Method of managing a plurality of radio links in wireless...

Details Method of managing a plurality of radio links in wireless... Method of managing a plurality of radio links in wireless...

2000-03-13

2003-04-29

Vuong, Quochien (Department: 2681)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S003050, C455S560000, C455S561000

Reexamination Certificate

active

06556827

ABSTRACT:

CLAIM OF PRIORITY
This application claims priority to an application entitled “Method of Managing a Plurality of Radio Links in Wireless Local Loop” filed in the Korean Industrial Property Office on Mar. 12, 1999 and assigned Serial No. 99-8196.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a wireless local loop (WLL), and in particular, to a method of managing a plurality of radio links in the WLL to set up, add, and release the plurality of radio links between a terminal and a base station (BS).
2. Description of the Related Art
A WLL system wirelessly links a wired subscriber terminal to a telephone office. The WLL system is basically the same as a mobile communication system, except for the fixedness of subscriber terminals.
FIG. 1
illustrates a general WLL configuration based on W-CDMA (Wide-band Code Division Multiple Access), which can be applied to any radio system using the WLL as a substitute for a subscriber line between a fixed network and a subscriber. As shown in
FIG. 1
, the WLL system includes a terminal
20
connected to a subscriber equipment
10
such as a facsimile or a wired telephone, a base station
30
connected to the terminal
20
via a radio link, a base station controller (BSC)
40
connected to the base station
30
by a trunk line, a local exchange (LE)
50
connected to the BSC
40
by a trunk line, and a public switched telephone network (PSTN)
60
for connecting the LE
50
to another network.
A data link layer, being a layer
2
(L
2
), manages the radio link between the base station
30
and the terminal
20
. The data link layer establishes and releases a radio channel in a radio interface between the base station
30
and the terminal
20
, and manages the data transmission between them by W-CDMA technology.
In the thus-constituted WLL, if the base station
30
or terminal
20
requests a call set-up, the BSC
40
commands the base station
30
to assign radio resources (radio channel). Then, the data link layer of the base station
30
controls the terminal
20
and assigns the radio resources to the radio interface.
The terminal
20
is connected to at least one subscriber equipment
10
(facsimile, wired telephone, or personal computer). If the terminal
20
is connected to a plurality of subscriber's equipment
10
, a plurality of calls should be set up between the base station
30
and the terminal
20
.
When the radio interface is in a single mode, the data link layers of the base station
30
and the terminal
20
assign an extra signaling radio channel for each call every time the call is attempted.
However, when the radio interface is in a multiple mode, a data link layer checks whether a signaling channel already has been assigned to a terminal which attempts a call, and sets up only a new radio link for sharing the assigned channel in the presence of the assigned channel. That is, the multiple-mode data link layer divides one channel into a plurality of radio links using the link Ids, and uses one radio link for each call.
FIG. 2
depicts a message flow for the radio links between the general data link layers in a conventional radio link managing method. If the BSC
40
sends an establish request message APL
2
_EST_REQ to the base station
30
. The base station
30
determines the ID (LID) of a radio link to be established and sends a receive ready message (RR message) including the LID to the terminal
20
, in step M
120
.
After setting up a radio link corresponding to the LID included in the RR message, at step M
130
, the terminal
20
sends an RR message (ACK RR message) including the LID, indicating acknowledgment to the base station
30
. At step M
140
, upon the receipt of the ACK RR message, the base station
30
sends the BSC
40
an establish confirm message APL
2
_EST_CNF, notifying the set-up of the radio link with the LID. When the radio link is completely established, the base station
30
and the terminal
20
communicate over the radio link.
If a call is connected between another subscriber linked to the terminal
20
and the base station
30
during the communication, the BSC
40
requests the set-up of an additional radio link to the base station
30
. This procedure is called “add.” In this case, at step M
150
, the BSC
40
sends an add request message APL
2
_ADD_REQ to the base station
30
. At step M
160
, the base station
30
sends the terminal
20
an RR message including a new LID.
At step M
170
, the terminal
20
sets up the additional radio link with the new LID and sends an ACK RR message to the base station
30
. At step M
180
, upon receipt of the ACK RR message, the base station
30
sends the BSC
40
an add confirm message APL
2
_ADD_CONF, notifying that the radio link that the new LID is added.
If calls are released from some or all of the radio links established between the terminal
20
and the base station
30
, the BSC
40
sends the base station
30
and the terminal
20
a release request message in step M
190
. Then, the base station
30
and the terminal
20
release some or all of the established radio links.
However, a problem with the conventional radio link managing method is that if a BSC requests the set-up of a radio link to a base station, the base station cannot find out whether the requested radio link is to be a newly established radio link or an additional radio link (an add). Then, the radio link already established for a certain subscriber equipment is set up for another subscriber equipment, or the established radio link is released, thereby disconnecting a call. Consequently, the radio link management is implemented by influencing an existing call on another established radio link in the conventional method.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a multiple radio link managing method in a WLL, wherein the data link layers of a terminal and a base station are able to set up a new radio link, add an extra radio link, and release an established radio link without influencing an existing call.
To achieve the above object, there is provided a method of managing a plurality of radio links in a WLL. In the present invention, the state of each radio link is defined as: (1) L
2
_NewLid, indicates that establishment of a radio link is requested but not completed; (2) LNK which indicates that a new connection is established to the radio link; and, (3) L
3
_AddReq, which indicates that the establishment of the radio link is pending. In a method of managing a plurality of radio links between a base station and a terminal according to an aspect of the present invention, the base station receives a radio link establish request message. Then, a data link layer of the base station sets the LNK of a radio link to be established to a logic 1, transmits a request for establishing the radio link to the terminal, receives an acknowledgment from the terminal, notifies a BSC that the radio link is established upon the receipt of the acknowledgrnent, and initiates a service between the terminal and the base station on the established radio link.
In a method of managing a plurality of radio links between a base station and a terminal according to another aspect of the present invention, a data link layer of the base station receives an add request message for a new radio link on a radio link, and checks L
2
_NewLid and LNK of the new radio link to be added if the data link layer is in a multi-frame established state. If L
2
_NewLid and LNK are logic 1s, the data link layer adds the new radio link. If L
2
_NewLid is logic 1 and LNK is logic 0, the data link layer determines that frame errors have occurred and performs an add failure operation. If L
2
_NewLid is logic 0 and LNK is logic 1, the data link layer performs an add failure operation. If both L
2
_NewLid and LNK are logic 0s, the data link layer sets both L
2
_NewLid and LNK of the new radio link to logic 1s and adds the new radio link.
According to a further aspect of the present invention, a method of managing a plurality of radi

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