# How a telecom network actually moves a call or byte
You press play on a video call. Within about 20 milliseconds, your phone has negotiated with a cell tower, your voice and image have been chopped into thousands of tiny packets, and those packets have raced across fiber, through a data center, and possibly out to a peering point where two networks shake hands. Multiply that by billions of simultaneous streams and you have the daily job of a telecom operator.
This lesson follows one video stream end to end. Along the way, you will see where telcos spend their capital (money on physical assets), where the real bottlenecks live, and why some parts of the network cost far more than others.
The radio access network (RAN) is everything between your device and the tower. It is the part most people picture when they think "wireless."
Your phone talks to a base station, the equipment mounted on a tower, rooftop, or pole. In 4G this is called an eNodeB; in 5G, a gNodeB. The base station converts your data into radio waves and back.
Here is the first hard truth: radio spectrum is scarce and expensive. Spectrum is the range of frequencies an operator is licensed to use. Governments auction it, and operators spend enormous sums to win it. In many markets, spectrum licenses are among the largest single costs a carrier bears, sometimes rivaling the cost of the equipment itself.
The RAN is also where most network capital goes. Industry estimates commonly attribute the majority of a mobile operator's capital spending to the RAN, because towers, antennas, and radios must be deployed everywhere people live and travel.
Spectrum is shared. When a stadium empties after a match and 40,000 people all open their phones, the local cell gets congested. Your video may stutter not because the internet is slow, but because too many devices are competing for the same slice of air.
Operators fight this with three levers:
Once your packets reachreachThe number of unique people exposed to your message in a given period. Unlike impressions, reach counts each person once, no matter how often they see it.Voir la définition complète → the base station, they need to travel inland. That link is called backhaul, the connection between a cell site and the operator's core network.
Backhaul is usually fiber optic cable, though some remote towers use microwave links (point to point radio beams between dishes). Fiber carries vastly more traffic and is preferred wherever it is economical to lay.
Backhaul is a quiet but major cost. Trenching fiber to thousands of tower sites is slow and expensive, and in rural areas the economics are brutal: few customers, long distances. This is a core reason rural coverage lags and why governments subsidize it.
Your packets now arrive at the core network, the centralized set of systems that authenticate you, apply your data plan, and route traffic to its destination.
The core does jobs you never see:
Modern cores are increasingly software running in data centers rather than dedicated hardware boxes. The industry term is network function virtualization (NFV): replacing specialized equipment with software on general purpose servers. This lets operators scale and update faster, similar to how cloud software works.
In 5G, the core is redesigned around a cloud native, service based architecture. A key feature is network slicing: carving one physical network into multiple virtual networks, each tuned for a purpose. One slice might serve low latency factory robots, another might serve mass consumer video. You can read a solid primer on 5G architecture from the 3GPP, the body that sets global mobile standards.
Here is a detail that surprises many people. Your video stream often does not travel across the whole internet to reachreachThe number of unique people exposed to your message in a given period. Unlike impressions, reach counts each person once, no matter how often they see it.Voir la définition complète → you. Large content providers place copies of popular content in content delivery networks (CDNs), caches of data stored close to users.
Sometimes these caches sit inside the telecom operator's own data centers. When you stream a popular show, the bytes may travel only a short hop from a local cache, not across an ocean. This slashes cost and latency (the delay before data arrives).
If the content is not cached locally, your packets must leave your operator's network and cross to another. This handoff happens at peering points, physical locations (often called internet exchanges) where networks interconnect.
Two arrangements dominate:
This is where telecom economics gets political. Large operators and large content companies negotiate hard over who pays whom. When a hugely popular service sends massive video traffic into an operator's network, disputes arise over whether the content company should help fund the capacity. These fights have triggered regulatory attention in several regions.
Net neutrality, the principle that operators should treat all internet traffic equally without blocking or favoring certain services, sits right on top of this layer. Rules vary widely by country and change over time.
Vérification des acquis
1. When a stadium empties and thousands of fans' phones suddenly stream video, causing playback to stutter, what is the most likely underlying cause according to the lesson's reasoning?
2. Why does the majority of a mobile operator's capital spending tend to go toward the radio access network (RAN)?
3. The lesson states spectrum is 'scarce and expensive.' What concept does this scarcity best illustrate about telecom economics?
4. Select ALL correct answers about the radio access network (RAN).
Sélectionnez toutes les réponses correctes.
5. Select ALL correct answers about why some parts of a telecom network cost more than others.
Sélectionnez toutes les réponses correctes.
Now that you have seen the full path, here is the honest mapmapUsing software to automate repetitive marketing tasks and campaigns, enabling personalisation at scale across channels like email, web, and social.Voir la définition complète → of spending.
1. The RAN dominates capital.
Towers, radios, antennas, and spectrum licenses absorb the largest share of mobile capital spendingcapital spendingCapital Expenditure (CapEx) is money spent to acquire, upgrade, or extend long-lived assets like equipment, property, or software that deliver value over multiple years.Voir la définition complète →. Every new generation (4G, 5G, and beyond) means another expensive refresh cycle across tens of thousands of sites.
2. Fiber is the long game.
Backhaul and the growing fiber footprint (including fiber to the home) require patient, heavy investment. Fiber lasts decades once laid, so operators view it as durable infrastructure, but the upfront trenching cost is enormous.
3. The core is shifting to software.
As cores virtualize, some spending moves from custom hardware toward servers, software licenses, and cloud partnerships. This can lower cost over time but requires new skills.
4. Energy is a rising operating cost.
Running tens of thousands of cell sites and data centers consumes significant electricity. As traffic grows, so does the power bill, which is why energy efficiency is now a genuine engineering priority.
1. Your phone negotiates with the nearest base station over licensed spectrum.
2. Packets travel via fiber or microwave backhaul to the operator's core.
3. The core authenticates you, applies your plan, and routes the request.
4. The video is served from a nearby CDN cache if available, or fetched across peering and transit links if not.
5. The stream flows back down the same path, reassembled on your screen in real time.
Every layer is a place where money is spent and where things can slow down. Understanding which layer causes a given problem is the difference between a vague complaint ("the network is bad") and a precise diagnosis ("the cell is congested" or "the peering link is saturated").