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Recently, the service of cellular phone which is dependent on the location is spreading widely. Various techniques are suggested for the location estimation in indoor, however, indoor location estimation techniques have many subjects with a cost and an aspect of the accuracy. To deal with these subjects, we propose a quite new hybrid indoor location estimation method for paying attention to a smart...
The positional estimate system which is represented in GPS is applied from the convenience to various fields, and to be used as a navigation system for pedestrians in recent years. However, GPS has a weak point that it is not possible to use in indoors such as underground stations, buildings, etc. This is because GPS needs a radio wave from GPS space satellites. To tackle this subject, a lot of method...
In this paper, we propose a novel multi-antenna utilization scheme for avoiding the packet congestion around the gateway (GW) of the ad-hoc wireless networks. In our previous work, we have discussed the number of antenna design for suitable for packet congestion around the GW. However, only multi-user access with multi-antenna is considered at the receiver node. Moreover, we do not consider the effective...
Cognitive radio offers a tempting solution to increase the spectrum usage efficiency by proposing opportunistic usage of frequency bands among licensed users and secondary users. This paper focuses on mitigating the interference that may occur when the secondary user is unaware of the primary user's active period; known as hidden terminal problem. Path attenuation and shadowing effect are also considered...
In wireless ad hoc networks, the wireless link SNR varies due to fading after determining a multi-hop route. This causes a temporary link error and blocks the multi-hop packet transmission. A cognitive temporary-bypassing method and its protocol are proposed to improve transmission quality in wireless ad hoc networks. Packet success probability with this method has been analyzed for Rayleigh faded...
In this paper, we propose a soft decision based cooperative sensing method for cognitive radio (CR) in ad-hoc networks. A CR can sense a surrounding radio environment and adapt to the environment by the reconfigurability to achieve more effective frequency utilization. Observing the environment, CR should detect presence or absence of primary user and exploits this information to opportunistically...
This paper proposes a MAC protocol for efficient broadcasting in ad hoc networks. Since pure flooding leads to serious redundant rebroadcasts, packet contention and packet collision, known as the broadcast storm problem, this paper focuses on how to reduce redundant rebroadcasts. Several broadcast protocols periodically exchange hello packets to predetermine effective sets of rebroadcasting nodes,...
The cognitive radio is a secondary wireless communication system that can overlap the frequency band assigned to the primary system by recognizing the frequency status. Ad-hoc cognitive radio is considered for realizing the cognitive radio by using multi-hop communication networks without giving the large interference toward the primary system. We have proposed the STBC distributed ARQ system applied...
In this paper, we propose a new concept namely forward interference avoidance (FIA) using adaptive array antennas (AAAs) for wireless mobile ad hoc networks (MANETs). It enables nodes to avoid interfering with other nodes so that it results in increasing the number of co-existent wireless links. The performance improvement of MANET in terms of the increase of the number of co-existent communication...
In this paper, we focus on the cognitive radio, which reconfigures the radio transceiver according to the surrounding radio environment. We introduce a development to an ad-hoc cognitive radio that can realize a frequency sharing system under existing communication systems using a multi-hop small power communication. Here, we discuss the surrounding radio environment recognition methods in the distributed...
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