Cognitive Radio for Broadband Access in Rural Africa and other Developing Countries

This thesis examines how Cognitive Radio (CR) can impact broadband access in rural Africa and other developing countries. We investigate how CR through dynamic spectrum access facilitates the efficient use of underutilized spectrum (white spaces) in rural areas. Until now much of the research and development of CR standardization is focussed on developed countries deployment scenarios e.g. IEEE 802.22, ACME-92, IEEE 80.11af standards in TVWS. Such countries have a highly developed infrastructure capable of supporting the use of real time database access, and a requirement for broadband data rates. Due to financial constraints and lack of supporting infrastructure in developing countries a different approach may be required to maximize the use of CR. This thesis identifies GSM white space as a potential candidate band for CR applications in rural Africa/developing countries. We use Monte Carlo simulation techniques as an analytical tool to assess the coexistence performance between CR systems and GSM. It is shown that the INR threshold below 30 dB corresponding to a -91 dBm signal detection threshold is required to fully protect GSM systems from excessive interference from CR systems. These values are relatively higher than the noise level which means simple sensing techniques such as energy detection can be employed by the CR systems to determine white space. This minimizes the complexity of CR by avoiding the use of complex sensing techniques and real time database access which may add cost, the critical factor for rural deployment. It is also shown that at GSM channel load below 0.5 Erlang CR systems can operate in the GSM band and achieve a coverage of up to 1 km at a transmit power of 800 mw ( -1 dBW) without causing excessive interference on primary GSM users. This means that in areas where the GSM band is underutilized such as rural areas, CR systems can opportunistically exploit GSM white spaces. From the regulatory perspective it is found out that dynamic spectrum sharing policies are more adaptive to current trends in technological advancement, which means new technologies such as CR systems can be accommodated.