45 research outputs found
Joint Domain Based Massive Access for Small Packets Traffic of Uplink Wireless Channel
The fifth generation (5G) communication scenarios such as the cellular
network and the emerging machine type communications will produce massive small
packets. To support massive connectivity and avoid signaling overhead caused by
the transmission of those small packets, this paper proposes a novel method to
improve the transmission efficiency for massive connections of wireless uplink
channel. The proposed method combines compressive sensing (CS) with power
domain NOMA jointly, especially neither the scheduling nor the centralized
power allocation is necessary in the method. Both the analysis and simulation
show that the method can support up to two or three times overloading.Comment: 6 pages, 5 figures.submitted to globecom 201
Fairness Comparison of Uplink NOMA and OMA
In this paper, we compare the resource allocation fairness of uplink
communications between non-orthogonal multiple access (NOMA) schemes and
orthogonal multiple access (OMA) schemes. Through characterizing the
contribution of the individual user data rate to the system sum rate, we
analyze the fundamental reasons that NOMA offers a more fair resource
allocation than that of OMA in asymmetric channels. Furthermore, a fairness
indicator metric based on Jain's index is proposed to measure the asymmetry of
multiuser channels. More importantly, the proposed metric provides a selection
criterion for choosing between NOMA and OMA for fair resource allocation. Based
on this discussion, we propose a hybrid NOMA-OMA scheme to further enhance the
users fairness. Simulation results confirm the accuracy of the proposed metric
and demonstrate the fairness enhancement of the proposed hybrid NOMA-OMA scheme
compared to the conventional OMA and NOMA schemes.Comment: 6 pages, accepted for publication, VTC 2017, Spring, Sydne
Improving performance of far users in cognitive radio: Exploiting NOMA and wireless power transfer
In this paper, we examine non-orthogonal multiple access (NOMA) and relay selection strategy to benefit extra advantage from traditional cognitive radio (CR) relaying systems. The most important requirement to prolong lifetime of such network is employing energy harvesting in the relay to address network with limited power constraint. In particular, we study such energy harvesting CR-NOMA using amplify-and-forward (AF) scheme to improve performance far NOMA users. To further address such problem, two schemes are investigated in term of number of selected relays. To further examine system performance, the outage performance needs to be studied for such wireless powered CR-NOMA network over Rayleigh channels. The accurate expressions for the outage probability are derived to perform outage comparison of primary network and secondary network. The analytical results show clearly that position of these nodes, transmit signal to noise ratio (SNR) and power allocation coefficients result in varying outage performance. As main observation, performance gap between primary and secondary destination is decided by both power allocation factors and selection mode of single relay or multiple relays. Numerical studies were conducted to verify our derivations.Web of Science1211art. no. 220
Outage analysis and power allocation in uplink non-orthogonal multiple access systems
We propose a tractable expression for the outage probability in single-cell uplink non-orthogonal multiple access (NOMA) systems serving an arbitrary number of users. The
expression is obtained by approximating the inter-user interference using a shifted-gamma distributed random variable. We then formulate and propose an efficient iterative algorithm for
the outage-constrained min-max power allocation problem for the NOMA system. To give a rigorous comparison, we solve the
outage-constrained min-max power allocation problem for the orthogonal multiple access (OMA) counterpart where both the user power allocation and the radio resource division pattern are optimized. Simulations confirm the accuracy of the derived outage probability expression for the NOMA system. Also, we
demonstrate that fairness among users in terms of transmission power can be achieved by NOMA. Moreover, NOMA can bring
significant power savings to the users as compared to OMA