Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
1999-10-20
2003-03-18
Chin, Vivian (Department: 2682)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S342000, C375S130000
Reexamination Certificate
active
06535495
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of operating a radio communication system, and further relates to such a system and to primary and secondary stations for use in such a system. While the present specification describes a system with particular reference to the emerging Universal Mobile Telecommunication System (UMTS), it is to be understood that such techniques are equally applicable to use in other mobile radio systems.
BACKGROUND OF THE INVENTION
A number communication systems, both existing and emerging, use Code Division Multiple Access (CDMA) techniques, one example being UMTS when operating in a wide band Code Division Multiple Access (CDMA) frequency division duplex mode. Such systems are typically cellular, with a Base Station (BS) servicing a plurality of Mobile Stations (MS) in a cell.
FIG. 1
is a block schematic diagram of a radio communication system using CDMA, comprising a primary station (BS)
100
and a plurality of secondary stations (MS)
110
. The BS
100
comprises a microcontroller (&mgr;C)
102
, transceiver means
104
connected to radio transmission means
106
, and connection means
108
for connection to the PSTN or a private network. Each MS
110
comprises a microcontroller (&mgr;C)
112
and transceiver means
114
connected to radio transmission means
116
. Communication from BS
100
to MS
110
takes place on a downlink channel
122
, while communication from MS
110
to BS
100
takes place on an uplink channel
124
.
FIG. 2
shows an example of a known arrangement for spreading and scrambling using Quadrature Phase Shift Keying (QPSK) modulation. Data is supplied on input line
202
to a serial to parallel converter
204
, which maps each pair of data bits to I and Q branches respectively. A channelisation code
210
is supplied to mixers
206
,
208
in the I and Q branches to spread the data to the chip rate. The data is then scrambled by a BS-specific scrambling code
216
supplied to I and Q mixers
212
,
214
. The resultant data is used to modulate a cosine carrier
220
by an I mixer
218
, and a sine carrier
224
by a Q mixer
222
. The I and Q branches are then combined by a combiner
226
before being passed to radio broadcast means
228
for transmission as a QPSK signal.
If a BS supports more than one cell (for example in a sectorised transmission arrangement), the scrambling code
216
could be cell-specific instead of BS-specific.
Different physical channels use different channelisation codes (usually orthogonal), while the scrambling code is the same for all physical channels in one cell.
On the downlink channel
122
a number of channelisation codes (usually orthogonal) are used to separate transmissions intended for different users, and an additional scrambling code is applied to distinguish the transmitting BS
100
. Hence, to decode a message intended for it a MS
110
has to know both the code for the BS
100
sending the data and the code for its channel.
Similarly on the uplink channel
124
a channelisation code is used to select the channel on which the MS
110
is to transmit and a scrambling code, specific to the MS
110
, is used.
A problem with this arrangement is the possible lack of channelisation codes for the downlink
122
since codes which have been allocated to one user, but are not currently in use, may not be available for another user. One possibility for relieving this shortage is to use more than one scrambling code per cell. However, this has the disadvantage that signals transmitted to one user with one scrambling code will not be orthogonal to signals transmitted to a different user with a different scrambling code, resulting in increased interference. SUMMARY OF THE INVENTION
An object of the present invention is to reduce the problems caused by the use of more than one scrambling code in a cell.
According to a first aspect of the present invention there is provided a method of operating a radio communication system employing a code division multiple access technique, comprising a primary station transmitting data to a plurality of secondary stations, the primary station encoding different portions of said data with different scrambling codes, characterised by using a primary and a secondary scrambling code to encode data for transmission to a single secondary station.
According to a second aspect of the present invention there is provided a radio communication system employing a code division multiple access technique comprising a primary station and a plurality of secondary stations, the primary station having means for transmission of data to the secondary stations and means for encoding different portions of said data with different scrambling codes, characterised in that the primary station has means for using a primary and a secondary scrambling code to encode data for transmission to a single secondary station.
According to a third aspect of the present invention there is provided a primary station for use in a radio communication system employing a code division multiple access technique, the primary station having means for transmission of data to the secondary stations and means for encoding different portions of said data with different scrambling codes, characterised in that the primary station has means for using a primary and a secondary scrambling code to encode data for transmission to a single secondary station.
According to a fourth aspect of the present invention there is provided a secondary station for use in a radio communication system employing a code division multiple access technique, characterised in that the secondary station has means for receiving data from a single primary station encoded using a primary and a secondary scrambling code.
The present invention is based on the recognition, not present in the prior art, that a plurality of scrambling codes can be allocated for transmissions from one BS to a single MS.
REFERENCES:
patent: 4965826 (1990-10-01), Caprarese et al.
patent: 5533014 (1996-07-01), Willars et al.
patent: 5539746 (1996-07-01), Huang et al.
patent: 5828956 (1998-10-01), Shirai
patent: WO9429981 (1994-12-01), None
Chin Vivian
Halajian Dicran
Koninklijke Philips Electronics , N.V.
Ramos-Feliciano Eliseo
LandOfFree
Radio communication system with multiple and simultaneous... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radio communication system with multiple and simultaneous..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radio communication system with multiple and simultaneous... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3025024