Radio Access Network (RAN)
The state-of-the-art RANs for rural access, as provided currently by small-scale commercial wireless ISPs (WISP), use point-to-multipoint WiFi (e.g., Ubiquiti’s AirMAX) or lower-cost LTE (e.g., Baicells) equipment in the CBRS (3.5 GHz) bands. All such equipment is deployed on large towers allowing for wide-area coverage. We seek to push the boundaries of RAN through the installation and deployment of two primary access technologies: 1) OpenCellular, a novel open-hardware LTE solution, to allow for exploration of LTE-License Assisted Access (LTE- LAA) WiFi coexistence and Narrowband IoT (NB-IoT) and 2) 60 GHz mmWave massive MIMO radio interfaces (developed by co-PI Zhang and AirFide Inc.) for high-speed connectivity for drones and users when near towers.
OpenCellular
OpenCellular (OC) is a software-defined radio (SDR) open-hardware implementation of a cellular access point developed by the Telecom Infrastructure Project (TIP) and Facebook. The hardware itself is customizable and capable of running a variety of open- source implementations including SRSlte (LTE) and Osmocom (GSM) and operations in different bands depending on the frontend installed.
- LTE-License Assisted Access (LTE-LAA)
- LTE-LAA, defined in 3GPP Rel.13, enables LTE operation in unlicensed bands using a “Listen Before Talk” contention protocol to coordinate spectrum access with nearby 802.11 networks.
- Used to provide in-building access for our partners with larger campuses, allowing us to explore and test coexistence mechanisms in a real world environment
- Explore outdoor coverage in unlicensed bands
- NB-IOT and LoRa
- The second OpenCellular component of WiNEST is supporting the wide-area Internet of Things (IoT) through the use of Narrowband IoT (NB-IoT), a Low Power Wide Area Network protocol and LoRA.
- NB-IoT is a low power extension to LTE, specified in LTE release 13
- LoRA is a similar competing protocol, operating in the sub-gigahertz bands and capable of extreme wide-area coverage
mmWave
WiNEST will also deploy multi-Gbps portable mmWave radio for air-to-ground drone networking or last-hop wireless fiber access. We will develop two versions with different levels of programmability and bit-rate.
The mmWave radio V1.0 will be based on professor Xinyu Zhang’s recent work, which enabled partially programmable 802.11ad radios. Each radio provides 4 Gbps rate at short range and 400 Mbps even at around 500m.
Edge Compute
Each tower, already home to the access points and backhaul, will also be equipped with lightweight edge computing capabilities that allows for flexible placement of services near specific users and application domains. This function will leverage PI Banerjee’s existing ParaDrop project that provides lightweight virtualization using multiple container technologies, and a framework to easily deploy new services for experimentation.
Spectrum Monitoring & Dynamic Spectrum Access (DSA)
Given that spectrum sharing between licensed and unlicensed parties will be a necessity in several scenarios (e.g., LTA- LAA), as well as supporting general network operations and planning, we will deploy spectrum monitoring units (for collection of spectrum use measurements) and build databases and analytic tools to enable DSA. The spectrum sensors will be deployed in three form factors:
- co-located with our base stations and hotspots
- vehicle-mounted (both terrestrial and purpose-deployed aerial ones)
- handheld portables
Backup: COTS 5G
Though we provide a variety of RAN solutions, all of the above require engineering and development and thus introduce some technical risk. To mitigate this, we will be sourcing Nokia 5G NR access points though they will likely not be connected to the management platform due to their “black box” nature.
Backhaul
The state of the art in backhaul for rural networks is either unlicensed microwave built on the 802.11 protocols (e.g., Ubiquiti’s AirFiber) or licensed microwave in the 6 GHz or 11 GHz bands, placed line-of-sight towers, potentially located kilometers apart.
X’s Long-Range FSOC Backhaul Radio
We will employ the Free Space Optics Communication (FSOC) technology from X (formerly Google X) to establish ultra-high-rate, long-range optical backhaul links.
FSOC provides a custom-built RFIC, radio front-end, and directional antenna module, all working at the 193 GHz spectrum. Under clear-weather conditions, FSOC can achieve 20 Gbps peak rate at a distance of 20 km.
Backup — Commercial Microwave Backhaul Radio
For backhaul reliability, we will co-locate each FSOC radio with a microwave-band backhaul radio from Ariat Networks, that can reach 50 km range, with a maximum bit-rate of 1 Gbps.
Network Core
Resource isolation is crucial for experimentation, and we plan to include an SDN swtich with each WiNode tower site to support appropriate isolation on the paths. While wireless resource isolation is a hard problem in general, the advantage in WiNEST is that rural environments typically have less interference and contention, and so many simple resource management approaches will work. In particular, we will utilize APIs provided by each technology, e.g., FSOC, OpenCellular, and others, to appropriately configure node parameters to meet such goals.
OpenAirInterface
OpenAirInterface is the defacto standard open-source implementation of the LTE EPC. Maintained by Eurocom, it has been in use among the research team for the last six months in an active deployment in rural Indonesia serving dozens of active customers [JSJ+2018]. This particular deployment involved the hardening of the OAI codebase, in partnership with Facebook, to make it more “production-ready” and stable. Despite this, more extensions are needed to make the OAI EPC support the WiNEST platform goals, including extensions for NB-IoT support, integration into the management platform, development of research infrastructure, and any other research designs suggested by the research community. We believe the contribution to the open-source OAI code base will be a core enabler of wireless connectivity projects both inside and outside of the WiNEST platform.
Backup COTS EPC
Because of the known limitations of the OAI EPC, we will include a backup commercial off-the-shelf EPC to support the network in case of OAI outages. Primarily, it will operate as a “bridge” between the desire for cutting edge functionality at the RAN and the eventual implementation of those services in the core network. The COTS EPC will also operate the COTS 5G NR access points and a provide SON spectrum coordination solution. As a backup component, the COTS EPC will not be configurable via the management platform.
Use of Unmanned Aerial Vehicles
WiNEST will incorporate retrofitted and/or custom-built UAVs as aerial basestations operating either as
- an extension to existing cellular network via operations as network relay or
- part of a multi-UAV ad-hoc network.
As such, operational modes will vary from tethered UAV (for power and connectivity) hotspots to operation over a wider area using a swarm with mission planning. Software defined UAV nodes will enable experiments with network protocol stack, to demonstrate the above operational modes that will necessarily rely on spectrum sharing in 4G/5G bands since no separate allocations have been identified for UAV operations. Hence the network management system will need to incorporate UAS management component, involving both UAVs and ground-based nodes for enabling efficient and secure mission plans.
WiNEST will incorporate software-defined (SD) drones and ground station nodes in support of various WiNEST Concept of Operations. Each node will be equipped with a custom SD radios and protocol stack, a low power onboard processor for performing onboard guidance computations, and a vision sensor for basic collision avoidance. The onboard avionics will house stable autopilot code, the SDR and guidance computer will house new software that allows experimentation with protocol stack concepts.