Amjad Ali

Cognitive Radio-Based Vehicular Ad Hoc and Sensor Networks

Current advancements in vehicular networking lead to amplifying the issue of spectrum scarcity. Cognitive radio (CR) has emerged as the key technology that enables flexible, efficient, and reliable spectrum exploiting by unlicensed networks to use licensed spectrum bands in an opportunistic manner to alleviate the spectrum scarcity issue. We have already proposed vehicular ad hoc and sensor networks (VASNET) as a new networking paradigm for vehicular communication by utilizing wireless sensor nodes in two mobile and stationary modes. The nodes are employed to sense vehicles activity, for example, car crashes. Like other unlicensed networks, VASNET is supposed to operate over unlicensed spectrum bands. However, due to emergency nature of accident alarms in VASNET that must be received in minimum period of time and avoiding packet loss, in this paper we investigate CR-based VASNET, named as CR-VASNET. Various challenges and issues are discussed in details. In order to save stationary nodes power and enlarge the network lifetime, an optimization technique for relay node selection is proposed. Furthermore, for primary users (PU) protection, an energy detection-based scheme is suggested to calculate the probability of PU arrival. Our theoretical discussions and simulation results proved the efficient functionality of the proposed CR-VASNET as a promising vehicular networking paradigm.

Persistent packet reordering attack in TCP based Ad hoc wireless networks

This paper investigates congestion behavior of TCP and its variants TCP Reno, TCP NewReno, TCP Sack1, TCP Vegas, TCP Rbp and TCP Fack for AODV (Ad hoc Ondemand Distance Vector) and DSR (Dynamic Source Routing) routing protocols under persistent packet reordering attack through simulations in NS-2. It also proposes a solution to counter misinterpretation packet reordering with packet loss when retransmissions are due to persistent packet reordering by malicious nodes rather than packet loss due to traditional reasons.

Evaluation of resistance to different insecticides in field strains of Helicoverpa armigera (Lepidoptera: Noctuidae) in Punjab, Pakistan

Susceptibility of field populations of Helicoverpa armigera (Lepidoptera: Noctuidae) from Punjab, Pakistan to selected insecticides was evaluated using the leaf dip method. The resistance factors varied between populations. The general trends were low to moderate resistance to endosulfan; very low to low resistance to chlorpyrifos and profenofos; very low resistance to spinosad, indoxacarb and thiodicarb; moderate to high resistance to bifenthrin; high to very high resistance to cypermethrin; and very high resistance to lambda‐cyhalothrin. Integrated pest management strategies aimed at reducing pesticide application, such as rotating the conventional insecticides having low resistance with newly developed synthetic insecticides and conserving natural enemies, are recommended.

Resource Optimization Scheme for Multimedia-Enabled Wireless Mesh Networks

Wireless mesh networking is a promising technology that can support numerous multimedia applications. Multimedia applications have stringent quality of service (QoS) requirements, i.e., bandwidth, delay, jitter, and packet loss ratio. Enabling such QoS-demanding applications over wireless mesh networks (WMNs) require QoS provisioning routing protocols that lead to the network resource underutilization problem. Moreover, random topology deployment leads to have some unused network resources. Therefore, resource optimization is one of the most critical design issues in multi-hop, multi-radio WMNs enabled with multimedia applications. Resource optimization has been studied extensively in the literature for wireless Ad Hoc and sensor networks, but existing studies have not considered resource underutilization issues caused by QoS provisioning routing and random topology deployment. Finding a QoS-provisioned path in wireless mesh networks is an NP complete problem. In this paper, we propose a novel Integer Linear Programming (ILP) optimization model to reconstruct the optimal connected mesh backbone topology with a minimum number of links and relay nodes which satisfies the given end-to-end QoS demands for multimedia traffic and identification of extra resources, while maintaining redundancy. We further propose a polynomial time heuristic algorithm called Link and Node Removal Considering Residual Capacity and Traffic Demands (LNR-RCTD). Simulation studies prove that our heuristic algorithm provides near-optimal results and saves about 20% of resources from being wasted by QoS provisioning routing and random topology deployment.

Genetic divergence in sugarcane genotypes.

To assess genetic divergence of sugarcane germplasm, an experiment comprising 25 sugarcane genotypes was conducted at Sugar Crops Research Institute (SCRI), Mardan, Khyber Pakhtunkhwa, Pakistan, in quadruple lattice design during 2008-09. Among the 14 parameters evaluated, majority exhibited significant differences while some showed nonsignificant mean squares. The initial correlation matrix revealed medium to high correlations. Principal Component Analysis (PCA) showed that there were two principal components accounting for 88% of the total variation in the tested breeding material. The new components were named “Vigor”, and “Quality”. Principal Component Regression (PCR) indicated that these two accounted for 93.64% and 7.36% of variation in the yield, thus signifying the role of the “Vigor” Component. Cluster analysis using Ward’s method on the newly created variables using principal components revealed that there were 3 clusters at a linkage distance of 4.5. Cluster I and III had 11, and cluster II had 3 genotypes. Cluster I showed high mean values for Vigor Component while Cluster II for Quality Component and Cluster III showed genotypes with high mean yield. There was no correspondence of the clustering with the geographic location of the genotypes. It could be concluded from these analyses that there are two main components i.e. vigor, and quality accounting for Research Article American Journal of Experimental Agriculture, 3(1): 102-109, 2013 103 maximum variation in yield. The genotypes in cluster I and II could be utilized as source for future selection or hybridization program for the improvement of these characters in sugarcane.

Merge-and-forward: a cooperative multimedia transmissions protocol using RaptorQ codes

Recently, nodes cooperation has emerged as a popular means for improving the quality of multimedia delivery over fifth-generation cellular networks. However, in the conventional relaying scheme such as amplify-and-forward (AaF), there is a higher probability of duplicate packets at the receiver node which affect the decoding probability and consequently deteriorate the quality of multimedia transmission. In this study, the authors propose a cooperative multimedia transmission protocol based on a novel merge-and-forward relaying and the best relay selection (RS) schemes. Their best RS scheme is based on two important parameters: (i) two-hop link distances and (ii) minimum block error rate value. Moreover, to combat the packet loss for enhanced and reliable video delivery, they adopt application layer forward error correction scheme which is based on the most improved and advanced version of fountain codes (i.e. RaptorQ codes). They evaluate the performance of the proposed scheme under different time-sharing scenarios between the direct and best indirect transmission links in terms of decoding failure probability, decoding overhead, peak signal-to-noise ratio, and mean opinion score. Simulation results show that the proposed scheme outperforms the conventional AaF relaying scheme.

PAD-MAC: Primary User Activity-Aware Distributed MAC for Multi-Channel Cognitive Radio Networks

Cognitive radio (CR) has emerged as a promising technology to solve problems related to spectrum scarcity and provides a ubiquitous wireless access environment. CR-enabled secondary users (SUs) exploit spectrum white spaces opportunistically and immediately vacate the acquired licensed channels as primary users (PUs) arrive. Accessing the licensed channels without the prior knowledge of PU traffic patterns causes severe throughput degradation due to excessive channel switching and PU-to-SU collisions. Therefore, it is significantly important to design a PU activity-aware medium access control (MAC) protocol for cognitive radio networks (CRNs). In this paper, we first propose a licensed channel usage pattern identification scheme, based on a two-state Markov model, and then estimate the future idle slots using previous observations of the channels. Furthermore, based on these past observations, we compute the rank of each available licensed channel that gives SU transmission success assessment during the estimated idle slot. Secondly, we propose a PU activity-aware distributed MAC (PAD-MAC) protocol for heterogeneous multi-channel CRNs that selects the best channel for each SU to enhance its throughput. PAD-MAC controls SU activities by allowing them to exploit the licensed channels only for the duration of estimated idle slots and enables predictive and fast channel switching. To evaluate the performance of the proposed PAD-MAC, we compare it with the distributed QoS-aware MAC (QC-MAC) and listen-before-talk MAC schemes. Extensive numerical results show the significant improvements of the PAD-MAC in terms of the SU throughput, SU channel switching rate and PU-to-SU collision rate.

Modelling cyber security for software-defined networks those grow strong when exposed to threats

With each passing day, the information and communication technologies are evolving with more and more information shared across the globe using the internet superhighway. The threats to information, while connected to the cyber world are getting more targeted, voluminous, and sophisticated requiring new antifragile and resilient network security mechanisms. Whether the information is being processed in the application, in transit within the network or residing in the storage, it is equally susceptible to attack at every level of abstraction and cannot be handled in isolation as the case has been with conventional security mechanisms. The advent of Software-Defined Networks (SDN) has given a new outlook to information protection, where the network can aid in the design of a system that is secure and dependable in case of cyber threats. The nature of SDN, mainly its programmability and centrality of network information and control has led us to think of security in an antifragile perspective. Our networks can now thrive and grow stronger when they are exposed to volatility by overwhelming cyber threats. However, SDN infrastructure itself is susceptible to severe threats that may mutilate the provision of its usability as security provider. Both these perspectives of “Security with SDN” and “Security for SDN” have invited research and innovations, yet both these approaches remain disintegrated, failing to support each other. The contribution of this paper is threefold, with first reviewing the current state of the art work for both perspectives of SDN security. Second, it advocates the necessity and introduces a novel approach of antifragile cyber security within SDN paradigm and finally it proposes a unified model for integrating both approaches of “Security with SDN” and “Security for SDN” to achieve the overall objective of protecting our information from cyber threats in this globally connected internetwork.

Assessment of Genotype X Environment Interaction and Stability of Promising Sugarcane Genotypes for Different Agronomic Characters in Peshawar Valley

Sugarcane germplasm screening and testing for superior attributes is a regular feature of the breeding program at Sugar Crops Research Institute, Mardan, Khyber Pakhtunkhwa, Pakistan. Sixteen genotypes which were in the final stages of selection were evaluated in three different environments for Genotype by Environment (G x E) interaction and stability performance. Combined analysis of variance showed highly significant variances for Environments (E), Genotypes (G), and their interaction (G x E). The effect of environments was very pronounced for all the characters highlighting their importance in the performance of genotypes. None of the genotypes was stable across the three environments for all characters. However, genotypes Mardan 93 and CP 77/400 showed a comparative stability for cane yield (t/ha).

Effect of weather factors on populations of Helicoverpa armigera moths at cotton-based agro-ecological sites

Pheromone trapping was used to monitor populations of the moth Helicoverpa armigera at five cotton‐based agro‐ecological sites – river, vegetable, orchard, forest and clean cultivation (areas under only cotton cultivation) – in the Bahawalpur district, Pakistan. Three locations at each site were chosen and three pheromone traps at each location were installed in cotton fields. Moth catches were recorded at 15–20 day intervals from 24 October 2004 to 19 December 2006. In 2004, the river sites showed the maximum trapped population of H. armigera (0.22/trap) followed by 0.165 per trap at the vegetable sites. Orchard, clean cultivation and forest sites had zero moth catches. In 2005, the river sites again showed the highest trapped population (0.57/trap), followed by clean cultivation (0.45/trap), vegetable (0.44/trap), orchard (0.40/trap) and forest (0.29/trap). The moths appeared during July to December and March to May. In 2006, sites showed non‐significant difference, with a population range of 0.47 to 0.97 moths per trap. On average, river sites peaked at 0.49 per trap, followed by vegetable (0.38), clean cultivation (0.47), orchard (0.35) and forest (0.25) sites. The peak was observed on 3 April 2006, and moths appeared during February to July and October to December. The minimum temperature in river, forest and clean cultivation sites; the maximum temperature in orchard sites; and the average temperature in river, orchard, forest and clean cultivation sites showed significant positive correlations with trapped moth populations. Relative humidity showed significant negative correlation with population at the orchard sites in 2005. All weather factors during 2004 and 2006 showed non‐significant correlations with the moth populations. No model was found to be best fit by multiple linear regression analysis; however, relative humidity, minimum temperature, maximum temperature, minimum temperature and maximum temperature contributed 8.40, 10.23, 2.43, 4.53 and 2.53% to the population fluctuation of the moth at river, vegetable, orchard, forest and clean cultivation sites, respectively.