Jumpei Taketsugu

Learn More
IEEE standard 802.15.4 defines the physical (PHY) and medium access control (MAC) layers for low-cost and very low-power short-range wireless communications. One of the promising applications offered by the standard is wireless sensor networks. To begin with, this paper shows the propagation characteristics of the IEEE 802.15.4 radio signal in indoor(More)
IEEE 802.11 defines distributed coordination function (DCF), which is characterized by CSMA/CA and binary exponential backoff (BEB) algorithm. Most modifications on DCF so far have focused on updating of the contention window (CW) size depending on the outcome of own frame transmission without considering freezing periods experienced in the backoff(More)
Most modifications on IEEE 802.11 DCF (distributed coordination function) so far have focused on updating of the CW (Contention Window) value and the carrier sense mechanism during a backoff interval is not considered. In this paper, we propose two novel schemes for DCF, which effectively utilize the carrier sense mechanism during backoff interval. The(More)
We propose the use of MDS codes in cooperative multi-hop networks and evaluate its outage probability by means of a non-homogeneous absorbing Markov chain. The proposed scheme can apply to cooperative multi-hop networks with the arbitrary number of relay nodes and require no feedback channels between nodes. In the proposed scheme, a message block is encoded(More)
Abstract—It has been widely recognized that bistable behavior of random access protocols may suddenly deteriorate the performance of the system due to the unexpected slip into an undesired stable operating point. The catastrophe theory succeeds in presenting the bistable region of random access protocols, where packet retransmissions occur in a memoryless(More)
It has been well-known that slotted ALOHA systems exhibit unfavorable bistable behavior, since 1970s. It was proved that we can eliminate bistable region by limiting the number of allowable transmission attempts per packet to eight or less. In this paper, we investigate bistable behavior of slotted ALOHA systems with delay constraints and geometric(More)
Bistable behavior of slotted ALOHA systems has been extensively investigated. It is proved that bistable region can be eliminated by limiting the number of allowable transmission attempts per packet to eight or less. In this paper, we investigate bistable behavior of slotted ALOHA systems with delay constraints in terms of the catastrophe theory. A lifetime(More)