Highlights of ITU-R report: IMT TERRESTRIAL BROADBAND REMOTE COVERAGE

Introduction:

Almost three years in the making (see References below),  this ITU-R report on IMT TERRESTRIAL BROADBAND REMOTE COVERAGE provides details on scenarios associated with the provisioning of enhanced mobile broadband services in sparsely populated and underserved remote areas with a discussion on enhancements of user and network equipment. Mobile broadband access in rural and remote areas can be done by various existing user equipment and additionally, broadband can be delivered also by FWA (Fixed Wireless Access) type of consumer premises equipment (CPEs). It offers technical solutions for certain deployment scenarios prevailing in developing countries and is meant to be used in accordance with the existing regulations in those countries.

In many countries, national policymakers have recognized the necessity to introduce polices and solutions to ensure connectivity in underserved and remote areas.

Further challenges that limit the reach of mobile broadband in sparsely populated areas are, for example, infrastructure requirements, backhaul connectivity, operation and maintenance, sparse distribution of population and so on. However, some of the remote areas have industrial plants, excavation units and mining with temporary human occupancy or shelters, which would benefit from broadband connectivity.

Remote coverage might in the future be driven by the need for national security and public safety connectivity, intelligent traffic systems, internet of things, industry automation and end users need for home and commercial broadband services as an alternative to fiber connections. In order to fulfil the needs of remote coverage, it is important to identify viable solutions for mobile and fixed wireless broadband services.

Solutions that support remote sparsely populated areas providing high data rate coverage:

Possible technical solutions to achieve both extended coverage as well as high capacity in remote areas could be to use dual frequency bands at the same time, one lower band for the uplink (UL) and one higher band for the downlink (DL), in aggregated configurations.

Combining spectrum bands in the mid-band range (1-6 GHz) and the low-band range (below 1 GHz) on an existing grid can provide extended capacity compared to a network only using the low-band range.

An alternative technical solution to provide extended coverage in a remote area using existing or reduced number of terrestrial base station (BS) sites requires careful selection of proper locations and technical characteristics compared to configurations of suburban networks. Realizing such extended network configuration for coverage, several considerations need to be taken into account, both at a BS site and at customer premises. Considerations of accommodating BSs on high towers

in sparsely populated areas could be further studied1. Performance limitations usually arise in the uplink, arising from the handset designs : higher noise figure and, (due to regulation) limited transmission power of 23 dBm. Such large cell designs therefore typically rely on the use of external customer premises equipment (CPE) with large gain antennas, and high processing and computation power and stable power supply.

In order to extend broadband services to remote areas, IMT systems can benefit by employing high gain antennas.. One proposed solution is to use a few high-gain (up to 29.5 dBi), narrow beam x-pole antennas on a strategically placed high ground tower, where power and backhaul exist. Each of the very high gain antennas (VEGA) can cover a 15 to 35 km range, depending on deployment parameters like frequency, antenna height, ground surface and vegetation. See also in ITU-D 2021 final Report ‘Telecommunications/ICTs for rural and remote areas). The directive antennas improve the quality of service by increasing the signal-to-noise ratio (SNR) and Eb/N0 of the downlink (DL) and uplink (UL) signals.

Note 1. Such opportunities rest with traditionally high tower used for analogue or digital television with an average inter-site distance (ISD) of the order of 60 km to 80 km designed to provide blanket coverage of national terrestrial television services.

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Such very high gain multi-beam antennas provide gain, wider combined beamwidth, as well as broadband with a three-fold capacity, wherever needed. One tower implementing several high-gain beam-antennas, each providing high quality service to its dedicated target area, saves the necessity of additional building, maintaining (and guarding) several towers, each with a full BS and microwave backhaul or a fiber link. For these reasons, these antennas operate in remote sites, to cover those distant underserved communities at a shorter time.

With potential enhancements of base station (BS), user equipment (UE), and customer premises broadband configurations, it is deemed feasible to deploy a standalone network in the bands identified for IMT within the in 1-6 GHz range (see revision 6. of Recommendation ITU-R M.1036 -not yet completed/agreed) providing high capacity and coverage over tens of kilometres in remote sites. This could potentially be a promising solution for bringing IMT broadband (e.g., IMT‑2020/5G) in remote sites.

Aggregation of carriers from existing 4G LTE in low-band with 5G New Radio (NR) in the bands identified for IMT within the mid-range (~1-6 GHz) can provide such extended coverage along with capacity enhancement.

Generally, at a BS site, the antenna height, the radio frequency output power and antenna gain impact the coverage and capacity performance. Effective performance solutions are also represented by a high level of antenna sectorization, high antenna beamforming gain, and the use of Multiple Input Multiple Output (MIMO) antennas, as well as the use of carrier-aggregation. Furthermore, additional spectrum bands and bandwidth, and usage of redundant signalling protocol will improve performance.

Extending cell-coverage is limited by the uplink performance. Enhancing UE transmission capabilities is key to enabling extended coverage along with the Downlink coverage. For a fixed wireless broadband deployment in a “wireless fibre” configuration, using an outdoor directional antenna mounted line-of-sight (LOS) to the BS antenna site extends the coverage range significantly by avoiding building penetration losses. Conventional, mobile devices are UEs with power class of maximum 23 dBm transmit power. At higher carrier frequencies in the mid-band (between 1-6 GHz), a standalone network will be limited by uplink coverage than the downlink when deployed for extended coverage in remote areas. Hence, it is important to provide adequate extended coverage in the UL direction for the users located at the cell edge along with DL enhancements by using the dual band carriers in the deployment.

It is assumed that conventional IMT antenna arrangements are used for the UL system. For the DL, IMT-2020/5G bands identified for IMT within the in 1-6 GHz range, an antenna array is assumed to have 64 dual-polarized antenna elements installed on very high television towers. The considered ISD is regarded to be representative for a conventional 2G network grid. For extended coverage, adding a new band from bands identified for IMT within the 1-6 GHz range for mobile and fixed wireless broadband connectivity, networks can clearly deliver on the promise to increase on the coverage requirements for IMT-2020/5G services, but only adequately in the DL direction. This additional band also helps distribute the UL traffic through the 4G low-band at the cell-edge.

With dual bands, a very high gain antenna covering all lower bands as well as bands in 1-6 GHz enables easy implementation of the carrier aggregation, as well as strong DL on the higher bands (and good UL using the lower bands). The solutions employing a higher BS or UE power or other parameters/values different than typical deployments, should be used in accordance with the existing regulations of those countries.

Figure 1. Remote Coverage using High Gain Multi Beam Antenna

References:

ITU-R Report: Terrestrial IMT for remote sparsely populated areas providing high data rate coverage

ITU-R work in progress: Providing enhanced mobile broadband services to remote sparsely populated and underserved areas

Editor’s Note: This is an excerpt of an ITU-R working document, subject to significant revision(s). It has no official status and has NOT been approved by ITU-R WP5D.  ITU TIES account holders may access the document on the ITU-R WP 5D website as an October 2020 meeting contribution .

ATDI proposes to insert text (not included here) at Section 4 ‘Solutions that support remote sparsely populated areas providing high data rate coverage’ of the Draft Working Document.

Why this is an important topic:  

Many people in developing countries like India live in villages or rural areas.  In most cases they have little or no mobile broadband coverage. 

In the U.S., the  Federal Communications Commission (FCC) estimates that 26.4% of rural America, or 16.9 million people, lack access to a broadband connection of 25Mbps downstream/3Mbps upstream. This has been proven to be a highly conservative estimate because of the way the FCC collects broadband data. More accurate studies suggest the FCC’s estimates could be off by upwards of 50%. A 2017 study by Microsoft, for instance, found that half of all Americans, or 162.8 million people, lack access to broadband. Also, many wireless telcos are hesitant to roll out mobile broadband to rural America because of a perceived lack of return on investment.

According to data from the FCC, 39% of people living in rural areas in the United States lack access to high-speed broadband, compared with just 4% of urban Americans.

In addition to using IMT 4G/5G for mobile communications (discussed in the draft report below), 5G Fixed Wireless Access (FWA) will make a significant impact on global markets, both developing and developed.  In the U.S., sparsely populated, rural areas currently lag far behind metro area cities in broadband access.  As there is no standard for 5G FWA, it will likely be based on the enhanced Mobile Broadband use case for IMT 2020, or proprietary versions of IEEE 802.11ax (WiFi 6).

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Introduction:

On a global basis, the total number of mobile subscriptions was around 8 billion in Q3 2019, with 61 million subscriptions added during the quarter, the mobile subscription penetration is at 104 percent. There are 5.9 billion unique mobile subscribers using mobile networks, while 1.8 billion people remain unconnected. In year 2025 it is forecasted to be 2.6 billion 5G subscriptions and 8.6 billion mobile subscriptions globally at a penetration level of about 110%1. In year 2025 there may be up to 6.8 billion unique mobile subscribers using mobile networks, while 1.5 billion people remain unconnected, many of whom are below the age of nine.

The prospect of providing mobile and home broadband services for most of the 1.5 billion unconnected people, living in such underserved rural areas, is largely related to techno-economic circumstances.

This Report provides details on scenarios associated with the provisioning of enhanced mobile broadband services to remote sparsely populated and underserved areas with a discussion on enhancements of user and network equipment.

1 Ericsson Mobility Report, November 2019, mobile broadband includes radio access technologies HSPA (3G), LTE (4G), 5G, CDMA2000 EV-DO, TD-SCDMA and Mobile WiMAX.

Background:

Deploying networks in remote areas is normally more expensive, and at the same time, expected revenues are lower in comparison with deployments in populated areas. A further reason for not being incentivized to deploy new IMT broadband (e.g. IMT-2020/5G) Base Stations (BS) in these areas is the expected number of new BS sites. Therefore, the total economic incentives to deploy traditional networks in sparsely populated areas are consequently narrowed.

The competition model, applying to densely populated areas, is normally not providing rural coverage expansion at a speed that society wish. Connectivity in underserved remote areas is important to national policy makers facing needs of consumers, to service providers for reasons of branding, and to satisfy regulatory conditions in countries.

When expanding coverage in remote areas, it may imply an undesirable local monopoly, suggesting that only one service provider would expand in to such a remote area due to a low consumer base.

Rural coverage might in the future be driven by the need for national security and public safety connectivity, intelligent traffic systems, internet of things, industry automation and end users need for home broadband services as an alternative to fiber connections. In order to fulfil the needs of rural coverage, it is a matter of urgency to identify viable solutions for mobile and home broadband services.

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Solutions that support remote sparsely populated areas providing high data rate coverage:

Possible technical solutions to achieve both extended coverage as well as high capacity in remote areas could be to use dual frequency bands at the same time, one lower band for the uplink (UL) and one higher band for the downlink (DL), in aggregated configurations.

Combining spectrum bands in the mid-band range and the low-band range on an existing grid can provide extended capacity compared to a network only using the low-band range.

An alternative technical solution to provide extended coverage in a remote area using a reduced number of terrestrial BS sites, aiming to bringing cost down, requires careful selection of proper locations and technical characteristics compared to configurations of suburban networks. Realizing such extended network configuration for coverage, several considerations need to be taken into account, both at a BS site and at customer premises. Considerations of accommodating BSs on high towers in sparsely populated areas could be further studied. Such opportunities rest with traditionally high tower used for analogue or digital television with an average inter-site distance (ISD) of the order of 60 km to 80 km designed to provide blanket coverage of national terrestrial television services. 

Other sections of this report: 

  • Analyzing configurations for an IMT broadband network operating in dual bands

Combining spectrum bands in the mid-band range 3.5 GHz and the low-band range, e.g. 600 MHz, 700 MHz or 800 MHz, on an existing grid can provide extended capacity compared to a network only using the low-band range. The reason being that the mid-band range offer access to more spectrum bandwidth, and the low-band range combined, can provide the coverage for cell edge users in a unified manner.

  • Analyzing configurations for an IMT broadband network operating only in the band 3.5 GHz

In underserved remote areas, the DL capacity performance can be significantly improved by using the band 3.5 GHz whilst the UL coverage is representing the bottleneck in attempts of satisfying needs for coverage. With potential upgrades of BS and consumer premises UE configurations, the feasibility of providing improved remote area coverage is considered by using only the band 3.5 GHz. 

References:

ITU-R Report: Terrestrial IMT for remote sparsely populated areas providing high data rate coverage