The goals for 5G New Radio (NR) technology are to deliver wireless communications with higher capacity, performance, and efficiency compared with current mobile technologies. 5G NR will make effective use of the millimetre wave frequency spectrum to achieve these goals. However, these higher frequencies experience greater signal attenuation due to increased path loss and blockages. To overcome these, it is necessary to use high-gain directional active array antenna systems (AAS) at both ends of the communications link, which can steer the radiating beam in multiple directions. The cost-effective and compact implementation of the AAS requires the RF transceiver and antenna array to be highly integrated, making it impossible to independently test the performance of the constituent components due to the lack of inter-stage connectors. Further, the propagation channel is highly dynamic in both temporal and spatial domains. Hence, conformance testing of such systems is most effectively carried out using Over-The-Air (OTA) testing, since traditional conducted non-spatial test methods will not predict the radiated performance in space and the action of the RF transceiver, in particular, the beamformer. This paper presents a highly novel millimetre wave OTA test method facilitating the excitation of a Device Under Test (DUT) from multiple dynamic narrow angles of illumination, thus representing typical operating conditions and avoids the need for physical RF connections. This new method exploits the reflective properties of ellipsoidal surfaces and offers a cost-effective means when compared with other OTA test methods.

In-Band Full Duplex (IBFD) transceivers can potentially provide significant increases in spectral efficiency by allowing simultaneous transmit and receive on the same frequency at the same time. However any such gains are conditional on effective cancellation of the self-interference. The performance of a self-interference cancellation transceiver depends not only on the system design, but also on implementation specific parameters of the transceiver and cancellation circuitry. Thus, realistic evaluation of cancellation performance can only be performed using hardware prototypes. This paper provides a detailed overview of a highly flexible and reconfigurable self-interference cancellation testbed, which combines active cancellation with either separate Tx and Rx antennas, or an Electrical Balance Duplexer, along with digital baseband cancellation. The system can facilitate investigation on self-interference cancellation performance across a range of physical layer configurations, and provide a platform for the rapid prototyping of digital baseband algorithms within an operational self-interference cancelling transceiver.

Electrical balance duplexers can provide high transmit-to-receive isolation whilst facilitating transmission and reception from a single antenna, can be implemented on-chip, and are widely tunable, making this an attractive technology for implementing full duplex architectures in small form factor devices. This paper presents measurements from a novel hardware prototype full-duplex transceiver architecture combining electrical balance and active analog cancellation. The prototype duplexer achieves >80dB transmit-to-receive isolation over a 20MHz bandwidth at both 890MHz and 1890MHz, exceeding the performance of antenna separation architectures where the antenna isolation is limited to the levels achievable in hand held devices.

A key issue impacting the transmit to receive (TX-RX) isolation in Electrical Balance (EB) Duplexers is dynamic matching of the antenna impedance by the balancing network. Circuit simulations including embedded antenna measurements have been used to investigate the variation in TX-RX isolation due to interaction with the user and the local environment. Simulated results at 847MHz and 1960MHz show user interaction causes over 25dB of variation in the mean isolation over a 20MHz bandwidth. However, in reflective indoor environments, user interaction on average improves TX-RX isolation. This observed performance improvement is a result of reduced antenna radiation efficiency, which makes reflections from objects at longer ranges less significant and thereby reduces frequency domain variation in the antenna reflection coefficient.

This paper investigates electrical balance (EB) in hybrid junctions as a method of achieving transmitter-receiver isolation in single antenna full duplex wireless systems. A novel technique for maximizing isolation in EB duplexers is presented, and we show that the maximum achievable isolation is proportional to the variance of the antenna reflection coefficient with respect to frequency. Consequently, antenna characteristics can have a significant detrimental impact on the isolation bandwidth. Simulations that include embedded antenna measurements show a mean isolation of 62 dB over a 20-MHz bandwidth at 1.9 GHz but relatively poor performance at wider bandwidths. Furthermore, the operational environment can have a significant impact on isolation performance. We present a novel method of characterizing radio reflections being returned to a single antenna. Results show as little as 39 dB of attenuation in the radio echo for a highly reflective indoor environment at 1.9 GHz and that the mean isolation of an EB duplexer is reduced by 7 dB in this environment. A full duplex architecture exploiting EB is proposed.

An activity has been set up to develop a public standard for trunked radio and mobile data systems. The standards being developed are generically known as TETRA, standing for trans-European trunked radio. The ETSI is responsible for defining the TETRA standard. TETRA is really a family of standards. One branch of the family is a set of radio and network interface standards for trunked voice (and non-optimised data) services; the other branch is an air-interface standard optimised for providing classic wide-area packet data services at mobile access points, allowing a packet data network to be built with both fixed and mobile subscribers and supporting standard network access protocols. The paper gives an overview of the TETRA mobile data standard at its current stage of development. It discusses the general service requirements for the network, then concentrates on the design of the lower layers of the air-interface protocol itself.>