Nokia Flexi Metro remote radio head (RRH) fronthaul - usually requires optical fibre due to the high bandwidth and tight delay constraints of the baseband signal. An example low-power RRH product is illustrated in Figure 6.7. A more detailed list of features is shown in Table 6.5. Table 6.5 Nokia Flexi Metro RRH specifications Weight Volume 5 litres Temperature range -40°C to +55°C Output power Min 2 X 50 mW Max 2 X 5 W Antennas Integrated and external MIMO support 2 x 2 MIMO Power consumption <100 W Max capacity 840 connected users Feature parity with macro cell Synchronization GPS, IEEE 1588v2 or SyncE Fronthaul OBSAI over fibre LTE Small Cell Optimization Optical fibre LAN cable Digital CPRI Digital CPRI Figure 6.8 Lampsite architecture 6.6.1 Alternative Remote Radio Head Designs for Indoor Use For indoor use, two alternative RRH designs are discussed in the following paragraphs. Both utilize the combination of optical fibre and LAN cabling. Optical fibre facilitates wide reach in large buildings or campuses, while the use of LAN cabling for the transmission and PoE in the last section is simple and cost efficient. Both systems lend themselves to medium to large indoor deployments, but may be too costly in smaller indoor environments compared to pico BTSs, for example. The first, Huawei Lampsite, is a three-stage solution composed of a baseband unit (BBU), remote radio unit hub (RHUB) and pico remote radio units (pRRUs). The BBU may be connected to several RHUBs and each RHUB may be connected to several pRRUs. The Lampsite architecture is presented in Figure 6.8. The baseband signal is transported over an optical fibre to the remote radio hub. This node converts the digital optical signal into a digital electrical signal for transmission over a LAN cable to the pico RRH. The RHUB also provides PoE feed to the pRRUs. The pRRUs can be equipped with various radio access technology (RAT)-specific modules to support multiple radio technologies simultaneously: WCDMA, LTE and Wi-Fi. The second alternative, presented 