Collision Avoidance In Cognitive Radio Adhoc Networks Using Leach Algorithm

One of the most important operation in ad hoc networks is the broadcast whose protocol is very useful in the wireless system. In earlier days infrastructure based networks were used which denied secondary users from using the free channels. The existence of ad hoc networks makes the cognitive radio very useful. A stream of channels are available for the secondary users in cognitive radio along with the primary users. In this paper, we discuss the modified version of a fully-distributed Broadcast protocol in multi-hop Cognitive Radio ad hoc networks with collision avoidance, BRACER. We consider the availability of spectrum for the unlicensed users along with the primary user for the transmission to take place

隠れ端末問題及びフロー内干渉キャンセルを考慮したワイヤレスアドホックネットワークに関する研究

Performance of CSMA/CA (carrier sense multiple access/collision avoidance) wireless ad hoc network is severely affected by hidden terminal (HT) problem that results in the failure of carrier sense and causes the packet error due to collision. This thesis proposes a method of improving the performance of multi-hop ad hoc network by 4 steps which can be summarized as follows. First, the thesis analyzes HT effect on CSMA/CA unicast communication taking into account actual radio environments including both fading and capture effect. Based on the analysis results, it is predicted that multi-hop transmission is vulnerable to HT problem because of intra-flow interference (IFI). Regarding to this issue, as the second step, a CINR (carrier to interference and noise ratio) -based analysis method is proposed that can precisely estimate the packet delivery probability for CSMA/CA multi-hop transmission suffering from HT-caused IFI under fading environment. The results prove that conventional CSMA/CA media access control cannot achieve efficient multi-hop transmission. Therefore, as the third step, this thesis further proposes IFI-canceling multi-hop transmission (IFIC-MHT) scheme that enables efficient relaying with the highest traffic load for half-duplex multi-hop networks. The interference cancellation (IC) technique employs adaptive signal processing with a normalized least mean square (NLMS) algorithm for channel estimation and has good BER (bit error rate) and PER (packet error rate) performance under a wide range of SNR (signal to noise ratio) and SIR (signal to interference ratio) conditions. A multi-hop packet transmission frame format dedicated to the IFIC is designed. Finally, this thesis studies the effect of IFIC on large-scale ad hoc network where both intra-flow interference and inter-flow interference take place and together affect the multi-hop transmission.電気通信大学201

Fault Tolerant Wireless Sensor MAC Protocol for Efficient Collision Avoidance

In sensor networks communication by broadcast methods involves many hazards, especially collision. Several MAC layer protocols have been proposed to resolve the problem of collision namely ARBP, where the best achieved success rate is 90%. We hereby propose a MAC protocol which achieves a greater success rate (Success rate is defined as the percentage of delivered packets at the source reaching the destination successfully) by reducing the number of collisions, but by trading off the average propagation delay of transmission. Our proposed protocols are also shown to be more energy efficient in terms of energy dissipation per message delivery, compared to the currently existing protocol.Comment: 14 page

Model checking medium access control for sensor networks

We describe verification of S-MAC, a medium access control protocol designed for wireless sensor networks, by means of the PRISM model checker. The S-MAC protocol is built on top of the IEEE 802.11 standard for wireless ad hoc networks and, as such, it uses the same randomised backoff procedure as a means to avoid collision. In order to minimise energy consumption, in S-MAC, nodes are periodically put into a sleep state. Synchronisation of the sleeping schedules is necessary for the nodes to be able to communicate. Intuitively, energy saving obtained through a periodic sleep mechanism will be at the expense of performance. In previous work on S-MAC verification, a combination of analytical techniques and simulation has been used to confirm the correctness of this intuition for a simplified (abstract) version of the protocol in which the initial schedules coordination phase is assumed correct. We show how we have used the PRISM model checker to verify the behaviour of S-MAC and compare it to that of IEEE 802.11