CN110401933B - Vehicle-mounted communication mode for enhancing reliability of media access control layer - Google Patents

Vehicle-mounted communication mode for enhancing reliability of media access control layer Download PDF

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CN110401933B
CN110401933B CN201910715452.0A CN201910715452A CN110401933B CN 110401933 B CN110401933 B CN 110401933B CN 201910715452 A CN201910715452 A CN 201910715452A CN 110401933 B CN110401933 B CN 110401933B
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counter
information
selection
selection window
vehicle
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CN110401933A (en
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张锋辉
汪茂
符茂胜
孙博
肖明
陈帅帅
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West Anhui University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W28/00—Network traffic management; Network resource management
    • H04W28/02—Traffic management, e.g. flow control or congestion control
    • H04W28/04—Error control
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/30—Services specially adapted for particular environments, situations or purposes
    • H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
    • H04W4/48—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for in-vehicle communication

Abstract

The invention discloses a vehicle-mounted communication mode for enhancing the reliability of a media access control layer, which belongs to the technical field of communication, wherein counter information and offset information are added in bypass control information, a distributed algorithm is adopted for selecting a counter in a protocol based on a vehicle-mounted communication mode of a mode 4 in LTE-V2X, an automobile respectively calculates the starting time of a selection window when other vehicles perform resource selection next time, the overlapping area of the selection window with the other vehicles appearing next time is calculated in the selection range of the own counter, the maximum value of the counter corresponding to the selection window with the minimum overlapping area is selected to be determined as the own counter, the offset information of the current selected resource relative to the starting position of the window is recorded, and binary information representing the counter and the offset is added into the own bypass control information. The invention avoids packet collision caused by overlapping of the selection windows to the greatest extent, and improves the reliability of the transmission of the Media Access Control (MAC) layer of the mode 4 in LTE-V2X.

Description

Vehicle-mounted communication mode for enhancing reliability of media access control layer
Technical Field
The invention relates to the technical field of communication, in particular to a vehicle-mounted communication mode for enhancing the reliability of a media access control layer.
Background
The 3-month LTE in 2017 introduced the vehicle communication modes of mode 3 and mode 4 in the V2X Rel-14 release. Of these, mode 4 is mainly used for communication between vehicles in a non-cellular coverage condition, and it employs a perception-based semi-persistent scheduling in a Medium Access Control (MAC) layer. The main contents of semi-persistent scheduling are: before the vehicle selects the channel resources, the occupied positions of the channel resources of other vehicles and the occupied periods of the channel resources are sensed within the previous 1000 milliseconds, then the channel resources reserved by other vehicles are excluded from the own selection window, and the selection is carried out in the rest idle sub-channels. And the collision of packets in the MAC layer can be greatly reduced by adopting semi-static scheduling, so that the reliability of communication is improved. However, this method can only avoid some collisions, and when different vehicles select resources within a similar time, the selection windows may partially or even completely overlap, and when 2 or more vehicles simultaneously select one resource, a collision may occur, but such a collision cannot be avoided based on the perceived semi-static scheduling.
Disclosure of Invention
1. Technical problem to be solved
The technical problem to be solved by the present invention is to provide a vehicle-mounted communication mode for enhancing the reliability of the media access control layer, which greatly avoids packet collision caused by overlapping selection windows, and improves the reliability of mode 4MAC layer transmission in LTE-V2X.
2. Technical scheme
In order to solve the problems, the invention adopts the following technical scheme:
a vehicle carried communication mode of enhancing the reliability of media access control layer, it adds counter information and offset information in the bypass control information first, the value of the counter is chosen in the range that every vehicle reserves the interval and stipulated, add to the bypass control information after expressing the counter information with 6bit binary code; the offset information refers to the position information of the subframe in the selection window, the time axis of the selection window is averagely divided into 4 parts, the offset information is the part where the subframe is positioned, and the 4 parts are represented by the remaining 4 binary codes of the 4-bit binary codes for representing the resource reservation interval in the bypass control information; then based on the vehicle-mounted communication mode of the mode 4 in the LTE-V2X, a distributed algorithm is adopted by a counter in a protocol, in the distributed algorithm, the automobile respectively calculates the starting time of the appearance of the selection window when other vehicles perform resource selection next time, then in the selection range of the own counter, the selection window with the smallest area of collision with the selection window appearing next time of other vehicles is calculated, the maximum value of the counter corresponding to the selection window with the smallest overlapping area is selected, the counter is determined as the own counter, meanwhile, the offset information of the current selected resource relative to the starting position of the window is recorded, and binary information representing the counter and the offset is added into the bypass control information of the automobile.
Specifically, the method comprises the following steps:
the time axis of the selection window is in the range of [ T + Ts,T+TL]Wherein, Ts≤4，20≤TLLess than or equal to 100; the time axis of the selection window is divided into 4 parts on average
Figure BDA0002155248410000021
Figure BDA0002155248410000022
The 4 parts of the time axis of the selection window are represented by binary codes 1100, 1101, 1110, 1111, respectively.
The calculation formula of the starting time of the appearance of the selection window when the resource selection is carried out on other vehicles next time is as follows: p'i＝ri·(ci-1)+bi+piOf which is P'iIndicates the starting time, r, of the next occurrence of the position of the ith vehicleiAnd ciRespectively representing the resource reservation interval and the value of the counter of the ith vehicle, biIndicating the location of the ith vehicle resource,
Figure BDA0002155248410000031
3. advantageous effects
According to the method, counter information and offset information are added into bypass control information (SCI), then a random selection algorithm of a counter in a protocol of LTE-V2X mode 4 is replaced by a distributed algorithm provided by the invention, in the distributed algorithm, the automobile respectively calculates the starting time of the appearance of a selection window when other vehicles perform resource selection next time, then in the selection range of the counter of the automobile, the selection window with the smallest area of collision with the selection window appearing next time of other vehicles is calculated, the maximum value of the counter corresponding to the selection window with the smallest overlapping area is selected to be determined as the counter of the automobile, the offset information of the current selected resource relative to the starting position of the window is recorded, and binary information representing the counter and the offset is added into the bypass control information of the automobile. Experiments and researches prove that under the conditions of different channel busy rates, the collision rate of packets in the scheme provided by the invention is obviously lower than that of the semi-static scheduling scheme based on perception, and the packet passing rate of the scheme provided by the invention is obviously higher than that of the semi-static scheduling scheme based on perception; when the channel busy rate is below 50%, the average throughput rate of the packets in the scheme provided by the invention is higher than 0.9999, so that the scheme provided by the invention can greatly avoid packet collision caused by selection window overlapping, and the reliability of mode 4MAC layer transmission in LTE-V2X can be greatly improved.
Drawings
FIG. 1 shows the packet collision rate over time for different channel busy rate conditions;
FIG. 2 shows the packet throughput rate as a function of the channel busy rate;
fig. 3 is a packet throughput rate under the condition that the channel busy rate is 50% in ten experiments;
fig. 4 is a block diagram of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Examples
An on-vehicle communication mode for enhancing the reliability of a media access control layer is based on an on-vehicle communication mode of a mode 4 in LTE-V2X, and the format requirement of bypass control information (SCI) in LTE-V2X is as follows:
Figure BDA0002155248410000041
firstly, adding counter information and offset information to bypass control information (SCI):
the value of the counter is selected in the range specified by the reserved interval of each vehicle, the maximum difference value between the upper limit and the lower limit is 50, and the value is specifically shown in table 1:
table 1 table of correspondence between value ranges of counters and reserved intervals
Reserved interval Value range of counter
A multiple of 100ms, but less than or equal to 1000ms [5,15]
50ms [10,30]
20ms [25,75]
The information of the counter needs to use 6 bits of storage space, which can represent 64 kinds of information, and the maximum value of the number of the counter information is 51, so that the counter information can be completely represented by 6 bits.
The offset information refers to the position information of the subframe in the selection window, the time axis of the selection window is averagely divided into 4 parts, the part where the subframe is located is judged, and 4 pieces of information are total;
the 4-bit binary code in the bypass control information (SCI) represents the resource reservation interval, which can represent 16 information, but the resource reservation interval is only 12, so that the remaining 4 information can be represented as the position of the selection window where the selected resource is located (i.e. the 4 information corresponding to the offset information), and the binary code representing the information is added to the SCI information of the user.
Secondly, the random selection algorithm of the counter in the protocol of mode 4 in LTE-V2X is then replaced by a distributed algorithm:
in the distributed algorithm, the automobile respectively calculates the starting time of the appearance of the selection window when other vehicles select resources next time, then in the selection range of the own counter, calculates the selection window with smaller area colliding with the selection window appearing next time of other vehicles, and the pseudo code of the algorithm is as follows:
inputting: the number of other vehicles, the range of the counter, the time of the next selection window, the length of the time axis of the selection window of the vehicle, the frequency occupied by the window, the time axis position of the resource selected by the vehicle at this time and the repetition period.
Initialization: ,
and (3) outputting: selecting the maximum value of the counter corresponding to the window overlap area
Figure BDA0002155248410000061
Finding the smallest ones;
the maximum value of the counter in the minimum overlap areas is returned and output.
And selecting the maximum value of the counter corresponding to the selection window with the minimum overlapping area, determining the counter as the own counter, and adding binary information representing the value into the SCI information of the own counter.
Specifically, analysis is done in conjunction with FIG. 4:
when the car viSensing that a packet needs to be sent at the moment T, wherein the unit of T is millisecond, and counting the counter c of the vehicleiWhen 0, the vehicle v needs to reselect the resource (i.e. the resource reservation interval r), and the time range of reselection is T + Ts,T+TL]Wherein, Ts≤4，20≤TL≤100，TsIndicates the maximum time, T, for a packet to be processed and transmitted after its arrivalLIndicating the maximum delay time allowed for the packet. And calculating the occupation condition of the resources within the previous 1000 milliseconds at the arrival time of the package, and calculating the number and the positions of the reserved resources in the reselection interval according to the received SCI information of other vehicles. The vehicle v randomly selects the resource from the rest time-frequency resources and determines the resource within the reselection rangeA part b, in which the position interval is divided into 4 parts, respectively
Figure BDA0002155248410000071
Figure BDA0002155248410000072
They are represented by binary codes and then can be fed into SCI information, such as: 1100, 1101, 1110, 1111 represent these 4 parts, respectively, and the car v adds these information to its own SCI information.
Automobile viIn acquiring other vehicles v-iResource reservation interval r-iAt the same time, counter information and position information c of other vehicles are also acquired-i. The formula for the starting moment of the next occurrence of the position of the respective vehicle is as follows:
p'i＝ri·(ci-1)+bi+pi
wherein P'iIndicates the starting time, r, of the next occurrence of the position of the ith vehicleiAnd ciRespectively representing the resource reservation interval and the value of the counter of the ith vehicle, biIndicates the offset of the ith vehicle resource due to biThe invention adopts an approximate method to express as follows:
Figure BDA0002155248410000073
example (c): when the resource is in the position
Figure BDA0002155248410000074
biIs approximated as
Figure BDA0002155248410000075
After the position of the next selection window of other automobiles is calculated, the automobile viWithin its allowable counter range, the minimum area of overlap with other car selection windows is calculated and the set of counters with the minimum overlap area is determined.
And selecting the largest counter in the counter set with the smallest overlapping area as the counter value of the current transmission, and placing the value into the reserved resource space of the SCI after the value is represented by a binary code. The information may then be sent.
1. The packet collision rates of the sensing-based semi-static scheduling scheme and the scheme of the invention under different channel busy rates (the channel busy rate refers to the busy degree of a channel, for example, the channel busy rate is 50% which indicates that 50% of the channels are occupied) are studied, and the results are shown in fig. 1 by taking 25%, 50% and 75% as examples;
as can be seen from fig. 1, under different channel busy rate conditions, the collision rate of the packet in the scheme of the present invention is significantly lower than that in the semi-persistent scheduling scheme based on sensing, and when the channel busy rate is 25% or 50%, the collision rate of the packet in the scheme of the present invention is 0.
2. The packet throughput rate under different channel busy rate conditions based on the sensing semi-static scheduling scheme and the scheme proposed by the present invention is studied, and the result is shown in fig. 2;
as can be seen from fig. 2, when the channel busy rate gradually increases, the packet throughput rate of the scheme proposed by the present invention is significantly higher than that of the semi-persistent scheduling scheme based on sensing, and when the channel busy rate is in a range lower than 50%, the packet throughput rates of the scheme proposed by the present invention are all close to 1 (i.e. 100%), so that the reliability of the mac layer can be greatly improved.
3. Under the condition that the channel busy rate is 50%, respectively carrying out ten times of tests on the packet passing rates in the sensing-based semi-static scheduling scheme and the scheme provided by the invention, wherein the data results are shown in a table 2;
table 2 throughput of packets when channel busy rate is 50%
Figure BDA0002155248410000081
Figure BDA0002155248410000091
Plotting the data into a histogram, as shown in FIG. 3;
as can be seen from table 2 and fig. 3, when the channel busy rate is 50%, the packet throughput rate of the scheme provided by the present invention is higher than that of the semi-persistent scheduling scheme based on sensing, and the packet throughput rate of the scheme provided by the present invention can reach as low as 0.9999, so that the reliability of the mac layer can be greatly improved.
It should be understood by those skilled in the art that the above embodiments are only for illustrating the present invention and are not to be used as a limitation of the present invention, and that changes and modifications to the above embodiments are within the scope of the claims of the present invention as long as they are within the spirit and scope of the present invention.

Claims (3)

1. A vehicle carried communication method for enhancing reliability of media access control layer is characterized in that counter information and offset information are added in bypass control information, the value of the counter is selected in the range specified by each vehicle reserved interval, and 6bit binary codes are used for representing the counter information and then added in the bypass control information; the offset information refers to the position information of the subframe in the selection window, the time axis of the selection window is averagely divided into 4 parts, the offset information is the part where the subframe is positioned, and the 4 parts are represented by the residual 2-bit binary codes of the 4-bit binary codes used for representing the resource reservation interval in the bypass control information; then based on the vehicle-mounted communication mode of the mode 4 in the LTE-V2X, enabling counters in a protocol to adopt a distributed algorithm, respectively calculating the starting time of the appearance of a selection window when other vehicles select resources next time in the distributed algorithm, then in the selection range of the own counter, calculating the selection window with the minimum area for colliding with the selection window appearing next time of other vehicles, selecting the maximum value of the counter corresponding to the selection window with the minimum overlapping area, determining the maximum value as the own counter, simultaneously recording the offset information of the selected resources relative to the starting position of the window, and adding binary information representing the counter and the offset into the bypass control information of the own;
time axis of the selection windowIn the range of [ T + Ts,T+TL]Wherein, TsIndicates the maximum time, T, for a packet to be processed and transmitted after its arrivalLRepresents the maximum delay time allowed for the packet; the time axis of the selection window is divided into 4 parts on average
Figure FDA0003672728140000011
Figure FDA0003672728140000012
Figure FDA0003672728140000013
The calculation formula of the starting time of the appearance of the selection window when the resource selection is carried out on other vehicles next time is as follows: pi'＝ri·(ci-1)+bi+piIn which P isi' denotes the start time of the next occurrence of the ith vehicle, riAnd ciRespectively representing the resource reservation interval and the value of the counter of the ith vehicle, biIndicating the location of the ith vehicle resource,
Figure FDA0003672728140000021
2. the method of claim 1, wherein T is Ts≤4，20≤TL≤100。
3. The method of claim 2, wherein the binary codes 1100, 1101, 1110 and 1111 represent 4 portions of the time axis of the selection window respectively.
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