Simulating time-variant channel impulse response for mmWave I2I channels using Doppler spread information

Dr Anirban Ghosh

Dr Anirban Ghosh, Assistant Professor, Electronics and Communication Engineering, has recently published a paper titled “Time Variance of 60 GHz VI2I channel”. The paper is published in the renowned journal Elsevier-Vehicular Communication with an Impact Factor of 4.7. This paper explores the implementation challenges in unlicensed 60 GHz frequency band for autonomous vehicle infrastructure. This work has been implemented in collaboration with his colleagues from NIT Durgapur and collaborators from Brno University under the aegis of Prof. Ales Prokes. This work is also funded by the Science Foundation grant (Czech) and National Sustainability Program grant (Czech) and DST-Core Research Grant(India).

Fig 1: Field test setup at the measurement site

Smart cities are cities on the move; having a mission of delivering people and goods with zero congestion, zero fatality and zero energy wastage. For realising this mission, a smart city needs an intelligent transport system (ITS). As far as the communication aspect of ITS is concerned, historically, the urban ITS planners were more concerned about vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) modes of communication. This is because the V2V and V2I channels are essentially wireless, and establishing reliable low-latency links over these channels is challenging. Infrastructure-to-infrastructure (I2I) communication is also an integral part of the ITS initiative, and due to their rapid, dynamic and non-invasive nature of the installation, wireless I2I links are preferred over wired links in several smart-road based ITS applications. In order to implement wireless I2I communication, transceivers may be fitted with different kinds of roadside units (RSUs), e.g., short height traffic signposts, overhead gantries, and cantilever sign supports. The traditional role of these RSUs is to support the basic ITS goals, i.e. driver assistance or traffic management. As the vehicular networks scale-up, ITS computations are being shifted to the edge, and the RSUs are going to play more prominent roles in the form of edge computing devices. For example, RSUs can form the cloudlet layer of a vehicular fog computing (VFC) architecture for the internet of vehicles (IoV).

Vehicular wireless I2I channels realise fixed-to-fixed (F2F) radio communication between two RSUs. For any F2F radio channel with stationary transmitter (TX) and receiver (RX), the time-variance is caused by the mobility of the scatterers. These mobile scatterers, say passersby for an indoor scenario, or passing vehicles for an outdoor scenario, cause changes in path lengths in a fading multipath channel. When viewed in frequency-domain, this yields a change in carrier frequency termed as Doppler shift which is proportional to the velocity of the scatterer, and the spectral broadening caused by the time rate of change of the channel is measured with the Doppler spread. Information about Doppler spread is critical for V2V applications such as platooning. In the context of V2I applications, accurate estimation of the Doppler spread is required for designing adaptive transceivers, smart antennas and for determining cellular handoffs. Doppler spread information can also be used for I2I applications like speed estimation. The radar-based solution has a lower latency compared to a camera-based solution, owing to the video acquisition and processing time of the later. As the Doppler shift is a linear function of the carrier frequency, it is of greater concern while moving up in the frequency ladder to the millimetre wave (mmWave) regime. The Doppler spread in the unlicensed 60 GHz mmWave band would be 10-30 times that in the current sub-6 GHz band, with a range spanning from 10 Hz to 20 kHz depending on the velocity of the scatterers. Moreover, compared to V2V links, the effect of moving scatterers is much more pronounced in F2F links; walking pedestrians with a velocity order of ∼ 1 m/s or even the tree leaves fluttering in the wind are important for F2F channel modelling. For highways, the moving vehicles have a velocity an order higher (> 10 m/s) and contribute significantly to the time-variance of the roadside wireless I2I links.

Fig 2: Comparison of the measured and
proposed models of ACF and Doppler
Spectrum with existing analytical models

In this paper, Dr Ghosh studied the time-variance of a roadside infrastructure to infrastructure (I2I) channel operating at 60 GHz millimetre wave (mmWave) band, where the time-variance is caused by moving vehicles acting as scatterers. At first, measurement data is obtained by placing the transmitter (TX) and the receiver (RX) at different heights to emulate a link between two nonidentical roadside units (RSUs), and time-domain channel sounding is performed by sending complementary Golay sequences from the TX to the RX. A linear piecewise interpolation of the corresponding temporal auto-correlation function (ACF) is used to find the Doppler spread of the I2I channel, where their interpolation method compensates for a slower sampling rate. Next, a framework is presented for the time-variant channel impulse response (CIR) simulation, which focuses on moving scatterers only and validates the linear piecewise ACF model. The framework is useful for time-variant vehicular I2I channel simulation and in speed estimation related vehicular applications. Finally, a double-slope curve-fitted analytical model for ACF is proposed as a generalisation to the linear piecewise model. The proposed model and its Doppler spectrum are found to be in agreement with the analytical results for fixed-to-fixed (F2F) channels with moving scatterers and matches perfectly with the measured data. “Our research has explained a framework for simulating time-variant channel impulse response (CIR) for mmWave I2I channels with moving scatterers using Doppler spread information – which provides means to study the various characteristics of an I2I channel even without carrying out any expensive channel sounding campaign”, said Dr Ghosh.

Dr Ghosh and his collaborators are currently exploring further challenges in communication between vehicles (V2V) in the same frequency range (60 GHz).

To know more about the paper, please visit- https://www.sciencedirect.com/science/article/abs/pii/S2214209620300590?dgcid=coauthor

Dr Somesh Tiwari has received Mentoring of Engineering Teachers by INAE (Indian National Academy of Engineering) Fellowship -2020.

Dr Somesh Vinayak Tewari, Assistant Professor, Department of Electronics and Electrical Engineering, brings another honour for SRM University-AP. He has been selected for Mentoring of Engineering Teachers by INAE (Indian National Academy of Engineering) Fellowship -2020. His mentor during the programme will be Dr Archana Sharma, FIE, FNAE, Outstanding Scientist, Bhabha Atomic Research Centre.

The INAE (Indian National Academy of Engineering) provides funding to an Engineering Teacher for carrying out research in the selected/proposed area to be mentored by an INAE fellow. The scheme attempts to increase the knowledge base and is instrumental in building long term collaborations. Such mentoring program helps in bridging the collaboration between an academic area and a research and development organization which is extremely necessary to sow the seeds of research in young and energetic brains so that they are able to translate their research ideas for further growth. This interaction of ideas leads to a win-win situation for both the University and the research organization. The prestigious and highly competitive fellowship receives thousands of applications nationwide though only fifteen of them finally are selected for the fellowship this year by INAE. Dr Somesh is one of fifteen outstanding researchers.

Dr Tiwari will be working on the proposed research topic- “Studies on Inertial Electrostatic Confinement Concept in Deuterium gas environment”. Inertial Electrostatic Confinement (IEC) is an alternative concept to Magnetic and Inertial fusion. IEC fusion device is an extremely compact and simple device, running by high voltage as discharge on Deuterium -Deuterium/Deuterium-Tritium/Deuterium -3He fuel gases. Studies related to IEC find application in the areas of dosimeter calibration, isotope production, radiography, and has medical applications. Such a research is multifaceted and helps an engineering teacher to enhance his skills in experimental areas of high voltage, plasma physics, vacuum techniques, radiation detection and measurement and in numerical methods and simulation leading to a comprehensive analysis of a given problem. During the two months of the fellowship, Dr Archana Sharma will be mentoring the project. It is an excellent opportunity for our faculty to work with such a renowned scientist in such close proximity. The collaboration will be beneficial for both institutions.

Dr Om Jee Pandey Two research papers of Dr Om Jee Pandey, Assistant Professor, Department of Electronics and Communication Engineering, have been accepted in reputed IEEE Journals. The papers titled “Multiuser Full-Duplex IoT Networks with Wireless-Powered Relaying: Performance Analysis and Energy Efficiency Optimization,” and “Time Synchronized Node Localization Using Optimal H-Node Allocation in a Small World WSN” are going to be published in IEEE Transactions on Green Communications and Networking and IEEE Communications Letters, respectively. The paper “Multiuser Full-Duplex IoT Networks with Wireless-Powered Relaying: Performance Analysis and Energy Efficiency Optimization,” was pursued in collaborations with Prof. Ha H. Nguyen, Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, Canada, and Dr Mahendra K. Shukla, who is associated with Macau University of Science and Technology as a Post Doctoral Fellow.


Block diagram of the full-duplex
wireless-powered relay based on power splitting
There has been a growing interest in improving energy efficiency for next-generation Internet of Things (IoT) networks due to the increasing demand for green communications. Motivated by this demand, energy efficiency maximization has been investigated for several networks. Specifically, without considering simultaneous wireless information and power transfer networks, various works have extensively studied energy efficiency maximization for half-duplex networks and full-duplex networks. Further, by considering simultaneous wireless information and power transfer networks, several works have examined energy efficiency maximization in half-duplex networks. Moreover, energy efficiency for next-generation IoT networks with simultaneous wireless information and power transfer has also been studied by considering half-duplex transceivers. It appears that energy efficiency problems for multiuser full-duplex IoT networks have not been studied in the open literature.

Multiuser FD-IoT network with
wireless-powered TWR
Motivated by the above discussion, in this work we consider a full-duplex IoT network in which a multi-antenna access point and several single antenna IoT devices exchange information bidirectionally with the aid of a wireless-powered single-antenna relay, under generalized Nakagami-m fading channels. In particular, we consider the power splitting protocol at the full-duplex relay terminal, and each communication terminal operates in the full-duplex mode. For such a network, we first formulate the instantaneous end-to-end signal-to-interference-plus-noise ratios (SINRs) by employing maximum-ratio transmission (MRT) beamforming and maximum-ratio combining (MRC) at the access point A, as well as IoD scheduling. Then, based on the obtained SINRs, we evaluate the overall outage probability and ergodic sum-rate of the network. Furthermore, we develop an optimal power allocation to maximize the network’s EE.

Integral area for the
overall outage probability
Recently, with many technological advancements in wireless data transmission, IoT is expected to affect all aspects of our daily lives with its ever-growing and emerging applications. Traditional wireless communication networks are usually limited by the operational time of energy-constrained devices, and therefore energy consumption minimization is a crucial factor in IoT networks. Simultaneous wireless information and power transfer have emerged as a sustainable solution to the scenarios where replacing or recharging batteries is very costly, and may even be impossible. The basic idea of simultaneous wireless information and power transfer is that since radio frequency signals can carry information and energy at the same time, the received radio frequency signals can be utilized for energy harvesting to keep the energy-constrained devices operational. Existing studies adopt two different protocols, namely time switching and power switching, to implement simultaneous wireless information and power transfer receiver architecture. With these protocols, either the power or time of the received signal is split so that one part is used for information processing, and the other is used for energy harvesting.

The proposed research can play a crucial role in societal development as it can be applied in developing many state-of-the-art applications in the areas related to green healthcare systems, energy-efficient agriculture systems, green transportation, low power home automation, green manufacturing, low power smart utilities, and energy-efficient industries etc.

His other paper “Time Synchronized Node Localization Using Optimal H-Node Allocation in a Small World WSN”, DOI (identifier) 10.1109/LCOMM.2020.3008086, has been done in collaborations with Prof. Rajesh M Hegde, Department of Electrical Engineering, IIT Kanpur and Dr Mahendra K. Shukla, Post Doctoral Fellow at Macau University of Science and Technology. To know more about Dr Pandey’s work in the domain of Small-World Wireless Sensor Network, visit- https://srmap.edu.in/news/dr-om-jee-pandey-small-world-wireless-sensor-network-help-making-smart-applications-industries/.

Dr Pandey is now not only working for the commercial applications of his current research but also has devoted himself to his future projects, that include-
Full-Duplex Network Development for Green Healthcare Systems.
Energy-Efficient Cyber-Physical Systems and Internet of Things.
Development of Energy-Efficient Agriculture Systems.
Green and Intelligent Transportation over Full-Duplex Context-Aware Pervasive Systems.

The Department of Student Affairs brings another exciting session of THE NEWSMAKERS today. Dr Tousif Khan N, who was very recently honoured with APJ Abdul Kalam Memorial International Travel Award for his remarkable research on “Online adaptive fast output voltage tracking in DC power supply system”, will be joining the participants to share his research experience with them. Dr Khan is the Assistant Professor and Head of the Department of Electronics and Electrical Engineering and internationally acclaimed for his impactful research. Join Dr Khan on July 21st 2020, between 5.00 to 6.00 pm to know more from the man himself.

To watch the session live on our official Facebook page, stay tuned on – https://www.facebook.com/SRMUniversityAmaravati/

https://youtu.be/FJr-FMIZ3bk

“He shines Hot, I absorb the heat intense;
He comes down with all blaze, I disappear slow;
He boasts his victory Grand, roars High;
The world surrenders to his Will and Grace”

Dr Ram Kulesh Thakur’s poem titled ‘The War’ is a metaphoric poetic tale that depicts the strife and struggle of the human race against the challenges that question their identity and existence. The poem has been recently published in the reputed journal “Contemporary Literary Review India” in its May 2020 edition where it was avidly congratulated by the readers.

The poem ‘The War’ reflects the continuous state of turmoil that any sensible person faces each second, each day. One has to be mighty enough to deal with all the impediments and strive to better one’s life; not only for the personal benefit but at the same time for the entire Humanity. In the poem, the speaker, a tiny water droplet, dares to war against the imperious and despotic Sun and in the attempt loses its identity itself. However, the droplet does not lose hope. It makes an attempt to survive and joins others to form a cloud. The Cloud, as known, can fight gloriously and save the world from the intense heat of the Sun. Thus, the water droplet stands victorious. The poem reminds us of how determination and wisdom can eradicate all hindrances that lie in our paths. The poem teaches and inspires one to fight for good and never to give up until one succeeds.

Dr Thakur belongs to the school of thought that advocates “Art for Life’s Sake”; and therefore, he celebrates ‘life’ and illustrates his ‘day to day experiences’ in his creative write-ups. Whenever Dr Thakur can manage some time between his teaching duties as an Assistant Professor at the Department of English, he indulges in publishing both ‘Academic’ and ‘Creative’ write-ups in noted Journals and Newsletters such as Indian Book Chronicle, Poetcrit, Contemporary Literary Review India, Akshara. His natural inclination is towards the ‘Academic’ writing. Presently, two of his essays are under review to find its place in the most reputed international magazine ‘World Literature Today’.

Dr Thakur finds his inspirations in every author he reads, though celebrated authors Ruskin Bond, Haruki Murakami, Shashi Tharoor, Gita Hariharan, and Paulo Coelho hold a special place in his heart.

Dr Thakur has been working on two major and a few minor projects simultaneously. His latest creations, “Teaching English to Non-English”, a compilation of essays celebrating his personal ESL/EFL Classroom experiences; and “Shadow under the Shade”, a novella with 12 chapters, are expected to hit the bookstores by January 2021.

The Poem:

The ‘WAR’
– Dr Ram Kulesh Thakur

The arrogant Sun mocks my little stature,
Challenges my weak and fragile form;
I stand firm to show the worth of a pure Soul,
Prepare for the tussle Great;
He shines Hot, I absorb the heat intense;
He comes down with all blaze, I disappear slow;
He boasts his victory Grand, roars High;
The world surrenders to his Will and Grace;
At once, it grows dark, the birds chirp;
The delight to each floats on air,
They look to the Savior above:
To see a CLOUD, that was a water-drop.

Dr. Nimai Mishra

Dr. Sudipta Ghosh

Dr. Ayesha Parveen Haroon

Dr. Ghanshyam S. Bopche

Dr. GVP Bhagath Singh