I-Te Lin

Grid-based routing protocol using cell rotation to reduce packets latency and energy consumption in wireless sensor networks

We propose a grid-based routing protocol which divides the network area for large side length of square cells by using cell rotation to reduce the number of relay nodes between the source node and the mobile sink. The proposed scheme divides each cell into multiple sub-cells, and assumes one or two sub-cells to be active-cells. Then, the proposed scheme confines the existing area of active nodes to each active-cell. Because the maximum transmission range is a fixed value, the side length of square cells can be enlarged by confining the area where the active node exist in each cell. Therefore, the proposed scheme decreases the number of relay nodes between the source node and the mobile sink due to the large cells divided, and reduces the data packets delivery latency and the energy consumption. The simulation results show that the proposed scheme improves the packets latency and the energy consumption efficiency.

Dijkstra-Based Higher Capacity Route Selection Algorithm Using Bounded Length and State Change for Automobiles

In general, automobiles travel from the origin to the destination using a shortest route. However, the shortest route may not be a highest wireless connection-capacity route, because of availability of wireless services (base station and access points etc.) along the route. To the best of our knowledge, currently no algorithm exists for selecting a route that maximizes wireless connection-capacity, while keeping route length shortest and close to shortest. In this paper, we propose two modified version of Dijkstra route selection algorithms: one for selecting a maximum connection capacity shortest route, and the other is for discovering higher wireless connection-capacity routes; the length of the route could be larger than a shortest route, but no larger than predetermined bound. The second proposed algorithm exploits the state change of the intersection to broaden the search range of possible routes. Results from our extensive simulation for a Manhattan-street type grid network with the heterogeneous IEEE 802.11a wireless access, show that for a 50% increase in route length and 15 Access Points (APs), the proposed algorithm can increases wireless connection-capacity by 35.67% and 31.27% compared to the shortest and random route selection algorithms, respectively.

Distributed Ad Hoc Cooperative Routing in cluster-based multihop networks

In cluster-based multihop networks, the Ad Hoc Routing (AHR) scheme has been proposed to reduce the implementation complexity of the optimal routing scheme. However, this complexity reduction also causes performance loss. In addition, when the practical distributed relay selection is considered, further performance loss occurs due to the relay selection error. In this paper, we exploit cooperative diversity to compensate these performance losses, address the problem of the conventional distributed relay selection scheme, and then propose a novel Distributed Ad Hoc Cooperative Routing (DAHCR) scheme. In the proposed approach, the sender selects not only the receiver but also one relay to form a cooperative communication to reduce the power consumption. Simulation results reveal that the performance improvements achieved by the cooperative diversity and the proposed DAHCR scheme are the trade-offs of increased complexity.

Asynchronous receiver-initiated MAC protocol with the stair-like sleep in wireless sensor networks

We propose the asynchronous receiver-initiated MAC protocol with the stair-like sleep that each node reduces its own sleep time by the sleep-change-rate depending on the number of hops from the source to the sink in wireless sensor networks (WSNs). Using the stair-like sleep, our protocol achieves the high delivery ratio, the low packet delay, and the high energy efficiency due to the reduction of the idle listening time. Our protocol can formulate the upper bound of the idle listening time because of the feature that the sleep time decreases in the geometric progression, and the reduction of the idle listening time is obtained by using the stair-like sleep. In our proposed scheme, the sink calculates the sleep change rate based on the number of hops from the source to the sink. By using the control packets which have the role of ACK, our proposed protocol can achieve the stair-like sleep by no additional control packets. In addition, even in the network condition that multi-targets are detected, and hops to the sink are changed frequently, our proposed protocol can change the sleep change rate adaptively because the sink can always obtain the number of hops from the source to the sink. Simulation results show that the proposed protocol can improve the performances in the packet delivery ratio, the packet delay, and the energy efficiency compared to the conventional receiver-initiated MAC (RI-MAC) protocol.

Cooperative MAC protocol with distributed relay selection using group-based probabilistic contention

For cooperative wireless networks, we propose a medium access control (MAC) protocol with distributed relay selection using group-based probabilistic contention and reparticipation. The relay with the minimum outage probability is selected in a distributed way. Based on the achievable outage probability, relay candidates are divided into multiple groups, and each relay candidate in a group uses a probability to send the acknowledgement (ACK) packet back to the source to contend for being selected. Each group is defined by a specified range of the outage probability. Relays in a group with lower outage probability range contend earlier. In addition, the relay candidate that does not send the ACK packet in the current time slot is assigned with a higher probability to contend in the next time slot. Once a relay candidate survives, the contention process is terminated. Thus, transmitting the unnecessary ACK packets for contention is avoided. Simulation results show that compared to the conventional scheme, the proposed one has a better performance in terms of the outage probability, shortens the contention period, and reduces the number of ACK packets for contention.

A primary traffic based multihop routing algorithm using cooperative transmission in cognitive radio ad hoc networks

We propose a primary traffic based multihop routing with the cooperative transmission (PTBMR-CT) algorithm that enlarges the hop transmission distances to reduce the number of cognitive receivers on the route from the cognitive source (CS) to the cognitive destination (CD). In each hop, from the cognitive nodes in a specified area depending on the status of the primary traffic, the cognitive node that is farthest away from the cognitive sender is selected as the cognitive receiver. However, when the primary source (PS) is transmitting the data to the primary destination (PD), another cognitive node is also selected to be the cognitive receiver for the cooperative transmission from the cognitive nodes that are in a specified area. The cooperative transmission is performed if the PS still transmits the data to the PD when the cognitive receiver of the next hop is being searched. The simulation results show that the average number of cognitive receivers is reduced by the PTBMR-CT compared to the conventional primary traffic based farthest neighbor routing (PTBFNR), and the conventional PTBFNR is outperformed by the PTBMR-CT in terms of the average end-to-end reliability, the average end-to-end throughput, and the average required transmission power of transmitting the data from the CS to the CD.