Packet Collision Rate Research Articles

A Scalable CSMA and Self-Organizing TDMA MAC for IEEE 802.11 p/1609.x in VANETs

vehicular ad hoc networks (VANETs) have been a key topic for research community and industry alike. The wireless access in vehicular environment standard employs the IEEE 802.11p/1609.4 for the Medium Access Control (MAC) layer implementation for VANETs. However, the carrier sense multiple access (CSMA) based mechanism cannot provide reliable broadcast services, and the multi-channel operation defined in IEEE 1609.4 divides the available access time into fixed alternating control channel intervals (CCH) and service channel (SCH) intervals, which may lead to the low utilization of the scarce resources. In this paper, a novel multichannel MAC protocol called CS-TDMA considering the channel access scheduling and channel switching concurrently is proposed. The protocol combines CSMA with the time division multiple access (TDMA) to improve the broadcast performance in VANETs. Meanwhile, the dwelling ratio between CCH and SCH changes dynamically according to the traffic density, resulting in the improvement of resource utilization efficiency. Simulation results are presented to verify the effectiveness of our mechanism and comparisons are made with three existing MAC protocols, IEEE MAC, SOFT MAC and VeMAC. The simulation results demonstrate the superiority of CS-TDMA in the reduction of transmission delay and packet collision rate and improvement of network throughput.

On the Queue Dynamics of Multiuser Multichannel Cognitive Radio Networks

For protocol and system design in cognitive radio networks (CRNs), it is essential to identify which system settings or environmental conditions have great impacts on the quality-of-service (QoS) performance for secondary users (SUs) and how they influence it, which are still open issues. In this paper, an analytical framework to quantify the queue dynamics of a multi-SU multichannel CRN is developed. In the analytical framework, we consider the important lower-layer mechanisms and settings, including spectrum sensing errors, medium-access control (MAC) protocols, link adaptation technologies such as adaptive modulation and coding (AMC) and automatic repeat request (ARQ), and limited buffer size. By modeling the queue dynamics as a discrete-time finite-state Markov chain (FSMC), we derive the analytical expressions of the average queue length, packet-dropping rate, and packet-collision rate. Based on these expressions, the QoS metrics including average queueing delay, packet-loss rate, and effective throughput are obtained. Simulation and numerical results are presented to verify the accuracy of the proposed analytical framework and investigate the QoS performance of SUs.

CLUSTER BASED TIME DIVISION MULTIPLE ACCESS SCHEDULING SCHEME FOR ZIGBEE WIRELESS SENSOR NETWORKS

In IEEE 802.15.4 ZigBee Wireless Sensor Networks, an efficient scheduling mechanism is required for reliable data transmission. Further, concurrent transmission of huge data through CSMA/CA incurs more packet collision rate. This complicated condition has to be eliminated to improve the system throughput. In this study, we propose to deploy cluster based TDMA scheduling mechanism for IEEE 802.15.4 ZigBee Wireless Sensor Networks. This TDMA slot allocation strategy allocates slots to the nodes based on queue occupancy information. It assigns TDMA slots starting from nodes with high queue occupancy value. Nodes that have high queue occupancy value will probably get long TDMA slot period. We prove the proficiency of our mechanism using Network Simulator 2 (NS-2). Our approach fairly allocates slots to the nodes and considerably reduces packet collision rate.

Improving Cooperative Positioning for Vehicular Networks

Cooperative positioning (CP) can potentially improve the accuracy of vehicle location information, which is vital for several road safety applications. Although concepts of CP have been introduced, the efficiency of CP under real-world vehicular communication constraints is largely unknown. Our simulations reveal that the frequent exchange of large amounts of range information required by existing CP schemes not only increases the packet collision rate of the vehicular network but reduces the effectiveness of the CP as well. To address this issue, we propose simple easily deployable protocol improvements in terms of utilizing as much range information as possible, reducing range broadcasts by piggybacking, compressing the range information, tuning the broadcast frequency, and combining multiple packets using network coding. Our results demonstrate that, even under dense traffic conditions, these protocol improvements achieve a twofold reduction in packet loss rates and increase the positioning accuracy of CP by 40%.

On Joint Frequency and Power Allocation in a Cross-Layer Protocol for Underwater Acoustic Networks

Path loss in an underwater acoustic channel depends not only on the transmission distance, but also on the signal frequency. As a result, the useful bandwidth decreases with distance, a feature not normally present in terrestrial radio networks. This fact motivates the use of multihop communications in an acoustic network, and strongly influences its design, since the same set of protocols will exhibit different performance when operating in a different frequency range. Multihop transmission is considered for large area coverage in acoustic networks, with an eye towards efficient power and bandwidth allocation. Power control is used as a practical means of optimizing the overall performance across the physical, medium access control (MAC) and routing layers. A geographic routing technique, called the focused beam routing (FBR), which requires each node to know only its own location and that of the final destination, is coupled with the distance aware collision avoidance protocol, which regulates the channel access. Results show that the average energy per bit consumption is reduced by adjusting the power, center frequency, and bandwidth in accordance with the network node density. Specifically, as the density increases, greater bandwidths offer per-hop energy reduction as well as a reduced packet collision rate.

Hierarchy Schedule-Sensing Protocol for CDMA Wireless Data-Centric Networks With Multiple Packet Collision and Capture Effect

This paper focuses on performance analysis of a CDMA wireless data network based on hierarchy schedule-sensing (HSS) protocol, in which a common-code permission frame beacon is used to schedule request transmissions to avoid packet collisions. To further reduce scheduling delay, hierarchical group-based coding is adopted in the scheme. The performance of such a network is evaluated considering packet collisions with and without packet capture effect using a two-dimensional Markovian chain model. In particular, this paper will study the impact of multiple packet-collision effect on network performance with the help of the average packet-collision rate derived explicitly in the paper. The obtained results show that, despite its low implementation complexity, the HSS protocol is a fairly robust medium-access control protocol featuring uniformly high throughput and short delay even under very high traffic load, which especially suits data-centric wireless networks with relatively small coverage area and great node density.

A comparison study of HSS and triple-R protocols for CDMA wireless data networking with packet collision and capture effect

This paper proposes a new multiple access control protocol, the hierarchy schedule sensing (HSS) protocol, for CDMA wireless data networking with high terminal density in a relatively small area, a typical example of which is a data-centric device network based on Bluetooth technology to provide device-to-device wireless connections. This paper studies the packet collision effect on network performance under the (HSS) protocol, in which a common-coded permission frame (PF) beacon is employed to schedule request transmissions to avoid packet collisions. To reduce the scheduling delay, hierarchical group-based codes are adopted in the scheme. The performance of such a network is evaluated by a Markov chain model. The average packet collision rate with capture effect is derived explicitly. The performance of the proposed protocol is compared with the triple-receiver-based code (triple-R) protocol, which does not use the PF beacon to regulate request packet transmissions. It is revealed from the obtained results in this paper that, despite of its low implementation complexity, the HSS protocol is a fairly robust multiple access control protocol featured by uniformly high throughput, low delay and stable performance, even under a relatively heavy offered traffic load. Copyright © 2003 AEI.