Summary of the invention
The objective of the invention is to overcome the problem that above-mentioned existing ARQ agreement exists, a kind of self adaptation ARQ design of protocol method that is applicable to asymmetric Burst Channel is proposed, obtain higher link effective rate of utilization with lower protocol overhead, improve the adaptability of existing ARQ mode simultaneously, satisfy the demand of utilizing asymmetric Burst Channel efficient communication nonsymmetric channel.
For achieving the above object, technical scheme of the present invention comprises the steps:
(1) communication ends receives data, if the data information frame of reception then deposits it in the reception buffer area, the memory location according to correct information frame in the buffer area produces the reception bitmap then, if the data supervisory frame of reception then enters step (3);
(2) extract the transfer rate control information and reception indication information that receives in the buffer area information frame, utilize the channel symmetry decision algorithm to estimate the current symmetric case of channel, if channel is asymmetric, then the asymmetric kind according to current channel adopts corresponding feedback system to send receiving feedback signals to information transmitting terminal; If the channel symmetry then adopts the state transitions algorithm to determine the send mode and the frequency of feedback signal according to receiving bitmap;
(3) retransmit requirement according to the other side who receives, deposit required retransmission information frame in the transmission buffer area, if there is remaining space in buffer area, then continue to deposit in the information frame that the upper strata requires transmission, send according to current transmission rate then, the court verdict according to step (2) sends receiving feedback signals in the corresponding moment simultaneously;
The information frame identical with current upper strata required frame sequence number that (4) will receive presented the upper-layer user, and repeating step (1) is to step (3), all finishes whole receptions to desired data up to communicating pair.
The present invention compared with prior art has the following advantages:
1, the present invention proposes the notion that receives bitmap, promptly with a length and receive buffer area and can store Serial No. reflection that frame number equates and receive in the buffer area the correctly storage condition of frame, make the information frame receiving terminal can inform the information frame of the required re-transmission of transmitting terminal with less protocol overhead.
2, the present invention utilizes the short supervisory frame of length that the information frame reception condition is fed back rapidly, can shorten the stand-by period of packet retransmissions present, reduce unnecessary retransmission, the link effective rate of utilization of raising system, improve the correct transmission probability of feedback signal simultaneously, enhanced system is to the adaptability of burst nonsymmetric channel.
3, the present invention utilizes transfer rate control information and reception indication information that the channel symmetry of current time is estimated accurately, makes system can effectively utilize channel resource more, improves data and correctly passes through probability.
Embodiment
With reference to Fig. 1, the present invention comprises following steps:
Step 1. receives data, and the judgment frame type also produces the reception bitmap.
During the communication beginning, communication ends produces a length can store the full null sequence that frame number equates with the reception buffer area, is referred to as the bitmap sequence, when data arrived, the upper strata produced one and receives interruption, and system begins to receive, if receiving data is supervisory frame, enter step 4, the supervisory frame structure is referring to Fig. 3;
If receiving data is information frame, deposit this frame in the reception buffer area, and it is missed frame detect, the structure of information frame is referring to Fig. 2, if information frame is not found mistake after tested, it is correct to think that then this information frame receives, and the correspondence position on this frame graphic sequence on the throne is designated 1, otherwise does not identify;
Check the sequence number of correct information frame,, enter step 5,, temporarily be kept at this frame in the buffer area if inequality if the sequence number of this frame is identical with the current required frame sequence number in upper strata;
After all information frames detected through the mistake frame in the buffer area, the bitmap sequence that can reflect correct frame position in the buffer area that system obtains was the reception bitmap.
Step 2, transfer rate control information in the information extraction frame and reception indication information are estimated channel symmetry.
2a) communication ends extracts transfer rate control information and receives indication information from the information frame that receives the buffer area stored, this transfer rate control information is represented by two bits in the information frame control field, four kinds of situations of high, medium and low speed and maintenance present rate of difference corresponding data transmission rate, the corresponding informance of transmission rate and control bit sees Table 1;
Table 1 speed change degree corresponding informance
Rate control information |
b1b2 |
At a high speed |
11 |
Middling speed |
10 |
Low speed |
01 |
Keep |
00 |
Receive indication information and represented that by bit in the information frame control field on behalf of the transmitting terminal of this information frame, sign 1 receive information frame in a transmission cycle, information frame is not received in sign 0 representative; 2b) hypothesis A end carries out full-duplex communication with the B end, and transmission rate is respectively R
AWith R
B, at T observing time
DIn, it is (T that the A end sends frame number to the B end
DR
A-N
A τ), it is (T that the B end sends frame number to the A end
DR
B-N
B τ), N wherein
A τBe A end free time equivalence transmission frame number, N
B τBe B end free time equivalence transmission frame number, free time is meant that system does not send the time of information frame, and the free time of establishing A end and B end is respectively τ
AWith τ
B, N then
A τ=τ
AR
A, N
B τ=τ
BR
BIf the number of sign 1 is n in the reception indication information that the A end extracts
A, the number of sign 1 is n in the reception indication information that the B end extracts
B, then A holds the frame number N that actual reception arrives
A=n
BR
B/ R
A, the frame number N that B end actual reception arrives
B=n
AR
A/ R
B
If N
B<<(T
DR
A-N
A τ), prove that then A holds B end channel not exist, otherwise this channel exists; If N
A<<(T
DR
B-N
B τ), prove that then B holds A end channel not exist, otherwise this channel exists.
Step 3, according to the channel symmetry estimated result with receive message bit pattern and determine the send mode and the transmission frequency of feedback signal.
3a) do not exist to the channel of communication ends B as communication ends A, and communication ends B is when the channel of communication ends A exists, B end continuous feedback two frame supervisory frames send information frame continuously to the A end, and A end low speed sends information frame continuously simultaneously; Do not exist when B holds to the channel of A end, and A holds when the channel of B end exists, A end continuous feedback two frame supervisory frames send information frame continuously to the B end, and B end low speed sends information frame continuously simultaneously; Hold when the channel of A end does not all exist when A holds to B end, B, A end, B hold mutual low speed to send information frame; Hold when the channel of A end all exists when A holds to B end, B, A end, B end send information frame mutually, and utilize the state transitions algorithm to determine the send mode and the transmission frequency of feedback information according to receiving bitmap;
3b) in the state transitions algorithm, establishing and receiving the bitmap total length is L, wherein identifies 1 number and be l (0≤l≤L); Making supervisory frame feedback minimum threshold is l
0, as l≤l
0The time, adopt incidentally mode to feed back negative response NAK signal; Work as l
0During<l≤L-1, feedback supervisory frame signal; When l=L, adopt incidentally mode to feed back the affirmative acknowledgement ack signal, and the submission user that will divide into groups;
3c) with l
0~L-1 zone further is divided into 4 ranks to determine the transmission frequency of supervisory frame, and each other threshold value of level is respectively l
1, l
2, l
3And l
4, l wherein
4=L-1, when l was in different stage, the transmission frequency of supervisory frame was carried out state transitions according to Fig. 4, promptly worked as l
I-1<l≤l
iThe time, the transmission frequency of supervisory frame is in i level i=1, and 2,3,4, corresponding transmission period T
iBe every reception k
iIndividual information frame sends supervisory frame, wherein a k
1>k
2>k
3>k
4, transmission frequency is the inverse in transmission cycle.
Step 4 requires to send information frame with the upper layer data transmission requirement according to retransmitting, and sends feedback signal according to feedback system and the feedback frequency that step 3 is determined.
If the feedback signal that communication ends is received is an ack signal, then send the new information frame that the upper strata requires transmission according to current transmission rate; If feedback signal is the NAK signal, then resend all information frames in a last moment according to current transmission rate; If feedback signal is to comprise the supervisory frame signal that communication counterpart receives bitmap, the information frame that then will receive 0 sign position correspondence in the bitmap deposits the transmission buffer area in, and continue to deposit in the upper strata and require the information frame that sends, do not have remaining space up to sending buffer area, send according to current transmission rate then; If in the overtime repeating transmission time period, do not receive any feedback signal, then resend all information frames in a moment;
If determine that according to step 3 current time should send supervisory frame, then communication ends is carried out framing to comprising the supervisory frame that receives bitmap, then it is sent.
Step 5 is submitted the correct information frame that receives to, finishes the reception and the transmission of desired data.
If this moment, the information frame sequence number received was identical with the required frame number in current upper strata and this frame is errorless, then present the upper-layer user, current information needed frame number is upgraded in receive window downslide simultaneously, carries out the reception of a new round;
Repeating step 1 is to step 4, all finishes whole receptions to desired data up to communicating pair.
Effect of the present invention can further specify by following simulation example:
One, simulated conditions
Simulated environment of the present invention is a laboratory environment, carries out channel simulation and is energy emulation by MATLAB software.Following definition is adopted in the emulation of link utilization theoretical value:
Wherein N is the totalframes that communication ends sends, the frame number of n for correctly being received in the information frame that sends; Following definition is adopted in the emulation of link effective rate of utilization theoretical value:
U
e=U·λ (2)
Effective information modifying factor in the formula, it is defined as
Wherein k/r is (r, the k) code check of linear code, I
n, A
n, C
n, FCS
nBe respectively the length of information field in the information frame, address field, control field and check field.
The major parameter value of emulation is as shown in the table:
The value of the major parameter of table 2 emulation
Parameter name |
Span |
The channel time span that on average happens suddenly |
300ms |
Carrier frequency (communicating pair) |
39.5MHz/41.5MHz |
Frame error rate |
1% to 25% |
The channel symmetric case |
Symmetry, asymmetric degree 75% |
Total relative time delay |
1.5ms |
Two, emulation content and result
Emulation 1: the link utilization of the present invention and existing ARQ agreement and the theoretical value of link effective rate of utilization are carried out emulation, simulation result such as Fig. 5 and Fig. 6.
Emulation 2: the present invention and existing ARQ agreement are carried out emulation, simulation result such as Fig. 7 and Fig. 8 in symmetry and the link effective rate of utilization under the asymmetric Burst Channel environment
Three, analysis of simulation result
The link utilization theoretical value curve of four kinds of agreements shown in Figure 5 calculates by definition (1).As can be seen from Figure 5, the theoretical value of link utilization reduces along with the increase of frame error rate, when the channel frame error rate is higher, link utilization of the present invention all has a more substantial increase than moving back N step ARQ agreement and stop and wait ARQ agreement, proof the present invention has link utilization performance preferably in the comparatively abominable asymmetric Burst Channel of communication environment, only be lower than to select to retransmit the ARQ agreement.
The link effective rate of utilization theoretical value curve of four kinds of agreements shown in Figure 6 calculates by definition (2).Because the purpose of communication is data information transmission in the information frame, so the link effective rate of utilization can reflect protocol capabilities more exactly.As can be seen from Figure 6, the theoretical value of link effective rate of utilization of the present invention is very near selecting to retransmit ARQ, far above moving back N step ARQ agreement and stop and wait ARQ agreement.
According to the analysis of Fig. 5 and Fig. 6 as can be known, the present invention can realize higher link utilization and link effective rate of utilization with less protocol overhead in theory.
Fig. 7 be in front and back to channel when symmetry, the simulation curve schematic diagram of the present invention and existing ARQ agreement link effective rate of utilization under different frame error rate conditions.As can be seen from Figure 7, the link effective rate of utilization of agreement reduces along with the increase of frame error rate, when the channel frame error rate is lower than 2%, moves back N step ARQ performance a little more than performance of the present invention, but along with the increase of channel frame error rate, performance of the present invention will be far above moving back N step ARQ.To the present invention among Fig. 7 with move back the link effective rate of utilization numerical value of N step ARQ agreement under different frame error rate situations and calculate and can draw, in front and back to channel when symmetry, in the emulation scope of channel frame error rate from 0 to 0.25, link effectively on average improves 39.4% compared to moving back N step ARQ.
Fig. 8 is for being 75% o'clock in the channel degree of asymmetry, the simulation curve schematic diagram of the present invention and existing ARQ agreement link effective rate of utilization under different frame error rate conditions.As can be seen from Figure 8, the channel effective rate of utilization be followed successively by from high to low and select retransmit ARQ agreement, the present invention, move back N step ARQ agreement and etc. stop formula ARQ agreement.Compare as can be seen when protocol link effective rate of utilization with channel when asymmetric and channel symmetry, except the present invention, the link effective rate of utilization of all the other agreements all has decline in various degree, the present invention further increases the increase rate that moves back N step ARQ performance, and the gap of the present invention and selection re-transmission ARQ performance further reduces.
To the present invention among Fig. 8 with move back the link effective rate of utilization numerical value of N step ARQ agreement under different frame error rate situations can be by calculating, asymmetric at channel is 75% o'clock, in the emulation scope of its channel frame error rate from 0 to 0.25, link effective rate of utilization of the present invention has on average improved 65.3% than the existing N of moving back step ARQ, proves that the present invention has adaptability preferably to nonsymmetric channel.
In sum, the present invention can be applicable to asymmetric Burst Channel, though its protocol overhead is basic identical with the existing N step ARQ agreement of moving back, but obtained and the essentially identical link effective rate of utilization of selection re-transmission ARQ agreement, for the communication system of using asymmetric Burst Channel provides reliably ARQ protocol scheme efficiently.