ABSTRACT
Contents 12.1 Introduction ................................................................................. 434 12.2 Evolution of 4G OFDMA-based RANs ............................................ 436
12.2.1 UMTS Radio Access Network .............................................. 436 12.2.2 Long-Term Evolution RAN (E-UTRAN) .............................. 438 12.2.3 LTE-Advanced RAN .......................................................... 439
12.3 4G Radio Resource Management ..................................................... 440 12.3.1 Overview of OFDMA RRM ................................................ 440 12.3.2 Transmission Scheduling in Time and Frequency ................... 441 12.3.3 Adaptive Modulation and Coding ........................................ 443 12.3.4 Power Control ................................................................... 444 12.3.5 Interference Avoidance ........................................................ 444 12.3.6 RRM Techniques for Multihop OFDMA Networks ............... 445
12.4 Advanced RANs for Beyond-4G Networks ....................................... 447 12.4.1 Advanced RANs for Beyond 4G ........................................... 448 12.4.2 Open Issues in RRM Optimization in Advanced RANs ........... 451
12.5 Summary ...................................................................................... 451 References .............................................................................................. 452
12.1 Introduction Current state-of-the-art standardization activities of the 3rd Generation Partnership Project (3GPP) long-term evolution (LTE) [1] and worldwide interoperability for microwave access (WiMAX) [2] have resulted in cellular standards with high data rates, close to the IMT-advanced spectral efficiency requirements of 15 bits/sec/Hz peak downlink and 6.75 bits/sec/Hz uplink [3]. Due to a spectrum limitation of 20 MHz, these standards fall short of the IMT-advanced data rate requirements of 600 Mbps peak downlink and 270 Mbps peak uplink at 40 MHz bandwidth. Current standardization activities are aiming for even higher data rates of 1 Gbps for downlink and 500 Mbps for uplink [4], as originally proposed in IMT-advanced [5]. Although it is still early for standardization bodies to consider beyond-4G data rates (tens of gigabits per second on the downlink), this is clearly a major research topic due to the exponential growth of user traffic on existing networks.
