how to cover a warehouse the size of three football fields with wireless telephony

DECT is a wireless IP telephony standard, an alternative to Wi-Fi telephony and cellular communications. It has many applications, but for covering large areas with complex layouts (for retail, manufacturing) it is unrivaled.

In the article I will compare different solutions for wireless telephony, tell you how and where DECT is used and why it is needed if you already have Wi-Fi. Using an example of a project for a large retailer, I will show how we deployed DECT in a huge food warehouse, what difficulties we encountered and what non-obvious details need to be taken into account when implementing the technology.

About DECT

DECT (digital enhanced cordless telecommunications) is a standard for wireless telephony and IoT communications. It is familiar to us from ordinary home cordless phones. But the superpower of DECT is the ability to switch the handset between base stations. That’s why the DECT network is called microcellular: in essence, it is a private cellular network that is capable of providing telephone communications to large objects.

The DECT infrastructure consists of a set of base stations (BSs) that provide radio coverage to telephones and a control core. The core must be connected to the SCS, and stations can communicate with their DECT network via both the SCS and the radio channel. Handsets for DECT require special ones, just like for cellular or Wi-Fi telephony.

DECT is a flexible standard. It is used in small scale homes and small offices. But the greatest advantages over other types of telephony appear when it is necessary to provide communication in large premises with a complex layout, in which subscribers do not have fixed workplaces: warehouses, large service stations, stadiums, sports centers, medical institutions, large manufacturing and industrial enterprises.

In addition to telephony itself, DECT is used for messaging and M2M interactions. For example, broadcast alerts like “there is an emergency situation at the production site” or more complex commands that take into account the location can be transmitted to handsets: “the nearest nurse should urgently approach such and such a ward.”

DECT vs other wireless telephony implementations

Solutions available for wireless telephony are based on:

• provider infrastructure – cellular (Fixed Mobile Convergence, FMC technology).

• own infrastructure: Wi-Fi and DECT.

Comparison of methods for organizing wireless IP telephony

In the segment of large facilities with complex layouts, such as warehouses or industrial premises, the use of cellular communications is complicated, at a minimum, by the presence of “blind spots”. Therefore, the choice remains between Wi-Fi and DECT.

DECT vs Wi-Fi

Both DECT and Wi-Fi create physical and data link layer communications (in the OSI model). At the same time, DECT was originally designed for voice transmission; for this task it is more reliable and stable.

Frequencies. DECT operates at frequencies of 1880-1900 MHz, Wi-Fi at frequencies of 2.4, 5 and 6 GHz. The Wi-Fi spectrum is noisier, including other Wi-Fi networks, and voice traffic is sensitive to delays. In addition, due to the higher frequency of the Wi-Fi radio signal, phones use more energy and die faster.

Encryption. DECT uses voice encryption at the implementation level of its protocol. Wi-Fi also has encryption, but the choice of protocol depends on the network administrator; you need to understand which protocol is secure and which is not.

Roaming and handover. Handover (handover of a call between BSs while moving) and roaming (registration of a handset in different friendly networks) during a DECT call occurs smoother and faster. In a Wi-Fi network, due to proper network planning and configurations, it is also possible to achieve switching within, say, 50 ms from point to point, but this will require special client devices that support the required 802.11r/k/v protocol stack.

Isolation from the Internet. The DECT channel is isolated from the Internet, which is certainly safer. Wi-Fi-based telephony usually has a connection to a local network and often to the Internet, and you have to additionally think about how to implement network and cryptographic protection.

Number of base stations. To cover the same area with wireless communications, Wi-Fi requires twice as many BSs as DECT.

Of course, most of the features mentioned can be implemented for Wi-Fi. But to achieve the same voice quality, safety, and absence of handover problems, you need dancing with a tambourine additional efforts that require knowledge, resources, additional technical solutions and focus. All this creates room for mistakes.

The main reason why they still choose Wi-Fi-based telephony is the ability to use the already deployed Wi-Fi infrastructure convergently, for transmitting both data and voice traffic. The implementation of DECT involves the creation of a parallel specialized wireless network. Not everyone wants to pull the cable twice, buy equipment, or add new support tasks.

Wi-Fi-based telephony is implemented using applications on smartphones or specialized Wi-Fi phones. This is suitable when you need only 5-10 handsets in an office with plasterboard walls, where the spectrum noise is low and the utilization of Wi-Fi channels has a good supply. But if you have hundreds of tubes that move between rooms, basements and warehouses, where there is a lot of reflected signal, and the points hang high under the ceiling, Wi-Fi will be difficult.

Companies deploying DECT most often deploy Wi-Fi in parallel to transmit other data, and sometimes other networks (for example, access control systems).

Case of DECT implementation in a warehouse

Using the example of our recent project for a large Russian retailer, where we deployed DECT, I will show how the layout and features of the premises themselves affect the network configuration.

The project started at the end of 2023. It was necessary to deploy a DECT wireless telephony system in a warehouse. The total area is several tens of thousands of square meters, a height of 50 meters, many walls, separate rooms, complex objects like a huge metal door, etc.

The warehouse is located in two buildings. One of them has just been built, where DECT needs to be deployed from scratch, in parallel with Wi-Fi and SCS for other types of traffic. The second warehouse building was built a long time ago and already has deployed DECT based on the vendor Gigaset. The DECT version is old and does not allow scaling telephony to meet current needs, including the number of supported phones. It is necessary to replace the old DECT version (N720 IP Pro) with a new one (N870 IP Pro), which will support the required scaling. The new version of the network was immediately deployed at the new warehouse.

DECT from Gigaset

Gigaset's DECT infrastructure looks like this:

• Phones. The line includes beautiful color phones, and there are handsets with protection against dust and liquids IP65, which can be dropped into lava the vendor defiantly throws it on the floor at every conference.

• BS. External antennas can be attached to the basic version of the stations, which increase coverage.

• DECT Manager – a control device that can control a system up to 60 BS in size.

• Integrator – additional control device for combining the BS under the control of several DECT dispatchers into one system.

The DECT manager and integrator are the control devices and are called the core of the network. In the core, DECT phones are registered using IPUI (the international user identifier of each handset) and are linked to a short corporate SIP number managed by a third-party IP-PBX.

The BS, DECT manager and integrator are deployed as the same PAC, to which the corresponding roles can be assigned. In addition, the integrator can be deployed as a virtual machine.

Gigaset DECT versions:

Gigaset has special solutions for M2M, allowing you to send messages to subscribers or notifications to applications on devices that lead to automatic actions. In this project we did not need it, in others we use it.

We love working with Gigaset solutions. The vendor has a proactive position, and its employees, including the technical director of the Russian representative office, are easy to contact. Correctly configured and connected points can be left untouched for years. Gigaset offers detailed and well-structured manuals and provides technical support in Russia. This is one of the few European vendors who have not left the Russian market.

Implementation implementation

Project phases

1. Technical preparation of the project, planning of equipment placement: 4 weeks.

2. Our contractor installs the SCS.

3. We prepare and configure the BS and core devices, the contractor installs them.

4. We configure and commission the kernel and BS: 4 days.

5. We connect phones: 4 days.

Planning for BS placement. The positions of the stations on the building map were calculated using software that overlays radio signal sources on the building map, taking into account the thickness and materials of the walls (sandwich panels, concrete, iron mesh, etc.). The distance between the two stations was 30-50 m.

If you need to measure power very accurately in a real room, the vendor provides measuring equipment. Radio signal sources are placed at the required points, and its power is measured on site. In this project we did not need such super-precision.

Deployed infrastructure. An integrator, 2 DECT dispatchers and 50 BS are deployed at the new warehouse, while at the old warehouse there is a DECT dispatcher and 16 BS. Both warehouses are connected via SCS. Communication switches when employees move between warehouses due to roaming. In total, 80 phones are used in warehouses, but their number will grow and now there are no restrictions for this.

Inconsistency with the building plan. In some places, the actual layout did not correspond to the diagram provided by the customer and according to which we calculated the placement of equipment. Sometimes this affected the coating, sometimes the possibility of installation. We had to adjust the position of the BS, sometimes create creative fastenings where there was no wall that we were counting on.

Connecting complex areas via SCS. BSs standardly exchange all service information (synchronize) with the DECT core via radio. Without this, the BS cannot service phones. We connected premises that are inaccessible to the main system via radio to the core via SCS.

For example, the signal from the warehouses simply did not reach the checkpoint, so the BS at the checkpoint was connected to the core via a wired connection. Another room to which the signal did not reach was a battery room for charging electric forklifts. Its walls shield the signal, and the three of us opened the huge doors, seven meters high. With the door open, a radio signal is received inside, but with the door closed, it is dull. We also solved this by connecting the premises via SCS.

Tyranny of design. On the day of acceptance, the customer suddenly discovered that the color of the BS patch cords did not match the walls. On the same day we re-hanged the patch cords so that they were the right color. This was unexpected; this topic had not come up before in negotiations with the customer. However, in some organizations, designers are required to participate in coordinating the deployment of equipment.

Transfer of subscribers from the old version of DECT. We did not find any automatic tools to transfer phones from N720 to N870. We announced downtime for several hours. There was a queue of people with phone bags from entire departments. To connect subscribers to the new network, we manually linked the IPUI of each user to a SIP account in the DECT manager interface and then performed all the necessary operations on each phone to register the user in the new network. In total, 70 phones were transferred this way.

Result. The old and new warehouses are completely covered by wireless telephony, employees are always in touch. If necessary, the space between warehouses can also be covered with telephony; for this purpose, all-weather cases with thermoregulation are added to the BS, and tubes with external antennas can be used to expand radio coverage. So far, however, there is no such request.

Bottom line

So, of all wireless telephony solutions, DECT is most suitable for large areas with complex layouts.

• Compared to cellular communications, DECT makes all connections through its own infrastructure, the user controls access to it independently. In addition, DECT provides communication in “blind spots” where the cellular signal does not reach.

• Compared to Wi-Fi, DECT is better suited for secure and reliable voice connections that do not compete with other types of traffic.

If you are also interested in reading about the implementation of telephony, read how we transferred a customer from a Western vendor to Russian SATEL