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Funded PhD Opportunity

Non-Orthogonal Multiple Access for 5G and Beyond Systems

Subject: Engineering


Current and previous generations of cellular systems use orthogonal multiple access (OMA) techniques mainly to provide voice 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, in addition to voice and data communications. 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.

So far, 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.

Essential criteria

  • Upper Second Class Honours (2:1) Degree or equivalent from a UK institution (or overseas award deemed to be equivalent via UK NARIC)


    Vice Chancellors Research Scholarships (VCRS)

    The scholarships will cover tuition fees and a maintenance award of £14,777 per annum for three years (subject to satisfactory academic performance). Applications are invited from UK, European Union and overseas students.


    The scholarship will cover tuition fees at the Home rate and a maintenance allowance of £ 14,777 per annum for three years. EU applicants will only be eligible for the fees component of the studentship (no maintenance award is provided).  For Non EU nationals the candidate must be "settled" in the UK.

Other information

The Doctoral College at Ulster University

Key dates

Submission deadline
Monday 19 February 2018

Interview Date
Mid March 2018

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