Regulators are in the process of framing regulations to allow secondary use of vacant TV channels while protecting TV broadcast services from harmful interference. While the US and UK regulators have already passed such regulations in 2008 and 2015 respectively, other countries are still in drafting stages and the underlying circumstances in these countries could be different from those of the US and UK. Malawi released its final draft regulations in 2016. While the US and UK legislate for dynamic spectrum access and licence-exemption for secondary users, Malawi's draft regulations require such users to apply for a licence for assigned TV white space spectrum. This paper provides an analytical review of Malawi's regulations and a comparison with FCC and Ofcom regulations, which new regulations can build on. This analysis will also inform future work on network management tools that can enable practical deployment and coexistence of large-scale TV white space networks in a dynamic spectrum access environment in Africa.
performance degradation as a result of interference among the secondary user networks when the amount of available channels is not enough to allow exclusive channel operation for each network. The coexistence challenge among secondary user networks is exacerbated by the presence of heterogeneous radio access technologies (RATs) and lack of coordinated radio resource allocation among the secondary users themselves. The gains in spectrum utilisation as a result of DSA policy can potentially be diminished by the impact of interference.Spectrum utilisation can be improved by spatial reuse of channels. However, licence-exempt spectrum is likely not to be enough for exclusive channel operation, especially in urban areas. Hence, spectrum utilisation may be further improved through co-sharing among neighbour networks that can effectively coordinate access to a shared channel, as long as the total channel occupancy rate (COR) is less than unity to prevent spectrum starvation [1]. This paper therefore focuses on the design of a radio resource allocation framework for maximising spectrum utilisation through spectrum sharing, while ensuring coexistence among heterogeneous secondary user networks.In this paper, heterogeneous networks refers to networks that use different RATs. Such networks may not effectively coordinate access to a shared spectrum due to incompatible wireless protocols. The IEEE 802.19.1 standard specifies high level, network-based coexistence methods for geo-locationcapable devices operating under general authorization access (GAA) or licence-exemption. However, actual implementation of modelling techniques and radio resource allocation algorithms of the coexistence system is left to the industry [2].A hypergraph is a generalization of an undirected graph in which a hyperedge is a subset of vertices of arbitrary cardinality [3]. A radio frequency (RF) environment can be represented by a hypergraph, whereby radio devices or networks are represented by vertices and properties of different subsets are represented by hyperedges. Use of hypergraphs for modelling of cumulative interference and network dependency properties in radio resource allocation schemes has been proposed in literature [4]-[7].This paper proposes application of hypergraph theory in modelling of spectral coexistence capabilities of radios in a heterogeneous RF environment in order to implement a co-Abstract-Traditional graph theory is typically used to model interference relations among networks to realise channel assignment that enables improvement in spectrum utilisation through spatial re-use of the channels. Studies have shown that spectrum utilisation could be further improved through co-sharing among networks that are capable of spectral coexistence as long as the channel load is not excessive. The co-sharing networks use their inherent media access control (MAC) techniques to coordinate access to a shared channel. However, the concept of an edge in a traditional graph, which is a two-element subset, is not sufficient to model subsets o...
Dynamic Spectrum Access (DSA) is regarded as a promising solution for efficient spectrum management. Regulators have also approved licence-exemption or general authorisation access (GAA) to further improve spectrum accessibility for DSA systems in the Television (TV) and 3.5 GHz bands. However, heterogeneous DSA radio standards have been developed and the gains in spectrum efficiency could be undermined by coexistence challenges. Hence, the IEEE 802.19.1 standard for wireless network coexistence methods was published, but it leaves algorithmic implementation of the methods to the industry. When the spectrum is not sufficient for exclusive channel allocation, the standard includes a method for co-channel sharing among coexistent neighbour networks. In previous work, channel sharing was introduced on top of the exclusive channel allocation. However, channel sharing options could be significantly limited by the outcome of the exclusive channel allocation. Alternatively, this paper proposes use of hypergraph theory to model the cosharing strategy for coexistence management of heterogeneous radio systems. Results demonstrate that the hypergraph method achieves higher average spectrum utilisation by up to 8% and requires up to 5 fewer channels to achieve, on average, 100% operational networks than the previous method.
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