Tutorial 9: 5G Networks and Emerging Mobile Technologies

eMBB (Enhanced Mobile Broadband), URLLC (Ultra‑Reliable Low‑Latency Communications), and mMTC (Massive Machine‑Type Communications).

FR1: sub‑6 GHz (including bands up to 7.125 GHz), and FR2: millimeter wave (24.25 GHz to 71 GHz).

A Resource Block (RB) consists of 12 consecutive subcarriers in the frequency domain.

15 kHz (µ=0) is the basic SCS, and other spacings are 15 × 2^µ kHz (µ=1,2,3,4 giving 30, 60, 120, 240 kHz).

AMF handles registration, connection management, mobility management, paging, and access authentication.

SMF (Session Management Function).

Network slicing enables the creation of multiple logical networks (slices) on a common physical infrastructure, each optimised for a specific service (e.g., eMBB, URLLC, mMTC) with isolated resources and QoS.

UPF is the user‑plane anchor that routes and forwards packets, applies QoS policies, and serves as the interface to the data network (e.g., Internet).

It increases SINR by focusing energy towards the user, improves coverage, and enables spatial multiplexing (MU‑MIMO), boosting capacity and spectral efficiency.

1 ms (or less) for the air‑interface latency, and end‑to‑end latency under 5 ms with edge computing.

A mini‑slot is shorter than a regular slot (e.g., 2, 4, or 7 symbols) and allows for ultra‑low‑latency transmissions without waiting for the slot boundary.

LDPC (Low‑Density Parity‑Check) codes, which offer high performance and low decoding complexity.

NSSF selects the appropriate network slice for a UE based on the requested S‑NSSAI (Single‑Network Slice Selection Assistance Information) and the UE's subscription.

Wi‑Fi 6E opens up the 6 GHz band (5.925‑7.125 GHz) providing more spectrum, less interference, and more channels, enabling higher throughput and capacity.

LEO satellites orbit at lower altitudes (500‑2000 km) compared to GEO (~36,000 km), resulting in much lower latency (20‑50 ms vs. 600 ms) and better signal quality.

PCF provides policy and charging rules for the network, including QoS policies, traffic steering, and charging control.

AUSF performs authentication of the UE using 5G‑AKA or EAP‑AKA protocols.

NSA uses 5G NR for data but relies on the LTE core (EPC) and LTE for control signalling. SA uses the 5G core (5GC) and NR for both control and data, enabling network slicing and full 5G capabilities.

20 Gbps (theoretical peak, under ideal conditions).

1 million devices per square kilometre.

UDM manages subscriber data, including authentication credentials, subscription profiles, and service authorisation.

MEC brings compute and storage resources to the network edge (near the UE), enabling low‑latency applications, local data processing, and reduced backhaul traffic.

Polar codes have excellent performance for short block lengths and low latency, making them ideal for control signalling (e.g., PDCCH).

Beam management includes beam sweeping, measurement, reporting, and switching to ensure that the gNB and UE maintain the optimal beam pair for communication, especially in mmWave where beams are narrow.

NWDAF provides network analytics (e.g., traffic patterns, user behaviour, performance predictions) to assist in network optimisation, slice management, and service assurance.

For 30 kHz SCS, slot duration = 1/30 kHz = 0.5 ms (2 slots per ms). Each slot has 14 symbols. PRBs = 273. REs per slot = 273 × 12 × 14 = 45864. Bits per RE = 8 (256‑QAM) × 0.925 = 7.4 bits. With 4 layers: 45864 × 7.4 × 4 = 1,357,694.4 bits per slot. With 2 slots per subframe (2 ms? Actually subframe is 1 ms, so for 30 kHz, there are 2 slots per 1 ms), so bits per subframe = 1,357,694.4 × 2 = 2,715,388.8 bits. For 1000 subframes/sec, rate = 2.715 Gbps. With 10% overhead, ≈ 2.44 Gbps. For 60 kHz, slot duration 0.25 ms, 4 slots per ms; similar calculation yields higher rate but limited by bandwidth.

A URLLC slice for factory automation dedicates: 1) RAN: reserved resource blocks, shorter scheduling intervals (mini‑slots), and prioritised HARQ. 2) Transport: dedicated bandwidth with low‑latency routing. 3) Core: dedicated UPF and SMF with low‑latency processing. QoS is guaranteed via slice‑specific QoS parameters (5QI for URLLC), isolation from other slices, and admission control.

CP‑OFDM is the default waveform for both DL and UL, offering high spectral efficiency but higher PAPR. DFT‑s‑OFDM (also known as SC‑FDMA) is used for uplink when coverage is a concern because it has lower PAPR, allowing the power amplifier to operate more efficiently, improving cell‑edge performance.

Gain = 10 × log10(64) = 10 × 1.806 = 18.06 dB. In free‑space, path loss ∝ d², so a 18 dB gain corresponds to a distance increase of 10^(18/20) = 10^0.9 ≈ 7.94 times (for the same received power).

1. UE sends RRC setup to gNB. 2. UE sends Registration Request (NAS) to gNB, which forwards to AMF. 3. AMF may authenticate the UE via AUSF/UDM. 4. AMF performs location update to UDM. 5. AMF selects SMF and initiates PDU session establishment. 6. SMF allocates IP address and sets up UPF. 7. AMF sends Registration Accept to UE. 8. UE acknowledges.

Wi‑Fi 6: lower cost, easier deployment, higher peak rates (up to 9.6 Gbps with 160 MHz), good for high‑density indoor environments with OFDMA and MU‑MIMO. 5G NR: provides better mobility, lower latency, guaranteed QoS, and can support URLLC. 5G requires licensed spectrum (or shared) and higher infrastructure cost. Hybrid solutions are common.

Flexible TDD allows the configuration of UL/DL slots dynamically based on traffic demand (e.g., more DL slots for video streaming, more UL slots for IoT uplink). This improves resource utilisation and can be adapted to cell‑specific or even UE‑specific needs.

Mini‑slots (2‑7 symbols) reduce the transmission time. HARQ with fast retransmissions (often with incremental redundancy) reduces error rates. Resource allocation is pre‑configured (semi‑persistent scheduling) to avoid contention. Also, ultra‑reliable coding (low code rate) and lower MCS are used to ensure high reliability.

PCF defines QoS policies (e.g., 5QI, ARP, GBR). SMF retrieves these policies during session establishment and configures UPF accordingly. UPF enforces the policies by performing packet marking, shaping, and policing.

LEO satellites provide coverage to remote and rural areas, maritime, and aviation, complementing terrestrial 5G. Challenges: high Doppler shift, longer propagation delays (though less than GEO), and integration with 5GC (support for non‑terrestrial networks – NTN). 3GPP has specified NTN enhancements in Release 17.

BSS coloring assigns a colour (identifier) to each BSS. Stations can detect the colour in the PHY header. If a station receives a frame with a different colour and the signal level is below a threshold, it may ignore the NAV and transmit, allowing concurrent transmissions from overlapping BSSs, increasing spatial reuse.

Wi‑Fi 7 offers 320 MHz channel bandwidth, 4096‑QAM, and multi‑link operation (MLO) which allows aggregation of multiple channels across different bands (2.4, 5, 6 GHz) for higher throughput and lower latency. 5G NR provides better mobility, wider coverage, and URLLC. MLO in Wi‑Fi 7 improves reliability and throughput by using multiple links simultaneously and enabling load balancing.

Rate = (N_PRB × 12 × N_sym × Q_m × R × n_layers × (1 - OH) × N_slots × 1000) / 1e6 Mbps, where N_slots is the number of slots per subframe (depends on SCS: for 15 kHz, 1; 30 kHz, 2; 60 kHz, 4; etc.). Larger SCS gives more slots per ms, increasing the rate, but the bandwidth per RB is the same, and the number of PRBs is limited by the channel bandwidth.

5G‑AKA is an evolution of EPS‑AKA, but with stronger key derivation and protection against downgrade attacks. EAP‑AKA is used for integration with non‑3GPP access. 5G introduces SUCI (Subscription Concealed Identifier) to protect the IMSI, and key separation between different network functions.

Network slicing allows operators to sell dedicated slices to verticals (e.g., automotive, manufacturing) with guaranteed QoS. This opens new revenue streams. Challenges: managing end‑to‑end slices across RAN, transport, and core; ensuring isolation; dynamic lifecycle management; and integration with OSS/BSS.

AI/ML can be used for: 1) Predictive maintenance (detecting anomalies). 2) Dynamic resource allocation (adaptive scheduling, beam management). 3) Traffic prediction for load balancing. 4) Energy savings by switching off cells during low traffic. 5) Automated fault remediation. The NWDAF in 5G provides data for such analytics.

NTN integration addresses coverage extension using satellites. Challenges: high Doppler shift (compensated by frequency pre‑compensation), long propagation delay (affecting HARQ and timers), and limited link budgets. Enhancements include timing advance adjustments, HARQ enhancements, and mobility management for satellite‑handover.

5G uses QoS flows identified by QFI (QoS Flow Identifier) and 5QI values. It supports reflective QoS (where the UE can infer QoS from DL packets). 5G also supports more 5QI values and more granular traffic differentiation, and the SBA allows per‑flow policy control.

The tactile Internet requires latency below 1 ms, ultra‑high reliability, and haptic feedback. 5G URLLC can approach this but with challenges: end‑to‑end latency includes backhaul and core, which may exceed 1 ms. Edge computing (MEC) and deterministic networking are needed. 5G is a step, but complete tactile Internet may require 6G.

Private 5G is a dedicated network for a specific enterprise, offering guaranteed QoS, high security, and local control. Advantages: URLLC, massive IoT, and predictable performance. Spectrum options: licensed (e.g., 3.5 GHz CBRS in US), shared, or unlicensed (5G NR‑U).

EPC uses fixed functional entities and point‑to‑point interfaces, making it monolithic. 5GC uses service‑based architecture (SBA) with microservices, HTTP/2 interfaces, and stateless NFs. This enables cloud‑native: containerization, auto‑scaling, and flexible deployment in public/private clouds.

mmWave offers high bandwidth for FWA, but requires line‑of‑sight and has limited range, so it is best for suburban/rural with clear paths. Challenges: high equipment cost, installation alignment, and weather susceptibility (rain fade). Also, spectrum availability and coverage economics may make sub‑6 GHz more viable.

FR1 bands: n1 (2100 MHz) good coverage, n3 (1800 MHz) widely used, n28 (700 MHz) for rural, n78 (3.5 GHz) prime for capacity. FR2: n257 (28 GHz), n258 (24 GHz), n260 (39 GHz) for dense urban hotspots and FWA. Lower bands offer better coverage, higher bands offer more capacity.

Deploy a private 5G network using 3.5 GHz spectrum. Use network slicing: URLLC slice with dedicated resources (mini‑slots, low MCS, HARQ). eMBB slice with carrier aggregation and high MIMO. mMTC slice with NB‑IoT integrated. Deploy MEC at the factory for low latency. Use a 5GC with local UPF. Ensure high‑capacity backhaul (fiber).