Mobile data offloading is an emerging technology to alleviate cellular network congestion and improve user service quality. In this paper, we investigate the economics of mobile data offloading through access points (APs) deployed by small cell service providers (SSPs), implementing uniform volume prices for all the mobile users (MUs) in each SSP's coverage including the overlapping area. In particular, we consider a data offloading game with a single mobile network operator (MNO) and two SSPs with overlapping coverage areas, where each SSP announces a uniform price for serving the cellular traffic within its coverage, and the MNO determines the traffic volumes to offload. We show that there is no pure Nash equilibrium (PNE) under such price competition, and determine the corresponding mixed strategy Nash equilibrium (MNE) using price randomization. As a practical solution, we propose a simple one shot auction mechanism that is easy to implement and has PNEs which is payoff equivalent with the MNE under price competition. We believe that this simple mechanism due to its simplicity of determining the equilibrium prices could be used in the negotiation between the SSPs and the MNO to determine the average service prices. Finally, we study the strategic topological infrastructure placement problem using a 1-dimension (1D, linear) user traffic flow model and a 2-dimension (2D) user traffic flow model when SSPs compete assuming uniform price competition as above. We show that the first mover in the placement problem will deploy its APs to cover more than half of the total flow volume and has an advantage to obtain a higher equilibrium payoff.

Mobile data offloading is an emerging technology to alleviate cellular network congestion and improve user service quality. In this paper, we investigate the economics of mobile data offloading through access points (APs) deployed by small cell service providers (SSPs), implementing uniform volume prices for all the mobile users (MUs) in each SSP's coverage including the overlapping area. In particular, we consider a data offloading game with a single mobile network operator (MNO) and two SSPs with overlapping coverage areas, where each SSP announces a uniform price for offloading the cellular traffic within its coverage, and the MNO determines the traffic volumes to offload. We show that there is no pure Nash equilibrium (PNE) in the data offloading game, and prove the existence of the mixed strategy Nash equilibrium (MNE) by price randomization. Furthermore, we propose a simple one shot auction mechanism that is easy to implement and has PNEs which yield SSPs the same equilibrium payoffs compared to the expected payoffs obtained at the above MNE.

This study addresses the pilot scheduling problem in multiuser multi‐cell massive multiple‐input–multiple‐output (MIMO) systems, aiming at mitigating the inter‐cell interference (pilot contamination), which constitutes a bottleneck of the system performance. First, the authors investigate the pilot reuse and scheduling problem in cellular systems with unlimited number of base station antennas, only considering the large fading coefficients. Three low‐complexity pilot scheduling schemes are then proposed by maximising the system achievable sum rate, including the greedy algorithm, the tabu search (TS) algorithm and the greedy TS algorithm. Second, they investigate the pilot reuse problem among the inter‐cell user terminals (UTs) under spatially correlated channels for massive MIMO transmission, trying to distinguish UTs sharing the same time‐frequency resources from the spatial domain. A closed‐form expression of the non‐asymptotic downlink achievable rate is derived by exploiting the second‐order channel statistical information. On the basis of the degree of the UTs’ covariance matrices overlap with each other, they further propose a spatial orthogonality‐based greedy pilot scheduling algorithm. The proposed approaches can provide much better performance in the presence of pilot contamination. Theoretical analysis and numerical results both verify the effectiveness of the proposed algorithms.

Most of digital signatures require the secret key when signing a message, however, there does exists a kind of signature scheme which is able to sign by appending new message only, so-called append-only signature (AOS). Motivated by its numerous useful applications in network security such as secure routing, etc., in this paper, we propose new efficient AOS scheme with shorter public key (parameters) using ID- based cryptographic techniques. To our surprise, it is the first time to achieve a practical, adaptively secure AOS via ID-based encryption approach. The proposed signature enjoys the merit of security against adaptive attack, while the previously presented AOS is only secure in a weak sense of selective unforgeability. Finally, we also present a new restricted AOS (RAOS) signature, which may be of independent interest in practice.