Research On Frequency Hopping OFDM And Related Technology

Frequency Division Multiplexing (OFDM) is an effective multi-carrier solution for broadband wireless communication. In the OFDM system, the data stream with high rate is transformed into a number of lower rate components. Then, the lower rate components are mapped onto different subcarriers which are orthogonal in frequency domain. Since the bandwidth of each subcarrier in OFDM is narrower than the coherent bandwidth of the propagation channel, the frequency-selective fading is transformed to flat fading. Orthogonal Frequency Division Multiplexing Address (OFDMA), which is the multi-user vision of OFDM, prevails in the proposed future wireless network standards like 4G cellular networks. In OFDMA networks, the interference between different cells, which is called inter-cell interference (ICI), cause performance degradation. In order to solve this problem, this paper research on the frequency hopping OFDM related technology.The predetermined OFDMA could average the inter-cell interference to improve the performance of the system. In the proposal of Long Term Evolution, several frequency hopping patterns has been proposed. Analyzing the existed frequency hopping patterns, we proposed the new frequency hopping algorithm as invoking the Residue Number System (RNS). Compared to the conventional hopping patterns, the frequency hopping patterns based on RNS achieves less collisions of hopping pattern while having small complexity. However, the residue number system has the restriction due to its inner quality. The paper proposed the Advanced Residue Number System hopping algorithm (ARNS) employing the Goldbach conjecture to solve the problem. The ARNS frequency hopping algorithm has much wider range of applications than the traditional one. Implicating the hopping patterns to fast frequency hopping OFDMA (FFH-OFDMA), the system could achieve better performance in the fast changing channel environment.After that, the multi-group frequency hopping OFDMA (MG-FH OFDMA) based on the statistical multiplexing is proposed for the downlink cellular system. Compared with the existed random frequency hopping OFDMA (RFH-OFDMA) system utilizing the statistical multiplexing, the proposed MG-FH OFDMA invokes the deterministic hopping pattern to reduce the number of subcarrier collisions. By dividing all users into different groups, the subcarriers are utilized sufficiently. Latin Square hopping pattern and user index updating scheme are applied to randomize the subcarrier collisions among users. The user capacity, defined as the maximum number of users served with a basic data-rate in a cell, is calculated with the consideration of intra-cell capacity and the other cell interference (OCI). Results show that the proposed MG-FH OFDMA achieves higher user capacity than that of the RFH-OFDMA.The future networks contain the interference limited networks such as homecell and so on. Since the environment of the homecells is uncertain, the current solutions are not feasible. Considering the interference avoidance by cooperative resource allocation, this paper presents the solution of the utility greedy discrete bit loading (UG) for interference limited multi-cell OFDM networks. Setting the utility as the sum of consumed power proportions, the algorithm follows greedy way to achieve the maximum throughput of the system. Simulation has shown that the proposed algorithm have better performance and lower complexity than the traditional optimal algorithm. The discussion of the results is also provided.