Research On Key Technologies In Hybrid Gigabit Passive Optical Network (HGPON)

Nowadays, as the transport network media has developed from twisted-pair based copper cables to optical fibers, the access technology has developed from ADSL (Asymmetric Digital Subscriber Line) to the advanced PON (Passive Optical Network). PON provides customers with high-speed voice、video and data access services. The PON topology is a asymmetrical PTMT (Point to Multi-Point) architecture with the broadcast downstream transmission scheme. PON adopts multiple-access schemes such as TDMA (Time Division Multiple Assess)、WDMA (Wavelength Division Multiple Assess) or CDMA (Code Division Multiple Assess) to share the upstream channel. First of all, as the transmission speed and length are keeping increasing, novel physical setup of PON system has become an important issue. Second, in the MAC layer of PON, DBA (Dynamic Bandwidth Allocation) algorithms with multiple QoS classification and resources scheduling should be investigated intensively to improve the network performances. After all, the main ideas of this paper are presented as follows:(1) Based on the development trend from TDM-PON to WDM-PON, a novel TDM/WDM hybrid PON (HGPON) architecture is proposed in this paper. The physical layer topology and MAC layer signaling process are both introduced and simulated in OPNET network simulation platform. HGPON network is devised by advanced passive optical components to provide full services access with high speed and flexibility. Simulation results confirm that HGPON can make full use of wavelength and bandwidth resources based on the designed signaling and algorithms the MAC layer.(2) A proposed queuing model is proposed with time delay analysis for the HGPON MAC layer signaling process. A novel multi-thread bandwidth allocation algorithm is introduced and analyzed in this paper. The algorithm adopts the WDM wavelength scheduling to increase the network capability and mitigate the traffic congestion. Simulation results show that the network performances of the HGPON network are improved dramatically as the multi-thread number increases. However, the algorithm complexity is also enlarged with the multi-thread number linearly and cannot be overlooked. As a result, the optimum multi-thread number should be chosen in consideration of both network performance and algorithm expense.(3) Recently researches show that access traffics such as voice traffic have the bursty and time-sensitive characteristics. The upstream bandwidth allocation algorithm should be designed to restrain the traffic access time delay. EBA (Estimated Bandwidth Allocation) algorithm is studied in this paper. The EBA algorithm is composed of SEBA (Static Estimated Bandwidth Allocation) algorithm and SEBA (Static Estimated Bandwidth Allocation) algorithm. Both the theoretical evaluation and simulation results verified that the DEBA algorithm exhibits better performance than the SEBA algorithm. Moreover, the estimated bandwidth should be adjusted dynamically according to the traffic load in the DEBA algorithm.(4) Considering the multiple characteristics of the access network traffics, the multi-services QoS classification and resources scheduling algorithm are studied in this paper. A novel tri-level QoS classification scheme is proposed to provide priorities between ONU groups, between ONU within one group and within each ONU. Furthermore, to realize the priority scheduling and solve the tidal effect, a two-layer resource scheduling scheme is proposed and simulated. Finally, simulation results testify the correctness and effectiveness of the proposed algorithms.