Francis Group, LLC Long Term Evolution: 3 GPP LTE Radio and Cellular Technology BS (NLOS, IF) BS (LOS, IF) RN1 (NLOS, IF) RN2 (NLOS, IF) Cell Radius (m) Figure 8.15 SINR at certain positions apart from the BS. Around the relays RN1 and RN2, the signal level is high enough to support a good PHY mode. 8.5.2 Ideal Cellular Scenario A coverage increase layout means the cell geometry is extended, for example, with three relays (as shown in Figure 8.3) SO that the covered area is three times the original area (+200%). Another geometry is shown in Figure 8.17; six relays BS (NLOS, IF) RN1 (NLOS, IF) RN2 (NLOS, IF) Cell Radius (m) Figure 8.16 Supported rate around BS, RN1, and RN2. The first hop resources are taken into account; this is the reason for the reduced maximum rate by the RNs. Nevertheless, they are better beyond 1,800 m. © 2009 by Taylor & Francis Group, LLC Multihop Extensions to Cellular Networks provide fourfold coverage (+300%) compared to a single cell. In Figure 8.18, the area served by the BS (the best serving station is indicated by shade) is small compared to the coverage achieved by the relays. The SINR condition at the possible receiver positions is shown in deci- bels in Figure 8.19. Figure 8.20 shows that the maximum rate (numbers in megabits per second) around the RNs is only half of the BS rate, but in Figure 8.17 Multihop cellu- areas the BS would never cover. Thus, although lar geometry with six relays. the inner cell still has capacity to offer (though not in saturated traffic load conditions), this can be used to extend the coverage very economically. A capacity increase layout is when relays are placed within the normal radius of the single-hop cell (Figure 8.2). In this case, the BS is able to provide coverage for all UTs in the cell, even without relays. But there are areas near the cell bor- der where an RN provides much better service in terms of SINR (Figure 8.22) and especially regarding the offered capacity for the UT (Figure 8.23). Thus, the cell border is no longer an area of the 