Background
In the research of the radio frequency energy capture network, the selection of the relay node is an important problem. Since in a multipath environment the radio frequency signal strength decays at a rate that is more than the power of 2 times the propagation distance. If the distance between the sender and the receiver is large, the signal intensity will be rapidly attenuated, so that the error rate is increased, and the packet loss number is increased. This requires increased transmit power or retransmission of the data packet to deliver the data packet to the receiver, which increases the power consumption of the network.
To overcome this phenomenon, it is feasible to add a relay node between the rf transmitter and receiver for forwarding information. Existing research mainly selects a suitable relay node according to the energy captured by the relay node and the energy consumed by forwarding a data packet, and does not consider the characteristics of the data packet. Such as the size of the data volume, the packet arrival rate, and what distribution is obeyed.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a double-cache queue-based energy capture network relay selection method, which aims to obtain the queuing time delay of the whole system so as to select the optimal relay, analyzes the state transition conditions of a source node and a relay node cache queue in the system according to a double-cache queue model on the basis, obtains the state probability in a steady state, and provides a double-cache queue-based relay selection algorithm according to the queuing time delay of the system. The data packet arrival source node and the relay node are considered to be two Poisson distributions in the double buffer queues, and queuing delay of the two buffer queues is analyzed according to the energy capture capacity of the relay node and the energy consumption of the forwarded data packet, so that a proper relay node is selected; compared with the traditional relay selection method of the radio frequency energy capture network, the method mainly considers the aspects of the size of data volume, the arrival rate of data packets and the poisson distribution of the data packet to reduce the system delay.
The technical scheme adopted by the invention is as follows:
a relay selection method of an energy capture network based on double buffer queues comprises the following steps:
step 1: data packets at an average rate λ1Arrives at the source node, which is at the forwarding rate μ1nArriving at the relay node, the relay node forwards at a rate mu2nForwarding the data packet to the destination node with an energy at an average rate of lambda2The poisson distribution reaches an energy buffer queue of the relay node;
step 2: calculating the forwarding rate of the data packet at the source node
p
sThe transmit power for the data packet of the source node,
h
nas a source node and a relay node R
nChannel gain of between, delta
2Is noise;
and step 3: calculating the energy captured by the relay node as
η
nIndicating the efficiency with which the nth relay captures energy,
representing the acquisition power, τ, of the relay node
iRepresenting the time required to capture energy;
and 4, step 4: calculating a relay node forwarding rate of
g
nChannel gain between the relay node and the destination node;
and 5: solving the state of the data packet when the system reaches the steady state
Q
I(i) Indicating the number of data packets in the buffer queue of the ith time slot of the source node,
respectively representing the number of data packets in the ith time slot buffer queue of the nth relay node;
step 6: according to the high green of the steady state data packet state, the average queue length of the data packet in the system is obtained
And 7: calculating the average time delay of the data packets in the system:
and 8: and selecting the relay node with the least time consumption as the most suitable relay node according to the time delay of the data packet in the system.
The invention has the beneficial effects that: the system time delay is reduced and the transmission speed of the network is improved in the aspects of the size of data volume, the arrival rate of data packets and the Poisson distribution of data packet service.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, a network relay selection method based on dual-queue buffer energy capture includes the following steps:
step 1: data packets at an average rate λ1Arrives at the source node, which is at the forwarding rate μ1nArriving at the relay node, the relay node forwards at a rate mu2nForwarding the data packet to the destination node with an energy at an average rate of lambda2The poisson distribution reaches an energy buffer queue of the relay node;
step 2: and calculating the forwarding rate of the data packet at the source node. Since the forwarding rate of a source node is related to the quality of its channel, there are, according to the shannon formula
p
sThe transmit power for the data packet of the source node,
h
nas a source node and a relay node R
nChannel gain of between, delta
2Is noise;
and step 3: in the calculationThe energy captured by the relay node is
η
nIndicating the efficiency with which the nth relay captures energy,
representing the acquisition power, τ, of the relay node
iRepresenting the time required to capture energy;
and 4, step 4: and calculating the forwarding rate of the relay node. The power forwarded by the relay node is
According to the formula of Shannon, there are
g
nChannel gain between the relay node and the destination node;
and 5: solving the state probability of the data packet when the system reaches the steady state:
Q
I(i) indicating the number of data packets in the buffer queue of the ith time slot of the source node,
respectively representing the number of data packets in the ith time slot buffer queue of the nth relay node, and according to the queuing theory, Q is arranged in the source node queue
I(i) State probability of each packet:
similarly, the relay node queue has
State probability of each packet:
since the two queues are independent of each other, so
Namely, it is
Step 6, calculating the average queue length of the data packet in the system according to the state probability of the steady-state data packet
And 7: calculating the average time delay of the data packets in the system:
and 8: and selecting the relay node with the least time consumption as the most suitable relay node according to the time delay of the data packet in the system.