Faith (Yakeen) and Doubt (Waswasa)

TITLE: 5G TECHNOLOGY OF MOBILE COMMUNICATION

ABSTRACT

5G is set to be a trend-changing technology due to the benefits it carries such a smart health care (5G-smart diabetes, remote surgery), automotive (self-driving cars) and Business (virtual reality) to name a few examples. The currently used cellular technologies, 3G and 4G LTE networks, have limitations in latency, data rates, signal throughput, frequency spectrum and capacity. Although 5G network is expected to overcome these limitations, but they still pose a considerable challenge. This proposal, proposes methodology for overcoming the loss of signal and coverage phenomenon, as well as, focuses on beam forming techniques in massive MIMO and the implementation of a heterogeneous network to get high data rates.

LITERATURE REVIEW

The interest in millimetre wave frequency band (30-300 GHz) for cellular technology such as 5G networks started a few years back [1]. Conventional microwave communication signals which operate at carrier frequency below 6 GHz have a high wavelength as compared to shorter wavelength of millimeter wave signals. This leads to a high path loss for millimeter wave signals even if all conditions for both are same. Millimeter wave frequencies have potential for sending extremely high data rates in cellular networks, however there are some major technical challenges such as signal loss leading to coverage issues [2, 3]. 5G networks are expected to provide better coverage than its predecessors owing to high demand of customers [4]. However, many techniques being sought to overcome coverage and signal loss issues are not implemented and remain in testing stages.
On the other hand, millimetre wave frequencies enable the deployment of a massive MIMO antenna array due to immense physical size of this array, calculating the frequency responses of the actual propagation channels [5]. Beamforming is considered a process designed to generate the radiated beam patterns of the antennas by constructing the processed signals in the azimuth of any desired terminals and cancelling beams of interfering signals [6]. Massive MIMO can be considered as a form of beamforming, since beamforming can be used in transmit and receive antennas for cellular frequency bands giving the same effect as propagation properties of millimetre wave band [7, 8]. Beamforming not only provides narrow bandwidth and high spatial selectivity [9] but also spectral efficiency while eliminating inter-cell interference in a MIMO array [10]. However, even in presence of few beamforming techniques such as analog, digital, hybrid, omni directional etc, there exists a need for a technique suitable for all scenarios [6].
Heterogeneous networks will play an important role in providing high data rates in ultra- dense environment, as these networks are composed of low power Base transceiver stations (BTS) [11, 12]. Different types of BTS’s, such as macro-, micro-, pico-, and femto-BTS’s can form a Heterogeneous network as they are considered necessary to enhance capacity of an operating network while being properly managed [13]. The energy efficiency can be maximized in hybrid heterogeneous network with femtocells overlaid on a macrocell, the outer layer ensures higher data rates in the femtocells [14, 15]. To use different frequencies for radio capacity, the Co-channel frequency deployment will use the same frequency in different layers of Heterogeneous networks [16]. To achieve high data rates, the indoor users only need to communicate with indoor wireless access points (not outdoor BTS’s) and many technologies can be utilized that are suitable for short-range communications forming part of heterogeneous network [17].

RESEARCH QUESTIONS

1. How can we use the millimetre wave frequencies to overcome the uncertainty of coverage and signal loss in 5G network?

2. Is it possible to use beamforming techniques to address the issues concerning massive MIMO deployment?

3. How can we achieve high data rates in 5G technology by employing a cellular heterogeneous architecture?

SIGNIFICANCE

The annual growth rate for traffic volumes between the years 2012–2016 was 78% but the industry is set to prepare for a huge 1000-fold of data traffic increase for 2020 and 10000-fold increase in 2025, envisioned through 5G network [6, 16]. Broadcast of data (in Gigabits) to supporting almost 65,000 connections is expected from 5G technology with an astounding connection speed of 25Mbps [18]. This will be a major leap from 4G technology which provides a connection speed between 5 to 12 Mbps. The high data rate makes real-time video applications possible, a significant expectation from 5G networks, which was not possible in 4G and previous networks.[19]

CONNECTION TO THE CURRENT BODY OF KNOWLEDGE

The bandwidth used by mobile networks (2G, 3G, 4G) currently is smaller than 780 MHz and most cellular operators have only a total of about 200MHz spectrum. This bandwidth cannot be considered sufficient for transferring high data rates to multiple devices, but millimetre wave bands have large chunks of bandwidth available [2]. Millimeter wave channels encounter some propagation effects, such as atmospheric absorption for longer links, reflection on rough surfaces and poor diffraction [3]. The millimetre wave backhaul systems and BTS’s will be installed together in dense urban, urban, suburban and rural areas leading to high losses in signal propagation affecting coverage[20]. I aim to use proper design of channel state feedback algorithms, link adaptation schemes and beam-tracking algorithms, as well as ensuring efficient design of MAC and Network layer transmission control protocols (TCP) that induce re-transmissions, since scattering of signals from rough surfaces may introduce large signal variations over very short travel distances. This answers my first research question.

Massive MIMO signal processing can be performed locally at each antenna which gives a distinctive advantage of conjugate beamforming and matched filtering [5]. Massive MIMO provides high beamforming gain which makes up the larger propagation loss in the higher frequency bands while also spatially multiplexing a larger number of data streams but the deployment of digital beamforming in massive MIMO antenna systems is a big challenge because of its complexity, energy consumption, and cost [6]. I plan to use Adaptive arrays which are beam steerable because a larger antenna gain at higher frequency will require adaptive beam steering for use at both the BTS and UE(user equipment), instead of a usually mobile antenna with lower gain. The beam steerable antenna technology can calculate directions of arrival and then direct beam patterns to mitigate interference to capture the signal of interest. This answers my second research question.

Heterogeneous networks use the small cells consisting of Pico-cells, Femto-cells etc, featuring different capabilities such as transmission powers, coverage, and deployment scenarios [12]. Since Heterogeneous network includes a coexistence of Base Stations (BTSs) which are different coverage, radio resources, and energy requirement, therefore, the energy consumption of heterogeneous network can be inconsistent and very high as the number of small BTS’s in network increase [14]. I am going to propose the use of Remote Radio Heads (RRH’s) linked with Baseband Units of Radio Access Network equipment. RRH can be utilized to support high data rates transmissions without the use of physical cell identifier (PCI). The RRH can cover the hot spots requiring huge data rates as some communication technologies such as (IEEE 802.11 ac/ad, millimeter wave communication, and even optical communication) in the physical layer can be adopted in RRHs to improve transmission bit rates. This answers my third research question.

EXPECTED OUTCOMES

The concluding benefits of this proposal for 5G technology will help in generating more traffic and data rates through heterogeneous networks since in 2014, 60% voice traffic and 70% data traffic occurred indoors but in the 5G technology, the indoor usage and hotspot traffic may approach 90% [16]. The millimetre wave spectrum is expected to be 10–100 times cheaper per Hz than the 3G and 4G spectrum under 3 GHz. Deployment of small cells is expected be 10–100 times cheaper and more power efficient than typical BTS [21]. Therefore this proposal is not only technologically efficient but also cost effective.

REFERENCES

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[17] C. X. Wang et al., "Cellular Architecture and Key Technologies for 5G Wireless Communication Networks," IEEE Communications Magazine, vol. 52, no. 2, pp. 122-130, Feb 2014.

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[19] M. Jaber, M. A. Imran, R. Tafazolli, and A. Tukmanov, "5G Backhaul Challenges and Emerging Research Directions: A Survey," IEEE Access, vol. 4, pp. 1743-1766, 2016.

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[21] J. G. Andrews et al., "What Will 5G Be?," IEEE Journal on Selected Areas in Communications, vol. 32, no. 6, pp. 1065-1082, Jun 2014.