How to Design a DECT System

August 17, 2010 by Garrett Smith

If you read my previous post which detailed what DECT technology is, how it applies to VoIP, and the benefits it offers over its closest competitor; Wi-Fi phones, and are interested in building your own DECT solution, whether it be at your home, small office, or enterprise, this post is for you.

Obviously IP DECT solutions offer many benefits to its end users, the first and most obvious is mobility. Most of us have grown accustomed to living in a world where “we can always be reached”, and usually when we find ourselves in a position where we can communicate with outside world, we panic because we have come so accustomed to always being connected.

As it relates to VoIP, mobility is offered in many different ways weather that be via a wireless headset connected to your desk phone, a cordless Wi-FI solution leveraging your existing WLAN, cordless soft phones installed on laptops, or VoIP DECT solutions.

Consumer Versus Enterprise DECT Solutions

When we speak about VoIP DECT solutions, we usually like to separate the solution and distinguish between a consumer grade DECT solution or enterprise grade DECT solution. Most consumer grade DECT solutions are found in a home or small office environment with usually 1-8 users. A DECT solution could meet your complete phone system needs in a SOHO environment.

An enterprise DECT solution is meant for those large environments where we are dealing with anywhere from 10 to 1500 users. Most of these solutions can be found in large manufacturing facilities, healthcare, college campuses, and government applications.

As it relates to the environment, obviously there are different DECT solutions and products that achieve both the requirements of a SOHO or Enterprise DECT Solution.

Planning a DECT System

When it comes to planning out a DECT solution, there are many factors to consider especially if you are planning an enterprise-like deployment. You will want to meet all of your users needs as well as present the best quality as it relates to functionality, voice quality, and mobility. Below, we will detail a few of these considerations.

  • Number of Users- How many DECT handsets will you need to completely satisfy all of your users. Like I said, most SOHO DECT solutions can handle 6-8 Users. This is a limitation of the solution itself as the base station used in these applications can only support 6-8 total DECT handsets paired to it. If you are customer that needs more than 8 DECT handsets, then you will need to look at an enterprise grade DECT solution.
  • Call Control Platform- Most SOHO DECT applications have been tested to work with most SIP based PBX’s or service providers. I can tell you that I have personally tested many of the SOHO based DECT solutions with in-house asterisk software or open-sourced distributions of asterisk and the solutions work like a charm. If you are using a service provider, you will want to check with them first to ensure your DECT solution will work with their network and call control platform. Some Enterprise DECT solutions also work on a SIP Based call control platform but some offer interfaces to the Cisco Call Manager or Unified Communications platform, interfaces to older legacy (analog PBX’s) via the use of a special DECT gateway.
  • Size of the DECT signal coverage- DECT operates on the 1.9GHZ frequency has the ability to span anywhere from 300 meters to 1000 meters from one particular DECT Base station or Access Point. Obviously signaling and the strength of the DECT Frequency is affected by any physical barriers which we will talk about in our next considerations. The Snom M3 SOHO DECT solution offers DECT repeaters which simply repeat DECT signal even farther out from the Main DECT base station to offer you even more DECT coverage in those hard to reach places. DECT repeaters, in most cases must be in the same DECT signal coverage as the MAIN DECT base as pictured below and the number of additional repeaters vary between solutions. Some SOHO solutions don’t even offer a repeater solution. Keep this in mind when planning your deployment. Also DECT signal can be broadcasted in either horizontal or vertical applications to meet you many floors you may have in an office building.
  • Physical Barriers- Obviously, in a solution where there are little barriers in the way of the DECT frequency being broadcasted, the solution scales to a much larger coverage area. However, this does not mean that the frequency can’t penetrate any barriers you may have. DECT frequency can get through walls including concrete walls, but obviously the signal strength is degraded. When designing your solution, you will want to test your known or thought to be known “dead spots”. You will also want to physically place the DECT base station in the middle of your coverage area or center of your building. This will offer you the greatest coverage end to end or wall to wall. Like I said, you will want to test those dead spots, the corner of your office, any rooms separated by concrete walls, and you may also want to check your outdoor coverage as well as often times this frequency has a tendency to overlap outer walls and reach to outdoors. Theoretically, your users may be able to step outside and still make and receive calls on their DECT handset. A good way to pinpoint your physical barriers is to dust off those old blue-prints and map out where these may be.
  • Outdoor Scalability- While I mentioned that some SOHO DECT solutions can broadcast outdoors, none of the physical Base stations or repeaters were designed however to be in the outdoor environment. In larger deployments such as college campuses, the need for outdoor Access Points or repeaters is eminent. In this case, you will only find outdoor access points in enterprise level DECT solutions.

As you can see, there are a number of different considerations to think of when designing and deploying a VoIP DECT solution. In our next segment, we will offer a few product suggestions to meet the needs of a SOHO and Enterprise DECT solution. This will include DECT bases, repeaters, handsets, and other requirements needed.


2 Comments

  • Mark Petersen

    Number of Channels – you also need to decide how many concurrent calls you need
    having a DECT base that support 6 handsets but only one channel might be a problem
    a normal SoHo only have 1 channel but some have support for more
    snom m3 (3 channels / 8 handsets)
    polycom kws300 (4 channels / 12 handsets)
    polycom kws6000 (256*12 channels / 4096 handsets)

  • chris heinrich

    @Mark
    You are correct, stay tuned to my next post that will describe the number of concurrent calls supported on each DECT solution as well as offer a few good solutions like you have mentioned above.

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