A multiple‑access impairment in which a transmitter close to a receiver (or base station) produces a much larger received power than more distant transmitters on the same shared resource, so that the stronger signal overwhelms the weaker ones and prevents their correct detection or decoding.

Principle

Received power imbalance on a shared channel reduces the SINR of distant users; without power control, scheduling, orthogonalization, or interference cancellation, the strongest signals dominate reception and can suppress weaker users’ access.

Demonstration

Illustrative scenario → In an uplink to a base station using a shared code or random access, Mobile A is 10 m from the base station while Mobile B is 500 m away. A’s signal arrives with much higher power, causing the base station receiver to decode A while B’s packet is lost due to insufficient SINR despite correct transmission parameters.

Misapplication

Equating the near‑far problem with purely physical proximity or with hidden terminals. The semantic error is ignoring pathloss, fading and power control: ‘near’ refers to received power dominance, not geographic distance alone.

Consequence

Unfair access, decreased aggregate throughput for distant users, higher retransmission and latency for weak users; practical responses include closed‑loop power control, user scheduling, spread‑spectrum power balancing, or successive interference cancellation.

Reversal

Systems with orthogonal resource allocation (FDMA/TDMA), effective power control that equalizes received powers, or receivers implementing SIC can largely eliminate the near‑far effect; conversely, in uncontrolled random access or poorly tuned power control, the problem persists.

Boundary

Clearly within: CDMA uplink or unscheduled shared uplink where no effective power control is applied and one transmitter’s received power dominates. Boundary case: partial power control that reduces but does not equalize received powers. Clearly outside: fully orthogonalized links or centrally scheduled per‑user power allocation producing comparable received powers.

Semantic Tension

Fairness ↔ Efficiency — aggressive scheduling or power control that enforces fairness can reduce instantaneous throughput or increase control overhead; allowing power disparities can maximize throughput for close users at the expense of distant ones.

Synthesis

The near‑far problem is fundamentally about received‑power asymmetry on a shared medium; solving it requires controlling or exploiting power relationships (control, scheduling, orthogonality or advanced receivers) rather than solely altering physical node placement.