Kosasih, Alva (2017) Study On Expectation Propagation As A Low Complexity Detector Algorithm For 5g Wireless System. Magister thesis, Universitas Brawijaya.
Abstract
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English Abstract
In near future fifth generation of wireless system (5G), a huge number of transceivers antennas will be employed. Specifically, the 5G system will employ hundreds even thousands antennas that known as massive Multiple-Input Multiple-Output (MIMO) technology. It brings a lot of advantages such as maximization of spectral efficiency (SE) and larger channel capacity [1], [2]. However, the implementation of high dimensional antennas results a technical issue that needs to be solved. This mainly issue regarding unaffordable complexity. Considering the symbols detection at the massive MIMO receiver side, the conventional symbols detector algorithm such as maximum a posteriori (MAP) can no longer be used due to the unaffordable complexity. The conventional detector algorithm complexity increases exponentially with the dimension of the system because it needs to calculate the feedback loop operation in every iteration. Therefore, a low complexity detector algorithm becomes the main requirement in order to implement the massive MIMO systems. In this thesis, we propose two major contributions. First, we propose a low complexity detection method for the SCMA detector named the expectation propagation algorithm (EPA). The EPA approximates the marginal distribution of the posterior probability by using an exponential family [3]. Given that the probability in exponential family is easy to compute, the EPA is suitable to deal with high order and dimensional system. We also provide theoretical analysis to evaluate the performance of EPA SCMA. We show that the EPA for SCMA can achieve near optimal detection performance as the numbers of transmit and receive antennas grow. With the theoretical promise, we investigate the necessity of constellation rotation, which is used to increase the degree of freedom [4, 5]. We show that for the uplink scheme, channel responses from different users vary and thus increase the identifiability of each user. Therefore, appending a rotation value in SCMA encoder is unnecessary. The removal of the rotation, value can omit many unnecessary calculations not only in decoding but also in SCMA encoding. ii Second, we propose a novel algorithm i.e. decentralized expectation propagation algorithm (EPA) to support massive MU-MIMO system which outperforms decentral- ized AMP [6]. We also investigate the EPA complexity which lies on the dimension of the EP inverse matrix. Originally, the dimension of the EP inverse matrix is equal with the dimension of transmitter antennas. By implementing the partially decentral- ized system, we significantly reduce the dimension of the inverse matrix to become C times smaller than the original one, where C denotes the number of the decentralized system we have. In addition, we provide the theoretical analysis for each decentralized EP systems.
| Item Type: | Thesis (Magister) |
|---|---|
| Identification Number: | TES/624.177 4/KOS/s/2017/041712459 |
| Uncontrolled Keywords: | EXPECTATION - MAXIMIZATION ALGORITHM, WIRELESS COMMUNICATION SYSTEMS |
| Subjects: | 600 Technology (Applied sciences) > 621 Applied physics > 621.3 Electrical, magnetic, optical, communications, computer engineering; electronics, lighting > 621.38 Electronics, communications engineering > 621.382 Communications engineering > 621.382 028 5 Wireless communication systems --Data processing |
| Divisions: | S2/S3 > Magister Teknik Elektro, Fakultas Teknik |
| Depositing User: | Nur Cholis |
| Date Deposited: | 11 Apr 2018 01:35 |
| Last Modified: | 25 Nov 2021 06:33 |
| URI: | http://repository.ub.ac.id/id/eprint/9318 |
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Bab V.pdf Download (61kB) | Preview |
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Bagian Depan.pdf Download (957kB) | Preview |
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