective participant moves, is assigned.

It is z. B. proposed, the direction of movement of the mobile subscriber to use as a selection criterion to increase the capacity of the Radio transmission medium to split several participants. In order to can z. B. at two vehicles to drive towards each other from the outset be ensured that due to the opposite directions of movement from the two participants different, non-conflicting Capacities of the radio transmission medium, such as different time slots are used.

The method is particularly suitable for communication protocols, in which the use of the radio transmission medium on a defined channel, ie a fixed frequency range in time division by allocation of time slots a transmission sequence takes place. In such a time-division multiplex protocol is then an assignment of time slots for use for the transmission of communication data packets by individual participants depending on the direction of movement of the respective subscriber in the allocation of the allocation of the radio transmission medium and a transmission of communication data packets of a plurality of subscribers in successive time slots a communication interval.

So For example, in the negotiation phase, you can select the assignment of time slots in particular depending on the Movement direction of the mobile subscriber take place. In the assignment and selection of time slots can be next to the direction of movement if applicable, also take into account further criteria such as the priority of the data transfer through mobile subscribers. As prioritization parameters are different Features in question, such as the order of the vehicles in a lane - the danger of a vehicle collision with the first or last vehicle of a column is in most Cases greatest (example: rear-end collisions at the end of the jam).

The Priority can be determined by the urgency of a message, the speed of the mobile subscriber or the like be determined.

at the communication control by time slot allocation, it is advantageous if the radio transmission medium through the subscriber is continuous is observed and timeslots reserved by send-willing participants where the selection of time slots of a communication interval depending on the direction of movement the send-willing participant takes place. The continuous observation and reservation of time slots is, for example, off the medium access control level (MAC) protocols for ad hoc mobile networks.

The Occupancy of the radio transmission medium can avoid data collision also by assigning transmission frequencies or transmission channels be controlled as the access to the medium in Frequency Division Multiple Access (FDMA) procedure is typically regulated. Then the assignment of the transmission frequencies and the transmission channels takes place for use in the transmission of messages by displaying the participants depending on the direction of movement of the respective participant.

The Occupancy of the radio transmission medium can avoid data collision can also be controlled by assigning codes that allow access to the medium in Code Division Multiple Access (CDMA) procedures typically regulated. Then the assignment of the codes takes place for use in the transmission of messages by displaying or filtering the participants depending on the direction of movement of the respective participant. advantageously, are the most vulnerable to vehicle collisions Driving directions with relative angles of 90 °, 180 ° and 270 ° to particularly orthogonal codes in the sense of the CDMA method.

Next the consideration of the direction of movement in the assignment the assignment of the radio transmission medium, the assignment continue to be based on other criteria, which are related to the route of the subscriber, such as Track number, street numbers or geographical dependencies, such as B. Modulo latitude / minute / second.

task The present invention further provides an improved subscriber radio transmission device with a wireless communication unit for wireless communication between mobile subscribers via one shared by subscribers Radio transmission medium and with a communication control unit to accomplish.

The Task is with such a subscriber transfer device solved by the fact that the communication control unit for assigning the occupation of the radio transmission medium the subscriber radio transmission device in dependence from the direction of movement in which the participants move on radio transmission equipment, is set up. Advantageous embodiments are in described the subclaims.

The Invention will be described below with reference to embodiments explained in more detail with the accompanying drawings. Show it:

1 - Sketch of a subscriber radio transmission device with a communication control unit for assigning the occupancy of the radio transmission medium;

2 - Sketch of a railway line with oncoming, ad-hoc communicating trains;

3 - Sketch of a road intersection with due to their direction of movement in different time slots communicating vehicles.

1 leaves a sketch of a subscriber radio communication device 1 recognize that at For example, in a vehicle, such as a motor vehicle or a train is installed. The subscriber radio communication device 1 has a radio communication unit 2 for wireless communication between mobile subscribers via a radio transmission medium shared by subscribers. In order to prevent a collision in the radio transmission by the mobile subscriber and to carry out the radio transmission according to a transmission protocol known to the subscribers, the radio communication unit is 2 with a communication control unit 3 connected. The communication control unit 3 is particularly suitable for controlling radio communication in mobile ad hoc networks z. For example, according to the Carrier Sense Multiple Access / Collision Avoidance Protocol (CSMA / CA) or the Self-Organized Time Division Multiple Access Protocol (SOTDMA). In this case, an allocation of time slots in the negotiation phase (contention phase) by the communication control unit 3 depending on the direction of movement of the subscriber, in which the subscriber radio transmission device 1 is installed. The direction of movement can, for example, with a locating module 4 the subscriber radio communication device 1 be determined. As a locating module 4 In particular, a compass is optionally suitable with an acceleration sensor and / or a satellite-based location system.

Alternatively or additionally, the communication control unit 3 also via an interface 5 with a navigation device 6 be connected, which is usually installed in the vehicle anyway. The direction of movement is then using the navigation device 6 determined and via the interface 5 to the communication control unit 3 transfer.

The selection of the time slots, for example on the medium access control (MAC) level in ad hoc mobile networks, using the communication control unit 3 according to which direction the mobile subscriber is moving. Particularly vulnerable subscribers can significantly reduce the probability that the communication on the medium access control level is not disturbed by an access conflict as compared to a random selection by disjoint selection of the time slots to be used. This principle can be applied to both point-to-point (unicast), point-to-multipoint (multicast) and broadcast (broadcast) and their derivatives such as geocast.

2 shows a sketch of a railway line 7 with two oncoming trains 8a . 8b that communicate with each other on an ad-hoc basis, for example to avoid a collision. The two trains 8a . 8b make their request to transmit on different time slots Slot A, Slot B of the negotiation phase known. In the negotiation phase, there are two time slots slot A and slot B available, each of which has a preferred direction of travel assigned to it. For example, subscribers traveling eastbound with a heading of 0 ° ≤ 179 ° will be assigned the slot A slot, and for heading westbound travelers (180 ≤ heading ≤ 359 °) slot B will be allocated in this way 340 ° moving train 8b for communication the timeslot Slot B and the train traveling at a rate of about 160 ° 8b assigned to the time slot slot A. Due to the opposite directions of travel, a collision-free time slot assignment is thus prescribed in the negotiation phase.

3 leaves a sketch of a road network in the area of a junction with four at the intersection 9 meeting road sections 10a . 10b . 10c and 10d detect. Each on a specific section of road 10a . 10b . 10c . 10d in the intersections 9 incoming vehicle 11a . 11b . 11c . 11d can announce its readiness to send on another timeslot Slot A to Slot D, if more than those in 2 shown two time slots are available. For example, in the case of four available time slots, an assignment could be made as follows: Slot A: 0 ° ≤ course ≤ 89 ° Slot B: 90 ° ≤ heading ≤ 179 ° Slot C: 180 ° ≤ heading ≤ 269 ° Slot D: 270 ° ≤ heading ≤ 359 °.

Under But it is also cheaper, more as two time slots the further time slots before the special one Background of other use cases. So is it in the case of collision collisions at the railway quite normal that which ultimately collide after a turnout crossing Trains previously on parallel tracks in the same Drive direction. This would be after the above Procedure to use the same time slots lead. To further reduce the risk of such collisions, it is advantageous if two time slots are used alternately or more geographic dependencies on time slot selection be taken into account, for. B. Modulor latitude / minute / second.

Conceivable But also a selection of time slots is still dependent from the identified track number, street number or Lane to make in overlapping directions of movement to ensure a collision-free time slot assignment. This typically requires a sufficiently accurate self-locating ability the communication partner.

A another way to use more than two time slots is the mapping of other coding schemes to the time slots. So z. For example, a hybrid media access control approach is implemented be such. B. a combined TDMA-CDMA method on the basis a MAC method with four time slots, as for example in Tetra communication system is used. This z. B. two codes and two time units to one of four time slots displayed.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1744585 A2 [0010]

Cited non-patent literature

• - P. Karn: "MACH - A new channel access method for packet radio, ARRL / CRRL, Amateur Radio 9th Computer Networking Conference, 1990, pages 134 to 140 [0004]
• NM Rabadi, SM Mahmud, "Priority-based MAC Protocol For Vehicle Collision Avoidance System Via Inter-Vehicle Communication Networks", in: PROC. of the 5th Annual Intelligent Vehicle Systems Symposium of National Defense Industries Association (NDIA), National Automotive Center and Vectronics Technology, June 13-16, 2005, Michigan, pp. 205-212 [0011]

Claims (9)

Method for controlling wireless communication between mobile participants via one of participants in common used radio transmission medium, characterized by Assigning the occupation of the radio transmission medium by a participant depending on the direction of movement, in which the respective participant moves. Method according to claim 1, characterized by allocating time slots for use for transmission of communication data packets by individual subscribers in dependence from the direction of movement of the respective participant in the assignment the occupancy of the radio transmission medium and transmission of communication data packets of a plurality of subscribers in successive time slots of a communication interval. Process according to claim 2, characterized by continuous Watching the radio transmission medium by the participants and reserving timeslots by senders and subscribers by selecting time slots of a communication interval in Dependence on the direction of movement of the respective willing to send Participant. A method according to claim 2 or 3, characterized by specifying course heading ranges for timeslots and allocating a timeslot for use by a participant moving in a certain course direction so that the course direction of the participant in the for the assigned sub-slot respectively specified course direction range lies. Method according to one of the preceding claims, characterized by assigning transmission frequencies or transmission channels for use for the transmission of messages by individual participants depending on the direction of movement of the respective Participant in the assignment of the occupancy of the radio transmission medium. Method according to one of the preceding claims, characterized by allocating the occupancy of the radio transmission medium continue depending on the route of the participant related criteria. Subscriber radio equipment ( 1 ) with a radio communication unit ( 2 ) for wireless communication between mobile subscribers via a radio transmission medium shared by subscribers and with a communication control unit ( 3 ), characterized in that the communication control unit ( 3 ) for assigning the occupancy of the radio transmission medium by the subscriber radio transmission device ( 1 ) depending on the direction of movement in which the subscriber radio transmission device ( 1 ), is set up. Subscriber radio equipment ( 1 ) according to claim 7, characterized in that the subscriber radio transmission device ( 1 ) has an integrated compass for determining the direction of movement. Subscriber radio equipment ( 1 ) according to claim 7, characterized in that the subscriber radio transmission device ( 1 ) an interface ( 5 ) to a navigation device ( 6 ) of the subscriber and transmission of movement direction information of the subscriber from the navigation device ( 6 ) to the communication control unit ( 3 ) Has.