August 14, 2009 | LTE standards are in matured state now with release 8 frozen. While LTE Advanced is still under works. Often the LTE standard is seen as 4G standard which is not true. 3.9G is more acceptable for LTE. So why it is not 4G? Answer is quite simple - LTE does not fulfill all requirements of ITU 4G definition.

Brief History of LTE Advanced: The ITU has introduced the term IMT Advanced to identify mobile systems whose capabilities go beyond those of IMT 2000. The IMT Advanced systems shall provide best-in-class performance attributes such as peak and sustained data rates and corresponding spectral efficiencies, capacity, latency, overall network complexity and quality-of-service management. The new capabilities of these IMT-Advanced systems are envisaged to handle a wide range of supported data rates with target peak data rates of up to approximately 100 Mbit/s for high mobility and up to approximately 1 Gbit/s for low mobility.
 
In order to meet this new challenge, 3GPP widened its scope to include systems beyond 3G. LTE Advanced would fulfil the 4G requirements as set by ITU. In 2008 3GPP held workshops on IMT Advanced, where the “Requirements for Further Advancements for E-UTRA” were gathered. The resulting Technical Report 36.913 has been now published.

Let us see some requirements which differentiate LTE & LTE Advanced.

Peak data rate:

• LTE - DL: 100 Mbps, UL: 50 Mbps
• LTE Advanced - DL: 1 Gbps, UL: 500 Mbps

Transmission bandwidth:

• In comparison to LTE, LTE Advanced is wider than approximately 70 MHz in DL and 40 MHz in UL.

Latency:

• LTE - C-plane from Idle (with IP address allocated) to Connected in <100 ms, U-plane latency of less than 5 ms in unload condition (ie single user with single data stream) for small IP packet.
• LTE Advanced - C-plane from Idle (with IP address allocated) to Connected in <50 ms, U-plane latency reduced compared to Release 8 E-UTRA and E-UTRAN, specifically in situations where the UE does not have a valid scheduling assignment or the UE needs to synchronize and obtain a scheduling assignment.

Peak spectrum efficiency:

• LTE - DL 3 to 4 times Release 6 HSDPA , UL - 2 to 3 times Release 6 Enhanced Uplink  
• LTE Advanced - DL 30 bps/Hz and UL 15 bps/Hz.

C-plane capacity:

• LTE - At least 200 users per cell should be supported in the active state for spectrum allocations up to 5 MHz.
• LTE Advanced - At least 300 active users without DRX in a 5 MHz bandwidth.

Mobility:

• LTE - Support mobility across the cellular network for various mobile speeds up to 350km/h (or perhaps even up to 500km/h depending on the frequency band).
• LTE Advanced - Same as that in LTE, System performance shall be enhanced for 0 to 10km/h

LTE Advanced would operate in spectrum allocations of different sizes including wider spectrum allocations than those of Release 8 to achieve higher performance and the target peak data rate, e.g. up to 100 MHz.