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MPP 6800 series - DECT Deployment Guide
DECT stands for Digital Enhanced Cordless Telecommunications and is a standard for wireless voice services in buildings (domestic and business). Originated in Europe it was adopted across the globe. The US had a slight delay due to regulatory compliance but after some minor changes in frequencies used it was adopted in North America as well.
Current list of regulatory areas covered with Cisco DECT solutions
- 1880-1895 (Taiwan)
- 1880-1900 MHz (Australia and New Zealand – power <= 158 mW)
- 1880-1900 MHz (E.U. and APAC)
- 1910-1930 MHz (LATAM and Argentina)
- 1910-1920 MHz (Brazil and Uruguay)
- 1910-1920 MHz (Uruguay – power <= 100 mW)
- 1910-1930 MHz (Chile – power <= 158 mW)
- 1920-1930 MHz (U.S. and Canada)
All base stations, DBS-210 (Multi Cell) and DBS-110 (Single Cell) have the same signal strength capacity.
- Indoor 20-50/60-150 meters/feet
- Outdoor 300/900 meters/feet
Single Cell
A single radio bases station with a limit of 10 handsets, 3 repeaters for extended range. The bases station can handle up to 10 active Narrow Band audio calls or 5 Wide Band audio calls.
Mostly used in small business and domestic setups.
NB audio calls are using G.711, G.729 or G726 and for WB audio calls use G.722.2 (AMR-WB).
Multi Cell
Multi Cell DECT consists of base stations where the radio signals overlap, resulting in a network that supports seamless handover. As DECT uses Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) as a system to have 2 dimensions for transport on the physical layer (time and frequency). A Multi Cell base station has therefor a separate clock chip and syncs its clock signal either over the air or over a LAN.
When this requirement is met, and the base stations are in sync seamless handover between the different base stations is possible. Second benefit of Multi Cell installations is the added capacity of handsets as each base station in the Multi Cell can handle between 10-30 handsets with a limit of 1000 handsets in total for a Multi Cell.
Make your choice: Multi Cell or Single Cell
Let’s first address the question: why not use Mobile instead of WLAN or DECT based VoIP?
Mobile networks become more and more pervasive yet have a couple of issues or challenges that need to be addressed.
First of all, the cost of a mobile (4G or upcoming 5G phones) and the durability of these handsets. Second the lack of or challenges faced when you need business phone features like conference calls, corporate directories, alarm buttons, centralized call control, etc. To overcome these challenges there are basically two wireless technologies that could address this: WLAN based mobile phones or DECT based mobile phones.
Voice services place stringent performance requirements on the entire network. Because digitized voice is a sampling of an analog signal (verbal communication), its transmission is very sensitive to delays during transit. In fact, in order for voice to work correctly over any infrastructure, the end- to-end transit time (cumulative time encoding the packet, leaving the sending client, traversing the network, and then being decoded at the receiving client) must be less than 150 ms. Issues encountered during transit result in imperfections in the reconstituted signal; also known as jitter. The jitter is basically the variation in delay that the system is experiencing.
Because a WLAN is based on a random-access protocol, and although it allows clients to roam freely, it is a shared medium among all wireless devices, with particular security protocols associated with it, adding voice services has implications in several areas, including:
- Coverage requirements and deployment planning
- Network infrastructure and logical subnet design
- Wireless “over-the-air” quality of service (QoS)
- Network security architecture
- Voice client feature requirements
DECT as a wireless voice solution was designed from the ground up to address these challenges and is way easier to design, deploy and secure. Coverage of DECT networks in office buildings, campuses and warehouse situations is excellent without the design challenges of a WLAN network. Voice clarity, roaming and overall quality relies on the base stations deployed in your setup without the interference from other endpoints in the 2.4GHz or 5GHz as DECT uses its own regulatory space. And last but not least the average talk/standby time exceeds that of mobile devices easily.
The main choice to be made is to select between Single Cell or Multi Cell setups. Extremely simplified: Do you need a high density of handsets (>10) or a very large area to cover, then the answer is Multi Cell (e.g. an entire office building, a warehouse). If the need is just a few phones and the area that need to be covered isn’t large then most likely Single Cell is the best choice.
Example 1
Small office with 4 employees – Less than 10 and small area => Single Cell.
Example 2
Small business that is expanding with 6 employees => Multi Cell as during the business expansion most likely a larger office will be used and employee count goes beyond 10.
Example 3
Small size warehouse with 30 employees, only a few in the warehouse during a shift. => Single Cell with multiple Repeaters to get full coverage.
Example 4
Large warehouse with 20 employees. => Multi Cell due to the large area and more than 10 handsets at the same time.
Multi Cell Design
A multi cell setup with the Cisco DECT DBS-210 can be done in 2 ways:
- Over the Air synchronization
- IEEE1588 LAN synchronization
Synchronization is the key element that enables the seamless roaming across base stations with handsets. Synchronization between the base stations is the process to align Frequency and Time in a diffuse/disperse area. As a handset scans for Frequency/Time channels on both the current base station as well as the surrounding base stations. If they are in sync then a handset can move to a different base stations for example based on signal strength (RSSI value).
Over the Air synchronization
Over the Air synchronization is the easiest way to synchronize and “only” requires that each base station can see its neighbors. Although this seems relatively simple there are a couple of challenges:
- Subject to signal interference
- Although DECT communicates in a spectrum not used by other devices like WLAN access points, Bluetooth, interference still takes place (sometimes even by own base stations due unmanaged signal reflections. Other signal interference is for example due to metal struts in a wall, reinforcement in concrete, etc
Base stations need to overlap its neighbor
- Although DECT communicates in a spectrum not used by other devices like WLAN access points, Bluetooth, interference still takes place (sometimes even by own base stations due unmanaged signal reflections. Other signal interference is for example due to metal struts in a wall, reinforcement in concrete, etc
- Base needs to overlap neighbor
As the base stations need to keep their Frequency/Time channels in sync that means they need to see each other to get and keep in this state.
IEEE1588 LAN Synchronisation
Using Lan synchronisation the overall distance between base stations can be improved while still maintaining seamless roaming. An added benefit is also the structural challenges can be easier overcome as interference from walls or other objects poise less of a challenge. Although this is the most scalable architecture it does rely on a proper designed switching network.
In old buildings sometimes due to building code or historic reasons running cables in a switched infrastructure might not be allowed. In those cases Radio Synchronisation might be the only viable solution.
Multicell in Broadworks
Before setting up your first base station
Install DTAF files on BWKS (system level)
Create Device Profile (group or system level)
Set User and Password for this device profile in the authentication section (which can then be used in EDOS as a ZTP redirect).
By default the DTAF creates a single xml file, %BWMACADDRESS%.xml with the MAC address being dynamically populated when bases reach DMS to pull the file.
Make sure that basic authentication is set as the authentication type for the %BWMACADDRESS%.xml file in the edit file section.
Set Custom DECT tags on BWKS (group level)
- %AC_CODE% (AC to join handsets to bases, for example 1111)
- %MULTICELL_PRIMARY_MAC% (MAC address of the base which will be primary in the multicell)
- %MULTICELL_CHAIN_ID% (random number that needs to match between all bases in the multicell)
- %MULTICELL_SYSTEM% (yes/no, to enable or disable multicell operation)
- %FW_UPGRADE_RULE% (point towards the firmware upgrade rules on DMS – if using upgrade rules set on EDOS, this tag is not needed)
- %DIAL_PLAN_1% (if you need a different dial plan than the default US dial plan
Configure Broadworks User(s)
Create users in the same way that they would be created for MPP
Go to profile of user
Assign address(es) to user(s) using the device profile of the multicell device profile created
Rebuild files on device profile (pulls in the assigned addresses and creates extensions).
To reduce file download size, remove empty tags if not needed, for example, extension tags not used etc.
Extra base stations for the same multicell tree will use the same device profile. Subsequent addresses in the device profile will be assigned to extensions that register though bases in the multicell tree.
Configure EDOS
Assign a profile to EDOS (using the credentials set in the device profile of the multicell). Also including upgrade rules if necessary.
Example:
