A number of battery-driven sensor nodes are deployed to operate a wireless sensor network, and many routing protocols have been proposed to reduce energy consumption for data communications. This letter proposes a novel routing framework for multihop networks, which is based on transmission power control, nearest forwarding and packet progress toward a sink, in consideration of reducing the extra number of hops in the networks. The energy consumption for the topology employing the proposed forwarding is evaluated by simulation, and it is shown that the proposed scheme is more energy-efficient than the shortest-path tree constructed by Dijkstra’s algorithm.

We propose a novel direction finding algorithm by exploiting a coprime array configured at the receiver of a transmit-diversity multiple-input-multiple-output (MIMO) radar system. The algorithm uses the inter-difference set of virtual sensor positions incoprime array to construct an observation vector which behaves like a data vector obtained from a uniform linear array (ULA). Then the forward-backward spatial smoothing and shift-invariance techniques are combined to effectively estimate the angles of multiple targets. The maximum number of identifiable targets is analyzed. Compared with conventional ULA-based algorithm in MIMO radars, the proposed algorithm can achieve larger array aperture and higher spatial resolution.

This paper presents an effective data collection scheme to provide group communications among appropriate members selected by each user’s geographic situation and preference (real-spatial information). When each user directly notifies central servers of user’s information via wireless network infrastructure (Wi-infra), message delivery latency and losses drastically increase due to the network congestion. Therefore, we employ representative nodes (RNs) selected in a distributed manner. The RN first collects the real-spatial information from neighboring nodes via an ad hoc network and then notifies the server via Wi-infra. From simulation experiments, our scheme can drastically reduce both message delivery latency and losses.

This paper focuses the interference from GFDM signal to already-existing OFDM signal when both signals coexist in same band, considering some migration scenario from 4G to 5G mobile system. After defining system model, the mathematical expression is derived theoretically and numerically verified by computer simulation. This mathematical expression indicates that the time difference does not affect the cross-correlation between GFDM and OFDM symbols, and that the interference decreases approximately by square of subcarrier interval between those symbols. Derived formula can be used not only for the interference evaluation in various configurations, but also for designing the waveform filter of GFDM.

It is important to understand the DOA characteristics in order to develop massive-array antennas for 5^th generation mobile communication systems. We introduce a simple but effective method for measuring direction of arrival (DOA) that combines synthetic aperture (SA) processing with a receiving-system that consists of a turntable, vector receiver, and horn antenna. This report shows by simulation the effectiveness of synthetic aperture processing. The validity of this method is clarified by measurements in a chamber.

This paper proposes a scheme to reduce an initial learning period of Q-routing. Q-routing is a routing scheme to guide a packet on the fastest route. A neighbor node with the lowest Q value, which is determined by a remaining time to the destination, is selected to send the packet. Before the routing is stable, the node learns the Q value at the initial period. The Q-routing performs well in only a high traffic network, compared to a shortest path routing scheme. The proposed scheme reduces the initial learning period of Q-routing by considering a throughput of the node.