Impact of transmit power on throughput performance in wireless
ad hoc networks with variable rate control
Xu Zhang, Qiang Gao
*
, Jun Zhang, Gang Wang
School of Electronics and Information Engineering, Beihang University, XueYuan Road No. 37, HaiDian District, Beijing 100083, PR China
article info
Article history:
Received 18 December 2007
Received in revised form 18 June 2008
Accepted 18 June 2008
Available online 28 June 2008
Keywords:
Network throughput
Optimal power
Variable rate control
Ad hoc networks
Capture probability
abstract
In this paper, the capacity of ad hoc networks employing pure aloha MAC protocol is studied under the
effect of different transmission power levels and variable data rate control. The data rate of a certain link
is related to SINR, and SINR is, in turn, related to transmitted power and link distance. The increasing of
power conducts a high data rate, while results in a high interference of the network. Consequently, the
optimum power that yields maximum network throughput is a tradeoff between transmission rate
and network interference. Mathematical models for analysis of ad hoc networks capacity is presented,
and a revised expression to approximate the capture probability of the network is also proposed. It is
demonstrated that the optimal transmission power, thus the optimal range, which maximize the
throughput of the network by theoretical and simulation results.
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
It is well known that ad hoc networks can be constructed with
neither fixed infrastructures nor central controllers. After the devel-
opment of nearly 30 years, ad hoc networks, nowadays, are required
to support different high quality of services (QoS) demanded by
many applications, such as audio, video streaming and time-sensi-
tive information transportation [1]. For these kinds of QoS to be
guaranteed, the total network capacity, in terms of throughput, is
considered as one of the most important parameters [2]. Many fac-
tors contribute in network throughput enhancement, such as trans-
mission power, data rate, interference and spatial reuse.
Many researches have been done to evaluate the power (range)
control required to improve network throughput. Early research
could be traced in [3], where an optimum transmission radius
was derived to maximize the throughput of a stationary packet
radio networks using S-ALOHA. This work was extended to
802.11 MAC protocols in mobile ad hoc networks [4]. Common
ranges were used in [3,4].In[5], a variable power control scheme
was proposed, that every node has an identical number of neighbor
nodes. Authors in [6] investigated the impact of variable-range
power transmission control on network capacity. Physical and
network connectivity, as well as power saving in wireless multi-
hop networks were also evaluated.
On the other hand, when multiple modulating and coding
schemes became available as well as hardware implemented, the
multiple-rate control was considered as a promising scheme to
increase the network throughput. Enhancing network’s capacity
was investigated in [7] using variable data rate. Selection of the
appropriate modulation/coding scheme (MCS) in fixed data rate
networks may greatly improve throughput performance level [8].
The study impact of the transmission power combined with
variable rate on throughput of ad hoc networks is sparse [9].
In [9], variable power and rate control is used in Spatial TDMA
to adapt traffic variability and to improve throughput. In addi-
tion, both transmission power control scheme and data rate con-
trol scheme could also improve energy efficiency in ad hoc
networks [14,15].To our knowledge, there have been no prior
works which investigate the optimum power combined with
variable rate control in ad hoc networks to maximize the net-
work throughput.
All nodes in the network are assumed to use the same transmis-
sion power. Increasing transmitted power will reflect to higher sig-
nal power obtained at the receiver, thus providing higher Signal
and Interference to Noise Ratio (SINR), and consequently offering
higher data rate, which intuitively enhances network throughput.
However, high transmission power will also increase the interfer-
ence conducted by potential transmitters, which will result in
low spatial reusing as the number of simultaneous transmission
links reduced. Therefore, it is required to tradeoff between ade-
quate transmission rate and accepted interference level in order
to find an optimum transmitted power (optimum range) that
achieves maximum network throughput.
This paper is organized as follows: the first section was devoted
for studying previous articles in this field as well as presented the
0140-3664/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.comcom.2008.06.018
* Corresponding author. Tel.: +86 10 82338705.
E-mail address: gaoqiang@buaa.edu.cn (Q. Gao).
Computer Communications 31 (2008) 3638–3642
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