Power Allocation Adaptation With Coherence Time for Nonorthogonal Multiple Access on Downlink Transmission

Nonorthogonal multiple access (NOMA) methods are expected to improve spectral efficiency or increase sum rate in a recent mobile communication network. The performance of the power-domain NOMA highly relies on the effectiveness of successive interference cancelation (SIC) and power allocation techniques. This paper proposes an adaptive power allocation method according to analytical coherence time of time-varying channels to improve the SIC effectiveness. Simulations show that the proposed technique can improve SIC, therefore reducing error probability without reduction of the sum rate.

Multiuser Detection using Noma Technique in FD-MC-CDMA System in Fading Channels

Non-Orthogonal Multiple Access which is an emerging technique which performs good in any aspects. Multiple users can share the resources that are available and also user can be identified, which adopts successive interference cancelation (SIC). The power domain is considered for detection of power allocation for the base stations. The performance of errors in selective channels like frequency channels is demonstrated with the help of code division multiple access which is a multi carrier (MC-CDMA), in which the frequency diversity can be resolved quickly. Due to high range of multiple access interferences the performance of MC-CDMA is been restricted. To overcome the problems in MC-CDMA, a new technique is proposed i.e frequency division multi carrier code division multiple access by which the multiple access interferences can be reduced by exploiting the available range of frequencies. NOMA is one of the emerging technique used as an answer to boost the spectral potency whereas permitting some extent of accessibility for multiple interferences at receiver end. By using NOMA-FD-MC-CDMA the range of spectrum can be increased and reduced the interferences. Bit error rate(BER) is evaluated and compared with other existing technique. The experimental results are performed using Mat lab tool.

NOMA for Multinumerology OFDM Systems

Nonorthogonal multiple access (NOMA) is a promising technique which outperforms the traditional multiple access schemes in many aspects. It uses superposition coding (SC) to share the available resources among the users and adopts successive interference cancelation (SIC) for multiuser detection (MUD). Detection is performed in power domain where fairness can be supported through appropriate power allocation. Since power domain NOMA utilizes SC at the transmitter and SIC at the receiver, users cannot achieve equal rates and experience higher interference. In this paper, a novel NOMA scheme is proposed for multinumerology orthogonal frequency division multiplexing system, that is, different subcarrier spacings. The scheme uses the nature of mixed numerology systems to reduce the constraints associated with the MUD operation. This scheme not only enhances the fairness among the users but improves the bit error rate performance as well. Although the proposed scheme is less spectrally efficient than conventional NOMA schemes, it is still more spectrally efficient than orthogonal multiple access schemes.