Mobile Broadband Scaling and Enhancement for Fast Moving Trains

Internet is an important part of our life, whether traveling or at home. The broadband services available at home are reliable and are usually at constant speed. The people traveling especially in fast moving trains are at higher mobility and may be moving in areas of less connectivity, and providing a reliable service to them is a challenging task. One possible solution to this is to provide communication through an on-board Wi-Fi, which takes services from a central Wi-Fi situated in the middle of the train, which is connected to cellular radio service long-term evolution for railways. The network consists of LTE-R which is dedicated for railway communication only, a public mobile network, which supports LTE-R in the areas of no coverage and high traffic conditions and a public safety network in emergency conditions. The work is verified with the help of simulations on MATLAB, considering different traffic scenarios. The BSs placed at a distance of 2.5 Km and antenna height used is 45 m are equipped with 3G and 4G interfaces, a universal mobile telecommunications services (UMTS) and radio access network (RAN). The UMTS interface is used for voice services and handover when spectrum available in the next cell is less

Evaluation of antenna and relay scheme for cooperative non‐orthogonal multiple access

Abstract An antenna selection followed by a relay selection scheme (ASRS) is proposed for cooperative non‐orthogonal multiple access (NOMA)‐based network. The proposed work selects an antenna to maximise the instantaneous rate of poor channel condition users while providing good quality of services (QoS). The outage probability performance of the proposed scheme is plotted for different antenna configuration while varying the SNR and distance with variable number of antennas and available relays. The fairness factor of the proposed work is also discussed, considering three different density areas. The proposed scheme is compared with novel schemes in literature for average sum rate and average energy efficiency to show its superiority

Call departure reassignment and performance enhancement of OVSF codes in downlink of CDMA based networks

The use of orthogonal variable spreading factor (OVSF) codes give an additional advantage of addressing variable rate requirement of CDMA networks. However, these codes suffer from code blocking problem which further increases due to random nature of call arrival and departure. When a call departs the vacant capacity of the call creates fragmentation in the sub tree where it belongs. The proposed assignment schemes in this paper, in order to reduce fragmentation assigns fragmented vacant capacity of this sub tree to other sub tree(s) and vice versa using reassignment. The proposed schemes guarantees reduced blocking of future high rate calls. It also leads to good system throughput and fairness. Through simulations, it has been demonstrated that the proposed scheme(s) not only adequately reduces code blocking probability but also requires significantly lesser number of code searches as reassignment process is activated in offline mode and online mode is used to locate a vacant code for assignment, which makes it suitable for the real time calls

Radio reservation for handoff calls and resource management for efficient utilization in mobile telecommunications system

The paper proposes a universal mobile telecommunications system (UMTS), UMTS-NSA multicode scheme for a 4G network which uses a long term evolution (LTE) for high speed data calls. The base station (BS) contains both interfaces LTE and UMTS. The 3GPP UMTS interface uses the VSF-OFCDM which allocates OVSF codes which are orthogonal codes. The codes are spread in both frequency and time domain. The proposed scheme assigns number of codes to a new call on the basis of its current location. It increases and decreases the number of codes assigned to a new call when the distance from the BS decreases and increases respectively. The scheme also consider the loading effect on BS i.e number of calls handled by a sub tree which leads to less interference. The simulations and results indicates that the proposed UMTS-NSA scheme performs better as compare to other scheme for capacity utilization and blocking probability

Error Detection and Correction On-Board Nanosatellites Using Hamming Codes

The field of nanosatellites is constantly evolving and growing at a very fast speed. This creates a growing demand for more advanced and reliable EDAC systems that are capable of protecting all memory aspects of satellites. The Hamming code was identified as a suitable EDAC scheme for the prevention of single event effects on-board a nanosatellite in LEO. In this paper, three variations of Hamming codes are tested both in Matlab and VHDL. The most effective version was Hamming [16, 11, 4]2. This code guarantees single-error correction and double-error detection. All developed Hamming codes are suited for FPGA implementation, for which they are tested thoroughly using simulation software and optimized

Hybrid backscatter communication for IoT devices in remote areas

The IoT devices placed in remote locations require a battery replacement very often, which is not a convenient option. Backscatter communication can resolve this problem, as backscatter communication is a data transmission in which an RF signal incident from the gateway is used for energy harvesting, and this energy will be employed for data transmission. In this paper, a hybrid contention-based TDMA scheme is proposed, which provides slots to devices by dividing them into groups, and then contention is employed in groups to acquire a slot; if a device is not able to transmit during harvest, then transmit (HTT) period, then it can transmit in variable sub frame and the devices which are not able to completely transmit during HTT period can reserve subframes. The proposed hybrid scheme is compared with the TDMA scheme for average transmission delay.The proposed scheme provides scalability. The difference between the average transmission delay of TDMA and the proposed hybrid scheme is from 6 to 20 s, depending on the number of devices added and when traffic is generated

Vertical Handover Prediction Based on Hidden Markov Model in Heterogeneous VLC-WiFi System

Visible light communication (VLC) channel quality depends on line-of-sight (LoS) transmission, which cannot guarantee continuous transmission due to interruptions caused by blockage and user mobility. Thus, integrating VLC with radio frequency (RF) such asWireless Fidelity (WiFi), provides good quality of experience (QoE) to users. A vertical handover (VHO) scheme that optimizes both the cost of switching and dwelling time of the hybrid VLC–WiFi system is required since blockage on VLC LoS usually occurs for a short period. Hence, an automated VHO algorithm for the VLC–WiFi system based on the hidden Markov model (HMM) is developed in this article. The proposed VHO prediction scheme utilizes the channel characterization of the networks, specifically, the measured received signal strength (RSS) values at different locations. Effective RSS are extracted from the huge datasets using principal component analysis (PCA), which is adopted with HMM, and thus reducing the computational complexity of the model. In comparison with state-of-the-art VHO handover prediction methods, the proposed HMM-based VHO scheme accurately obtains the most likely next assigned access point (AP) by selecting an appropriate time window. The results show a high VHO prediction accuracy and reduced mixed absolute percentage error performance. In addition, the results indicate that the proposed algorithm improves the dwell time on a network and reduces the number of handover events as compared to the threshold-based, fuzzy-controller, and neural network VHO prediction schemes. Thus, it reduces the ping-pong effects associated with the VHO in the heterogeneous VLC–WiFi network