Internet of things (IoT) is a new paradigm that involves the interconnection of thousands of devices and home appliances. Due to the scarcity of the spectrum suitable for wireless electromagnetic transmission, many communication systems and devices are close to each other, or even overlapping in spectrum, thus incurring complicated interference situations. Therefore, interference in IoT is worthy of thorough investigation and should be well addressed. There have been numerous interference management (IM) proposals at the interfering transmitter or the interfered transmitter/receiver separately or cooperatively. Moreover, the existing IM schemes rely mainly on the use of channel state information (CSI). However, in some communication scenarios, the option to adjust the interferer is not available, and, in the case of downlink transmission, it is always difficult or even impossible for the interfered receiver to acquire necessary information for IM. Based on the above observations, we first propose a novel IM technique, called interference steering (IS). By making use of both CSI with respect to and data carried in the interfering signal, IS generates a signal to modify the spatial feature of the original interference, so that the steered interference at the interfered receiver is orthogonal to its intended signal. We then apply IS to a wireless local area network (WLAN) based IoT in which the same frequency band is reused by adjacent basic service sets (BSSs) with overlapping areas. With IS, multiple nearby access points (APs) could simultaneously transmit data on the same channel to their mobile stations (STAs), thus enhancing spectrum reuse. Our in-depth simulation results show that IS significantly improves network SE over existing IM schemes.

Both interference alignment (IA) and interference neutralization (IN) are exploited for Coordinated Multi-Point (CoMP) communications. With the base station’s (BS’s) cooperation, a transmit precoder and a receive filter are designed jointly, and concurrent transmissions of multiple data streams are then enabled. In the design of precoder, IN is applied to the interferences carrying same data so as to align the interfering signals in the opposite directions in a subspace. On the other hand, for interferences carrying different information, IA is employed to align them in the same direction in a subspace, thus reducing the interference signal observed at the receiver side. Based on different precoding schemes at the transmitter’s side, receivers adopt zero-forcing (ZF) so as to recover the desired data. The proposed interference alignment and neutralization based CoMP (IAN-CoMP) mechanism can achieve effective interference cancellation and suppression by exploiting limited and flexible collaboration at the BS side. It can also make a flexible tradeoff between the cooperation overhead and the system’s achievable degrees of freedom (DoFs). We extend the mechanism to general cases where the antenna configurations at both transmitter and receiver sides, the number of transmitters participating in CoMP and that of simultaneously served users are variable. Moreover, we discuss both single-location and multi-location-based realizations of the IAN-CoMP. Finally, by defining average transmit and receive cooperation order, we analyze the upper bound for IAN-CoMP. Our in-depth simulation shows that IAN-CoMP can significantly improve the spectral efficiency (SE) for cell-edge users.

In this brief, a balanced dual-band bandpass filter (BPF) using quad-mode ring loaded resonator (RLR) is presented. The resonance characteristics of the proposed quad-mode RLR are analyzed and the design graphs of the electrical lengths and the four resonant modes are given. Based on the above analysis, four resonant modes are applied to achieve two differential-mode (DM) passbands. U-shaped microstrip lines and stepped impedance microstrip/slotline (MS) transition structures are employed to achieve good common-mode (CM) rejection without affecting DM ones. In addition, an additional transmission pole is realized in the lower passband due to the stepped impedance slotlines. Meanwhile, six transmission zeros (TZs) are generated due to the horizontal transmission interference of the resonator and new coupling path, which improves the selectivities of the passbands. Furthermore, based on the proposed filter, a balanced dual-band filtering power divider (FPD) is designed for miniaturization. By loading isolation resistors on the slotline, the output ports isolation is improved. To verify the theoretical design, two proposed designs have been manufactured and measured. The measured and simulated results are presented with a good agreement.

With the rapid development of wireless communication technologies, interference has become a main impediment to network performance, making interference management (IM) a critical issue. Interference steering (IS) is emerging as a novel way of IM, which can steer the spatial feature of interference to a target subspace by exploiting the interactions of multiple signals over the air to avoid the disturbance to the interfered receiver. In reality, there always exist multiple interference from single or multiple sources. We propose three ways to realize IS. The first two of them are categorized as individual interference steering (IIS), in which multiple interfering signals are adjusted separately to either an identical direction (single-target IS, STIS) or different directions (multi-target IS, MTIS), incurring single or multiple degrees of freedom (DoFs) overheads, respectively. Furthermore, by recognizing that the goal of IM is to limit the effect of interference — i.e., the effective portion of interference imposed on the intended transmission — we propose aggregated interference steering (AIS) that exploits the constructive or destructive effects of multiple interfering signals. By considering the overall effect of multiple interference, the DoF cost of AIS is reduced to one regardless of the number of interference to be managed. Finally, the proposed three IS realizations are adapted to minimize the power cost of steering interference. Our theoretical analysis and in-depth simulation results have shown that the proposed IS schemes can effectively manage multiple interference via better utilizing the DoF and transmit power. AIS is shown to be advantageous in both power cost and DoF consumption.

In recent years, Cognitive Radio Networks (CRNs) have emerged as a transformative solution to address the growing demand for wireless spectrum resources and the inefficiencies of traditional static spectrum allocation policies

The low-cost and easy-deployable mobile ad hoc networks (MANETs) have great potential to serve as the underlay network architecture for implementing lots of critical applications. In order to support different demands in such applications, understanding the fundamental performance of the MANETs and exploring their performance enhancement are of great importance. To this end, this paper, for the first time, investigates the performance enhancement of the MANETs by appropriately allocating the network resource. Specifically, we consider both the transmission resource and storage resource of a network node and use a two-tuple to depict a general resource allocation configuration. First, for a MANET with any given resource allocation configuration, we establish an analytical framework to model the network dynamics as queuing processes. With the help of the network modeling, we then derive the expressions of fundamental performance metrics, including per node throughput, expected an end-to-end delay, and throughput capacity. Based on these results, we further develop optimal resource allocation algorithms to determine the optimal setting of resource allocation, for enhancing network performance. Finally, we provide extensive simulation and numerical results to verify the efficiency of our theoretical modeling and illustrate the effects of resource allocation on network performance.