Power Allocation with Buffer Constraint for
Distributed Antenna System in High-Speed
Railway Scenarios
Mi Yu
1
, Xiaoming Wang
1
, Youyun Xu
1
, Dapeng Li
1,2
, Jianping Chen
3
1.National Engineering Research Center of Communications & Networking
Nanjing University of Posts and Telecommunications, Nanjing 210003, China
2.National Mobile Communications Research Laboratory
Southeast University Nanjing 210096, China
3.Nanjing Ticom Tech Co. Ltd, Nanjing, Jiangsu China, 210039
Email: {1017010126, xmwang, yyxu, dapengli}@njupt.edu.cn, chenjianping@ticom.com.cn
Abstract—To meet the increasing demands of high data-
rate service in high-speed railway (HSR) scenarios, the two-
hop architecture with distributed antenna system (DAS) is a
good choice. In this architecture, the transmit and receive
sides of HSR system are both equipped with distributed
antennas, then base stations (BSs) communicate with users
via mobile relays (MRs) on the top of train. Thus, the
data will be buffered when the wireless transmission rate
can not satisfy the requirement of data arrival rate. In this
paper, we focus on the efficient power allocation method
with buffer and delay constraint on the basis of predicted
path loss characteristic in downlink HSR communications.
Firstly, the relationship between the data arrival rate and
instantaneous wireless transmission rate is analyzed where
BSs transmit with constant power. Secondly, the transmit
power optimization problem with the requirement of buffer
size and delay is formulated. The optimal power allocation
scheme can be obtained through Lagrangian dual method.
Simulation results demonstrate that the proposed power
allocation scheme can achieve a lower consumed power and
avoid data overflow and infinite delay as well.
Index Terms—Power allocation, buffer size, distributed
antenna system, high-speed railway.
I. INTRODUCTION
With the rapid development of high-speed railway (H-
SR), it is becoming more and more popular with peo-
ple for the superiority such as high mobility, time sav-
ing and reliability [1][2]. Furthermore, the demand for
broadband wireless communication of HSR has increased
significantly and the quality-of-service (QoS) requirements
of information transmission is growing strictly. However,
high bandwidth and QoS requirements lead to high power
consumption, which is inconsistent with the development
trend of green communication [3][4]. Adopting multiple
antennas at both transmitter side and receiver side is by now
recognized as a good solution to avoid frequent handover
and increase the transmission rate to receivers without
addition of extra transmit power[5]-[7]. In addition, high-
speed movement of trains and the large-scale fading lead
to the fast time-varying of channel states, which create
special challenges for efficient resource utilization such
as reducing power consumption while satisfying the QoS
requirement. A general solution to these challenges is to
dynamically optimize the allocation of power on the basis
of channel states.
Since the most promising scheme is to adopt the two-
hop architecture in HSR scenarios [8][9], it is of great
significance to match the data arrival process and wire-
less transmission process at the base station (BS) based
on the distributed antenna system (DAS). However, most
existing works are insufficient in considering the matching
problem with the multi-antenna system both [10]-[12].
For instance, Yunquan Dong et al in [10] introduced four
traditional power allocation methods without considering
the two factors. Tao Li et al in [11] derived the optimal
QoS-distinguished time-domain power allocation method
to achieve the largest reachable rate region for hybrid
streams composed by delay-insensitive and delay-sensitive
stream. Ke Xiong et al in [12] proposed a power allocation
scheme to achieve the tradeoff between the proportional
and water-filling power allocation. In these papers, the
power allocation was not subject to these two constraints.
Additionally, there are some works on power allocation
considered DAS or the matching problem of data arrival
and processing separately [13]-[17]. A power optimization
allocation scheme for satisfying buffer constraint by match-
ing data arrival process and wireless transmission process
under single antenna is proposed in [13]. A rate control
policy to minimize the total energy expenditure over a
time-varying channel was obtained in [14], which only
considered the deadline-constrained transmission similar to
the matching problem. The problem on maximizing energy
efficiency coordinated power allocation for a multi-cell
DAS was addressed in [15]. An effective handover scheme
in DAS for ground-train communication was studied in
[16]. The power allocation method with antenna selection
to minimize the average transmit power was proposed in
[17]. The multi-antenna transmission and reception for
HSR communication was only taken into account in these
papers.
In this paper, we propose an optimal power allocation
scheme to achieve the minimum power of DAS in HSR
scenarios while satisfying the buffer constraint. We first
analyze the dynamic matching process of data arrival and
wireless transmission at the central unit (CU) when it is
transmitted at constant power. Then, we formulate a power
optimization problem based on the analysis of matching the
data arrival rate and wireless transmission process at the
CU. By solving the formulated optimization problem with
the Lagrangian dual method, we can obtain the optimal
The 28th Wireless and Optical Communication Conference (WOCC 2019)
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