Throughput Fairness Enhancement Using Differentiated Channel Access in Heterogeneous Sensor Networks

Nowadays, with wireless sensor networks (WSNs) being widely applied to diverse applications, heterogeneous sensor networks (HSNs), which can simultaneously support multiple sensing tasks in a common sensor field, are being considered as the general form of WSN system deployment. In HSNs, each application generates data packets with a different size, thereby resulting in fairness issues in terms of the network performance. In this paper, we present the design and performance evaluation of a differentiated channel access scheme (abbreviated to DiffCA) to resolve the fairness problem in HSNs. DiffCA achieves fair performance among the application groups by providing each node with an additional backoff counter, whose value varies according to the size of the packets. A mathematical model based on the discrete time Markov chain is presented and is analyzed to measure the performance of DiffCA. The numerical results show that the performance degradation of disadvantaged application groups can be effectively compensated for by DiffCA. Simulation results are given to verify the accuracy of the numerical model

Throughput Fairness Enhancement Using Differentiated Channel Access in Heterogeneous Sensor Networks

Nowadays, with wireless sensor networks (WSNs) being widely applied to diverse applications, heterogeneous sensor networks (HSNs), which can simultaneously support multiple sensing tasks in a common sensor field, are being considered as the general form of WSN system deployment. In HSNs, each application generates data packets with a different size, thereby resulting in fairness issues in terms of the network performance. In this paper, we present the design and performance evaluation of a differentiated channel access scheme (abbreviated to DiffCA) to resolve the fairness problem in HSNs. DiffCA achieves fair performance among the application groups by providing each node with an additional backoff counter, whose value varies according to the size of the packets. A mathematical model based on the discrete time Markov chain is presented and is analyzed to measure the performance of DiffCA. The numerical results show that the performance degradation of disadvantaged application groups can be effectively compensated for by DiffCA. Simulation results are given to verify the accuracy of the numerical model

A Novel 3D Indoor Localization Scheme Using Virtual Access Point

The global positioning system (GPS) is a popular choice for accurate location sensing and is often used in navigation systems. However, GPS fails to operate inside buildings because satellite signals are blocked. Thus, GPS cannot be used for localization indoors. Moreover, it is difficult to distinguish between the different floors. Research to overcome this problem using the ultrawideband (UWB), radio frequency identification (RFID), and infrared ray (IR) has been conducted. These methods, however, have drawbacks, such as the need for an additional communication module and database. Wireless local area network (WLAN) access point (AP) is widely installed at various locations, and using these WLAN APs can be a viable alternative. The proposed system in this paper indicates the location information in the service set identifier (SSID) of virtual AP. Therefore, merely by scanning the WLAN signals, mobile users can detect their location indoors

Selective Cooperative Transmission in Ad Hoc Networks with Directional Antennas

This paper presents a selective cooperative transmission scheme (abbreviated SCT) for ad hoc network with directional antennas that leverages the benefits of directional-only antenna approach and cooperative communication. The main feature of SCT is its adaptability to the channel condition in the network. In other words, when the node sends data, SCT determines its transmission strategy on either direct or cooperative transmission via a relay node called a forwarder, depending on the transmission time. Simulation results are provided to validate the effectiveness of the proposed scheme

Latency and Jitter Analysis for IEEE 802.11e Wireless LANs

This paper presents a numerical analysis of latency and jitter for IEEE 802.11e wireless local area networks (WLANs) in a saturation condition, by using a Markov model. We use this model to explicate how the enhanced distributed coordination function (EDCF) differentiates classes of service and to characterize the probability distribution of the medium access control (MAC) layer packet latency and jitter, on which the quality of the voice over Internet protocol (VoIP) calls is dependent. From the proposed analytic model, we can estimate the available number of nodes determining the system performance, in order to satisfy user demands on the latency and jitter

TSCH Multiple Slotframe Scheduling for Ensuring Timeliness in TS-SWIPT-Enabled IoT Networks

This paper presents a time-slotted channel hopping (TSCH) multiple slotframe scheduling (TMSS) protocol to ensure the timeliness of energy harvesting and data transmission for sensor devices with different transmission periods in Internet of Things (IoT) networks enabled with time-switching simultaneous wireless information and power transfer (TS-SWIPT). The TMSS uses a modified three-step 6P transaction to allocate power and data cells within the slotframe. The sensor device sets the slotframe length equal to the transmission period and estimates the number of power and data cells for allocation in the configured slotframe and requests cell allocation to the hybrid access point (HAP). Upon request from a sensor device, the HAP executes a cell-overlapping prevention (COP) algorithm to resolve the cell-overlapping problem and responds to the sensor device with a candidate cell list. Upon receiving the response from HAP, the sensor device determines its power and data cells by referring to the cell list. We conducted experimental simulations and compared the TMSS performance to that of the legacy TSCH medium access control (MAC) with a single slotframe and the harvest-then-transmit-based modified enhanced distributed coordination function (EDCF) MAC protocol (HE-MAC). The results showed that TMSS outperforms legacy TSCH MAC and HE-MAC in terms of delay, effective throughput and energy utilization

Distributed Relay-Assisted Retransmission Scheme for Wireless Home Networks

A relay transmission is a promising technology to improve network performance in dynamic infrastructure. In this paper, we propose a distributed relay-assisted retransmission (DRR) scheme in multirate wireless home networks. The idea is to exploit overhearing nodes to retransmit on behalf of sender node after receiving the block acknowledgement (B-ACK) from destination node. For the first transmission, a basic relay (BR) node is used by considering the high data rate between source node and BR node. And then, for the retransmission, a retransmission relay (RR) node is used by considering the high data rate between RR node and destination node. The DRR scheme extends a distributed reservation protocol in WiMedia home networks and inquires the candidate relay node as BR nodes and RR nodes during beacon period. In addition, the DRR scheme can minimize control overhead for relay transmission because all nodes should send and listen to the beacon frames of neighbor nodes during beacon period. We also present the relay decision scheme and channel allocation procedure for maximizing the efficiency in the DRR scheme. Extensive simulation results demonstrate that the DRR scheme can improve the overall throughput by 40% and reduce the energy consumption by 47% compared with nonrelay transmission schemes when the number of nodes increases

Queuing Analysis for IEEE 802.11e Networks in Non-Saturation Environments

This paper presents an analytical model for the performance evaluation of an IEEE 802.11e network in non-saturation environments. We first characterize the probability distribution of the MAC layer packet service time. Based on the probability distribution model of the MAC layer packet service time, we then study the queuing performance of the wireless local area networks (WLANs) at different traffic loads based on the IEEE 802.11e MAC protocol. The numerical results show that we can choose a feasible number and bandwidth of the node which determines the system performance that a user demands