Data transmission method between a base station controller...

Details Data transmission method between a base station controller... Data transmission method between a base station controller...

1999-05-11

2001-12-25

Olms, Douglas (Department: 2732)

Multiplex communications

Communication over free space

Using trunking

C455S123000

Reexamination Certificate

active

06333927

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data transmission method between a base station controller (BSC) and a base transceiver station (BTS) in a digital mobile communication system (such as a digital cellular system, a personal communication system, and a digital trunked radio system) employing a code division multiple access (CDMA) mode.
2. Description of Related Art
Generally, the digital mobile communication system applies to mobile objects such as a person, automobile, ship, train, and airplane.
FIG. 1
is a block diagram showing such conventional digital mobile communication system.
As shown in
FIG. 1
, the conventional digital mobile communication system comprises: mobile station (MS)
10
carried by a subscriber for wireless telecommunication; base transceiver station (BTS)
20
for receiving a call processing request from the MS
10
and transmitting a call transmission request from base station controller (BSC)
30
to the MS
10
; BSC
30
for controlling the BTS
20
to perform the signal processing between the BTS
20
and mobile switching center (MSC)
40
; and MSC
40
connected to the BSC
30
for transmitting the call processing request from the MS
10
via a public network or a private network to a public switching telephone network (PSTN) or advanced mobile phone service (AMPS) and another communication network to offer mobile communication service.
In this conventional mobile communication system, if a subscriber having his/her MS
10
attempts to use the mobile communication service within a service radius of the MSC
40
, the MSC
40
catches the location of the MS
10
and operates to perform voice/facsimile information service according to the request of the MS
10
or connects the MS to another communication network to perform the mobile communication service.
FIG. 2
is a block diagram showing data transmission between the BSC
30
and the BTS
20
.
As shown in
FIG. 2
, the BSC
30
comprises: vocoder
31
for compressing voice or data received from the MSC
40
to generate packets and transmitting voice or data received from the BTS
20
to the MSC
40
; selection unit
32
for generating frames from the voice or data packets received from the vocoder
31
and analyzing frames received from the BTS
20
; global positioning system (GPS) receiver
33
for receiving time/frequency from a GPS satellite and generating reference clocks for synchronization of the digital mobile communication system; and E1/T1 interface
34
for transmitting the frames received from the selection unit
32
via a trunk to the BTS
20
in synchronization with the reference clocks generated from the GPS receiver
33
and receiving the frames from the BTS
20
.
The BTS
20
comprises: base station common processor (BCP)
21
for controlling frame transmission between the MS
10
and BSC
30
, generating frames from voice or data received from the MS
10
, and analyzing frames received from the BSC
30
; channel card interface
22
corresponding to the vocoder
31
of the BSC
30
one to one, for modulating the frames received via an E1/T1 trunk from the BSC
30
according to control of the BCP
21
and demodulating voice or data received from the MS
10
; GPS receiver
23
for receiving time/frequency from a GPS satellite and generating reference clocks for synchronization of the digital mobile communication system; and E1/T1 interface
24
for transmitting the frames generated from the BCP
21
via the E1/T1 trunk to the BSC
30
in synchronization with the reference clocks generated from the GPS receiver
23
and receiving the frames from the BSC
30
via the E1/T1 trunk.
The following description concerns how a high level data link control (HDLC) frame is transmitted via the E1/T1 trunk between the BSC
30
and BTS
20
.
Primarily, transmission of frames from the BSC
30
to the BTS
20
is performed as follows. Once voice or data is transmitted from the MSC
40
, the vocoder
31
in the BSC
30
receives the voice or data and compresses a transmission band to provide an output to the selection unit
32
. At this time, the vocoder
31
transmits the voice or data to the selection unit
32
at a full rate if an amount of voice or data is received from the MSC
40
. The vocoder
31
controls packet transmission according to a transmission rate of the voice or data to be transmitted to the selection unit
32
. For example, if the transmission rate of the voice or data to be transmitted to the selection unit
32
is of the order of half the full rate, the vocoder
31
transmits a voice or data packet to the selection unit
32
at a half rate. In such manner, the voice or data is transmitted from the MSC
40
to the selection unit
32
via the vocoder
31
at different transmission rates, such as the full rate and transmission rates ½, ¼, and {fraction (
1
/
8
)}, depending upon circumstances.
When the voice or data packet is transmitted from the vocoder
31
at one of the different transmission rates, the selection unit
32
writes the voice or data packet onto a corresponding field in an HDLC frame to generate the frame. The selection unit
32
writes the received packet onto a voice/data field having a fixed length of 20 bytes regardless of the transmission rate of the voice or data packet and writes onto header and tail fields in the frame to generate the frame having a fixed length of 48 bytes. The generated frame of the fixed length is transmitted to the E1/T1 interface
34
. The E1/T1 interface
34
transmits the frame via the E1/T1 trunk to the BTS
20
according to the reference clock output from the GPS receiver
33
.
The same bandwidth is used when transmitting packets from the vocoder
31
to the BTS
20
at a low transmission rate such as the transmission rate ⅛ and at the full rate. This results in waste of bandwidth in case of data transmission at the low rate such as the transmission rate ⅛.
In other words, the conventional data transmission method between the BSC
30
and the BTS
20
using the E1/T1 trunk is a fixed rate non-channelized HDLC method, wherein the bandwidth of 2.048 Mbps used in case of the E1 and the bandwidth of 1.544 Mbps used in case of the T1 are shaped into the fixed length transmission frame of 48 bytes regardless of channels.
The E1 trunk has transmission capacity to transmit one frame per 20 msec, thus transmitting 2400 bytes (48*50) per 1 second in the 48-byte fixed length frame transmission. Therefore, the data transmission via the E1 trunk has the bandwidth of 19.2 kbps (2400*8) and the capacity of the trunk is 2048 kbps/19.2 kbps=106. Such transmission capacity of the E1 trunk is effected when the vocoder of 8 kbps is applied.
Once the fixed length frame from the BSC
30
is received by the E1/T1 interface
24
in the BTS
20
via the E1/T1 trunk, the base station common processor
21
analyzes the received fixed length frame. The channel card interface
22
modulates the analyzed data before transmitting it to the MS
10
.
Next, the description on transmission of voice or data of the MS
10
from the BTS
20
to the BSC
30
in the 48-byte fixed length frame will be set forth. The 48-byte frame is generated at the base station common processor
21
in the BTS
20
and transmitted via the E1/T1 trunk to the BSC
30
. The selection unit
32
in the BSC
30
then receives and analyzes the frame and transmits the analyzed voice or data to the vocoder
31
for transmission to the MSC
40
.
In this case of transmitting the data from the BTS
20
to the BSC
30
, the data is also transmitted in the form of the 48-byte fixed length frame.
As illustrated above, the conventional method of transmitting the data between the BSC and BTS in the mobile communication system using the E1/T1 trunk transmits the data in the form of a frame of the same length both when the voice or data is transmitted at the full rate and when the voice or data is transmitted at the low rate such as the transmission rate ⅛. Therefore, there is a problem of wasting the bandwidth

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