A Man-in-the-Middle (MiM) can collect over-the-air packets whether from a mobile or a base station, process them, possibly modify them, and forward them to the intended receiver. This paper exhibits the REVEAL protocol that can detect a MiM, whether it has half-duplex capability, full-duplex capability, or double full-duplex capability. The REVEAL protocol creates a sequence of timing-based challenge packets where the transmission times of the packets, their durations, and their frequencies, are chosen to create conflicts at the MiM, and make it impossible for the MiM to function. Implementing the REVEAL protocol in 4G/5G technology, we instantiate a MiM between the 4G/5G base station and a mobile, and exhibit the successful detection mechanisms. With the shared source code, the MiM can be reproduced using software defined radios and protocol efficacy can be verified using any open software defined cellular networks with off-the-shelf devices.

This paper addresses two challenges faced by mm-Wave communication systems in outdoor environments. A temporary blockage of the narrow Line of Sight (LoS) beam between the base station and the mobile, e.g., by an interposed hand, face or a pedestrian, can cause an outage. It has been suggested that a dense deployment of base stations is necessary to combat blockage, which is however a capital expensive proposition. This paper presents a low cost solution. It shows that in outdoor environments with hard surfaces, such as pavements, parking lots, etc., there is generally a ground reflected beam that allows sufficient data rate for a control channel to maintain time synchronization during the blockage of the LoS beam. This makes possible a quick reversion to the LoS beam as soon as the temporary blockage ends. The design of a protocol TERRA is described, and is experimentally shown to avoid outage$84.5~\%$of the time during pedestrian blockages in outdoor environments. The protocol TERRA also addresses a second problem: when the blockage is permanent, or due to mobility, the user has moved away from the earlier serving base station. In such cases a handover to a neighbor base station is needed. There are several challenges of ensuring a soft handover due to the narrow mmWave beams. Since blockages are sudden, the mobile will need to be always ready to switch to a neighbor base station’s beam. This requires that it always have in hand a suitable neighbor base station, as well as continually realign its beam to that neighbor base station while it is mobile. TERRA shows how this is to be done without the neighbor base station’s active cooperation, since connection with it is not yet established. At the same time, TERRA also needs to and does continually realign the mobile’s beam with its presently serving base station to counteract its mobility. TERRA thereby enables the mobile to perform a soft handover to a neighbor base station in the event of a permanent blockage, without requiring any side information, unlike the existing works. Evaluations show that TERRA maintains received signal strength close to the optimal solution while keeping track of the neighbor base station.

RAN Intelligent Control (RIC) has developed in parallel with Open Radio Access Networks (O-RAN) as a means of utilizing newly available interfaces. Focus has been largely on non-realtime (non-RT: > 1 sec) dealing with RAN management and offline training, and near-realtime (near-RT: 10 ms to 1 sec) dealing with UE load balancing and RAN configuration. We contend that the true power of RIC can be unleashed only with realtime (RT: < 100 μs) measurement, optimization, and control of RAN resources, corresponding to the cellular transmission time interval (TTI: 125 μs to 1 ms).

Management of narrow directional beams is critical for mm-wave communication systems. Translational or rotational motion of the user can cause misalignment of transmit and receive beams with the base station losing track of the mobile. Reacquiring the user can take about one second in 5G New Radio systems and significantly impair performance of applications, besides being energy intensive. It is therefore important to manage beams to continually maintain high received signal strength and prevent outages. It is also important to be able to recover from sudden but transient blockage caused by a hand or face interposed in the Line-of-Sight (LoS) path. This work presents a beam management protocol called BeamSurfer that is targeted to the use case of users walking indoors near a base station. It is designed to be minimalistic, employing only in-band information, and not requiring knowledge such as location or orientation of the mobile device or any additional sensors. Evaluations under pedestrian mobility show that 96% of the time it employs beams that are within 3 dB of what an omniscient Oracle would have chosen as the pair of optimal transmit-receive LoS beams. It also recovers from transient LoS blockage by continuing to maintain control packet communication over a pre-selected reflected path that preserves time-synchronization with the base station, which allows it to rapidly recover to the LoS link as soon as it is unblocked.

Whittle index policy is a powerful tool to obtain asymptotically optimal solutions for the notoriously intractable problem of restless bandits. However, finding the Whittle indices remains a difficult problem for many practical restless bandits with convoluted transition kernels. This paper proposes NeurWIN, a neural Whittle index network that seeks to learn the Whittle indices for any restless bandits by leveraging mathematical properties of the Whittle indices. We show that a neural network that produces the Whittle index is also one that produces the optimal control for a set of Markov decision problems. This property motivates using deep reinforcement learning for the training of NeurWIN. We demonstrate the utility of NeurWIN by evaluating its performance for three recently studied restless bandit problems.Our experiment results show that the performance of NeurWIN is significantly better than other RL algorithms.

Narrowband Internet of Things (NB-IoT) is a recent feature introduced by 3rd Generation Partnership Project (3GPP). It is a low power wide area network technology that will enable cellular service to a massive number of low throughput IoT devices. The NB-IoT is a derivative of existing 3GPP Long Term Evolution (LTE) that has to be delay tolerant with low cost devices. In LTE, the decoding of Physical Downlink Control Channel (PDCCH) consumes a significant amount of user equipment's (UE) battery power because of its high computational complexity and complicated search space design. Hence, the existing downlink control channel scheduling schemes for LTE cannot be reused for NB-IoT. The reduction in available bandwidth and introduction of repetitions for achieving wider coverage makes the Narrowband PDCCH (NPDCCH) search space design and its allocation even more challenging. In this paper, we first explain the NPDCCH in detail and present its design rationale. We propose several novel downlink control channel scheduling schemes for 3GPP NB-IoT and compare their performance through extensive Monte Carlo simulations.