Irish Powerline Communications (PLC) By Michael Field M.Sc. Communications Systems Theory

Transcription

1 Irish Powerline Communications (PLC) By Michael Field M.Sc. Communications Systems Theory

2 Background Power Line Communications refers to the transmission of fast IP data using radio frequency (RF) carriers (Spectrum) at speeds of up to 45Mbps (more usually 2-5Mbps) over conventional AC power cables at low to medium voltages (220V to 38kV typically). In the case of access PLC, this data rate is shared among a number of simultaneous users. As PLC uses the Internet Protocol (IP), the main application of PLC could be also described as "Internet from the socket".

3 System Description The end user s PC connects to a home gateway plugged into the Low Voltage (LV) 220V mains electricity supply. This connects to a local node or repeater in a street cabinet at the local three phase 400V system and then via repeaters to the Medium Voltage (MV) 10kV three phase node. This node is then linked back to a fiber or radio point of presence on the SDH backbone by MV PLC or high bit rate WiFi.

4 PLC Concept

5 PLC in Ireland Power Line Communications (PLC) trial is currently underway on the ESB network in Tuam, Co. Galway. Jointly funded ESB and Department of Communications Marine and Natural Resources (DCMNR) The ESB have selected two manufacturers - EBA (Brazil, using the DS2 Chipset) - Main.net (Israel).

6 EBA (using DS2 Chipset) The modulation method used is OFDM and the system uses 3840 carriers in 38MHz of spectrum. The EBA products use several frequency bands, called Links, for communication and the default configuration has four links Link 1 - Used for transmission between the Head End and the Home Gateway 2.46 to MHz Link 2 - In home Home Gateway to Consumer Premises equipment (CPE) MHz

7 EBA (Using DS2 Chipset) Link 3 - In home (alternative access technologies) MHz Link 4 - Used for HE to CPE but the frequencies used for upstream and downstream are the inverse of Link MHz Each link has a total of 1280 carriers. The output power is programmable from 90dBm/Hz to 50dBm/Hz. The system has the ability to configure the output power on a carrier by carrier basis.

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9 EBA Results Particular concern is the interference to an HF (Trans Oceanic) VOLMET service at 11250kHz USB. This service gives expected weather conditions at European airports for transatlantic flights. High level of interference received by their equipment on the power lines. This interference decreases the required signal to noise ratio to the point where repeaters would be required every 200m. This anomaly was subsequently investigated at the request of the ESB. All of the frequencies were identified as legitimate transmissions with most of them identified as being expected continental European shortwave broadcasts.

10 Main.net The trial is using 1st Generation equipment from Main.Net. This utilises a Direct Sequence Spread Spectrum modulation technique. The stated frequency range is 1.7 to 30MHz. On DSSS modulation frequency notches can be applied in which no transmission will be allowed. Later generations of the suppliers equipment will use OFDM with the same frequency range.

11 Main.net Repeater power levels can be adjusted to transmit at lower power levels in areas where interference is suspected Use of additional repeaters can allow for reduction of transmit power levels LV default: -50dBm/Hz - it can be configured to be stronger by 6 db or weaker by 15 db. MV units: up to -35 dbm/hz

12 Main.net s System: Flexible and Easily Integrated with Existing Network and Technologies Wireless to Home RpPLUS Internet Utility Fiber Network PLC to Home PLC on MV Wireless to CuPLUS CuPLUS PLC to Home RpPLUS Gig E CuPLUS PLC to Building PLC on MV CuPLUS Gig E Gig E PLC on MV PLC to Home PLC on MV RpPLUS PLC to Home Gig E Gig E CuPLUS PLC in Building

13 Main.net Results Overall the Main.net equipment met the Irish cable leakage limits comfortably in most instances. The use of Direct Sequence Spreading by the Main.net equipment has had two noticeable traits: 1. Minimising the effect of ingress (broadcast signals) on the PLC equipment. 2. Minimised the amount of discernable egress from the ESB network. The majority of the network used for the Main.net trial was underground and egress may be more prominent from an overhead network.

14 Conclusions Currently The DSS modulation scheme used by Main.net poses less of a threat to radio services than the EBA OFDM scheme. Both systems need to notch out HF safety of life service frequencies in their relevant bands of operation but especially the EBA system. The EBA equipment also needs to be programmed to exclude the Amateur bands. (Currently taking place) The power injected onto the line by both systems should be reduced (EBA by 12dB and Main.net by around 3dB) respectively to that strictly necessary for maintaining a useable carrier to noise ratio.

15 Conclusions Conductive measurements need to be performed on the fully operational system to assess the possibility of mains borne interference to TVs, Radios, Videos, Baby Alarms, PMR base stations and other radio equipment.

16 Questions?