PhD Study : Non-Orthogonal Multiple Access for 5G and Beyond Systems

Summary

Current and previous generations of cellular systems use orthogonal multiple access (OMA) techniques mainly to provide voice, multimedia, and data communications. For instance, frequency-division multiple access (FDMA), time-division multiple access (TDMA), code-division multiple access (CDMA), and orthogonal frequency division multiple access (OFDMA) were adopted for the 1st generation (1G), 2G, 3G, and 4G systems, respectively. The main reason behind using OMA techniques is to simplify the receiver design and the implementation of scheduling algorithms. 5G systems are expected to provide new wireless services, such as, machine-to-machine communications for connected health solutions and vehicle-to-vehicle communications as part of smart cities.

Accordingly, future cellular systems face significant challenges due to the expected tremendous increase of data rate and massive connectivity required by the new services. For instance, it is crucial to significantly improve the spectral efficiency to handle the expected 1000-fold of mobile internet data traffic increase by 2020. Additionally, due to the rapid development of the Internet of Things (IoT) for various applications, e.g., smart cities and connected health, 5G systems needs to support massive connectivity of devices with low power, low latency, and high-priority requirements. Several potential candidates have been proposed to address the challenges of 5G systems.

In this project, we focus on a novel multiple access technique, named, non-orthogonal multiple access (NOMA), which is expected to increase the spectral efficiency, accommodate massive connectivity for IoT applications including connected health, and provide low transmission latency. In NOMA, users share the same resources, e.g., time slots and frequency bands, for transmission; but there are distinguished mainly either via power-domain or code-domain multiplexing. That said, NOMA systems can accommodate much more users when compared to OMA systems that can at best support a number of users equal to or less than the number of available resources. The main obstacle in designing NOMA systems is the inter-user interference, and proper interference cancellation techniques should be used to minimize the inflicted interference effect on each user while guaranteeing the required quality of service.

Our objective in this project is to design efficient power-domain NOMA systems for wireless applications with low-power and high-priority requirements, such as connected health solutions. To properly address the high-priority requirement, we need to evaluate the impact of the residual cancellation errors resulting from the imperfect self-interference cancellation (SIC) on the performance of the connected health solutions. This can be achieved by evaluating the outage probability or the outage capacity as a function of the variance of the residual errors. To address the low-power requirement, we need to develop robust optimization techniques that jointly optimize the transmission rate and power of each node to maximize the energy-efficiency or the nodes life time, while constraining the outage probability.

Please note the student working on this project is expected to have an optimization theory and signal processing background and very good experience in one of the programming language. The student will work in an office environment and use programming language, e.g., Matlab, on a daily basis to test the developed theory.

Essential criteria

Applicants should hold, or expect to obtain, a First or Upper Second Class Honours Degree in a subject relevant to the proposed area of study.

We may also consider applications from those who hold equivalent qualifications, for example, a Lower Second Class Honours Degree plus a Master’s Degree with Distinction.

In exceptional circumstances, the University may consider a portfolio of evidence from applicants who have appropriate professional experience which is equivalent to the learning outcomes of an Honours degree in lieu of academic qualifications.

Funding and eligibility

The University offers the following levels of support:

Vice Chancellors Research Studentship (VCRS)

The following scholarship options are available to applicants worldwide:

• Full Award: (full-time tuition fees + £19,000 (tbc))
• Part Award: (full-time tuition fees + £9,500)
• Fees Only Award: (full-time tuition fees)

These scholarships will cover full-time PhD tuition fees for three years (subject to satisfactory academic performance) and will provide a £900 per annum research training support grant (RTSG) to help support the PhD researcher.

Applicants who already hold a doctoral degree or who have been registered on a programme of research leading to the award of a doctoral degree on a full-time basis for more than one year (or part-time equivalent) are NOT eligible to apply for an award.

Please note: you will automatically be entered into the competition for the Full Award, unless you state otherwise in your application.

Department for the Economy (DFE)

The scholarship will cover tuition fees at the Home rate and a maintenance allowance of £19,000 (tbc) per annum for three years (subject to satisfactory academic performance).

This scholarship also comes with £900 per annum for three years as a research training support grant (RTSG) allocation to help support the PhD researcher.

• Candidates with pre-settled or settled status under the EU Settlement Scheme, who also satisfy a three year residency requirement in the UK prior to the start of the course for which a Studentship is held MAY receive a Studentship covering fees and maintenance.
• Republic of Ireland (ROI) nationals who satisfy three years’ residency in the UK prior to the start of the course MAY receive a Studentship covering fees and maintenance (ROI nationals don’t need to have pre-settled or settled status under the EU Settlement Scheme to qualify).
• Other non-ROI EU applicants are ‘International’ are not eligible for this source of funding.
• Applicants who already hold a doctoral degree or who have been registered on a programme of research leading to the award of a doctoral degree on a full-time basis for more than one year (or part-time equivalent) are NOT eligible to apply for an award.

Due consideration should be given to financing your studies. Further information on cost of living