In this paper, we analyze the spectral coexistence between the second generation terrestrial digital video broadcasting (DVB) and the long term evolution (LTE) networks. In particular, the global spectral efficiency (SE) of both systems is investigated when a partial spectral overlap between DVB and LTE signals occurs. Our contribution lies in twofold: 1) the interfering signal variance in each network is derived analytically according to the frequency overlap while taking into account the difference between the characteristics of LTE and DVB networks, especially the OFDM subcarrier spacing and then the OFDM symbol duration and 2) SE is derived with uniform and non uniform power allocation between overlapped and non overlapped subcarriers of the two networks. This derivation offers an analytical evaluation of the effect of the spectral overlap ratio variation and different power allocation scenarios and provides insightful results on the cooperation between the two networks.

/pdf/spectral-overlap-optimization-for-dvb-t2-and-lte-coexistence-3ipmh9reat.pdf

Spectral Overlap Optimization for DVB-T2 and LTE Coexistence

Spectrum access system (SAS) is a spectrum sharing framework proposed to share the spectrum between the incumbent users and the citizen broadband radio service devices, i.e. Priority access users and general authorized access (GAA) users. In this paper, we propose an interfering angle based method for the joint resource (channel and transmit power) allocation problem to the mobile and fixed GAA users. With mobile GAA users, the set of GAA users that can hear each other will change at different time instants making the resource allocation problem more challenging. The resource allocation of fixed and mobile GAA users is done considering coexistence with priority users, as well as coexistence between mobile and fixed GAA users. For the conflict-free resource allocation to fixed and mobile GAA users, we propose to use the maximum allowed transmit power for the beams of fixed GAA users that lie within the interference range of mobile GAA users. The simulation results show improved capacity from our proposed method while satisfying a predetermined interference constraint.

/pdf/resource-allocation-in-moving-and-fixed-general-authorized-40euf546hp.pdf

Resource Allocation in Moving and Fixed General Authorized Access Users in Spectrum Access System

In cognitive radio network, channel decision is critical assignment to utilize the unused spectrum band as secondary user without interfering with the primary user. Thus different criteria of available spectrum are exploited as per the requirement of secondary user to establish connectivity with the network for data transmission. Here multi-objective optimization based on ratio analysis (MOORA) algorithm is proposed as multiple criteria decision-making method for channel decision in cognitive radio environment. MOORA method acquires contradictory appearances such as criteria and alternative available. A matrix of response of alternatives to the criteria is considered, and ratio analysis is performed to find ranking of available channel. Finally a decision-making problem with different weighted matrix based on user application and criteria is illustrated, and results show that proposed MOORA algorithm outperforms similar other algorithms in terms of diverse criteria features, complexity and practicality.

To Mitigate with Trusted Channel Selection Using MOORA Algorithm in Cognitive Radio Network

The 5G mobile networks will increase the amount of available spectrum by using new licensed and unlicensed bands. However, most of the newly allocated bandwidth is restricted to higher frequencies, that provides smaller coverage. Lower frequencies, that provide higher ranges, are mostly occupied by either radio or television channels. With the move to digital television, some analog TV channels are available in specific regions, opening the possibility of frequency reuse by third parties. Geolocation databases and collaborative sensing techniques are used to locate and use the available TV Whitespaces (TVWS) for mobile transmission. This paper presents the proposal of a cognitive cycle in the ns-3 simulator (LENA/LTE), which includes collaborative sensing and a cognitive radio resource scheduler. The simulations were done considering a rural area and the results show that the implementation may be useful for further research in developing new solutions for the 5G Cognitive MAC Layer.

/pdf/a-tool-for-developing-collaborative-sensing-and-cognitive-3bwa1gz2fq.pdf

A Tool for Developing Collaborative Sensing and Cognitive MAC Layer Solutions for 5G in Rural Areas

The growing shortage in available wireless spectrum has resulted in opening of new frequency bands by the FCC. Some bands that have previously been underutilized are now opened for public usage under the 3-tier spectrum sharing framework. Spectrum access is regulated by a Spectrum Access System (SAS). The three user tiers are incumbent users - military, federal and satellite operators, Priority Access License (PAL) holders - operators which have purchased a license for exclusive access to the spectrum when not used by incumbents, and General Authorized Access (GAA) users who may only use it opportunistically. The SAS coordinates access to the spectrum, and can grant access to lower tier users when it is not being utilized by any users in higher tiers. Because spectrum licenses are granted for large geographic regions - counties, in ten year increments, service providers are highly motivated to obtain PALs as soon as possible to avoid being locked out of a market. This may lead to a sub-optimal utilization of the spectrum by the PAL holder in cases where licenses are obtained before the network is deployed in the entire county. The unused portions of the area represent a loss to the PAL holder, as they will end up being used by the third tier users without any compensation to the license holder. The second tier operator can choose to sub-lease the license in these areas. This paper proposes a market model for sub-leasing with short-term license allocation in smaller areas. The model assumes that interested parties periodically make bids for sub-leased licenses in the small area defined by the bid. The sub-leased licenses are allocated by the SAS in a way that maximizes the financial gain to the PAL holder. This paper shows a basic sub-lease allocation model and two improved hypergraph based models. The improved models result in the financial gain increase between 15 and 35% over the base model, depending on the geographical distribution of the sub-lease bid regions.

Design of a Secondary Market for Fractional Spectrum Sub-leasing in Three-Tier Spectrum Sharing

Spectrum Access System (SAS) is a three tier spectrum sharing framework proposed by the FCC. In this framework the aggregate interference of tier-3 General Authorised Access (GAA) users should be below a predetermined threshold anywhere within the tier-2 Priority Access Licensee (PAL) exclusion zone. GAA are expected to use a diverse range of Radio Access Technologies (RATs) with different levels of loading. We propose an optimal transmit power and probability of spectrum utilisation allocation scheme for GAA users that meets the average aggregate interference constraint within the GAA network. Most of the capacity maximisation studies consider the instantaneous aggregated interference from secondary users. In this paper we present an average aggregated interference method to optimise the capacity of GAA users in a single channel. Simulation results suggest that we can significantly increase the capacity of the channel by considering the probability spectrum utilisation of GAA users.

/pdf/opportunistic-access-to-pal-channel-for-multi-rat-gaa-jlehiphu9v.pdf

Opportunistic Access to PAL Channel for Multi-RAT GAA Transmission in Spectrum Access System

Digital dividend spectrum, that is released after the digitalisation of analog TV broadcasting is harmonized internationally for the use of Long Term Evolution (LTE) technology. When LTE and digital television services operate in adjacent UHF bands, LTE transmitters can cause harmful interference to television reception. Thus in this paper, we study the compatibility of operating LTE services in the digital dividend spectrum identified in Australia based on the recently allocated band plan. We have used interference analysis method to calculate the minimum separation distance between LTE and DVB-T1 system and Monte Carlo Simulation for outage probability.

https://www.researchgate.net/profile/Shubhekshya_Basnet/publication/272747392_Interference_Analysis_in_Digital_TV_Reception_with_LTE_Systems_In_Adjacent_Bands_In_Australian_Context/links/54ed46070cf28f3e65358296.pdf?disableCoverPage=true

Interference analysis in digital TV reception with LTE systems in adjacent bands in Australian context

The optimal use of spectrum is a key focus for all regulatory bodies. Federal Communications Commission has introduced Spectrum Access System (SAS) to maximise the spectrum utilisation in the US 3.5 GHz band. SAS is a three-tier spectrum sharing framework where Citizen Broadband Radio Service (CBRS) devices can access the channel when it is not used by Incumbent Access users. CBRS consists of Priority Access Licensee (PAL) and General Authorized Access (GAA). In this paper, we consider the problem of optimum transmit power allocation for GAA users using a carrier sensing range i.e. maximum distance a user can be sensed while guaranteeing the interference to PAL from GAA users is below the threshold. We use carrier sensing range to find the sets of GAA users that cannot transmit at the same time and adjust the interference budget of transmitting GAA users. We present an algorithm for transmit power allocation for GAA users in the SAS. The proposed algorithm uses the transmission characteristics and location information provided by Citizen Broadband Radio Service Devices to SAS to maximise the peak capacity of GAA users ensuring the interference constraint to PAL. Simulation results show that the proposed algorithm significantly increases the peak capacity of GAA users by considering the carrier sensing range and adjusted interference budget.

Transmit Power Allocation for General Authorized Access in Spectrum Access System Using Carrier Sensing Range

To enable spectrum sharing the Federal Communication Commission (FCC) has proposed the Spectrum Access System (SAS). In SAS General Authorised Access (GAA) can opportunistically access any part of the 3.5 GHz band. In SAS prior information regarding the time usage of spectrum is not provided by Priority Access Licensee (PAL) and when PAL operation starts the GAA needs to ensure they do not cause interference above a predetermined threshold. In this work we propose a method for GAA Citizen Broadband Radio Service Devices (CBSDs) to switch to different channel considering the probability of spectrum utilisation of GAA. Switching overhead is the time delay when switching the channel from one to another. In our work we proposed the method to calculate switching overhead and maximised average sum capacity of GAA CBSDs considering switching overhead and Root Mean Square (RMS) interference at PAL protection area. Simulations result shows that average sum capacity of GAA CBSDs can be maximised using the proposed method.

Shubhekshya Basnet

Papers

Opportunistic Access to PAL Channel for Multi-RAT GAA Transmission in Spectrum Access System

Resource Allocation in Moving and Fixed General Authorized Access Users in Spectrum Access System

Interference analysis in digital TV reception with LTE systems in adjacent bands in Australian context

Transmit Power Allocation for General Authorized Access in Spectrum Access System Using Carrier Sensing Range

Considering switching overhead for transmit power allocation for GAA in spectrum access system