Dr Indu L Shakya: Latest Projects

2022+: Adaptive Constellation Multiple Access: a Response to NOMA, RSMA, SCMA Proposals

2019-2021: Adaptive Multi-user Transmission and Detection Techniques for Ultra High Density Beyond-5G Cell-Free Massive MIMO Wireless Communications

2017-2018 : Modulation Multiplexing Techniques for Collaborative Multiuser Massive MIMO

2016-2018: Collaborative Multi-user Massive MIMO (Modulation and Multiple Access Techniques for LTE-A+ and 5G Systems)

2022+: Adaptive Constellation Multiple Access: a Response to NOMA, RSMA, SCMA Proposals

A novel adaptive non-orthogonal multiple access scheme--referred to as ACMA, that offers many advantages over existing NOMA schemes--is investigated. ACMA addresses key challenges of non-orthogonal multiple access (NOMA) like detection unreliability, high signalling overheads--enabling its use for 5G NR Advanced and future 6G mobile systems. A base-station groups small number of users to transmit their combined data using power and signal space domains optimized for demodulation. A receiver performs modified joint detection of composite signals with minimal loss of useful signal energy. This approach is able to resolve any power differences to operate in extreme co-channel interference scenarios where other NOMA schemes fail even under infinite signal-to-noise ratio (SNR).

Salient Features of ACMA

No concept of signal vs interference and not dependent on instantaneous SINR like NOMA, SCMA, RSMA.
Unlike NOMA and RSMA, ACMA is not control signal intensive and can resolve error floors conditions even when SINR is too low.
Uses open loop architecture and can be integrated with OFDMA, TDMA, SCMA; this can increase multiple access system capacity much further.

Sum throughput of ACMA against different NOMA schemes, K=2, M1=16, M2=16

2019-2021: Adaptive Multi-user Transmission and Detection Techniques for Ultra High Density Beyond-5G Cell-Free Massive MIMO Wireless Communications

With the wide deployment of 3G and 4G wireless mobile systems, data access anytime, anywhere is now becoming reality. It is anticipated that the demand for higher rate data access in the wireless environment will grow significantly in coming years due to the use of Internet and media rich applications requiring data rates of several or tens of Gbps. Spatial multiplexing (SM) schemes that use multiple antennas at the transmitter and receiver also called multiple input multiple output (MIMO) architecture and layered space-time decoding at the receiver promise enormous spectral efficiency in a range of 4-40 bits/sec/Hz and much-improved error performance over conventional single input single output (SISO) antenna systems in rich scattering multipath channel environments. MIMO is therefore regarded as the fundamental enabling technology that can fulfill the high spectral efficiency demand of fourth generation cellular wireless systems such as WiMAX and 3GPP Long Term Evolution (LTE), potentially leading to multi-Gigabits wireless systems. In the context of point-to-point based single user scenario, SM techniques such as Bell-Labs Layered Space-time (BLAST) detection have been investigated extensively. However, multi-user and cellular wireless systems have to allow simultaneous access to the data for many users, which requires a very different and more complex transmission and detection approach to optimize the system performance.

Salient Features

Great capacity gains (e.g. 240 bits/s/Hz to 120) possible by simply exploiting the already available channel state information and light signal processing.
Extremely low complexity implementation (20-100 times less CPU) yet approaches or surpasses the performance of MMSE, MMSE-SIC.
Perfectly suited for dynamism of users and wireless propagation conditions in dense and spare distribution of access points

SER performance of the proposed Adaptive multistage BLAST detection of Massive MIMO system using QPSK and consisting of K=80 single antenna users and N=100 antennas at the AP side achieving 160 b/s/Hz for different stages (T=1,2,3) with computations O(KNT) compared with tradition MMSE OSIC based VBLAST with O(K3N)

2017-2018 : Modulation Multiplexing Techniques for Collaborative Multiuser Massive MIMO

The aim of this project is to assess the impact on performance of system when we multiplex transmission from multiple users at the same time, frequency resource to approach capacity limit and close the gap of multiple access channels.

SIR vs required Es/No required of proposed Collaborative scheme under co-channel interference conditions

2016-2018: Collaborative Multi-user Massive MIMO (Modulation and Multiple Access Techniques for LTE-A+ and 5G Systems)

This project, backed by extensive analysis and simulation results shows some radical new system approaches and techniques to address the above-discussed challenges that are fundamental to efficient and cost-effective deployment of SM based SDMA techniques in practical wireless environments. The main idea is to allow two or more users to collaborate to form groups, so the available system resources such as power and bandwidth are utilized most efficiently, and design hybrid receiver to extract users' data, leading to much higher sum rate and user capacity. Research investigations under typical multi-cellular settings with aggressive frequency reuse pattern and sum rate optimization while combating the effects of intra and inter-cell interference will be carried out. Furthermore, the project encompasses work on cooperative and relay assisted spatial diversity and other expertise gained from previous research projects to increase robustness for practical applications of advanced air interface technologies (IEEE 802.11 AC, IEEE 802.16m and LTE-Advanced).

System model and performance of the proposed system MMSE detection method

To demonstrate the capacity gains of the new approach, in figure 3 its detection performance is compared with LTE-A MIMO scheme employing 6x8, 7x8 and 8x8 antennas with each antenna transmitting QPSK stream. these correspond to spectral efficiencies (SE) of 12, 14 and 16 b/s/Hz, respectively. the proposed collaborative scheme using 6x2 transmitters and 8 receiver antennas giving se of 24 b/s/Hz provides SER performance better than conventional LTE-A that achieve only 14 and 16 b/s/Hz.