CN113098732B - Method for calculating transmission time of effective load - Google Patents

Abstract

The invention provides a method for calculating the transmission time of an effective load, aiming at the problem that the network throughput S and the time delay E [ D ] are synchronously increased along with the increase of the length of a data packet. In the invention, firstly, the throughput time Sv is defined as the ratio of the transmission time of the effective load to the time delay, and the calculation formula is the ratio of the throughput to the data transmission rate. Then, a system analysis model of F = Sv/E [ D ] (throughput duration/network delay) was designed. After the protocol is determined, the analysis model F is a function of the transmission time of the effective load, and the range and the optimal value of the transmission time of the effective load can be analyzed to obtain the throughput duration growth rate higher than the network delay. With the DATA/ACK mode parameter in IEEE802.11, the optimal payload transmission time is independent of the number of nodes, only by the frame interval and propagation time of the access parameter. The system analysis model and conclusions may be used for other protocols for DATA/ACK.

Description

Method for calculating transmission time of effective load

Technical Field

The invention relates to the technical field of communication, in particular to a method for calculating the transmission time of a payload.

Background

The existing protocol performance analysis generally studies the network performance in a saturation state. The saturation state generally means that a node always has data to transmit. The length of data to be transmitted is a research focus, and related protocols, such as IEEE802.11, also provide schemes such as TXOP, a-MSDU and a-MPDU.

In the existing optimization scheme, the length of a data frame is generally used as an optimization parameter to study how to achieve the target of maximum throughput performance. Meanwhile, the network delay performance is analyzed based on the maximum throughput performance. The optimization scheme has two main problems: 1) the data transmission rates are different, and the length parameter of the data frame cannot reflect the efficiency of the node for occupying the channel; 2) as the data frame length increases, both throughput and latency values increase, however, increasing latency values can degrade network performance.

Aiming at the influence of data transmission rate and time delay growth on performance, the method provided by the invention is used for establishing a throughput duration parameter of a ratio of throughput to data transmission rate and determining the optimal throughput duration.

Disclosure of Invention

The invention mainly researches the relationship between throughput and different growth rates of network delay and establishes a throughput performance system analysis model based on the network delay.

The classical throughput calculation model is:

. The invention adopts a throughput calculation formula based on average time delay,

. Wherein, E [ P_E[D]]Represents the time delay E [ D ]]The payload is successfully over-transmitted. Average time delay E [ D ]]The contents are shown in figure 1:

fig. 1 is a diagram illustrating the contents of network delay.

I.e., E [ D ]]=T_DATA+T_Ctrl+T_Col+T_Idle. Wherein, T_IdleIndicating channel idle time; t is_ColRepresenting the time of collision in the channel; t is_CtrlThe method comprises the steps of representing the transmission time of a control frame in the successful transmission process, wherein the transmission time comprises the frame header control information transmission time of a data frame; t is_DATARepresenting the payload transmission time.

In the invention, on the basis of a throughput calculation formula, a parameter throughput duration S is further provided_VThe throughput time calculation formula is the effective load transmission time length in the average time delay. Let v (t) represent the data transmission rate, resulting in the calculation formula: s_V=(E[P_E[D]]／V(t))／E[D]=T_DATA／E[D]. The calculation formula eliminates the ambiguity of the comparison of different data transmission rates to throughput performance,the information such as effective use efficiency of the channel can be better reflected.

Based on the throughput duration and the network delay parameters, a system analysis model is defined as follows: f = S_V／E[D]. With the increase of the length of the data frame, the system analysis model can analyze the relationship between the throughput length growth rate and the delay growth rate and acquire the balance point of the throughput length growth rate and the delay growth rate. According to the defined time delay composition, F (T) can be further reduced_DATA)=S_V／E[D]= T_DATA /( T_DATA+T_Ctrl+T_Col+T_Idle)². Once the protocol of information interaction is determined, the analytical model F is about T_DATAAs a function of (c).

Let T be_DATAFor continuous functions, by analysing their derivatives, when T_DATA≤T_Ctrl+T_Col+T_IdleThe throughput duration growth rate is greater than the delay growth rate; when T is_DATA>T_Ctrl+T_Col+T_IdleThe delay growth rate is greater than the growth rate of the throughput duration. Thus, when T is obtained_DATA=T_Ctrl+T_Col+T_Idle，F(T_DATA) And obtaining an optimal value, namely that the throughput time length growth rate is maximum compared with the time delay growth rate.

Drawings

Fig. 1 is a detailed diagram of network latency.

Detailed description of the preferred embodiments

The invention mainly researches different growth amplitude relations of the throughput growth rate and the delay growth rate. In the present embodiment, only the basic access scheme and access parameter implementation of IEEE802.11 is given.

The implementation scheme of the invention adopts a DATA/ACK DATA interaction mode in an IEEE802.11 protocol. Successful transmission time T_SAnd collision determination time T_CRespectively as follows:

。

wherein, T_HEADRepresenting headers in data framesInformation, which is typically transmitted at a rate lower than the payload transmission rate. σ represents the propagation time of the information in the medium. T is_SIFSAnd T_DIFSRespectively representing SIFS and DIFS inter frame interval transmission times. T is_ACKIndicating the ACK acknowledgement frame transmission time. t is t_DATARepresenting the transmission time of a frame of payload.

According to the last reference, the time delay calculation formula can be obtained as follows:

wherein, T_S=T_HEAD+t_DATA+2σ+T_SIFS+T_ACKAnd E [ D ]]=T_DATA+T_Ctrl+T_Col+T_Idle；p_SIndicating the probability of successful transmission of data; p is a radical of_CRepresenting the collision probability in the data transmission process; p = p_S+p_CIndicating the conditional collision probability, i.e. the probability that the channel is busy; e [ U ]^(j)]Representing the average number of idle slots required for the jth backoff.

Definition of

，

And p_ST_DIFS+p_CT_EIFS+T_SLOTIs pi₁，π₂，β₁Respectively representing the average idle time, the average collision times and the average idle time after the channel is busy, which are required by the nodes to successfully transmit data; time delay E [ D ]]Can be written as E [ D ]]=t_DATA·(1+p_·π₁+π₂)+β₂。

Wherein the content of the first and second substances,

。

a throughput duration of S_V=S/V(T) =t_DATA(1+p_S·π₁)／E[D]Analysis ofModel (model)

. Let t_DATAFor continuous variable, the first derivative is calculated for the analysis model to obtain

(ii) a Wherein the content of the first and second substances,

,

。

when t is_DATAG is less than or equal to g, the throughput duration growth rate is greater than the delay growth rate, and the recommended range of the value of the effective load transmission time is selected; when t is_DATA>g, the throughput duration growth rate is smaller than the delay growth rate.

When t is_DATAAnd = g, obtaining an optimal value of the transmission time of the payload, wherein the ratio of the throughput duration growth rate to the delay growth rate reaches the highest value, and the value of the throughput duration is irrelevant to the number of nodes and only relevant to the access parameters and the propagation duration.

The above description is only exemplary of the present invention and is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and equivalent arrangements can be made without departing from the spirit and scope of the present invention.

Reference Chun S. Adaptive Access with optical content Window Based on Node Number Estimation Using Multiple Thresholds [ J ]. IEEE Transactions on Wireless Communications, 2012, 11(6): 2046-.

Claims (1)

1. A method for calculating effective data transmission time in a communication process is characterized by comprising the following steps:

step 1: calculating network delay E [ D ]]，E[D] = t_DATA*(1+p*π₁+π₂)+β₂Wherein, in the step (A),

t_DATAwhich represents the time of transmission of the payload,

p=p_S+p_Crepresenting the conditional collision probability, p, in the channel_SIndicating the probability of successful transmission of data, p, by only one node of the channel_CRepresenting the probability of two or more nodes in the channel transmitting data simultaneously,

and

respectively representing the average number of idle time slots pi required for successful transmission of a frame of data₁And average number of collisions pi₂K denotes the maximum data transfer retry threshold, E [ U ]^(j)]Representing the average number of free slots required for the jth backoff,

β₁=p_S*T_DIFS+p_C*T_EIFS+T_SLOT indicating a slot length T_SLOT And the extra average time p of successful transmission due to other nodes' transmission behavior within a time slot_S*T_DIFSAnd extra mean time of transmission collision p_C*T_EIFS ，T_DIFSAnd T_EIFSIndicating a DIFS inter frame interval time and an EIFS inter frame interval time,

β₂=(T_HEAD+T_SIFS+σ)*( 1+p*π₁+π₂) + (σ+T_ACK)*(p_S*π₁+1) + T_DIFS*( p_C*π₁+π₂)+β₁*π₁ ，

T_HEADrepresenting header information in a data frame, sigma representing the propagation time of the information in the medium, T_SIFSAnd T_ACKRespectively representing SIFS frame interval time and ACK response frame transmission time;

step 2: calculating throughput time length, enabling E [ P ] to represent effective data successfully transmitted in network delay E [ D ], enabling V (t) to represent effective data transmission rate, enabling the throughput time length Sv to represent the ratio of effective data transmission time to network delay, and the throughput time length calculating method comprises the following steps: sv = (E (p)/v (t))/E [ D ];

and step 3: establishing an analysis model based on the throughput duration and the network delay, wherein the analysis model F represents the ratio of the throughput duration to the network delay, and the calculation method of the analysis model comprises the following steps: f (t)_DATA)=Sv/E[D]=(t_DATA(1+p_S*π₁))/(t_DATA*(1+p*π₁+π₂)+β₂)² ；

And 4, step 4: let t_DATAFor continuous variables, the first derivative is calculated for the analytical model in step 3 to obtain F' (t)_DATA)=-(t_DATA-g)*G(t_DATA) Wherein, G (t)_DATA)= ((1+p_S*π₁)*(1+p*π₁+π₂))/(t_DATA*(1+p*π₁+π₂)+β₂)³ ，

g=β₂/((1+p*π₁+π₂))≈T_HEAD+T_SIFS+T_DIFS+T_EIFS+σ，

When t is_DATA<g, the throughput duration growth rate is larger than the network delay growth rate,

when t is_DATA= g, obtain the optimal value of payload transmission time.

Images