5.2. The RF head requires also low latency in addition to the high data rate. The one-way delay must LTE Small Cell Optimization Table 5.2 Comparison of backhaul and fronthaul requirement Backhaul Fronthaul Bandwidth 20 MHz 2x2 MIMO Up to 150 Mbps* 2 Gbps Bandwidth 40 MHz 2x2 MIMO Up to 300 Mbps* 4 Gbps Bandwidth 40 MHz 4x2 MIMO Up to 300 Mbps* 8 Gbps Latency <5-10 ms <0.5 ms Jitter <1-5 ms <8 ns Practical transport options Microwave radio, GPON, CWDM, CWDM, VDSL, HFC NGPON2 GPON, gigabit passive optical network; CWDM, coarse wavelength division multiplexing; VDSL, very high bit rate digital subscriber line; HFC, hybrid fiber coaxial. *Backhaul capacity can be less than the peak rate. Trunking gain can be used to connect multiple base stations. Fronthaul capacity is required also in the case of low traffic radio heads. be clearly below 0.5 ms to run the low latency functions including retransmissions from the baseband. Therefore, the baseband processing cannot be faraway in the cloud but the physical location needs to be relatively close to the RF. Also the delay jitter must be very low in the order of a few nanoseconds. The very high data rate means that it is difficult to use wireless backhaul for the RF head especially when LTE-Advanced increases bandwidth and number of antennas leading to higher fronthaul data rate requirements. The very low latency and jitter means that IP routing cannot be used in the fronthaul. We have now learnt that RF heads have some benefits over all-in-one base stations but RF heads also require very fast and low latency transport network. Therefore, small cells with RF heads are practical in those networks with rich fibre infrastructure, like in Korea. The RF heads also need tight interaction between radio and transport teams to troubleshoot any potential issues. 5.4 Frequency Usage The operators will aggregate all their spectrum between 700 and 2600 MHz together into one pool with carrier aggregation. That solution maximizes the macro cell data rates and capacity and is supported by