CN104601287B - The relaying method for precoding of information and energy is transmitted in wireless cognition network - Google Patents

The relaying method for precoding of information and energy is transmitted in wireless cognition network Download PDF

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Publication number
CN104601287B
CN104601287B CN201510026603.3A CN201510026603A CN104601287B CN 104601287 B CN104601287 B CN 104601287B CN 201510026603 A CN201510026603 A CN 201510026603A CN 104601287 B CN104601287 B CN 104601287B
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energy
user
relay
information
transmitted
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CN104601287A (en
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宋苗苗
归琳
张萌
秦熠
罗汉文
宫博
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Shanghai Jiaotong University
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Shanghai Jiaotong University
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0009—Systems modifying transmission characteristics according to link quality, e.g. power backoff by adapting the channel coding
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations
    • H04B7/15528—Control of operation parameters of a relay station to exploit the physical medium
    • H04B7/15535—Control of relay amplifier gain
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H04L1/0637—Properties of the code

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Quality & Reliability (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

The relaying method for precoding of information and energy is transmitted in a kind of wireless cognition network, including at least a base station, multiple relayings and a user, wherein, the information of base station transmission is repeated to be transmitted to user, relay simultaneously and send energy to user, step includes base station and carries out uplink and downlink channel estimation, and sends a signal to relaying；In the case of relaying the channel errors under consideration after between user, robustness precoding is carried out；The energy that relaying sends the information after processing and expectation to receiving terminal is sent；User receives information and the energy signal that relaying is sent.The present invention transmits power to user by via node, meets the energy requirement of user, ensures that the transmission power of relaying is less than a threshold value, and for the method that the SNR of the receiving terminal probability used with the energy value received limits, with more feasibility.

Description

Relay precoding method for transmitting information and energy in wireless cognitive network
Technical Field
The invention relates to the technical field of wireless communication, in particular to a relay precoding method for simultaneously transmitting information and energy in a wireless cognitive network.
Background
With the development of wireless networks, wireless transmission of information and energy between devices has received increasing attention. In order to meet the increasing experience requirements of people, the functions of the intelligent terminal are continuously increased, and the power consumption of the intelligent terminal is increased. Energy limitation is an important factor that limits the service time of intelligent terminals. Although the service time of the intelligent terminal can be prolonged by replacing the battery, the convenience of the intelligent terminal is reduced, and the use cost of a user is increased. A more convenient, safe, green alternative is to harvest energy from the environment. This provides an almost constant source of energy for the wireless terminal. Solar energy and wind energy can be used as energy sources, and radio frequency signals can be used as a new energy source. It is noted that the energy extracted from the radio frequency signal is generally suitable for low power consuming networks, such as sensor networks. However, if a dedicated wireless energy transmission network is established, the wireless radio frequency signal can be used as a stable and reliable energy supply source. The topic is not only studied in a wide range of academic aspects, but also is regarded as important in the field of industrial application. An important issue to be solved is to effectively design a method for transmission between devices to help solve the problem of information and energy transmission in reality.
The invention firstly provides a transmission flow for simultaneously transmitting information and energy based on a wireless relay network. Where the channel between the base station and the relay is an ideal channel, but the channel between the relay and the user has a norm-limited error. Aiming at the existing errors, the invention provides a robust precoding design scheme of information and energy transmission precoding. Compared with a non-robust precoding design scheme, the scheme not only can effectively reduce the power consumed by the relay, but also can ensure the service quality and the energy acquisition quantity of a receiving end.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a relay precoding method for transmitting information and energy in a wireless cognitive network.
The technical solution of the invention is as follows:
a relay precoding method for transmitting information and energy in a wireless cognitive network is characterized in that the network at least comprises a base station, a plurality of relays and a user, wherein the information sent by the base station is forwarded to the user through the relays, and meanwhile, the relays send energy to the user, and the method specifically comprises the following steps:
step 1, a base station carries out uplink and downlink channel estimation and sends signals to a relay;
step 2, the relay performs robust precoding under the condition of considering channel errors between the relay and a user, namely, the received information from the base station and the energy expected to be transmitted to a receiving end are subjected to robust precoding to obtain a robust precoding matrix W of the received information and a robust precoding matrix of the energy expected to be transmitted to the receiving end;
the robust precoding matrix is used for ensuring the signal-to-noise ratio (SNR) of users>SthIs the most probable precoding matrix, where SthIs a preset value of SNR;
step 3, the relay sends out the processed information and the energy expected to be transmitted to the receiving end;
and 4, receiving the information and energy signals transmitted by the relay by the user.
The base station sends the information to the relay, so that the base station can measure the channel state information between the base station and the relay and send the information to the relay. The received signal is relayed as
yr＝Hs+nr(1)
Where s is data transmitted from the base station, H is a channel between the base station and the relay, and nrIs gaussian noise.
The signal to be retransmitted by the relay comprises an information signal and an energy signal. The relay performs precoding design on the two signals respectively. The relayed transmission signals are as follows:
xr＝WHs+Wnr+Va (2)
w in the formula is a precoding matrix of the relay to the received information, and V is a precoding matrix a of the relay to the energy signal. Energy of relay transmission which satisfies
The signal received by the user comprises a signal forwarded by the relay and noise. The signal received by the user can be written as:
yd＝G(WHs+Wnr+Va)+nd(3)
in the formula, G represents a downlink channel between the receiving end and the user. n isdIs additive white gaussian noise between the user and the relay.
The channel information of the whole model is an ideal channel when the signal between the base station and the relay exists, the channel between the relay and the user has errors, and the channel matrix between the relay and the user is modeled as
Wherein,is the CSI estimate and ag is the corresponding channel state information error.
If each node has perfect channel information, thenIn a matrix ofDeltag are all independent and identically distributed gaussian variables,
the SNR of the user is expressed as
The energy received by the receiving end is yEGVa, the following condition needs to be satisfied:
Z＝wwH,Y＝vvHwhere W and V are diagonal matrices of W and V, respectively, and then using equation XyyHXH＝YxxHYHAnd (5) and (6) are transformed, wherein X is diag (X) and Y is diag (Y).
The robust precoding design of the relay transmission signal is to maximize the probability that the SNR value of the user is greater than a preset value, and simultaneously guarantee the service quality and the energy receiving quantity of the user, and the following optimization problem is given (P1):
s.t.E(||xr||2)≤Pr(7b)
Prob{E(||ye||2)≥Pth}≥r (7c)
the invention uses strict norm limitation to replace probability limitation, and SNR received by user and energy received by receiving end can be rewritten as
SNR-Sth＝ΔGQ1ΔGH+2Re(ΔGr1)+s1≥0 (8)
E[||yE||2]-Pth＝ΔGQ2ΔGH+2Re(ΔGr2)+s2≥0 (9)
Wherein, Q2＝Y，
according to S-lemma, (7) (8) can be further limited to:
wherein,
the transmission power of the relay is satisfied
Wherein,Q2＝Y。
thus, the optimization problem (P1) can be represented as (P2):
s.t.Tr(QrZ)+Tr(Q2)≤Pr(13b)
t1≥0,t2≥0,0≤t≤1 (13e)
Rank(Y)＝1,Rank(Z)＝1 (13f)
since the rank of Y, Z in (13f) is 1, making (P2) not a problem for convex optimization, the present invention uses semi-positive relaxation to discard the matrix constraint, first keeping the optimization problem convex, and then using dichotomy to find the optimal solution to the problem. The specific algorithm is as follows:
1, initialization:
1) introduction of tmin,tmaxN, η and NmaxThey correspond to the lower search bound of the dichotomy algorithm, the upper bound of the dichotomy algorithm, the iteration number technique, the precision of the dichotomy algorithm and the maximum iteration number, respectively.
2) Respectively calculating Q by using formulas1,r1,S1,d1,Q2,r2,S2,d2,Qr,Z。
2, iteration step:
1)t＝(tmin+tmax)/2；
2) calculating Y in (P2) using CVX(n),Z(n)；
3) If step 2) can find a feasible solution, tminOtherwise, tmax＝t；
And 3, finishing conditions:
when t ismax-tminη or N is less than or equal to Nmaxthe dichotomy algorithm ends, where η is a predetermined threshold, NmaxIs that
Maximum number of iterations, output topt＝t，Yopt＝Y(n),Zopt＝Z(n). Otherwise, n is n +1, and returns to step 2.
The invention has the advantages of effectively reducing the power consumed by the relay and ensuring the service quality and the energy acquisition quantity of the receiving end. It should be noted that the method using probability limits can more easily obtain larger feasible values than the method using strict limits.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 is a flow chart of a communication method based on a wireless communication relay system according to a preferred embodiment of the invention;
fig. 2 is a schematic diagram of a wireless information and energy relay transmission network in accordance with a preferred embodiment of the present invention.
FIG. 3 is a graph showing the time when S is presentth＝5、PthWhen the value of r is 2, the distribution of the user throughput is different.
FIG. 4 is a variation of Sth、PthThe power consumed by the relay under the conditions.
FIG. 5 is a graph showing the time when S is presentth＝5、PthWhen the r value is 2, the distribution of the energy received by the user is different.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
The concrete implementation steps comprise the following steps:
first, system parameters and constraints are initialized. The embodiment includes one base station, one user, and two relays. The base station, the relay, and the user are all single antenna. Uplink channel H ∈ CM×1Is an ideal channel complying with the Rayleigh distribution, and a downlink channel not only complies with the Rayleigh channel G epsilon C1×MIn addition, a norm-limited error term Δ G is included. This embodiment simulates 10000 results for different uplink and downlink channels.
Second, Z and Y are calculated. The specific calculation method is that the user feeds back the energy requirement and SNR limit to the relay, the relay can obtain each formula in (13) according to the power limit condition of the relay, and then Z and Y can be calculated by using a convex optimization tool CVX.
And thirdly, calculating the transmitting power of the relay, the SNR of the receiving user and the received energy. The SNR and the received energy of the user in the robust and non-robust schemes are calculated according to equations (5) and (6), respectively. The power consumed by the relay can be calculated according to equation (12).
And fourthly, comparing the robustness and the non-robustness performance of the user SNR, the energy and the probability of relay consumption obtained in the third step through matlab simulation.
FIG. 3 is a graph showing the time when S is presentth＝5、PthWhen the value of r is 2, the distribution of the user throughput is different. Robust precoding is shown to guarantee the quality of service for the receiver over non-robust performance.
FIG. 4 is a variation of Sth、PthThe power consumed by the relay under the conditions. As can be seen from the figure, the robust scheme consumes more power than the non-robust scheme because the case of poor channel is considered in the robust scheme.
FIG. 5 is a graph showing the time when S is presentth＝5、PthWhen the r value is 2, the distribution of the energy received by the user is different. As can be seen from the figure, as the threshold value r increases, the user absorbs relatively more energy.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (3)

1. A relay precoding method for transmitting information and energy in a wireless cognitive network is characterized in that the network at least comprises a base station, a plurality of relays and a user, wherein the information sent by the base station is forwarded to the user through the relays, and meanwhile, the relays send energy to the user, and the method specifically comprises the following steps:
step 1, a base station carries out uplink and downlink channel estimation and sends information to a relay;
step 2, the relay performs robust precoding under the condition of considering channel errors between the relay and a user, namely, the received information from the base station and the energy expected to be transmitted to a receiving end are subjected to robust precoding to obtain a robust precoding matrix W of the received information and a robust precoding matrix of the energy expected to be transmitted to the receiving end;
the robust precoding matrix of the information and the robust precoding matrix of the energy enable the signal-to-noise ratio SNR of the user>SthIs the most probable precoding matrix, where SthIs a preset value of SNR;
step 3, the relay sends out the processed information and the energy expected to be transmitted to the receiving end;
and 4, receiving the information and the energy transmitted by the relay by the user.
2. The relay precoding method for transmitting information and energy in the wireless cognitive network according to claim 1, wherein the channel error existing between the relay and the user in the step 2 is: gaussian error exists in downlink channel between relay and userIn the formula,is to estimate the channel and deltag is the channel estimation error.
3. The relay precoding method for transmitting information and energy in the wireless cognitive network according to claim 1, wherein in step 2, the user feeds back the energy requirement and SNR limit of the user to the relay under the condition of channel error between the relay and the user, and the relay obtains a robust precoding matrix W for the received information and a robust precoding matrix V for the energy transmitted by the relay through a convex optimization method according to the power limit condition of the relay.
CN201510026603.3A 2015-01-20 2015-01-20 The relaying method for precoding of information and energy is transmitted in wireless cognition network Expired - Fee Related CN104601287B (en)

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CN105610486B (en) * 2015-12-21 2019-01-25 东南大学 A kind of portable communications system bi-directional relaying selection method based on weight
CN105490724A (en) * 2015-12-21 2016-04-13 东南大学 Energy-carrying communication system bidirectional relay selection scheme based on maximization of minimum receiving signal-to-noise ratio
CN108347275B (en) * 2018-02-08 2021-03-30 广东工业大学 Optimal wave beam vector design method and device of wireless energy-carrying communication signal source

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