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Intent-Driven Campus Network Deployment Practices
Published in Ningguo Shen, Bin Yu, Mingxiang Huang, Hailin Xu, Campus Network Architectures and Technologies, 2021
Ningguo Shen, Bin Yu, Mingxiang Huang, Hailin Xu
The egress devices and core devices of University A are all deployed in the core equipment room, resulting in lower management network construction costs. Consequently, out-of-band management mode is most suitable for our needs. In addition, the services running on the egress and core devices are complex, requiring onsite commissioning by network engineers during deployment. As such, the local command line interface (CLI) or web system is used for deployment. Many devices, including aggregation devices, access devices, and access points (APs), are sparsely deployed below the core layer and feature similar service configurations. To simplify deployment in this scenario, in-band management and plug-and-play deployment are recommended. Table 10.10 provides management network and deployment mode planning.
Networking: Concepts and Technology
Published in P. S. Neelakanta, ATM Telecommunications, 2018
The frame-relay technique was therefore, developed to overcome the overhead of X.25 imposed on end-user systems and packet-switching networks. The differences between frame-relaying and the conventional X.25 packet-switching are as follows: ▪ Call control signaling is implemented in the frame-relay transmissions on a separate logical connection from user data. This is known as out-of-band signaling. Thus, intermediate nodes need not maintain state-tables or process messages relating to call control on an individual per-connection basis▪ In the frame-relay operation, the multiplexing and switching aspects of logical connections take place at layer 2 (instead of layer 3 of the protocol stack as in X.25) thereby eliminating an entire layer of processing (Fig. 3.64)▪ The hop-by-hop flow and error controls are removed in the frame-relay. Any end-to-end flow and error control, if they are employed at all, would be the responsibility of a higher layer. Thus, the intermediate nodes are relieved of the burdens on error and flow controls.
Protecting the Infrastructure
Published in Curtis Franklin, Brian J. S. Chee, Securing the Cloud, 2019
Curtis Franklin, Brian J. S. Chee
Why out-of-band management? The unfortunate answer is that most management facilities were tacked on as an afterthought, and in too many cases, they have relatively weak security capabilities. We strongly recommend that you consider using some sort of authentication server and avoid using local accounts. The simple fact is that those local accounts on a multitude of management devices tend to be forgotten, and either the passwords are forgotten or they are not changed during personnel changes. Having a backdoor admin still makes sense, but not one that’s used outside of emergencies. Better to have these passwords stored in someone’s safe or secure filing cabinet.
VHF high-power tunable low-pass filter based on nested coupled helical inductor
Published in International Journal of Electronics, 2021
Zhengwei Huang, Yong Cheng, Yuanjian Liu
A tunable filter is indispensable in radio frequency (RF) and microwave communication systems. It can suppress the harmonic and stray of signal energy in the RF front end of transmitter and the interference signal out of band in the RF front end of receiver, greatly improve the communication distance. Present advances in tunable filter mainly focus on the following points: wide tuning range, high tuning speed, high linearity, high-power processing capacity, miniaturisation and integration, and high reliability. Many varactor tunable filters have been reported in the past (Abbosh, 2012; Chen et al., 2018; Ebrahimi et al., 2018; Kumar & Parihar, 2018; Li et al., 2019; G. Zhang et al., 2018), where the value of the varactor can be changed constantly, to continuously adjust the frequency of the filter. However, the Q value of the filters is low, which leads to large insertion loss in the filter. The tunable filter based on RF MEMS (Radio-Frequency MicroElectroMechanical System) (Yang et al., 2018; N. Zhang et al., 2017) has a smaller insertion loss, but the slow tuning speed makes it impractical for frequency-hopping communications. PIN diodes are used to realise tunable filters with continuously variable capacitance (Arain et al., 2018; Masood & Suseela, 2018) for use in frequency-hopping communication to achieve a high Q value, fast tuning speed, and higher power capacity.
Surfing the Radio Spectrum Using RTL-SDR
Published in IETE Journal of Education, 2019
Antonios Valkanas, Divyanshu Pandey, Harry Leib
A simple telescopic antenna comes by default with the dongle which can be used for many simple applications. The tuner chip used in the dongle defines the frequency range over which the dongle can operate. A variety of different tuner chips which use different frequency ranges, amplifiers and filters are compatible with the RTL 2832U chip. The most commonly used tuner is Rafael Micro R820T which works in the range of 24–1850 MHz [29]. The general architecture of the tuner is based on the super-heterodyne principle. A simplified overview of signal processing done inside the tuner is shown in Figure 2. The received signal at the antenna is amplified by a low noise amplifier (LNA) whose gain can be controlled through Automatic Gain Control (AGC) or manually through configurable options in the SDR software which is discussed in the next sub-section. Following the LNA is an RF Bandpass filter used to eliminate the unwanted signal lying out of band and pass the signal in the desired frequency range. Further, a mixer is used to convert the received signal onto a low intermediate frequency.
Peak-to-Average-Power-Ratio (PAPR) Reduction Methods with Wavelet Transform in MIMO-OFDM
Published in IETE Journal of Research, 2018
In recent years, a recommended method for meeting the requirements of the wireless communication systems in frequency-selective fading channels has been the Orthogonal Frequency Division Multiplexing (OFDM) system [1]. The necessary requirements are secure communication, bandwidth efficiency, high data rate, etc. according to the location of the signals. Advantages such as high data transmission rate, bandwidth saving, and reliability are available in the OFDM systems. Moreover, the OFDM system effectively provides numerous parallel narrow band channels and is used along with the Multiple Input–Multiple Output (MIMO) systems, which in turn increases the data transmission rate, diversity gain, and system capacity [1,2]. MIMO-OFDM systems are regarded as key technology for wireless communication systems with high data rate in the current communication systems and are used in Digital Subcarrier Lines, IEEE802.11, IEEE802.16, and IEEE 802.15.3a, and satellite connections in 4G technology [3]. Despite it being a key technology, there are also problems in MIMO-OFDM systems. The Peak-to-Average-Power-Ratio (PAPR) problem is one of the most significant of these problems and there are several recommended methods to solve this [4–9]. These methods are discussed in two groups. The first group includes signal jamming methods (clipping, peak windowing, etc.). Of these methods, the clipping method is the simplest one for the PAPR reduction. However, the method jams the signal due to the out-of-band emission and interference [10].