UAV-Relaying-Assisted Secure Transmission With Caching

TLDR: A novel scheme to guarantee the security of UAV-relayed wireless networks with caching via jointly optimizing the UAV trajectory and time scheduling and a benchmark scheme in which the minimum average secrecy rate among all users is maximized and no user has the caching ability.

Abstract: Unmanned aerial vehicle (UAV) can be utilized as a relay to connect nodes with long distance, which can achieve significant throughput gain owing to its mobility and line-of-sight (LoS) channel with ground nodes. However, such LoS channels make UAV transmission easy to eavesdrop. In this paper, we propose a novel scheme to guarantee the security of UAV-relayed wireless networks with caching via jointly optimizing the UAV trajectory and time scheduling. For every two users that have cached the required file for the other, the UAV broadcasts the files together to these two users, and the eavesdropping can be disrupted. For the users without caching, we maximize their minimum average secrecy rate by jointly optimizing the trajectory and scheduling, with the secrecy rate of the caching users satisfied. The corresponding optimization problem is difficult to solve due to its non-convexity, and we propose an iterative algorithm via successive convex optimization to solve it approximately. Furthermore, we also consider a benchmark scheme in which we maximize the minimum average secrecy rate among all users by jointly optimizing the UAV trajectory and time scheduling when no user has the caching ability. Simulation results are provided to show the effectiveness and efficiency of our proposed scheme.

Figures

TABLE IV SECRECY RATE OF THE PROPOSED AND BENCHMARK SCHEMES

Fig. 4. Secrecy rate comparison of the 2nd user and the 3rd user for different schemes and different T , when the horizontal location of the eavesdropper is we = (700m, 0m).

Fig. 5. Secrecy rate comparison of our proposed scheme with different number of time slots N1 allocated for the UAV to obtain files from the BS, when we = (500m, 0m).

Fig. 3. Secrecy rate comparison of the 2nd user and the 3rd user for different schemes and different T , when the horizontal location of the eavesdropper is we = (500m, 0m).

Fig. 6. Secrecy rate convergence of the 3rd user in Algorithm 1, when T = 200 s and N = 200.

TABLE I PARAMETERS FOR THE SIMULATIONS

Frequently asked questions

Q1. What are the contributions mentioned in the paper "Uav relaying assisted secure transmission with caching" ?

In this paper, the authors propose a novel scheme to guarantee the security of UAV-relayed wireless networks with caching via jointly optimizing the UAV trajectory and time scheduling. The corresponding optimization problem is difficult to solve due to its non-convexity, and the authors propose an iterative algorithm via successive convex optimization to solve it approximatively. Furthermore, the authors also consider a benchmark scheme in which they maximize the minimum average secrecy rate among all users by jointly optimizing the UAV trajectory and time scheduling when no user has the caching ability. 

Q2. What is the effect of a larger T on the user?

larger T will also result in higher energy consumption and larger access delay since each user need to wait for longer time to communicate with the UAV in the next cycle. 

Q3. What is the effect of a larger flight period?

The authors can observe that a larger flight period T will achieve higher throughput since more time can be provided for the UAV to fly closer to each ground user to make better wireless channel. 

Q4. what is the optimum secrecy rate of user i3?

It’s obvious to find that the optimized secrecy rate of User i3 at each time slot must be higher than or equal to 0, due to the fact that if the secrecy rate of User i3 is less than 0 at the nth time slot, αi3 [n] will be equal to 0 for maximizing the minimum average secrecy rate of the users without caching. 

Q5. How can the authors optimize the secrecy rate of all the uncached users?

the minimum secrecy rate of all the uncached users can be optimized to be 0.607 bit/s/Hz, with the secrecy rate of cached users higher than η = 0.6 bit/s/Hz.Finally, the authors consider the scenario in which no user has caching ability, and the authors maximize the minimum secrecy rateamong all users by jointly optimizing the UAV trajectory and time scheduling according to (P2). 

Q6. How can the authors maximize the secrecy rate of all the uncached users?

The authors aim to maximize the minimum secrecy rate of all the uncached users by jointly optimizing the UAV trajectory and time scheduling, with the secrecy rate of other caching users guaranteed. 

Q7. How can the authors conclude that N1 should be set as small as possible?

the authors can conclude that N1 should be set as small as possible to achieve better performance, on the condition that the optimization problem can be solved. 

Q8. What is the way to prevent eavesdropping?

When two users have cached the file required by the other, the UAV can broadcast the files to them and disrupt the eavesdropping. 

Q9. What is the average transmission rate from the UAV to the ith user?

(10)The average transmission rate from the UAV to the ith user can be presented asR[i] = 1N ∑N n=1 αi[n]ru,i[n], i ∈ I1 ∪ I2 ∪ I3. 

Q10. How many iterations can the authors guarantee the convergence of the proposed algorithm?

From the results, the authors can see that the proposed Algorithm 1 can be guaranteed to converge for both the authors = (700m, 0m) and the authors = (500m, 0m) within about 5 iterations, which is consistent with the analysis in Proposition 1. 

Q11. Why is the secrecy rate of the uncached users higher than 0?

This is because the instantaneous secrecy rate of all the users in each time slot should be higher than 0; otherwise, the UAV will serve other users with positive secrecy rate to improve the network security.