Performance analysis and evaluation of IEEE 802.11 distributed coordination function using OPNET

This paper discusses the distributed coordination function (DCF) access mechanism which is a carrier sense multiple access with collision avoidance (CSMA/CA) scheme. Simulation projects for different DCF performance parameters have been built using the OPNET network simulator. The projects are mainly basic service set (BSS) topology simulated under different parameter values (data rate, fragmentation, RTS/CTS, number of nodes, and load condition). Simulation results show when the DCF access mechanism is better under what load condition, and how to choose the best fragmentation threshold and other access-mechanism specific parameters according to the network conditions. Simulation results were validated against a theoretically calculated maximum throughput (the simulation maximum throughput was about 70% of the theoretically calculated maximum throughput).

Throughput and delay analysis for IEEE 802.11 multi-hop networks considering data rate

In an IEEE 802.11 Distributed Coordination Function–based wireless network with multiple hops, a node operates on its own with several predefined data rates (i.e. following modulation and coding schemes). Moreover, the IEEE 802.11 Distributed Coordination Function node’s communication is characterized by transmission and carrier-sensing distances. The transmission one is, in general, reverse proportional to the data rate. Meanwhile, the carrier distance keeps constant regardless of the modulation and coding scheme. Therefore, when a node has a high transmission rate, within its carrier-sensing range, the number of nodes may increase. The previous works have not yet extensively investigated the impact of data rates on such a scenario. This article addresses that issue aiming to quantify the network performance of the multi-hop IEEE 802.11 networks. As a solution, we propose the mathematical expressions, which consider data rates, for end-to-end throughputs, as well as delays in the network with string topology. We confirm the expressions’ correctness by presenting the quantitative agreements between the analytical and simulation results.

Improvement of Network Utility and Energy Efficiency in DSME based Internet of Things Networks

This paper provides a comparison between IEEE 802.11 and IEEE 802.15.4e standards in the context of Internet of Things (IoT). These emerging standards are the amendments of IEEE 802.11 and IEEE 802.15.4 to support IoT based applications. The 802.11 has a channel access scheme, Distributed coordination function (DCF). On the other hand, IEEE 802.15.4e introduces five MAC behavior mode. Among these five modes, DSME is well suited for IoT. A comparison between these two standards is discussed in this paper by using an analytical model and are validated through ns-3 simulations. Results show that the DSME show significant improvement in the performance of DSME when compared to the legacy IEEE 802.11 DCF.

Link Reliable On-demand Multipath Distance Vector routing for reliable video streaming in MANET

: Due to the generic feature of AOMDV, it is widely used in Long-Term Evolution (LTE) networks such as the Internet which requires new challenges to deploy conversational real-time applications like VoIP (Voice over IP) and video conferencing. In AOMDV, the multiple routes between any source and destination pair are selected based on minimal hop count which does not ensure reliable video content delivery as the communicating nodes along the paths are prone to link failures and route breaks. To overcome such problems, the Link Reliable On-demand Multipath Distance Vector (LROMDV) is proposed by modifying the Ad hoc On-demand Multipath Distance Vector (AOMDV). The LROMDV uses an enhanced Cumulative Expected Transmission Count (enh-CETX) for selecting multiple routes between any source and destination pair to avoid link failures and route breaks in Long-Term Evolution (LTE) networks. The performance of LROMDV on H.264/MPEG-4 AVC video streaming under both Distributed Coordination Function (DCF) and Enhanced Distributed Coordination Function (EDCF) using NS2.34 and Enhanced EvalVid framework is evaluated and the simulation result shows the effectiveness of LROMDV.

Interference-Aware Adaptive Beam Alignment for Hyper-Dense IEEE 802.11ax Internet-of-Things Networks

The increased deployment of IoT devices in specific areas results in an interference among them and the quality of communications can be severely degraded. To deal with this interference issue, the IEEE 802.11ax standard has been established in hyper-densely wireless networking systems. The 802.11ax adopts a new candidate technology that is called multiple network allocation vector in order to mitigate the interference problem. In this paper, we point out potential problem in multiple network allocation vector which can cause delays to the communication among IoT devices in hyper-dense wireless networks. Furthermore, this paper introduces an adaptive beam alignment algorithm for interference issue resolution. In addition, we analyze potential delays of communications among IoT devices under interference conditions. Lastly, we simulate our proposed algorithm in densely deployed environment and show that the interference issue can be mitigated and the IEEE 802.11ax-based IoT devices can utilize the air interface more fairly compared to conventional IEEE 802.11 distributed coordination function.