Can Unlicensed Bands Be Used by Unlicensed Usage?

Since their introduction, unlicensed ISM bands have resulted in a wide range of new wireless devices and services. It is fair to say that the success of ISM was an important factor in the opening of the TV white space for unlicensed access. Further bands (e.g., 3550-3650 MHz) are being studied to support unlicensed access. Expansion of the unlicensed bands may well address one of the principle disadvantages of unlicensed (variable quality of service) which could result in a vibrant new group companies providing innovative services and better prices. However, given that many commercial mobile telephone operators are relying heavily on the unlicensed bands to manage growth in data traffic through the “offloading” strategy, the promise of these bands may be more limited than might otherwise be expected (Musey, 2013).\ud \ud Wireless data traffic has exploded in the past several years due to more capable devices and faster network technologies. While there is some debate on the trajectory of data growth, some notable reports include AT&T, which reported data growth of over 5000% from 2008 to 2010 and Cisco, who predicted that mobile data traffic will grow to 6.3 exabytes per month in average by 2015 (Hu, 2012). Although the data traffic increased dramatically, relatively little new spectrum for mobile operators has come online in the last several years; further, the “flat-rate” pricing strategy has led to declining Average Revenue Per User (ARPU) for the mobile operators. Their challenge, then, is how to satisfy the service demand with acceptable additional expenditures on infrastructure and spectrum utilization.\ud \ud A common response to this challenge has been to offload data traffic onto unlicensed (usually WiFi) networks. This can be accomplished either by establishing infrastructure (WiFi hotspots) or to use existing private networks. This phenomenon leads to two potential risks for spectrum entrants: (1) the use of offloading may overwhelm unlicensed spectrum and leave little access opportunities for newcomers; (2) the intensity of the traffic may increase interference and degrade innovative services.\ud \ud Consequently, opening more unlicensed frequency bands alone may not necessarily lead to more unlicensed usage. In this paper, we will estimate spectrum that left for unlicensed usage and analyze risks for unlicensed users in unlicensed bands in terms of access opportunities and monetary gain. We will further provide recommendations that help foster unlicensed usage in unlicensed bands

Tradeable Spectrum Interference Rights

Spectrum rights have gained increasing attention since Ronald Coase pointed out that the most efficient way to assign spectrum is to give it to those users who value it most through property-like rights and secondary markets. Defining spectrum rights turns out to be difficult due to the nature of electronic emissions[1]. As a result, it may be more practical to define interference rights (similar to pollution rights) rather than exclusive usage rights. Interference rights give a user the right to interfere with another user up to a specified level. In this paper, we develop the idea of a market in spectrum interference rights and, using some plausible use cases, illustrate its characteristics. The paper therefore includes a detailed description of interference rights along with some first order quantitative modelling of the use cases coupled with qualitative analysis

Optimization of Plasma Plume Characteristics Based on Multi-anode Coaxial Ablative Pulsed Plasma Thruster

A special surface discharge is proposed based on the multi-anode electrode geometry. Instead of the traditional surface flashover of creepage on the insulator surface between the electrodes, a surface discharge with one of the electrodes being placed far away from the insulator is achieved in this paper. The unique electric field distribution due to the multi-anode electrode geometry has a significant influence on the discharge process of the surface discharge. It changes the generation and propagation process of the plasma, forming a plasma plume contributes to the propulsion performance of the thruster. Through theoretical analysis of the obtained plume data, it is indicated that the ablative pulsed plasma thruster based on multi-anode electrode geometry (short for multi-anode APPT) promotes the internal pressure of the plasma jet during its propagation and significantly increases the density and energy of charged particles. The discharge phenomena manifest that the multi-anode APPT and the helix-coil multi-anode APPT effectively increase the intensity of the plasma plume. Through electron density spatial distribution measurement, it has been found that the helix-coil multi-anode APPT increases the density of plasma in the axial direction to more than 4 times of the conventional coaxial APPT and reduces the electron density in other directions. In the propulsion test, it has been demonstrated that the multi-anode APPT and the helix-coil multi-anode APPT have better performance in terms of the impulse bit and the thrust-to-power ratio. In addition, it is also identified that the pinch effect will be enhanced with the increase of discharge power and the propulsion performance is promoted more distinctly. The multi-anode APPT and the helixcoil multi-anode APPT have been proved to have potential application advantage in the field of micro-satellite propulsion.Comment: 12 pages, 12 figure