LTE-Advanced: Carrier Aggregation

LTE has a speed limit: each channel maxes out at 20 MHz. Want to go faster? Use more channels at once.

Carrier Aggregation = using multiple channels simultaneously, like adding lanes to a highway.

The Simple Idea

Think of bandwidth like lanes on a highway:

  • 1 channel = 1 lane = 20 MHz
  • 2 channels = 2 lanes = 40 MHz
  • 5 channels = 5 lanes = 100 MHz

LTE-Advanced allows up to 5 channels (called “component carriers”):

5×20 MHz=100 MHz5 \times 20 \text{ MHz} = 100 \text{ MHz}

Maximum bandwidth = 100 MHz.

Two Ways to Combine Channels

Intra-band

All channels come from the same frequency band.

Like adding lanes to the same highway.

Inter-band

Channels come from different frequency bands.

Like using lanes from multiple different highways at once.

Inter-band is more common because operators usually own spectrum in multiple bands.

Why Use Different Bands?

Band TypeStrengthWeakness
Low frequencyBetter coverage, goes through wallsLess capacity
High frequencyMore capacity, faster speedsShorter range

With inter-band CA, your phone uses both at the same time. You get coverage and speed.

Maximum Bandwidth

What is the maximum achievable channel bandwidth with standardized 20 MHz channels in inter-band Carrier Aggregation?

5×20 MHz=100 MHz5 \times 20 \text{ MHz} = \boxed{100 \text{ MHz}}

Key Takeaway

WhatValue
Max channels5
Max per channel20 MHz
Max total100 MHz

Carrier Aggregation breaks the 20 MHz barrier. Instead of one channel, use five.