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Editor's Notes

1. 3G operators have already experienced difficulties in coping with data-hungry smart phones that saturate the network and can prevent subscribers from making voice calls. LTE promotes an even richer and more diverse mix of subscriber services – including voice, video, web browsing, e-mail and social networking – that will have very different data traffic profiles and therefore impact the network performance in a way that is difficult to predict. This is much more difficult to test than for 2G networks like GSM, where the bulk of traffic is centred on voice and SMS. At the same time, compared to UMTS, the LTE standard has removed the Radio Network Controller (RNC) that was a governing element in the UMTS Radio Access Network (UTRAN). This was traditionally used as the access point into the 3G network for high capacity testing, so it becomes necessary to test over the air interface. For 2G and 3G networks, some operators adopted the ‘wall of phones’ approach for end-to-end testing into the NodeB in the UTRAN, but due to the larger number of UEs per cell that LTE supports, along with the increased service complexity and feature churn, this becomes impractical. Figure 2 shows a comparison of the UTRAN with the LTE network architecture. As mentioned above, the LTE network has been simplified compared to 3G UTRAN with the removal of the RNC node. This simplification of the network has concentrated more functionality into the eNodeB base station, which can now communicate directly with other eNBs to handle functionality such as device handover between base stations. A flatter network architecture leads to improved data latency (the transmission delay between the transmitter sending data and the receiver receiving it) and better support of delay-sensitive, interactive and real-time communications.