Achievable Rate Region Bounds and Resource Allocation for Wireless Powered Two Way Relay Networks

( Xiaofei Di ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.2

This paper investigates the wireless powered two way relay network (WPTWRN), where two single-antenna users and one single-antenna relay firstly harvest energy from signals emitted by a multi-antenna power beacon (PB) and then two users exchange information with the help of the relay by using their harvested energies. In order to improve the energy transfer efficiency, energy beamforming at the PB is deployed. For such a network, to explore the performance limit of the presented WPTWRN, an optimization problem is formulated to obtain the achievable rate region bounds by jointly optimizing the time allocation and energy beamforming design. As the optimization problem is non-convex, it is first transformed to be a convex problem by using variable substitutions and semidefinite relaxation (SDR) and then solve it efficiently. It is proved that the proposed method achieves the global optimum. Simulation results show that the achievable rate region of the presented WPTWRN architecture outperforms that of wireless powered one way relay network architecture. Results also show that the relay location has significant impact on achievable rate region of the WPTWRN.

Characterization of the Pareto Boundary for the Two-User Symmetric Gaussian InterferenceChannel

Hojin Song,Jong Yeol Ryu,Wan Choi IEEE 2014 IEEE TRANSACTIONS ON COMMUNICATIONS Vol.62 No.8

<P>We characterize the Pareto boundary of the achievable rate region of the two-user symmetric Gaussian interference channel when transmitters control their transmission power and receivers have successive interference cancellation capability. By identifying the shape of achievable rate region according to the strength of interference channels, we find combinations of decoding and power allocation strategies achieving the Pareto boundary. We also characterize the Pareto boundary of the achievable rate region when time sharing is additionally considered.</P>

Bi-Directional Half-Duplex Relaying Protocols

Kim, Sang-Joon,Devroye, Natasha,Tarokh, Vahid The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.5

The bi-directional relay channel is the natural extension of a three-terminal relay channel where node a transmits to node b with the help of a relay r to allow for two-way communication between nodes a and b. That is, in a bi-directional relay channel, a and b wish to exchange independent messages over a shared channel with the help of a relay r. The rates at which this communication may reliably take place depend on the assumptions made on the relay processing abilities. We overview information theoretic limits of the bi-directional relay channel under a variety of conditions, before focusing on half-duplex nodes in which communication takes place in a number of temporal phases (resulting in protocols), and nodes may forward messages in four manners. The relay-forwarding considered are: Amplify and forward (AF), decode and forward (DF), compress and forward (CF), and mixed forward. The last scheme is a combination of CF in one direction and DF in the other. We derive inner and outer bounds to the capacity region of the bi-directional relay channel for three temporal protocols under these four relaying schemes. The first protocol is a two phase protocol where a and b simultaneously transmit during the first phase and the relay r alone transmits during the second. The second protocol considers sequential transmissions from a and b followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. We provide a comprehensive treatment of protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.

Bi-Directional Half-Duplex Relaying Protocols

Sang Joon Kim,Natasha Devroye,Vahid Tarokh 한국통신학회 2009 Journal of communications and networks Vol.11 No.5

The bi-directional relay channel is the natural extension of a three-terminal relay channel where node a transmits to node b with the help of a relay r to allow for two-way communication between nodes a and b. That is, in a bi-directional relay channel, a and b wish to exchange independent messages over a shared channel with the help of a relay r. The rates at which this communication may reliably take place depend on the assumptions made on the relay processing abilities. We overview information theoretic limits of the bi-directional relay channel under a variety of conditions, before focusing on half-duplex nodes in which communication takes place in a number of temporal phases (resulting in protocols), and nodes may forward messages in four manners. The relay-forwarding considered are: Amplify and forward (AF), decode and forward (DF), compress and forward (CF), and mixed forward. The last scheme is a combination of CF in one direction and DF in the other. We derive inner and outer bounds to the capacity region of the bi-directional relay channel for three temporal protocols under these four relaying schemes. The first protocol is a two phase protocol where a and b simultaneously transmit during the first phase and the relay r alone transmits during the second. The second protocol considers sequential transmissions from a and b followed by a transmission from the relay while the third protocol is a hybrid of the first two protocols and has four phases. We provide a comprehensive treatment of protocols in Gaussian noise, obtaining their respective achievable rate regions, outer bounds, and their relative performance under different SNR and relay geometries.

Achievable Zero-Error Rate Regions using Novel Location Assisted Coding (LAC) for Short Range FSO Communications

Thuan Nguyen,Duong Nguyen-Huu,Thinh Nguyen 한국통신학회 2021 Journal of communications and networks Vol.23 No.4

Recent free-space optical (FSO) communication tech nologies have demonstrated the feasibility of building WiFO, a highcapacity indoor wireless network using the femtocell architecture. In this paper, we introduce a cooperative transmission frameworkusing location assisted coding (LAC) technique to increase the over all wireless capacity. For a given network topology, LAC pro vides three different schemes with different coding/decoding pro cedures. Based on these schemes, achievable zero-error rate re gions for WiFO using LAC will be characterized. Both numericaland theoretical analyses are given to validate the proposed codingschemes.

Design of Distributed Beamforming for Dual-Hop Multiple-Access Relay Networks

Binyue Liu 한국전자통신연구원 2014 ETRI Journal Vol.36 No.4

This paper studies a dual-hop multiple-access relaynetwork where two independent source nodes transmitinformation to a common destination node with the aid ofmultiple single-antenna amplify-and-forward relays. Eachrelay node is subject to an individual power constraint. Wefocus on the design of distributed beamforming schemesfor the relays to support the transmission raterequirements of the two sources. To this end, we firstcharacterize the achievable rate region for this networkvia solving a sequence of corner point optimizationproblems proposed in this paper. We also develop severallow-complexity suboptimal schemes in closed form. Twoinner bounds of the achievable rate region aretheoretically shown to be approximately optimal in twospecial scenarios. Finally, numerical results demonstratethe effectiveness of our proposed approaches.

On Practical Issue of Non-Orthogonal Multiple Access for 5G Mobile Communication

Kyuhyuk Chung 한국인터넷방송통신학회 2020 International Journal of Internet, Broadcasting an Vol.12 No.1

The fifth generation (5G) mobile communication has an impact on the human life over the whole world, nowadays, through the artificial intelligence (AI) and the internet of things (IoT). The low latency of the 5G new radio (NR) access is implemented by the state-of-the art technologies, such as non-orthogonal multiple access (NOMA). This paper investigates a practical issue that in NOMA, for the practical channel models, such as fading channel environments, the successive interference cancellation (SIC) should be performed on the stronger channel users with low power allocation. Only if the SIC is performed on the user with the stronger channel gain, NOMA performs better than orthogonal multiple access (OMA). Otherwise, NOMA performs worse than OMA. Such the superiority requirement can be easily implemented for the channel being static or slow varying, compared to the block interval time. However, most mobile channels experience fading. And symbol by symbol channel estimations and in turn each symbol time, selections of the SIC-performing user look infeasible in the practical environments. Then practically the block of symbols uses the single channel estimation, which is obtained by the training sequence at the head of the block. In this case, not all the symbol times the SIC is performed on the stronger channel user. Sometimes, we do perform the SIC on the weaker channel user; such cases, NOMA performs worse than OMA. Thus, we can say that by what percent NOMA is better than OMA. This paper calculates analytically the percentage by which NOMA performs better than OMA in the practical mobile communication systems. We show analytically that the percentage for NOMA being better than OMA is only the function of the ratio of the stronger channel gain variance to weaker. In result, not always, but almost time, NOMA could perform better than OMA.