Adaptive Resource Allocation Based Packet
Scheduling For LTE Uplink
Sha Xuejun, Sun Jin, Wu Tonghui, Liu Liang
School of Electronics and Information Engineering
Harbin Institute of Technology
Harbin, China.
shaxuejun @hit.edu.cn
Abstract—UTRAN Long Term Evolution (LTE), marked as 4G
LTE, is a standard for wireless communication developed by
3GPP, which is aiming to provide a spectral efficiency 2 to 4
times higher than its predecessor HSUPA/HSDPA Release 6. As
an uplink access scheme for LTE, the Single-Carrier Frequency
Division Multiple Access (SC-FDMA) technology has to allocate
continuous resources to one single-user, so this limitation will
reduce the allocation flexibility and bring more challenges to
design an effective packet scheduling algorithms. In this paper,
we propose a new algorithm, named as Adaptive Resource
Allocation Based Packet Scheduling (ARABPS) algorithm, which
can allocate resources to a single-user flexibly as possible as we
can. The simulation result indicated two major conclusions: one
is that the ARABPS algorithm in this paper could gain 35% ~
75% throughput than the Roundup Robin algorithm and the
other is that the ARABPS could provide the better fairness
relative to the Max C/I algorithm.
Keywords- LTE; SC-FDMA; throughput; fairness
I. INTRODUCTION
The 3rd Generation Partnership Project (3GPP) is currently
finalizing the standardization of the UTRA Long Term
Evolution(LTE). This system is expected to provide peak data
rates of 100 Mbit/s in downlink and 50 Mbit/s in uplink with a
20 MHz system bandwidth. Orthogonal frequency division
multiple access (OFDMA) has been selected as the downlink
access scheme for LTE, and single-carrier frequency division
multiple access (SC-FDMA) has been chosen as the uplink
access scheme[1].
SC-FDMA requires to allocate the adjacent subcarriers and
the Physical Resource Blocks (PRBs) to a single terminal,
which requirements make the system more completed. Such as
in any multi-user communication system, based on some
optimization criterion the Packet Scheduler(PS) plays a
fundamental role in time and frequency domains of
multiplexing User Equipments (UEs) .
Most of previous works are focused on the topic of uplink
(UL) PS by either removing the constraint on the contiguity of
Physical Resource Blocks (PRB) for one UE required by the
single carrier technology [2] or setting a fixed bandwidth to
each UE for simplicity[3], but it seems like that these two
methods are limited by their complexity in algorithms. In this
paper, we proposed a new algorithm based on the downlink
(DL) scheduler in [4,5] to exploit the bandwidth to produce a
flexible frequency resource allocation to closely resemble the
optimum (defined according to a specific criterion) on the basis
of satisfying the single carrier constraint. The size of the
bandwidth is thus decided as part of the allocation algorithm
performed by the scheduler[6].
In this paper, we proposed a new scheduler algorithm called
ARABPS to perform the PS scheduling in the uplink of the
LTE system. The remainder of this paper is organized as
follows: section II indicates the system and problem
description. In section III, the proposed scheduler is described.
Simulation and results are shown in section IV. Section V
draws conclusions.
II. U
PLINK SCHEDULING PROCESS
The physical layer resources include PRB, Modulation and
Coding Scheme (MCS), and choosing users who are allowed to
use resources each scheduling cycle. The main role of the
scheduling is to determine which user can use which space and
time interface resources according to the channel conditions
and network load conditions. Either in the uplink or downlink
scheduling, the scheduler is located in the eNodeB side, and
one scheduling cycle is the a Transmission Time Interval (TTI),
where each TTI is 1ms. The smallest unit of scheduling is
called RB where each RB in the time domain is 0.5ms (six or
seven SC-FDMA symbol, respectively for the extended cyclic
prefix (CP) and conventional CP), and 12 sub-carrier in the
frequency domain (180kHz). Scheduling techniques includ the
scheduling algorithm and the support of the scheduling
signaling. As mentioned above, the processing of scheduling
should consider not only the channel condition, but also the
information of the transferred user data.
In the uplink processing, the UE is the data sender, and the
scheduler is located in the eNodeB side. Due to the carrying
capacity of the control frame, the general processing is based
on the UE approach, and the eNodeB only perform the function
to simply control the total amount of resources allocated to the
UE or the total amount of data allowed to be transferred. In
order to enable UE to allocate resources between different RBs,
it needs to ensure that high priority RB is able to obtain more
resources to transfer data. This allocation features simple
control and small signaling overhead, but in the other hand it is
unable to obtain precise control for the scheduling and the
second highest priority business service delay may be too large.
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