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위성 네트워크에서 처리량 향상을 위한 충돌 인식 랜덤 액세스 기법
- Author(s)
- Noh HongJun
- Advisor
- 임재성
- Department
- 일반대학원 컴퓨터공학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2015-02
- Language
- eng
- Alternative Abstract
- Satellite networks (SATNETs) have become important for next-generation communication infrastructures because of their advantages, such as wide service areas, centralized management, and ease of installation at any geographic location. Next-generation SATNETs require an efficient multiple access scheme that is able to handle a large number of satellite terminals and bursty traffic conditions. Random access (RA) schemes are suitable for these conditions. For transmitting user traffic through an RA channel, the enhancement of the throughput is the most important aspect. For this reason, many enhanced RA schemes that use successive interference cancellation (SIC) have been developed. However, when the traffic load exceeds a certain amount, the throughput decreases sharply because of the increasing number of collisions that cannot be resolved by SIC. Thus, for a further improvement in the throughput, the development of new RA schemes to reduce collision probability and overcome collision effects is required. This dissertation addresses traffic load control (TLC) schemes for the stabilization of a traffic-load-sensitive RA channel and presents the design of new RA schemes based on advanced coding techniques. We propose two TLC schemes: 1) access control contention resolution diversity slotted ALOHA (AC-CRDSA), and 2) fast congestion control (FCC). These schemes provide an environment in which the SIC for RA schemes can fully operate. We also propose two RA schemes based on advanced coding techniques: 3) analog network coding ALOHA (ANC-ALOHA), and 4) augmented cyclic code shift keying spread spectrum ALOHA (ACCSK/SSA). These schemes facilitate the alleviation of collision effects and maximization of SIC utilization in the slotted and asynchronous RA system. For enhanced RA schemes using SIC and packet repetition, AC-CRDSA provides an accurate traffic load estimation technique. AC-CRDSA controls the traffic load on a channel according to the estimated traffic load and maintains the maximum throughput under a high traffic load. The inflow of excessive traffic larger than the maximum throughput causes congestion in an RA channel. The operation of FCC is based on the backlogged traffic load that has suffered transmission failures in previous frames, and ensures the transmission priority of backlogged traffic. Thus, FCC guarantees both maximum throughput and a low packet loss ratio under severe time-varying traffic conditions. In a slotted RA channel, ANC-ALOHA provides a connection establishment between two users who want to use analog network coding (ANC), and guarantees successful transmission from start to finish. It also provides a channel estimation technique for slotted channels, which is a prerequisite of SIC. By exploiting the inherent advantages of ANC, ANC-ALOHA almost doubles the throughput of slotted RA schemes. In an asynchronous RA channel, ACCSK/SSA significantly improves spectral efficiency and simplifies the correlator configuration. Combined with SIC, ACCSK/SSA achieves additional throughput enhancement, even in the presence of unbalanced packet power.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Computer Engineering > 4. Theses(Ph.D)
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