# An Improved Dynamic Joint Resource Allocation Algorithm Based on SFR
## 1 Introduction  
With the rapid increasing data rate requirements of mobile users on multimedia applications, the design of spectrum resource allocation methods with high system throughput and spectral efficiency [1] has become one of the hot issues in LTE [2] and LTE-A [3]. In the multi-cell resource allocation environment, ICI is a major problem affecting system throughput, especially for the cell edge users. Fractional frequency reuse (FFR) and soft frequency reuse (SFR) are two common deployments to improve spectral efficiency and reduce ICI. However, FFR eliminates frequency collisions at the cost of spectrum efficiency. The reason for this lies in interior users being forbidden to share the spectrum with cell-edge users in FFR. Soft frequency reuse (SFR) emerged as an alternative resource planning scheme to effectively mitigate ICI in cellular systems. SFR offers cell-center users access to spectrum with a frequency reuse factor equal to one, and cell-edge users with a frequency reuse factor which is greater than one. Reference [4] has proved that SFR outperforms FFR in spectrum efficiency. The original frequency reuse schemes are static frequency reuse. References [5] and [6] described static FFR and SFR, respectively. Although the so-called static frequency reuse scheme demands relatively lower complexity and overhead, it fixes the allocation of power and subcarriers in each cell beforehand, which greatly limits the communication performance. To overcome this drawback, dynamic resource assignment has arisen. The authorsof [7; 8; 9; 10] introduced several dynamic FFR schemes. Dynamic SFR approaches were illustrated in [11; 12; 13; 14]. However, there are no works about joint resource allocation for the SFR, except for the method proposed by [PERSON] in [15; 16], where [16] is the improvement of [15]. In this paper, we put forward an improved dynamic joint resource allocation algorithm based on SFR, referred to as DJRA. The new algorithm aims at solving several problems in [16]. [PERSON] firstly utilizes joint resource allocation in SFR and proposes an adaptive soft frequency reuse scheme (ASFR). Nevertheless, ASR can not guarantee that all the users have available resources. Accordingly, we propose two methods to solve this problem. Firstly, DJRA monitors edge-user distribution in the system before using an exhaustive search, which not only guarantees all the users have available resources but also reduces the number of iterations. Secondly, we take the multi-cell resource allocation fairness principle into account by utilizing the proportional fair algorithm (PF). To further mitigate interference, this paper presents the sector partition method in a cell-center.  
DJRA obtains the optimal single cell resource allocation scheme by dynamically adjusting resource block (RB) and power allocation according to the real-time distribution of users per cell, and then uses an iteration method to acquire the optimum resource allocation scheme. Compared with previous schemes, it is worth pointing out that the improved dynamic joint resource allocation scheme reduces the influence of ICI, acquires a better cell edge user performance, and guarantees all the users have available resources.  
The rest of this paper is structured as follows. Section 2 introduces the system model. The method of dynamic joint resource allocation algorithm based on SFR is described in detail in Section 3. Section 4 provides the results of simulation analysis. Finally, conclusing remarks are presented in Section 5.