Downlink Non-Orthogonal Multiple Access Implementation

Downlink Non-Orthogonal Multiple Access Implementation
Introduction : Non-orthogonal multiple access (NOMA), which can significantly improve the spectrum efficiency (SE) is a promising candidate for 5G wireless communications, in which the superposed coded signal can be successfully decoded and de-modulated at the receiver by applying successive interference cancellation (SIC). Unlike orthogonal multiple access (OMA), the multiple users in NOMA can be assigned to the same frequency, time, and code, but in different power domain to improve the SE of the system.

SIMULINK Implementation : The aim of this work package is to design a 2 user equipment (UE) downlink NOMA system using simulink which provides a software-defined radio (SDR) based platform for hardware implementation. A basic example is [SRef]. The Simulink models in [SRef] are designed for AWGN and Rayleigh fading channels considering both ideal and non-ideal SIC cases. However, the authors in [SRef] only present the block diagrams of established model for ideal/perfect SIC receivers.

SDR Implementation : This can be implemented in the following manner
1. Transceiver Design : The new transceiver needs to be designed to support the superposition, reconstitution and cancellation in NOMA system, which is implemented by the authors in [DRef] by introducing new communications modules to the OMA evolved node B (eNB) and user equipment (UE) in OpenAir Interference (OAI) platform. Especially, we need to focus on the implementation of the transceiver on physical downlink shared channel (PDSCH).
2. Multi-thread processing method : In the downlink NOMA system, decoupling the superposed signal of multiple users is realized by SIC receiver at the UE side. There are several key baseband signal processing modules in a SIC receiver including signal decoding, reconstitution and cancellation, and all these modules are of high computation complexity. In order to efficiently carry out the baseband signal processing in real time, the multi-thread processing method needs to be used [DRef].
3. New DCI Format : In the NOMA system proposed in [DRef], there are two users UE-1 and UE-2. Herein, the UE-2 receiver has to firstly decode and reconstitute the UE-1’s signal before it can demodulate and decode the signal intended for itself. Therefore, UE-1 employs the DCI format 1A. For another, a new DCI format based on DCI format 1A is designed and implemented for UE-2, which contains some additional fields for UE-2 receiver to decode and reconstitute the UE-1’s signal.
4. Upper layer protocol for NOMA : Without the deployment of evolved packet core (EPC), some parts of upper layer protocols of the current LTE systems have to be modified to provide the application services over our NOMA system [Dref].

Future Work : A more interesting approach for the system will be to come up with a better version of DCI format as presented in [Dref] so that it requires minimal or no change in the current LTE DCI format.
[SRef] M. B. Shahab, M. F. Kader and S. Y. Shin, "Simulink implementation of non-orthogonal multiple access over AWGN and Rayleigh fading channels,”in Proc. International Conference on Smart Green Technology in Electrical and Information Systems (ICSGTEIS), pp. 107-110, 2016.
[DRef] X. Wei et al., "Software Defined Radio Implementation of a Non-Orthogonal Multiple Access System Towards 5G," in IEEE Access, vol. 4, pp. 9604-9613, 2016.

Supervisor name: 
Dr. Mathini Sellathurai
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Deputy name: 
Dr Khandaker