Performance modeling and analysis of the ADHOC MAC protocol
for vehicular networks
Qiong Wu
1,2
•
Jun Zheng
1
Published online: 30 June 2015
Springer Science+Business Media New York 2015
Abstract The ADHOC MAC protocol is a classical
MAC protocol for supporting reliable broadcast services in
vehicular ad hoc networks (VANETs). This paper develops
an analytical model for analyzing the access performance
of the ADHOC MAC protocol. A Markov chain is first
constructed to describe the number of vehicles which have
acquired a timeslot successfully at the end of a frame when
using the ADHOC MAC protocol. Based on the Markov
model, an analytical model is then derived to describe the
relationship between the frame length and the channel
utilization. Based on the derived analytical model, an
optimal frame length that maximizes the channel utiliza-
tion is further obtained. Simulation experiments are con-
ducted to verify the eff ectiveness of the analytical model.
Keywords ADHOC MAC Perf ormance modeling
VANET
1 Introduction
Vehicular ad hoc networks (VANETs) promise a variety of
safety and entertainment applications by providing vehicle-
to-vehicle (V2V) and vehicle-to-infrastructure (V2I) com-
munications [1]. In a VANET, most of safety applications
are based on one-hop broadcast of safety related informa-
tion. For example, for safety applications using V2V
communication, such as pre-crash sensing and blind spot
warning, each vehicle periodically broadcasts the infor-
mation on its posi tion, speed, and tur ning signal status to
all vehicles within its one-hop neighborhood [1]. Similarly,
for safety applications using V2I communication, such as
curve speed warning and traffic signal violat ion warning, a
roadside unit periodically broadcasts the information on the
traffic signal status and timing, and road surface type to all
the vehicles within its one-hop neighborhood [1]. Since the
safety applications in VANETs are usually related to the
safety of people and most of the safety applications are
based on one-hop broadcast of safety related information, it
is critical to design a medium access control (MAC) pro-
tocol with an efficient broadcast service for VANETs.
The IEEE 802.11p [2] standard is a MAC standard
proposed for a VANET. However, the access mechanism
of the IEEE 802.11p standard has the following limitations
for broadcast service:
1. For a broadcast service, the access mechanism neither
uses an RTS/CTS exchange during the access proce-
dure nor uses an acknowledgement message after a
vehicle receives a packet. This makes it difficult to
detect a hidden terminal problem, i.e., a collision
occurs at a vehicle when two other vehicles which are
not in each other’s one-hop neighborhood communi-
cate with the vehicle simultaneously, and thus reduces
the packet delivery ratio.
2. Unlike the unicast case, the contention window size of
the access mechanism is not doubled when a collision
occurs, which would not reduce the collision proba-
bility in the network.
3. In the access mechanism, a high-priority safety mes-
sage will be assigned to a high-priority access
catalogue (AC) which contends for a channel using a
& Jun Zheng
junzheng@seu.edu.cn
1
National Mobile Communications Research Laboratory,
Southeast University, Nanjing 210096, Jiangsu, China
2
The State Key Laboratory of Integrated Services Networks,
Xidian University, Xi’an 710071, Shanxi, China
123
Wireless Netw (2016) 22:799–812
DOI 10.1007/s11276-015-1000-6
