Evolved Packet System (EPS): The LTE and SAE Evolution of 3G UMTS

2.1 The Access Network Requirements

As stated in the previous chapter, one of the main objectives of Evolved UMTS is to design a high-performance radio interface. The rest of this section describes in more detail the performance criteria and the associated requirements of this new Radio Access Network. These include:

• Radio interface throughput.
• Data transmission latency.
• Terminal state transition requirements.
• Mobility requirements.
• Flexibility in spectrum usage.
• Mobility requirements between systems.

In this section, as well as in the rest of this book, E-UTRAN (Evolved Universal Terrestrial Radio Access Network) is referred to as the access network of Evolved UMTS (or EPS for Evolved Packet System), which not only includes the radio interface, but also the network nodes and terrestrial interfaces supporting the radio-related features.

2.1.1 Radio Interface Throughput

The radio interface of E-UTRAN shall be able to support an instantaneous downlink (from network to terminal) peak data rate of 100Mb/s within a 20 MHz downlink spectrum allocation and an instantaneous uplink (from terminal to network) peak data rate of 50Mb/s within a 20 MHz uplink spectrum allocation. This corresponds to a spectrum efficiency of 5bits/s/Hz for the downlink, and 2.5bits/s/Hz for the uplink.

It is interesting to compare those requirements with the initial objectives of UMTS, as defined in 1998. At that time, 3G systems were expected to provide the following throughput:

• 144Kb/s in rural outdoor radio ...