Enhancing Performance of Random Caching in Large-Scale Heterogeneous Wireless Networks With Random Discontinuous Transmission

Abstract

To make better use of file diversity provided by random caching and improve the successful transmission probability (STP) of a file, we consider retransmissions with random discontinuous transmission (DTX) in a large-scale cache-enabled heterogeneous wireless network (HetNet) employing random caching. We analyze and optimize the STP in two mobility scenarios, i.e., the high mobility scenario and the static scenario. First, in each scenario, by using tools from stochastic geometry, we obtain a closed-form expression for the STP in the general signal-to-interference ratio (SIR) threshold regime.The analysis shows that a larger caching probability corresponds to a higher STP in both scenarios; random DTX can improve the STP in the static scenario and its benefit gradually diminishes when mobility increases. In each scenario, we also derive a closed-form expression for the asymptotic outage probability in the low SIR threshold regime. The asymptotic analysis shows that the diversity gain is jointly affected by random caching and random DTX in both scenarios. Then, in each scenario, we consider the maximization of the STP with respect to the caching probability and the BS activity probability, which is a challenging non-convex optimization problem. In particular, in the high mobility scenario, we obtain a globally optimal solution using interior point method. In the static scenario, we develop a low-complexity iterative algorithm to obtain a stationary point using alternating optimization.Finally, numerical results show that the proposed solutions achieve significant gains over existing baseline schemes and can well adapt to the changes of the system parameters to wisely utilize storage resources and transmission opportunities. Index TermsRandom caching, retransmission, random discontinuous transmission (DTX), heterogeneous wireless networks, optimization, stochastic geometry.Y. Cui is with the

Enhancing Physical Layer Security of Random Caching in Large-Scale Multi-Antenna Heterogeneous Wireless Networks

“…From the figure, we can see that, when the cache size is large enough, the baselines may not be feasible, while our proposed scheme can still be feasible, but at the cost of the average RTP decrement. This observation indicates that increasing the cache sizes at the BSs does not always increase the average RTP, which is significantly different from the observations in the existing works without considering the secrecy constraints, e.g., [10]- [13]. This can be explained as follows.…”

“…We consider that there exist N files, denoted by the set N {1, 2, · · · , N }, to be cached in the considered HetNet. All the files have the same size (as in [7]- [13]) and each file n ∈ N has its own popularity (i.e., the probability that file n is requested by a user), denoted by a n ∈ [0, 1], where n∈N a n = 1. Without loss of generality (w.l.o.g.…”

“…Specifically, in [5], the most popular caching scheme was studied, in which each BS only stores the most popular files. However, such a caching scheme may not yield the optimal network performance, since it cannot provide any content diversity [11]- [13]. To tackle this issue, random caching scheme was considered in [6]- [15].…”

“…Convergence of Algorithm 1 and Algorithm 2. The step size for Algorithm 1 is ζ (t) = c 2+t 0.55[13].…”

Enabling Location Privacy Preservation in MANETs Based on Distance, Angle, and Spatial Cloaking

“…For instance, in the initial stage of some k-anonymity or spatial cloaking methods, the locations of users are transmitted to a trusted third party [10], which provides the chance for the attacker to eavesdrop users' locations through the wireless channel. Furthermore, it is expected that the development of caching technology will result in more distributed LBS/OSN servers or location verifiers [11,12], e.g., the AP. In conclusion, the privacy protection of locations in the wireless channel is essential for the pervasive public networks.…”