Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2000-02-29
2002-05-21
Vo, Nguyen T. (Department: 2682)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S557000, C455S550100, C455S553100, C455S003050
Reexamination Certificate
active
06393280
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of controlling multiple/single mode in a wideband wireless local loop (W-WLL) network system. More particularly, the present invention relates to a radio interface unit (RIU) and a method of controlling multiple/single mode of such an RIU in a wireless local loop (WLL) system, in which both the multiple and single mode services can be performed by a single algorithm, and a modulator-demodulator (modem) used in RIU is modeled as “master” and “slave”, respectively, to thereby allow a rapid handling of service, a stabilized system, and an efficient utilization of wireless systems.
2. Description of the Related Art
In general, WLL system is similar to a mobile communication network in that WLL system uses wireless channels as a communication medium. However, WLL system is not provided with mobility, and therefore, a communication environment thereof is further excellent than that of mobile communication system.
WLL system has further advantage in that a line-of-sight environment is secured and a propagation path loss is low, say, is approximately 20 dB/decade, thus allowing a wide area service using the same amount of transmitting power. In addition, WLL system is a fixed communication system employing a point-to-point transmission method, and has less fading caused by a multiple path than the propagation environment of mobile communication system that employs a point-to-station transmission method.
Due to such advantages, development and study on WLL system has been actively performed.
FIG. 1
is a schematic view of a common WLL network system having the above-described advantages.
The WLL network system shown in
FIG. 1
consists of a terminal
10
, a radio interface unit(RIU)
20
, a radio port (RP)
30
, a radio port controller
40
, a WLL exchanger
50
, and a radio port operation & maintenance center (RPOM)
60
.
An inter-working function (IWF)
70
, and a home location resister/authentication center are added to thus-configured WLL system.
WLL system further includes a network management center
90
connected to RPOM
60
and WLL exchanger
50
, and a charging center
100
connected to WLL exchanger
50
and IWF
70
.
Thus-configured WLL has an interface method among network components as follows.
A common WLL interface standard is used as an interface standard between RIU
20
and RP
30
, wherein a channel bandwidth is 10 MHz. Either E
1
wire connection or HDSL is used as an interface standard between RP
30
and RP controller
40
, and link access procedure D(LAPD) as a signal transmission protocol. E
1
wire connection is used as an interface standard between RP controller
40
and WLL exchanger
50
, and ITU.T G.965 as a signal transmission method. Ethernet is used between RP controller
40
and RPOM
60
as an interface standard, and simple network management protocol (SNMP), filter transfer protocol (FTP), telecommunication network (TELNET) and the like as a signal transmission method. E
1
wire connection is employed between RP controller
40
and IWF
70
as an interface standard, and LAPD as a signal transmission protocol. In addition, E
1
wire connection is employed as an interface standard between WLL exchanger
50
and IWF
70
, and R
2
as a signal transmission method. E
1
wire connection is employed as an interface standard between WLL exchanger
50
and home location register (HLR), and IS-41C as a signal transmission method.
A conventional WLL system has the above-described components operating as follows.
First, RP
30
is made up of a radio port control module for performing an overall management function onto the radio port, a modem module for performing CDMA channel-related signal processing function, an RF module for performing a high power/low noise amplification and a transmitting/receiving frequency converting function, and a line connection module for linking to E
1
wire connection for a match with RP controller
40
.
Thus-structured RP
30
performs such functions as a transmitted signal amplification, low noise amplification of a received signal, frequency upward/downward conversion, diversity receipt via two antennas, high power/low noise amplification, and transmitting/receiving frequency conversion. In addition, modem module performs provider function of CDMA channel(pilot channel, synchronization channel, paging channel, access channel, signaling channel, traffic channel, packet traffic channel and packet access channel), digital baseband function, and CDMA channel coding and decoding-related function. In addition, line connection module performs data communication with the RP controller in regards of traffic and control data, and link line (E
1
/HDSL) function for a match with RP controller.
RP controller
40
for controlling RP
30
includes a transcoder module, a call processing module, a switching module, and a matching module.
The transcoder module further includes a transcoder for converting to 64 kbps PCM voice coded signal, and is provided with an echo canceller function. The call processing module is a processor for performing various kinds of call processing functions, for example, supporting of transmitted/received call processing of radio port, and processing of messages, and other functions like management of subsystem within RP controller and formatting of control signal between WLL exchanger and subscriber interface equipment. The call processing module has a duplex structure for system reliability enhancement.
The switching module provides a traffic path between an RP matching equipment and a transcoder in RP. The matching module consists of an WLL exchanger matching module, an RP matching module, and an RPOM matching module, wherein WLL exchanger matching module performs E
1
/G.965 digital link matching function when the RP controller is installed in remote location with respect to the WLL exchanger. The RP matching module serves as a match of E
1
/LAPD, HDSL link line between RP and RP controller, and RPOM matching module serves as a match of Ethernet/SNMP, FPT, TELNET between RPOM and RP controller.
RPOM
60
operates RPC
40
, RP
30
, and RIU
20
, and serves to the maintenance of the above-described equipment.
RIU
20
includes a high frequency processing module
21
, a modem
22
for processing a digital signal, and a subscriber interface module
23
, as shown in FIG.
2
.
Here, high frequency processing module
21
amplifies a transmitted signal, low noise of a received signal, and performs a frequency upward/downward converting function. That is, high frequency processing module
21
transmits/receives data to/from a radio port via an antenna. Subscriber interface module
23
consists of BRI, SLIC, and SIO, etc, wherein BRI provides ISDN U-interface function for a physical interface with ISDN subscribers. SLIC performs A/D conversion and D/A conversion by being linked to an analog line, and serves as a line feeder, and ring signal and tone signal provider. SIO interfaces with RS-232C for a connection with a serial port so as to provide a digital data terminal interface function.
Modem
22
, a digital processing block, is connected to high frequency processing module
21
in a searcher
22
a
so as to extract only a desired channel signal from the received signal. A power controller
22
b
controls power by detecting the strength of the channel signal extracted by searcher
22
a
. In addition, a phase tracking portion
22
c
traces a phase from a channel signal extracted by searcher
22
a
, and performs an automatic frequency control function, when phase difference occurs, so as to compensate such a phase difference. An automatic gain controller
22
d
variably controls the gain of the amplifier in accordance with the strength of the received signal obtained from searcher
22
a
. A receiver
22
e
serves to convert CDMA signal of RF band passed through searcher
22
a
to a baseband signal. Thus-converted baseband signal undergoes a series of process, say, demodulation, de-interleaving, and channel decoding in a channel
Choi Sung-Gyu
Eo Su-Man
Hur Sang-Jin
Kim Yunn-Ghee
Lee Hun
Bryan Cave LLP
Kurland, Esq. Lawrence G.
Nguyen Duc
Vo Nguyen T.
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