Moshe T. Masonta

5G: The Convergence of Wireless Communications

As the rollout of 4G mobile communication networks takes place, representatives of industry and academia have started to look into the technological developments toward the next generation (5G). Several research projects involving key international mobile network operators, infrastructure manufacturers, and academic institutions, have been launched recently to set the technological foundations of 5G. However, the architecture of future 5G systems, their performance, and mobile services to be provided have not been clearly defined. In this paper, we put forth the vision for 5G as the convergence of evolved versions of current cellular networks with other complementary radio access technologies. Therefore, 5G may not be a single radio access interface but rather a “network of networks”. Evidently, the seamless integration of a variety of air interfaces, protocols, and frequency bands, requires paradigm shifts in the way networks cooperate and complement each other to deliver data rates of several Gigabits per second with end-to-end latency of a few milliseconds. We provide an overview of the key radio technologies that will play a key role in the realization of this vision for the next generation of mobile communication networks. We also introduce some of the research challenges that need to be addressed.

Energy efficiency in future wireless networks: Cognitive radio standardization requirements

Energy consumption of mobile and wireless networks and devices is significant, indirectly increasing greenhouse gas emissions and energy costs for operators. Cognitive radio (CR) solutions can save energy for such networks and devices; moreover, the energy consumption of CR technologies themselves have to be considered. This paper discusses ways in which standardization efforts can assist the use of CR to both save energy for mobile/wireless communications, and ensure that the energy consumption in CR networks and devices is minimized. Compelling argument for such solutions are presented.

First large TV white spaces trial in South Africa: A brief overview

The paper overviews African first of the really large scale trials of television (TV) white space (TVWS) technology and white space devices (WSDs) designed to co-use the frequency spectrum allocated to TV broadcasting. The WSD obtains information about availability of the spectrum in a particular area for a particular period of time from a geolocation spectrum database (GLSD). The GLSD bases its estimations about the availability on stored information about primary users/transmitters in the area, propagation prediction algorithms and local spectrum management regulations. As the overall system is fairly complex and new, extensive testing and trials are required to prove its functionality and compatibility with existing users of the spectrum. Some of the experiences, specifically those from the largest in Africa TVWS trial providing Internet to 10 large schools, held in Tygerberg, South Africa, and conclusions on testing of WSD and use of white space are overviewed.

Framework for TV white space spectrum access in Southern African Development Community (SADC)

The global migration of television (TV) from analogue to digital broadcast will see a large amount of TV spectrum available (called TV white space - TVWS) for other services such as mobile and broadband wireless access (BWA). Leading spectrum regulation authorities, such as the Federal Communications Authority (FCC) and the Office of Communication (Ofcom) are already defined rules and policies for licence-exempt access of the TVWS for BWA, especially for rural areas. Key to these rules and policies are the transmission and operating parameters to ensure protection of TV incumbents from harmful interference that might be caused by the white space devices (WSD). In this paper we propose a framework for TVWS access and key transmission parameters for licence-exempt operation of WSD for providing rural BWA within the Southern African Development Community (SADC). These parameters are determined based on extensive studies and consultations completed by the FCC and Ofcom, but are optimized for the SADC rural environment. We believe that this paper will serve as an important guideline document for the SADC regulators to decide suitable technology and policies when opening TVWS for BWA, especially for the rural communities.

Using TV White Spaces and e-Learning in South African rural schools

This paper uses the example of the television white space (TVWS) project in Limpopo Province of South Africa to consider benefits of TVWS technology to enable e-Learning environment and introduce pupils and teachers previously unfamiliar with Internet to information and communication technologies (ICT) including Internet. The Limpopo TVWS project uses TVWS to provide broadband Internet to five schools which are up to 10 km away around the University of Limpopo (UL) in the rural Mankweng Township. Each one of the participating five schools was donated 31 tablets, an overhead projector and smart phone to enable e-learning delivery. The paper presents preliminary results on a socio-economic study conducted at the five participating schools, and also discusses various benefits of availability of connectivity and of e-Learning.

A comparative study of cognitive radio platforms

Cognitive radio (CR) technology has become one of the buzzwords within the wireless communications community over the past 12 years. Its ability to learn, decide and adapt to the external environment made CR attractive to regulators, researchers, academia, politicians and the industry. CR promises to bring a paradigm shift in spectrum management policies from command-and-control regime to dynamic and opportunistic spectrum access. Despite more than a decade of research in the CR area, there are too little CR systems ready for the market. This lack of ready CR systems may reflect an overemphasis in the CR literature on theory and simulations with less work done in experimental-based-research and publications. In order to fast-track the real-life deployments of CR systems, the research community is now focusing on the development of CR platforms. With different software defined radio (SDR) packages and hardware available, it is confusing to decide which one to build or use. The objective of this paper is to study the design of CR platforms making use available SDR software packages and hardware. Our conclusion is that CR research should now focus on experimental-based results using real-life CR platforms in order to realize market-ready CR systems.

Network performance analysis of the Limpopo TV white space (TVWS) trial network

Television white spaces (TVWS) refers to vacant channels in the ultra-high frequency (UHF) band between 470 and 690 MHz assigned for television broadcast and can be used opportunistically by secondary users (SUs). Research has shown that when the spectrum allocation is managed appropriately, SUs can co-exist on the same radio frequency (RF) spectrum band with licensed networks. This paper introduces the Limpopo TVWS trial network, which provides a point-to-point Internet connectivity to five rural secondary schools. A set of 24 hours RF monitoring results of the TVWS trial network are presented which shows the behaviour of white space devices with respect to incumbent TV band services. The network performance results with respect to average throughput, average latency, and jitter are also presented. The performance results show that good throughput for each link which is in the magnitude of 4 to 8 Mbps and latency of less than 10 ms for typical packet sizes ranging from 32 to 1500 bytes are achievable.

The Television White Space Opportunity in Southern Africa: From Field Measurements to Quantifying White Spaces

The lack of sufficient fixed-line communication infrastructure in African rural areas has resulted in wireless communication being the only cost effective alternative solution for broadband connectivity. However, access to valuable spectrum—specifically sub-1 GHz spectrum—is mostly allocated to broadcasting or mobile telephony. The global digital switch over (DSO) of television (TV) broadcasting systems will see more sub-1 GHz TV band spectrum being made available for the digital dividend and also result in more TV white space (TVWS) spectrum. In order to ensure dynamic and efficient utilization of the TV white space spectrum, there is an increasing trend to use cognitive radiosystems that use geo-location spectrum databases and spectrum sensing as an enabling technology. In this paper, we overview the relevant signals and standards and present field measurement results showing the actual usage of TV bands before the DSO in selected urban and rural areas of Southern Africa. Measurements were conducted using low-cost and high-grade radio instruments. The low-cost spectrum analyser was built in-house using the Universal Software Radio Peripheral (USRP-2) and GNU Radio software. A metric to quantify available TV white space, based on the minimum acceptable field strength, is introduced and applied to quantify the availability of TV white space. Our results show medium spectrum usage in urban areas and very low spectrum usage in rural areas, making TVWS an attractive solution for rural broadband connectivity.

Light-weight IP Multimedia Subsystem (IMS) client for mobile devices

IP multimedia subsystem was introduced by the third generation partnership project (3GPP) to enable 3G mobile systems to provide ubiquitous cellular access to all the services that the Internet provides, with improved quality of service, appropriate charging and integration of services. For users to access the IMS services, IMS capable User Equipments are required. In this paper we present an IMS Client compliant to 3GPP, European telecommunications standards institute and Internet engineering task force (IETF) specifications. Though some work has been done in the development of the IMS Client, such clients cannot be deployed in the mobile devices. Our IMS client is developed under Java 2 micro-edition (J2ME) platform so it can be deployed in the mobile devices. The implementation and demonstration of the IMS client on the IMS Testbed are presented. Our proposed IMS client could perform the user registration and Instant messaging communication.

Towards energy efficient mobile communications

The rapid growth and development of wireless communication services and applications corresponds to an increase in associated energy consumption. For broadband wireless network deployment in rural areas affected by unreliability and unavailability of national grid electricity supply, energy efficiency becomes a major design criterion to be considered. In such areas, diesel powered generators are normally used as the main power source, while batteries become the most preferred source of energy to power wireless communication devices. In order to address increasing energy requirements, we propose an energy saving technique for mobile stations (MSs) operating under the wireless broadband access systems in this paper. Our proposed scheme is limited to the power saving class (PSC) of Type I in IEEE 802.16. Our numerical results show that more energy can be saved if the listening interval is considered under non-sleep or awake mode.