Access
Understanding the Access Network (RAN)
The global internet is divided into two massive halves: The Core and the Access.
The Core is clean and simple. It is massive fiber-optic cables buried deep under the ocean, shooting light at the speed of light. The Core never moves, and it never deals with interference.
The Access Network is the exact opposite. It is the violent, chaotic edge of the internet.
The Geography of the Edge
The Access Network is everything that touches the physical air:
- The massive 5G macro antennas bolted to the tops of skyscrapers.
- The tiny Small Cells strapped to streetlamps.
- The Wi-Fi routers mounted to the ceiling of an airport.
- The microscopic silicon antennas inside your smartphone.
The job of the Access Network is to take the pristine data from the Core fiber-optic cables, convert it into massive, invisible electromagnetic radio waves, and blast it through the air. It must successfully hit a smartphone sitting inside a moving car driving 80 mph down a highway, while actively dodging the violent RF noise created by rain, concrete buildings, and other cell phones.
The Financial Burden of Access
Building a Core data center is relatively cheap. Building the Access Network is astronomically expensive. Because radio waves cannot travel forever, a telecom carrier like Verizon or T-Mobile must literally buy, build, and power over 100,000 massive steel cell towers across the United States just to maintain the Access Network. This physically requires climbing mountains, digging trenches in every city, and constantly upgrading the heavy metal antennas every time a new standard (like 6G) is invented.
Key Equations
C = N×Ruser (total throughput)
N = number of simultaneous users
FDMA:
N = BWtotal/BWuser
TDMA:
N = Tframe/Tslot
CDMA:
N = W/(R×Eb/N0×(1+f)) (Viterbi)
f = other-cell interference ratio
Comparison
| Method | Users/cell | SE (bps/Hz) | Advantage | Generation |
|---|---|---|---|---|
| FDMA | 30–60 | 0.3 | Simple | 1G AMPS |
| TDMA | 60–120 | 0.6 | Digital | 2G GSM |
| CDMA | 60–100 | 0.5–1.0 | Soft capacity | 3G UMTS |
| OFDMA | 200–500 | 2–5 | Freq selective | 4G LTE |
| NOMA | 300–600+ | 3–8 | Power domain | 5G/6G |
Frequently Asked Questions
What is Fixed Wireless Access (FWA)?
FWA is when a telecom carrier uses the 5G cellular network to replace the cable guy. Instead of digging up your yard to run a coaxial cable to your house, the carrier gives you a square box to put in your window. The box acts exactly like a smartphone, grabbing a massive 5G mmWave signal from a tower down the street, and instantly converting it into blazing-fast Wi-Fi for your entire house without a single wire.
What does Multiple Access mean?
It is the mathematical foundation of the Access Network. If 1,000 people are connected to the same cell tower, they cannot all talk at exactly the same time, or the radio waves will crash. Engineers invent complex 'Multiple Access' algorithms. TDMA (Time Division) gives everyone a split-second turn to talk. CDMA (Code Division) gives everyone a secret mathematical code. OFDMA (Orthogonal Frequency) slices the channel into tiny, distinct frequencies.
Why is the Access Network getting 'Open'?
For decades, the Access Network was a closed monopoly. If AT&T bought an Ericsson antenna, they were legally forced to buy the heavy Ericsson computer to run it. The new O-RAN (Open Radio Access Network) movement legally forces the massive hardware vendors to open their software APIs. This allows carriers to buy cheap antennas from one company and advanced AI software from a completely different company, shattering the monopoly.