My publications


Yu Wenjuan, Musavian Leila, ul Quddus Atta, Ni Qiang, Xiao Pei (2018) Low latency driven effective capacity analysis for non-orthogonal and orthogonal spectrum access,Proceedings of 2018 IEEE Global Communications Conference (GLOBECOM) Institute of Electrical and Electronics Engineers (IEEE)
In this paper, we theoretically investigate the performance
of non-orthogonal and orthogonal spectrum access
protocols (more generically known as NOMA) in supporting
ultra-reliable low-latency communications (URLLC). The theory
of effective capacity (EC) is adopted as a suitable delayguaranteed
capacity metric to flexibly represent the users? delay
requirements. Then, the total EC difference between a downlink
user-paired NOMA network and a downlink orthogonal multiple
access (OMA) network is analytically studied. Exact closed-form
expressions and the approximated closed-forms at high signal-tonoise
ratios (SNRs) are derived for both networks and validated
through simulation results. It is shown that for a user pair in
which two users with the most distinct channel conditions are
paired together, NOMA still achieves higher total EC (compared
to OMA) in high SNR regime as the user group size becomes
larger, although the EC performance of both NOMA and OMA
reduces with the increase in group size. It is expected that the
derived analytical framework can serve as a useful reference and
practical guideline for designing favourable orthogonal and nonorthogonal
spectrum access schemes in supporting low-latency
Farooq-I-Azam Muhammad, Yu Wenjuan, Ni Qiang, Dong Mianxiong, ul Quddus Atta (2018) Location assisted subcarrier and power allocation in underlay mobile cognitive radio networks,Proceedings of 2018 IEEE Global Communications Conference (GLOBECOM) Institute of Electrical and Electronics Engineers (IEEE)
In this paper we perform subcarrier and power
allocation for the downlink transmission in a cognitive radio network
by exploiting the location information of mobile secondary
users. A mixed integer nonlinear problem is formulated which
maximizes the aggregate capacity of the secondary network,
subject to the constrained interference at the primary user and
the maximum transmit power limit of the secondary base station.
To solve the formulated problem, an optimal subcarrier allocation
is first obtained based on a practical assumption, followed by an
optimal power allocation achieved using standard optimization
methods. The proposed solution can facilitate to reduce latency
and provide high speed communication of big data for mobile
secondary users since speed, direction and location are all taken
into account for effective allocation of resources. Simulation
results verify our design intentions and confirm the efficiency
of the proposed resource allocation strategy.
Yu Wenjuan, ul Quddus Atta, Vahid Seiamak, Tafazolli Rahim (2018) Opportunistic spectrum access in support of ultra-reliable and low-latency communications,Proceedings of 2018 IEEE Global Communications Conference (GLOBECOM) Institute of Electrical and Electronics Engineers (IEEE)
This paper addresses the problem of opportunistic
spectrum access in support of mission-critical ultra-reliable and
low latency communications (URLLC). Considering the ability
of supporting short packet transmissions in URLLC scenarios,
a new capacity metric in finite blocklength regime is introduced
as the traditional performance metrics such as ergodic capacity
and outage capacity are no longer applicable. We focus on an
opportunistic spectrum access system in which the secondary
user (SU) opportunistically occupies the frequency resources of
the primary user (PU) and transmits reliable short packets to
its destination. An achievable rate maximization problem is then
formulated for the SU in supporting URLLC services, subject to
a probabilistic received-power constraint at the PU receiver and
imperfect channel knowledge of the SU-PU link. To tackle this
problem, an optimal power allocation policy is proposed. Closedform
expressions are then derived for the maximum achievable
rate in finite blocklength regime, the approximate transmission
rate at high signal-to-noise ratios (SNRs) and the optimal average
power. Numerical results validate the accuracy of the proposed
closed-form expressions and further reveal the impact of channel
estimation error, block error probability, finite blocklength and
received-power constraint.
Chu Zheng, Yu Wenjuan, Xiao Pei, Zhou Fuhui, Al-Dhahir Naofal, ul Quddus Atta, Tafazolli Rahim (2019) Opportunistic Spectrum Sharing for D2D-Based URLLC,IEEE Transactions on Vehicular Technology pp. 1-1 Institute of Electrical and Electronics Engineers (IEEE)
A device-to-device (D2D) ultra reliable low latency communications (URLLC) network is investigated in this paper. Specifically, a D2D transmitter opportunistically accesses the radio resource provided by a cellular network and directly transmits short packets to its destination. A novel performance metric is adopted for finite block-length code. We quantify the maximum achievable rate for the D2D network, subject to a probabilistic interference power constraint based on imperfect channel state information (CSI). First, we perform a convexity analysis which reveals that the finite block-length rate for the D2D pair in short-packet transmission is not always concave. To address this issue, we propose two effective resource allocation schemes using the successive convex approximation (SCA)-based iterative algorithm. To gain more insights, we exploit the mono- tonicity of the average finite block-length rate. By capitalizing on this property, an optimal power control policy is proposed, followed by closed-form expressions and approximations for the optimal average power and the maximum achievable average rate in the finite block-length regime. Numerical results are provided to confirm the effectiveness of the proposed resource allocation schemes and validate the accuracy of the derived theoretical results.
Mheich Zeina, Yu Wenjuan, Xiao Pei, Quddus Atta, Maaref Amine (2020) On the Performance of HARQ Protocols With
Blanking in NOMA Systems
IEEE Transactions on Wireless Communications Institute of Electrical and Electronics Engineers
In this paper, we investigate the throughput performance
of single-packet and multi-packet hybrid-automatic repeat
request (HARQ) with blanking for downlink non-orthogonal
multiple access (NOMA) systems. While conventional singlepacket HARQ achieves high throughput at the expense of high latency, multi-packet HARQ, where several data packets are sent in the same channel block, can achieve high throughput with low latency. Previous works have shown that multi-packet HARQ outperforms single-packet HARQ in orthogonal multiple access
(OMA) systems, especially in the moderate to high signal-tonoise ratio regime. This work amalgamates multi-packet HARQ with NOMA to achieve higher throughput than the conventional single-packet HARQ and OMA, which has been adopted in the
legacy mobile networks. We conduct theoretical analysis for the throughput per user and also investigate the optimization of the
power and rate allocations of the packets, in order to maximize the weighted-sum throughput. It is demonstrated that the gain of multi-packet HARQ over the single-packet HARQ in NOMA systems is reduced compared to that obtained in OMA systems due to inter-user interference. It is also shown that NOMAHARQ cannot achieve any throughput gain with respect to OMAHARQ when the error propagation rate of the NOMA detector is above a certain threshold.