Technology

Power Line Communication modem
embedded in the IDC2000 : Overview

The Embedded PLC modem PLC-Link™, supplies exclusively fast and reliable two-way communication between any network devices over Power Line, without any additional wiring.

Data for other systems taken from Powerline Control Systems "Universal Powerline Bus Overview", 01/08/2002.
Data from Systel:
(*1) Synchronized to Zero-Cross
(*2) < BER 10ˆ10, S/N = 6dB
(*3) PLC Modem is embedded at no additional cost in the IDC2000 single chip controller applicable in ballasts, multiple networkable sensors, etc. For wall control and for other remote control elements of the control system, the PLC Modem as a stand alone device that can be implemented with the IDC2020 which is the smallest device in the IDC2000 IC family.

Comparison: UPB versus X-10
From the system-wise point of view the features attributed to the X-10 are in principle similar to the system based on the UPB power line carrier. On the communication performance side, the main difference between the X-10 and the UPB seems to be the number of bits/second and lower frequency of the communication signal pulses adopted by the UPB method.

These improvements provide a much stronger solution in comparison to the X-10.  The UPB has 250 bits/sec and low frequency command signals and the X-10 has 120 bits/sec and command signals in the order of 120KHz. Systel power line communication method has 2000 - 4000 bit/sec, depending on the selected carrier frequency (100-200 kHz respectively). For additional details refer to Comparison between building control systems using the IDC2000 embedded PLC and the X-10 method . In this comparison the power line communication protocol used is PLC-Link, Systel's property/patented solution. ESLS (Energy Savings Lighting Systems) is the name of its application for a decentralized building control system. Due to the similarity in application of the X-10 and the UPB this can assist in understanding the differences between a solution based on Systel's power line carrier and a solution based on the latter method.

Noise Immunity of Power Line Communication Methods
The UPB method is in fact an upgrade solution of the X-10 but lacks noise immunity in its low frequency range of signals (several kHz). There are noise interference signals in the order of several Volts rms With the UPB method, in buildings at that low frequency range.  On the other hand, the noise interference signals in the working frequency range of Systel's PLC method, the LonWorks, CEBus and X-10 are only in the order of a few hundred mV or less. In the frequency range of 100 to 200 KHz, where Systel's PLC works, the use of simple back filters with 40 dB attenuation, as proposed in Systel's aforementioned ESLS application ( Click for detailed info in SYANL407 ), will further reduce this interference noise to a few mV rms. This solution provides a very high S/N (signal to noise) ratio and consequently, high noise immunity.

To overcome the low frequency high interference noise signals which exist typically in building s  the UPB uses a high voltage communication signal in combination with repeaters and a larger bit count message of about 192 bits to increase the signal recognition capability. However, this will enormously reduce the communication rate of a single command to lasting 0.3 sec (0.6 sec when using a single repeater), 20 times less than Systel's command bit rate . If there is a collision of signal messages this may extend to seconds!!! This could be acceptable in residential applications with a limited number of addressable devices, but in larger networks such as in any typical commercial building the reaction time (command execution time) decreases as the number of addressable devices and the lengths of the electrical circuits increase. Therefore, the UPB method is not recommended, from the technical point of view, for building energy savings system applications unless the reaction time and or access to individual elements of the network is not a relevant issue.

Neither the UPB nor the X-10 specifies S/N (signal to noise ratio) data for the BER (bit error rate) which results in a given network depending on the addressable devices count, electrical input characteristics of the devices and the length of the circuit to the furthest device. In the case of Systel's reference ESLS application system for an  S/N of 6dB the guaranteed BER is at least 10-7 , Click for SYTRL400 test report , in a network composed of branches with 64 ballasts and 160 meters in length. This means one error message in millions of command attempts.

High Frequency versus Low Frequency Communication Signals
In the case of PLC communication, working with carrier frequency in the range of 100-200 kHz, the signals are attenuated along the network due to the low input capacitance of the power line and the connected devices. This is true for the X-10, LonWorks and Systel's PLC. CEBus works at even higher frequencies.

Repeaters could be used in all PLC method applications to overcome the attenuation impact in the transmitted signals, but they will decrease the execution time. Typically, each repeater will multiply by twice the command execution time in the respective transmission power line. In case of the LonWorks, CEBus, Systel PLC or others, that have a communication rate of 2000 to 10000 bits/sec or higher, the use of repeaters are effective in distributed systems but in centralized ones may be unsuitable. However, in the case of the X-10 with 120 bits/sec or even the UPB with 480 bit/sec due to its relatively larger bit count message the repeaters will intensify the latency of the commands and make these PLC methods inappropriate in applications where the largest execution command time should be less than 0.5 sec.

In summary, as the size of the system increases and with it the number of addressable devices and the lenghs of the transmitting power lines grow, the application of the LonWorks or CEBus in a centralized control system approach, using a repeater, starts to be cumbersome and the duration of the command execution becomes marginal and sometimes unacceptable in the case of signal collisions, common in such systems. Furthermore, in centralized systems in which a reliable system requests acknowledgment from a Communication Master the reaction time could be worst and this becomes a major problem in larger networks.

The UPB method, which is a modification of the X-10 system, applies low frequency pulse signals to avoid the above mentioned attenuation problem. The input capacitance of the devices connected within the network has little influence on the UPB signals and therefore, in this respect, it is much more robust than the X-10 and is able to transmit at longer distances in the same network. However, in larger networks the UPB requires the use of repeaters to keep the required noise immunity.

Systel's ESLS application solution is based on a decentralized system and will eliminate the technical traditional PLC barriers. Click for IDC2000 technology and applications presentation. Refer to slides 61 to 70 . This provides an inherent very low access time with its communication rate of 2000 to 4000 bits/sec. and the collision effect is minimal. In comparison to centralized solutions, Systel's PLC-Link protocol provides much lower execution (access) time of about 32 ms, for a system with many more addressable devices (65,000 addressable devices) than a centralized system which handles only 2,500. In addition, the need for multiple repeaters is nullified due to the distributed control concept. Systel's solution enjoys lower signal attenuation in each lighting circuit, achieved by the special approach of Systel's reference design ballasts with a lower input capacitance and the limited lengths of the individual circuits.

Cost effectiveness
A second main issue under contention besides the system performance is the system component cost. The cost of the transmitter and receiver unit is high but an additional factor to be considered is that any group of electronic ballasts requires its interface element to translate the UPB signals to the particular communication interface of the ballasts. Further control selectivity of different elements requesting additional addressable receivers raises the system cost. In building energy savings applications, access to each individual element is required which is not affordable with the X-10 or the UPB.

For a simple two-lamp ballast based on the IDC2000 featuring an integrated power line communication transceiver the component cost will be in the same range as that of a standard dimmable ballast based on DALI or a DC control type. For additional details refer to Comparison between building control systems using the IDC2000 embedded PLC and the DALI method. However, two, three or four-lamp ballasts deployed with Systel's IDC2000 in combination with the patented multi channel topology, will be of premium quality at a significantly lower cost and present exceptional energy savings attributes. Each lamp could be of a different type and separately protected, operated and controlled remotely for On, Off or dimmed in the entire range down to less than 1%. For more details : click for press release and Click for brochure . For more details click on ballast application note SYANL 104 For cost differentiation, Click for IDC2000 technology and applications presentation . and refer to slide #50 for "Differentiators Provided by the IDC2000 in Dimmable Electronic Ballast Applications".

Furthermore, one ballast residing in a fixture can operate adjacent fixtures (one or more), or be located outside the fixtures and operate up to eight with different lamp types (central ballast solution), where each fixture can be individually switched On or Off, or dimmed. In addition, fixtures can be installed at varied distances without affecting light quality. These properties allow the design and manufacture of networkable ballasts with PLC interface at a fraction of the price of the DALI or DC control. Moreover, considering that the component cost of the Systel PLC modem embedded in the IDC2000 is in the order of 1/100 of other PLC or wireless methods, and doesn't require any additional intermediate receiver device to operate individually each ballast or a group of them, it can be said that a system based on the IDC2000 offers the ultimate solution at the lowest price in the market regarding any other PLC or wireless solution. In addition, since the installation of the DALI requires costly wiring, it is clear that the solution offered by the IDC2000 outshines all other solutions in the market.

In summary, with the IDC2000 each fixture or lamp will be controlled individually by the user or from a central computer (BMS) with a high specification/highly specified ballast as well as each separate component of the HVAC at 50% to 25% system cost of other market solutions. In addition, the IDC2000 provides together with an ideal load shedding solution the highest possible energy savings cost for the shortest ROI without affecting users comfort.

An additional advantage of the IDC2000 is that when deployed in unusual electrical circuits, having large number of addressable devices and or very long power lines is that each of the ballasts can operate as a repeater, thus providing an additional saving factor in the total system components and installation cost.

	SYTRL400 – A PLC test report A test report presenting the characterization test results of the Power Line Carrier (PLC) Modem embedded in the IDC2000 ICs family. This report also includes the results of the communication test performed using the PLC transceivers in the wall control and the ballast reference designs of Systel's Lighting Evaluation Kit based on the IDC2000 ICs. This report also describes the test method applied and includes the Bit Error Rate (BER) versus S/N achieved in the communication test. Date: November 5, 2006
	Application Note SYANL404 PLC-Link™ Power Line Carrier Communication for a Building Control based on IDC2000 devices.
	Application Note SYANL405 PLC Communication Protocol for Building Control System based on IDC2000 devices

Application Note SYANL407 Back-Filters Reference Designs for 20A and 16A Single Phase Branches for the Energy Savings Lighting System (ESLS) using PLC-Link™ Communication based on the IDC2000 devices.