业界专家最近的一次网络研讨会上表示，关键任务推送通话服务已经现实世界中部署，用户专门构建的LTE网络上应该对MCPTT语音充满信心，不过，用户离开网络时，通向强健的MCPTT的道路仍然不明朗
. 然而，据Softil产品和营销副总裁Sagi Subocki称，MCPTT服务已经韩国提供，Softil已经开发了MCPTT软件客户端的核心. “我们这里要说的是3GPP MCPTT/MCX标准不再只是一个理论。这是实地考察中的一个现实。这基本上是将关键任务通信提升到一个新的水平。”
业界专家最近的一次网络研讨会上表示，关键任务推送通话（MCPTT）服务已经现实世界中部署，用户专门构建的LTE网络上应该对MCPTT语音充满信心，不过，用户离开网络时，通向强健的MCPTT的道路仍然不明朗
AT T宣布，FirstNet用户将能够明年下半年订阅符合3GPP标准的MCPTT服务。然而，据Softil产品和营销副总裁Sagi Subocki称，MCPTT服务已经韩国提供，Softil已经开发了MCPTT软件客户端的核心
Subocki说，除了参与旨验证供应商解决方案工作和互操作性的MCPTT插件测试外，Softil的解决方案是该技术两个部署的一部分，不仅是MCPTT，还包括与韩国铁路通信相关的任务关键数据和视频（MCX）
“这不是概念证明或现场测试，”Subocki上周的网络研讨会上说>“我们这里要说的是3GPP MCPTT/MCX标准不再只是一个理论。这是实地考察中的一个现实。这基本上是将关键任务通信提升到一个新的水平。”
Subocki说，一个实现中，Softil客户端产品运行使用三星服务器的韩国电信网络上。他说，如果所有组件都符合3GPP标准，就会有很多好处
Subocki说：“一旦你实施了你的解决方案标准，那么你就能够为最终用户提供代理、客户——挑选和选择的能力。”。“他们可以利用我们的客户机，让它Sonim设备上运行，一个Nemergent服务器
“一切都将无缝运行，而且都符合标准并经过测试，可互操作；没有供应商锁定。而且，将来，如果您想更改任何带有internetwork的组件，这不是问题，因为您将从一个供应商将一个标准组件更改为另一个也符合标准的组件。”
关键任务开放平台（MCOP）计划的协调人Fidel Liberty也强调了MCPTT开放标准的重要性，MCPTT标准包含的关键绩效指标（KPI）与美国主要公共安全LMR协议P25几乎相同
“MCPTT的绩效目标与PMR相当，”Liberty说。“这是可行的，是可以实现的，我们将不久的将来看到这一点。”
考虑到MCPTT功能的这一基准目标，所有四位网络研讨会专家都表示，他们相信，当用户使用宽带网络时，符合标准的MCPTT将满足公共安全的语音通信需求，该网络为推送通话语音提供了适当的优先级和服务质量
国家公共安全电信委员会（NPSTC）LMR LTE集成和互操作性工作组主席Chris Kindelspire表示：“我对此感到非常满意。”。“你说的关键部分是：我（网络）的报道中，我有我需要的所有不同的部分和机制，使它都能工作……如果这是一个完美的环境，我会感到非常自信。”
Sonim Technologies负责公共安全细分市场的副总裁BobEscalle也表达了这种观点
“网络上，绝对（MCPTT会起作用的），”埃斯卡尔说。“我认为，有了优先权、抢占权、QoS和专用的EPC核心，我认为人们的信心不断增长和建立，而且今天还。”
但是，当不存健壮的宽带网络时，说话人对MCPTT的信心水平就大不相同了，因为3GPP标准中没有能够提供远程通信的非网络解决方案，而LMR可以网络不可用的情况下提供这种远程通信
金德尔斯皮尔说：“公共安全是直接模式、非网络（通信）的主要用户。”。“这是一个关键的部分，我觉得我们正努力克制，等待，看看这一部分将是什么。公共安全将如何采用这些措施？
“今天，我们两个不同的环境中工作。我们使用广域集群网络进行调度，但对于重大事件，我们仍然会关闭网络。”
MCPTT标准包括一个近距离服务（ProSe）标准，它不仅支持语音（MCPTT）的设备间通信，还支持数据（MCDATA）和视频（MCVIDEO）的设备间通信。然而，散文的范围是有限的，因为LTE设备通常只使用0.25瓦来与通常具有内部天线的设备传输信号
相比之下，LMR便携式设备配备了一个外部天线，可以支持信号以1瓦到5瓦的更高功率水平传输，换句话说，是典型LTE设备的4到20倍的功率水平，通常频谱上提供比商业运营商使用的电波更好的传播特性
此外，Escalle和Liberty表示，芯片制造商专注于支持自主汽车所需的5G和基于车辆的通信（V2X），因此他们并没有表现出对散文的兴趣或支持，三星表示已经开发出一种支持散文的芯片，并已将其嵌入设备中，但该公司迄今尚未披露这些芯片试用中的表现信息
埃斯卡尔说，这些挑战意味着公共安全和其他任务关键型用户“可能要等很长一段时间”，才能开发出一种类似于直接模式LMR通信的简单解决方案
考虑到这一点，Sonim技术公司一直寻求解决直接模式困境的替代方案，Escalle说。一个是Sonim LTE设备的900 MHz附件，它利用LoRa技术进行设备间通信。这个解决方案支持1-2英里的范围，但它不能与现有的LMR协议进行互操作，Escalle说
索尼姆还正开发Sonim LMR可拆卸式（SLED），该公司预计将3月的IWCE 2019活动期间展示。该底座设计用于连接Sonim XP8坚固的LTE智能手机，从而形成类似LMR的外形，并允许用户宽带网络不可用时利用高功率LMR直接模式通信
对于任何一个DMSLED操作，都可以用什么样的方法来解决这个问题。他说，利用现有的LTE无线电波将限制功率输出，并可能产生严重的干扰问题，但利用现有的LMR频谱，互操作性和互助信道可以有效地工作
埃斯卡尔说：“我们是否可以将其中的一些频道用于设备对设备的这项工作，这样我们就可以更容易地现有窄带资产（和MCPTT设备）之间实现互操作性。”。“我认为，如果我们不解决和实施一些符合标准或基于标准的设备到设备（解决方案），除了我们可以使用的散文外，我认为我们不会像大家希望的那样迅速地采用关键任务的PTT。”
除了基于设备的解决方案，专家们指出，业界正开发其他方法来解决这样一个问题，即当宽带网络不可用时，确保用户“非网络”情况下可以进行可靠的按键通话通信。一些值得注意的可能性包括“带着你的网络”解决方案，这些解决方案以背包或鹈鹕箱等小尺寸的形式被提出到大型车辆驱动的可部署解决方案中
金德尔斯皮尔说：“我不认为这是一个技术障碍。“我认为现它真的试图弄清楚生态系统会是什么样子。”
Mission-critical-push-to-talk (MCPTT) services already have been deployed in real-world situations, and users should be confident in MCPTT voice when on a purpose-built LTE network, although the path to robust MCPTT when users are off network remains unclear, industry experts said during a recent webinar.
AT T has announced that FirstNet users should be able to subscribe to MCPTT services that are “fully compliant” with the 3GPP standard during the second half of next year. However, MCPTT services already are being provided in South Korea, according to Sagi Subocki, vice president of products and marketing for Softil, which has developed the core of an MCPTT software client.
In addition to participating in MCPTT plugtests that are designed to validate that vendors’ solutions work and interoperate, Softil’s solution is part of two deployments of the technology—not just MCPTT, but also mission-critical data and video (MCX)—associated with South Korea railway communications, Subocki said.
“This is not proof-of-concept or field testing,” Subocki said during last week’s webinar (click here for free registration to an on-demand archive of the event). “This is actually commercially deployed, running MCPTT communications.
“What we’re trying to say here is that the 3GPP MCPTT/MCX standard is no longer just a theory. This is a reality in the field running. It’s basically taking mission-critical communications to the next level.”
In one implementation, the Softil client offering is running on the Korea Telecom network that utilizes a Samsung server, Subocki said. If all components meet the 3GPP standard, there are many benefits, he said.
“Once you implement your solution standard, then you are able to provide the end user—the agencies, the customer—[the ability to] pick and choose,” Subocki said. “They can take our client and have it running on a Sonim device, a Nemergent server.
“Everything will run seamlessly, and it’s all standard-compliant and tested to be interoperable; there’s no vendor lockdown. And, in the future, if you want to change any component with internetwork, it’s not a problem, because you are changing one standards component from one vendor to another that is also standards-compliant.”
Fidel Liberal, coordinator of the Mission Critical Open Platform (MCOP) initiative, also emphasized the importance of open standards for MCPTT, a standard that includes key performance indicators (KPIs) that are almost identical to those of P25, the primary public-safety LMR protocol in the U.S.
“The performance targets defined for MCPTT are comparable with PMR,” Liberal said. “It’s doable, it’s achievable, and we will be seeing this in the near future.”
Given this baseline target for MCPTT functionality, all four webinar panelists said they are confident that standards-compliant MCPTT will meet the voice-communications needs of public safety when the user is on a broadband network that provides the appropriate priority and quality of service to push-to-talk voice.
“I’d feel pretty comfortable with that,” according to Chris Kindelspire, who chairs the National Public Safety Telecommunications Council (NPSTC) LMR LTE Integration and Interoperability Working Group. “You said the key piece: I’m in [network] coverage, I have all of the different pieces I need and mechanisms to make it all work … If it’s a perfect environment, I’d feel pretty confident.”
Bob Escalle, Sonim Technologies’ vice president for public-safety market segments, echoed this sentiment.
“On network, absolutely [MCPTT will work],” Escalle said. “I think, with priority, preemption, QoS and a dedicated EPC core, I think the confidence level is growing and building and is there today.”
But the speakers’ confidence level with MCPTT is very different when a robust broadband network is not available, as there is no off-network solution within the 3GPP standard that can provide the kind of long-range communications that LMR can provide on a radio-to-radio basis when the network is unavailable.
“Public safety is a heavy user of direct-mode, off-network [communications],” Kindelspire said. “That’s one key piece that I feel like we’re trying to hold back and wait and see what that piece is going to be. How is public safety going to adopt those pieces?
“Today, we work in two different environments. We work on a wide-area trunked network for dispatch, but we still go off network for major incidents.”
The MCPTT standard includes a Proximity Services (ProSe) standard to support device-to-device communications—not just for voice (MCPTT), but also for data (MCDATA) and video (MCVIDEO). However, the range of ProSe is limited, as LTE devices typically use only 0.25 watts to transmit signals with devices that usually have an internal antenna.
By comparison, LMR portables feature an external antenna that supports signals being transmitted at much higher power levels of between 1 watt and 5 watts—in other words, four to 20 times the power levels of a typical LTE device—often on spectrum that provides better propagation characteristics than the airwaves used by commercial carriers.
In addition, Escalle and Liberal said that chipmakers are focused on 5G and vehicle-based communications (V2X) needed to support autonomous cars, so they have not demonstrated much interest or support for ProSe, Samsung has said that it has developed a chip that supports ProSe and has embedded it in devices, but the company has not disclosed information about the performance of those chips in trials to date.
These challenges mean that public safety and other mission-critical users “may be waiting for a very, very long time” for a ProSe solution to be developed that is comparable to direct-mode LMR communications, Escalle said.
With this in mind, Sonim Technologies has been pursuing alternative solutions to the direct-mode dilemma, according to Escalle. One is a 900 MHz accessory to Sonim LTE devices that leverages LoRa technology for device-to-device communications. This solution supports a range of 1-2 miles, but it does not interoperate with existing LMR protocols, Escalle said.
Sonim also is developing the Sonim LMR Enabled Detachable (SLED), which the company expects to showcase during the IWCE 2019 event in March. The SLED is designed to attach to a Sonim XP8 rugged LTE smartphone, resulting in an LMR-like form factor and allowing the user to take advantage of high-powered LMR direct-mode communications when a broadband network is not available.
While the SLED could be designed to utilize any LMR protocol—P25, DMR or TETRA—one unanswered question is what spectrum should be used for such alternative direct-mode operations, Escalle said. Leveraging existing LTE airwave for this purpose would limit the power output and could create significant interference issues, but utilizing existing LMR spectrum—notably, interoperability and mutual-aid channels—could work effectively, he said.
“Can we dedicate a few of those channels to this work effort on device-to-device, so we can have an easier way to have interoperability between our existing narrowband assets [and MCPTT devices],” Escalle said. “I think, if we don’t solve and implement some standards-compliant or standard-based device-to-device [solution] outside of ProSe being available to us, I think we’re not going to get to the adoption of mission-critical PTT as quickly as we’d all like.”
In addition to device-based solutions, panelists noted that industry is developing other approaches to tackle the issue of ensuring that users can have reliable push-to-talk communications in “off-network” scenarios when a broadband network is not available. Some notable possibilities include “bring the network with you” solutions that have been proposed in form factors as small as backpacks or Pelican cases to large vehicle-driven deployable solutions.
“I don’t really see that as a technology hurdle,” Kindelspire said. “I think right now it’s really trying to figure out what the ecosystem’s going to be.” |
