Simultaneous random access of massive machine type communications (MTC) devices are expected to cause congestion in the radio access network. Not only the performance of MTC, but the coexisting human to human (H2H) communications would also degrade dramatically without an appropriate medium access control (MAC) protocol. However, most existing solutions focus on the random access procedure without dealing with the sunsequent data transmission procedure. In this paper, we firstly derive a packet size threshold based on the capacity analysis of slotted ALOHA (S-ALOHA) and time division multiple access (TDMA) protocols. Then a novel hybrid S-ALOHA/TDMA MAC protocol (HSTMAC) is presented for massive MTC access, in which the resources are separated for beta distributed machine to machine (M2M) traffic with small size packets and high priority H2H traffic with large size packets. Considering access class barring (ACB) scheme as an overload control method, the system equilibrium under arbitrary retransmission limit is analyzed rigorously, which can provide insights on quality of service (QoS) guarantee. Finally, a dynamic pre-backoff (DPBO) algorithm is designed for load balance by adaptively scattering the highly synchronized M2M traffic over the transmission interval. Numerical and simulation results validate our analysis and show that the HSTMAC protocol is superior to pure S-ALOHA protocol and pure TDMA protocol. The proposed DPBO algorithm can achieve a higher success probability and resource utilization ratio with a much reduced average delay than that of uniform pre-backoff (UPBO) scheme.

Flying Ad Hoc Networks (FANETs) are an essential component of future integrated air-space strategic systems. To achieve efficient and reliable network communication between nodes, a routing protocol capable of adapting to dynamic network changes and complex electromagnetic environments is required. This paper explores routing protocols for reliable networking between flight platforms in highly contested environments and the main idea is introducing link quality factors. Based on the integration of link quality for routing establishment, this study further investigates the performance of a cross-layer anti-jamming multi-hop routing protocol based on spatial disturbance resistance capabilities of nodes. It comprehensively evaluates link quality, incorporating nodes’ spatial disturbance resistance capabilities, to identify the most reliable routes in FANETs. Simulation results indicate that when nodes possess certain spatial disturbance resistance capabilities, routing established based on link quality can further ensure the network’s average throughput under interference conditions, as well as maintain a low packet loss rate.

With the rapid growth of IoT devices, machine communication is becoming more and more popular in 5G wireless communication systems. This paper proposes a novel MAC protocol for the Internet of Things (IoT) in a scenario with a gateway and multiple IoT devices. The IoT devices with packets (active IoT devices) send independent double-pilot(IDP). The gateway takes the number and ID of IoT devices and allocates appropriate power to IoT devices. These IoT devices adjust the power and transmit packets using the Power domain Non-Orthogonal Multiple Access Protocol (PD-NOMA). Compared with the traditional single pilot scheme (TSP), the independent double-pilot can dramatically reduce the pilot collision probability, although it will probably bring a moderate increase in detection workload. Furthermore, the IDP-NOMA protocol proposed in this paper dramatically improves the system throughput and the probability of transmission success.

The fifth-generation (5G) systems have to deal with massive deployment of machine-type-communication (MTC) devices. System overload may occur during a random access procedure under a limited number of preamble resources and physical uplink shared channel resources especially when there exist massive MTC devices in a cell. In order to resolve the system overload (caused by the massive MTC deployment), the 3GPP proposed the adopted a group paging (GP)-based uplink access technique. But its performances dramatically decrease as the number of MTC devices increases. In this paper we propose a novel method, named ACB-based group paging overload control method (AGO). To reduce the number of simultaneous access MTC devices, AGO first scatters the MTC devices over a GP interval, and then automatically adjusts ACB parameters according to the load conditions. By doing so, AGO achieves high-channel access probability for MTC devices. Simulation results show that this method is superior to the GP and Pre-backoff mechanisms in terms of success and collision probability, average access latency and resource utilization rate.

This work considers a secure multiple‐input multiple‐output (MIMO) channel where the energy receiver (ER) is a potential eavesdropper (Eve). Specifically, we aim to maximize the secrecy energy efficiency (SEE) via jointly designing the transmit precoding matrix and the artificial noise (AN) covariance at the base station (BS), as well as the power splitting (PS) ratio at the desired receiver (DR), subject to the constraints of the transmit power budget and harvested energy threshold. To handle the formulated highly nonconvex fractional problem, we apply the successive convex approximation (SCA) method to transform the objective and constraint into a tractable form. Then, a penalty‐based iterative algorithm is proposed. Finally, simulation results validate the performance of the proposed design.