If we see the graph of advancements made by Wireless Technology in the past few years, we will be seeing that the graph has progressed constantly and it has reached a stage where it has become an indispensable and irreplaceable part of our lives. In order to guarantee digital connectivity on a Global Scale, wireless connections have now become more persuasive. The smartphones these days have really become smart and they can perform a host of functions and can support numerous applications which require high speed internet to work efficiently. It is expected that 5G technology will be able to provide an increase in the following when compared to the current LTE(Long Term Evolution) and LTE Advanced systems used commonly in 4G Networks:
- Network Throughput.
- Cell-Edge Data rates.
- Massive Connectivity.
- Superior Efficiency of Spectrum.
- High Energy Efficiency.
- Low Latency.
However, the requirements of 5G networks are very challenging to fulfill and in order to satisfy and fulfill these demands, we are using the technologies of Radio-Air Interface and Radio Access Network i.e RAN in traditional PHY Designs. These days, Non-Orthogonal Multiple Access or NOMA has been gaining popularity and attention from researchers belonging to both Industrial and Academic Backgrounds because of its potential to be a radio access technique. Some examples include the likes of Multi User Shared Access(MUSA), Resource Spread Multiple Access(RSMA), Sparse Code Multiple Access(SCMA) and Pattern Division Multiple Access(PDMA) proposed by leading leaders in Telecom Industry like Qualcomm, Huawei, ZTE, T mobile etc.
We might also make the use of Multicarrier(MC) technology which can be used to the spectrum of frequency into multiple narrow channels like Filterbank Multicarrier(FBMC) and GFDM i.e Generalized Frequency Division Multiplexing. This concept is now attracting a lot of attention from scientists and introducing new concepts for Dynamic Access Spectrum Management(DASM) and many other cognitive radio applications.
Let us discuss these access schemes in detail:
- OFDMA or Orthogonal frequency division multiple access:
OFDMA is a widely used technology and is considered to be very useful because we currently make use of OFDMA in our existing 4G technology and it also has the ability to act as a multiple access scheme for upcoming 5G networks. However, it might not be the most effective access scheme because it requires the use of OFDM which requires the carriers to be Orthogonal and there are some drawbacks of using Cycle Prefixes.
- Sparse Code Multiple Access(SCMA):
SCMA is a combination of CDMA and OFDMA and this is exactly why it is considered to be a better access scheme for 5G networks. A carrier or multiple carriers are allotted to a user in the OFDMA technology but it would be much more effective if each carrier is accompanied with a spreading code because then multiple users can either be shared the data with or they can share the data themselves.
- Non-Orthogonal Multiple Access or NOMA:
NOMA is another technique which is considered to be capable of acting as an access point for the upcoming 5G Networks because it can superpose multiple users in a power domain and it can remove the more powerful signals using the cancellation techniques.