Two ways radios systems play a crucial role in both general commercial use and large enterprises or institutions like police, army and more institutions. In the realm of virtual trunked systems, Hytera has introduced the XPT cluster system, known as the small cluster, which is ideal for businesses with significant volumes but limited budgets. Let’s delve into the world of Hytera XPT enhanced wireless intercom virtual cluster technology.
Table of Contents
Why virtual trunked systems are needed?
While digital conventional communication systems bring together the benefits of two-way wireless communication and digital technology, they have limitations when it comes to channel resources. Typically, a conventional system can support only two simultaneous calls, restricting the number of terminals that can initiate different calls concurrently. On the other hand, digital trunked systems provide broader coverage, superior noise resistance, and automatic allocation of channel resources. However, building a cluster system in this environment is complex, and upgrading a conventional system to a cluster system is inconvenient and expensive.
What is XPT ?
XPT (Extended PseudoTrunk, Enhanced Virtual Trunk) is an innovative-distributed cluster solution developed by Hytera. It combines Hytera’s self-developed virtual cluster technology with the advantages of a digital virtual trunked system. The XPT system offers three primary advantages: the absence of a special control channel, low construction cost, and load balancing. XPT fills this gap by offering an affordable digital upgrade solution that connects multiple turntables to form a virtual clustering system. It caters to professional digital business-critical users who require high-density voice and data communications on a single site. XPT leverages clustering technology to provide scalability, efficiency, and clear audio quality, expanding communication capacity by sharing logical channel resources. It enables more users to engage in rapid and efficient voice and data communications within the same system.
In a typical XPT system network topology, various components come into play, including terminals, turntables, Ethernet switches, routers, IPPBX, third-party applications, RDACs, and telephone networks. Terminals communicate with other devices through the relay station, and the relay stations are connected through switches. The XPT site connects to the WAN (Wide Area Network), third-party applications, and RDACs via routers. The XPT system can also be connected to the telephone system through an IPPBX device. The diagram below illustrates this topology.
How It Works ?
XPT integrates multiple turntables operating in digital transit mode within the same area to create an XPT site. By sharing the logical channels of the turntables, terminals are allowed to communicate across all turntables in the station without the need for a dedicated control channel. This setup improves channel utilization significantly. In the XPT system mode, a call is initiated on the terminal’s main transfer platform. When the terminal’s main transfer console is busy, the terminal can seamlessly move to other available transfer repeater to initiate voice or data services. This reduces waiting time for terminal access to the system and maximizes communication capacity while ensuring a certain level of service quality. The probability of all logical channels being occupied simultaneously is low, resulting in a much lower call rejection rate compared to systems with only one conventional channel. With XPT, enterprise users can communicate quickly and efficiently through voice and data on the same system.
Virtual Trunked Network topology
Main Transfer Table
Every terminal within an XPT site has its designated main turntable. For example, let’s assign R1 as the main turntable for G1, G2, and G3. When the terminal’s main turntable is idle, it always listens to its primary turner and determines if there is an ongoing call in the current XPT system based on the system broadcast of the main turner. When an idle timeslot is available on the primary transit console, the endpoint takes priority in initiating a call on its main turntable.
Group Membership
Within an XPT site, a turntable can be associated with one or more groups, representing active end-user groups in the system. Each user group can only belong to one transfer console, and duplicate belonging groups of different transfer stations within the same site are not allowed. For instance, if G1, G2, and G3 are set as the home group for transfer station R1, they cannot be set as belonging groups for other transfer consoles.
When a transfer station receives a group call request while idle, it determines whether the group call belongs to the groups associated with the transfer station within the site. If it does, the relay station informs other relay stations in the site that it is updating its status by relaying the group call and broadcasts it to terminals listening to it. This ensures that members of the belonging group receive the group call. If a terminal initiates a group call request for a group that does not belong to the site, the transfer station rejects the request, and the terminal cannot initiate the group call.
When a transfer station receives information about other transfer stations relaying group calls while in idle state, it determines whether the group call belongs to the group it belongs to. If it does, the relay station immediately starts transmission and broadcasts it to terminals listening to it. This ensures that members of the belonging group promptly switch to the relay station relaying the group call to receive it. If the group call does not belong to the group, the relay station ignores it.
Free Transfer Table
When the terminal’s main turntable is busy, it switches to listen to the free turner and utilizes the idle timeslot on the free turner to initiate a call. For instance, if G1 and G2 calls are being relayed on R1’s timeslot 1 and timeslot 2, members of G3 will switch to the free turntable R3 to listen or initiate a new call. Each XPT site needs to designate a free turntable at all times unless all relay stations in the site are occupied. In each LAN site, any successfully registered and idle relay station can be elected as the free relay station, allowing only one free relay station to exist at a time.
Turntable Assignment
Terminals need to configure their main turntable within the XPT site using CPS (Customer Programming Software) by writing the appropriate frequency. All stations must evenly distribute terminals across their main turntables to ensure optimal system access performance. Endpoints within the site should be distributed evenly to different primary turntables to maximize their entry into the XPT system with the best performance. Group calls that are not configured within any system site cannot be initiated within the system.
Distribution of Free Transfer Table
- At any given time, only one free turntable can exist within the XPT system.
- Any successfully registered and idle turntable within the XPT site is eligible to be elected as a free turntable.
- When the free relay station is busy, it reassigns another idle relay station as the new free turntable, allowing terminals to re-initiate calls using the free turntable.
Multiple XPT single-station systems can be connected through an IP network to form an IP interconnected digital virtual trunked system, which is known as the XPT multi-station cluster system. This multi-station system ensures the sharing of channel resources among XPT single-station cluster systems and expands the communication coverage of the XPT system.
By upgrading the terminal and software module of the turntable, an XPT system can be formed based on the existing digital conventional system. This solution satisfies the requirements of enterprises to flexibly expand their call capacity within the existing system, while minimizing the need for additional equipment and reducing upgrade costs. The XPT system provides a cost-effective digital clustering solution with the scale, efficiency, clearer audio quality, and expanded communication capacity necessary for professional digital business-critical users.
About Juan D. Guerra
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