Multiplex communications – Communication over free space – Having a plurality of contiguous regions served by...
Reexamination Certificate
2000-09-22
2004-08-24
Nguyen, Hanh (Department: 2662)
Multiplex communications
Communication over free space
Having a plurality of contiguous regions served by...
C370S510000, C370S350000, C370S342000, C370S412000
Reexamination Certificate
active
06781976
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a time-alignment apparatus for providing data frames of a plurality of channels with predetermined time-offsets. The time-alignment apparatus is provided in a transmitter of a telecommunication system and receives successive data frames, each containing a predetermined number of data symbols, respectively from a number of channels and outputs the data symbols successively with predetermined time-offsets relative to a common synchronization clock. The invention also relates to a method for performing such a time-alignment, a transmitter of a telecommunication system and a telecommunication system, in which such a time-alignment is performed in a transmitter.
Typically, the time-alignment apparatus and the method are used in a telecommunication system based on a time division multiplexing or CDMA transmission. In such systems, the time-offset relative to a common synchronization signal indicates the beginning of the radio frames of the corresponding channels on the radio link (air interface or antenna). Before the transmission onto the radio link, the individual data frames must be stored and must then be provided with the time-offset. The invention particularly relates to the problem of how the different time-offsets between the data frames of a great number of user channels can be handled, in particular for a CDMA telecommunication system.
BACKGROUND OF THE INVENTION
In many telecommunication systems, the individual data frames of a number of channels are generated asynchronously, i.e. ATM data frames are not generated aligned to a given synchronization clock in the transmitter. If the individual channels have the same basic transmission rate TR
B
(on the air interface) the data frames will contain the same number of data symbols, however, they will still not be aligned to a common synchronization clock. The task of the transmitter is, despite the asynchronously arriving data packets from the individual channels, to transmit the data frames (or more precisely their data symbols) on the radio link with a predetermined respective time-offset per channel, which then characterizes the beginning of data frames of this particular user channel. The transmission to the receiver can introduce further time delays between the individual data frames, for example due to varying distances during the transmission, such that the receiver must perform a time-alignment with respect to a common synchronization clock provided in the receiver. The present invention relates to the time-offset adjustment in the transmitter.
An example of a mobile radio communication system, where such a time-offset adjustment is required, is a CDMA mobile radio communication system.
FIG. 5
shows a block diagram of a base transceiver station BTS in such a CDMA communication system.
FIG. 6
shows the encoder unit ENC of the base transmitter station BTS in FIG.
6
. It should be noted that hereinafter the invention and their problems will be considered with respect to the CDMA system shown in
FIGS. 5
,
6
, however, the time-alignment is also applicable to any communication system requiring a time-offset adjustment.
In all telecommunication systems, where several channels each comprising successive data frames are provided, a separate encoder dedicated to a specific user channel must be provided in order to encode the successively arriving data frames of one particular channel. However, this would result in e.g. up to 300 encoder units, which is unacceptable in terms of the required hardware effort. For this reason, there is always the problem of how a common encoder resource can be used efficiently for encoding the data frames of all channels. In principle, this can be achieved if the time, which the encoder spends on encoding one data frame is much shorter than the duration of the data frame itself. Then, the encoder can process the data frames of several channels one after the other within one data frame period. Since the data frames of the individual channels do not arrive synchronized to a common synchronization clock and must be provided with a predetermined time-offset per channel to the air interface, the arriving data frames must be buffered in a memory, before a predetermined time-offset can be applied to them such that the data symbols can be delivered in form of a constant stream of data symbols to the modulation unit (e.g. the CDMA modulator BBTX in FIG.
6
).
The invention particularly relates to the problem of how different time-offsets c an be applied to the (possibly asynchronously) arriving data frames of a great number of channels.
SUMMARY OF THE INVENTION
As described above, due to the fact that the time-offsets indicate the beginning of the individual radio frames of the corresponding channel on the radio link, the encoder unit must ensure that the individually (possibly asynchronously) arriving data frames from the user channels are available with a unique time-offset on the radio link. In addition to the problem that the data frames have to be provided with unique time-offsets, often an interleaving of data frame, more precisely of the data symbols contained therein, must be performed, i.e. the data symbols should be rearranged (interleaved) before the data symbols are provided as a data symbol stream to the modulator. The time-offset provision is to achieve minimum interference between the individual channels, i.e. it shall improve the correlation properties of a CDMA receiver. An additional interleaving improves the data reception at the receiver in fading channel environments which introduce burst errors in the received data frames.
Therefore, the object of the invention is to provide a time-alignment apparatus, a transmitter of a telecommunication system, in particular an encoder unit of a CDMA-system, a telecommunication system and a time-alignment method, which enable user data arriving in data frames from a plurality of user channels to have individually assigned unique time-offsets before transmission into the air, such that the interference between the code channels, for example the CDMA channels in a CDMA system, is minimized.
Another object of the invention is to provide a time-alignment apparatus, a transmitter of a telecommunication system, a telecommunication system and a time-alignment method, with which the encoder hardware can be used efficiently even for a large number of user channels.
SOLUTION OF THE OBJECT
This object is solved by a time-alignment apparatus of a transmitter of a telecommunication system for receiving successive data frames, each containing a predetermined number of data symbols, respectively from a number of channels, and for successively outputting the data symbols with a predetermined time-offset relative to a common synchronization clock, comprising:
a) at least a first, second and third read/write frame memory, each having a number of storage resources each for storing the data symbols of one data frame of a respective channel, sa-id frame memories each having a write state in which data is written to said frame memories by an input means and a read state (in which data is read from said frame memories by an output means;
b) a control unit for cyclically switching said three frame memories through a first to third alignment mode synchronized to said common synchronization clock such that
b1) in said first alignment mode said first and second frame memory are in a write state and said third frame memory is in a read state;
b2) in said second alignment mode said second and third frame memory are in a write state and said first frame memory is in a read state; and
b3) in said third alignment mode said third and first frame memory are in a write state and said second frame memory is in a read state;
c) a write/read address providing means for providing a respective frame start write address (corresponding to said time-offset individually for each storage resource of a frame memory having a write state, and successive read addresses commonly for all storage resources of a frame memory having a read state;
d
Huaman-Bollo Gian
Sönning Raimund
Nguyen Hanh
Nixon & Vanderhye P.C.
Telefonaktiebolaget LM Ericsson (publ)
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