Physical Layer Medium Access Control Research Articles

Using NOMA for Enabling Broadcast/Unicast Convergence in 5G Networks

This paper addresses the challenge of broadcast and unicast convergence by proposing a PHY/MAC (Physical Layer/Medium Access Control) architecture for 5G New Radio (NR). The solution is based on Power domain Non Orthogonal Multiple Access (P-NOMA). The main PHY/MAC configuration parameters have been analyzed theoretically and their impact on the service configurations is presented in this manuscript. The system concept has been translated into a prototype model and different evaluation tests are presented. First, simulations show that the PHY layer performs better than Time Division Multiplexing/Frequency Division Multiplexing (TDM/FDM) choices of current broadband access systems. Second, performance tests using a network simulation tool are described. The results for capacity, latency and reliability demonstrate that the proposed solution offers an excellent broadcast/unicast convergence choice with significant gain values with respect to legacy PHY/MAC alternatives.

Delay-aware reliable broadcast scheme based on power control for VANETs

In vehicular Ad-hoc network (VANET), many multi-hop broadcast schemes are employed to widely propagate the warning messages among vehicles and the key is to dynamically determine the optimal relay vehicle for retransmission. In order to achieve reliable and fast delivery of warning messages, this paper proposes a delay-aware and reliable broadcast protocol (DR-BP) based on transmit power control technique. First, a comprehensive model is derived to evaluate the transmission in vehicle-to-vehicle communications. This model considers the wireless channel fading, transmission delay and retransmissions characters occurring in the physical layer/medium access control (PHY/MAC) layer. Then, a local optimal relay selection mechanism based on the above model is designed. In DR-BP scheme, only the vehicle selected as the optimal relays can forward warning messages and the transmit power is time-varying. Finally, extensive simulations verify the performance of DR-BP under different traffic scenarios. Simulation results show that DR-BP outperforms the traditional slotted 1-persistence (S1P) and flooding scheme in terms of packets delivery ratio and transmission delay.

Impact of MAC frame length on energy efficiency in 6LowPAN

To reach necessary end-to-end connectivity between the Internet and wireless sensor networks (WSNs), the Internet Engineering Task Force (IETF) IPv6 over low power wireless personal area network (6LowPAN) working group has been established and introduced an adaptation layer for integration of IEEE 802.15.4 physical layer/media access control (PHY/MAC) layers and the upper layers of any Internet protocol (IP)-based networks, such as the Internet. The energy efficiency is one of the most important performance measures in WSNs because most sensor nodes are only battery powered so we should reduce the energy consumption to the lowest to extend the life of nodes. Therefore the determination of MAC frame length should be carefully considered since that the radio frequency (RF) module consumes most the energy of a sensor node meanwhile the MAC protocol is the direct controller of RF module. In this paper, we provide a star-shaped 6LowPAN non-beacon mode with unslotted carrier sense multiple access with collision avoidance (CSMA/CA) mechanism to access to the channel and model the stochastic behavior of a target end node as the M/G/1 queuing system. Analytical expressions for some parameters such as channel busy probability, packet loss probability and energy efficiency are obtained in this paper and our analytical results can clearly show the impact of MAC frame length on the energy efficiency of a target node in both ideal and lossy channel.