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