Recently, active intelligent reflecting surface (IRS) has attracted much attention because it can solve the double-fading attenuation caused by cascaded channels. In this paper, the one-bit precoding vector at base station and the reflecting matrix at IRS are optimized jointly to minimize the mean squared error in the sub-connected active IRS-aided multiuser multiple-input single-output system. The resulted optimization problem is non-convex, for which an efficient alternating optimization algorithm is proposed. Concretely, the alternating direction method of multipliers, coordinate descent, and accelerate proximal gradient are utilized to optimize the one-bit precoding vector, discrete reflecting phase, and amplification factor, respectively. Finally, computer simulations are given to verify the proposed method in terms of energy efficiency and bit error rate.

Recently, the application of intelligent reflecting sur-face in wireless communications has attracted considerable attention. In this paper, the precoding of IRS-aided multiuser multiple-input single-output systems with one-bit digital analog converter at base station and discrete reflecting phase shifter at IRS is studied. The non-linear one-bit precoding and discrete phase are optimized jointly to minimize the mean square error. To solve this optimization, the alternate minimization strategy is employed to optimize precoding vector and discrete phase alternately. Moreover, the optimization for both constant-modulus phase-shift-keying (PSK) and general quadrature amplitude modulation (QAM) are considered. Concretely, the alternating direction method of multipliers algorithm and coordinate descent method (CDM) are utilized to acquire the one-bit precoding vector for PSK and QAM, respectively. In both PSK and QAM, CDM are employed to acquire the discrete phase optimization. Finally, computer simulations are given to demonstrate the effectiveness of proposed method.

A distributed access control module in wireless sensor networks (WSNs) allows the network to authorize and grant user access privileges for in-network data access. Prior research mainly focuses on designing such access control modules for WSNs, but little attention has been paid to protect user's identity privacy when a user is verified by the network for data accesses. Often, a user does not want the WSN to associate his identity to the data he requests, particularly in a single-owner multi-user WSN. In this paper, we present the design, implementation, and evaluation of a novel approach, Priccess, to ensure privacy-preserving access control. In addition to the theoretical analysis that demonstrates the security properties of Priccess, this paper also reports the experimental results of Priccess in a network of Imote2 motes, which show the efficiency of Priccess in practice.

Seamless roaming over wireless networks is highly desirable to mobile users, and security such as authentication of mobile users is challenging. In this paper, we propose a privacy-preserving universal authentication protocol, called Priauth, which provides strong user anonymity against both eavesdroppers and foreign servers, session key establishment, and achieves efficiency. Most importantly, Priauth provides an efficient approach to tackle the problem of user revocation while supporting strong user untraceability.