Ramshah Ahmad

Bio: Ramshah Ahmad is an academic researcher from Ghulam Ishaq Khan Institute of Engineering Sciences and Technology. The author has contributed to research in topics: Transmission system & Optical communication. The author has an hindex of 1, co-authored 3 publications receiving 6 citations.

Hybrid opto-digital signal processing in 112 Gbit/s DP-16QAM and DP-QDB transmission for long-haul large-$$\hbox {A}_\mathrm{eff}$$Aeff pure-silica-core fiber links

Abstract: By means of numerical simulations, we demonstrated that all-optical signal processing methods (XPM-suppressor module and in-line nonlinear equalization) significantly increase the system performance of digital nonlinear compensation (digital backward propagation) and improve the system performance in five-channel 112 Gbit/s DP-16QAM and DP-QDB transmission over 2400 km large- effective-area pure-silica-core fiber ($$\hbox {LA}_\mathrm{eff}$$LAeff-PSCF). The system performance is quantified with the help of Q-factor (dB) for both dispersion-managed and nondispersion-managed fiber links.

Comparative Performance Analysis of UWB Antenna on Various Substrates

Abstract: This paper presents a microstrip patch antenna for Ultra-Wideband (UWB) applications. Coplanar waveguide feed is used to excite the radiator. The simple and compact geometry of the design is beneficial from the fabrication point of view. The paper further presents an analysis of changing substrates with the same design. The varying thicknesses of substrates also affect the results. The summarized report will help antenna designers for the choice of the substrate. Rigid and commercially available substrates can be applied in economical solutions. Semiflexible and flexible substrates are used in antennas for conformal applications.

Bandwidth Optimization using Flex Grid over Conventional Grid for 5G Optical Networks

Abstract: This research paper is aim to analyze the difference between fix and flex grid plans for 5G multiple-input multipleoutput (MIMO) transmission system. Analysis will be made for different bandwidths i.e., 500GHz, 400GHz, and 350GHz for 20km transmission distance of Multi-mode Fiber (MMF). Both fix and flex-grid plans are studied under the fixed transmission rate (100G) and for different data rates (20G/40G/100G). Purpose of changing the grid plan is to save the bandwidth of an optical communication system that is useless because of guard bands. We have evaluated the spectrum utilization gains using OFDM based transmitters and receivers in MIMO optical networks with flexible grid, and then compared to a conventional grid MIMO transmission optical networks. Results shows that there will be an overall improvement of 30% in capacity of a communication network in using flex-grid plan over the fix-grid plan.

ON-OFF Body Ultra-Wideband (UWB) Antenna for Wireless Body Area Networks (WBAN): A Review

Abstract: Ultra-wideband (UWB) technology can offer broad capacity, short-range communications at a relatively low level of energy usage, which is very desirable for wireless body area networks (WBANs). The involvement of the human body in such a device poses immense difficulties for both the architecture of the wearable antenna and the broadcast model. Initially, the bonding between the wearable antenna and the human body should also be acknowledged in the early stages of the design, so that both the potentially degrading output of the antenna as a consequence of the body and the possibility of exposure for the body may be handled. Next, the transmission path in WBAN is affected by the constant activity of the human body, leading to the time-varying dispersion of electromagnetic waves. Few researchers were interested in this field, and some substantial progress has recently been considered. On the other hand, this paper covered both wearable and Non-wearable UWB antenna designs and applications with respect to their substrate characteristics. Finally, this review prospectively exposes the upgraded developments of (ON-OFF) body antennas in the area of wearable and Non-wearable UWB and their implementations in the WBAN device and aims to evaluate the latest design features that inspire the performance of the antennas.

Connectivity properties for UAVs networks in wireless ultraviolet communication

Abstract: The ultraviolet (UV) scattering communication can be applied in military networked on-the-move and unattended ground sensor networks. This paper focuses on the connectivity properties of unmanned aerial vehicles (UAVs) network based on UV communication that ensures the secret communications between UAVs. UAVs network is consisting of a group of UAVs, each of which moving according to a particular mobility model. We discuss random waypoint (RWP) mobility model and circle movement based model (CMBM), which can describe the actual movement of UAVs, respectively. In this paper, the approximations of the probability that the network is k-connected are provided with consideration of transmission using on–off keying and pulse position modulation. More precisely, we evaluate the effects of node density, transmission power, and data rate on k-connectivity. The numerical examples show that the mobility degrades the connectivity probability. When the numbers of nodes $$n=500$$ and data rate $$R_b =10\,\hbox {kbps}$$ , the required transmission power for nodes moving according to RWP is lower than CMBM in order to achieve 2-connectivity of the UAVs network, but it is about twice that for uniformly distributed nodes.

Nonlinear mitigation using carrier phase estimation and digital backward propagation in coherent QAM transmission

Abstract: We investigate the performance of carrier phase estimation (CPE) and digital backward propagation (DBP) in compensating fiber nonlinearity for 224Gbps PM-4QAM and PM-16QAM coherent systems. In the presence of CPE, the number of DBP steps can be reduced.