TY - JOUR
T1 - On the Impact of Time-Correlated Fading for Downlink NOMA
AU - Cai, Donghong
AU - Xu, Yanqing
AU - Fang, Fang
AU - Ding, Zhiguo
AU - Fan, Pingzhi
N1 - Funding Information:
Manuscript received August 9, 2018; revised November 16, 2018 and January 23, 2019; accepted February 25, 2019. Date of publication March 7, 2019; date of current version June 14, 2019. The work of D. Cai and P. Fan was supported by NSFC project No.61731017, NSFC-NRF project No.61661146003/NRF2016NRF-NSFC001-089, and the 111 Project No.111-2-14. The work of D. Cai was also supported by Doctoral Innovation Fund Program of Southwest Jiaotong University. The work of Y. Xu was supported by the fundamental Research Funds for the Central Universities under Grant No. 2018YJS206. This paper was presented in part at the IEEE Global Communication Conference (GLOBECOM) Workshop, Abu Dhabi, United Arab Emirates, December, 2018 [1]. The associate editor coordinating the review of this paper and approving it for publication was H. Zhang. (Corresponding author: Donghong Cai.) D. Cai and P. Fan are with the Institute of Mobile Communications, Southwest Jiaotong University, Chengdu 610031, China (e-mail: cdhswjtu@ 163.com; [email protected]).
Publisher Copyright:
© 1972-2012 IEEE.
PY - 2019/6
Y1 - 2019/6
N2 - This paper investigates the performance of non-orthogonal multiple access (NOMA) systems over time-correlated Rayleigh fading channels, where the users have heterogeneous quality of service requirements, e.g., a latency-critical user with a low target rate and a delay-tolerant user with a large target rate. In order to meet the different requirements of the users, two partial hybrid automatic repeat request (HARQ) schemes, including partial HARQ with chase combining (HARQ-CC) and HARQ with incremental redundancy (HARQ-IR), are proposed. The closed-form expressions of outage probabilities for NOMA with and without re-transmission are derived. With the developed outage probabilities, a condition on the superiority of NOMA to orthogonal multiple access (OMA) is obtained. In particular, the condition is characterized by the transmit powers for NOMA without re-transmission and is obtained by using the bisection method in the case with re-transmission. To further improve the performance of the HARQ enabled NOMA schemes, we consider an average transmit power minimization problem by optimizing the transmit power among different transmission rounds with outage constraints. However, due to the complexity of the developed outage probabilities, the formulated problem is non-convex and challenging to solve. Then we approximate the original problem by deriving the upper-bound approximations of the outage probabilities and solve it by using the geometric programming method. Simulation results demonstrate the accuracy of the developed analytical results. It is shown that the performance of NOMA is superior to OMA, only when the obtained condition is satisfied. HARQ-CC and HARQ-IR can enhance the outage performance of NOMA over time-correlated fading channels and the HARQ-IR has excellent performance in terms of energy efficiency.
AB - This paper investigates the performance of non-orthogonal multiple access (NOMA) systems over time-correlated Rayleigh fading channels, where the users have heterogeneous quality of service requirements, e.g., a latency-critical user with a low target rate and a delay-tolerant user with a large target rate. In order to meet the different requirements of the users, two partial hybrid automatic repeat request (HARQ) schemes, including partial HARQ with chase combining (HARQ-CC) and HARQ with incremental redundancy (HARQ-IR), are proposed. The closed-form expressions of outage probabilities for NOMA with and without re-transmission are derived. With the developed outage probabilities, a condition on the superiority of NOMA to orthogonal multiple access (OMA) is obtained. In particular, the condition is characterized by the transmit powers for NOMA without re-transmission and is obtained by using the bisection method in the case with re-transmission. To further improve the performance of the HARQ enabled NOMA schemes, we consider an average transmit power minimization problem by optimizing the transmit power among different transmission rounds with outage constraints. However, due to the complexity of the developed outage probabilities, the formulated problem is non-convex and challenging to solve. Then we approximate the original problem by deriving the upper-bound approximations of the outage probabilities and solve it by using the geometric programming method. Simulation results demonstrate the accuracy of the developed analytical results. It is shown that the performance of NOMA is superior to OMA, only when the obtained condition is satisfied. HARQ-CC and HARQ-IR can enhance the outage performance of NOMA over time-correlated fading channels and the HARQ-IR has excellent performance in terms of energy efficiency.
KW - chase combining
KW - hybrid automatic repeat request (HARQ)
KW - incremental redundancy
KW - Non-orthogonal multiple access (NOMA)
KW - time-correlated fading channel
UR - http://www.scopus.com/inward/record.url?scp=85063430862&partnerID=8YFLogxK
U2 - 10.1109/TCOMM.2019.2903501
DO - 10.1109/TCOMM.2019.2903501
M3 - Article
AN - SCOPUS:85063430862
SN - 0090-6778
VL - 67
SP - 4491
EP - 4504
JO - IEEE Transactions on Communications
JF - IEEE Transactions on Communications
IS - 6
M1 - 8662694
ER -