Research On Technologies Of Multi-relay Cooperation And Optimal Resource Allocation In Spatial Information Networks

Nowadays,spatial information network（SIN）is widely used in various space internet of things（Io T）communication fields due to their advantages in wide coverage and robustness,and occupy an important position in future space Io T network development.However,it still suffers from power limitation,high deployment cost,slow response rate and high bit error rate（BER）.Faced with the above problems,research on SIN multi-relay cooperation and its resource optimization allocation technology has been carried out.First,a brief introduction of the SIN background,research significance and corresponding domestic and international research status is given.Second,for the SIN relay resource constraint problem,the study analyzes the relay communication model and proposes an incremental selection hybrid decode-amplify-forward（ISHDAF）scheme with uniform scheduling through the destination node.Then,a low-complexity amplify-and-forward multi-relay selection and power allocation scheme is proposed.Finally,a joint symbol convergence cyclic redundancy check（CRC）-assisted early termination iteration algorithm is proposed for traditional CRC-assisted belief propagation（BP）decoding based on high-performance polar codes in channel coding.The main content and contributions are concluded and listed as follows:1.To solve the limited relay power and high deployment cost in SIN,an ISHDAF scheme with unified scheduling by destination node for low-complexity relay networks is proposed based on the existing ISHDAF scheme.First,an incremental mechanism is used to avoid redundant signal transmission to improve spectral efficiency.Second,three cooperative modes,amplify-and-forward（AF）,decode-and-forward（DF）,and source node retransmission are simultaneously combined to improve diversity gain.Finally,the destination node is used to unify the signaling process of the network system,and the relay only performs cooperation based on the destination feedback to simplify its structure and reduce deployment costs,and power loss.Simulation results show that it has less power consumption and relay deployment costs than those of the current ISHDAF scheme given the same outage performance,especially when the relay is close to the destination.When the relay distance factor ratio is 0.9 and the total system power is 10 W,the proposed scheme through power allocation outperforms the ISHDAF scheme by the average transmission power of approximately 1 W.2.A low-complexity AF multi-relay selection and its power allocation scheme are proposed based on the existing multi-relay selection scheme for SIN with limited computing resource and slow response speed.First,the statistical channel characteristics are used to increase the correction factor to realize the multi-relay selection for AF under the condition of fully utilizing the power resources.Second,an improved low-complexity power allocation scheme is obtained by unifying the relay link ratios for the selected set of relay power allocations to obtain optimization of the outage performance.The proposed scheme avoids solving the transcendence equation of power allocation to reduce the computational complexity and response time.The simulation results show that when the bit error rate is 10^-4,compared with the pre-select single relay amplify-and-forward（SAF）and all relay amplify-and-forward（AAF）schemes,the proposed scheme reduces the required signal-to-noise ratio（SNR）by about 2.5 d B and 5.3 d B.Its performance is comparable to that of the exhaustive scheme,and the difference between the two required SNRs is only about 0.01 d B.3.To overcome the problem of high BER in SIN with complex channels,polar channel coding is used to improve reliability.In addition,a joint symbol convergence CRC-assisted early termination iterative BP decoding algorithm is proposed based on the existing polar code CRC-assisted early termination iterative BP decoding scheme to solve the problem of scarce computational resources.First,a symbolic convergence judgment criterion is introduced.Second,the criterion is used to compare the decoding results of the two iterations before and after the CRC check code to determine whether it converges or not,to avoid blind check,and to reduce the computational complexity.Finally,when the check bits converge,we first judge whether the information bits converge,and if the judgment is successful,we directly stop the iterations to avoid additional execution of CRC to reduce the computation,and at the same time reduce the additional iterations caused by CRC miscalculation and lower the average number of iterations.The proposed scheme reduces the computational complexity of the CRC-assisted early termination iteration scheme from square order O（MK）to linear order O（M）without loss of bit-error performance.The simulation results show that the BER of the proposed scheme is almost the same as that of the CRC scheme when the signal-to-noise ratio is 1 d B.The average number of iterations of the polar BP decoding is cut as about 2%.By optimizing the cooperative communication algorithm and polar coding,this thesis solves the problems of power limitation,high deployment cost,slow response rate,and high outage and BER of the multi-relay SIN.In addition,it improves the overall performance of SIN from the perspectives of relay cooperation,multi relay selection and channel coding,which is helpful for the application of the next generation 6G SIN systems.