Channel Selection and Frequency Assignment for General Authorized Accesses: Mechanism Design and Implementation

• Main Authors: Cheng-Feng Yang, 楊晟豐
• Other Authors: Shi-Chung Chang
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/d5m6pw

碩士 === 國立臺灣大學 === 電機工程學研究所 === 106 === In view of tremendous traffic growth of wireless communications, Federal Communications Commission(FCC) announced an innovative, 3-tiered regulatory framework of spectrum sharing to raise spectrum utilization and mitigate spectrum deficiency. The three layers are: Incumbent (IA, tier-1) which has highest access priority, Priority Access License (PAL, tier-2) whose users access can be protected with interference limit, General Authorized Access (GAA, tier-3) whose base station users may access through 3.55-3.7GHz and shall have no expectation of interference protection from other users. Wireless innovation forum(WInnF) proposed management system architecture for Citizens Broadband Radio Service(CBRS) consisting of spectrum access system(SAS), Domain Proxy(DP) and Network Management System(NMS) which manage the base station(CBSD). Although the rulings that overall GAAs can use at least 80 MHz bandwidth have been announced by FCC, detailed mechanism design is an immature stage. In this thesis, we worked on mechanism design and implementation aspects for GAA operators because there is lack of available solutions for fair accesses by GAA operators that increases spectrum efficiency yet. In specific, we shall focus on frequency assignment in SAS and channel selection in DP. The role of channel selection(CS) is to determine channel combinations for GAA CBSDs of operator that enhance its total capacity so that the users’ quality of service(QoS) are raised. The role of frequency assignment(FA) is to coordinate operators’ channel selection by assigning channels that maximizes total capacity of operators as well as protecting IAs and PALs’ QoS. Specific research problems of channel selection and frequency assignment(CSFA) mechanism design have two folds: I. Channel Selection: How does one operator determine channel selection that maximizes total capacity considering how interference affects total capacity? The challenges lie in highly non-linear relationship between interference and Shannon capacity and many combinations of channel selection. II. Frequency Assignment: How does SAS coordinate operators’ channel selections by assigning channels that aims to maximize total capacity of GAA operators while maintaining fairness among operators? The challenges lie in how should fairness among GAA operators be defined and how should SAS assign channel/frequency according to fairness and Shannon capacity maximization when operators’ total demands exceed available channels. To address problem I and its challenges, we designed a novel functionality of channel selection for single operator called single operator channel selection(SOCS). The SOCS design is non-linear knapsack problem(KP)-based formulation that maximizes the total capacity of operator and integrates two innovations. The first innovation is that our design complies with WInnF-TS-0016 DP/CBSD-SAS protocol. The second is we formulated the channel demand satisfaction concept as constraint based on the essences of equal access priority and no expectation of interference protection among GAAs. To address problem II and its challenges, we designed a functionality of SAS frequency assignment called multiple operator frequency assignment(MOFA). The MOFA design is I/O information items complying with WInnF-TS-0016 DP/CBSD-SAS data exchange protocol and non-linear KP-based formulation that maximizes total average capacity of GAA operators and integrates three innovations. The first innovation is defining proportional basic capacity fairness(PBCF) based on the essences of SAS that tries to do best effort to match demands of each operator and the equal quality among GAAs. The second is formulating the PBCF concept as a constraint. The third is defining and formulating coordination index into frequency assignment that try to match operators’ channel selections as much as SAS can. In SOCS scenarios, the findings and insights of our results are as follows: I1) In the spectrum scarcity scenarios with distributed distributions, operator will select an exclusive channel for the CBSD that has minimum total distance with other CBSDs. I2) In the spectrum scarcity scenarios with clustered distributions, operator will select one channel for most of required CBSDs and let remaining CBSDs monopolize other available channels. In MOFA scenarios, the findings and insights of our results are as follows: F1) In the abundant spectrum scenarios, if operators select the same channels to their CBSDs, then SAS coordinates operators’ channel selection until each CBSD monopolizes one channel. I3) In the spectrum scarcity scenarios with distributed distributions, total capacity of operators in SAS frequency assignment(coordination) is always higher than or equal to in operators’ channel selection. I4) In the spectrum scarcity scenarios with clustered distribution, proportional basic capacity fairness will decrease and SAS will assign channels to operators with maximum basic capacity of each CBSD (i.e. Q_max). In other words, the fairer total capacity among GAA operators in clustered distributions. F2) The computation time of SOCS and MOFA grows exponentially with number of required CBSDs and available channels. The time complexity of algorithms are O(NK^N), where K is total number of available channels and N is total number of required CBSDs. In the scenario with 10 required CBSDs and 3 available channels, the computation time of CS is 16-19 seconds and FA is 19-23 seconds. Furthermore, this thesis implements an online platform of channel selection and frequency assignment for operator. We implement a part of WInnF-TS-0016 DP/CBSD-SAS protocol in our platform. The CSFA system proofs of concepts by demonstrating two scenarios to capture the characteristics of CSFA and the feasibility of the system. Each channel has 10 MHz bandwidth and the time period of spectrum assignment is 6 hours. The environment of Scenario I: single operator with 3 required CBSDs and there are 2 available channels. Scenario II: Two operators, each operator has 2 required CBSDs and there are 4 available channels. After SAS replies the response to DP, CBSDs transmit on the channel based on the frequency assignment results. Moreover, in our system, we combine Gemtek X-Cell as CBSD to transmit throughout 3.55-3.6GHz. After channel selection and frequency assignment are done, our platform will control the transmission of X-Cell automatically. The overall processing time is around 28 seconds which algorithms run within 0.05 second, requests and responses of procedures take around 2 seconds and the time from DP control X-Cell’s configuration to X-Cell start transmitting is around 25 seconds.