 be was started, 3GPP decided to make sure that an operator delivered by HSPA Evolution. This approach reduces the can coexist easily between HSPA Evolution and LTE cost of deployment since LTE do not need to be build for through an evolved core network, the Evolved Packet nationwide coverage from day one. Chapter 4.3 High data rates in mobile communications Erik Dahlman, Stefan Parkvall, Johan Skold and Per Beming As discussed in Chapter 4.2, one main target for the N denotes the power of the white noise impairing the evolution of 3G mobile communication is to provide the received signal. possibility for significantly higher end-user data rates Already from (4.3.1) it should be clear that the two compared to what is achievable with, for example, the fundamental factors limiting the achievable data rate first releases of the 3G standards. This includes the are the available received signal power, or more possibility for higher peak data rates but, as pointed out generally the available signal-power-to-noise-power in the previous chapter, even more SO the possibility for ratio S/N, and the available bandwidth. To further significantly higher data rates over the entire cell area, clarify how and when these factors limit the achievable also including, for example, users at the cell edge. The data rate, assume communication with a certain in- initial part of this chapter will briefly discuss some of the formation rate R. The received signal power can then more fundamental constraints that exist in terms of what be expressed as S = Eb.R where Eb is the received data rates can actually be achieved in different scenarios. energy per information bit. Furthermore, the noise This will provide a background to subsequent discussions power can be expressed as N = No. BW where No is in the later part of the chapter concerning different the constant noise power spectral density measured in means to increase the achievable data rates in different W/Hz. mobile-communication scenarios. Clearly, the information rate can never excee