CN103826312A - Improved LTE (Long Term Evolution) scheduling method based on exponential rule - Google Patents

Abstract

The invention discloses an improved LTE (Long Term Evolution) scheduling method based on EXP (Exponential rule) scheduling algorithm, mainly to solve the problem that the existing algorithm is not applicable to mixed services. The method is that a weight factor in a scheduling priority coefficient is calculated according to the instantaneous rate at a nth TTI (Transmission Time Interval), the average transmission rate of a former (n-1)th TTI by the user i, and GBR (Guaranteed Bit Rate) parameters required by each service. The realization process comprises steps of calculating the signal-to-noise ratio at each subcarrier of user i, calculating the effective signal-to-noise ratio at each RB (Resource Block) of user i, calculating the instantaneous transmission rate reached at each RB of the nth TTI of the user i according to the corresponding GBR demand of each service, calculating the scheduling priority coefficient at each RB of the user i according to the corresponding GBR demand of each service.

Description

A kind of based on the improved LTE dispatching method of index criterion

Technical field

The present invention relates to LTE(Long Term Evolution) middle downlink resource piece (Resource Block) dispatching technique field, be specifically related to a kind of LTE system descending RB resource prioritization dispatching method based on mixed service in system.

Background technology

In recent years, along with the fast development of access demand and wireless communication technology widely of hybrid multimedia business in the Internet, there is explosive growth in wireless cellular network technology and market.Next generation mobile communication system 3GPP LTE, except high broadband demand, also will meet the quality of service requirement of Novel multimedia business simultaneously.

At present, main packet radio dispatching algorithm can be divided into two classes, one class is to consider the packet scheduling algorithm of physical layer (PHY-layer) channel quality, as max carrier to interference (Max C/I) dispatching algorithm, poll (Round Robin, RR) dispatching algorithm and equitable proportion (Proportional Fairness, PF) dispatching algorithm; Another kind of is the cross-layer packet scheduling algorithm that combines physical layer channel quality and media access control layer (MAC-layer) buffer queue, as M-LWDF(Modified Largest Weighted Delay First) dispatching algorithm and EXP dispatching algorithm.From algorithm starting point, the former does not consider the data cases in user link buffer queue, does not have delay constraint condition, is not suitable for real time business; Although and the latter is applicable to high-rate service, guaranteeing to have made improvement aspect time delay and optimization system capacity, its performance at the aspect such as packet loss and time delay also has certain deficiency.So on the whole, above-mentioned two class algorithms lack with Radio Resource and change the mechanism of dynamically adjusting its scheduling strategy the scheduling of mixed service.

Summary of the invention

The present invention will overcome the above-mentioned deficiency of prior art, a kind of dispatching method that is applicable to LTE system user mixed service is proposed, can be according to the variations situation of user's experience, and each business real-time demand and required assurance bit rate (GBR) require calculating priority level, not only to consider the GBR requirement of real time business, but also the business that will limit low GBR speed obtains too much Resource Block, give priority compensation for not meeting the business of GBR requirement.

To achieve these goals, the present invention takes following technical scheme:

A kind of based on the improved LTE dispatching method of EXP algorithm, comprise the following steps:

The calculated signals that step 1 receives according to user i goes out the signal to noise ratio of user i at each subcarrier;

Step 2 goes out the effective signal-to-noise ratio of user i at Resource Block according to user i in the snr computation of each subcarrier;

Step 3 is the effective signal-to-noise ratio on Resource Block according to user i, calculates the instantaneous transmission speed of user i at n TTI;

Step 4 at the instantaneous transmission speed at n TTI, is upgraded the average transmission rate of front n the TTI of user i according to user i;

Packet delay, time delay threshold value, the time delay of the user i queue heads packet that step 5 is obtained according to base station end exceedes maximum probability and the descending information flow number that enlivens in real time of time delay threshold value, calculates dispatching priority coefficient ω _i,jin parameter χ:

$x=\frac{1}{N_{\mathrm{rt}}}\underset{i=1}{\overset{N_{\mathrm{rt}}}{\mathrm{\Σ}}}{a}_i\·D_{\mathrm{HOL},i}$

Step 6, according to the parameter that whether Business Stream is real-time and step 1 to 5 is calculated, selects corresponding priority formula to calculate dispatching priority coefficient ω _i,j;

Wherein, N _rtfor the descending number that enlivens in real time information flow; r _i,jthe representative of consumer i moment transmission rate that j channel is supported in the time of n TTI; R _ifor the Mean Speed of channel support; GBR _iit is the GBR requirement of real time business.D _{hOL, i}for the HOL packet delay of user i in buffer queue; α _irepresent QoS rank,

wherein τ _ithe time delay threshold value of representative of consumer i, δ _iit is the time delay D of team's packet _{hOL, i}exceed the maximum probability of time delay threshold value.

Step 7: repeating step 1～6, obtains all users' dispatching priority coefficient, and obtained dispatching priority coefficient is carried out to size sequence, the user by resource block assignments to dispatching priority coefficient maximum.

Above-mentioned based in the improved LTE dispatching method of EXP algorithm, in n TTI, the signal to noise ratio of user i on subcarrier is arbitrarily:

${\mathrm{SINR}}_{i,k}\left(n\right)=\frac{P_k*{\mathrm{Gain}}_{i,k}\left(n\right)}{I+N_o}$

Wherein, P _kthe transmitting power of base station at k subcarrier, N _obe noise power, I is the interference power of minizone, Gain _i,k(n) be the channel gain of user i k subcarrier in n TTI, as shown in the formula:

${\mathrm{Gain}}_{i,k}\left(n\right)={10}^{\left(\frac{{\mathrm{pl}}_{i,k}\left(n\right)}{10}\right)}{*10}^{\left(\frac{{\mathrm{\ξ}}_{i,k}\left(n\right)}{10}\right)}{*10}^{\left(\frac{{\mathrm{mpath}}_{i,k}\left(n\right)}{10}\right)}$

Wherein pl _ik(n), ξ _ik(n), mpath _ik(n) be respectively path loss, shadow fading gain and the multipath fading gain of nth user i for k subcarrier.

Above-mentioned based in the improved LTE dispatching method of EXP algorithm, in n TTI, the signal to noise ratio of user i on j RB is:

${\mathrm{SNR}}_{i,j}\left(n\right)=\mathrm{EESM}({\mathrm{SINR}}_{i,j}\left(n\right),\mathrm{\σ})=-\mathrm{\σ}\·\ln \left(\frac{1}{M}{\underset{k}{\mathrm{\Σ}}e}^{-\frac{{\mathrm{SINR}}_{i,k}\left(n\right)}{\mathrm{\σ}}}\right)$

Wherein, σ is the factor changing with different coding modulation system (MCS); SINR _i,k(n) be in n TTI, the signal to noise ratio of user i on any subcarrier; K is norator carrier number in RB; M is a number of sub carrier wave in Resource Block.

In the above-mentioned step 3 based on the improved LTE dispatching method of EXP algorithm, user i is at the instantaneous transmission speed of n TTI:

r _i(n)=log ₂(1+SNR _i(n))。

The average transmission rate that upgrades user in the above-mentioned step 4 based on the improved LTE dispatching method of EXP algorithm is:

$R_i\left(n\right)=(1-\frac{1}{T_c})\·R_i(n-1)+\frac{1}{T_c}{r}_i\left(n\right)$

Wherein r _i(n) represent the instantaneous transmission speed of user i in the time of n TTI, T _cfor window update time.R _i(n-1) represent the average transmission rate in a previous n-1 TTI

In the above-mentioned step 6 based on the improved LTE dispatching method of EXP algorithm according to the whether corresponding computational methods of real-time selection of Business Stream.If non-real-time service stream, the computing formula while stream according to non-real-time service in formula is calculated dispatching priority coefficient ω _i,j.If real time business stream, according to the real time business stream computing formula calculating priority level coefficient ω in formula _i,j.

The present invention, compared with existing dispatching method, has the following advantages:

First whether the present invention be real-time according to Business Stream, selects corresponding formula calculating priority level coefficient.In the time that real time business flows, consider the GBR requirement of real time business, the business that limits low GBR speed obtains too much Resource Block, gives priority compensation for not meeting the business of GBR requirement.

item is new weight factor of adding, as a customer service Mean Speed R _i(n), while meeting the GBR of its speed assurance requirement, this value is 1, as a customer service Mean Speed R _i(n) while being less than the GBR of its speed assurance requirement, this value

therefore do not meet the customer service of minimum speed limit requirement by priority allocation Resource Block, obtain

compensation.Work as R _iand GBR _igap larger, weight factor is just larger, the priority of the Resource Block that user obtains is just higher.For having reached the user of business GBR requirement and the user that Non-GBR requires, the value of weight factor is 1, still according to original algorithmic formula calculating priority level, new algorithm had both utilized the advantage of EXP algorithm like this, also by limiting and add weight factor and guaranteed the GBR requirement of customer service, can support LTE mixed service scene.

Accompanying drawing explanation

Fig. 1 scheduling flow figure of the present invention

Fig. 2 priority calculation flow chart of the present invention

Embodiment

Further illustrate in real time of the present invention below in conjunction with accompanying drawing, accompanying drawing described herein is used to provide a further understanding of the present invention, a part that forms the application, its explanation of illustrative examples level of the present invention is used for explaining the present invention, does not form inappropriate limitation of the present invention.

Referring to Fig. 1, first, the signal receiving according to user i, calculate user i at n TTI the channel gain at all carrier waves, as shown in the formula:

${\mathrm{Gain}}_{i,k}\left(n\right)={10}^{\left(\frac{{\mathrm{pl}}_{i,k}\left(n\right)}{10}\right)}{*10}^{\left(\frac{{\mathrm{\ξ}}_{i,k}\left(n\right)}{10}\right)}{*10}^{\left(\frac{{\mathrm{mpath}}_{i,k}\left(n\right)}{10}\right)}$

Wherein pl _ik(n), ξ _ik(n), mpath _ik(n) be respectively path loss, shadow fading gain and the multipath fading gain of nth user i for k subcarrier.

The calculated signals receiving according to user i goes out the signal to noise ratio of user i at each subcarrier, as shown in the formula:

${\mathrm{SINR}}_{i,k}\left(n\right)=\frac{P_k*{\mathrm{Gain}}_{i,k}\left(n\right)}{I+N_o}$

Wherein, P _kthe transmitting power of base station at k subcarrier, N _obe noise power, I is the interference power of minizone, Gain _i,k(n) be the channel gain of user i k subcarrier in n TTI.

The signal to noise ratio of all carrier waves by user i in its shared each RB is converted into the effective signal-to-noise ratio of this RB:

${\mathrm{SNR}}_{i,j}\left(n\right)=\mathrm{EESM}({\mathrm{SINR}}_{i,j}\left(n\right),\mathrm{\σ})=-\mathrm{\σ}\·\ln \left(\frac{1}{M}{\underset{k}{\mathrm{\Σ}}e}^{-\frac{{\mathrm{SINR}}_{i,k}\left(n\right)}{\mathrm{\σ}}}\right)$

Wherein, SINR _i,k(n) be in n TTI, the signal to noise ratio of user i on any subcarrier; K is norator carrier number in RB; M is a number of sub carrier wave in Resource Block, if use the frame structure of common prefix, the value of M is 7, if use the frame structure of expanded prefix, M value is 6; σ is the factor changing with different coding carving mode processed (MCS), and value can be inquired about by table 1:

Table 1

Calculate user i at n TTI instantaneous transmission speed:

r _i(n)=log ₂(1+SNR _i(n))。

At n TTI instantaneous transmission speed, upgrade the Mean Speed R of front n the TTI of user i according to user i _i(n):

$R_i\left(n\right)=(1-\frac{1}{T_c})\·R_i(n-1)+\frac{1}{T_c}{r}_i\left(n\right)$

The packet delay DHOL of the user i team packet then obtaining according to base station segment, i, time delay threshold tau i and time delay exceed the maximum probability δ of time delay threshold value _i, the descending information flow number N of enlivening in real time _rt, calculate dispatching priority coefficient ω _i,jin parameter χ:

$x=\frac{1}{N_{\mathrm{rt}}}\underset{i=1}{\overset{N_{\mathrm{rt}}}{\mathrm{\Σ}}}{a}_i\·D_{\mathrm{HOL},i}$

Described dispatching priority coefficient ω _i,jfor:

The Business Stream transmitting according to different user is real time business stream or non-real-time service stream, and the parameter of step 1 to 5 gained, adopts respectively different scheduling formula calculating priority level.In the time that Business Stream is real time business stream (as video flowing, VIDEO), computing formula when real time business flows in employing formula is carried out calculating priority level; When non-real-time service flows in this way (as Best-Effort service stream (Best Effort, BE)), the computing formula that is according to the non-real-time service stream in formula is carried out calculating priority level, and whole flow process is shown in Fig. 2.

The weight factor of adding is

as a customer service Mean Speed R _iwhile meeting the GBR of its speed assurance requirement, this value is 1.As a customer service Mean Speed R _iwhile being less than the GBR of its speed assurance requirement, this value

therefore do not meet the customer service of minimum speed limit requirement by priority allocation Resource Block, obtain

compensation.Work as R _iand GBR _igap larger, weight factor is just larger, the priority of the Resource Block that user obtains is just higher, and for the user who has reached user that business GBR requires and Non-GBR and require, the value of weight factor is 1.

According to above step, obtain the dispatching priority sequence of k the upper all users of RB in n TTI, resource is distributed to scheduling highest-ranking user, the namely user of priority factor maximum.

Claims (6)

1. based on the improved LTE dispatching method of EXP algorithm, it is characterized in that, said method comprising the steps of:

The calculated signals that step 1 receives according to user i goes out the signal to noise ratio of user i at each subcarrier;

Step 2 goes out the effective signal-to-noise ratio of user i at each Resource Block according to user i in the snr computation of each subcarrier;

Step 3 is the effective signal-to-noise ratio on each Resource Block according to user i, calculates the instantaneous transmission speed of user i at n TTI;

Step 4 is the instantaneous transmission speed at n TTI according to user i, upgrades the average transmission rate of user i front n TTI moment;

Packet delay, time delay threshold value, the time delay of the user i queue heads packet that step 5 is obtained according to base station end exceedes maximum probability and the descending information flow number that enlivens in real time of time delay threshold value, calculates dispatching priority coefficient ω _i,jin parameter χ:

Step 6, according to the Business Stream parameter that requirement of real-time and step 1 to 5 are calculated, selects corresponding priority formula to calculate dispatching priority coefficient;

Described dispatching priority coefficient ω _i,jfor:

Wherein, N _rtfor the descending number that enlivens in real time information flow; r _i,jthe representative of consumer i moment transmission rate that j channel is supported in the time of n TTI; R _ifor the Mean Speed of channel support; GBR _iit is the GBR requirement of real time business; D _{hOL, i}for the HOL packet delay of user i in buffer queue; α _irepresent QoS rank,

wherein τ _ithe time delay threshold value of representative of consumer i, δ _iit is the time delay D of team's packet _{hOL, i}exceed the maximum probability of time delay threshold value;

Step 7: repeating step 1～6, obtains all users' dispatching priority coefficient, and obtained dispatching priority coefficient is carried out to size sequence, the user by resource block assignments to dispatching priority coefficient maximum.

2. method according to claim 1, in described step 4, in n TTI, the signal to noise ratio of user i on any subcarrier is:

Wherein, P _kthe transmitting power of base station at k subcarrier, N _obe noise power, I is the interference power of minizone, Gain _i,k(n) be the channel gain of user i k subcarrier in n TTI, as shown in the formula:

Wherein pl _ik(n), ξ _ik(n), mpath _ik(n) be respectively path loss, shadow fading gain and the multipath fading gain of nth user i for k subcarrier.

3. method according to claim 1, in described step 2, in n TTI, the signal to noise ratio of user i on j RB is:

Wherein, σ is the factor changing with different coding modulation system (MCS); SINR _i,k(n) be the signal to noise ratio of user i on any subcarrier in n TTI; K is norator carrier number in RB; M is a number of sub carrier wave in Resource Block.

4. method according to claim 1, the instantaneous transmission speed of user i in the time of n TTI in described step 3:

r _i(n)=log ₂(1+SNR _i(n))?。

5. method according to claim 1, the average transmission rate that upgrades user in described step 4 is:

Wherein r _i(n) represent the instantaneous transmission speed of user i in the time of n TTI, T _cfor window update time.R _i(n-1) represent the average transmission rate in a previous n-1 TTI.

6. method according to claim 1, according to the whether corresponding computational methods of real-time selection of Business Stream, if non-real-time service stream, calculates dispatching priority coefficient ω according to computing formula when non-real-time service stream in formula in described step 6 _i,j; If real time business stream calculates dispatching priority coefficient ω according to the real time business stream formula in formula _i,j; Try to achieve thus the priority factor of this user i at j channel.

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