# An Improved Radio Resource Management with Carrier Aggregation in LTE Advanced
## 1 Introduction
Therefore, each of the CCs will have an independent packet scheduling algorithm which performs the allocation of time-frequency resources of each CC--called resource blocks (RB)--to each user at every transmission time interval (TTI). An efficient scheduling algorithm can resolve conflict amongst the users and eNBs and it is also important to maximize the system throughput, fairness, spectral efficiency, and to reduce the delay among the users. Figure 1: RRM framework with carrier aggregation. Channel dependent packet schedulers are more accurate in real life scenarios as they consider more parameters than channel independent schedulers. Most of the previous researchers have used proportional fairness (PF) [5; 6; 7], Round Robin (RR) [8; 9] and other algorithms [10; 11; 12; 13; 14; 15; 16; 17] for resource allocation with CA in an LTE-A system. However, some important parameters, such as packet delay or error rate are not considered. This paper implements Modified Largest Weighted Delay First (MLWDF) algorithm to ensure ideal throughput to the system and to maintain fairness to all users [18; 19]. This scheduler largely depends on QoS and packet delay. A QoS-related 'discard timer' is set on all packets when they arrive to the eNodeB. The packets being waited in the queue until they are successfully transmitted or the 'discard timer' expires. This queueing delay (elapsed time since the user packet arrived in the queue) is denoted as the head of line (HOL) delay in the MLWDF algorithm [20]. If the HOL delay exceeds the predefined delay threshold of the user application, Packet Data Convergence Protocol (PDCP) layer discards the user packets according to the standard [21]. The PDCP entity in the receiving end will not wait for any packet which is not transmitted. MLWDF algorithm is a throughput optimal algorithm as it makes scheduling decisions based on the queue situation and the rate of successful packet transmission. This algorithm also gives priority to the users who have the best channel condition to prevent the data loss before it reaches a certain limit in the queue. Link Adaptation (LA) and Hybrid ARQ (HARQ) are working independently for each CC. LA based on adaptive modulation and coding (AMC) can adapt the modulation and coding scheme (MCS) [22]. The higher the SINR (Signal-to-Interference plus Noise Ratio), the higher the coding rate and spectral efficiency. The proposed method calculates gain for all users to assign the CC with highest gain. Queue length of individual CC is also measured to balance the load of all CCs. Consideration of the queue length also allows the scheduler to reduce the packet waiting time in the queue and significantly improves the QoS. Then HOL delay and the probability of packet loss are calculated to find out the highest metric for individual users [23]. Subsequently, CCs are assigned to the user according to the metric until it reaches any terminating condition. The rest of the paper is constructed as follows. In Section 2, related works on radio resource management are discussed. In Section 3, new greedy-based model with computational complexity is proposed. Discussion on simulation settings and obtained results are reported in Section 4. Some limitations and future plans are mentioned in Section 5 and finally, Section 6 concludes the paper.