Spatially optimized wireless multicast networks with guaranteed bit-rate

Multicasting is a mode of transmission in which the same information is relayed to a subset of users. Delivering the same information to multiple users of the subset via a series of one-to-one (unicast) transmissions quickly exhausts bandwidth. Delivering information in a series of one-to-all (broadcast) transmissions such that each subset receives its information in a round-robin manner causes latency, or equivalently, a reduction in bandwidth. The techniques of this disclosure estimate the angular locations of each multicast subset using channel state information received across an antenna array. The locations are clustered using machine learning models. The available transmit power is allocated amongst clusters via spatially directed beams. The power allocation is designed to optimize the aggregate multicast bit rate while guaranteeing a minimum per-user bit-rate. Relevant information is beamed in a focused manner to each multicast subset, thus increasing the throughput to a subset while reducing interference to other subsets

Wideband Frequency Selective Surface Based Transmitarray Antenna at X-Band

In this paper, a wideband multilayer transmitarray antenna is designed for Ku frequency band. The unit cell is designed at 12GHz using frequency selective surface structure. Double square ring with center patch based multilayer unit cell is simulated. The effect of substrate thickness variation on transmission coefficient magnitude and phase range is discussed. The horn antenna designed at X-band will be used as feed source for transmitarray antenna. Transmitarray simulation results show wide impedance bandwidth from 10 to 13GHz. Wide gain bandwidth of 1.975GHz with peak gain of 18.96dB is achieved. The proposed transmitarray design will find applications in high gain, directional, low profile antennas for X-band communication systems

Sparse Array Architectures for Wireless Communication and Radar Applications

This thesis focuses on sparse array architectures for the next generation of wireless communication, known as fifth-generation (5G), and automotive radar direction-of-arrival (DOA) estimation. For both applications, array spatial resolution plays a critical role to better distinguish multiple users/sources. Two novel base station antenna (BSA) configurations and a new sparse MIMO radar, which both outperform their conventional counterparts, are proposed.\ua0We first develop a multi-user (MU) multiple-input multiple-output (MIMO) simulation platform which incorporates both antenna and channel effects based on standard network theory. The combined transmitter-channel-receiver is modeled by cascading Z-matrices to interrelate the port voltages/currents to one another in the linear network model. The herein formulated channel matrix includes physical antenna and channel effects and thus enables us to compute the actual port powers. This is in contrast with the assumptions of isotropic radiators without mutual coupling effects which are commonly being used in the Wireless Community.\ua0Since it is observed in our model that the sum-rate of a MU-MIMO system can be adversely affected by antenna gain pattern variations, a novel BSA configuration is proposed by combining field-of-view (FOV) sectorization, array panelization and array sparsification. A multi-panel BSA, equipped with sparse arrays in each panel, is presented with the aim of reducing the implementation complexities and maintaining or even improving the sum-rate.\ua0We also propose a capacity-driven array synthesis in the presence of mutual coupling for a MU-MIMO system. We show that the appearance of\ua0grating lobes is degrading the system capacity and cannot be disregarded in a MU communication, where space division\ua0multiple access (SDMA) is applied. With the aid of sparsity and aperiodicity, the adverse effects of grating lobes and mutual coupling\ua0are suppressed and capacity is enhanced. This is performed by proposing a two-phase optimization. In Phase I, the problem\ua0is relaxed to a convex optimization by ignoring the mutual coupling and weakening the constraints. The solution of Phase I\ua0is used as the initial guess for the genetic algorithm (GA) in phase II, where the mutual coupling is taken into account. The\ua0proposed hybrid algorithm outperforms the conventional GA with random initialization.\ua0A novel sparse MIMO radar is presented for high-resolution single snapshot DOA estimation. Both transmit and receive arrays are divided into two uniform arrays with increased inter-element spacings to generate two uniform sparse virtual arrays. Since virtual arrays are uniform, conventional spatial smoothing can be applied for temporal correlation suppression among sources. Afterwards, the spatially smoothed virtual arrays satisfy the co-primality concept to avoid DOA ambiguities. Physical antenna effects are incorporated in the received signal model and their effects on the DOA estimation performance are investigated

Efficient Modeling of an Array Antenna and Requirements for Maritime Mobile Reception of Meteorological Satellite Imagery

Wireless communication is an integral part of safety at sea. Direct broadcasts from public weather satellites on L- and X-band provide real-time weather observations and weather product dissemination to end users. These high-bandwidth broadcasts offer enhanced data throughput and require accurate pointing of high-gain antennas. An electronically-steered array antenna can provide high gain and rapid beam steering without moving parts, suitable for deployment on small vessels offshore. Figures of merit, such as array antenna gain and input impedance, vary with the beam steering angle as a consequence of mutual coupling between array elements. The electromagnetic design of an electronically-steered array antenna is more complex than a parabolic dish or a fixed broadside array, requiring an iterative development process and a computationally efficient method of simulating the array. This work addresses the validation of an efficient method for array simulation, a necessary first step in the design process of a deployable array. Starting with a small L-band subarray, a Fourier windowing method is applied to approximate the scan-dependent behavior of an electronically-steered array from an efficient numerical model in a periodic unit cell. Results are validated against experimental measurements of hardware prototypes and explicit numerical models of the subarray. The iterative design of antenna elements in an array environment and construction of a full-size array are left for future work

Efficient Modeling of an Array Antenna and Requirements for Maritime Mobile Reception of Meteorological Satellite Imagery

Wireless communication is an integral part of safety at sea. Direct broadcasts from public weather satellites on L- and X-band provide real-time weather observations and weather product dissemination to end users. These high-bandwidth broadcasts offer enhanced data throughput and require accurate pointing of high-gain antennas. An electronically-steered array antenna can provide high gain and rapid beam steering without moving parts, suitable for deployment on small vessels offshore. Figures of merit, such as array antenna gain and input impedance, vary with the beam steering angle as a consequence of mutual coupling between array elements. The electromagnetic design of an electronically-steered array antenna is more complex than a parabolic dish or a fixed broadside array, requiring an iterative development process and a computationally efficient method of simulating the array. This work addresses the validation of an efficient method for array simulation, a necessary first step in the design process of a deployable array. Starting with a small L-band subarray, a Fourier windowing method is applied to approximate the scan-dependent behavior of an electronically-steered array from an efficient numerical model in a periodic unit cell. Results are validated against experimental measurements of hardware prototypes and explicit numerical models of the subarray. The iterative design of antenna elements in an array environment and construction of a full-size array are left for future work