Mohammad Shahnoor Islam Khan

On the selection of working channels in a channel-hopping cognitive PAN

In a channel-hopping Cognitive Personal Area Network (CPAN), the main objective of the working channel selection mechanism is to avoid collisions with unpredictable primary user activity. As the result, the manner in which the working channel for the next hop is selected, is among the most important determinants of CPAN piconet performance. In this paper we investigate the performance of two working channel selection algorithms and compare them with the simple random selection approach. We show that a simple algorithm where the working channel is selected amongst those that have most recently turned idle offer better performance in the homogeneous case (i.e., where the primary user activity on all channels follows a similar pattern), while the case with heterogeneous primary user activity on different channels is better handled by the algorithm in which predicted probability distribution of channel idle times is used to select the next working channel.

Impact of Network Load on the Performance of a Polling MAC With Wireless Recharging of Nodes

Wireless radio frequency (RF) recharging is a promising approach to prolong the lifetime of wireless sensor networks. In this paper, we describe a polling-based MAC protocol with a round robin, one-limited service policy. Upon a specific request from one or more nodes, the coordinator sends an RF recharging pulse during which regular communication is suspended. We develop a complete probabilistic model of the energy depletion process within the proposed MAC protocol as well as a queuing model of the node behavior, and use it to investigate the behavior of the time interval between successive recharging events and the packet waiting time under varying traffic load and number of nodes in the network.

Performance of simple polling MAC with wireless re-charging in the presence of noise

We consider a simple Medium Access Control (MAC) protocol that lends itself well for the operation of wireless sensor networks (WSN) with wireless RF recharging of sensor node energy source. Since individual nodes are equipped with a single antenna, data transmission must be temporarily interrupted when one or more nodes request energy recharging. We develop a probabilistic model of the energy depletion process within the proposed round-robin MAC operating with a 1-limited scheduling policy. We evaluate the impact of recharging period on the MAC operation under varying traffic load and varying bit error rate.

Self-optimizing control parameters for minimizing ping-pong handover in Long Term Evolution (LTE)

This paper presents a new self-optimizing ping-pong handover (HOPP) control mechanism for Long Term Evolution (LTE) networks. The proposed mechanism tunes the handover (HO) parameters Hysteresis and Time-To-Trigger (TTT) based on a predefined policy that aims to reduce the negative impact caused by HOPP. To this end, we define the HOPP performance indicator (HPIHPP) and then use it to adjust the HO parameters. Simulation results show clear performance improvement over the static parameter setting, especially when a history-based weighting of the HPIHPP performance indicator is used.

Zoning Based MAC with Support for Recharging Process in WSN

Radio-frequency (RF) based recharging of sensor nodes is a promising way to reduce maintenance and extend the operational life of wireless sensor networks. However RF attenuation causes the network nodes with largest distance from the access point (master node) to dictate the rate of recharging which imposes unnecessary breaks in the operation of nodes closer to the master. This deteriorates the throughput of the nodes close to the master. To solve this problem we have designed location aided MAC protocol which supports recharging such that all nodes deplete their batteries at approximately the same time so that recharging pulse comes on time for all the nodes. To achieve that we have partitioned network nodes into circular zones around the master and assigned implicit priorities among the zones. Priorities decrease towards the edge of the network and regulate relative throughput among the zones. We have built probabilistic performance model to evaluate the impact of the recharging process on data communication of different zones by varying traffic load and network size.

A polling MAC with reliable RF recharging of sensor nodes

We describe a wireless sensor network with a medium access control (MAC) protocol that supports wireless recharging of nodes. The MAC protocol uses round-robin scheduling with 1-limited service for simplicity. Nodes that are running out of energy may request a recharge through a radio-frequency pulse. To reduce the likelihood of energy outage, we propose a collaborative protocol in which nodes that hear another nodes recharge request will repeat it until the master node responds with a recharge pulse. Performance of the proposed protocol is evaluated using a probabilistic energy expenditure model. Our results indicate that the collaborative protocol can ensure uninterrupted network operation under a widely varying range of parameter values.

Simple solutions may still be best: on the selection of working channels in a channel-hopping cognitive network

Spectrum decision-that is, the selection of a channel for the next hop-is one of the most important factors that affect the performance of a channel-hopping cognitive network. In this paper, we compare the performance of a number of channel selection algorithms through the probability of collisions with primary user transmissions. The results indicate that a simple histogram-based selection algorithm performs the best, except in the somewhat unrealistic scenario where primary users are homogeneous with respect to mean period and mean duty cycle of their channel activity, in which case selecting the next-hop channel among those that have most recently turned idle offers the best performance. Furthermore, histogram-based selection is shown to be quite resilient to errors inherent to channel sensing and is thus a primary candidate for a wide range of applications of channel-hopping cognitive networks. Copyright

Zoning and Relaying-Based MAC Protocol With RF Recharging

Radio-frequency (RF) recharging can extend maintenance-free operation of wireless sensor networks. However, the period between recharging is limited by the distance between the most distant sensor node and the master, which sends out recharging pulses. To increase this period, we propose a zoning scheme in which nodes are logically grouped into circular zones centered at the master so that nodes in a given zone send their data to their neighbors in the next closer zone, which act as relays. We describe and analyze a polling Medium Access Control (MAC) protocol that supports zoning and relaying through a probabilistic model of the energy depletion process and a queueing model of the packet transmission process. Our results indicate that zoning extends the time interval between recharge pulses and leads to equalization of node lifetimes, but limits the available data transmission bandwidth as well.

Optimum Zoning in RF-Recharged Sensor Networks

Wireless sensor networks with radio frequency recharging of node batteries suffer from an imbalance in recharge amount on account of different distance to the master node. We describe an approach in which nodes are logically partitioned into a number of zones so that nodes in a closer zone act as relays for nodes in the next more distant zone. We show that the optimum partitioning can be found through exhaustive search, and propose a simple heuristic algorithm that can improve the performance without undue deterioration of the network bandwidth.

Recharge Interval and Packet Delay in Wireless Sensor Network with RF Recharging

Radio frequency (RF) recharging can extend maintenance-free operation of wireless sensor networks. However, the period between recharging is limited by the distance between the most distant sensor node and the master which sends out recharging pulses. To increase this period, we propose a scheme in which nodes are logically grouped into circular zones centered at the master, so that nodes in a given zone act as relays for their counterparts in the more distant zones. We describe and analyze a polling MAC protocol that supports zoning and relaying through a probabilistic model of the energy depletion process as well as a queueing model of packet transmission process. Our results indicate that zoning extends the time interval between recharge pulses and leads to equalization of node lifetimes.