e WL link. The solution in Figure 7.11f comprises different embodiments of cooperative relaying solutions. It can be seen at once that traffic on the X2 interface is zero and traffic from S1 interface is shifted to WL. (f1) uses decode and forward (D&F) relays with the CU located at the serv- ing eNB SO that quantized and encoded Tx signals are being transmit- ted from eNB to RNs. (f2) is basically the same solution as (f1) with the main difference that amplify and store and forward (A&S&F) relays in combination with remodulation are being used. The "store" operation is required to avoid feedback loops over the air, while remodulation allows adapting the © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology d1 +d2+d3 d3 = 300Mb/s d1 = 300Mb/s d2 = 300Mb/s eNB3: RRH 100Mb/s 100Mb/ eNB1: CU 100Mb/s 6 times (dOBSAI + dcsi) eNB2: RRH Only if routed 30000 over backbone NB3 contr 25000 NB3 contr 20000 NB2 contr NB2 contr 15000 CU contr 10000 CU contr (all data rate values in Mbit/s) (a) Conventional (b) Full cooperation over OBSAI (e.g., RRH) d1 + d2 + d3 d1 + d2 + d3 multicast eNB3: mirror eNB1: CU eNB1: CU 6 times (dQAM + dcsi) eNB2: mirror 3°d Control + 6 Assumptions for X2 min: May be reduced by multicasting mean dcsi = 3 bit/s data only for cooperating UEs NB3 contr NB3 contr NB2 contr NB2 contr CU contr CU contr X2 min X2 min (c) Full Cooperation Quantized Tx-signals (d) Full Cooperation Over Mirror CUs Figure 7.11 a-f: traffic on S1, X2, and WL connections for different types of cooperation. C 2009 by Taylor & Francis Group, LLC Cooperative Transmission Schemes NB3: mirror d1+d2+d3 NB1: CU NB2: mirror Control 4 dcsi or 2 . d CB (per sector) (a<1) (f1) D&F; Precoder at CU; Quantized Tx Signals WLopt: simulcast of control + reduced CB size WLopt: simulcast of control & data from CU to RNs NB3 contr NB2 contr UE-RN contr RN-UE CU contr RN-CU contr CU-RN CU-RN contr WLopt WLopt (f2) A&S&F&remodulate; Precoder at CU (f3) D&F; Recalculated CBs (or quantized Tx) Control: 4* d