Pure ALOHATransmit whenever you have data, no coordination at all. Simple, but collisions are frequent.

Slotted ALOHATime is divided into slots; you can only start transmitting at the beginning of a slot. Cuts the collision window in half compared to pure ALOHA.

CSMACarrier Sense Multiple Access — listen before transmitting. Reduces but doesn't eliminate collisions (two stations can still sense "silence" at the same instant and both transmit).

CSMA/CDAdds Collision Detection — keep listening WHILE transmitting, and stop immediately if a collision is detected. Used in classic wired Ethernet.

CSMA/CACollision Avoidance instead of detection — used in wireless (Wi-Fi), where a station often can't reliably "hear" a collision while transmitting, covered fully in its own topic below.

ReservationStations reserve a time slot in advance before actually sending data.

PollingA central controller asks ("polls") each station in turn whether it has data to send.

Token passingA special "token" frame circulates; only whoever holds the token may transmit — used in Token Ring / Token Bus, covered later in this chapter.

FDMAFrequency Division — each station gets its own permanent frequency band.

TDMATime Division — each station gets the full frequency, but only during its own assigned time slot.

CDMACode Division — every station transmits simultaneously across the whole frequency band, but using a unique code, letting the receiver mathematically separate out just the signal it wants. This is the technology behind older 3G mobile networks.