Local access network

Details Local access network Local access network

1997-06-09

2002-05-21

Marcelo, Melvin (Department: 2663)

Multiplex communications

Data flow congestion prevention or control

Flow control of data transmission through a network

C370S395100, C370S434000, C370S468000

Reexamination Certificate

active

06392995

ABSTRACT:

The present invention concerns a local mobile access network equipped with means for managing the resources in said network.
A local mobile access network RLAM to which the present invention can be applied is shown in FIG.
1
. This local network consists of a number of radio terminals BR each connected, via a multiplex marked P
4
, to a number of concentrators CTR (three here). Each concentrator CTR is connected, by a multiplex marked P
3
, to a virtual circuit switch VCX which, in turn, is connected, by a multiplex marked P
0
, to a general network RG. Each element of the local network RLAM uses the technology known under the name ATM (Asynchronous Transfer Mode).
It will be noted that the multiplexes marked P
4
, P
3
and P
0
are bidirectional multiplexes.
With this type of access network, communications are managed in the switch circuit VCX. They can be local when they are established between mobile units linked to the local network RLAM in question. They can be outgoing when they are established between mobile units linked to the network RLAM in question and to any terminal equipment of the general network RG.
In the present description, we shall say that a mobile unit is linked to a local network RLAM when it passes under the radio coverage of one of the terminals BR connected to this network. By way of example, the coverage of such a network could be of an average agglomeration. Always by way of example, several networks of this type can be juxtaposed to increase the geographic area covered. Thus, a large-scale regional or national network should amalgamate a more or less significant number of local access networks RLAM.
It is understood that the present invention is not limited to an access network like the one shown in FIG.
1
. It could be applied to a network having a more complex architecture because it consists of a number of more significant concentration and switching stages.
In the present description, we shall call the concentration stage and the virtual circuit switch(es) concentrators CTR of the network.
Moreover, in this description, the local networks will be considered to be both dedicated and shared. In both cases, the architectures are very similar, the only differences being in the fact that the second has terminal installations other than mobile.
A mobile unit which is already connected and which is thus linked to one of the terminals BR can, when it is shifted, find itself covered by a second or several other radio terminals BR. Thus, it can be momentarily linked to several terminals BR. It can then be said that this mobile unit is in a “hand-over” phase. In this phase, the information which it transmits is received simultaneously by the terminals BR to which it is linked and it, in turn, receives information coming simultaneously from said terminals BR.
The local mobile networks RLAM generally comprise macrodiversity server equipment OPM whose role is described in greater detail below. Equipment of this type is shown in
FIG. 1
which is connected to the switch VCX by two multiplexes marked P
1
and P
2
.
It will be noted that, contrary to the multiplexes P
4
, P
3
and P
0
, the multiplexes P
1
and P
2
are unidirectional multiplexes. This is shown by the arrows for the unidirectional multiplexes which are, moreover, absent for the bidirectional multiplexes.
FIG. 2
a
shows, in the network RLAM shown in
FIG. 1
, the ascending direction (mobile to network) of a communication example during a hand-over phase. The mobile unit MB is linked to three terminals BR
1
, BR
2
and BR
3
, two of which BR
1
and BR
2
are connected to the same concentrator CTR
1
and the third BR
3
to concentrator CTR
2
. In this ascending direction, the information transmitted by the mobile unit MB is then recopied three times in the local network RLAM. The flow is then multiplied by two on the multiplex P
3
between concentrator CTR
1
and switch VCX and it is multiplied by 3 on multiplex P
2
.
Generally, in the ascending direction, the mobile unit MB is linked to the local network RLAM as many times as there are terminals BR monitoring the mobile unit and the flow consumed in the network is increased to the different points of concentration.
From a general point of view, the function of the macrodiversity server equipment OPM is to filter the flow (here three) coming from the same mobile unit MB and present on the multiplex P
2
and to retain only one, generally the one which has the best quality, that it delivers on the multiplex P
1
, in order to not unnecessarily “encumber” the network RLAM. This operation is generally called a “macrodiversity” operation.
It is specified that, when a mobile unit is covered by several terminals, the radio links are generally of a very unequal quality.
In
FIG. 2
a
, on multiplex P
1
, the filtered flow is unique. In this
FIG. 2
a
, an outgoing communication is considered even though the flow present on multiplex P
1
is then found on multiplex P
0
. It will be noted that, in the case of a local communication, the flow on multiplex P
1
is shunted, by switch VCX, toward the concentrator CTR with which the addressee is connected.
FIG. 2
b
shows the descending direction (network to mobile unit) of the information. The switch VCX transmits the signal to the two concentrators CTR
1
and CTR
2
. The concentrator CTR
1
transmits to the two terminals BR
1
and BR
2
while concentrator CTR
2
transmits to terminal BR
3
. The same signal is then received three times by the mobile unit MB. More generally, the processing of the macrodiversity is carried out in the mobile unit MB itself and does not pose any specific problems at the level of the network RLAM. It will be noted that the descending connection is of the point-to-multipoint type.
In an ATM network, whatever it may be, a virtual connection is established by marking a path and requires the reservation of a passband on this path in accordance with the requirements expressed and required, by the caller at the time the connection is established, for the service performed on this path.
Although in the case of telephony, the resources consumed are limited to a few ten Kbits/s for a communication, in the case of videophony, on the other hand, the resources consumed attain several hundred Kbits/s, or even more.
Conventionally, an ATM multiplex supports a passband higher than 100 Mbits/s. Thus, at least at the level of the local part of the network, the number of connections for telephony simultaneously established will never permit this limit to be attained. That is not the case for videophony.
Henceforth, two factors should be taken into account which risk significantly increasing the flow rate and which require implementing methods which enable maximum management of the flow rates. On the one hand, the perspective of a future deployment on the radiotelephony networks for new services is inescapable. On the other hand, the macrodiversity which is a feature suitable for this type of network results in an increase of the flow rates during hand-over phases.
Therefore, the object of the invention is to propose a mobile access network which makes it possible to take into account the increase in the flow rate which results from hand-over phases.
To this end, a mobile access network of the type which generally comprises a number of radio terminals linked via concentration stages, to another concentration stage composed of a virtual circuit switch, is characterized therein that at least said concentration stage comprised of said virtual circuit switch is equipped with macrodiversity management equipment and therein that each concentration stage downstream from the or a concentration stage equipped with a macrodiversity management equipment is furnished with a management device for the flow rates provided to manage the resources on the multiplex which is located directly above the concentration stage which it supplies.
In the present description, it is considered that the links are called ascending when they originate with a radio terminal and terminate at the main virtual circuit switch of the net

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