Abstract:
Non Orthogonal Multiple Access (NOMA) a prominent fifth generation (5G) wireless
communication technique which ensures spectral efficiency, low latency, high data rates with
throughput and massive connectivity. NOMA outperforms other OMA techniques like OFDMA
etc. NOMA is further divided as power domain NOMA and code domain NOMA. This research
thesis consists of two phases SISO downlink power domain NOMA and SISO downlink hybrid
CDMA-NOMA. In the first phase we proposed downlink power domain NOMA for multiuser
environment. Capacity and performance of multiuser NOMA systems are analyzed in AWGN
and NYUSIM channel model. Accurate power allocation in multiuser case is crucial to deal with.
We proposed power allocation strategy in multiuser NOMA system on the basis of distances
with different UE’s around base station (BS). We also proposed phase shift phenomena to further
enhance the system performance with capacity. Interference between users signals are reduced
by assigning with different phase shifts at the time of modulation. In the second phase we
proposed hybrid CDMA-NOMA approach to ensure serving of simultaneous users having same
distances with respect to the base station (BS). User clustering technique is proposed to group
UE’s on the basis of distances or channel conditions. Grouping of two, three and four UE’s per
cluster are made. Simulations are done with single base station antenna to serve one, two and
four clusters around base station. We can add up to an n number of clusters also. Each cluster of
hybrid CDMA-NOMA system are assigned with unique spreading codes, PN codes (nonorthogonal)
and Walsh codes (orthogonal) to ensure the rejection of inter-cluster interference.
While intra-cluster interference is controlled through Successive Interference Cancellation (SIC)
technique of NOMA scheme. We further proposed joint systems which accurately serve users
with CDMA, NOMA and hybrid CDMA-NOMA simultaneously. BER performance of four, six,
eight and sixteen users are observed with different SNR values. This research work provides a
foundation of achieving capacity with performance in 5G NOMA systems in the coming future.
