How LTE450 Works

The Radio Access Network

The LTE radio access network, formally termed the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), consists of base stations called eNodeBs (evolved Node Bs, often written eNB). Each eNodeB manages one or more radio cells, controlling the transmission and reception of radio signals within its coverage area. Unlike earlier mobile architectures where base stations were coordinated by a separate Radio Network Controller (RNC), in LTE the eNodeBs are largely autonomous and communicate directly with one another over the X2 interface to support handover and coordination.

An LTE450 eNodeB operating at 450 MHz will typically be a macro base station – a full-height installation on a mast, tower or rooftop, capable of covering tens of kilometres. The base station comprises the baseband processing unit (BBU) and one or more remote radio units (RRUs) or remote radio heads (RRHs) mounted close to the antennas to minimise feeder cable losses. The antenna system at 450 MHz must physically accommodate the longer wavelength: a half-wave dipole at 450 MHz is approximately 33 cm long, meaning MIMO antenna arrays are substantially larger than at higher frequencies.

OFDMA at 450 MHz: Channel Bandwidth Constraints

LTE uses OFDMA (Orthogonal Frequency Division Multiple Access) in the downlink. The radio channel is divided into multiple subcarriers, each 15 kHz wide. These subcarriers are grouped into Resource Blocks (RBs), each comprising 12 subcarriers over one 0.5 ms slot. The number of available resource blocks depends on the channel bandwidth: a 5 MHz channel provides 25 RBs; a 3 MHz channel provides 15 RBs; a 1.4 MHz channel provides 6 RBs.

At 450 MHz, the available spectrum is relatively narrow. The channel bandwidths available are typically 1.4, 3 or 5 MHz, compared to 5, 10, 15 or 20 MHz at higher LTE bands. This limits the peak throughput achievable per cell, but for the utility and IoT applications that LTE450 serves, this is not a significant constraint. A 5 MHz LTE450 cell can comfortably support tens of thousands of smart meters, each sending a few kilobytes of data per day, while simultaneously carrying SCADA traffic for dozens of substations and telemetry streams for hundreds of remote assets.

FDD Operation: Uplink and Downlink Separation

LTE450 deployments universally use Frequency Division Duplex (FDD) operation, where the uplink (device to base station) and downlink (base station to device) transmissions occur on different frequencies simultaneously. The frequency separation – the duplex spacing – is defined in the band plan: for Band 31, it is 10 MHz; for Band 72, it is also 10 MHz. This separation prevents the transmitter from interfering with the receiver in the same device and allows simultaneous full-duplex communication.

FDD is preferred over Time Division Duplex (TDD) for LTE450 utility applications because it provides more predictable latency. TDD systems alternate between uplink and downlink time slots, introducing a frame-synchronisation dependency that can add jitter to latency-sensitive applications such as protection relaying. For SCADA and smart grid applications requiring sub-20 ms latency, FDD’s inherent symmetry and predictability is advantageous.

Link Budget: Why 450 MHz Achieves Greater Range

The link budget determines the maximum allowable path loss between a transmitter and receiver, which in turn determines the maximum cell radius. The link budget equation is: MAPL = TxPower + TxGain – TxCableLoss – RxNoiseFigure – SINR_required – Implementation_margin + RxGain.

At 450 MHz, two factors improve the link budget compared to higher bands. First, the free-space path loss is lower: for a given distance d, FSPL (dB) = 20log10(d) + 20log10(f) + 20log10(4π/c). With f = 450 MHz versus 900 MHz, the FSPL is 6 dB lower. Second, the antenna gain achievable with physically larger antennas at 450 MHz tends to be higher for a given physical size relative to wavelength.

In flat rural terrain, LTE450 base stations routinely achieve cell radii of 50-80 km. In hilly or forested terrain, the effective range is typically 20-40 km. Actual deployments in Germany and Finland have demonstrated coverage from individual sites of over 100 km under optimal propagation conditions (flat terrain, over water).

Evolved Packet Core for Private LTE450 Networks

The Evolved Packet Core (EPC) is the brain of the LTE network – the set of network functions that handle authentication, session management, QoS policy, routing, and interconnection with external data networks. In a public mobile network, the EPC is operated by the mobile network operator in carrier-grade data centres. For private LTE450 networks, the operator deploys their own EPC, either on-premise (at their own data centre or primary site), in a private cloud, or as a managed service from a specialist vendor.

The key EPC components are the Mobility Management Entity (MME), which handles signalling and authentication; the Serving Gateway (S-GW), which routes user data; the Packet Data Network Gateway (P-GW), which connects the network to external IP networks; and the Home Subscriber Server (HSS), which stores subscriber profiles and authentication credentials. For a private LTE450 utility network, the HSS holds the credentials for every SIM in every connected device, and the P-GW controls routing to the utility’s operational technology (OT) network and corporate IT systems.

Quality of Service Management

One of the most important advantages of a private LTE450 network over public mobile is QoS control. In LTE, QoS is managed through EPS Bearers, each assigned a QoS Class Identifier (QCI) that determines its priority, packet delay budget, packet error rate, and whether it is Guaranteed Bit Rate (GBR) or Non-GBR. The network operator can assign specific QCIs to different application types, ensuring that protection relaying traffic (requiring sub-20 ms latency) always takes priority over bulk AMI meter reading data.

In a private LTE450 network, the operator has full control over QCI assignment. This is impossible on a public mobile MVNO arrangement, where the network operator’s QoS policies are fixed and shared with all customers. This controllability is a key reason why mission-critical utility operators choose private LTE450 over public MVNO arrangements.