A hybrid approach for rural broadband access networks

Recent regulatory developments by the US’s Federal Communications Commission and the UK’s Office of Communications (Ofcom) have opened up new opportunities for wireless systems to utilize unoccupied TV ‘White Space’ (TVWS) channels now available after analog switchover for secondary use as shown in Fig. 1a. TV-band spectrum has favourable radio propagation characteristics that allow signals to travel relatively long distances over hilly terrain or in built-up urban areas. This, coupled with the fact that the regulations currently being drawn up by the FCC and Ofcom are widely expected to allow licence-exempt access to TVWS spectrum, make TVWS attractive for applications such as: i) rural broadband; ii) high-definition CCTV transmissions in towns and cities; iii) data offloading for already-congested cellular networks; iv) machine-to-machine (M2M) communications; etc

"WindFi" - a renewable powered base station for rural broadband

The HopScotch rural wireless broadband access test bed uses a network of low power base stations, powered by renewable energy sources to provide a low-cost rural broadband solution. In this paper we discuss the low power design aspects of the HopScotch base station and the impact on the required generation potential of renewable sources, battery bank sizing and the use of tracking PV arrays

Enabling rural broadband via TV "white space"

The use of multiple frequency bands within a wireless network allows the advantages of each band to be exploited. In this paper we discuss how HopScotch, a rural wireless broadband access test bed running in the Scottish Highlands and Islands, uses both 5 GHz and ultra high frequency "white space" bands to offer large data rates and expansive coverage whilst reducing the number of base stations or required transmission power. This reduction in energy consumption allows HopScotch to provide a low-cost and green solution for rural broadband delivery

Efficient TV white space filter bank transceiver

Future devices operating in the TV white space (TVWS) spectrum will require to access different bands at different locations and times in order to avoid interference to incumbent users, requiring agility and sufficient spectral masks to satisfy regulators. Further, with very high-speed ADCs and DACs becoming reality, the purpose of this paper is to present a transceiver front-end capable of simultaneously up- and downconverting a significant portion of the UHF band. The proposed approach takes a two-stage filter-bank conversion for implementation on state-of-the-art FPGAs. We present three different parameterisations, which are compatible with the 40 TVWS channels between 470 and 790MHz in Europe, and compare them in terms of complexity and latency

Digital RF multiplexing for a TVWS transceiver implementation

Future devices operating in the TV white space (TVWS) spectrum will require to access different bands at different locations and times in order to avoid interference to incumbent users, requiring agility and sufficient spectral masks to satisfy regulators. In order to realise radio devices capable of this, we briefly review design efforts on a radio transceiver capable up- and downconverting the 40 8MHz TVWS channels residing between 470MHz and 790MHz. While we briefly address the overall proposed structure, the aim of this contribution is to address the practical issues of interfacing data conversion devices sampling at RF to state-of-the-art FPGAs which can then perform the digital operations required for up- and downconversion

TVWS filter bank transceiver on OMAP-L137 evaluation module

Communications devices operating in the TV white space (TVWS) spectrum will be strictly regulated, requiring compliance with spectral masks to protect incumbent users and sufficient frequency agility to allow access to numerous frequency bands at different times and locations. Therefore, future designs operating at radio frequency (RF) have been proposed. The purpose of this paper is to demonstrate an implementation of such a transceivers at a scale-down frequency implemented on the OMAP--L137 evaluation module, whereby the RF link can be replaced by the device's audio I/O, thus enabling easier observation and algorithm testing for students

Design considerations for a filter bank based TVWS transceiver

This paper discusses the design of a filter bank based transceiver capable of simultaneously up- or downconverting the entire TV white space (TVWS) frequency band. The spectral mask requirements favour a filter bank based approach, whereby RF sampling and the use of an FPGA for digital up- and down-conversion dictates a two-stage approach. Some of the design considerations, including filter design approaches, are discussed in this contribution

Partially reconfigurable TVWS transceiver for use in UK and US markets

With more and more countries opening up sections of unlicensed spectrum for use by TV White Space (TVWS) devices, the prospect of building a device capable of operating in more than one world region is appealing. The difficulty is that the locations of TVWS bands within the radio spectrum are not globally harmonised. With this problem in mind, the purpose of this paper is to present a TVWS transceiver design which is capable of being reconfigured to operate in both the UK and US spectrum. We present three different configurations: one covering the UK TVWS spectrum and the remaining two covering the various locations of the US TVWS bands

HopScotch - a low-power renewable energy base station network for rural broadband access

The provision of adequate broadband access to communities in sparsely populated rural areas has in the past been severely restricted. In this paper, we present a wireless broadband access test bed running in the Scottish Highlands and Islands which is based on a relay network of low-power base stations. Base stations are powered by a combination of renewable sources creating a low cost and scalable solution suitable for community ownership. The use of the 5~GHz bands allows the network to offer large data rates and the testing of ultra high frequency ``white space'' bands allow expansive coverage whilst reducing the number of base stations or required transmission power. We argue that the reliance on renewable power and the intelligent use of frequency bands makes this approach an economic green radio technology which can address the problem of rural broadband access