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

3.4 Architecture of the Base Station

3.4.1 The Block Scheme of the Base Station

Figure 3.26 presents an example of an E-UTRAN base station, able to support a large number of users. The architecture below is provided for illustrative purpose. This base station is connected to the backhaul network by means of physical interfaces like optical fibre, like STM1 of large data rate or even more classical E1/T1 2-Mb/s data link. It receives its user data information from the Serving Gateway through the S1 interface based on IP packet transport protocol.

(i) The Downlink Case

The downlink information coming from the MME/serving gateway to Node B reaches an IP routing module, typically called a Core Control Module (CCM). Then, each packet is routed to a modem – the Channel Element Module (CEM) – which is able to support all types of physical coding for any type of physical possible channels: pilots, common channels, dedicated channels, etc.

This module is able to treat N channels (flows) in parallel, performing for each the channel coding, the radio conditioning of the signal: OFDM modulation, cyclic prefix insertion, etc.

The processing of all the signals dedicated to one sector can happen in the channel module.

Each channel module then addresses the signals relative to a given sector to the routing module, whose output feeds a Transceiver Radio Module (TRM) connected physically to the relevant sector. According to some choices of architecture, a radio operator module can then address a ...