Primary User Protection Contour and No-Talk Zone Characterization for TV Whitespace Spectrum Reuse in Nigeria.

Abstract

To encourage secondary spectrum access within the TV broadcast bands in Nigeria, the propagation properties of TV signals on the VHF and UHF frequency ranges were empirically studied through measurements carried from two TV stations. The Pathloss exponent for the VHF band was found to be 1.9 with a characterised Pathloss equation for VHF band computed as 𝑷𝑳 (𝒅𝑩)=𝟖𝟒.𝟎𝟒+𝟏𝟗.𝟎𝟑𝒍𝒐𝒈𝟏𝟎(𝒅), where (𝒅) is the distance from the transmitter to the receiver. The UHF band Pathloss exponent was computed to be 1.8 with a Pathloss equation characterised as 𝑷𝑳 (𝒅𝑩)=𝟓𝟕.𝟑𝟓+𝟏𝟕.𝟗𝟔𝒍𝒐𝒈𝟏𝟎(𝒅). The findings re-echoed the need for specific prediction model to accurately estimate the service coverage of TV stations and facilitate effective utilization of spatial TV white space as it was found that there were divergence in coverage prediction between the measured model and some of the conventional models. Using the protection view point, the protection contour in kilometers for TV signals propagating in the UHF band in Nigeria was characterized to be 𝒅𝒓𝒑= 𝟏𝟎[𝑷𝒕+𝟑𝟐.𝟔𝟓 𝟏𝟕.𝟗𝟔].. Where (𝒅𝒓𝒑) is the protection contour radius modeled as a function of the transmit power of the TV station in decibels with reference to one milliwatt (dBm) for co-channel and adjacent channel coverage. Similarly, the no-talk-zone in kilometers was characterized as a function of the transmit power of the secondary user device in dBm for co-channel usage to be 𝒅(𝒓𝒏−𝒓𝒑)=𝒂𝒏𝒕𝒊𝒍𝒐𝒈[𝑷𝒔−𝟖𝟗.𝟕𝟔𝟏𝟕.𝟗𝟔] modeled as a function of the secondary user transmit power 𝑷𝒔. The separation distance in kilometers from the TV station to the possible secondary user transmitter beyond which no interference exist was computed to have a relationship equal to 𝒂𝒏𝒕𝒊𝒍𝒐𝒈⟦𝑷𝒕+𝑷𝒔−𝟓𝟕.𝟏𝟏𝟏𝟕.𝟗𝟔⟧. This model will facilitate TVWS co-channel coexistence using the specified equation to determine the separation distances between television transmitters and secondary user transmitters.