Wireless, Mobile and Satellite Networks

Introduction

Wireless networks replace a fixed transmission medium with a time-varying radio or free-space channel. This creates mobility, rapid deployment and broad coverage, but also introduces interference, fading, spectrum scarcity, Doppler shift, security exposure and energy constraints. Modern communication systems therefore combine radio propagation models, cellular architecture, packet networking, optimization and distributed control.

This chapter examines cellular, Wi-Fi, ad hoc, mesh, cognitive-radio, low-power wide-area (LPWAN), satellite and non-terrestrial networks. Particular attention is given to 4G/5G architecture, radio-resource management (RRM), mobility and handover, interference, MIMO and beamforming, outage probability, and satellite link-budget and coverage decisions.

Learning Objectives

After completing this chapter, the reader should be able to:

1. Explain cellular architecture and compare 4G EPC with 5G core and RAN functions.

2. Model path loss, fading, interference and outage probability.

3. Analyse scheduling, admission control, power control and spectrum allocation.

4. Explain mobility management, measurement reporting and handover failure mechanisms.

5. Compare Wi-Fi, ad hoc, mesh, cognitive-radio and LPWAN systems.

6. Perform a dimensionally consistent satellite link-budget calculation.

7. Evaluate coverage, capacity, reliability, energy and regulatory trade-offs in terrestrial and non-terrestrial networks.

1. Cellular Architecture and Evolution

1.1 The cellular principle

A service area is divided into cells served by base stations. Frequencies may be reused in geographically separated cells, allowing capacity to scale with area rather than with a single transmitter. The ideal hexagon is a planning abstraction; real coverage follows terrain, clutter, antenna patterns and propagation conditions.

A cellular system contains:

• User equipment (UE): the mobile terminal and its radio functions.
• Radio access network (RAN): base stations, antennas, radio units and control protocols.
• Transport network: fronthaul, midhaul and backhaul connecting radio sites to the core.
• Core network: authentication, mobility, policy, session control and interconnection with external networks.
• Operations systems: configuration, assurance, charging, analytics and security management.

Cell splitting increases capacity by deploying smaller cells, but raises handover frequency and site density. Sectorization reduces interference by using directional antennas. Heterogeneous networks combine macro, micro, pico and indoor cells; however, interference coordination and mobility become more difficult.

1.2 4G and 5G architecture

In LTE, the eNodeB performs radio scheduling, link adaptation, HARQ and much of mobility control. The Evolved Packet Core (EPC) includes the Mobility Management Entity (MME), Serving Gateway (S-GW), Packet Data Network Gateway (P-GW), Home Subscriber Server (HSS) and policy functions. The user plane and control plane are logically distinct, although many functions are integrated in practical deployments.

In 5G, the gNodeB is commonly split into a Central Unit (CU) and Distributed Unit (DU), with a Radio Unit (RU) connected through standardized functional splits. The 5G Core uses service-based functions including the Access and Mobility Management Function (AMF), Session Management Function (SMF), User Plane Function (UPF), Unified Data Management (UDM), Authentication Server Function (AUSF), Policy Control Function (PCF) and Network Exposure Function (NEF). The architecture supports network slicing, edge computing, massive machine-type communication and ultra-reliable low-latency communication (URLLC).

A slice is a logical service configuration with specified performance, security and isolation requirements. It is not automatically a physically isolated network; the degree of isolation depends on implementation, orchestration and resource controls. Multi-access edge computing places selected UPF and application functions nearer to users, reducing latency and backhaul load.

1.3 Air-interface advances

LTE uses OFDMA in the downlink and SC-FDMA, or DFT-spread OFDM, in the uplink. 5G NR uses scalable numerology, in which subcarrier spacing is commonly represented as

Δf = 15 × 2^μ kHz,

where μ is a non-negative numerology index. Larger spacing reduces OFDM symbol duration and can support lower latency, but generally increases sensitivity to phase noise and reduces coverage for a given cyclic-prefix design. The equation describes the nominal subcarrier spacing, not a guarantee of end-to-end latency.

Massive MIMO uses many antenna elements to form spatially selective beams. In time-division duplex systems, channel reciprocity can support downlink precoding after calibration; in frequency-division duplex systems, downlink channel-state information often requires feedback. Beam management includes beam sweeping, measurement, reporting, refinement and recovery.

2. Radio Propagation and Interference

2.1 Link budget and path loss

A received-power model in decibels can be written as

P_r(dBm) = P_t(dBm) + G_t(dBi) + G_r(dBi) − L_p(dB) − L_o(dB),

where L_p is propagation loss and L_o includes feeder, connector, polarization and implementation losses. The free-space path loss between isotropic antennas is

L_FS(dB) = 20 log10(4πd/λ),

provided d and λ use the same length units. This is a line-of-sight reference model and should not be used uncritically in obstructed urban or indoor channels.

A log-distance model is

PL(d) = PL(d_0) + 10n log10(d/d_0) + X_σ,

where n is the path-loss exponent and X_σ is a zero-mean Gaussian variable in dB with standard deviation σ for a lognormal-shadowing model. The model is statistical, and its parameters must be calibrated for the relevant frequency, environment and antenna heights.

2.2 Noise, SINR and interference

For a receiver with bandwidth B, reference temperature T_0 and noise factor F, thermal noise power is

N = kT_0BF,

where k = 1.380649 × 10⁻²³ J/K. In decibels, the familiar −174 dBm/Hz value is an approximation at 290 K before receiver noise figure is added. Alternatively, one may use system noise temperature T_sys and write N = kT_sysB. These are alternative representations: using T_sys must not be combined with a separate F that represents the same receiver noise.

For user i, the instantaneous signal-to-interference-plus-noise ratio is

SINR_i = S_i /(N_i + Σ_j I_{ij}),

where S_i is desired received power, I_{ij} is interference from transmitter j, and N_i is receiver noise power. In a reuse network, interference may be co-channel, adjacent-channel, inter-cell, intra-cell or cross-link interference.

Interference coordination methods include fractional frequency reuse, almost blank subframes, enhanced inter-cell interference coordination, coordinated multipoint, beam coordination, power control and dynamic spectrum partitioning. Each method trades spectral efficiency, coordination overhead, latency and robustness.

2.3 Outage probability

For a target threshold γ_th, outage probability is

P_out = Pr{SINR < γ_th}.

For a noise-limited link with Rayleigh fading, if the average received signal-to-noise ratio is \bar{γ}, the instantaneous SNR is exponentially distributed and

P_out = 1 − exp(−γ_th/\bar{γ}).

This expression assumes a single independently fading branch, a fixed threshold and no interference. It must not be applied directly to MIMO, shadowing, interference-limited or adaptive-modulation systems without an appropriate model. With MRC reception over L independent equal-average Rayleigh branches, the outage is lower and follows a gamma-distribution expression; diversity changes the distribution rather than merely adding a fixed dB gain.

Worked example. Suppose a single-branch Rayleigh link has average SNR 10 dB and requires 3 dB SNR. In linear units, \bar{γ}=10 and γ_th≈1.995. Thus

P_out = 1 − e^(−1.995/10) ≈ 1 − 0.819 = 0.181.

The predicted outage is approximately 18.1 percent under the stated assumptions. Shadowing and interference would generally increase or otherwise alter this value.

3. Radio Resource Management

RRM allocates time, frequency, power, antennas and coding resources while meeting service and fairness constraints. Its main functions are admission control, scheduling, link adaptation, power control, load balancing, interference management and mobility-aware resource reservation.

3.1 Scheduling

A proportional-fair scheduler often assigns a resource to user i according to

M_i(t) = r_i(t)/\bar{R}_i(t),

where r_i(t) is the currently achievable rate and \bar{R}_i(t) is a moving average of past throughput. It balances instantaneous channel quality with long-term fairness. A maximum-throughput scheduler selects the largest r_i(t), increasing cell efficiency but potentially starving cell-edge users. A strict-priority scheduler can protect URLLC traffic but may reduce eMBB throughput.

The optimization objective should reflect service requirements. A weighted utility formulation is

maximize Σ_i w_i U_i(R_i),

subject to power, bandwidth, queue, latency and reliability constraints. Concave utilities often provide a controllable fairness-efficiency trade-off. Real schedulers use approximations because channel states, queues and interference change rapidly.

3.2 Link adaptation and HARQ

Adaptive modulation and coding selects a modulation order and coding rate using channel-state information. Higher-order modulation increases bits per symbol but requires higher SINR. Hybrid automatic repeat request combines forward-error correction with retransmission, usually through soft combining. The target block-error rate, channel-estimation quality, feedback delay and HARQ process limits must be considered jointly.

3.3 Power control and admission

Open-loop power control compensates for path loss and statistical conditions; closed-loop control reacts to measured interference or received quality. Excessive uplink power raises inter-cell interference and battery consumption. Admission control should reject or defer sessions when accepting them would violate existing guarantees. In 5G, policy control and slice-level resource quotas may be combined with real-time RAN control.

3.4 Massive MIMO and beamforming

For a narrowband transmitted vector x and channel matrix H, the received vector can be represented as

y = Hx + n.

A linear precoder forms x = Ws, where s contains user symbols and W is selected using channel-state information. Zero-forcing precoding attempts to suppress inter-user interference when H has adequate rank and channel estimates are reliable. Maximum-ratio transmission maximizes array gain but does not fully suppress inter-user interference. Regularized zero forcing provides a compromise, particularly at finite SNR or with imperfect channel knowledge.

MIMO gains are not unlimited. Correlated antennas, pilot contamination, hardware impairments, channel aging, blockage and calibration errors reduce spatial multiplexing. Beamforming may also create coverage holes when a beam is blocked, making beam recovery and multi-connectivity important.

4. Mobility and Handover

Mobility management maintains registration, reachability, session continuity and location information. A UE performs cell selection when idle and measurement-based cell reselection or handover when connected. Measurements may include reference-signal received power, reference-signal received quality, SINR and neighboring-cell beam quality.

A simplified event-based handover condition is that a neighbor exceeds the serving cell by a hysteresis margin for a time-to-trigger interval. Hysteresis reduces ping-pong handovers; time-to-trigger filters short fades. Excessive values cause late handovers and radio-link failures, while small values cause unnecessary signaling and oscillation.

Handover stages include measurement, decision, preparation, execution and path-switch completion. Failure may arise from insufficient target resources, poor timing, authentication delay, backhaul failure, inaccurate measurements or rapid channel variation. 5G supports conditional handover, dual connectivity and make-before-break procedures to improve reliability, at the cost of additional radio and signaling resources.

Mobility in satellite and high-altitude networks differs substantially. Large footprints may reduce handover frequency, but low-earth-orbit constellations produce frequent satellite changes and rapidly varying Doppler and propagation delay. Seamless service requires ephemeris-aware prediction, timing compensation, gateway diversity and inter-satellite or feeder-link coordination.

5. Wi-Fi, Ad Hoc and Mesh Networks

Wi-Fi is generally infrastructure-based, with stations associated with access points. IEEE 802.11 uses carrier sensing and collision avoidance rather than cellular-style centrally scheduled exclusive access in its traditional operation. Hidden terminals, exposed terminals, contention overhead and unequal airtime affect throughput. Modern Wi-Fi includes OFDMA, multi-user MIMO, target wake time and coordinated operation, but performance remains sensitive to channel occupancy and deployment density.

An ad hoc network has no fixed infrastructure and uses multi-hop forwarding. It is useful for disaster response, military operations and temporary sensing, but topology changes, limited battery power, routing overhead and security are significant constraints. Reactive protocols discover routes when needed; proactive protocols maintain routing information continuously; hybrid schemes combine both approaches.

A mesh network uses multiple forwarding nodes and can be infrastructure-based, client-based or hybrid. Mesh planning must address channel assignment, gateway placement, routing metrics, interference and failure recovery. A shortest-hop route is not necessarily best: a longer route with low interference and high link reliability may provide greater end-to-end capacity.

6. Cognitive Radio and Dynamic Spectrum Access

Cognitive radio systems seek to use spectrum dynamically while protecting incumbent or primary users. A secondary system may sense spectrum, consult a database, or use a coordinated authorization mechanism. Spectrum sensing can be based on energy detection, matched filtering or feature detection. Energy detection is simple but sensitive to noise uncertainty and hidden terminals.

The cognitive cycle consists of spectrum observation, analysis, decision, access and learning. A practical design must specify detection probability, false-alarm probability, sensing time, reporting reliability and incumbent-protection rules. Machine learning can classify signals or predict occupancy, but distribution shift, adversarial manipulation, explainability and insufficient labeled data limit uncritical deployment. Spectrum access remains governed by national regulations and licensing conditions; cognitive capability does not itself grant transmission rights.

7. LPWAN and IoT Connectivity

LPWAN technologies serve sensors requiring small payloads, long battery life and wide coverage. They commonly use narrowband or spread-spectrum signaling, low data rates, duty-cycle or airtime constraints and star-of-stars architectures. Link budgets can be large because of low data rates and receiver processing gain, but latency, downlink availability, capacity and regulatory duty-cycle limits constrain applications.

Typical design choices compare licensed cellular IoT with unlicensed systems. Licensed systems provide managed interference and mobility support but incur subscription and operator dependence. Unlicensed systems may be inexpensive and widely deployable but experience uncontrolled interference and regional regulatory constraints. Confirmed retransmissions improve delivery probability but consume energy and airtime; application-layer acknowledgements should therefore be used selectively.

8. Satellite and Non-Terrestrial Networks

8.1 Orbit and architecture

Geostationary satellites provide apparently fixed coverage and large footprints, but introduce substantial propagation delay. Medium-earth-orbit systems provide a compromise between coverage and latency. Low-earth-orbit constellations reduce propagation delay and path loss but require many satellites, frequent handovers, tracking and inter-satellite coordination.

A satellite system may contain user terminals, payload transponders or regenerative processors, feeder links, gateways, network-control centers and inter-satellite links. Transparent payloads frequency-convert and amplify signals; regenerative payloads demodulate, process and retransmit, enabling more flexible routing but increasing payload complexity.

8.2 Correct link-budget formulation

The carrier-to-noise-density ratio is

C/N₀ (dB-Hz) = EIRP (dBW) + G/T (dB/K) − L (dB) − 10log₁₀(k),

where EIRP is equivalent isotropically radiated power, G/T is receive antenna gain divided by system noise temperature, L includes free-space, atmospheric, polarization, pointing, implementation and other losses, and k is Boltzmann’s constant in joules per kelvin. Since

10log₁₀(k) ≈ −228.6 dBW/K/Hz,

−10log₁₀(k) ≈ +228.6 dB,

so the commonly used form is

C/N₀ = EIRP + G/T − L + 228.6 dB-Hz.

The units are consistent because EIRP is dBW and G/T is dB/K; the Boltzmann term converts the physical noise-density unit into the dB-Hz representation. If EIRP is in dBm, the constant must be used consistently with the chosen power unit.

For bandwidth B in hertz,

C/N = C/N₀ − 10log₁₀(B),

and for bit rate R_b,

E_b/N₀ = C/N₀ − 10log₁₀(R_b),

with all quantities in dB or dB-Hz as appropriate. Required implementation margin, coding/modulation threshold and availability objective determine the design margin.

Free-space loss is

L_FS = 20log₁₀(4πd/λ),

and atmospheric attenuation may include gaseous absorption, rain, cloud and scintillation. At higher frequencies, rain fade can dominate and site diversity or adaptive coding and modulation may be required.

Worked satellite example. Consider a link with EIRP = 50 dBW, G/T = 20 dB/K, total loss L = 205 dB, and bandwidth B = 36 MHz. Then

C/N₀ = 50 + 20 − 205 + 228.6 = 93.6 dB-Hz.

The bandwidth conversion is

10log₁₀(36 × 10⁶) ≈ 75.56 dB,

so C/N ≈ 18.04 dB. If the modem requires 6 dB C/N for the selected waveform and coding, the nominal margin is approximately 12.0 dB before additional availability allowance. This result is illustrative; a real design must include rain statistics, pointing loss, interference, adjacent-satellite constraints and worst-case geometry.

8.3 Coverage and capacity decisions

Coverage is not determined by footprint alone. A usable service region requires adequate received power, acceptable elevation angle, gateway visibility, interference protection, regulatory authorization and capacity. Lower elevation angles increase slant range and atmospheric path length and are more vulnerable to blockage.

A planning workflow is:

1. Define traffic distribution, service rate, availability and latency requirements.

2. Select orbit, frequency band, antenna type and minimum elevation angle.

3. Calculate worst-case slant range and link budget.

4. Model rain, atmospheric, pointing and polarization losses statistically.

5. Evaluate beam geometry, frequency reuse, gateway placement and spectrum coordination.

6. Test handover, congestion and gateway-outage scenarios.

7. Compare capital cost, energy, spectrum fees, terminal complexity and lifecycle risk.

Spot beams improve frequency reuse and capacity but require accurate pointing and beam-handover control. Wide beams simplify coverage but dilute spatial reuse and may increase interference.

9. Applied Case: Hybrid Rural Connectivity

Background

This illustrative case considers a mountainous region with dispersed villages, intermittent terrestrial backhaul and seasonal population changes. A planner must provide public-safety communication, basic broadband and low-rate agricultural sensing.

Problem

A single macrocell cannot economically cover all valleys. Fibre deployment is slow, while a satellite-only solution has higher delay and limited shared capacity. Terrain also creates shadowed areas and unreliable line-of-sight paths.

Analysis

The planner classifies requirements: public safety needs high availability and priority; broadband requires capacity during evening peaks; sensors need long battery life and small messages. A propagation survey identifies ridge-top macro sites, indoor shadow zones and potential gateway locations. Terrestrial links are assessed using measured shadowing distributions rather than free-space loss alone. Satellite links are checked for minimum elevation, rain margin and gateway diversity.

Approach and solution

A hybrid architecture is selected. LTE/5G small cells provide local access at villages, with microwave or fibre where feasible. A satellite feeder link serves remote aggregation sites and provides backup for critical traffic. LPWAN gateways collect agricultural sensor data. Network slicing or policy classes reserve priority resources for emergency traffic. Store-and-forward operation is used for delay-tolerant sensor data, while interactive services are routed through the lowest-latency available path.

RRM uses admission control during peak periods, proportional-fair scheduling for broadband, and priority scheduling for emergency packets. Dual connectivity or make-before-break procedures reduce interruption near coverage boundaries. Solar power and battery telemetry are included in site planning.

Outcome and learning points

The design improves resilience because failure of one backhaul path does not eliminate all service. It also reveals that a nominal coverage map is insufficient: capacity, elevation, rain margin, energy, congestion and handover behaviour determine actual service quality. The principal lesson is that heterogeneous networks should be designed against service-level objectives rather than against radio range alone.

10. Challenges, Governance and Best Practices

Wireless systems must comply with national spectrum allocations, licensing, emission masks, exposure requirements, satellite coordination rules and lawful-intercept obligations. Location and mobility data create privacy risks; data minimization, access control, retention limits and auditable use are essential. Automated RRM can disadvantage users at cell edges or in underserved areas if its training data and objectives are poorly designed.

Security concerns include rogue base stations, signalling attacks, jamming, spoofing, compromised IoT devices, insecure roaming interfaces and supply-chain vulnerabilities. Strong identity management, mutual authentication, key separation, secure boot, software updates and network segmentation are foundational controls.

Best practice includes calibrated channel models, explicit uncertainty margins, drive testing or site measurements, closed-loop performance monitoring, failure-mode analysis, capacity stress testing and independent validation of AI-assisted decisions. Engineers should report assumptions, units, confidence intervals and worst-case conditions rather than presenting a single optimistic coverage value.

Chapter Summary

Wireless and non-terrestrial networks combine radio propagation, shared-spectrum control, packet architecture and mobility management. Cellular systems scale through reuse, sectorization, densification and coordinated interference control. LTE and 5G differ in core-network functions, RAN disaggregation, service-based control, slicing and edge integration. RRM coordinates scheduling, link adaptation, power, admission, beams and handovers under changing channel and traffic conditions.

Path loss and SINR models must be interpreted within their assumptions. Outage probability depends on the fading and interference model; MIMO and beamforming alter both capacity and reliability. Wi-Fi, ad hoc, mesh, cognitive-radio and LPWAN systems make different trade-offs among infrastructure, contention, energy, spectrum rights and mobility.

Satellite design requires a complete link budget. In particular, C/N₀ in dB-Hz includes the Boltzmann term: EIRP + G/T − L + 228.6. Coverage decisions must include capacity, elevation, atmospheric loss, interference, gateway availability, handover and regulation. Hybrid terrestrial–satellite systems often provide the most resilient solution for geographically difficult environments.

Key Terms

Cellular architecture: Division of a service area into radio cells for frequency reuse.

RAN: Radio access network connecting user equipment to the core.

5G Core: Service-based core network supporting mobility, sessions, policy and slicing.

Network slicing: Logical service-specific partition of network functions and resources.

SINR: Ratio of desired signal power to interference plus noise power.

Outage probability: Probability that instantaneous SINR falls below a required threshold.

RRM: Allocation and control of radio, time, frequency, power and antenna resources.

Proportional fairness: Scheduling principle balancing instantaneous rate and historical throughput.

Massive MIMO: Multi-antenna system using many elements for spatial multiplexing and beamforming.

Beamforming: Spatial shaping of transmitted or received radio energy.

Handover: Transfer of an active connection between serving cells or beams.

Hysteresis: Margin used to prevent rapid back-and-forth handovers.

Mesh network: Multi-hop network in which nodes relay traffic for one another.

Cognitive radio: Radio capable of sensing or using information to adapt spectrum access.

LPWAN: Low-power wide-area network for low-rate, energy-constrained devices.

EIRP: Equivalent isotropically radiated power.

G/T: Receive antenna gain divided by system noise temperature.

C/N₀: Carrier-to-noise-density ratio, expressed in dB-Hz.

Non-terrestrial network: Network using satellites or other aerial platforms for connectivity.

Frequency reuse: Use of the same spectrum in sufficiently separated coverage areas.

Review Questions

Short Answer Questions

1. What functions are performed by radio-resource management?

2. Distinguish between path loss, shadowing and small-scale fading.

3. Why are hysteresis and time-to-trigger used in handover decisions?

4. What is the purpose of network slicing in 5G?

5. Why must the Boltzmann constant term appear in a satellite C/N₀ equation?

Long Answer Questions

1. Compare LTE EPC and 5G Core architecture, including control-plane and user-plane functions.

2. Explain how massive MIMO, beamforming and channel-state information affect interference and capacity.

3. Discuss proportional-fair, maximum-throughput and priority scheduling, including their limitations.

4. Compare infrastructure Wi-Fi, ad hoc, mesh, cognitive-radio and LPWAN networks.

5. Explain the complete satellite link-budget process and the principal causes of availability degradation.

Analytical / Application Questions

1. A single-branch Rayleigh link has average SNR 8 dB and a required threshold of 2 dB. Using the outage model in this chapter, calculate the outage probability and state the model assumptions.

2. A satellite link has EIRP 46 dBW, G/T 17 dB/K and total loss 198 dB. Calculate C/N₀ and C/N for a 20 MHz channel, using 228.6 dB for −10log₁₀(k). Interpret whether a modem requiring 5 dB C/N has nominal margin.

3. Design a rural hybrid network combining cellular, LPWAN and satellite access. Specify traffic classes, handover strategy, RRM policy, coverage constraints and at least three risks requiring validation.

Multiple Choice Questions with Answers

Question 1

Which expression correctly gives C/N₀ in dB-Hz when EIRP is in dBW and G/T is in dB/K?

A. EIRP + G/T − L

B. EIRP + G/T − L + 228.6

C. EIRP − G/T + L + 228.6

D. EIRP + G/T + L − 174

Correct Answer: B. EIRP + G/T − L + 228.6

Question 2

A single-branch Rayleigh link has average SNR 10 dB and threshold 3 dB. What is its outage probability under the model stated in the chapter?

A. Approximately 1.8%

B. Approximately 8.2%

C. Approximately 18.1%

D. Approximately 81.9%

Correct Answer: C. Approximately 18.1%

Question 3

Which quantity is specifically used by a proportional-fair scheduler?

A. Instantaneous rate divided by average past throughput

B. Transmit power divided by carrier frequency

C. Noise power divided by antenna gain

D. Cell radius divided by handover margin

Correct Answer: A. Instantaneous rate divided by average past throughput

Question 4

What is the main purpose of handover hysteresis?

A. Increase thermal noise

B. Prevent rapid back-and-forth cell changes

C. Remove all co-channel interference

D. Guarantee zero packet loss

Correct Answer: B. Prevent rapid back-and-forth cell changes

Question 5

Which statement about using system noise temperature is correct?

A. It must always be combined with receiver noise factor F

B. It can represent receiver and antenna noise without separately double-counting the same receiver noise

C. It is measured in dB-Hz

D. It replaces propagation loss in a link budget

Correct Answer: B. It can represent receiver and antenna noise without separately double-counting the same receiver noise

Question 6

For a satellite link with C/N₀ = 93.6 dB-Hz and bandwidth 36 MHz, what is C/N approximately?

A. 18.0 dB

B. 36.0 dB

C. 75.6 dB

D. 169.2 dB

Correct Answer: A. 18.0 dB

Question 7

Which technique primarily provides spatially selective transmission using multiple antenna elements?

A. Beamforming

B. Duty cycling

C. Frequency hopping alone

D. Packet fragmentation

Correct Answer: A. Beamforming

Question 8

Which characteristic is most associated with LPWAN systems?

A. High-rate continuous video as the primary design target

B. Low-power operation with small payloads and wide-area coverage

C. Mandatory fibre backhaul to every sensor

D. Zero airtime or regulatory constraints

Correct Answer: B. Low-power operation with small payloads and wide-area coverage

Question 9

Why can a lower satellite elevation angle degrade a link?

A. It always increases antenna gain

B. It generally increases slant range and atmospheric path length

C. It eliminates rain attenuation

D. It guarantees shorter propagation delay

Correct Answer: B. It generally increases slant range and atmospheric path length

Question 10

In the simple SINR model, what appears in the denominator besides interference?

A. Desired signal power

B. Receiver noise power

C. Antenna height only

D. Cell identity

Correct Answer: B. Receiver noise power