CN107295623B - The communication means and full duplex relaying system of a kind of full duplex relaying system - Google Patents
The communication means and full duplex relaying system of a kind of full duplex relaying system Download PDFInfo
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- CN107295623B CN107295623B CN201710439182.6A CN201710439182A CN107295623B CN 107295623 B CN107295623 B CN 107295623B CN 201710439182 A CN201710439182 A CN 201710439182A CN 107295623 B CN107295623 B CN 107295623B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/18—TPC being performed according to specific parameters
- H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
- H04W52/243—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters taking into account interferences
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- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/30—TPC using constraints in the total amount of available transmission power
- H04W52/34—TPC management, i.e. sharing limited amount of power among users or channels or data types, e.g. cell loading
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
- H04W52/04—TPC
- H04W52/38—TPC being performed in particular situations
- H04W52/46—TPC being performed in particular situations in multi hop networks, e.g. wireless relay networks
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Abstract
The invention discloses the communication means and full duplex relaying system of a kind of full duplex relaying system, in time slot t=1, by information source S with power PSSignal x (t) is sent to full duplex relaying node R, x (t) is received and decoded by R；In time slot t+1, if R successfully decodeds, R is with power PRThe signal x (t) of successfully decoded is sent to stay of two nights D, and S is with PSThe new signal x (t+1) produced is sent to R, signal x (t+1) is received and decoded under the loop self-interference of signal x (t) by R；In time slot t+1, if R decoding failures, S is with PSThe new signal x (t+1) produced is sent to R, signal x (t+1) is received and decoded by R, wherein, PS、PRDetermined by the adaptive tracking control strategy based on information interference and coupling characteristic or the combined signal source relay power allocation strategy based on information interference and coupling characteristic.The present invention reaches system under conditions of target outage probability is met, the purpose of lifting system efficiency by reasonable distribution information source and the transmission power of relaying.
Description
Technical Field
The present invention belongs to the field of wireless communication technologies, and in particular, to a communication method of a full-duplex relay system and the full-duplex relay system.
Background
The cooperative relay technology can effectively enlarge the coverage area of a wireless communication system, enhances the robustness of the system, and becomes one of key technologies of the wireless communication system. Conventionally, a relay node generally operates in a half-duplex mode, and must allocate channel resources orthogonal to each other for its reception and transmission signals. This severely compromises the spectrum utilization of the wireless communication system. In order to compensate for the spectrum efficiency loss caused by the traditional half-duplex relay mode, researchers propose a full-duplex relay forwarding technology.
By deploying at least two antennas, the full-duplex relay node can receive a new signal sent by a current time slot information source while forwarding a signal received by a previous time slot. Compared with a traditional half-duplex relay system, theoretically, the full-duplex relay system can improve the frequency spectrum efficiency by almost one time. However, since the full-duplex relay-forwarded signal causes loop self-interference to its destination received signal, the coupling characteristics of the information signal and the self-interference signal are caused. On one hand, if the transmission power of the relay node is too low, the communication quality of a relay-sink link is damaged; on the other hand, if the transmission power of the relay node is too high, serious loop self-interference influence can be caused, and the communication quality of the source-relay link is further damaged. Therefore, in order to effectively improve the communication performance of the full-duplex relay system, it is necessary to balance the mutual constraint relationship between the information signal and the interference signal, and between the source transmission power and the intermediate transmission power.
In the current full-duplex relay system, although a large amount of work considers the problem of loop self-interference of the full-duplex relay node, the system performance is not optimized from the point of the mutual restriction relationship between the source transmission power and the intermediate transmission power, and therefore, better system energy efficiency cannot be obtained.
Disclosure of Invention
In view of the above drawbacks or needs for improvement in the prior art, an object of the present invention is to provide a communication method for a full-duplex relay system and a full-duplex relay system, so as to solve the technical problem of low system energy efficiency in the existing full-duplex single-relay system.
To achieve the above object, according to an aspect of the present invention, there is provided a communication method of a full-duplex relay system, including:
s1, in time slot t =1, the source S generates a signal x (t) and with a power P S Transmitting a signal x (t) to a full-duplex relay node R, receiving and decoding the signal x (t) by the full-duplex relay node R, wherein the power P S Determined by a preset power distribution strategy;
s2, if the full-duplex relay node R can be successfully decoded, executing a step S3, otherwise, executing a step S4;
s3, in the time slot t +1, the full-duplex relay node R uses the power P R Sending a successfully decoded signal x (t) to a sink D while the source S is at the power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R under the loop self-interference of the signal x (t), and then executing the step S5, wherein the power P R Determined by the preset power allocation strategy;
s4, in a time slot t +1, the source S uses the power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R, and then executing the step S5;
s5, judging whether the signal transmission process is finished or not, and if so, executing the step S6; otherwise, returning to execute the step S2;
s6, judging whether the relay node R can successfully decode the latest received signal or not, and if the relay node R successfully decodes the latest received signal, the relay node R uses power P R The successfully decoded signal is forwarded to an information destination D, and the transmission process is ended; otherwise, the transmission process is directly ended.
Preferably, the power P S Determined by a preset power allocation strategy and the power P R Determined by the preset power allocation strategy, including:
since the relay R operates in the full duplex mode, at the time slot t +1, the information signal x (t) forwarded to the sink D by the relay R generates loop self-interference for the relay receiving the information signal x (t + 1) from the source S, thereby generating coupling between the information signal and the self-interference signal, in order to balance the relationship between the two-hop transmission of the "information signal" and the "interference signal" and between the "source-relay" and the "relay-sink";
setting the transmitting power P of the information source S S And adaptively adjusting the transmitting power P of the full-duplex relay node R R To optimize the energy efficiency EE of the system on the premise of reaching the target interruption probability, where P R ∈[0,P max ]，P max Is the maximum transmit power that the full duplex relay node R can reach.
Preferably, the transmission power P R The method comprises the following steps:
byCalculating P corresponding to the optimal energy efficiency EE of the system R Value as target P R The value is obtained.
Preferably, said power P S Determined by a preset power allocation strategy and the power P R Determined by the preset power allocation strategy, including:
since the relay R operates in the full duplex mode, at the time slot t +1, the information signal x (t) forwarded to the sink D by the relay R generates loop self-interference for the relay receiving the information signal x (t + 1) from the source S, thereby generating coupling between the information signal and the self-interference signal, in order to balance the relationship between the two-hop transmission of the "information signal" and the "interference signal" and between the "source-relay" and the "relay-sink";
transmitting power P of the information source S S Is set to P S = α P, setting the transmit power of the full-duplex relay node R to P R = 1- α P, where P denotes the total power consumption of the system in each time slot, and α denotes the power allocation ratio.
Preferably, the method for obtaining the α value is as follows:
byAnd calculating an alpha value corresponding to the optimal energy efficiency EE of the system as a target alpha value.
Preferably, the method for obtaining the energy efficiency EE of the system comprises the following steps:
for any time slot t, obtaining the probability pi of the full-duplex relay node R successfully decoding the source signal x (t) 1 And probability of failure pi 0 ：Wherein, P 10 Indicating the probability of failure of decoding at the time slot t +1 when the full-duplex relay node R has loop self-interference, P 01 The probability that the full-duplex relay node R can successfully decode in the time slot t +1 when loop self-interference does not exist is represented;
by pi 0 And pi 1 Obtaining the average interruption probability P of the system out ：P out ＝π 0 +π 1 (1-P d ) Wherein P is d Represents the probability that the sink D can successfully decode the signal from the full-duplex relay node R;
average probability of interruption P by the system population out And the total power consumption P of the system in each time slot obtains the energy efficiency EE of the system:wherein EE represents the amount of data that can be successfully transmitted per unit of energy consumed, R T Representing a nominal data transmission rate of said source S signal.
Preferably, the full-duplex relay node R has a probability P that the signal x (t + 1) can be successfully decoded in the time slot t +1 when the loop self-interference exists 11 And probability of decoding failure P 10 Respectively as follows:
when no loop is interfered by the full-duplex relay node R, the probability P of successful decoding of the signal x (t + 1) in the time slot t +1 01 And probability of decoding failure P 00 Respectively as follows:
P 01 ＝Pr{log 2 (1+|g S,R | 2 P S )≥R T }
P 00 ＝Pr{log 2 (1+|g S,R | 2 P S )<R T }
wherein, g S,R Gain g of the channel from the source S to the full-duplex relay node R R,R Loop self-interference channel gain, P, for the full-duplex relay node R SI ＝P R 1-μ Represents the power of the loop self-interference actually received by the full-duplex relay node R, and the R is more than 0 and less than 1 T Is the nominal data transmission rate of the source S signal.
Preferably, in step S4, the probability P that the sink D can successfully decode the signal from the full-duplex relay node R d Comprises the following steps: p d ＝Pr{log 2 (1+|gR ,D | 2 P R )≥R T In which g is R,D Channel gain for the full-duplex relay node R to the sink D.
Preferably, P 11 、P 10 、P 01 And P 00 The signal y actually received by the full-duplex relay node R at time slot t +1 R (t + 1) is obtained as d Signal y received by the sink D in time slot t +1 D (t + 1) is obtained, wherein:
considering the loop self-interference generated by the forwarding signal x (t) to the target received signal of the full-duplex relay node R in the time slot t +1, the signal y actually received by the full-duplex relay node R R (t + 1) is:
wherein n is R Is additive white Gaussian noise, n, at the full-duplex relay node R D Is additive white gaussian noise at the sink D.
According to another aspect of the present invention, there is provided a full-duplex relay system, including: an information source S, an information sink D and a full-duplex relay node R;
wherein the full-duplex relay node R is deployed between the source S and the sink D;
the full-duplex relay system is configured to perform any one of the methods provided in the embodiments of the present invention.
In general, compared with the prior art, the method of the invention can obtain the following beneficial effects:
(1) The invention reasonably distributes the transmitting power of the information source and the relay through the preset power distribution strategy, thereby achieving the purpose of improving the energy efficiency of the system under the condition that the system meets the target interruption probability.
(2) The invention can obtain the successful decoding probability of each time slot in the stable state of the information source-relay, further obtain the interruption probability and the energy efficiency of the system and simplify the analysis and derivation processes.
(3) The invention provides a self-adaptive power distribution method of a full-duplex relay system, which reduces the influence of the mutual coupling effect between a relay information signal and a self-interference signal on the system by self-adaptively adjusting the transmission power of a relay, reduces unnecessary system energy consumption and optimizes the energy efficiency of the system on the premise that the system reaches the target interruption probability.
(4) The invention provides a joint source-relay power distribution method under the condition that the total power consumption of a full-duplex relay system is limited. The characteristic that two-hop transmission, namely 'information source-relay' and 'relay-information sink', is mutually restricted due to coupling between an information signal and a self-interference signal is fully utilized, the transmitting power of the information source and the relay is reasonably distributed on the premise that the total power consumption of the system is limited, and the performance of the system is remarkably improved.
Drawings
Fig. 1 is a schematic model diagram of a full-duplex relay system according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of a communication method of a full-duplex relay system according to an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating a relationship between a relay transmission power and a system outage probability in an adaptive power allocation method based on information-interference coupling characteristics;
fig. 4 is a schematic diagram illustrating a relationship between relay transmission power and system energy efficiency in an adaptive power allocation method based on information-interference coupling characteristics;
fig. 5 is a schematic diagram of a relationship between a power distribution coefficient and a system interrupt probability in a joint source-relay power distribution method under a condition that total power consumption of a system is limited;
fig. 6 is a schematic diagram of a relationship between a power distribution coefficient and system energy efficiency in a joint source-relay power distribution method under a condition that total power consumption of a system is limited.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The invention discloses a communication method of a full-duplex relay system and the full-duplex relay system, wherein when power distribution of an information source and a full-duplex relay node is carried out, an adaptive power control method based on information-interference coupling characteristics or a combined information source-relay power distribution method under the condition that the total power consumption of the system is limited are adopted. In order to improve the communication quality between the information source and the information sink which are far away from each other, the full-duplex relay node is arranged between the information source and the information sink to assist in forwarding the information source signal, so that the frequency spectrum efficiency of the traditional half-duplex relay system can be effectively improved. Because the full-duplex relay node can receive and decode a new signal transmitted by the current time slot source while forwarding the source signal received in the previous time slot, the signal transmitted by the relay node generates loop self-interference on the signal received by the relay node, thereby causing the coupling between two-hop transmission, namely 'relay-sink' and 'source-relay'. On one hand, if the transmission power of the full-duplex relay is too low, the communication quality of a relay-sink link is damaged; on the other hand, if the transmission power of the relay node is too high, the loop self-interference is easily caused to be too strong, and the communication quality of the source-relay link is further damaged. In view of this, in order to balance the relationship between the two-hop transmission of the "information source-relay" and the "relay-information sink" and optimize the system energy efficiency on the premise of ensuring the established communication quality, the invention provides a joint information source-relay power distribution method under the condition that the total power consumption of the system is limited and an adaptive power control method based on the information-interference coupling characteristic. By reasonably distributing power between the information source and the relay, the system can obviously improve the energy efficiency of the system under the condition of meeting the target interruption probability.
As shown in fig. 1, the system includes a source S, a sink D, and a full-duplex relay node R. The relay R is arranged between the information source S and the information sink D, signals sent by the information source need to be transmitted to the information sink through two hops of information source-relay and relay-information sink, the single-hop communication link distance is shortened, the reduction of communication quality caused by long distance between the information source S and the relay D or poor channel condition is effectively improved, and the communication quality and robustness of the system are improved.
Because the relay node R works in a full duplex state, the relay node R can receive and decode a new signal sent by an information source at the current moment while forwarding a signal received at the previous time slot. Therefore, the relayed transmitted signal may generate loop self-interference to the received signal, causing coupling of the received signal and the retransmitted signal.
In time slot t =1, the source S generates a signal x (t) and with a power P S Sending x (t) to a relay R, and receiving and decoding a signal x (t) by the R;
at time slot t = t +1, t ≧ 1, relay R applies power P to successfully decoded signal x (t) R And sent to the sink D. At the same time, the source S generates a new signal x (t + 1) and with a power P S X (t + 1) is sent to relay R, which receives and decodes signal x (t + 1). Because the relay R operates in full duplex mode, the signal transmitted by the relay may generate loop self-interference to the signal received by the relay R, resulting in coupling of the received signal with the forwarded signal.
Fig. 2 is a schematic flow chart of a communication method of a full-duplex relay system according to an embodiment of the present invention, where the method shown in fig. 2 includes:
s1, in time slot t =1, the source S generates a signal x (t) and with a power P S Transmitting a signal x (t) to a full-duplex relay node R, receiving and decoding the signal x (t) by the full-duplex relay node R, wherein the power P S Determining by a preset power distribution strategy;
s2, if the full-duplex relay node R can successfully decode, executing the step S3, otherwise, executing the step S4;
s3, in the time slot t +1, the full-duplex relay node R uses the power P R Sending the successfully decoded signal x (t) to the sink D, while the source S is at power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R under the loop self-interference of the signal x (t), and then executing the step S5, wherein the power P R Determining by a preset power distribution strategy;
in the time slot, the signal y 'received by the signal sink D and the relay R' R (t+1)、y D (t + 1) are respectively:
wherein, g S,R 、g R,D Channel gains, g, from source S to relay R and relay R to sink D, respectively R,R The loop for the relay node R is the self-interference channel gain. n is R 、n D Additive white gaussian noise at relay R and sink D, respectively.
The relay R may perform loop self-interference cancellation on the signal received by the relay R in time slot t +1 using the decoded signal x (t) as a priori information. However, due to the near-far effect and the limitation of the practical system, the relay R cannot completely eliminate the loop self-interference, and therefore the power of the relay R actually receiving the loop self-interference is defined as P SI ＝P R 1-μ 0 < mu < 1, wherein the larger mu represents the smaller residual self-interference intensity; the smaller μ represents the greater the residual self-interference intensity. Therefore, the signal actually received by relay R is:
since the relay R successfully decodes the signal x (t) transmitted by the source S in the time slot t, the relay R receives a new signal x (t + 1) transmitted by the source S in the time slot t +1, and thus suffers from loop self-interference generated by forwarding the signal x (t) to the sink D. Therefore, in the time slot t +1, the probability P that the relay R succeeds in decoding when the loop self-interference exists 11 And probability of decoding failure P 10 Respectively expressed as:
wherein R is T Is the nominal data transmission rate of the source signal.
S4, in the time slot t +1, the source S uses power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R, and then executing the step S5;
in time slot t +1, relay R only attempts to receive and decode the new signal x (t + 1) transmitted by source S, since relay R cannot successfully decode signal x (t) transmitted by source S in time slot t. Thus, the probability P that the relay R successfully decodes the signal x (t + 1) without loop self-interference 01 And probability of decoding failure P 00 Can be expressed as:
P 01 ＝Pr{log 2 (1+|g S,R | 2 P S )≥R T }
P 00 ＝Pr{log 2 (1+|g S,R | 2 P S )<R T }
s5, judging whether the signal transmission process is finished or not, and if so, executing the step S6; otherwise, returning to execute the step S2;
s6, judging whether the relay node R can successfully decode the latest received signal or not, and if the relay node R successfully decodes the latest received signal, the relay node R uses power P R The successfully decoded signal is forwarded to an information destination D, and the transmission process is finished; otherwise, the transmission process is directly ended.
Wherein, the direct link between the source and the sink is not considered in the present invention because the distance between the source S and the sink D is long or the channel quality is poor. The sink D is therefore only disturbed by additive white gaussian noise when receiving the signal from the relay R. Therefore, the probability P that the sink D can successfully decode the signal from the relay R d Comprises the following steps: p d ＝Pr{log 2 (1+|g R,D | 2 P R )≥R T }。
Preferably, the present invention provides two methods for allocating source and relay power, which are respectively:
the self-adaptive power distribution method based on the information-interference coupling characteristics comprises the following steps: since the relay R operates in full duplex mode, in the time slot t +1, the information signal x (t) forwarded to the sink D by the relay generates loop self-interference to the information signal x (t + 1) received from the source, thereby generating coupling between the information signal and the self-interference signal. On the one hand, if a higher relay transmission power is adopted, although the communication quality of the relay-sink link can be improved, the higher relay transmission power can bring more serious loop self-interference to the relay R. On the other hand, if a lower relay transmission power is adopted, although the loop self-interference effect of the relay R can be reduced, the communication quality of the relay-sink link cannot be guaranteed. Thus, at a set source S transmit power P S The overall performance of the system can then be improved by selecting the appropriate relay transmit power through adaptive power control of the full-duplex relay, where the transmit power P S The set value of (c) can be determined according to actual requirements.
The power of the transmitted signal of the relay R is denoted as P R And in the presence of P R ∈[0,P max ]，P max Is the maximum transmit power that the relay R can achieve. The system reduces unnecessary system energy consumption and optimizes the energy efficiency of the system by adaptively controlling the transmission power of the relay on the premise of achieving the target interruption probability, wherein the target interruption probability can be determined according to actual requirements.
Preferably, can be prepared fromCalculating the corresponding P when the energy efficiency EE of the system reaches the optimum R Value as target P R The value is obtained.
The joint source-relay power distribution method under the condition that the total power consumption of the system is limited comprises the following steps: the setting of the transmission power of the full-duplex relay R is important because the coupling characteristic between the information signal and the self-interference signal can cause the mutual restriction between the two-hop transmission of the "source-relay" and the "relay-sink". In order to balance the information signal "And the relation between the interference signals and the two-hop transmission of the source-relay and the relay-sink, the patent provides a combined source-relay power distribution method under the condition of limited total power consumption of a full-duplex relay system. The total power consumption of each time slot of the system is recorded as P, and the power of the signal transmitted by the information source S is recorded as P S And P is S = ap, the transmit power of the relay R can be represented as P R ＝(1-α)P。
Then, by selecting a proper alpha value to configure the transmitting power of the information source and the relay, and further balancing the relation between the two-hop transmission of the information source-relay and the relay-information sink, the unnecessary system energy consumption can be reduced and the energy efficiency of the system can be optimized on the premise that the system reaches the target interruption probability.
Preferably, can be prepared fromAnd calculating an alpha value corresponding to the optimal energy efficiency EE of the system as a target alpha value.
Considering any time slot t, defining the success probability of the relay decoding source signal x (t) as pi 1 The probability of failure is pi 0 Then:
then the average outage probability P for the system population out Can be expressed as
P out ＝π 0 +π 1 (1-P d )
The energy efficiency EE of a system is defined as the amount of data that can be successfully transmitted per unit of energy consumed, i.e. the amount of energy consumed
Selecting proper relay transmitting power P according to the two power setting methods R Or the power distribution coefficient alpha ensures that the energy efficiency EE of the system reaches the optimum, namely the total power consumption of the systemThe energy efficiency of the system is optimized by power allocation between the source and the relay under limited conditions.
As shown in fig. 3, the relation between the relay transmission power and the system outage probability in the adaptive power allocation method based on the information-interference coupling characteristics is shown. The source transmission power is 35dB, and it can be seen from the figure that on the premise of a certain source transmission power, the transmission power of the relay is continuously increased, and the interruption probability of the system shows a trend of first decreasing and then increasing, because when the secondary transmission power is too small, the link quality of the relay-sink is affected, and when the secondary transmission power is too large, the transmission power of the relay forwarding signal causes strong self-interference. Under the same source and relay transmitting power, as the value of mu increases, the interruption probability of the system shows a descending trend, because the larger the value of mu is, the smaller the self-interference of the residual loop of the relay is, and therefore the interruption probability of the system is reduced. In addition, as the value of μ increases, the optimal relay transmission power tends to increase, because the larger the value of μ is, the smaller the residual self-interference of the relay forwarding signal to itself is, that is, the smaller the degree of coupling between two hops of "source-relay" and "relay-sink" is, the gain brought by properly boosting the relay transmission power to the link of "relay-sink" is greater than the loss brought by the link in "source-relay", and thus the optimal transmission power tends to increase with the increase of the value of μ.
As shown in fig. 4, the relationship between the relay transmission power and the system energy efficiency in the adaptive power allocation method based on the information-interference coupling characteristics is shown. The source transmission power is 35dB, and it can be seen from the figure that on the premise that the source transmission power is constant, the transmission power of the relay is continuously increased, and the energy efficiency of the system shows a trend of increasing first and then decreasing, for the same reason as in the third figure. However, it can be seen that the optimal transmission power of fig. 4 is significantly lower than that of fig. three, because when the energy efficiency of the system is maximized, the relay transmission power is continuously increased, and the system needs to increase a large amount of power consumption to bring about a slight decrease in the interruption probability. Furthermore, as the μ value increases, the energy efficiency of the system shows an upward trend.
As shown in fig. 5, the relationship between the power distribution coefficient and the system outage probability in the joint source-relay power distribution method under the condition of limited total system power consumption is shown. It can be seen from the figure that under the condition that the total power consumption of the system is limited, the system has an optimal power distribution coefficient to minimize the probability of system interruption, and the probability of system interruption is increased when the power distribution coefficient alpha is too large or too small. This is because when α is too large, the transmission power allocated to the relay by the system is too small, affecting the communication quality of the "relay-sink" link. This is because when α is too small, the transmission power allocated to the source by the system is too small, which affects the communication quality of the "source-relay" link. The total power consumption of the system also affects the setting of the power distribution coefficient alpha, and when the total transmission power of the system increases, the optimal power distribution coefficient alpha decreases, because the increase of the transmission power of the relay brings about a much larger improvement to the communication quality of the system relay-sink link than the increase of the relay self-interference brings about the influence to the communication quality of the source-relay link.
As shown in fig. 6, the relationship between the power distribution coefficient and the system capacity efficiency in the joint source-relay power distribution method under the condition that the total power consumption of the system is limited. As can be seen from the figure, under the condition that the total power consumption of the system is limited, the system has an optimal power distribution coefficient so that the energy efficiency of the system is maximum, and when the power distribution coefficient α is too large or too small, the energy efficiency of the system is reduced. On the premise that the total power consumption of the system is constant, the interruption probability and the energy efficiency of the system are in inverse proportion. It can also be seen from the figure that when the total power consumption of the system increases when the power distribution coefficient of the system is constant, the energy efficiency of the system does not necessarily increase.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (5)
1. A communication method of a full-duplex relay system is characterized by comprising the following steps:
s1, in time slot t =1, the source S generates a signal x (t) and with a power P S Transmitting a signal x (t) to a full-duplex relay node R, receiving and decoding the signal x (t) by the full-duplex relay node R, wherein the power P S Determining by a preset power distribution strategy;
s2, if the full-duplex relay node R can successfully decode, executing the step S3, otherwise, executing the step S4;
s3, in the time slot t +1, the full-duplex relay node R uses the power P R Sending a successfully decoded signal x (t) to a sink D while the source S is at the power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R under the loop self-interference of the signal x (t), and then executing the step S5, wherein the power P R Determined by the preset power allocation strategy;
s4, in a time slot t +1, the source S uses the power P S Sending the generated new signal x (t + 1) to the full-duplex relay node R, receiving and decoding the signal x (t + 1) by the full-duplex relay node R, and then executing the step S5;
s5, judging whether the information source signal transmission process is finished or not, and if so, executing a step S6; otherwise, returning to execute the step S2;
s6, judging whether the relay node R can successfully decode the latest received signal, if so, the relay node R uses power P R The successfully decoded signal is forwarded to an information destination D, and the transmission process is ended; otherwise, directly ending the transmission process;
wherein the power P S Determined by a preset power allocation strategy and the power P R Determined by the preset power allocation policy, including:
setting the transmission power P of the information source S S And is composed ofCalculating the corresponding P when the energy efficiency EE of the system reaches the optimum R Value as target P R Value, P max Is the maximum transmit power that the full duplex relay node R can reach; or, the transmitting power P of the information source S is used S Is set to P S = α P, setting the transmit power of the full-duplex relay node R to P R = 1- α P, where P represents the total power consumption of the system in each timeslot, α represents the power allocation ratio, and the α value is obtained by: byCalculating a corresponding alpha value when the energy efficiency EE of the system is optimal as a target alpha value;
the method for obtaining the energy efficiency EE of the system comprises the following steps:
for any time slot t, obtaining the probability pi of the full-duplex relay node R successfully decoding the source signal x (t) 1 And probability of failure pi 0 ：Wherein, P 10 Indicating the probability of failure of decoding at the time slot t +1 when the full-duplex relay node R has loop self-interference, P 01 Representing the probability that the full-duplex relay node R can successfully decode in a time slot t +1 when no loop self-interference exists;
by pi 0 And pi 1 Obtaining the average interruption probability P of the system out ：P out ＝π 0 +π 1 (1-P d ) Wherein, P d Represents the probability that the sink D can successfully decode the signal from the full-duplex relay node R;
average probability of interruption P by the system population out And the total power consumption P of the system in each time slot obtains the energy efficiency EE of the system:wherein EE represents the amount of data that can be successfully transmitted per unit of energy consumed, R T Representing the nominal data transmission rate of said source S signal.
2. The method of claim 1, wherein the full-duplex relay node R has a probability P that a signal x (t + 1) can be successfully decoded in a time slot t +1 when loop self-interference exists 11 And probability of decoding failure P 10 Are respectively as
When no loop is interfered by the full-duplex relay node R, the probability P of successful decoding of the signal x (t + 1) in the time slot t +1 01 And probability of decoding failure P 00 Respectively as follows:
P 01 ＝Pr{log 2 (1+|g S,R | 2 P S )≥R T }
P 00 ＝Pr{log 2 (1+|g S,R | 2 P S )<R T }
wherein, g S,R For the channel gain, g, from the source S to the full-duplex relay node R R,R Loop self-interference channel gain, P, for said full-duplex relay node R SI ＝P R 1-μ Represents the power of the loop self-interference actually received by the full-duplex relay node R, and the power is more than 0 and less than 1 T Is the nominal data transmission rate of the source S signal.
3. Method according to claim 2, characterized in that the probability P that the sink D can successfully decode the signal from the full-duplex relay node R d Comprises the following steps: p is d ＝Pr{log 2 (1+|g R,D | 2 P R )≥R T In which g is R,D Channel gain for the full duplex relay node R to the sink D.
4. The method of claim 3, wherein P is P 11 、P 10 、P 01 And P 00 The signal y actually received by the full-duplex relay node R at time slot t +1 R (t + 1) is obtained, P d Signal y received by the sink D in time slot t +1 D (t + 1) in which:
considering the loop self-interference generated by the forwarding signal x (t) to the target receiving signal x (t + 1) of the full-duplex relay node R in the time slot t +1, the signal y actually received by the full-duplex relay node R is considered R (t + 1) is:
wherein n is R Is additive white Gaussian noise, n, at the full-duplex relay node R D Is additive white gaussian noise at the sink D.
5. A full-duplex relay system, comprising: an information source S, an information sink D and a full-duplex relay node R;
wherein the full-duplex relay node R is deployed between the source S and the sink D;
the full-duplex relay system is used for executing the method of any one of claims 1 to 4.
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