Technical Field of the invention
The present invention relates to provisioning of new
broadband communication services over copper plants.
Technical Background of the invention
Distribution Point Units (DPU) serving subscribers with
new copper access technologies for broadband communication
services (e.g., G.fast) are typically deployed at a maximal
distance of a few hundreds meters from the subscriber premises
(e.g., 200m for G.fast) in order to achieve the expected high
data rates (e.g., 1 Gbps as aggregated data rates for G.fast).
This means that the DPU will be located closer to the subscriber
premises compared to current deployments. A local power supply
to power the DPU is not always available at the DPU location.
Therefore operators are requesting methods to feed the DPU via
Reverse Power Feeding (RPF) .
A Power Sourcing Equipment (PSE) installed at the
subscriber premises provides a DC current to power the DPU via
the same copper pair as used for broadband communication. The
PSE is powered by the AC mains of the household. A Power Supply
Unit (PSU) inside the DPU converts the DC voltage supplied by
the PSE, typically 57V minus the DC voltage drop caused by the
DC resistance along the copper pair, to a number of lower DC
voltages used inside the DPU (e.g., 12v, 5V, 3v3, etc).
It is expected that operators will gradually upgrade
their subscribers from a legacy communication service to the new
broadband communication service provided by the DPU. These
legacy communication services typically refer to the various
Digital Subscriber Line flavors (xDSL) , with o r without the
presence of Plain old Telephone System (POTS). The legacy
communication services are typically deployed from a Central
Office (CO) cabinet, so are for instance the ADSL o r ADSL2+
communi cation services, from a Remote Unit (RU) , so are for
instance the VDSL2 communication services, o r from a Local
Exchange (LEX), so are for instance the POTS communication
services .
A t a given time, a particular subscriber is upgraded
from the legacy communication service deployed from the legacy
network equipment over the (long) legacy copper pair to the new
broadband communication service deployed from the DPU over the
(short) terminal segment of the copper pair.
To this end, a bypass switch is provisioned within the
DPU. The bypass switch typically consists of a persistent relay
with two switching states, namely:
- the bypass state wherein the end user is transparently
connected through the DPU to the legacy network equipment via
the (long) legacy copper pair for support of the legacy
communication service; o r
- the termination state wherein the (short) terminal segment of
the copper pair (i.e., the segment spanning from the DPU down
to the subscriber premises) is connected to a transceiver of
the DPU for operation of the new broadband communication
service, while the network segment of the copper pair (i.e.,
the segment spanning from the DPU up to the legacy network
equipment) is disconnected and open-circuited at the DPU side.
At the given time, the bypass relay shall thus be
switched from the bypass state to the termination state for that
particular subscriber. Preferably, this is accomplished without
any human interaction (zero-touch installation).
Yet, there are a number of technical hurdles to
overcome during the service upgrade.
initially, when the very first user switches from a
legacy communication service to the new broadband communication
service, the DPU is unpowered since that user is also the very
first user to feed the DPU. Hence, there is no power available
at the DPU to switch the bypass relay either.
Furthermore, when a POTS service is present on the
copper pair, no DC feed can be inserted on the copper pair by
the PSE as this would conflict with the DC power source from the
LEX (typically 48v, 53v o r 60v) . Although the DPU can directly
get power from the latter, the DPU can only drain a little
current during the ONHOOK state (typically from a few hundreds
mA up to a few mA) so as not to trigger an ONHOOK -> OFFHOOK
state transition and the insertion of the dial tone at the LEX,
yielding a too long time to accumulate sufficient energy to
switch the bypass relay and power its control logic.
if there is no POTS service delivered to the user,
there is no DC voltage present on the copper pair either, and
the PSE can start delivering DC power at once for the DPU to
swi tch the bypass rel ay. However , some basi c i ni t i a i zati on
protocol i s sti l l needed for the DPU t o di sti ngui sh between DC
power from the LEX wi t h very l i ttl e power avai l abl e and DC power
from the PSE wi t h p enty of power avai ab e.
Summary of the invention
I t i s an object of the present i nventi on t o f l awl essl y
provi si on new broadband communi cation servi ces over copper
pl ants wi t h mi ni ma /no human i nteracti on whi l e overcomi ng the
aforementi oned i ssues .
i n accordance wi t h a f i st aspect of the i nvention , a
method for provi si oni ng a new broadband communi cation servi ce
compri ses i nserti ng an access node adapted t o operate the new
broadband communi cation servi ce al ong a subscri ber l oop ;
confi gu r i ng a swi tch of the access node i n a f i st i ni t i al
swi tchi ng state wherei n a f i st pai of termi nal s coupl ed t o a
l egacy subscri ber devi ce vi a a termi nal segment of the
subscri ber l oop i s connected t o a second pai of termi nal s
coupl ed t o a l egacy network equi pment vi a a further segment of
the subscri ber l oop ; operati ng at l east one l egacy communi cation
servi ce over the subscri ber l oop whi l e the swi tch i s i n the
f i st swi tchi ng state ; connecti ng a power sou ci ng equi pment
adapted t o i nject a power feedi ng si gnal for reverse power
feedi ng of the access node and a new subscri ber devi ce adapted
t o operate the new broadband communi cati on servi ce t o the
termi nal segment of the subscri ber l oop . The method further
compri ses , by the power sourci ng equi pment , transmi tti ng a
sequence of successive command si gnal s over the termi nal segment
of the subscri ber l oop prior t o the i nsertion of the power
feedi ng si gnal ; by the access node , accumul ati ng an el ectri cal
charge from at l east one command si gnal of the sequence of
successive command si gnal s ; by the access node and by means of
the so accumul ated el ectri cal charge , detecti ng a val i d command
si gnal i n the sequence of successi ve command si gnal s , and
thereupon confi guri ng the swi tch i n a second swi tchi ng state
wherei n the f i st pai of termi nal s i s connected t o a thi d pai
of termi nal s coupl ed t o a transcei ver adapted t o operate the new
broadband communi cation servi ce and t o a power suppl y uni t
adapted t o suppl y power t o the access node from the power
feedi ng si gnal ; by the power sourci ng equi pment , i njecti ng the
power feedi ng si gnal over the termi nal segment of the subscri ber
l oop for reverse power feedi ng of the access node ; and operati ng
the new broadband communi cati on servi ce over the termi nal
segment of the subscri ber l oop .
i n one embodi ment , the command s i gnal s are i ndi cati ve
of a prel i mi nary operati onal state at the power sourci ng
equi pment .
i n one embodiment , the command s i gnal i s detected as
bei ng va i d when a payl oad of the command s i gnal matches a given
pattern .
i n one embodiment , the at l east one l egacy
communi cation servi ce compri ses at l east one of an Asymmetri c
Di gi tal Subscri ber Li ne ADSL communi cati on servi ce , an
Asymmetri c Di gi tal Subscri ber Li ne wi t h extended bandwi dth
ADSL2+ communi cation servi ce , a Very-hi gh speed Di gi tal
Subscri ber Li ne VDSL2 communi cation servi ce , and a Pl ai n Ol d
Tel ephony Servi ce POTS .
i n one embodiment , the command s i gnal s are generated by
modul ation of at l east one AC carri ers .
i n one embodi ment , the at l east one AC carri ers are
s i tuated i n a frequency band not currentl y used by the at l east
one l egacy communi cati on servi ce .
i n one embodiment , the frequency band i s the voi ce band
of P ai n O d Te ephony Servi ce POTS .
i n accordance wi t h another aspect of the i nvention , an
access node compri ses a transceiver adapted t o operate a new
broadband communi cation servi ce over a termi nal segment of a
subscri ber l oop ; a power suppl y uni t adapted t o suppl y power t o
the access node from a power feedi ng s i gnal i njected by a power
sourci ng equi pment over the termi nal segment of the subscri ber
l oop ; a swi tch havi ng a f i s t pai of termi nal s for coupl i ng t o
the termi nal segment of the subscri ber l oop , a second pai of
termi nal s for coupl i ng t o a further segment of the subscri ber
l oop , and a thi d pai of termi nal s coupl ed t o the transcei ver
and t o the power suppl y uni t ; and a swi tch control l e r adapted t o
confi gu re the swi tch i n a f i s t swi tchi ng state wherei n the
f i s t and second pai s of termi nal s are connected t o each other ,
or i n a second swi tchi ng state wherei n the f i s t and thi d pai s
of termi nal s are connected t o each other . The access node
f urther compri ses a power accumul ator adapted t o accumul ate an
el ectri cal charge from at l east one command s i gnal of a sequence
of successive command s i gnal s transmi tted over the termi nal
segment of the subscri ber l oop by the power sou rci ng equi pment
while the switch is configured in the first switching state. The
access node further comprises a receiver coupled to the power
accumulator and adapted to detect a valid command signal in the
sequence of successive command signals by means of the soaccumulated
electrical charge. The switch controller is coupled
to the power accumulator and is further adapted, upon detection
of the valid command signal, to configure the switch in the
second switching state by means of the so-accumulated electrical
charge .
Such an access node typically refers to a DPU, but may
alternatively refer to any network equipment providing new
broadband communication services to subscribers through a copper
plant, and that is remotely fed from the subscriber premises
through the same copper plant, such as a remotely deployed
Digital Subscriber Line Access Multiplexer (DSLAM) making use of
RPF.
in accordance with still another aspect of the
invention, a power sourcing equipment comprises a power injector
adapted to inject a power feeding signal over a terminal segment
of a subscriber loop for reverse power feeding of an access
node. The power sourcing equipment further comprises a
transmitter adapted to transmit a sequence of successive command
signals over the terminal segment of the subscriber loop prior
to the insertion of the power feeding signal. The sequence of
successive command signals are transmitted for initial and
partial reverse power feeding of the access node, and further
for connection of the terminal segment of the subscriber loop to
a transceiver of the access node adapted to operate a new
broadband communication service and to a power supply unit of
the access node adapted to supply power to the access node from
the power feeding signal.
in one embodiment, the power sourcing equipment is
further adapted, after transmission of the sequence of
successive command signals, to determine whether a measured DC
load impedance of the subscriber loop matches a given signature
resistance, to insert the power feeding signal over the
subscriber loop if the given signature resistance is
successfully detected, else to repeatedly transmit the sequence
of successive command signals over the terminal segment of the
subscriber loop till the given signature resistance is
successfully detected.
Such a power sourcing equipment can be manufactured as
a standalone equipment, o r can be part of a subscriber device,
such as a modem, a router, etc.
in accordance with still another aspect of the
invention, a data communication system comprises an access node
and a power sourcing equipment as per the present invention.
The present invention proposes a solution to
automatically provision new broadband communication services
using RPF that is applicable to legacy deployments with o r
without POTS. This is achieved by the PSE preliminarily sending
successive command signals on the copper pair which contains
both the required protocol information to initiate RPF
operation, as well as enough electrical energy to power a
detection module and to switch the bypass relay at the DPU.
The PSE tries first to detect the presence of POTS over
the copper pair before initiating RPF operation, e.g. by
determining whether there is any DC voltage present over the
copper pair, if so, then the PSE sends a sequence of successive
command signals over the copper pair to instruct the DPU to
switch the bypass relay. The commands signals are designed to
have enough RMS power for the DPU to accumulate enough
electrical charge in a relatively short amount of time (up to a
few tens of seconds) in order to power the basic detection
circuitry and the control logic of the bypass switch, yet
without impacting POTS legacy communication service by causing
an improper OFFHOOK detection at the LEX.
The PSE next determines whether the bypass relay has
been properly switched at DPU side by measuring the DC load
impedance of the copper pair, and by determining whether the
measured impedance matches a given signature resistance, if so,
then the PSU is assumed to be correctly connected at the remote
end of the copper pair, and the PSE can start injecting the DC
power feeding signal for remote power feeding of the DPU as it
would no longer conflict with POTS operation.
It is noteworthy that, even if POTS is not present over
the copper pair (e.g., xDSL legacy deployments without POTS),
the PSU shall mandatorily detect a valid signature resistance on
the copper pair and make sure the bypass relay is properly
configured at DPU side before injecting the DC power feeding
s ignal .
Preferably, the command signals are generated by
modulation of one o r more AC carriers situated in a frequency
band not currently used by any legacy communication service
deployed over the copper pair.
For instance, the command signals can use the POTS
voice band, namely [300Hz; 3400Hz] frequency range, provided the
line is ONHOOK (which is likely to be the case as POTS is being
decommissioned for that subscriber). hen a voice call is
ongoing and an OFFHOOK condition is detected, then the command
signals sha not be transmitted.
Brief Description of the Drawings
The above and other objects and features of the
invention w i become more apparent and the invention itself
will be best understood by referring to the following
description of an embodiment taken in conjunction with the
accompanying drawings wherein:
- fig. 1 to 4 represent a communication network that is being
upgraded from a legacy communication service to a new
broadband communication service;
- fig. 5 and 6 represent further details about a bypass
detection module in an access node;
- fig. 7A, 7B and 7C represent various voltage/current plots
versus time within the bypass detection module; and
- fig. 8 represents a state diagram for PSE operation.
Detailed Description of the invention
There is seen in fig. 1 a legacy communication network
comprising the following network elements:
- a LEX 10;
- a RU 20;
- a splitter 30;
- a telephone handset 40; and
- a legacy Customer Premises Equipment (CPE) 50 (or LCPE) .
The LEX 10 is coupled to the RU 20 via a first copper
pair segment 61, and is for operating POTS.
The RU 20 is for operating a legacy broadband
communication service, presently VDSL2 communication service,
and is typically situated in a remote street o r pole cabinet
closer to subscriber premises. The RU 20 is coupled to the
splitter 30 through a second (shorter) copper pair segment 62.
The RU 20 accommodates a low-pass filter 21 and a highpass
filter 22 for respectively multiplexing/de-multiplexing the
POTS s i gnal and the VDSL2 s i gnal i nto/from the combi ned
POTS/VDSL2 s i gnal transi t i ng over the second copper pai segment
62 . The l ow-pass f i l ter 21 i s coupl ed t o the second copper pai
segment 62 and i s remotel y coupl ed t o the LEX 10 vi a the f i s t
copper pai segment 61 . The hi gh-pass f i l ter 22 i s coupl ed t o
the second copper pai segment 62 and i s l ocal l y coupl ed t o a
VDSL2 transcei ver 23 (or VTU-O) .
The spl i tter 30 compri ses a l ow-pass f i l ter 31 coupl ed
t o the second copper pai segment 62 , and i s for
mu t i p exi ng/de-mul t i p exi ng the POTS s i gnal i nto/from the
combi ned POTS/VDSL2 s i gnal transi t i ng over the second copper
pai segment 62 . The POTS s i gnal s i s suppl i ed t o the tel ephone
handset 40 , whi l e the combi ned POTS/VDSL2 s i gnal i s
transparentl y passed t o the l egacy CPE 50 .
The l egacy CPE 50 compri ses a hi gh-pass f i l ter 51
coupl ed t o the second copper pai segment 62 for
mu t i p exi ng/de-mul t i p exi ng the VDSL2 s i gnal i nto/from the
combi ned POTS/VDSL2 s i gnal transi t i ng over the second copper
pai segment 62 , and a VDSL2 transceiver 52 (or VTU-R) coupl ed
t o the hi gh-pass f i l ter 51.
The cut-off frequency f l of the l ow-pass f i l ters 21 and
31 i s typi ca y about 4kHz , and the cut-off frequency f 2 of the
hi gh-pass f i l ters 22 and 51 i s typi cal l y about 25kHz .
The VDSL2 transcei vers 23 and 52 operate a bi -
di recti onal VDSL2 broadband communi cati on channel over the
copper pai segment 62 . The LEX 10 and the tel ephone handset 40
operate a bi -di recti onal voi ce channel vi a the copper pai
segments 61 and 62 .
The LEX 10 , the RU 20 and the l egacy CPE 50 have
respective l ocal power suppl i es avai l abl e for power feedi ng ,
typi ca y 110-240V AC o r 48-60V DC .
There i s seen i n f i g . 2 the i nstal ati on of a new
network equi pment for upgradi ng the subscri ber base t o a new
broadband communi cati on servi ce offeri ng hi gher data rates ,
presentl y G. fast communi cation servi ce .
At some poi nt even cl oser t o the subscri ber premi ses ,
the copper pai segment 62 i s spl i t i nto two segments 63 and 64
for i nsertion of a DPU 100 . The copper pai segment 64 that
connects the DPU 100 down t o the subscri ber premi ses i s referred
t o as the termi nal segment , whi l e the copper pai segment 63
that connects the DPU 100 up t o the RU 20 and further up t o the
LEX 10 i s referred t o as the network segment .
The DPU 100 compri ses :
- a hi gh-pass f i l ter 110 for mu t i p exi ng/de-mul t i p exi ng the
G. fast si gnal i nto/from the combi ned DC/ G. fast si gnal s
transi t i ng over the termi nal segment 64 ;
- a G. fast transcei ver 120 (or FTU-O) ;
- a l ow-pass f i l ter 130 for mu t i p exi ng/de-mul t i p exi ng the DC
power feedi ng si gnal i nto/from the combi ned DC/ G. fast si gnal s
transi t i ng over the termi nal segment 64 ;
- a PSU 140 for extracti ng power from the DC power feedi ng
si gnal s suppl i ed by the various acti ve subscri bers and for
generati ng the necessary i nternal vol tage l evel s for operati on
of the DPU 100 ;
- a bypass swi tch 150 (or SW) wi t h two swi tchi ng states Si and
S2 , such as a l atchi ng rel ay;
- a bypass detecti on modul e 160 (or BP_MOD) for control i ng the
bypass swi tch 150 .
The cut-off frequency f 3 of the l ow-pass f i l ter 130 i s
typi cal l y greater than 4kHz , and the cut-off frequency of the
hi gh-pass f i l ter 110 i s typi cal l y about 2MHz .
ini t i al l y , the spl i tter 30 and the l egacy CPE 50 are
sti l l present at subscri ber si de . The DPU 100 i s thus confi gured
i n bypass (or transparent) mode : the bypass swi tch 150 i s
confi gu red i n the swi tchi ng state Si wherei n the termi nal
segment 64 i s connected t o the network segment 63 so as the DPU
100 i s ful l y transparent t o the end-users . The subscri bers can
keep on usi ng the l egacy communi cation servi ces , such as maki ng
voi ce cal s wi t h the handset 40 and connecti ng t o the i nternet
t hrough the l egacy CPE 50 .
At a l atter t i me , a new CPE 70 (or NCPE) supporti ng the
new G. fast communi cati on servi ce i s del ivered t o the subscri ber ,
together wi t h a PSE 200 . The CPE 70 and the PSE 200 can be
merged wi thi n one si ngl e equi pment . The l egacy network equi pment
30 , 40 and 50 are decommi ssi oned at subscri ber si de , and
repl aced by the newl y-suppl i ed network equi pment 70 and 200 . The
new network topol ogy i s depi cted i n f i g . 3.
The new CPE 70 compri ses a hi gh-pass f i l ter 71 coupl ed
t o the termi nal segment 64 for mu t i p exi ng/de-mul t i p exi ng the
G. fast si gnal i nto/from the combi ned DC/ G. fast si gnal transi t i ng
over the termi nal segment 64 , and a G. fast transcei ver 72 (or
FTU-R) coupled to the high-pass filter 71. The high-pass filter
71 has f4 as cut-off frequency.
The PSE 200 comprises:
- a low-pass filter 210,
- a power injector 220 (or RPF) ;
- an AC signaling means 230; and
- a measurement means 240 (or MEAS + MDSU) .
The low-pass filter 210 has f3 as cut-off frequency,
and is coupled to the terminal segment 64 in parallel with the
new CPE 70. The Low-pass filter 210 is further coupled to the
power injector 220, to the AC signaling means 230 and to the
measurement means 240.
The power injector 220 is for injecting a DC power
feeding signal DC_RPF_signal over the terminal segment 64 for
remote power feeding of the DPU 100.
The AC signaling means 230 is for transmitting a
sequence of successive AC command signals AC_cmd_si gnal s over
the terminal segment 64 for instructing the DPU 100 about the
availability of the RPF function at subscriber side, and for
requesting the DPU to configure the bypass switch 150 in the
switching state S2. in the switching state S2, the terminal
segment 64 is connected to the transceiver 120 and to the PSU
140 (i.e., the DPU 100 terminates the terminal segment 64) so as
the new G.fast communication service can be operated over the
terminal segment 64
The command signals are generated by means of Frequency
Shift Keying (FSK) modulation with 1300Hz and 2100Hz as
reference frequencies. These two frequencies are situated in the
POTS voice band, and the PSE 200 has first to make sure that no
OFFHOOK condition is active over the copper pair 64 before
transmitting such command signals in order not to interrupt an
ongoing phone call, such as an emergency call.
The AC signaling means 230 further accommodates a band
pass filter (not shown) to pass frequencies between 1300Hz and
2100Hz, and to attenuate frequencies outside this band.
Of course, the command signals can use another
modulation scheme, such as BPSK o r 4/16 QAM, and other carrier
frequencies, such as carrier frequencies situated in the
frequency range spanning from the upper bound of the POTS voice
band (3400Hz) up to the lower bound of the VDSL2 frequency band,
o carri er frequenci es si tuated bel ow the l ower bound of the
POTS voi ce band (bel ow 300 Hz) .
Yet , the usage of frequenci es i n the POTS voi ce band i s
benefi c i al for the hardware impl ementati on , indeed , the coupl i ng
capaci tors need t o sustai n hi gh DC vol tages , and usi ng hi gher
frequenci es al l ow smal l er val ue capaci tors , whi ch i s decreasi ng
the si ze and cost of the equi pment .
The amount of energy that needs t o be transferred by
means of the command si gnal s AC_cmd_si gnal s i s very l i mi ted as
the power i s onl y needed for two functions , namel y t o decode one
of the command si gnal s AC_cmd_si gnal s transmi tted by the PSE 200
over the termi nal segment 64 , and t o provi de the necessary
current t o swi tch the bypass swi tch 150 i nto the swi tchi ng state
S2 .
The RMS vol tage of the command si gnal s AC_cmd_si gnal s
shoul d however be l ow enough i n order t o not tri p the safety
protection i n the LEX 10 . Assumi ng an i nput i mpedance of 900W
for the POTS l i ne and negl ecti ng the l oop i nsertion l oss , we can
appl y 27VRMS between the t i p and r i ng of the copper pai (or 38v
or 76Vpp) t o keep the RMS current bel ow 30mA for i nstance . Thi s
i s suffi ci ent t o charge a capaci tor i n a reasonabl e amount of
t i me .
The measu rement means 240 i s for measu r i ng the DC
vol tage present between the t i p and r i ng of the copper pai 64 ,
and for measu r i ng the DC impedance l oadi ng the copper pai 64
fol l owi ng the so-cal l ed Metal i c Detecti on Start-Up (MDSU)
procedu r e ;
The MDSU requi es the i njection of one o r more
i ntermedi ary DC vol tages over the copper pai 64 , and next the
measurement of the correspondi ng DC l oad i mpedance i n order t o
detect a parti cul ar si gnatu r e resi stance i ndi cati ve of a PSU
bei ng remotel y connected t o the copper pai 64 .
Once the MDSU test i s successful , the PSE 200 can start
wi t h standardi zed RPF start-up protocol , e . g . as descri bed i n
ETSI 101548v010101 .
Thi s l ast step i s depi cted i n f i g . 4 , wherei n a DC
power feedi ng si gnal DC_RPF_si gnal i s i nserted over the termi nal
segment 64 by the PSE 200 . The DC_RPF_si gnal i s used by the PSU
140 (possi bl y wi t h other DC power feedi ng si gnal s from other
subscri bers) for generation of the necessary i nternal DC
vol tages (e . g . , 12v , 5V and 3v3) . These vol tages a e t hen
di s t r i buted t o t he res pecti ve acti ve ci rcu i t s of t he DPU 100 f or
no rmal ope rati on of t he DPU 100 . The reu pon , a G. fas t bi
di recti onal commu ni cati on channel can be establ i s hed between the
t ran scei ve r s 120 and 72 ove r the t e rmi nal segment 64 .
Fu rth e r detai l s abou t t he bypas s detecti on modu l e 300
a r e depi cted i n f i g . 5 and 6.
The bypas s detecti on mod ul e 300 con s i sts of a numbe r of
di ffe rent ha rdwa r e bl ocks se r i al l y cou pl ed t o each othe r ,
namel y :
- an i sol ati on and l oad ci cui t 301 ,
- a DC bl oc ki ng ci cui t 302 ;
- a recti f i e r 303 ;
- a powe r accumu l ato r 304 ;
- a DC regu l ato r 305; and
- a mi c rocont ro e r (o r mi c rop roces sor ) 306 .
An outpu t of t he mi c rocont ro e r 306 i s cou pl ed t o a
cont rol i nput of a l atch i ng rel ay 150 , wh i ch keeps i t s pr i or
swi tch i ng s tate when unpowe red .
The bypas s detecti on modu l e 300 f urthe r comp r i ses a
t ran scode r 307 f o r conve rti ng t he AC di ffe ren t i al s i gnal at t he
output of the DC bl ocki ng ci cui t 302 i nt o a s i ngl e-wi e s i gnal
fed t o an i nput of t he mi c rocont ro e r 306 f or protocol
detecti on . The t ran scode r 307 may f urthe r i ncl ude a demodu l ato r
f o r demod ul ati ng t he AC comman d s i gna s AC_cmd_si gna s i nt o a
baseban d s i gna .
The i sol ati on and l oad ci rcu i t 301 togeth e r wi t h t he DC
bl oc ki ng ci rcu i t 302 f o rm the i sol ati on pa r t . Thi s pa r t i s i n
di rect con tact wi t h t he coppe r pai r i n orde r t o l i mi t the
i mpact on POTS and xDSL l egacy s e rvi ces , i t i s req ui ed t o have
a hi gh i nput i mpedan ce . Thi s i s accompl i s hed wi t h two i sol ati on
res i sto r s Rl s e r i al l y cou pl ed t o the coppe r pai r , typi cal l y i n
t he o rde r of 8k pe r wi e (wh i ch i s al so s uffi ci ent t o not l oad
t he coppe r pai f or xDSL freq uenci es ) .
The DC bl oc ki ng ci rcu i t 302 typi cal l y comp r i s es two
capaci t or s Cl s e r i al l y cou pl ed t o the res i sto r s Rl , and provi des
i sol ati on f rom t he POTS DC vol tage wh i ch mi ght be present on the
coppe r pai .
The val ues of Rl and Cl s hal l be sel ected ca refu l l y as
t hi s i mpacts t he cha rge t i me of t he cha rge capaci t o r C2 .
The rectifier 303 and the power accumulator 304 forms
the energy storage part. A full wave rectifier bridge rectifies
the negative swings of the AC command signals AC_cmd_si gnal s . A
full wave rectifier is required as the polarity is unknown prior
to installation. The output of the bridge rectifier is connected
to a charge capacitor C2. A n increasing DC voltage V 2 thus
develops across the charge capacitor C2 while the AC command
signals AC_cmd_signal s are being received from the PSE 200.
The DC regulator 305, the microcontroller 306 and the
bypass switch 150 form the load part. A low-drop linear
regulator converts the voltage across the charge capacitor C2 to
a lower voltage to power the microcontroller. A low-drop linear
regulator is preferred over a swi tched-mode regulator to avoid
costly and bulky inductors. Due to the small current (< 1mA
typically for low-power controller), power losses in the lowdrop
linear regulator can be minimized. Once powered, the
microcontroller starts decoding one o r more of the AC command
signals AC_cmd_signal s transcoded by the differential monitoring
block. hen a valid pattern is detected, the microcontroller
will steer the bypass relays to connect the user to a G.fast
transceiver and a PSU. The energy needed to drive the bypass
relay is directly taken from the charged capacitor C2.
Size and cost are very important for DPU's. A s
indicated on fig. 5 , the bypass relay, the isolation part, the
rectifier and the transcoder are required per line, but the
charge capacitor, the DC regulator and the microcontroller can
be shared over multiple subscriber line ports of multi-port DPU
units .
The DC regulator 305 is an optional block as the
required energy can directly be drained from the power
accumulator 304. This configuration is possible when the
microcontroller 306 can tolerate a large power supply range
(e.g., 1.8v - 5.5V). Such devices are commercially available.
Avoiding the low-drop linear regulator results in an additional
cost saving.
Fig. 7A represents a time plot of the voltage Vl at the
input of the bypass detection module 300 and of the voltage V 2
that develops across the charge capacitor C2.
The PSE 200 sends successive AC command signals
AC_cmd_si gnal s on the copper pair 64, which results in a given
s i gnal wi t h ampl i tude V1 a whi ch i s superponated on a DC POTS
vol tage V1 d i f any (for conveni ence , the AC command s i gnal s
are pl otted unmodul ated) .
The AC s i gnal whi ch i s presented at the i nput of the
ful l wave recti f i e r bri dge a l l ows t o store a DC vol tage across
the charge capaci tor C2 . After a gi ven amount of t i me , the
capaci tor C2 i s charged t o a vol tage V2 ha ged . As l ong as the
l ow-drop l i near regul ator i s not started , no current i s taken
from the charge capaci tor C2 (except some l eakage current) ,
hence the capaci tor vol tage V2 can i ncrease i n t i me .
he n the vol tage V2 i s equal t o a predefi ned l evel , the
l ow-drop l i near DC/DC regul ator i s enabl ed through the vol tage
di vi der R2a and R2B (see f i g . 6) . The l ow-drop l i near regul ator
converts the vol tage V2 across the capaci tor C2 t o a l ower
vol tage V3 , whi ch powers the mi crocontrol e r . A hysteresi s i n
the l ow-drop l i near regul ator i s requi ed t o sti l l enabl e the
output whi e the capaci tor C2 i s di schargi ng .
Fi g . 7B shows V2 and V3 vol tages versus t i me . The
vol tage V2 over C2 starts i ncreasi ng up t o t i me t , when the
l ow-drop regul ator i s enabl ed . From that time onwards , a l ower
vol tage V3 i s generated at the output of the l ow-drop l i near
regul ator , whi ch feeds the l ow-power mi crocontrol e r . Due t o the
current taken from the mi crocontrol e r and the l ow-drop l i near
regul ator , the vol tage V2 across C2 starts decreasi ng .
Once powered , the mi crocontrol e r starts t o decode the
AC s i gnal whi ch i s sensed before the recti f i e r bri dge and
transcoded by the di fferenti a l moni tori ng bl ock t o decode the
protocol i nformation transmi tted by the PSE . The protocol
i nformati on modul ated on the respective AC carri ers may be very
basi c , such as the presence of one or more HDLC f l ags , or may
compri ses some f urther i nformati on e l ements , as wel l a s some
pari t y check .
when the mi croprocessor detects a val i d code , the gate
of the MOSFET transi stor i s enabl ed : a current Isw f l ow through
the bypass rel ay , and i t s swi tchi ng state i s changed from Si t o
S2 . The current t o drive the bypass rel ay (whi ch i s typi cal l y a
l oadi ng coi l ) i s di rectl y del i vered from the charge capaci tor
C2 . Other means t o drive and feed the bypass rel ay are al so
possi bl e , such as a thyri stor , a l ow-vol tage rel ay, etc .
This is depicted in fig. 7B and 7C. After time t , the
microcontroller starts to decode the AC signal before the
rectifier bridge. At time t3 a valid code is detected, and the
relay control signal is toggled to switch the bypass relay into
the switching state S2. From time t3 , additional current Isw is
taken to drive the bypass relay. The current Isw is directly
delivered by the charge capacitor C2, hence V2 is reducing
faster after t3. if C2 is discharged below the point where the
low-drop linear regulator is no longer enabled and if no valid
code has been detected so far, then the microcontroller shuts
down and the process restarts autonomously some time later after
the capacitor C2 is charged again.
Additional components for lightning protection and
protection for ringing voltages should typically be added. These
are orthogonal to the invention and should be part of design
process .
It is noteworthy that the charge capacitor C2 is also
charged when ringing voltage is applied on the line. The
microcontroller will start to decode the (ringing) signal, but
since no valid code is detected, the bypass relays is not
switched.
The bypass detection module 300 is connected between
the bypass switch 150 and the network segment 63. The POTS
bypass detection module is no longer attached to the copper line
once the bypass relay 150 is switched to the switching state S2.
This adds the advantage that the bypass detection module 300 can
be made transparent up to 17MHz o r 30MHz (for VDSL2) , and not up
to 106MHz o r 212MHz (for G.fast) since it will never be
connected to copper pairs over which G.fast communication
services are operated.
An alternative implementations is possible, wherein the
bypass detection module 300 is connected between the bypass
switch 150 and the terminal segment 64. The advantage of this
second implementation is that the detection circuit could also
be used for upstream communication between the PSE 200 and the
DPU 100, for instance to share battery status, serial number,
power capabilities, and so forth.
There is seen in fig. 8 a state diagram for PSE
operation .
A s a matter of introduction, different voltage
thresholds VT, Vl, V2, V 3 and V 4 have been plotted on a vertical
axis with VT < V l < V 2 < V 3 < V4. These voltage thresholds are
used for assessing the POTS operational status of a subscriber
line.
Let VDC denote the DC voltage as measured by the PSE 200
between the tip and ring of the copper pair 64. if V 3 < VDC < V 4
then POTS service is assumed to be operational over the line and
the line is assumed to be in the ONHOOK state, meaning no voice
ca is being made, if V l < VDC < V 2 then POTS service is
assumed to be operational over the line and the line is assumed
to be in the OFFHOOK state, meaning a voice ca is ongoing over
the line (such a situation barely occurs as the handset 40 is
expected to be decommissioned at subscriber side when connecting
the PSE 200). Finally, if VDC < VT then POTS service is assumed
to be no longer operational over the line. This does not
necessarily mean that the bypass switch is already in the right
position and that the DPU is ready to operate the new broadband
communication service over the line, indeed, a legacy xDSL
communication service may have been deployed over that line
without POTS, and the bypass switch is still to be properly
configured for that line.
Let us set forth now the steps through which the PSE
200 goes through when starting up.
in step 1001, the PSE 200 starts up and run through
some b 1tin tests to make sure it is ready for operation.
in step 1002, the DC voltage between the tip and the
ring of the copper pair 64 is measured by the measurement means
240, thereby yielding a measured voltage value V D
if the measured DC voltage VDC is between V 3 and V4,
then POTS service is operational and the line is in the ONHOOK
state. The PSE 200 goes to step 1003 and the A C signaling means
230 transmits a sequence of successive AC commands signals over
the copper pair 64 for T l seconds in order to force the by-pass
switch at the D P ) side to the switching state S2. After T l
seconds, the PSE 200 returns to step 1002, and measures the DC
voltage again.
if the measured DC voltage VDC is between V l and V2,
then POTS service is operational and the line is in OFFHOOK
state. The PSE 200 cannot transmit the A C command signals as
this would conflict with an on-going voice call (only in case
the AC signals use the POTS voice band). The PSE 200 thus
transitions to step 1005 , waits for T2 seconds, and next returns
to step 1002 for a new measurement round.
The branch 1002 - > 1005 - > 1002 can also be used if the
measured DC voltage VDC is outside the allowed voltage ranges
(see hatched areas in fig. 8) . Such a situation is not expected
to occur, and rather is indicative of a network failure that
needs to be first identified and repaired.
Finally, if the measured DC voltage VDC is below a given
threshold VT , then POTS service is no longer operational over
the line. The PSE 200 goes to step 1004 , and the measurement
means 240 performs a MDSU test over the copper pair 64 .
Successive intermediary voltage levels are applied to the copper
pair 64 , and the DC load impedance of the copper pair 64 is
measured for detection of a particular signature resistance, if
a signature resistance is successfully detected over the copper
pair 64 , meaning the bypass switch at DPU side is in the
switching state S2 and a PSU is connected to the remote end of
the copper pair 64 , the MDSU test passes (see "pass" branch in
fig. 8) , and the PSE 200 can transition to final step 1006 . The
power injector 220 injects a DC power feeding signal over the
copper pair 64 for remote power feeding of the DPU. Else, if the
PSE 200 fails to detect the signature resistance over the copper
pair, then the MDSU test fails (see "fail" branch in fig. 8) ,
and the PSE 200 transitions to step 1003 for transmitting a
sequence of AC command signals for Tl seconds over the copper
pair 64 . Thereafter, the PSE 200 returns to step 1003 , and so
forth.
Of course, other voltage thresholds can be used to
determine the POTS operational status. For instance, the voltage
thresholds V2 and V3 can be merged into one single threshold,
and/or so can be the thresholds VT and Vl. The upper bound
voltage threshold V4 can be similarly ignored, in this case, if
the measured DC voltage is below VT=V1 , then POTS is no longer
operational, if the measured DC voltage is between VT=V1 and
V2=v3 , then POTS is operational yet the line is OFFHOOK. And
last, if the measured DC voltage is above V2=v3 , then POTS is
operational and the line is ONHOOK.
Although the above description was primarily concerned
with upgrading a data communication system from VDSL2 (with o r
wi thout POTS) t o G. fast , i t si mi l arl y appl i es t o ADSL or ADSL2+
depl oyments (wi t h or wi thout POTS) wherei n the DSLAM i s col
ocated wi t h the LEX at the CO. The copper pai segment 61 then
corresponds t o a l ocal connecti on between the LEX and the CO,
typi ca y vi a a Mai n Di stri bution Frame (MDF) , and the copper
pai segment 62 corresponds t o the mai n subscri ber l oop spanni ng
from the CO down t o the subscri ber premi ses . Thi s subscri ber
l oop i s then spl i t i nto two segments (as per the segments 63 and
64) for i nsertion of a DPU and G. fast servi ce upgrade as per the
present i nvention .
I t i s t o be noti ced that the term ' compri si ng ' shoul d
not be i nterpreted as bei ng restri cted t o the means l i sted
thereafter . Thus , the scope of the expressi on ' a devi ce
compri si ng means A and B' shoul d not be l imi ted t o devi ces
consi sti ng onl y of components A and B. I t means that wi t h
respect t o the present i nventi on , the rel evant components of the
devi ce are A and B .
I t i s t o be further noticed that the term ' coupl ed '
shoul d not be i nterpreted as bei ng restri cted t o di rect
connections onl y . Thus , the scope of the expression ' a devi ce A
coupl ed t o a device B' shoul d not be l imi ted t o devi ces or
systems wherei n an output of devi ce A i s di rectl y connected t o an
i nput of devi ce B, and/or vice-versa. I t means that there exi sts
a path between an output of A and an i nput of B, and/or vi ceversa
, whi ch may be a path i nc udi ng other devi ces or means .
The descri ption and drawi ngs merel y i l l ustrate the
pri nci pl es of the i nventi on . I t wi l l thus be appreci ated that
those ski ed i n the art wi l l be abl e t o devi se various
arrangements that , al though not expl i ci t l y descri bed or shown
herei n , embody the pri nci pl es of the i nvention . Fu rthermore , al l
exampl es reci ted herei n are pri nci pal l y i ntended expressl y t o be
onl y for pedagogi cal pu rposes t o ai d the reader i n understandi ng
the pri nci pl es of the i nvention and the concepts contri buted by
the i nventor(s) t o f urtheri ng the art , and are t o be construed
as bei ng wi thout i mi tati on t o such speci f i ca y reci ted
exampl es and condi tions . Moreover , al l statements herei n
reci t i ng pri nci pl es , aspects , and embodi ments of the i nvention ,
as wel l as speci f i c exampl es thereof, are i ntended t o encompass
equi val ents thereof.
The functions of the various el ements shown i n the
f i gu res may be provi ded t hrough the use of dedi cated hardware as
wel l as hardware capabl e of executi ng software i n associ ati on
wi t h appropri ate software . he n provi ded by a processor , the
functi ons may be provi ded by a s i ngl e dedi cated processor , by a
s i ngl e shared processor , o r by a pl ural i t y of i ndi vi dual
processors , some of whi ch may be shared . Moreover , a processor
shoul d not be construed t o refer excl usivel y t o hardware capabl e
of executi ng software , and may i mpl i ci t l y i ncl ude , wi thout
l i mi tation , Di gi tal Si gnal Processor (DSP) hardware , network
processor , Appl i cation speci f i c integrated c i rcui t (ASIC) , Fi el d
Programmabl e Gate Array (FPGA) , etc . Other hardware ,
conventional and/or custom, such a s Read Onl y Memory (ROM) ,
Random Access Memory (RAM) , and non vol ati l e storage , may a l so
be i nc uded .

CLAIMS
1 . A method for provi sioni ng a new broadband
communication service ( G. fast) , and compri si ng :
- i nserti ng an access node (100) adapted t o operate the new
broadband communi cation servi ce al ong a subscri ber loop (62) ;
- confi gu r i ng a switch (150) of the access node i n a f i rst
initial switching state (si) wherei n a f i rst pai r of
termi nal s coupl ed t o a legacy subscriber device (40 ; 50) vi a
a termi nal segment (64) of the subscri ber l oop i s connected t o
a second pai r of termi nal s coupl ed t o a legacy network
equi pment (10 ; 20) vi a a further segment (63) of the
subscri ber l oop ;
- operati ng at least one legacy communication service (POTS ;
VDSL2) over the subscri ber l oop whi l e the swi tch i s i n the
f i st swi tchi ng state ;
- connecti ng a power sourcing equi pment (200) adapted t o i nject
a power feedi ng signal (DC_RPF_si gnal ) for reverse power
feedi ng of the access node and a new subscriber device (70)
adapted t o operate the new broadband communi cation servi ce t o
the termi nal segment of the subscri ber l oop ,
wherein the method further compri ses :
- by the power sourci ng equi pment , transmi tti ng a sequence of
successive command signals (AC_cmd_si gnal s) over the termi nal
segment of the subscri ber l oop pri or t o the i nserti on of the
power feedi ng si gnal ;
- by the access node , accumul ati ng an electrical charge from at
least one command signal of the sequence of successi ve command
si gnal s ;
- by the access node and by means of the so accumul ated
el ectri cal charge , detecti ng a val i d command signal i n the
sequence of successive command si gnal s , and thereupon
confi gu r i ng the swi tch i n a second switching state (S2)
wherei n the f i st pai of termi nal s i s connected t o a thi rd
pai r of termi nal s coupl ed t o a transceiver (120) adapted t o
operate the new broadband communi cati on servi ce and t o a power
supply unit (140) adapted t o suppl y power t o the access node
from the power feedi ng si gnal ;
- by the power sou rci ng equi pment , i njecti ng the power feedi ng
si gnal over the termi nal segment of the subscri ber l oop for
reverse power feedi ng of the access node ; and
- operati ng the new broadband communi cati on servi ce over the
termi nal segment of the subscri ber l oop .
2 . A method accordi ng t o cl aim 1 , wherein the command
si gnal s are i ndi cative of a prelimi nary operational state at
the power sourci ng equi pment .
3 . A method accordi ng t o cl aim 1 , wherein the command
si gnal i s detected as bei ng val i d when a payload of the command
si gnal matches a given pattern .
4 . A method accordi ng t o c ai m 1 , wherein the at l east
one l egacy communi cati on servi ce compri ses at l east one of an
Asymmetri c Di gi tal Subscri ber Li ne ADSL communi cation servi ce ,
an Asymmetri c Di gi tal Subscri ber Li ne wi t h extended bandwi dth
ADSL2+ communi cati on servi ce , a Very-hi gh speed Di gi tal
Subscri ber Li ne VDSL2 communi cati on servi ce , and a Pl ai n Ol d
Te ephony Servi ce POTS .
5. A method accordi ng t o cl aim 1 , wherein the command
si gnal s are generated by modul ation of at least one AC
carriers .
6 . A method accordi ng t o cl aim 5, wherein the at l east
one AC carri ers are si tuated i n a frequency band not currentl y
used by the at l east one l egacy communi cation servi ce .
7 . A method accordi ng t o cl ai m 6 , wherein the frequency
band i s the voi ce band of P ai n O d Te ephony Servi ce POTS .
8 . An access node (100) compri si ng :
- a transceiver (120) adapted t o operate a new broadband
communication service ( G. fast) over a terminal segment (64)
of a subscriber loop (62) ;
- a power supply unit (140) adapted t o suppl y power t o the
access node from a power feedi ng signal (DC_RPF_si gnal )
i njected by a power sourci ng equi pment (200) over the termi nal
segment of the subscri ber l oop ;
- a switch (150) havi ng a f i rst pai r of termi nal s for coupl i ng
t o the termi nal segment of the subscri ber l oop , a second pai r
of termi nal s for coupl i ng t o a further segment (63) of the
subscri ber l oop , and a thi rd pai r of termi nal s coupl ed t o the
transceiver and t o the power suppl y uni t ;
- a switch control ler (300) adapted t o confi gure the swi tch i n a
f i rst switchi ng state (si) wherei n the f i st and second pai s
of termi nal s are connected t o each other , or i n a second
switching state (S2) wherei n the f i st and thi r d pai s of
termi nal s are connected t o each other ,
wherein the access node f urther compri ses a power accumulator
(303+304) adapted t o accumul ate an electrical charge from at
least one command signal of a sequence of successive command
signal s (AC_cmd_si gnal s) transmi tted over the termi nal segment
of the subscri ber l oop by the power sourci ng equi pment whi l e the
swi tch i s confi gu red i n the f i st swi tchi ng state ,
wherein the access node further compri ses a receiver (300)
coupl ed t o the power accumul ator and adapted t o detect a val i d
command signal i n the sequence of successi ve command si gnal s by
means of the so-accumul ated el ectri cal charge ,
and wherein the swi tch control l er i s coupl ed t o the power
accumul ator and i s f urther adapted , upon detecti on of the val i d
command si gnal , t o confi gure the swi tch i n the second swi tchi ng
state by means of the so-accumul ated el ectri cal charge .
9. An access node (100) accordi ng t o cl aim 8, wherei n
the access node i s a Di stribution Point Unit DPU (100) .
10 . An access node (100) accordi ng t o cl ai m 8, wherei n
the access node i s a remotely deployed Digital Subscri ber Li ne
Access Multiplexer DSLAM maki ng use of remote power feedi ng .
11. A power sourci ng equipment (200) compri si ng a power
i njector (220) adapted t o i nject a power feeding signal
(DC_si gnal ) over a termi nal segment (64) of a subscri ber loop
(62) for reverse power feedi ng of an access node (100) ,
wherein the power sou rci ng equi pment f urther compri ses a
transmitter (230) adapted t o transmi t a sequence of successive
command signal s (AC_cmd_si gnal s) over the termi nal segment of
the subscri ber l oop pri or t o the i nsertion of the power feedi ng
si gnal ,
and wherein the sequence of successive command si gnal s are
transmi tted for i ni t i al and parti al reverse power feedi ng of the
access node , and f urther for connecti on of the termi nal segment
of the subscriber loop to a transceiver (120) of the access node
adapted to operate a new broadband communication service
(G.fast) and to a power supply unit (140) of the access node
adapted to supply power to the access node from the power
feeding signal .
12. A power sourcing equipment (200) according to claim
7 , wherein the power sourcing equipment is further adapted,
after transmission of the sequence of successive command
signals, to determine whether a measured DC load impedance of
the subscriber loop matches a given signature resistance, to
insert the power feeding signal over the subscriber loop if the
given signature resistance is successfully detected, else to
repeatedly transmit the sequence of successive command signals
over the terminal segment of the subscriber loop till the given
signature resistance is successfully detected.
13. A subscriber device comprising a power sourcing
equipment (200) according to claim 11 o r 12.
14. A data communication system comprising an access
node (100) according to any of claims 8 to 10, and a power
sourcing equipment (200) according to claim 11 o r 12.