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Published in Gillian M. Davis, Noise Reduction in Speech Applications, 2018
To deal with unwanted echo, functional components known as “echo cancellers” are deployed in the local exchange, the VoIP gateway, or the VoIP terminal (e.g., PC, IP telephone), usually as close as possible to the tail circuit that generates the echo. Referring to Figure 11.8, an echo canceller next to the hybrid on User B’s side of the network “faces out” at User B and cancels the echo of User A’s voice that would otherwise be heard by User A.
Mobile Internet
Published in K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic, Wireless Multimedia Communications, 2018
K.R. Rao, Zoran S. Bojkovic, Dragorad A. Milovanovic
Another cellular-based solution emulates a traditional GSM visitor location register (VLR) for WiFi-based VoIP calls. The objective is to enable roaming between WiFi networks. A VoIP gateway emulates a serving mobile switching center (MSC) to register the IP interface of the phone and perform handoffs from/to the WiFi access domain using standard VLR techniques.
Design and implementation of a VoIP PBX integrated Vietnamese virtual assistant: a case study
Published in Journal of Information and Telecommunication, 2023
Hai Son Hoang, Anh Khoa Tran, Thanh Phong Doan, Huu Khoa Tran, Ngoc Minh Duc Dang, Hoang Nam Nguyen
The core components of a VoIP network, as shown in Figure 1, include the gateway, VoIP server, and end-user equipment (Gohel & Lakhtaria, 2010; Martin et al., 2018; Montazerolghaem et al., 2016; Senthil Kumar et al., 2015; Suwannaraj & Boonkrong, 2014). Gateway: This component helps to convert analogue signals into digital signals (and vice versa).VoIP gateways: These act as a bridge between the regular telephone network PSTN and the VoIP network.VoIP server PBX: The central server has the function of routeing and securing VoIP calls. In the H.323 network, it is called the gatekeeper. In an SIP network, servers are known as SIP servers.End-user equipment, i.e. a softphone and personal computer: This includes a headphone, software, and an Internet connection. Popular free software includes Skype or MS Teams.Phone to communicate with IP adapter: to use a VoIP service, a regular phone must be attached to an IP adapter to connect to the VoIP server. An adapter is a device with at least one RJ11 port (for attachment to the phone), an RJ45 (for attachment to the Internet or PSTN line), and one power port.IP phones: phones used exclusively for VoIP networks. IP phones do not need a VoIP adapter because they are built-in to enable direct connection to the VoIP server.
NomadicBTS: Evolving cellular communication networks with software-defined radio architecture and open-source technologies
Published in Cogent Engineering, 2018
Emmanuel Adetiba, Victor O. Matthews, Samuel N. John, Segun I. Popoola, Abdultaofeek Abayomi
As illustrated in Figure 1, the VoIP PABX carries out functions like call control and mobility management. It also implements voice mail server and VoIP gateway. The VoIP gateway provides interconnection to the PSTN and to the traditional GSM network using SIP and Real-time Transport Protocol (RTP) via an Internet Telephony Service Gateway (ITSG). In this study, the VoIP PABX section of the NomadicBTS architecture was realized using Asterisk, which is a leading software VoIP PABX (Imran, Qadeer, & Khan, 2009).