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| A health check on DECT |
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| Wednesday, 04 August 2004 | |
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The promise of convergence, the report of the death of the patient, the slight exaggerations and why the patient was not found: Stoyan Baev and Kevin Flynn report on the condition of DECT…
It is an inescapable fact that hype has entered in to the world of (tele)communications, filling a gap where there used to be a respectful silence between a good idea and its coming to fruition in the form of a new product. Darwin's theory of natural selection is redundant as the survival of the fittest has been replaced by buzzwords that can unduly influence who are the winners of the technology race. 'IP' is one such buzzword and 'Everything IP' in converging the existing telephony (PBX) and data (LAN) networks is bringing a lot of excitement, both positive and negative. It is true that integrating voice and data into a single network is bringing advantages, however, these advantages are not yet big enough to undo the deafening effect the term 'replacement cost' has on our accounting departments. The promise of mobility 'Everything IP' does not fully describe the complex picture of converged networks. Two other buzzwords have their role too: 'wireless' and 'mobility'. They are nothing new in the telephony world, but they are now 'hot stuff' in the LAN. Not surprisingly each of the two sides, telephony and LANs, have their favorites here: PBX has DECT and the LAN has WLAN, which means that the battle for converged PBX-LAN IP hearts and minds is heating up. DECT is a mature technology which had its hype a little less than 10 years back. VoWLAN is hyping today which explains the fact why some of its supporters were quick to pronounce the death of DECT. Is DECT dead? In the home, DECT now outsells any other technology for cordless telephones with more than 80% market share on some markets. Now in the office DECT is having its day, a technology of choice covering single and multi-site enterprises, with hundreds of cordless handsets. All this with technology that has been around for ten years and is now providing economies of scale that make price levels more and more attractive; rumours of the death of DECT have been greatly exaggerated! Here are 10 reasons why DECT is, and will be, successful in the business environment: • speech flow and seamless handover: seamless handover (or 'handoff') is very important to voice mobility. It has been used by WLAN and by DECT but has been used differently in each case. In DECT seamless handover means that when a handset moves between different Radio Fixed Parts (RFPs -the DECT equivalent of WLAN's Access Points) there is no interruption in the speech flow. This means that what you hear from your peer is not "I c_n't he_r y_u" but "I can hear you". In VoWLAN the same term means only that the call is not disconnected, meaning the call is still subject to interruption of the speech flow; • voice quality: neither LAN (and IP based networks) nor WLAN were designed with voice in mind - PBXs and DECT were! Quality of Service (QoS), regardless of how magic it may sound, is not sufficient for voice quality to be guaranteed. Packet loss and coping with it, jitter and the wireless link quality for example are issues that need solutions of their own. DECT does not have a feature called QoS, because DECT was designed for quality voice in the first place. VoDECT is a circuit switched technology and that is what voice likes; DECT has an exclusive DECT-only frequency band in Europe and employs proven robust mechanisms allowing for excellent performance in bands to be shared with other technologies. Uncontrollable interference and congestion are big VoWLAN problems and a big challenge. Engineers like challenges, users do not; • capacity and co-existence: studies have shown that a WLAN AP can support, in perfect conditions, up to 5-6 simultaneous calls. A DECT RFP can do up to 12. Link quality deterioration in VoWLAN brings the number rapidly down. DECT is a FD (Frequency Division) and TD (Time Division) technology which when combined with the famous Dynamic Channel Selection (DCS) mechanism gives to DECT terminals the possibility to chose the best channel out of at least 120 available. This, among other factors, brings the advantage of reduced deployment troubles; • interoperability: there is no perfect technology and the younger a technology, the less perfect it is. The problem with VoWLAN is that its rush to market has meant that the process of de-bugging and extending the standards has been skipped. The result is proprietary solutions filling the gaps. QoS, Security and Privacy are examples of VoWLAN interoperability issues now having to be re-addressed. DECT on the contrary offers an extensive set of standardised, hard proven, interoperable services, such as basic voice call, subscription, authentication, encryption, mobility and a number of supplementary services, to name but a few; • security and confidentiality: no doubt security is an issue in wireless communications; that is very much the case in business wireless communications. The support of security protocols in DECT has been mandatory since the beginning and includes secure access rights allocation, authentication and speech encryption procedures based on 64 and 128 bits long keys, none of which is distributed over the air. DECT has no proprietary security related solutions; • site coverage: voice mobility requirements and data mobility requirements are not the same. WLAN success has been in hot spot type deployments. For voice mobility, however, range is what matters and for range what matters are things like walls and floors and more walls and more floors and what they are made from, as well as transmission power, frequency band, interference and, well lots of other things too. DECT is the better performer here and as an additional feature, DECT offers a device called a repeater which does not need a cable to be connected to the base station and extends twice the distance between a portable and a RFP; • consumption and terminal size: business people have high expectations when it comes down to their phones' power consumption and size. Best figures for VoWLAN handsets today show 3h talk and 24h standby time in comparison to 18h and 288h respectively for DECT. Size differences are more difficult to show with numbers, nevertheless DECT handsets can have the same size and weight of a mobile phone (eg GSM) and the only limit is usability; • network management: as the name 'network management' suggests; the converged IP based LAN-PBX management issue is mainly a network issue. Consequently, it is difficult to argue whether VoDECT or VoWLAN will make life easier. Our belief is that because VoDECT assumes termination of IP addressing in the Radio Fixed Part (ie in the AP) the network management has one less problem to deal with - it does not need to take care of moving IP addresses. Separating voice from data traffic at the end user side by having high demand data dedicated WLAN APs and mixed voice and low data dedicated DECT RFPs (even combined in one access terminal) could bring some advantages as well; • return on investment (ROI); anyone in this business knows that market price does not always reflect proportionally the development cost and often comprises contributions related to the technology, its maturity, the number of units sold, and, marketing polices. If we could remove the policy part and compare apples with apples DECT is the clear winner here. At the time of writing this more than 150mn DECT units have been sold and a DECT handset, at average, costs three times less than a VoWLAN one. As for the network side the number of APs (RFPs) and their cost including installation are making the big difference. Although it is difficult to provide exact figures here many of the DECT technology properties discussed earlier guarantee lower DECT cost; • Voice+: user's expectations for their communication experience are rapidly changing. Voice is not enough. On-site messaging, M2M communication, up to 20Mbits/s standardised packet data, phones designed for specific sensitive environments and dual mode with cellular phones are just few advanced applications that help to ensure that DECT will cope with the demands placed on it. Some final conclusions This article is part of the background noise of hype and promotion and the reader is right to assume that there is another side to the story. The truth is that if "Convergence is the hope that the whole will be greater than the sum of the parts" then, to make the whole greater than the sum of its parts, requires parts that deliver what the customer needs! We believe that VoWLAN will have a market, but that market will not dent the success of DECT in this domain. In non voice communications DoDECT will make a contribution, but will not dent the success of the WLAN. DECT and WLAN are parts that make the whole somewhat greater! When it comes down to additional services, as messaging, we believe that they will not have greater impact on the decision making as both WLAN and DECT can, and will, do this well; other wireless technologies, such as Bluetooth, will have their contributions here too. Our formula for success is as follows: BusinessCommunications=IP(LAN+PBX)+DECT+WLAN+X The patient should take an aspirin and go straight to bed and everything will be fine in the morning. Stoyan Baev is a Senior Consultant currently with ComSquare Ltd in Switzerland. He is former Chairman of various ETSI DECT and DECT Forum WGs and rapporteur of 100+ DECT standards editions. He can be contacted at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it Kevin Flynn is an employee of the European Telecommunications Standards Institute, where he is responsible for Press coordination. He can be contacted at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it |
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