Simultaneous Clock Synchronization in Double
Broadcast Domain of WSN
Xiaoji Li
噛ʿ
, Xiuying Qin
噛
, Lin Zheng
噛
, Hongbing Qiu
噛
噛Guangxi Key Lab of Wireless Wideband Communication & Signal Processing, Guilin Univ. of Electronic Technology, Guilin,
China, 541004
*Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory, ShiJiaZhuan
g, China, 050081
# National Key Lab. of Integrated Service Networks, Xidian University, Xi’an, China, 710071
Contact: lixj@guet.edu.cn, gwzheng@gmail.com
Abstract—In order to reduce the energy requirement in wireless
sensor networks, an energy-efficient multihop broadcast
synchronization algorithm simultaneously operated in double
broadcast domain is proposed. The algorithm is based on
receiver-receiver synchronization (RRS). Node synchronization
range is expanded to two broadcast domains by peer-to-peer
broadcasting message in a pair of synchronized nodes which need
to broadcast message one more time. Then, building a
hierarchical structure with two root nodes, the algorithm is
extended to the network-wide. Simulation results show that the
proposed algorithm requires much less timing messages, then
lower energy-consumption for network-wide synchronization
then other well-known algorithms.
Keywords- wireless sensor networks; clock synchronization;
receiver-receiver synchronization (RRS); energy-efficient
I. INTRODUCTION
In the wireless sensor networks (WSNs), node localization,
sleep and wake-up control, data fusion, MAC-layer scheduling,
and data time stamp are dependent on clock synchronization
between nodes [1]. However, the traditional clock
synchronization protocols, such as NTP (Network Time
Protocol) and GPS (Global Positioning System), cannot be
directly applied to WSNs [1-2]. Therefore, research on clock
synchronization receives an increasing attention in recent years.
For the WSNs clock synchronization issues, domestic and
foreign scholars have launched a lot of research. Now basic
synchronization mechanism divided into sender-receiver
synchronization (SRS) and receiver-receiver synchronization
(RRS).The SRS also divided into two types, one is based on
one-way message. It estimated message propagation delay in
the channel, and just sends a broadcast message to achieve the
synchronization between nodes. DMTS [3] and FTSP [4]
protocol are the typical representative of one-way SRS.
Another is based on two-way message between a pair of nodes.
TPSN [5], LTS [6] protocol both use this synchronization
mechanism. RRS use the third party’s referenced broadcast
message to eliminate the influence of synchronous precision
from sender delay. RBS [7] protocol is a typical RRS
implementation. Among the iterations [3-7], the algorithm with
above basic synchronization mechanism as the foundation,
implement the single-hop synchronization between two
adjacent nodes, and then expand to the network-wide
synchronization through network hierarchy.
In recent years, many lightweight algorithms based on
broadcast domain synchronization have been put forward. By
using the broadcast domain of node as basic synchronous units,
the algorithms synchronize through two nodes broadcasts or
retransmit message in the domain, thus the rest of nodes only
need to receives the message to achieve synchronization. In
final, we can arrive at network-wide synchronization by
expand the broadcast domain synchronization. Reducing the
requirement of the number of messages in broadcast domain
synchronization, or expanding the broadcast domain with same
number of messages can reduce the overhead in entire network
synchronization. HRTS [8], BTS [9], PBS [10], MBS [11]
protocol are the typical representative of this algorithm. They
can effectively reduce the network energy consumption, but
did not take full advantage of the wireless channel nature of
broadcast. In addition, HRTS/BTS and PBS belongs to the
SRS/RRS mixed scheme. Their synchronous precision depends
on the sender high-accuracy timestamp marker technology,
such as the MAC-layer timestamp mark [5]. However, in the
MBS single broadcast domain algorithm, the center of the
relaying node does not directly obtain synchronization.
Therefore, multiple broadcast domains of MBS are difficult to
achieve.
Based on the above considerations, this paper proposes an
Energy-Efficient Multi-hop Broadcast Synchronization
algorithm (EMBS). By using peer-to-peer broadcasting
message in the broadcast domain of two nodes, and almost the
same number of timing messages in the MBS single broadcast
domain algorithm, EMBS is able to synchronize all the nodes
of this two broadcast domain simultaneously. For multihop
expanding, a hierarchical structure with two root nodes is made.
According to synchronous nodes in upper layer, the sub-layer
nodes are synchronized by proposed algorithm, thus the
synchronization problems of relaying node in MBS is no
longer in existence.
367
2012 5th Global S
mposium on Millimeter Waves (GSMM 2012) Harbin, China
978-1-4673-1305-6/12/$31.00 ©2012 IEEE Ma
27-30, 2012