CN103929255A - Cognitive user energy efficiency optimization method based on multiple channels - Google Patents

Abstract

The invention discloses a cognitive user energy efficiency optimization method based on multiple channels, and belongs to the technical field of digital communications. The method is based on a multi-channel energy efficiency model of cognitive radio, optimization of the cognitive user energy efficiency is converted into optimization of the dual problem of the energy efficiency model, based on a transmission structure of a data frame, the optimized total transmission power (at the free state and at the busy state) corresponding to a plurality of detection time points within the perceptive searching time period in which the optimal perceptive time occurs possibly is calculated, and then the total transmission power and detection time points corresponding to the minimum energy efficiency are found out, are stored in a frame structure of the data frame to be sent currently and serve as the optimal perceptive time and the optimal distribution power of the current data frame. The method is used for a cognitive radio communication system, and has the advantages that the optimal perceptive time point and the transmission power distribution of cognitive users are output efficiently, and the energy efficiency of the communication transmission system is optimized under the shortage of spectrums.

Description

A kind of based on multi channel cognitive user efficiency optimization method

Technical field

The present invention relates to digital communicating field, particularly a kind of cognitive user efficiency optimization method in the multichannel system based on cognitive radio technology.

Background technology

Along with the development of wireless communication technology, especially 3G, the continuous maturation of LTE technology, people constantly expand the demand of data service, and current frequency spectrum resource can not meet data traffic requirement.For above problem, a communication technology that is called cognitive radio (CR) is arisen at the historic moment, and CR refers to one to be had perception, possess the wireless communication system of " learning ability " environment.Actual conditions by cognitive nodes to environment measuring, dynamic-configuration and the relevant parameter of communicating by letter (as coded modulation, access way, network etc.), guarantee system communication quality, rationally, efficient utilize " frequency spectrum cavity-pocket ", in communication process, in the situation that insuring telecommunication service quality, how consumption of energy is also the focus of paying close attention to now as much as possible less simultaneously.

Current existing be for single-channel situation mostly by cognitive radio and efficiency the energy-saving and cost-reducing of consideration wireless communication procedure of optimizing integration, for example document " Y.Wu and D.H.K.Tsang, " Energy-efficient spectrum sensing and transmission for cognitive radio system[J] .Communications Letters, IEEE, 2011, 15 (5): 545-547. " pointed out under single channel perception power consumptions different in radio cognitive radio system, through-put power consumes, the impact of no-load power consumption on optimum detecting period, and document " L.Li, X.Zhou, H.Xu, et al., Energy-efficient transmission in cognitive radio networks[C] .CCNC IEEE2010, 9 (1): 1-5. " in, mention under single channel to optimal transmission and power allocation scheme under the interference-limited of authorized user.And at document " Y.Pei, Y.C.Liang, K.C.The, et al.Energy-efficient design of sequential channel sensing in cognitive radio networks:optimal sensing strategy, power allocation, and sensing order[J] .Selected Areas in Communications, IEEE Journal on, 2011, 29 (8): 1648-1659. " in, a kind of efficiency optimization based on multi channel cognitive user has been proposed, it is by the serial perception to multichannel cognitive user, when analyzed perceptual strategy (starts and finishes perception, transmission), access strategy (through-put power size) and perception order (channel-aware order) impact on cognitive user efficiency, but because its implementation procedure is the mode of serial, cause the implementation procedure of its efficiency optimization to have inefficient defect, can not meet preferably the communications demand of cognitive radio system.

Summary of the invention

Goal of the invention of the present invention is: the frequency spectrum perception technology based under multichannel, proposes a kind of parallel cognitive user efficiency optimization method based under multichannel, the treatment effeciency of optimizing to improve efficiency.

One of the present invention, based on multi channel cognitive user efficiency optimization method, comprises the following steps:

Step 1: the frame transmission time T based on Frame, section search time of detecting period is set, by described search time section be separated into the identical test detecting period point τ in multiple intervals _test;

Step 2: before current data to be transmitted frame transmission, aware services device is successively to each test detecting period point τ _testcalculate preferred overall transmission power with preferably efficiency η (τ _test, P ⁽⁰⁾, P ⁽¹⁾) ^*:

201: two variable parameter: λ 1, λ 2 are set, and the initial value of λ 1 is that the initial value of 0, λ 2 is greater than 10^ (10);

202: judge that whether λ 2 and the difference of λ 1 are less than or equal to preset value ε, if so, perform step 204; Otherwise execution step 203, described preset value ε is for being less than or equal to the positive number of 10^ (10);

203: calculate F (λ by calling interior point method function f mincon (x, y, z) _mid) value, if F (λ _mid) be less than or equal to 0, make λ 2 equal λ _mid, and perform step 202; If F is (λ _mid) be greater than 0, make λ 1 equal λ _mid, and perform step 202;

Wherein λ _midrepresent the average of λ 1 and λ 2;

In described interior point method function f mincon (x, y, z),

The corresponding optimization aim min{E of x (τ _test, P ⁽⁰⁾, P ⁽¹⁾)-λ _midc (τ _test, P ⁽⁰⁾, P ⁽¹⁾), the overall average energy of multichannel cognitive user $E({\mathrm{\τ}}_{\mathrm{test}},P^{\left(0\right)},P^{\left(1\right)})=E[{\mathrm{MP}}_{\mathrm{sens}}{\mathrm{\τ}}_{\mathrm{test}}+\underset{i=1}{\overset{M}{\mathrm{\Σ}}}(T-{\mathrm{\τ}}_{\mathrm{test}})P_i],$ The average transmission rate of multichannel cognitive user symbol E[] expression averaged, P ⁽¹⁾represent the overall transmission power of cognitive user under busy condition, P ⁽⁰⁾represent the overall transmission power of cognitive user under idle condition, P _sensthe perception power that represents cognitive user, M represents the number of subchannels of cognitive user, P _i=α _{0, i}p ⁽⁰⁾+ α _{1, i}p ⁽¹⁾+ β _{0, i}p ⁽⁰⁾+ β _{1, i}p ⁽¹⁾represent the average transmission gross power of subchannel i, C _i=α _{0, i}r _{00, i}+ α _{1, i}r _{01, i}+ β _{0, i}r _{10, i}+ β _{1, i}r _{11, i}represent the average transmission rate of subchannel i, wherein α _{0, i}, α _{1, i}, β _{0, i}, β _{1, i}represent that channel i is the probability of detected state a, b, c, d, r _{00, i}, r _{01, i}, r _{10, i}, r _{11, i}transmission rate while representing detected state a, b, c, the d of respective channels i, described detected state a, b, c, d are followed successively by: detected state a, cognitive user and authorized user are idle condition; Detected state b, cognitive user is that idle condition and authorized user are busy condition; Detected state c, cognitive user is that busy condition and authorized user are idle condition; Detected state d, cognitive user and authorized user are busy condition;

Y represents the total mean power restrictive condition of cognitive user M sub-channels wherein P _avrepresent the average maximum transmission power of cognitive user;

Z represents the average interference power restrictive condition of every sub-channels wherein Ii represents the interference power that in subchannel i, authorized user is received, represent the maximum average interference that authorized user can be accepted;

204: parameters λ ^*, the value of described λ * is λ 1～λ 2, and optimizes formula F (λ)=min{E (τ based on efficiency _test, P ⁽⁰⁾, P ⁽¹⁾)-λ C (τ _test, P ⁽⁰⁾, P ⁽¹⁾), the value of getting variable λ is parameter lambda ^*time corresponding overall transmission power P ⁽¹⁾and P ⁽⁰⁾for current test detecting period point τ _testpreferred overall transmission power with , and according to efficiency formula calculate and described preferred overall transmission power with corresponding preferred efficiency η (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*;

Step 3: each perception test time point τ obtaining based on described step 1 and 2 _testcorresponding preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*in, get minimum preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*corresponding perception test time point, preferred overall transmission power with for optimum detecting period, the optimum allocation power of current data to be transmitted frame.

In sum, owing to having adopted technique scheme, the invention has the beneficial effects as follows: in multi channel radio cognitive radio system, optimum detecting period point and the transmit power allocation of parallel output cognitive user, realized the efficiency of optimize communicate transmission system in the situation that of frequency spectrum shortage.

Brief description of the drawings

Fig. 1 is the traffic model schematic diagram of cognitive user and authorized user;

Fig. 2 is the wide band detection schematic diagram of cognitive user;

Fig. 3 is the data frame structure of cognitive user.

Embodiment

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with execution mode and accompanying drawing, the present invention is described in further detail.

In cognitive user as shown in Figure 1 and the traffic model of authorized user, utilize dispensing device to be divided into the equal subchannel of disjoint M bandwidth on frequency spectrum the bandwidth B of an authorized user (access frequency spectrum B), on this M sub-channels, transmit data or in resting state simultaneously, cognitive user is utilized the authorized user state of its wide band detection device perception simultaneously M sub-channels, as shown in Figure 2, if there is energy, be expressed as busy condition, otherwise be idle condition.

But we select broadband perceived spectral shared access scheme for cognitive user, in this access scheme, no matter authorized user is in which kind of state, cognitive user is all by insertion authority user's mandate band transmissions data, and adjusts through-put power according to sensing results.If authorized user is in seizure condition (being busy condition), cognitive user transmission adopts lower-wattage, the interference of restriction to authorized user; If authorized user is in idle condition, cognitive user transmission adopts higher-wattage.And utilize the authorized user state of cognitive user wide band detection device (the down converter f1～fM shown in figure and energy detector 1～M) perception simultaneously M sub-channels as shown in Figure 2.Suppose i (i=1,2 ... M) channel authorization user's state is detected as free time (H _{0, i}) time, the total power consumption (transmission consumes and circuitry consumes sum, also claims the average transmission gross power of channel i) of cognitive user is designated as P _i ⁽⁰⁾, and i channel authorization user's state is detected as and takies (H _{1, i}) time, the total power consumption of cognitive user is designated as P _i ⁽¹⁾, in the detected state schematic diagram of the output shown in Fig. 2, " 0 " the corresponding idle condition in each subscript, " 1 " corresponding busy condition; To the average transmission gross power P of channel i _i, distinguish idle condition and busy condition by subscript " (0) " and " (1) ".

Owing to being a binary test problems to the state-detection of channel i, therefore there are four kinds of detected states that may exist, be respectively: detected state a, b, c, d are followed successively by: detected state a, cognitive user and authorized user are idle condition; Detected state b, cognitive user is that idle condition and authorized user are busy condition; Detected state c, cognitive user is that busy condition and authorized user are idle condition; Detected state d, cognitive user and authorized user are busy condition.Under above-mentioned four kinds of detected states, remember that its corresponding probability is respectively α _{0, i}, α _{1, i}, β _{0, i}, β _{1, i}(lower target state indications depends on the state of authorized user), can be calculated the transmission rate under detected state a, b, c, d of channel i by shannon formula, it is expressed as successively: r _{00, i}, r _{01, i}, r _{10, i}, r _{11, i}, the average transmission rate of subchannel i can be expressed as C _i=α _{0, i}r _{00, i}+ α _{1, i}r _{01, i}+ β _{0, i}r _{10, i}+ β _{1, i}r _{11, i}, the overall transmission power of channel i is expressed as P _i=α _{0, i}p _i ⁽⁰⁾+ α _{1, i}p _i ⁽¹⁾+ β _{0, i}p _i ⁽⁰⁾+ β _{1, i}p _i ⁽¹⁾.

Meanwhile, in order to keep the long-term power budget of cognitive user, the total mean power of cognitive user M sub-channels will be restricted, and restrictive condition is wherein T, τ is the frame structure parameter of cognitive user Frame, and as shown in Figure 3, T represents the frame transmission time of Frame, and τ represents detecting period, P _avrepresent the average maximum transmission power of cognitive user; In order not affect the transfer of data of authorized user, the average interference power of every sub-channels also should be restricted, and the average interference power restrictive condition of subchannel i is wherein I _irepresent the interference power that in subchannel i, authorized user is received, represent the maximum average interference that authorized user can be accepted.

The multichannel efficiency Optimized model based on cognitive radio can be expressed as:

$\underset{\mathrm{\τ},P^{\left(0\right)},P^{\left(1\right)}}{\min }\mathrm{\η}(\mathrm{\τ},P^{\left(0\right)},P^{\left(1\right)})=\frac{E(\mathrm{\τ},P^{\left(0\right)},P^{\left(1\right)})}{C\mathrm{\τ},P^{\left(0\right)},P^{\left(1\right)})}=\frac{E[{\mathrm{MP}}_{\mathrm{sens}}\mathrm{\τ}+\underset{i=1}{\overset{M}{\mathrm{\Σ}}}(T-\mathrm{\τ})P_i]}{E\left[\underset{i=1}{\overset{M}{\mathrm{\Σ}}}(T-\mathrm{\τ})C_i\right]}---\left(1\right)$

Constraints is: $f_0=\frac{T-\mathrm{\τ}}{T}E\left[\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{P}_i\right]-P_{\mathrm{av}}\≤0$

Efficiency η (τ, P ⁽⁰⁾, P ⁽¹⁾) represent the energy of every transmission one Bit data of user required consumption, i.e. energy efficiency, referred to as efficiency, wherein, E (τ, P ⁽⁰⁾, P ⁽¹⁾) represent the overall average energy of multichannel cognitive user, C (τ, P ⁽⁰⁾, P ⁽¹⁾) represent the average transmission rate of multichannel cognitive user, symbol E[] represent to ask for the mean value in square brackets, P ⁽¹⁾represent the overall transmission power of cognitive user under busy condition, P ⁽⁰⁾represent the overall transmission power of cognitive user under idle condition, P _sensrepresent the perception power of cognitive user.

The present invention is by being converted to above-mentioned efficiency Optimized model expression formula (1) its dual problem F (λ)=min{E (τ, P ⁽⁰⁾, P ⁽¹⁾)-λ C (τ, P ⁽⁰⁾, P ⁽¹⁾) optimization, concrete optimization implementation is:

Ste _p1: the frame transmission time T based on Frame, section search time of detecting period τ is set, concrete value, based on practical situations, in present embodiment, arranges ST section for [0,0.5T], is separated into the identical test detecting period point τ in multiple intervals _test, in the present embodiment, each tests the 0.05s that is spaced apart of detecting period point, when actual use, can set voluntarily according to demand;

Step2: before current data to be transmitted frame transmission, aware services device is successively to each perception test time point τ _testcalculate preferred overall transmission power with preferred energy efficiency _η(τ, P (0), P (1)) *, even given perception τ is perception test time point τ _test, execution step 201～204:

201: two variable parameter: λ are set _minand λ _max, λ _mininitial value be 0, λ _maxinitial value be set to be greater than 10^ (10), in this embodiment, the initial value of λ 2 is 10^ (6);

202: if λ _max-λ _min≤ ε, performs step 204; Otherwise execution step 203, preset value ε is for being less than or equal to the positive number of 10^ (10);

203: λ is set _mid=(λ _min+ λ _max)/2, call interior point method function f mincon (x, y, z) and calculate F (λ _mid) value,

If F is (λ _mid)≤0, makes λ _max=λ _mid, and perform step 202; If F is (λ _mid) > 0, make λ _min=λ _mid, return to step 202;

In interior point method function f mincon (x, y, z), the corresponding optimization aim min{E of x (τ, P ⁽⁰⁾, P ⁽¹⁾)-λ _midc (τ, P ⁽⁰⁾, P ⁽¹⁾), y represents the total mean power restrictive condition f of cognitive user M sub-channels ₀; Z represents the average interference power restrictive condition f of every sub-channels _i;

204: by repeated execution of steps 202 and 203, constantly approach λ _minand λ _maxvalue, work as λ _max-λ _minwhen≤ε, obtain preferred λ ^*, its value is λ ^*=λ _min(in actual applications, because λ _minand λ _maxvalue approach very much, preferably λ ^*value also can get λ ^*=λ _max, or λ _minand λ _maxbetween arbitrarily count);

Based on preferred λ ^*, by formula F (λ)=min{E (τ, P ⁽⁰⁾, P ⁽¹⁾)-λ C (τ, P ⁽⁰⁾, P ⁽¹⁾) to P ⁽0), P ⁽¹⁾ask local derviation to show that cognitive user is at current test detecting period point τ _testtime preferred overall transmission power with , and according to the efficiency formula shown in formula (1) obtain with with corresponding energy efficiency η (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*, and record and current test detecting period point τ _testcorresponding and η (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*;

Step 3: get each perception test time point τ at repeating step 1 and 2 _testcorresponding preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*after, find out minimum preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*as optimum efficiency η (τ, P ⁽⁰⁾, P ⁽¹⁾) ^optimal, by corresponding this optimum efficiency detecting period point τ _test, preferred overall transmission power with for the frame structure of current data to be transmitted frame, as its optimum detecting period, optimum allocation power, after the current data frame end of transmission, aware services device carries out perception and the optimization of a new round.

The above, be only the specific embodiment of the present invention, and arbitrary feature disclosed in this specification, unless narration especially all can be replaced by other equivalences or the alternative features with similar object; Step in disclosed all features or all methods or process, except mutually exclusive feature and/or step, all can be combined in any way.

Claims (4)

1. based on a multi channel cognitive user efficiency optimization method, it is characterized in that, comprise the following steps:

Step 1: the frame transmission time T based on Frame, section search time of detecting period is set, by described search time section be separated into the identical test detecting period point τ in multiple intervals _test;

Step 2: before current data to be transmitted frame transmission, aware services device is respectively to each test detecting period point τ _testcalculate preferred overall transmission power with preferably efficiency η (τ _test, P ⁽⁰⁾, P ⁽¹⁾) ^*:

201: two variable parameter: λ 1 and λ 2 are set, and the initial value of λ 1 is that the initial value of 0, λ 2 is greater than 10^ (10);

202: judge that whether λ 2 and the difference of λ 1 are less than or equal to preset value ε, if so, perform step 204; Otherwise execution step 203, described preset value ε is for being less than or equal to the positive number of 10^ (10);

203: calculate F (λ by interior point method function f mincon (x, y, z) _mid) value, if F (λ _mid) be less than or equal to 0, make λ 2 equal λ _mid, and perform step 202; If F is (λ _mid) be greater than 0, make λ 1 equal λ _mid, and perform step 202;

Wherein λ _midrepresent the average of λ 1 and λ 2;

In described interior point method function f mincon (x, y, z),

The corresponding optimization aim min{E of x (τ _test, P ⁽⁰⁾, P ⁽¹⁾)-λ _midc (τ _test, P ⁽⁰⁾, P ⁽¹⁾), the overall average energy of multichannel cognitive user $E({\mathrm{\τ}}_{\mathrm{test}},P^{\left(0\right)},P^{\left(1\right)})=E[{\mathrm{MP}}_{\mathrm{sens}}{\mathrm{\τ}}_{\mathrm{test}}+\underset{i=1}{\overset{M}{\mathrm{\Σ}}}(T-{\mathrm{\τ}}_{\mathrm{test}})P_i],$ The average transmission rate of multichannel cognitive user symbol E[] expression averaged, P ⁽¹⁾represent the overall transmission power of cognitive user under busy condition, P ⁽⁰⁾represent the overall transmission power of cognitive user under idle condition, P _sensthe perception power that represents cognitive user, M represents the number of subchannels of cognitive user, P _i=α _{0, i}p ⁽⁰⁾+ α _{1, i}p ⁽¹⁾+ β _{0, i}p ⁽⁰⁾+ β _{1, i}p ⁽¹⁾represent the average transmission gross power of subchannel i, C _i=α _{0, i}r _{00, i}+ α _{1, i}r _{01, i}+ β _{0, i}r _{10, i}+ β _{1, i}r _{11, i}represent the average transmission rate of subchannel i, wherein α _{0, i}, α _{1, i}, β _{0, i}, β _{1, i}represent that channel i is the probability of detected state a, b, c, d, r _{00, i}, r _{01, i}, r _{10, i}, r _{11, i}transmission rate while representing detected state a, b, c, the d of respective channels i, described detected state a, b, c, d are followed successively by: detected state a, cognitive user and authorized user are idle condition; Detected state b, cognitive user is that idle condition and authorized user are busy condition; Detected state c, cognitive user is that busy condition and authorized user are idle condition; Detected state d, cognitive user and authorized user are busy condition;

Y represents the total mean power restrictive condition of cognitive user M sub-channels represent the average maximum transmission power of cognitive user;

Z represents the average interference power restrictive condition of every sub-channels wherein Ii represents the interference power that in subchannel i, authorized user is received, represent the maximum average interference that authorized user can be accepted;

204: parameters λ ^*, described λ ^*value be λ 1～λ 2, and optimize formula F (λ)=min{E (τ based on efficiency _test, P ⁽⁰⁾, P ⁽¹⁾)-λ C (τ _test, P ⁽⁰⁾, P ⁽¹⁾), the value of getting variable λ is parameter lambda ^*time corresponding overall transmission power P ⁽¹⁾and P ⁽⁰⁾for current test detecting period point τ _testpreferred overall transmission power with and according to efficiency formula calculate and described preferred overall transmission power with corresponding preferred efficiency η (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*;

Step 3: each perception test time point τ obtaining based on described step 1 and 2 _testcorresponding preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*in, get minimum preferred energy efficiency eta (τ, P ⁽⁰⁾, P ⁽¹⁾) ^*corresponding perception test time point, preferred overall transmission power with for optimum detecting period, the optimum allocation power of current data to be transmitted frame.

2. the method for claim 1, is characterized in that, each perception test time point τ _testthe time interval is 0.1ms～0.5ms.

3. the method for claim 1, is characterized in that, described search time, section was [0, kT], and the span of k is 0.4～0.6.

4. the method for claim 1, is characterized in that, in described step 201, the initial value of λ 2 is 10^ (6).