Fundamentos teóricos

The TV White Space Optimization Software (TWHISO) produced has been tested and found to achieve the following:

Discovering of unused channels: One of the prevailing problems in spectrum management is the method of allocation that has made spectrum look scarce because of increase in the need wireless device. In this dissertation, alternative way of serving some wireless devices has been discovered through the use of UHF channels in the terrestrial television bands.

Interference reduction between communication devices: The spectrum management and allocation using geolocation technique in this dissertation reduced the possible occurrence of interference. This was done by making sure that optimal fitness is not adjacent to primary user and occupied channel. If adjacent the system assign a value of 0 which indicate that it is not fit for allocation. If not adjacent the system assign a 1 meaning it is fit for allocation without interference.

Optimal allocation of TVWS to WSDs: The dissertation was able to achieve this due to the nature of the algorithm used, the inference rules were well chosen which was used to form the knowledge base. The system communicates with the knowledge base and all necessary conditions are tested before declaring a channel fit for allocation to WSDs.

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Continuity in communication by WSDs: There is continuity in communication between the WSDs. This is being made possible because of the switching ability the dissertation offers. When a WSD is transmitting and moves to another location, it’s transmitting channel changes from location A to location B. on location B the WSD is automatically switched to available channel in its new location.

Protection of primary users: With the combination of geolocation technique and sensing, the licensed user of the spectrum is protected with more accuracy than using sensing alone. This dissertation employed geolocation technique with sensing for maximum protection of licensed user of the spectrum. White Space Devices (WSD) are in constant interaction with the database to make sure that any harmful interference is avoided.

Providing channel information: The dissertation provided information on the list of frequencies that could be used within each location. In order to allow variable size bandwidths to be used the dissertation also provided start and end frequencies which are considered more appropriate. In addition the maximum transmit power was provided for each frequency assignment. This would allow the devices to operate accordingly in order to minimize the possible interference or to increase the flexibility of the device.

Increase in spectrum Access: Spectrum access to white spaces would enhance spectrum utilization, while also testing the approach of controlling the interference between different systems directly rather than through the transmission power. The amount of interference generated to the license holder can be controlled by our sensing model capabilities and geolocation database access.

Hybrid combination: Many previous researches in this domain either use sensing techniques alone in detection of spectrum holes or employ the use of geolocation database to identify list of available spectrum holes. This dissertation

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extended the research by taking into consideration the two separate entities into one for optimum result. The use of geolocation technique and sensing in determining the spectrum holes and protecting the primary users has optimized spectrum usage.

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5.3.4 Benefits of the System

The following are the benefits of this dissertation

Long Range: TVWS are found in the VHF and UHF TV broadcasting frequencies, especially between 474−866 MHz as found in our analysis. At lower frequencies, radio signals have a very long range. As a result, fewer base stations are required for providing the same level of coverage, resulting in cheaper networks as this reduces both capital expenditure on network equipment and network maintenance and operation (e.g. power for base stations) costs. Long signal range is beneficial especially for providing coverage in rural areas, where the alternative solutions are expensive.

Better Speeds: The frequencies used for television broadcasting were chosen in the first place because they were good at transmitting information quickly.

Whereas Wi-Fi can shuttle data at 160-300 megabits (Mbps) per second, white-space can do so at 400-800 Mbps per second.

In-Building Penetration: The excellent propagation of TVWS radio signals provides deep in-building coverage, allowing ubiquitous (or near-ubiquitous) coverage. Their non-line-of-sight performance offers the ability to penetrate obstacles such as trees, buildings and rugged terrain.

Free, Unlicensed Spectrum: TVWS are being opened up for new uses on a free and unlicensed basis. Regulators are considering or have already allowed TVWS devices to operate in the TV band provided that they do not cause interference to the primary spectrum users. Free spectrum significantly reduces the costs of operating wireless networks.

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Increasing Economic and Social Development of the Country: Proper implementation of TVWS will open up mobile broad and allow for more data usage with the following benefits more productive farming (e.g. through online access to key information), a stimulus to the development of local e-commerce businesses, enhancing delivery of teaching and training materials to rural schools and reducing the cost of health care delivery. Communication with distant family members will be enhanced – for example through video communication – and it will be easier to keep in contact through online social networks.

Globally harmonized spectrum: TV bands are harmonized worldwide, so white space can be expected to be available globally. Having a global marketplace offers the prospect of economies of scale for network equipment and devices.

This will spur the development of common standards and technologies while allowing manufacturers to mass-produce equipment driving down unit costs.

Furthermore, recent developmental trends in wireless technologies are not only providing various opportunities for entrepreneurs, but also overhauling the character of entrepreneurship by pioneering new business models. To date, an array of competing wireless technologies have entered the market and these range from Wireless Mesh technology, WiFi, WiMAX (802.16), Cellular such as Universal Mobile Telecommunication Services/Wideband Code Division Multiple Access (UMTS)/WCDMA and High speed Downlink Packet Access (HSPDA), Long-Term Evolution (LTE) and Advanced LTE. To this end, among these developments in the market, wireless mesh networks (WMNs), have indisputably and justifiably been touted as a candidate technology that is set to facilitate ubiquitous connectivity to the end user in underprivileged, under provisioned, and remote areas. The WMNs comprise wireless routers and clients as well as an endowed ability to dynamically self organize, and self configure to the extent of nodes in the network being able to establish and maintain

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connectivity among themselves. The candidature of this technology justifiably emanates from its characteristic low upfront cost, ease of maintenance, robustness as well as reliable service coverage. Indisputably, WMNs have found applications ranging from broadband home networking, community and neighbourhood networks, enterprise networking, building automation and other public safety areas etc. However, while the currently deployed WMNs provide flexible and convenient services to the clients, the performance, growth and spread of WMNs is still constrained by several design limitations such as limited usable frequency resource. The design constraints are a consequence of WMNs in the unlicensed Industrial, Scientific and Medical (ISM) band being mostly adopted for access communications. Subsequently this adoption renders the WMN susceptible to competition with all other devices in this particular ISM band eg. near by WLANS and Bluetooth devices. Ultimately, the limited bandwidth of the unlicensed bands cannot cope with the evolving network applications and this has led to the spectrum scarcity problem. However, with the discovery of TVWS and proper method of assignment to unlicensed device will provide an opportunity to significantly enhance the performance of WMNs and other wireless technologies.

This will no doubt bring a lot of innovations like fostering hundreds of small scale incremental innovations due to the low costs involved.