there is a trade-off the solutions for the old terminals. between user experience and system performance. The Naturally, HSPA5 does not include all the technologies better the system performance is, the lower the cost of considered for LTE. Therefore, a study in 3GPP was the network. However, the end users also need to get initiated to see how far it is possible to take HSPA within adequate performance which often is in conflict with the the current spectrum allocation of 5 MHz and still 5 When operating with HSDPA and Enhanced UL, the system is known as HSPA. The motives behind the 3G evolution CHAPTER 4.2 respect the backward compatibility aspect. Essentially, Furthermore, when going to the data rates that LTE is the target with HSPA Evolution is to reach near the targeting, achieving low delay and high data rates at the characteristics of LTE when using a 5 MHz spectrum and cell edges are more important requirements than the at the same time being backward compatible. peak data rate. Thus, a more pronounced requirement Thus, 3GPP is working on two approaches for 3G for LTE is the low delay with high data rates at the cell evolution: the LTE and the HSPA Evolution. Both ap- edges than it was when WCDMA was designed in the proaches have their merits. LTE can operate in new and late 1990s. more complex spectrum arrangements (although in the Although not backward compatible with WCDMA, same spectrum bands as WCDMA and other 3G tech- LTE design is clearly influenced by the WCDMA and the nologies) with the possibility for new designs that do not HSPA work in 3GPP. It is the same body, the same need to cater for terminals of earlier releases. HSPA people, and companies that are active and more impor- Evolution can leverage on the installed base of equipment tantly, WCDMA and HSPA protocols are a good foun- in the 5 MHz spectrum but needs to respect the back- dation for the LTE design. The philosophy is to take what ward compatibility of earlier terminals. is good from WCDMA and HSPA, and redo those parts that have to