Robust Connectivity in Time-Frequency Dual Fading Channels for the 6G Satellite IoT: Chirp and FRFT

Software-defined networking proposes to physically separate control and data plane. This raises the question on how these two planes communicate, especially if the control channel is in-band, i.e., it shares physical network paths with normal network traffic. In-band control requires calculating multi-hop paths between controller and switches. Connectivity of the control channel is critical regarding network operation. Routing should provide robust connectivity under failures.We propose to achieve robust connectivity by distributing responsibility of maintaining connectivity of the control channel to the switches. We further present the design of a new distributed routing protocol Izzy for in-band SDN control channels. Izzy is based on a combination of a spanning tree with temporary addresses and includes state-of-the-art robustness mechanisms. In this paper, we describe Izzy, while focusing on update consistency on top of temporary addresses.

In software-defined networks (SDN), network control logic is implemented in a (logically-) centralized SDN controller that communicates with SDN switches via an SDN control channel. As the ability of the controller to communicate with switches is critical for the operationability of the network, reliable connectivity of the control channel must be provided. This question is especially important for in-band control channels, where no separate management network is available and most switches are not directly connected to the controller(s). In our previous work [1], we argued for providing reliable connectivity for the in-band control channel using a distributed routing protocol. We presented the protocol Izzy which is optimized for robust connectivity between a single SDN controller and the switches under its control. Realistic deployments, however, use logically-centralized controller clusters for reliability and scalability reasons. In this paper, we describe how to extend Izzy to support such logically-centralized clusters. We propose to divide controllers into groups based on distance between them. Each such group runs a separate instance of Izzy. This paper presents the distributed algorithm Seedling that accomplishes the former. We describe how Seedling works in static scenarios followed by an outline of necessary steps to extend it to dynamic settings including changes to both the number and location of controllers as well as to network topology, especially link failures.

We determine a duality between broadcast and multiple access channels that can be used to obtain the capacity region and optimal transmission strategy for one channel based on the capacity-achieving transmission strategy and region for the dual channel. This duality result in applicable to additive Gaussian noise and fading channels for several different notions of fading channel capacity, including ergodic capacity, outage capacity, and minimum rate capacity. We show that duality can be used to obtain any of these capacities for the fading broadcast channel from the same capacity on the dual MAC channel, and vice versa. We then apply this general result to obtain the minimum rate capacity of the fading multiple access channel, which also yields the ergodic and outage capacity as special cases. Next we turn our attention to broadcast channels with multiple antennas at the transmitter and receiver (the MIMO channel). Since this channel is in general non-degraded, its capacity region remains an unsolved problem. We establish a duality between the achievable region of the MIMO broadcast channel using Costa’s “dirty-paper” coding and the capacity region of the MIMO multiple-access channel, which is easy to compute. We also show that the dirty paper achievable region yields the sum-rate capacity of the MIMO broadcast channel.

An analytical expression for the switching rate of a dual branch selection diversity combiner in kappa-mu and alpha-mu distributed fadings is derived. Independent and identically distributed (i.i.d.) kappa-mu as well as alpha-mu fading channels are considered. The switching rates for dual i.i.d. Rayleigh, Rician and Nakagami-m fading channels are special cases of the switching rate for dual i.i.d. kappa-mu fading channels. Similarly, the general switching rates for dual alpha-mu fading channels also include special cases such as Rayleigh, Nakagami-m, and Weibull fading channels.

Switching rate is an important parameter in selection diversity receiver design because the switching transients increase the system outage. An exact closed-form solution for the switching rate of dual selection diversity in kappa-mu and alpha-mu distributed fadings is derived. Independent and identically distributed (i.i.d.) kappa-mu and alpha-mu fading channels are considered. The switching rate for dual i.i.d. kappa-mu distributed fading includes the switching rate for dual i.i.d. Rayleigh, Rician and Nakagami-m fading channels as special cases. Similarly, the switching rate for dual alpha-mu fading channels also includes special cases such as Rayleigh, Nakagami-m and Weibull fading channels.

In this paper, we investigate the multiuser performance in a 2-D spreading orthogonal frequency coded division multiplexing (OFCDM) communication system over frequency and time selective fading channels. To compromise between the diversity gain and the multiple access interference (MAI), we propose an adaptive fuzzy logic to infer adequate 2-D spreading codes and to assign the OVSF codes to active users for OFCDM mobile communication systems. Moreover, we develop a look-up table to simplify the complexity. Simulation results show that the proposed both fuzzy logic code allocator (FLCA) and look-up table can not only suppress the MAIs induced by the non-orthogonality but also exploit the diversity gain over dual (time and frequency) selective fading channels.

In Wireless communication, the rapid fluctuations in the amplitude and phase of received radio signal are called fading. It has a significant impact on the quality of the demodulated signal. Fading can cause increase in bit error rate and leads to poor performance of the communication system. Thus fading model has to be selected which suits for the environments like urban, suburban and rural areas. The common type of model considered for urban region is Rayleigh-model. In practice, the fading can be weak and also severe than Rayleigh-model. Thus Nakagami-m model is selected to suits the conditions weaker and severe than Rayleigh fading. Diversity reception methodology can improve the performance of the communication system. The combined output of the diversity system will have an improved signal to noise ratio (SNR). In this paper, the performance of dual channel maximal ratio combiner (MRC) has been analyzed over Nakagami-m fading channels. A new method is used to derive the PDF and CDF of output SNR of the dual channel MRC combiner. Further using these expressions, the outage probability for dual channel MRC, SER for modulation schemes MPSK and MQAM have been derived. The obtained expressions have been evaluated numerically and compared with the available analytical results.

Performance analysis of decode and forward relaying over dual-hop mixed fading channels

In Wireless Communications, Cognitive radio (CR) emerges as a boon to the mankind as it reduces the spectrum scarcity problem. Spectrum Sensing, the method to detect the presence or absence of licensed user is the fundamental problem of this system. This method employs different detection techniques in order to sense the radio environment simultaneously without interfering with the primary users. Energy Detection is the most popular among all the detection technique because of its low computational cost, easy implementation and less complexity. This technique is the most suitable for any environment since it does not require any knowledge of the primary user. In this paper, an analytical expression is derived for the corresponding average probability of detection over dual correlated Nakagami-m fading channel. The results suggest that the detection probability highly depends upon the severity of fading. This analytical expression is then verified using Monte Carlo simulation.

The mean time to loss of lock and the average switching rate of an automatic frequency control (AFC) loop are derived in this paper for the case of two received signals in dissimilar fading channels. The general case of modulated carriers is considered while the results are also applicable to unmodulated carriers. The channels are assumed to have Rayleigh, Rician and Nakagami-m distributions. Numerical examples are provided to illustrate the effect of these fading scenarios on the performance of an AFC in the presence of cochannel interference.

Experimental study of structural fire behaviour of steel beam to concrete filled tubular column assemblies with different types of joints

Dual-mode channel equalizer is proposed for IEEE 802.15.3.a (i.e. MB-UWB) and IEEE 802.16d (i.e. fixed WiMAX) OFDM systems. The proposed scheme comprises channel estimator (CE), frequency domain equalizer (FDE), phase error tracker (PET), and adaptive channel tracker to solve non-ideal effects, such as multi-path fading channel, AWGN, carrier frequency offset (CFO) and sampling clock offset (SCO). In MB-UWB system simulation, the proposed dual-mode channel equalizer contributes 2.06~9.7dB gain in SNR for 8% packet error rate (PER) specification in different transmission mode. On the other hand, it can also obtain 0.5~3.9 dB gain in SNR for 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> bite error rate (BER) requirement in WiMAX system. In hardware implementation, the architecture of proposed scheme uses two-parallelism to achieve high throughput rate up to 528M sample/s. Most of the functional blocks are reused to enhance the hardware efficiency. The design occupies only 130k equivalent gate count in UMC 0.18 μm technology.

In order to improve the accuracy and efficiency of signal selection in time-varying channel of remote network communication, a channel time-varying signal selection technology in remote network communication is proposed. Firstly, the basic characteristics of time-varying channel in remote communication network are analyzed from two aspects of time and frequency, and the sparse representation of signal is transformed by compressed sensing theory. According to the analysis results, a dual selective fading channel model based on BEM model is established, The CS algorithm is used to select the signal, and the best signal result is calculated by iteration. The simulation results show that the MSE and BER of the proposed method are always lower than those of the comparison method in the process of signal selection, and the time consumption is kept within 0.1ms, which shows that the multi extraction technology has a certain research value.

This paper presents the dual (2times2) MIMO channel capacity over the Hoyt fading channel. The joint eigenvalue distribution of the channel matrix is obtained and it is shown that the effect of the Hoyt parameter b can degrade around 8.5% the channel capacity. For the ttimesr case, an asymptotic result is also derived. All the results are validated by numerical Monte Carlo simulations and are in excellent agreement

In order to improve the energy efficiency of the optical wireless communications, a joint power allocation and relay selection scheme is proposed for a relay assisted non-line-of-sight optical wireless communication system employing coherent detection with a dual optical channel multiplexing technique. The proposed joint power allocation and relay selection scheme aims to improve energy efficiency of the optical wireless communication system by minimizing the total average transmit power, and provides the delay aware quality-of-service guarantee through maintaining a minimum required effective capacity over the atmospheric turbulence fading channels. The joint power allocation and relay selection problem is formulated as a non-convex and combinatorial optimization problem, and the solution of this optimization problem is obtained using a time-sharing relaxation technique. Subsequently, a fast-convergent algorithm is proposed for the joint power allocation and relay selection by considering the delay aware quality-of-service requirements of the services transmitted over the optical wireless communication channels. Numerical results demonstrate the advantages of the proposed joint power allocation and relay selection scheme in terms of the energy saving for different statistical delay constraints.