Push-to-talk Research Articles

The Real-Time Framework of the Push-to-Talk (PTT) Synchronization Scheme for Distributed SAR

Distributed synthetic aperture radar (SAR) has various applications, including multi-angle imaging, SAR tomography, and interferometric SAR. However, these applications are affected by several factors, especially clock synchronization. Recently, an innovative push-to-talk (PTT) scheme was proposed to tackle the clock synchronization problem. As the PTT scheme can directly obtain the time and frequency deviations of the ultra-stable oscillators (USOs), it gives the possibility to achieve the clock synchronization of distributed SAR in real-time. Therefore, this paper builds a real-time framework of the PTT scheme. Compared with the previous clock synchronization module (CSM), an estimation module and a control module are added in this framework to fabricate an improved CSM (ICSM). The time and frequency deviations obtained by the ICSM are used to directly correct the GPS disciplined rubidium clocks. Based on the ICSM, some simulations are performed. The results indicate that the established real-time framework can achieve high precision time and frequency synchronization. In addition, we discuss the system implementation.

An Innovative Push-To-Talk (PTT) Synchronization Scheme for Distributed SAR

Bistatic/multistatic synthetic aperture radar (Bi-/M-SAR) has extensive applications, including cross- and along-track interferometry, multiangle imaging, and so on. However, these applications are affected by several factors, especially the time and frequency synchronization that this article focuses on. Here, the new insights about the focus are described, based on which an innovative push-to-talk (PTT) scheme is first put forward to solve the time and frequency synchronization problems of distributed SAR. It realizes unidirectional and long-distance synchronization through the two-segment frequency rate (TSFR) waveform composed of the two linear frequency modulation (LFM) signals with different frequency rates and achieves radar imaging and synchronization with a high rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{\mathrm{ syn}}$ </tex-math></inline-formula> ) at the same time by the frequency diversity (FD) waveforms and bandpass filters. To clarify the PTT scheme, its system framework and synchronization error models are detailed. Besides, the channel impulse response, multiple errors, the signal-to-noise ratio (SNR) of synchronous links, and time synchronization accuracy are analyzed. In addition, some simulations are carried out to evaluate its performance. Those results demonstrate that the PTT scheme can perform the long-distance synchronization with high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{ syn}}$ </tex-math></inline-formula> , its synchronization accuracy increases with the improvement of SNR and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{ syn}}$ </tex-math></inline-formula> , and it can measure the time and frequency deviations in different ranges accurately. In a word, the PTT scheme has the potential to be used in future distributed SAR missions.

A Push-to-Talk Application as an Inter-Professional Communication Tool in an Emergency Department During the COVID-19 Pandemic.

ObjectiveTo assess the effects of using a smartphone-based push-to-talk (PTT) application on communication, safety, and clinical performance of emergency department (ED) workers during the COVID-19 outbreak.DesignAn observational, cross-sectional study.SettingED in an academic medical center.ParticipantsAll ED staff members, including physicians (consultants, specialists, residents, and interns), nurses, emergency medical services staff, technicians (X-ray), and administration employees.InterventionsEligible participants (n=128) were invited to fill out an online questionnaire 30 days after using a PTT application for sharing instant voice messages during the COVID-19 outbreak.Main Outcome MeasuresSelf-reported data related to communication, implementation of personal protective measures, and clinical performance at the ED were collected and analyzed on a 5-item Likert scale (from 5 [strongly agree] to 1 [strongly disagree]). Also, the proportions of favorable responses (agree or strongly agree) were calculated.ResultsResponses of 119 participants (51.3% females, 58.8% nurses, and 34.5% physicians; 90.4% received at least one notification per day) were analyzed. The participants had favorable responses regarding all domains of communication (between 63.0% and 81.5%), taking precautionary infection control measures (between 49.6% and 79.0%), and performance (between 55.5% and 72.3%). Receiving fake and annoying alerts and application breakdowns were the lowest perceived limitations (between 12.5% and 21.0%).ConclusionThe assessed PTT application can be generalized to other departments and hospitals dealing with patients with COVID-19 to optimize staff safety and institutional preparedness.

Push-to-talk apps for disaster communications: Hurricane season brings technology adaptation.

Effective communication during disasters is essential for emergency management, responders, and impacted populations. Recent hurricanes have drawn attention to the potential utility of push-to-talk (PTT) applications with some such as Zello, garnering over 6 million downloads during the week prior to Hurricane Irma. PTT technology integrates a two-way radio system to transmit and receive messages via point-to-point communication lines. With rapid implementation of newer technology and applications often driven by anecdotal reports and the media, the actual performance impact of such technology in the face of disasters is challenging to assess. This article attempts to characterize advantages and limitations of PTT in the context of hurricanes through primary news article sources.

Push-To-Talk 재난 서비스 환경에서 전송 지연 최소화를 위한 고속 데이터 복사 및 키 성능 지표 개선 방안

유무선 통신 기술 및 Internet Protocol (IP) 기술의 발전 및 보편화에 따라 최근 다양한 데이터 서비스가 등장하게 되었다. 이에 따라 1:1 데이터 전송을 주된 형태로 하는 전통적인 서비스와는 다르게, 1:N 데이터 전송을 활용하는 다양한 서비스가 등장하고 있으며, 이 서비스들은 1:N 전송의 효율성 및 성능 향상을 요구하고 있다. 특히 최근 많은 관심을 받고 있는 국가재난안전통신망에서 가장 중요한 서비스인 Push-To-Talk (PTT) 서비스의 경우 서비스 서버가 다수의 그룹 수신자에게 동일한 음성 데이터를 실시간 및 최소 지연 시간으로 전달해야 한다. 본 논문에서는 이런 서비스 요구 경향에 따라, 동일 데이터를 다수의 수신자에게 전달하기 위한 효율을 높이는 방법을 제시한다. 또한, 실제 유무선 통신망이 구축된 필드 환경에서 1:N 전송 성능을 어느 정도까지 높일 수 있는지 그 가능성에 대해 PTT 서비스 핵심 성능 지표 관점에서 분석해보고자 한다. A art from the typical data services based on 1:1 data communications, various new services based on 1:N communications have recently appeared. These services are becoming to require advanced 1:N communication schemes which can transfer the same data to many receivers efficiently and in high-performance. Especially, a Push-To-Talk (PTT) service, which is an important service in public safety communication system, requires a service server to disseminate the same voice media data to multiple receivers in a group in real-time and low latency. In this paper, we propose an efficient scheme to disseminate the same data to multiple receivers in low latency. In addition, we provide an analysis which gives a guide the performance of the 1:N communications in practical wired/wireless system environments in the perspective of the PTT service index.

Enabling Device to Device Broadcast for LTE Cellular Networks

In recent years, the public safety community has been aligning behind Long Term Evolution (LTE) technology as the basis for next generation public safety networks. Correspondingly, the 3rd Generation Partnership Project (3GPP) standards body has started multiple technical work initiatives on LTE enhancements to better support public safety use cases and requirements. Of particular importance to the public safety community is the addition of direct device-to-device (D2D) broadcast capability that can enable off-network push-to-talk (PTT) group communications in a manner equivalent to existing public safety communication systems. In this paper, we briefly explore the design objectives for, and challenges associated with, providing a D2D broadcast service. We then present and analyze a new distributed media access control (MAC) scheme for interference-aware coordination of both unicast and broadcast transmission. System-level simulation results are provided to validate the performance and the effectiveness of our approach, using a CSMA-based approach as a basis for comparison.

이종 기기 간 음성통신을 위한 자동전환장치의 구현

무전기의 음성통신은 PTT(: Push To Talk)를 이용한 반이중(half-duplex) 방식으로, 송신 시 단일 통화선로를 점유한다. 전화와 무전기간, UHF와 VHF 간의 인터페이스와 같이 서로 다른 이종 장치 간 음성통신을 위해서는 두 장치간의 자동전환장치가 요구되고, 이 장치는 입력 신호로부터 전송해야 할 음성을 검출하는 음성전환장치의 성능에 따라 전송되는 음성신호의 손실여부에 많은 영향을 받는다. 기존방식은 단순 입력신호의 크기 즉, 에너지 레벨을 통해 기준을 정함으로써 잡음에도 반응하는 문제점을 지니고 있다. 본 논문에서는 음성신호처리기법을 이용하여 입력된 신호가 음성임을 판별함으로써, 이종 기기 사이의 음성을 자동으로 전달하는 장치를 구현하였다. 이를 통해 음성 자동전환장치의 성능향상을 확인하였고, 이종 기기 간 음성 손실 없는 전송을 수행할 수 있었다. A radio is a half-duplex voice communication method using the PTT(: Push To Talk), occupy a single line calls during transmission. As an interface between the telephone and the radio, UHF and VHF, for voice communication between the different heterogeneous devices, A device automatically switches between the two devices is required. Therefore, in accordance with the performance of the voice switching apparatus for detecting a voice to be transmitted from an input signal, loss of the audio signal to be transmitted is subjected to Significant influence. Conventional method has the problem responding to noise by setting the level through simple means of amplitude of input signal, in other words, the energy level of the input signal. This paper, by using the audio signal processing techniques, this discriminated what the voice is among the input signal and substantiated a device for the automatic voice transmission between heterogeneous devices. With this proposal, I was confirmed of improvement of performance in the automatic voice switching device, could perform loss-less transmission of voice between heterogeneous devices.

PTT Service Interworking Between IMS Based Networks and P2P Overlay Networks

The demand for multimedia streaming services is increasing rapidly. To meet this demand, there has been much research and many practical developments for providing multimedia services. A push-to-talk (PTT) service is one of the multimedia streaming services that have been deployed not only over IP multimedia subsystem (IMS) but also in peer-to-peer (P2P) overlay networks. The benefit of PTT has been demonstrated in the literature. However, the need for using PTT service in communication can be arbitrary among users, regardless what kind of PTT services they use. This demand does not support current PTT systems, so an expansion of PTT services still be limited. Moreover, the combination of PTT services in IMS and P2P networks will help operators to provide more scalable PTT services. Therefore, in this paper, we proposed a model to support PTT service interworking between IMS and P2P overlay networks. We also introduced our system design and some interworking service scenarios. We confirmed our architecture through implementation and testing.

Public Safety Mobile Broadband: A Techno-Economic Perspective

Wireless communications are critical to supporting the operational capabilities of public protection and disaster relief (PPDR) organizations. The private/professional mobile radio (PMR) technologies currently used for PPDR communications offer a rich set of voice-centric services [e.g., push-to-talk (PTT) group calls] but have very limited data transmission capabilities and are unable to cope with increasing demands in the PPDR community for mobile data-centric applications. Introducing PPDR mobile broadband communications faces a number of technical and economic/business challenges. It is believed that the current paradigm for PPDR communications provisioning based on dedicated technologies, dedicated networks, and dedicated spectrum no longer constitutes the main approach for introducing PPDR mobile broadband, and hence new paradigms and innovative solutions are needed. Thus, this article first identifies and discusses the main techno-economic drivers across the technology, network, and spectrum dimensions that are anticipated to lay the foundations for future PPDR communications to be efficient and cost-effective. Then, relevant estimations and illustrative figures are provided to add perspective and valuable insight into the economic roots of the envisioned future PPDR mobile broadband communications.

Research of SIP Compression Based on SigComp

SIP (Session Initiation Protocol) has been chosen as the core signaling protocol of the NGN (Next Generation Network), but the large SIP message which is text-based is an obstacle with the planned usage of SIP in wireless mobile networks. Based on the SigComp (Signaling Compression) framework, some further improvements are made to the Deflate algorithm according to the characteristics of SIP in this study. Experiments show that the improved Deflate algorithm can compress the SIP message greatly and reduce the bandwidth requirements signally, so it is highly valued in IMS (IP Multimedia Subsystem), PTT (Push To Talk) and other wireless real-time SIP applications.

A new call control scheme of Push-To-Talk system

For Push-To-Talk (PTT) system based on Public Mobile Data Network (PMDN), the end-to-end time delay is the key aspect of the user’s experience. The Push-Over-Cellular (POC) scheme defined by Open Mobile Alliance (OMA) is based on the VoIP phone model and use SIP protocol as the call control scheme. The call setup time delay in SIP may reach to several seconds, which is unacceptable for the PTT service. In this paper, we provide a new call control scheme for PTT system based on PLMN network. By combining the apriority knowledge of PTT call model and the priority control scheme, we encapsulate the signaling message and the voice data into a same data packet, when the user push the button, the voice and the call control signaling are sent to the server at the same time. So the long time delay of call setup procedure of POC scheme can be eliminate. The end-to-end call delay can be decreased significantly. The experiment result based on the commercial CDMA2000 1X network of China Unicom shows that the call delay can be decreased to 600 ms, which approach to the traditional trunk communication system’s requirement.

Multimedia push-to-talk service in home networks

We propose a distributed Push-to-Talk (PTT) system model to support a one-to-many multimedia content distribution service. We also present a home-monitoring service scenario as an example that demonstrates how a multimedia PTT service can be used in wireless mesh-formed home networks. The proposed system uses wireless mesh routers for a home network. Centralized server-based functionalities for SIP session control and PTT service management are distributed over a set of mesh routers in manner of peer-to-peer system. To realize this service system, the system model and the implementation architecture were proposed and verified by real implementation.

Performance analysis of Push-To-Talk over IEEE 802.16e with sleep mode and idle mode

We investigate how much power saving can be achieved for a Push-To-Talk (PTT) service by employing sleep mode and idle mode in the IEEE 802.16e. In this paper, a mobile station by employing sleep mode during an on-session and idle mode during an off-session of the PTT service is modeled as a semi-Markov chain. We obtain power consumption of the mobile station, call setup delay and talker arbitration delay. Using our mathematical model, we can find the optimal sleep window satisfying the required quality of service (QoS) on call setup delay and talker arbitration delay. The numerical examples show that the sleep mode and idle mode provide a considerable reduction on energy of the mobile stations.

Cross-layer resource allocation for push to talk service over orthogonal frequency division multiple access-based networks with heterogeneous traffic

In this study, the authors propose a cross-layer resource allocation scheme for push to talk (PTT) service over orthogonal frequency division multiple access (OFDMA)-based networks. In our modelling, the authors consider two traffic types: streaming traffic, which requires a maximum guaranteed average delay and elastic traffic with flexible rate requirements. PTT traffic is also considered as a streaming traffic with more flexible delay requirements comparing to conventional streaming traffic. The authors consider queue state information as well as channel state information in a cross-layer framework to maximise the total transmission rate of the elastic users, while average delay constraint for streaming users, and maximum transmission power constraint are satisfied. An algorithm is then proposed based on dual decomposition method to obtain the subcarrier assignment and power allocation for each user. Using simulations, the authors then evaluate the impact of the streaming PTT traffic and other system parameters on the total rate of elastic users.

Design and implementation of the push-to-talk service in ad hoc VoIP network

Push-to-talk (PTT) is a walkie-talkie like service which performs an efficient and instant voice over Internet protocol (VoIP) communication in mobile ad hoc network especially for certain circumstances, such as battle field and earthquake or disaster relief. The authors have designed and implemented the PTT mechanism in ad hoc VoIP network. The PTT server and user agent combined with the pseudo session initiation protocol (SIP) server in the implementation provide the PTT service without standalone SIP server support. The authors also conduct the experimental measurements, in terms of delay and packet loss, in the test-bed to demonstrate the realisation of PTT service in ad hoc VoIP network.

Optimization of mobile ad-hoc network using distributed Push-to-Talk mechanism

In servicing based on Push-to-Talk (PTT) only one of several members of a group is allowed to send a message. In the present article a distributed PTT mechanism for a mobile ad-hoc network is considered. Precisely which member of the group is allowed to send messages is determined by means of distributed interaction.

Calculation of the average time of data transmission in a mobile ad-hoc network based on a distributed push-to-talk mechanism

Push-to-talk (PTT) service allows only a single member of a talk group to transmit a message. In this paper, a distributed PTT mechanism for a mobile ad-hoc network is considered. The group member who is allowed to transmit messages is determined by a distributed interaction.

IPTT: peer‐to‐peer push‐to‐talk for VoIP

AbstractThis paper proposes iPTT, a peer‐to‐peer (P2P) Push‐to‐Talk (PTT) service for Voice over IP (VoIP). In iPTT, a distributed and mobile‐operator independent network architecture is presented to accelerate the deployment of the PTT service. Based on the serverless architecture, we develop two mechanisms, that is, flooding‐based floor control mechanism (FFC) and tree‐based floor control mechanism (TFC), for real‐time talk‐burst determination. The determination algorithms and the corresponding message flows for these two mechanisms are designed to show the feasibility of FFC and TFC. The performance of FFC and TFC is investigated through our analytical and simulation models in terms of the determination latency and the number of floor‐control message exchanges. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Voice communications over zigbee networks

This article provides an overview of ZigBee-enabled wireless networks and discusses the feasibility of supporting voice communications over ZigBee networks. We begin by providing an overview of the ZigBee technology followed by an evaluation of voice quality and performance over such an impoverished wireless channel. Two types of voice communications, namely full-duplex voice over IP (VoIP) and half-duplex push-to-talk (PTT) are considered. Voice quality of VoIP is measured using the R-factor [1] (a well known objective speech quality metric). The quality of PTT, however, is evaluated based on packet-loss rate, delay, and jitter. The simulation results demonstrate that a low-power, low-rate wireless sensor network can support a limited range of voice services.

Push-to-Talk Service for Intelligent Transportation Systems

Push to talk (PTT) is a walkie-talkie like service. In this service, several predefined group members participate in one PTT session. At any time, only one group member is allowed to speak. Therefore, a mechanism is required to determine the member that is permitted to speak. In Open Mobile Alliance (OMA), a central arbitrator coordinates the permission to speak among the group members. In the Intelligent Transportation System (ITS) environment, the centralized OMA approach is not appropriate. This paper proposes a distributed PTT mechanism for the ITS environment, which does not require any central arbitrator. The group member permitted to speak is automatically determined through distributed learning interaction. We also explore the properties and model the performance of the proposed PTT mechanism.